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ORDERS OF CLASS
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ORDERS OF CLASS REPTILIA 1. Anomodontia.—Bones of postero-lateral region of See also:skull forming a See also:complete roof over the temporal and masseter muscles, or contracted into a single broad zygomatic See also:arch, leaving a See also:superior-temporal vacuity. Pineal foramen See also:present. Ribs completely or imperfectly See also:double-headed. No abdominal ribs. A large separately ossified epicoracoid. Limbs for support as well as progression; third and See also:fourth digits with not more than three phalanges. Dermal See also:armour feeble or absent. Range.—See also:Permian and Triassic. 2. Chelonia.—Postero-lateral region of skull as in Anomodontia, except bones of See also:ear-See also:capsule more modified. No pineal foramen. Ribs single-headed. No sternum. See also:Pectoral and pelvic See also:arches unique in being situated completely inside the ribs. No epicoracoid. Abdominal ribs replaced by three or four pairs of large plates, which, with the clavicles and interclavicle, See also:form a plastron. Limbs only for progression; third and fourth digits with not more than three phalanges. A See also:regular dorsal See also:carapace of bony plates intimately connected with the neural spines, and ribs of seven to nine dorsal vertebrae. Range.—Upper Triassic.to See also:Recent. 3. Sauropterygia.—Bones of postero-lateral region of skull contracted into a single broad zygomatic arch, leaving a superior-temporal vacuity. Pineal foramen present. No fused sacral vertebrae. All dorsal ribs single-headed, articulating with transverse processes of the neural arches. Abdominal ribs forming dense plastron. Apparently no sternum. Coracoid, pubis and ischium in form of much-See also:expanded plates. Limbs modified as paddles, with not more than five digits, of which the third and fourth always have more than three phalanges; all digits usually consisting of numerous phalanges. No dermal armour. Range.—Upper Triassic to Cretaceous. 4. Ichthyopterygia.—Bones of postero-lateral region of skull contracted into a single broad zygomatic arch, leaving a superior-temporal vacuity. Pineal foramen present. Vertebral centra See also:short and deeply biconcave, with feeble neural arches which are almost or completely destitute of zygapophyses. No fused sacral vertebrae. Cervical and dorsal ribs double-headed, articulating with tubercles on the vertebral centra. Abdominal ribs forming dense plastron. Apparently no sternum. Coracoid an expanded See also:plate, probably with cartilaginous epicoracoid. See also:Pelvis very small, not connected with vertebrae. Limbs modified as paddles, with digits of very numerous short phalanges, which are closely pressed together, sometimes with supplementary rows of similar ossicles. No dermal armour. A See also:vertical triangular caudal fin, not supported by skeletal rays. Range.—Triassic to Cretaceous. 5. See also:Rhynchocephalia.—Bones of postero-lateral region of skull contracted into two slender zygomatic bars, leaving a superior-temporal and a lateral-temporal vacuity, and partly exposing the quadrate See also:bone from the See also:side. Pineal foramen present o absent. Ribs single-headed. Abdominal ribs present. Sternum present. Epicoracoid cartilaginous. Limbs only for progression; third and fourth digits with four or five phalanges. Dermal armour feeble or absent. Range.—See also:Lower Permian to Recent. 6. Dinosauria.—Postero-lateral region of skull as in Rhynchocephalia. No pineal foramen. Cervical and dorsal ribs double-headed. Rarely abdominal ribs. Sternum present, but apparently no clavicular arch. Limbs for support as well as progression; third and fourth digits with four and five phalanges respectively. Dermal armour variable. Range.—Triassic to Cretaceous. 7. Crocodilia.—Postero-lateral region of skull as in Rhynchocephalia. No pineal foramen. Cervical and dorsal ribs double-headed. Abdominal ribs present. Sternum present; also inter-clavicle, but no clavicles. Limbs only for progression on See also:land or See also:swimming; third and fourth digits with four or five phalanges. Dermal armour variable. Range.—Lower See also:Jurassic to Recent. 8. Ornithosauria.—All bones extremely dense, See also:light and hollow, the organism being adapted for See also:flight. Postero-lateral region of skull as in Rhynchocephalia. No pineal foramen. Cervical and dorsal ribs double-headed. Abdominal ribs present. Sternum present, and keeled for See also:attachment of pectoral muscles; no clavicular arch. Fifth See also:digit of See also:hand much elongated to support a wing-membrane, but with only four phalanges. See also:Hind See also:limb feeble. No dermal armour. Range.