Ichnological evidence for small quadrupedal ornithischians from the basal Cretaceous of SE Asia and North America: implications for a global radiation

Abstract

Tracks of small quadrupedal ornithischians with five manual and four pedal digits have been recorded from sedimentary rocks near the Late Jurassic-Early Cretaceous (TithonianBerriasian) boundary in NE Thailand and British Columbia. These are compared with larger tracks of gracile, quadrupedal ornithopods from the earliest Cretaceous of Spain and smaller tracks of a quadruped of unknown age from Zimbabwe. The Thai and Canadian tracks are similar to the Early Jurassic (Liassic) ichnogenus Anomoepus and the small ornithopod tracks from the Late Jurassic of Spain. They are the only known post-Liassic ornithischian tracks in which up to five discrete manus digit impressions are clearly visible. Based on strong heteropody (manus much smaller than pes) in all cases we infer an ornithopod trackmaker rather than another ornithischian. The scattered, but widespread earliest Cretaceous occurrence of this ichnotaxon, herein assigned to Neoanomoepus perigrinatus ichnogen. and ichnosp. nov., on the basis of type material from Canada, suggests that these hitherto unknown earliest Cretaceous ichnofaunas may represent a radiation of small basal ornithopods (pes length less than 15 cm), appearing before the widespread radiation of large ornithopods (pes length up to 60 cm or more) later in the Neocomian (Valanginian-Barremian), Aptian-Albian and Late Cretaceous. The primitive condition of the trackmaker is indicated by the pedal and manual morphology, which consists of four and five digits respectively that are not enclosed by well-developed fleshy padding or integument. In contrast, all larger Cretaceous ornithopod tracks, mostly from post-Berriasian strata, have only three pedal digits enclosed in fleshy pads and a manus in which all functional digits are reduced and enclosed by substantial flesh.

Trackways of the American Crocodile (Crocodylus acutus) in Northwestern Costa Rica: Implications for Crocodylian Ichnology

“…Comparisons of fossil trackways of quadrupedal archosaurs besides crocodylians (e.g. Klein, 2000, 2002;Lockley and Meyer, 2000;Rainforth, 2003;Gand et al, 2007;Porchetti and Nicosia, 2007;Romano et al, 2007;Avanzini and Petti, 2008;Lockley et al, 2009;Marty et al, 2010;Petti et al, 2010;Klein et al, 2011;Li et al, 2012;Contessi, 2013;Boutakiout et al, 2014;Masrour and Pérez-Lorente, 2014;McCrea et al, 2014;Xing et al, 2015) with modern crocodylian trackways may allow inferences about terrestrial locomotion of the extinct trackmakers (Carpenter, 2009). Consequently we believe that detailed information about traces made by extant crocodylian species will be of considerable value for interpreting traces attributed to living crocodylians as well as those of ancient crocodylomorphs and other quadrupedal archosaurs.…”

Vertebrate ichnites from the Boulder Creek Formation (Lower Cretaceous: middle to ?upper Albian) of northeastern British Columbia, with a description of a new avian ichnotaxon, Paxavipes babcockensis ichnogen. et isp. nov.

“…20), similar to Neoanomoepus ichnosp (Lockley et al, 2009). However, PRPRC 2005.001.075 is partially covered by adhering sediment that obscures details necessary for precise ichnotaxonomic identification.…”

Lower Cretaceous Dinosaur Tracks from Puebla, Mexico

“…However, Berriasian dinosaur footprints are known from the Mist Mountain Formation in Canada [28]. Most of these are records from a few geological formations such as the Gates in Alberta (Canada) and in the United States such as the Cedar Mountain (Utah) and the Dakota Group in Colorado, New Mexico, Oklahoma, Kansas, and Utah [14,27].…”