Brachauchenius Temporal range: Late Cretaceous, | |
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Holotype specimen of B. lucasi (USNM 4989), as view in its original position | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Superorder: | † Sauropterygia |
Order: | † Plesiosauria |
Family: | † Pliosauridae |
Subfamily: | † Brachaucheninae |
Genus: | † Brachauchenius Williston, 1903 |
Type species | |
†Brachauchenius lucasi Williston, 1903 |
Brachauchenius (meaning 'short neck') is an extinct genus of pliosaurs that lived during the Late Cretaceous in what are now North America and North Africa. Only one species is known, B. lucasi, initially described by Samuel Wendell Williston in 1903 from a partial fossil skeleton discovered in a quarry in Kansas, United States. Many other fossil specimens attributed to the species were subsequently discovered, including an individual from Morocco whose presence was made official in 2016. Many contemporary pliosaur specimens were formerly attributed to Brachauchenius, but have since been reidentified as belonging to other genera or are recognized as indeterminate.
In 1884, a partial skeleton of a marine reptile was discovered by the owner of a quarry near Delphos, in Ottawa County, Kansas. News of this find thus reached Charles H. Sternberg, who was then collecting fossils for Othniel Charles Marsh. Sternberg then wrote several letters to Marsh seeking his permission and funding to exhume the specimen, which he allowed. After exhumation, Sternberg gave the specimen to the Peabody Museum of Natural History for Marsh, but it turned out that Marsh would do little with it. [1] The fossil was eventually transferred to the United States National Museum of Natural History and subsequently given the code name USNM 4989. This same specimen consists of a nearly complete skull measuring 90 cm (35 in) long, followed by thirty-seven vertebrae and associated ribs. [2] [3] [4] [5] Historical documentation from the museum where the specimen has since resided notes that Sternberg was allegedly helped by a certain “John Potts” in its exhumation. [4] [1] In 1903, Samuel Wendell Williston designated the fossil as the holotype of a new plesiosaur genus and species under the name Brachauchenius lucasi. [6] The generic name Brachauchenius derives from the Ancient Greek words βραχύς (brakhys, "short") and αὐχήν (aukhḗn, "neck"), followed by the Latin suffix ius, all meaning "short neck". [7] Williston chose this name because this specimen was considered the shortest-necked plesiosaur ever described. [6] [8] The specific name lucasi is named in honor of Frederic Augustus Lucas for his notable contributions to American paleontology. [6] [8] [7]
In his article, Williston only mentions the origin locality of the specimen, and does not detail any elements regarding the discovery of the latter. Thus, the circumstances surrounding the discovery of USNM 4989 remained unclear until 2007, when letters from Sternberg obtained by Kenneth Carpenter were formalized in an article written by his colleague Michael J. Everhart. [1] The stratigraphic provenance of the holotype specimen remained also uncertain for decades. Williston notes that it comes from the "Benton Cretaceous", [6] but it turns out that three geological formations outcrop the locality where the specimen was discovered. [4] In 1996, Carpenter listed the specimen as coming from the Greenhorn Limestone, [9] but he does not, however, support any evidence for this assertion. A microscopic examination of the fossils published in 2005 revealed that the specimen came from either the upper level of the Greenhorn Limestone or the lower level of the Fairport Chalk Member of the Carlile Shale, suggesting that the specimen dates to the early Middle Turonian. [4]
In 2016, a pliosaur mandible from Turonian deposits near Goulmima, Morocco were referred to the species Brachauchenius lucasi. [10]
In 1860, Richard Owen documented a partial skull having been discovered around an unspecified date by George Cubitt in Cretaceous sediments from the town of Dorking, in the county of Surrey, England. Based on teeth characteristics, Owen referred this specimen to Polyptychodon interruptus , a species of pliosaurid that he himself had already named in 1841 from fossils dating from the same period which were discovered in the counties of Sussex and Kent. [11] The following year, Owen cited that the specimen was discovered during the construction of a railway tunnel through the Chalk Group, near Frome, Somerset. [12] However, this locality was most likely confused with those of other specimens assigned to this genus, and with multiple reported evidence, it seems more likely that the first locality originally mentioned is the most likely. This specimen has since resided in the local museum of Dorking, where it is cataloged as DOKDM G/1-2. [a] In a phylogenetic study published in 2013, Roger B. J. Benson and colleagues recovered it as being close to several other specimens assigned to Brachauchenius, and therefore suggested that it would be better to refer it to that genus as well, although without specific affiliation. [14] In his revision of Polyptychodon published in 2016, Daniel Madzia designates this genus as a nomen dubium due to the lack of accessibility and diagnostics regarding the holotype tooth of the taxon, the latter having possibly even been lost. However, he considers it likely that DOKDM G/1-2 could be designated as the neotype of this genus in order to maintain its validity, but he refrains from doing so at this time since the descriptions provided by Owen are obsolete. [15] In a 2017 conference, Madzia and colleagues judge the Dorking specimen to be potentially diagnostic despite its incomplete preservation. [16]
