The Vertebrates P-Z

Taxon Index: P-Z

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  1. Pachycephalosauria X: Pachycephalosaurus > Triceratops
  2. Pachycephalosauridae X:  the classic bone-dome dinosaurs
  3. Pachycormiformes X: possibly the sister group of the teleosts, and probably the largest actinopterygians ever
  4. Pachygenelius X: a trithelodont cynodont from the Early Jurassic of South Africa and perhaps elsewhere
  5. Pachyophiidae X: a controversial family of Late Cretaceous aquatic snakes
  6. Pachypleurosauridae X: small, Middle to Late Triassic aquatic lepidosauromorphs, cousins of the notosaurs
  7. Paenungulata: the part of Afrotheria that is morphologically sound -- elephants, sea cows, & hyraxes
  8. Pakicetidae X: the first cetaceans, from the Early Eocene of South Asia
  9. Palaeoryctidae X: very early (Cretaceous?) members of the shrew lineage ... maybe
  10. Palaeospinacidae X: Synechodus and others probably just outside the crown group of living sharks (Neoselachii)
  11. Paleognathae: ratites and their ancestors
  12. Paleorhinus X: a large, somewhat confused, genus of phytosaurs
  13. Panderichthys X: a well-known almost-tetrapod from the Late Devonian of the Baltics
  14. Paraconodontida X: very basal Cambrian conodonts
  15. Paralititan X: Josh Smith's giant Egyptian sauropod
  16. Parapternodontidae X: probably the sister group of living shrews, from the Eocene of North America
  17. Paraorthacodus X: a tooth genus of palaeospinacid sharks
  18. Parasemionotidae X: earliest (Triassic) and most basal family of halecomorph neopterygian fishes
  19. Parasuchus X: a phytosaur -- probably a synonym of Paleorhinus
  20. Parathrinaxodon X: a basal cynodont, possibly synonymous with Procynosuchus
  21. Paratypothorax X: a late surviving phytosaur
  22. Pareiasauria X: very large anapsid herbivores of the Permian -- possible turtle ancestors.
  23. Parvicursor X: a tiny, poorly known alvarezsaurid bird from the Late Cretaceous of Mongolia
  24. Parvipelvia X: Jurassic ichthyosaurs and their Cretaceous descendants
  25. Passeriformes: perching songbirds
  26. Patagonykus X: an alvarezsaurid ?bird from the Late Cretaceous of South America
  27. Patagopterygiformes X: a family of rather modern-looking ornithurine birds from the Early Cretaceous of South America and ?China
