Editor-In-Chief Henry A. Hoff
Zoology is a biological science that pertains to animals. Animals choose to move whereas plants are moved. Animals feed on bio-organic material and digest it internally. Plants can convert inorganic and organic material into bio-organic material. Cell walls of an animal are flexible. Animal cells possess junctions which are impermeable to fluids (tight junctions), junctions which allow intercellular communication, or the transfer of low molecular-weight substances (gap junctions), and structures which adhere to other cells to form tissue via structural units (desmosomes).
Genetics is the study of the genes, how they affect organisms, and how they are passed from one generation to the next. A scientist that studies genetics is called a geneticist.
DNA, deoxyribonucleic acid, is a molecule found in almost every cell of every body of every organism. DNA contains genes, which are the basic instruction codes for making and running a living organism. Strands of DNA make up chromosomes. (Chromosomes are made of DNA, which is made up of genes.)
Genes, through DNA and chromosomes, are passed from one generation to the next by inheritance. Because of this, offspring resemble their parents. Through mixing and occasional mutation, genes can change. When genes change, how the organism forms and how it works may be changed.
How all these changes affect individuals, populations, and entire species is the work of geneticists. ______
"A recent comparison of the draft sequences of mouse and human genomes has shed light on the selective forces that have predominated in their recent evolutionary histories. In particular, mouse-specific clusters of homologues associated with roles in reproduction, immunity and host defence appear to be under diversifying positive selective pressure, as indicated by high ratios of non-synonymous to synonymous substitution rates. These clusters are also frequently punctuated by homologous pseudogenes. They thus have experienced numerous gene death, as well as gene birth, events. These regions appear, therefore, to have borne the brunt of adaptive evolution that underlies physiological and behavioural innovation in mice. We predict that the availability of numerous animal genomes will give rise to a new field of genome zoology in which differences in animal physiology and ethology are illuminated by the study of genomic sequence variations."
On the right is a drawing of the archaean Haloquadratum walsbyi.
As the study of biology is the study of all living organisms, zoology is a specialty of biology. All zoologists are also considered biologists.
Other branches of biology include botany (the study of plants), mycology (the study of fungi), phycology (the study of algae), and virology (the study of viruses).
The biological definition of animals includes all members of the kingdom Animalia.
Def. "a multicellular organism that is usually mobile, whose cells are not encased in a rigid cell wall (distinguishing it from plants and fungi) and which derives energy solely from the consumption of other organisms" is called an animal.
Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, and unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which are autotrophs, producing their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With very few exceptions, animals breathe oxygen and respire aerobically. All animals are motile (able to spontaneously move their bodies) during at least part of their life cycle, but some animals, such as sponges, corals, mussels, and barnacles, later become sessile. The blastula is a stage in embryogenesis, embryonic development, that is unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a relatively flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible. This may be calcified, forming structures such as an exoskeleton of shells, bones, and spicules. In contrast, the cells of other multicellular organisms (primarily algae, plants, and fungi) are held in place by cell walls, and so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, and desmosomes.
With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues. These include muscles, which enable locomotion, and nerve tissues, which transmit signals and coordinate the body. Typically, there is also an internal digestive chamber with either one opening (as in flatworms) or two openings (as in deuterostomes).
Nearly all animals make use of some form of sexual reproduction. They produce haploid gametes by meiosis; the smaller, motile gametes are spermatozoa and the larger, non-motile gametes are ova. These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, and develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement. It first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm, also develops between them. These germ layers then differentiate to form tissues and organs.
Repeated instances of inbreeding, mating with a close relative, during sexual reproduction generally leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for inbreeding avoidance, or avoiding close inbreeding. In some species, such as the splendid fairywren (Malurus splendens), females benefit by mating with multiple males, thus producing more offspring of higher genetic quality.
Some animals are capable of asexual reproduction, which often results in a genetic clone of the parent. This may take place through fragmentation; budding, such as in Hydra and other cnidarians; or parthenogenesis, where fertile eggs are produced without mating, such as in aphids.
Animals are categorised into ecological groups depending on how they obtain or consume organic material, including carnivores, herbivores, omnivores, detritivores, and parasites. Interactions between animals form complex food webs. In carnivorous or omnivorous species, predation is a consumer-resource interaction where a predator feeds on another organism (called its prey). Selective pressures imposed on one another lead to an evolutionary arms race between predator and prey, resulting in various anti-predator adaptations. Almost all multicellular predators are animals. Some consumers use multiple methods; for example, in parasitoid wasps, the larvae feed on the hosts' living tissues, killing them in the process, but the adults primarily consume nectar from flowers. Other animals may have very specific feeding behaviours, such as hawksbill sea turtles that primarily eat sponges.
Most animals rely on the energy produced by plants through photosynthesis. Herbivores eat plant material directly, while carnivores, and other animals on higher trophic levels, typically acquire energy (in the form of reduced carbon) by eating other animals. The carbohydrates, lipids, proteins, and other biomolecules are broken down to allow the animal to grow and to sustain biological processes such as locomotion. Animals living close to hydrothermal vents and cold seeps on the dark sea floor do not depend on the energy of sunlight. Rather, archaea and bacteria in these locations produce organic matter through chemosynthesis (by oxidizing inorganic compounds, such as methane) and form the base of the local food web.
Animals originally evolved in the sea. Lineages of arthropods colonised land around the same time as land plants, probably between 510–471 million years ago during the Late Cambrian or Early Ordovician. Vertebrates such as the Sarcopterygii, lobe-finned fish, Tiktaalik started to move on to land in the late Devonian, about 375 million years ago. Animals occupy virtually all of earth's habitats and microhabitats, including salt water, hydrothermal vents, fresh water, hot springs, swamps, forests, pastures, deserts, air, and the interiors of animals, plants, fungi and rocks. Animals are however not particularly heat tolerant; very few of them can survive at constant temperatures above 50 °C. Only very few species of animals (mostly nematodes) inhabit the most extreme cold deserts of continental Antarctica.
Def. "that part of biology which relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct" is called zoology.
"Compare both photos, in the photo above and the "civil war soldiers". All this is model of a pterodactyl. Not sure of the age, but I'm sure it was like a practical joke back in the day. The "bigfoot" of it's day so to speak. Compare the photos and you'll see that it's the exact same model. The above photo would be a better looking fake than the civil war photo. Any real dead animal is limp until rigor sets in, and even then, it has to [weigh] something right? Why is the guy in the center of the above photo not holding up the main weight of the body? He's practically leaning on it. It's because it's a stiff model that supports itself. And I'm willing to bet that if you were to look at some older photos around the turn of the 19th century of some paleontology exhibits, you'd find this exact same model at some point. The Bone Wars started in the 1880s and made dinosaurs all the rage."
Zoography is descriptive zoology. Animals are described in comparison with other organisms, and their surroundings. This comparison takes into account variation among individuals and populations, and organizes it into systems and classifications that are used for making predictions, such as the evolutionary relationships among organisms.
The branches of zoology focusing on a particular taxonomic group (mammals, etc.) are often considered part of zoography.
Def. a "description of animals, their forms, and habits; descriptive zoology" is called zoography.
Vertebrate zoology is the study of vertebrates, the animals that have a spinal column. This covers only about 3% of all known species.
Scientists who study mammalogy are called mammalogists.
Mammals are endothermic vertebrates that have fur or hair and feed milk to their young. Milk is a fluid produced by mammary glands.
There are about 5000 species of living mammal known to science. Mammals live in every habitat on Earth. They range in size from the Etruscan shrew (Suncus etruscus), the smallest living mammal, to the blue whale (Balaenoptera musculus) which is the largest animal to have ever lived. Humans (Homo sapiens) are also mammals. They are placed in the taxonomic class Mammalia.
Def. a "taxonomic clade within the clade Reptiliomorpha – the most recent common ancestor of extant mammals and reptiles, and all its descendants; the reptiles, birds and mammals, collectively, all of which have an amnion during development" is called the Amniota.
- [American Society of Mammalogists]
- [Mammalian Species] a journal that consists of species accounts of mammals from around the world.
Def. the study of the Archosauria is called archosaurology.
The Archosauria include the Pseudosuchia and the Ornithodira.
The Pseudosuchia include the Crocodylomorpha: Crocodylia, †Aetosauria, †Phytosauria, †Rauisuchia and the unplaced families: †Atoposauridae, †Bernissartiidae, and †Peirosauridae.
The Ornithodira include the Dinosauromorpha and †Pterosauromorpha.
The Dinosauromorpha include the Dinosauria.
Def. "the scientific study of birds" is called ornithology.
Scientists who study ornithology are called ornithologists.
Birds are endothermic vertebrates that have feathers and lay eggs. Birds are considered the only living direct descendants of dinosaurs. They belong to the taxonomic class Aves.
There are about 10,000 species of living bird known to science. Birds live in every habitat on Earth. They range in size from the Bee Hummingbird (Mellisuga helenae), the smallest living bird, to the Common Ostrich (Struthio camelus), which standing up to 8 feet (2.4 m) tall, is the tallest living bird.
Def. the group containing the most recent common ancestor of archosaurs and lepidosaurs and all its descendants is called the Sauria.
Sauria may be a crowned-base grouping of diapsids. However, recent genomic studies and comprehensive studies in the fossil record suggest that turtles are closely related to archosaurs, not to parareptiles as previously thought.
- [Avibase] a world bird database.
Buried "beneath the dry, dusty plains of Central Argentina [was] the fossilized bones of Argentavis magnificens, now the world's largest known flying bird. With a wingspan of twenty-five feet, and stretching eleven feet from the tip of its bill to the tip of its tail [...] The giant bird, a new genus and species of teratorn (from the Greek teratos-, meaning wonder, and ornis, meaning bird), was discovered a few years ago by two well-known Argentinian paleontologists, Drs. Eduardo Tonni and Rosendo Pascual. [...] Argentavis magnificens is the oldest known teratorn. It has been dated at between five and eight million years old, or from the late part of the Miocene epoch, on the basis of the fossil mammals found in the same deposits as the fossil bird. Fossils of these same species of mammals have been found at other sites in Argentina for which radiaometric dates are available."
Def. the "branch of paleontology that focuses on studying dinosaurs" is called dinosaurology.
Usually allied with geology rather than biology, paleontology is the study of past life. Dinosaurology is the specific branch of paleontology that is the study of dinosaurs. Because birds are the living descendants of dinosaurs, ornithology might be considered a branch of dinosaurology.
Scientists who study dinosaurs are usually called paleontologists, but might also be called dinosaurologists.
The non-avian dinosaurs lived during the Mesozoic Era, the time period between roughly 252 and 65 million years ago. The first dinosaurs evolved about 225 million years ago, and all but the birds became extinct by the end of the Mesozoic Era.
Dinosaurologists, like other paleontologists need a good grounding in geology and anatomy, as well as whatever other fields their particular study may involve.
Def. the study of the Crocodylomorpha is called crocodylomorphology.
Def. the "study of the Archelosauria" is called archelosaurology.
The Archelosauria include the Crurotarsi and Pan-Testudines.
The Crurotarsi include the Archosauria.
The Pan-Testudines include the Testudinata (turtles and tortoises) and †Sauropterygia.
Def. the scientific study of turtles is called cheloniology.
Def. the scientific study of tortoises is called testudinology.
Def. a "study of Lepidosauria" is called lepidosaurology.
Def. a "study of lizards" is called saurology.
Def. the "study of snakes"is called ophiology.
Ophiology is a specialization of herpetology. Scientists who study ophiology are called herpetologists.
The name of this specialty comes from the Greek word for snake, ophis.
Def. the "branch of biology dealing with reptiles (Reptilia) and amphibians" is called herpetology.
Scientists who study herpetology are called herpetologists.
Reptiles and amphibians are ectothermic vertebrates that have scales or naked skin. Reptiles lay shelled eggs or give birth to live young. Amphibians lay eggs without shells.
There are more than 10,000 species of reptile.
Reptiles also live in every terrestrial habitat on Earth except the artic and antarctic, but some species also occur in marine environments. Reptiles comprise the taxonomic class Reptilia. The living reptiles include lizards, snakes, tuataras, crocodilians, and turtles.
Def. the "study of amphibians" is called batrachology.
Batrachology is a specialty within herpetology. Scientists who study Batrachology are called herpetologists.
The name of this specialty comes from the Ancient Greek word for frog, batrakhos.
There are about 8000 species of living amphibian known to science.
Amphibians live in every terrestrial habitat on Earth except in the arctic and antarctic. Amphibians are also absent from marine environments. The amphibians comprise the taxonomic class Amphibia. The living amphibians include frogs and toads, salamanders and newts, and caecilians.
Def. "the study of fish" is called ichthyology.
Scientists who study ichthyology are called ichthyologists.
Fishes are endothermic vertebrates that live in the fresh or marine water.
Living species are extremely diverse, and belong to three taxonomic groups, Superclass Agnatha (jawless fishes), Class Chondrichthyes (sharks and rays), and the Osteichthyes (the bony fishes).
There are about 30,000 species of living fish known to science. Fish live in every aquatic habitat on Earth.
