Scientists Found the ‘Chunkiest’ Jurassic Squid Relative Ever Known

Its bizarre fossil skeleton was three times wider than those of its Jurassic neighbors.

Among the countless fossils buried in Wyoming’s rocks, belemnites are hardly celebrities. These extinct relatives of squids look like hard, elongated bullets, and they’re common finds. In fact, they’re so common that local fossil hunters jokingly call them “squid butts.”

But paleontologists encountered one that looked as if someone had inflated the usual design.

The newly named Wyoteuthis linsterorum lived about 160 million years ago, when a shallow sea covered much of what is now the western United States. Its internal skeleton was extraordinarily broad — roughly 10 centimeters long but up to 6 centimeters wide. Researchers describe it as the thickest, or “chunkiest,” belemnite yet known. CT scans also revealed a bigger surprise: the animal belonged to an ancient lineage scientists thought had vanished millions of years earlier.

An absolute unit

Belemnites were marine cephalopods, part of the broader group that includes living squid, octopuses and cuttlefish. They flourished in prehistoric seas and became particularly abundant during the Jurassic and Cretaceous periods.

Typically, it’s the “rostrum” or guard that survives as a fossil: a dense internal structure toward the back of the animal. Think of it as a counterweight and support structure rather than an external shell.

Most belemnite guards recovered from Wyoming’s Sundance Formation measure about 5 to 10 centimeters long and just 1 to 2 centimeters across. But this one had a guard around 10 centimeters long and 6 centimeters wide. Instead of resembling a rifle bullet, it looked thick and barrel-shaped. The researchers estimate the complete living animal, arms included, may have reached about 60 centimeters in length.

Body proportions are important. They offer clues about how an extinct animal swam, balanced itself and interacted with other species. Yet the researchers only have two specimens, so reconstructing Wyoteuthis’ lifestyle isn’t straightforward.

How did it get so big?

One possibility is that size helped it hunt other cephalopods.

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“A possible explanation is that their relatively large size gave them an advantage when hunting co-occurring smaller belemnites,” paleontologist Alexey Ippolitov said in a University of Manchester release.

Living squid readily prey on other cephalopods and sometimes even members of their own species. So, today’s modern life supports this idea as a valid hypothesis. But no fossilized meal proves Wyoteuthis did the same. Its strange proportions could reflect another ecological specialization entirely.

Then, the fossil has another surprise.

Researchers used CT scanning, essentially a three-dimensional X-ray technique, to peer inside the guards without cutting them apart. Internal structures placed Wyoteuthis in the family Megateuthididae, an older lineage of belemnites whose known fossil record had appeared to end earlier. Practically, this means that the animal isn’t just an unusually fat version of a familiar Jurassic species. Rather, it’s a surviving member of an ancient evolutionary branch hanging on in a place and time where scientists had not expected to find it.

The fossil waited decades for an explanation

The discovery itself unfolded almost as slowly as the Jurassic rocks that preserved it (well, not quite, but it was still slow).

Burkhard Pohl, founder of the Wyoming Dinosaur Center, unearthed the first specimen in the late 1990s. Its enormous width stood out immediately, but the fossil remained in the museum collection for years without a formal scientific description. Plus, there was only one specimen.

Then fossil collector Cliff Linster found a second specimen near Ten Sleep, Wyoming. He donated it to the Wyoming Dinosaur Center in 2019. So researchers now had two examples, and they could finally show that the odd anatomy was not simply an abnormal individual or a damaged fossil. They had a new genus and species.

The scientists named it Wyoteuthis linsterorum: roughly, “Wyoming squid,” with the species name honoring Linster and his family. Linster died in June 2026, shortly before the study appeared, but he knew researchers were working to describe his find.

It’s an important and humbling find. Paleontologists have recovered millions of belemnite fossils there from sediments deposited in a Jurassic inland sea. Scientists could reasonably consider the animals among the formation’s most familiar fossils. And yet two exceptionally broad “squid butts” were enough to reveal a body plan nobody had recognized before — and a lineage that apparently survived longer than expected.

The study was published September 10 in Papers in Palaeontology.