Deinosuchus hatcheri, a new genus and species of crocodile from the Judith River beds of Montana

by W. J. Holland

page 281

By W.J. Holland

Upon the occasion of the geological reconnaissance undertaken by Mr. T. W. Stanton and Mr. J. B. Hatcher under the auspices of the United States Geological Survey in the summer of the year 1903, Mr. Hatcher found on Willow Creek, three miles west of Nolan and Archer's ranch, in Fergus County, Montana, some fragmentary remains lying upon the surface of the soil. He picked up a couple of scutes, which he brought back with him to the Carnegie Museum, and at the same time referred them provisionally to Stereocephalus tutus Lambe.^[3] Mr. W. H. Utterback was sent to the locality by Mr. Hatcher in the fall of 1903 with instructions to thoroughly explore the spot, and recover whatever could be found.

Mr. Utterback only succeeded in finding two vertebrae, one cervical rib, one fairly complete dorsal rib, fragments of other dorsal ribs, an os pubis, a large number of scutes, some of them quite perfect, and several hundred fragments of bones, some of them no doubt belonging to the skull, others to the vertebrae and ribs, but all of them so badly broken, and a few even water-worn, that it is impossible to refer them with any degree of certainty to their true position. The vertebrae and the ribs upon examination conclusively demonstrated, as the writer pointed out to Mr. Hatcher, that the animal was a huge crocodile. Mr. Hatcher immediately lost interest in the material, and though on several occasions urged to figure and describe the bones, turned from them to other things, which at the time possessed greater interest, and then came his untimely and melancholy end.

In 1905 Professor S. W. Williston urged the writer to describe the specimen, but, though the work was begun, it is only recently that the page 282 writer has found time to complete the brief sketch of these interesting remains, which is here given.

The type (No. 963 Carnegie Museum Catalog of Vertebrate Fossils) consists of two vertebrae; a cervical rib; the first dorsal rib of the left side; fragments of several other dorsal ribs; an os pubis; twenty-five scutes in fairly good condition, and numerous fragments of others; and in addition several hundreds of comminuted fragments of vertebrae, ribs, and bones of the skull, which furnish no contacts, and defy efforts to successfully collocate them. Some of these fragments are more or less water-worn, and consist simply of bits of bone which were for the most part found by Mr. Utterback upon the surface, where the skeleton had been weathered out, and trodden under foot. Some of them suggest that they have been exposed to the action of fire, and this might well have been the case when prairie-fires swept over the spot.

FIG. 1. Lateral view of left side of seventh(?) dorsal vertebra of D. hatcheri. 1/9 nat. size.

Generic characters of Deinosuchus so far as known. Great size, exceeding that of any other representative of the Crocodilia thus far described from North America.^[4] Scutes massive and possessing great vertical height in comparison with their breadth, many of the smaller scutes being almost hemispherical, and some of the smallest subglobose. Pubis straighter and less deeply excavated posteriorly than in recent crocodilia. Extremities of dorsal spines of vertebrae broad transversely and thickened for attachments, much more so than in existing genera. The postzygapophyses of the vertebrae more nearly on the same plane as the transverse processes and not looking outwardly as much as in other crocodiles.

FIG. 2. Anterior view of seventh(?) dorsal vertebra of D. hatcheri. 1/9 nat. size.

SEVENTH (?) DORSAL VERTEBRA.

The specimen, which almost beyond a doubt is the seventh in the dorsal series, is the better preserved of the two vertebrae which were recovered. It is procoelous. At the extremities of the transverse page 283 processes it shows the articulating surfaces for the ribs. It is a very massive bone and the dorsal spine is broad above, being greatly thickened transversely for attachment to adjacent structures. The postzygapophyses do not look as strongly outwardly as in the recent crocodilia, the under surfaces lying at their outer extremities nearly in the same plane as the upper surface of the transverse processes. Three views of the vertebra are given in Figures 1-3.

FIG. 3. Posterior view of seventh(?) dorsal vertebra of D. hatcheri. 1/9 nat. size.

LAST (?) LUMBAR VERTEBRA.

FIG. 4. Lateral view of the left side of the last(?) lumbar vertebra of D. hatcheri. 1/9 nat. size.

