Resumen de Biostratinomic Patterns in Archosaur Fossils: Influence of Morphological Organization on Dispersal

Óscar Cambra Moo, Ángela Delgado Buscalioni

• The dispersal of 122 specimens of fossil archosaurs and lepidosaurians from different localities throughout the world, catalogued as fossil-lagerstätten, has been characterized. The analysis is based on the quantification of dispersal by the evaluation of burial position, anatomical disarticulation, overlap and significant absences of bony elements. Our goal is to identify commonalities of morphological organization, and to reveal dispersal patterns. First, we explore a theoretical space of burial positions, and seek logical alignments of variables in order to understand the sequence of the earliest biostratinomic phenomena. Dinosauria and the basal avian specimens (Archaeopteryx-like organisms) are biased towards lateral burials with crossed forelimbs or hindlimbs. Pterosauria and Ornithuromorpha have ambivalent burial positions, while Enantiornithes and Confuciusornithidae adopt preferentially dorso-ventral burial positions. There is a significantly negative regression coefficient relating overlap and disarticulation-absence. A high percentage overlap corresponds to a high percentage articulation and completeness of body elements, particularly in laterally lying fossils. Conversely, overlap and disarticulation are not significantly related in specimens with a dorso-ventral burial position. Ambivalence in burial positions is associated with singularities in disarticulation patterns. Aves and Pterosauria both diverge from the general disarticulation sequence of diapsids. The results indicate that dispersal has a strong biological component at least in the initial steps of the biostratinomic process.