File:The Ceratopsia (1907) (20580101102).jpg

Title: The Ceratopsia
Identifier: ceratopsia00hatc (find matches)
Year: 1907 (1900s)
Authors: Hatcher, J. B. (John Bell), 1861-1904; Lull, Richard Swann, 1867-1957; Osborn, Henry Fairfield, 1857-1935; Marsh, Othniel Charles, 1831-1899
Subjects: Ceratopsia
Publisher: Washington, Govt. Print. Off.
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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86 THE CERATOPSIA. to a young individual. In this respect this element resembles very closely the same portion of the squamosal in Marsh's type of Sterrholophus flabellatus, founded on a very complete skull of a young individual, and I am inclined to the opinion that the smooth surface of the squamosals and parietals upon which Marsh largely based his generic distinctions was due rather to the immature age of the individual than to generic differences. The supraorbital horns in the type of the present species appear to be attached by suture to their supporting elements and to have been developed from distinct and separate centers of ossification, much as the horn cores in the giraffe. In other words,they seem to have an origin independent of the other elements of the skull, which serve them simply as supports. In each supraorbital horn core in the present instance there . appears at the base a distinct ridge, well shown in the accompanying fig- ures, entirely encircling the base of the horn and giving the appear- ance of a suture which has not yet been fully obliterated, owing, per- haps, to the somewhat immature age of the individual. This lat- ter condition is further indicated by the somewhat imperfect union of the epoccipitals already re- ferred to. Certain characters j ust referred to in the present skull would seem to suggest that the supraorbital horn cores in the earlier Ceratopsia at least were developed independently of the other cranial elements, while the nasal horn was derived in part also from a distinct center of ossification. ,• The material above described, which forms the type of the pres- ent species, represents an ani- mal of considerable dimensions. Though smaller than any of the Ceratopsia from the Lara- mie of Wyoming, Montana, or Colorado, it was nevertheless decidedly larger than most of those known from the Judith River beds. In the development of the supraorbital horn •cores it shows a very decided advance over M. crassus, the type species of the genus, provided the supraorbital horn referred to by Cope really pertained to that species. The fragment of squamosal preserved also shows a very marked modification in the direction shown in the genera Ceratops, Triceratops, and Sterrholophus of Marsh. It is so different and distinct from that of the type species of the genus M. crassus that when it is considered in connection with the other structural differences found in other portions of the skull, more especially the horn cores, I do not hesitate to refer it to a distinct genus, Ceratops of Marsh, founded on very similar
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PlG. 90.—A, Lateral view of type of Monoclonius recurvicornis Cope, No. 3999, American Museum of Natural History; B, front view of same; C, top view of nasal horn of same, nas, Nasal; nh, nasal horn core; o, orbit; soft, supraorbital horn core. All one- sixth natural size. After Cope.o a From Am. Naturalist, vol. 23, PI. XXXIV.

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