About the Photo: Considered a "living fossil" because it is an ancient class of lobe-limbed fish that otherwise went extinct more than 70 million years ago, the first living coelacanth was caught off the east coast of South Africa near the Chalumna River in 1938. Today, at least two major populations of coelacanths are known: one off east Africa, and another near Indonesia. Coelacanths cannot be eaten; their flesh contains an oil that is highly distasteful to human beings. This specimen in the image above weighs 160 pounds (72.6 kg) and measures 5.5 feet (1.67 m) in length.
See also: Fish
Invertebrate zoology is the study of animals that lack a spinal column. This covers approximately 97% of all known living species.
Def. study of the echinoderms is called echinodermology.
Echinodermology is a specialty of invertebrate zoology that studies echinoderms. The echinoderms include sea stars, urchins, and crinoids. All species are marine, so this is also a specialty of marine biology. Scientists who study echinoderms most often are called either marine biologists or invertebrate zoologists.
Def. the "study of molluscs" is called malacology.
Def. "the scientific study of squid (often extended to all cephalopods)" is called teuthology.
Def. the "study of arthropods" is called arthropodology.
The Arthropoda include the Chelicerata, Crustacea, Hexapoda, Myriapoda, †Marrellomorpha and the †Trilobitomorpha.
The classes of the Arthropoda include the Arachnida, Branchiopoda, Cephalocarida, Chilopoda, Diplopoda, Entognatha, Insecta, Malacostraca, Maxillopoda, Merostomata, Ostracoda, Pauropoda, Pycnogonida, Remipedia and Symphyla.
The Chelicerata contains the classes: Arachnida, Merostomata, Pycnogonida, †Aglaspidida, †Chasmataspidida, and †Eurypterida.
The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda that contains the sea spiders, arachnids (including scorpions, spiders, and potentially horseshoe crabs), and several extinct lineages, such as the eurypterids.
Arachnology is the study of spiders, scorpions, and related arthropods. Scientists who study arachnology are called arachnologists.
Def. the "study of the Arachnida" is called arachnology.
The Arachnida include the following orders (Ordines): Amblypygi, Araneae, †Haptopoda, Holothyrida, Ixodida, Mesostigmata, Opilioacarida, Opiliones, Palpigradi, †Phalangiotarbida, Pseudoscorpiones, Ricinulei, Sarcoptiformes, Schizomida, Scorpiones, Solifugae, Thelyphonida, †Trigonotarbida, Trombidiformes, †Uraraneida.
Def. the "study of ticks and mites" is called acarology.
"The 6 ordines Holothyrida, Ixodida, Mesostigmata, Opilioacarida, Sarcoptiformes and Trombidiformes are sometimes grouped together as Acari, but there is no consensus on classification above ordinal level, making a Linnean classification difficult."
Def. the "study of the spider, a branch of arachnology" is called araneology.
Def. the "scientific study of scorpions" is called scorpiology.
The order (Ordo) is Scorpiones.
Xiphosura is an order of arthropods related to arachnids, or, according to one recent study, actual arachnids, sometimes called horseshoe crabs (a name applied more specifically to the only extant family, Limulidae).
Def. the study of the Merostomata, or Xiphosura, is called Xiphosurology.
Def. the study of the Pycnogonida is called pantopodology.
Def. the "study of crustaceans" is called carcinology.
The Crustacea contain the classes: Branchiopoda, Cephalocarida, Hexanauplia, Ichthyostraca, Malacostraca, Maxillopoda, Ostracoda and Remipedia.
Def. the study of Branchiopoda is called branchiopodology.
The Cephalocarida are a class in the subphylum Crustacea comprising only 12 benthic species discovered in 1955 by Howard L. Sanders, and are commonly referred to as horseshoe shrimps.
Def. the study of the Brachypoda is called brachypodology.
Def. the study of the Malacostraca is called Malacostracology.
Def. the study of the Maxillopoda is called maxillopodology.
Maxillopoda is a diverse class of crustaceans including barnacles, copepods and a number of related animals that does not appear to be a monophyletic group, and no single character unites all the members.
Def. the study of the Ostracoda is called ostracodology.
Def. the study of the Remipedia is called remipediology.
The Hexapoda consist of the following classes: Entognatha and Insecta.
"Phylogenetic tree of [the] Hexapoda [is shown on the right]. Hexapoda (insects and their six-legged relatives) comprise more than half of all described species and dominate terrestrial and freshwater ecosystems. The tree shown is from a maximum likelihood analysis of 8 genes, calibrated by 89 fossils. Membership of major clades is denoted by coloration of the ring (grey: Entognatha, black: basal insects, cyan: Palaeoptera, magenta: Polyneoptera, green: Paraneoptera, red: Holometabola). Changes in branch coloration denote diversification shifts identified using TurboMEDUSA. Branch colors identify regions of the tree with the same underlying diversification model. Symbols at shifts denote a net upshift (diamond) or down shift (circle). Coloration of symbols reflects the robustness of the shift event across 500-scaled samples taken from the post-burin MCMC chain (black: shift recovered in >80% of samples, grey with black outline: recovery >50%, grey with pale outline: recovery >30%, pale grey: recovery<30%). Black rings are shown at 100 Ma increments from the present."
Def. the study of the Entognatha is called entognathology.
Entomology is the study of insects (Insecta). Scientists who study entomology are called entomologists.
Def. the "scientific study of insects" is called entomology.
The orders (Ordines) for the Insecta include: Archaeognatha, "Blattodea", Coleoptera, Dermaptera, Diptera, Embiidina, Ephemeroptera, Hemiptera, Hymenoptera, Isoptera, Lepidoptera, Mantodea, "Mecoptera", Megaloptera, Neuroptera, Notoptera, Odonata, Orthoptera, Phasmatodea, Phthiraptera, Plecoptera, "Psocoptera", Raphidioptera, Siphonaptera, Strepsiptera, Thysanoptera, Trichoptera, Zoraptera, and Zygentoma.
Def. the "scientific study of beetles" is called coleopterology.
Def. the "scientific study of butterflies and moths" is called lepidopterology.
On the right is an example of Callioratis grandis from Mulanje Mountain, Africa.
Lepidopterology is the study of the Lepidoptera, the group of insects that includes butterflies and moths. It is a specialty of entomology, which is the overall study of insects. Most scientists who study the lepidoptera consider themselves to be entomologists.
Def. the "study of ants" is called myrmecology.
Def. the "scientific study of myriapods" is called myriapodology.
The Myriapoda include the classes: Chilopoda, Diplopoda, Pauropoda, Symphyla, and †Arthropleuridea.
Def. the study of the Chilopoda is called chilopodology.
Most centipedes are generally venomous and could inflict a painful bite, injecting their venom through pincer-like appendage known as forcipules, where despite the name, centipedes can have a varying number of legs, ranging from 30 to 354 and centipedes always have an odd number of pairs of legs. Therefore, no centipede has exactly 100 legs. Similar to spiders and scorpions, centipedes are predominantly carnivorous.
Def. the study of the Diplopoda is called diplopodology.
Def. the study of the Pauropoda is called pauropodology.
Def. the study of the Symphyla is called symphylology.
Def. the study of the †Arthropleuridea is called arthropleurideology.
Marrellomorphs are a group of arthropods known from the Cambrian to the Early Devonian.
Trilobites meaning "three lobes" are a group of extinct marine arachnomorph arthropods that form the class Trilobita. The trilobites were among the most successful of all early animals, existing in oceans for almost 300 million years.
Trilobites are often placed within the arthropod subphylum Schizoramia within the superclass Arachnomorpha (equivalent to the Arachnata), although several alternative taxonomies are found in the literature.
Trilobites had many lifestyles; some moved over the sea bed as predators, scavengers, or filter feeders, and some swam, feeding on plankton; lifestyles expected of modern marine arthropods are seen in trilobites, with the possible exception of parasitism (where scientific debate continues). Some trilobites (particularly the family Olenidae) are even thought to have evolved a symbiotic relationship with sulfur-eating bacteria from which they derived food.
Def. the "study of trilobites" is called trilobitology.
The earliest indisputable fossils of the Annelida appear in the Tertiary period, which began 66 million years ago.
There are over 22,000 living annelid species, ranging in size from microscopic to the Australian giant Gippsland earthworm and Amynthas mekongianus (Cognetti, 1922), which can both grow up to 3 meters long. Although research since 1997 has radically changed scientists' views about the evolutionary family tree of the annelids, most textbooks use the traditional classification into the following sub-groups:
- Polychaetes (about 12,000 species). As their name suggests, they have multiple chetae ("hairs") per segment. Polychaetes have parapodia that function as limbs, and nuchal organs that are thought to be chemosensors. Most are marine animals, although a few species live in fresh water and even fewer on land.
- Clitellates (about 10,000 species ). These have few or no chetae per segment, and no nuchal organs or parapodia. However, they have a unique reproductive organ, the ring-shaped clitellum ("pack saddle") around their bodies, which produces a pupa (cocoon) that stores and nourishes fertilized eggs until they hatch  or, in moniligastrids, yolky eggs that provide nutrition for the embryos. The clitellates are sub-divided into:
- Oligochaetes ("with few hairs"), which includes earthworms. Oligochaetes have a sticky pad in the roof of the mouth. Most are burrowers that feed on wholly or partly decomposed organic materials.
- Hirudinea, whose name means "leech-shaped" and whose best known members are leeches. Marine species are mostly blood-sucking parasites, mainly on fish, while most freshwater species are predators. They have suckers at both ends of their bodies, and use these to move rather like inchworms.
The Archiannelida, minute annelids that live in the spaces between grains of marine sediment, were treated as a separate class because of their simple body structure, but are now regarded as polychaetes. Some other groups of animals have been classified in various ways, but are now widely regarded as annelids:
- Pogonophora / Siboglinidae were first discovered in 1914, and their lack of a recognizable gut made it difficult to classify them. They have been classified as a separate phylum, Pogonophora, or as two phyla, Pogonophora and Vestimentifera. More recently they have been re-classified as a family, Siboglinidae, within the polychaetes.
- The Echiura have a checkered taxonomic history: in the 19th century they were assigned to the phylum "Gephyrea", which is now empty as its members have been assigned to other phyla; the Echiura were next regarded as annelids until the 1940s, when they were classified as a phylum in their own right; but a molecular phylogenetics analysis in 1997 concluded that echiurans are annelids.
- Myzostomida live on crinoids and other echinoderms, mainly as parasites. In the past they have been regarded as close relatives of the trematode flatworms or of the tardigrades, but in 1998 it was suggested that they are a sub-group of polychaetes. However, another analysis in 2002 suggested that myzostomids are more closely related to flatworms or to rotifers and acanthocephales.
- Sipuncula was originally classified as annelids, despite the complete lack of segmentation, bristles and other annelid characters. The phylum Sipuncula was later allied with the Mollusca, mostly on the basis of developmental and larval characters. Phylogenetic analyses based on 79 ribosomal proteins indicated a position of Sipuncula within Annelida. Subsequent analysis of the mitochondrion's DNA has confirmed their close relationship to the Myzostomida and Annelida (including echiurans and Siboglinidae (pogonophorans). It has also been shown that a rudimentary neural segmentation similar to that of annelids occurs in the early larval stage, even if these traits are absent in the adults.
On the right, "This is a parchment worm (Thelepus cincinatus) that is out of its tube. It is also called a Bristleworm and puts out its tentacles to collect its microscopic food."
Def. the study of the Brachiopoda is called brachiopodology.
Lineages of brachiopods that have both fossil and extant taxa appeared in the early Cambrian, Ordovician, and Carboniferous periods, respectively.
The largest brachiopods known – Gigantoproductus and Titanaria, reaching 30 to 38 cm in width – occurred in the upper part of the Lower Carboniferous.
Brachiopod shells can be classified according to the angle between the cardinal plane and the plane where the shells join (commissure); anacline shells have an angle of less than 90°, whereas aspacline shells have a higher angle.
Def. a "branch of zoology specializing in Bryozoa" is called bryozoology.
The Chaetognatha fossil range is Lower Cambrian to Recent.
All chaetognaths are carnivorous, preying on other planktonic animals.
Chaetognaths swim in short bursts using a dorso-ventral undulating body motion, where their tail fin assists with propulsion and the body fins with stabilization and steering. Some species are known to use the neurotoxin tetrodotoxin to subdue prey.
Def. the study of the Cnidaria is called cnidariology.
Def. the study of the Myxozoa is called myxozoology.
Myxozoans were originally considered protozoan, and were included among other non-motile forms in the group Sporozoa. As their distinct nature became clear through 18S ribosomal DNA (rDNA) sequencing, they were relocated in the metazoa. Detailed classification within the metazoa was however long hindered by conflicting rDNA evidence: although 18S rDNA suggested an affinity with Cnidaria, other rDNA sampled, and the HOX genes of two species, were more similar to those of the Bilateria.
Further testing resolved the genetic conundrum by sourcing the first three previously identified discrepant HOX genes (Myx1-3) to the bryozoan Cristatella mucedo and the fourth (Myx4) to Northern pike, the respective hosts of the two corresponding Myxozoa samples. This explained the confusion: the original experiments had used samples contaminated by tissue from host organisms, leading to false positives for a position among the Bilateria. More careful cloning of 50 coding genes from Buddenbrockia firmly established the clade as severely modified members of the phylum Cnidaria, with medusozoans as their closest relatives. Similarities between myxozoan polar capsules and cnidarian nematocysts had been drawn for a long time, but were generally assumed to be the result of convergent evolution.
