Dataset Information

The completeness of the fossil record of plesiosaurs, marine reptiles from the Mesozoic.

ABSTRACT: Plesiosaurs were a highly successful group of marine reptiles occurring worldwide in the Jurassic and Cretaceous, but to date few studies have focused on their preservation through time. Here, we conduct the first detailed assessment of the quality of the plesiosaur fossil record. Data was compiled for 178 specimens representing 114 valid species. For each species we calculated the character completeness metric (CCM: percentage of phylogenetic characters from a cladistic dataset that can be scored for that species) and the skeletal completeness metric (SCM: percentage of the overall skeleton that is preserved for that species). Average CCM and SCM values were calculated for individual geological stages. A strong significant positive correlation was recovered between CCM and SCM, suggesting that the two metrics are recording the same signal, at least for this clade. Although a significant correlation between changes in sea level and changes in plesiosaur completeness was not recovered, an underlying negative relationship may be present but obscured by poorly sampled time bins. Plesiosaur completeness though time is not significantly correlated with that for contemporary terrestrial groups (sauropods, pterosaurs, birds), but is significantly correlated with that for ichthyosaurs, suggesting common controls on skeletal preservation in the marine realm. Significantly higher median completeness values in plesiosaurs and ichthyosaurs than in contemporary terrestrial groups support the hypothesis that the marine tetrapod fossil record is more complete than that of terrestrial tetrapods. A collector's curve for plesiosaurs shows a generally slow constant rate of discovery from the latter part of the 19th century until the 1990s, at which point the rate of discovery increased substantially and shows no sign of slowing. A significant but very weak negative correlation between SCM and the year in which a taxon was named suggests a weak tendency for more recently named species to have less complete skeletons.

SUBMITTER: Tutin SL

PROVIDER: S-EPMC5828107 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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The completeness of the fossil record of plesiosaurs, marine reptiles from the Mesozoic.

Tutin Samuel L SL Butler Richard J RJ

Acta palaeontologica Polonica 20170101 3

Plesiosaurs were a highly successful group of marine reptiles occurring worldwide in the Jurassic and Cretaceous, but to date few studies have focused on their preservation through time. Here, we conduct the first detailed assessment of the quality of the plesiosaur fossil record. Data was compiled for 178 specimens representing 114 valid species. For each species we calculated the character completeness metric (CCM: percentage of phylogenetic characters from a cladistic dataset that can be scor ...[more]

PMID: 29497243

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Project description:Many palaeobiological analyses have concluded that modern birds (Neornithes) radiated no earlier than the Maastrichtian, whereas molecular clock studies have argued for a much earlier origination. Here, we assess the quality of the fossil record of Mesozoic avian species, using a recently proposed character completeness metric which calculates the percentage of phylogenetic characters that can be scored for each taxon. Estimates of fossil record quality are plotted against geological time and compared to estimates of species level diversity, sea level, and depositional environment. Geographical controls on the avian fossil record are investigated by comparing the completeness scores of species in different continental regions and latitudinal bins. Avian fossil record quality varies greatly with peaks during the Tithonian-early Berriasian, Aptian, and Coniacian-Santonian, and troughs during the Albian-Turonian and the Maastrichtian. The completeness metric correlates more strongly with a 'sampling corrected' residual diversity curve of avian species than with the raw taxic diversity curve, suggesting that the abundance and diversity of birds might influence the probability of high quality specimens being preserved. There is no correlation between avian completeness and sea level, the number of fluviolacustrine localities or a recently constructed character completeness metric of sauropodomorph dinosaurs. Comparisons between the completeness of Mesozoic birds and sauropodomorphs suggest that small delicate vertebrate skeletons are more easily destroyed by taphonomic processes, but more easily preserved whole. Lagerstätten deposits might therefore have a stronger impact on reconstructions of diversity of smaller organisms relative to more robust forms. The relatively poor quality of the avian fossil record in the Late Cretaceous combined with very patchy regional sampling means that it is possible neornithine lineages were present throughout this interval but have not yet been sampled or are difficult to identify because of the fragmentary nature of the specimens.

Dataset Information

The completeness of the fossil record of plesiosaurs, marine reptiles from the Mesozoic.

Publications

The completeness of the fossil record of plesiosaurs, marine reptiles from the Mesozoic.

Similar Datasets

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