| Stenopterygius | |
|---|---|
 | |
| S. quadriscissus adult and juvenile | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | † Ichthyosauria |
| Family: | † Stenopterygiidae |
| Genus: | † Stenopterygius Jaekel, 1904 |
| Species | |
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Stenopterygius is an extinct genus of thunnosaur ichthyosaur known from Europe (England, France, Germany, Luxembourg and Switzerland). [1] [2]
Stenopterygius was originally named by Quenstedt in 1856 as a species of Ichthyosaurus , I. quadriscissus. Otto Jaekel in 1904 reassigned it to its own genus, Stenopterygius. The type species is therefore Ichthyosaurus quadriscissus but the combinatio nova Stenopterygius quadriscissus. [2] The generic name is derived from stenos, Greek for "narrow", and pteryx (πτερυξ), Greek for "fin" or "wing". [3] The specific name means "split in four" referring to the presumed condition of the first finger.
Stenopterygius was a medium-sized ichthyosaur, [1] with S. quadriscissus and S. triscissus reaching a maximum length of about 3.5 metres (11 ft), with S. aaleniensis being of similar size, [4] while the larger S. uniter could exceed 4 metres (13 ft). [5] Young adults reached at least 2 m (6.6 ft) long, as indicated by the type specimen of S. triscissus measuring 2.2 m (7.2 ft) long. [6] This genus was physically similar to the better known Ichthyosaurus , but had a smaller skull and narrower flippers. Beautifully preserved fossils of Stenopterygius have been found in Germany. [7] Its skull was extended into a kind of a beak and was armed with a quantity of large teeth. The limbs had been transformed to fin-like structures. The tail terminated in a large, semicircular, leathery, vertical caudal fin and even a triangular dorsal fin was present. One well-preserved fossil of Stenopterygius preserves traces of skin, from which the animal's coloration was discovered to be countershaded (darker on the back than the underbelly). [8]
Most of the known specimens of Stenopterygius, more than 100, were redescribed by Michael W. Maisch in 2008. He found that S. quadriscissus (the combinatio nova of the type species Ichthyosaurus quadriscissus) also includes S. eos, S. incessus, and S. macrophasma, as well as specimens previously referred to S. hauffianus and S. megacephalus. Maisch followed Woodward (1932) and considered Ichthyosaurus triscissus to be a valid species of Stenopterygius. The type specimens of S. longifrons, S. megacephalus, and S. megalorhinus were all referred to this species, as the name I. triscissus has a priority over them. Some specimens previously referred to S. megalorhinus, as well as the holotype of S. cuneiceps, were found to belong to a species of their own for which the binomen Stenopterygius uniter can be used. [2]
As the holotype of S. uniter was destroyed in World War II, Maisch proposed a neotype. Maisch also found that S. promegacephalus is a nomen dubium , as it is based on a juvenile specimen, and that the lectotype of S. hauffianus can be determined as Stenopterygius cf. S. quadriscissus at best, so this species should be considered a nomen dubium. He found out that most specimens previously referred to S. hauffianus can be referred to S. quadriscissus, while the rest belongs to a highly distinctive new taxon that cannot be referred to any valid species of Stenopterygius. This species was reassigned to its own genus, Hauffiopteryx . [2]
Stenopterygius is known from the lectotype GPIT 43/0219-1 (also registered as GPIT-PV-30028 and PV 7532), articulated complete skeleton which preserved a very large embryo. The animal is about 3.15 m (10.3 ft) in length. It was collected from the Harpoceras elegantulum-exaratum ammonoid subzones (more specifically Lias ε II3-4), Harpoceras falcifer zone, of the famous Posidonien-Schiefer lagerstätte (Posidonia Shale) of Holzmaden, dating to the early Toarcian stage of the Early Jurassic, about 182 million years ago. Maisch referred to the type species 30 additional specimens, all came from Dobbertin of Mecklenburg-Vorpommern and Holzmaden, Germany and Dudelange, Luxembourg. They were collected from the Harpoceras palum to H. falciferum ammonoid subzones (Lias ε I2-II11, lower-middle early Toarcian), Harpoceras tenuicostatum-falcifer zones, of the Posidonia Shale. S. triscissus is known from the holotype GPIT 12/0224-2, articulated almost complete skeleton. The animal is a young adult about 2.2 m (7.2 ft) in length. [6] It was collected from the Harpoceras exaratum-elegans ammonoid subzones (more specifically Lias ε II6), Harpoceras falcifer zone, of the Posidonia Shale in Ohmden, dating to the middle Early Toarcian stage of the Early Jurassic. Maisch referred to this species 13 additional specimens, all came from various localities in England, France, Germany, Luxembourg and Switzerland. They were collected from the Lias ε II1-III, dating to the middle-late Early Toarcian.