Taxonomists now recognize the outdated subgroup Actinosporea as a life-cycle phase of Myxosporea.
Def. the study of the Ctenophora is called ctenophorology.
The Beroida, also known as Nuda, have no feeding appendages, but their large pharynx, just inside the large mouth and filling most of the saclike body, bears "macrocilia" at the oral end which are fused bundles of several thousand large cilia are able to "bite" off pieces of prey that are too large to swallow whole – almost always other ctenophores.
In front of the field of macrocilia, on the mouth "lips" in some species of Beroe, is a pair of narrow strips of adhesive epithelial cells on the stomach wall that "zip" the mouth shut when the animal is not feeding, by forming intercellular connections with the opposite adhesive strip, which streamlines the front of the animal when it is pursuing prey.
Def. the study of the Cycliophora is called cycliophorology.
Def. the study of the Gastrotricha is called gastrotrichology.
As of 2011, around 790 species have been described. The phylum contains a single class, divided into two orders: the Macrodasyida and the Chaetonotida. The Macrodasyida are wholly marine, but two rare and poorly known species, Marinellina flagellata and Redudasys fornerise, are known from fresh water. The Chaetonotida comprise both marine and freshwater species.
Phylogenetics places the Gastrotricha as close relatives of the flatworms Platyhelminthes, the Ecdysozoa or the Lophotrochozoa.
Def. the study of the Gnathostomulida is called gnathostomulidology.
The Gnathostomulida were first recognised and described in 1956.
In many Bursovaginoidea, one of the major group of gnathostomulids, the neck region is slightly narrower than the rest of the body, giving them a distinct head.
Like flatworms they have a ciliated epidermis, but in contrast to flatworms, they have one cilium per cell.
The only sense organs are modified cilia, which are especially common in the head region.
The basal plate is used to scrape smaller organisms off of the grains of sand that make up their anoxic seabed mud habitat.
The mouth opens into a blind-ending tube in which digestion takes place; there is no true anus. However, there is tissue connecting the intestine to the epidermis which may serve as an anal pore.
Def. the study of the Hemichordata is called hemichordatology.
The extinct class Graptolithina is closely related to the pterobranchs.
Acorn worms are solitary worm-shaped organisms that generally live in burrows (the earliest secreted tubes).
While the family Torquaratoridae are free living detritivores, many are well known for their production and accumulation of various halogenated phenols and pyrroles. Pterobranchs are filter-feeders, mostly colonial, living in a collagenous tubular structure called a coenecium.
A post-anal tail is present in juvenile member of the acorn worm family Harrimaniidae.
Def. the study of the Kamptozoa is called kamptozoology.
Entoprocta, coined in 1870, means "anus inside". The alternative name "Kamptozoa", meaning "bent" or "curved" animals, where the prefix "campto-" is explained was assigned in 1929. Some authors use Entoprocta while others prefer Kamptozoa.
Def. the study of the Kinorhyncha is called kinorhynchology.
Modern species of the Kinorhyncha are 1 mm or less, but Cambrian forms could reach 4 cm.
Unlike some similar invertebrates, they do not have external cilia, but instead have a number of spines along the body, plus up to seven circles of spines around the head.
The head is completely retractable, and is covered by a set of neck plates called placids when retracted. The short hind-gut is lined by cuticle, and empties into an anus at the posterior end of the trunk. The excretory system consists of two protonephridia emptying through pores in the final segment. Some species have simple ocelli on the head, and all species have tiny bristles on the body to provide a sense of touch.
Def. the study of the Loricifera is called loriciferology.
Loricifera is a phylum of very small to microscopic marine cycloneuralian sediment-dwelling animals with 37 described species, in nine genera. Aside from these described species, there are approximately 100 more that have been collected and not yet described. Their sizes range from 100 µm to ca. 1 mm. Their habitat is in the spaces between marine gravel to which they attach themselves. The phylum was discovered in 1983 by Reinhardt Kristensen, in Roscoff, France. They are among the most recently discovered groups of Metazoans. They attach themselves quite firmly to the substrate, and hence remained undiscovered for so long. The first specimen was collected in the 1970s, and later described in 1983. They are found at all depths, in different sediment types, and in all latitudes.
The armor-like lorica consists of a protective external shell or case of encircling plicae. Many of the larvae are acoelomate, with some adults being pseudocoelomate, and some remaining acoelomate.
Fossils have been dated to the late Cambrian.
Morphological studies have traditionally placed the phylum in the Vinctiplicata with the Priapulida; this plus the Kinorhyncha constitutes the taxon Scalidophora, or Cephalorhyncha, where the three phyla share four characters in common — chitinous cuticle, rings of scalids on the introvert, flosculi, and two rings of introvert retracts. However, mounting molecular evidence indicates a closer relationship with the Panarthropoda.
Def. the study of the Micrognathozoa is called micrognathozoology.
Limnognathia maerski is a microscopic platyzoan freshwater animal, discovered living in warm springs on Disko Island, Greenland in 1994, that has variously been assigned as a class or subphylum in the phylum Gnathifera or as a phylum in a Gnathifera superphylum, named Micrognathozoa, related to the rotifers and gnathostomulids, grouped together as the Gnathifera.
Def. the study of the Nematoda is called nematodology.
Nematods are found in every part of the earth's lithosphere, even at great depths, 0.9–3.6 km below the surface of the Earth in gold mines in South Africa. They represent 90% of all animals on the ocean floor. In total, 4.4 × 1020 nematodes inhabit the Earth's topsoil, or approximately 60 billion for each human, with the highest densities observed in tundra and boreal forests. Their numerical dominance, often exceeding a million individuals per square meter and accounting for about 80% of all individual animals on earth, their diversity of lifecycles, and their presence at various trophic levels point to an important role in many ecosystems. They have been shown to play crucial roles in polar ecosystem. The roughly 2,271 genera are placed in 256 families. The many parasitic forms include pathogens in most plants and animals. A third of the genera occur as parasites of vertebrates; about 35 nematode species occur in humans.
"In short, if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes. The location of towns would be decipherable, since for every massing of human beings, there would be a corresponding massing of certain nematodes. Trees would still stand in ghostly rows representing our streets and highways. The location of the various plants and animals would still be decipherable, and, had we sufficient knowledge, in many cases even their species could be determined by an examination of their erstwhile nematode parasites."
Def. the study of the Nematomorpha is called nematomorphology.
The adult worms are free-living, but the larvae are parasitic on arthropods, such as beetles, cockroaches, mantids, orthopterans, and crustaceans. About 351 freshwater species are known and a conservative estimate suggests that there may be about 2000 freshwater species worldwide. The name "Gordian" stems from the legendary Gordian knot. This relates to the fact that nematomorpha often tie themselves in knots.
The nervous system consists of a nerve ring near the anterior end of the animal, and a ventral nerve cord running along the body.
Def. the study of the Nemertea is called nemerteology.
In 1995, a total of 1,149 species had been described and grouped into 250 genera.
Nemertea are named after the Greek sea-nymph Nemertes, one of the daughters of Nereus and Doris. Alternative names for the phylum have included Nemertini, Nemertinea, and Rhynchocoela. The Nemertodermatida are a separate phylum, whose closest relatives appear to be the Acoela.
Def. the study of the Onychophora is called onychophorology.
Onychophora, commonly known as velvet worms (due to their velvety texture and somewhat wormlike appearance) or more ambiguously as peripatus (after the first described genus, Peripatus), is a phylum of elongate, soft-bodied, many-legged panarthropods. In appearance they have variously been compared to worms with legs, caterpillars, and slugs.
"Because they resemble worms with legs ... Superficially they resemble caterpillars, but have also been compared with slugs."
It is the only phylum within Animalia that is wholly endemic to terrestrial environments. Velvet worms are considered close relatives of the Arthropoda and Tardigrada, with which they form the taxon Panarthropoda.
Def. the study of the Phoronida is called phoronidology.
Phoronis is the name of one of the two genera of Phoronids.
As of 2010 there are no indisputable body fossils of phoronids.
Phoronids may be members of the protostome super-phylum Lophotrochozoa.
Phoronids and brachiopods may be sister-groups, while others place phoronids as a sub-group within brachiopoda.
Most adult phoronids are 2 to 20 cm long and about 1.5 mm wide,  although the largest are 50 cm long. Their skins have no cuticle but secrete rigid tubes of chitin, similar to the material used in arthropods' exoskeletons, and sometimes reinforced with sediment particles and other debris. Most species' tubes are erect, but those of Phoronis vancouverensis are horizontal and tangled. Phoronids can move within their tubes but never leave them. The bottom end of the body is an ampulla (a flask-like swelling in a tube-like structure), which anchors the animal in the tube and enables it to retract its body when threatened, reducing the body to 20 percent of its maximum length. Longitudinal muscles retract the body very quickly, while circular muscles slowly extend the body by compressing the internal fluid.
For feeding and respiration each phoronid has at the top end a lophophore, a "crown" of tentacles with which the animal filter-feeds. In small species the "crown" is a simple circle, in medium-size species it is bent into the shape of a horseshoe with tentacles on the outer and inner sides, and in the largest species the ends of the horseshoe wind into complex spirals. These more elaborate shapes increase the area available for feeding and respiration. The tentacles are hollow, held upright by fluid pressure, and can be moved individually by muscles.
The mouth is inside the base of the crown of tentacles but to one side. The gut runs from the mouth to one side of the stomach, in the bottom of the ampulla. The intestine runs from the stomach, up the other side the body, and exits at the anus, outside and a little below the crown of tentacles. The gut and intestine are both supported by two mesenteries (partitions that run the length of the body) connected to the body wall, and another mesentery connects the gut to the intestine.
The body is divided into coeloms, compartments lined with mesothelium. The main body cavity, under the crown of tentacles, is called the metacoelom, and the tentacles and their base share the mesocoelom. Above the mouth is the epistome, a hollow lid which can close the mouth. The cavity in the epistome is sometimes called the protocoelom, although other authors disagree that it is a coelom and Ruppert, Fox and Barnes think it is built by a different process.
Def. the study of the Placozoa is called placozoology.
The Placozoa are a basal form of free-living (non-parasitic) multicellular organism. They are the simplest in structure of all animals. Three genera have been found: the classical Trichoplax adhaerens, Hoilungia hongkongensis, and Polyplacotoma mediterranea, where the last appears most basal. The last two have been found only since 2017. Although the Placozoa were first discovered in 1883 and since the 1970s more systematically analyzed, a common name does not yet exist for the taxon; the scientific name means "flat animals".
Def. the study of the Platyhelminthes is called platyhelminthology.
Like other bilaterians, they have three main cell layers (endoderm, mesoderm, and ectoderm), while the radially symmetrical cnidarians and ctenophores (comb jellies) have only two cell layers. Beyond that, they are "defined more by what they do not have than by any particular series of specializations." Unlike other bilaterians, Platyhelminthes have no internal body cavity, so are described as acoelomates. They also lack specialized circulatory and respiratory organs, both of these facts are defining features when classifying a flatworm's anatomy. Their bodies are soft and unsegmented.
Def. the study of the Porifera is called poriferology.
Def. a "branch of zoology concerning sponges or Porifera" is called spongiology.
Def. the study of the Rhombozoa is called rhombozoology.
However, other molecular phylogenies have placed the dicyemids more closely related to the Nematoda (roundworms). Additional molecular evidence suggests that this phylum is derived from the Lophotrochozoa.
The phylum is not divided in classes or orders, but contains three families, Conocyemidae, Dicyemidae, and Kantharellidae.
Def. the study of the Rotifera is called rotiferology.
Def. any "of many minute aquatic multicellular organisms, of the phylum Rotifera, that have a ring of cilia resembling a wheel" is called a rotifer.
Def. the study of the Scalidophora is called scalidophorology.
Scalidophora is a group of marine pseudocoelomate protostomes that was proposed on morphological grounds to unite three phyla: the Kinorhyncha, the Priapulida and the Loricifera. The three phyla have four characters in common — chitinous cuticle that is moulted, rings of scalids on the introvert, flosculi, and two rings of introvert retracts. However, the monophyly of the Scalidophora is not supported by molecular studies, where the position of the Loricifera was uncertain or as sister to the Panarthropoda.
The group has also been considered a single group, Cephalorhyncha, with three classes.
The group is named after the spines (scalids) covering the introvert (head that can be retracted into the trunk).
Def. the study of the Sipuncula is called sipunculology.
The worm Sipunculus nudus was first described in 1767. In 1814, the word "Sipuncula" was used to describe the family (now Sipunculidae), and in time, the term came to be used for the whole phylum. This is a relatively understudied group, and it is estimated there may be around 162 species worldwide.
