Shonisaurus popularis
Encyclopedia
Shonisaurus is a genus of ichthyosaur
. At least 37 incomplete specimens of the marine reptile have been found in the Luning Formation of Nevada
, United States
. This formation dates to the late Carnian
age of the late Triassic
period, about 215 million years ago.
stage of the late Triassic
period. S. popularis measured around 15 metres (49.2 ft) long. A second species from British columbia
was named Shonisaurus sikanniensis in 2004. S. sikkanniensis was one of the largest marine reptiles of all time, measuring 21 metres (68.9 ft). However, phylogenetic studies later showed S. sikanniensis to be a species of Shastasaurus
rather than Shonisaurus.
Shonisaurus had a long snout, and its flippers were much longer and narrower than in other ichthyosaurs. While Shonisaurus was initially reported to have had socketed teeth (rather than teeth set in a groove as in more advanced forms), these were present only at the jaw tips, and only in the very smallest, juvenile specimens. All of these features suggest that Shonisaurus may be a relatively specialised offshoot of the main ichthyosaur evolutionary line. It was historically depicted with a rather rotund body, but studies of its body shape since the early 1990s have shown that the body was much more slender than traditionally thought. S. popularis had a relatively deep body compared with related marine reptiles.
Shonisaurus was also traditionally depicted with a dorsal fin, a feature found in more advanced ichthyosaurs. However, other shastasaurids likely lacked dorsal fins, and there is no evidence to support the presence of such a fin in Shonisaurus. The upper fluke of the tail was probably also much less developed than flukes found in later species.
s of Shonisaurus were first found in a large deposit in Nevada
in 1920. Thirty years later, they were excavated, uncovering the remains of 37 very large ichthyosaurs. These were named Shonisaurus, which means "Lizard from the Shoshone Mountains
", after the formation where the fossils were found.
S. popularis, was adopted as the state fossil
of Nevada in 1984. Excavations, begun in 1954 under the direction of Dr. Charles Camp and Dr. Samuel Welles of the University of California, Berkeley
, were continued by Camp throughout the 60s. It was named by Charles Camp in 1976.
The Nevada fossil sites can currently be viewed at the Berlin-Ichthyosaur State Park
.
In a 2011 lecture to the Geological Society of America, Mark McMenamin
and Dianna Schulte McMenamin, geologists from Mount Holyoke College, put forward the controversial hypothesis that the large assemblage of remains were placed in deep water by an unidentified, gigantic, squid-like predator they referred to as a "kraken
". The McMenamins went on to suggest that the arrangement of the vertebrae, which appear to resemble cephalopod suction organs of cephalopod tentacles in their round, concave shape, were purposefully arranged by a Triassic Kraken
(which they suggested would have had to be extremely intelligent) in order to create a work of art, specifically a self-portrait of its own tentacles. This hypothesis was widely reported by the news media when the Geological Society of America issued a press release in October of 2011. Critics were concerned that there was only trace fossil evidence favoring the existence of the Triassic Kraken. Science author Brian Switek, writing for the Wired magazine's Laelaps web log, made the following comment:
Other writers responded more favorably to the McMenamins' proposal. Writing for About.com, Andrew Alden wrote that the concept of high intelligence in the Triassic Kraken hypothesis "is its most valuable contribution: why should we rule out intelligence in the distant past? And what would the signs of it be?"
Ichthyosaur
Ichthyosaurs were giant marine reptiles that resembled fish and dolphins...
. At least 37 incomplete specimens of the marine reptile have been found in the Luning Formation of Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. This formation dates to the late Carnian
Carnian
The Carnian is the lowermost stage of the Upper Triassic series . It lasted from about 228.7 till 216.5 million years ago . The Carnian is preceded by the Ladinian and is followed by the Norian...
age of the late Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
period, about 215 million years ago.
Description
Shonisaurus lived during the NorianNorian
The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...
stage of the late Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
period. S. popularis measured around 15 metres (49.2 ft) long. A second species from British columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
was named Shonisaurus sikanniensis in 2004. S. sikkanniensis was one of the largest marine reptiles of all time, measuring 21 metres (68.9 ft). However, phylogenetic studies later showed S. sikanniensis to be a species of Shastasaurus
Shastasaurus
Shastasaurus is an extinct genus of ichthyosaur from the middle and late Triassic, and is the largest marine reptile that has yet been found. Specimens have been reported from the United States, Canada, and China...
rather than Shonisaurus.
Shonisaurus had a long snout, and its flippers were much longer and narrower than in other ichthyosaurs. While Shonisaurus was initially reported to have had socketed teeth (rather than teeth set in a groove as in more advanced forms), these were present only at the jaw tips, and only in the very smallest, juvenile specimens. All of these features suggest that Shonisaurus may be a relatively specialised offshoot of the main ichthyosaur evolutionary line. It was historically depicted with a rather rotund body, but studies of its body shape since the early 1990s have shown that the body was much more slender than traditionally thought. S. popularis had a relatively deep body compared with related marine reptiles.
