Translator Disclaimer
1 August 2008 Ossification Heterochrony in the Therian Postcranial Skeleton and the Marsupial–Placental Dichotomy
Author Affiliations +
Abstract

Postcranial ossification sequences in 24 therian mammals and three outgroup taxa were obtained using clear staining and computed tomography to test the hypothesis that the marsupial forelimb is developmentally accelerated, and to assess patterns of therian postcranial ossification. Sequence rank variation of individual bones, phylogenetic analysis, and algorithm-based heterochrony optimization using event pairs were employed. Phylogenetic analysis only recovers Marsupialia, Australidelphia, and Eulipotyphla. Little heterochrony is found within marsupials and placentals. However, heterochrony was observed between marsupials and placentals, relating to late ossification in hind limb long bones and early ossification of the anterior axial skeleton. Also, ossification rank position of marsupial forelimb and shoulder girdle elements is more conservative than that of placentals; in placentals the hind limb area is more conservative. The differing ossification patterns in marsupials can be explained with a combination of muscular strain and energy allocation constraints, both resulting from the requirement of active movement of the altricial marsupial neonates toward the teat. Peramelemorphs, which are comparatively passive at birth and include species with relatively derived forelimbs, differ little from other marsupials in ossification sequence. This suggests that ossification heterochrony in marsupials is not directly related to diversity constraints on the marsupial forelimb and shoulder girdle.

Vera Weisbecker, Anjali Goswami, Stephen Wroe, and Marcelo R. Sánchez-Villagra "Ossification Heterochrony in the Therian Postcranial Skeleton and the Marsupial–Placental Dichotomy," Evolution 62(8), 2027-2041, (1 August 2008). https://doi.org/10.1111/j.1558-5646.2008.00424.x
Received: 21 February 2007; Accepted: 25 April 2008; Published: 1 August 2008
JOURNAL ARTICLE
15 PAGES

This article is only available to subscribers.
It is not available for individual sale.
+ SAVE TO MY LIBRARY

SHARE
ARTICLE IMPACT
RIGHTS & PERMISSIONS
Get copyright permission
Back to Top