S. uniter is known from the holotype SMNS 14216, articulated complete skeleton which was destroyed in World War II. The animal is an adult about 3.35 m (11.0 ft) in length. The proposed neotype is GPIT 1491/10, articulated almost complete skeleton. The animal is a young adult about 2.34 m (7.7 ft) in length. It was collected from the Harpoceras falcifer ammonoid subzones (more specifically Lias ε II10), Harpoceras falcifer zone, of the Posidonia Shale in Holzmaden, dating to the middle Early Toarcian stage of the Early Jurassic. Maisch referred to this species 10 additional specimens, all came from Holzmaden. They were collected from the Harpoceras exaratum to H. falciferum ammonoid subzones (Lias ε II6-II11, middle early Toarcian), Harpoceras falcifer zones, of the Posidonia Shale. [2]
Additional materials were described by Hannah Caine and Michael J. Benton in 2011, from the early Toarcian Beacon Limestone of Strawberry Bank, Ilminster of England. [9] The specimens are all juveniles or infants, which were preserved mostly by almost complete skeletons and some skulls. They include BRLSI M1405, BRLSI M1407, BRLSI M1408, BRLSI M1409. Caine and Benton referred these specimens to S. triscissus. [10]
A Middle Jurassic species from southwestern Germany, Stenopterygius aaleniensis, was described in 2012. [4]
Maisch and Matzke (2000) and Maisch (2010) regarded Chacaicosaurus and Hauffiopteryx to be stenopterygiids. [1] [11] However, they didn't perform any cladistic analyses to confirm these claims. Fischer et al. (2011) performed a cladistic analysis that found Chacaicosaurus to be a basal thunnosaur which is placed outside both Stenopterygiidae and Ophthalmosauridae. [12] Both Maisch (2008) and Caine and Benton (2011) performed cladistic analyses that found Hauffiopteryx to be either a basalmost member of Eurhinosauria or a basalmost member of Thunnosauria (which is an equivalent position to a basalmost member of Stenopterygiidae sensu Maisch [2008] with exclusion of Ichthyosaurus). [2] [10] These results mean that the Stenopterygiidae are a monotypic family that includes only the type genus Stenopterygius. [12]
The cladogram below follows the topology from a 2010 analysis by Patrick S. Druckenmiller and Erin E. Maxwell. [13]
| Thunnosauria |
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The habits of Stenopterygius spp. were similar to those of present-day dolphins. They spent most of their lives in the open sea, where they hunted fish, cephalopods, and other animals. The abdominal cavities of skeletons of this ichthyosaur often contain the remains of such food. [15] [16]
One famous fossil is that of a mother and baby that died in childbirth (ichthyosaurs were viviparous). Stenopterygius had a preference for tail-first birth, like modern day cetaceans. However, there are specimens known with fetuses in utero suggesting a head-first birth. [17] [18]
Stenopterygius was a very fast swimmer, with a cruising speed similar to that of tuna, which is among the fastest of all living fishes.[ citation needed ]
In 2018, a Stenopterygius specimen was reported with evidence of having had blubber, which indicates that other ichthyosaurs and it were homeothermic ("warm blooded"). The same specimen also suggests that ichthyosaurs would have been countershaded, on the basis of distributional variation of melanophores that contain eumelanin. [8]
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.
Temnodontosaurus is an extinct genus of ichthyosaur from the Early Jurassic period. They lived between 200 and 175 million years ago (Hettangian-Toarcian) in what is now Western Europe and possibly Chile. It lived in the deeper areas of the open ocean. University of Bristol paleontologist Jeremy Martin described the genus Temnodontosaurus as "one of the most ecologically disparate genera of ichthyosaurs," although the number of valid Temnodontosaurus species has varied over the years.
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.
