Jorge Fernández, Pedro Bondesio, Rosendo Pascual


"Upper and lower dental plates of a lungfish are here described. The plates have been found in the Lumbrera Formation (Salta Group) from the upper course of the Yacoraite river (Jujuy province, Argentina). The first part of this paper is devoted to describe the stratigrapbical position of the Lumbrera Formation, its lithological characteristics and those of the related lithological units. Fossil mammals also found in this formation, as well as those found in other lithologically similar units of the Santa Bárbara Subgroup (ex Margas Multicolores), point to an Eogene age, probably representing the Paleocene-Eocene lapse. The identical morphological pattern of the plates with that of the living Lepidosiren paradoxa induced the authors to the same specific assignment. A brief account of the dipnoan history is
made. The evidences provided both by the fossil record and the paleogeography have led to the hypothesis that the two living Lepidosirenidae evolved as a consequence of the continental drift and the isolation of the African and South American masses, from the upper Jurassic on. Finally it is concluded that the present local position of the Lumbrera Formatian, higher than 3000 m above the sea level and under semiarid conditions, obviously is the effect of the late Andean cenozoic diastrophism; its sediments were deposited under environmental conditions similar to those prevailing today in the area as where Lepidosiren paradoxa is still living."

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