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A review of large Cretaceous ornithopod tracks, with special reference to their ichnotaxonomy

A review of large Cretaceous ornithopod tracks, with special reference to their ichnotaxonomy
A review of large Cretaceous ornithopod tracks, with special reference to their ichnotaxonomy
Trackways of ornithopods are well-known from the Lower Cretaceous of Europe, North America, and East Asia. For historical reasons, most large ornithopod footprints are associated with the genus Iguanodon or, more generally, with the family Iguanodontidae. Moreover, this general category of footprints is considered to be sufficiently dominant at this time as to characterize a global Early Cretaceous biochron. However, six valid ornithopod ichnogenera have been named from the Cretaceous, including several that are represented by multiple ichnospecies: these are Amblydactylus (two ichnospecies); Caririchnium (four ichnospecies); Iguanodontipus, Ornithopodichnus originally named from Lower Cretaceous deposits and Hadrosauropodus (two ichnospecies); and Jiayinosauropus based on Upper Cretaceous tracks. It has recently been suggested that ornithopod ichnotaxonomy is oversplit and that Caririchnium is a senior subjective synonym of Hadrosauropodus and Amblydactylus is a senior subjective synonym of Iguanodontipus. Although it is agreed that many ornithopod tracks are difficult to differentiate, this proposed synonymy is questionable because it was not based on a detailed study of the holotypes, and did not consider all valid ornithopod ichnotaxa or the variation reported within the six named ichnogenera and 11 named ichnospecies reviewed here. We therefore emphasize the need to base comparisons between ichnotaxa on type material, and not on selected referred material. It is concluded that there is considerable variation in the morphology of the holotypes, as well as variation in size and quality of the samples and the mode of preservation. Conversely, there is considerable overlap in morphology among other tracks that have been informally attributed to these ichnotaxa. These factors make it difficult to synonymize any of the existing ichnotaxa without detailed revision of the samples from which the type material originates. Nevertheless, a review of the type material of all ichnotaxa is presented as a basis for further discussion and, as a first step, the ichnofamily Iguanodontipodidae is proposed to accommodate Amblydactylus, Caririchnium and Iguanodontipus.
footprints, ichnology, iguanodontids, vertebrate ichnology
0024-4066
721-736
Lockley, Martin G.
ff3fe08a-e144-47a5-9ab6-0b81daad5c17
Xing, Lida
195654f1-e2f6-41a5-9c00-32ca3476fc93
Lockwood, Jeremy A.F.
df85e113-c842-45b2-8d23-1e034c61aa9d
Pond, Stuart
50436147-54f6-4e54-a907-df67bd97e3c3
Lockley, Martin G.
ff3fe08a-e144-47a5-9ab6-0b81daad5c17
Xing, Lida
195654f1-e2f6-41a5-9c00-32ca3476fc93
Lockwood, Jeremy A.F.
df85e113-c842-45b2-8d23-1e034c61aa9d
Pond, Stuart
50436147-54f6-4e54-a907-df67bd97e3c3

Lockley, Martin G., Xing, Lida, Lockwood, Jeremy A.F. and Pond, Stuart (2014) A review of large Cretaceous ornithopod tracks, with special reference to their ichnotaxonomy. Biological Journal of the Linnean Society, 113 (3), 721-736. (doi:10.1111/bij.12294).

Record type: Article

Abstract

Trackways of ornithopods are well-known from the Lower Cretaceous of Europe, North America, and East Asia. For historical reasons, most large ornithopod footprints are associated with the genus Iguanodon or, more generally, with the family Iguanodontidae. Moreover, this general category of footprints is considered to be sufficiently dominant at this time as to characterize a global Early Cretaceous biochron. However, six valid ornithopod ichnogenera have been named from the Cretaceous, including several that are represented by multiple ichnospecies: these are Amblydactylus (two ichnospecies); Caririchnium (four ichnospecies); Iguanodontipus, Ornithopodichnus originally named from Lower Cretaceous deposits and Hadrosauropodus (two ichnospecies); and Jiayinosauropus based on Upper Cretaceous tracks. It has recently been suggested that ornithopod ichnotaxonomy is oversplit and that Caririchnium is a senior subjective synonym of Hadrosauropodus and Amblydactylus is a senior subjective synonym of Iguanodontipus. Although it is agreed that many ornithopod tracks are difficult to differentiate, this proposed synonymy is questionable because it was not based on a detailed study of the holotypes, and did not consider all valid ornithopod ichnotaxa or the variation reported within the six named ichnogenera and 11 named ichnospecies reviewed here. We therefore emphasize the need to base comparisons between ichnotaxa on type material, and not on selected referred material. It is concluded that there is considerable variation in the morphology of the holotypes, as well as variation in size and quality of the samples and the mode of preservation. Conversely, there is considerable overlap in morphology among other tracks that have been informally attributed to these ichnotaxa. These factors make it difficult to synonymize any of the existing ichnotaxa without detailed revision of the samples from which the type material originates. Nevertheless, a review of the type material of all ichnotaxa is presented as a basis for further discussion and, as a first step, the ichnofamily Iguanodontipodidae is proposed to accommodate Amblydactylus, Caririchnium and Iguanodontipus.

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Published date: November 2014
Keywords: footprints, ichnology, iguanodontids, vertebrate ichnology
Organisations: Ocean and Earth Science

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Local EPrints ID: 370238
URI: http://eprints.soton.ac.uk/id/eprint/370238
ISSN: 0024-4066
PURE UUID: 1780715f-b724-4f77-a673-7b278d850180

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Date deposited: 20 Oct 2014 09:58
Last modified: 15 Jul 2019 21:41

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