Rugose coral calceola sandalina Age: Devonian (360 million years ago) Location: west Sahara, Morocco
These are the fossilised remains of an solitary rugose coral. The fossils look like little shoes. The morphology of a fossil often gives clues to its lifestyle. In this case, the corals lay flat on the seabed (sole down), with the apex (toe of the shoe) pointing into the current. The peculiar shape represents the growth of the animal: the exoskeleton flared out as the animal grew. Somewhat unusually, this kind of coral had a little lid called an operculum. The operculum might have been protective, but may also have been used to move the coral around the seafloor. This kind of movement, not only prevented the coral from being buried in sediment, but also allowed it to find the best position for feeding and waste management.
Did you know? The first coral evolved during the Cambrian (about half a billion years ago). There were two main lineages -- rugose and tabulate coral. A mass extinction event called the great dying happened at the end of the Permian (about 252 million years ago). Ninety-six percent of the diversity of all life on Earth was wiped out. Both lineages of coral became extinct at this point. Coral turns up in the fossil record again about fifty million years later. Paleontologists initially considered it a Lazarus taxon (you think its died, but it didn't). However subsequent work found some big differences between modern (Scleractinian) coral and the ancient varieties. This appears to be an example of convergent evolution -- animals which live in similar environments and perform similar functions tend to have similar forms.
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