Taxon Index: P-Z
- Pachycephalosauria X: Pachycephalosaurus > Triceratops
- Pachycephalosauridae X: the classic bone-dome dinosaurs
- Pachycormiformes X: possibly the sister group of the teleosts, and probably the
largest actinopterygians ever
- Pachygenelius X: a trithelodont cynodont from the Early Jurassic of South Africa
and perhaps elsewhere
- Pachyophiidae X: a controversial family of Late Cretaceous aquatic
- Pachypleurosauridae X: small, Middle to Late Triassic aquatic lepidosauromorphs,
cousins of the notosaurs
- Paenungulata: the part of Afrotheria that is morphologically sound -- elephants, sea
cows, & hyraxes
- Pakicetidae X: the first cetaceans, from the Early Eocene of South
- Palaeoryctidae X: very early (Cretaceous?) members of the shrew lineage ... maybe
- Palaeospinacidae X: Synechodus and others probably just outside the crown group
of living sharks (Neoselachii)
- Paleognathae: ratites and their ancestors
- Paleorhinus X: a large, somewhat confused, genus of phytosaurs
- Panderichthys X: a well-known almost-tetrapod from the Late Devonian
of the Baltics
- Paraconodontida X: very basal Cambrian conodonts
- Paralititan X: Josh Smith's giant Egyptian sauropod
- Parapternodontidae X: probably the sister group of living shrews, from the Eocene of
- Paraorthacodus X: a tooth genus of palaeospinacid sharks
- Parasemionotidae X: earliest (Triassic) and most basal family of halecomorph
- Parasuchus X: a phytosaur -- probably a synonym of Paleorhinus
- Parathrinaxodon X: a basal cynodont, possibly synonymous with Procynosuchus
- Paratypothorax X: a late surviving phytosaur
- Pareiasauria X:
very large anapsid herbivores of the Permian -- possible turtle ancestors.
- Parvicursor X: a tiny, poorly known alvarezsaurid bird from the Late Cretaceous
- Parvipelvia X: Jurassic ichthyosaurs and their Cretaceous descendants
- Passeriformes: perching songbirds
- Patagonykus X: an alvarezsaurid ?bird from the Late Cretaceous of South
- Patagopterygiformes X: a family of rather modern-looking ornithurine birds
from the Early Cretaceous of South America and ?China
- Paucituberculata: rat opossums, South American marsupials
- Paulchoffatiidae X: the most basal multituberculates -- from the Late
Jurassic of Europe.
- Pelecaniformes: pelicans, frigate birds, and tropic birds.
- Pelomedusidae: medium to large size freshwater aquatic turtles from Africa and South
- Pelomedusoidea: all derived pleurodire (side-necked) turtles, i.e. pelomedusids +
- Peloneustes X: a relatively small, squid-eating pliosaur from the Late Jurassic
- Pelorosaurus X: a poorly known, possibly non-existent, brachiosaurid dinosaur from the Early
Cretaceous of Europe
- Peramelina: bilbeys and bandicoots
- Perissodactyla: horses, rhinos & tapirs
- Petalichthyida X: a peculiar, hard-to-place group of placoderms from
the Early Devonian
X: indescribably weird-looking early
chondrichthyans, e.g., Balantsea
- Petromyzontiformes: lampreys
- Phacochoerini: wart hogs
- Phacochoerus: the extant African warthog
- Pharyngolepis X: a very basal
anaspid from the Silurian of Europe
- Phasianidae: chickens, pheasants, peacocks, turkeys, etc
- Phlebolepis X: a relatively well-known and widely distributed Silurian
- Phlyctaenioidei X: a group of arthrodire
- Phoebodontidae X: broad-headed, blunt-snouted ctenacanthiform sharks
from the Devonian to the Triassic
- Phoenicopteriformes: flamingos
- Pholiderpeton X: an odd, long-bodied Bashkirian embolomere from Scotland
- Pholidogaster X: an earlier embolomere, also Scottish, with reduced limbs
- Pholidota: pangolins (armored eutherian mammals)
- Phthinosuchidae X: very poorly known, very basal therapsids from the
Late Permian of Russia
- Phyllolepida X: large, late placoderms with terassed armor
- Physeteroidea: sperm whales and relatives
big, gavial-like (but more terrestrial) proto-crocs from the Late Triassic
Piciformes: woodpeckers & toucans
- Pistosaurus X: the sister of Plesiosauria -- and more than half-way between
nothosaurs and plesiosaurs
Pituriaspida X: a unique, but poorly known group of cephalaspid
fishes from the Early Devonian of Australia
- Placerias X: a huge, well-known Kannemeyerid dicynodont from the Triassic of
- Placodermi X: placoderms
- Placodontia X: big, walrus-like sauropterygians from the Triassic of Europe.
