
This is an ark shell, a member of the bivalve family Arcidae, which has members still living today. If you are a shell collector this one probably looks very familiar. It is Arca zebra abisiniana, described by Weisbord in 1964 in Bulletins of American Paleontology no. 204. It is the holotype, collected from the Abisinia formation of Playa Grande village in northern Venezuela. It is a very young fossil, Pleistocene in age or less than 2 million years old.
The species: This specimen was described as a subspecies of Arca zebra, the modern "Turkey Wing" shell found today from North Carolina through the Caribbean. The fossil subspecies is said to differ from the living species by lacking the broad radial depression so characteristic of the modern form (although in my experience, this is a highly variable feature even today). The living species is striped brown and white, as reflected by the species name "zebra." The fossil subspecies is named after its fossil formation.
The publication: BAP 204 is a 564-page monograph entitled "Late Cenozoic Pelecypods from Northern Venezuela." In addition to its fossils, it covers many living species from the region, and is lavishly illustrated, plus includes an extensive bibliography.
The author: Norman Weisbord (1901-1990) was a student of PRI-founder Gilbert Harris. He received an Associate degree from Cornell University in 1923, followed by a Masters degree in 1926, and had a very successful career in the petroleum business (which hired paleontologists in those days). Warren Allmon's history of PRI, "The First 75 Years," tells us that as part of his job, Weisbord worked for long stretches abroad, and sent specimens to PRI from foreign locales. He published 19 major paleontological monographs in the Bulletins alone, covering a wide diversity of topics from corals to mollusks, mostly from the Cenozoic of the circum-Caribbean.
Text by Paula Mikkelsen


