The Shonisaurus was a gigantic marine reptile which existed during the Upper Triassic period. It lived on the earth about 220 to 205 million years ago. This time frame was included in the Norian and Rhaetian ages of the Triassic period.
The Shonisaurus is classified under the group of reptiles called ichthyosaurs. It was among the primitive ichthyosaurs, with evolved species been seen in the Jurassic period.
The Shonisaurus was considered the largest ichthyosaur ever to be seen on the earth for a substantial period of time. It was dethroned by the discovery of the Shastasaurus. Nonetheless, its dimensions were enormous. Its length was as much as 50 feet and its weight is estimated to be around 30 to 35 tons. It is still one the largest animals to ever inhabit the earth.
The Shonisaurus was named after the location of its discovery.
The prefix 'shoni' is derived from the Shoshone Mountains in Nevada where the holotype of the Shonisaurus was discovered. The term 'saurus' is inspired from the Greek word 'sauros' which means 'lizard'. The appearance of the Shonisaurus was nothing like a lizard or a dinosaur. But its size and the nature of its fossils warranted such a name. Thus, its name roughly translates to 'the lizard hailing from the Shoshone Mountains'.
The species name Shonisaurus popularis was selected for the organism because its fossils were numerous and complete.
The Shonisaurus was named by scientist Charles Camp.
Discovery of fossils
- The remains if the Shonisaurus were finally found after twenty years of work. The University of California, Berkeley had undertaken an excavation expedition in the year 1954. It was headed by Charles Camp and Sam Welles.
- The fossils of the Shonisaurus were discovered in the year 1976. They were first seen by Margaret Wheat and she brought them to Camp. This region has since then been maintained as the Berlin-Ichthyosaur State Park.
- Since then, many specimens have been found in the regions around the Shoshone Mountains. Juvenile as well as adult fossils have been discovered.
- Incidentally, Nevada is a land locked state. Thus it sounds that a large marine reptile should be found there. But Nevada was surrounded by the Pacific Ocean in the Jurassic period.
- Fossils were discovered in Canada in 2004 which were grouped as a larger sub species of Shonisaurus. They were later found to belong to the Shastasaurus.
The Shonisaurus is the best known ichthyosaur. No other ichthyosaur fossils outnumber those of the Shonisaurus today.
The Shonisaurus is classified under Ichthyosauria, infraorder Shastasauria and family Shastasauridae. There was no confusion about its classification since its discovery.
Only one species is included in genus Shonisaurus, the S. popularis. The S. sikanniensis was moved to the genus Shastasaurus.
Current location of fossils
The Shonisaurus fossils have not been moved to any museum and are preserved at the location of their discovery, the Berlin-Ichthyosaur State Park.
Charles Lewis Camp was as American paleontologist. He was born in Jamestown in North Dakota. He was particularly interested in marine biology.
Camp studied as an undergraduate at UC Berkeley. His major at that time was zoology. He took a hiatus from his education to serve the United States in the First World War. After coming back from the war, he finished his under graduation and joined the Museum of Paleontology as a research associate.
Camp has travelled to Europe, Africa and Asia for paleontological excursions during the course of his career. He eventually became the director of the UC Museum of Paleontology.
Camp succumbed to cancer at the age of eighty two.
- The Shonisaurus was a large reptile. It could grow to a length of 15 meters.
- Its weight has been a matter of debate. Most artistic impressions represent the Shonisaurus to be much more bulky than it actually was. Its mass is believed to be about 30,000 kilos. But it is usually depicted as a creature weighing 40,000 to 50,000 kilos.
- The forelimbs and hind limbs of the Shonisaurus were modified to form flippers. They were short as compared to the rest of its body.
- Many drawings also show the Shonisaurus with a dorsal fin. There is no skeletal evidence that it possessed such a fin. The more evolved ichthyosaurs had them.
- It is possible that it had a dorsal fin but it was made of connective tissue that wasn’t bony. Hence it was not seen in the fossils.
- It may have ossified after millions of years of evolution and was thus seen in the later ichthyosaurs.
- But without further evidence, this theory cannot be proved.
- The juvenile specimens of the Shonisaurus had teeth in their jaws while the older ones lacked them. This is again an unusual finding.
- The Shonisaurus most likely had a rounded torso.
- Its tail was thick and had two prongs.
Habits and habitat
The Shonisaurus dwelled in deep oceanic waters. It is unlikely that a creature as big as the Shonisaurus could survive in shallow water bodies. Its body was completely adapted for an aquatic lifestyle.
It was a carnivorous reptile. Since adult specimens lacked teeth, it is believed that the Shonisaurus ate soft animals that lacked a hard exoskeleton. Or it is possible it swallowed its prey whole. The juveniles probably possessed teeth for self-defense.
The Shonisaurus was a slow swimmer. It relied on its size and strength to catch its prey unawares.
The reproductive habits of the Shonisaurus are unknown.
The Shonisaurus was closely related to the Shastasaurus. Ichthyosaurs show a great morphological variety and thus it can be deduced that they evolved separately to adjust to their environment. Thus the Shonisaurus may not be very intimately related to other ichthyosaurs.
The Kraken controversy
Mark and Diana McMenamin proposed a hypothesis in 2011 that Shonisaurus was predated upon by a large octopus. They name this creature a ‘kraken’ after the fabled European sea monster. The premise of this theory was that one of the fossils of the Shonisaurus had the ribs arranged in a circular manner. The McMenamins stated that this was done by an intelligent kraken to create an artwork resembling itself.
As there is no data which confirms the existence of such a ‘kraken’, most of the scientific community has debunked this theory.
The Shonisaurus is one of the best known Triassic reptiles. Its size and the mystery surrounding its supposed predator have made this creature very popular in the media.
Kraken-food or not, the Shonisaurus interests paleontologists even today since it resembled modern whales and sharks in many ways.