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A hidden extinction in
tetrapods at the Jurassic-
Cretaceous boundary
Jonathan Tennant
Thanks! • NERC
• PALASS
• SVP
History of the Jurassic/Cretaceous boundary
• Pioneering work by Newell, Raup, Sepkoski (and his compendia)
• Originally c...
The structure of the fossil record
Jon Tennant Background
Smith and McGowan (2011)
Tennant et al. (2016)
Raw diversity is ...
Why the J/K boundary?
Jon Tennant Background
Benson and Butler (2011)
Nicholson et al. (2015)
Zanno and Makovicky (2013)
B...
What do we want to know?
1. What is the structure of changes in tetrapod
diversity over the J/K transition? Was there a
‘h...
Data. More data.
• 4907 species
• 15,472 occurrences, 7314 references
• Split into higher taxonomic clades
• Fully aquatic...
Methodological approach
•Subsampling (SQS) and
phylogenetic diversity
estimates (PDE)
•Model-fitting of extrinsic
paramete...
• Tetrapod SQS diversity
falls in both the non-
marine and marine realms
• Finer clade-level dynamics
obscured
• Bootstrap...
Dinosaur diversity
Jon Tennant Results
• SQS shows greatest decline in theropods
• Sauropods too poorly sampled in Berrias...
Non-dinosaurian tetrapod diversity
Jon Tennant Results
• Staggered pulses of decline and radiation of new clades
• No sing...
Marine tetrapod diversity
Jon Tennant Results
• Earliest Cretaceous very poorly sampled
• Seems to track pattern of a glob...
A hidden mass extinction at the J/K
boundary?
• No. A prolonged wave of extinctions through the ‘transition’,
coupled with...
What controls global J/K diversity?
Jon Tennant Results
Group
Non-marine
rho p-value
Adjusted
p-value
r p-value
Adjusted
p...
What controls regional subsampled diversity?
(Europe)
Jon Tennant Results
rho p-value
Adjusted
p-value
r p-value
Adjusted
...
What controls regional subsampled diversity? (N.
America)
Jon Tennant Results
rho p-value
Adjusted
p-value
r p-value
Adjus...
Environmental factors governing diversity
Jon Tennant Results
Likelihood Weight rho
adjusted
p-value
r
adjusted
p-value
Cr...
What controls Jurassic/Cretaceous diversity?
• Primary driver on a global scale was eustatic sea level
• Palaeotemperature...
• Major flood basalt and bolide activity
• Marine revolution in micro-organism communities
• Oligotrophic marine condition...
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Romer session presentation

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Society of Vertebrate Paleontology 2016, Salt Lake City, Utah

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Romer session presentation

  1. 1. A hidden extinction in tetrapods at the Jurassic- Cretaceous boundary Jonathan Tennant
  2. 2. Thanks! • NERC • PALASS • SVP
  3. 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. 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. 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. 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. 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. 8. Methodological approach •Subsampling (SQS) and phylogenetic diversity estimates (PDE) •Model-fitting of extrinsic parameters Jon Tennant Methods
  9. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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

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