Strange-looking aquatic arthropod had no eyes and moved on stilts

(ORDO NEWS) — Paleontologists recently announced the discovery of an “exceptionally well-preserved” ancient animal off the eastern shore of Lake Simcoe in southern Ontario, Canada, in a rock quarry that is such a hotbed of marine fossils that scientists dubbed the area “Paleo-Pompeii.”

Named Tomlinsonus dimitrii, the species represented by the specimen belongs to an extinct group of arthropods known as marrelomorphs that lived approximately 450 million years ago, during the Ordovician period, the research team reports in a new study.

Other fossil echinoderms that are found in abundance in the area usually contain mineralized body parts that are more likely to survive over time, but this species is completely soft-bodied, which makes the find all the more striking.

“We didn’t expect to find a soft-bodied species at this location,” said study lead author Joseph Moisyuk, a doctoral student in the Department of Ecology and Evolutionary Biology at the University of Toronto and a research fellow at the Royal Ontario Museum (ROM).

“When we think of fossils, we usually think of things like dinosaur bones and shells. However, soft tissues are very rarely preserved, and there are only a few places in the world where soft-bodied organisms have been found,”.

The 2-inch (6-centimeter) specimen slightly less than the length of an index finger and can fit in the palm of the hand has an ornate head shield that bears two curved horns covered with feather-like spikes. The animal’s segmented body resembles that of other arthropods such as insects and spiders and contains several sets of segmented limbs, including one very unusual pair.

“Under the head is an amazing pair of limbs, very long and with protrusions resembling feet at the ends, which we think were most likely used for movement on the seabed,” Moysiuk said. “He is also apparently blind as he has no eyes at all.”

Researchers discovered the bizarre arthropod last summer during an official excavation of a working quarry owned by the Tomlinson Group, an infrastructure maintenance company based in eastern Canada. (The paleontologists named the species Tomlinsonus dimitrii in gratitude to the Tomlinson Group for allowing them to excavate.)

Prior to this excavation, which was led by George Campouris, a co-author of the article and an independent paleontologist who has been exploring the fossil beds of the quarry since 2014, marrelomorphs were found predominantly in older fossil sites, such as the Burgess Cambrian Shale in British Columbia’s Canadian Rocks.

strange looking aquatic arthropod had no eyes and moved on stilts 2

Paleontologists say the recently described specimen is similar to another extinct soft-bodied arthropod called Marrella splendens found in the Burgess Shale.

Like the Burgess Shale, the Lake Simcoe Quarry was once submerged and was part of a shallow tropical sea that covered most of what is now Canada. Over millions of years, the seafloor has been covered with a layer of sediment formed as a result of storms.

“We are seeing rapid burial of these organisms that lived on the flat, shallow ocean floor and were repeatedly smothered by large underwater mudflows resulting from storm events,” Moysiuk said.

“You can imagine how hurricanes hit this shallow shelf and bury the entire community of organisms, which is why we nicknamed this place “Paleo-Pompeii.” These organisms were buried exactly where they lived, and what we see is organisms frozen in time.

Moysyuk and colleagues hope the discovery will help “close a gap” in the fossil record for this group of arthropods, they write in their study.

A specimen of Tomlinsonus dimitrii is now in the ROM collection and is currently on display at the Willner Madge Gallery as part of the Dawn of Life museum display.


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