New Jurassic belemnite was the broadest ever found

A new species of Jurassic belemnite has been identified from two rare fossils found in Wyoming, revealing an animal with a skeleton far broader than any previously recorded member of its group.

The species, Wyoteuthis linsterorum, lived roughly 160 million years ago. It was an ancient cephalopod, related to today’s squid and octopuses, and may have measured about 60 centimetres from its rear skeleton to the tips of its arms. Its unusually robust remains distinguish it from the slender, bullet-like fossils normally associated with belemnites.

The discovery is described in Papers in Palaeontology by researchers from the United States, Britain and New Zealand. The findings were reported by manchester.ac.uk, which included Dean Lomax, an honorary research fellow at The University of Manchester, among the study’s authors.

A strikingly different fossil

Belemnites were marine animals whose internal support structures are commonly preserved as hard, tapered fossils called rostra, or guards. These remains are found around the world, including in large numbers in Wyoming’s Sundance Formation. The rocks were formed in an inland sea that once extended across much of the western United States.

Typical belemnite fossils from the formation are approximately 5 to 10 centimetres long and only 1 to 2 centimetres across. The two specimens assigned to the new species are about 10 centimetres long, but their width reaches as much as 6 centimetres. That gives them a short, thick profile more like a barrel than a bullet.

The first fossil was found in the late 1990s by Burkhard Pohl, founder of the Wyoming Dinosaur Center. It remained in the museum’s collection for years without being investigated. A second example was later discovered near Ten Sleep, Wyoming, by fossil collector Cliff Linster, who donated it to the same institution in 2019.

Together, the specimens gave scientists enough evidence to establish a new species. The genus name refers to a squid from Wyoming, while the species name recognises Linster and his family. Linster died in June this year, but had known that researchers were examining his find and was looking forward to its formal publication.

Scanning reveals an ancient survivor

The research team used computed tomography to study the fossils without breaking them open. The scans exposed internal characteristics that placed the animal within an old belemnite lineage. That group had been believed to have vanished millions of years before this animal lived, making its presence in the Jurassic rocks unexpected.

Alexey Ippolitov, a belemnite specialist now based at Victoria University of Wellington, said the animal’s extreme difference from known examples was surprising because the group has been studied for more than two centuries. The researchers suggest that its size may have helped it prey on smaller belemnites of the genus Pachyteuthis.

That idea remains a possible explanation rather than a demonstrated fact. Modern squid are known to eat other cephalopods, including members of their own species, so a large belemnite could have occupied a similar predatory niche. The animal’s scarcity may also reflect a specialised adaptation to the conditions of the ancient sea, although the fossils cannot establish why it was uncommon.

Fossil hunters and scientific discovery

The work began with Pohl’s unusually large specimen and progressed after Linster’s donation brought a second example to researchers’ attention. Jessica Lippincott, a Wyoming palaeontologist and study co-author, said the find demonstrates that amateur collectors and people who search for invertebrate fossils can make valuable contributions to research.

The Linster family has a history of notable discoveries, including the dinosaur Bambiraptor. Lomax had previously worked with Cliff and his wife, Sandy, excavating a dinosaur bonebed on their property in northern Montana. He also has experience collecting fossils and excavating marine reptiles in Wyoming’s Sundance Formation.

Lomax said naming the species after Linster was meaningful, while acknowledging that Linster did not live to see the study published. The name now records the contribution of the collector who found one of only two known examples.

Both fossils are currently displayed at the Wyoming Dinosaur Center in Thermopolis, Wyoming, where visitors can see the specimens that revealed this unusually bulky member of the Jurassic seas.