Tylosaurus was a mosasaur, a large, predatory marine lizard closely related to modern monitor lizards and to snakes. Along with plesiosaurs, sharks, fish, and other genera of mosasurs, it was a dominant predator of the Western Interior Seaway during the Late Cretaceous. Tylosaurus proriger was among the largest of all the mosasaurs (along with Hainosaurus and Mosasaurus hoffmannii), reaching maximum lengths of 15 meters or more (49+ ft). A distinguishing characteristic of Tylosaurus is its elongated, cylindrical premaxilla (snout) from which it takes its name and which may have been used to ram and stun prey and also in intraspecific combat. Stomach contents associated with specimens of Tylosaurus proriger indicate that this ferocious mosasaur had a varied diet, including fish, sharks, smaller mosasaurs, plesiosaurs, and flightless diving birds such as Hesperornis. In some paleoenvironments, Tylosaurus seems to have preferred shallow, nearshore waters (as with the Eutaw Formation and Mooreville Chalk Formation of Alabama), while favoring deeper water farther out from shore in other environments (as with the Niobrara Chalk of the western U.S.).
It was one of the largest hunters of the Cretaceous seas. Tylosaurus used its snout to locate prey, which, once inside this mosasaur's menacing jaws, was swallowed whole. When the sea monster opened wide for the final gulp, two extra rows of teeth on the roof of its mouth allowed crippled captives no escape. According to a new study, it hunted like an Orca ramming the prey from below before killing it.
Discovery and naming[]
Complete skeleton of Tylosaurus dyspelor.
Like many other mosasaurs, the early history of this taxon is complex and involves the infamous rivalry between two early American paleontologists, Edward Drinker Cope and Othniel Charles Marsh. Originally, the name "Macrosaurus" proriger was proposed by Cope for a fragmentary skull and thirteen vertebrae collected from near Monument Rocks in western Kansas in 1868. It was placed in the collections of the Harvard Museum of Comparative Zoology. Only a year later, Cope redescribed the same material in greater detail and referred it, instead, to the English mosasaur taxon Liodon. Then, in 1872, Marsh named a more complete specimen as a new genus, Rhinosaurus ("nose lizard"), but this name soon proved to be preoccupied. Cope suggested that Rhinosaurus be replaced by yet another new name, Rhamposaurus which also proved to be preoccupied. Marsh finally erected Tylosaurus later in 1872, to include the original Harvard material as well as additional, more complete specimens which had also been collected from Kansas. A giant specimen of T. proriger, recovered in 1911 by C. D. Bunker near Wallace, Kansas is one of the largest skeleton of Tylosaurus ever found. It is currently on display at the University of Kansas Museum of Natural history.
In 1918, Charles H. Sternberg found a Tylosaurus, with the remains of a plesiosaur in its stomach. The specimen is currently mounted in the United States National Museum (Smithsonian) and the plesiosaur remains are stored in the collections. Although these important specimens were briefly reported by C. H. Sternberg (1922), the information was lost to science until 2001. This specimen was rediscovered and described by Everhart (2004a). It is the basis for the story line in the new (2007) National Geographic IMAX movie - "Sea Monsters", and a book by the same name (Everhart, 2007).
Note that the "early photograph" of a Tylosaurus skull (above) was taken by George F. Sternberg about 1926 after he collected and prepared the specimen. It was discovered in the Smoky Hill Chalk of Logan County, Kansas. Sternberg offered the specimen to the Smithsonian and included this photograph in his letter to Charles Gilmore. Copies of the original photos are in the archives of the Sternberg Museum of Natural History (FHSM). The specimen is FHSM VP-3, the exhibit specimen in the same museum.
Species[]
Tylosaurus proriger specimen which was found with a plesiosaur in its stomach.
Though many species of Tylosaurus have been named over the years, only a few are now recognized by scientists as taxonomically valid. They are as follows: Tylosaurus proriger (Cope, 1869), from the Santonian and lower to middle Campanian of North America (Kansas, Alabama, Nebraska, etc.); Tylosaurus nepaeolicus (Cope, 1874), from the Santonian of North America (Kansas); Tylosaurus haumuriensis (Hector, 1874; =Taniwhasaurus oweni), from the lower to middle Campanian of New Zealand; Tylosaurus kansasensis Everhart, 2005, from the late Coniacian of Kansas.
