The famous Sharktooth Hill Bone Bed near Bakersfield has tantalized the imagination of scientists and laymen alike since it was first discovered in the 1850s. How did a six-to-20-inch-thick layer of fossil bones, gigantic shark teeth and turtle shells three times the size of today’s leatherbacks come to be?

Was this a killing ground for C. megalodon, a 40-foot long shark that roamed the seas until 1.5 million years ago? Perhaps a great catastrophe like a red tide or volcanic eruption led to animal mass-death in the region? Or is this simply the result of Sharktooth Hill being used as a breeding ground for generations of marine mammals throughout the millennia?

A research team consisting of palaeontologists from the United States and Canada are now offering their take on the Bone Bed, suggesting it is not the result of a sudden die-off or a certain predator. Instead, the North American team sees it as a 700,000-year record of normal life and death, kept free of sediment by unusual climatic conditions between 15 million and 16 million years ago.

The research team bases its hypothesis on a new and extensive study of the fossils and the geology of Sharktooth Hill. Roughly 3,000 fossilized bone and teeth specimens found in various museums, including the Natural History Museum of Los Angeles County (NHM) and UC Berkeley’s Museum of Paleontology (UCMP), have been scrutinized, and the researchers also cut out a meter-square section of the bone bed, complete with the rock layers above and below.

“If you look at the geology of this fossil bed, it’s not intuitive how it formed,” says Nicholas Pyenson, a former UC Berkeley graduate student who is now a post-doctoral fellow at the University of British Columbia. “We really put together all lines of evidence, with the fossil evidence being a big part of it, to obtain a snapshot of that period of time.”

The existence of a 700,000-year window through which we can catch a glimpse of the past is naturally magnificent news for anyone interested in evolution and Earth’s history.

When the Central Valley was a sea

When the Sharktooth Hill Bone Bed formed between 15,900,000 and 15,200,000 years ago, the climate was warming up, ice was melting and the sea level was much higher than today. What is today California’s Central Valley was an inland sea with the emerging Sierra Nevada as its shoreline.

After closely examining the geology of the Sharktooth Hill area, the research team was able to confirm that it had once been a submerged shelf inside a large embayment, directly opposite a wide opening to the sea.

Several feet of mudstone interlaced with shrimp burrows is present under the bone bed, which is typical of ocean floor sediment several hundred to several thousand feet below the surface. Inside the bone bed, most of the bones have separated joints, indicating that they have been scattered by currents.

“The bones look a bit rotten, as if they lay on the seafloor for a long time and were

abraded by water with sand in it“, says UC Berkeley integrative biology professor Jere Lipps.

Many bones also had manganese nodules and growths on them, something which can form when bones sit in sea water for a long time before they are covered by sediment. According to the team, the most likely explanation for this is that the bones have lain exposed on the ocean floor for 100,000 to 700,000 years while currents have carried sediment around the bone bed. The prevailing climatic conditions at the time have made it possible for the bones to accumulate in a big and shifting pile at the bottom of the sea.

“These animals were dying over the whole area, but no sediment deposition was going on, possibly related to rising sea levels that snuffed out silt and sand deposition or restricted it to the very near-shore environment,” says Pyenson. “Once sea level started going down, then more sediment began to erode from near shore.”

The team discards the breeding-ground hypothesis due to the scarcity of remains from young and juvenile animals. Hungry Megalodon sharks being the main contributors to the bone pile is also unlikely, since few bones bear any marks of shark bites. If the bone bed was the result of mass-death caused by an erupting volcano the absence of volcanic ash in the bed would be very difficult to explain, and the presence of land animals like horses and tapirs that must have washed out to sea make the red-tide hypothesis equally thin.

Amazing remains from the past

The Sharktooth Hill Bone Bed covers nearly 50 square miles just outside and northeast of Bakersfield in California and is one of the richest and most extensive marine deposits of bones in the world. Studied parts of the bone bed average 200 bones per square meter, most of them larger bones. Ten miles of the bed is exposed, and the uppermost part of the bed contains complete, articulated skeletons of whales and seals.

Within the bone bed, scientists have found bones from many species that are now extinct and the bed provides us with invaluable information about the evolutionary history of whales, seals, dolphins, and other marine mammals, as well as of turtles, seabirds and fish. Sharktooth Hill is naturally the sight of some impressive shark findings too, including shark teeth as big as a hand and weighing a pound each.