—Lower Jurassic to Cretaceous. i IICI,I, i I I~ ~~~ i lhll I~ r zr plupl II III See also:mll~1lN ~~4i14~1, qu 4u Lcu. j A B After See also:Credner. After C. W. See also:Andrews. B, See also:Palate of Mesozoic Reptile (See also:Plesiosaurus macrocephalus). b.occ, basioccipital; bs, basisphenoid; eept, ectopterygoid; i.pt, interpterygoid vacuity; j, jugal; mx, maxilla; pas, parasphenoid; pl, See also:palatine; pmx, premaxilla; pt, pterygoid; pt. See also:par, posterior pares; qu, quadrate; s.o, suborbital vacuity; v, vomer. See also:pax.. mac ,.pt.nar pt. ncsr... S. o. 9. Squamata.—Bones of postero-lateral region of skull much reduced and partly absent, never forming more than a slender superior-temporal See also:bar, thus completely exposing the quadrate, which is only loosely attached to the cranium at its upper end. Pineal foramen present. Ribs single-headed. No abdominal ribs. Sternum present when there are limbs. Limbs, when present, only for progression; third and fourth digits at least with more than three phalanges. Dermal armour feeble or absent. Range.—Cretaceous to Recent. See also:Order I. ANOMODONTIA.—The Anomodonts are so named in allusion to the See also:peculiar and unique dentition of the first-discovered genera. They are precisely intermediate between theand See also:India, but they are best represented in the Karoo formation (Permian and Triassic) of See also:South See also:Africa. The Pariasauria most closely resemble the Labyrinthodont See also:Amphibia, but have a single occipital condyle. Pariasauria itself is a massive herbivorous reptile, with a short tail, and the limbs adapted for excavating in the ground. It is known by several nearly complete skeletons, about 3 metres in length, from South Africa and See also:northern See also:Russia. Elginia, found in the See also:Elgin sandstones of Morayshire, See also:Scotland, is provided with See also:horn-like bony bosses on the skull. Another apparently allied genus (Otocoelus) has a carapace suggesting that it may be an ancestral Chelonian. The Therio- B. ~~V... See also:im" s: "~m~ptt+t ~I~III!lI1~11~NI Illl~uoL 7J- F qu. From A. S. See also:Woodward, Outlines of Vertebrate Palaeontology. fr, frontal; j, jugal; 1, lateral temporal vacuity; la, lachrymal; mx, maxilla; n, narial opening; na, nasal; o, See also:orbit; Pa, parietal; pmx, premaxilla; prf, prefrontal; ptf, postfrontal; pto, postorbital; q.j, quadrato-jugal; qu, quadrate; s, supratemporal vacuity; s.t, supratemporals and prosquamosal; sq, squamosal. Vacuities shaded with vertical lines, See also:cartilage bones dotted. sq. Labyrinthodont See also:Batrachia and the lowest or Monotreme See also:Mammalia. They flourished at the See also:period when the former are known to have reached their See also:culmination, and when the latter almost certainly began to appear. Many of them would, indeed, be regarded as See also:primitive Mammalia, if they did not retain a pineal foramen, a See also:free quadrate bone, and a complex mandible. The See also:term Theromorpha or Theromora is thus sometimes applied to the order they represent. So far as known, they are all land-See also:reptiles, with limbs adapted for habitual support of the See also:body, and their feet are essentially identical with those of primitive mammals. Most of them are small, and none attain a gigantic See also:size. They first appear in the Permian of See also:Europe and See also:North See also:America, and also occur in the Triassic both of Europe dontia exhibit the marginal See also:teeth differentiated (in shape) into incisors, canines and molars (fig. 3). They have two occipital condyles, as in mammals. They seem to have been all carnivorous, or at least insectivorous, but the malariform teeth vary much in shape in the different genera. Cynognathus (fig. 3) and Lycosaurus have cutting teeth, while Tritylodon and Gomphognathus possess powerful grinders. The Dicynodontia have one pair of upper tusks or are toothless: their occipital condyle is See also:trefoil-shaped, as in Chelonia. Dicynodon itself occurs in the Karoo formation of S. Africa, while other genera are represented in India, N. Russia and Scotland. Order 2. CHELONIA.