- Plagiosauridae X: bizarre, crescent-headed temnospondyls (like Gerrothorax)
from the Triassic of Europe and Greenland
- Plagiosauroidea X: Triassic temnospondyls with short, wide skulls and
- Plataleidae: ibis and spoonbills
- Plateosauridae X: European prosauropods of the Late Triassic and Early
- Platycraniellus X: a poorly known Early Triassic galesaurid cynodont from South
- Platypterygius X widely occuring large Cretaceous ichthyosaur, distinguished by longer body and paddles than its Jurassic ophthalmosaur ancestors. Divided into a number of subgenera
- Platyrrhini: New World monkeys
- Plesiadapiformes X: Paleocene and Eocene mammals, the sister group of Primates
Plesiopleurodon X: a pliosaurid from the Late Cretaceous of North America.
- Plesiosauria X: all plesiosaurs and pliosaurs
- Plesiosauroidea X: the plesiosaurs -- small-headed, long-necked aquatic reptiles
- Plesiosaurus X: the best known plesiosaur, from the Early Jurassic of Europe
- Pleurodira: one of
the two great turtle lineages, now restricted to Gondwanan lands
- Pleurosauridae X: Jurassic and Cretaceous marine rhynchocephalians,
sister to the sphenodonts
- Pliosauridae X: Jurassic and Cretaceous pliosaurs with very large skulls
- Pliosauroidea X: all pliosaurs, medium to very large marine reptiles of the Mesozoic.
- Pliosaurus X: a large pliosaurid from the Jurassic of Europe.
- Podocnemidae: Fresh water turtles from South America.
- Podcnemoidae: podcnemid turtles and their extinct bothremyid sister group.
- Poebrotherium X: : the earliest of the Camelidae
Polybranchiaspidida X: Devonian galeaspid fishes with many (10-45) gill openings
Polybranchiaspidiformes X: a paraphyletic group of late (Devonian) galeaspid
Polycotylidae X: a
family of Cretaceous plesiosaurs, sister of the elasmosaurs
- Polycryptodira: living cryptodire (Gondwanan) turtles
Polyosteorhynchus X: a Bear Gulch actinistian
- Polypteriformes: a strange living order of very basal actinopterygian fishes, including
bichirs and reedfish
- Poposauridae X: a family of archosaurs wedged between the
rauisuchids and the crocodylomorphs
Porolepiformes X: Devonian sarcopterygian fishes, sister to either the lungfishes or the
- Potamochoerini: the bush pig & giant forest hog of Africa
- Powichthys X: probably a very early lungfish (dipnomorph)
- Presbyornis X: a very important and succesful early duck/goose, known from the
Cretaceous to the Late Eocene
- Presbyornithidae X: the family of Presbyornis
- Prestosuchidae X: the most basal family on the croc side of the croc-dinosaur
- Priacodon X: a triconodont spanning the Jurassic-Cretaceous divide
- Primates: Anglican archbishops, monkeys, etc.
- Primatomorpha: monkeys > tree shrews? Originally defined as Dermoptera + Primates.
- Prioniodinida X: : conodont group including the soft tissue fossil Promissum
- Prioniodontida X: conodonts with hairpin S-elements and more gracile P-elements
- Priscagamidae X: Late Cretaceous lizards on the agamid-chameleonid stem lineage
- Pristerodontia X:
- Procolophonia - herbivorous reptiles of the Permian and Triassic; may be ancestral to turtles.
