Stegosaur tracks from the Upper Jurassic of Portugal: new occurrences and perspectives

Abstract

The record of Late Jurassic stegosaur tracks from the Lourinhã Formation (Kimmeridgian-Tithonian) is here revised. Thirty-eight dinosaur tracks, preserved as natural infill casts, are here reported, and thirty-two of them are attributed to the ichnogenus Deltapodus. Four of those present impressions of skin, with polygonal scales and random pattern. Deltapodus is the most common ichnogenus in the track record of the Lourinhã Formation. The sizes and shape suggest one single dacentrurine trackmaker, which could be Miragaia longicollum, also common in the same horizons.

The complexity of tracking stegosaurs and their gregarious behavior

“…2 ). This size variation ranges between the values described for ichnogenus Deltapodus 7 , 8 , 10 , 15 .…”

“…Currently, three different ichnospecies are considered valid within Deltapodus : D. brodricki , the type ichnospecies described in the Middle Jurassic strata of England 3 , 4 , the aforementioned D. ibericus analyzed here in the Late Jurassic strata of Spain 5 and D. curriei in the Lower Cretaceous strata of China 6 , 15 . Since the description of the holotype trackway 1CA at the El Castellar (CT-1) tracksite, it has been the only tracksite where this ichnospecies has been identified, and some of the posteriorly described specimens have been classified only at the ichnogenus level (see Table 1 in 10 ) in some cases e.g., 20 , assuming that several of the diagnostic characteristics of D. ibericus are based on trackway data. Although some trackway parameters are indeed diagnostic, the ichnospecies D. ibericus is also based on characteristic features in both the manus and pes (see the diagnosis in 5 ).…”

“…The type ichnospecies D. brodricki was originally described from Middle Jurassic strata in England 3 , 4 . Since then, Deltapodus tracks have been described with confidence in several areas that span the Middle Jurassic–Early Cretaceous interval in Europe (e.g., 5 , 7 – 10 and references therein), America (e.g., 11 – 13 ), Africa 14 and Asia 6 , 15 .…”

“…In the last decade, researchers have reported several localities with Deltapodus tracks on the Iberian Peninsula, which is one of the areas with the most track occurrences globally. Thus, Deltapodus is currently a commonly identified ichnotaxon in the Late Jurassic and Jurassic‒Cretaceous transitional units, with significant tracksites in the Maestrazgo 5 , 16 – 20 , Cameros 8 , 21 and Asturian 22 – 24 Basins in Spain and in the Lusitanian Basin 7 , 10 in Portugal. The presence of Deltapodus tracks and their attribution to stegosaur trackmakers in the Iberian Peninsula is reinforced by the presence of ample stegosaur osteological remains in Late Jurassic deposits of the Iberian Peninsula (e.g., 5 , 25 – 28 and references therein).…”

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“…Beautiful examples of skin impressions have been described in stegosaur, ornithopod and sauropod tracks (Fig. 2A, B) in the Iberian Peninsula (García-Ramos et al, 2006;Navarrete et al, 2014;Cobos et al, 2016;Herrero-Gascón & Pérez-Lorente, 2017;Guillaume et al, 2022). Another kind of skin trace is the longitudinal grooves preserved on the sides of the tracks (Fig.…”