An ancient graveyard full of fossils of extinct marine reptiles may have served as the birthplace 230 million years ago.
Berlin Ichthyosaur State Park (BISP) in Nevada, USA, houses the remains of at least 37 ichthyosaurs – fish-shaped reptiles that were once the size of a school bus.
Now scientists at the Smithsonian Institution in Washington DC believe the site is the final resting place of so many because they went there to give birth.
Ichthyosaurs, which became extinct about 90 million years ago, migrated to the site to avoid danger, as do today’s blue and humpback whales.
Ichthyosaurs, or Shonisaurus popularis, were a species of reptile that thrived in the Triassic, Jurassic, and Cretaceous periods. Pictured: Artist’s reconstruction of the life of adult and neonatal Triassic ichthyosaurs
3D model of the ichthyosaur fossil bed from above in Quarry 2. Fossilized bones representing at least seven separate ichthyosaur skeletons have been color-coded, with each color corresponding to a different skeleton
WHAT WERE ICHYTHYOSAURS?
Ichthyosaurs were an extremely successful group of marine reptiles that became extinct about 90 million years ago.
They emerged during the Triassic, peaked during the Jurassic, and disappeared during the Cretaceous.
Often misidentified as swimming dinosaurs, these reptiles appeared before the first dinosaurs appeared.
They evolved from a yet-unidentified land reptile that moved back into the water.
Scientists calculate that one species had a cruising speed of 36 km/h.
The largest ichthyosaur species is believed to have grown to over 20 meters in length.
At 3.5 m (11 ft), the largest complete fish explorer fossil ever discovered still has a fetus in its womb.
Ichthyosaurs, or Shonisaurus popularis, were a species of reptile that thrived in the Triassic, Jurassic, and Cretaceous periods.
They emerged from the ocean about 252 million years ago and migrated to land before eventually evolving back into water.
Their name means “fish lizards” in Greek and they are famous for their fish-like shape, which resembles today’s dolphins.
A collection of 50-foot-long ichthyosaurs fossilized in stone at the BISP has baffled paleontologists for more than half a century.
Many theories have been put forward as to why they all died there, including a mass stranding event or that they were poisoned by a toxin from a nearby algal bloom.
However, enough evidence has yet to be found to undeniably prove one of them.
For the study, published today in Current Biology, researchers took a closer look at the ichthyosaur fossils in BISP’s “Quarry 2” to see if they could find any.
The seven people remaining there all appear to have died around the same time.
Researchers physically measured and documented their bones and reanalyzed archived museum data.
They also created a 3D model of the fossil repository using hundreds of photos and millions of point measurements taken on site.
dr Neil Kelley of Vanderbilt University said this model allowed them “to study the way these large fossils were arranged in relation to each other without losing the ability to go bone by bone.”
A collection of 50-foot-long ichthyosaurs fossilized in stone at the BISP has baffled paleontologists for more than half a century. Pictured: Fossil ichthyosaur skeletons in Quarry 2 of the BISP
Many theories have been put forward as to why they all died there, such as a mass stranding event or that they were poisoned by a toxin from a nearby algal bloom. Pictured: Ichthyosaur skeleton at BISP
The team also collected samples from the rock surrounding the fossils and conducted geochemical tests that could reveal what killed the animals.
The first was for mercury, which would suggest the culprit was a large-scale volcanic eruption, but no significant amounts were found.
Next, they checked the presence of different types of carbon, which would indicate a rapid increase in organic matter in marine sediments from an algal bloom.
Algae can deprive the water of oxygen and suffocate marine life, and while ichthyosaurs breathed air, an event like this could have deprived them of prey.
Again, there was no evidence of this, so the team next examined the geology and fossils in the limestone surrounding Quarry 2.
They found geological evidence that suggests the bones of the ichthyosaurs sank to the ocean floor after they died, rather than a flat shoreline.
This ruled out a mass stranding event as the reason for the dense fossil bed.
Berlin Ichthyosaur State Park (BISP) in Nevada, USA, houses the remains of at least 37 ichthyosaurs – fish-shaped reptiles that were once the size of a school bus. Pictured: modern (left) and approximately 230 million years ago paleomap (right) of western North America
For the study, the researchers physically measured and documented their bones and reanalyzed archived museum data. Pictured: skeletal reconstruction of Triassic ichthyosaurs
Ichtyhosaurs — meaning “fish lizards” in Greek — were a species of reptile that thrived in the Triassic, Jurassic, and Cretaceous periods, between 252 and 90 million years ago
The researchers also found that apart from the remains of ichthyosaurs, there was very little fossil evidence that other vertebrates were present at the site.
co-author dr. Nicholas Pyenson said: “In this place there are so many large adult skeletons of this one species and almost nothing else.
“There are virtually no remains of things like fish or other marine reptiles for these ichthyosaurs to feed on, nor are there any juvenile Shonisaurus skeletons.”
This suggests that the only ones present had reached sexual maturity.
The researchers found that apart from the remains of ichthyosaurs, there was very little fossil evidence that other vertebrates were present at the site. Pictured: Fossil ichthyosaur skeletons in Quarry 2 of the BISP
Eventually, the paleontologists found evidence that supported a theory instead of disproving it — tiny bones and teeth.
Visualization with micro-CT X-ray scans and comparison with other remains revealed that these were from embryonic and newborn ichthyosaurs.
“When it became clear that there was nothing to eat here and that there were large adult Shonisaurus along with embryos and newborns but no juveniles, we began to seriously consider whether this could have been a birthplace,” said Dr. Kelly.
Modern sea giants like blue, humpback and gray whales are migrating to warmer waters where there are fewer predators to mate and give birth to offspring.
Sometimes they travel thousands of miles to the same areas every year, and this research suggests that ichthyosaurs have done the same.
The rock strata housing various BISP fossil deposits suggest that they were used up to millions of years apart. Pictured: fragment of the snout of an ichthyosaur
Further research will examine other ichthyosaur fossil beds in North America and attempt to identify them as other breeding or feeding grounds. Pictured: fragment of the snout of an ichthyosaur with a tooth
The rock strata housing various BISP fossil deposits suggest that they were used up to millions of years apart.
As a result, researchers believe the same growing medium has been used by ichthyosaurs for generations.
said dr pyenson “This is a clear ecological signal, we argue, that this was a place where Shonisaurus once gave birth, very similar to modern-day whales.”
“Now we have evidence that this type of behavior is 230 million years old.”
Further research will examine other ichthyosaur fossil beds in North America and attempt to identify them as other breeding or feeding grounds.
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Ichthyosaurs had BLUBBER just like whales
From seals to whales, many marine animals have a thick layer of fat known as blubber just under their skin.
Now a new study has shown for the first time that ichthyosaurs — ancient marine reptiles that lived 150 million years ago — also had blubber.
Scientists from the Natural History Museum in Oslo have examined the remains of an ichthyosaur discovered near Solnhofen in southern Germany.
The specimen contains the complete internal skeleton, which the team said was remarkably well preserved thanks to its blubber.
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