Temnodontosaurus (Greek for "cutting-tooth lizard"–temno, meaning "to cut", odont meaning "tooth" and sauros meaning "lizard") is an extinctgenus of ichthyosaur from the Early Jurassic period. They lived between 200 and 175 million years ago (Hettangian-Toarcian) in what is now WesternEurope (England, France, Luxembourg, Germany and Belgium) and possibly Chile.[3] It lived in the deeper areas of the open ocean.[4] University of Bristol paleontologist Jeremy Martin described the genus Temnodontosaurus as "one of the most ecologically disparate genera of ichthyosaurs,"[5] although the number of valid Temnodontosaurus species has varied over the years.
Temnodontosaurus was one of the largest ichthyosaurs, reaching up to 8–10 metres (26–33ft) in maximum body length. It is known for its incredibly large eyes which, at approximately 20cm (7.9in) in diameter, are believed to be the largest of any known animal. It possessed a tail bend that was characteristic of Jurassic ichthyosaurs and had many conical teeth filling its jaw that were set in a continuous groove.[6][7]
History of discovery
Illustrations of the first skull and skeleton (NHMUK PV R1158) of T. platyodon found by Joseph and Mary Anning in 1811-12
The first ichthyosaur skull ever discovered was that of Temnodontosaurus platyodon. The specimen (BMNH 2149; now NHMUK PV R1158) was found in the Lias of Lyme Regis by Joseph Anning in 1811. The rest of the skeleton was recovered in 1812 by his sister, Mary Anning, but was later lost and never recovered. The ichthyosaur was subsequently described by the anatomist Sir Everard Home in what was the first scientific description of an ichthyosaur. T. platyodon is the most common species of Temnodontosaurus. The type of skull is currently located at the Natural History Museum in London. The specimen was originally named Ichthyosaurus platyodon but then renamed Temnodontosaurus. The genus Temnodontosaurus was named by Richard Lydekker in 1889.[8][7][9]
The species Temnodontosaurus platyodon was named by William Conybeare in 1822 from the specimen BMNH 2003 from the Lyme Regis. The specimen is located at the British Museum of Natural History. T. platyodon is from the Upper Hettangian-Lower Sinemurian. It is the type species for Temnodontosaurus. T. platyodon specimens have been found in England, Germany, Belgium and Luxembourg. This includes the Lyme Regis in Dorset England, Herlikofen in Germany, Arlon in Belgium and Cloche d'or in Luxembourg. Only one known complete skeleton of T. platyodon exists (formerly BMNH 2003, now NHMUK OR 2003), and there is also a well-preserved skull (formerly BMNH R1158, now NHMUK PV R1158).[10][8][11]
In 1995, Christopher McGowan explained that the previously named T. risor species were really juvenile versions of T. platyodon. The specimen he used to back up his argument was one collected by David Sole in 1987 from Black Ven (East of Lyme Regis). The previously known T. risor specimens (three skulls) were seen as different from the T. platyodon species because they had larger orbits, smaller maxillae and curved snouts. However, McGowan described them as juveniles because of the small size of the forefin relative to the skull. The T. risor skulls are thought to be juveniles because the skull is relatively long compared to the postcranial skeleton.[10]
The species T. acutirostris was initially named by Richard Owen in 1840. This holotype (formerly BMNH 14553, now NHMUK OR 14553) was from the Alum Shale Formation of Lower Toarcian in Whitby, Yorkshire, England. Michael Maisch, in 2000, described it as belonging in the genus Temnodontosaurus. However, in 2010, Maisch published a paper stating that the specimen didn't belong in Temnodontosaurus, as he had thought previously, and should probably be assigned to Ichthyosaurus instead.[12][11] As of 2022, this species has been placed as species inquirenda.[2]
T. trigonodon was named by von Theodori in 1843. The type specimen for T. trigonodon is an almost complete skeleton from the Upper Liassic of Banz, Germany of the Lower Toarcian. The specimen is roughly 9.8m (32ft) long with a 1.8m (5.9ft) long skull. Other specimens have been found in Germany, as well as in France from the Lower Toarcian of Saint Colombe in Yonne. A T. trigonodon specimen from the Upper Toarcian, Aalen, Baden-Württemberg, Germany is at the Staatliches Museum für Naturkunde, Stuttgart in Germany.[11][13][5]
The species T. eurycephalus has only one specimen: a holotype. The specimen (NHMUK PV R1157) is a skull and was named in 1974 by McGowan. It is from the Lower Sinemurian, Bucklandi Zone, and was found in Lyme Regis, Dorset, England, in a limestone bed called Broad Ledge. The T. eurycephalus specimen (R 1157) is currently located at the Natural History Museum in London.[11][14][5]
Skulls referred to T. burgundiae
