NUEVOS APORTES AL CONOCIMIENTO DE LA ICNOFAUNA DE TETRÁPODOS DEL TRIÁSICO SUPERIOR DE LOS MENUCOS

Nadia S. Domnanovich, Rodrigo Tomassini, Teresa Manera de Bianco, Marcelo Dalponte

Abstract


The Los Menucos ichnofauna from the Río Negro province
in Argentina, is at present a unique Triassic track association known from Patagonia. The new footprints described
in the present study were collected from the same levels where the original tetrapod ichnites from
Casamiquela´s works were exhumed. The track-bearing levels are included in the Los Menucos Complex and correspond
to fine-grained tuffaceous sandstones interbedded with tuffaceous mudstones that contain a rich "Dicroidium-
type Flora". In the present study new groups of trackmakers, that included footprints assigned to terapsid
dicynodonts (Pentasauropus sp. Ellenberger) and putative "lepidosaurs" (Rhynchosauroides Maidwell) were identified.
The new specimens described do not include ichnites related to archosaurs (basal archosaurs and/or dinosaurs),
which are the dominant component in most known Late Triassic Gondwanan tetrapod faunas. Previous assumptions
about the relative abundance and high diversity of small therapsids, probably theriodonts represented by the
footprint assemblage are corroborated by the new evidence. This unusual situation, which is supported by the new
findings, might be due to the record of an endemic fauna actually dominated by therapsid taxa in northern
Patagonia.

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