Relative of one of Cambrian Period's stranger critters discovered

[rogue06]

"The weirdest wonder of the Cambrian no longer stands alone" is the concluding sentence of a recently released paper regarding a discovery in Utah in Cambrian aged deposits that is now being classified as a relative of the strange creature known as Opabinia regalis.

Until now Opabinia, an extinct, stem group arthropod from the Middle Cambrian Burgess Shale of British Columbia, was so unique (described as "alien-faced") that scientists had never discovered anything else in the fossil record that appears to fit into its family.

Basically, Opabinia was a soft-bodied creature up to 7cm (2¾") long possessing five eyes and a long striped proboscis that resembled an elephant's trunk, or a vacuum cleaner hose, terminating with a claw-like structure that likely passed food to the mouth. -- which was located under the head, behind the proboscis, and pointed backwards. It probably lived on the seafloor, using the proboscis to seek out small, soft food.

But enough about Opabinia. What's new is that researchers apparently discovered a relative that lived a few million years after Opabinia further south in the roughly 507 myo Wheeler Formation in Millard County, western Utah that is called Utaurora comosa.

The creature's first or genus name is a combination of Utah (where the specimen was found) and Aurora (name of a Roman goddess who turned a lover into an insect, and Utaurora is an early species close to the origin of arthropods), while the second or species name is Latin for "hairy" or "leafy" which refers to Utaurora's hairy-looking dorsal surface and leaf-like arrangement of caudal blades on its tail.

Utaurora's tail is spiker than the fan-like one possessed by Opabinia (having nearly twice as many caudal blades) and IIRC the proboscis is missing from the specimen so we don't know what it was like.

Until now it was regarded as potential relative of the apex Cambrian predator -- the Anomalocaris (another bizarre organism from that time). But unlike Anomalocaris, the much smaller Utaurora had no appendages on its head and possessed a body that was segmented into 14 or 15 furrow that were each tipped with a flap -- like what is seen on Opabinia.

This led a team of researchers, led by Stephen Pates of Harvard's Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, to reexamine Utaurora conducting a series of various phylogenetic tests which compared 125 of the fossil’s traits with more than 50 groups of both extant (still living) and extinct arthropods.

The team's analysis allowed them to construct detailed evolutionary trees permitting them to eliminate any relationship with the radiodont family and instead conclude that Utaurora was almost certainly closely related to Opabinia.

Source: One of Evolution’s Oddest Creatures Finds a Fossilized Family Member

Opabinia, which swam the seas of Earth’s Cambrian era some 500 million years ago, was not just a one hit wonder.

Of all the strange creatures unearthed from the Burgess Shale — a cache of remarkable Cambrian fossils deposited in the Canadian Rockies — none has been quite as transfixing as Opabinia. And for good reason — with five compound eyes and a trunk-like nozzle that ended in a claw, Opabinia seems otherworldly, like something imagined in a science fiction novel, rather than a swimmer in Earth’s oceans some 500 millions years ago.

In “Wonderful Life,” his best-selling opus on the Burgess Shale, the evolutionary biologist Stephen Jay Gould labeled Opabinia as a “weird wonder,” and said it belonged among the pantheon of evolutionary icons like Archaeopteryx, Tyrannosaurus rex and archaic human ancestors.

However, Opabinia has remained shrouded in evolutionary mystery because of a frustrating lack of fossils. The bulk of Opabinia specimens were collected more than a century ago and the creature has never been found outside of the Burgess Shale.

Which was why Stephen Pates, a paleontologist, was so perplexed when he stumbled upon an odd fossil stored at the Natural History Museum at Kansas University in 2017. At the time, Dr. Pates was a graduate student studying the diversity of radiodonts, Cambrian predators that sported grasping, claw-like appendages. But the ghostly orange imprint before him lacked the trademark appendages.

“When I first looked at it, I wasn’t sure what it was, but I wasn’t sold that it was a radiodont,” said Dr. Pates, who is currently a researcher at the University of Cambridge.

The fossil had been unearthed in western Utah, and it had zigzagging body flaps and a tail brimming with enough spikes to make a Stegosaurus jealous. The traits were reminiscent of Opabinia, but the creature’s poorly preserved head was little more than a crimson smear, obscuring the proboscis and generous allotment of eyes.

To determine the identity of the Cambrian creature, Dr. Pates teamed up with several researchers at Harvard University, where he was a postdoctoral researcher, to run the fossil through a variety of phylogenetic tests. They compared 125 of the fossil’s traits with more than 50 groups of modern and extinct arthropods and built detailed evolutionary trees.

