Romer session presentation

A hidden extinction in tetrapods at the Jurassic-

Cretaceous boundaryJonathan Tennant

Thanks! • NERC• PALASS• SVP

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)

The structure of the fossil record


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’

Why the J/K boundary?


Benson and Butler (2011)

Nicholson et al. (2015)

Zanno and Makovicky (2013)Bronzati et al. (2015)

Newham et al. (2014)

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

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)

Methodological approach

•Subsampling (SQS) and phylogenetic diversity estimates (PDE)•Model-fitting of extrinsic parameters

Jon Tennant Methods

• 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

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

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

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’

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

What controls global J/K diversity?

Jon Tennant Results

Group

Non-marinerho p-value

Adjusted p-value

r p-valueAdjusted p-value

Aves 0.321 0.498 0.988 -0.174 0.708 0.865Choristoderes -0.500 1.000 1.000 -0.509 0.660 0.865Crocodyliformes 0.273 0.448 0.988 0.015 0.967 0.967Lepidosauromorphs 0.050 0.912 1.000 0.317 0.406 0.757Lissamphibians 0.000 1.000 1.000 -0.340 0.371 0.757Mammaliaformes 0.079 0.838 1.000 -0.292 0.413 0.757Ornithischians 0.209 0.539 0.988 0.424 0.539 0.847Pterosaurs 0.521 0.123 0.451 0.309 0.387 0.757Sauropodomorphs 0.736 0.024 0.264 0.733 0.031 0.171Testudines -0.117 0.776 1.000 -0.094 0.810 0.891Theropods 0.531 0.079 0.435 0.790 0.004 0.044

MarineChelonioides -0.500 1.000 1.000 -0.474 0.686 0.842Crocodyliformes 0.690 0.069 0.138 0.740 0.036 0.144Ichthyopterygians 0.612 0.060 0.138 0.479 0.166 0.332Sauropterygians 0.335 0.263 0.351 0.061 0.842 0.842

Spearman's rank Pearson's PMCC

Tetrapod-bearingCollections

No correlations withFormations

Raw diversity is over-printed by sampling

What controls regional subsampled diversity? (Europe)

Jon Tennant Results

rho p-valueAdjusted p-value


Raw richness 0.671 0.006 0.034 0.513 0.042 0.167Collections 0.468 0.070 0.140 0.474 0.064 0.167

Occurrences 0.512 0.045 0.135 0.446 0.084 0.167Good'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 0.256Global sea-level -0.115 0.660 0.660 -0.153 0.557 0.557

Subsampled richnessCrocodyliformes 0.036 0.964 0.964 0.381 0.400 0.599

Lepidosauromorpha 0.657 0.175 0.525 0.449 0.372 0.599Ornithischia 0.091 0.811 0.964 0.323 0.363 0.599Pterosauria -0.107 0.840 0.964 0.277 0.547 0.657Testudines -0.257 0.658 0.964 0.034 0.949 0.949Theropoda 0.527 0.123 0.525 0.605 0.064 0.383

EuropePearson'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

What controls regional subsampled diversity? (N. America)

Jon Tennant Results




Occurrences 0.386 0.157 0.309 0.388 0.153 0.305Good'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 0.589Global sea-level 0.581 0.016 0.098 0.630 0.007 0.040

Subsampled richnessOrnithischia 0.150 0.708 0.708 0.268 0.485 0.485Theropoda -0.452 0.268 0.536 -0.404 0.321 0.485

North AmericaPearson's PMCCSpearman's rank




Occurrences 0.146 0.602 0.683 0.474 0.074 0.133Good'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 0.221Global sea-level 0.463 0.063 0.332 0.702 0.002 0.010

North AmericaSpearman'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’

Environmental factors governing diversity

Jon Tennant Results

Likelihood Weight rhoadjusted p-value

radjusted p-value

Crocodyliformes (marine) Palaeotemp. 22.741 0.237 -0.524 0.634 -0.522 0.678Crocodyliformes (non-marine) Sea level 26.285 0.969 0.750 0.175 0.846 0.028Lissamphibia Palaeotemp. 38.260 0.796 0.700 0.301 0.742 0.154Mammaliaformes Sea level 51.394 0.931 -0.450 0.537 -0.666 0.301Ornithischia Sea level 60.106 0.391 0.200 0.681 0.047 0.898Pterosauria Sea level 33.261 0.872 0.714 0.406 0.647 0.581Sauropodomorpha Sea level 41.191 0.501 0.310 0.810 0.457 0.564Sauropterygia Sea level 41.820 0.409 0.055 0.906 0.065 0.985Testudines Palaeotemp. 50.648 0.258 0.343 0.880 0.462 0.891Theropoda Sea level 72.931 0.534 -0.018 0.968 0.037 0.954

AICc Pearson's PMCCSpearman's rankGroup Parameter

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

• 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

Romer session presentation

Science

Transcript of Romer session presentation