Romer session presentation
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1. The study analyzed tetrapod diversity over the Jurassic-Cretaceous boundary using subsampling methods to account for biases in the fossil record. 2. Results showed a prolonged decline in tetrapod diversity through the transition period rather than a single mass extinction event. Extinctions targeted more basal groups and were highest in late Jurassic. 3. Primary drivers of global diversity changes were found to be eustatic sea level changes and paleotemperature, though sampling effects could not be fully ruled out.
Romer session presentation
- 1. A hidden extinction in tetrapods at the Jurassic- Cretaceous boundary Jonathan Tennant
- 2. Thanks! NERC PALASS SVP
- 3. History of the Jurassic/Cretaceous boundary Pioneering work by Newell, Raup, Sepkoski (and his compendia) Originally considered to be a major extinction Understood general controls on the fossil record Current consensus: NOT a mass extinction Jon Tennant Background Raup (1976) Raup and Sepkoski (1982) Hallam (1986)
- 4. The structure of the fossil record Jon Tennant Background Smith and McGowan (2011) Tennant et al. (2016) Raw diversity is not a reliable estimate of true or relative diversity The fossil record is affected by several levels of sampling filters/biases
- 5. Why the J/K boundary? Jon Tennant Background Benson and Butler (2011) Nicholson et al. (2015) Zanno and Makovicky (2013) Bronzati et al. (2015) Newham et al. (2014)
- 6. What do we want to know? 1. What is the structure of changes in tetrapod diversity over the J/K transition? Was there a hidden mass extinction? 2. What external factors were responsible for mediating these changes? Jon Tennant Methods
- 7. Data. More data. 4907 species 15,472 occurrences, 7314 references Split into higher taxonomic clades Fully aquatic or non-marine Palaeocontinents Time binning methods Jon Tennant Methods Tennant et al. (2016)
- 8. Methodological approach Subsampling (SQS) and phylogenetic diversity estimates (PDE) Model-fitting of extrinsic parameters Jon Tennant Methods
- 9. Tetrapod SQS diversity falls in both the non- marine and marine realms Finer clade-level dynamics obscured Bootstrapping provides constraints to overall patterns Jon Tennant Results
- 10. Dinosaur diversity Jon Tennant Results SQS shows greatest decline in theropods Sauropods too poorly sampled in Berriasian PDE shows greatest decline in sauropods Decline less emphasised in theropods
- 11. Non-dinosaurian tetrapod diversity Jon Tennant Results Staggered pulses of decline and radiation of new clades No singular marked event at the boundary itself Smaller bodied sized animals generally more poorly sampled
- 12. Marine tetrapod diversity Jon Tennant Results Earliest Cretaceous very poorly sampled Seems to track pattern of a global eustatic lowstand Similar pattern seen in PDE Sampling from continuous lineages great for filling in the gaps
- 13. A hidden mass extinction at the J/K boundary? No. A prolonged wave of extinctions through the transition, coupled with radiations of new groups Extinctions target more basal groups, and are highest at the end of the Jurassic Magnitude of diversity loss varies ~33% for ornithischians to 75-80% for theropods and pterosaurs High Late Jurassic origination rates for different groups do not confer an extinction survival advantage Jon Tennant Conclusions
- 14. What controls global J/K diversity? Jon Tennant Results Group Non-marine rho p-value Adjusted p-value r p-value Adjusted p-value Aves 0.321 0.498 0.988 -0.174 0.708 0.865 Choristoderes -0.500 1.000 1.000 -0.509 0.660 0.865 Crocodyliformes 0.273 0.448 0.988 0.015 0.967 0.967 Lepidosauromorphs 0.050 0.912 1.000 0.317 0.406 0.757 Lissamphibians 0.000 1.000 1.000 -0.340 0.371 0.757 Mammaliaformes 0.079 0.838 1.000 -0.292 0.413 0.757 Ornithischians 0.209 0.539 0.988 0.424 0.539 0.847 Pterosaurs 0.521 0.123 0.451 0.309 0.387 0.757 Sauropodomorphs 0.736 0.024 0.264 0.733 0.031 0.171 Testudines -0.117 0.776 1.000 -0.094 0.810 0.891 Theropods 0.531 0.079 0.435 0.790 0.004 0.044 Marine Chelonioides -0.500 1.000 1.000 -0.474 0.686 0.842 Crocodyliformes 0.690 0.069 0.138 0.740 0.036 0.144 Ichthyopterygians 0.612 0.060 0.138 0.479 0.166 0.332 Sauropterygians 0.335 0.263 0.351 0.061 0.842 0.842 Spearman's rank Pearson's PMCC Tetrapod-bearing Collections No correlations with Formations Raw diversity is over- printed by sampling
