Cambrian Explosion: a complex animal from Utah (Introduction)

by David Turell @, Saturday, September 15, 2018, 19:46 (67 days ago) @ David Turell

Many new areas are opened to the Cambrian fossils, this one in Utah has been known for almost 50 years and is hig holy complex and helps in the food chain:

https://phys.org/news/2018-09-half-billion-year-old-fossils-clues-life-sea.html

"With Dr. Rudy Lerosey-Aubril from New England University (Australia), he meticulously re-examined fossil material collected over 25 years ago from the mountains of Utah, USA.

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"Twenty hours of work with a needle on the specimen while submerged underwater exposed numerous, delicate microscopic hair-like structures known as setae. This revelation of a frontal appendage with fine filtering setae has allowed researchers to confidently identify it as a radiodont – an extinct group of stem arthropods and distant relatives of modern crabs, insects and spiders.

"'Our new study describes Pahvantia hastasta, a long-extinct relative of modern arthropods, which fed on microscopic organisms near the ocean's surface," says Stephen Pates. "We discovered that it used a fine mesh to capture much smaller plankton than any other known swimming animal of comparable size from the Cambrian period. This shows that large free-swimming animals helped to kick-start the diversification of life on the sea floor over half a billion years ago."


"Causes of the Cambrian Explosion—the rapid appearance in the fossil record of a diverse animal fauna around 540-500 million years ago—remain hotly debated. Although it probably included a combination of environmental and ecological factors, the establishment of a system to transfer energy from the area of primary production (the surface ocean) to that of highest diversity (the sea floor) played a crucial role.

"Even though relatively small for a radiodont (FIG), Pahvantia was 10-1000 times larger than any mesoplanktonic primary consumers, and so would have made the transfer of energy from the surface oceans to the deep sea much more efficient. Primary producers such as unicellular algae are so small that once dead they are recycled locally and do not reach the deep ocean.

"In contrast large animals such as Pahvantia, which fed on them, produce large faecal pellets and carcasses, which sink rapidly and reached the seafloor, where they become food for bottom-dwelling animals.

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"The study has produced the most up-to-date analysis of evolutionary relationships between radiodonts. It shows that filter feeding evolved twice, possibly three times in this group, which otherwise essentially comprised fearsome predators such as Anomalocaris canadensis from the Burgess Shale in Canada.

"Pahvantia adds to an ever-growing body of evidence that radiodonts were vital in the structure of Cambrian ecosystems, in this case linking the primary producers of the surface waters to the highly diverse fauna on the sea floor."

Comment: An early example of balance of nature. And once again, a highly complex animal with no demonstrated precursor from the Ediacaran.


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