Igdabatis marmii sp. nov. (Myliobatiformes) from the lower Maastrichtian (Upper Cretaceous) of north-eastern Spain: an Ibero-Armorican origin for a Gondwanan batoid

Abstract

Microvertebrate fossil assemblages (chondrichthyans, osteichthyans, lissamphibians and squamates) from the Campanian and Maastrichtian of south-western Europe include taxa with very different palaeobiogeographical affinities. However, most of these biogeographical histories remain unclear. As inhabitants of shallow marine waters, batoids are considered good palaeobiogeographical indicators that could reveal connections between continental platforms. Igdabatis is a stingray (Myliobatiformes) with an abundant Gondwanan fossil record, whereas its occurrence in the Ibero-Armorican landmass is intriguing. In this paper, a new species of Igdabatis – Igdabatis marmii sp. nov. – is reported from the lower Maastrichtian of Spain. Based on this new record, the phylogenetic relationships of Myliobatiformes are assessed, including Igdabatis taxa for first time. In addition, three new morphological characters are proposed based on the diagnoses of the different species and added to the dataset. The palaeobiogeographical events that these stingrays underwent during their speciation were explored through a Statistical Dispersal-Vicariance Analysis (S-DIVA) performed in RASP 2.1. The phylogenetic analysis suggests a highly nested position within Myliobatidae for the genus Igdabatis; and the new species was recovered as the most basal taxon in the clade. The S-DIVA results point to an Ibero-Armorican ancestral area for Igdabatis, from where its species diverged by a combination of vicariant and dispersal events. Both phylogenetic and palaeobiogeographical analyses were congruent with occurrences in the fossil record. Results and fossil evidence allow the proposal of a dispersal route between European and Gondwanan landmasses for these stingrays. The dispersal of Igdabatis between Ibero-Armorica and India during the Late Cretaceous was promoted by the proximity of the European and African continental platforms and then by the Kohistan-Ladakh island arc.

http://zoobank.org/urn:lsid:zoobank.org:pub:F5C51029-2E26-48C6-8A87-A2D4310887EF

Keywords:

• Palaeobiogeography
• Batoidea
• trans-Tethyan pathway
• S-DIVA
• sympatric speciation
• parapatric speciation

Acknowledgements

The author is supported by the program ‘Axudas á etapa postdoutoral da Xunta de Galicia 2017 - Modalidade A’. Special thanks are given to: Josep Marmi and Bernat Vila who collected the fossil material studied here; Marc Riera for sample preparation; David Seoane for his useful comments on the analyses; Olalla Carrillo, Adriana López Arbarello and Nicola Heckeberg for their help with software and databases; Mercedes Calvo for her comments on the English spelling; and Oriol Oms for providing helpful illustrations. Thanks are also given to both editors and reviewers, whose helpful comments improved the quality of the final manuscript. Finally, I want to acknowledge again Josep Marmi for his careful supervision during my palaeontological training, for his kind help, and for his trust during these last years. I hope this paper rewards his hard work.