...Systematic Catalogue of Vertebrata of the Eocene of New Mexico: Collected in 1874Geographical Surveys West of the 100th Meridian (U.S.), Edward Drinker Cope, Geographical Surveys West of the 100th Meridian (U.S.). U.S. Government Printing Office, 1875 - 37 pages |
Other editions - View all
Common terms and phrases
Ambloctonus AMBLYPODA angle antepenultimate molar anterior cusps ANTIACODON articulation Artiodactyla astragalus basal base Bathmodon border calcaneum CALIFORNIA LIBRARY canine carapace Carnassials Carnivora Chief of Engineers cingulum concave cone Costal crest CROCODILUS cuboid cuneiform dentition Depth of ramus DERMATEMYS Diameter Didymictis E. D. COPE Elephantida elevated Eocene external fourth premolar frontal bone genera genus heel Hyopsodus incisor inner side inner tubercle internal cusp last inferior molar last molar last premolar latter Leidy Length of crown Length of last Length of penultimate lower molar Mammalia mandibular ramus Marsh Mesonyx metacarpal Mexico navicular oblique ridge obtuse Orohippus Orotherium OXYÆNA Pelycodus penultimate molar Perissodactyla PHENACODUS portion posterior cusp posteriorly PROTOTOMUS Quadrumana Report U. S. Geol resembles robust rugose second true molar species specimen subequal superior molars Survey Terrs symphysis third premolar tooth transverse tubercular carnassials unciform UNIVERSITY OF CALIFORNIA vertebrata Vertebrate Vertebrate Fossils WHEELER Width of crown Width of penultimate
Popular passages
Page 3 - Artiodactyla, &c. The simplicity of structure resembles, on the other hand, that found in the opossum and various Insectivora, Rodentia, and Quadrumana, and in the Proboscidia, most of which have the generalized type of feet. The structure indicates that the carnivorous genera named were plantigrade — a conclusion which is in conformity with the belief already expressed, that the mammalia of the Eocene exhibit much less marked ordinal distinction than do those of the Miocene or the recent periods....
Page 3 - ... performing the functions of life. These Eocene carnivores also (according to Cope) showed a primitive character in the tibioastragalar articulation, or " ankle-joint." " The astragalus is flat, and the applied surfaces are nearly a plane, and without the pulleyshaped character seen in existing carnivora, as dogs, cats, and, in a less degree in the bears and in other mammalia with specialized extremities, as Perissodactyla, Artiodactyla, &c. The simplicity of structure resembles, on the other...
Page 2 - Hymnodontidce, as is known, possess three carnassial teeth without inner tubercles. The history of this form is as yet uncertain, as it was evidently not derived from contemporary forms of the Eocene with tubercular sectorials. The development of...
Page 3 - In other words, the numerous types of digitigrade carnivora which have survived, are those developing but one sectorial tooth (whose earliest representative is Didymictis). The increased perfection of the sectorial has been associated with a reduction in the number of other molars, first posterior, then anterior to it. which reduction has been accompanied by an increased relative size of the sectorial. By this process concentration of the carnassial function has been gained, and increased robustness...
Page 2 - The development of the carnassial dentition has thus been accomplished, first, by an addition of an anterior cusp, and subsequently by the subtraction of the inner and posterior cusps, so that of the original four of the quadrituberculate molar but a single one, ie, the anterior external, remains. The same process may be observed in the successional modifications of the entire dentition of the jaws. The Eocene forms of carnivora frequently display more numerous sectorial teeth (such as they are)...
Page 2 - ... connects them is now a cutting blade. The posterior portion of the tooth does not share in this elevation, and its two tubercles are in some genera obsolete, and in others replaced by an elevation of one margin, which leans obliquely toward the middle of the crown. In Mesonyx this is represented by a median longitudinal crest. If the two tubercles of the posterior part of this tooth (which may be termed a tubercular sectorial) are elevated and acute, we have the molar of many recent and extinct...