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Pterosaur fossil record controlled by preservational bias

Ben Creisler

A new paper:

Christopher D. Dean, Philip D. Mannion andRichard J. Butler (2016)
Preservational bias controls the fossil record of pterosaurs.
Palaeontology (advance online publication)
DOI: 10.1111/pala.12225

Pterosaurs, a Mesozoic group of flying archosaurs, have become a focal
point for debates pertaining to the impact of sampling biases on our
reading of the fossil record, as well as the utility of sampling
proxies in palaeo-diversity reconstructions. The completeness of the
pterosaur fossil specimens themselves potentially provides additional
information that is not captured in existing sampling proxies, and
might shed new light on the group's evolutionary history. Here we
assess the quality of the pterosaur fossil record via a character
completeness metric based on the number of phylogenetic characters
that can be scored for all known skeletons of 172 valid species, with
averaged completeness values calculated for each geological stage. The
fossil record of pterosaurs is observed to be strongly influenced by
the occurrence and distribution of Lagerstätten. Peaks in completeness
correlate with Lagerstätten deposits, and a recovered correlation
between completeness and observed diversity is rendered
non-significant when Lagerstätten species are excluded. Intervals
previously regarded as potential extinction events are shown to lack
Lagerstätten and exhibit low completeness values: as such, the
apparent low diversity in these intervals might be at least partly the
result of poor fossil record quality. A positive correlation between
temporal patterns in completeness of Cretaceous pterosaurs and birds
further demonstrates the prominent role that Lagerstätten deposits
have on the preservation of smaller bodied organisms, contrasting with
a lack of correlation with the completeness of large-bodied
sauropodomorphs. However, we unexpectedly find a strong correlation
between sauropodomorph and pterosaur completeness within the
Triassic–Jurassic, but not the Cretaceous, potentially relating to a
shared shift in environmental preference and thus preservation style
through time. This study highlights the importance of understanding
the relationship between various taphonomic controls when correcting
for sampling bias, and provides additional evidence for the prominent
role of sampling on observed patterns in pterosaur macroevolution.