DISCOVERY OF THE TITANOTHERES AND ORIGINAL DESCRIPTIONS 



145 



rado, where he not only discovered and explored "an 

 extensive outcrop of the true Mauvaises Terres, or 

 White River formation," but also procured some mag- 

 nificent specimens of titanotheres (including the types 

 of Brontotherium gigas and B. ingens), which he de- 

 scribed and figured three years later. Marsh was also 

 able to solve the problem of the ordinal relationships 

 of the titanotheres (1873.1, p. 486), showing that his 

 Brontotherium gigas was a "true perissodactyl with 

 limb bones resembling those of Rhinoceros. The genus 

 is related to Titanotherium, and the two appear to form 

 a distinct family, which may be called Brontotheridae." 

 He was able in a very few words to throw a flood of 

 light upon the characters of the skeleton, hitherto 

 known chiefly from fragments : 



It closely resembles that in recent perissodactj^ls but shows 

 some approach to the Proboscidea. The femur has a third 

 trochanter, and its head a pit for the round ligament. The 

 fibula is entire and slender. The astragalus is remarkably 

 short. It has a deep groove on its upper surface, and the 

 articular facets for the navicular and cuboid are nearly equal. 

 In the manus there are four toes of nearly equal size, the first 

 digits being rudimentary or wanting. There were three digits 

 only in the pes, the first and fifth being entirely wanting. The 

 toes were short and thick, as in proboscidians. The meta- 

 carpals and metatarsals are longer than in the elephant, and 

 the phalanges shorter. The foot was also more inclined. The 

 carpal and tarsal bones are very short and form interlocking 

 series. The tail was long and slender. 



An important point not touched upon in this com- 

 munication was the presence or absence of horns. 



Prof. Edward D. Cope was not far behind Marsh in 

 contributions to the literature of the titanotheres. 

 Two years after Marsh had made his explorations in 

 Colorado, Cope, in 1872, discovered a number of re- 

 markable skulls (now in the Cope collection of the 

 American Museum of Natural History) which, in bul- 

 letins pubhshed in 1873 and 1874, he made the types 

 of Symhorodon torvus, Megaceratops acer, M. heloceras, 

 Symborodon hucco, S. dltirosfris, S. trigonoceras. He 

 states (1873.2, pp. 2, 3) that "Leidy and Marsh have 

 described two genera of this group, viz, Titanotherium 

 and Brontotherium, but without certain indications of 

 their possession of horns." He regards them as "all 

 true perissodactyls and allied to the Rhinoceros and 

 Palaeotherium." His genus Symhorodon, like Menodus, 

 Titanotherium, and Brontotherium, was "established 

 on mandibular rami only, which can not be certainly 

 associated with crania," the last phrase suggesting one 

 of the most troublesome and obdurate of titanothere 

 problems, which from the first has caused confusion in 

 the systematic nomenclature. Cope regarded the 

 absence of incisors as one of the generic characters 

 that separated Symhorodon from Titanotherium and 

 Brontotherium, thus first raising the problem how far 

 differences in the number of incisors may correspond 

 to true generic differences. The discovery of so many 

 more or less complete skulls enabled Cope to infer 



specific and generic characters from the variations in 

 form of the horn cores, skull top, nasals, and zygo- 

 matic arches. Thus the discoveries of Cope and 

 Marsh, although they settled the ordinal relationships 

 of the titanotheres, began to complicate the problem 

 of their interrelationships. 



SUMMARY OF MAESH'S CONTRIBTTTIOKS 



In Marsh's paper "On the structure and affinities 

 of the Brontotheridae" (1874.1) he developed further 

 the family characters of the group, separating them 

 from the Rhinocerotidae, "apparently their near 

 allies," establishing the number of digits in the fore 

 and hind feet and the general characters of the skull, 

 lower jaw, vertebrae, and limbs. This paper is ac- 

 companied by the first of a series of excellent litho- 

 graphic plates, illustrating some of Professor Marsh's 

 superb specimens of titanotheres from Colorado. 

 Marsh contributed another short but pregnant article 

 on the "Principal characters of the Brontotheridae" 

 in 1876 (1876.1), and after that he published at in- 

 tervals brief descriptions of supposedly new genera 

 and species, not all of them accompanied by illustra- 

 tions, until September, 1891, the date of his last 

 published contribution to the subject. 



Marsh's most valuable contributions to our knowl- 

 edge of the titanotheres may be summarized as follows: 

 (1) He and his party explored the White River forma- 

 tion in Colorado and collected from it many remark- 

 ably fine specimens; (2) he demonstrated the ordinal 

 position of the group, classifying its members as 

 perissodactyls; (3) he recognized the fact that the 

 titanotheres constitute a distinct family, which he 

 named the Brontotheridae; (4) he made the illuminat- 

 ing observation that his upper Eocene genus Diplaco- 

 don served to connect the Oligocene Brontotheridae 

 with the Eocene "Limnohyidae"; (5) he published 

 many excellent lithographs and woodcuts, showing 

 chiefly the skulls and dentition of titanotheres, but 

 including also (1889) an excellent restoration of 

 Brontops rolustus; (6) he supervised the preparation 

 of a fine series of lithographic plates for the present 

 work; (7) under the auspices of the United States 

 Geological Survey he founded the present series of 

 monographs on fossil vertebrates; (8) he began the 

 preparation of the present monograph, although he 

 left no manuscript for it; (9) he obtained for the 

 National and Yale Museums their superb specimens of 

 titanotheres, most of which were collected by his field 

 assistant J. B. Hatcher, who in turn also made valuable 

 scientific contributions to our knowledge of these 

 animals. 



Marsh's detailed systematic work on the titanotheres 

 was less fortunate than his broader contributions, 

 owing chiefly to confusion in regard to features of the 

 skull and jaw. After founding the genus and species 

 Brontotherium gigas upon a lower jaw, he referred to the 



