Wonky whales: the evolution of cranial asymmetry in cetaceans
Abstract Background Unlike most mammals, toothed whale (Odontoceti) skulls lack symmetry in the nasal and facial (nasofacial) region. This asymmetry is hypothesised to relate to echolocation, which may have evolved in the earliest diverging odontocetes. Early cetaceans (whales, dolphins, and porpois...
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ftdoajarticles:oai:doaj.org/article:dfbbf54dab1741028baf1cf86a2ff373 2023-05-15T15:37:14+02:00 Wonky whales: the evolution of cranial asymmetry in cetaceans Ellen J. Coombs Julien Clavel Travis Park Morgan Churchill Anjali Goswami 2020-07-01T00:00:00Z https://doi.org/10.1186/s12915-020-00805-4 https://doaj.org/article/dfbbf54dab1741028baf1cf86a2ff373 EN eng BMC http://link.springer.com/article/10.1186/s12915-020-00805-4 https://doaj.org/toc/1741-7007 doi:10.1186/s12915-020-00805-4 1741-7007 https://doaj.org/article/dfbbf54dab1741028baf1cf86a2ff373 BMC Biology, Vol 18, Iss 1, Pp 1-24 (2020) Trait evolution Asymmetry Cetaceans Morphometrics Macroevolution Biology (General) QH301-705.5 article 2020 ftdoajarticles https://doi.org/10.1186/s12915-020-00805-4 2022-12-31T04:03:25Z Abstract Background Unlike most mammals, toothed whale (Odontoceti) skulls lack symmetry in the nasal and facial (nasofacial) region. This asymmetry is hypothesised to relate to echolocation, which may have evolved in the earliest diverging odontocetes. Early cetaceans (whales, dolphins, and porpoises) such as archaeocetes, namely the protocetids and basilosaurids, have asymmetric rostra, but it is unclear when nasofacial asymmetry evolved during the transition from archaeocetes to modern whales. We used three-dimensional geometric morphometrics and phylogenetic comparative methods to reconstruct the evolution of asymmetry in the skulls of 162 living and extinct cetaceans over 50 million years. Results In archaeocetes, we found asymmetry is prevalent in the rostrum and also in the squamosal, jugal, and orbit, possibly reflecting preservational deformation. Asymmetry in odontocetes is predominant in the nasofacial region. Mysticetes (baleen whales) show symmetry similar to terrestrial artiodactyls such as bovines. The first significant shift in asymmetry occurred in the stem odontocete family Xenorophidae during the Early Oligocene. Further increases in asymmetry occur in the physeteroids in the Late Oligocene, Squalodelphinidae and Platanistidae in the Late Oligocene/Early Miocene, and in the Monodontidae in the Late Miocene/Early Pliocene. Additional episodes of rapid change in odontocete skull asymmetry were found in the Mid-Late Oligocene, a period of rapid evolution and diversification. No high-probability increases or jumps in asymmetry were found in mysticetes or archaeocetes. Unexpectedly, no increases in asymmetry were recovered within the highly asymmetric ziphiids, which may result from the extreme, asymmetric shape of premaxillary crests in these taxa not being captured by landmarks alone. Conclusions Early ancestors of living whales had little cranial asymmetry and likely were not able to echolocate. Archaeocetes display high levels of asymmetry in the rostrum, potentially related to directional ... Article in Journal/Newspaper baleen whales toothed whale Directory of Open Access Journals: DOAJ Articles BMC Biology 18 1 |
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Directory of Open Access Journals: DOAJ Articles |
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English |
topic |
Trait evolution Asymmetry Cetaceans Morphometrics Macroevolution Biology (General) QH301-705.5 |
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Trait evolution Asymmetry Cetaceans Morphometrics Macroevolution Biology (General) QH301-705.5 Ellen J. Coombs Julien Clavel Travis Park Morgan Churchill Anjali Goswami Wonky whales: the evolution of cranial asymmetry in cetaceans |
topic_facet |
Trait evolution Asymmetry Cetaceans Morphometrics Macroevolution Biology (General) QH301-705.5 |
description |
Abstract Background Unlike most mammals, toothed whale (Odontoceti) skulls lack symmetry in the nasal and facial (nasofacial) region. This asymmetry is hypothesised to relate to echolocation, which may have evolved in the earliest diverging odontocetes. Early cetaceans (whales, dolphins, and porpoises) such as archaeocetes, namely the protocetids and basilosaurids, have asymmetric rostra, but it is unclear when nasofacial asymmetry evolved during the transition from archaeocetes to modern whales. We used three-dimensional geometric morphometrics and phylogenetic comparative methods to reconstruct the evolution of asymmetry in the skulls of 162 living and extinct cetaceans over 50 million years. Results In archaeocetes, we found asymmetry is prevalent in the rostrum and also in the squamosal, jugal, and orbit, possibly reflecting preservational deformation. Asymmetry in odontocetes is predominant in the nasofacial region. Mysticetes (baleen whales) show symmetry similar to terrestrial artiodactyls such as bovines. The first significant shift in asymmetry occurred in the stem odontocete family Xenorophidae during the Early Oligocene. Further increases in asymmetry occur in the physeteroids in the Late Oligocene, Squalodelphinidae and Platanistidae in the Late Oligocene/Early Miocene, and in the Monodontidae in the Late Miocene/Early Pliocene. Additional episodes of rapid change in odontocete skull asymmetry were found in the Mid-Late Oligocene, a period of rapid evolution and diversification. No high-probability increases or jumps in asymmetry were found in mysticetes or archaeocetes. Unexpectedly, no increases in asymmetry were recovered within the highly asymmetric ziphiids, which may result from the extreme, asymmetric shape of premaxillary crests in these taxa not being captured by landmarks alone. Conclusions Early ancestors of living whales had little cranial asymmetry and likely were not able to echolocate. Archaeocetes display high levels of asymmetry in the rostrum, potentially related to directional ... |
format |
Article in Journal/Newspaper |
author |
Ellen J. Coombs Julien Clavel Travis Park Morgan Churchill Anjali Goswami |
author_facet |
Ellen J. Coombs Julien Clavel Travis Park Morgan Churchill Anjali Goswami |
author_sort |
Ellen J. Coombs |
title |
Wonky whales: the evolution of cranial asymmetry in cetaceans |
title_short |
Wonky whales: the evolution of cranial asymmetry in cetaceans |
title_full |
Wonky whales: the evolution of cranial asymmetry in cetaceans |
title_fullStr |
Wonky whales: the evolution of cranial asymmetry in cetaceans |
title_full_unstemmed |
Wonky whales: the evolution of cranial asymmetry in cetaceans |
title_sort |
wonky whales: the evolution of cranial asymmetry in cetaceans |
publisher |
BMC |
publishDate |
2020 |
url |
https://doi.org/10.1186/s12915-020-00805-4 https://doaj.org/article/dfbbf54dab1741028baf1cf86a2ff373 |
genre |
baleen whales toothed whale |
genre_facet |
baleen whales toothed whale |
op_source |
BMC Biology, Vol 18, Iss 1, Pp 1-24 (2020) |
op_relation |
http://link.springer.com/article/10.1186/s12915-020-00805-4 https://doaj.org/toc/1741-7007 doi:10.1186/s12915-020-00805-4 1741-7007 https://doaj.org/article/dfbbf54dab1741028baf1cf86a2ff373 |
op_doi |
https://doi.org/10.1186/s12915-020-00805-4 |
container_title |
BMC Biology |
container_volume |
18 |
container_issue |
1 |
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1766367690489856000 |