The phylogenetic placement of this phylum in the past has proved troublesome. Originally classified as annelids, despite the complete lack of segmentation, bristles and other annelid characters, the phylum Sipuncula was later allied with the Mollusca, mostly on the basis of developmental and larval characters. Currently these two phyla have been included in a larger group, the Lophotrochozoa, that also includes the annelids, the nemertea (ribbon worms) and several other phyla. Phylogenetic analyses based on 79 ribosomal proteins indicated a position of Sipuncula within Annelida. Subsequent analysis of the mitochondrion's DNA has confirmed their close relationship to the Myzostomida and Annelida (including echiurans and Siboglinidae (pogonophorans)). It has also been shown that a rudimentary neural segmentation similar to that of annelids occurs in the early larval stage, even if these traits are absent in the adults.
Def. the study of the Tardigrada is called tardigradology.
Tardigrades, known colloquially as water bears or moss piglets, are a phylum of water-dwelling eight-legged segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them little water bears. In 1777, the Italian biologist Lazzaro Spallanzani named them Tardigrada, which means "slow steppers".
They have been found everywhere, from mountaintops to the deep sea and mud volcanoes, and from tropical rain forests to the Antarctic. Tardigrades are among the most resilient animals known, with individual species able to survive extreme conditions—such as exposure to extreme temperatures, extreme pressures (both high and low), air deprivation, radiation, dehydration, and starvation—that would quickly kill most other known forms of life. Tardigrades have survived exposure to outer space. About 1,150 known species form the phylum Tardigrada, a part of the superphylum Ecdysozoa. The group includes fossils dating from 530 million years ago, in the Cambrian period.
Tardigrades are usually about 0.5 mm long when fully grown. They are short and plump, with four pairs of legs, each ending in claws (usually four to eight) or sucking disks. Tardigrades are prevalent in mosses and lichens and feed on plant cells, algae, and small invertebrates. When collected, they may be viewed under a very low-power microscope, making them accessible to students and amateur scientists.
Def. the study of the Xenacoelomorpha is called xenacoelomorphology.
Xenacoelomorpha is a basal bilaterian phylum of small and very simple animals, grouping the xenoturbellids with the acoelomorphs. This grouping was suggested by morphological synapomorphies, and confirmed by phylogenomic analyses of molecular data.
The clade Xenacoelomorpha, grouping Acoelomorpha and the genus Xenoturbella, was revealed by molecular studies. Initially it was considered to be a member of the deuterostomes, but a more recent transcriptome analysis concluded that it is the sister group to the Nephrozoa, which includes the protostomes and the deuterostomes, being therefore the basalmost bilaterian clade.
Systematics & Taxonomy
Systematics is the study of the evolutionary relationships among organisms. It includes taxonomy, which is the study of the names of organisms and their organization into categories. Scientists who study systematics are called systematists, while taxonomists primarily study taxonomy. Most systematists are also taxonomists.
Living organisms are grouped into a hierarchy of categories. The main categories are Kingdom (or Regnum, pl. Regna), Phylum (pl. Phyla), Class, Order, Family, Genus (pl. Genera), and Species (pl. Species). Every living organism is classified into one, and only one, of each of those categories. There are additional categories used for some groups, but not all.
The classification of organisms can change as more is learned about the living world around us.
Below are two ideas of how life may be divided into Kingdoms (Regna).
- Four Regna listed by Whittaker & Margulis (1978): Animalia - Plantae - Fungi - Protista
- Five Regna listed Cavalier-Smith (1981): Animalia - Plantae - Fungi - Chromista - Protozoa
Below is one recent list of the Phyla of within the Kingdom Animalia. Note number 8, Chordata. That is the Phylum that includes vertebrates, the animals with a spinal column that includes humans.
Regnum: Animalia Phyla (36):
"Humans are hosts to nearly 300 species of parasitic worms and over 70 species of protozoa, some derived from our primate ancestors and some acquired from the animals we have domesticated or come in contact with during our relatively short history on Earth". ______________
Parasitology is the study of parasites. In this context, a parasite is usually an invertebrate, and as such parasitology is a specialization of invertebrate zoology. Scientists that study parasites are called parasitologists.
Parasites are organisms that live on or in, and take their nutrition from, another living organism called a host. Rarely do parasites kill their hosts, since finding a new host can be quite difficult. Individual parasites may do little harm to their host, but large numbers of them can cause great problems. This kind of relationship where one organism lives off another giving either nothing in return or causing harm is called parasitism.
Parasites may be found in many invertebrate taxonomic groups. Commonly encountered parasites include tapeworms, roundworms, and lice.
Def. the "branch of zoology related to the study of helminths (parasitic worms)" is called helminthology.
Def. the study of the Acanthocephala is called acanthocephalology.
The "Acanthocephala are descended from, and should be considered as, highly modified rotifers. Genetic research has determined this is unequivocal; the Acanthocephalans are modified rotifers".
Acanthocephalans have complex life cycles, involving at least two hosts, which may include invertebrates, fish, amphibians, birds, and mammals. About 1420 species have been described.
Def. the study of the Orthonectida is called orthonectidology.
Orthonectida is a small phylum of poorly known parasites of marine invertebrates.
The adults are microscopic wormlike animals, consisting of a single layer of ciliated outer cells surrounding a mass of sex cells, that swim freely within the bodies of their hosts, which include flatworms, polychaete worms, bivalve molluscs, and echinoderms, and are gonochoristic, with separate male and female individuals.
When they are ready to reproduce, the adults leave the host, and sperm from the males penetrate the bodies of the females to achieve internal fertilisation, where the resulting zygote develops into a ciliated larva that escapes from the mother to seek out new hosts so as to lose its cilia and develop into a syncytial plasmodium larva, which, in turn, breaks up into numerous individual cells that become the next generation of adults.
An hypothesis is a scientific statement made to explain some part of the world. It is not a guess. It is testable by scientific means, and is falsifiable (able to be disproved) by those means. Coming up with hypotheses and testing them are the main occupation of science.
- The genetic classification of animals may not match the current classification before genetic evidence.
The content on this page was first contributed by: Henry A. Hoff.
Initial content for this page in some instances came from Wikiversity.
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- Biology (22 kB) (8 August 2019)
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- Evolution (39 kB) (8 August 2019)
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- Melanocytes (49 kB) (17 September 2019)
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- Pharyngeal systems
- Proteins (26 kB) (1 September 2019)
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- Zoology (178 kB) (1 October 2019)
- SemperBlotto (6 November 2005). "genetics". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2014-05-07.
- 220.127.116.11 (22 December 2008). "genetics". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2014-05-07.
- Richard D. Emes, Leo Goodstadt, Eitan E. Winter and Chris P. Ponting (2003). "Comparison of the genomes of human and mouse lays the foundation of genome zoology". Human Molecular Genetics. 12 (7): 701–9. doi:10.1093/hmg/ddg078. Retrieved 2014-05-18.
- biology. San Francisco, California: Wikimedia Foundation, Inc. 23 February 2015. Retrieved 2015-02-23.
- Animal, In: The American Heritage Dictionary (4th ed.). Houghton Mifflin Company. 2006.
- 18.104.22.168 (21 April 2003). "animal". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2016-03-27.
- animal, In: English Oxford Living Dictionaries. Retrieved 26 July 2018.
- Boly, Melanie; Seth, Anil K.; Wilke, Melanie; Ingmundson, Paul; Baars, Bernard; Laureys, Steven; Edelman, David; Tsuchiya, Naotsugu (2013). "Consciousness in humans and non-human animals: recent advances and future directions". Frontiers in Psychology. 4: 625. doi:10.3389/fpsyg.2013.00625. PMC 3814086. PMID 24198791.
- The use of non-human animals in research. Retrieved 7 June 2018.
- Nonhuman definition and meaning | Collins English Dictionary. Collins. Retrieved 7 June 2018.
- Avila, Vernon L. (1995). Biology: Investigating Life on Earth. Jones & Bartlett Learning. pp. 767–. ISBN 978-0-86720-942-6.
- Palaeos:Metazoa. Retrieved 25 February 2018.
- Davidson, Michael W. Animal Cell Structure. Retrieved 20 September 2007.
- Bergman, Jennifer. Heterotrophs. Retrieved 30 September 2007.
- Douglas, Angela E.; Raven, John A. (January 2003). "Genomes at the interface between bacteria and organelles". Philosophical Transactions of the Royal Society B. 358 (1429): 5–17. doi:10.1098/rstb.2002.1188. PMC 1693093. PMID 12594915.
- Mentel, Marek; Martin, William (2010). "Anaerobic animals from an ancient, anoxic ecological niche". BMC Biology. 8: 32. doi:10.1186/1741-7007-8-32. PMC 2859860. PMID 20370917.
- Saupe, S. G. Concepts of Biology. Retrieved 30 September 2007.
- Minkoff, Eli C. (2008). Barron's EZ-101 Study Keys Series: Biology (2nd, revised ed.). Barron's Educational Series. p. 48. ISBN 978-0-7641-3920-8.
- Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter (2002). Molecular Biology of the Cell (4th ed.). Garland Science. ISBN 978-0-8153-3218-3.
- Sangwal, Keshra (2007). Additives and crystallization processes: from fundamentals to applications. John Wiley and Sons. p. 212. ISBN 978-0-470-06153-4.
- Becker, Wayne M. (1991). The world of the cell. Benjamin/Cummings. ISBN 978-0-8053-0870-9.
- Magloire, Kim (2004). Cracking the AP Biology Exam, 2004–2005 Edition. The Princeton Review. p. 45. ISBN 978-0-375-76393-9.
- Starr, Cecie (2007-09-25). Biology: Concepts and Applications without Physiology. Cengage Learning. pp. 362, 365. ISBN 978-0495381501.
- Hillmer, Gero; Lehmann, Ulrich, translated by J. Lettau (1983). Fossil Invertebrates. CUP Archive. p. 54. ISBN 978-0-521-27028-1.
- Knobil, Ernst (1998). Encyclopedia of reproduction, Volume 1. Academic Press. p. 315. ISBN 978-0-12-227020-8.
- Schwartz, Jill (2010). Master the GED 2011. Peterson's. p. 371. ISBN 978-0-7689-2885-3.
- Hamilton, Matthew B. (2009). Population genetics. Wiley-Blackwell. p. 55. ISBN 978-1-4051-3277-0.
- Ville, Claude Alvin; Walker, Warren Franklin; Barnes, Robert D. (1984). General zoology. Saunders College Pub. p. 467. ISBN 978-0-03-062451-3.
- Hamilton, William James; Boyd, James Dixon; Mossman, Harland Winfield (1945). Human embryology: (prenatal development of form and function). Williams & Wilkins. p. 330.
- Philips, Joy B. (1975). Development of vertebrate anatomy. Mosby. p. 176. ISBN 978-0-8016-3927-2.
- The Encyclopedia Americana: a library of universal knowledge, Volume 10. Encyclopedia Americana Corp. 1918. p. 281.
- Romoser, William S.; Stoffolano, J. G. (1998). The science of entomology. WCB McGraw-Hill. p. 156. ISBN 978-0-697-22848-2.
- Charlesworth, D.; Willis, J.H. (2009). "The genetics of inbreeding depression". Nat. Rev. Genet. 10 (11): 783–796. doi:10.1038/nrg2664. PMID 19834483.
- Bernstein, H.; Hopf, F.A.; Michod, R.E. (1987). The molecular basis of the evolution of sex. Adv. Genet. 24. pp. 323–370. doi:10.1016/s0065-2660(08)60012-7. ISBN 9780120176243. PMID 3324702.
- Pusey, Anne; Wolf, Marisa (1996). "Inbreeding avoidance in animals". Trends Ecol. Evol. 11 (5): 201–206. doi:10.1016/0169-5347(96)10028-8. PMID 21237809.
- Petrie, M.; Kempenaers, B. (1998). "Extra-pair paternity in birds: Explaining variation between species and populations". Trends in Ecology and Evolution. 13 (2): 52–57. doi:10.1016/s0169-5347(97)01232-9. PMID 21238200.
- Adiyodi, K. G.; Hughes, Roger N.; Adiyodi, Rita G. (July 2002). Reproductive Biology of Invertebrates, Volume 11, Progress in Asexual Reproduction. Wiley. p. 116. ISBN 978-0-471-48968-9.
- Schatz, Phil. Concepts of Biology | How Animals Reproduce. OpenStax College. Retrieved 5 March 2018.
- Marchetti, Mauro; Rivas, Victoria (2001). Geomorphology and environmental impact assessment. Taylor & Francis. p. 84. ISBN 978-90-5809-344-8.
- Levy, Charles K. (1973). Elements of Biology. Appleton-Century-Crofts. p. 108. ISBN 978-0-390-55627-1.
- Begon, M.; Townsend, C.; Harper, J. (1996). Ecology: Individuals, populations and communities (Third ed.). Blackwell Science. ISBN 978-0-86542-845-4.
- Allen, Larry Glen; Pondella, Daniel J.; Horn, Michael H. (2006). Ecology of marine fishes: California and adjacent waters. University of California Press. p. 428. ISBN 978-0-520-24653-9.
- Tim Caro (2005). Antipredator Defenses in Birds and Mammals. University of Chicago Press. pp. 1–6 and passim.
