Some new non-dino papers:
At least twentyâsix species of crocodylian populate the globe today, but this richness represents a minute fraction of the diversity and disparity of Crocodyliformes. Fossil forms are far more varied, spanning from erect, fully terrestrial species to flippered, fully marine species. To quantify the influence of a marine habitat on the directionality, rate, and variance of evolution of body size in Crocodyliformes and thereby identify underlying selective pressures, we compiled a database of body sizes for 264 fossil and modern species of crocodyliform covering terrestrial, semiâaquatic, and marine habitats. We find increases in body size coupled with increases in strength of selection and decreases in variance following invasions of marine habitats but not of semiâaquatic habitats. A model combining constraints from thermoregulation and lung capacity provides a physiological explanation for the larger minimum and average sizes of marine species. It appears that constraints on maximum size are shared across Crocodyliformes, perhaps through factors such as the allometric scaling of feeding rate versus basal metabolism with body size. These findings suggest that broadâscale patterns of body size evolution and the shapes of body size distributions within higher taxa are often determined more by physiological constraints than by ecological interactions or environmental fluctuations.
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We document an apparent mass-death assemblage of Eremotherium giant ground sloths.
This multigenerational group likely congregated and died in a shallow marsh.
The die-off may have been caused by contamination of the wallow by fecal material.
Some ground sloths may have been ecologically similar to modern hippos.
Some species of ground sloths may have been gregarious.
Abstract
Extinct giant ground sloths are a common taxon in New World Quaternary deposits, but relatively little is known about individual species' behavior or social structure. In this paper, we investigate the development of the late-Pleistocene locality Tanque Loma on the southwest coast of Ecuador, which preserves remains of at least 22 individuals of the giant ground sloth, Eremotherium laurillardi in asphaltic sediments. Multiple lines of evidence suggest that these sloths may have congregated and died in a mass mortality event in a marshy riparian habitat. Such evidence includes (1) a dense, laterally-extensive, bonebed-style accumulation; (2) a multigenerational age structure with adult and large juvenile individuals well-represented; (3) sediments suggestive of a low-energy anoxic aquatic environment; and (4) the presence of abundant plant material consistent with digested fodder representing coprolites or gut contents of E. laurillardi. Taking observations from modern megafaunal ecosystems as an analogue, we suggest that this death event could have resulted from drought and/or disease stemming from the contamination of the wallow, paralleling situations observed among hippopotamus populations in watering holes on the present-day African savannah.
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