Wednesday, July 21, 2010
Fossil of the Week
If you have ever seen a majestic whale breaking the surface of the ocean then you have very likely encountered a relative of this fossil as well. This interesting bowl-shaped specimen is a whale barnacle. These specialized barnacles attach only to whales, and once an individual whale is chosen, the barnacle will remain attached for its entire life, feeding on the same clouds of plankton that their host consumes.
All barnacles belong to the phylum Arthropoda, meaning they are related to crabs and lobsters- this may seem surprising since their lifestyle and hard shell resemble that of many sedentary mollusks. In fact though, barnacle shells are not single, solid units like mollusk shells, but instead are composed of multiple plates arranged around the soft body of the animal. In life, this barnacle would also have had two opercular valves, the shelly “doors” that cover the opening of living barnacles today, but they were not preserved in the fossil. The photograph shown here was taken above the barnacle, looking down into the cavity in which the animal lived.
The whale barnacle above belongs to the family Coronulidae. Its scientific name is Coronula macsotayi and it hails from Venezuela. It was found at an exposure of the Mare Formation on a hillside above the west bank of Quebrada Mare Abajo, about 22 miles north of the city of Caracas. This exposure is Lower Pliocene in age, meaning our fossil here lived about 3 to 5 million years ago. Coronula macsotayi was named for Oliver Macsotay, the paleontologist and stratigrapher who discovered this barnacle. Macsotay sent this specimen to Norman Weisbord at Florida State University in 1969 and in 1971 Weisbord published a manuscript in Bulletins of American Paleontology volume 60 (No. 265) describing the specimen as a new species of Coronula and discussing the stratigraphy of its locality in Venezuela. Since this specimen (PRI catalog no. 28292) was the first used to describe Coronula macsotayi it is known as the holotype for this species, making it a very important resource for scientists interested in studying this fossil species.
Text by Steve Durham