Ramírez-Chaves, Héctor E; Weisbecker, Vera; Wroe, Stephen; Phillips, Matthew J

Author(s)

Ramírez-Chaves, Héctor E

Weisbecker, Vera

Wroe, Stephen

Phillips, Matthew J

Publication Date

2016-08-24

Abstract

Background: The minute, finely-tuned ear ossicles of mammals arose through a spectacular evolutionary transformation from their origins as a load-bearing jaw joint. This involved detachment from the postdentary trough of the mandible, and final separation from the dentary through resorption of Meckel's cartilage. Recent parsimony analyses of modern and fossil mammals imply up to seven independent postdentary trough losses or even reversals, which is unexpected given the complexity of these transformations. Here we employ the first model-based, probabilistic analysis of the evolution of the definitive mammalian middle ear, supported by virtual 3D erosion simulations to assess for potential fossil preservation artifacts. Results: Our results support a simple, biologically plausible scenario without reversals. The middle ear bones detach from the postdentary trough only twice among mammals, once each in the ancestors of therians and monotremes. Disappearance of Meckel's cartilage occurred independently in numerous lineages from the Late Jurassic to the Late Cretaceous. This final separation is recapitulated during early development of extant mammals, while the earlier-occurring disappearance of a postdentary trough is not. Conclusions: Our results therefore suggest a developmentally congruent and directional two-step scenario, in which the parallel uncoupling of the auditory and feeding systems in northern and southern hemisphere mammals underpinned further specialization in both lineages. Until ∼ 168 Ma, all known mammals retained attached middle ear bones, yet all groups that diversified from ∼ 163 Ma onwards had lost the postdentary trough, emphasizing the adaptive significance of this transformation.

Citation

Frontiers in Zoology, v.13, p. 1-10

ISSN

1742-9994

Pubmed ID

27563341

Link

https://hdl.handle.net/1959.11/30640

Publisher

BioMed Central Ltd

Rights

Attribution 4.0 International

Title

Resolving the evolution of the mammalian middle ear using Bayesian inference

Type of document

Journal Article

Entity Type

Publication

Author(s)	Ramírez-Chaves, Héctor E Weisbecker, Vera Wroe, Stephen Phillips, Matthew J
Publication Date	2016-08-24
Abstract	<b>Background:</b> The minute, finely-tuned ear ossicles of mammals arose through a spectacular evolutionary transformation from their origins as a load-bearing jaw joint. This involved detachment from the postdentary trough of the mandible, and final separation from the dentary through resorption of Meckel's cartilage. Recent parsimony analyses of modern and fossil mammals imply up to seven independent postdentary trough losses or even reversals, which is unexpected given the complexity of these transformations. Here we employ the first model-based, probabilistic analysis of the evolution of the definitive mammalian middle ear, supported by virtual 3D erosion simulations to assess for potential fossil preservation artifacts.<br/> <b>Results:</b> Our results support a simple, biologically plausible scenario without reversals. The middle ear bones detach from the postdentary trough only twice among mammals, once each in the ancestors of therians and monotremes. Disappearance of Meckel's cartilage occurred independently in numerous lineages from the Late Jurassic to the Late Cretaceous. This final separation is recapitulated during early development of extant mammals, while the earlier-occurring disappearance of a postdentary trough is not.<br/> <b>Conclusions:</b> Our results therefore suggest a developmentally congruent and directional two-step scenario, in which the parallel uncoupling of the auditory and feeding systems in northern and southern hemisphere mammals underpinned further specialization in both lineages. Until ∼ 168 Ma, all known mammals retained attached middle ear bones, yet all groups that diversified from ∼ 163 Ma onwards had lost the postdentary trough, emphasizing the adaptive significance of this transformation.
Citation	Frontiers in Zoology, v.13, p. 1-10
ISSN	1742-9994
Pubmed ID	27563341
Link	https://hdl.handle.net/1959.11/30640
Publisher	BioMed Central Ltd
Rights	Attribution 4.0 International
Title	Resolving the evolution of the mammalian middle ear using Bayesian inference
Type of document	Journal Article
Entity Type	Publication

Resolving the evolution of the mammalian middle ear using Bayesian inference

Files: