A New Fossil Crocodilian from Mongolia, by Charles C

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AMERICAN MUSEUM NOVITATES Published by Number 1097 THE AMERICAN MUSEUM OF NATURAL hIISTORY December 26, 1940 New York City

A NEW FOSSIL CROCODILIAN FROM MONGOLIA, BY CHARLES C. MOOK2

In the field season of 1930 the Central SPECIFIC CHARACTERS.-Symphysis extending of The American back to level of the sixth mandibular teeth, the Asiatic Expedition two rami of the mandible diverging at a moder- Museum of Natural History collected some ately wide angle, dental row shorter than post- crocodilian remains from the Irdin Manha dental portion of jaw, teeth stout and faintly Beds of Upper Eocene age at a locality striated, interfenestral plate flat, sutures of seven miles west of Camp Margetts, Mon- nasals with lachrimals considerably shorter than golia. These remains consisted of portions sutures with prefrontals. of at least two individuals. A portion of DETAILED DESCRIPTION OF TYPE MATERIAL. -The lateral borders of the nasals are parallel the skull including parts of the frontal, for a considerable distance. The sutures of the prefrontal, lachrimal, nasal, and maxillary nasals with the lachrimals are shorter than their bones, indicates an individual of fairly sutures with the prefrontals. The interorbital small size. An interorbital consisting plate is of moderate breadth and is flat. The plate, snout exhibits a slight constriction at the level of parts of the frontal and nasal bones, indi- of what are apparently the sixth maxillary teeth. cates a individual. A of lower larger pair The two rami of the mandible diverge at a jaws, with the two rami separated, and fairly broad angle. The symphysis is moder- somewhat broken and crushed, indicate a ately broad. Its exact breadth cannot be deter- fairly large individual corresponding in mined because of crushing, especially of the left size with that represented by the inter- ramus. The symphysis extends back to the level of what are apparently the sixth mandibular orbital plate. These remains exhibit dis- teeth. tinctive characters and are accordingly re- The tips of both rami are missing with the ferred to a new genus and species of croco- alveoli of the first mandibular teeth. The first dilians, which may be designated Asiato- alveoli preserved are those of the second mandib- suchu.s grangeri in allusion to its occurrence ular teeth. The numbers indicating teeth in in central Asia and in honor of Dr. Walter this description refer to the morphological number of the teeth in the jaw and not to the Granger, of the Asiatic Expedition. preserved teeth or alveoli in the specimen. The second and third alveoli are of moderate size ASIATOSUCHUS, NEW GENUS and are slightly separated from each other. TYPE.-Asiatosuchus grangeri. The fourth tooth is preserved in the left ramus GENERIC CHARACTERS.-Similar to those of only. It is stout and faintly striated. The Crocodilus, but with at least seventeen teeth in corresponding alveolus in the right ramus is the each ramus of the lower jaw; splenial bones do largest in the jaw. The fifth and sixth alveoli not reach forward to the symphysis. are slightly smaller than the second and third and are close together in position. Following Asiatosuchus grangeri, new species the sixth are seven obscure alveoli of moderate size (seventh to thirteenth, inclusive) whose ex- TYPE.-Lower jaws, Amer. Mus. No. 6606. ternal borders are indefinite and whose internal PARATYPES.-Portion of snout, Amer. Mus. borders are missing. The alveoli of the right No. 6607; and interorbital plate, Amer. Mus. eighth and ninth teeth are confluent with each No. 6608. other. The crown of the fourteenth tooth is TYPE LOCALITY AND LEVEL.-Twenty-five present, now imbedded in plaster. It is elon- miles southwest of Iren Dabasu, Inner Mon- gate fore and aft, low vertically, with broadly golia; Irdin Manha Formation, Upper Eocene, rounded anterior and posterior surfaces. There 1930. is a prominent ridge on the anterior edge and 1 Publications of the Asiatic Expeditions of The another on the posterior edge. There are faint, American Museum of Natural History. Contribu- irregular, rugose striations on various parts of the tion No. 141. of the tooth 2 Contributions to the Osteology, Affinities, and crown. The length antero-poste- Distribution of the Crocodilia No. 31. riorly approximately equals the height of the 2 AMERICAN MUSEUM NOVITA TES [No. 1097

A.M. 6606 TYPE 4

Fig. 1. Asiatosuchus grangeri, n. sp. Type, lower jaws, Amer. Mus. No. 6606, one-fourth natural size, A, superior view; B, lateral view, right side. crown. The transverse diameter at the base is Length, anterior end as preserved about half the height. to border of last alveolus ...... 245 Posterior to this tooth are four or possibly five Length, tooth row of left ramus, alveoli. This makes the total number of teeth in estimated ...... 257 each ramus eighteen or nineteen. The length of Length, posterior border of last the tooth row was undoubtedly less than the alveolus to posterior border of length of the jaw from the last tooth to the tip of glenoid surface...... 192 the articular process. The actual distance from Length, symphysis, estimated.... 90 the last alveolus to the posterior edge of the Distance from anterior end of glenoid surface is slightly less than the length of splenial to symphysis...... 10 the tooth row. Length, glenoid surface, antero- The anterior end of each splenial almost posterior ...... 31 reaches the symphysis but does not actually do so. Breadth, glenoid surface transverse 56

There is a very slight degree of festooning on Breadth of symphysis, estimated. . 124 the borders of the lower jaws. Antero-posterio diameter of 4th tooth...... 16 MEASUREMENTS Transverse diameter of 4th tooth. 14 Antero-posterior diameter of 14th Type, Amer. Mus. No. 6606 tooth...... 13 Left ramus of mandible Transverse diameter of 14th tooth. 13 Length, as preserved ...... 476 mm. Height diameter of 14th tooth.... 6 1940] NEW FOSSIL CROCODILIAN FROM MONGOLIA 3

Paratype, Amer. Mus. No. 6607 Paratype, Amer. Mus. No. 6608 Portion of snout Frontal and prefrontals Length of specimen as preserved.. 84 mm. Length of specimen as preserved.. 73 mm. Maximum breadth...... 71 Breadth across posterior end ..... 40 Breadth across 5th maxillary Breadth across interorbital plate.. 23 teeth...... 64 Height...... 24

A.M.6608 A.M. 6607 Fig. 2.AfAsiatosuchus grangeri, n. sp. Paratypes, one-half natural size. A, portion of snout, Amer. Mus. No. 6607, superior view; B, portions of frontal and prefrontal bones of another individual, Amer. Mus. No. 6608, superior view.