- Simpson, Alastair G.B; Roger, Andrew J (2004). "The real 'kingdoms' of eukaryotes". Current Biology. 14 (17): R693–6. doi:10.1016/j.cub.2004.08.038. PMID 15341755.
- Stevens, Alison N. P. (2010). "Predation, Herbivory, and Parasitism". Nature Education Knowledge. 3 (10): 36. Retrieved 12 February 2018.
- Jervis, M. A.; Kidd, N. A. C (November 1986). "Host-Feeding Strategies in Hymenopteran Parasitoids". Biological Reviews. 61 (4): 395–434. doi:10.1111/j.1469-185x.1986.tb00660.x.
- Meylan, Anne (1988-01-22). "Spongivory in Hawksbill Turtles: A Diet of Glass". Science. 239 (4838): 393–395. Bibcode:1988Sci...239..393M. doi:10.1126/science.239.4838.393. JSTOR 1700236. PMID 17836872.
- Clutterbuck, Peter (2000). Understanding Science: Upper Primary. Blake Education. p. 9. ISBN 978-1-86509-170-9.
- Gupta, P. K. (1900). Genetics Classical To Modern. Rastogi Publications. p. 26. ISBN 978-81-7133-896-2.
- Garrett, Reginald; Grisham, Charles M. (2010). Biochemistry. Cengage Learning. p. 535. ISBN 978-0-495-10935-8.
- New Scientist. 152 (2050–2055): 105. 1996.
- Castro, Peter; Huber, Michael E. (2007). Marine Biology (7th ed.). McGraw-Hill. p. 376. ISBN 978-0-07-722124-9.
- Rota-Stabelli, Omar; Daley, Allison C.; Pisani, Davide (2013). "Molecular Timetrees Reveal a Cambrian Colonization of Land and a New Scenario for Ecdysozoan Evolution" (PDF). Current Biology. 23 (5): 392–8. doi:10.1016/j.cub.2013.01.026. PMID 23375891. Retrieved 1 March 2018.
- Daeschler, Edward B.; Shubin, Neil H.; Jenkins, Farish A., Jr. (6 April 2006). "A Devonian tetrapod-like fish and the evolution of the tetrapod body plan". Nature. 440 (7085): 757–763. Bibcode:2006Natur.440..757D. doi:10.1038/nature04639. PMID 16598249.
- Jennifer A. Clack (21 November 2005). "Getting a Leg Up on Land". Scientific American.
- Lynn Margulis, Karlene V. Schwartz, Michael Dolan (1999). Diversity of Life: The Illustrated Guide to the Five Kingdoms. Jones & Bartlett Learning. pp. 115–116. ISBN 978-0-7637-0862-7.
- Clarke, Andrew (2014). "The thermal limits to life on Earth". International Journal of Astrobiology. 13 (2): 141–154. Bibcode:2014IJAsB..13..141C. doi:10.1017/S1473550413000438.
- Land animals. British Antarctic Survey. Retrieved 7 March 2018.
- zoology. San Francisco, California: Wikimedia Foundation, Inc. May 8, 2014. Retrieved 2014-05-18.
- C Otto (12 September 2012). "Another photo of cowboys with a pterodactyl". Civil War Horrors. Retrieved 24 September 2019.
- Nadando (14 May 2009). "zoography". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 22 September 2019.
- mammalogy. San Francisco, California: Wikimedia Foundation, Inc. 16 December 2014. Retrieved 2015-02-23.
- DCDuring (27 January 2014). "Synapsida". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 22 September 2019.
- SemperBlotto (16 May 2008). "Synapsida". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 22 September 2019.
- SemperBlotto (17 January 2007). "Amniota". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 22 September 2019.
- DCDuring (23 February 2014). "Amniota". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 22 September 2019.
- ornithology. San Francisco, California: Wikimedia Foundation, Inc. 16 December 2014. Retrieved 2015-02-23.
- Gauthier, J. A., Kluge, A. G., & Rowe, T. (1988). The early evolution of the Amniota. The phylogeny and classification of the tetrapods, 1, 103-155.
- Ezcurra, M. D.; Scheyer, T. M.; Butler, R. J. (2014). "The origin and early evolution of Sauria: reassessing the Permian saurian fossil record and the timing of the crocodile-lizard divergence". PLOS ONE. 9 (2): e89165. doi:10.1371/journal.pone.0089165. PMC 3937355. PMID 24586565.
- Wang, Zhuo (27 March 2013). "The draft genomes of soft-shell turtle and green sea turtle yield insights into the development and evolution of the turtle-specific body plan". Nature Genetics. 45 (701–706): 701–6. doi:10.1038/ng.2615. PMC 4000948. PMID 23624526.
- Crawford, Nicholas G., et al. "More than 1000 ultraconserved elements provide evidence that turtles are the sister group of archosaurs." Biology letters 8.5 (2012): 783-786.
- Jarvis, E.D.; et al. (2014). "Whole-genome analyses resolve early branches in the tree of life of modern birds". Science. 346 (6215): 1320–1331. doi:10.1126/science.1253451. PMC 4405904. PMID 25504713.
- Lee, M. S. Y. (2013). "Turtle origins: Insights from phylogenetic retrofitting and molecular scaffolds". Journal of Evolutionary Biology. 26 (12): 2729–2738. doi:10.1111/jeb.12268. PMID 24256520.
- Kenneth E. Campbell (Fall 1980). "The World's Largest Flying Bird" (PDF). Terra, The Natural History Magazine of the West. 19 (2): 20–23. Retrieved 24 September 2019.
- dinosaurology. San Francisco, California: Wikimedia Foundation, Inc. 4 February 2015. Retrieved 2015-02-23.
- DCDuring (1 July 2019). "Lepidosauria". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 22 September 2019.
- SemperBlotto (4 March 2006). "Lepidosauria". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 22 September 2019.
- Mellohi! (30 October 2017). "lizard". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Paul G (9 August 2004). "lizard". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- 22.214.171.124 (24 July 2006). "lizard". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- 126.96.36.199 (11 June 2008). "saurology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- ophiology. San Francisco, California: Wikimedia Foundation, Inc. 16 December 2014. Retrieved 2015-02-23.
- herpetology. San Francisco, California: Wikimedia Foundation, Inc. 25 April 2016. Retrieved 2016-05-05.
- batrachology. San Francisco, California: Wikimedia Foundation, Inc. 16 June 2014. Retrieved 2015-02-23.
- DCDuring (21 October 2012). "Reptiliomorpha". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 22 September 2019.
- SemperBlotto (26 January 2012). "Reptiliomorpha". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 22 September 2019.
- Tedius Zanarukando (30 March 2005). ichthyology. San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2015-02-23.
- Piolinfax (11 November 2003). "mollusc". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- EncycloPetey (6 March 2006). "mollusc". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Pathoschild (30 December 2006). "mollusc". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Eclecticology (3 April 2005). "malacology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- William C. Summers (1990). Daniel L. Gilbert, William J. Adelman Jr. and John M. Arnold, ed. Natural History and Collection, Chapter 2, In: Squid as Experimental Animals. Springer. pp. 11–25. doi:10.1007/978-1-4899-2489-6_2. ISBN 978-1-4899-2491-9. Retrieved 2015-01-31.
- DCDuring (7 December 2013). "arthropodology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Ballesteros, J. A.; Sharma, P. P. (14 February 2019). "A Critical Appraisal of the Placement of Xiphosura (Chelicerata) with Account of Known Sources of Phylogenetic Error". Systematic Biology. doi:10.1093/sysbio/syz011. PMID 30917194.
- 188.8.131.52 (19 March 2012). "arachnology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Vildricianus (24 June 2006). "acarology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Stho002 (27 December 2011). "Arachnida". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 25 September 2019.
- Ungoliant MMDCCLXIV (23 December 2017). araneology. San Francisco, California: Wikimedia Foundation, Inc. Retrieved 24 September 2018.
- Equinox (14 March 2019). "scorpiology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Sharma, Prashant P.; Ballesteros, Jesús A. (14 February 2019). "A Critical Appraisal of the Placement of Xiphosura (Chelicerata) with Account of Known Sources of Phylogenetic Error". Systematic Biology. doi:10.1093/sysbio/syz011.
- Mortsggah (8 April 2007). "carcinology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Howard L. Sanders (1955). "The Cephalocarida, a new subclass of Crustacea from Long Island Sound". Proceedings of the National Academy of Sciences. 41 (1): 61–66. Bibcode:1955PNAS...41...61S. doi:10.1073/pnas.41.1.61. JSTOR 89010. PMC 528024. PMID 16589618.
- Joel W. Martin & George E. Davis (2001). An Updated Classification of the Recent Crustacea (PDF). Natural History Museum of Los Angeles County. p. 132.
- James L. Rainford , Michael Hofreiter, David B. Nicholson, and Peter J. Mayhew (2 October 2014). "Phylogenetic Distribution of Extant Richness Suggests Metamorphosis Is a Key Innovation Driving Diversification in Insects". PLoS ONE. 9 (10): e109085. doi:10.1371/journal.pone.0109085. Retrieved 25 September 2019.
- SemperBlotto (27 February 2005). "entomology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Rising Sun (26 March 2010). "coleopterology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- lepidopterology. San Francisco, California: Wikimedia Foundation, Inc. 7 October 2013. Retrieved 2015-02-23.
- EncycloPetey (11 February 2006). "myrmecology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 26 September 2019.
- Equinox (6 July 2014). "myriapodology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Lloyd, John (2006). The Book of General Ignorance. London: Bloomsbury House. p. 119. ISBN 978-0571273782. Retrieved June 10, 2014.
- Arthur, W. (2002). "The interaction between developmental bias and natural selection from centipede segmentation to a general hypothesis". Heredity. 89 (4): 239–246. doi:10.1038/sj.hdy.6800139. PMID 12242638.
- Arthur, Wallace; Chapman, Ariel D. (2005). "The centipede Strigamia maritima: what it can tell us about development and evolution of segmentation". BioEssays. 27 (6): 653–660. doi:10.1002/bies.20234. PMID 15892117.
- Lewis, J. G. E. (2007). The Biology of Centipedes. Cambridge University Press. ISBN 978-0-521-03411-1.
- Rak, Š. P. N. (2011). "A revision of the Late Ordovician marellomorph arthropod Furca bohemica from Czech Republic". Acta Palaeontologica Polonica. doi:10.4202/app.2011.0038.
- Jones, Daniel (2003) . Peter Roach; James Hartmann; Jane Setter, eds. English Pronouncing Dictionary. Cambridge: Cambridge University Press. ISBN 978-3-12-539683-8.
- Attenborough, David. "Learn more about First Life". David Attenborough's First Life. Archived from the original on 2011-01-26. Retrieved 2011-03-10.
- Cotton, T. J.; Braddy, S. J. (2004). "The phylogeny of arachnomorph arthropods and the origins of the Chelicerata". Transactions of the Royal Society of Edinburgh: Earth Sciences. 94 (3): 169–193. doi:10.1017/S0263593303000105.
- Fortey, Richard (2004). "The Lifestyles of the Trilobites" (PDF). American Scientist. 92 (5): 446–453. doi:10.1511/2004.49.944.
- Fortey, Richard (June 2000). "Olenid trilobites: The oldest known chemoautotrophic symbionts?". Proceedings of the National Academy of Sciences. 97 (12): 6574–6578. Bibcode:2000PNAS...97.6574F. doi:10.1073/pnas.97.12.6574. PMC 18664. PMID 10841557.
- Metaknowledge (22 January 2013). "trilobitology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 21 September 2019.
- Renne, Paul R.; Deino, Alan L.; Hilgen, Frederik J.; Kuiper, Klaudia F.; Mark, Darren F.; Mitchell, William S.; Morgan, Leah E.; Mundil, Roland; Smit, Jan (7 February 2013). "Time Scales of Critical Events Around the Cretaceous-Paleogene Boundary" (PDF). Science. 339 (6120): 684–687. Bibcode:2013Sci...339..684R. doi:10.1126/science.1230492. PMID 23393261.
- Rouse, G.W. (2002). "Annelida (Segmented Worms)". Encyclopedia of Life Sciences. John Wiley & Sons, Ltd. doi:10.1038/npg.els.0001599. ISBN 978-0470016176.
- Blakemore, R.J. (2012). Cosmopolitan Earthworms. VermEcology, Yokohama.
- Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Annelida". Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 414–420. ISBN 978-0-03-025982-1.
- Lavelle, P. (July 1996). "Diversity of Soil Fauna and Ecosystem Function" (PDF). Biology International. 33. Retrieved 2009-04-20.
- Struck, T.H.; Schult, N.; Kusen, T.; Hickman, E.; Bleidorn, C.; McHugh, D.; Halanych, K.M. (5 April 2007). "Annelid phylogeny and the status of Sipuncula and Echiura". BMC Evolutionary Biology. 7: 57. doi:10.1186/1471-2148-7-57. PMC 1855331. PMID 17411434.
- Hutchings, P. (2007). "Book Review: Reproductive Biology and Phylogeny of Annelida". Integrative and Comparative Biology. 47 (5): 788–789. doi:10.1093/icb/icm008.
