Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/483

Rh DISTRIBUTION IN TIME.] REPTILES 465 Deiters, "Gehb'rorgan d. Amphibien," in Archiv f. Anat. und Physiol., 1862; Kuhn, "Hautige Labyrinth d. Reptilien," Archiv f. Mikroskop. Anat., xx., p.,271, 1881 ; B. Solger, " Nasen-Wandung u. Nasen-Muscheln d. Rcptilien,'' in Morphol. Jahrb., i. p. 467, 1876; E. Clason, "Morphol. d. Gehororgans <d. Eideclisen," in C. Hasse's Anat. Studien, p. 300, 1879; C. Hasse, in his Anat. Studien, p. 679, 1873. EMBRYOLOGY. F. Balfour, Comparative Embryology, vol. ii. pp. 167-176; Id., " Development of Lacertilia," Quart. Jour. Micr. Sci., vol. xix., 1879 ^Eimer, "Unters. d. Eier der Reptilien," Archiv f. Mikros. Anat., viii., 1872; Kupffer and Benecke, "Die Erste Entwickiung am Ei d. Reptilien, Kb'nigsberg, 1878 ; Emmert and Hoclutetter, " Unters. iib. d. Entwick. d. Eiclechsen," lieil's ser. 4, vol. xxvii., 1862 ; H. Rathke, Entwickl. d. Natter, Konigsberg, 1839 ; Id., Ueber d. Entwickelung d. Schildkroten, Brunswick, 1848 ; Id., Ueber d. Entwickelung d. Krokodile, Brunswick, 1866 ; Id., Die Entwickelung u. Korperbau d. Crocodile, Brunswick, 18(56; L. Agassiz, "Embryology of the Turtle," in Contrib. Nat. Hist. United States, vol. ii., 1857. MONOGRAPHS. Bojanus, Anatome Testudinis Europium, 1819; Tiedemann, Anat. u. Natwgesch. des Drachens, Nuremberg, 1811; Gunther, " Hatteria," Phil. Trans., 18t;7, pt. 2; Id., "Gigantic Land Tortoises," Phil. Trans., clxv., pt. 1 ; Id., Gigantic Land Tortoises in British Museum, 1877 ; A, Fritsch, "Anat. d. Elephanten-Scliildkrote," in Abhand. d. Konigl. Bbhm. Gesellsch. d. Wissen- schaften ; M. Salverda, Vergel. Ontleedk. Aanieekeningen over Calotes, 1863 ; J. H. Troschel, " Heloderma horridum," in Archie f. Naturg., Jahrg. 19, 1853, p. 294; Peters, De Serpentum Familia Uropeltaceorum, Berlin, 1861. (ST G. M.) DISTRIBUTION OF REPTILES IN TIME. ai m- The first appearance of Reptiles on the surface of the ons globe is indicated by very fragmentary remains. Speci- ' r;> mens of deeply biconcave vertebrae of Carboniferous age from Nova Scotia are believed to be those of a marine Saurian (Eosaurus acadianus); if this view is correct, this oldest of Reptiles would bear the stamp of one of the most Fish-like of the class. run. Formations of Permian age in North America as well as in Europe contain fossils with undoubtedly Reptilian characters ; they are still associated with true Labyrintho- donts, and with remains which are too fragmentary to be assigned with certainty either to Labyrinthodonts or Reptiles. The vertebrae of all are amphicoelous. These Reptiles are Rhynchocephalians, the oldest and best preserved being Proterosaurus from the Copper-Slate of Thuringia, a Reptile about six feet in length, with a com- paratively long neck (which, however, was composed of seven or nine vertebrae only), with numerous abdominal splints, a long tail, and well developed and differentiated limbs. i .oic. In the Mesozoic times the Reptilian type appears in such variety and in such a high state of development that this era has been distinguished as the " Reptilian age." Yet we know chiefly such forms only as possessed bones of a size and solidity sufficient to ensure their preservation. Of small Reptiles, animals under or scarcely exceeding two feet in length, comparatively few have been discovered, although they too must have existed in abundance. In i;ic. the Trias there appear first of the marine Saurians large Sauropterygians with narrow ossifications between the vacuities of the skull, such as Simosaurus, Nothosaurus, and Pistosaurus from the German Muschelkalk. The highly interesting genus Neusticosaurus, the smallest of the group, with the four limbs modified into paddles, but with the hind limbs retaining the structure of those of a terrestrial animal, seems to afford evidence of this order having been developed from a terrestrial type. Fragments of true Plesiosaurus and Ichthyosaurus begin to appear in the Rhaetic bone beds of England. Also the Placodonts, the systematic affinities of which are not yet satisfactorily understood, are contemporaries of these early Enalio- saurians. The precursors of our Crocodiles were two genera, Belodon and Steganolepis, with dorsal scutes, but with amphiccelian vertebrae and anterior choanae, neither palatines nor pterygoids being dilated into the osseous palate which is characteristic of later