- Procolophonidae X - stocky, Triassic lizard-like herbivores
- Procolophonoidea X: Procolophonids and their immediate ancestors and relatives
- Proconodontidae X:
- Procynosuchidae X:
- ProcynosuchusX: Late Permian amphibious cynodont
- Progalesaurus X:
- Prosauropoda X:
Protaspididae X: Early Devonian heterostracan fishes, morphologically intermediate between
pteraspids and psammosteids
Protaspidoidea X: Devonian heterostracan fishes, sister group of the pteraspids and
including protaspidids and psammosteids
Proterochampsidae X: poorly known croc-like archisauriforms from the
Middle and Late Triassic of West Gondwana
- Proterochersis X: the oldest known pleurodire turtle, from the Late
Triassic of Europe
- Proterogyrinus X: an Early Carboniferous embolomere -- looks like a lizard,
put together like an amphibian
Proterosuchidae X: a short branch from the archosauriform tree that never went
anywhere, with very odd rostra.
- Prothoosuchus X: might be the same as Thoosuchus, a trematosauroid
temnospondyl from the Early Triassic of Russia
- Protoceratopsidae X: the most basal ceratopsian dinosaurs
- Protocetidae: the first real radiation of whales
- 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
- Protorothyrididae X:
- Protosuchia X:
- Psarolepis X: the most primitive sarcopterygian, from the Early Devonian of
- Pseudictopidae X: poorly known fox-sized mammals, with trigonid much taller than
talonid, from the Eocene of Central Asia
- Pseudopalatinae X: large, Late Triassic phytosaurs with a sagittal crest and orbits directed obliquely outwards and
- Pseudopalatus X: a pseudopalatinine phytosaur closely related to Redondasaurus
- Psittaciformes: parrots
- Psittacosauridae X: a very basal family of ceratopsid dinosaurs from the
Early Cretaceous of Asia
Pteraspidida X: pteraspidiforms (jawless fish group) with separate cornual plates
and unfused dorsal shield
Pteraspididae X: typical pteraspids with the long rostrum, lateral & dorsal spines and
Pteraspidiformes X: the dominant group of Siluro-Devonian heterostracan
Pteraspidina X: a rather primitive group of pteraspidiforms
- Pteraspidomorphi X: "alternate vertebrates" from the
Ordovician through Devonian, with little internal skeleton and no paired
- 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.
- Pterosauria X: the pterosaurs
Pterygolepis X: a Late Silurian anaspid (very primitive jawless fish)
- Ptyctodontida X: I once described ptyctodonts as looking like an
upper class Englishman dressed for dinner. I stand by that description.
- Pycnodontiformes X: deep-bodied, durophagous halecostome fishes from the Triassic to
Pycnosteidae X: deeply-keeled psammosteids from the Middle and Late Devonian of Europe
- Pythonomorpha: mosasaurs + snakes
- Quaesitosaurus X: a Mongolian sauropod and close relative of Nemegtosaurus.
Rajiformes: extant rays
- Raoellidae X: an Eocene group of basal suines
- Rapetosaurus X: "the most complete titanosaur yet discovered" from
the Late Cretaceous of Madagascar
- Ratites: ostrich,
emu, cassowary, kiwis, moas and various others
- Rauisuchia: Rauisuchus > Aetosaurus -- easy to define, but very uncertain
what it incudes
- Rauisuchidae X: serious competitors of the early theropod dinosaurs
- Rauisuchiformes: probably includes all but the most basal crurotarsans
Rebbachisauridae X: a
poorly known, but perhaps widely-spread group of Cretaceous
Rebbachisaurus X: yet another poorly-known basal Gondwanan
X: a rather non-descript North American aetosaur
Remingtonocetidae X: the first clearly aquatic members of the
X:a Carboniferous actinistian from Britain
- Rhabdosteidae X:
- Rhamphorhynchoidea X: a group of long-tailed Jurassic pterosaurs with
long, pointed jaws
- Rhenanida X: a strange group of ray-like placoderms
- Rhinatrematidae: a family of caecilians with more open skulls than most
- Rhinesuchidae X: a key group of large, Permo-Triassic temnospondyls from South
- Rhinesuchus X: an early member of the family
- Rhipidistia: a
big group of more derived sarcopterygians, with membership changing over
- Rhizodontiformes X:
Rhomaleosauridae X: a group of big-headed Jurassic pliosaurs with spatulate skulls
Rhomaleosaurus X: a speciose genus of this family
- Rhynchocephalia: Sphenodon > snakes
- Rhyncholepidida X: a group of Silurian jawless fishes, part of the
- Rhynchosauria X:
- Rhytidosteidae X:
- Riebeeckosaurus X
- Riojasaurus X
- Riojasuchus X
- Rodentia: rodents, of course
- Ruminantia: giraffes, deer & bovines
X a typical Carnian phytosaur
- Rutiodontinae X: large phytosaurs with rounded skulls and laterally-facing eyes
- Salmoniformes: salmon and osmeroid fishes
- Saltasaurinae X: advanced, armored titanosaurs of the Late Cretaceous
- Saltasaurus X: a small member of the above family
- Sanitheriidae X: a small family of suoids from the first half of the Miocene.