Rhomaleosaurus is an extinct genus of Early Jurassic rhomaleosaurid pliosauroid known from Northamptonshire and from Yorkshire of the United Kingdom. It was first named by Harry Seeley in 1874 and the type species is Rhomaleosaurus cramptoni. It was one of the earliest large marine reptile predators which hunted in the seas of Mesozoic era, measuring about 7 metres (23 ft) long. Like other pliosaurs, Rhomaleosaurus fed on ichthyosaurs, ammonites and other plesiosaurs.
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.
Undorosaurus is an extinct genus of ophthalmosaurid ichthyosaur known from western Russia, Svalbard, and Poland. It was a large ichthyosaur, with the type species measuring 4–6 metres (13–20 ft) long.
Mollesaurus is an extinct genus of large ophthalmosaurine ophthalmosaurid ichthyosaur known from northwestern Patagonia of Argentina.
Chacaicosaurus is a genus of neoichthyosaurian ichthyosaur known from the Middle Jurassic of Argentina. The single known specimen of this genus was excavated from the Los Molles Formation in Neuquén Province, and is housed at the Museo Olsacher under the specimen number MOZ 5803. This specimen consists of a skull, forelimb, some vertebrae, and some additional postcranial elements. The genus was named by Marta Fernández in 1994, and contains a single species, Chacaicosaurus cayi, making it the first named distinctive ichthyosaur from the Bajocian stage. It is a medium-sized ichthyosaur with a very long snout, which bears a ridge running along each side. The forelimbs of Chacaicosaurus are small and contain four main digits.
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.
Hauffiosaurus is an extinct genus of Early Jurassic pliosaurid plesiosaur known from Holzmaden of Germany and from Yorkshire of the United Kingdom. It was first named by Frank Robin O’Keefe in 2001 and the type species is Hauffiosaurus zanoni. In 2011, two additional species were assigned to this genus: H. longirostris and H. tomistomimus.
Plesiopterys is an extinct genus of plesiosaur originating from the Posidonienschiefer of Holzmaden, Germany, and lived during the Early Jurassic period. It is thought to be the sister taxon to all other plesiosauroids including the Plesiosaurus, and is placed outside of the Plesiosauroidea group. Plesiopterys wildi is the one known species within the genus, and is 220 centimeters long, or about 7.2 feet, and its body and skull are both relatively small. It possesses a unique combination of both primitive and derived characters, and is currently displayed at the State Museum of Natural History, Germany.
The Posidonia Shale geologically known as the Sachrang Formation, is an Early Jurassic geological formation of southwestern and northeast Germany, northern Switzerland, northwestern Austria, southern Luxembourg and the Netherlands, including exceptionally well-preserved complete skeletons of fossil marine fish and reptiles.
Suevoleviathan is an extinct genus of primitive ichthyosaur found in the Early Jurassic (Toarcian) of Holzmaden, Germany.
Meyerasaurus is an extinct genus of rhomaleosaurid known from Holzmaden, Baden-Württemberg of southwestern Germany.
Hauffiopteryx is an extinct genus of ichthyosaur known from Germany, Luxembourg and Somerset of the United Kingdom. Two species are known: H. typicus and H. altera.
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.
Cleviceras is an extinct genus of cephalopod belonging to the family Hildoceratidae. These cephalopods existed in the Jurassic period, during Toarcian and possibly even uppermost Pliensbachian age. Sometimes, it is considered to be a synonym of Eleganticeras.
The Sachrang Formation or "Posidonienschiefer" Formation is a geological formation of southwestern Germany, northern Switzerland, northwestern Austria, southeast Luxembourg and the Netherlands, that spans about 3 million years during the Early Jurassic period. It is known for its detailed fossils, especially sea fauna, listed below. Composed mostly by black shale, the formation is a Lagerstätte, where fossils show exceptional preservation, with a thickness that varies from about 1 m to about 40 m on the Rhine level, being on the main quarry at Holzmaden between 5 and 14 m. Some of the preserved material has been transformed into fossil hydrocarbon Jet, specially wood remains, used for jewelry. The exceptional preservation seen on the Posidonia Shale has been studied since the late 1800s, finding that a cocktail of chemical and environmental factors let to such an impressive conservation of the marine fauna. The most common theory is the changes in the oxygen level, where the different anoxic events of the Toarcian left oxygen-depleted bottom waters, with the biota dying and falling to the bottom without any predator able to eat the dead bodies.
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.
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