  28. Paucituberculata: rat opossums, South American marsupials
  29. Paulchoffatiidae X: the most basal multituberculates -- from the Late Jurassic of Europe.
  30. Pelecaniformes: pelicans, frigate birds, and tropic birds.
  31. Pelomedusidae: medium to large size freshwater aquatic turtles from Africa and South America
  32. Pelomedusoidea: all derived pleurodire (side-necked) turtles, i.e. pelomedusids + podcnemoids
  33. Peloneustes X: a relatively small, squid-eating pliosaur from the Late Jurassic of Europe
  34. Pelorosaurus X: a poorly known, possibly non-existent, brachiosaurid dinosaur from the Early Cretaceous of Europe
  35. Peramelina: bilbeys and bandicoots
  36. Perissodactyla: horses, rhinos & tapirs
  37. Petalichthyida X: a peculiar, hard-to-place group of placoderms from the Early Devonian
  38. Petalodontiformes X: indescribably weird-looking early chondrichthyans, e.g., Balantsea
  39. Petromyzontiformes: lampreys
  40. Phacochoerini: wart hogs
  41. Phacochoerus: the extant African warthog
  42. Pharyngolepis X: a very basal anaspid from the Silurian of Europe
  43. Phasianidae: chickens, pheasants, peacocks, turkeys, etc
  44. Phlebolepis X: a relatively well-known and widely distributed Silurian katoporid thelodont
  45. Phlyctaenioidei X: a group of arthrodire placoderms
  46. Phoebodontidae X: broad-headed, blunt-snouted ctenacanthiform sharks from the Devonian to the Triassic
  47. Phoenicopteriformes: flamingos
  48. Pholiderpeton X: an odd, long-bodied Bashkirian embolomere from Scotland
  49. Pholidogaster X: an earlier embolomere, also Scottish, with reduced limbs
  50. Pholidota: pangolins (armored eutherian mammals)
  51. Phthinosuchidae X: very poorly known, very basal therapsids from the Late Permian of Russia
  52. Phyllolepida X: large, late placoderms with terassed armor
  53. Physeteroidea: sperm whales and relatives
  54. PhytosauridaeX: big, gavial-like (but more terrestrial) proto-crocs from the Late Triassic
  55. Piciformes: woodpeckers & toucans
  56. Pistosaurus X: the sister of Plesiosauria -- and more than half-way between nothosaurs and plesiosaurs
  57. Pituriaspida X: a unique, but poorly known group of cephalaspid fishes from the Early Devonian of Australia
  58. Placerias X: a huge, well-known Kannemeyerid dicynodont from the Triassic of North America
  59. Placodermi X: placoderms
  60. Placodontia X: big, walrus-like sauropterygians from the Triassic of Europe.
  61. Plagiosauridae X: bizarre, crescent-headed temnospondyls (like Gerrothorax) from the Triassic of Europe and Greenland
  62. Plagiosauroidea X: Triassic temnospondyls with short, wide skulls and pustular ornamentation
  63. Plataleidae: ibis and spoonbills
  64. Plateosauridae X: European prosauropods of the Late Triassic and Early Jurassic
  65. Platycraniellus X: a poorly known Early Triassic galesaurid cynodont from South Africa
  66. Platypterygius X widely occuring large Cretaceous ichthyosaur, distinguished by longer body and paddles than its Jurassic ophthalmosaur ancestors. Divided into a number of subgenera
