NEW CLAM SHRIMP FROM THE JURASSIC NTUMBE MEMBER OF THE DANDE FORMATION, ZIMBABWE

Mesozoic terrestrial ecosystems in Africa are poorly known. Field investigations of the Jurassic Ntumbe Member of the Dande Formation (Dande Sandstone) in the Chewore Safari Area of northern Zimbabwe yielded a collection of very well-preserved clam shrimp. The sedimentology of Ntumbe Member is characterized by repeated upward coarsening successions of carbonaceous black shales with clam shrimp at the base, overlain by oxidized red shales with minor evaporites, deep mud cracks and abundant dinosaur trackways, and capped by tabular sandstone beds. Today, extant clam shrimp are specialists in ephemeral freshwater habitats, and their presence in the Ntumbe Member, support the interpretation of an ephemeral deposystem for the lower part of this member.

The clam shrimp appear to be a new species belonging to the genus Carapacestheria. Carapacestheria was first identified in Jurassic sediments in Antarctica. It has subsequently been identified elsewhere (Argentina, China, and the United Kingdom). This is suggestive of a wide distribution. This new occurrence of the genus in Africa helps connect these previously known occurrences. The familial-level assignment of Carapacestheria is currently in question. In the last five years, it has been assigned to both Eosestheriidae and Triglyptidae. The well-preserved ornamentation patterns will hopefully shed light on the evolution of the genus.