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alphynix · 4 years ago

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Cambrian Explosion Month #03: Phylum …Porifera?

Sponges were major reef builders during the Cambrian Explosion, and for the first half of the Cambrian Period the dominant reef-forming group were the bizarre archaeocyathans.

Although their reign was geologically short, lasting only about 15 million years, these tiny calcified sponges were incredibly numerous and diverse during that time, with hundreds of different species known from warm shallow marine waters all around the world. They came in a huge range of shapes, including cups, cones, funnels, towers, and irregular blobs, and were so weird that they weren't even properly recognized as being sponges until the 1990s.

And Yukonensis yukonensis was one of the strangest-looking examples.

Found in Western and Northern Canada (and with a similar species also known from Alabama, USA), this archaeocyathan lived towards the end of the group's heyday about 516-513 million years ago. It was only a few centimeters tall and less than 5mm wide (0.2"), and was made up of a stack of bulbous modular segments (up to at least 18 in some specimens), with whorls of spines with a sort of "webbing" between them giving it an overall appearance vaguely resembling a miniature horsetail or a pagoda.

It's not clear what the purpose of this unusual arrangement was. The spines might have served a defensive function, or the webbing might have hosted symbiotic algae, or the spines and webbing might have been covered in cilia in life to help direct water flow for filter feeding.

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Meanwhile, the evolutionary relationships of another odd group called the chancelloriids are still uncertain.

These animals had bag-like bodies with a single opening at the top, no evidence of defined internal organs, and their skin was bristling with mineralized spines that gave them a cactus-like appearance.

Much like sponges they were sessile filter-feeders that lived anchored to the sea floor, and they're often considered to be "sponge-grade" animals that were either a weird branch of the sponge lineage or very early eumetazoans. (There's also a competing theory that they were instead closely related to the mollusc-like halkieriids due to strong similarities in the structure of their spines, but there were still huge differences in the rest of their anatomy so this idea is currently looking rather unlikely.)

Chancelloria eros was a widespread species of chancelloriid found in mid-Cambrian deposits (~525-505 million years ago) around most of the world, including in the Americas, Europe, Asia, and Australia. It grew up to about 7cm tall (2.75") and was shaped like a slim cone with the wider end at the top.

Both of these groups declined rapidly in the late Cambrian and were completely extinct by the end of the period, probably due to anoxic events and changes in climate and sea level eliminating much of their shallow-water coastal habitats.

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#science illustration #paleontology #paleoart #palaeoblr #cambrian explosion 2021 #yukonensis #archaeocyatha #porifera #sponge #chancelloria #chancelloriid #eumetazoa #animalia #art #i didn't really known about archaeocyathans before i started researching for this month #and honestly? they're super cool and it's a shame they're so obscure compared to the more charismatic cambrian weirdos :c

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wikipress01 · 6 years ago

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‘Nude’ Sea-Creature Belonging To Mysterious Group Identified From Ancient Fossils

An worldwide staff of scientists discovered stays of a “nude” sea-creature, an uncommon animal that lived on Earth greater than half a billion years in the past.

The creature, which has now been named Allonnia nuda, was recognized from fossils found within the Chengjiang deposits of China’s Yunnan province. The stays have been hiding in plain sight, which is why researchers posited the animal in query should have had a “naked” look.

Though there’s hardly any details about the newly-discovered species, the preliminary evaluation of the fossil advised the creature had a surprisingly massive tube-shaped physique again within the day, measuring roughly as much as 50 cm or extra. It even had a couple of tiny spines on its physique.

On the premise of those options, the group has advised the animal belonged to a mysterious group of creatures generally known as chancelloriids.

The new species of fossil chancelloriid: an enigmatic animal from the Cambrian Period with a tube-like physique, “minotaur-horn” spines, and doughnut-shaped scars. Photo: Derek Siveter/Tom Harvey/Peiyun Cong

According to the scant quantity of fossil proof recovered until date, chancelloriids represented a lineage of spiny tube-shaped animals that got here to be in the course of the Cambrian explosion — an evolutionary occasion that occurred 510 to 540 million years in the past and marked a serious surge in Earth’s variety.

The animals thrived for a while after which went extinct, hardly leaving any proof to know their origin or demise. Many theories have been posited to offer perception into the mysterious animals, however none of it may assist scientists decide the place the creatures match within the tree of life.

“Fossil chancelloriids have been first described round 100 years in the past, however have resisted makes an attempt to put them within the tree of life,” Tom Harvey, a member of the staff behind the brand new discover stated in a assertion.

Among varied theories advised for chancelloriids, one indicated the traits of the creature have been fairly much like sponges, a gaggle of easy filter-feeding animals. The thought was broadly debated for a while however dismissed later.

However, the invention of the brand new “nude” sea-creature is as soon as once more supporting the case of sponges. According to the group, the fossil of historic species holds clues in regards to the sample of physique progress and signifies a transparent connection to modern-day sponges.

“We argue that their sample of physique progress helps a hyperlink to sponges, reinvigorating an previous speculation,” Harvey added. “We’re not suggesting that it is “case closed” for chancelloriids, however we hope our outcomes will encourage new analysis into the character of the earliest animals.” The researchers even added that the findings recommend chancelloriids have been extra various than beforehand thought and plenty of extra such fossils might be hiding in plain sight.

The research detailing the fossil discovery was printed June 19 within the journal Proceedings of the Royal Society B.

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from http://www.wikipress.co.uk/science/nude-sea-creature-belonging-to-mysterious-group-identified-from-ancient-fossils/

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