Palatal morphology predicts the paleobiology of early salamanders

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Abstract

Ecological preferences and life history strategies have enormous impacts on the evolution and phenotypic diversity of salamanders, but the yet established reliable ecological indicators from bony skeletons hinder investigations into the paleobiology of early salamanders. Here we statistically demonstrate, by using time-calibrated cladograms and geometric morphometric analysis on 71 specimens in 36 species, that both the shape of the palate and many non-shape covariates particularly associated with vomerine teeth are ecologically informative in early stem- and basal crown-group salamanders. Disparity patterns within the morphospace of the palate in ecological preferences, life history strategies and taxonomic affiliations were analyzed in detail, and evolutionary rates and ancestral states of the palate were reconstructed. Our results show that the palate is heavily impacted by convergence constrained by feeding mechanisms and also exhibits clear stepwise evolutionary patterns with alternative phenotypic configurations to cope with similar functional demand. Salamanders are diversified ecologically before the Middle Jurassic and achieved all their present ecological preferences in the Early Cretaceous. Our results reveal that the last common ancestor of all salamanders shares with other modern amphibians a unified biphasic ecological preference, and metamorphosis is significant in the expansion of ecomorphospace of the palate in early salamanders.

Data availability

All data needed to evaluate the conclusions are included in the manuscript and the Supplementary file 1. Details of specimens, CT parameters and raw landmark coordinates and centroid sizes are available in three CSV files in the online Dryad repository (https://doi.org/10.5061/dryad.c59zw3r8x). Source codes for R and SAS used in this study is available at GitHub (https://github.com/PaleoSalaman).

The following data sets were generated

1. JIA J
2. Li G
3. Gao K
(2022) Specimen list and landmark coordinates for the palate of early salamanders
Dryad Digital Repository, doi:10.5061/dryad.c59zw3r8x.

https://dx.doi.org/10.5061/dryad.c59zw3r8x

Article and author information

Author details

Jia Jia

Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada

For correspondence
jia.jia@ucalgary.ca

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-8243-0156
Guangzhao Li

Department of Microbiology, Immunology and Tropical Medicine, George Washington University, Washington, United States

Competing interests
The authors declare that no competing interests exist.
Ke-Qin Gao

School of Earth and Space Sciences, Peking University, Beijing, China

For correspondence
kqgao@pku.edu.cn

Competing interests
The authors declare that no competing interests exist.

Funding

National Natural Science Foundation of China (41702002)

Jia Jia

National Natural Science Foundation of China (41872008)

Ke-Qin Gao

State Key Laboratory of Palaeobiology and Stratigraphy (193111)

Jia Jia

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.