Abstract
A fragmentary cervico-pectoral lateral spine and partial humerus of an ankylosaur from the Early Cretaceous (early Valanginian) of Gronau in Westfalen, northwestern Germany, are described. The spine shows closest morphological similarities to the characteristic cervical and pectoral spines of Hylaeosaurus armatus from the late Valanginian of England. An extensive comparison of distal humeri among thyreophoran dinosaurs supports systematic differences in the morphology of the distal condyli between Ankylosauria and Stegosauria and a referral of the Gronau specimen to the former. The humerus fragment indicates a rather small individual, probably in the size range of H. armatus, and both specimens are determined herein as ?Hylaeosaurus sp.. A short overview of other purported ankylosaur material from the Berriasian-Valanginian of northwest Germany shows that, aside from the material described herein, only tracks can be attributed to this clade with confidence at present.
Highlights
The Gerdemann clay-pit in Gronau in Westfalen has yielded a considerable amount of vertebrate fossils, including remains of fishes, turtles, plesiosaurs, crocodilians and dinosaurs [1,2,3,4,5]
The western part of the basin, including the Gronau region, occasionally came under brackish to marine influence via passages to the Boreal Sea ([6]; Fig. 2). These brackish and marine intervals increase in number and prominence in the youngest part of the succession and may correlate with diversity peaks in the aquatic fossil faunas
Because of the morphological similarity of the Gronau osteoderm with the pectoral spines of Hylaeosaurus armatus Mantell, 1833 [10], we decided to apply the anatomical orientation of these elements [11]
Summary
The Gerdemann clay-pit in Gronau in Westfalen (northwestern Germany, Fig. 1a) has yielded a considerable amount of vertebrate fossils, including remains of fishes, turtles, plesiosaurs, crocodilians and dinosaurs [1,2,3,4,5]. The western part of the basin, including the Gronau region, occasionally came under brackish to marine influence via passages to the Boreal Sea ([6]; Fig. 2). These brackish and marine intervals increase in number and prominence in the youngest part of the succession and may correlate with diversity peaks in the aquatic fossil faunas. Subaqueous density flows have played a role in the formation of this taphocoenosis by transporting carcasses from the littoral zone deeper into the basin [5]
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