According to Joanna Wolfe, a research associate at Harvard and co-author of the new research, the evolutionary trees allowed the team to rule out radiodonts and conclude that the new fossil was likely closely related to Opabinia, the Burgess Shale’s lonely wonder.

In a paper published Wednesday in Proceedings of the Royal Society B, the team described the fossil as only the second opabiniid ever discovered. They named the new species Utaurora comosa, after the Roman goddess of the dawn, Aurora, who turned her lover into a cicada — one of the innumerable arthropods that came after Utaurora.

While the animal still looks more alien than arthropod, the researchers believe that Utaurora represents an important predecessor to the evolution of insects and crustaceans. Opabiniids were the first groups to possess backward-facing mouths and their furrowed flaps appear to have been a precursor to segmentation, both common characteristics of modern arthropods, according to Dr. Pates.

However, it wouldn’t resemble any arthropod living today. As it undulated through an ancient sea with its flaps and spiky tail fan, Utaurora likely wielded its proboscis to shovel food into its mouth. Opabinia looked similar, although there were key differences between the two species. The younger Utaurora sported more spikes on its tail and, at just over 1 inch long, its body was half the size of Opabinia’s.

The researchers believe the new discovery puts Opabinia in context, illustrating that one of the planet’s strangest creatures was not just a one hit wonder. “They were part of the bigger picture of what was going on and not just this weird curiosity,” Dr. Pates said.

While Opabinia is no longer unique, the minuscule sea creature is no less captivating to Dr. Wolfe, who grew up reading “Wonderful Life,” and credits Gould’s enthralling description of Opabinia as a catalyst for her paleontological career.

“I guess it’s not actually such a weird wonder now, but I don’t think that makes it less of a wonder,” she says. “It’s just not so weird.”



Source

© Copyright Original Source

The entire paper, New opabiniid diversifies the weirdest wonders of the euarthropod stem group is available for reading at the provided hyperlink, and the abstract from it is below:

Abstract

Once considered ‘weird wonders’ of the Cambrian, the emblematic Burgess Shale animals Anomalocaris and Opabinia are now recognized as lower stem-group euarthropods and have provided crucial data for constraining the polarity of key morphological characters in the group. Anomalocaris and its relatives (radiodonts) had worldwide distribution and survived until at least the Devonian. However, despite intense study, Opabinia remains the only formally described opabiniid to date. Here we reinterpret a fossil from the Wheeler Formation of Utah as a new opabiniid, Utaurora comosa nov. gen. et sp. By visualizing the sample of phylogenetic topologies in treespace, our results fortify support for the position of U. comosa beyond the nodal support traditionally applied. Our phylogenetic evidence expands opabiniids to multiple Cambrian stages. Our results underscore the power of treespace visualization for resolving imperfectly preserved fossils and expanding the known diversity and spatio-temporal ranges within the euarthropod lower stem group.

rspb20212093f01 (1).gif
Comparison of Opabinia regalis (top), and Utaurora comosa (bottom two)

[rogue06]

i2784R.jpg

tumblr_cc8574f14ae81b649161d898b89151b1_f90f0733_540.gif
A gif I ran across illustrating Opabinia's snout range of motion and
expected movement to reach the anterior appendage to the mouth
[mouth & digestive tract in yellow]

[TheLurch]

Wait, is that a chart of phylogenetic relationships among Cambrian animals? I've been told that is unpossible multiple times in other threads, so I fear I must be hallucinating.

[rogue06]

Wait, is that a chart of phylogenetic relationships among Cambrian animals? I've been told that is unpossible multiple times in other threads, so I fear I must be hallucinating.

I'm deeply saddened that it wasn't the gif that drew your attention.


Endeavoring to persevere... here's the entire figure:

rspb20212093f04.jpg

Figure 4. Phylogenetic relationships of opabiniids and lower stem group euarthropods. (a) Summarized topology
based on the consensus tree retrieved with BI under minimize assumptions parameters. Numbers at the key
node indicate posterior probabilities from this analysis, and from BI under maximize information parameters.
(b) Treespace plotted by bipartition resolving Utaurora. Points are coloured by relationships for this taxon. (c) Treespace plotted by analysis.

Credits removed but are in the original

[lee_merrill]

Wait, is that a chart of phylogenetic relationships among Cambrian animals? I've been told that is unpossible multiple times in other threads, so I fear I must be hallucinating.

I don't say it's impossible, I only say a procedure that can generate inconsistent results is in trouble.

Blessings,
Lee

[TheLurch]

I don't say it's impossible, I only say a procedure that can generate inconsistent results is in trouble.

That's actually not what you said, but I'm no longer surprised that you don't remember your own arguments.