Re-characterization of Tylosaurus nepaeolicus (Cope, 1874) and Tylosaurus kansasensis Everhart, 2005: Ontogeny or sympatry?

Jiménez-Huidobro, Paulina; Simões, Tiago R.

doi:10.1016/j.cretres.2016.04.008

Cited by 13 publications

(20 citation statements)

References 19 publications

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“…Despite the change in the outgroup, and minor updates in the ingroup taxa and scorings, the analysis with Co-UMP (the coding and search method used by most mosasauroid phylogenies) provided results (Fig 1A) that are generally similar to the most recent analyses of mosasauroid relationships [12, 25, 26]. Namely, aigialosaurs lie at the base of the lineage leading to mosasaurids; Mosasaurinae is monophyletic (and inclusive of Halisaurinae and Dallasaurus ); and Russellosaurina is also monophyletic (inclusive of yaguarasaurines, tethysaurines, plioplatecarpines and tylosaurines).…”

Section: Resultssupporting

confidence: 60%

Mosasauroid phylogeny under multiple phylogenetic methods provides new insights on the evolution of aquatic adaptations in the group

et al. 2017

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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.

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Section: Resultssupporting

confidence: 60%

Mosasauroid phylogeny under multiple phylogenetic methods provides new insights on the evolution of aquatic adaptations in the group

et al. 2017

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“…New reappraisals of certain tylosaurine species have also been published recently. For example, Hainosaurus pembinensis and H. bernardi , the latter being the type species of Hainosaurus , have been assigned to Tylosaurus ( Bullard & Caldwell, 2010 ; Jiménez-Huidobro & Caldwell, 2016 , respectively), and Tylosaurus kansasensis was proposed to be a juvenile of T. nepaeolicus , and thus removed from the data set ( Jiménez-Huidobro, Simões & Caldwell, 2016 ). However, T. pembinensis is not included in the recent version of the data set, which does not enable to further test the newly proposed hypotheses.…”

Section: Discussionmentioning

confidence: 99%

Inferring ‘weak spots’ in phylogenetic trees: application to mosasauroid nomenclature

Madzia

Cau

2017

PeerJ

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Mosasauroid squamates represented the apex predators within the Late Cretaceous marine and occasionally also freshwater ecosystems. Proper understanding of the origin of their ecological adaptations or paleobiogeographic dispersals requires adequate knowledge of their phylogeny. The studies assessing the position of mosasauroids on the squamate evolutionary tree and their origins have long given conflicting results. The phylogenetic relationships within Mosasauroidea, however, have experienced only little changes throughout the last decades. Considering the substantial improvements in the development of phylogenetic methodology that have undergone in recent years, resulting, among others, in numerous alterations in the phylogenetic hypotheses of other fossil amniotes, we test the robustness in our understanding of mosasauroid beginnings and their evolutionary history. We re-examined a data set that results from modifications assembled in the course of the last 20 years and performed multiple parsimony analyses and Bayesian tip-dating analysis. Following the inferred topologies and the ‘weak spots’ in the phylogeny of mosasauroids, we revise the nomenclature of the ‘traditionally’ recognized mosasauroid clades, to acknowledge the overall weakness among branches and the alternative topologies suggested previously, and discuss several factors that might have an impact on the differing phylogenetic hypotheses and their statistical support.

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“…The study revealed a significant correlation of all individual bone measurements with total skull length (TSL), as well as isometric growth for all characters except quadrate height (QH), which was found to be positively allometric, and premaxillary predental rostrum length, which was found to be negatively allometric. They also rejected the hypothesis that T. kansasensis represent juveniles of T. nepaeolicus ( Jiménez-Huidobro, Simões & Caldwell, 2016 ), stating that the growth trends between T. kansasensis and T. nepaeolicus do not match what is seen in T. proriger , and that there is not enough evidence to support the proposed ontogenetic characters.…”

Section: Introductionmentioning

confidence: 99%

“… Jiménez-Huidobro, Simões & Caldwell (2016) proposed that specimens of two sympatric species of Tylosaurus , T. kansasensis ( Everhart, 2005 ) and T. nepaeolicus , are synonymous, and that T. kansasensis specimens are juveniles. They identified several characters in T. kansasensis that purportedly show the juvenile conditions seen in another species of Tylosaurus , T. proriger , and concluded that there are “no differences between the two nominal species that cannot be attributed to size, and thus ontogenetic stage” ( Jiménez-Huidobro, Simões & Caldwell, 2016 : 80), and that T. kansasensis are therefore juveniles of T. nepaeolicus . Also, the authors suggested that T. proriger may be paedomorphic relative to T. nepaeolicus due to the presence of a dorsal midline crest on the frontal and convex lateral borders of the parietal table, features purportedly seen in T. kansasensis , but not T. nepaeolicus .…”

Section: Introductionmentioning

confidence: 99%

Craniofacial ontogeny in Tylosaurinae

Zietlow

2020

PeerJ

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Mosasaurs were large, globally distributed aquatic lizards that lived during the Late Cretaceous. Despite numerous specimens of varying maturity, a detailed growth series has not been proposed for any mosasaur taxon. Two taxa—Tylosaurus proriger and T. kansasensis/nepaeolicus—have robust fossil records with specimens spanning a wide range of sizes and are thus ideal for studying mosasaur ontogeny. Tylosaurus is a genus of particularly large mosasaurs with long, edentulous anterior extensions of the premaxilla and dentary that lived in Europe and North America during the Late Cretaceous. An analysis of growth in Tylosaurus provides an opportunity to test hypotheses of the synonymy of T. kansasensis with T. nepaeolicus, sexual dimorphism, anagenesis, and heterochrony. Fifty-nine hypothetical growth characters were identified, including size-dependent, size-independent, and phylogenetic characters, and quantitative cladistic analysis was used to recover growth series for the two taxa. The results supported the synonymy of T. kansasensis with T. nepaeolicus and that T. kansasensis represent juveniles of T. nepaeolicus. A Spearman rank-order correlation test resulted in a significant correlation between two measures of size (total skull length and quadrate height) and maturity. Eleven growth changes were shared across both species, neither of the ontogram topologies showed evidence of skeletal sexual dimorphism, and a previous hypothesis of paedomorphy in T. proriger was not rejected. Finally, a novel hypothesis of anagenesis in Western Interior Seaway Tylosaurus species, driven by peramorphy, is proposed here.

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Re-characterization of Tylosaurus nepaeolicus (Cope, 1874) and Tylosaurus kansasensis Everhart, 2005: Ontogeny or sympatry?

Cited by 13 publications

References 19 publications

Mosasauroid phylogeny under multiple phylogenetic methods provides new insights on the evolution of aquatic adaptations in the group

Mosasauroid phylogeny under multiple phylogenetic methods provides new insights on the evolution of aquatic adaptations in the group

Inferring ‘weak spots’ in phylogenetic trees: application to mosasauroid nomenclature

Craniofacial ontogeny in Tylosaurinae

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