Mollusks are one of the most diverse organisms of the animal kingdom. They inhabit most types of habitats and are extremely diverse in their forms. Octopi and the extinct ammonoids are also mollusks. Within the Mollusca, the so-called phylum of the mollusks, there is the Bivalvia or bivalves. The bivalves are also diverse in their shape, form, and habitat. The group includes clams, cockles, mussels, oysters, and scallops. They have existed for at least 520 million years - since the early Cambrian and appear in most part of the Earth's fossil record.
During the Eocene - or about 33 to 56 million years ago, the Antillean islands did not exist in the configuration that is known today. In fact, most paleogeographic reconstructions suggest the whole area was a deep marine environment, flanked by two main bank systems (Florida and Yucatan), with small volcanic islands scattered through. The rocks and substructures that would make the Greater Antillean arch later, during the late Eocene - early Oligocene (~33 million years ago), did not yet exist. However, there is no doubt these waters held mollusk faunas - a story that can be told by their fossils.
Our recent paper in the Journal of South American Earth Sciences (here) describes two unreported species from the Cuban Eocene: the genera Schedocardia and Acanthocardia. The fossilized remains of these mollusks, still encased in rock-matrix, were collected at the Madruga Formation a couple of years ago by Yasmani Ceballos, one of the authors of our paper. This Formation includes microscopic organisms, corals, brachiopods, and sea urchins from the Late Paleogene and Early Eocene - and thus provides a window into the marine life of Cuba's early seas. Equally important, these two fossils represent forms that had not been reported from the Cuban fossil record!
A free copy of our paper can be downloaded for free on the ScienceDirect page, but only until September 18, 2020. Don't miss the opportunity to acquire the paper now.
Orihuela, J., Y. Ceballos Izquierdo, R. W. Portell (2020). First report of the Eocene bivalve Schedocardia (Mollusca, Cardiidae) from Cuba. Journal of South American Earth Sciences, Vol. 103. https://doi.org/10.1016/j.jsames.2020.102771