Fam. 3. Macrorhynchidae, in the freshwater deposits of the Purbeck, Wealden, and Greensand of Europe. Snout long and slender. The nasals are narrow, and so elongated that they meet a similar long extension of the premaxillaries. Choanae between the palatines and pterygoids. Vertebrae amphicoelous. Dermal armour consisting of two imbricating dorsal and eight ventral rows, e.g. Pholidosaurus of the English Wealden.
Fam. 4. Gavialidae.–Snout long and slender. The choanae are situated entirely within the pterygoids. Vertebrae procoelous. Members of this family make their first appearance in the littoral marine deposits of the Upper Chalk of Europe and North America; others are common in tertiary, marine, and freshwater deposits, whilst only two genera and species occur now in the Oriental sub-region.
Thoracosaurus in the Upper Chalk of New Jersey and France and Belgium is intermediate between Gavialis and Tomistoma. The prefrontal bones are very small, while the lacrymals are very long and surround the nasals posteriorly. The nasals themselves are slender, and reach the posterior likewise long and narrow prolongations of the premaxillaries.
Gavialis.–The snout is extremely long and slender. The mandibular symphysis is so long that it comprises a great portion of the splenial bones, and extends backwards almost to the level of the last teeth and to the palatal foramina. The nasal bones are very short, and are separated from the premaxillaries by the long suture of the maxillaries. About twenty-eight upper and twenty-five lower teeth on each side.
G. gangeticus, the only recent species, is essentially Indian, inhabiting chiefly the basins of the Ganges, Brahmaputra, and Indus; it occurs also in the Mahanadi of Orissa and in Arakan, but does not live in the Irrawaddy, nor in the Narbada, Kistna, and farther south. In spite of its great size, which reaches 20 feet or even more, it is harmless, and lives entirely upon fish; hence its Hindustani name, gharial, meaning fish-eater, of which the generic name is a corruption.
The nuchal and dorsal scutes form a continuous shield, but there are two small postoccipital scutes. General colour, dark olive-brown above; the young are paler, with dark markings. The male is remarkable for several peculiarities. The nose is very much swollen, and can be inflated like a bag when the nostrils are closed. In connexion herewith, probably produced by the recoil of the air in the long narial passages towards the choanae or posterior nares, there is a pair of hollow globular swellings, in large specimens of the size of a goose's egg. The shell of these globes is formed by the dorsal wings of the palatine bones above the floor of the choanae, and they extend forwards to the right and left of the ethmoid almost to the vertical downward process of the prefrontals.
Fig. 106.–Skull of Gavialis gangeticus (the Gharial). × ⅛. F, frontal; J, jugal; L, lacrymal; Mand, mandible; Mx, maxillary; Na, nasal; Par, parietal; Pm.c, premaxillary; Prf, prefrontal; Ptf, postfrontal; Qj, quadrato-jugal; Sq, squamosal.
Although the Gharial is common enough, we know next to nothing about its habits, and in zoological gardens it is rather rare. A. Anderson[[139]] has, however, made the following observations. Forty eggs were dug out of the sand, where they were lying in two tiers, twenty below and twenty above, with a foot of sand between. The young ran with amazing rapidity the moment they were hatched. Some of them actually bit his fingers before he had time to remove the shell from their bodies! The length of these new-born creatures was 15 to 16 inches, 9 of which belonged to the long and slender tail.
Several fossil species have been described from the Pliocene deposits of the Sivalik Hills of India; and in the same district occurred the closely allied Rhamphosuchus crassidens, which reached the gigantic length of about 50 feet!