Samuel Wendell Williston.

Water reptiles of the past and present online

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digital formula 2, 3, 4, 5, 3 or 4. Most other turtles have the same



Fig. 131. вАФ A spider -e-
tes, a trionychoid turtle
from the Eocene of
New Mexico; front leg.
(From Hay.)



248 WATER REPTILES OF THE PAST AND PRESENT

numbers of bones in the digits that mammals have, that is, two
phalanges in the thumb and big toe and three in each of the other
digits. The river turtles have a larger number in the fourth digit,
either four or five. It seems to be a law that evolution is irre-
versible, and if so could the river turtles have been descended from
forms with a less number of phalanges ? But, the skeleton of the
Trionychoidea resembles the more specialized turtles in so many
ways that one can hardly believe they were all accidental or parallel.

We may then assume that at about the time that the ordinary
marsh turtles took to the sea to become marine, others took ad-
vantage of the fresh-water ponds and rivers, and in doing so, like
the marine turtles, lost their horny epidermal shields, and became
thinner in shape, thereby reducing the resistance to the water.
Instead, however, of reducing the costal plates over the ribs, they
retained them intact and complete for some reason or other, but
lost instead the marginal row of bones, unlike the marine turtles
which retained them even after they had lost nearly all of the costal
plates. Possibly also they regained additional bones in the fourth
digit, a sort of hyperphalangy like that of the more strictly aquatic
reptiles. Or, possibly, they may have descended from some branch
of the turtles which had not yet lost these bones, retaining them
because they were still serviceable for swimming. We know
nothing yet about the structure of the feet of the early turtles, and
it is possible that not all had acquired the reduced phalangeal
formula.

In the development of aquatic habits the river turtles do not
show the same degree of specialization in the limbs that the strictly
marine forms do. The humerus (Fig. 131) is a slender bone, with
the tuberosities for the attachment of the muscles situated near
the proximal end. The radius and ulna are relatively short, and
the foot is long. The hind legs, as would be supposed, are less
highly specialized as swimming paddles, and are relatively smaller.
Nevertheless the Trionychoidea present an interesting type of
adaptation to water habits, both in body and in limbs.



INDEX



Adaptation to aquatic life, 59.

Aetosauria, 187.

Aigialosaurs, 146.

Alligator, 142, ig?.

Amblyrhynchus, 142.

Andrews, C. W., 75.

Angistorhinus, 190.

Anomodontia, 102.

Aquatic reptiles, adaptation of, 59.

Araeoscelis, 133, 138.

Archelon, 234, 236, 238, 239.

Archosauria, 33.

Aspiderectes, 246, 24/.

Baptanodon, 113, 114, 117.
Baur, George, 119, 120, 185, 234.
Belodon, 185, i8g, igi.
Belodontia, 185.
Beche, De la, 73.
Bogalobou, 75.

Broom, Robert, 5, 102, 103, 129.
Brown, Barnum, 93, 179.
Buckland, Dean, 75, 77.

Cacops, 35.

Camper, Adrian, 149, 166.

Camper, Peter, 149, 166.

Captorhinus, 4g.

Caretta, 230.

Carpus, 38.

Casea, 53.

Case, E. C, 234.

Champsosaurus, 79, 180, 181, 182,

Chelone, 220, 229.

Chevrons, 32.

Choristodera, 178.

Classification of reptiles, 13.

Clavicles, 37.

Cleithrum, 36.

Clidastes, 147, 154, 155, 157, 166.

Collection of fossils, 10.

Colpochelys, 222.

Conybeare, Rev., 73, no, 149.

Cope, E. D., 126, 176, 178, 185, 231, 233.

Coracoid, 36.

Cotylosauria, 16.

Cryptodira, 226.

Cretaceous of Kansas, 8.

Crocodiles, ancient, 204; marine, 207;

modern, 195.
Crocodilia, 15, 194.
Crocodilus, ig$.
Cuvier, Georges, 73, 97, 107, no, 149.



Darwin, Charles, 142.
De Fond, St. Faujas, 148.
Dermochelys, 241, 242.
Desmatochelys, 231, 232.
Dimetrodon, 36, 31.
Dinosauria, 18.
Dolichosaurs, 145.
Dolichobrachium, 54.
Dollo, Louis, 167, 179.

Edaphosaurus, 22.

Elasmosaurus, 78, 84, 86, gi.

Enaliosauria, 75.

Eosauravus, 52.

Episcoposaurus, 190.

Eretmochelys, 230.

Eryops, 31, 47.

Eusuchia, 195.

Exoskeleton, 43.

Extinct reptiles of North America, 52.

Femur, 41.
Fibula, 41.
Foot, 42.

Fraas, Eberhard, 74, 75, 99, in, 115, 185,
213.

Gastroliths, 92, 200.

Gavial, Borneo, 201; Gangetic, ig8, igg

202.
Gavialidae, 203.
Geological Ages, 46.
Geosaurus, 208, 210, 211, 212, 214.
Gervais, Professor, 126.
Gilmore, Charles, 113, 167.
Globidens, 167.
Goldfuss, August, 151.
Graptemys, 218.

Hadrosaurus, 56.

Hand, 38.

Hauff, B., 122.

Hay, Oliver P., 220, 227, 228, 234, 242.

Hofmann, Dr., 148.

Holops, 207.

Home, Everard, no.

Homo diluvii testis, 108.