- 15. What controls regional subsampled diversity? (Europe) Jon Tennant Results rho p-value Adjusted p-value r p-value Adjusted p-value Raw richness 0.671 0.006 0.034 0.513 0.042 0.167 Collections 0.468 0.070 0.140 0.474 0.064 0.167 Occurrences 0.512 0.045 0.135 0.446 0.084 0.167 Good's u -0.147 0.616 0.660 -0.348 0.223 0.267 Formations 0.326 0.173 0.259 0.328 0.171 0.256 Global sea-level -0.115 0.660 0.660 -0.153 0.557 0.557 Subsampled richness Crocodyliformes 0.036 0.964 0.964 0.381 0.400 0.599 Lepidosauromorpha 0.657 0.175 0.525 0.449 0.372 0.599 Ornithischia 0.091 0.811 0.964 0.323 0.363 0.599 Pterosauria -0.107 0.840 0.964 0.277 0.547 0.657 Testudines -0.257 0.658 0.964 0.034 0.949 0.949 Theropoda 0.527 0.123 0.525 0.605 0.064 0.383 Europe Pearson's PMCCSpearman's rank Raw tetrapod diversity strongly correlates with outcrop area (non-marine) SQS diversity for individual clades shows no relationship No correlations with outcrop area in the marine realm
- 16. What controls regional subsampled diversity? (N. America) Jon Tennant Results rho p-value Adjusted p-value r p-value Adjusted p-value Raw richness 0.346 0.206 0.309 0.278 0.315 0.464 Collections 0.446 0.097 0.292 0.561 0.030 0.089 Occurrences 0.386 0.157 0.309 0.388 0.153 0.305 Good's u -0.073 0.839 0.965 -0.290 0.387 0.464 Formations -0.012 0.965 0.965 -0.146 0.589 0.589 Global sea-level 0.581 0.016 0.098 0.630 0.007 0.040 Subsampled richness Ornithischia 0.150 0.708 0.708 0.268 0.485 0.485 Theropoda -0.452 0.268 0.536 -0.404 0.321 0.485 North America Pearson's PMCCSpearman's rank rho p-value Adjusted p-value r p-value Adjusted p-value Raw richness 0.429 0.113 0.332 0.509 0.053 0.133 Collections 0.154 0.584 0.683 0.454 0.089 0.133 Occurrences 0.146 0.602 0.683 0.474 0.074 0.133 Good's u 0.300 0.683 0.683 0.298 0.626 0.626 Formations 0.479 0.166 0.332 0.457 0.185 0.221 Global sea-level 0.463 0.063 0.332 0.702 0.002 0.010 North America Spearman's rank Pearson's PMCC Non-marine Marine Outcrop area correlates with sea level in marine and non-marine realms Therefore cannot rule out regional level common cause
- 17. Environmental factors governing diversity Jon Tennant Results Likelihood Weight rho adjusted p-value r adjusted p-value Crocodyliformes (marine) Palaeotemp. 22.741 0.237 -0.524 0.634 -0.522 0.678 Crocodyliformes (non-marine) Sea level 26.285 0.969 0.750 0.175 0.846 0.028 Lissamphibia Palaeotemp. 38.260 0.796 0.700 0.301 0.742 0.154 Mammaliaformes Sea level 51.394 0.931 -0.450 0.537 -0.666 0.301 Ornithischia Sea level 60.106 0.391 0.200 0.681 0.047 0.898 Pterosauria Sea level 33.261 0.872 0.714 0.406 0.647 0.581 Sauropodomorpha Sea level 41.191 0.501 0.310 0.810 0.457 0.564 Sauropterygia Sea level 41.820 0.409 0.055 0.906 0.065 0.985 Testudines Palaeotemp. 50.648 0.258 0.343 0.880 0.462 0.891 Theropoda Sea level 72.931 0.534 -0.018 0.968 0.037 0.954 AICc Pearson's PMCCSpearman's rank Group Parameter
- 18. What controls Jurassic/Cretaceous diversity? Primary driver on a global scale was eustatic sea level Palaeotemperature also an important factor Sampling over-prints raw diversity estimates Subsampling methods appear to alleviate sampling issues Cannot rule out evidence of a local common cause factor in North America Jon Tennant Conclusions
- 19. Major flood basalt and bolide activity Marine revolution in micro-organism communities Oligotrophic marine conditions likely related to the sea-level regression across the J/K boundary Have to consider all levels of an ecosystem and the environment to build a complete picture