The validity of the species T. burgundiae has been disputed. In 1995, McGowan proposed Leptopterygius burgundiae should be placed in Temnodontosaurus.[13] The paleontologist Michael Maisch does not see T. burgundiae as belonging to Temnodontosaurus. In 1998, Maisch identified this name as a junior synonym of T. trigonodon.[15] Martin Sander, in 2000, recognsizedT. burgundiae as a separate species, describing specimens from the Toarcian of the Holzmaden area of Germany and France as being Temnodontosaurus burgundiae.[6] However, this again has been met disagreement, for McGowan and Motani (2003) argued that all specimens of the Toarcian T. burgundiae belong to T. trigonodon and that although there are small osteological differences, they are not sufficient enough to keep this species valid.[16]
The species T. azerguensis was described in 2012 by Jeremy Martin of the University of Bristol, based on a holotype that is almost a complete skeleton from the Bifrons ammonite zone of the Middle Toarcian. It was found in 1984 by M. Dejob and Ms. Laurent from the Lafarge Quarry in Belmont d’Azergues, Rhone, France. The specific name derives from the name of the river and valley near the Belmont quarry where it was found: 'Azergues'. It is currently located at the Musee des Amis de la Mine in Saint-Pierre La Palud, Rhone department, France.[5]T. azerguensis is younger than other ichthyosaurs. It had a similar size and postcranial anatomy to other Temnodontosaurus species; however, its cranial morphology differed. The rostrum was more elongated and thin and had a reduced quadrate. Since T. azerguensis either had very small teeth or no teeth at all, it has been proposed that it was probably not effective at eating hard-shelled or bony prey and instead had a diet of smaller and softer prey compared to the other Temnodontosaurus species.
The holotype of T. crassimanus is on display at the Yorkshire Museum, but it has remained understudied, and the validity of the species has long been questioned. Swaby and Lomax (2020) highlighted several morphological features of the postcranial skeleton and determined that T. crassimanus is a valid species of the genus Temnodontosaurus and includes several distinct characters that can be used to distinguish it from T. trigonodon, to which it was once assigned.[17]
The largest temnodontosaurus known, the "Rutland Sea Dragon", about 10 metres long and 181 million years old, was discovered largely intact in 2021 in an English reservoir, Rutland Water, after water levels were lowered for winter maintenance.[18]
Description
Temnodontosaurus with a human for scale
Temnodontosaurus was a large ichthyosaur, with a maximum body length of approximately 8–10 metres (26–33ft).[19][20] Initial length estimates for the specimen SMNS 50000 that had a 1.5m (4.9ft) long skull ranged between 9 and 12m (30 and 39ft) to even 15m (49ft),[10][11] but the 2015 study argued that the previous studies have overestimated the size of this particular specimen which wouldn't have exceedeed 6–7m (20–23ft) in real life.[19]
The forefins and hindfins of Temnodontosaurus were of roughly the same length and were rather narrow and elongated. This characteristic is unlike other post-Triassic ichthyosaurs such as the thunnosaurians, which had forefins at least twice the length of their hindfins. It was different from other post-Triassic ichthyosaurs like Ichthyosaurus, possessing an unreduced, tripartite pelvic girdle and having only 3 primary digits with one postaxial accessory digit. Like other ichthyosaurs, the fins exhibited strong hyperphalangy, but the fins were not involved in body propulsion; only the tail was used as the main propulsive force for movement, although it had a weak tail bend at an angle of less than 35°. Its caudal fin has variously been described as either lunate or semi-lunate; it was made of two lobes, in which the lower lobe was skeletally supported whereas the upper lobe was unsupported. The proximal elements of the fin formed a mosaic pattern, while the more distal elements were relatively round. It also had a triangular dorsal fin and had two notches on the fin's anterior margin; the paired fins were used to steer and stabilize the animal while swimming instead of paddling or propulsion devices.[7][11][6][5] It had roughly less than 90 vertebrae, and the axis and atlas of the vertebrae were fused together, serving as stabilization during swimming. T. trigonodon possessed unicipital ribs near the sacral region and the bicipital ribs more anteriorly, which helped to increase flexibility while swimming.[15]
Restoration of T. platyodon
Like other ichthyosaurs, Temnodontosaurus likely had high visual capacity and used vision as its primary sense while hunting. Temnodontosaurus had the largest eyes of any ichthyosaur and of any animal measured. The largest eyes measured belonged to the species T. platyodon. Despite the enormous size of its eyes, Temnodontosaurus had blind spots directly above its head due to the angle at which its eyes were pointed. The eyes of Temnodontosaurus had sclerotic rings, hypothesized to have provided the eyes with rigidity. The sclerotic rings of T. platyodon were at least 25cm in diameter.[21][7]
