Sclerotic Rings in Mosasaurs (Squamata: Mosasauridae): Structures and Taxonomic Diversity

“…The different shape of the rings in birds is a consequence of millions of years of evolution; however, similar morphological patterns are maintained in species belonging to the same order. 7,31 The absence of sulci and tuberosities (or any other bone markings indicating a muscle-insertion site) on the anterior and posterior faces, respectively, differed from the report of Yamashita et al, 10 who described, in fossils of prehistoric marine reptiles of the family Mosasauridae, a sulcus on the anterior face by the sigmoid flexure and a tuberosity on the posterior face for possible muscular fixation. Perhaps the comparison of these data corroborates the reports of questions about the endoskeletal function of the scleral ring.…”

“…7,31,32 The most frequent number of ossicles per ring (between 11 and 12) was higher than the count previously reported for some species of turtles, but was within the range found for reptiles (Table 6). There are different criteria for this count 36 ; the one adopted for this study was the method used by Yamashita et al, 10 because it follows the ossicular ossification sequence, which starts with the SO in the lateral position and continues to those in the middle-inferior position. 37 The four previously described ossicular types 10 were observed in the SORs of the animals in the present study.…”

“…There are different criteria for this count 36 ; the one adopted for this study was the method used by Yamashita et al, 10 because it follows the ossicular ossification sequence, which starts with the SO in the lateral position and continues to those in the middle-inferior position. 37 The four previously described ossicular types 10 were observed in the SORs of the animals in the present study. In addition, the +V and -V types were classified for the first time.…”

“…(c) SOs 241 from 12 articulated SORs and the 8 disarticulated SORs were counted and numbered by the technique of Yamashita et al 10 All of the SORs were identified (separated by sample in individualized containers). The SOs were numbered from the first ossicle positioned laterally in the inferior‐middle portion of the SOR to the last ossicle located immediately medial to ossicle 1.…”