Палеонтологичид Вайоминг мужийн эртний дотоод тэнгисийн ёроолоос олдсон олдворт үндэслэн Wyoteuthis linsterorum хэмээх цоо шинэ төрлийн амьтныг тодорхойлжээ.
Эрдэмтдийн “Papers in Palaeontology” сэтгүүлд нийтэлснээр, энэхүү амьтан нь наймаалж, далайн хясаа зэрэг цефалоподын төрөлд хамаарах бөгөөд 160 сая жилийн тэртээх Юрдийн галавын үед амьдарч байжээ. Wyoteuthis linsterorum нь уг бүлгийн амьтдын түүхэн дэх хамгийн бүдүүн биетэй зүйлүүдийн нэгд тооцогддог байна. Энэхүү олдворыг анх нээсэн, талийгаач Клифф Линстерийн дурсгалыг хүндэтгэн ийнхүү нэрлэжээ.
Орчин үеийн далайн хясаатай төстэй 10 тэмтрүүлтэй энэ амьтан нь кальцитаар бүрхэгдсэн, ойролцоогоор 160–175 мм урттай, өргөн биетэй “рострум” буюу дотоод ясан бүтэцтэй байв. Судлаачдын тооцоолсноор, уг амьтны нийт урт нь 55–60 см орчим байсан бөгөөд биеийн бүтэц нь тухайн үеийн бусад амьтдаас эрс ялгарч байжээ.
Эрдэмтэд Wyoteuthis нь ховор тохиолддог, тодорхой амьдрах орчин эсвэл идэш тэжээлд дасан зохицсон, өвөрмөц төрөл зүйл байсан хэмээн таамаглаж байна. Энэ нь Юрдийн галавын үед олноор устаж үгүй болсон Megateuthididae овогт хамаарах бөгөөд геологийн цаг хугацааны туршид амьд үлдсэн цөөн хэдэн төлөөлөгчийн нэг байж болох юм.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
Paleontologists have identified an entirely new Jurassic squid-like creature from a pair of fossils retrieved from the bed of an ancient inland sea in Wyoming.
They say it’s one of the “chunkiest known species” of its prehistoric group.
Wyoteuthis linsterorum is the species name, in recognition of seasoned fossil collector Cliff Linster, who discovered one of the fossils, but passed away earlier this year. It’s the only Wyoteuthis species so far.
The species has made its scientific debut in the journal Papers in Palaeontology.
Wyoteuthis is a member of an extinct order of cephalopods, belemnites, that proliferated during the Jurassic. Their living relatives include octopuses and squids.
Like modern-day squids, belemnites had 10 appendages, but they also had a cone-shaped internal shell. Part of the shell was made of aragonite, like that of living cephalopods. You might’ve seen the buoyant, foam-like bone of a cuttlefish wash up on the beach: that’s aragonite.
But the other part of a belemnite’s internal structure – known as the guard, or rostrum – is made of calcite.
It’s those calcitic structures that are scattered through the Sundance Formation and other fossil deposits across the world, evidence that belemnites were once plentiful in Jurassic seas. The Wyoteuthis fossils are around 160 million years old.
But Wyoteuthis is like no other belemnite the experts have ever seen, with a rostrum so rotund that even the scientists have literally described it as “one of the chunkiest known species in the paleontological history of the group”.
Wyoming paleontologist Bill Wahl, who has been combing Wyoming for fossils for much of his career, says the species “stuck out like a sore thumb”.
Most belemnite fossils found in Wyoming (and there are masses of them) are about 500–100 mm (2–4 inches) long and 10–20 mm wide.
“With a diameter reaching ~60 mm at the anterior end, these rostra are the thickest known for belemnites so far,” writes belemnite expert Alexey Ippolitov and his colleagues.
The specimens are a bit broken, but based on what remains, the researchers estimate Wyoteuthis‘ rostrum was around 160–175 mm long.
“In other words, Wyoteuthis was a ‘chunky’ but rather short squid,” the team writes.
Existing methods for calculating the full length of a belemnite, arms and all, suggest Wyoteuthis was about 55–60 cm (22–24 inches) long, from the tip of its mantle to the end of its arms.
But, the researchers add, “the rostrum size does not automatically indicate a large size of animal and a high position in the trophic pyramid.”
The researchers think its rarity could be the result of a narrow ecological specialization: Perhaps it was picky about its prey, or the kind of habitat it lived in.
“Wyoteuthis linsterorum is a thick and peculiar belemnite, only rarely seen in the Redwater Shale Member of the Sundance Formation,” they note.
It was part of the family Megateuthididae – which includes Megateuthis, the largest known belemnite – a group that had a really good run in the wake of the Toarcian extinction event, when the ocean lost massive amounts of oxygen.
Creatures that are more resilient to change can thrive under these circumstances, and cephalopods are especially known for such a knack.
But then, in the Middle Jurassic, most megateuthidid lineages went extinct, overtaken by other belemnites.
The researchers say Wyoteuthis is most likely “a portly survivor of a lineage otherwise lost in the depths of geological time”.
The research has been published in Papers in Palaeontology.
This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
