Deep in the rocks buried beneath the North Sea, layers from the Jurassic period have preserved an unusual record of ancient marine life, not in the form of a complete skeleton or a huge predator's tooth, but in small clumps of food remains spat out by a marine animal about 160 million years ago, which then turned into fossils over time.
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Dirk adds: "The first possibility was that the shells had accumulated due to storms or ocean currents, but their shape did not match this scenario, because the material was not distributed in an extended layer, but rather confined within dense, limited-sized blocks, and some of the edges appeared to be eroded or etched in a way consistent with their passage through a digestive system."
According to the study, the presence of large amounts of undigested food, along with the irregular shape of the lumps and their calcareous nature rather than the usual phosphate composition of hardened feces, makes interpreting them as hardened vomit more likely than considering them as fecal remains or preserved intestinal contents.
The more difficult question was identifying the animal that left these remains, because the Jurassic Sea was home to sharks, marine reptiles, sea crocodiles and other predators capable of devouring creatures with hard shells, but Dirk believes that medium-sized, long-necked plesiosaurs are the strongest candidate.
This interpretation is supported by the fact that these reptiles, some of which ranged in length from 4 to 8 meters, had small, sharp, closely spaced teeth, which they may have used to capture crustaceans, mollusks, worms, and other benthic animals, while previous discoveries of stomach contents in their relatives showed remains of shells and sea lilies similar to what was found inside the Norwegian blocks, according to the study.
Dirk suggests that the animals fed in more open marine areas, then moved closer to coastal and deltaic environments where they deposited these masses and were quickly buried in sediments, a process that helped preserve them before they were destroyed by currents or bottom-dwelling organisms.
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