  67. Platyrrhini: New World monkeys
  68. Plesiadapiformes X: Paleocene and Eocene mammals, the sister group of Primates
  69. Plesiopleurodon X: a pliosaurid from the Late Cretaceous of North America.
  70. Plesiosauria X: all plesiosaurs and pliosaurs
  71. Plesiosauroidea X: the plesiosaurs -- small-headed, long-necked aquatic reptiles
  72. Plesiosaurus X: the best known plesiosaur, from the Early Jurassic of Europe
  73. Pleurodira: one of the two great turtle lineages, now restricted to Gondwanan lands
  74. Pleurosauridae X: Jurassic and Cretaceous marine rhynchocephalians, sister to the sphenodonts
  75. Pliosauridae X: Jurassic and Cretaceous pliosaurs with very large skulls
  76. Pliosauroidea X: all pliosaurs, medium to very large marine reptiles of the Mesozoic.
  77. Pliosaurus X: a large pliosaurid from the Jurassic of Europe.
  78. Podicipediformes: grebes
  79. Podocnemidae: Fresh water turtles from South America.
  80. Podcnemoidae: podcnemid turtles and their extinct bothremyid sister group.
  81. Poebrotherium X: : the earliest of the Camelidae
  82. Polybranchiaspidida X: Devonian galeaspid fishes with many (10-45) gill openings
  83. Polybranchiaspidiformes X: a paraphyletic group of late (Devonian) galeaspid jawless fishes
  84. Polycotylidae X: a family of Cretaceous plesiosaurs, sister of the elasmosaurs
  85. Polycryptodira: living cryptodire (Gondwanan) turtles
  86. Polyosteorhynchus X: a Bear Gulch actinistian
  87. Polypteriformes: a strange living order of very basal actinopterygian fishes, including bichirs and reedfish
  88. Poposauridae X: a family of archosaurs wedged between the rauisuchids and the crocodylomorphs
  89. Porolepiformes X: Devonian sarcopterygian fishes, sister to either the lungfishes or the osteolepiforms
  90. Potamochoerini: the bush pig & giant forest hog of Africa
  91. Potamochoerus: bush pig
  92. Powichthys X: probably a very early lungfish (dipnomorph)
  93. Presbyornis X: a very important and succesful early duck/goose, known from the Cretaceous to the Late Eocene
  94. Presbyornithidae X: the family of Presbyornis
  95. Prestosuchidae X: the most basal family on the croc side of the croc-dinosaur split.
  96. Priacodon X: a triconodont spanning the Jurassic-Cretaceous divide
  97. Primates: Anglican archbishops, monkeys, etc.
  98. Primatomorpha: monkeys > tree shrews? Originally defined as Dermoptera + Primates.
  99. Prioniodinida X: : conodont group including the soft tissue fossil Promissum
  100. Prioniodontida X: conodonts with hairpin S-elements and more gracile P-elements
  101. Priscagamidae X: Late Cretaceous lizards on the agamid-chameleonid stem lineage
  102. Pristerodontia X:
  103. Pristidae
  104. Pristiophoridae
  105. Probainognathia
  106. Proboscidea
  107. Procellariiformes
  108. Procolophonia - herbivorous reptiles of the Permian and Triassic; may be ancestral to turtles.
  109. Procolophonidae X - stocky, Triassic lizard-like herbivores
  110. Procolophonoidea X: Procolophonids and their immediate ancestors and relatives
  111. Proconodontidae X:
  112. Procynosuchidae X:
  113. ProcynosuchusX: Late Permian amphibious cynodont
  114. Progalesaurus X:
  115. Proganochelys X
  116. Prolacertiformes X:
  117. Prosauropoda X:
  118. Protaspididae X: Early Devonian heterostracan fishes, morphologically intermediate between pteraspids and psammosteids
  119. Protaspidoidea X: Devonian heterostracan fishes, sister group of the pteraspids and including protaspidids and psammosteids
  120. Proterochampsidae X: poorly known croc-like archisauriforms from the Middle and Late Triassic of West Gondwana
  121. Proterochersis X: the oldest known pleurodire turtle, from the Late Triassic of Europe
  122. Proterogyrinus X: an Early Carboniferous embolomere --  looks like a lizard, put together like an amphibian
  123. Proterosuchidae X: a short branch from the archosauriform tree that never went anywhere, with very odd rostra.
  124. Prothoosuchus X: might be the same as Thoosuchus, a trematosauroid temnospondyl from the Early Triassic of Russia
  125. Protoceratopsidae X: the most basal ceratopsian dinosaurs
  126. Protocetidae: the first real radiation of whales
  127. Protopanderodontida X: a euconodont group, sister of the Prioniodontida, with a pair of incisor-like elements and a connected set of four pairs of relatively gracile (S?) elements
  128. Protopteraspididae X:
  129. Protorothyrididae X:
  130. Protospinax X
  131. Protosuchia X:
  132. Psammolepis X
  133. Psammosteida X
  134. Psammosteidae X:
  135. Psarolepis X: the most primitive sarcopterygian, from the Early Devonian of China
  136. Pseudictopidae X: poorly known fox-sized mammals, with trigonid much taller than talonid, from the Eocene of Central Asia
  137. Pseudopalatinae X: large, Late Triassic phytosaurs with a sagittal crest and orbits directed obliquely outwards and upwards
  138. Pseudopalatus X: a pseudopalatinine phytosaur closely related to Redondasaurus
  139. Psittaciformes: parrots
  140. Psittacosauridae X: a very basal family of ceratopsid dinosaurs from the Early Cretaceous of Asia
  141. Pteraspidida X: pteraspidiforms (jawless fish group) with separate cornual plates and unfused dorsal shield
  142. Pteraspididae X: typical pteraspids with the long rostrum, lateral & dorsal spines and small scales
  143. Pteraspidiformes X: the dominant group of Siluro-Devonian heterostracan jawless fishes
  144. Pteraspidina X: a rather primitive group of pteraspidiforms
  145. Pteraspidomorphi X: "alternate vertebrates" from the Ordovician through Devonian, with little internal skeleton and no paired appendages
  146. Pterodactyloidea X: advanced pterosaurs from the Late Jurassic and Cretaceous with short tails and long necks, often with head crests and with teeth reduced or absent.
  147. Pterosauria X: the pterosaurs
  148. Pterygolepis X: a Late Silurian anaspid (very primitive jawless fish)
  149. Ptyctodontida X: I once described ptyctodonts as looking like an upper class Englishman dressed for dinner. I stand by that description.
