Megalneusaurus

Last updated

Megalneusaurus
Temporal range: Late Jurassic (Oxfordian to Kimmeridgian), 160–150  Ma
Megalneusaurus.jpg
Illustration of some of the holotype fossils
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder:† Sauropterygia
Order:† Plesiosauria
Family:† Pliosauridae
Genus:† Megalneusaurus
Knight, 1898
Type species
Megalneusaurus rex
(Knight, 1895)
[originally Cimoliosaurus ]
Synonyms
  • Cimoliosaurus rexKnight, 1895

Megalneusaurus is an extinct genus of large pliosaurs that lived during the Oxfordian and Kimmeridgian stages of the Late Jurassic in what is now North America. It was provisionally described as a species of Cimoliosaurus by the geologist Wilbur Clinton Knight in 1895, before being given its own genus by the same author in 1898. The only species identified to date is M. rex, known from several specimens identified in the Redwater Shale Member, within the Sundance Formation, Wyoming, United States. A specimen discovered in the Naknek Formation in southern Alaska was referred to the genus in 1994, without a specific assignment. In Ancient Greek, the generic name literally translates to "large swimming lizard", due to the measurement of the fossils of the holotype specimen.

Contents

Estimated to be around 7–9 metres (23–30 ft) long, Megalneusaurus is the largest known North American pliosaur dating from the Jurassic. As its name suggests, the genus was considered the largest sauropterygian identified before the discovery of some Kronosaurus fossils in 1930. Based on comparisons made with other pliosaurs, Megalneusaurus is generally viewed as a pliosaurid. Some researchers consider the fossil material to be non-diagnostic, making Megalneusaurus a possible nomen dubium , although opposing views are nevertheless maintained. Based on stomach contents, the animal fed on cephalopods and fish, although it is not excluded that it would have attacked and fed on contemporary plesiosaurs.

Research history

In 1895, geologist Wilbur Clinton Knight discovered and exhumed fossils of a partially articulated but incomplete skeleton of a pliosaur near the small town of Ervey, Wyoming, United States. The discovery consists of a specimen, cataloged as UW 4602, which preserves ribs, vertebrae, two more or less partial flippers and part of the shoulder girdle, [1] from a specimen that would have reached adulthood. [2] [3] : 29  The same year, Knight formalized his discovery via an announcement that was published by Science Magazine , where he briefly described certain fossils. As the fossils were not exhumed from their geological matrix at the time of publication of his announcement, Knight was uncertain about the generic positioning of the specimen. He therefore erected a new species of Cimoliosaurus , C. rex, to which he provisionally classified it pending a more in-depth description. [4] [5] : 358  It was three years later, in 1898, that Knight described the specimen in more detail and erected the distinct genus Megalneusaurus to include it, the species thus becoming M. rex. [6] The generic name is formed from the words in Ancient Greek μέγας (mégas, "great") and νηκτός (nêktós, "swimmer") prefixed onto σαῦρος (saûros, "lizard"). The specific name rex means "king" in Latin. [7] [8] Although no description of the meaning of this etymology was given in his 1898 description, Knight would likely have named the taxon thus due to the rather considerable measurements of this specimen for the time, [7] which he judges according to his words to be "the largest known animal of the order Sauropterygia". [6] [5] : 358 

North America laea relief location map with borders.jpg
Red pog.svg
Steel pog.svg
class=notpageimage|
Various localities from where Megalneusaurus fossils have been discovered. The red point shows the location of the type locality of the taxon, while the gray point shows that of the referred specimen.

