Animals

Tarbosaurus — Asian Late Cretaceous tyrannosaurid Tarbosaurus Large Late Cretaceous tyrannosaurid from Mongolia and China, noted for its robust skull, powerful bite, and role as a top predator in riverine floodplain ecosystems; studied for it…

Tardigrade (water bear): microscopic, resilient eight-legged animals Tardigrade Tardigrades are microscopic, segmented animals known for extreme resilience and cryptobiosis. Found worldwide in mosses, freshwater and marine environments, they are important in e…

Taricha (western newts): overview, species, biology, and conservation Taricha Taricha is a small genus of North American newts (family Salamandridae) including three species. This article covers identification, life cycle, toxicity, distribution, ecology, an…

Tarsal formula (arthropod leg segmentation) Tarsal formula A concise guide to the tarsal formula: the count of tarsal segments (tarsomeres) on an insect's fore, middle and hind legs, its notation, taxonomic use, limitations and practical n…

Tarsier: small nocturnal primates of Southeast Asia Tarsier Tarsiers are small, nocturnal primates with elongated ankle bones, large eyes, and a carnivorous diet. Native to Southeast Asia, they are unique among primates in anatomy, behavior…

Tasmanian devil (Sarcophilus harrisii) Tasmanian devil A small, carnivorous marsupial native to Tasmania, known for its powerful jaws, nocturnal scavenging, distinctive vocalizations and current conservation challenges.

Tawny Owl (Strix aluco): description, behaviour and distribution Tawny owl Stocky, medium-sized woodland owl of Eurasia. Resident and territorial, known for nocturnal hunting, silent flight, asymmetrical hearing, cavity nesting and varied plumage across s…

Taxis (directed movement of organisms toward or away from stimuli) Taxis Taxis is the oriented movement of an organism toward or away from a directional stimulus. It requires motility and receptor-mediated sensing; common forms include phototaxis and ch…

Teinolophos: an early Cretaceous monotreme from Australia Teinolophos Teinolophos trusleri, known from a partial jaw discovered in Victoria, dates to the Lower Cretaceous. It represents an early branch of monotremes and informs studies of mammal orig…

Teleosts: diversity, evolution, anatomy, and human importance Teleost Teleosts are the largest group of living bony fishes. This article surveys their defining features, evolutionary history, diversity, ecological roles, and significance to people.

Telmatosaurus (marsh lizard) Telmatosaurus Telmatosaurus is a small, basal hadrosauroid dinosaur from the Late Cretaceous of Romania, known from Hațeg Basin fossils and important for studies of insular dwarfism and European…

Temnodontosaurus — large Early Jurassic ichthyosaur Temnodontosaurus Temnodontosaurus was a large marine reptile of the early Jurassic known from England and Germany. Noted for its long jaws, enormous eyes and whale-sized body, it was an apex predat…

Temnospondyls: an overview of a diverse early amphibian group Temnospondyl Temnospondyls were a varied group of early amphibian tetrapods that lived from the Carboniferous into the Cretaceous, occupying aquatic and terrestrial niches and leaving a rich fo…

Tenontosaurus (Early Cretaceous ornithopod) Tenontosaurus Tenontosaurus was a medium-to-large herbivorous ornithopod from Early Cretaceous North America, once grouped with hypsilophodonts and now seen as a primitive iguanodont with distin…

Tenrec: a diverse family of Malagasy and African mammals Tenrec Tenrecs are a varied group of mammals (family Tenrecidae) native mainly to Madagascar, showing remarkable convergent forms, unique anatomy, and close ties to other afrotherian mamm…

Tentaculata — the tentacled comb jellies Tentaculata Tentaculata is a class of comb jellies (phylum Ctenophora) characterized by a pair of retractable tentacles bearing adhesive colloblasts; widely distributed gelatinous plankton wit…

Tenualosa ilisha (hilsa): biology, cultural importance, and management Tenualosa ilisha Tenualosa ilisha, commonly called hilsa or ilish, is an anadromous shad of the herring family prized across South Asia for its taste and economic role; it faces conservation and ma…

Teratorns — giant prehistoric birds of the Americas Teratorn Teratorns were a family of very large predatory and scavenging birds that lived across the Americas from the Oligocene to the end of the Pleistocene. They include some of the large…

Tergum — dorsal plate of an arthropod segment Tergum The tergum (plural terga) is the dorsal portion of an arthropod body segment, often divided into tergites. It forms sclerites used in morphology, taxonomy and functional anatomy ac…

Termite Termites are eusocial insects that decompose cellulose, form complex colonies with distinct castes, and influence ecosystems; some species can be economically destructive to wood s…

Tern — slender seabirds: appearance, behavior, and conservation Tern Terns are slender, long-winged seabirds in the family Laridae, found near coasts, rivers and wetlands. This article covers their appearance, nesting, feeding, migrations, notable s…

Terrapin (small brackish- and freshwater turtles) Terrapin Terrapin is a common name for several small turtles that live in fresh or brackish water. The term is not a taxonomic group and is applied to species across different families; not…

Terrestrial animal A terrestrial animal is a species that spends the majority of its life on land. This article explains traits, major groups, ecological roles, evolution, and distinctions from aquat…

Terrier — characteristics, history, and common breeds Terrier Terriers are energetic dogs developed to hunt and control vermin. This article explains their origins, typical traits, grooming and training needs, roles, and notable breeds and di…