- Rouse, G. (1998). "The Annelida and their close relatives". In Anderson, D.T. Invertebrate Zoology. Oxford University Press. pp. 176–179. ISBN 978-0-19-551368-4.
- Rouse, G. (1998). "The Annelida and their close relatives". In Anderson, D.T. Invertebrate Zoology. Oxford University Press. pp. 179–183. ISBN 978-0-19-551368-4.
- Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Annelida". Invertebrate Zoology (7 ed.). Brooks / Cole. p. 459. ISBN 978-0-03-025982-1.
- Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Annelida". Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 471–482. ISBN 978-0-03-025982-1.
- Halanych, K.M.; Dahlgren, T.G.; McHugh, D. (2002). "Unsegmented Annelids? Possible Origins of Four Lophotrochozoan Worm Taxa". Integrative and Comparative Biology. 42 (3): 678–684. doi:10.1093/icb/42.3.678. PMID 21708764.
- McHugh, D. (July 1997). "Molecular evidence that echiurans and pogonophorans are derived annelids". Proceedings of the National Academy of Sciences of the United States of America. 94 (15): 8006–8009. doi:10.1073/pnas.94.15.8006. PMC 21546. PMID 9223304. Retrieved 2009-04-02.
- Hausdorf, B.; et al. (2007). "Spiralian Phylogenomics Supports the Resurrection of Bryozoa Comprising Ectoprocta and Entoprocta". Molecular Biology and Evolution. 24 (12): 2723–2729. doi:10.1093/molbev/msm214. PMID 17921486.
- Shen, X.; Ma, X.; Ren, J.; Zhao, F. (2009). "A close phylogenetic relationship between Sipuncula and Annelida evidenced from the complete mitochondrial genome sequence of Phascolosoma esculenta". BMC Genomics. 10: 136. doi:10.1186/1471-2164-10-136. PMC 2667193. PMID 19327168.
- Wanninger, Andreas; Kristof, Alen; Brinkmann, Nora (Jan–Feb 2009). "Sipunculans and segmentation". Communicative and Integrative Biology. 2 (1): 56–59. doi:10.4161/cib.2.1.7505. PMC 2649304. PMID 19513266.
- Torres-Martínez, M.A., Sour-Tovar, F. (2016). "Braquiópodos discínidos (Lingulida, Discinoidea) de la Formación Ixtaltepec, Carbonífero del área de Santiago Ixtaltepec, Oaxaca". Boletín de la Sociedad Geológica Mexicana. 68 (2): 313–321. doi:10.18268/BSGM2016v68n2a9.
- Moore, R.C. (1965). Brachiopoda. Treatise on Invertebrate Paleontology. Part H., Volume I. Boulder, Colorado/Lawrence, Kansas: Geological Society of America/University of Kansas Press. pp. H440. ISBN 978-0-8137-3015-8.
- http://www.encyclopedia.com/doc/1O13-apsacline.html; http://www.mcz.harvard.edu/Departments/InvertPaleo/Trenton/Intro/PaleoPage/Terminology&Morphology/Terminology&Morphology.htm#InclinationofBra
- Marine Species Identification Portal : Brachiopoda of the North Sea
- Equinox (10 August 2015). "bryozoology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 26 September 2019.
- Vannier J, Steiner M, Renvoisé E, Hu SX, Casanova JP (March 2007). "Early Cambrian origin of modern food webs: evidence from predator arrow worms". Proceedings of the Royal Society B: Biological Sciences. 274 (1610): 627–33. doi:10.1098/rspb.2006.3761. PMC 2197202. PMID 17254986.
- "World Register of Marine Species".
- Bone Q, Kapp H, Pierrot-Bults AC, eds. (1991). The Biology of Chaetognaths. London: Oxford University Press. ISBN 978-0-19-857715-7.
- Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 1046–1050. ISBN 978-0-03-056747-6.
- Haddock SH, Case JF (20 January 1994). "A bioluminescent chaetognath". Nature. 367 (6460): 225–226. Bibcode:1994Natur.367..225H. doi:10.1038/367225a0.
- Thuesen EV, Goetz FE & Haddock SH (October 2010). "Bioluminescent organs of two deep-sea arrow worms, Eukrohnia fowleri and Caecosagitta macrocephala, with further observations on Bioluminescence in chaetognaths". The Biological Bulletin. 219 (2): 100–11. doi:10.1086/BBLv219n2p100. PMID 20972255.
- Jordan CE (1992). "A model of rapid-start swimming at intermediate Reynolds number: undulatory locomotion in the chaetognath Sagitta elegans". Journal of Experimental Biology. 163 (1): 119–137.
- Bone Q, Kapp H, Pierrot-Bults AC, eds. (1991). "The Tetrodotoxin Venom of Chaetognaths". The Biology of chaetognaths. Oxford University Press. pp. 55–60. ISBN 978-0-19-857715-7.
- Štolc, A. (1899). "Actinomyxidies, nouveau groupe de Mesozoaires parent des Myxosporidies". Bull. Int. l'Acad. Sci. Bohème. 12: 1–12.
- Edwin Lanfranco, 2007, A phylogenetic classification of organisms other than animals.
- Smothers, J.F.; et al. (September 1994). "Molecular evidence that the myxozoan protists are metazoans". Science. 265 (5179): 1719–1721. Bibcode:1994Sci...265.1719S. doi:10.1126/science.8085160. PMID 8085160.
- A.S. Monteiro; et al. (June 1, 2002). "Orphan worm finds a home: Buddenbrockia is a Myxozoan". Mol. Biol. Evol. 19 (6): 968–71. doi:10.1093/oxfordjournals.molbev.a004155. PMID 12032254.
- J. Zrzavy & V. Hypsa (April 2003). Myxozoa, Polypodium, and the origin of the Bilateria: The phylogenetic position of "Endocnidozoa" in light of the rediscovery of Buddenbrockia. Cladistics. 19. pp. 164–169. Bibcode:2002clad.book.....S. doi:10.1111/j.1096-0031.2003.tb00305.x.
- C. L. Anderson, E. U. Canning & B. Okamura (March 1999). "A triploblast origin for Myxozoa?". Nature. 392 (6674): 346–347. Bibcode:1998Natur.392..346A. doi:10.1038/32801. PMID 9537319.
- E. Jímenez-Guri; et al. (July 2007). "Buddenbrockia is a cnidarian worm". Science. 317 (116): 116–118. Bibcode:2007Sci...317..116J. doi:10.1126/science.1142024. PMID 17615357.
- Kent M. L., Margolis L., Corliss J.O. (1994). "The demise of a class of protists: taxonomic and nomenclatural revisions proposed for the protist phylum Myxozoa Grasse, 1970". Canadian Journal of Zoology. 72 (5): 932–937. doi:10.1139/z94-126.
- Tamm, S.L.; Tamm, S. (1985). "Visualization of changes in ciliary tip configuration caused by sliding displacement of microtubules in macrocilia of the ctenophore Beroe". Journal of Cell Science. 79: 161–179. PMID 3914479.
- Tamm, Sidney L.; Tamm, Signhild (1991). "Reversible epithelial adhesion closes the mouth of Beroe, a carnivorous marine jelly". Biological Bulletin. 181 (3): 463–473. doi:10.2307/1542367. JSTOR 1542367. PMID 29304670.
- Zhang, Z.-Q. (2011). "Animal biodiversity: An introduction to higher-level classification and taxonomic richness" (PDF). Zootaxa. 3148: 7–12.
- Ruppert, Edward E.; Fox, Richard, S.; Barnes, Robert D. (2004). Invertebrate Zoology, 7th edition. Cengage Learning. pp. 753–757. ISBN 978-81-315-0104-7.
- Todaro, M. A.; Dal Zotto, M.; Jondelius, U.; Hochberg, R.; Hummon, W. D.; Kånneby, T.; Rocha, C. E. F. (14 February 2012). "Gastrotricha: A Marine Sister for a Freshwater Puzzle". PLoS ONE. 7 (2): e31740. doi:10.1371/journal.pone.0031740. PMC 3279426. PMID 22348127.
- Todaro, M. A. (2014-01-03). "Gastrotricha". Retrieved 2014-01-23.
- Ax, P. (1956). "Die Gnathostomulida, eine rätselhafte Wurmgruppe aus dem Meeressand". Abhandl. Akad. Wiss. U. Lit. Mainz, Math. - Naturwiss. 8: 1–32.
- Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 311–312. ISBN 0-03-056747-5.
- Ruppert, Edward E., Fox, Richard S., Barnes, Robert D. (2004) Invertebrate Zoology (7th edition). Brooks/Cole-Thomson Learning, Belmont, US
- Barnes, R.F.K. et al. (2001). The Invertebrates: A Synthesis. Oxford: Blackwell Science.
- Knauss, Elizabeth (December 1979). "Indication of an Anal Pore in Gnathostomulida". Zoologica Scripta. 8 (1–4): 181–6. doi:10.1111/j.1463-6409.1979.tb00630.x.
- Sato, Atsuko; Rickards RB; Holland PWH (December 2008). "The origins of graptolites and other pterobranchs: a journey from 'Polyzoa'". Lethaia. 41 (4): 303–316. doi:10.1111/j.1502-3931.2008.00123.x.
- Caron, J. B.; Morris, S. C.; Cameron, C. B. (2013). "Tubicolous enteropneusts from the Cambrian period". Nature. 495 (7442): 503–506. Bibcode:2013Natur.495..503C. doi:10.1038/nature12017. PMID 23485974.
- Giray, Cem; G.M. King (1997). "Predator deterrence and 2,4-dibromophenol conservation by the enteropneusts, Saccoglossus bromophenolosus and Protoglossus graveolens". Marine Ecology Progress Series. 159: 229–238. Bibcode:1997MEPS..159..229G. doi:10.3354/meps159229.
- Sato, Atsuko; Bishop JDD; Holland PWH (2008). "Developmental biology of pterobranch hemichordates: history and perspectives". Genesis. 46 (11): 587–91. doi:10.1002/dvg.20395. PMID 18798243.
- Tassia, MG; Cannon, JT; Konikoff, CE; Shenkar, N; Halanych, KM; Swalla, BJ (2016). "The Global Diversity of Hemichordata". PLOS ONE. 11 (10): e0162564. Bibcode:2016PLoSO..1162564T. doi:10.1371/journal.pone.0162564. PMC 5049775. PMID 27701429.
- Wood, T.S. (2005). "Loxosomatoides sirindhornae, new species, a freshwater kamptozoan from Thailand (Entoprocta)". Hydrobiologia. 544: 27–31. doi:10.1007/s10750-004-7909-x.
- Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Kamptozoa and Cycliophora". Invertebrate Zoology (7th ed.). Brooks/Cole. pp. 808–812. ISBN 0-03-025982-7.
- Gledhill, D. (2008). The names of plants. Cambridge University Press. p. 88. ISBN 0-521-86645-6. Retrieved 10 Sep 2009.
- Oestreich, A.E.; Kahane, H.; Kahane, R. (1983). "Camptomelic dysplasia". Pediatric Radiology. 13 (4): 246–247. doi:10.1007/BF00973171.
- "ITIS Standard Report Page: Entoprocta". Integrated Taxonomic Information System. 2006. Retrieved 2009-08-26.
- Nielsen, C. (2002). "Entoprocta". Encyclopedia of Life Sciences. John Wiley & Sons, Ltd. doi:10.1038/npg.els.0001596. ISBN 0-470-01617-5.
- Wasson, K. (1997). "Systematic revision of colonial kamptozoans (entoprocts) of the Pacific coast of North America". Zoological Journal of the Linnean Society. 121 (1): 1–63. doi:10.1111/j.1096-3642.1997.tb00146.x.
- Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Lophoporata". Invertebrate Zoology (7th ed.). Brooks / Cole. pp. 829–845. ISBN 0-03-025982-7.
- Little, W.; Fowler, H.W.; Coulson, J. & Onions, C.T. (1964). "Zooid". Shorter Oxford English Dictionary. Oxford University Press. ISBN 0-19-860613-3.
- 'Mindblowing' haul of fossils over 500m years old unearthed in China | Science | The Guardian
- Brusca, Richard C; Brusca, Gary J (2003). Invertebrates. ISBN 978-0-87893-097-5. page 347
- Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 286–288. ISBN 978-0-03-056747-6.
- Neves, Ricardo Cardoso; Reichert, Heinrich; Sørensen, Martin Vinther; Kristensen, Reinhardt Møbjerg (November 2016). "Systematics of phylum Loricifera: Identification keys of families, genera and species". Zoologischer Anzeiger. 265: 141–70. doi:10.1016/j.jcz.2016.06.002.
- Gad, Gunnar (17 June 2005). "Successive reduction of the last instar larva of Loricifera, as evidenced by two new species of Pliciloricus from the Great Meteor Seamount (Atlantic Ocean)". Zoologischer Anzeiger. 243 (4): 239–71. doi:10.1016/j.jcz.2004.09.001.
- Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D., eds. (2004). Invertebrate Zoology (7th ed.). p. 776. ISBN 978-0-03-025982-1.
- Heiner, Iben. "Preliminary account of the Loriciferan fauna of the Faroe Bank (NE Atlantic)". Annales Societatis Scientiatum Færoensis Supplementum. 41: 213–9.