—This order occurs first in the Upper Triassic of See also:Wurttemberg, where a complete " See also:shell" has been found (Proganochelys). Its members are proved to have been toothless since the Jurassic period, and have only changed very From A. S. Woodwartl, Outlines of Vertebrate Palaeontology. d, dentary; j, jugal; l.t.f, incipient lateral temporal vacuity; la, lachrymal; nix, maxilla; na, nasal; See also:orb, orbit; pa, parietal; pmx, premaxilla; prf, prefrontal; pia., postorbital; ptf, See also:post-frontal; s.t, supratemporal (prosquamosal); sq, squamosal. slightly since their first See also:appearance. The marine turtles seem to have first: acquired elongated paddles and vacuities in the shell during the Cretaceous period, and the Trionychia, destitute of epidermal See also:shields, apparently arose at the same See also:time. Order 3. SAUROPTERYGIA.—These are amphibious or aquatic reptiles (fig. 4). The See also:head is comparatively small in most genera, and the See also:neck is usually elongated though not flexible. The tail is insignificant, generally short, and both pairs of paddles seem to have been concerned in progression. The order appears to have arisen from a See also:group of land-reptiles, for its earliest members, from the Triassic of Europe (Lariosaurus) and from the Permo-Carboniferous of S. Africa (Mesosaurus) and See also:Brazil (Stereosternum), are all amphibious animals. They are comparatively small, and their limbs are only just becoming See also:paddle-like. The skull suggests See also:affinities with the terrestrial effective paddles with elongated digits, and as the genera are traced upwards in the See also:geological formations it is possible to observe how the arches supporting the limbs become more rigid until the maximum of strength is reached. A few genera, such as Pliosaurus from the Jurassic and Polyptychodon from the Cretaceous of Europe, are distinguished by their relatively large head and stout neck. Some of the largest Upper Jurassic and Cretaceous See also:species must have been so metres in length. They were See also:cosmopolitan in their See also:distribution, but became See also:extinct before the See also:dawn of the See also:Tertiary period. Order 4. ICHTHYOPTERYGIA.—The Ichthyosaurians are all See also:fish-shaped, with a relatively large head and very short neck. Both pairs of paddles are retained, but the hinder pair is usually. very small, and locomotion seems to have been chiefly effected by a large caudal fin. This fin, as shown in impression by certain fossils from Wurttemberg and See also:Bavaria, is a vertical, triangular, dermal expansion, without any skeletal support except the hindermost See also:part of the attenuated vertebral See also:column, which extends along the border of its lower See also:lobe (fig. 5). Another triangular fin, without skeletal support, is known to occur on the back, at least in one species (fig. 5). Some of the genera are proved to have been viviparous. Like the Sauropterygia, the Ichthyopterygia appear to have originated from terrestrial ancestors, for their earliest Triassic representatives (Mixosaurus) have the teeth less See also:uniform and the limbs slightly less paddle-. shaped than the latter genera. In this connexion it is noteworthy that their hollow conical teeth exhibit curious infoldings of the See also:wall, like those observed in many Labyrintho.donts, while their short, biconcave vertebrae almost exactly resemble those of the Labyrinthodont Mastodonsaurus and its See also:allies. As the Ichthyosaurs are traced up-wards in geological time, some genera become almost, or quite, toothless, while the paddles grow wider, and are rendered more flexible by the persistence of . cartilage See also:round their constituent bones (Ophthalmosaurus). They were cosmopolitan in distribution, but disappeared from all seas at the See also:close of the Cretaceous period. The largest forms, with a skull 2 metres in length, occur in the Lower See also:Lias. Order 5. RHYNCHOCEPHALIA.—TheSe are small See also:lizard-shaped reptiles, which have scarcely changed since the Triassic period. Though now represented only by See also:Sphenodon or Hatteria, which survives in certain islands off New See also:Zealand, in the Mesozoic See also:epoch they ranged at least over Europe, See also:Asia.and North America. They comprise the earliest known reptile, Palaeohatteria, from the Lower Permian of See also:Saxony, which differs from the Triassic and later genera in having an imperfectly ossified pubis and ischium, more numerous abdominal ribs, and the fifth metatarsal Lias, Wurttemberg. (After E. See also:Fraas.) The irregularities behind the triangular dorsal fin are torn pieces of skin, Anomodontia, and the shape of the scapula seems to show some connexion with the Chelonia. The truly aquatic Sauropterygians of the Jurassic (fig. 4) and Cretaceous periods possess most bone normal. Additional information and CommentsThere are no comments yet for this article.
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