Ophthalmosaurus
Encyclopedia
Ophthalmosaurus is an ichthyosaur
of the Middle
to Late Jurassic
period (165 to 145 million years ago), named for its extremely large eyes. It had a graceful 6 metre long dolphin-shaped body, and its almost toothless jaw was well adapted for catching squid. Major fossil finds of this genus have been recorded in Europe
and North America
.
The genera
Apatodontosaurus, Ancanamunia, Baptanodon, Mollesaurus, Paraophthalmosaurus, Undorosaurus and Yasykovia were all considered junior synonyms of Ophthalmosaurus by Maisch & Matzke, 2000. However, all recent cladistic analyses found that Mollesaurus
periallus from Argentina
is a valid genus of ophthalmosaurid. Ophthalmosaurus natans is probably not a species of Ophthalmosaurus either, for which the generic name Baptanodon Marsh, 1880 is available. Undorosaurus
s validity is now accepted by most authors, even by Maisch (2010) who originally proposed the synonymy. and the two other russian taxon might be also valid. Ophthalmosaurus chrisorum Russell, 1993 was moved to its own genus Arthropterygius
in 2010 by Maxwell.
Within Ophthalmosauridae
, Ophthalmosaurus is most closely related to Aegirosaurus
.
Ophthalmosaurus had a body shaped like a tear-drop and a caudal fin like a half-moon. Its forelimbs were more developed than the hind ones, which suggests that the front fins did the steering while the tail did the propelling. Ophthalmosaurus chief claim to fame is its eyes which, at 4 inches in diameter, were extremely large in proportion to its body. The eyes occupied almost all of the space in the skull and were protected by bony plates (sclerotic ring
s), which most likely assisted to maintain the shape of the eyeballshttp://www.ucmp.berkeley.edu/people/motani/ichthyo/eyes.html against water pressure at depth.
The size of the eyes and the sclerotic rings suggests that Ophthalmosaurus hunted at a depth where there is not much light or that it may have hunted at night when a prey species was more active.
Calculations suggest that a typical Ophthalmosaurus could stay submerged for approximately 20 minutes or morehttp://www.ucmp.berkeley.edu/people/motani/ichthyo/diving.html. The swimming speed of Ophthalmosaurus has been estimated at 2.5 m/s or greater, but even assuming a conservative speed of 1 m/s, an Ophthalmosaurus would be able to dive to 600 meters and return to the surface within 20 minutes.
In the bone joints of Ophthalmosaurus skeletons traces of decompression sickness (the bends)
have been found, possibly caused as a result of evasive tactics. Modern whales have been known to get the bends when ascending rapidly to escape predators.
Ichthyosaur
Ichthyosaurs were giant marine reptiles that resembled fish and dolphins...
of the Middle
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....
to Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
period (165 to 145 million years ago), named for its extremely large eyes. It had a graceful 6 metre long dolphin-shaped body, and its almost toothless jaw was well adapted for catching squid. Major fossil finds of this genus have been recorded in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
.
Discovery and species
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Apatodontosaurus, Ancanamunia, Baptanodon, Mollesaurus, Paraophthalmosaurus, Undorosaurus and Yasykovia were all considered junior synonyms of Ophthalmosaurus by Maisch & Matzke, 2000. However, all recent cladistic analyses found that Mollesaurus
Mollesaurus
Mollesaurus is an extinct genus of large ophthalmosaurid ichthyosaur known from northwestern Patagonia of Argentina.-Description:Mollesaurus is known from the holotype MOZ 2282 V, articulated partial skeleton which preserved partial skull and most of the vertebral column...
periallus from Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
is a valid genus of ophthalmosaurid. Ophthalmosaurus natans is probably not a species of Ophthalmosaurus either, for which the generic name Baptanodon Marsh, 1880 is available. Undorosaurus
Undorosaurus
Undorosaurus is an extinct genus of ophthalmosaurid ichthyosaur known from Ul'yanovsk Province of western Russia.-Description:Undorosaurus is known from the holotype UPM EP-II-20 , a partial three-dimensionally preserved skeleton which preserved partial skull...
s validity is now accepted by most authors, even by Maisch (2010) who originally proposed the synonymy. and the two other russian taxon might be also valid. Ophthalmosaurus chrisorum Russell, 1993 was moved to its own genus Arthropterygius
Arthropterygius
Arthropterygius is an ichthyosaur which existed in Canada during the late Jurassic period. It contains the type species Arthropterygius chrisorum, named in 2010 by Erin E. Maxwell. Arthropterygius is the generic replacement name for Ophthalmosaurus chrisorum, named in 1993 from fossils found on ...
in 2010 by Maxwell.
