First record of fossil sergestid decapods and fossil brachyuran crab larvae (Arthropoda, Crustacea), with remarks on some supposed palaemonid fossil

A new genus and species of shrimp is described from limestone concretions of the Romualdo Member. These shrimps occur within the matrix of concretions and in the stomach contents of the teleost fish Rhacolepis. Based on rostral and car-apace characters, it is suggested that these deca-pods are representatives of the family Sergestidae. Other fossil decapods recovered from the stomach contents of a different fish {Tharrhias) are iden-tified as "protozoea " larvae of a brachyuran crab. This new discovery suggests that some brachyu-rans completed part of their life cycle within a restricted marine or brackish environment in the Araripe Basin. It also indicates that Tharrhias was a plankton feeder, and probably did not compete with predators such as Rhacolepis, which preferred to eat benthic decapods and small pelagic fishes. The fact that Rhacolepis and Tharrhias rarely oc-cur in the same horizon suggests that their pre-ferred food sources usually did not occur together. New morphological information is also provided for the supposed palaemonid Beurlenia from freshwater strata of the Crato Member. Although this taxon is a caridean decapod, its palaemonid affinity is questionable