. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. EPIPTERYGOID—ALISPHENOID TRANSITION IN THERAPSIDA 409 ossify, extends as a rod-like structure to the skull roof. The primitive quadrate, when well ossified, ran forward to meet the epipterygoid. When the quadrate is less fully ossified, a cartilaginous area may have bridged the gap between the quadrate and the epipterygoid (fig. 8). It is presumed that the tendency for the epipterygoid to remain unossified is a degenerate feature (Romer, 1956). The earliest known reptiles date from the Carboniferous
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. EPIPTERYGOID—ALISPHENOID TRANSITION IN THERAPSIDA 409 ossify, extends as a rod-like structure to the skull roof. The primitive quadrate, when well ossified, ran forward to meet the epipterygoid. When the quadrate is less fully ossified, a cartilaginous area may have bridged the gap between the quadrate and the epipterygoid (fig. 8). It is presumed that the tendency for the epipterygoid to remain unossified is a degenerate feature (Romer, 1956). The earliest known reptiles date from the Carboniferous but knowledge of their anatomy is fragmentary. Abundant forms appear in the Upper Carboniferous and Lower Permian but as these include not only primitive forms but also more advanced types, it is certain that a very important section of the early history of the reptiles is still unknown. In diadectids both epipterygoid and quadrate are greatly developed. Diadectes itself features a quadrate of considerable height and width but little length (Romer, 1956). In the South African pareiasaurs both epipterygoid and quadrate are plate-like. The epipterygoid, which has a slender ascending process, furthermore stands transversely on the quadrate ramus of the pterygoid near its articulation with the basipterygoid process (Boonstra, 1934). According to Romer (1956) the margins of the base of the epipterygoid in pareiasaurians are unfinished, indicating a cartilaginous connection with the quadrate which has a similarly unfinished surface facing towards the epipterygoid. The captorhinomorphs Limnosceles, Captorhinus and Labidosaurus from the Lower Permian of the American Southwest are among the oldest cotylosaurs. PTERYGOID CARTii_AGiNOuS PORTiON OF PALATO QUADRATE RECONSTRUCTED QUADRATE Fig. 8. Seymouria. Lateral view of the skull with dermal bones removed. Cartilaginous portion of palatoquadrate reconstructed. (After Romer, 1956.). Please note that these images are extracted from scanne
Size: 1769px × 1412px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
