Journal of the Arkansas Academy of Science

Volume 9 Article 6

1956 Scheme of General Classification in the Phylum Chordata Paul R. Harding Hendrix College

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A SCHEME OF GENERAL CLASSIFICATION IN THE PHYLUM CHORDATA

Paul R. Harding, Jr. Hendrix College

Phylum, Chordata Subphylum, Hemichordata Balanoglossus, Sacco- glossus (Dolichoglossus ) Subphylura, Protochordata Class, Cephalochordata Branchiostoma (Am- phioxus) Class, Urochordata (Tunicata) Order, sea squirts Order, salpians Order, larvacians Subphylum, Vertebrata (Craniata) Branch, (Monorhina) with single nos- tril and circular mouth without jaws Class, Ostracodermi armored ; ex- tinct Orders: Osteostraci, Heterostraci, An- aspida Class, Unarraored, eel-like Order, Myxinoidea Order, Petromyzontia lampreys Branch, (Amphirhina) two nos- trils and with jaws Grade, Pisces fishlike gnathostomes Class, (Aphetohyoidea) ar- mored fishes; extinct Orders: Arthrodira, Acanthodii, An- tiarchi , Petalichthyida, Rhenanida, Palaeospondylia Class, ( Elasmobranchii) Cartilaginous fishes with gill septa (separate gill clefts)

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Order, Cladoselachii Cladoselache; extinct Order, Pleuracanthodii Pleuracan- thus, extinct Order, Selachii Suborder, Squali sharks Suborder, Raji () skates, rays, sawfish, guitar Order, Bradyodonti Ancestral to Ho- locephali. Extinct. Coch- liodus; Psammodus Order, Holocephali chimeras Class, bony fishes with- out separate gill clefts Subclass, Choanichthyes primitive bony fishes; nostrils con- nected to mouth cavity Order, Crossopterygii lobe-finned fishes; ancestral to Tetra- poda Suborder, Actinistia Family, Coelacanthidae chalumnae (193B, 1952, 1953, 1954) Suborder, Rhipidistia Families: Osteolepidae, Rhi- zodontidae, Urostheneidae, Holoptychiidae, Tarrasi- idae Order, Dipnoi (Dipneusti) Lung- fishes proper Subclass, (Teleostomi) ray-finned fishes; nos- trils not connected to mouth cavity Superorders: Chondrostei, Holo- stei, Teleostei Grade, Tetrapoda

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Subgrade, Anamniota without extraem- bryonic membranes Class, Amphibia Subclass, Stegocephalia skull and cheeks roofed with bony plates Order, Labyrinthodontia teeth with abundantly infolded dentine in the pulp cavityj body armored with scales or plates; extinct Order, Gymnophiona (Apoda)-- Caecilians Subclass, Caudata (Urodela) sal- amanders and newts Subclass, Salientia (Anura) frogs and toads Subgrade, Araniota with extraembryonic membranes Class, Reptilia Order, Suborder, Lacertilia () lizards Suborder, Ophidia (Serpentes) snakes Order, Spheno- don, unampsosaurusChamps osaurus Order, Testudinatainata (Chelonia)--(Chelon tortoises, terrapins, tur- tles Order, Crocodilia (Loricata) — crocodiles, alligators, gavials, caimans Order, Cotylosauria Primitive extinct , closely resembling the most primi- tive (Labyrin- thodontia) and of great phylogenetic importance as

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links with them. Example: Seymouria . Order, Mosasauria Extinct large aquatic reptiles with long snake-like scaly bodies, a crocodile-like head, strong recurved teeth, and two pairs of flippers in place of legs. Examples: Mosa- saurus , Clidastes, Tylo- saurus, etc. Order, Ichthyosauria —Extinct fish- like reptiles with long tapering rostrum. Exam- ples : Ichthyosaurus, Sten- opterygius . Order, Plesiosauria Extinct long- necked aquatic reptiles with flippers in place of legs. Example: ELasmosau- rus. Order, Pterosauria Extinct flying reptiles, pterodactyls . Examples: Pteranodon,Hham- phorhynchus. Order, Thecodontia (Phytosauria) Extinct crocodile-like reptiles with long narrow jaws, and nostrils close in front of the eyes rather than on the end of the snout. Examples: Belodon , Hystriosuchus . Order, Pelycosauria Fin -back lizards; extinct. Exam- pies: Dimetrodon, Eda- phosaurus. Ophiacodonti- dae (example: Ophiacodon) ancestral to .

