Novedoso hallazgo de egagrópilas para el Mioceno tardío de la provincia de Catamarca, Formación Andalhuala, Argentina

Abstract

We report the finding of two fossil bird pellets recovered from outcrops of Andalhuala Formation (Late Miocene), Santa María valley, Catamarca province, Argentina.The pellets are composed by several microvertebrate fossil bones and teeth included in a sandy matrix. We interpret that these structures were produced by the trophic activity of small predator, the "terror birds" (Phorusrhacidae, Psilopterinae), that lived in the area during the late Miocene. The pellets have centimetrical size scale, subovoid shape, and a highly calcareous matrix, and content highly concentrated and well preserved several cranial and postcranial fragmentary remains belonging to small rodents (Octodontidae and Cricetidae). Some long bones are nearly complete (diaphysis plus epiphyses),other bones are articulated and others are irregularly disposed. Some teeth show clear evidence of corrosion in enamel (pitting), due to digestive process of predators. This finding constitutes the oldest direct physic evidence of a bird pellet in South America and the oldest record of a cricetid rodent in this continent.

En el presente trabajo se realiza un estudio paleontológico en la Formación Lampazar que aflora en la localidad Angosto de La Quesera, franja oeste de la Cordillera Oriental, provincia de Salta. En dicha unidad se ha registrado el género Strepsodiscus Knight (Gastropoda, Bellerophontoidea), el cual ha reforzado anteriores investigaciones que revelan una edad cámbrica tardía para la asociación fosilífera y los estratos portadores. En esta oportunidad se realiza un diagnóstico de la morfología funcional de la especie Strepsodicus austrinus Pinilla et al., la cual se documenta asociada a trilobites característicos de la Biozona de Parabolina frequens argentina [Parabolina (Neoparabolina) frequens (Barrande), Olenidae indet., Micragnostus sp.], Hyolitha gen et sp. indet., placas de crinoideos y trazas fósiles de la ichnofacies de Cruziana.