FOSSIL TORTOISE EGGSHELLS OF THE CANARY ISLANDS

SABINA RODRÍGUEZ-GONZÁLEZ; ESTHER MARTÍN-GONZÁLEZ; CAROLINA CASTILLO RUIZ; MIGUEL MORENO-AZANZA; PENÉLOPE CRUZADO CABALLERO

Congreso; 2nd Palaeontological Virtual Congress; 2020

The Canary Islands are an archipelago of volcanic origin located 97 kmnorthwest of the African coast in the Atlantic Ocean. The archipelago presents an interesting fossil record of tortoises, including osteological (Tenerife and Gran Canaria islands) and oological remains (Gran Canaria, Lanzarote and Fuerteventura islands).Two extinct tortoise species haven been described: Geochelone burchardi from the Pleistocene of Tenerifeand Geochelone vulcanica from the Pliocene of Gran Canaria. Although previous microscopy studies in eggshells have confirmed their chelonian origin, little is known about the oodiversity in the islands. Using Scanning Electron Microscopy and Polarized Light Microscopy, we re-examined the eggshells from Gran Canaria island as well as new material from Lanzarote and Fuerteventura islands in order to verifying the assignment to Testudines group and determine the diversity of ootaxa within the samples. Furthermore, eggshells of the live African species Centrochelys sulcata were used as the comparative material. All the specimens show radial aragonite ultrastructure and subcylindrical tightly-packed shell units, with eggshell thickness of 390?670 μm and shell unit height/width ratio of 2/1, so they can be assigned to the oofamily Testudoolithidae, oogenus Testudoolithus. The eggshells also present a structure similar to Centrochelys (Geochelone) sulcata, a living taxon related to the extinct tortoises that inhabited the Canary Archipelago during the Neogene and Quaternary. Small differences in eggshell thickness range and shell unit proportions can be observed between the samples from the different localities, but more data is needed to precise if one or two Testudoolithus oospecies are represented in the Canary Island fossil record.