  150. Pycnodontiformes X: deep-bodied, durophagous halecostome fishes from the Triassic to Eocene
  151. Pycnosteidae X: deeply-keeled psammosteids from the Middle and Late Devonian of Europe
  152. Pythonomorpha: mosasaurs + snakes


  1. Quaesitosaurus X: a Mongolian sauropod and close relative of Nemegtosaurus


  1. Rajiformes: extant rays
  2. Raoellidae X: an Eocene group of basal suines
  3. Rapetosaurus X: "the most complete titanosaur yet discovered" from the Late Cretaceous of Madagascar
  4. Ratites: ostrich, emu, cassowary, kiwis, moas and various others
  5. Rauisuchia: Rauisuchus > Aetosaurus -- easy to define, but very uncertain what it incudes
  6. Rauisuchidae X: serious competitors of the early theropod dinosaurs
  7. Rauisuchiformes: probably includes all but the most basal crurotarsans
  8. Rebbachisauridae X: a poorly known, but perhaps widely-spread group of Cretaceous diplodocomorphs
  9. Rebbachisaurus X: yet another poorly-known basal Gondwanan diplodocomorph
  10. Redondasuchus X: a rather non-descript North American aetosaur
  11. Remingtonocetidae X: the first clearly aquatic members of the whale lineage
  12. Reptilia
  13. Reptiliomorpha
  14. Rhabdoderma X:a Carboniferous actinistian from Britain
  15. Rhabdodon  X
  16. Rhabdosteidae X:
  17. Rhamphorhynchoidea X: a group of long-tailed Jurassic pterosaurs with long, pointed jaws
  18. Rhenanida X: a strange group of ray-like placoderms
  19. Rhinatrematidae: a family of caecilians with more open skulls than most
  20. Rhinesuchidae X: a key group of large, Permo-Triassic temnospondyls from South Africa
  21. Rhinesuchus X: an early member of the family
  22. Rhipidistia: a big group of more derived sarcopterygians, with membership changing over the years.
  23. Rhizodontiformes X:
  24. Rhomaleosauridae X: a group of big-headed Jurassic pliosaurs with spatulate skulls
  25. Rhomaleosaurus X: a speciose genus of this family
  26. Rhynchocephalia: Sphenodon > snakes
  27. Rhyncholepidida X: a group of Silurian jawless fishes, part of the anaspid radiation
  28. Rhynchosauria X:
  29. Rhytidosteidae X:
  30. Riebeeckosaurus X
  31. Riojasaurus X
  32. Riojasuchus X
  33. Rodentia: rodents, of course
  34. Ruminantia: giraffes, deer & bovines
  35. Rutiodon X  a typical Carnian phytosaur
  36. Rutiodontinae X: large phytosaurs with rounded skulls and laterally-facing eyes


  1. Salmoniformes: salmon and osmeroid fishes
  2. Saltasaurinae X: advanced, armored titanosaurs of the Late Cretaceous
  3. Saltasaurus X: a small member of the above family
  4. Sanitheriidae X: a small family of suoids from the first half of the Miocene.
  5. Sarcopterygii: fishes with paired fins with a single basal and muscular lobes, cosmine scales, and enamelled on teeth -- including us.
