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Centrosaurus apertus (Ceratopsia) bonebed from Upper Oldman Formation, Alberta

Ben Creisler

A recent paper:

Kentaro Chiba, Michael J. Ryan, Dennis R. Braman, David A. Eberth,
Evan E. Scott, Caleb M. Brown, Yoshitsugu Kobayashi and David C. Evans
Taphonomy of a monodominant Centrosaurus apertus (Dinosauria:
Ceratopsia) bonebed from the Upper Oldman Formation of southeastern
Palaios 30(9): 655-667
doi: 10.2110/palo.2014.084

The horned dinosaur Centrosaurus apertus from the Belly River Group
(Campanian) is represented by multiple articulated skulls and
skeletons, and is particularly notable for its occurrence in dozens of
large-scale monodominant bonebeds, which have been found in the
Dinosaur Park Formation across southern Alberta and Saskatchewan. Here
we present a detailed taphonomic analysis of the first large-scale
Centrosaurus apertus bonebed (McPheeters bonebed) from the Oldman
Formation of southeastern Alberta. The McPheeters bonebed rivals the
richest bonebeds in the Dinosaur Park Formation in terms of bone
density and size, and the complete disarticulation of elements. The
bonebed occurs in an overbank facies and is dominated by small bone
clasts, suggesting that only low energy water current contributed to
the formation of the bonebed before its final burial event. Patterns
of taphonomic modification suggest that bones experienced little
weathering, breakage, or scavenging. In turn, these conclusions are
compatible with an overall interpretation of rapid burial in humid
conditions after the disarticulation of elements. These taphonomic
features are virtually identical to those seen in the well-documented
bonebeds of this species in the Dinosaur Park Formation, which are
interpreted to represent mass death events caused by seasonal tropical
storms and associated large-scale flooding. Late Cretaceous dinosaur
species typically have small geographic and stratigraphic ranges
defined by the extent of single geological formations. The new bonebed
extends the distribution of Centrosaurus apertus to the upper Oldman
Formation, which is interpreted as more inland than the coastally
influenced Dinosaur Park Formation, and suggests that mass death
events related to seasonal tropical storms occurred over a broader
geographic area and in a greater range of paleoenvironments than
previously documented.