Taxon Index: L-O
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-L-
- Labridae: wrasses
- Labroidei: cichlids, wrasses, damselfish, parrotfishes
- Laccocephalus X: a rhinesuchid temnospondyl from just before or just after the end-Permian extinction
- Lagerpeton X: an ornithodiran archosaur from the Middle Triassic of South America, the sister of all other dinosauromorphs
- Lagomorpha: rabbits & pikas
- Lagosuchidae X : important protodinosaurs from Triassic South America
- Laidleria X: a notably flat and triangular-headed temnospondyl from the Early Triassic of South Africa
- Lambeosaurinae X: advanced Late Cretaceous hadrosaurs with expansive hollow crests.
- Lamniformes: mackerel and Basking sharks
- Lampridiformes: opahs, crestfish, ribbonfish, oarfish
- Lanarkia X: a thelodontid thelodont -- the only thelodont with two distinct, but mixed, types of body scales.
- Lanthanosuchidae X: they look like temnospondyls but are actually anapsids
- Lanthanotidae: earless monitor lizards
- Lapillopsidae X: a small group of small temnospondyls from the Early Triassic of Australia
- Lapparentosaurus X: a close relative of Brachiosaurus, from the Middle Jurassic of Madagascar.
- Lariosaurus X: a Middle Triassic nothosaur from Europe with peculiarly expanded forearms
- Larvacea : tiny, planktonic urochordates which build gelatinous "houses"
- Leaellynasaurua X: a small hypsilophodont dinosaur from the middle Cretaceous of Australia
- Lemuriformes: indri and lemurs
- Lemuroidea: lemurs
- Lepidosauria: sphenodonts, lizards, mosasaurs & snakes
- Lepidosauriformes: probably mosasaurs > plesiosaurs
- Lepidosauromorpha: lizards > buzzards
- Lepisosteiformes: gars
- Lepospondyli: toads > Texans
- Leptictida X: possibly the stem group of Pholidota (pangolins)
- Leptocleidus X: a smallish rhomaleosaurid pliosaur from the Early Cretaceous.
- Leptotyphlopidae: small (10-25 cm) fossorial snakes, near the base of the snake radiation
- Lexovisaurus X: a European cousine of Stegosaurus.
- Libycosuchidae X: short-snouted, hyena-like crocs from the Cretaceous of Africa
- Limnarchia X: all temnospondyls except edopoids and Euskelia
- Liopleurodon X: the classic big, mean, Jurassic pliosaur
- Lissamphibia: living amphibians
- Lithornithiformes X: early paleognathous birds from the Paleocene and Eocene
- Livoniana X
- Lochmocercus: X another Bear Gulch actinistian
- Loganellia X: a rather gnathostome-like jawless fish of the thelodont persuasion
- Loganiidae X: Silurian theolodonts, possible sister group of the gnathostomes
- Longosuchus X
- Lorisiformes: pottos, lorises & galagos (lemur-like primates)
- Lourinhasaurus X: an early camarasaur from Portugal
- Loxomma X: a baphetid tetrapod from the Early Carboniferous
- Lupeosaurus X: a poorly-known edaphosaurid from Texas
- Luzocephalidae X: some of the first temnospondyls to appear after the end-Permian extinction
- Lydekkerinidae X: Triassic capitosaur temnospondyls
- Lysorophia X: Permo-Carboniferous microsaurs, possible sister group of living amphibians
- Lystrosaurus X: the well-known South African dicynodont almost synonymous with the Permo-Triassic transition.
-M-
- Macronaria X: Brachiosaurus > Diplodocus.
- Macroplata X: an Early Jurassic pliosaur
- Macroscelidea: elephant shrews
- Macrosemiiformes X Mesozoic neopterygians with 7 odd, scroll-shaped infraorbitals
- Macrostomata: advanced snakes with large gapes (Crotalus > Anilius)
- Madtsoiidae X: basal macrostomate snakes from Gondwana which persisted in Australia through the Pleistocene
- Magyarosaurus X: a "dwarf" titanosaur from the Late Cretaceous of Eastern Europe
- Mamenchisauridae X: perhaps the world's longest neck on some Chinese sauropods of uncertain relationships
- Mammalia: mammals, used here as the crown group monotremes + mastodons
- Mammaliaformes: mammals and not quite mammals -- defined as a crown group for some reason -- Sinocodon + snow leopards
- Mandageria X: a derived tristichopterid sarcopterygian fish from the Late Devonian of Australia
- Maniraptora: birds and specialized, bird-like theropods
- Maniraptoriformes: Ornithomimus + birds, although we think this is a pretty useless definition.
- Maresaurus X: a Middle Jurassic South American pliosaur with a large flat snout.
- Marginocephalia X: pachycephalosaurs and ceratopsians
- Massospondylidae X: a widely-distributed family of moderately large prosauropods closely related to plateosaurs.
- Mastodonsaurus X: a huge, stout temnospondyl from the Middle Triassic.