  6. Sarcosuchus X: Paul Sereno's big croc, from the middle Cretaceous of Africa
  7. Sauria: archosaurs + lepidosaurs
  8. Saurichthyidae X: sort of proto-pike -- long, skinny fishes of the Early Mesozoic
  9. Saurischia: birds > Triceratops
  10. Sauropoda X: giant herbivorous dinosaurs
  11. Sauropodomorpha X: the stem group of sauropods: titanosaur > titmouse
  12. Sauroposeidon X: Brachiosaurus on steroids; possibly the largest terrestrial vertebrate of all time
  13. Sauropsida: snakes > St. Patrick
  14. Sauropterygia X: placodonts + plesiosaurs
  15. Saurosuchus X: a huge prestosuchid
  16. Scandentia: tree shrews
  17. Scelidosauridae X: a family of Jurassic ankylosauromorphs
  18. Scincomorpha: skinks
  19. Scleroglossa: all lizards and snakes except the Iguania
  20. ScleromochlusX:
  21. Sclerorhynchidae X: Mostly Late Cretaceous chondrichthyans intermediate between sawfish & rays.
  22. Scolecophidia: "blind snakes," tiny, very basal snakes.
  23. Scopelomorpha: blackchins and lanternfishes
  24. Scutellosaurus X: a small, Tithonian dinosaur, sister of the Thyreophoran group.
  25. Sebecosuchidae X: an interesting, poorly known group of early Cenozoic South American crocodiles.
  26. Selenodontia: all artiodactyls who aren't pigs.
  27. Selmacryptodira: all cryptodire turtles except Kayentachelys.
  28. Semionotiformes X: an important group of helecostome fishes through the entire Mesozoic.
  29. Serpentes: all snakes
  30. Serpianosaurus X: a rather nothosaur-like pachypleurosaur from the Middle Triassic of Europe
  31. Seymouriamorpha X: Permian competitors of the amniotes.
  32. Shastasauria X: the latest and greatest of the Triassic ichthyosaurs
  33. Shielia X: perhaps the most gnathostome-like of all thelodonts, from the Wenlock of Europe
  34. Shuvuuia X : a flightless alvarezsaurid protobird from the Late Cretaceous of Mongolia, with a well-preserved skull
  35. Siberiaspidoidei X: jawless amphiaspid fishes from the Early Devonian of Siberia, perhaps with two lateral line systems
  36. Siluriphysi: cat fishes, electric eels, and close relatives
  37. Simoedosauridae X: an obscure group of champsosaurs
  38. Simolestes X: a poorly known rhomaleosaurid pliosaur from the Early Jurassic
  39. Simosaurus X: somewhat intermediate between pachypleurosaurs and nothosaurs
  40. Sinamiidae X: Early Cretaceous neopterygian fishes, sister of the Amiidae
  41. Sinolepidae X: early antiarch placoderms with big, squarish heads
  42. Sinraptoridae X: a well known basal allosauroid group from the Late Jurassic of China.
  43. Sirenia: manatees & dugongs.
  44. Sirenidae: the crown group of living salamanders
  45. Smilosuchus X
  46. Solenodontidae: a tiny group of Carribean shrew-like insectivores
  47. Solnhofenamia X: Late Jurassic amiid fishes from Germany & France
  48. Somphospondylii X: Titanosaurs and their older cousins
  49. Sonorasaurus X: a middle Cretaceous brachiosaurid from North America.
  50. Soricidae: shrews
  51. Soricinae: Northern Hemisphere shrews with pigmented teeth and very high metabolic rates
  52. Soricoidea: shrews > moles
  53. Soricomorpha: shrews > hedgehogs
  54. Spalacotheriidae X: a small group of late "acute angle symmetrodonts." from China and North America.
  55. Spalacotheroidea X: possible mammals, including essentially all of the later "symmetrodonts"
  56. Spathicephalus X: a shovel-headed Carboniferous proto-baphetid known from both sides of the Atlantic.
  57. Sphenacodon X: an Early Permian "pelycosaur" -- close relative of Dimetrodon, but without the sailback fin.
  58. Sphenacodontia: Dimetrodon + Marilyn Monroe
  59. Sphenacodontidae X: Big sail-back carnivorous pelycosaurs and relatives. The dominant carnivores of the Early Permian.
