| Summary: | The validity of the genus Retrotapes del Río is discussed and Retrotapes newtoni ( Wilckens), R. antarcticus (Sharman and Newton) and R. robustus (Stilwell and Zinsmeister), from the Eocene strata of the Antarctic Peninsula (La Meseta Formation), are described and illustrated. The stratigraphic range of R. robustus is extended from the Acantilados allomember to the Cucullaea I allomember. The morphogeometric analysis performed, allows the recognition of ontogenetic variations of R. antarcticus and R robustus, as well as to shed light on their taxonomic status. The present is the oldest record of Retrotapes, a taxon that would have originated in the Antarctic region, from where it would have dispersed northwards to lower latitudes during Miocene times when it was widely represented in the Patagonian seas.
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