Sea level regulated tetrapod diversity dynamics through the Jurassic/Cretaceous interval

Abstract

Reconstructing deep time trends in biodiversity remains a central goal for palaeobiologists, but our understanding of the magnitude and tempo of extinctions and radiations is confounded by uneven sampling of the fossil record. In particular, the Jurassic/Cretaceous (J/K) boundary, 145 million years ago, remains poorly understood, despite an apparent minor extinction and the radiation of numerous important clades. Here we apply a rigorous subsampling approach to a comprehensive tetrapod fossil occurrence data set to assess the group's macroevolutionary dynamics through the J/K transition. Although much of the signal is exclusively European, almost every higher tetrapod group was affected by a substantial decline across the boundary, culminating in the extinction of several important clades and the ecological release and radiation of numerous modern tetrapod groups. Variation in eustatic sea level was the primary driver of these patterns, controlling biodiversity through availability of shallow marine environments and via allopatric speciation on land.

Figure 1. Raw taxonomic diversity.

Taxonomic diversity estimate (TDE) for marine and non-marine Jurassic and Cretaceous tetrapods, grouped into approximately equal 10 million year time bins.

Figure 2. Global non-marine Late Jurassic to Early Cretaceous subsampled diversity.

SQS diversity for (a) major dinosaur groups; (b) testudines, crocodylomorphs and pterosaurs; and (c) mammals, lepidosaurs and lissamphibians. Shaded areas represent stage boundaries. Where gaps in the curve exist this is due to poor sampling and failure to adequately recover a subsampling diversity estimate. Silhouettes from Phylopic courtesy of Michael Keesey, Grad McFeeters, Scott Hartman, Mark Witton, Ville Veikko Sinkkonen and Hanyong Pu (see http://phylopic.org/ for additional license information).

Figure 3. Global marine SQS diversity for major Late Jurassic to Early Cretaceous pelagic clades.

Sea level curve from Miller et al.. Silhouettes from Phylopic courtesy of Gareth Monger and Michael Keesey (see http://phylopic.org/ for additional license information).

Figure 4. Regional outcrop area and collection counts.

For the (a) non-marine record of Europe; (b) marine record of Europe (c) non-marine record of North America; and (d) marine record of North America. European outcrop area from Smith and McGowan, and North American outcrop area from Peters and Heim. Note the discontinuity between the availability of the rock record and the number of collections in the earliest Cretaceous of North America.