HUANTRAICONELLA N. GEN. DEL TERCIARIO INFERIOR (OSTRACODA, BUNTONIlNAE) (DANIANO) DE ARGENTINA

Abstract

The new genus Huantraiconella, with rhe species Huantraiconella prima, is described and figured. The new genus shows a similar anatomy with the other taxa included in the subfamily Buntoniinae Apostolescu, 1961. The fol1owing features are typical for the new genus: Carapace of medium to large size, piriform, inflated; surface strongly reticulate, with Iongitudinal ridges strongly developed forming three low and broad longitudinal plications: one dorsal ridge, a second medium plication directed from the antero-ventral to the postero- dorsal region and a third ventral plication or fold; left valve larger than right; eye spots and subcentral tubercule present but slightly developed; strong post-ocular furrow behind the eye tubercule which breacks the continuity from the anterior and dorsal outline; inner lamella wide and -regular.v-with numerous marginal pore-canals, simple, curved and unbranched, no vestibule, selvage subperipheral; hinge holamphidont; central scars forrned by four adductor muscle scars and one frontal U shape scar; sexual dimorphism strong. Huantraiconella n. gen. resembles Buntonia Howe, 1935 in muscle scars and marginal zone characters; it differs in shape, by the presence of eye spots, subeerrtral rubercules and post-ocular furrow and a lack of bar crenuJations; from Cytberetta Mueller, J894 it differs by lacking the wide and sinous marginal area and from Mosaeleberis Deroo, 1966 by differ- ences in outline and hinge-structure, Samples from me Roca Formation, exposed in many outcrops of North Patagonia show that Huantraiconella prima is abundant, distinctive, and can be used as a stratigraphic guide fossil in the Argentina Lower Tertiary (Danian ), since it is restricted to strata from this age.