A closely related genus, Hainosaurus ("Haine lizard", named after the Haine River in Belgium) is known from the Creatceous of North America and Europe. Both Tylosaurus and Hainosaurus are grouped together into the subfamily Tylosaurinae and are referred to informally as "tylosaurines" or "tylosaurs." Bell placed the tylosaurines together with the plioplatecarpine mosasaurs (Platecarpus, Plioplatecarpus, etc.) in an informal monophyletic grouping which he called the "Russellosaurinae."
Description[]
A distinguishing characteristic of Tylosaurus is the elongated conical rostrum that protrudes from its snout, from which the genus is named. Unlike typical mosasaurs, Tylosaurus did not have teeth up to the end of the snout nor on the bony protuberance that is the rostrum, and scientists believe that this feature was primarily used for combative purposes such as ramming. This is supported with a uniquely broad and somewhat rectangular internarial bar (the extension of the premaxilla on the top of the skull that held together the nasal and upper jaws) that provided high cranial stability and resistance to stress forces. In addition, the development of the elongated rostrum in infant Tylosaurus rules out the alternative explanation that it was developed as a function of sexual behavior. Tylosaurus also had 24 to 26 teeth in the upper jaw, 20 to 22 teeth on the palate, 26 teeth on the lower jaw, 29 to 30 vertebrate between the skull and hip, 6 to 7 vertebrae in the hip, 33 to 34 vertebrae in the tail with chevrons, and a further 56 to 58 vertebrae making up the tip of the tail.
Size[]
Estimated size range of Tylosaurus compared with a human
Tylosaurus was one of the largest mosasaurs of all time. The largest known specimen, a skeleton of T. proriger from the University of Kansas Natural History Museum nicknamed "Bunker" (KUVP 5033), has been estimated to measure between 12–15.8 meters (39–52 ft) long. Some isolated fragments have been estimated to belong to individuals measuring 14 meters (46 ft) or more. The genus exhibits Cope's rule, in which its body size has been observed to generally increase over geologic time. In North America, the earliest representatives of Tylosaurus during the Turonian and Coniacian (90-86 mya), which included early T. nepaeolicus and its precursors, typically measured 5–7 meters (16–23 ft) long and weighed between 200–500 kilograms (440–1,100 lb). During the Santonian (86-83 mya), T. nepaeolicus and newly-appearing T. proriger were 8–9 meters (26–30 ft) long and weighed around 1,100 kilograms (2,400 lb). By the Early Campanian, T. proriger attained lengths of 13–14 meters (43–46 ft).
Commenting on the maximum sizes of large mosasaurs, paleontologist Mike Everhart, a leading expert on mosasaurs, speculated that it would be possible for some extremely old Tylosaurus individuals to reach 20 meters (66 ft) in absolute maximum length. However, this is with awareness that there is no fossil evidence suggesting such sizes and that the odds of preserving such a rare individual are "far too great."
In 2014, the Guinness World Records awarded the Canadian Fossil Discovery Centre a record for "Largest mosasaur on display," specifically, a 13.05 m (42.8 ft) long skeleton of T. pembinensis nicknamed "Bruce." However, the skeleton was assembled for display prior to a 2010 reassessment of the species that found its original number of vertebrae to be exaggerated, implying that the actual size of the animal was likely smaller
Tylosaurus length varies between 9-14 meters and it's mass varies between 4-11 tonnes, making it one of the largest of the marine reptiles. The size variation is quite extensive, mainly because most Tylosaurus specimens are around 9 meters long. But we also have several very large specimens like "Sophie" or "Bunker", which are both over 12 meters long and weigh over 9 tonnes. The largest known specimen "Bonker" (FHSM VP-2496) is assumed to even surpass 14 meters in length and 20 tonnes in weight, making Tylosaurus the largest mosasaur and one of the biggest marine reptiles of all time. Like all mosasaurs, a long and muscular, vertically flattened tail powered Tylosaurus through the water, allowing it to ambush its prey with rapid bursts of acceleration. Paddle-like limbs helped steer the slim body covered in lizard-like scales through the water.
