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[dinosaur] South Dakota Standing Rock hadrosaur site taphonomy + turtle shell impression in coprolite

Ben Creisler

A new paper:

Paul V. Ullmann, Allen Shaw, Ron Nellermoe, and Kenneth J. Lacovara (2017)
Taphonomy of the Standing Rock hadrosaur site, Corson County, South Dakota.
PALAIOS 32(12):779-796
doi: https://doi.org/10.2110/palo.2017.060

We present taphonomic analyses of the Standing Rock Hadrosaur Site (SRHS), a vast Edmontosaurus annectens bonebed in the Maastrichtian Hell Creek Formation of South Dakota, which yields important insights into hadrosaurid paleobiology and environmental settings recorded by basal Hell Creek strata. Though Edmontosaurus bonebeds have been described from other Late Cretaceous formations in the Western Interior, namely the Lance, Prince Creek, and Horseshoe Canyon formations, our study provides the first thorough description of an Edmontosaurus bonebed from the Hell Creek Formation. SRHS is also the first formally described bonebed of E. annectens. Taphonomically, representation of every skeletal element, horizontality of most bones, and rarity of weathering and abrasion suggest brief preburial exposure and transport with minimal sorting bias. Near-universal disarticulation and disassociation, localized orientation of bones, and infrequent preburial breakage indicate moderate flow energy during deposition. Additional fauna, though rare, are indicative of a fluvial-coastal setting, and palynofloral analyses signify deposition in a small, shallow floodplain lake surrounded by cypress forests. Cumulatively, these data indicate that a herd of primarily subadult and adult Edmontosaurus died in a nearby fluvial setting in a mass mortality event and, following brief decay and scavenging by theropods, their bones were buried in a shallow floodplain pond by a flooding event/crevasse splay. Our findings provide supporting evidence for the hypotheses of gregarious herding behavior in hadrosaurids and age structuring of Edmontosaurus herds.


Stephen J. Godfrey, Robert E. Weems & Billy Palmer (2017)
Turtle Shell Impression in a Coprolite from South Carolina, USA.
Ichnos (advance online publication)
doi:Â https://doi.org/10.1080/10420940.2017.1386662Â Â

Coprolites (fossilized feces) can preserve a wide range of biogenic components. A mold of a hatchling turtle partial shell (carapace) referable to Taphrosphys sulcatus is here identified within a coprolite from Clapp Creek in Kingstree, Williamsburg County, South Carolina, USA. The specimen is the first-known coprolite to preserve a vertebrate body impression. The small size of the turtle shell coupled with the fact that it shows signs of breakage indicates that the turtle was ingested and that the impression was made while the feces were still within the body of the predator. The detailed impression could only have survived the act of defecation if the section of bony carapace was voided concurrently and remained bonded with the feces until the latter lithified. Exceptionally, the surface texture of the scutes is preserved, including its finely pitted embryonic texture and a narrow perimeter of hatchling scute texture. The very small size of the shell represented by the impression makes it a suitable size for swallowing by any one of several large predators known from this locality. The coprolite was collected from a lag deposit containing a temporally mixed vertebrate assemblage (Cretaceous, Paleocene and Plio-Pleistocene). The genus Taphrosphys is known from both sides of the CretaceousâPaleogene (KâPg) boundary so, based on the size of the coprolite and the locally-known predators, the juvenile turtle could have been ingested by a mosasaur, a crocodylian, or a theropod dinosaur. Unlike mosasaurs and theropod dinosaurs, crocodylian stomachs have extremely high acid content that almost always dissolves bone. Therefore, the likely predator of this turtle was a mosasaur or a (non-avian or avian) theropod dinosaur.

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