- Megalichthyidae X: actually not-so-"mega" osteolepiforms which survived into the Permian
- Megalocephalus X: a well-known baphetid of the Early Pennsylvanian
- Megapodidae: brush turkeys of Australia
- Megazostrodontidae X: docodont pammamiforms from the Triassic and Jurassic of Africa
- Meiolania X: huge, "horned" turtles
- Melanorosauridae X: very large prosauropods from the Late Triassic of South America
- Menaspidae X: odd and early holocephalians of the PermoCarboniferous
- Mergini: sea ducks
- Meridiungulata X: originally, all endemic South American ungulates. This may not be a clade, so we're not sure what's in this box.
- Merriamosauria X: ichthyosaurs characterized by having their teeth set in a groove, without ankylosis to the jaw
- Mesoeucrocodylia: a clade containing most marine & amphibious crocs from the Mesozoic and Cenozoic
- Mesonychia X: Medium to large-sized, possibly dominant predators or scavengers of the mid-Paleocene to Early Oligocene.
- Mesosauridae X: a small group of secondarily aquatic forms with elongated snout & neck, sister group of the reptiles.
- Metasuchia: Notosuchus + Crocodylus, including all Cenezoic crocs and some Cretaceous forms
- Metatheria: marsupials
- Metaxygnathus: X this jaw taxon and Ventastega may be the sister of Tetrapoda
- Metoposauroidea X: A group of large flat-headed aquatic temnospondyls, rather similar to the capitosaurids in size and body proportions.
- Metornithes: alvarezsaurs + living birds, birds with fused carpometacarpus and reduced fibula
- Metriorhynchidae X: highly aquatic Jurassic thalattosuchian crocs
- Microbiotheria: very small, mouse-like marsupials from South America
- Microbrachiidae X: Tiny (<2 cm) Middle or Late Devonian antiarch placoderms transitional between Yunnanolepidoids and Bothriolepidoids
- Microcleidus X: an early Jurassic elasmosaur of uncertain affinities.
- Micropternodontidae X: widespread, but poorly known, basal Insectivores of the Paleocene through Miocene.
- Microsauria: diverse, small, long-bodied lepospondyls best known from the Permo-Carboniferous -- probable ancestors of at least some living amphibians
- Miguashaia X: the earliest known actinistian (coelacanth lineage)
- Millerettidae X: lizard-like things from the Late Permian -- quite likely the sister of all other anapsids
- Minicrania X: Tiny antiarch placoderms (<2cm) intermediate between yunnanolepidoids & euantiarchs, from the Early Devonian of China.
- Minmi X: the only Gondwanan ankylosaur
- Miolabinae X:
- Mixosaurus X: a small, very basal, early ichthyosaur from the Middle Triassic of nearly everywhere
- Molybdopygus X: a poorly-known dinocephalian from the Late Permian of Russia.
- Monolophosaurus X: a carnosaur with a unique, single ridge-like head crest running from its nose to the rear of the skull, from the Middle Jurassic of China
- Mononykinae X: the Asian Alvarezsaurids, flightless birds with small, weird arms.
- Mononykus X: perhaps the best known of the alvarezsaurs, from the Late Cretaceous of Mongolia
- Monotremata: the egg-laying mammals (platypi & echidnas) and their ancestors
- Monstersauria: venemous varanoid lizards, such as the gila monster
- Morganucodontidae X: the best-known Mesozoic mammaliaforms
- Mosasauroidea X: mosasaurs
- Moschops X: perhaps the largest and most bone-headed of the tapinocephalids
- Mucrovenator X: a rather advanced little Middle Triassic North American shark tooth genus)
- Multituberculata X: the "rodents of the Mesozoic," a prolific and long lived group of "maybe-mammals"
- Muraenosaurus X: a classic medium-sized plesiosauroid from the Late Jurassic
- Musophagidae: mouse birds
- Muttaburrasaurus X: the National Iguanodont of Australia (mid-Cretaceous)
- Mycterosaurinae X: a widespread clade of varanopsid "pelycosaurs" from the Middle and Late Permian
- Mycterosaurus X: the best-known member of the previous group, from the Middle Permian of North America
- Myriacanthoidei X: a weird & enigmatic family of chimaeriforms, mostly from the Jurassic of Europe.
- Mysticeti: the baleen whales
- Mystriosuchus X: a late and specialized fish-eating phytosaur from the Late Triassic of Europe
- Myxinoidea: the hagfishes
-N-
- Nanictosaurus X: a Late Permian galesaurid cynodont
- Nanocynodon X: another Late Permian cynodont, this one from Russia -- very small but very carnivorous
- Nanyangosaurus X: an early hadrosauroid from the middle Cretaceous of China -- hard to distinguish from Iguanodon.
- Narcinidae: a family of electric rays
- Nectridia X: Permo-Carboniferous newt-like lepospondyls, including the boomerang-head forms like Diplocaulus.
