Jan. 22, 1874J 



NA TURE 



ii"] 



THE " BRONTOTHERID^," A NEW 

 FAMILY OF FOSSIL MAMMALS 



A AERY nearly a year ago Prof. O. C. Marsh, of Yale 

 V College, announced the discovery of a new order of 

 Mammalia, the Dinocerata, huge elephantine forms, with 

 three pairs of horns and large canine teeth, from the 

 Eocene deposits of the country to the east of the Rocky 

 Mountains, including the states of Dakota, Nebraska, 

 Wyoming and the " Bad Lands " of Colorado, which was 

 described and one of its species figured in this journal at 

 the time (Nature, vol. vii. p. 366). This same able 

 zoologist has the opportunity of adding still another un- 

 expected group of animals, this time from the Miocene 

 beds of the same district, which, though Ungulate and 



Fig. i.~IJ}cK:oiht:riniii ingcns^ Marsh. 



almost certainly Perissodactylate, are very different from 

 any known form. 



Brontotlicriiim ingens\% the. name given by Prof. Marsh 

 to the animal, the upper and side view of whose skull are 

 shown in the accompanying drawings, copied from his 

 paper in the American journal of Science and Art for 

 this month. The specimen here figured is 36 in. long, 

 and 20 in. between the tips of the two horn-cores. The 



proportions of the skull are peculiar, the whole being 

 elongate and very slight in depth. The high zygomatic 

 arches, without any well-marked postorbital processes on 

 them, or on the frontal bones, to divide off the temporal 

 from the orbital fossa;, also add to the uncomplicated 

 general appearance of the skull, whose aspect is rendered 

 more abnormal by the development of a huge pair of 

 horn-cores, which spring almost entirely from the firmly 

 " coossified " nasal bones, which make the anterior region 

 of the face exceptionally broad and heavy. The upper 

 part of each horn-core is rugose and the base contains 

 large air cells. 



The teeth present many points of interest. The dental 

 formula is /. - c— p.m. 1. m. -^ =38. The upper in- 

 cisors are quite small, and so are the lower. The canines 

 are short, stout, and not removed from the premolars by any 

 interval. The premolars are much smaller than the molars, 

 those of the lower jaw being very rahcothcrium-like. The 

 lachrymal foramina are small, and the infraorbital for- 

 amina are peculiarly large, as are the occipital condyles. 

 The cervical and most of the dorsal vertebrre are dis- 

 tinctly opisthocoilous. The atlas is much expanded 

 transversely ; the odontoid process of the axis is stout 

 and conical. The epiphyses of the vcrtebrre are, in most 

 specimens, loosely united to the centra. The caudal 

 vertebrse give indications of the tail having been long 

 and slender. 



The limbs are shorter than in the Elephant, having the 

 toes arranged as in the Tapir, four in front and three 

 behind. The whole of the distal end of the humerus is 

 occupied by the articulation ; the radius and ulna are 

 distinct. The phalanges are all short, and the terminal 

 ones are short and tubercular, as in the elephant. The 

 femur has a small third trochanter ; the tibia and fibula 

 are separate, and each complete. The distal facets on 

 the tarsal naviculare are subequal. 



Prof. Marsh remarks that " the wide narial opening, 

 the rugose extremity of the nasals, and the very large 

 infra-orbital foramen, naturally suggest that there must 

 have been an elongated, flexible nose, possibly as exten- 

 sive as in the tapir. That there was no long proboscis, 

 as in the elephant, is indicated with equal certainty by 

 the length of the head and neck, which renders such an 

 organ unnecessary." 



That Titanotherium pro7itii of Leidy is closely allied 

 to Bro/ilotherium, Prof. Marsh considers very probable ; 

 but the former genus was determined from a specimen 

 which wanted the skull, and it differs in some respects. 

 Mcgacerops of Leidy, as well as Symborodon and Mioba- 

 sileits of Cope, belong to the same group, but their identi- 

 fication has been established on data too imperfect for 

 complete and correct description. 



We have adopted Prof. iSIarsh's term horn-cores for the 

 large conical bony processes on the nasal bones ; but it is 

 not at all certain that such is the nature of these pro- 

 tuberances ; for it seems improbable that any large horns 

 could be efficiently employed by its owner at the free end 

 of so elongate and flat a skull ; at the same time that if 

 they were directed forward, they would seriously interfere 

 with the animal's power of grazing. It must also be 

 remembered that in Rhinoceros the horn is not supported 

 on any osseous core, whilst ia the wart-hog {Phacochwriis) 

 the wart has a conical osseous support. 



The discovery of these entirely new and unexpected 

 types of previously existing animals in the comparatively 

 unexplored region of the Rocky Mountains must give a 

 great stimulus to evolutionary thought ; for, more than 

 anything, it helps to illustrate to what extent the geological 

 record is incomplete ; and further, how great stress ought to 

 be laid on the imperfection, not of the geological record — 

 but of what seems to vary very nearly inversely as it- 

 human pateontological information. The recent exhu- 

 mation of these several fully differentiated mammals from 

 American Eocene and Miocene beds, when considered in 

 connection with the occurrence of equally speciahsed and 

 somewhat parallel lines of development in Europe, tends 

 to substantiate the considerable antiquity and the wide 

 distribution of the higher members of the vertebrate sub- 

 kingdom, and ought to lead to a more thorough search 

 for prototypal forms in the higher secondary strata, other 

 than the few at present known, so that the vast gap 

 which at present exists in our knowledge of the pedigree 

 of the mammalia, may be filled, partly at least, from the 

 record of Mesozoic formations. 