- Heiner, Iben; Kristensen, Reinhardt Møbjerg (18 March 2005). "Two new species of the genus Pliciloricus (Loricifera, Pliciloricidae) from the Faroe Bank, North Atlantic". Zoologischer Anzeiger. 243 (3): 121–38. doi:10.1016/j.jcz.2004.05.002.
- Kristensen, R. M. (July 2002). "An Introduction to Loricifera, Cycliophora, and Micrognathozoa". Integrative and Comparative Biology. 42 (3): 641–51. doi:10.1093/icb/42.3.641. PMID 21708760.
- Heiner, Iben; Sorensen, Martin Vinther; Kristensen, Reinhardt Mobjerg (2004). Loricifera (Girdle Wearers) in Grzimek's Animal Life Encyclopedia Volume 1. New York, NY: Van Nostrand Reinhold Company. p. 343–350.
- "Discovery of new fossil from half billion years ago sheds light on life on Earth: Scientists find 'unfossilizable' creature".
- Yamasaki, Hiroshi; Fujimoto, Shinta; Miyazaki, Katsumi (2015-06-30). "Phylogenetic position of Loricifera inferred from nearly complete 18S and 28S rRNA gene sequences". Zoological Letters. 1: 18. doi:10.1186/s40851-015-0017-0. ISSN 2056-306X. PMC 4657359.
- Kristensen RM (July 2002). "An Introduction to Loricifera, Cycliophora, and Micrognathozoa". Integr Comp Biol. 42 (3): 641–51. doi:10.1093/icb/42.3.641. PMID 21708760.
- Gordon, Dennis P. (2009). "Towards a management hierarchy (classification) for the Catalogue of Life: Draft Discussion Document". In Species 2000 & ITIS Catalogue of Life: 2009 Annual Checklist (Bisby FA, Roskov YR, Orrell TM, Nicolson D, Paglinawan LE, Bailly N, Kirk PM, Bourgoin T, Baillargeon G., eds). CD-ROM; Species 2000: Reading, UK.  2009-08-08 }}
- Classification of Animal Parasites
- Garcia, Lynne (October 29, 1999). "Classification of Human Parasites, Vectors, and Similar Organisms" (PDF). Los Angeles, California: Department of Pathology and Laboratory Medicine, UCLA Medical Center. Retrieved July 21, 2017.
- Hodda, M (2011). "Phylum Nematoda Cobb, 1932. In: Zhang, Z.-Q. (Ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness". Zootaxa. 3148: 63–95. doi:10.11646/zootaxa.3148.1.11.
- Zhang, Z (2013). "Animal biodiversity: An update of classification and diversity in 2013. In: Zhang, Z.-Q. (Ed.) Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013)". Zootaxa. 3703 (1): 5–11. doi:10.11646/zootaxa.3703.1.3.
- Borgonie G, García-Moyano A, Litthauer D, Bert W, Bester A, van Heerden E, Möller C, Erasmus M, Onstott TC (June 2011). "Nematoda from the terrestrial deep subsurface of South Africa". Nature. 474 (7349): 79–82. Bibcode:2011Natur.474...79B. doi:10.1038/nature09974. hdl:1854/LU-1269676. PMID 21637257.
- Lemonick MD (2011-06-08). "Could 'worms from Hell' mean there's life in space?". Time. ISSN 0040-781X. Retrieved 2011-06-08.
- Bhanoo SN (2011-06-01). "Nematode found in mine is first subsurface multicellular organism". The New York Times. ISSN 0362-4331. Retrieved 2011-06-13.
- "Gold mine". Nature. 474 (7349): 6. June 2011. doi:10.1038/474006b. PMID 21637213.
- Drake N (2011-06-01). "Subterranean worms from hell: Nature News". Nature News. doi:10.1038/news.2011.342. Retrieved 2011-06-13.
- Borgonie G, García-Moyano A, Litthauer D, Bert W, Bester A, van Heerden E, Möller C, Erasmus M, Onstott TC (2 June 2011). "Nematoda from the terrestrial deep subsurface of South Africa". Nature. 474 (7349): 79–82. Bibcode:2011Natur.474...79B. doi:10.1038/nature09974. hdl:1854/LU-1269676. ISSN 0028-0836. PMID 21637257.
- Danovaro R, Gambi C, Dell'Anno A, Corinaldesi C, Fraschetti S, Vanreusel A, Vincx M, Gooday AJ (January 2008). "Exponential decline of deep-sea ecosystem functioning linked to benthic biodiversity loss". Curr. Biol. 18 (1): 1–8. doi:10.1016/j.cub.2007.11.056. PMID 18164201. Lay summary – EurekAlert!.
- van den Hoogen, Johan; Geisen, Stefan; Routh, Devin; Ferris, Howard; Traunspurger, Walter; Wardle, David A.; de Goede, Ron G. M.; Adams, Byron J.; Ahmad, Wasim (2019-07-24). "Soil nematode abundance and functional group composition at a global scale". Nature. 572 (7768): 194–198. doi:10.1038/s41586-019-1418-6. ISSN 0028-0836.
- Platt HM (1994). "foreword". In Lorenzen S, Lorenzen SA. The phylogenetic systematics of freeliving nematodes. London, UK: The Ray Society. ISBN 978-0-903874-22-9.
- Cary, S. Craig; Green, T. G. Allan; Storey, Bryan C.; Sparrow, Ashley D.; Hogg, Ian D.; Katurji, Marwan; Zawar-Reza, Peyman; Jones, Irfon; Stichbury, Glen A. (2019-02-15). "Biotic interactions are an unexpected yet critical control on the complexity of an abiotically driven polar ecosystem". Communications Biology. 2 (1): 62. doi:10.1038/s42003-018-0274-5. ISSN 2399-3642. PMC 6377621. PMID 30793041.
- Adams, Byron J.; Wall, Diana H.; Storey, Bryan C.; Green, T. G. Allan; Barrett, John E.; S. Craig Cary; Hopkins, David W.; Lee, Charles K.; Bottos, Eric M. (2019-02-15). "Nematodes in a polar desert reveal the relative role of biotic interactions in the coexistence of soil animals". Communications Biology. 2 (1): 63. doi:10.1038/s42003-018-0260-y. ISSN 2399-3642. PMID 30793042.
- Roy C. Anderson (8 February 2000). Nematode Parasites of Vertebrates: Their development and transmission. CABI. p. 1. ISBN 978-0-85199-786-5.
- Cobb, Nathan (1914). "Nematodes and their relationships". Yearbook. United States Department of Agriculture. pp. 472, 457–490. Archived from the original on 2016-06-09. Retrieved 2012-09-25.
Quote on p. 472.
- Hanelt, B, F. Thomas, and A. Schmidt-Rhaesa (2005). Biology of the phylum Nematomorpha. Advances in Parasitology. 59. pp. 244–305. doi:10.1016/S0065-308X(05)59004-3. ISBN 9780120317592. PMID 16182867.
- Poinar Jr., G (January 2008). "Global diversity of hairworms (Nematomorpha: Gordiaceae) in freshwater". Hydrobiologia. 595 (1): 79–83. doi:10.1007/s10750-007-9112-3.
- Ross Piper (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press.
- Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 307–308. ISBN 978-0-03-056747-6.
- Integrated Taxonomic Information System https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=57411 Nemertea February 18, 2011
- Scott, Thomas (1996). "Nemertini, Rhynchocoela, Nemertea, Nemertinea". Concise Encyclopedia of Biology. Walter de Gruyter. pp. 815–816. ISBN 978-3-11-010661-9.
- R. Gibson (1995). "Nemertean genera and species of the world: an annotated checklist of original names and description citations, synonyms, current taxonomic status, habitats and recorded zoogeographic distribution". Journal of Natural History. 29 (2): 271–561. doi:10.1080/00222939500770161.
- Barnes, Richard Stephen Kent (2001). "The worms". The Invertebrates: a Synthesis. Wiley-Blackwell. pp. 81–83. ISBN 978-0-632-04761-1. Retrieved 27 Jan 2011.
- Paps J, Baguñà J, Riutort M (April 2009). "Lophotrochozoa internal phylogeny: new insights from an up-to-date analysis of nuclear ribosomal genes". Proceedings of the Royal Society B. 276 (1660): 1245–54. doi:10.1098/rspb.2008.1574. PMC 2660960. PMID 19129141.
- Jimenez-Guri E, Paps J, Garcia-Fernandez J, Salo E (2006). "Hox and ParaHox genes in Nemertodermatida, a basal bilaterian clade". International Journal of Developmental Biology. 50 (8): 675–9. doi:10.1387/ijdb.062167ej. PMID 17051477.
- Holm, E.; Dippenaar-Schoeman, A. (2010). The Arthropods of Southern Africa. ISBN 978-0-7993-4689-3.[page needed]
- Prothero, D. R.; Buell, C. D. (2007). Evolution: What the Fossils Say and Why It Matters. New York: Columbia University Press. p. 193. ISBN 978-0-231-13962-5.
- Ruppert, E. E.; Fox, R. S.; Barnes, R. D. (2004). Invertebrate Zoology: A Functional Evolutionary Approach (7th ed.). Belmont: Thomson-Brooks / Cole. p. 505. ISBN 978-0-03-025982-1.
- Piper, Ross (2007). "Velvet Worms". Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals. Greenwood Press. pp. 109–11. ISBN 978-0-313-33922-6.
- Fishelson, L. (1978). Zoology. 1 (3rd ed.). Israel: Hakibutz Hameuchad Publishing. p. 430.
- Emig, Christian C. (2003). "Phylum: Phoronida" (PDF). In Bernhard Grzimek; Devra G. Kleiman; Michael Hutchins. Grzimek's Animal Life Encyclopedia. 2: Protostomes (2 ed.). Thompson Gale. pp. 491–495. ISBN 978-0-7876-5362-0. Retrieved 2011-03-01.
- Taylor, Paul D.; Olev Vinn; Mark A. Wilson (2010). "Evolution of biomineralization in 'Lophophorates'". Special Papers in Palaeontology. 84: 317–333. doi:10.1111/j.1475-4983.2010.00985.x (inactive 2019-08-20).
- Helmkampf, Martin; Iris Bruchhaus; Bernhard Hausdorf (August 2008). "Phylogenomic analyses of lophophorates (brachiopods, phoronids and bryozoans) confirm the Lophotrochozoa concept". Proceedings of the Royal Society B. 275 (1645): 1927–1933. doi:10.1098/rspb.2008.0372. PMC 2593926. PMID 18495619.
- Halanych, K.M (15 December 2004). "The new view of animal phylogeny" (PDF). Annual Review of Ecology, Evolution, and Systematics. 35: 229–256. doi:10.1146/annurev.ecolsys.35.112202.130124. Retrieved 2011-03-09.
- Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Lophophorata: Phoronida". Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 817–821. ISBN 978-0-03-025982-1.
- Doherty, P.J. (1998). "The lophophorates – Phoronida, Brachiopoda and Ectoprocta". In D.T. Anderson. Invertebrate Zoology (1 ed.). Oxford University Press Australia. pp. 346–349. ISBN 978-0-19-553941-7.
- Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Arthropod". Invertebrate Zoology (7 ed.). Brooks / Cole. p. 518. ISBN 978-0-03-025982-1.
- Hinton, Sam (1987). Seashore life of southern California: an introduction to the animal life of California beaches south of Santa Barbara. University of California Press. ISBN 978-0-520-05924-5. Retrieved 2011-08-28.
- Morris, Christopher G. (1992). "Ampulla". Academic Press dictionary of science and technology. Gulf Professional Publishing. p. 102. ISBN 978-0-12-200400-1.
- Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Compartmentalization". Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 205–206. ISBN 978-0-03-025982-1.
- Bartolomaeus, T. (February 2001). "Ultrastructure and formation of the body cavity lining in Phoronis muelleri (Phoronida, Lophophorata)". Zoomorphology. 120 (3): 135–148. doi:10.1007/s004350000030.
- Placozoa at the US National Library of Medicine Medical Subject Headings (MeSH)
- Voigt, O; Collins AG; Pearse VB; Pearse JS; Hadrys H; Ender A (23 November 2004). "Placozoa — no longer a phylum of one" (PDF). Current Biology. 14 (22): R944–5. doi:10.1016/j.cub.2004.10.036. PMID 15556848.
- Eitel, Michael; Osigus, Hans-Jürgen; DeSalle, Rob; Schierwater, Bernd (2 April 2013). "Global Diversity of the Placozoa". PLOS One. 8 (4): e57131. Bibcode:2013PLoSO...857131E. doi:10.1371/journal.pone.0057131. PMC 3614897. PMID 23565136.
- Eitel, Michael; Francis, Warren; Osigus, Hans-Jürgen; Krebs, Stefan; Vargas, Sergio; Blum, Helmut; Williams, Gray Argust; Schierwater, Bernd; Wörheide, Gert (2017-10-13). "A taxogenomics approach uncovers a new genus in the phylum Placozoa". bioRxiv: 202119. doi:10.1101/202119.
- Francis, Warren R.; Wörheide, Gert (2017-06-01). "Similar Ratios of Introns to Intergenic Sequence across Animal Genomes". Genome Biology and Evolution. 9 (6): 1582–1598. doi:10.1093/gbe/evx103. PMC 5534336. PMID 28633296.
