The evolution of the synapsid tusk: insights from dicynodont therapsid tusk histology
| Autor: | Megan R. Whitney, Christian A. Sidor, Kenneth D. Angielczyk, Brandon R. Peecook |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Mammals
General Immunology and Microbiology biology Permian Fossils Vertebrate General Medicine Dicynodont biology.organism_classification Biological Evolution General Biochemistry Genetics and Molecular Biology Synapsid Evolutionary biology Palaeobiology biology.animal visual_art Tusk visual_art.visual_art_medium Animals General Agricultural and Biological Sciences Therapsid Tooth Phylogeny General Environmental Science |
| Zdroj: | Proc Biol Sci |
| Popis: | The mammalian tusk is a unique and extreme morphotype among modern vertebrate dentitions. Tusks—defined here as ever-growing incisors or canines composed of dentine—evolved independently multiple times within mammals yet have not evolved in other extant vertebrates. This suggests that there is a feature specific to mammals that facilitates the evolution of this specialized dentition. To investigate what may underpin the evolution of tusks, we histologically sampled the tusks of dicynodont therapsids: the earliest iteration of tusk evolution and the only non-mammalian synapsid clade to have acquired such a dentition. We studied the tissue composition, attachment tissues, development and replacement in 10 dicynodont taxa and show multiple developmental pathways for the adult dentitions of dicynodont tusks and tusk-like caniniforms. In a phylogenetic context, these developmental pathways reveal an evolutionary scenario for the acquisition of an ever-growing tusk—an event that occurred convergently, but only in derived members of our sample. We propose that the evolution of an ever-growing dentition, such as a tusk, is predicated on the evolution of significantly reduced tooth replacement and a permanent soft-tissue attachment. Both of these features are fixed in the dentitions of crown-group mammals, which helps to explain why tusks are restricted to this clade among extant vertebrates. |
| Databáze: | OpenAIRE |
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