The head of Temnodontosaurus had a long robust snout with an antorbital constriction. It also had an elongated maxilla, a long cheek region, and a long postorbital segment. The carotid foramen in the basisphenoid in the skull was paired and was separated by the parasphenoid. Also, the parasphenoid had a processus cultriformis. The skull of T. platyodon measured about 1.5m (4.9ft) long, while T. eurycephalus had a shorter rostrum and a deeper skull compared to other species, perhaps serving to help crush prey. T. platyodon and T. trigadon had a very long snout that was slightly curved on its dorsal side and ventrally curved, respectively. It also had many pointed conical teeth that were set in continuous grooves, rather than having individual sockets. This form of tooth implantation is known as aulacodonty. Its teeth typically had two or three carinae; notably, T. eurycephalus possessed bulbous roots, while T. nuertingensis had no canine or bulbous roots.[10][11][6][7]
Temnodontosaurus was an apex predator in the Early Jurassic seas. Its diet likely consisted mainly of vertebrates such as fish, plesiosaurs and other ichthyosaurs. It may have also preyed on cephalopods. It is the only Jurassic ichthyosaur genus for which a mainly-vertebrates diet has been proposed. One T. trigonodon specimen (located at the Staatliches Museum für Naturkunde in Stuttgart) shows remains of Stenopterygius, another ichthyosaur, in its abdominal cavity. Due to its more robust teeth and deeper jaw, T. eurycephalus probably ate large prey such as other ichthyosaurs, while species with pointed but more modest-sized teeth, such as T. platyodon, perhaps preferred soft-bodied prey and smaller vertebrates such as fish. Temnodontosaurus likely utilised ram feeding methods of predation. The movements of its jaw were likely rapid and so it probably used snapping rather than chewing mechanisms to eat its prey.[5][7][22][13][23]
Swimming and movement style
Like other ichthyosaurs, Temnodontosaurus was a fast cruiser or swimmer. Jurassic ichthyosaurs such as Temnodontosaurus swam via the lateral oscillation of their caudal fluke on a flexible tailstock. T. trigonodon had a highly flexible, long, thin body with a high vertebral count and modest regional differentiation. It used its large limbs as rudders. Its style of swimming was thunniform, unlike more basal ichthyosaurs whose swimming was anguilliform. This trait can be inferred in Temnodontosaurus and other Jurassic and post-Jurassic ichthyosaurs because of their semi-lunate tail fins and shortened bodies relative to the tail.[6][7][15]
Classification
Temnodontosaurus is the only genus in the familyTemnodontosauridae.[24][14] The family Temnodontosauridae was described by C. McGowan and is from the Lower Liassic. Temnodontosauridae is part of the monophyletic group Neoichthyosauria, a clade named by Martin Sander in 2000 that includes the families Temnodontosauridae, Leptonectidae and Suevoleviathanidae.[11]Temnodontosaurus is one of the most basal post-Triassic ichthyosaurs.[12]
T. platyodon skeletons in London, including the neotype NHMUK PV OR 2003 (center)
The cladogram below is based on Maisch and Matzke (2000)[11] and Maisch and Matzke (2003)[25] with clade names following Maisch (2010):[12]
The 2022 study which revived T. zetlandicus created a new majority rule consensus cladogram based on "non-clock Bayesian analysis," which found T. azerguensis to be too distant in relation compared to other species of Temnodontosaurus. The study also removed T. acutirostris from the genus, placing it as species inquirenda.[2]
Palaeoecology
The habitat of Temnodontosaurus was the open ocean, away from the shoreline.[4] It lived in the pelagic zone of the water column and didn't associate with the seafloor.[6]
Fossils of Temnodontosaurus have been found in England, Germany and France from rocks associated with marine environments. Specimens have been found especially in the Lias of the Lyme Regis in Dorset, England. The Lias is made up of alternating units of limestone and mudstone and contains many ammonites.[26] The newly described species T. azerguensis was found in a belemnite rich marlstone bed in the Bifrons ammonites zone, Middle Toarcian, in Belmont d’Azergues, Rhone, France.[5]
Temnodontosaurus fossils have been found in the Posidonia Shale near Holzmaden, Germany.[22] The Posidonia Shale is composed of black bituminous shales with intercalated bituminous limestone. The environment is known to have been marine because fossils of marine animals such as plesiosaurs, crocodylians and especially ammonites have been found there in abundance.[27]
Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides.
