A weird sea creature was anatomically unlike anything ever seen — flipping it around led to a revelation

by | Jun 24, 2024 | Science

Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.An extinct ribbonlike sea creature about the size of a human hand was one of the earliest animals to evolve a precursor of a backbone. Scientists recently identified the animal’s nerve cord by using a topsy-turvy twist. They turned its fossils upside down.Paleontologist Charles Doolittle Wolcott first encountered fossils of Pikaia in the Burgess Shale deposits of British Columbia, dating to 508 million years ago, and described them in a 1911 treatise. The animal measured roughly 6.3 inches (16 centimeters) long and had a flattened, sinuous body and a tiny head, tipped with two tentacles and fringed with external gills. These were originally thought to be rudimentary legs, so the animal was positioned with these structures facing downward.In 2012, after decades of studying Pikaia fossils, researchers described its fossilized internal structures in great detail. They identified a long strand near the belly as a blood vessel and named a sausage-shaped 3D structure running below the animal’s back as a dorsal organ, possibly used for internal support, though such an organ was anatomically unlike anything seen in fossils or in living animals.However, recent analysis of Pikaia fossils by another team of scientists, published June 11 in the journal Current Biology, has upended this view and all other earlier studies about Pikaia.According to the researchers, earlier anatomical interpretations positioned the animal wrong side up. The so-called dorsal organ was actually located in the belly and was Pikaia’s gut. The presumed blood vessel was a nerve cord, a feature associated with the animal group known as chordates, in the phylum Chordata. Annotated photos show the newly revised organization of Pikaia gracilens. Abbreviations in box C indicate key features in the fossil seen in box B: tentacles on Pikaia’s head (Tc); innervati …

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[mwai_chat context=”Let’s have a discussion about this article:nnSign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.An extinct ribbonlike sea creature about the size of a human hand was one of the earliest animals to evolve a precursor of a backbone. Scientists recently identified the animal’s nerve cord by using a topsy-turvy twist. They turned its fossils upside down.Paleontologist Charles Doolittle Wolcott first encountered fossils of Pikaia in the Burgess Shale deposits of British Columbia, dating to 508 million years ago, and described them in a 1911 treatise. The animal measured roughly 6.3 inches (16 centimeters) long and had a flattened, sinuous body and a tiny head, tipped with two tentacles and fringed with external gills. These were originally thought to be rudimentary legs, so the animal was positioned with these structures facing downward.In 2012, after decades of studying Pikaia fossils, researchers described its fossilized internal structures in great detail. They identified a long strand near the belly as a blood vessel and named a sausage-shaped 3D structure running below the animal’s back as a dorsal organ, possibly used for internal support, though such an organ was anatomically unlike anything seen in fossils or in living animals.However, recent analysis of Pikaia fossils by another team of scientists, published June 11 in the journal Current Biology, has upended this view and all other earlier studies about Pikaia.According to the researchers, earlier anatomical interpretations positioned the animal wrong side up. The so-called dorsal organ was actually located in the belly and was Pikaia’s gut. The presumed blood vessel was a nerve cord, a feature associated with the animal group known as chordates, in the phylum Chordata. Annotated photos show the newly revised organization of Pikaia gracilens. Abbreviations in box C indicate key features in the fossil seen in box B: tentacles on Pikaia’s head (Tc); innervati …nnDiscussion:nn” ai_name=”RocketNews AI: ” start_sentence=”Can I tell you more about this article?” text_input_placeholder=”Type ‘Yes'”]
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