Ichthyosaurs were silent assassins of Jurassic seas
More than 180 million years ago, the ichthyosaurs ruled the first Jurassic oceans. Carnivorous marine reptiles varied from the size of a cheaper case than a school bus. The largest of these whale creatures were the predators of apex, the hunt for old fish, the ammonites and even their reptile little parents. While they were looking for prey, some may have swam with surprising stealth.
A well -preserved ichthyosaur fossil (discovered for the first time on a construction site) reveals a series of unique adaptations to reduce sound, according to a study published on July 16 in the journal Nature. The evolutionary oddities unveiled by the new research offer an overview of how a subset of ichthyosaurs lived and hunted – and could lead to a better understanding of the existing fossils in the file.
“The preservation of soft tissues in this fossil is only one of those incredible discoveries that you fall once in a life, perhaps,” says Lars Schmitz, paleontologist and functional morphologist at Claremont McKenna College who was not involved in the study, says Popular science. But what makes work particularly exciting is not only “pure luck”, says Schmitz. It is also the thoroughness with which the authors approached the discovery.
“It is a really unique and very interdisciplinary analysis, with a whole range of innovative techniques,” he notes. Using advanced imaging tools such as electron microscopes and X -rays, coupled with computer modeling, scientists have reconstructed the “what” and the “why” of a puzzle of the Jurassic era puzzle.
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Resolve the puzzle
In this case, “puzzle” puzzle “is not really a metaphor. The fossil was unearthed on a construction site in southwest Germany in 2009. A controlled explosion has traveled a layer of loose limestone from shale, and dispersed pieces of rock bearing a detailed impression of an ichthyosaur fin. A collector of fossils, given a few hours to study the construction area, gathered all the parts he could – amassing a range of strange size slabs.
From there, the fragments were transmitted to various experts in ichthyosaurus and fossils, who tried to assemble them. Finally, more than a decade later, Johan Lindgren, a paleontologist at Lund University in Sweden and the study of the study, gave him a chance.
“One day, around Christmastime for a year, I thought,” Now let’s solve that once and for all, “he said Popular science.
Lindgren seated a large table, reorganizing the pieces of sand. He was able to combine all the segments in a complete and coherent form after realizing that some of the bits included a second smaller freak. “It was a great breakthrough. Then I realized: yes, everything is here. ”
The resolution of the physical puzzle turned out to be the beginning. Once the fin is assembled, it was clear that this separate fossil was worth a more in -depth examination. Long skin and flesh had left rare marks in the rock, alongside the more standard bones. According to Lindgren and his colleagues, the fossil is the First of all Printing soft fabrics found from Tempnodontosaurus. This kind of large ichthyosaur (some exceeding 30 feet long) was the first to be discovered in the 1810s by Mary and Joseph Anning.
The fossil fascinating first is also full of idiosyncrasies. “I have studied these critters for some time now, and I have never seen anything like this before,” explains Lindgren.
An adjustment of the Naignée Dévelélé for a predator
On the one hand, the proportions of the fin are unique – it is particularly long and thin. The end of the fin lacking bone, leaving a gentle and flexible point that we do not see in other examples of known or known extinguished animals. Then there are uniformly spaced lines over the entire surface and distinct lace on the leak edge. X -ray microscopy has shown that these lace was entirely composed of cartilage integrated into the skin, another oddity. Some animals, including living reptiles and mammals, have pieces of bone in their skin to protect themselves, called osteoderms. But no other known animal shows signs of cartilage intertwined in the skin in the same way, notes Lindgren. He and his co-authors offer a new term for the structures never seen before: chondrodermsAfter the Greek words for cartilage and skin.
“This document shows that there are still surprises to find in Ichthyosaur Evolution,” explains Nicholas Pyenson, paleontologist and conservative at the Smithsonian Museum of Natural History, says Popular science. “And that we have to look at our fossils much more carefully,” he adds.
So what were all these remarkable features for? Considering both human inventions and birds brought Lindgren to a hypothesis. Wind turbines, propellers and planes are often built with a serrated leakage edge to reduce noise. The owls manage the almost silent flight with a similar structure: the shred edges along the bottom of their wings. And if the same was true for Temnodontosaurus?
Chicken from the sea, meet the ocean owl
Genre individuals had the greatest eyes of all known vertebrates, alive or extinct. Previous studies have suggested that their peepers in the size of a dinner plate had giant reptiles to navigate and hunt in weakly lit environments, either at night or in deep water, adding fuel to the comparison of owls. In these contexts, the sound would have been the key to prey who try to avoid being eaten and for the predators who are trying to listen to their food. The two factors may have contributed to the evolutionary pressure on ichthyosaurs, promoting furtive swimming, explains Lindgren.
“I thought, okay, and then if we essentially had a owl 10-meter underwater,” he said.
To check the idea, the team created a partial computer model of the fossil, including lace and parallel horizontal ridges. Using previous research, estimating ichthyosaurs’ swimming speeds and educated hypotheses on the angle of attack, they tested the effects of each trait on swimming noises of the variable frequency. The surface crests and the on -board serrated have proven to be promising to minimize noise, depending on the simulation – especially for the low frequencies that travel the furthest underwater. The reduction in modeled sound was as high as 10 decibels – roughly the equivalent of the effect of carrying foam ear caps. The flexible tip of the fin and other features such as the body shape may have added additional detangling, says Lindgren. However, he and his colleagues have not yet created the additional complex models necessary to test it.
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Inspire life in the fossil file
“They did the right absolute thing,” says Pyenson. “They have experimental data to show the effect of the structure of the alleged function. It is about as convincing as you get … This breathes life in the fossil file.”
However, certain conclusions are impossible to draw from a single fin, all sources say Popular science. The rest of Temnodontosaurus’ The characteristics of the soft tissues remain a mystery, and the fin fossil has no key details, such as the lateral profile of the appendix, which would have a great impact on the way it moved into the water. In addition, strategic stealth may not explain everything on the fossil fin. Schmitz says that it is possible that the unique characteristics have been motivated by something more direct: speed and maneuverability.
“My intestine is that it was probably a hydrodynamics first, then a damping of the sound was a beautiful side effect,” he explains. He hopes to see other modeling experiences dig into alternative explanations.
Schmitz also hopes that other scientists take note. Now that these characteristics of the soft tissue have been identified on an ichthyosaurus, paleontologists can revisit other fossils to see what is potentially neglected. It could even stimulate the reassessment of modern marine animals, adds Schmitz. There may be a crest, a bump or a cartilaginous piece with an acoustic goal still unknown, hiding on a porpoise.
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