. Bulletin - United States National Museum. Science. OSTEOLOGY OF THE AKMOEED DINOSAUEIA. 55 In S. ungulatus and S. armatus, No. 4936, as shown in figure 22, the ends of four ribs unite to form this yoke, while in S. stenops only three participate in its forma- tion. Marsh laid considerable stress on the manner of the articulation of the sacral ribs with their respective centra, and even went so far as to establish * the species 8. duplex largely on these differences. He says: In the sacrum of tliis species each vertebra supports its own transverse process or rib as in the Sauro- poda, Willie
. Bulletin - United States National Museum. Science. OSTEOLOGY OF THE AKMOEED DINOSAUEIA. 55 In S. ungulatus and S. armatus, No. 4936, as shown in figure 22, the ends of four ribs unite to form this yoke, while in S. stenops only three participate in its forma- tion. Marsh laid considerable stress on the manner of the articulation of the sacral ribs with their respective centra, and even went so far as to establish * the species 8. duplex largely on these differences. He says: In the sacrum of tliis species each vertebra supports its own transverse process or rib as in the Sauro- poda, Willie m S. ungulalus the sacral ribs have sliifted somewhat forward, so that they touch, also, the vertebra in front, thus showing an approach to some of the Fig. 23.âPelvic region of Steggsadeus stenops Mabsh. Cat. no. 4S34, Type About -^ n\t size Ventral vieav snow as found in situ. A, Acetabulum; Co, fifth caudal; , caudal eib; cs, caudo-saceal' D, dorsal vertebra, or presacral no. 23; F. left femur; F', eight femue; 11, ilia; Is, left ischium- /y right ischium; P, left pubis; F', eight pubis; r, Rins of left side; r', Ems or eight shje; st, sf, sS, sacral vertebrae one, two, and three; si, dorso-sacral or presacral no. 27; X, last free rib articulated with prfsace\l NO. 20; y, BUTTKESS from the FffiST SACRAL WHICH ABUTS AGAINST 'M. THE BEAD OF THE RIGHT FEMUK \ND portion OF THE RIGHT PUBIS ARE REMOVED TO BETTER SHOW THE SACRAL VERTEBRAE. After comparing Marsh's drawing of the sacrum of S. ungulatus (fig. 22) with the sacra m the National Museum the actual dift'erences in this respect are so slight it appears to be entirely one of degree which may readily be accounted for on the ground of relative age. â Amer. Joum. Sci., vol. 34, pt. 9,1S87, p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble t
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