A small portion of the bone bed was added to the National Natural Landmark registry in 1976 but the rest is in dire need of protection.

A collaborative effort

The research team, who’s study will be published in the June 2009 issue of the journal

Geology, consisted of:

– UC Berkeley integrative biology professor Jere Lipps, who is also a faculty curator in UC Berkeley’s Museum of Paleontology.

– Nicholas Pyenson, a UC Berkeley Ph.D who is now a post-doctoral fellow at the University of British Columbia.

– Randall B. Irmis, a UC Berkeley Ph.D who is now an assistant professor of geology and geophysics at the University of Utah.

– Lawrence G. Barnes, Samuel A. McLeod, and Edward D. Mitchell Jr., three UC Berkeley Ph.D’s who are now with the Department of Vertebrate Paleontology at the Natural History Museum of Los Angeles County.

The remains of a 15 meter[1] long sea living predator has been found in Svalbard, an archipelago located about midway between mainland Norway and the North Pole. The animal, a species of pliosaur dubbed Predator X by the group of scientists who discovered it, lived in the ocean 147 million years ago during the Jurassic period.

Predator X hunting (Photo: Atlantic Productions)

The skull of Predator X is twice as big as the skull of a Tyrannosaurus Rex and researchers believe the jaws of this hunter could exert a pressure of 15 tonnes[2]. The weight of the live animal is estimated to be around 45 tonnes[3].

“It is the largest sea dwelling animal ever found and as far as we know it is an entirely new species”, says palaeontologist Espen Madsen Knutsen[4] from the Olso University in Norway to Swedish newspaper Dagens Nyheter.

Knutsen is a part of the research team who dug out the skull and backbone of the creature during a two week long research expedition to Svalbard in June 2008. The remains were first discovered by Professor Jörn Hurum[5] from the Natural History Museum at Oslo University in 2007. Hurum noticed a piece of bone sticking up from the permafrost, but since it was the last day of the 2007 expedition the group was forced to leave the bone behind without any further investigation after having jotted down its GPS position.

Parts of the head and backbone was dug out during the abovementioned June 2008 expedition and together with an earlier find of a smaller specimen of the same species located just a few kilometres away, scientists have now managed to map together a good picture of what the live animal once looked like.

“We haven’t unearthed a high number of parts yet, but the parts that we do have are important ones and this has made it possible for us to create an image of what Predator X once looked like”, says Knutsen.

The digg site (Photo: Atlantic Productions)

In the excavated area, palaeontologist have found roughly 20,000 bone fragments – the remains of at least 40 different sea dwelling Jurassic animals. Once you’ve started digging in this region, it is fairly easy to spot the bones since their pale colour contrasts sharply against the black earth of the Svalbard tundra. The main difficulty is instead the short dig period and the fact that much time is spent restoring the excavated area after each dig.

“Each time we leave a dig site we have to restore the area. There can be no traces of our activities. This forces us to use half of our time digging up the same spot all over again when we return”, Kutsen explains.

Svalbard lies far north of the Arctic Circle and the average summer temperature is no more than 5°C (41°F), while the average winter temperature is a freezing −12 °C (10 °F). In Longyearbyen, the largest Svalbard settlement, the polar night lasts from October 26 to February 15. From November 12 to the end of January there is civil polar night, a continuous period without any twilight bright enough to permit outdoor activities without artificial light.

The team plans to return to Svalbard this summer to carry out more digging. They hope to find another specimen in order to make the skeleton more complete, and they also wish to unearth the remains of other animals that inhabited Svalbard at the same time as Predator X.

If you wish to learn more, you can look forward to the documentary shot by Atlantic Productions during the Svalbard excavations. The name of the documentary will be Predator X and the animal is actually named after the film, not the other way around. The film will be screened on History in the USA in May, Britain, Norway and across Europe later this year and distributed by BBC Worldwide.

Pliosaur crushing down on Plesiosaur with 33,000lb bite force (Ill.: Atlantic Productions)

All the scientific results will be published in a full scientific paper later this year.

You can find more Predator X information (in English) at the Natural History Museum, University of Oslo: http://www.nhm.uio.no/pliosaurus/english/