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Order, Dinosauria Extinct gen- eralized -like and li- zard-like forms; contains ttie largest, most grotesque and most variable reptiles. Suborder, Ornithischia With bird -like pelvis; bird- beaked, duck-billed, bird- footed, seme ostrich-like, etc. Examples: Ornithom- imus and Struthiomimus , ostrich- like; Trachodon , duck -bUlsd dinosaur; £qry- thosaurus, hooded duck-bill dinosaur; Stegosaurug, two rows of vertical plates on back, brain exceptionally- small, spinal cord vdth brachial and sacral en- largements ; Trlceratops , head with three horns and the skull extended like a shield over the back and shoulde rs ; Ankylosaurus , armored . Suborder, -Saurischia VJ±fcli li- zard like pelvis. Exam- ples : Tyrannosaurus, Brcn- tosaurus, Brachiosaurus , Diplodocus, Comosognathus . Order, Therapsida Extinct - like reptiles. Example: Cynognathus . Evolved fro:n order Pelycosauria, but not ancestral to mammals. Class, Aves Subclass, Archaeornithes "Ancient birds" showing reptilian ancestry; extinct. Exam-

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pies: Archaeornis , Ar- chaeopteryx. Subclass, Neornithes "New birds" Superorder, Odontormae Ich- thyornis; extinct. Toothed; good flyer. Superorder, Odontolcae Hes- perornis; extinct. Also with true teeth in sockets; a flightless (wingof hum- erus only) diver. Superorder, Ratitae Cursorial flightless birds with un- keeled sternum. Examples: ostrich, rhea, emu, casso- wary, kiwi, elephant bird, moa. Superorder, Carinatae Adapted for flight, sternum keeled. Great majority of modern birds. Class, Mammalia Subclass, Prototheria egg-laying mammals . Order, Monotremata duckbill and spiny anteater. Order, Multituberculata an extinct group of doubtful position. Subclass, Theria viviparous mam- mals. Infraclass, Metatheria (Didel- phia) —viviparous mammals usually without allantoic placenta. Order, Marsupialia pouched mammals. Opossum, kanga- roo, wombat, wallaby, fly- ing phalange r, koala, mar-

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supial mole, bandicoot, marsupial mouse, Tasmanian wolf, Tasmanian devil, ti- ger cat, etc. Extinct orders of doubtful position: ffcntotheria (also called Trituberculata probably ancestral to la- ter types of mammals). Triconodonta, Symmetrodon- ta. Infraclass, Eutheria (Monodel- fhia) viviparous mammals with allantoic placenta. Superorder, Unguiculata clawed mammals . Sloths, pangolin or scaly anteater, hairy anteater, rabbi ts , armadillos, aardvark, ro- dents, bats, carnivores, insect ivores, sealions, seals, walruses, etc. Superorder, Primates mam- mals with nails Order, Lemuroidea le- murs . Ruff e d lemur, mouse lemur, tiee shrews, slowloris, aye-aye (Chi- romys ), etc. Order, Tarsioidea tar- siers Order, Anthropoidea an- thropoids. Men, apes, monkeys . Superorder, Ungulata —hoofed mammals. Order, Condylarthra — condylarths; extinct

