A incomum associação de peixes e caranguejos da Formação Romualdo, Aptiano-Albiano da Bacia sedimentar do Araripe, NE do Brasil

The unusual association of fish and crabs from Romualdo Formation, Aptian–Albian of the Araripe sedimentary Basin, NE Brazil. In a study and collection of fossils from the Romualdo Formation in “Araripe pernambucano”, an association of Vinctifer comptoni and Rhacolepis buccalis with eubrachyurans and orithopsids crabs was observed in four calcareous nodules. Associations were discussed based on ecological and taphonomic hypotheses. It is noted from the degree of articulation of the organisms, that either the death or the availability of crab moults in the sediment possibly occurred before the death of the fish. In addition, the fish do not have teething consistent with feeding on crabs. Thus, this association would occur due to fossilization processes and not due to ecological interactions. The study also emphasized systematic and paleogeographic aspects of the groups. Romualdocarcinus salesi is probably related to the “higher” true crabs (Eubrachyura), a hypothesis already raised in previous works, due to the preservation of its dorsal carapace next to a pleon of subquadrangular shape similar to those seen in this group. The occurrence of Exucarcinus gonzagai associated with fish, in concretions in the shales, can raise the question of E. gonzagai and Araripecarcinus ferreirai species as synonyms. The data obtained with the survey of the paleogeographic distribution of fish and crabs in geological formations of correlated age corroborates the hypothesis of the Tethyan marine influence in Araripe. Keywords: ichthyolites, decapods, paleoecology, taphonomy, Santana Group, Cretaceous.