Noura Lkebir, Tanguy Rolland, Fabrice Monna, Moussa Masrour, Lhoussaine Bouchaou, Emmanuel Fara, Nicolas Navarro, Josef Wilczek, El Hassan Beraaouz, Carmela Chateau-Smith & FÃlix PÃrez-Lorente (2020)
Anza palaeoichnological site, Late Cretaceous, Morocco. Part III: Comparison between traditional and photogrammetric records.
Journal of African Earth Sciences 103985
Processing DEM of ichnosites may help to better identify dinosaur tracks and trackways.
Morphometric measurements of tracks can be performed from processed DEM.
At the Anza ichnosite, the proposed protocol outperforms the traditional recording method.
The present study evaluates a methodological workflow that could identify dinosaur tracks and trackways more comprehensively at outcrop scale. The approach described here is based both on 3D modelling by photogrammetry at different resolutions, and on suitably processed digital elevation models (DEMs). The ichnosite of Anza, Morocco, was chosen to demonstrate the efficiency of the proposed pipeline, because 323 dinosaur and pterosaur tracks discovered there have already been published. One subsector containing 89 tracks, identified in the two companion works that followed a traditional approach, was selected and divided into four subzones. By combining different DEM processes (hill-shade, slope, sky-view factor, and positive openness), almost twice as many tracks (175 vs 89) are now identified in these subzones. However, the improvement is not homogeneous. In the first subzone, the previous works reported 25 tracks vs. 22 with the 3D modelling techniques used here, whereas results for the second and third subzones show considerable improvement with 3D (21 vs 38 tracks and 42 vs 81 tracks, respectively). The enhancement is even more dramatic for the fourth subzone, where 34 new tracks are now identified, whereas with the traditional approach, only one track was previously reported. It is likely that such improvements depend on several factors, i.e. the surface conditions of the rocks (e.g. irregularities, cracking, etc.), and on the preservation state and depth of the tracks. Morphometric measurements of tracks and trackways obtained from 3D models are very similar to those derived from traditional fieldwork methods. The digital approach can be applied rapidly at different resolutions, but the models acquired with the pole-mounted camera provide a good compromise, with a resolution high enough (â2 mm/pix) to spot tracks, while respecting computational constraints. Once treated, DEMs greatly facilitate the reproduction of track outlines, drawn according to criteria defined by the operator.
A new Batrachopus, crocodilian fossil print, has been described.
Webbed pes and a protrusiÃn of toe V are two singular and differential anatomical characters.
High-walking and lack of tail marks trackways.
The only Batrachopus ichnogenus of Middle?-Upper Jurassic age.
The first mention of Batrachopus ichnogenus in the African continent.
In this work we present the description and analysis of a palaeoichnological site (7.9TAG) that only contains crocodile tracks. The site contains well preserved and abundant crocodilian manus and pes prints; there are no belly and/or tail traces. The crocodile tracks have been mapped and the biomorphic and morphometric characters of the tracks and trackways have been studied. Between the digit traces of the pes prints (not in manus prints) there is a graded depression that indicates the presence of a foot webbing. The number of crocodilian footprints (93) and trackways (8) of the site is sufficient to define, and to support with confidence the data shown in the article. As consequence a crocodiliform ichnogenus, Batrachopus has been defined, characterized by the presence of a trace of a probably interdigital membrane in the pes prints, the trace of a bulge on toe V, the lack of tail traces, and the very narrow gauge trackway. A comparative study is done with all the fossil crocodile footprints described so far. The 7.9TAG footprints printed on sediments of Middle?-Upper Jurassic age (Isli Formation) are the first Batrachopus ichnites described both from this age and in the African continent.