Sarcopterygii: fishes with paired fins with a single basal and muscular lobes, cosmine
scales, and enamelled on teeth -- including us.
- Sarcosuchus X: Paul Sereno's big croc, from the middle Cretaceous of Africa
- Sauria: archosaurs + lepidosaurs
- Saurichthyidae X: sort of proto-pike -- long, skinny fishes of the Early Mesozoic
- Saurischia: birds
- Sauropoda X: giant herbivorous dinosaurs
Sauropodomorpha X: the stem group of sauropods: titanosaur >
- Sauroposeidon X: Brachiosaurus on steroids; possibly the largest
terrestrial vertebrate of all time
- Sauropsida: snakes > St. Patrick
- Sauropterygia X: placodonts + plesiosaurs
- Saurosuchus X: a huge prestosuchid
- Scandentia: tree shrews
- Scelidosauridae X: a family of Jurassic ankylosauromorphs
- Scincomorpha: skinks
- Scleroglossa: all lizards and snakes except the Iguania
Sclerorhynchidae X: Mostly
Cretaceous chondrichthyans intermediate between sawfish & rays.
- Scolecophidia: "blind snakes," tiny, very basal snakes.
- Scopelomorpha: blackchins and lanternfishes
- Scutellosaurus X: a small, Tithonian dinosaur, sister of the Thyreophoran group.
- Sebecosuchidae X: an interesting, poorly known group of early Cenozoic
South American crocodiles.
- Selenodontia: all artiodactyls who aren't pigs.
all cryptodire turtles except Kayentachelys.
Semionotiformes X: an important group of helecostome fishes through the entire
- Serpentes: all
Serpianosaurus X: a rather nothosaur-like pachypleurosaur from the
- Seymouriamorpha X: Permian competitors of the amniotes.
- Shastasauria X: the latest and greatest of the Triassic ichthyosaurs
- Shielia X: perhaps the most gnathostome-like of all thelodonts, from the
Wenlock of Europe
a flightless alvarezsaurid protobird from the Late Cretaceous of Mongolia,
with a well-preserved skull
- Siberiaspidoidei X: jawless amphiaspid fishes from the Early Devonian of Siberia,
perhaps with two lateral line systems
- Siluriphysi: cat
fishes, electric eels, and close relatives
Simoedosauridae X: an obscure group of champsosaurs
- Simolestes X: a poorly known rhomaleosaurid pliosaur from the Early Jurassic
- Simosaurus X: somewhat intermediate between pachypleurosaurs and nothosaurs
- Sinamiidae X: Early Cretaceous neopterygian fishes, sister of the Amiidae
- Sinolepidae X: early antiarch placoderms with big, squarish heads
- Sinraptoridae X: a well known basal allosauroid group from the
Jurassic of China.
- Sirenidae: the
crown group of living salamanders
- Smilosuchus X
- Solenodontidae: a tiny group of Carribean shrew-like insectivores
- Solnhofenamia X: Late Jurassic
amiid fishes from Germany & France
Somphospondylii X: Titanosaurs and their older cousins
- Sonorasaurus X: a middle
Cretaceous brachiosaurid from North America.
- Soricinae: Northern Hemisphere shrews with pigmented teeth and very high metabolic
Soricoidea: shrews > moles
Soricomorpha: shrews > hedgehogs
Spalacotheriidae X: a small group of late "acute angle
symmetrodonts." from China and North America.
Spalacotheroidea X: possible mammals, including essentially all of the
Spathicephalus X: a shovel-headed Carboniferous proto-baphetid known from both sides
of the Atlantic.
- Sphenacodon X: an Early Permian "pelycosaur" -- close
relative of Dimetrodon, but without the sailback fin.
- Sphenacodontia: Dimetrodon + Marilyn Monroe
- Sphenacodontidae X: Big sail-back carnivorous pelycosaurs and relatives.
The dominant carnivores of the Early Permian.