Due to the discovery of other large pliosaurs found elsewhere in the world, [9] the attention of Megalneusaurus by paleontologists has generally been "forgotten", [1] being only very briefly mentioned in 20th and early 21st century scientific literature. [10] : 37, 45  [11] : 341  [12] [2] In 1995, the Tate Geological Museum of Casper planned to create an exhibit showcasing marine reptiles discovered in the Sundance Formation. During the collections, researchers came across a cast of the original forelimb originally discovered by Knight, the actual fossil being preserved at the Geological Museum of the University of Wyoming. Based on this same casting, paleontologist William Wahl of the Wyoming Dinosaur Center, began to take a particular interest in this taxon, which led him to open an investigation to find the location of the original type locality of Megalneusaurus, previously unmentioned in Knight's work. However, Knight having written a considerable number of letters for many paleontologists of his time, these are then used by researchers as clues to make the reunion. It was therefore during the summer of 1996 that the type locality was finally found, corresponding to the Redwater Shale Member, located in the upper part of the Sundance formation, in the eastern Rocky Mountains. This precise part of the formation dates from the Oxfordian stage of the Late Jurassic. After the rediscovery of this place, new excavations were launched in the field and additional fossils were found. [1] [2] [8] About 20 m (66 ft) from the area where the first known fossils of Megalneusaurus were discovered, a large bone fragment probably coming from the shoulder or pelvic girdle was exhumed and described in an article published in 2007. [2] In 2008, it was a fully articulated and almost complete forelimb coming directly from the holotype specimen which was exhumed, [1] and it is described in detail in 2010. [13] Fossils coming possibly from two other specimens have also been reported. The first is an isolated neural arch, cataloged as UW 24238, while the second is a propodial (upper limb bone), cataloged as WDC SS019. [2] [13] [8] Other fossil finds referred to Megalneusaurus were made in this area over an additional period from 2009 until 2011, but these have not yet been officially described. [1] In 2003, Richard Ellis reported that Robert Bakker should re-examine the holotype specimen in more detail, something that has apparently not been done since. [14]

Megalneusaurus was then historically only known from Wyoming, but another specimen referred to the genus was discovered in southern Alaska. It was in June 1922 that W. R. Smith of the United States Geological Survey received two bone fragments from a certain Jack Mason. These two bone fragments were collected from the Kejulik River, located on the Alaska Peninsula, and consist of the proximal and distal ends of the same large humerus, which would subsequently be cataloged as USNM 418489. The stratigraphic unit to which this specimen was discovered corresponds to the Snug Harbor Siltstone Member of the Naknek Formation, dating from between the Oxfordian and Kimmeridgian stages of the Late Jurassic. It was only in 1994 that Robert E. Weems and Robert B. Blodgett described this fossil in detail to which they referred it to the genus on the basis of comparisons made with the holotype specimen. However, as their description and comparison is only based on an isolated humerus, they refer it under the name Megalneusaurus sp., the authors being uncertain as to whether the specimen would belong to another species or to the type species. [15]

Description

Life restoration Megalneusaurus027.jpg
Life restoration

The various genera of pliosaurids that are regularly compared with Megalneusaurus are today classified in the Thalassophonea clade, which are characterized by an elongated skull connected to a short neck, unlike many other plesiosaurs, which have a long neck and a small head. Like all plesiosaurs, however, short tail, a massive trunk and two pairs of large flippers. [5] : 3  [16] : 3 

Size

Megalneusaurus is the largest Jurassic pliosaurid identified in North America. [1] [2] [9] Most studies and descriptions qualify Megalneusaurus as the largest pliosaur to have been identified in the North American continent of any period, [1] [2] but some related genera such as Megacephalosaurus , dating from the Upper Cretaceous, are of comparable size. [17] The taxon was even considered to be the largest known pliosaur in the world until some fossils of the Australian pliosaurid Kronosaurus were described in 1930. [7] [18] [5] : 25, 358  Several estimates of the size of Megalneusaurus have been given throughout research. In 2006, Wahl gave the animal a length of approximately 13 m (43 ft), [12] before the same author and his colleagues reduced its size to just 10 m (33 ft) the following year. [2] In his thesis published in 2009, Australian paleontologist Colin McHenry estimates the size of the animal at between 10 and 12 m (33 and 39 ft) long based on measurements of the femurs given by Knight in 1898. [5] : 419, 436  However, most recent estimates reduce the size of Megalneusaurus to between 7.6 and 9.2 m (25 and 30 ft) long. [1] [19] Based on a skeleton preserved in the Museum of Comparative Zoology of Harvard attributed to Kronosaurus, Bakker suggests that the animal would have had a skull measuring 3.3 m (11 ft) long, although the relevant material is not known. [14] In 2024, Ruizhe Jackevan Zhao suggests that Megalneusaurus would have been similar in size to Pliosaurus funkei , which according to his model was approximately 9.8 m (32 ft) long with a body mass of 12 t (12 long tons; 13 short tons). [16] : 36–37, 39  The referred specimen from Alaska is smaller in measurement than the holotype specimen, although no estimate of its size has been given. [15]