Huene, Friedrich von, 131, 185.

Humerus, 38.

Huxley, Thomas, 185, 207.

Hydrus, i6g.

Hyperphalangy, 118.

Hypocentrum, 36.



249



250 WATER REPTILES OF THE PAST AND PRESENT



Ichthyosauria, 17, 107.

Ichthyosaurus, 108, 112, 119, 121, 122.

Iguana, 140.

Ilium, 39.

Interclavicle, 37.

Intercentrum, 30.

Ischium, 39.

Jaeger, George, 184.
Jaekel, 185.

Karoo beds, 102.
Koenig, no.

Labidosaurus, 22, 26, 50.

Laecertilia, 140.

Lariosaurus, gg, 100.

Leather-back turtles, 241.

Leidy, Joseph, 151.

Limnoscelis, 20, 47.

Lizards, 140; flatheaded, 144; Galapagos,

142.
Lull, Richard, 54.
Lystrosaurus, 103, 104.
Lortet, M., 135.

McGregor, J. H., 126, 129, 131, 185, 186,

189.
Mandible, 25.
Mantell, Dr., 75.
Marsh, O. C., 54, 185.
Merriam, J. C., 112, 120, 171, 174.
Merriamia, 118.
Mesosaurus, 126, 127, 128.
Mesosuchia, 185, 204.
Meyer, Herman von, 75, 87, 132, 134, 184.
Mixosaurus, 119.
Monitor lizards, 144.
Mosasauria, 148, 166.
Mosasaurus, 148; hofmanni, 149; maxi-

miliani, 151.
Minister, Georg von, 97.
Mudge, B. F., 93.
Mystriosuchus, 185, 188, i8g, igi.

Nares, 23.
Nectosaurus, 175.
Nothosauria, 95.
Nothosaurus, g6, gy, g8.

O'Fallen, Major, 151.

Ophiacodon, 30, 32, 37, 38, 40, 42.

Ophidia, 168.

Ophthalmosaurus, 118, 125.

Orders of reptiles, 16.

Osborn, H. F., 126.

Ostodolepis, 33.

Owen, Richard, 75, 103, no, in, 185.

Paleorhinus, 190.
Paliguana, 5.



Parasuchia, 18, 184.

Parietal foramen, 23.

Pectoral girdle, 34.

Pelvic girdle, 39.

Pelvis, 39.

Petycosauria, 186.

Pelycosimia, 187.

Phytosauria, 18, 187.

Phytosaurus, 186, 187.

Pineal foramen, 23.

Platecarpus, 151, 155, 156, 158, ifg, 166.

Platynota, 148.

Plesiosauria, 77.

Plesiosaurus, 74.

Pleurodira, 224.

Pleurosaurus, 134, 136, 177.

Polycotylus, 80.

Proatlas, 32.

Proganochelys, 217.

Proganosauria, 17.

Proteosaurus, no.

Protorosauria, 17, 132.

Protorosaurus, 132.

Protostega, 233, 234.

Protostegidae, 231.

Pseudosuchia, 185.

Pterosauria, 18.

Pubis, 39.

Pythonomorpha (Mosasauria), 166.

Range of Reptilia, 45.

Rhachitomous vertebrae, 17.

Rhynchocephalia, 17, 176.

Rhytidodon, 190.

Ribs, S3-

River turtles, 244.

Rutiodon, igo.

Sacrum, 32.
Sapheosaurus, 178.
Sauranodon (Baptanodon), 125.
Sauropterygia, 17, 73.
Scheuchzer, 107
Seeley, H. G., 75, 126, 132.
Seymouria, 21, 48.
Shoulder girdle, 34.
Simoedosaurus, 179.
Skeleton of reptiles, 19.
Skull of reptiles, 21. ,
Snakes, 168.
Spener, 132.

Sphenodon, 24, 132, 176.
Squamata, 17, 138.
Stegocephalia, 48.
Stereosternum, 126.
Sternum, 37.
Stomach stones, 200.

Tarsus, 42.
Teeth, 21, 25.



INDEX



251



Teleosaurus, 205.

Temporal openings, 23.

Testudo, 228.

Thalattosauria, 17, 171.

Thalattosaurus, 172, 173, 174.

Thalattosuchia, 207.

Therapsida, 16.

Theromorpha, 16.

Thaumatosaurus, 74.

Thoracosaurus, 207.

Tibia, 41.

Tomistomidae, 201.

Tortoises, 216; fresh-water, 226; land,

227; marsh, 226.
Toxochelys, 2ig, 231, 232.
Trachemys, 221.
Trimerorhachis, 25.
Trinacromerum, 77, 81, 83, 85, 88, 8g.



Trionychoidea, 244.

Trionyx, 245.

Tuatera, 176. See Sphenodon.

Turtles, 216; river, 244; sea, 229; ancient

sea, 231; side-necked, 224.
Tylosaurus, 153, 155, 157, 160, 165, 166.



Varanus, 144.

Varanops, 53.

Ventral ribs, 34.

Vertebrae, 28; notochordal, 29;

tomous, 31.
Versluys, 244.



rhachi-



Watson, D. M. S., 103.
Wieland, G. R., 234, 236, 239, 243.
Woodward, A. S., 126.
Zittel, Carl von, 185.



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Online LibrarySamuel Wendell WillistonWater reptiles of the past and present → online text (page 19 of 19)