Thunnosauria

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Thunnosaurians
Temporal range: Early Jurassic-Late Cretaceous, 199.6–93.5  Ma
Ichthyosaurus breviceps 2.jpg
Ichthyosaurus breviceps fossil
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Ichthyosauria
Node: Neoichthyosauria
Node: Thunnosauria
Motani, 1999
Subgroups

Thunnosauria (Greek for "tuna lizard" – thunnos meaning "tuna" and sauros meaning "lizard") is an extinct clade of parvipelvian ichthyosaurs from the Early Jurassic to the early Late Cretaceous (HettangianCenomanian) of Asia, Australia, Europe, North America, and South America. Named by Ryosuke Motani in 1999, it contains the basal taxa Ichthyosaurus and Stenopterygius and the family Ophthalmosauridae. In thunnosaurs, the fore fin is at least twice as long as the hind fin. [1] [2]

Phylogeny

Thunnosauria is a node-based taxon defined in 1999 as "the last common ancestor of Ichthyosaurus communis and Stenopterygius quadriscissus and all of its descendants". [1] The cladogram below follows the topology from a 2010 analysis by Patrick S. Druckenmiller and Erin E. Maxwell. [3]

Thunnosauria 

Ichthyosaurus Ichthyosaurus BW.jpg

Stenopterygius Stenopterygius BW.jpg

"Ophthalmosaurus" natans

  Ophthalmosauridae  

Aegirosaurus

Ophthalmosaurus Ophthalmosaurus BW.jpg

Mollesaurus

Athabascasaurus

Brachypterygius

Arthropterygius

Caypullisaurus

"Platypterygius" hercynicus

"Platypterygius" australis

Platypterygius

Maiaspondylus

"Platypterygius" americanus

Related Research Articles

Ichthyosaur Extinct order of large marine reptiles

Ichthyosaurs are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia.

<i>Ichthyosaurus</i> Genus of extinct marine reptile, type genus of Ichthyosauria

Ichthyosaurus is a genus of ichthyosaurs from the late Triassic and early Jurassic of Europe and Asia (Indonesia). It is among the best known ichthyosaur genera, as it is the type genus of the order Ichthyosauria.

<i>Ophthalmosaurus</i> Extinct genus of reptiles

Ophthalmosaurus is an ichthyosaur of the Jurassic period. Possible remains from the Cretaceous, around 145 million years ago, are also known. Named for its extremely large eyes, it had a 6 metres (20 ft) long dolphin-shaped body with jaws containing many small but robust teeth. Major fossil finds of this genus have been recorded in Europe with a second species possibly being found in North America.

<i>Mixosaurus</i> Extinct genus of reptiles

Mixosaurus is an extinct genus of Middle Triassic ichthyosaur. Its fossils have been found near the Italy–Switzerland border and in South China.

<i>Stenopterygius</i> Extinct genus of reptiles

Stenopterygius is an extinct genus of thunnosaur ichthyosaur known from Europe. This genus of ichthyosaur grew to a maximum length of 4 meters.

<i>Utatsusaurus</i> Extinct genus of reptiles

Utatsusaurus hataii is the earliest-known ichthyopterygian which lived in the Early Triassic period. It was nearly 3 metres (9.8 ft) long with a slender body. The first specimen was found in Utatsu-cho, Miyagi Prefecture, Japan. It is the only described species in the genus Utatsusaurus and the only member of the family Utatsusauridae. The name Utatsusaurus was given after the city. The fossils have been found from the Early Triassic Osawa Formation of Miyagi Prefecture, Japan and British Columbia, Canada.

Shastasauridae Extinct family of reptiles

Shastasauridae is an extinct family of Triassic ichthyosaurs that includes the genera Shastasaurus, Shonisaurus and Himalayasaurus. Many other Triassic ichthyosaurs have been assigned to Shastasauridae in the past, but recent phylogenetic analyses suggest that these species form an evolutionary grade of early ichthyosaurs rather than a true clade or evolutionary grouping that can be called Shastasauridae. Shastasauridae was named by American paleontologist John Campbell Merriam in 1895 along with the newly described genus Shastasaurus. In 1999, Ryosuke Motani erected the clade Shastasauria to include Shastasaurus, Shonisaurus, and several other traditional shastasaurids, defining it as a stem-based taxon including "all merriamosaurians more closely related to Shastasaurus pacificus than to Ichthyosaurus communis." He also redefined Shastasauridae as a node-based taxon including "the last common ancestor of Shastasaurus pacificus and Besanosaurus leptorhynchus, and all its descendants" and Shastasaurinae, which Merriam named in 1908, as a stem taxon including "the last common ancestor of Shastasaurus and Shonisaurus, and all its descendants." In an alternative classification scheme, paleontologist Michael Maisch restricted Shastasauridae to the genus Shastasaurus and placed Shonisaurus and Besanosaurus in their own monotypic families, Shonisauridae and Besanosauridae.

Ophthalmosauridae Extinct family of reptiles

Ophthalmosauridae is an extinct family of thunnosaur ichthyosaurs from the Middle Jurassic to the early Late Cretaceous worldwide. Almost all ichthyosaurs from the Middle Jurassic onwards belong to the family, until the extinction of ichthyosaurs in the early Late Cretaceous. Opthalmosaurids appeared worldwide during early Bajocian, subsequent to the disappearance of most other ichthyosaur lineages after the end of the Toarcian. Currently, the oldest known ophthalmosaurids is Mollesaurus from the early Bajocian of Argentina, as well as indeterminate remains of the same age from Luxembourg and Canada. Named by George H. Baur, in 1887, the family contains the basal taxa like Ophthalmosaurus. Appleby (1956) named the taxon Ophthalmosauria which was followed by some authors, but these two names are synonyms; Ophthalmosauridae has the priority over Ophthalmosauria.

