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[dinosaur] Dinosaur tridactyl track variations from Cretaceous Candeleros Formation, Argentina




Ben Creisler
bcreisler@gmail.com

A new paper:


Arturo M. Heredia, Pablo J. Pazos & Ignacio DÃaz-MartÃnez (2021)
Morphological variations in dinosaur tridactyl tracks from the Candeleros Formation (Upper Cretaceous) of northwestern Patagonia, Argentina
Journal of South American Earth Sciences 103212 (advance online publication)
doi: https://doi.org/10.1016/j.jsames.2021.103212
https://www.sciencedirect.com/science/article/abs/pii/S0895981121000596

Highlights

Several tridactyl trackways with morphological variations are documented.
Some trackways are preserved as both true tracks and undertracks.
The role of the substrate properties in track preservation is analysed.
Deep tridactyl tracks with metatarsal impressions indicate soft substrates.
The substrate consistency changed along the tracking surface.


Abstract

Several tridactyl tracks showing inter- and intra-trackways morphological variations from the Cenomanian Candeleros Formation of the NeuquÃn Basin, Argentina, have been documented. Footprints occur on three different stratigraphic levels and are impressed on medium-grained sandstone of fluvial origin. The Level 1 includes deep tridactyl tracks with metatarsal impressions (average length of 31âcm) preserved as true tracks and undertracks that could have been generated due to simply sinking of the pes into a soft substrate or by a continuous walk in a squatting position. The Level 2 shows the largest tridactyl tracks (average length of 58âcm) recognized in this work, situated a few meters close to an already studied sauropod trackway. The different preservation between these bipedal and quadrupedal tracks could be explained due to different substrate properties and dissimilarities of the pedal shape between trackmakers. Level 3 comprises small to large tridactyl tracks (length from 6 to 34âcm) including intra-trackway morphological variation, that is interpreted as a result of changes in the substrate properties, mainly moisture content, along the tracking surface. Taking into account that the footprints studied here are poorly preserved, they were not assigned to any particular ichnotaxon. The large tridactyl tracks have been attributed to carcharodontosaurid theropod trackmakers while medium and small tracks to undetermined bipedal dinosaur. One pair of these large theropod tracks were closely documented on the same tracking surface that a previously studied sauropod trackway attributed to rebbachisaurids. This suggests that both carcharodontosaurid and rebbachisaurid trackmakers coexisted in the same habitats as the osteological record noted. This tracksite represents an example of the morphological variability of dinosaur tridactyl tracks controlled mainly by the substrate properties, and how an approach aimed at understanding footprint formation and preservation is necessary before beginning ichnotaxonomical studies, among others.


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