All recognized fossils of the related and contemporary genus Megacephalosaurus were first interpreted as coming from Brachauchenius. [17] [18] The holotype specimen of the genus, cataloged as FHSM VP-321, was discovered in 1950 by teenage brothers Frank and Robert Jennrich near Fairport, Kansas. The Jenrich brothers, aided by George F. Sternberg and a local cow rancher named Jim Rouse, exhumed the skull later that year. Although initially thinking the specimen would be a mosasaur, G. F. Sternberg later identified it as an imposing specimen of B. lucasi, placing the skull and mandible on a single support showing only their dorsal sides. [17] [4] However, it was in 1996 that the skull was first described by Carpenter, who still identified it as such. [9] A new expedition carried out in November 2003 by R. Jennrich led scientists to discover that the specimen was exhumed from Fairport Chalk. In 2007, Everhart discovered photos of the skull's underside taken prior to its mounting, which revealed underside features that were different from those found in other B. lucasi skulls. The specimen is then removed from its mount, and is officially described in 2013 by Bruce A. Schumacher, Carpenter and Everhart as the holotype of a new genus and species which they name Megacephalosaurus eulerti. [18] Shortly before the description made by Schumacher et al., the phylogenetic study by Benson et al. classified the taxon as B. eulerti. [14] The history of the paratype skull, cataloged UNSM 50136, is much more obscure. Indeed, the latter presents very little contextual information on its discovery and its precise locality of origin, the only information known is that the specimen also comes from Kansas. It was first described in the scientific literature by Schumacher in 2008, who provisionally identified it under the name aff. B. lucasi. Although its locality of origin is unknown, matrix analysis extracted from the fossil identifies nannofossil assemblages that are associated with limestone deposits of the Greenhorn Formation. [19] When FHSM VP-321 was found to be a distinct genus, USNM 50136 was identified to be conspecific with it and was assigned to be its paratype. [18] Everhart blogged that other specimens currently attributed to Brachauchenius may actually belong to Megacephalosaurus. The most notable specimen in his line of sight being UNSM 112437, a partial skull having been collected from the Graneros Shale. [17]
In 2000, a relatively complete pliosaurid skeleton, since cataloged as VL17052004-1, was discovered in the town of Villa de Leyva in Boyacá, Colombia, before being exhumed during 2004-2005. [20] Coming from the Paja Formation, it was dated to the Upper Barremian, making the latter the oldest known example of the brachauchenines. The skeleton was first described in 2005 by Oliver Hampe as belonging to Brachauchenius, [21] before being designated as the holotype of a new genus and species under the name Stenorhynchosaurus munozi by María Eurídice Páramo and colleagues in 2016. [20]
Brachauchenius has a morphology typical of the pliosaurids of the thalassophonean group, which has a large elongated skull connected to a short neck, unlike many other plesiosaurs, which have a long neck and a small head. Like all other plesiosaurs, Brachauchenius has a short tail, a massive trunk and two pairs of large flippers. [22] [23] [24] Like most Turonian pliosaurs, the measurement of Brachauchenius is quite modest, [18] the holotype specimen having a maximum length estimated at 5.3 m (17 ft) for a body mass estimated at 2.2 t (2.2 long tons; 2.4 short tons). [25] [26]
The cladogram below is modified from Madzia et al. (2018): [13]
Thalassophonea |
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Plesiosauroidea is an extinct clade of carnivorous marine reptiles. They have the snake-like longest neck to body ratio of any reptile. Plesiosauroids are known from the Jurassic and Cretaceous periods. After their discovery, some plesiosauroids were said to have resembled "a snake threaded through the shell of a turtle", although they had no shell.
Elasmosaurus is a genus of plesiosaur that lived in North America during the Campanian stage of the Late Cretaceous period, about 80.5 million years ago. The first specimen was discovered in 1867 near Fort Wallace, Kansas, US, and was sent to the American paleontologist Edward Drinker Cope, who named it E. platyurus in 1868. The generic name means "thin-plate reptile", and the specific name means "flat-tailed". Cope originally reconstructed the skeleton of Elasmosaurus with the skull at the end of the tail, an error which was made light of by the paleontologist Othniel Charles Marsh, and became part of their "Bone Wars" rivalry. Only one incomplete Elasmosaurus skeleton is definitely known, consisting of a fragmentary skull, the spine, and the pectoral and pelvic girdles, and a single species is recognized today; other species are now considered invalid or have been moved to other genera.
