Morphological variation and ichnotaxonomy of dinosaur tracks: linking footprint shapes to substrate and trackmaker's anatomy and locomotion

Abstract

The study of tridactyl dinosaurs tracks from a morphological perspective is here presented in the form of a new look and approach to the classic ichnology. The mechanisms that mostly control and affect track morphology during its formation have been thoroughly analysed, so that the ultimate goal is to provide extensive quantitative data to discuss the main foundation of morphological variation registered in individual tracks, trackways and large sets of trackways. The compendium of this PhD collected six different studies from distinct geographical (Spain, Portugal, Morocco and Switzerland) and geological frames (from Middle Jurassic to present) and the proposal of a preliminary approach in a laboratory controlled-experiment. This experiment aims to extrapolate and determine all parameters (water content, substrate properties and composition, grain size, porosity) intervening in the track formation process on heterogeneous substrates during the mechanical indentation of a vulture foot cast (chapter 10). The Cameros basin (NW Spain) offered two Early Cretaceous different scenarios for this thesis, the re-interpretation of a long ornithopod trackway on homogeneous substrate at the Barranco de La Canal tracksite (chapter 5) and the new study of four previously unpublished theropod trackways inter-crossing a heterogeneous substrate at the El Frontal tracksite (chapter 9). The locality visited within the Argana basin (Morocco) provided neoichnological observations that are consider important for the identification of misinterpretations of ichnopathologies and sloping surfaces in the fossil record (chapter 8). These localities showed two different intra-trackway morphological variation patterns defined as alternate, which depends on the limb dynamics and foot anatomy of the trackmaker and continuous, which depends on the substrate consistency change along the tracking surface. The Lusitanian basin (Central-West Portugal) presented the previously known but unpublished Middle Jurassic quarry of Vale de Meios which underscores the importance of analyzing all types of track preservations in order to recognize the average morphology and that there should not be an assumption that vertebrate ichnotaxa are confined to specific ages or geographic regions (chapter 7). The Jura Carbonate platform (NW Switzerland) encompassed six Late Jurassic tracksites, which together with 49 trackways and 397 tracks provided the new and unpublished material for the description of a new ichnospecies and the discussion of track morphological variations, introducing the possibility that classic ichnoassociations might be the result of preservational variants of the same trackmaker (chapter 6). These two studies showed that when comparing multiple trackways on the same site or ichnoassemblage, taxonomical diversity and behavioural changes have to be considered together with substrate conditions and limb dynamics. Three-dimensional technologies have been the support and tool for all the quantitative analysis undertaken. LiDAR scans have been always complemented with a close range photogrammetry in order to give the highest morphological details and to provide a precise and systematic quantification of the track morphological variations recorded.

Date of Award	20 Jan 2017
Original language	Undefined/Unknown
Supervisor	Bernat Vila Ginestí (Director)