. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Figure 29. Malleus of Drytomomys aequatorialis, UCMP no. 41636, xi5. A. Dorsal view. B. Ventral view. C. Surface for articulation with the incus. Abbreviations: D—dorsal side; M—broken manubrium. cms longus of the incus, moderately so in heavy ossicles such as characterize most Thnjonomys (Tullberg, 1899: PI. 24, Fig. of the Hystricognathi. 14; Wood and Patterson, 1959: 293, n. 4), If the Caviomorpha were descended although Doran's figure does not show from rafted thryonomyoids, it seems most this, and almost as far a
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Figure 29. Malleus of Drytomomys aequatorialis, UCMP no. 41636, xi5. A. Dorsal view. B. Ventral view. C. Surface for articulation with the incus. Abbreviations: D—dorsal side; M—broken manubrium. cms longus of the incus, moderately so in heavy ossicles such as characterize most Thnjonomys (Tullberg, 1899: PI. 24, Fig. of the Hystricognathi. 14; Wood and Patterson, 1959: 293, n. 4), If the Caviomorpha were descended although Doran's figure does not show from rafted thryonomyoids, it seems most this, and almost as far as the incudal ar- amazing to us that the more primitive ticulation in bathyergids (Hyrtl, 1845; condition (occasional absence of fusion) Doran, 1879: 413; Tullberg, 1899: PI. 24, should be rather widespread among the Figs. 1-2). Hystrix (Doran; Tullberg), Caviomorpha, presumably descended Petromus (Tullberg and personal obser- from a small founder population, and un- vation), and all caviomorphs for which known in the Old World fonns. We know ossicles are known display no such ex- of no basis for assuming that there has tension. We do not, of course, feel that been a selective advantage for a neotenic the similar degree of fusion of the mal- retention of embryonic lack of fusion leus with the crus longus of the incus in- among the Caviomorpha that did not act dicates closer relationships of Thryono- on the Old World fomis. Therefore, we mys to the bathyergids than to Petromus. conclude that the status of fusion of the Among those hystricognaths—and they malleus and incus supports one of two constitute the great majority—in which possibilities. Either the Old World hys- fusion occurs, the time of onset of the fu- tricognaths were descended from cavio- sion during ontogeny is variable. Avail- morph ancestors; or (much more proba- able data are few but sufficient to dem- bly, in our opinion), fusion was either onstrate this. Doran has recorded fusion incipiently present am
Size: 1740px × 1435px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorharvarduniversity, bookcentury1900, booksubjectzoology
