Archive image from page 66 of A diapsid reptile from the. A diapsid reptile from the Pennsylvanian of Kansas . diapsidreptilefr00reis Year: 1981 1980 PENNSYLVANIAN DIAPSID REPTILE 57 ered by it, except in the region of the quad- rate foramen. The dorsal process of the quad- rate is inchned shghtly anterodorsally. In mesosaurs, early 'eosuchians,' captorhino- niorphs, pelycosaurs, procolophonids there is no otic notch. The stapes is massive and has both a dorsal process and a footplate. The mandible is long and slender. The coronoid region is little expanded. There is no retroarticular process
Archive image from page 66 of A diapsid reptile from the. A diapsid reptile from the Pennsylvanian of Kansas . diapsidreptilefr00reis Year: 1981 1980 PENNSYLVANIAN DIAPSID REPTILE 57 ered by it, except in the region of the quad- rate foramen. The dorsal process of the quad- rate is inchned shghtly anterodorsally. In mesosaurs, early 'eosuchians,' captorhino- niorphs, pelycosaurs, procolophonids there is no otic notch. The stapes is massive and has both a dorsal process and a footplate. The mandible is long and slender. The coronoid region is little expanded. There is no retroarticular process. (3) In most early reptiles the marginal teeth are arranged in a single row. They are simple conical structures, slightly recurved, with subthecodont implantation. An anterior food trap is partially associated with some caniniform tooth development. (4) Vertebrae are amphicoelous and noto- chordal. Relatively large intercentra are con- tinued in the tail as chevron bones. The atlantal intercentrum is very large, has a well- developed ventral median ridge, and a pair of articular facets for the capitulum of the atlantal rib. In most pelycosaurs, in millero- saurs, 'eosuchians' and captorhinomorphs the atlantal centrum is excluded from the ventral border of the column by the axis intercentnmi. In Hylonomiis, the earliest rep- resentative of the captorhinomoi'phs, the atlantal centrum is crescentic in outline and open ventrally. The axial intercentrum is longer than those in the rest of the column. In Petrolacosaurus the large axial intercen- Pu/c'olhyri' trum is ventral to the crescentic atlantal cen- trum and is loosely attached to it. Although these elements are disarticulated in Hylono- miis [BM(NH)R. 4168], their relative posi- tion was apparently similar. In all later captorhinomorphs, however, the axial inter- centrum and atlantal centrum are indistin- guishably fused. The axial neural arch of Petrolacosaurus is strongly built, and has a large spine that extends anteriorly
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