Classification[]
Restoration of T. pembinensis
As a mosasaur, Tylosaurus is classified within the family Mosasauridae in the superfamily Mosasauroidea. The genus is the type genus of its own subfamily, the Tylosaurinae. Other members of this group include Taniwhasaurus and possibly Kaikaifilu, and the subfamily is defined by a shared feature of an elongated conical rostrum that does not bear teeth.[5] The closest relatives of the Tylosaurinae include the Plioplatecarpinae and the primitive subfamilies Tethysaurinae and Yaguarasaurinae; together they are members of one of three possible major lineages of mosasaurs (the others being the Mosasaurinae subfamily and Halisauromorpha group) that was first recognized in 1993. This clade was named the Russellosaurina by Polcyn and Bell in 2005.[83][84][85
The Turonian-aged skull of T. sp. aff. kansasensis (SGM-M1) is the oldest known fossil of Tylosaurus.
Tylosaurus was among the earliest known derived mosasaurs. The oldest fossil attributed to the genus is of a skull (SGM-M1) recovered from Upper Turonian deposits of Ojinaga Formation in Chihuahua, Mexico,[2][5] which may date around 90 million years old at earliest based on correlations with index fossils.[1] This skull has been identified as an indeterminate species with significant affinities with T. kansasensis, which was previously considered the most primitive species. A tooth from a Late Maastrichtian deposit in Nasiłów, Poland dating close to the Cretaceous–Paleogene boundary has been attributed to Hainosaurus sp.[3][7] With the incorporation of Hainosaurus as a synonym of Tylosaurus, this also makes the genus one of the last mosasaurs. Currently, eight species of Tylosaurus are recognized by scientists as taxonomically valid. They are as follow: T. proriger, T. nepaeolicus, T. bernardi, T. gaudryi, T. ivoensis, T. iembeensis, T. pembinensis, and T. saskatchewanensis. The validity of two additional taxa remain unsettled; there is still debate whether T. kansasensis is synonymous with T. nepaeolicus, and T. borealis has yet to be described in a formal publication.
In 2020, Madzia and Cau performed a Bayesian analysis to better understand the evolutionary influence on early mosasaurs by contemporaneous pliosaurs and polycotylids by examining the rates of evolution in mosasauroids like Tylosaurus (specifically T. proriger, T. nepaeolicus, and T. bernardi). A Bayesian analysis in the study's implementation can approximate numerically-defined rates of morphological evolution and ages of divergence of clades. The Tylosaurinae was approximated to have diverged from the Plioplatecarpinae around 93 million years ago; the divergence was characterized by the highest rate of evolution among all mosasaurid lineages. This trend of rapid evolution coincided with the extinction of the pliosaurs and a decrease in polycotylid diversity. The study noted converging traits between Tylosaurus, pliosaurs, and some polycotylids in tooth morphology and body size. However, there was no evidence to suggest that Tylosaurus or its precursors evolved as a result of out-competing and/or driving to extinction the pliosaurs and polycotylids. Instead, Madiza and Cau proposed that Tylosaurus may have taken advantage of the extinction of the pliosaurs and decline of polycotylids to quickly fill the ecological void they left behind. The Bayesian analysis also approximated a divergence of T. nepaeolicus from the rest of the genus around 86.88 million years ago and a divergence between T. proriger and T. bernardi around 83.16 million years ago. The analysis also generated a paraphyletic status of the genus, approximating Taniwhasaurus to have diverged from Tylosaurus around 84.65 million years ago, but this result is not consistent with previous phylogenetic analyses.