Kronosaurus is an extinct genus of large short-necked pliosaur that lived during the Aptian to Albian stages of the Early Cretaceous in what is now Australia. The first known specimen was received in 1899 and consists of a partially preserved mandibular symphysis, which was first thought to come from an ichthyosaur according to Charles De Vis. However, it was 1924 that Albert Heber Longman formally described this specimen as the holotype of an imposing pliosaurid, to which he gave the scientific name K. queenslandicus, which is still the only recognized species nowadays. The genus name, meaning "lizard of Kronos", refers to its large size and possible ferocity reminiscent of the Titan of the Greek mythology, while the species name alludes to Queensland, the Australian state of its discovery. In the early 1930s, the Harvard Museum of Comparative Zoology sent an organized expedition to Australia that recovered two specimens historically attributed to the taxon, including a well known skeleton that is now massively restored in plaster. Several attributed fossils were subsequently discovered, including two large, more or less partials skeletons. As the holotype specimen does not present diagnostics to concretely distinguish Kronosaurus from other pliosaurids, these same two skeletons are proposed as potential neotypes for future redescriptions. Two additional species were proposed, but these are now seen as unlikely or belonging to another genus.
Pliosauroidea is an extinct clade of plesiosaurs, known from the earliest Jurassic to early Late Cretaceous. They are best known for the subclade Thalassophonea, which contained crocodile-like short-necked forms with large heads and massive toothed jaws, commonly known as pliosaurs. More primitive non-thalassophonean pliosauroids resembled plesiosaurs in possessing relatively long necks and smaller heads. They originally included only members of the family Pliosauridae, of the order Plesiosauria, but several other genera and families are now also included, the number and details of which vary according to the classification used.
The Plesiosauria or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia.
Liopleurodon is an extinct genus of carnivorous pliosaurid pliosaurs that lived from the Callovian stage of the Middle Jurassic to the Kimmeridgian stage of the Late Jurassic period. The type species is L. ferox, which is probably the only valid species. Some studies also include the second species L. pachydeirus, but this latter is considered as a probable junior synonym of L. ferox due to its lack of viable diagnosis. As the holotype specimen of L. ferox consists of a single tooth preserving questionable distinctive features, recent studies therefore recommend the necessary identification of a neotype in order to preserve the validity of the genus. Numerous fossil specimens attributed to Liopleurodon, even including numerous skeletons, have been discovered in Europe, Russia, and Mexico. Other additional species were even proposed, but these are currently seen as coming from other pliosaurid genera.
Plesiopleurodon is an extinct genus of Mesozoic marine reptiles, belonging to the Sauropterygia, known from the Late Cretaceous of North America. It was named by Kenneth Carpenter based on a complete skull with a mandible, cervical vertebra, and a coracoid. In naming the specimen, Carpenter noted "Of all known pliosauroids, Plesiopleurodon wellesi most closely resembles Liopleurodon ferox from the Oxfordian of Europe, hence the generic reference." It was initially described as a pliosauroid due to it short neck, a common trait of the superfamily. However, later exploration into the relationships of both groups indicate that not all pliosauroids have short necks and not all plesiosauroids have long necks. Later research indicates it is a member of the Polycotylidae, within the clade Occultonectia.
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Styxosaurus is a genus of plesiosaur of the family Elasmosauridae. Styxosaurus lived during the Campanian age of the Cretaceous period. Three species are known: S. snowii, S. browni, and S. rezaci.
Nichollssaura is an extinct genus of leptocleidid plesiosaur from the Early Cretaceous Boreal Sea of North America. The type species is N. borealis, found in the early Albian age Clearwater Formation near Fort McMurray, Alberta, Canada.
Simolestes is an extinct pliosaurid genus that lived in the Middle to Late Jurassic. The type specimen, NHMUK PV R 3319 is an almost complete but crushed skeleton diagnostic to Simolestes vorax, dating back to the Callovian of the Oxford Clay formation, England. The genus might also be known from the Tithonian Bhuj Formation of India (S.indicus), however the referral of this species to Simolestes is dubious. S.keileni from France was moved to the new genus Lorrainosaurus in 2023.
Polyptychodon is a genus of pliosaurid found in Middle-Late Cretaceous marine deposits in southern England, France and Argentina. It has been considered a nomen dubium in a 2016 review.
Ogmodirus is an extinct genus of plesiosaur found in the Cenomanian-Turonian Greenhorn Limestone of Kansas. The type species, O. martini, was named by Samuel Wendell Williston and Roy Lee Moodie in 1913.
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Megacephalosaurus is an extinct genus of short-necked pliosaur that inhabited the Western Interior Seaway of North America about 94 to 93 million years ago during the Turonian stage of the Late Cretaceous, containing the single species M. eulerti. It is named after its large head, which is the largest of any plesiosaur in the continent and measures up to 1.75 meters (5.7 ft) in length. Megacephalosaurus was one of the largest marine reptiles of its time with an estimated length of 6–9 meters (20–30 ft). Its long snout and consistently sized teeth suggest that it preferred a diet of smaller-sized prey.
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