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Dietary specializations and diversity in feeding ecology of the earliest stem mammals

Dietary specializations and diversity in feeding ecology of the earliest stem mammals
Dietary specializations and diversity in feeding ecology of the earliest stem mammals
The origin and radiation of mammals are key events in the history of life, with fossils placing the origin at 220 million years ago, in the Late Triassic period1. The earliest mammals, representing the first 50 million years of their evolution and including the most basal taxa, are widely considered to be generalized insectivores1, 2. This implies that the first phase of the mammalian radiation—associated with the appearance in the fossil record of important innovations such as heterodont dentition, diphyodonty and the dentary–squamosal jaw joint1, 3—was decoupled from ecomorphological diversification2, 4. Finds of exceptionally complete specimens of later Mesozoic mammals have revealed greater ecomorphological diversity than previously suspected, including adaptations for swimming, burrowing, digging and even gliding2, 5, 6, but such well-preserved fossils of earlier mammals do not exist1, and robust analysis of their ecomorphological diversity has previously been lacking. Here we present the results of an integrated analysis, using synchrotron X-ray tomography and analyses of biomechanics, finite element models and tooth microwear textures. We find significant differences in function and dietary ecology between two of the earliest mammaliaform taxa, Morganucodon and Kuehneotherium—taxa that are central to the debate on mammalian evolution. Morganucodon possessed comparatively more forceful and robust jaws and consumed ‘harder’ prey, comparable to extant small-bodied mammals that eat considerable amounts of coleopterans. Kuehneotherium ingested a diet comparable to extant mixed feeders and specialists on ‘soft’ prey such as lepidopterans. Our results reveal previously hidden trophic specialization at the base of the mammalian radiation; hence even the earliest mammaliaforms were beginning to diversify—morphologically, functionally and ecologically. In contrast to the prevailing view2, 4, this pattern suggests that lineage splitting during the earliest stages of mammalian evolution was associated with ecomorphological specialization and niche partitioning.
0028-0836
303-305
Gill, Pamela G.
7ce2ddcf-1ded-43cf-924a-47434922150a
Purnell, Mark A.
2db9c183-c013-4526-99f3-40f360bacf25
Crumpton, Nick
fb6a437c-5283-49df-bd1d-17e3d7f94c06
Brown, Kate Robson
75205491-6913-4dc2-8fce-e63cdb9a66c9
Gostling, Neil J.
4840aa40-cb6c-4112-a0b9-694a869523fc
Stampanoni, M.
73e4ac62-a50e-40b1-84e5-96b8ce7c1712
Rayfield, Emily J.
3f410fe1-b5cf-40dd-a7f8-edb13c24edf0
Gill, Pamela G.
7ce2ddcf-1ded-43cf-924a-47434922150a
Purnell, Mark A.
2db9c183-c013-4526-99f3-40f360bacf25
Crumpton, Nick
fb6a437c-5283-49df-bd1d-17e3d7f94c06
Brown, Kate Robson
75205491-6913-4dc2-8fce-e63cdb9a66c9
Gostling, Neil J.
4840aa40-cb6c-4112-a0b9-694a869523fc
Stampanoni, M.
73e4ac62-a50e-40b1-84e5-96b8ce7c1712
Rayfield, Emily J.
3f410fe1-b5cf-40dd-a7f8-edb13c24edf0

Gill, Pamela G., Purnell, Mark A., Crumpton, Nick, Brown, Kate Robson, Gostling, Neil J., Stampanoni, M. and Rayfield, Emily J. (2014) Dietary specializations and diversity in feeding ecology of the earliest stem mammals. Nature, 512 (7514), 303-305. (doi:10.1038/nature13622).

Record type: Article

Abstract

The origin and radiation of mammals are key events in the history of life, with fossils placing the origin at 220 million years ago, in the Late Triassic period1. The earliest mammals, representing the first 50 million years of their evolution and including the most basal taxa, are widely considered to be generalized insectivores1, 2. This implies that the first phase of the mammalian radiation—associated with the appearance in the fossil record of important innovations such as heterodont dentition, diphyodonty and the dentary–squamosal jaw joint1, 3—was decoupled from ecomorphological diversification2, 4. Finds of exceptionally complete specimens of later Mesozoic mammals have revealed greater ecomorphological diversity than previously suspected, including adaptations for swimming, burrowing, digging and even gliding2, 5, 6, but such well-preserved fossils of earlier mammals do not exist1, and robust analysis of their ecomorphological diversity has previously been lacking. Here we present the results of an integrated analysis, using synchrotron X-ray tomography and analyses of biomechanics, finite element models and tooth microwear textures. We find significant differences in function and dietary ecology between two of the earliest mammaliaform taxa, Morganucodon and Kuehneotherium—taxa that are central to the debate on mammalian evolution. Morganucodon possessed comparatively more forceful and robust jaws and consumed ‘harder’ prey, comparable to extant small-bodied mammals that eat considerable amounts of coleopterans. Kuehneotherium ingested a diet comparable to extant mixed feeders and specialists on ‘soft’ prey such as lepidopterans. Our results reveal previously hidden trophic specialization at the base of the mammalian radiation; hence even the earliest mammaliaforms were beginning to diversify—morphologically, functionally and ecologically. In contrast to the prevailing view2, 4, this pattern suggests that lineage splitting during the earliest stages of mammalian evolution was associated with ecomorphological specialization and niche partitioning.

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More information

Accepted/In Press date: 27 June 2014
e-pub ahead of print date: 20 August 2014
Published date: 21 August 2014
Organisations: Ocean and Earth Science, Centre for Biological Sciences

Identifiers

Local EPrints ID: 385749
URI: http://eprints.soton.ac.uk/id/eprint/385749
ISSN: 0028-0836
PURE UUID: faa90215-4816-4eba-beed-3c727629c6af

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Date deposited: 21 Jan 2016 16:15
Last modified: 15 Jul 2019 20:51

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Contributors

Author: Pamela G. Gill
Author: Mark A. Purnell
Author: Nick Crumpton
Author: Kate Robson Brown
Author: M. Stampanoni
Author: Emily J. Rayfield

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