Monday, 10 October 2011

Giant Creatures Of The Deep Were The Largest Predators In The Triassic Seas

An artists impression of Shonisaurus sikanniensis
Shonisaurus sikanniensis was one of the largest creatures to have ever lived in the sea. Despite being an early form of ichthyosaur, this dolphin-like creature was 20 metres in length, with some specimens potentially reaching 25. It was the largest predator in the Triassic seas, but now mysterious fossils of this remarkable creature suggest that even larger beasts lurked in the deep. While no fossils have yet been discovered of these giants, the fossils point to their existence.

Dr Mark McMenamin of the Mount Holyoke College excavated a series of Shonisaur fossils with his daughter over a few days in summer at the Berlin-Ichthyosaur State Park in Nevada, USA. While this might not sound very exciting, the fossils from this site have baffled many palaeontologists throughout the years. 'Charles Camp (a U.C Berkeley doctor and world expert on the fossil formation) puzzled over these fossils in the 1950s,' said McMenamin. 'In his papers he keeps referring to how peculiar this site is. We agree, it is peculiar.'

The creature that once comprised the bones died in shallow water. Camp suggested that this was due to them being stranded or from poisoning by blooms of toxic algae. The problem with these theories is the way the bones are laid. Rather than being scattered about the sea bed, they are neatly arranged into patterns and geometric forms. Careful analysis shows that the bones are not fakes and that they were laid down in this strange fashion millions of years ago. However geological processes cannot place bones into distinct forms.

What could have happened? Was this a shallow or deep ocean death?  'It became very clear that something very odd was going on there,' said McMenamin. 'It was a very odd configuration of bones. Yet the traces that did exist were distinctive.

A 'smaller' fossil specimen of Shonisaurus sikanniensis
Firstly a series of etchings on the bones showed that the Shonisaurs had died at different times and had been repositioned after death. While this fact does not reveal much, when viewed in conjunction with the next two clues, the story becomes much clearer. The bones were positioned in lines with an almost geometric precision and the vertebrae were arranged in a pattern akin to the sucker disks on a cephalopod tentacle. These facts gave McMenamin the idea that the Shonisaurs were killed by some kind of giant predator.

Due to the arrangement of the bones, he believes that some kind of giant cephalopod was the killer. Today, giant squid and octupi have been known to prey upon sharks. Shonisaurus sikanniensis was a predator similar in shape to a shark and therefore a predator prey relationship could have formed between the two animals. At first the theory might seem far-fetched, but when the situation is examined more closely, it becomes more plausible.

The vertebrae which mimic the pattern of suckers on a cephalopod tentacle
The bones were arranged in regular, geometric forms. Such behaviour has been observed on modern Octupi, as they play with the remains of fish. They have the dexterity and cognitive functions to be able to create such patterns. The vertebrae were in a pattern which mimicked the placement of suckers on a cephalopod tentacle. The only problem is size. Yet we know of giant 15 to 20 metre long squid which prey on whales in the deep oceans today and giant cephalopods did live in the oceans hundreds of millions of years ago.

Many complete Shonisaur skeletons display broken ribs and twisted necks. McMenamin suggests that these were caused by the powerful tentacles of a giant undiscovered predator that roamed the Triassic seas. The theory does parallel nicely the sentiment that no matter the size of a predator, there will always be a bigger one. The final piece needed to complete the theory is evidence of such a creature. Unfortunately it is a perfect Triassic crime as Octupi are soft bodied and are not often preserved to any degree. Personally, I hope that such finds will confirm the theory as it would be good to have a palaeontological root for the legend of the mighty kraken.