"Pholidophorus” argentinus DOLGOPOL DE SAEZ ,1939, AN ASPIDORHyNCHIDAE (ACTINOPTERYGII, ASPIDORHYNCHIFORMES) FROM THE VACA MUERTA FORMATION (UPPER JURASSIC) OF NEUQUÉN PROVINCE, ARGENTINA

GOUIRIC CAVALLI, SOLEDAD; CIONE, ALBERTO LUIS

Congreso; IV CONGRESO LATINOAMERICANO DE PALEONTOLOGÍA DE VERTEBRADOS; 2011

The order Pholidophoriformes Berg, 1940, was erected on the basis of several characters that are considered primitive or incorrect today. Consequently, “pholidophoriforms” are not considered monophyletic. The “pholidophoriforms” included numerous genera and species around the world that range in age from the Triassic to Cretaceous. The genus Pholidophorus Agassiz, 1832, was created to include two species from the Triassic of Seefeld in Austria. Characters used to define the genus included caudal fin with nearly equal lobes, large rhomboid scales, general body shape, vertebral patterns, etc. what caused that the genus became a “catch all” diagnosed by plesiomorphic or invalid traits. Recently, Arratia (2000) studied the phylogenetic relationships of certain specimens previously assigned to Pholidophoriformes and the definition of the genus Pholidophorus. In this study, she analyzed, among other characters, the structure of the scales of several Late Jurassic specimens from Germany. The author found some important differences in the type, ornamentation, and structure of the scales. Several pu- tative “Pholidoforiformes” were reported from Argentina: “?Pholidophorus” dentatus Rusconi, 1946, and “Pholidophorus” vallejensis Rusconi, 1947, from the Triassic continental deposits of the Potrerillos Formation in Mendoza Province; Pholidophorus argentinus Dolgopol de Saez, 1939, from the Jurassic marine deposits of the Vaca Muerta Formation in Neuquén Province, and several “pholidophorids” indet. from the Cretaceous continental deposits of the La Cantera Formation in San Luis Province. The diverse Jurassic marine fish fauna from Argentina is currently under study by the first author. As part of this study the holotype of “Pholidophorus argentinus” (housed in the La Plata Museum; MLP 39-VI-30-4) is redescribed. It consists of a caudal skeleton and posterior portion of the body preserved mainly as an impression. The study is based on the type material and a cast of this specimen. The distal part of the caudal rays are lost, some of them are not very well pre- served, and many are broken and disarticulated. Dolgopol de Saez assigned this specimen to the genus Pholidophorus based on a combination of characters that were posteriorly revised by one of us (AC) concluding that this specimen does not present any diagnostic character to be recognized as different species or even to allow an assignment to the genus Pholidophorus, assigning it instead to Halecomorphi indet. Our results reveal that the combination of structures such as number of basal fulcra, number of principal and precurrent [= procurrent] caudal rays, patterns of ramification of rays, form and type of scales among others) clearly resemble those of aspidorhynchiforms and consequently we interpret this specimen as an aspidorhynchiform.