MORPHOLOGICAL DIVERSITY OF OPHTHALMOSAURID FOREFINS

CAMPOS, L.; FERNÁNDEZ, M.S.; HERRERA, Y.

Congreso; 9th International Meeting on the Secondary Adaptation of Tetrapods to Life in Water; 2021

Ichthyosaurs were a diverse group of secondary marine reptiles that colonized the oceansfrom the beginning of the Triassic (Olenekian) until the Late Cretaceous (Cenomanian). Oneof the most significant events in the evolutionary history of the lineage took place in theAalenian-Bajocian interval (Middle Jurassic) with the rise of the ophthalmosaurids. UpperJurassic marine deposits worldwide depict ophthalmosaurid ichthyosaurs as one of the moreprolific and successful components of marine tetrapod communities. One of the major traitscharacterizing this clade is the complexity of their stylopodium-zeugopodium morphology.The ophthalmosaurid forefin has been a source of taxonomic characters since the firstattempts to understand their phylogenetic relationships, and it is frequently used to diagnosegenera and/or species. Here we analyse the morphological diversity of these regions of theappendicular skeleton of the ophthalmosaurids, using 2D geometric morphometrics of thehumerus and disparity analysis of the zeugopodium. We found a peak of zeugopodialdisparity occurred during the Kimmeridgian, followed by a decrease by the end of theJurassic and then a recovery by the Early Cretaceous. Our results also reveal a long durationdisparate humeral morphotype characterizing Arthropterygius spp. and closely related taxa.