- Sphenisciformes: penguins
- Sphenodontidae: clevosaurs and tuataras (Sphenodon).
- Sphenodontinae: Sphenodon + Eilenodon?
- Sphenosuchia X: paraphyletic group of all basal crocodylomorphs
- Sphenosuchidae X: erect, bipedal, terrestrial sphenosuchids of the
Triassic and Jurassic
Squalea: modern rays, skates, and non-galeomorph sharks
- Squalodontidae X: a family of dolphin-like whales from the Oligocene and Miocene
- Squalodontoidea X: rather small, early modern whales with long rostra and
- Squamata: lizards and snakes
- Squatinactida X: a skate-like group of Carboniferous sharks
- Squatinidae: angel sharks
- Stagonolepis X: an aetosaur from the Late Triassic of Europe and North America
Stegosauria X: Stegosaurus > Ankylosaurus
- Stegosauridae X: all stegosaurs except the basal Chinese forms
- Stegosaurinae X: the most specialized stegosaurs
- Stegosaurus X: the famous plate-backed dinosaur of North America
- Stenomylinae: X
- Stenopterygii: Mostly weird, deep-sea fishes, often with photophores and huge mouths
- Stenopterygius X: a Jurassic ichthyosaur similar to Ichthyosaurus
- Stereognathus X: one of the last basal cynodonts, from the Middle Jurassic of
- Stereospondyli X: all stereosponylomorphs except the Permian archegosauroids
- Stereospondylomorpha X: a large group including most Mesozoic temnospondyls and some close
Stethacanthidae X: best-known of the paleozic sharks (Symmoriida) with
an elaborate head-dress
Sthenarosaurus X: an Early Juassic elasmosaur of uncertain affinities
- Strepsirhini: lemurs, lorises, indri, and related forms
- Strunius X: a basal sarcopterygian fish which looks a lot like an
X a Guadalupian tapinocephalid -- not as hideous as most
- Struthioniformes: ostriches
X: the sister of Rhipidistia (tetrapods + lungfish)
- Styracocephalus X: a basal dinocephalian therapsid, from the Guadalupian of South
- Suchia: aetosaurs + alligators
- Suidae: pigs > peccaries
- Suina: pigs, hippos & extenct relatives
- Suinae: crown group of living suids
scrofa, the domestic pig, and very close relatives
- Suoidea: same as Suina, but without the oreodonts
- Sus: the domestic pig and its congenerics
- Symmetrodonta: by our reckoning, Kuehneotheriids + mammals
- Symmoriida X: symmoriid and stethacanthid sharks
- Symmoriidae X: symmoriid sharks with a single dorsal fin and
- Synapsida: Darwin
> Darwin's finches, from pelycosaurs to people.
- Synechodontiformes X: the Mesozoic sister group of the Neoselachii (living sharks)
- Synechodus X: the former Palaeospinax, about halfway from hybodonts to
galeomorphs, from the Triassic to Eocene.
- Syodon X: a small anteosaur with a large pineal foramen, from the Permian of Russia.
- Syodontidae X: a family od smallish Late Permian anteosaurs known from both
Russia and South Africa
- Tapinocaninus X: a very large tapinocephalid therapsid from the Middle Permian of
- Tapinocephalia X: the herbivorous half of the dinocephalian lineage of
- Tapinocephalidae X: specialized tapinocephalians with swollen cranial bones and
- Tapinocephalus X: a big, robust therapsid which gave its name to the famous Tapinocephalus
Zone of the Middle Permian Karoo.
- Tarsiiformes: tarsirs
- Tayassuidae: peccaries
- Teleosauridae X: Jurassic and Cretaceous crocs, marine but only
minimally adapted for aquatic life
- Teleostei: the
- Teleostomi: the huge group uniting bony fish and acanthodians
- Telmabates X: an Eocene presbyornithid duck from South America
- Temnodontosaurus X: a 9m ichthyosaur with the largest eye of any vertebrate and a key
transitional genus between Triassic and Jurassic ichthyosaurs
- Temnospondyls X: a large and succesful group of primitive amphibians from the Early
Carboniferous to the Cretaceous.
