Tuesday, October 1, 2019

[PaleoIchthyology • 2019] Lessiniabatis aenigmatica • A Bizarre Eocene Dasyatoid Batomorph (Elasmobranchii, Myliobatiformes) from the Bolca Lagerstätte (Italy) reveals A New, Extinct Body Plan for Stingrays


Lessiniabatis aenigmatica
Marramà, Carnevale, Giusberti, Naylor & Kriwet, 2019


Abstract
In the last few years, the detailed revision of the Eocene cartilaginous fishes (Chondrichthyes) from the Bolca Lagerstätte (Italy) has provided new insights into the fish biodiversity of the western Tethys. The morphological analysis of three previously undescribed specimens from the Pesciara deposit of Bolca revealed the existence of a new stingray taxon, †Lessiniabatis aenigmatica gen. et sp. nov., which is unique among the myliobatiform batoids in having the following unique combination of characters: low number of vertebrae posterior to the pelvic girdle (65–68); thoracolumbar synarcual extending backward beyond the pelvic girdle; tail extremely short not protruding from the posterior edge of the pectoral disc; radials proximally fused to each other; pelvic girdle extremely small and strongly arched; dorsal and caudal fins absent; tail stings and cartilaginous tail rod absent; and teeth of dasyatoid morphology with smooth enameloid surface. The phylogenetic analysis suggests that †Lessiniabatis gen. nov. is deeply nested within the benthic stingrays (Dasyatoidea) representing the sister to all dasyatids and potamotrygonids. Its unique anatomy clearly reveals the existence of a new hitherto unknown body plan experimented by benthic stingrays, whose evolution can be possibly linked to the adaptive fish radiation in the aftermath of the end-Cretaceous extinction.

Figure 1: Lessiniabatis aenigmatica gen. et sp. nov. from the Eocene of Bolca Lagerstätte. (a,b) the holotype MNHN F.Bol.566 in part and counterpart. Scale bars equal 100 mm.

 Systematic palaeontology
Class Chondrichthyes Huxley, 1880.

Superorder Batomorphii Cappetta, 1980.
Order Myliobatiformes Compagno, 1973.

Superfamily Dasyatoidea Compagno, 1973.
Family incertae sedis

Genus Lessiniabatis gen. nov.

Type species. Lessiniabatis aenigmatica sp. nov.

Etymology: After Lessinia, the Italian geographic area where the Bolca Lagerstätte is located, and from the Ancient Greek word ‘βατίς’ (batis), meaning ray or skate; gender feminine.

Diagnosis: A dasyatoid stingray unique in having a thoracolumbar synarcual extending backward beyond the pelvic girdle, a tail that is extremely short and not protruding from the posterior edge of the pectoral disc, and pectoral radials that are proximally fused with one another. Moreover, †Lessiniabatis gen. nov. is characterized by the following combination of traits: low number of vertebrae posterior to the pelvic girdle (65–68); dorsal and caudal fins absent; pelvic girdle extremely small and strongly arched; tail stings and cartilaginous tail rod absent; teeth with dasyatoid morphology; enameloid surface smooth; lingual tooth surface broad and slightly convex; labial tooth surface slightly concave; labial and lingual tooth faces not steep in lateral profile; tooth root bilobed, with a central foramen; holaulacorhizid root type with an elongated pulp cavity; sparse, star-shaped dermal denticles covering the whole body; about 130–135 pectoral-fin radials (of which 59–61 are propterygial, 16–18 are mesopterygial, and 54–57 are metapterygial); about 120 vertebral centra.

Composition of the genus: The genus is represented only by the type species †Lessianabatis aenigmatica sp. nov.

 Figure 2:Lessiniabatis aenigmatica gen. et sp. nov. from the Eocene of Bolca Lagerstätte. (a,b) the paratype MSNFI IGF 103555 in part and counterpart; (c) the paratype MFSN GP.864. Scale bars equal 100 mm.

Lessiniabatis aenigmatica sp. nov.

Urolophus crassicaudatus (Blainville, 1818): Raux (2014), Figs 1, 7–9, 1137.
Urolophus” crassicaudatus (Blainville, 1818): Marramà et al. (2018), Fig. 9A,B, non C-D15.

Etymology: After the Latin word ‘aenigmaticus’, -a, meaning enigmatic, puzzling, referring to its peculiar anatomy; gender feminine.

Holotype: MNHN F.Bol.566 (ex 11001 and 10997), nearly complete articulated skeleton, in part (566B) and counterpart (566 A); 466.8 mm DW (Fig. 1).

Type locality and horizon: Pesciara site, Bolca Konservat-Lagerstätte, Italy; lower Eocene, upper Ypresian, SB 11 and NP 14a Zones.

....

Figure 9: Silhouettes of selected living and fossil taxa as representatives for the modern stingray families and holomorphic fossil taxa.
(a) Hexatrygon bickelli (Hexatrygonidae); (b) Dasyatis marmorata (Dasyatidae); (c) Potamotrygon tigrina (Potamotrygonidae); (d) Urobatis halleri (Urobatidae); (e) Plesiobatis daviesi (Plesiobatidae); (f) Urolophus kapalensis (Urolophidae); (g) †Lessiniabatis aenigmatica gen. et sp. nov.; (h) †Asterotrygon maloneyi; (i) †Heliobatis radians; (j) Gymnura altavela (Gymnuridae); (k) †Promyliobatis gazolai; (l) Myliobatis hamlyni (Myliobatidae); (m) Aetobatus laticeps (Aetobatidae); (n) Rhinoptera bonasus (Rhinopteridae); (o) Mobula mobular (Mobulidae). Figures not to scale.

Giuseppe Marramà, Giorgio Carnevale, Luca Giusberti, Gavin J. P. Naylor and Jürgen Kriwet. 2019. A Bizarre Eocene Dasyatoid Batomorph (Elasmobranchii, Myliobatiformes) from the Bolca Lagerstätte (Italy) reveals A New, Extinct Body Plan for Stingrays. Scientific Reports. 9: 14087. DOI: 10.1038/s41598-019-50544-y

     

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