  60. Sphenisciformes: penguins
  61. Sphenodontidae: clevosaurs and tuataras (Sphenodon).
  62. Sphenodontinae: Sphenodon + Eilenodon?
  63. Sphenosuchia X: paraphyletic group of all basal crocodylomorphs
  64. Sphenosuchidae X: erect, bipedal, terrestrial sphenosuchids of the Triassic and Jurassic
  65. Squalea: modern rays, skates, and non-galeomorph sharks
  66. Squalodontidae X: a family of dolphin-like whales from the Oligocene and Miocene
  67. Squalodontoidea X: rather small, early modern whales with long rostra and shark-like teeth.
  68. Squalomorpha
  69. Squamata: lizards and snakes
  70. Squatinactida X: a skate-like group of Carboniferous sharks
  71. Squatinidae: angel sharks
  72. Stagonolepis X: an aetosaur from the Late Triassic of Europe and North America
  73. Stegosauria X: Stegosaurus > Ankylosaurus
  74. Stegosauridae X: all stegosaurs except the basal Chinese forms
  75. Stegosaurinae X: the most specialized stegosaurs
  76. Stegosaurus X: the famous plate-backed dinosaur of North America
  77. Stenomylinae: X
  78. Stenopterygii: Mostly weird, deep-sea fishes, often with photophores and huge mouths
  79. Stenopterygius X: a Jurassic ichthyosaur similar to Ichthyosaurus
  80. Stereognathus X: one of the last basal cynodonts, from the Middle Jurassic of Europe
  81. Stereospondyli X: all stereosponylomorphs except the Permian archegosauroids
  82. Stereospondylomorpha X: a large group including most Mesozoic temnospondyls and some close relatives
  83. Stethacanthidae X: best-known of the paleozic sharks (Symmoriida) with an elaborate head-dress
  84. Sthenarosaurus X: an Early Juassic elasmosaur of uncertain affinities
  85. Strepsirhini: lemurs, lorises, indri, and related forms
  86. Strigiformes: owls
  87. Strunius X: a basal sarcopterygian fish which looks a lot like an actinopterygian
  88. Struthiocephalus X a Guadalupian tapinocephalid -- not as hideous as most
  89. Struthioniformes: ostriches
  90. Styloichthys: X: the sister of Rhipidistia (tetrapods + lungfish)
  91. Styracocephalus X: a basal dinocephalian therapsid, from the Guadalupian of South Africa
  92. Suchia: aetosaurs + alligators
  93. Suidae: pigs > peccaries
  94. Suina: pigs, hippos & extenct relatives
  95. Suinae: crown group of living suids
  96. Suini: Sus scrofa, the domestic pig, and very close relatives
  97. Suoidea: same as Suina, but without the oreodonts
  98. Sus: the domestic pig and its congenerics
  99. Symmetrodonta: by our reckoning, Kuehneotheriids + mammals
  100. Symmoriida X: symmoriid and stethacanthid sharks
  101. Symmoriidae X: symmoriid sharks with a single dorsal fin and well-developed claspers
  102. Synapsida: Darwin > Darwin's finches, from pelycosaurs to people.
  103. Synechodontiformes X: the Mesozoic sister group of the Neoselachii (living sharks)
  104. Synechodus X: the former Palaeospinax, about halfway from hybodonts to galeomorphs, from the Triassic to Eocene.
  105. Syodon X: a small anteosaur with a large pineal foramen, from the Permian of Russia.
  106. Syodontidae X: a family od smallish Late Permian anteosaurs known from both Russia and South Africa


  1. Talpoidea: moles
  2. Tapinocaninus X: a very large tapinocephalid therapsid from the Middle Permian of South Africa
  3. Tapinocephalia X: the herbivorous half of the dinocephalian lineage of Permian therapsids
  4. Tapinocephalidae X: specialized tapinocephalians with swollen cranial bones and interdigitating teeth.
  5. Tapinocephalus X: a big, robust therapsid which gave its name to the famous Tapinocephalus Zone of the Middle Permian Karoo.
  6. Tarsiiformes: tarsirs
  7. Tarjadia: X
  8. Tayassuidae: peccaries
  9. Teleosauridae X: Jurassic and Cretaceous crocs, marine but only minimally adapted for aquatic life
  10. Teleostei: the teleost fishes
  11. Teleostomi: the huge group uniting bony fish and acanthodians
  12. Telmabates X: an Eocene presbyornithid duck from South America
  13. Temnodontosaurus X: a 9m ichthyosaur with the largest eye of any vertebrate and a key transitional genus between Triassic and Jurassic ichthyosaurs