- Tenontosauridae X: some rather late hypsilophodont-like iguanodonts
- Tenontosaurus X: a basal iguanodont from the middle Cretaceous of North
Tenrecoidea: tenrecs (endemic African shrew relatives)
- Terminonaris X: a very big croc from the Cretaceous of North America
- Testudines: turtles
- Tetanurae: all theropods except the ceratosaurs
- Tetraceratops X: either a very primitive therapsid or an aberrant
- Tetraconodontinae X: Miocene-Pliocene pigs often used in dating hominid localities
Tetrapoda: see explanation at
is a Tetrapod?"
Tetrapoda*: see explanation at
is a Tetrapod?"
- Tetrapodomorpha: lizards > lungfish
- Teviornis X: a Late Cretaceous duck from Mongolia
Thalassiodracon X: a rather plesiosaur-like pliosaur from the Triassic and Jurassic
- Thaliacea: Salps. Free-living urochordates morphologically like Ascidiacean adults
- Thalattosuchia X: highly marine-adapted late Mesozoic & early
Thecodontosaurus X: a small, very early prosauropod dinosaur.
Thelodonti: paraphyletic, very diverse group of small Paleozoic jawless fishes with
- Thelodontida X:
- Thelodontidae X:
- Therocephalia X:
- Theropoda: carnivorous dinosaurs and birds
- Thescelosaurus X: a small hypsilophodont dinosaur from the Late
- Thoosuchinae X: trematosauroid temnospondyls, in fact possibly sysnonymous with Trematosaurus,
from the Early Triassic of Russia
- Thoosuchus X: differs from Trematosaurus only in details of the
- Thrinaxodon X: a famous mammal-like cynodont from the Early
Triassic of South Africa
- Thunnosauria X: aptly named "tuna lizards" -- strongly fish-like
ichthyosaurs from the late Mesozoic.
Thyestiida X: almost finless, tadpole-like osteostracans from the Late Silurian
and Early Devonian of Europe
- Thyreophora X: stegosaurs, ankylosaurs and their stem group
- Ticinosuchus X: a very terrestrial prestosuchid from the
Middle Triassic of
- Tinamiformes: tinamous, living quail-like paleognathous flyers
Tinodontidae X: a common tooth taxon of mainly Jurassic spalacotheroid symmetrodont
X: the largest of the anteosaurs, a top predator of Late Permian
- Titanosauria X: the last and probably largest and longest-living
group of sauropods
- Titanosauridae X: a big family containing all the "traditional"
Titanosauriformes X: Titanosaurus + Brachiosaurus
- Titanosaurus X: a remarkably scrappy sauropod, considering its fame, from the
Late Cretaceous of India.
- Titanosuchidae X: a rather messy group of tapinocephalian therapsids from the Middle
Permian of South Africa
- Titanosuchus X: the standard-bearer of the titanosuchidae.
- Tomistominae X: the "false gharial" of SE Asia
Torpedinidae: the electric rays
Torpediniformes: the two main families of electric rays
Torvosauroidea X: spinosaurs and bunch of other basal theropods
- Toxodontia X: pig, hippo, and perhaps elephant analogs of the South American
Paleogene ungulate radiation.
- Trematosauria X: Trematosaurus > Parotosuchus
- Trematosauridae X: specialized long-snouted fish-eaters of the Early
Triassic, the only temnospondyls to adopt a marine existence
- Trematosauroidea X: Large, gharial-like forms with elongated rostrums,
probably specialized for catching fish.
- Trematosaurus X: the name-sake of these clades.
- Trialestidae X: small, lightly built crodylomorphs with elongate
limbs and digitigrade feet, from the Late Triassic of South America
- Tricleidia X: the last and most derived of the plesiosaurs
- Tricleidus X: a Late Jurassic plesiosaur of the above group
- Triconodonta X: carnivorous, cat-sized Mesozoic mammals who branched off after the
marsupials, but well before placentals and marsupials
- Triconodontidae X: Jurassic European and Cretaceous North American triconodonts
- Triisodontidae X: the largest mammals of the Paleocene
Trilophosauridae X: a very strange, herbivorous archosauromorph from the
Triassic of Texas (one of personal favorites)
- Trioracodon X: a triconodont which appears to bridge the gap between Jurassic
European and Cretaceous North American groups.
Tristichopteridae X: a family of very large Middle and Late Devonian
- Trithelodontidae X: sister of the mammaliaforms ... perhaps.
