Ankylosauria
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publication ID |
https://doi.org/ 10.5252/geodiversitas2022v44a25 |
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publication LSID |
urn:lsid:zoobank.org:pub:EA12DCB7-A5BE-4763-B805-25087EBD726D |
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DOI |
https://doi.org/10.5281/zenodo.6928910 |
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persistent identifier |
https://treatment.plazi.org/id/03C887B9-FF96-FFCA-713E-A04EFE92FE41 |
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treatment provided by |
Felipe |
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scientific name |
Ankylosauria |
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Ankylosauria indet.
( Fig. 23 View FIG A-C)
DESCRIPTION
The ankylosaurs are only represented in Angeac-Charente by a single tooth (ANG15-3980) and an osteoderm (ANG18- 6585). The tooth ( Fig. 23A, B View FIG ) was collected in 2015 from the unit 3 of the CG3 plot. The osteoderm ( Fig. 23C View FIG ) was found in 2018, in the CG9 plot, at the base of the bonebed (unit 2 of Rozada et al. 2021).
ANG15-3980 consists of a nearly complete, but worn tooth crown, with only the basal part of the root attached. The crown height is 9 mm, and the maximum width at the crown base is 8.5 mm. The crown is folidont, labiolingually compressed, and slightly recurved posteriorly. The labial and lingual crown surfaces are smooth and swollen around the base. The base of the crown is raised on the labial side ( Fig. 23B View FIG ), while there is a distinct cingulum at the base of the lingual side ( Fig. 23A View FIG ). A broad primary ridge extends vertically from the swollen base on both sides of the crown to form the apex of the tooth. The mesial and distal carinae bear 6 denticles, but there is no evidence of fluting as in stegosaurs and many Late Cretaceous ankylosaurs. There is a slight constriction of the root just below the crown. ANG15-3980 is nearly identical to NHMUK R2940, which is an isolated tooth from the Purbeck Group of Lulworth Cove, Dorset, referred to an ankylosaur ( Galton 1980, 1983). It is also similar to ankylosaur teeth reported from the Valanginian and Barremian of southern England ( Blows & Honeysett 2014).
Based on its shape and its size, ANG18-6585 is clearly distinct from other osteoderms found in Angeac-Charente that belong either to turtles, crocodyliformes or scincomorphs (see above). It has a pentagonal shape, with a maximum length of c. 10 cm and a thickness of c. 15 mm. ANG18-6585 possesses a marked keel on its exterior surface ( Fig. 23C View FIG ), while its base is nearly flat. The exterior surface of the osteoderm is marked with numerous grooves that give it a spongy texture. Such a morphology and structure have been reported in nodosaurid ankylosaurs ( Blows 2001), and is very similar to the large ossicles observed on the sacral shield of Polacanthus from the Barremian of the Isle of Wight ( Hulke 1887; Blows 1987, Pereda-Suberbiola 1994).
Although the material is very limited, the discovery of ankylosaur remains at Angeac-Charente is significant because these animals are very rare in the European fossil record in Purbeckian facies. Except for the Lulworth tooth ( Galton 1983) and a cervico-pectoral lateral spine associated with a distal humerus from the Early Valanginian of Gronau in Germany ( Sachs & Hornung 2013), there are no other known ankylosaur remains in Europe around the Jurassic/ Cretaceous boundary.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.