Sunday, August 7, 2022

One of the largest animals ever discovered in the Alps

Reconstruction of marine ecosystems after devastation at the end of the Permian invited many lineages of reptiles into marine habitats, leading to the famous explosive radiation of marine reptiles in the early Triassic and early Middle Triassic.

Two major lineages of marine reptiles, ichthyosaurs and sauropterygians, were part of this explosive radiation.

As reported in a new paper in the peer-reviewed Journal of Vertebrate Paleontology, paleontologists have discovered a set of fossils representing three new ichthyosaurs that may be one of the largest animals ever discovered.

Discovered in the Swiss Alps between 1976 and 1990, the discovery includes the largest ichthyosaur tooth ever found. The width of the tooth root is twice as large as that of any known aquatic reptile, the last being related to the largest 15 m long ichthyosaur.

Other incomplete skeletal remains include the largest trunk vertebrae in Europe, indicating another ichthyosaur that is the largest marine reptile fossil known today, the 21-metre-long Shastasaurus sikkeniensis from British Columbia, Canada.

Dr. Heinz Fürer, a co-author of this study, was part of a team that recovered fossils during geological mapping in the Kösen Formation of the Alps. Layers of rock covered the ocean floor more than 200 million years ago. However, with the fold of the Alps, they were finished at an altitude of 2,800 meters!

Now a retired curator at the Paleontological Institute and Museum of the University of Zurich, Dr. Furr said he had been “the world’s longest ichthyosaur; with the thickest teeth ever found and the largest trunk vertebrae in Europe!”

The lead author of the University of Bonn, P. Martin Sandler hopes that “perhaps there are more remains of giant sea creatures lurking beneath glaciers.”

“Bigger is always better,” he says. “There are distinct selective advantages to large body size. Life would go there if it could. There were only three animal groups whose mass exceeded 10–20 metric tons: the long-necked dinosaurs (sauropods); whales; and the Triassic giant ichthyosaurs.”

Ichthyosaurs quickly colonized the open ocean, explaining their occurrence throughout the Northern Hemisphere. Ichthyosaurs also grew surprisingly rapidly in body size, with their first appearance in the early Middle Triassic evolving into giant forms with a skull length of 2 m within 5 Ma. Throughout the Triassic, ichthyosaurs appear to have dominated the world’s oceans, showing high diversity and disparity.

These monstrous, 80-ton reptiles patrolled the world ocean around the supercontinent Pangea, Panthalassa, during the Late Triassic, about 205 million years ago. They also entered the shallow seas of Tethys on the eastern side of Pangea, as the new discoveries show.

Ichthyosaurs first emerged after the Permian extinction about 250 million years ago, when about 95 percent of marine species died out. The group reached its greatest diversity in the Middle Triassic, and some species persisted into the Cretaceous. Most s. siknensis and were much smaller than similarly sized species described in the paper.

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Roughly in size with contemporary whales, ichthyosaurs had elongated bodies and erect tail fins. Fossils are concentrated in North America and Europe, but ichthyosaurs have also been found in South America, Asia and Australia. The mammoth species has been traced mostly to North America, with rare discoveries from the Himalayas and New Caledonia, so the discovery of further behemoths in Switzerland represents an extension of their known range.

However, so little is known about these giants that there are only ghosts. A giant toothless jaw bone from the UK and tantalizing evidence from New Zealand suggest that some of them were the size of a blue whale. An 1878 paper reliably describes a 45 cm diameter ichthyosaur vertebra from there, but the fossil never made it to London and may have been lost at sea. Sander noted that “it amounts to a great embarrassment to paleontology that we know so little about these giant ichthyosaurs, despite the extraordinary size of their fossils. We hope to meet this challenge and soon.” New and better fossils will be discovered.

These new specimens probably represent the last Leviathan. “In Nevada, we see the beginning of true giants, and in the Alps, the end,” says Sander, who co-authored a paper last year about an early giant ichthyosaur from Fossil Hill, Nevada. “Only medium to large-sized dolphins—and orca-like forms—survived in the Jurassic.”

giant tooth fragment

“Many giant Late Triassic ichthyosaurs appear to lack teeth. The only definite exception is the Himalayansaurus (Motani et al., 1999) and the teeth described in this study PIMUZ A/III 670.” study is mentioned.