Ichthyosaurus is a genus of ichthyosaurs from the Early Jurassic, with possible Late Triassic record, from Europe. It is among the best known ichthyosaur genera, as it is the type genus of the order Ichthyosauria.
Ophthalmosaurus is a genus of ichthyosaur known from the Middle-Late Jurassic. Possible remains from the earliest Cretaceous, around 145 million years ago, are also known. It was a relatively medium-sized ichthyosaur, measuring 4 m (13 ft) long and weighing 940 kg (2,070 lb). Named for its extremely large eyes, it had a jaw 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.
Mixosaurus is an extinct genus of Middle Triassic ichthyosaur. Its fossils have been found near the Italy–Switzerland border and in South China.
Stenopterygius is an extinct genus of thunnosaur ichthyosaur known from Europe.
Eurhinosaurus is an extinct genus of ichthyosaur from the Early Jurassic (Toarcian), ranging between 183 and 175 million years. Fossils of the aquatic reptile have been found in Western Europe. They used to live in the deep, open sea area. Eurhinosaurus was a large genus of ichthyosaurs. An adult individual could reach up to 7 metres (23 ft) in length.
Utatsusaurus hataii is the earliest-known ichthyopterygian which lived in the Early Triassic period. It was nearly 2.5–3 metres (8.2–9.8 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.
Chaohusaurus is an extinct genus of basal ichthyopterygian, depending on definition possibly ichthyosaur, from the Early Triassic of Chaohu and Yuanan, China.
Excalibosaurus is a monotypic genus of marine prehistoric reptiles (ichthyosaurs) that lived during the Sinemurian stage of the Early Jurassic period in what is now England. It is characterized by the extreme elongation of the rostrum, with the lower jaw about three-quarters the length of the upper jaw, giving the animal a swordfish-like look. The only known species is Excalibosaurus costini.
Protoichthyosaurus is a genus of ichthyosaur from the early Jurassic of southern England. Two species are known, P. prostaxalis—the type species, named by Appleby in 1979—and P. applebyi. A third species, P. prosostealis, was named by Appleby, but it was removed from the genus in 2017 due to its similarity to Ichthyosaurus. The genus Protoichthyosaurus was synonymized with Ichthyosaurus by Maisch and Hungerbuhler in 1997, and again by Maisch and Matzke in 2000. However, it was found to be distinct in 2017 by Dean Lomax and colleagues, who separated it from Ichthyosaurus on account of differences in the arrangement and shape of the carpal ossifications, as well as the absence of the fifth digit. The species most likely lived during the Hettangian stage, but may have lived as early as the Rhaetian and as late as the Sinemurian.
Callawayia is an extinct genus of ichthyosaur. It contains the species Callawayia neoscapularis.
Parvinatator, from Latin, “parvus” little and “natator” swimmer, is an extinct genus of small ichthyopterygian marine reptile that lived during the Early to Middle Triassic. Its fossils have been found in British Columbia, Canada.
Suevoleviathan is an extinct genus of primitive ichthyosaur found in the Early Jurassic (Toarcian) of Holzmaden, Germany.
Toretocnemus is an extinct genus of ichthyosaur. Its remains have been found in California, United States, in Triassic layers of the Carnian Hosselkus Limestone.
Wimanius is a genus of ichthyosaur from the Middle Triassic of Switzerland, containing a single species, Wimanius odontopalatus. It was described by Michael Maisch and Andreas Matzke in 1998 based on an incomplete skull from Monte San Giorgio, a mountain on the Swiss-Italian border. Wimanius possesses teeth on its palate, though whether they were located on the palatine or pterygoid is disputed. Other features of Wimanius include a large orbit and jugals with two rami of similar lengths. Different phylogenetic placements of Wimanius have been recovered by different studies, including it being a mixosaurid relative or a merriamosaur, and a monotypic family, Wimaniidae has been named for it. However, its validity has also been questioned, and synonymy with various other genera has been proposed. The only specimen of Wimanius come from the Besano Formation. During the Anisian, this region was a lagoon populated by a wide variety of marine life, including a variety of other ichthyosaurs.
