Fossil Sand Dollars (echinoidea: Clypeasteroida) from the Southern Brazilian Coast

Quaternary sediments along the southernmost portion of the Brazilian coast are rich in fossil remains of various terrestrial and marine organisms. This paper presents a description of fossil irregular clypeasteroid echinoids found in this area, with observations on their taphonomy. The identified taxa are Encope emarginata (Leske) and Mellita quinquiesperforata (Leske), although the latter is very scarce. All fossils consist of fragments of the test, broken along the ambulacral or interambulacral sutures. The majority of the remains consist of abraded fragments; petaloids are found either intact or collapsed. Many fossils are represented by internal molds formed by the infilling of the organisms’ internal cavities by dark muddy matrix. The distribution of the fossils match the pattern observed on recent echinoid remains found along the coast. The relative absence of fossil and recent material of M. quinquiesperforata seems to be a result of taphonomic factors related to environmental processes.