Paleontologists solve mystery of fossil death bed - CNN

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The last resting spot for dozens of monolithic prehistoric marine reptiles lies successful what’s now Nevada’s Humboldt-Toiyabe National Forest.

But wherefore the ichthyosaurs died successful specified ample numbers astatine this 1 peculiar fossil tract some 230 cardinal years agone has agelong been a root of statement among paleontologists. Scientifically known arsenic Shonisaurus popularis, the taxon resembled a chunky dolphin and grew astatine slightest 50 feet (15.2 meters) long.

Theories suggested a wide stranding lawsuit oregon that the ichthyosaurs were poisoned by toxins from an algal bloom.

Now, though, scientists accidental that they person ruled retired these hypotheses and person a overmuch amended knowing of wherefore 37 of the past creatures died astatine the aforesaid location. The researchers judge their findings illuminate a fascinating facet of the reptile species reproductive behavior, which is shared by immoderate of today’s marine mammals.

“We contiguous grounds that these ichthyosaurs died present successful ample numbers due to the fact that they were migrating to this country to springiness commencement for galore generations crossed hundreds of thousands of years,” said survey coauthor Nicholas Pyenson, a probe geologist and curator astatine the Smithsonian National Museum of Natural History in Washington, DC, successful a quality release.

“That means this benignant of behaviour we observe contiguous successful whales has been astir for much than 200 cardinal years.”

Present-day whale species, including bluish and humpback whales, routinely migrate crossed oceans to breed and springiness commencement successful waters wherever predators are scarce. Many whales congregate twelvemonth aft twelvemonth on the aforesaid stretches of coastline.

“There are different examples of ichthyosaur embryos and newborns, but this is the archetypal clip we person beardown grounds for reproductive grouping behavior,” said study coauthor Randy Irmis, main curator and curator of paleontology astatine the Natural History Museum of Utah successful Salt Lake City.

“We cognize this is thing galore ample marine vertebrates grounds successful the present, truthful it makes consciousness that simialr behaviour occurred successful the past. But we truly didn’t cognize however acold back, particularly with extinct carnal groups similar ichthyosaurs, that person nary adjacent surviving relatives,” Irmis said successful an email to CNN.

The researchers from the United States, United Kingdom and Belgium utilized caller techniques, specified arsenic 3D modeling, to analyse the fossil site, which is portion of Berlin-Ichthyosaur State Park.

The squad examined the chemic constitution of rocks surrounding the fossils and recovered nary grounds of immoderate abrupt increases successful integrated matter, specified arsenic algae, that mightiness person starved the creatures of oxygen.

Geological grounds besides suggested the ichthyosaurs’ bones had sunk to the bottommost of the sea, which past covered overmuch of present-day Nevada, rather than on a shoreline shallow capable to suggest the marine reptiles had beached themselves.

What’s more, the squad noticed the fossils were predominantly of big ichthyosaurs, with precise fewer different marine vertebrates present. Nor were determination immoderate juvenile ichthyosaurs.

A breakthrough came erstwhile tiny ichthyosaur remains were identified among some caller fossils collected astatine the tract and wrong older depository collections. Micro-CT X-ray scans revealed the tiny bones belonged to embryonic and newborn ichthyosaurs.

“Once it became wide that determination was thing for them to devour here, and determination were ample big Shonisaurus on with embryos and newborns but nary juveniles, we started to earnestly see whether this mightiness person been a birthing ground,” said pb writer Neil Kelley, a probe adjunct prof successful Earth and biology sciences astatine Vanderbilt University successful Nashville, Tennessee, successful the quality release.

The authors concluded that the country indispensable person been a preferred birthing situation for the prehistoric creatures — and that the precocious fig of fossilized remains was a effect of the precocious numbers of ichthyosaurs that congregated there, possibly implicit millions of years, to springiness birth.

“This is simply a wide ecological signal, we argue, that this was a spot that Shonisaurus utilized to springiness birth, precise akin to today’s whales. Now we person grounds that this benignant of behaviour is 230 cardinal years old,” Pyenson said.

The diary Current Biology published the probe connected Monday.