![]() Furthermore, Garcia-Ortiz and Perez-Lorente (2014) noted that the opposite orientations in the trackways can be produced in environments with topographic barriers, as occurs in actual ecosystems such as lakesides and riversides. For example, multiple parallel trackways of the same morphotype in the same stratigraphic surface, and same footprint depth (Lockley, 1991 Lockley and Matsukawa, 1999) could be interpreted as several dinosaur individuals of the same taxon moving at the same place at the same time. They summarized several important criteria for inferring gregarious behaviour from tracksites. Garcia-Ortiz and Perez-Lorente (2014) analyzed the gregarious behavior based on Cretaceous dinosaur footprints from La Rioja. Therefore, taking into account the morphological features and the preservation of the La Rueda footprints (very shallow and not well-preserved footprints) we have assigned them to indeterminate ornithopod footprints. Both ichnotaxa are characterized for its resting traces, with metatarsal and hallux marks and the presence of pentadactyl manus prints, but also occurs in the form of multiple pesonly tracks (Olsen and Rainforth, 2003 Belvedere et al, 2011). ![]() Moyenisauropus and Anomoepus differ from them in the divarication between the digits II-IV and in the projection of the digit III, which are higher in the La Rueda footprints, but the other general features are similar (cf. Dineichnus has no pad impressions in each digit or a medial notch. 5H), and Dineichnus Lockley, Santos, Meyer and Hunt, 1998 (Fig. 5F-G), Moyenisauropus Ellenberger, 1970 (Fig. ![]() 5A-E) to some small ornithopod ichnotaxa such as Anomoepus Hitchcock, 1848 (Figs. La Rueda footprints are similar (roughly symmetrical, similar position, and the shape of the heel impression and claw marks) (Figs. In a broad sense, the avian ichnotaxa have high divarication, but they differ essentially from those of La Rueda in having more slender digits and a less projected digit III (cf. Thulborn, 1990 Perez-Lorente and Romero-Molina, 2001). Nevertheless, theropod tracks have generally less divarication than the La Rueda footprints and generally they are asymmetrical (cf. Most of the theropod ichnotaxa have claw marks and some pad impressions in each digit. Nevertheless, the number of small footprints in the Urbion Group is instead the product of by preservation biases (coarse grain sediments and fluvial erosive bases) and the weathering and erosion processes (brittle nature of the rock) that affect especially to small tracks than large ones identified in this Group. This scarcity could be explained as ecological biases (dearth of small individuals in an area). In the Urbion Group, large dinosaur tracks are much more frequent than small ones. Small dinosaur footprints are scarce in the worldwide fossil record. ![]() They are here classified as indeterminate ornithopod footprints and contribute to the increase in the dinosaur ichnodiversity of the Urbion Group. The footprints are approximately as long as wide and have high divarication angles between digits II-IV (~80), some pad impressions on each digit, claw marks, a medial notch and a circular heel pad impression. A new dinosaur tracksite (La Rueda) with ten small tridactyl footprints (the length ranges between 9 and 15 cm) from the Urbion Group (Cameros Basin, Lower Cretaceous, La Rioja, Spain) is described. ![]()
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