- Necrosauridae X: an ill-defined Cretaceous to Eocene taxon of extinct varanoid lizards
- Nemegtosauridae X: a titanosaurid group, perhaps Nemegtosaurus > Saltasaurus, with an odd distribution in Asia, India & Africa
- Nemegtosaurus X: a controversial titanosaur from the Late Cretaceous of China
- Neoaetosauroides X: a late, but primitive aetosaur from the end-Triassic of South America
- Neochoristodera X: champsosaurs, an odd, late-surviving archosauromorph line
- Neodiapsida: younginiforms + living reptiles
- Neognathi: the clade uniting pikes Neoteleosts -- teleosts with acellular bone and depressible teeth
- Neomorphidae: roadrunners
- Neopterygii: gars + teleosts -- actinopterygians with symmetrical tails
- Neornithes: the crown group of all living birds
- Neosauropoda X: diplodocids + titanosaurs, digitigrade sauropods
- Neoselachii: the crown group of living sharks and rays
- Neosuchia: extant crocs + dryosaurs
- Neoteleostei: most living teleosts
- Neotherapsida: anomodonts + theriodonts
- Neuquensaurus X: a medium-sized advanced titanosaur from the Late Cretaceous of South America
- Neusticosaurus X
- Nicrosaurus X
- Nigersaurus X
- Nikoliviidae X
- Nodosauridae X
- Nothosauria X: plesiosaurs > placodonts.
- Nothosauridae X
- Nothosaurus X: a large, well-known nothosaur from the Triassic of Europe.
- Notoryctemorphia: Notoryctes, the strange marsupial mole
- Notostylopidae X: an early (mostly Paleocene) group of notoungulates
- Notosuchidae X: very terrestrial, solid-looking crocs from the Late Cretaceous of South America
- Notosyodon X: a medium sized anteosaur (carnivorous therapsid) with a massive skull from the Late Permian of Russia
- Notoungulata X: one of the two main groups of South American endemic ungulates, Paleocene to Pleistocene
- Novumbra: the infamous Olympic mudminnow
- Numididae: guinea fowl, first cousins to the chicken
- Nyctitheriidae X: the most basal group on the line to shrews, Paleocene to Early Oligocene of North America & Europe.
-O-
- Obruchevichthys: X a near-tetrapod and close relative of Elginerpeton
- Odontoceti: dolphins, porpoises & toothed whales
- Odontophoridae
- Oikopleuridae
- Oligokyphus X: Jurassic tritylodont, a rodent-like cynodont
- Oligoryctidae X
- Onychodontiformes X a very primitive, perhaps paraphyletic, group of sarcopterygians with symphysial tooth whorls
- Onychodus X: A large onychodontiform
- Ophiacodon X: a large Permian pelycosaur from North America
- Ophiacodontidae X: early synapsids with tall, thin snouts
- Ophthalmosauria X: : Jurassic ichthyosaurs with huge eyes
- Ophthalmosaurus X the eponymous representative of the above group, sometimes divided into a number of (sub)genera
- Orectolobiformes: carpet sharks, wobbegons, and nurse sharks
- Oreodontoidea X: early members of the pig lineage, from the Eocene and Miocene of North America
- Ornithischia X: Triceratops > birds
- Ornithocheiroidea X: Pteranodon and related Cretaceous pterosaurs
- Ornithodira: the clade uniting pterosaurs and dinosaurs
- Ornitholestes X: a small, Late Jurassic coelurosaur from the Late Jurassic of North America
- Ornithomimosauria X: very bird-like Cretaceous theropods, sister of the Tyrannosouroidea
- Ornithopoda X: heterodontosaurs, hypsilophodonts, iguanodonts, and hadrosaurs
- Ornithosuchidae X: a strange family near the base of the split between croc and dinosaur lineages
- Ornithosuchus X: very large and theropod-like, but actually a member of the Crurotarsi (croc lineage)
- Ornithothoraces: the clade uniting Enantiornithes with living birds
- Ornithurae: hesperornithiforms and living birds
- Orodontida X: big eel-like primitive sharks from the Late Devonian and Carboniferous
- Ostariophysi: the dominant group of fresh water teleosts
- Osteichthyes: bony fish -- acanthodians, actinopterygians and sarcopterygians (us)
- Osteoglossomorpha: the aruana, elephant-nose fish and extincr relatives
- Osteolepididae X
- Osteolepiformes X: the group of sarcopterygian fishes which includes the tetrapods
- Osteostraci X: armored jawless fishes with massive cartilaginous skulls and paired pectoral fins, from the Silurian & Devonian of the Northern hemisphere
- Othnieliinae X: small Jurassic hypsilophodont dinosaurs with small, enamel-covered teeth
- Otophysi: the clade uniting catfishes and carp
- Ouranosaurus X: a hump-backed hadrosauroid, from the middle Cretaceous of Africa
- Oviraptorosauria X: oviraptors, bizarre dinosaurs from the Late Cretaceous of China & North America
- Owenettidae X: early anapsid insectivores from the Permian of Africa
- Oxyurini: Gondwanan ducks
- Ozarkodinida X: : possibly the best known large taxon of conodonts
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