<i>Brachypterygius</i> Extinct genus of reptiles

Brachypterygius is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur known from the Late Jurassic of England. The type species was originally described and named as Ichthyosaurus extremus by Boulenger in 1904. Brachypterygius was named by Huene in 1922 for the width and shortness of the forepaddle, and the type species is therefore Brachypterygius extremus. The holotype of B. extremus was originally thought to be from the Lias Group of Bath, United Kingdom, but other specimens suggest it more likely came from the Kimmeridgian Kimmeridge Clay of Kimmeridge Bay, Dorset, UK.

Mollesaurus is an extinct genus of large ophthalmosaurine ophthalmosaurid ichthyosaur known from northwestern Patagonia of Argentina.

<i>Baptanodon</i> Extinct genus of reptiles

Baptanodon is an ichthyosaur of the Late Jurassic period, named for its extremely large eyes. It had a graceful 6 m (19.5 ft) 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 North America. The type species, Sauranodon natans, was originally included under Sauranodon in 1879, but this name was preoccupied.

Maiaspondylus is an extinct genus of platypterygiine ophthalmosaurid ichthyosaurs known from Northwest Territories of Canada, the Cambridge Greensand of England and the Voronezh Region of Russia.

<i>Athabascasaurus</i> Extinct genus of reptiles

Athabascasaurus is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur known from Alberta, Canada.

Macgowania is an extinct genus of parvipelvian ichthyosaur known from British Columbia of Canada.

Parvipelvia Extinct clade of reptiles

Parvipelvia is an extinct clade of euichthyosaur ichthyosaurs that existed from the Late Triassic to the early Late Cretaceous of Asia, Australia, Europe, North America and South America. Named by Ryosuke Motani, in 1999, it contains the basal taxa like Macgowania and Hudsonelpidia. Maisch and Matzke (2000) found in their analysis seven synapomorphies that support Parvipelvia. They also found 10 synapomorphies that support the existence of post-Triassic clade of ichthyosaurs, for which the name Neoichthyosauria was found to be available.

Merriamosauria Extinct clade of reptiles

Merriamosauria is an extinct clade of ichthyosaurs. It was named by Ryosuke Motani in his 1999 analysis of the relationships of ichthyopterygian marine reptiles and was defined in phylogenetic terms as a stem-based taxon including "the last common ancestor of Shastasaurus pacificus and Ichthyosaurus communis, and all of its descendants." The name honours John Campbell Merriam. Based on this definition, Merriamosauria includes most ichthyosaurs except for several Triassic groups such as the clade Mixosauria, the family Cymbospondylidae, and perhaps the family Toretocnemidae. Merriamosaurs are characterized by features in their pectoral girdles and limb bones, including an extensive connection between the scapula and the coracoid bone, the absence of the first metacarpal and the absence of a pisiform bone.

Timeline of ichthyosaur research

This timeline of ichthyosaur research is a chronological listing of events in the history of paleontology focused on the ichthyosauromorphs, a group of secondarily aquatic marine reptiles whose later members superficially resembled dolphins, sharks, or swordfish. Scientists have documented ichthyosaur fossils at least as far back as the late 17th century. At that time, a scholar named Edward Lhwyd published a book on British fossils that misattributed some ichthyosaur vertebrae to actual fishes; their true nature was not recognized until the 19th century. In 1811, a boy named Joseph Anning discovered the first ichthyosaur fossils that would come to be scientifically recognized as such. His sister Mary would later find the rest of its skeleton and would go on to become a respected fossil collector and paleontologist in her own right.

Patrick Druckenmiller

Patrick S. Druckenmiller is a Mesozoic paleontologist, taxonomist, associate professor of geology, Earth Sciences curator, and museum director of the University of Alaska Museum of the North, where he oversees the largest single collection of Alaskan invertebrate and vertebrate fossils. He has published work on plesiosaurs, ichthyosaurs, mastodons, and dinosaurs in the United States, Svalbard, and Canada. He has co-authored papers on discussions of mass extinctions and biogeography. Much of his work has focused on Arctic species. He is a member of the Spitsbergen Jurassic Research group, which focuses on marine reptiles. Druckenmiller has named many new genera and species, including Edgarosaurus muddi, Nichollsia borealis, Athabascasaurus bitumineus, Cryopterygius kristiansenae, Spitrasaurus larseni, and Spitrasauruswensaasi.

References

  1. 1 2 Ryosuke Motani (1999). "Phylogeny of the Ichthyopterygia" (PDF). Journal of Vertebrate Paleontology. 19 (3): 472–495. doi:10.1080/02724634.1999.10011160.
  2. Michael W. Maisch & Andreas T. Matzke (2000). "The Ichthyosauria". Stuttgarter Beiträge zur Naturkunde. Serie B. 298: 1–159.
  3. Patrick S. Druckenmiller & Erin E. Maxwell (2010). "A new Lower Cretaceous (lower Albian) ichthyosaur genus from the Clearwater Formation, Alberta, Canada". Canadian Journal of Earth Sciences. 47 (8): 1037–1053. Bibcode:2010CaJES..47.1037D. doi:10.1139/E10-028.