Fossilized sharks' teeth from the Cretaceous may have been prized collectors’ items or imbued with some significance in biblical times, a new discovery suggests. Alternatively, some extinct sharks got themselves into places they really shouldn't have.
The Jerusalem old city is not only well inland, but at an altitude above 700 meters (2,500 feet). It's not the place you expect to find marine fossils. Nevertheless, that is indeed what archaeologists digging up a 2,900 year old house found. Scientists reporting on the discovery to the Goldschmidt Conference don't think this is another case like a patch of Kentucky far from the ocean being filled with shark remains from the time when the area was under water. Instead they report in Frontiers In Ecology and Evolution that the teeth got to the holy city via human intervention, teaching us something about ancient societies, rather than palaeography.
"These fossils are not in their original setting, so they have been moved. They were probably valuable to someone; we just don't know why,” said Dr Thomas Tuetken of the University of Mainz in a statement.
The find was made in excavations of the village of Silwan, which is thought to have been part of the original site of Jerusalem. Archaeological digging at the site has been controversial since the area has a predominantly Palestinian population, but approvals are granted by the Jerusalem council.
The teeth were found in material that had been used to fill in a pool that was acting as part of the water supply during a conversion to a large (for the era) house. Also in the material were fish bones, but these were definitely not related to the teeth. The bones were food waste from around the time the house was built, about half of them identified as coming from the Bardawil lagoon, Egypt, while the teeth are tens of thousands of times older.
The discovery is a testimony to the benefits of peer review. "We had at first assumed that the shark teeth were remains of the food dumped nearly 3,000 years ago, but when we submitted a paper for publication, one of the reviewers pointed out that the one of the teeth could only have come from a Late Cretaceous shark that had been extinct for at least 66 million years,” Tuetken said. “That sent us back to the samples, where measuring organic matter, elemental composition, and the crystallinity of the teeth confirmed that indeed all shark teeth were fossils. Their strontium isotope composition indicates an age of about 80 million years.”
All 29 shark teeth so far found in the area were from the late Cretaceous. Similar fossils are found in their natural environment in the Negev, at least 80 kilometers away and much closer to sea level. Upon further investigation Tuetken and colleagues have since found teeth from a variety of Cretaceous shark species at other archaeological sites from the same era, indicating their value was widespread.
"Our working hypothesis is that the teeth were brought together by collectors, but we don't have anything to confirm that. There are no wear marks which might show that they were used as tools, and no drill holes to indicate that they may have been jewellery,” Tuetken said. “We'll probably never really be sure.”