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Published on: December 3, 2016
Skeletal ossification and sequence heterochrony in xenarthran evolution.
Lionel Hautier1, Vera Weisbecker, Anjali Goswami
1Department of Zoology, University of Cambridge, Downing St., Cambridge CB2 3EJ, UK. ljh75@hermes.cam.ac.uk
Evolution & Development
|September 29, 2012
Summary
Xenarthran mammals show unique skeletal development patterns, with late sternum ossification and early phalange/pubis ossification. This contrasts with other placental mammals, highlighting developmental heterochrony in xenarthrans.
Area of Science:
- Developmental Biology
- Comparative Anatomy
- Mammalian Evolution
Background:
- Mammalian ossification sequences are crucial for understanding skeletal development.
- Previous studies primarily focused on monotremes, marsupials, and boreoeutherian placentals.
- Xenarthrans (armadillos, anteaters, sloths) have been less studied regarding ossification timing.
Purpose of the Study:
- To investigate the sequence of cranial and postcranial ossification in xenarthrans.
- To quantify heterochrony (developmental timing shifts) in xenarthran skeletal development.
- To compare xenarthran ossification patterns with those of other placental mammals.
Main Methods:
- Analysis of ossification sequences in xenarthran skulls and skeletons.
- Quantification of sequence heterochrony using sequence analysis of variance (ANOVA) and event-paring/Parsimov.
- Control for artifactual accumulation of ties in sequence data.
Main Results:
- Parsimov method showed limited ability to detect heterochronic shifts between xenarthrans and boreoeutherians.
- Sequence-ANOVA identified significant differences, particularly when controlling for ties.
- Xenarthrans exhibit a late ossification of the sternum and early ossification of phalanges and pubis compared to other placentals.
Conclusions:
- Heterochrony significantly influences xenarthran skeletal development.
- Xenarthran skeletal development is not developmentally homogeneous as previously suggested.
- These findings contribute to a nuanced understanding of mammalian skeletal evolution.
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