  14. Temnospondyls X: a large and succesful group of primitive amphibians from the Early Carboniferous to the Cretaceous.
  15. Tenontosauridae X: some rather late hypsilophodont-like iguanodonts
  16. Tenontosaurus X: a basal iguanodont from the middle Cretaceous of North America
  17. Tenrecoidea: tenrecs (endemic African shrew relatives)
  18. Terminonaris X: a very big croc from the Cretaceous of North America
  19. Testudines: turtles
  20. Tetanurae: all theropods except the ceratosaurs
  21. Tetraceratops X: either a very primitive therapsid or an aberrant pelycosaur
  22. Tetraconodontinae X: Miocene-Pliocene pigs often used in dating hominid localities
  23. Tetrapoda: see explanation at "What is a Tetrapod?"
  24. Tetrapoda*: see explanation at "What is a Tetrapod?"
  25. Tetrapodomorpha: lizards > lungfish
  26. Teviornis X: a Late Cretaceous duck from Mongolia
  27. Thalassiodracon X: a rather plesiosaur-like pliosaur from the Triassic and Jurassic of England
  28. Thaliacea: Salps. Free-living urochordates morphologically like Ascidiacean adults
  29. Thalattosuchia X: highly marine-adapted late Mesozoic & early Cenozoic crocs.
  30. Thecodontosaurus X: a small, very early prosauropod dinosaur.
  31. Thelodonti: paraphyletic, very diverse group of small Paleozoic jawless fishes with small scales
  32. Thelodontida X:
  33. Thelodontidae X:
  34. Therapsida
  35. Thereudontidae X:
  36. Theria
  37. Theriodontia
  38. Therizinosauridae X:
  39. Therizinosauroidea X
  40. Therocephalia X:
  41. Theropoda: carnivorous dinosaurs and birds
  42. Thescelosaurus X: a small hypsilophodont dinosaur from the Late Cretaceous
  43. Thoosuchinae X: trematosauroid temnospondyls, in fact possibly sysnonymous with Trematosaurus, from the Early Triassic of Russia
  44. Thoosuchus X: differs from Trematosaurus only in details of the squamosal
  45. Thrinaxodon X: a famous mammal-like cynodont from the Early Triassic of South Africa
  46. Thunnosauria X: aptly named "tuna lizards" -- strongly fish-like ichthyosaurs from the late Mesozoic.
  47. Thyestiida X: almost finless, tadpole-like osteostracans from the Late Silurian and Early Devonian of Europe
  48. Thyreophora X: stegosaurs, ankylosaurs and their stem group
  49. Ticinosuchus X: a very terrestrial prestosuchid from the Middle Triassic of Europe
  50. Tinamiformes: tinamous, living quail-like paleognathous flyers
  51. Tinodontidae X: a common tooth taxon of mainly Jurassic spalacotheroid symmetrodont mammals
  52. TitanophoneusX: the largest of the anteosaurs, a top predator of Late Permian Russia
  53. Titanosauria X: the last and probably largest and longest-living group of sauropods
  54. Titanosauridae X: a big family containing all the "traditional" titanosaurs
  55. Titanosauriformes X: Titanosaurus + Brachiosaurus
  56. Titanosaurus X: a remarkably scrappy sauropod, considering its fame, from the Late Cretaceous of India.
  57. Titanosuchidae X: a rather messy group of tapinocephalian therapsids from the Middle Permian of South Africa
  58. Titanosuchus X: the standard-bearer of the titanosuchidae.
  59. Tomistominae X: the "false gharial" of SE Asia
  60. Torpedinidae: the electric rays
  61. Torpediniformes: the two main families of electric rays
  62. Torvosauroidea X: spinosaurs and bunch of other basal theropods
  63. Toxodontia X: pig, hippo, and perhaps elephant analogs of the South American Paleogene ungulate radiation.
  64. Trematosauria X: Trematosaurus > Parotosuchus
  65. Trematosauridae X: specialized long-snouted fish-eaters of the Early Triassic, the only temnospondyls to adopt a marine existence
  66. Trematosauroidea X: Large, gharial-like forms with elongated rostrums, probably specialized for catching fish.
  67. Trematosaurus X: the name-sake of these clades.
  68. Trialestidae X: small, lightly built crodylomorphs with elongate limbs and digitigrade feet, from the Late Triassic of South America
  69. Tricleidia X: the last and most derived of the plesiosaurs
  70. Tricleidus X: a Late Jurassic plesiosaur of the above group
  71. Triconodonta X: carnivorous, cat-sized Mesozoic mammals who branched off after the marsupials, but well before placentals and marsupials
  72. Triconodontidae X: Jurassic European and Cretaceous North American triconodonts
  73. Triisodontidae X: the largest mammals of the Paleocene
  74. Trilophosauridae X: a very strange, herbivorous archosauromorph from the Triassic of Texas (one of personal favorites)
  75. Trioracodon X: a triconodont which appears to bridge the gap between Jurassic European and Cretaceous North American groups.