The vertebra under consideration is not so well preserved as the one described in the preceding paragraph, but the extremity of the left transverse process is sufficiently complete to show that it did not carry ribs. I assign it with doubt to the position of the last member of the lumbar series on account of the manner in which the spine and postzygapophyses overhang backwardly. If not that it must be one or the other of the two vertebrae immediately preceding. In general appearance it is not unlike the seventh (?) vertebra already described, except that the transverse processes are much narrower and the left, which is well preserved, shows no articular surfaces at the end. The spine has a much smaller anteroposterior diameter at the top than the seventh dorsal and its posterior margin is placed more decidedly caudad than in that vertebra. Fig. 4 shows the left side of the vertebra, which is the more complete, and which may be compared with the corresponding view of the seventh dorsal.

CERVICAL RIB.

A fairly well preserved specimen of the first cervical rib of the left side was found. At its proximal end it has been somewhat broken, but not enough to greatly diminish its length. Its proportions and general appearance are represented in Fig. 5, a representing the inner, and b the outer surface of the bone.

DORSAL RIBS.

FIG. 5. First cervical rib of D. hatcheri. 1/6 nat. size. a, inner surface; b, outer surface.

A fairly well preserved specimen of the first dorsal or thoracic rib of the left side was recovered. Its shape is represented in Fig. 6, A showing the posterior, and B the anterior surface of the rib. It had been broken about the middle of the shaft and was repaired in the laboratory. The writer has been assured that the contacts within, which are not now visible, justified the proportions which are shown by the specimen, but nevertheless is disposed to believe that the restored bone does not quite fully represent the entire length of the sternal part as it was in life. It is proportionately considerably shorter in its total length than the corresponding bone in other crocodilians. The relative length and shape of the capitulum and tuberculum is very like what is seen in the crocodiles of to-day. The tuberosity is well developed and directed forward and slightly more downward than in recent crocodilia.

In addition to the specimen which is here figured there were found a number of fragments of ribs, one of them apparently the proximal end with the capitulum of the third thoracic rib of the left side; another evidently a piece of the upper portion of the first rib of the right side carrying the tuberosity, but lacking the capitulum and tuberculum, and still another which is apparently the proximal end of the Fifth dorsal. A few fragments of the distal end of the ribs also occur in the mass of bones picked up by Mr. Utterback.

THE PUBIS.

A very well preserved specimen of the right pubic bone was recovered. It agrees very closely in its general outline and proportions with the corresponding bone in recent crocodiles, but is somewhat less rounded on its distal margin and decidedly less excavated on its posterior margin, at least when compared with the specimens of Crocodilius and Alligator before me. It is represented in Fig. 7, the illustration at the left of the cut showing the superior, and that on the right of the cut the inferior surfaces of the bone, the strongly curved, or excavated, side being the anterior margin.

THE SCUTES.

Of the scutes representing the specimen there are twenty-five, which are in fairly good condition, and numerous fragments of others.

In a beautifully perfect skeleton of Crocodilius acutus floridianus before me as I write I find that there are ninety-two osseous scutes entering into the dermal covering of the neck and back. The anterior series forms a transverse row of four scutes located immediately over and covering the spine of the axis; the second series consists of two transverse rows, the first made up of four scutes, the second of two scutes, and these overlie and cover the spines of the third, fourth, and fifth cervicals. The third series is composed of two scutes, covering the spine of the sixth cervical. The spine of the seventh cervicals is not shielded above by a row of scutes; and the spine of the eighth cervical is only partially covered by the first transverse row of the dorsal series of scutes. The dorsal series is made up of fifteen transverse rows of scutes, each row composed of four or six bony plates. Those containing six plates are the second, the fifth, the eighth, the tenth, eleventh, and twelfth rows, reckoning backward. The fifteenth transverse row of scutes, overlies and covers the spines of the third and fourth lumbar vertebrae. Following the dorsal series of scutes terminating at the point just stated, there are on either side, extending backward over the region of the sacrum,and the two anterior caudal vertebrae, six bony scutes diminishing in size backward and forming the backward prolongation of the second longitudinal row of scutes reckoning from the median line outwardly on either side. The arrangement of the scutes in C. floridianus is represented diagrammatically in Fig. 8.

All the scutes in D. hatcheri are characterized on the superior surface by an elevated longitudinal median ridge or carina, which does not, however, rise as sharply from the surface as in recent genera, and

1. δεινός = terrible; σουχος = crocodile.
2. I take pleasure in naming the species after my associate and friend, the late Mr. John Bell Hatcher, who was the discoverer of the specimen.
3. Contributions to Canadian Paleontology, Vol. III, pp. 55 et seq. Cf. Barnum Brown, Bull. Am. Mus. Nat. Hist., Vol. XXIV, pp. 187-201.
4. The writer has carefully examined and inquired in various museums at home and abroad and has been unable to find in any of them the fossil remains of any crocodile from North America equaling in size those here reported upon.