Mixosauridae was an early group of ichthyosaurs, living between 247.2 and 235 million years ago, during the Triassic period. Fossils of mixosaurs have been found all over the world: China, Timor, Indonesia, Italy, Germany, Spitsbergen, Switzerland, Svalbard, Canada, Alaska, and Nevada.
Macgowania is an extinct genus of parvipelvian ichthyosaur known from British Columbia of Canada.
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 Lhuyd 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.
Temnodontosaurus eurycephalus is an extinct species of marine reptile. It is thought to have been a nektonic carnivore. Its name comes from the Greek ευρύς, for "wide" and κεφαλή for "head". It possibly belongs to a new genus.
Magnipterygius is an extinct genus of primitive ichthyosaur found in the Early Jurassic Posidonia Shale of Dotternhausen, Germany. The holotype specimen is SMNS96922, a nearly complete articulated skeleton. This genus is well known as a small-sized ichthyosaur, of around 120 centimetres (3.9 ft) length, making it the second genus of that size after the Triassic. Due to the similarities with the genus Stenopterygius it has been classified as a member of the family Stenopterygiidae.
1 2 3 4 5 6 Sander,P.M.(2000). "Ichthyosauria: their diversity, distribution, and phylogeny", Paläontologische Zeitschrift 74: 1–35
1 2 3 4 5 6 7 McGowan, C. (1992). Dinosaurs, Spitfires, and Sea Dragons. Harvard University Press
1 2 Davis, Larry E. (2009). "Mary Anning of Lyme Regis: 19th Century Pioneer in British Palaeontology". Headwaters: The Faculty Journal of the College of Saint Benedict and Saint John’s University 26: 96-126
↑ Pierce, P. (2006). Jurassic Mary: Mary Anning and the Primeval Monsters. Sutton Publishing
1 2 3 4 McGowan, C. (1995). "Temnodontosaurus risor is a Juvenile of T. platyodon (Reptilia: Ichthyosauria)". Journal of Vertebrate Paleontology. 14 (4): 472–479
1 2 3 McGowan C. (1996). "Giant ichthyosaurs of the Early Jurassic". Canadian Journal of Earth Sciences 33(7): 1011-1021
1 2 McGowan, C. (1974). "A revision of the longipinnate ichthyosaurs of the Lower Jurassic of England, with descriptions of two new species (Reptilia, Ichthyosauria)". Life Sciences Contributions, Royal Ontario Museum 97: 1–37
1 2 3 Emily A. Buchholtz (2000). Swimming styles in Jurassic Ichthyosaurs. Journal of Vertebrate Paleontology, 21, 63-71
↑ McGowan, C. and Motani, R. 2003. Handbook of Paleoherpetology, Part 8 Ichthyopterygia. Verlag Dr. Friedrich Pfeil, Munich. 175 pp.
↑ Swaby. E.J and Lomax. D.R. (2020). A revision of Temnodontosaurus crassimanus (Reptilia: Ichthyosauria) from the Lower Jurassic (Toarcian) of Whitby, Yorkshire, UK. Historical Biology, https://doi.org/10.1080/08912963.2020.1826469.
↑ Motani R.(2005). Evolution of fish-shaped reptiles (Reptilia: Ichthyopterygia) in their physical environments and constraints. Annual Review of Earth and Planetary Sciences. 33: 395-420
1 2 Thies, D. & Hauff, R.B. (2013). A Speiballen from the Lower Jurassic Posidonia Shale of South Germany”. – N. Jb. Geol. Paläont. Abh., 267: 117–124; Stuttgart
↑ Scheyer, Torsten M. et al. (2014). Early Triassic Marine Biotic Recovery: The Predators’ Perspective. PLoS ONE 9.3 (2014): e88987
↑ Maisch MW, Matzke AT (2003). "Observations on Triassic ichthyosaurs. Part XII. A new Lower Triassic ichthyosaur genus from Spitzbergen". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 229: 317–338. doi:10.1127/njgpa/229/2003/317.
↑ “The lithostratigraphy of the Blue Lias Formation (Late Rhaetian–Early Sinemurian) in the southern part of the English Midlands”. Proceedings of the Geologists' Association. 112(2): 97-110
↑ Bottjer, Etter, Hagadorn, Tang, editors (2001). “Exceptional Fossil Preservation”. Columbia University Press
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
