. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. B -Time. I Figure 8. (A) Transition from apical ectodermal ridge (AER, left) to apical ectodermal fold (AEF, right) during early fin devel- opment. Cross section along proximodistal axis. (B) "Clock model" of heterochrony and phenotype. A developmentally early transition from AER to AEF would result in an "actinopterygian" phenotype (here represented by the pectoral fin of Amia). A developmentally later transition from AER to AEF would result in a "sarcopterygian" phenotype (here represen
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. B -Time. I Figure 8. (A) Transition from apical ectodermal ridge (AER, left) to apical ectodermal fold (AEF, right) during early fin devel- opment. Cross section along proximodistal axis. (B) "Clock model" of heterochrony and phenotype. A developmentally early transition from AER to AEF would result in an "actinopterygian" phenotype (here represented by the pectoral fin of Amia). A developmentally later transition from AER to AEF would result in a "sarcopterygian" phenotype (here represented by Eusthen- opteron). A and B modified from Thorogood (1991). Fins modified from Jarvik (1980; Early) and Andrews and Westell (1970; Late). discussions. Kalliopi Monoyios provided editorial assistance. This research was sup- ported by the Academy of Natural Sciences of Philadelphia and the National Science Foundation (EAR 9628163 to N. H. S.). LITERATURE CITED Ahlberg, p. E. 1989. Paired fin skeletons and rela- tionships of the fossil group Porolepiformes (Os- teichthyes: Sarcopterygii). Zoological Journal of the Linnean Society, 96: 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 the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
Size: 2031px × 1231px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorharvarduniversitymuseumofcomparat, booksubjectzoology
