Thomas here is a list from a friend in which he refers to as a "short list of transitional forms" complements to Santana Navarrette for organizing and compiling this list: Invertebrate to Vertebrate Unnamed Upper (U.) Pre-Cambrian chordate -- First to bear a primitive notochord; archaetypical chordate. Pikaia gracilens-- Middle (M.) Cambrian chordate with lancelet-like morphology. Haikouella-- Lower (L.) Cambrian chordate, first to bear a skull; archaetypical craniate. Haikouichthys-- L. Cambrian quasi-vertebrate, intermediate in developing a vertebral column; archaetypical vertebrate. Conodonts-- U. Cambrian to Triassic quasi-vertebrates with spinal cord; "bug-eyed lampreys". Myllokunmingia-- L. Cambrian vertebrate with primitive spinal column; oldest true crown-group vertebrate. Arandaspis-- L. Ordovician vertebrate, armoured jawless fish (ostracoderm), oldest known vertebrate with hard parts known from (mostly) complete fossils. **Jawless Fish to Jawed Vertebrate Birkenia-- Silurian primitive, jawless fish, a typical member of the Anaspida Cephalaspis-- Silurian armoured jawless fish, archaetypical member of the "Osteostraca," sister group to all jawed vertebrates. Shuyu-- Silurian to Devonian, armoured jawless fish belonging to Galeaspida, related to Osteostraca. Internal cranial anatomy very similar to the anatomy seen in basal jawed vertebrates. This similarity is directly implied with the translation of its name, "Dawn Fish," with the implication that it represents the "dawn of jawed vertebrates." Acanthodian to shark Ptomacanthus-- sharklike fish, originally described as an acanthodian fish: brain anatomy demonstrates that it is an intermediate between acanthodians and sharks. Cladoselache-- primitive/basal shark. Tristychius-- another sharklike fish. Ctenacanthus-- primitive/basal shark. Paleospinax-- sharklike jaw, primitive teeth. Spathobatis-- Ray-like fish. Protospinax-- Ancestral to both sharks and skates. Primitive jawed fish to bony fish Acanthodians-- superficially similar to early bony fishes, and some have been identified as being the ancestors of sharks. Palaeoniscoids-- primitive bony fishes. Canobius, Aeduella-- palaeoniscoids with more advanced jaws. Parasemionotus-- combination of modern cheeks with more primitive features, like lungs Oreochima-- first teleost fish Leptolepids-- vaguely herring-like ancestors of modern teleost fish. Lung modified into swim bladder. Amphistium and Heteronectes-- percomorphs that demonstrate the transition of the eye location of flatfishes. Fish to amphibian Paleoniscoids-- both ancestral to modern fish and land vertebrates. Osteolepis-- modified limb bones, amphibian like skull and teeth. Kenichthys-- shows the position of exhaling nostrils moving from front to fish to throat in tetrapods in its halfway point, in the teeth Eusthenopteron, Sterropterygion-- fin bones similarly structured to amphibian feet, but no toes yet, and still fishlike bodily proportions. Panderichthys, Elpistostege-- tetrapod-like bodily proportions. Obruchevichthys-- fragmented skeleton with intermediate characteristics, possible first tetrapod. Tiktaalik-- a fish with developing legs. Also appearance of ribs and neck. Acanthostega gunnari-- famous intermediate fossil. most primitive fossil that is known to be a tetrapod Ichthyostega-- like Acanthostega, another fishlike amphibian Hynerpeton-- A little more advanced then Acanthostega and Ichtyostega Labyrinthodonts-- still many fishlike features, but tailfins have disappeared Lungfish--A fish-that has lungs. Primitive to modern amphibians Temnospondyls Dendrerpeton acadianum Archegosaurus decheni Eryops megacephalus Trematops Amphibamus lyelli Doleserpeton annectens Triadobatrachus-- primitive frog Vieraella Karaurus-- primitive salamander Amphibian to reptile Proterogyrinus Limnoscelis Tseajaia Solenodonsaurus Hylonomus Paleothyris Early reptile to turtle Captorhinus Scutosaurus Odontochelys Semitestacea-- partial formation of a turtle shell, showing how the hard underbelly, or plastron, formed first. Deltavjatia vjatkensis Proganochelys Early reptile to diapsid (dinosaurs and modern reptiles except for turtle) Hylonomus Paleothyris Petrolacosaurus Araeoscelis Apsisaurus Claudiosaurus Planocephalosaurus Protorosaurus Prolacerta Proterosuchus Hyperodapedon Trilophosaurus Reptile to mammal Paleothyris Protoclepsydrops haplous Clepsydrops Archaeothyris Varanops Haptodus Dimetrodon Sphenacodon Biarmosuchia Procynosuchus Dvinia Thrinaxodon Cynognathus Diademodon Probelesodon Probainognathus Exaeretodon Oligokyphus Kayentatherium Pachygenelus Diarthrognathus Adelobasileus cromptoni Sinoconodon Kuehneotherium Eozostrodon Morganucodon-- a transition between "mammal-like reptiles" and "true mammals". Haldanodon Peramus Endotherium Kielantherium Aegialodon Steropodon galmani Vincelestes neuquenianus Pariadens kirklandi Kennalestes Asioryctes Cimolestes Procerberus Gypsonictops Dinosaur to bird Allosaurus--A large therapod with a wishbone Coelophysis Compsognathus--A small coeleosaur with a wishbone Eoraptor Epidendrosaurus Herrerasaurus Ceratosaurus Compsognathus Sinosauropteryx Protarchaeopteryx Caudipteryx Velociraptor Deinonychus Oviraptor Sinovenator Beipiaosaurus Lisboasaurus Sinornithosaurus Microraptor-- a feathered bird with distinctly dinosaurian characteristics, such as its tail. Xiaotingia-- slightly earlier than Archaeopteryx, slightly more like a dinosaur and less like a bird Archaeopteryx-- the famous bird-with-teeth. Rahonavis Confuciusornis Sinornis Patagopteryx Ambiortus Hesperornis Apsaravis Ichthyornis Columba-- One of many typical modern birds Primates Darwinius masillae-- a link between earlier primates and later ones. Non-human primate to human Sahelanthropus tchadensis-- One of the oldest known species in the human family tree. Lived around 6.5-7 million years ago, one of the earliest bi-pedal fossils. Orrorin tugenensis-- Over 20 fossils of the 6 million year old species have been found and show very human-like morphology. Ardipithecus ramidus-- 4.5 million year old species showing bi-pedal adaptations and opposable thumbs. Australopithecus-- a genus of bipedal apes Australopithecus anamensis Australopithecus afarensis Kenyanthropus platyops-- 3.5 million year old himinim fossil, most likely a subspecies of Australopithecus Australopithecus africanus Australopithecus garhi Australopithecus sediba-- advanced australopithecus showing more human features Australopithecus aethiopicus Australopithecus robustus Australopithecus boisei Homo habilis-- a transitional form from Australopithecus to later Homo Homo rudolfensis-- a type of Homo habilis or a different species Homo ergaster-- a form of Homo erectus or a distinct species Homo georgicus-- a form of Homo Erectus or a distinct species Homo erectus-- a transitional form from Australopithecus to later Homo (Latin for humans) species Homo antecessor-- is an extinct human species, or subspecies, dating from 1.2 million to 800,000 years ago Homo heidelbergensis-- A possible common ancestor of modern man and homo neanderthalensis Homo neanderthalensis-- They may or may not have done Humpy bumpy with modern humans. Homo floresiensis-- Extinct Homo species, living 94,000-12,000 years ago, used tools, bipedal, very human-like Cro-magnon-- considered early modern human and perhaps as smart as we are Cetaceans Indohyus-- a vaguely chevrotain-like or raccoon-like aquatic artiodactyl ungulate with an inner ear identical to that of whales. Ambulocetus-- an early whale that looks like a mammalian version of a crocodile Pakicetus-- an early, semi-aquatic whale, a superficially wolf-like animal believed to be a direct ancestor of modern whales. Rhodocetus-- An early whale with comparatively large hindlegs: not only represents a transition between semi-aquatic whales, like Ambulocetus, and obligately aquatic whales, like Basilosaurus. Basilosaurus-- A large, elongated whale with vestigial hind flippers: transition from early marine whales (likeRhodocetus) to modern whales Dorudon-- A small whale with vestigial hind flippers, close relative of Basilosaurus.
Posted on: Sun, 29 Sep 2013 23:57:20 +0000
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