Morphology

The majority of the anatomy of Megalneusaurus is only known from the holotype specimen and concerns only the postcranial parts of the animal, [2] [13] no cranial materials being known. [1] In addition, additional parts including cervical, dorsal and caudal vertebrae, a large part of the shoulder girdle and ribs, have also been lost, [13] the only remaining descriptions of them being made by Knight in 1898. [6]

Classification

When Knight made the discovery of the first known fossils of Megalneusaurus official in 1895, they were first classified in the genus Cimoliosaurus, [4] a plesiosauroid currently classified in the family Elasmosauridae. [20] However, this classification was deliberately provisional, because the fossils were at that time unprepared to allow the specimen to have taxonomic clarification. [4] It was in 1898 that Knight discovered that it was in fact a pliosaur, not hesitating to compare it to the pliosaurids Pliosaurus and Peloneustes . [a] However, Knight does not give any more precise classification of this genus. [6] Studies published from the second half of the 20th century agree that Megalneusaurus would most likely be a pliosaurid. [10] : 37  [11] : 341  [15] [2] [1] [19] In 2009, McHenry questioned the validity of Megalneusaurus, judging the holotype specimen to be non diagnostic and possibly representing a nomen dubium or another taxon better known in other localities around the world. [5] : 444, 451  Two years earlier, in 2007, French paleontologist Marie-Céline Buchy was already perplexed by the attribution of the Alaskan material to this genus, judging it as non-diagnostic as well. [3] : 29  Even before the writing of Buchy and McHenry's theses, Ellis already mentioned in 2003 that many researchers doubted the diagnostic nature of the holotype specimen due to the loss of the previously mentioned fossils, although he also points out that some are of the opposite opinion. [14] This would explain why the name Megalneusaurus is still preserved in some later studies. [13] [19] [21] [16] : 37, 39 

Paleobiology

Feeding

The stomach contents of the holotype specimen of M. rex contain numerous hooklets of coleoid cephalopods as well as a few rare fragments of fish bones. Similar stomach contents have also been documented in other contemporary plesiosaurs, such as Tatenectes and Pantosaurus , proving that these were common food sources for marine reptiles of the Sundance Formation. [2] [13] [19] Being a large pliosaurid, Megalneusaurus would likely have fed on other contemporary plesiosaurs, particularly juveniles or subadults. [19] A juvenile plesiosaur fossil identified in this formation also shows bite marks on the bones of one of its flippers, [12] although their origins have not been formally determined. [19]

Paleopathology

Both humeri of the M. rex holotype specimen are affected by avascular necrosis. [8] [22] A large number of other more or less related plesiosaur fossils also show this disease in both the humerus and the femur. This is the result of ascent too quickly after a deep diving. It is nevertheless uncertain to deduce the depth to which the animal would have descended because it is also possible that the avascular necrosis would have been caused by a few very deep dives, or by a large number of relatively shallow descents. The vertebrae, however, do not show such damage, being, during the lifetime of plesiosaurs, probably protected by a superior blood supply, made possible by the arteries penetrating the bone through the two foramina subcentralia, large openings in their lower face. [22]