The root of the tooth is found whose diameter is 60 mm. This makes it the thickest ichthyosaur tooth ever found. Credits: © Rosie Roth / University of Zurich

While small ichthyosaurs usually had teeth, most known giant species appear to be without teeth. One hypothesis suggests that they are fed by suction rather than capture their prey. “Bulk feeders among giants should be fed on cephalopods. Those with smaller teeth tend to eat smaller ichthyosaurs and larger fish,” suggests Sander.

The teeth described by the paper are only the second example of a giant ichthyosaur with teeth—the other being the 15-meter-long Himalayasaurus. These species have occupied ecological roles similar to those of modern sperm whales and killer whales. In fact, the teeth are curved inward like their mammalian successors, indicating a grasping method of food adapted to capture prey such as giant squid.

“It’s hard to say whether the tooth is from a large ichthyosaur with huge teeth or a giant ichthyosaur with average-sized teeth,” Sander admitted awkwardly. Because the tooth described in the paper was broken at the crown, the authors could not confidently assign it to a particular taxon. Nevertheless, a peculiarity of dental anatomy allowed researchers to identify it as belonging to ichthyosaurs.

“The teeth of ichthyosaurs have a characteristic that is almost unique among reptiles: the infiltration of dentin into the roots of their teeth,” explains Sander. “The only other group to show this are monitor lizards.”

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the largest vertebra

Two sets of skeletons, the vertebrae, ten rib fragments, and seven related vertebrae, have been assigned to the family Shastasauridae, which includes the giants Shastasaurus, Shonisaurus, and Himalayasaurus. Comparing vertebrae from one set suggests that they may be the same size or slightly smaller than those of S. These measurements are skewed slightly by the fact that the fossils have been tectonically deformed—that is, they have actually been crushed by the motion of tectonic plates, whose collision caused their movement from a former sea floor to a mountain. happened to the top.

Heinz Furrer - With the largest ichthyosaur vertebrae.
Heinz Furrer – With the largest ichthyosaur vertebrae. Credits: © Rosie Roth / University of Zurich

The rocks from which these fossils emerge, known as the Kosen Formation, were once at the bottom of a shallow coastal zone—a very wide lagoon or shallow basin.

This adds to the uncertainty about the habits of these animals, whose size indicates their suitability for the deep reaches of the ocean. “We think that the larger ichthyosaurs followed schools of fish in the lagoon. Fossils may also have been derived from strata dying there,” suggests Fürer.

“You have to be like a mountain goat to reach the respective beds,” Sander laughs. “They have the annoying property of not getting below about 8,000 feet, which is above the treeline.”

“95 million years ago, the northeastern part of Gondwana, the African Plate (which was part of the Kosen Formation) began to push against the European Plate, which ended with the formation of very complex piles of various rock units (called ” “Naps”) in the Alpine orogeny, about 30–40 million years ago, belongs to the furr. Once again found moving up to sea level to enter the scientific record.

Implications of the sample PIMUZ A/III 670:

  1. Many giant Late Triassic ichthyosaurs appear to lack teeth. The only definite exception is the Himalayansaurus (Motani et al., 1999) and the tooth PIMUZ A/III 670 described in this study.
  2. Together with the meager but morphologically different dental material of Himalayasaurus, the tooth suggests the existence of a diversity of giant tooth-bearing ichthyosaurs in the Late Triassic.
  3. The finding underscores the notion that Late Triassic ichthyosaurs were markedly larger than the more familiar Jurassic forms.

“The fossils described in this paper underscore the global distribution and ecological diversity of giant Norian and Ratian ichthyosaurs and the profound fauna trade-off among ichthyosaurs at the end of the Triassic.” Study finished.

journal reference

  1. P. Martin Sander, Pablo Romero Perez de Villar, Heinz Fürer and Tanja Wintrich. Giant Late Triassic ichthyosaurs and their paleobiological implications from the Kosen Formation of the Swiss Alps. Journal of Vertebrate Paleontology, DOI: 10.1080/02724634.2021.2046017
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