Re-evaluation of Chelichnus tazelwürmi, a non mammalian therapsid-grade track from the Upper Permian Arenaria di Val Gardena

Abstract

In this paper, a revision of tracks referred to as Chelichnus tazelwürmi is reported. The performed analysis, consisting of a holistic approach by means of a mainly morphological analysis, and a secondarily functional one, led to the proposal of a new ichnogenus, named as Contiichnus tazelwurmi. The three dimensional morphology of the tracks allows for the inference of a complex cycle of locomotion by the trackmakers. The tracks were formed in the main phases (i.e. touch-down, weight-bearing and kick-off) by different axes of body load and transference, indicating that the whole fore autopod was involved in the cycle of locomotion and actively contacted the substrate, while for the hind autopod the functional prevalence was markedly centro-medial. Some track features suggest a therapsid-grade synapsid as potential trackmaker. However, the reconstructed autopodial structure does not correlate with known autopods from the Late Permian body fossil record. These observations stress the importance of tetrapod ichnology studies in improving knowledge in the field of vertebrate palaeontology.