A walk in the maze: variation in Late Jurassic tridactyl dinosaur tracks from the Swiss Jura Mountains (NW Switzerland)

• DOI: 10.7717/peerj.4579
• Publication Date: 2018-04-02T07:22:44Z
• Authors: Diego Castanera; Matteo Belvedere; Daniel Marty; Géraldine Paratte; Marielle Lapaire-...; Christel Lovis; Christian A. Meyer
• Keywords: Footprint; Claw

Background Minute to medium-sized (footprint length (FL) less than 30 cm) tridactyl dinosaur tracks are the most abundant in Late Jurassic tracksites of Highway A16 (Reuchenette Formation, Kimmeridgian) Jura Mountains (NW Switzerland). During excavations, two morphotypes, one gracile and robust, were identified field. Furthermore, large-sized theropod ichnospecies ( Megalosauripus transjuranicus Jurabrontes curtedulensis ) an ornithopod-like morphotype (Morphotype II) have recently been described at these sites. Methods The quality morphological preservation (preservation grade), depth footprint, shape variation, footprint proportions (FL/footprint width (FW) ratio mesaxony) along trackways analyzed using 3D models false-color maps order determine exact number small morphotypes present tracksites. Results study footprints n = 93) recovered during excavations has made it possible identify characterize distinguished is mainly characterized by a high FL/FW ratio, mesaxony, low divarication angles clear, sharp claw marks, phalangeal pads (2-3-4). By contrast, robust lower weaker slightly higher marks (when preserved), whereas not clearly preserved although they might be present. Discussion analysis does allow associated within same continuum. Thus, cannot extramorphological variations similar produced single trackmaker. Comparison with larger formation M. , J. Morphotype spatio-temporal relationships suggest that smaller reliably considered as individuals any morphotypes. morphometric data some specimens (even values for length/width more ichnotaxon represented morphotype. features (cf. Kalohipus isp.) typical “grallatorid” ichnotaxa mesaxony those Therangospodus isp. ? reminiscent pandemicus . This work sheds new light on combining morphology through maps, ontogenetic identification small-sized description tracks.