Ontogram demonstrating the evolution of T. nepaeolicus into T. proriger through peramorphosis
In the Western Interior Seaway, two species—T. nepaeolicus and T. proriger—represent a chronospecies, in which they make up a single lineage that continuously evolves without branching off in a process known as anagenesis. This is evident by how the two species do not stratigraphically overlap, are sister species, share minor and intermediate morphological differences such as a gradual change in the development of the quadrate bone, and lived in the same locations. The means by which this lineage evolved has been hypothesized to be through one of two evolutionary mechanisms related to changes in ontogeny. First, Jiménez-Huidobro, Simões, and Caldwell proposed in 2016 that T. proriger evolved as a paedomorph of T. nepaeolicus, in which the descendant arose as a result of morphological changes through the retention of juvenile features of the ancestor in adulthood. This was based on the presence of a frontal crest and convex borders of the parietal bone of the skull shared in both juvenile T. nepaeolicus and all T. proriger but lost in adult T. nepaeolicus.[76][78] However, an ontogenetic study by Zietlow (2020) found that it was unclear whether this observation was a result of paedomorphosis, although this uncertainty may have been due that the sample size of mature T. nepaeolicus was too low to determine statistical significance. Second, the same study proposed an alternative hypothesis of peramorphosis, in which T. proriger evolved by developing traits found in mature T. nepaeolicus during immaturity. Based on results from a cladistical ontogram developed using data from 74 Tylosaurus specimens, the study identified a multitude of traits that were present in all T. proriger and mature T. nepaeolicus but absent in juvenile T. nepaeolicus: the skull size and depth are large, the length of the elongated rostrum exceeds 5% of the total skull length, the quadrate suprastapedial processes are thick, the overall quadrate shape converges, and the posteroventral process is fan-like.
Paleobiology[]
Ontogeny[]
In 2018, Konishi et al. assigned FHSM VP-14845, a small juvenile mosasaur, to Tylosaurus. The specimen has a skull length of about 30 centimeters (12 inches) long. They studied the braincase proportions and the tooth arrangements on the snout and palate. However, the bony knob found in juveniles of T. proriger and T. nepaeolicus is absent, the other juveniles having skull lengths from 40 to 60 centimeters (16 to 24 inches) long. This means that Tylosaurus quickly acquired the bony protrusion in life, and it did not develop for sexual selection. Konishi et al. concluded that the bony knob was likely used to ram into prey, an exploitation used by killer whales[1].
Diet[]
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Schematic of the gut content in a single Tylosaurus (SDSM 10439)
Stomach contents extracted from Tylosaurus remains suggest the animal had a wide diet, from fish and sharks, to plesiosaurs, flightless birds like Hesperornis and even smaller mosasaurs. A specimen known as the Talkeetna Mountains hadrosaur, a Hadrosauridae indet. collected from what was an outer shelf in the bathyalpelagic zone, now the Matanuska Formation. Any element of the skeleton not encased in concretions bore close-spaced ovular conical pits in them, ranging in diameter from 2.12-5.81 millimeters and 1.64-3.62 millimeters deep. They are likely bite marks. They are asymmetrical, meaning no gastropods could have burrowed into the bone and did not appear to be sponge borings. No fossil fish from the region fit the bites.
Skeletal reconstruction of Tylosaurus hunting a Xiphactinus at the Academy of Natural Sciences of Drexel University, Philadelphia
They do, however, match the teeth of T. proriger. They are unlikely to have happened before the carcass was washed to sea, which would have prevented fossilization. Some locations appear to have less damage, possibly where skin was still clung to the bones. Regions where skin was presumably devoid are considerably deeper. The carcass was likely attempted to fit into Tylosaurus' mouth, but when it could not, bones struck free were preserved in sandstone[1].
Paleoecology[]
Tylosaurus was one of several species of mosasaur extant during the final Maastrichtian stage of the Late Creteceous. It likely competed with Mosasaurus for territory and prey. It was the apex marine predator of the Western Interior Seaway which bisected North America in the Cretaceous period, around 80 million years ago, feeding on fish (including sharks), seabirds, pterosaurs, other marine reptiles and even dinosaurs. Its powerful tail and paddle-shaped limbs allowed it to swim quickly through the water, while its huge size and sharp teeth ensured that anything that crossed Tylosaurus' path was potential prey. Analysis of compression damage to the jaw of Tylosaurus fossils suggests that it rammed larger prey with its snout to stun it before returning to eat.[2]
Notable Specimens[]
- "Bruce": Added by Guinness World Records in 2014 as their Largest Publicly Displayed Mosasaur, and was added to their prints in 2016.
