[dinosaur] Crocodylomorph body size evolution (free pdf)

Ben Creisler
[email protected]


A new paper:

Free pdf:

Pedro L. Godoy, Roger B. J. Benson, Mario Bronzati & Richard J. Butler
(2019)
The multi-peak adaptive landscape of crocodylomorph body size evolution.
BMC Evolutionary Biology 19: 167
DOI: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1186_s12862-2D019-2D1466-2D4&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=0VybpwiXlAoPoFnf1HSd5ZjS37RN5anZNzGB-wlMoMc&s=S_wAPEtaDemWBldGnDEFnx0uTSjnadWeklR8TPZ5V6Q&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__link.springer.com_article_10.1186_s12862-2D019-2D1466-2D4&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=0VybpwiXlAoPoFnf1HSd5ZjS37RN5anZNzGB-wlMoMc&s=aMhH8y5NkGu54IPdOlGYd_0P-KifH5hkZNwjdD7CRCw&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__bmcevolbiol.biomedcentral.com_articles_10.1186_s12862-2D019-2D1466-2D4&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=0VybpwiXlAoPoFnf1HSd5ZjS37RN5anZNzGB-wlMoMc&s=sXSH3aS6TFEtXLyF6iFtGszgyYO0dx3fSVBw3qBO1nE&e= 

free pdf:
https://urldefense.proofpoint.com/v2/url?u=https-3A__link.springer.com_content_pdf_10.1186-252Fs12862-2D019-2D1466-2D4.pdf&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=0VybpwiXlAoPoFnf1HSd5ZjS37RN5anZNzGB-wlMoMc&s=FIrw9YpT2AN8oTMog0a8T97hF5QAGJkTHGWOdrIuSDw&e= 

Background

Little is known about the long-term patterns of body size evolution in
Crocodylomorpha, the > 200-million-year-old group that includes living
crocodylians and their extinct relatives. Extant crocodylians are mostly
large-bodied (3–7 m) predators. However, extinct crocodylomorphs exhibit a
wider range of phenotypes, and many of the earliest taxa were much smaller
(< 1.2 m). This suggests a pattern of size increase through time that could
be caused by multi-lineage evolutionary trends of size increase or by
selective extinction of small-bodied species. Here, we characterise
patterns of crocodylomorph body size evolution using a model
fitting-approach (with cranial measurements serving as proxies). We also
estimate body size disparity through time and quantitatively test
hypotheses of biotic and abiotic factors as potential drivers of
crocodylomorph body size evolution.

Results

Crocodylomorphs reached an early peak in body size disparity during the
Late Jurassic, and underwent an essentially continual decline since then. A
multi-peak Ornstein-Uhlenbeck model outperforms all other evolutionary
models fitted to our data (including both uniform and non-uniform),
indicating that the macroevolutionary dynamics of crocodylomorph body size
are better described within the concept of an adaptive landscape, with most
body size variation emerging after shifts to new macroevolutionary regimes
(analogous to adaptive zones). We did not find support for a consistent
evolutionary trend towards larger sizes among lineages (i.e., Cope’s rule),
or strong correlations of body size with climate. Instead, the intermediate
to large body sizes of some crocodylomorphs are better explained by
group-specific adaptations. In particular, the evolution of a more aquatic
lifestyle (especially marine) correlates with increases in average body
size, though not without exceptions.

Conclusions

Shifts between macroevolutionary regimes provide a better explanation of
crocodylomorph body size evolution on large phylogenetic and temporal
scales, suggesting a central role for lineage-specific adaptations rather
than climatic forcing. Shifts leading to larger body sizes occurred in most
aquatic and semi-aquatic groups. This, combined with extinctions of groups
occupying smaller body size regimes (particularly during the Late
Cretaceous and Cenozoic), gave rise to the upward-shifted body size
distribution of extant crocodylomorphs compared to their smaller-bodied
terrestrial ancestors.


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