The curious arrangement of giant bones in a prehistoric ocean graveyard has caused one paleontologist to propose the existence of a giant squid-like kraken that preyed on bus-size "sea monsters."
Other scientists, though, say the fossils can easily be explained without resorting to theories based on kraken—mythological sea monsters perhaps based on centuries-old sightings of giant squid or octopuses.
The fossils in question are about 350 miles (560 kilometers) northwest of Las Vegas, in Nevada's Berlin-Ichthyosaur State Park—a seafloor at the time the bones were deposited, some 200 million years ago. (See related pictures: "'Sea Monster' Graveyard Found in the Arctic.")
The fossils are circular vertebral discs, or backbones, that once belonged to Shonisaurus popularis, a species of dinosaur-age marine reptiles called ichthyosaurs.
Based on the sizes of the bones, scientists estimate the ichthyosaurs grew to lengths of 49 feet (15 meters) or longer.
(Related: "'Colossal Squid' Revives Legends of Sea Monsters.")
During a recent family trip to the fossil site, Mark McMenamin, a paleontologist at Mount Holyoke College in Massachusetts, noticed that some of the vertebrate fossils appeared to be neatly lined up into double rows.
Struck by the orderly arrangement of the bones, McMenamin came up with a remarkable idea for how they came to be that way, which he presented at a Geological Society of America meeting in Minnesota on Monday.
McMenamin's hypothesis: that a giant squid or octopus hunted and preyed on the ichthyosaurs and then arranged their bones in double-line patterns to purposely resemble the pattern of sucker discs on the predator's tentacles.
According to a press release detailing McMenamin's hypothesis—titled "Giant Kraken Lair Discovered"— "the vertebral disc 'pavement' seen at the state park may represent the earliest known self portrait."
"I think that these things were captured by the kraken and taken to the midden and the cephalopod would take them apart," McMenamin—who didn't respond to a request for an interview Tuesday—said in the statement.
The kraken, he said, "was either drowning [the ichythosaurs] or breaking their necks."
(See the first pictures of a live giant squid.)
Explanation Doesn’t Require an Artistic Kraken?
Paul "P.Z." Myers is an evolutionary biologist at the University of Minnesota Morris and the author of the Pharyngula science blog. (Pharyngula is part of ScienceBlogs, a network partially funded by the National Geographic Society, which owns National Geographic News.)
Myers called McMenamin's hypothesis a "bizarre and miraculous story" and said his evidence is "weirdly circumstantial."
The fossil arrangement "is not surprising," Myers said. "It doesn't take an artist octopus to do it."
One could imagine, Myers said, that as ichthyosaurs died and their bodies rotted, their vertebral discs fell apart.
The bones "are taller than they are wide, so they're just going to flop over to one side or the other and can just happen to fall into two parallel rows," which then get preserved as fossils, he said.
(Pictures: Largest "Sea Monster" Skull Revealed?)
Kraken "Fun to Think About"
McMenamin's kraken ideas have received widespread media attention partly because they were presented at a scientific conference, but that's no sign that a hypothesis is widely accepted or considered scientifically plausible, Myers added.
Scientific meetings "are where scientists go to talk with their peers and discuss preliminary data, so they naturally have fairly lax standards," Myers said.
Ryosuke Motani, a paleontologist at the University of California, Davis, who has also conducted research at Berlin-Ichthyosaur State Park, was equally skeptical of McMenamin's idea.
"It's fun to think about," Motani said, "but I think it's very implausible."
(Related: "'Sea Monster' Bones Reveal Ancient Shark Feeding Frenzy.")
Motani proposed an alternative hypothesis for how the bones came to be arranged the way they are.
"These bones are disc-shaped, so when they're disarticulated after rotting, they lay flat on the seafloor and can get gathered up and packed together by ocean currents," he said.
"This particular specimen [that McMenamin focused on] has two rows. But I've seen others that have three rows. ... It's natural that the bones get arranged like that."