- Tritylodon X: a Late Triassic or Early Triassic cynognathian cynodont from South
- Tritylodontidae X: the other possible candidate for mammaliaform sister
Troodontidae X: a
family of weird Cretaceous dinosaurs quite close to the birds
- Tropiduridae: a family of iguanuan lizards with big tails and coarse scales
Tubulidentata: aardvarks and their aancestors.
- Turiniidae X: a family of thelodont fishes that did very well in Devonian
- Typhlopidae: a family of small to medium-sized, primitive, fossorial snakes
- Typotheria X: South American analogue of the rodents, Paleocene to Pleistocene
- Typothorax X: Advanced large broad-bodied aetosaur from the Late Triassic of
Tyrannosauridae X: Tyrannosaurus + Aublysodon
- Tyrannosaurinae X: Tyrannosaurus + Albertosaurus + Gorgosaurus
- Tyrannosaurini X: Tyrannosaurus > (Albertosaurus and Gorgosaurus),
including Daspletosaurus and Tarbosaurus as well as the
- Tyrannosauroidea X: Tyrannosaurus > tiny birds (or any bird, for that
matter), including the whole Cretaceous clade from Eotyrannus to Tyrannosaurus.
- Ulemosaurus X: a grotesque and primitive tapinocephalid therapsid from the Late
Permian of Russia
- Umbra: the mudminnows
- Ungulata: the whole modern ungulate clan, used here as horses + cows.
- Ungulatomorpha: the ungulate stem group, cows > cats.
- Uranocentradon X: a fairly large and flatheaded rhinesuchid temnospondyl from the
Permo-Triassic boundary in South Africa.
- Urochordata: an ancient group of marine suspension feeders with chordate characters in
the larval stage.
- Urodela: salamanders
- Uropeltidae: "shield-tail snakes"
- Utatsusaurus X: the most primitive known ichthyosaurian, from the Early
Triassic of Japan & Canada
- Varanidae: varanid lizards, including the Komodo dragon, the monitor lizards, etc.
- Varanodontinae X: an interesting family of very early, very primitive
synapsid "pelycosaurs" from the Permo-Carboniferous
- Varanops X:
- Velosauria X
Venaticosuchus X: a long-legged ornithosuchid archosaur from the Late Triassic
of South America
- Venenosaurus X: a middle Cretaceous sauropod from Utah, one possible
sister of the Titanosauria
- Venyukovioidea X: small-headed anomodont therapsids, basal to the dromasaurs and
- Vertebrata: lampreys + gnathostomes: forms with at least some restriction of the
- Vidalamiinae X: big, nasty-looking amiid fishes from the Cretaceous to Eocene of
Africa and South America
- Viperidae: adders, vipers, & copperheads
- Viperinae: "pitless" viperids
Vulcanodontidae X: likely a poly- and/or paraphyletic group of very
- Vulturides: teratorns & New World vultures, condors.
- Wuerhosaurus X:
the sister genus of Stegosaurus, from the Early Cretaceous of China
- Xenacanthida X: Permo-Carboniferous fresh water sharks
- Xenarthra: armadillos, anteaters & sloths
- Xenocretosuchus X: a late tritylodont cynodont with moderately-well-developed
- Yarengia X: an obsucure Early Triassic trematosaurian temnospondyl
- Younginiformes X: Medium-sized lizard-like Permo-Triassic diaspids, some forms very aquatic,
closely related to the Sauria and to ichthyosaurs.
Youngolepis X: a very early member of the lungfish lineage, from
the Early Devonian of China
- Yunnanodon X: an Early Jurassic cynodont
- Yunnanolepidae X: Small, very primitive South China antiarch
placoderms from the Early Devonian
- Yunnanolepidoidei X: Early Devonian Chinese antiarch placoderms with
short, wide heads
- Yunnanosaurus X: a remarkably late (Pliensbachian) prosauropod from
Yuzhoupliosaurus X: a Middle Jurassic rhomaleosaurid from China, known only from a
- Zalambdalestidae X: well-known, but poorly understood, early Eutherian mammals from
the Asian Cretaceous
Zenaspidida X: a family of cornuate cephalaspids with particularly massive
headshield, from the Devonian.
- Zephyrosaurinae X: a small group of small dinosaurs -- North American hypsilophodonts
- Zhelestidae X: a (paraphyletic?) group of earliest ungulatomorphs.
- Zopherosuchus X: a small dinocephalian therapsid with thickened skull from
the Middle & Late Permian of Russia.