Paleoecology

Wyoming

Megalneusaurus comes from the Oxfordian-aged (Upper Jurassic) rocks of the Redwater Shale Member of the Sundance Formation. [1] [2] This member is about 30–60 meters (98–197 ft) thick. While mainly composed of grayish green shale, it also has layers of yellow limestone and sandstone, the former layers containing plentiful fossils of marine life. [23] The Sundance Formation represents a shallow epicontinental sea known as the Sundance Sea. [20] From the Yukon and Northwest Territories of Canada, where it was connected to the open ocean, this sea spanned inland southwards to New Mexico and eastward to the Dakotas. [23] [21] When Megalneusaurus was alive, most of the Sundance Sea was less than 40 meters (130 ft) deep. [24] Based on δ18O isotope ratios in belemnite fossils, the temperature in the Sundance Sea would have been 13–17 °C (55–63 °F) below and 16–20 °C (61–68 °F) above the thermocline. [23]

The paleobiota of the Sundance Formation includes foraminiferans and algae, in addition to a variety of animals. Many invertebrates are known from the Sundance Formation, represented by crinoids, echinoids, serpulid worms, ostracods, malacostracans, and mollusks. The mollusks include cephalopods such as ammonites and belemnites, bivalves such as oysters and scallops, and gastropods. Fish from the formation are represented by hybodont [24] and neoselachian chondrichthyans as well as teleosts (including Pholidophorus ). Marine reptiles are uncommon, but are represented by four species. [21] Of all the plesiosaurs, Megalneusaurus is the only pliosaurid identified in the Sundance Formation. [12] [1] [19] The other plesiosaurs known from this formation are the cryptoclidids Tatenectes and Pantosaurus . [21] Besides plesiosaurs, marine reptiles are also represented by the ichthyosaur Ophthalmosaurus (or, possibly, Baptanodon ) [25] natans, the most abundant marine reptile of the Sundance Formation. [2] [12]

See also

Notes

  1. ↑ According to Knight, some anatomical elements of Megalneusaurus are comparable to that of Plesiosaurus . [6]

Related Research Articles

<i>Kronosaurus</i> Pliosaur genus from the Early Cretaceous period of Australia

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.

<span class="mw-page-title-main">Pliosauroidea</span> Extinct clade of reptiles

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.

Peloneustes is a genus of pliosaurid plesiosaur from the Middle Jurassic of England. Its remains are known from the Peterborough Member of the Oxford Clay Formation, which is Callovian in age. It was originally described as a species of Plesiosaurus by palaeontologist Harry Govier Seeley in 1869, before being given its own genus by naturalist Richard Lydekker in 1889. While many species have been assigned to Peloneustes, P. philarchus is currently the only one still considered valid, with the others moved to different genera, considered nomina dubia, or synonymised with P. philarchus. Some of the material formerly assigned to P. evansi have since been reassigned to "Pliosaurus" andrewsi. Peloneustes is known from many specimens, including some very complete material.

<i>Rhomaleosaurus</i> Genus of rhomaleosaurid plesiosaur from the Early Jurassic period

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.

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

Microcleidus is an extinct genus of sauropterygian reptile belonging to the Plesiosauroidea. The species has 40 neck vertebrae and a short tail of 28 vertebrae. Fossils of the genus have been found in France, the Posidonia Shale in Germany and Luxembourg, and the Alum Shale Formation of England.

<i>Umoonasaurus</i> Extinct species of reptile

Umoonasaurus is an extinct genus of plesiosaur belonging to the family Leptocleididae. This genus lived approximately 115 million years ago during the Early Cretaceous period, in shallow seas covering parts of what is now Australia. It was a relatively small animal around 2.5 metres (8.2 ft) long. An identifying trait of Umoonasaurus is the presence of three crest-ridges on its skull.

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

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.