Within Ophthalmosauridae
Ophthalmosauridae
Ophthalmosauridae is an extinct family of thunnosaur ichthyosaurs from the Middle Jurassic to the early Late Cretaceous of Asia, Australia, Europe, North America and South America. Currently, the oldest known ophthalmosaurid is Mollesaurus from the early Bajocian of Argentina. Named by George H...
, Ophthalmosaurus is most closely related to Aegirosaurus
Aegirosaurus
Aegirosaurus is an extinct genus of ophthalmosaurid ichthyosaur known from the Late Jurassic and Early Cretaceous of Europe.-Discovery and species:...
.
Palaeobiology
Like other ichthyosaurs, Ophthalmosaurus gave birth to its pups tail-first to avoid drowning them. Skeletons of unhatched young have been found in over fifty females on fossil finds, and litter sizes ranged from two to eleven pups.Ophthalmosaurus had a body shaped like a tear-drop and a caudal fin like a half-moon. Its forelimbs were more developed than the hind ones, which suggests that the front fins did the steering while the tail did the propelling. Ophthalmosaurus chief claim to fame is its eyes which, at 4 inches in diameter, were extremely large in proportion to its body. The eyes occupied almost all of the space in the skull and were protected by bony plates (sclerotic ring
Sclerotic ring
Sclerotic rings are rings of bone found in the eyes of several groups of vertebrate animals, except for mammals and crocodilians. They can be made up of single bones or small bones together. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical,...
s), which most likely assisted to maintain the shape of the eyeballshttp://www.ucmp.berkeley.edu/people/motani/ichthyo/eyes.html against water pressure at depth.
The size of the eyes and the sclerotic rings suggests that Ophthalmosaurus hunted at a depth where there is not much light or that it may have hunted at night when a prey species was more active.
Calculations suggest that a typical Ophthalmosaurus could stay submerged for approximately 20 minutes or morehttp://www.ucmp.berkeley.edu/people/motani/ichthyo/diving.html. The swimming speed of Ophthalmosaurus has been estimated at 2.5 m/s or greater, but even assuming a conservative speed of 1 m/s, an Ophthalmosaurus would be able to dive to 600 meters and return to the surface within 20 minutes.
In the bone joints of Ophthalmosaurus skeletons traces of decompression sickness (the bends)
Decompression sickness
Decompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...
have been found, possibly caused as a result of evasive tactics. Modern whales have been known to get the bends when ascending rapidly to escape predators.
In popular culture
- Ophthalmosaurus was featured in the third episode of the BBCBBCThe British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
television series Walking with DinosaursWalking with DinosaursWalking with Dinosaurs is a six-part documentary television miniseries that was produced by BBC, narrated by Kenneth Branagh, and first aired in the United Kingdom, in 1999. The series was subsequently aired in North America on the Discovery Channel in 2000, with Branagh's voice replaced with that...
, with a male pupPupPup may refer to:In zoology:*Puppies, younger dogs*Pinniped young*Shark young*Rodent youngIn other uses:* Sopwith Pup, an aircraft used by the British in World War I* Beagle Pup, a 1960s British light aircraft...
being one of the main characters. - An Ophthalmosaurus named "Mo" was a featured character in the movie The Land Before Time IX: Journey to Big WaterThe Land Before Time IX: Journey to Big WaterThe Land Before Time IX: Journey to Big Water is a 2002 animated film and the ninth film in The Land Before Time series. It was produced and directed by Charles Grosvenor, with the last time they would use the soundtrack composed by James Horner...