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Discovery of 500-million-year-old fossil reveals astonishing secrets of tunicate origins

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Artistic reconstruction of Megasiphon thylakos, a benthic organism that lived directly on the seafloor. M. thylakos was also sessile (non-moving) and spent its time filter feeding using its prominent siphons. Also reconstructed in the vicinity are other species commonly found in the Marjum Formation, the site from which M. thyalkos was discovered. Nearby brachiopods (bottom center) and the spiny sponge Choia (center middle) are common in many Cambrian environments. In the background is the hemichordate Oesia, which lived in perforated tubes. Credit: Original artwork by Franz Anthony

Karma Nanglu says his favorite animal is whichever one he’s working on. But his latest subject may hold first place status for a while: a 500-million-year-old fossil from the wonderfully weird group of marine invertebrates, the tunicates.

“This animal is as exciting a discovery as some of the stuff I found when hanging off a cliffside of a mountain, or jumping out of a helicopter. It’s just as cool,” said Nanglu, postdoctoral researcher in the Department of Organismic and Evolutionary Biology at Harvard University.

In a new study in Nature Communications, Nanglu and co-authors describe the new fossil, named Megasiphon thylakos, revealing that ancestral tunicates lived as stationary, filter-feeding adults and likely underwent metamorphosis from a tadpole-like larva.

Tunicates are truly strange creatures that come in all shapes and sizes with a wide variety of lifestyles. An adult tunicate’s basic shape is typically barrel-like with two siphons projecting from its body. One of the siphons draws in water with through suction, allowing the animal to feed using an internal basket-like filter device. After the animal feeds, the other siphon expels the water.

There are two main tunicate lineages, ascidiaceans (often called “sea squirts”) and appendicularias. Most ascidiaceans begin their lives looking like a tadpole and mobile, then metamorph into a barrel shaped adult with two siphons. They live their adult life attached to the seafloor. In contrast, appendicularians retain the look of a tadpole as they grow to adults and swim freely in the upper waters.

“This idea that they begin as tadpole-looking larva that, when ready to develop, basically headbutts a rock, sticks to it, and begins to metamorphosis by reabsorbing its own tail to transform into this being with two siphons is just awe-inspiring,” sais Nanglu.

Discovery of 500-million-year-old fossil reveals astonishing secrets of tunicate origins
Comparisons between the new Cambrian tunicate Megasiphon thylakos (a,b) with some modern tunicates (c,d,e). In particular, M. thylakos shares the rounded vase or barrel-like body and prominent pair of siphons of the modern ascidiacean tunicates. Given the fact that M. thylakos is half-a-billion years old, this suggests that ancestrally, tunicates lived much like modern ascidiaceans: they had a non-moving adult form with siphons for filter feeding, a body plan that was arrived at after metamorphosing from a tadpole-like juvenile. The modern species represented are c: Ciona, d: Ascidiella, e: Molgula. Credit: Rudy Lerosey-Aubril (a,b) and Karma Nanglu (c,d,e)

Interestingly, tunicates are the closest relatives of vertebrates, which includes fish, mammals, and even humans. How this odd-looking creature could be related to vertebrates is hard to imagine were it not for that tadpole beginning. Tunicate’s close relationship to vertebrates makes studying them critical for understanding our own evolutionary origins. Unfortunately, it’s not easy to do as tunicates are almost completely absent from the entire fossil record, with only a handful of fossils appearing convincingly as members of the group.

With so few fossils, scientists relied mainly on what could be learned from modern tunicate species. Because no one knew the morphology and ecology of the last common ancestor of the tunicates, scientists could only hypothesize that it was either a benthic animal with two siphons, like the ascidiaceans, or a free-swimming animal like the appendicularians.

M. thylakos had all the basic hallmarks of an ascidiacean tunicate, a barrel-shaped body and two prominent siphon-like growths. But the feature that stood out to the team was the dark bands running up and down the fossil’s body.

High powered images of M. thylakos allowed the researchers to conduct a side-by-side comparison to a modern ascidiacean. The researchers used dissected sections of the modern tunicate Ciona to identify the nature of Megasiphon’s dark bands. The comparisons revealed remarkable similarities between Ciona’s muscles, which allow the tunicate to open and close its siphons, and the dark bands observed in the 500-million-year-old fossil.

“Megasiphon’s morphology suggests to us that the ancestral lifestyle of tunicates involved a non-moving adult that filter fed with its large siphons,” said Nanglu. “It’s so rare to find not just a tunicate fossil, but one that provides a unique and unparalleled view into the early evolutionary origins of this enigmatic group.”

M. thylakos is the only definitive tunicate fossil with soft tissue preservation that has been discovered to date. It is the oldest of its kind originating from the middle Cambrian Marjum Formation in Utah. The fossil was recognized as a tunicate by co-authors research associate, Rudy Lerosey-Aubril, and Professor Javier Ortega-Hernández (both in the Department of Organismic and Evolutionary Biology) while visiting the Utah Museum of Natural History (UMNH) in 2019.

Discovery of 500-million-year-old fossil reveals astonishing secrets of tunicate origins
Details of the anatomy of Megasiphon thylakos. M. thylakos had two prominent siphons and a barrel shaped body. It also had prominent longitudinal muscles running from the tips of the siphons to the base of the body. These are comparable with modern tunicates, including Ciona intestinalis, which is dissected in c and f. Even the micrometer sized individual muscle fibers can be compared between this 500-million year old fossil and modern tunicates. Credit: James Wheeler (a,d) and Karma Nanglu (b,c,e,f,g)

“The fossil immediately caught our attention,” said Ortega-Hernández, “although we mostly work on Cambrian arthropods, such as trilobites and their soft bodied relatives, the close morphological similarity of Megasiphon with modern tunicates was simply too striking to overlook, and we immediately knew that the fossil would have an interesting story to tell.”

Fossils from the Marjum Formation date from shortly after the Cambrian Explosion, one of the most significant evolutionary events in Earth’s history which occurred approximately 538 million years ago. During this time the most major animal groups appeared in the fossil record for the first time radically changing marine ecosystems. Tunicates, however, are noticeably absent in Cambrian rocks even though they are diverse and abundant in modern oceans.

There are many Cambrian fossil sites with exceptional preservation in the United States, but these are often overlooked compared to those from the Burgess Shale in Canada and Chengjiang in China. “The discovery of Megasiphon perfectly illustrates why Javier and I have been conducting fieldwork in Utah for the last ten years,” said Lerosey-Aubril. “The Marjum strata has all of our attention right now as we know that it preserves fossils of animal groups, such as tunicates or comb jellies, that are almost entirely absent from the Cambrian fossil record.”

Molecular clock estimates suggest that ascidiaceans originated 450 million years ago. However, at 500 million years old, M. thylakos provides the clearest view into the anatomy of ancient tunicates and their earliest evolutionary history. Significantly, M. thylakos provides evidence that most of the modern body plan of tunicates was already established soon after the Cambrian Explosion.

“Given the exceptional quality of preservation and the age of the fossil, we can actually say quite a bit about the evolutionary history of the tunicates,” said Nanglu. “This is an incredible find as we had virtually no conclusive evidence for the ancestral modes of life for this group before this.”

After collecting hundreds of new fossils again this spring, the researchers are convinced the Marjum Formation has only started to reveal its secrets.

More information:
A mid-Cambrian tunicate and the deep origin of the ascidiacean body plan, Nature Communications (2023). DOI: 10.1038/s41467-023-39012-4

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Harvard University, Department of Organismic and Evolutionary Biology

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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