Dino Death Pits in Feb. Palaios

[bh480@scn.org]

From: Ben Creisler bh480@scn.org


In case this paper has not been mentioned:

DAVID A. EBERTH, XU XING, and JAMES M. CLARK. 2010. 
DINOSAUR DEATH PITS FROM THE JURASSIC OF CHINA 
Palaios 25: 112-125 (Feb. 2010)

 
Abstract
Three newly discovered bonebeds from the Shishugou 
Formation of Xinjiang, China, are unusual in preserving 
vertically stacked and articulated to associated skeletons 
of at least 18 small, non-avian theropod dinosaurs in pits 
that are 1-2 m deep. The pits host a soft sediment-
deformed mixture of alluvial and volcanic mudstone and 
sandstone. There is no evidence that the pits were 
discrete depressions in the topography that filled through 
time. Rather, they appear to have been highly localized 
areas of liquefaction caused by large-dinosaur (possibly 
sauropod) trampling of saturated sediments. Evidence 
indicates that the small theropods, and some other small 
vertebrates, became mired and died in these mud-filled 
pits. High quality skeletal preservation suggests that 
most individuals were buried within days to months after 
their deaths. Carcasses were buried successively, coming 
to rest above previously buried individuals. In some 
cases, skeletal body parts became separated or were 
removed, probably during scavenging. Given the large sizes 
of the pits relative to the small body sizes of the 
vertebrates contained within them, we conclude that small 
vertebrates (<3 m long and <1 m tall) were particularly 
susceptible to miring at these sites. Although the small, 
presumably herbivorous ceratosaur, Limusaurus 
inextricabilis, dominates the combined small theropod 
assemblage from these bonebeds (minimum number of 
individuals [MNI] = 15), there is no evidence that any 
biological features other than its small size and a large, 
and possibly, gregarious local population were responsible 
for its becoming mired in large numbers. A bias for small 
theropods in these bonebeds, compared to their relatively 
low abundance in the overall Shishugou Formation fauna, 
underscores that small theropods are underrepresented in 
Mesozoic fossil assemblages collected from other ancient 
alluvial and paludal settings.