Challenges in palaeontology: resolving the lissamphibian origins debate
Challenges in palaeontology: resolving the lissamphibian origins debate
Categories: General, Lectures and Seminars, Receptions, Lunches and Dinners
3120 Herzberg Laboratories
1125 Colonel By Dr, Ottawa, ON
Contact Information
Sarah Adams, (613) 520-5633, sarah.adamsaston@carleton.ca
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No registration required.
Cost
Free
About this Event
Host Organization: Earth Sciences
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There remains debate amongst paleontologists as to how the three groups of living amphibians (lissamphibians: frogs, salamanders, and caecilians) are related to one another and to the various lineages of fossil amphibians. This lack of consensus hinders our ability to test evolutionary hypotheses since no single, widely agreed upon pattern of relationships currently exists. To address this problem, several key fossil taxa were studied with the goal of obtaining new data from the previously unexplored braincase region of the skull. Microsaurs, a group of Permian-aged amphibians, were recently hypothesized as the closest relatives of caecilians, separating them from frogs and salamanders. The use of 3D micro-computed tomography to examine details of braincase in the microsaur Carrolla reveals the traits linking caecilians and microsaurs are more likely shared due to convergence on a similar habit (burrowing) than evolutionary relatedness, as they are also found in distantly related reptile species. The controversial fossil Eocaecilia was also reexamined to test for indication of its affinity to living caecilians. Several new, definitively caecilian characteristics were identified in the braincase of Eocaecilia, thus firmly placing this fossil in the gap between putative relatives and the living forms. A number of traits additionally shared with frogs and salamanders lend support for uniting the living amphibians with one another. Reanalysis of evolutionary relationships of both extinct and extant amphibians incorporating these new data results in a common origin of Lissamphibia derived from the fossil group Temnospondyli. This hypothesis is consistent with broad scale transformations in the braincase that manifests as stepwise simplification towards the condition seen in the living forms. This improved framework of relationships forms the foundation of ongoing studies into the mechanistic basis of this transformation and others in the evolution of frogs, salamanders, and caecilians.