Ben Creisler
A new paper with free pdf:
Free pdf:
Highlights
The evolutionary processes underlying tooth loss in Mesozoic birds is debated.
Analyses reveal no long-term selective pressure or trend towards toothlessness.
Tooth loss was likely a result of local selective pressures on individual lineages.
The transition to crown bird toothlessness occurred later than previously hypothesized
Summary
Several potential drivers of avian tooth loss have been proposed, although consensus remains elusive as fully toothless jaws arose independently numerous times among Mesozoic avialans and dinosaurs more broadly. The origin of crown bird edentulism has been discussed in terms of a broad-scale selective pressure or trend toward toothlessness, although this has never been quantitatively tested. Here, we find no evidence for models whereby iterative acquisitions of toothlessness among Mesozoic Avialae were driven by an overarching selective trend. Instead, our results support modularity among jaw regions underlying heterogeneous tooth loss patterns, and indicate a substantially later transition to complete crown bird edentulism than previously hypothesized (~ 90 MYA). We show that patterns of avialan tooth loss adhere to Dolloâs law and suggest that the exclusive survival of toothless birds to the present represents lineage-specific selective pressures, irreversibility of tooth loss, and the filter of the K-Pg mass extinction.
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