Reappraisal of the Eocene whiptail stingrays (Myliobatiformes, Dasyatidae) of the Bolca Lagerstätte, Italy

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.

Mosaic of plesiomorphic and derived characters in an Eocene myliobatiform batomorph (Chondrichthyes, Elasmobranchii) from Italy defines a new, basal body plan in pelagic stingrays

“…8). The tree recovered is similar to the ones depicted by Marramà et al [32, 36] including an improved resolution of the positions of Plesiobatis as well as of the Eocene freshwater stingrays Asterotrygon and Heliobatis . The monophyly of the Myliobatiformes, as recognized by McEachran et al [4], Carvalho et al [3], McEachran and Aschliman [63], and Aschliman et al [5] is confirmed and strongly supported herein (Bremer value 9) by ten synapomorphies.…”

“…The monophyly of the Myliobatiformes, as recognized by McEachran et al [4], Carvalho et al [3], McEachran and Aschliman [63], and Aschliman et al [5] is confirmed and strongly supported herein (Bremer value 9) by ten synapomorphies. The phylogeny also detected a dichotomy within myliobatiforms (excluding Hexatrygon ) as recovered by Marramà et al [32, 36] with two main clades that partially correspond to the superfamilies Myliobatoidea and Dasyatoidea. The nature of the dichotomy is possibly linked to the different calcifications of radial cartilages, body shapes and swimming modes detected in these two groups by Schaefer and Summers [40].…”

“…The nature of the dichotomy is possibly linked to the different calcifications of radial cartilages, body shapes and swimming modes detected in these two groups by Schaefer and Summers [40]. For the discussion of the myliobatiform synapomorphies and the relationships within the Dasyatoidea (the benthic stingrays) we refer to the comprehensive discussion provided by Marramà et al [32, 36].

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“…The phylogenetic analysis is based on the morphological datasets of Marramà et al [32, 36], which in turn are based on the matrix of Claeson et al [10] extended with characters from Herman et al [37–39], Schaefer and Summers [40], Aschliman et al [5], and Last et al [7, 41] [see Additional file 1]. The coding of characters 52, 54, 55, 64 and 65 for some taxa was updated following Blanco [42].…”

Revision of the Eocene ‘Platyrhina’ species from the Bolca Lagerstätte (Italy) reveals the first panray (Batomorphii: Zanobatidae) in the fossil record

“… 2016 , 2019 ; Marramà et al . 2018a , b , c , 2019a , b , c, d ;). These batoids are represented by electric rays (Torpediniformes), guitarfishes (Rhinopristiformes), stingrays (Myliobatiformes) and three batoid species that were historically assigned to the thornback ray genus Platyrhina Müller & Henle, 1838 : † P. bolcensis Heckel, 1851 , † P. egertoni (De Zigno, 1876 ) and † P. gigantea (Blainville, 1818).…”