Remarkable multicuspid teeth in a new elusive skate (Chondrichthyes, Rajiformes) from the Mediterranean Pliocene

Abstract

Here we report on four highly peculiar skate teeth from Arcille and Certaldo, two Pliocene localities of Tuscany (central Italy). While being attributable to Rajiformes and somewhat reminiscent of Dipturus and Rostroraja, these specimens display an unusual multicuspid tooth design that does not match any extinct or extant skate taxon known to date. The studied teeth are thus referred to a new genus and species of Rajiformes, Nebriimimus wardi gen. et sp. nov., which is here tentatively assigned to the family Rajidae. Based on pronounced morphological similarities between the rather large-sized teeth of the latter and those of extant nurse sharks, we hypothesise that N. wardi might have been capable of actively foraging upon relatively large food items compared to other rays. This extinct skate species was likely not a common component of the Pliocene Tuscan marine vertebrate assemblages. The palaeoenvironmental scenarios that N. wardi inhabited were marginal-marine and open shelf settings characterised by tropical climate conditions. As N. wardi is currently known only from lower to mid-Pliocene deposits of the Mediterranean Basin, it is tempting to speculate that its speciation dates back to an earliest Pliocene phase of diversification that also contributed to the emergence of the Mediterranean endemic stock of extant skate species.

First fossils of the extant blacktip shark Carcharhinus limbatus from Europe and the Mediterranean Basin

“…The Mediterranean Pliocene Carcharhinus assemblage was recently summarised by MARSILI (2007MARSILI ( , 2008, who recognised teeth belonging to the following extant species: In light of the above considerations, the fossil teeth described herein from the lower Pliocene of Arcille represent the first occurrence of C. limbatus as a fossil from both Europe and the whole Mediterranean Basin. Furthermore, they also comprise a significant addition to the Mediterranean Pliocene shark fauna -one that also strengthens the notion that the continued study of the relatively well-investigated Neogene elasmobranch faunas of Italy can still result in significant novelties such as new distributional records (e.g., SPADINI & MANGANELLI 2015;COLLARETA et al 2018), descriptions of new taxa (e.g., COLLARETA et al 2021c) and other remarkable finds (e.g., CARNEVALE et al 2006;COLLARETA et al 2020a).…”

“…The sandstones from which the carcharhinid teeth described herein were collected testify to deltaic and shoreface, shallow-marine depositional settings (TINELLI 2013;DOMINICI & FORLI 2021). The associated shark and ray fauna consists of about 300 teeth and dermal denticles that have been assigned to several families of Squalomorphii (Hexanchidae), Squatinomorphii (Squatinidae), Galeomorphii (Carcharhinidae, Scyliorhinidae, Lamnidae and Carchariidae) and Batomorphii (Dasyatidae, Myliobatidae, Rajidae and Rhinobatidae) (BIANUCCI et al 2019;MERELLA et al 2020;COLLARETA et al 2021c). The above assemblage also includes the holotype of the recently described, putative rajid skate Nebriimimus wardi COLLARETA et al, 2021c.…”

“…The above assemblage also includes the holotype of the recently described, putative rajid skate Nebriimimus wardi COLLARETA et al, 2021c. Nonchondrichthyan vertebrate fossils from the same sediments consist of several skeletons of the extinct dugongid sirenian Metaxytherium subapenninum (BRUNO, 1839), two specimens of billfish (Makaira LACÉPÈDE, 1802), and the two known specimens of the extinct monodontid delphinoid Casatia thermophila BIANUCCI et al, 2019, along with teeth of bony fishes (mostly Labridae, Sparidae and Sphyraenidae) and rare remains of cheloniid turtles (SORBI et al 2012;TINELLI et al 2012;TINELLI 2013;BIANUCCI et al 2019;MERELLA et al 2020, in review;COLLARETA et al, 2021c).…”

First fossil record of Mustelus aff. punctulatus Risso, 1826: new evidence for a smooth-hound shark population in the Late Miocene North Sea Basin

“…Given that many niches were vacant, recolonization by species from the Atlantic and dispersal of survivors from intrabasinal refugia led to the introduction of multiple new species and a notable radiation in the early Pliocene Mediterranean (e.g. Tsigenopoulos et al, 2003;Triest & Sierens, 2014;Collareta et al, 2021a). Curiously, Mustelus is completely absent in the elasmobranch record of the Miocene Mediterranean (e.g.…”

Another thermophilic "Miocene survivor" from the Italian Pliocene: A geologically young occurrence of the pelagic eagle ray Aetobatus in the Euro-Mediterranean region

“…Vertebrate finds from these Tuscan Pliocene successions include marine mammals (both odontocete and mysticete cetaceans as well as sea cows and rarer pinnipeds), sea turtles, bony and cartilaginous fishes, and even terrestrial forms (e.g., DOMINICI et al, 2018, and references therein). In spite of a long history of palaeontological research, discoveries of new taxa or somewhat "exotic" vertebrate specimens are still relatively frequent from the Tuscan Pliocene marine and paralic sediments (e.g., SPADINI & MANGANELLI, 2015;COLLARETA et al, 2017aCOLLARETA et al, , 2017bCOLLARETA et al, , 2018COLLARETA et al, , 2020aCOLLARETA et al, , 2020cCOLLARETA et al, , 2020dCOLLARETA et al, , 2021BIA-NUCCI et al, 2019;MANGANELLI & SPADINI, 2019).…”