Abstract
The Eocene whiptail stingrays of the family Dasyatidae from the Bolca Lagerstätte, NE Italy, are revised herein in detail. The analysis of the anatomical and morphometric features allows us to identify the species “Dasyatis” zigni (Molin, 1861) as a junior synonym of “D.” muricatus (Volta, 1796), and to assign it to the new genus Tethytrygon gen. n. This new taxon exhibits a unique combination of features (e.g., rhombic disc wider than long, elongated tail folds fail to reach the tip of the tail, thorns absent, single serrated tail sting, “caniniform” teeth on upper jaw, tooth crown ornamentation absent, 175–179 vertebrae, 108–117 pectoral radials, 24–27 pelvic radials and other features of clasper anatomy) that clearly support its attribution to the subfamily Neotrygoninae of the stingray family Dasyatidae. The morphological and phylogenetic affinities of Tethytrygon gen. n. with the living neotrygonines (Neotrygon and Taeniura) suggest a close association of this taxon with the tropical shallow‐water habitats hypothesized for the Bolca palaeoenvironment during the early Eocene. Moreover, the analysis of the fossil occurrences of the neotrygonines provides new insights into the role of the Tethys for the origin and evolutionary history of certain whiptail stingrays.
Highlights
The family Dasyatidae, whose representatives are known as whiptail stingrays, includes about 86 living species in 19 genera of small to large stingrays living in demersal inshore habitats of continental and insular shelves up to a depth of 600 m (Last, Naylor, & Manjaji‐Matsumoto, 2016; Last, White, Carvalho, et al, 2016)
Of four major subgroups at subfamilial level: the Dasyatidae, Hypolophinae, Urogymninae and Neotrygoninae (Last, Naylor et al, 2016). The latter subfamily was created by Last, Naylor, et al (2016) and comprises species of Neotrygon and Taeniura, two genera today restricted to the Indian Ocean and Indo‐Australian Archipelago, which are unique among dasyatids in having a series of enlarged caniniform teeth on the upper jaw in both sexes and a short tail that is
Recent studies have provided a new perspective about the chondrichthyan palaeobiodiversity of this deposit, which includes possibly more than a dozen of species‐level taxa belonging to a variety of holocephalan, selachian and batoid lineages, including chimaeriformes, carcharhiniformes, lamniformes, torpediniformes, rhinopristiforms and myliobatiformes (Fanti, Minelli, Larocca Conte, & Miyashita, 2016; Marramà et al, 2018; Marramà, Carnevale, & Kriwet, 2018; Marramà, Claeson, Carnevale, & Kriwet, 2018; Marramà, Engelbrecht, Carnevale, & Kriwet, 2017)
Summary
The family Dasyatidae, whose representatives are known as whiptail stingrays, includes about 86 living species in 19 genera of small to large stingrays (up to 2.6 m disc width, weighing up to 600 kg) living in demersal inshore habitats of continental and insular shelves up to a depth of 600 m (Last, Naylor, & Manjaji‐Matsumoto, 2016; Last, White, Carvalho, et al, 2016). Some previous studies suggest that the Dasyatidae might be a non‐monophyletic group (e.g., Aschliman, Claeson, & McEachran, 2012; Carvalho, Maisey, & Grande, 2004; Lovejoy, 1996), recent morphological and molecular analyses proposed that this family should be regarded as monophyletic (e.g., Aschliman, Nishida, et al, 2012; Bertozzi, Lee, & Donnellan, 2016; Marramà, Klug, Vos, & Kriwet, 2018; Naylor et al, 2012) consisting The goal of this paper is to redescribe the anatomy of the two species from Bolca included in the family Dasyatidae (“Dasyatis” muricatus and “D.” zigni) in detail, to review their taxonomic status and to discuss their relationships within the Myliobatiformes
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