Shonisaurus was also traditionally depicted with a dorsal fin, a feature found in more advanced ichthyosaurs. However, other shastasaurids likely lacked dorsal fins, and there is no evidence to support the presence of such a fin in Shonisaurus. The upper fluke of the tail was probably also much less developed than flukes found in later species.
History
FossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s of Shonisaurus were first found in a large deposit in Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
in 1920. Thirty years later, they were excavated, uncovering the remains of 37 very large ichthyosaurs. These were named Shonisaurus, which means "Lizard from the Shoshone Mountains
Shoshone Mountains
also located in Nye County.The Shoshone Mountains, in central Nevada, make up one of the longest mountain ranges in the state. The range runs in a north-south direction, mostly in Nye County, but also occupies part of Lander County...
", after the formation where the fossils were found.
S. popularis, was adopted as the state fossil
State fossil
Most American states have made a state fossil designation, in many cases during the 1980s. It is common to designate one species in which fossilization has occurred, rather than a single specimen, or a category of fossils not limited to a single species....
of Nevada in 1984. Excavations, begun in 1954 under the direction of Dr. Charles Camp and Dr. Samuel Welles of the University of California, Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
, were continued by Camp throughout the 60s. It was named by Charles Camp in 1976.
The Nevada fossil sites can currently be viewed at the Berlin-Ichthyosaur State Park
Berlin-Ichthyosaur State Park
The environment of Nevada comprises diverse biotas, climates, and geologies. Environmental regulations and the environmental movement have aimed to respond to environmental threats.-Renewable Portfolio Standard:...
.
Bonebed interpretation
The Nevada bonebed represents a large assemblage of Shonisaurus which died at varying times and became preserved on the sea floor in a curiously regular arrangement of bones. The lack of fossil invertebrates encrusting the remains indicates that the carcasses sank in relatively deep water poor in oxygen.In a 2011 lecture to the Geological Society of America, Mark McMenamin
Mark McMenamin
Mark McMenamin is a tenured professor of geology at Mount Holyoke College. His research is primarily focused on paleontology, particularly the Ediacaran biota....
and Dianna Schulte McMenamin, geologists from Mount Holyoke College, put forward the controversial hypothesis that the large assemblage of remains were placed in deep water by an unidentified, gigantic, squid-like predator they referred to as a "kraken
Kraken
Kraken are legendary sea monsters of giant proportions said to have dwelt off the coasts of Norway and Iceland.In modern German, Krake means octopus but can also refer to the legendary Kraken...
". The McMenamins went on to suggest that the arrangement of the vertebrae, which appear to resemble cephalopod suction organs of cephalopod tentacles in their round, concave shape, were purposefully arranged by a Triassic Kraken
Triassic Kraken
The Triassic Kraken is a gigantic ancient cephalopod hypothesized to be responsible for the deaths of Triassic ichthyosaurs belonging the the genus Shonisaurus preserved at the Berlin-Ichthyosaur State Park in Nevada...
(which they suggested would have had to be extremely intelligent) in order to create a work of art, specifically a self-portrait of its own tentacles. This hypothesis was widely reported by the news media when the Geological Society of America issued a press release in October of 2011. Critics were concerned that there was only trace fossil evidence favoring the existence of the Triassic Kraken. Science author Brian Switek, writing for the Wired magazine's Laelaps web log, made the following comment:
"[T]he fact remains that journalists should have actually done their jobs rather than act as facilitators of hype. You don’t have to be a paleontologist to realize that there’s something fishy about claims that there was a giant, ichthyosaur-crunching squid when there is no body to be seen."
Other writers responded more favorably to the McMenamins' proposal. Writing for About.com, Andrew Alden wrote that the concept of high intelligence in the Triassic Kraken hypothesis "is its most valuable contribution: why should we rule out intelligence in the distant past? And what would the signs of it be?"
See also
- ShastasaurusShastasaurusShastasaurus is an extinct genus of ichthyosaur from the middle and late Triassic, and is the largest marine reptile that has yet been found. Specimens have been reported from the United States, Canada, and China...
, a relative of Shonisaurus - TemnodontosaurusTemnodontosaurusTemnodontosaurus was an ichthyosaur from the Early Jurassic, some 198 and 185 million years ago , in Europe...
, another large ichthyosaur - Largest prehistoric organismsLargest prehistoric organismsThe largest prehistoric organisms include both vertebrate and invertebrate species. Many are described below, along with their typical range of size...