150 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



afterward Leidy (1873.1, p. 27) described a skull, some 

 teeth, and parts of the limb bones of Palaeosyops and, 

 noting the similarities of this species to its supposed 

 allies Tapirus and Palaeoiherium, correctly referred it 

 to the perissodactyls — the odd-toed pachyderms. 

 Three other species (P. major, P. Tiumilis, P. Junius) 

 were also described by him from the Bridger beds 

 upon very fragmentary material. 



In developing our knowledge of the Eocene titano- 

 theres of the Bridger Basin, as in developing that of 

 the Oligocene titanotheres. Marsh and Cope were not 

 far behind Leidy. The first specimen of an Eocene 

 titanothere described by Marsh, however (1871.2), 

 was not recognized as such by him, as he mistook the 

 isolated second lower premolar of a Bridger Palaeosyops 

 for the fourth upper premolar of a dog and named it 

 "Canis montanus." The next year (1872.1) he de- 

 scribed some well-preserved remains under the name 

 Palaeosyops laticeps and also founded the genus 

 Telmatherium. Marsh's subsequent contributions to 

 our knowledge of middle Eocene titanotheres were not 

 especially significant, but in 1875 he described the 

 very important genus Diplacodon from the upper 

 Eocene Uinta beds of Utah and recognized its inter- 

 mediate position both in time and in structural 

 characters between his "Limnohyidae" (Palaeosyo- 

 pinae) and Brontotherium. 



Cope's explorations of the Bitter Creek or Wash- 

 akie Basin (middle Eocene) of Wyoming m 1872 led 

 to his describing the species "Palaeosyops" vallidens 

 and "Limnoliyus" laevidens, both represented by 

 imperfect remains. The former is now known to 

 belong to the long-headed genus Dolichorfiinus. 



The next year, 1873, Cope (1873.5) described the 

 species Limnoliyus ( = Palaeosyops) fonfinalis from the 

 lower levels of the Bridger formation (supposed 

 Bridger A), which is the oldest middle Eocene titano- 

 there yet discovered. His Palaeosyops diaconus, 

 from the upper levels of the Bridger Basin, is prob- 

 ably a synonym of Palaeosyops rohustus (Marsh). 



DISCOVERY IN HUNGAEY 



Shortly after these pioneer discoveries in America 

 Bockh and Maty (1876.1) described a large lower 

 jaw from Eocene deposits in Transylvania, in Hun- 

 gary. The animal was supposed to be allied to 

 Palaeoiherium and was named Brachydiastematherium 

 transilvanicum. Its affinities with the Palaeosyops 

 group long remained unnoted, and even to this day 

 it is the only known specimen of its kind in Europe. 



PEINCETOM AND COPE-WOETMAN EXPEDITIONS 



The Princeton expeditions sent to the Bridger and 

 Washakie Basins in 1877 and 1878 under Scott, 

 Osborn, and Speir brought to light much valuable 

 material of Palaeosyops and allied genera, especially 

 the types of "Leurocephalus" cultridens and the pecu- 

 liar form which was later described by Earle as 



Palaeosyops megarMnus. Thus by the end of 1878 re- 

 mains of the genus Palaeosyops and its allies had 

 been discovered in the middle Eocene Bridger and 

 Washakie Basins and in the upper Eocene Uinta 

 Basin. 



The next year (1879) Dr. J. L. Wortman, who was 

 collecting for Cope, extended the kiiown range of the 

 group into the lower Eocene Wind River formation of 

 Wyoming, where he discovered the very primitive 

 form which Cope in 1880 named Palaeosyops horealis 

 and which is now recognized as approximately ances- 

 tral to the middle Eocene titanotheres. Wortman 

 also discovered a very small form, which was described 

 by Cope in 1880 (1880.1) as Lamhdotherium popo- 

 agicum and recognized as more or less closely allied to 

 the Palaeosyops group. 



The next important expedition was that made by a 

 Princeton party under Scott and Speir in 1886 into 

 the Uinta Basin (upper Eocene). They collected 

 skeletal material, referred at that time to Diplacodon, 

 which was described by Osborn in 1890 (1890.51) and 

 which demonstrated the intermediate characters of 

 "Diplacodon" {Protitanoiherium) between the Oligo- 

 cene and middle Eocene titanotheres. In the same 

 publication Osborn also described "Palaeosyops" 

 hyognathus, a species based on a jaw that is now known 

 to represent the long-skulled genus DolichorMnus. 



FIRST SYSTEMATIC AND EVOLUTIONARY REVISION 

 (EARLE, 1889-1891) 



Although Cope in 1884 (1885.1) had republished 

 and partly extended the original descriptions of his 

 own species, with lithographic figures, no satisfactory 

 revision of the Palaeosyops group was possible at that 

 time or for many years later. 



In 1889 Charles Earle, at the invitation of Prof. 

 H. F. Osborn, began a careful study of the material 

 in the Princeton Museum and other collections, and 

 in 1892 he published a memoir "On the genus Palaeo- 

 syops Leidy and its allies" (1892.1). Earle gave a 

 very detailed description of the osteology of Palaeo- 

 syops and of the first attempted reconstruction of the 

 skeleton of an Eocene titanothere by Osborn. (See 

 fig. 86.) Owing in part to the lack of sufficient well- 

 associated material, in part to the confusing practice 

 of the earlier writers in designating and founding 

 species upon several specimens of doubtful specific 

 association, Earle's revision of the species and genera 

 was, as he himself recognized, by no means final. He 

 rightly regarded as distinct the genera Lamhdotherium, 

 Limnohyops, Palaeosyops, and "Telmatotherium," but 

 as he showed in his tentative phylogenetic scheme, 

 he, like other paleontologists at that time, did not 

 appreciate the polyphyletic character of groups and 

 consequently referred to a single main line of descent 

 a number of forms that belong to widely separated 

 phyla. 



