Lagerstätte effect drives notosuchian palaeodiversity (Crocodyliformes, Notosuchia)

ABSTRACT

Notosuchians are a crocodyliform clade with a rich Gondwanan fossil record, especially in Cretaceous South American deposits. More than half of all described species come from South America and, around one quarter, have been discovered in the Adamantina Formation (Bauru Group, Brazil). The large amount of notosuchian remains from this formation, along with its chronostratigraphic uncertainty, may be distorting notosuchian palaeodiversity estimates. In order to analyse how these factors could be biasing our interpretations, palaeodiversity estimates were performed excluding and including the Adamantina Formation occurrence data, as well as assigning them to the main age ranges that have been proposed for the formation (Turonian-Santonian and Campanian-Maastrichtian). Furthermore, as other factors might be influencing palaeodiversity fluctuations, a modelling approach was performed to assess which abiotic factors, sampling artefacts, or a combination of them, could be driving these palaeodiversity dynamics. The results showed that the Adamantina Formation is causing a Lagerstätte effect that is distorting palaeodiversity estimates and, depending on the age assigned to that formation, the tempo and magnitude of the maximum palaeodiversity reached during the Late Cretaceous substantially changes. The results also suggest that the temporal bias might affect palaeobiological reconstructions not only in notosuchians but also in other groups.

KEYWORDS:

• Adamantina Formation
• Bauru Group
• fossil record bias
• Late Cretaceous
• Notosuchia
• paleodiversity

Acknowledgments

We thank PBDB members who entered notosuchian occurrence data (P.D. Mannion, M. Carrano, J. Zijlstra, J. Tennant, J. Alroy; a comprehensive list of authors can be downloaded from the PBDB website). We thank J. Alroy and J. Tennant for sharing the R scripts for SQS in their websites. We thank C. Dean, M. Rabi and an anonymous reviewer for their suggestions to improve the quality of our manuscript.

Disclosure statement

The authors declare that they do not have competing interests.

Supporting information

Additional Supporting information can be found in the online version of this article:

Appendix S1. Raw Paleobiology Database (PBDB) data, final dataset of notosuchian occurrences and variables analyzed with generalised least squares (GLS) regressions.

Appendix S2. Results of raw species counts (TDEs), shareholder quorum subsampling estimates and generalised least squares (GLS).

Supplementary materials. Table S1 (countries composing each spatial region analyzed), Table S2 (time-bin schemes) and a note about new published notosuchian specimens.

Additional information

Funding

This work was supported by the Ministerio de Ciencia, Innovación y Universidades under an FPU fellowship (FPU 2016/01058; A.dC.).