Abstract
The Devonian period ended with one of the largest mass extinctions in the Earth history. It comprised a series of separate events, which eliminated many marine species and led to long-term post-extinction reduction in body size in some groups. Surprisingly, crinoids were largely unaffected by these extinction events in terms of diversity. To date, however, no study examined the long-term body-size trends of crinoids over this crucial time interval. Here we compiled the first comprehensive data sets of sizes of calyces for 262 crinoid genera from the Frasnian-Visean. We found that crinoids have not experienced long-term reduction in body size after the so-called Hangenberg event. Instead, size distributions of calyces show temporal heterogeneity in the variance, with an increase in both the mean and maximum biovolumes between the Famennian and Tournaisian. The minimum biovolume, in turn, has remained constant over the study interval. Thus, the observed pattern seems to fit a Brownian motion-like diffusion model. Intriguingly, the same model has been recently invoked to explain morphologic diversification within the eucladid subclade during the Devonian-early Carboniferous. We suggest that the complex interplay between abiotic and biotic factors (i.e., expansion of carbonate ramps and increased primary productivity, in conjunction with predatory release after extinction of Devonian-style durophagous fishes) might have been involved not only in the early Mississippian diversity peak of crinoids, but possibly also in their overall passive expansion into larger body-size niches.
Highlights
Body size is a key biological property of organisms, which has a significant influence on life functions, generation time, population and home range sizes[1]
One of the most intriguing evolutionary phenomenon is the Lilliput effect[11], which refers to a decrease in body size of fauna associated with the aftermath of extinctions
The crinoid class-level trend of increasing size throughout the investigated interval is supported by linear regressions [ordinary least squares (OLS) and reduced major axis (RMA) P < 0.05; details in Supplementary Figs S12– S15; Tables S18–S21]
Summary
Body size is a key biological property of organisms, which has a significant influence on life functions, generation time, population and home range sizes[1]. One of the most intriguing evolutionary phenomenon is the Lilliput effect[11], which refers to a decrease in body size of fauna associated with the aftermath of extinctions. Stromatoporoid sponges became totally extinct at around the Famennian/Tournaisian boundary This boundary corresponds to the so-called Hangenberg event marking the last spike in the Devonian extinctions. Recent study demonstrated that origination rates of crinoids exceeded extinction rates at around Devonian/ Carboniferous boundary[18]. Crinoids reached their Phanerozoic peak of generic richness and abundance in the early Mississippian, which has been referred to as the ‘Age of Crinoids’[19,20]. To test this we assembled a database comprising sizes of calyces for 262 crinoid genera occurring in the Frasnian-Visean
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