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

Dolichorhynchops is an extinct genus of polycotylid plesiosaur from the Late Cretaceous of North America, containing the species D. osborni and D. herschelensis, with two previous species having been assigned to new genera. Definitive specimens of D. osborni have been found in the late Coniacian to early Campanian rocks, while those of D. herschelensis have been found in the late Campanian to early Maastrichtian rocks. Dolichorhynchops was a prehistoric marine reptile measuring around 3 metres (9.8 ft) long. Its Greek generic name means "long-nosed face".

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

Brachauchenius 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.

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

Leptocleidus is an extinct genus of plesiosaur, belonging to the family Leptocleididae. It was a small plesiosaur, measuring only up to 3 m (9.8 ft).

<i>Polyptychodon</i> Genus of pliosaurid plesiosaur from the Cretaceous period

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.

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

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.

<i>Tatenectes</i> Genus of extinct plesiosaur from the upper Jurassic

Tatenectes is a genus of cryptoclidid plesiosaur known from the Upper Jurassic of Wyoming. Its remains were recovered from the Redwater Shale Member of the Sundance Formation, and initially described as a new species of Cimoliosaurus by Wilbur Clinton Knight in 1900. It was reassigned to Tricleidus by Maurice G. Mehl in 1912 before being given its own genus by O'Keefe and Wahl in 2003. Tatenectes laramiensis is the type and only species of Tatenectes. While the original specimen was lost, subsequent discoveries have revealed that Tatenectes was a very unusual plesiosaur. Its torso had a flattened, boxy cross-section and its gastralia exhibit pachyostosis (thickening). The total length of Tatenectes has been estimated at 2–3 meters (6.6–9.8 ft).

<i>Pachycostasaurus</i> Extinct species of reptile

Pachycostasaurus is an extinct Pliosauroid from the Oxford Clay formation of Peterborough, England.

<span class="mw-page-title-main">Timeline of plesiosaur research</span>

This timeline of plesiosaur research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, taxonomic revisions, and cultural portrayals of plesiosaurs, an order of marine reptiles that flourished during the Mesozoic Era. The first scientifically documented plesiosaur fossils were discovered during the early 19th century by Mary Anning. Plesiosaurs were actually discovered and described before dinosaurs. They were also among the first animals to be featured in artistic reconstructions of the ancient world, and therefore among the earliest prehistoric creatures to attract the attention of the lay public. Plesiosaurs were originally thought to be a kind of primitive transitional form between marine life and terrestrial reptiles. However, now plesiosaurs are recognized as highly derived marine reptiles descended from terrestrial ancestors.

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

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.

Luskhan is an extinct genus of brachauchenine pliosaur from the Cretaceous of Russia. The type and only species is Luskhan itilensis, named by Valentin Fischer and colleagues in 2017 from a well-preserved and nearly complete skeleton. As an early-diverging brachauchenine, Luskhan consequently exhibits an intermediate combination of traits seen in more basal and more derived pliosaurs. However, Luskhan departs significantly from other pliosaurs in that it exhibits a lack of adaptations in its skull to feeding on large prey; its slender snout, small teeth, and short tooth rows instead indicate a skull adapted for feeding on small, soft prey. With these features, it is the pliosaur that approaches closest to the distantly-related piscivorous polycotylids, having convergently evolved these traits more than 10 million years apart.

<i>Acostasaurus</i> Genus of pliosaurid (fossil)

Acostasaurus is an extinct genus of possibly Thalassophonean pliosaurid known from the Barremian of the Paja Formation, Colombia. The type specimen, UNDG R-1000, is known from a near complete skull, and postcranial elements including a complete hindlimb and various vertebrae. The specimen has an estimated size of over 4 metres (13 ft) in length.

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

Monquirasaurus is an extinct genus of giant short-necked pliosaurs who lived during the Early Cretaceous (Aptian) in what is now Colombia. One species is known, M. boyacensis, described in 2021 from an almost complete fossil skeleton, discovered in 1977 in the town of Villa de Leyva, located in Boyacá. Published descriptions of the holotype specimen estimate that it should reach a total size approaching 9–11 m (30–36 ft) in length and weighing 9–14 metric tons, making Monquirasaurus a large representative of the pliosaurids.

