CT scans of two Wyoming fossils place a new belemnite in a family thought long gone

The shape is the whole claim. Ordinary Wyoming belemnite guards run 5 to 10 centimetres long and 1 to 2 wide ^[3], which is a length-to-width ratio of about five to one. Wyoteuthis, at roughly 10 centimetres by 6 ^[4], comes in under two to one ^[1]. Assume a circular cross section and a 6-centimetre guard encloses about nine times the area of a 2-centimetre one ^[2]. The proportions changed here, not just the size, and that is why the field call was easy: Bill Wahl, who instigated the study, said the fossil stuck out like a sore thumb ^[14].

The outside oddity is not what settled the taxonomy. CT scanning let the team read internal structure without cutting either specimen, and those internal features placed the animal in an ancient belemnite family previously thought to have disappeared millions of years earlier ^[6]. This account does not specify which family, or how wide the gap is in millions of years, and that second number is what decides whether the paper reports a modest extension of a known range or a long unsampled interval.

Then the denominator. Millions of belemnite guards have come out of the Sundance Formation, laid down by an inland sea over the western United States ^[9]. Two of them are Wyoteuthis ^[1], which puts the recognised frequency on the order of two per million ^[4]. Collecting bias runs against explaining that away as neglect: a fat barrel is more likely to be picked up than another bullet, and the first specimen was noticed in the late 1990s precisely because it was bigger than anything the finder had seen ^[11].

Alexey Ippolitov, the belemnite specialist on the team, offers size-based predation as a possible explanation, with the animal taking smaller co-occurring Pachyteuthis and modern squid cannibalism as the behavioural analogy ^[8]. That is an inference from body size and shared occurrence rather than a measurement. Gut contents or bite damage would test it, and neither is reported. Only a small fraction of the animal is in hand: a 10-centimetre guard from a creature estimated at about 60 centimetres including arms ^[5] is roughly a sixth of its length ^[3], and the soft parts that would carry a feeding signal are the part that did not survive.

Specialist attention, not outcrop, was the scarce resource here. The description arrived almost 30 years after the first find ^[13], and it arrived when a second specimen turned up and a specialist looked ^[12]. Jessica Lippincott, a co-author, makes the point that people who rockhound or collect invertebrate fossils can contribute to science ^[17]; the species name linsterorum honours the collector who found the second specimen and his family ^[15], and he died in June ^[16]. For a group as heavily collected as belemnites, where Ippolitov says a find this different is exceptionally rare after more than two centuries of work ^[7], the cheaper place to look for the next unrecognised body plan is a museum drawer rather than a new quarry.