Insights about the rare occurrence of a small Paleohelcura tridactyla from the eolian Botucatu Formation (Cretaceous, Paraná Basin, Brazil)

Abstract Paleohelcura tridactyla is a trackway characterized by up to three round tracks per series, typically arranged linearly or triangularly, often with a medial impression. This pattern is consistently found in several eolian deposits and has been described in the Botucatu Formation in Brazil, an eolian sandstone unit in the Paraná Basin deposited during the earliest Early Cretaceous under arid conditions. Here, we describe a new small morphotype of Paleohelcura tridactyla in the Botucatu Formation. This morphotype is smaller than previously described specimens of Paleohelcura tridactyla, and although it shares a similar size with Paleohelcura araraquarensis, it differs both in track morphology and series arrangement. We propose three hypotheses for the new morphotype: (1) The trackway may have been produced by the juvenile stage of the arthropod responsible for the larger Paleohelcura tridactyla tracks. (2) The size difference may indicate sexual dimorphism within the same species. (3) Alternatively, it could represent a different arthropod species, which is smaller in size but leaves similar track patterns. This discovery reinforces the ichnotaxonomical distinction between P. tridactyla and P. araraquarensis and raises the possibility that another arthropod species may have been present in the Botucatu Paleodesert fauna.