Diversidad ictiologica en depositos continentales miocenos de la Formacion Cura-Mallin, Chile (37-39°S): implicancias paleogeograficas

Abstract

RESUMEN. La fauna estudiada representa el conjunto de peces fosiles mas diverso conocido hasta ahora en el Terciario de Chile. Procede de las unidades sedimentarias superiores, fluviolacustres, de la Formacion Cura-Mallin, asignadas al Mioceno, y que afloran en el sur de Chile entre los 37-39°S. El material identificado pertenece a los ordenes: Characiformes (Characidae indet.; Serrasalminae indet.); Siluriformes (Nematogenys sp.); Atheriniformes (Atherinidae indet.); Perciformes (Percichthys lonquimayiensis, P. sandovali, P. sylviae, Percichthys sp., Santosius? sp. y Percilia? sp.). Este constituye el primer registro fosil de Characiformes y Atheriniformes en Chile. El conjunto paleoictico reafirmaria el caracter morfologicamente estable de, al menos, parte de la fauna sudamericana desde comienzos o mediados del Terciario. Los grupos taxonomicos determinados estan principalmente relacionados con la Subregion ictiobiogeografica Austral, pero los restos de Characidae indet. y Serrasalminae indet. evidencian una mayor distribucion meridional y occidental de la fauna Brasilica durante el Mioceno. La fauna reciente del area se encuentra empobrecida debido a una extincion local que afecto a nivel generico y especifico a la familia Characidae, acompañada por una disminucion de la diversidad especifica de Percichthyidae. ABSTRACT Ichthyological diversity in Miocene continental deposits of the Cura-Mallin Formation, Chile (37-39°S): paleogeographical implications. The fish remains described herein are the most complete assemblage of Tertiary fishes known in Chile until today. They were collected from the assigned Miocene upper beds of the Cura-Mallin Formation (37-39°S), which represents a fresh water fluviolacustrine environment. The specimens identilied belong to the following orders: Characiformes (Characidae indet.; Serrasalminae indet.); Siluriformes (Nematogenys sp.); Atheriniformes (Atherinidae indet.); Perciformes (Percichthys lonquimayiensis, P. sandovali, P. sylviae, Percichthys sp , Santosius? sp. and Percilia? sp.). Both Characiformes and Atheriniformes are recorded as fossils for the first time in Chile. The fossil fish fauna would show stable morphologic patterns of, at least, part of the South American fauna since the early or middle Tertiary. Most of the specimens studied belong to the Austral lchthyobiogeographic Subregion. However, remains of Characidae indet. and Serrasalminae indet. illustrate a wider western and southern extension of the Brazilian fauna into the Austral Subregion for this time. The present day fish fauna in the area has been impoverished by a local extinction that affected the Characidae at generic and specific levels, accompanied by a reduction in the diversity of Percichthyidae species.