FIRST RECORD OF THE CO-OCCURRENCE OF PLATYXANTHID AND VARUNID CRABS FROM MID-HOLOCENE DEPOSITS OF NORTHEASTERN BUENOS AIRES PROVINCE, ARGENTINA. PALEOENVIRONMENTAL IMPLICATIONS

Abstract

Fossil fingers of crabs (Decapoda, Brachyura) coming from mid-Holocene deposits, Cerro de la Gloria, and Destacamento Río Salado members, from northeastern Buenos Aires, Argentina are herein described. These fossil fingers represent the first record of Danielethus crenulatus, and the first record of varunids from the Canal 15 site. The specimens show diagnostic features and confirm the presence of subtidalintertidal crabs at least from the mid-Holocene marine transgressive and regressive system tracts. This study also suggests that D. crenulatus could have been represented by large populations as in modern environments since food items (mollusks) were abundant during the midHolocene. Moreover, varunids, which feed on detritus, might also have had availability of organic matter during the late Quaternary according to previous fossil fauna records from other sites of Buenos Aires Province and uruguay, because the coastal plains were extensively developed. These crabs constitute important food items for a diverse fauna and modify the substrate allowing the settlement of a varied coastal flora and fauna.