"<i>Pliosaurus</i>" <i>andrewsi</i> Extinct species of pliosaurs

"Pliosaurus" andrewsi is an extinct species of pliosaurid plesiosaurs that lived during the Callovian stage of the Middle Jurassic, in what is now England. The only known fossils of this taxon were discovered in the Peterborough Member of the Oxford Clay Formation. Other attributed specimens have been discovered in various corners of Eurasia, but these are currently seen as indeterminate or coming from other taxa. The taxonomic history of this animal is quite complex, because several of its fossils were attributed to different genera of pliosaurids, before being concretely named and described in 1960 by Lambert Beverly Tarlo as a species of Pliosaurus. However, although the taxon was found to be valid, subsequent revisions found that it is not part of this genus, and therefore a taxonomic revision must be carried out on this species.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 Dean R. Lomax. "The Largest Pliosaurid from North America". PaleoNature.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 William R. Wahl; Mike Ross; Judy A. Massare (2007). "Rediscovery of Wilbur Knight's Megalneusaurus rex site: new material from an old pit" (PDF). Paludicola. 6 (2): 94–104.
  3. 1 2 Marie-Céline Buchy (2007). Mesozoic marine reptiles from north-east Mexico: description, systematics, assemblages and palaeobiogeography. Universität Karlsruhe (Thesis). doi: 10.5445/IR/1000007307 . S2CID   132738780.
  4. 1 2 3 Wilbur C. Knight (1895). "A new Jurassic plesiosaur from Wyoming". Science . 2 (40): 449. doi:10.1126/science.2.40.449.a. PMID   17759917. S2CID   30137246.
  5. 1 2 3 4 5 6 Colin R. McHenry (2009). Devourer of Gods: The palaeoecology of the Cretaceous pliosaur Kronosaurus queenslandicus (PhD). The University of Newcastle. hdl: 1959.13/935911 . S2CID   132852950.
  6. 1 2 3 4 5 Wilbur C. Knight (1898). "Some new Jurassic vertebrates from Wyoming". American Journal of Science . 5 (27): 378–381.
  7. 1 2 3 Ben Creisler (2012). "Ben Creisler's Plesiosaur Pronunciation Guide". Oceans of Kansas. Retrieved 2021-06-26.
  8. 1 2 3 4 "Megalneusaurus". Paleofile.
  9. 1 2 F. Robin O’Keefe; William Wahl Jr. (2003). "Current taxonomic status of the plesiosaur Pantosaurus striatus from the Upper Jurassic Sundance Formation, Wyoming" (PDF). Paludicola. 4 (2): 37–46.
  10. 1 2 Per Ove Persson (1963). "A revision of the classification of the Plesiosauria with a synopsis of the stratigraphical and geographical distribution of the group" (PDF). Lunds Universitets Arsskrift. 59 (1): 1–59.
  11. 1 2 David S. Brown (1981). "The English Late Jurassic Plesiosauroidea (Reptilia) and a review of the phylogeny and classification of the Plesiosauria". Bulletin of the British Museum (Natural History), Geology . 35 (4): 253–347.
  12. 1 2 3 4 5 William R. Wahl (2006). "A juvenile plesiosaur (Reptilia: Sauropterygia) assemblage from the Sundance Formation (Jurassic), Natrona County, Wyoming". Paludicola. 5 (4): 255–261.
  13. 1 2 3 4 5 6 William R. Wahl; Judy A. Massare; Mike Ross (2010). "New material from the type specimen of Megalneusaurus rex (Reptilia: Sauropterygia) from the Jurassic Sundance Formation, Wyoming". Paludicola. 7 (4): 170–180.
