Tropical freshwater teleosts from Miocene beds of Eastern Patagonia, Southern Argentina.

CIONE, ALBERTO; AZPELICUETA, MERCEDES; CASCIOTTA, JORGE; DOZO, MARÍA TERESA

GEOBIOS

ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER

Lugar: Paris; Año: 2005 vol. 38 p. 29 - 42

0016-6995

Loricariid and pimelodid-like siluriforms (along with undeterminated percomorph) are described for the first time from Patagonia. Fishes occur along continental mammal and bird remains.Vertebrate fossils were found in beds attributed to the top of the Puerto Madryn Formation. These levels supposedly corresponded to the "Rionegrense marino" of former authors. Mammals occurring in the site suggest a Huayquerian age for the bearing beds. The base of the Huayquerian was dated at about 9 Ma and the top is younger than 6.5 Ma.  Radioisotopic dating in the marine shell beds of the Puerto Madryn Formation ranges from 11 to 9 Ma.  Consequently, the section described here appears to be younger than the typical Puerto Madryn Formation from which is actually separated by an unconformity. The section would be correlated with the type Río Negro Formation from northern Patagonia which also include Huayquerian fossils. Freshwater fishes were unknown until now in beds younger than the middle Miocene in southern South America. Moreover, almost no vertebrate remains are known from beds younger than middle Miocene in Patagonia. Previously, only a few undescribed mammal remains from Miocene beds and several late Pleistocene mammal remains had been reported in this region. This is also the southernmost record of loricariid fishes. The peculiar association of aquatic continental and terrestrial vertebrates indicates temperate (or even warmer) climate and, for the first time in Península Valdés, beds of freshwater origin. The evidence apported by fossils is also in agreement with global climate trends. The local extinction of loricariids in Patagonia possibly occurred much later than the epoch when bearing beds deposited.