  76. Tristichopteridae X: a family of very large Middle and Late Devonian osteolepiforms
  77. Trithelodontidae X: sister of the mammaliaforms ... perhaps.
  78. Tritylodon X: a Late Triassic or Early Triassic cynognathian cynodont from South Africa
  79. Tritylodontidae X: the other possible candidate for mammaliaform sister group
  80. Troodontidae X: a family of weird Cretaceous dinosaurs quite close to the birds
  81. Tropiduridae: a family of iguanuan lizards with big tails and coarse scales
  82. Tubulidentata: aardvarks and their aancestors.
  83. Turiniidae X: a family of thelodont fishes that did very well in Devonian Gondwana
  84. Typhlopidae: a family of small to medium-sized, primitive, fossorial snakes
  85. Typotheria X: South American analogue of the rodents, Paleocene to Pleistocene
  86. Typothorax X: Advanced large broad-bodied aetosaur from the Late Triassic of North America.
  87. Tyrannosauridae X: Tyrannosaurus + Aublysodon
  88. Tyrannosaurinae X: Tyrannosaurus + Albertosaurus + Gorgosaurus
  89. Tyrannosaurini X: Tyrannosaurus > (Albertosaurus and Gorgosaurus), including Daspletosaurus and Tarbosaurus as well as the infamous Tyrannosaurus
  90. Tyrannosauroidea X: Tyrannosaurus > tiny birds (or any bird, for that matter), including the whole Cretaceous clade from Eotyrannus to Tyrannosaurus.


  1. Ulemosaurus X: a grotesque and primitive tapinocephalid therapsid from the Late Permian of Russia
  2. Umbra: the mudminnows
  3. Ungulata: the whole modern ungulate clan, used here as horses + cows.
  4. Ungulatomorpha: the ungulate stem group, cows > cats.
  5. Uranocentradon X: a fairly large and flatheaded rhinesuchid temnospondyl from the Permo-Triassic boundary in South Africa.
  6. Urochordata: an ancient group of marine suspension feeders with chordate characters in the larval stage.
  7. Urodela: salamanders
  8. Uropeltidae: "shield-tail snakes"
  9. Utatsusaurus X: the most primitive known ichthyosaurian, from the Early Triassic of Japan & Canada


  1. Varanidae: varanid lizards, including the Komodo dragon, the monitor lizards, etc.
  2. Varanodontinae X: an interesting family of very early, very primitive synapsid "pelycosaurs" from the Permo-Carboniferous
  3. Varanoidea
  4. Varanops X:
  5. Varanopseidae X
  6. Velosauria X
  7. Venaticosuchus X: a long-legged ornithosuchid archosaur from the Late Triassic of South America
  8. Venenosaurus X:  a middle Cretaceous sauropod from Utah, one possible sister of the Titanosauria
  9. Venyukovioidea X: small-headed anomodont therapsids, basal to the dromasaurs and dicynodonts
  10. Vertebrata: lampreys + gnathostomes: forms with at least some restriction of the notochord.
  11. Vidalamiinae X: big, nasty-looking amiid fishes from the Cretaceous to Eocene of Africa and South America
  12. Viperidae: adders, vipers, & copperheads
  13. Viperinae: "pitless" viperids
  14. Vulcanodontidae X: likely a poly- and/or paraphyletic group of very primitive sauropods
  15. Vulturides: teratorns & New World vultures, condors.


  1. Wuerhosaurus X: the sister genus of Stegosaurus, from the Early Cretaceous of China


  1. Xenacanthida X: Permo-Carboniferous fresh water sharks
  2. Xenarthra: armadillos, anteaters & sloths
  3. Xenocretosuchus X: a late tritylodont cynodont with moderately-well-developed molar-like cusps


  1. Yarengia X: an obsucure Early Triassic trematosaurian temnospondyl
  2. Younginiformes X: Medium-sized lizard-like Permo-Triassic diaspids, some forms very aquatic, closely related to the Sauria and to ichthyosaurs.
  3. Youngolepis X: a very early member of the lungfish lineage, from the Early Devonian of China
  4. Yunnanodon X: an Early Jurassic cynodont
  5. Yunnanolepidae X: Small, very primitive South China antiarch placoderms from the Early Devonian
  6. Yunnanolepidoidei X: Early Devonian Chinese antiarch placoderms with short, wide heads 
  7. Yunnanosaurus X: a remarkably late (Pliensbachian) prosauropod from China
  8. Yuzhoupliosaurus X: a Middle Jurassic rhomaleosaurid from China, known only from a mandible.


  1. Zalambdalestidae X: well-known, but poorly understood, early Eutherian mammals from the Asian Cretaceous
  2. Zenaspidida X: a family of cornuate cephalaspids with particularly massive headshield, from the Devonian.
  3. Zephyrosaurinae X: a small group of small dinosaurs -- North American hypsilophodonts
  4. Zhelestidae X: a (paraphyletic?) group of earliest ungulatomorphs.
  5. Zopherosuchus X: a small dinocephalian therapsid with thickened skull from the Middle & Late Permian of Russia.

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