  14. 1 2 3 Richard Ellis (2003). Sea Dragons: Predators of the Prehistoric Oceans . Lawrence: University Press of Kansas. p. 188. ISBN   978-0-7006-1394-6.
  15. 1 2 3 Robert E. Weems; Robert B. Blodgett (1994). "The pliosaurid Megalneusaurus: a newly recognized occurrence in the Upper Jurassic Naknek Formation of the Alaska Peninsula". U.S. Geological Survey Bulletin . 2152: 169–175.
  16. 1 2 3 Ruizhe Jackevan Zhao (2024). "Body reconstruction and size estimation of plesiosaurs". BioRxiv . doi: 10.1101/2024.02.15.578844 . S2CID   267760521.
  17. ↑ Bruce A. Schumacher; Kenneth Carpenter; Michael J. Everhart (2013). "A new Cretaceous Pliosaurid (Reptilia, Plesiosauria) from the Carlile Shale (middle Turonian) of Russell County, Kansas". Journal of Vertebrate Paleontology . 33 (3): 613–628. doi:10.1080/02724634.2013.722576. JSTOR   42568544. S2CID   130165209.
  18. ↑ Albert H. Longman (1930). "Kronosaurus queenslandicus : A Gigantic Cretaceous Pliosaur". Memoirs of the Queensland Museum . 10: 1–7.
  19. 1 2 3 4 5 6 7 Judy A. Massare; William R. Wahl; Mike Ross; Melissa V. Connely (2014). "Palaeoecology of the marine reptiles of the Redwater Shale Member of the Sundance Formation (Jurassic) of central Wyoming, USA". Geological Magazine . 151 (1): 167–182. doi:10.1017/S0016756813000472. S2CID   129170002.
  20. 1 2 F. Robin O'Keefe; Hallie P. Street (2009). "Osteology Of The cryptoclidoid plesiosaur Tatenectes laramiensis, with comments on the taxonomic status of the Cimoliasauridae" (PDF). Journal of Vertebrate Paleontology . 29 (1): 48–57. doi:10.1671/039.029.0118. S2CID   31924376.
  21. 1 2 3 4 Sharon K. McMullen; Steven M. Holland; F. Robin O'Keefe (2014). "The occurrence of vertebrate and invertebrate fossils in a sequence stratigraphic context: The Jurassic Sundance Formation, Bighorn Basin, Wyoming, USA" (PDF). PALAIOS. 29 (6): 277–294. Bibcode:2014Palai..29..277M. doi:10.2110/pal.2013.132. S2CID   126843460.
  22. 1 2 Bruce M. Rothschild; Glenn W. Storrs (2003). "Decompression syndrome in plesiosaurs (Sauropterygia: Reptilia)". Journal of Vertebrate Paleontology . 23 (2). Bibcode:2003JVPal..23..324R. doi:10.1671/0272-4634(2003)023[0324:DSIPSR]2.0.CO;2. JSTOR   4524320. S2CID   86226384.
  23. 1 2 3 Amanda Adams (2013). Oxygen Isotopic Analysis of Belemnites: Implications for Water Temperature and Life Habits in the Jurassic Sundance Sea (PDF) (Thesis). Gustavus Adolphus College. S2CID   132913195. Archived from the original (PDF) on 2020-02-16.
  24. 1 2 F. Robin O'Keefe; Hallie P. Street; Benjamin C. Wilhelm; Courtney D. Richards; Helen Zhu (2011). "A new skeleton of the cryptoclidid plesiosaur Tatenectes laramiensis reveals a novel body shape among plesiosaurs". Journal of Vertebrate Paleontology . 31 (2): 330–339. doi:10.1080/02724634.2011.550365. S2CID   54662150.
  25. ↑ Valentin Fischer; Michael W. Maisch; Darren Naish; Ralf Kosma; Jeff Liston; Ulrich Joger; Fritz J. Krüger; Judith Pardo Pérez; Jessica Tainsh; Robert M. Appleby (2012). "New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary". PLOS ONE . 7 (1): e29234. Bibcode:2012PLoSO...729234F. doi: 10.1371/journal.pone.0029234 . PMC   3250416 . PMID   22235274.
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.