Probable ankylosaur ossicles from the middle Cenomanian Dunvegan formation of northwestern Alberta, Canada.

Michael E Burns,Matthew J Vavrek,Peter Dodson

doi:10.1371/journal.pone.0096075

Abstract

A sample of six probable fragmentary ankylosaur ossicles, collected from Cenomanian deposits of the Dunvegan Formation along the Peace River, represent one of the first dinosaurian skeletal fossils reported from pre-Santonian deposits in Alberta. Specimens were identified as ankylosaur by means of a palaeohistological analysis. The primary tissue is composed of zonal interwoven structural fibre bundles with irregularly-shaped lacunae, unlike the elongate lacunae of the secondary lamellar bone. The locality represents the most northerly Cenomanian occurrence of ankylosaur skeletal remains. Further fieldwork in under-examined areas of the province carries potential for additional finds.

Highlights

Alberta is one of the most intensely studied areas in the world in regards to dinosaur palaeontology [1,2], skeletal fossils of dinosaurs from pre-Santonian rocks are virtually unknown [3]
Other than a recently recovered ankylosaur from marine sediments of the Albian Clearwater Formation of northeastern Alberta [4], and an isolated Ichthyornis sp. humerus from the Turonian Kaskapau Formation [5], no other dinosaur skeletal remains have been described from Alberta in rocks older than Santonian, there does exist a non-descriptive reference to Dunvegan Formation dinosaurs in an encyclopedia article [6]
The lines of zonation, are not as distinct enough to be confidently called lines of arrested growth because they do During the Cenomanian, the Dunvegan delta was located near the Arctic Circle, at about 65u N [14,15,16,17] Land temperatures during this time were, much warmer on average than the present day [18] with higher latitude regions in particular experiencing a greater amount of warming compared to more equatorial areas, leading to a reduced equator to pole thermal gradient [19]

Summary

Introduction

Alberta is one of the most intensely studied areas in the world in regards to dinosaur palaeontology [1,2], skeletal fossils of dinosaurs from pre-Santonian rocks are virtually unknown [3]. Humerus from the Turonian Kaskapau Formation [5], no other dinosaur skeletal remains have been described from Alberta in rocks older than Santonian, there does exist a non-descriptive reference to Dunvegan Formation dinosaurs in an encyclopedia article [6]. During the course of research for this paper, the authors were informed of some undescribed, indeterminate bones (possibly ornithischian) from the Blairmore Formation of southwestern Alberta Even outside of Alberta, there are virtually no skeletal remains of pre-Santonian dinosaurs from north of the 49th Parallel. Despite the lack of a recognized fossil record, there are relatively large exposures of lower Upper Cretaceous rocks in Alberta, primarily concentrated along large river channels in the northern portion of the province

Methods

Results

Conclusion