Ossification heterochrony in the therian postcranial skeleton and the marsupial-placental dichotomy

Vera Weisbecker, Anjali Goswami, Stephen Wroe, Marcelo R. Sánchez-Villagra

Research output: Contribution to journalArticle

88 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)2027-2041
Number of pages15
JournalEvolution
Volume62
Issue number8
DOIs
Publication statusPublished - Aug 2008
Externally publishedYes

Keywords

  • Event pair
  • Heterochrony
  • Life history
  • Neonate
  • Pouch
  • Theria

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