Traces from space

Battlestar_d

by Sancia van der Meij, Research Fellow

To understand how modern species evolved, we often turn to the fossil record, but this can be very difficult when the animal you would like to study is small and fragile. For example, the coral-dwelling crab family Cryptochiridae has more than 50 species today and occurs worldwide on coral reefs. These small crabs are less than 1 cm in size and have the unique ability to create little homes,or dwellings, in stony corals. This ability makes them an interesting study object to learn more about how different species cohabitate on reefs.

Modern cryptochirid crab in its coral home

Modern cryptochirid crab in its coral home

Unfortunately no fossils are known for these crabs; their size and thin carapace (shell) means they probably didn’t fossilise well. But together with colleagues from the United States, I’ve found crab dwellings in fossil corals for the very first time. The corals are several million years old and come from Florida and Cuba. Although we still don’t have fossils of the actual crabs, the holes, which are a type of trace fossil, are very valuable evidence.

Three dwellings on a fossil coral from the lower-middle Pleistocene. Found in Palm Beach County, Florida. A close-up of one pit can be seen at the top of this post.

Three dwellings on a fossil coral from the lower-middle Pleistocene, found in Palm Beach County, Florida. A close-up of one pit can be seen at the top of this post.

To sci-fi fans, the dwellings have an extra significance. The shape of the entrance is very similar to the shape of the spaceship in the American science fiction series Battlestar Galactica, so the scientific name of the trace fossils is Galacticus duerri.

We’ve published a paper in the journal Scientific Reports on the first fossil evidence of these crabs.

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