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Order, Dinocerata Uin- tatheres; extinct Order, Sirenia dugongs and manatees. Large fishlike forms believed to have an ungulate or- igin. Order, Peris sodactyla foot withan odd number of toes, each usually sheathed in a cornified hoof. Asses, zebras, horses, tapirs, rhinoc- eroses, titanotheres, chalicotheros . Order, Artiodactyla foot with even number of toes, each usually- sheathed ina cornified hoof. Pigs, hippopot- amuses, and such rumi- nants as camels, chev- rotians (mouse deer), deer, elk, moose, an- telope, giraffes, cat- tle, bison, ox, water buffalo, cape buffalo, sheep, goats, musk ox, llama, etc. Order, Proboscidea —num- ber of toes odd or even, each with small nail- like hoof, nose and up- per lip combined into along muscular probos- cis. Elephants, masto- dons, mammoths. Order, Hyracoidea four toes on fore limb, three ihttp://scholarworks.uark.edu/jaas/vol9/iss1/6 27 27 Journal of the Arkansas Academy of Science, Vol. 9 [1956], Art. 6

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on hind; superficially like guinea pigs, but related to hoofed ani- mals. Coneys, Pro cavia (Hyrax). Superorder, Cetacea body superficially fishlite; fore limbs of broad and paddle - like flippers with embedded digits and no claws; no hind limbs; tail ending in two broad transverse fleshy flukes. Order, Odontoceti toothed whales. Sperm whale or chacalot, kil- ler whale, narwhal, porpoises, blackfish, beaked whale, pygmy sperm whale, etc. Homo- dont dentition. Order, Mysticeti whale- bone whales or baleen whales. No teeth mouth with numerous parallel horny plates of "whale- bone" or "baleen" on sides of upper jaw used to strain smalL from water. Right whale, rorqual, gray whale, blue or sulphur-bottom whale, humpback whale, etc. Order, Archaeoceti zeuglodont whales; ex- tinct. Dentition het- erodont.

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In preparing the system of general classification presented here, the writerhas acted under the adop- tion of a constructive policy, and has contrived to make no radical departures from conventional methods. Indeed, it has been the writer's wish to improve or build further upon the better foundations of general classification. In order to provide an understanding of the man- ner of grouping, brief notes are given with the names of most of the different main taxa. For clarity, sy- nonymy has been indicated. •.: In reviving usch groupings as Ungulata and Ungu- iculata, the writer has wished not to show any ten- dencies toward an artificial system. It will be noticed that the chalicotheres (horse allies with clawlike terminal phalanges) have been placed in the Ungulata. Dinosauria has been regarded by others as an artificial taxonomic group, and in reviving its use as a definite taxon, the writer feels that he is justified because Saurischia and Ornithischia are well related through their general similarity of limbs, ribs, vertebrae, and skulls.

LITERATURE CITED Colbert, E.H. The Dinosaur Book. 2nd ed. 1951 Goodrich, E.S. Vertebrata (Craniata). First Fasci- cle: Cyclostomes and Fishes. Part IX of Treatise on Zoology edited by Sir Ray Lankester. 1909. Harmer, Herdman, Bridge, and Boulenger. Fishes, As- cidians, etc. Vol. VII of The Cambridge Natural History edited by S. F. Harmer and A. E. Shipley. 1904. Reprinted 1910. Hegner, R.W. and K.A. Stiles. College Zoology. 6th ed. 1951. Hyman, L.H. Comparative Anatomy, 2nd ed. 1942. Jordan, David Starr. Fishes. 1925 Newman, H.H. The Phylum Chordata. 1939-

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Parker, T.J. andW.A. Haswell. A Textbook of Zoology^ Vol. II. 6th ed. Revised by Otto Lowenstein and C. Forster-Cooper. 1951. Pirsson, L.V. and C. Schuchert. A Textbook of Geol- ogy. Parts Iand II. Physical and Historical Ge- ology. 2nd ed. 1920. Romer, A.S. Man and the . 1941. Schuchert ,C. and C. 0. Dunbar. A Textbook of Geol- ogy. Part II. Historical Geology. 3rd ed. 1933. Storer, T.I. General Zoology. 2nd ed. 1951. Walter, H.E. and L.P. Sayles. Biology of the Verte- brates. 3rd ed. 1949. Zittel, Karl A. von. Textbook of Paleontology. Vols. I, IIand III. Edited, translated and revised by Charles R. Eastman et al. 1925-1932.

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