- KUVP 5033 "Bunker": A massive Tylosaurus proriger first assigned to Macrosaurus by Cope (1869)[3]. Bunker was found in 1911, and restored by Triebold Paleontology Inc. and the KU Natural History Museum in 3D in 1997[4]. It is 14 meters (46 feet) long[5].
- "Mandy": A Tylosaurus specimen that preserves most of the body. Mandy was discovered by Anthony Maltese in June 2020, having 63 vertebrae, 55 chevrons, many shed shark teeth and an embedded Pachyrhizodus jaw[6]. It was found when Maltese's wife uncovered the first caudal vertebrae[7].
- FFHM 1997-10: One of the most complete T. proriger crania[8].
- "Sophie": A Tylosaurus skull with both halves, including the mandible and braincase.
- "Alfred": A large T. proriger from the Mooreville Chalk[9].
Dinosaur Field Guide Description[]
Tylosaurus ("knob lizard") has Al large, strong chest and arms, big hands, a long body with weak legs, and a strong tail for swimming. It has a ram-shaped snout and big conical teeth for catching prey. It is a mosasaur, or Meuse River lizard, a true marine lizard. The mosasaurs are related to the modern monitor lizards (like the Komodo dragon), Gila monsters, and snakes. Mosasaurs, however, lived their whole lives in the water. As in ichthyosaurs, their young developed inside the mother and were born live into the water. Mosasaurs were probably not as fast as the earlier ichthyosaurs had been, and instead ambushed their prey the way many sharks do today. Some mosasaurs had flatter teeth than Tylosaurus, which they used for cracking open shellfish.
Fun Facts[]
A fossil of a giant sea turtle has been found with a flipper bitten off-probably by a Tylosaurus.
Trivia[]
Mosasaurs were the first group of extinct reptiles known to science.
Gallery[]
Appearance in other media[]
Jurassic Park[]
- A Tylosaurus appears in Jurassic Park: The Game where it consumes Dr Laura Sorkins and attempt to eat the rest of the survivors. The cloned Tylosaurus had a row spikes running down its neck to its upper back like outdated depictions of mosasaurs from the late 1800s. It also lacked a tail fluke, with another row of spikes covering the tail. The clone's skull was unlike Tylosaurus being as short as the mosasaur Platecarpus with the jaws not being completely straight. The skin color of the cloned Tylosaurus was a shade of blue with black striping and a yellowish white underbelly. It was originally the unnamed marine reptile in the game being only referred to as "Mosasaur". In Laura Sorkin's research journal, she describes the creature and labels it "Mosasaur". She also writes: "Upwards of 50 feet long, depending on genus." From this text it is clear that she doesn't know its genus, indicating that she calls the creature "Mosasaur", she refers to the family to which it belongs; which is Mosasaurs (Mosasauridae). The identity of Jurassic Park's Mosasaur was ultimately revealed to be Tylosaurus in the InGen Field Guide.
- Tylosaurus is number 127 of the Carnivore Threes that can be created in Jurassic Park III: Park Builder. As a carnivore, it should be placed in its own enclosure, considering that if it gets placed with another animal, it will kill it. In-game it looks like a plesiosaur, probably because the game makers didn't have large enough a budget to make its own model.
- Tylosaurus appears in the underwater park update for the game Jurassic Park: Builder.
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Read more Tylosaurus on Jurassic Park Wiki |
References[]
- ↑ 1.0 1.1 Cite error: Invalid
<ref>tag; no text was provided for refs named1: - ↑ Tylosaurus. Prehistoric Wildlife. Retrieved October 14, 2022.
- ↑ E.D. Cope. 1869. [On some specimens of fossil reptiles of interest]. Proceedings of the Academy of Natural Sciences of Philadelphia 21:123
- ↑ https://twitter.com/TrieboldPaleo/status/1430538403360165896
- ↑ https://twitter.com/ToddRockford/status/1500230443504967682
- ↑ https://twitter.com/Mosasaurologist/status/1326195418347286533
- ↑ https://twitter.com/Mosasaurologist/status/1288218681789632512
- ↑ https://twitter.com/palaeotheoryum/status/1227493599689920512
- ↑ https://twitter.com/auntbeast/status/1536727417804492802?t=NKJG2TuFYfDJzGk_2iZCgg&s=19