The synarcual cartilage of batoids with emphasis on the synarcual of Rajidae
Article first published online: 20 JUL 2011
Copyright © 2011 Wiley-Liss, Inc.
Journal of Morphology
Volume 272, Issue 12, pages 1444–1463, December 2011
How to Cite
Claeson, K. M. (2011), The synarcual cartilage of batoids with emphasis on the synarcual of Rajidae. J. Morphol., 272: 1444–1463. doi: 10.1002/jmor.10996
- Issue published online: 10 NOV 2011
- Article first published online: 20 JUL 2011
- Manuscript Accepted: 23 APR 2011
- Manuscript Revised: 14 MAR 2011
- Manuscript Received: 10 NOV 2010
- Banks Fellowship for Paleontology
- The NSF DeepFin Student Research Exchange
- The Society of Vertebrate Paleontology Predoctoral Award
Comparison of embryonic specimens with juvenile and mature specimens of other skates indicates that the relative developmental sequence of events is maintained among several taxa within larger clades. However, there is a fundamental difference between the pattern of chondrification and the pattern of calcification in skates. Early in ontogeny a short synarcual surrounds the first free vertebral centrum. Additional neural arch segments are incorporated from anterior to posterior and the relative length of the synarcual cartilage to total length of the body normalizes early. A secondary direction of chondrification, from ventral to dorsal, is also present. Juveniles and subadults show that synarcual calcification is relatively late compared to the calcification of other regions of the skeleton and proceeds from lateral to medial. Comparison with extinct taxa also indicates that there is a decrease in vertebral centrum involvement with the synarcual cartilage over the evolutionary history of the clade. Results from exploratory analyses of morphospace and taxonomy reveal that phylogeny explains part, but not all, of the data on the synarcual in Rajidae. There is evidence of individual and ontogenetic variation among all species of skates examined, however, phylogenetically informative variation prevails. Comparison with other batoids demonstrates a trend where the number of vertebral centra flanked by the synarcual cartilage decreases among more derived taxa indicating a high degree of convergent morphology among batoids with potential functional significance. J. Morphol., 2011. © 2011 Wiley-Liss, Inc.