- Schierwater, Bernd; Kamm, Kai; Herzog, Rebecca; Rolfes, Sarah; Osigus, Hans-Jürgen (2019-03-04). "Polyplacotoma mediterranea is a new ramified placozoan species". Current Biology. 29 (5): R148–R149. doi:10.1016/j.cub.2019.01.068. ISSN 0960-9822. PMID 30836080.
- F. E. Schulze "Trichoplax adhaerens n. g., n. s.", Zoologischer Anzeiger (Elsevier, Amsterdam and Jena) 6 (1883), p. 92.
- Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia: Holt-Saunders International. pp. 84–85. ISBN 978-0-03-056747-6.
- Grell, K. G. (1971). "Trichoplax adhaerens, F. E. Schulze und die Entstehung der Metazoen". Naturwissenschaftliche Rundschau. 24: 160.
- Rüdiger Wehner & Walter Gehring (June 2007). Zoologie (in German) (24th ed.). Stuttgart: Thieme. p. 696.
- Walker, J.C.; Anderson, D.T. (2001). "The Platyhelminthes". In Anderson, D.T. Invertebrate Zoology. Oxford University Press. pp. 58–80. ISBN 978-0-19-551368-4.
- Hinde, R.T. (2001). "The Cnidaria and Ctenophora". In Anderson, D.T. Invertebrate Zoology. Oxford University Press. pp. 28–57. ISBN 978-0-19-551368-4.
- Barnes, R.S.K. (1998). The Diversity of Living Organisms. Blackwell Publishing. pp. 194–195. ISBN 978-0-632-04917-2. Retrieved 2008-12-21.
- Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. pp. 226–269. ISBN 978-0-03-025982-1.
- Klaus Rohde (2001). Platyhelminthes (flat worms). Encyclopaedia of Life Sciences. doi:10.1038/npg.els.0001585. ISBN 978-0470016176.
- Jberkel (22 August 2016). "spongiology". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 29 September 2019.
- Aruga J, Odaka YS, Kamiya A, Furuya H (25 October 2007). "Dicyema Pax6 and Zic: tool-kit genes in a highly simplified bilaterian". BMC Evol. Biol. 7: 201. doi:10.1186/1471-2148-7-201. PMC 2222250. PMID 17961212.
- Tsai-Ming Lu; Miyuki Kanda; Noriyuki Satoh; Hidetaka Furuya (May 2017). "The phylogenetic position of dicyemid mesozoans offers insights into spiralian evolution". Zoological Letters. 3 (1). doi:10.1186/s40851-017-0068-5. PMC 5447306.
- Pawlowski J, Montoya-Burgos JI, Fahrni JF, Wüest J, Zaninetti L (October 1996). "Origin of the Mesozoa inferred from 18S rRNA gene sequences". Mol. Biol. Evol. 13 (8): 1128–32. doi:10.1093/oxfordjournals.molbev.a025675. PMID 8865666.
- Kobayashi M, Furuya H, Wada H (2009) Molecular markers comparing the extremely simple body plan of dicyemids to that of lophotrochozoans: insight from the expression patterns of Hox, Otx, and brachyury. Evol Dev 11(5):582-589
- Suzuki TG, Ogino K, Tsuneki K, Furuya H (2010) Phylogenetic analysis of dicyemid mesozoans (phylum Dicyemida) from innexin amino acid sequences: dicyemids are not related to Platyhelminthes. J Parasitol 96(3):614-625
- "Kantharellidae". Integrated Taxonomic Information System.  5 April 2010}}
- SemperBlotto (13 February 2007). "rotifer". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 29 September 2019.
- Telford, M. J.; Bourlat, S. J.; Economou, A.; Papillon, D.; Rota-Stabelli, O. (27 April 2008). "The evolution of the Ecdysozoa". Philosophical Transactions of the Royal Society B. 363 (1496): 1529–1537. doi:10.1098/rstb.2007.2243. PMC 2614232. PMID 18192181.
- Yamasaki, Hiroshi; Fujimoto, Shinta; Miyazaki, Katsumi (2015-06-30). "Phylogenetic position of Loricifera inferred from nearly complete 18S and 28S rRNA gene sequences". Zoological Letters. 1: 18. doi:10.1186/s40851-015-0017-0. ISSN 2056-306X. PMC 4657359. PMID 26605063.
- Heiner, I., Kristensen, R.H. 2005. Two new species of the genus Pliciloricus (Loricifera, Pliciloricidae) from the Faroe Bank, North Atlantic. Zoologischer Anzeiger. 243: 121–138.
- Dirnberger, J. "Explanations and Difficulties in Invertebrate Phylogeny". Invertebrate Zoology. Kennesaw State University. Retrieved 2012-08-11.
- Dunn, C. W.; Hejnol, A.; Matus, D. Q.; Pang, K.; Browne, W. E.; Smith, S. A.; Seaver, E.; Rouse, G. W.; Obst, M. (10 April 2008). "Broad Phylogenomic Sampling Improves Resolution of the Animal Tree of Life". Nature. 452 (7188): 745–749. doi:10.1038/nature06614. PMID 18322464.
-  José Saiz-Salinas, 2009 Sipunculus (Sipunculus) nudus Linnaeus, 1766 27 February 2019
- Rafinesque, Constantine Samuel (1814). Précis des découvertes et travaux somiologiques de m.r C. S. Rafinesque-Schmaltz entre 1800 et 1814 ou Choix raisonné de ses principales découvertes en zoologie et en botanique. Royale typographie militaire, aux dépens de l'auteur. p. 32.
-  2018 Sipuncula 27 February 2019
- Pancucci-Papadopoulou, M.A.; Murina, G.V.V.; Zenetos, A. (2014). "The phylum Sipuncula in the Mediterranean Sea" (PDF). National Centre for Marine Research. Retrieved 10 February 2019.
- Struck, T. H.; Paul, C.; Hill, N.; Hartmann, S.; Hösel, C.; Kube, M.; Lieb, B.; Meyer, A.; Tiedemann, R.; Purschke, G. N.; Bleidorn, C. (3 March 2011). "Phylogenomic analyses unravel annelid evolution". Nature. 471 (7336): 95–98. doi:10.1038/nature09864. PMID 21368831.
- Wanninger, Andreas; Kristof, Alen; Brinkmann, Nora (Jan–Feb 2009). "Sipunculans and segmentation". Communicative and Integrative Biology. 2 (1): 56–59. doi:10.4161/cib.2.1.7505. PMC 2649304. PMID 19513266.
- Miller, William (2017-02-06). "Tardigrades". American Scientist. Retrieved 2018-04-13.
- Simon, Matt (21 March 2014). "Absurd Creature of the Week: The Incredible Critter That's Tough Enough to Survive in the vacuum of Space". Wired. Retrieved 2014-03-21.
- Copley, Jon (23 October 1999). "Indestructible". New Scientist (2209). Retrieved 2010-02-06.
- "Stanford Tardigrade Project". Foldscope. 2016-08-10. Retrieved 2017-03-23.
- Dean, Cornelia (September 9, 2015). "Meet tardigrade, the water bear". The Hindu. Retrieved August 9, 2019.
- Bordenstein, Sarah. "Tardigrades (Water Bears)". Microbial Life Educational Resources. National Science Digital Library. Retrieved 2014-01-24.
- "The strange worms that live on erupting mud volcanoes". BBC Earth. Retrieved 2017-04-15.
- "Tardigrades". Tardigrade. Retrieved 2015-09-21.
- Guarino, Ben (14 July 2017). "These animals can survive until the end of the Earth, astrophysicists say". Washington Post. Retrieved 14 July 2017.
- Sloan, David; Alves Batista, Rafael; Loeb, Abraham (2017). "The Resilience of Life to Astrophysical Events". Scientific Reports. 7 (1): 5419. arXiv:1707.04253. Bibcode:2017NatSR...7.5419S. doi:10.1038/s41598-017-05796-x. PMC 5511186. PMID 28710420.
- "'Water Bears' are first animal to survive vacuum of space". New Scientist. Archived from the original on 10 September 2008. Retrieved 10 September 2008.
- "'Water Bears' Able To Survive Exposure To Vacuum Of Space". Science Daily. Archived from the original on 11 September 2008. Retrieved 10 September 2008.
- Degma, Peter; Bertolani, Roberto; Guidetti, Roberto. "Actual checklist of Tardigrada species (2009–2015, Ver. 28: 31-03-2015)" (PDF). Archived from the original (PDF) on 8 May 2010.
- "Tardigrada (water bears, tardigrades)". biodiversity explorer. Retrieved 2013-05-31.
- Nelson, Diane (1 July 2002). "Current status of Tardigrada: Evolution and Ecology". Integrative and Comparative Biology. 42 (3): 652–659. doi:10.1093/icb/42.3.652. PMID 21708761.
- Shaw, Michael W. "How to Find Tardigrades". Tardigrade USA. Archived from the original on 10 February 2014. Retrieved 2013-01-14.
- Philippe, H.; Brinkmann, H.; Copley, R. R.; Moroz, L. L.; Nakano, H.; Poustka, A. J.; Wallberg, A.; Peterson, K. J.; Telford, M. J. (10 February 2011). "Acoelomorph flatworms are deuterostomes related to Xenoturbella". Nature. 470 (7333): 255–258. Bibcode:2011Natur.470..255P. doi:10.1038/nature09676. PMC 4025995. PMID 21307940.
- Lundin, K (1998). "The epidermal ciliary rootlets of Xenoturbella bocki (Xenoturbellida) revisited: new support for a possible kinship with the Acoelomorpha (Platyhelminthes)". Zoologica Scripta. 27 (3): 263–270. doi:10.1111/j.1463-6409.1998.tb00440.x.
- Hejnol, A.; Obst, M.; Stamatakis, A.; Ott, M.; Rouse, G. W.; Edgecombe, G. D. (2009). "Assessing the root of bilaterian animals with scalable phylogenomic methods". Proceedings of the Royal Society B: Biological Sciences. 276 (1677): 4261–4270. doi:10.1098/rspb.2009.0896. PMC 2817096. PMID 19759036.
- Perseke, M.; Hankeln, T.; Weich, B.; Fritzsch, G.; Stadler, P.F.; Israelsson, O.; Bernhard, D.; Schlegel, M. (August 2007). "The mitochondrial DNA of Xenoturbella bocki: genomic architecture and phylogenetic analysis" (PDF). Theory Biosci. 126 (1): 35–42. CiteSeerX 10.1.1.177.8060. doi:10.1007/s12064-007-0007-7. PMID 18087755.
- Cannon, J.T.; Vellutini, B.C.; Smith, J.; Ronquist, F.; Jondelius, U.; Hejnol, A. (4 February 2016). "Xenacoelomorpha is the sister group to Nephrozoa". Nature. 530 (7588): 89–93. Bibcode:2016Natur.530...89C. doi:10.1038/nature16520. PMID 26842059.
- "Eukaryota, In: Wikispecies". San Francisco, California: Wikimedia Foundation, Inc. 13 November 2015. Retrieved 2016-01-21.
- Cox F.E.G. 2002. "History of human parasitology"
- Ronald L. Shimek (January 2006). Nano-Animals, Part I: Rotifers. ReefKeeping.com. Retrieved 2016-01-21.
- de Buron, I.; Golvan, Y. J. (1986). "Les hôtes des Acanthocéphales. I — Les Hôtes intermédiaires". Annales de Parasitologie Humaine et Comparée. 61 (5): 581–592. doi:10.1051/parasite/1986615581. ISSN 0003-4150.
- Golvan, Y. J.; De Buron, I. (1988). "Les hôtes des Acanthocéphales. II — Les hôtes définitifs. 1. Poissons". Annales de Parasitologie Humaine et Comparée. 63 (5): 349–375. doi:10.1051/parasite/1988635349. ISSN 0003-4150. PMID 3059956.
- Roberts, Larry S.; Janovy, Jr., John (2009). Foundations of Parasitology (Eighth ed.). McGraw-Hill. p. 502. ISBN 9780073028279.
- Freeman, Scott, Lizabeth Allison, Michael Black, Greg Podgorski, and Kim Quillin. Biological Sciences. 5th ed. Glenview, Il: Pearson, 2014. 638. Print.
- Encyclopedia of Life, retrieved 24 July 2015
- Hanelt, B; Van Schyndel, D; Adema, C. M; Lewis, L. A; Loker, E. S (1996). "The phylogenetic position of Rhopalura ophiocomae (Orthonectida) based on 18S ribosomal DNA sequence analysis". Molecular Biology and Evolution. 13 (9): 1187. doi:10.1093/oxfordjournals.molbev.a025683. PMID 8896370.
- Robert D. Barnes (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 247–248. ISBN 0-03-056747-5.
- Zverkov OA, Mikhailov KV, Isaev SV, Rusin LY, Popova OV, Logacheva MD, Penin AA, Moroz LL, Panchin YV, Lyubetsky VA, Aleoshin VV (2019) Dicyemida and Orthonectida: Two Stories of Body Plan Simplification. Front Genet 10:443
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