Tiago R. Simões , Oksana Vernygora, Ilaria Paparella, Paulina Jimenez-Huidobro, Michael W. Caldwell
Published: May 3, 2017 https://doi.org/10.1371/journal.pone.0176773
Mosasauroids were a successful lineage of squamate reptiles (lizards and snakes) that radiated during the Late Cretaceous (95–66 million years ago). They can be considered one of the few lineages in the evolutionary history of tetrapods to have acquired a fully aquatic lifestyle, similarly to whales, ichthyosaurs and plesiosaurs. Despite a long history of research on this group, their phylogenetic relationships have only been tested so far using traditional (unweighted) maximum parsimony. However, hypotheses of mosasauroid relationships and the recently proposed multiple origins of aquatically adapted pelvic and pedal features in this group can be more thoroughly tested by methods that take into account variation in branch lengths and evolutionary rates. In this study, we present the first mosasauroid phylogenetic analysis performed under different analytical methods, including maximum likelihood, Bayesian inference, and implied weighting maximum parsimony. The results indicate a lack of congruence in the topological position of halisaurines and Dallasaurus. Additionally, the genus Prognathodon is paraphyletic under all hypotheses. Interestingly, a number of traditional mosasauroid clades become weakly supported, or unresolved, under Bayesian analyses. The reduced resolutions in some consensus trees create ambiguities concerning the evolution of fully aquatic pelvic/pedal conditions under many analyses. However, when enough resolution was obtained, reversals of the pelvic/pedal conditions were favoured by parsimony and likelihood ancestral state reconstructions instead of independent origins of aquatic features in mosasauroids. It is concluded that most of the observed discrepancies among the results can be associated with different analytical procedures, but also due to limited postcranial data on halisaurines, yaguarasaurines and Dallasaurus.
Citation: Simões TR, Vernygora O, Paparella I, Jimenez-Huidobro P, Caldwell MW (2017) Mosasauroid phylogeny under multiple phylogenetic methods provides new insights on the evolution of aquatic adaptations in the group. PLoS ONE 12(5): e0176773. https://doi.org/10.1371/journal.pone.0176773
Editor: Thierry Smith, Royal Belgian Institute of Natural Sciences, BELGIUM
Received: February 15, 2017; Accepted: April 17, 2017; Published: May 3, 2017
Copyright: © 2017 Simões et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting Information files.
Funding: Support for this project came from a PhD scholarship to TRS (Izaak Walton Killam Memorial Scholarship) and by an NSERC Discovery Grant (#23458) to MC.
Competing interests: The authors have declared that no competing interests exist.
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