Cambrian Explosion: new complete early form (Introduction)

by David Turell , Wednesday, September 28, 2022, 12:08 (787 days ago) @ David Turell

Just reported from China:

https://www.cell.com/current-biology/fulltext/S0960-9822(22)01455-5?dgcid=raven_jbs_aip...

"We describe the first articulated camenellan tommotiid, from the early Cambrian
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Camenellans had seriated, annelid-like chaetal bundles and body outgrowths
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Early lophophorates were armored, vagile animals prior to becoming sessile
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Soft anatomy is vital for understanding the oldest skeletal fossils

"Among extant animals, Lophotrochozoa accounts for the majority of phyla. This bilaterian clade radiated rapidly during the Cambrian explosion, obfuscating its phylogenetic relationships and rendering many aspects of its early evolution uncertain. Many early lophotrochozoans are known only from isolated skeletal microfossils, “small shelly fossils,” often derived from larger animals with complex multi-element skeletons. The discovery of articulated fossils has revealed surprising insights into the animals from which these skeletal pieces were derived, such as paired shells in the mollusc Halkieria. Tommotiids are a key group of phosphatic early skeletal fossils that first appear in the late early Cambrian. Although their affinities were previously obscure, discoveries of partial scleritomes and investigations of growth and microstructure provide links with Brachiopoda7 and Phoronida, two of the lophophorate phyla. By contrast, the body plan of camenellan tommotiids remains a palaeontological mystery, with hypothetical reconstructions representing motile, benthic, dorsally armored worms. Here, we describe an articulated camenellan from the Cambrian Chengjiang Biota, China, revealing the morphology of the scleritome and the first soft tissues from an adult tommotiid. Wufengella carries two dorsal rows of sclerites in a highly asymmetric arrangement, flanked by smaller, cap-shaped sclerites. The scleritome was fringed by iterated fascicles of chaetae and two layers of flattened lobes. Phylogenetic analysis confirms that camenellans occupy a deep branch in lophophorate phylogeny, prior to the acquisition of a sessile lifestyle. Wufengella reveals direct evidence for a metameric body plan reminiscent of annelids early in the evolutionary history of lophophorates."

Commemt: a highly technical article, describing an early Cambrian the point being as usual, nothing like an Edicaran.