Crocodiles. Another order, the Anomodontia, flourished and died in this epoch ; some fifteen genera have been distinguished, all from the South-African Trias ; however, this type is probably also represented in Russian formations of the same age. Rhynchocephalians continue in several genera in Euro- pean and American strata. But the largest of terrestrial Reptiles belonged to the Dinosaurs, whose presence in numerous species belonging to distinct groups, some with three, others with five toes to the hind feet, is testified by their osseous remains as well as by the tracks of their hind feet, which they left during their bipedal progression over stiff mud. These Triassic Dinosaurs were chiefly herbi- vorous, arid already much more numerous in North America than in Europe (Zandodon). This Reptilian fauna continued to flourish in the Jurassic Jurassic, period ; the types of the Trias increased in variety ; still more gigantic forms were developed ; and new orders which were absent in the preceding period were added. Of the marine Saurians alone some fifty species are known from European formations : the Ichthyosauri inhabited chiefly the northern seas of the eastern hemisphere, and were re- placed in the western by Reptiles of similar structure and size, but without teeth (Sauranodon) ; the Sauropterygians have considerably advanced beyond their Triassic precursors in having more solidly ossified skulls, and are also repre- sented by a greater number of genera in America as well as Europe ; of Plesiosaurus alone some twelve species are known from the Lias and seven from the Oolite. Ptero- , dactyles make their first appearance. Crocodilians have developed into the " Mesosuchian " type, their palatine bones being prolonged, pushing the choanae backwards to the middle of the under surface of their skull, but their vertebrae are still amphiccelian ; they appear in numerous genera (Teleosaurus) and species. Terrestrial Reptiles keep pace in development with the marine and freshwater types ; the giants of the order of Dinosaurs have left their remains in a more or less perfect condition in the Jurassic strata of both hemispheres (Cetiosaurus, Atlantosaurus, Iguan- odon, Morosaurus, Apatosaurus) ; forms with three toes on the hind feet lived simultaneously with four- or five-toed ones ; carnivorous types (Megalosaurus, Creosaurus, &c.) represent in habit as well as relative size Mammalian Carni- vora; they preyed upon the gigantic but weaker members of the order. The Dinosaurian type extended also into the southern hemisphere, as is testified by the West- Australian genus Deuterosaurus. The Chelonians, which appear first in the Upper Keuper, are in the Lias of highly advanced types, and not essentially different from recent families ; they occur in many localities of Europe as Freshwater Turtles, chiefly ChelydidsK ; but Emydidse, are also repre- sented, showing, however, a less solid ossification of the carapace than the recent forms. No distinct evidence of the presence of Marine Turtles and Trionyx has been found hitherto in Jurassic formations. This abundance of Reptilian life not only continues in Creta- the Cretaceous period, but is still more increased in ceous. variety and reaches its highest point of culmination. Ich- thyopterygians and Sauropterygians reached an enormous size ; Discosaurus, with a neck 22 feet long and composed of sixty vertebrae, must have been the most formidable enemy to the Fishes of the sea. Moreover these large Saurians which survived from the preceding period were now joined by a new type of marine monsters with a Snake-like body and very short extremities, the Mosa- saurians, which attained to a length of from 10 to 80 feet and veritably filled the place of Sea-Serpents. Although their skull exhibits not a few Ophidian characters, their genetic relation to that order is not by any means proved. They were most numerous in the western hemisphere, some forty American species referable to many genera having been described by North- American authors ; in Europe they are comparatively scarce. On the other hand no less than fifteen species of Pterodactyles are known from European formations, all armed with formidable teeth, whilst the gigantic Pterodactyles of North America are, with one exception, toothless. Together with the sur- XX. - 59
 * Archiv, vol. x., 1811; Lereboullet, " Embryologie du Le"zard," Ann. Sc. Nat.,