A baffling extinct animal was actually a marine reptile that may have used its extremely long neck to ambush prey.
Fossils of Tanystropheus were identified over 100 years ago, but the animal’s true nature has long been a mystery. It lived around 242 million years ago, in the Triassic period. Life on Earth was still recovering from the end-Permian mass extinction of 252 million years ago, and the first dinosaurs were emerging.
Tanystropheus was a reptile. Its most striking feature was its disproportionately long neck, which was three times the length of its body. Fossil remains of it fell into two groups: large specimens up to 6 metres long and small ones up to 1.5m. But questions remained.
“Is it terrestrial or is it marine? Are those juveniles and adults, or are they two different species?” says Olivier Rieppel of the Field Museum of Natural History in Chicago.
His team re-examined a skull from a large specimen. The skull had been crushed, but the individual bones were undamaged. So the team was able to CT scan them and digitally reposition them to reconstruct the skull, revealing crucial anatomical details.
The skull is unmistakably that of a marine animal, says Rieppel. For instance, its nostrils are on the top of the snout, to allow it to breathe when it surfaced. “Biomechanically, that neck doesn’t make sense on land.”
Meanwhile, the bones of the smaller fossils showed multiple growth rings, indicating they belonged to adults, not juveniles. This means the large and small fossils are actually different species, not adults and juveniles of the same species, says Rieppel.
The two species were able to coexist in the same waters because they ate different foods. The large species ate fish and cephalopods like squid, while the smaller one probably ate tiny invertebrates like shrimp.
“Somehow this neck was functional, probably in ambush predation,” says Rieppel. Tanystropheus may have hidden its body and used its long neck to surprise its prey.
Despite its peculiar appearance, Tanystropheus seems to have flourished. Fossils have been found in Europe, Israel and China, indicating it was widespread. “In spite of its long neck, it was obviously a very successful animal, with a wide geographic distribution,” says Rieppel.
Journal reference: Current Biology, DOI: 10.1016/j.cub.2020.07.025
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