New remains of Titanochelon richardi (Testudines, Testudinidae) from the Upper Miocene of the Vallès-Penedès Basin: taxonomic and phylogenetic implications.

The alpha-taxonomy of continental giant tortoises (Testudinidae, Titanochelon) from the European Neogene is far from settled, which has implications for inferring their phylogenetic relationships. The diagnosis of the type species (Titanochelon bolivari) is dubious because it considered Titanochelon richardi as a junior subjective synonym. Here we describe a new partial skeleton (skull, partial carapace, plastron, and multiple postcranial elements) from the Late Miocene (9.4–9.1 Ma, MN10) of the Ronda Oest de Sabadell locality ROS-D6 (Vall es-Pened es Basin, NE Iberian Peninsula) that is assigned to T. richardi based on cranial and shell morphology. This skeleton enables a more complete assessment of the skull and postcranium of this species. On this basis, we discount the purported synonymy of T. richardi with T. bolivari and provide an emended diagnosis for the former. We also assess the phylogenetic relationships of Titanochelon species by means of standard maximum parsimony, implied weighting maximum parsimony and Bayesian analyses with morphological and with combined (morphological and molecular) data. Our comparisons support T. richardi as a distinct species unambiguously recorded from the Vall es-Pened es and the Duero basins, from MN7+8 to MN10 (Middle–Late Miocene), whereas T. bolivari appears restricted to MN5–MN6 of the Madrid Basin. Additional Iberian material ranging from MN2 to MN10 should be revised to further clarify the geographic distribution and temporal range of these species. Finally, our analyses provide a better resolved phylogeny for Titanochelon species other than Titanochelon vitodurana and support a sister-taxon relationship between T. bolivari and T. richardi.