Terror birds (Phorusrhacidae): flightless predatory birds of South America Terror birds Extinct family Phorusrhacidae, large flightless carnivorous birds that dominated many South American ecosystems in the Cenozoic; some species dispersed into North America during th…

Tetrigidae — pygmy grasshoppers, groundhoppers, and grouse locusts Tetrigidae Tetrigidae is a family of small Orthoptera known as pygmy grasshoppers or groundhoppers. About 1,600 species worldwide; distinctive for an extended pronotum and association with da…

Tettigoniidae — katydids and bush‑crickets (long‑horned orthopterans) Tettigoniidae Tettigoniidae is a large family of long‑antennaed insects (katydids or bush‑crickets) in the suborder Ensifera, known for their songs, leaf mimicry, varied diets and worldwide dist…

Texas coral snake (Micrurus tener) Texas coral snake A concise encyclopedia entry on the Texas coral snake: appearance, behavior, venom, range, identification tips, and human interactions, with notes on mimic species and conservation…

Texas toad (Anaxyrus speciosus): appearance, habitat, and behavior Texas toad Small, stout toad native to the southern Great Plains. Overview of identification, range, habitat, life cycle, ecological role, taxonomy, and how it differs from similar species.

Thalassodromeus — large crested pterosaur from Brazil Thalassodromeus Thalassodromeus is an Early Cretaceous pterosaur from northeastern Brazil, notable for its enormous cranial crest, toothless beak and debated feeding ecology. It illustrates pteros…

Thalassomedon — a long‑necked plesiosaur of the Cretaceous seas Thalassomedon Thalassomedon was an elasmosaurid plesiosaur from the Late Cretaceous Western Interior Seaway, known from fossils found in Kansas and described by Samuel Welles in 1943.

Thaliacea (pelagic tunicates) Thaliacea Thaliacea are free‑living, often transparent tunicates — including salps, doliolids and pyrosomes — that filter plankton, alternate sexual and asexual generations, and play a large…

Thelyphonida (whip scorpions or vinegaroons): biology, behavior, and facts Thelyphonida Thelyphonida, also called whip scorpions or vinegaroons, are an order of nonvenomous arachnids known for their whip-like tail and defensive acetic acid spray. Overview, anatomy, be…

Therapsids: early synapsids ancestral to mammals Therapsid Therapsids are a major group of synapsids that includes the lineage leading to mammals. They show many transitional features—differentiated teeth, altered jaw and limb anatomy—and…

Theria — the live‑bearing subclass of mammals Theria Theria is the mammal subclass that includes nearly all living species that bear live young. It is divided into Metatheria (marsupials) and Eutheria (placentals) and excludes egg-la…

Theridiidae — the tangle‑web or comb‑footed spiders Theridiidae Theridiidae is a large, worldwide family of araneomorph spiders that build irregular cobwebs and use a comb of serrated bristles to subdue prey; includes widow and false‑widow spid…

Therizinosaur: the unusual clawed theropods adapted for herbivory Therizinosaur Therizinosaurs (segnosaurs) are maniraptoran theropods with large hand claws, likely herbivorous adaptations, feather-like integument and a Cretaceous distribution across Asia and…

Therizinosaurus — the giant clawed maniraptoran of the Late Cretaceous Therizinosaurus Therizinosaurus was an unusually built, large herbivorous maniraptoran dinosaur of the Late Cretaceous, notable for enormous hand claws, a long neck and its role in revealing thero…

Therocephalia — extinct theriodonts bridging non-mammalian synapsids and mammals Therocephalia Therocephalia were a diverse group of theriodont synapsids from the middle Permian to the middle Triassic. Their skulls, dentition and distribution illuminate mammal-like anatomica…

Theropod: bipedal saurischian dinosaurs and the evolutionary lineage of birds Theropod Theropods are chiefly bipedal saurischian dinosaurs that gave rise to modern birds. They varied in size and diet, shared features like feathers and hollow bones, and include many w…

Thescelosaurus: a late Cretaceous herbivore of North America Thescelosaurus Thescelosaurus was a small-to-medium herbivorous dinosaur from the latest Cretaceous of North America, known from well-preserved skeletons and skin impressions and often cited amon…

Thomson's gazelle (Gazella thomsonii) Thomson's gazelle A small, common East African antelope known as a 'tommie'. Describes appearance, behaviour, habitat, history, threats, and differences from similar gazelles.

Thorny devil (Moloch horridus) Thorny devil A distinctive spiny Australian lizard adapted to arid environments; known for its ant-specialized diet, water-collection skin, and dramatic camouflage and spines.

Thoroughbred (horse breed) Thoroughbred Thoroughbred: a horse breed developed for speed and stamina, notable for racing, detailed pedigrees and influence on many sport-horse types worldwide.

Thread snake (slender blind snake) Thread snake Small, slender fossorial snakes in the family Leptotyphlopidae and related groups. Overview of appearance, behavior, distribution, diet, reproduction, and notable facts.

Threat display Threat displays are behaviours or signals animals use to deter rivals or predators by appearing dangerous, larger, or otherwise undesirable to attack; they are widespread and often…

Thrush nightingale (Luscinia luscinia) Thrush nightingale A small migratory songbird of the genus Luscinia, once placed with thrushes and now treated as an Old World flycatcher; known for its secretive habits, insect diet and strong, melo…

Thylacine (Tasmanian tiger): biology, history and extinction Thylacine Extinct carnivorous marsupial once native to Australia, Tasmania and New Guinea. Overview of its appearance, fossil record, decline, cultural role, and ongoing research.