A new large species of weakfish (Acanthuriformes: Sciaenidae: Cynoscion) from the Late Miocene of Argentina

NORIEGA, JORGE I.; PERALTA, MATÍAS J.; MONSALVO, SEBASTIÁN; BRUNETTO, ERNESTO; GOTTARDI, M GRISELDA; SCHMIDT, GABRIELA I.; DIEDERLE, JUAN M.; TARQUINI, JULIANA; BRANDONI, DIEGO

Mendoza

Jornada; Reunión de Comunicaciones de la Asociación Paleontologica Argentina; 2024

APA, IDEVEA (CONICET, UTN)

Sciaenidae is a diverse cosmopolitan family of Teleostei, occurring in tropical to temperate marine coasts, brackish estuaries, and freshwater. The sciaenid fossil record starts in the Eocene of USA, but most fossils concentrate in the Oligocene and Neogene marine deposits of Europe and America. In South America, skeletal remains referred to Stelliferinae and to Pogonias blettleri were recently reported from the Late Miocene of Chile and Argentina, respectively. The specimens herein presented are deposited at the CICYTTP (Centro de Investigación Científica y de Transferencia Tecnológica a la Producción, Diamante, Entre Ríos), and were recovered by us along three decades in different western localities of Entre Ríos Province (Argentina) from two Upper Miocene units, the marine Paraná Formation and the overlying fluvial Lower Member of the Ituzaingó Formation. They comprise many disarticulated skull bones (67 anguloarticulars, 57 dentaries, 13 maxillae, 28 premaxillae, three hyomandibulars, and three prevomers) previously identified as Sciaenidae indet. A comparative morphological analysis allowed us to recognize these materials as belonging to a new species of the sciaenid Cynoscion. The approximately 25 extant species of Cynoscion are distributed around the Americas in the Eastern Pacific and Western Atlantic oceans. They are commonly known as weakfishes or "pescadillas", having elongated and compressed bodies and usually large oblique mouth bearing a pair of well-developed sharp canines at the upper jaw. The following characters of the anguloarticular (CICYTTP-PV-P-4-522) support our assignment: broad and saddle-shaped articular facet for quadrate and hooked posterior process; upper ramus inclined cranially at angle of approximately 25˚; deep lateroventral trough for mandibular sensory canal, covered by narrow strut, dorsally bordered by robust bony strip and, ventrally, by straight and flat bony sheet with finely sculptured surface. Other referred bones are characterized by: retroarticular extending more caudally than anguloarticular; long and subrectangular-shaped dentary, with wide and deep laterosensory canal interrupted by four robust bony struts; oblong articular process of premaxilla, as well as long and curved alveolar process, with small hump on posterodorsal margin; teeth alveoli of premaxilla of varied sizes, aligned along three or two rows, with large alveoli for canines only at anterior tip; medial condyle of maxilla large, quadrangular, and very well developed craniomedially; shaft of maxilla with slight hump on dorsal edge, becoming straighter posteriorly and widening only well caudally. A preliminary metrical analysis shows that the size of the new taxon was similar to that of the largest extant species of the genus.Financial support provided by: CONICET PIP Nº 1230.