The Bentiaba (or Rio de São Nicolau or Saint Nicolas River) is a river in southern Angola . Its mouth is at the Atlantic Ocean near the commune of Bentiaba in Namibe Province .
108-618: The riverbank has produced a number of Cretaceous fossils including mosasaurs from Itombe Formation. Bentiaba is also the name given to the Cretaceous bonebed. This article related to a river in Angola is a stub . You can help Misplaced Pages by expanding it . Mosasaur Mosasaurs (from Latin Mosa meaning the ' Meuse ', and Greek σαύρος sauros meaning 'lizard') are an extinct group of large aquatic reptiles within
216-422: A 2009 analysis by Dutchak and Caldwell instead found that Dallasaurus was ancestral to both russellosaurines and mosasaurines, although results were inconsistent in later studies. A 2017 study by Simoes et al. noted that utilization of different methods of phylogenetic analyses can yield different findings and ultimately found an indication that tethysaurines were a case of hydropedal mosasaurs reversing back to
324-400: A 45° downward angle. A similar deflection appears in some juvenile T. nepaeolicus quadrates. Emerging from the posteroventral margin of the alar conch is the infrastapedial process. Its shape appears to changes ontogenetically in T. nepaeolicus and T. proriger ; in the former, the process is absent in juveniles but appears as a small bump in adults, while in T. proriger , it is present as
432-438: A blunt, elongated "knob." The snout is heavily built, supported by a broad and robust internarial bar (comprising the posterodorsal process of the premaxilla, nasals, and anterior process of the frontal), which provided effective shock absorption and stress transfer. Because of this, it has been proposed that the tylosaurine rostrum was elongated for use in ramming prey or rivals, but recent research on Taniwhasaurus found
540-405: A breaststroke motion to gain added bursts of speed during an attack on prey. More recently, a fossil of Platecarpus tympaniticus has been found that preserved not only skin impressions, but also internal organs. Several reddish areas in the fossil may represent the heart, lungs, and kidneys. The trachea is also preserved, along with part of what may be the retina in the eye. The placement of
648-506: A century ago indicate that mosasaurs gave birth to live young, and that they spent their early years of life out in the open ocean, not in sheltered nurseries or areas such as shallow water as previously believed. Whether mosasaurs provided parental care, like other marine reptiles such as plesiosaurs, is currently unknown. The discovery of young mosasaurs was published in the journal Palaeontology . A 2020 study published in Nature described
756-415: A complex neurovascular system in the snout, suggesting that the rostrum was extremely sensitive, and therefore it is unlikely that the rostrum was used as a ramming weapon. The snout holds the terminal branches for the trigeminal nerves through randomly scattered foramina on the rostrum and along the ventral margin of the maxilla, above the gum line . The premaxilla, maxilla, and frontal bones border
864-415: 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
972-407: A distinct downward curve, suggesting the presence of a tail fluke . Fossil evidence of the skin of Tylosaurus in the form of scales has been described since the late 1870s. These scales were small and diamond-shaped and were arranged in oblique rows, comparable to that found in modern rattlesnakes and other related reptiles. However, the scales in the mosasaur were much smaller in proportion to
1080-399: 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
1188-663: A hydropedal form independently, the former through the tethysaurines, meaning that their placement within the Mosasauridae creates an unnatural polyphyly and thus potentially invalid. Caldwell informally proposed in a 2012 publication that the definition of a mosasaur must thus be redefined into one that does not consider russellosaurines and halisauromorphs as true mosasaurs, but as an independent group of marine lizards. However, phylogenetic studies of mosasaurs can be fickle, especially when wild card taxa like Dallasaurus remain poorly understood. For example, some studies such as
SECTION 10
#17327931204021296-588: A large fossilized hatched egg from Antarctica from the very end of the Cretaceous , about 68 million years ago. The egg is considered one of the largest amniote eggs ever known, rivalling that of the elephant bird , and due to its soft, thin, folded texture, it likely belonged to a marine animal. While the organism that produced it remains unknown, the egg's pore structure is very similar to that of extant lepidosaurs such as lizards and snakes, and presence of mosasaur fossils nearby indicates that it may have been
1404-399: A method similar to the one used today by conger eels and sea snakes , undulating their entire bodies from side to side. However, new evidence suggests that many advanced mosasaurs had large, crescent-shaped flukes on the ends of their tails, similar to those of sharks and some ichthyosaurs . Rather than use snake-like undulations, their bodies probably remained stiff to reduce drag through
1512-421: A mosasaur egg. It is unknown whether the egg was laid on land or in the water. The egg was assigned to the newly described oospecies Antarcticoolithus bradyi . However, it has been proposed that this egg belonged to a dinosaur. Paleontologists compared the taxonomic diversity and patterns of morphological disparity in mosasaurs with sea level, sea surface temperature , and stable carbon isotope curves for
1620-493: A mosasaur. Mosasaurs were likely countershaded , with dark backs and light underbellies, much like a great white shark or leatherback sea turtle , the latter of which had fossilized ancestors for which color was also determined. The findings were described in Nature . Mosasaurs possessed a thecodont dentiton , meaning that the roots were cemented deeply into the jaw bone. Mosasaurs did not use permanent teeth but instead constantly shed them. Replacement teeth developed within
1728-400: A pair of faint buccal and lingual carinae, except in T. gaudryi , in which the teeth are mediolaterally compressed. Carinae are not serrated. The anterior surface tends to be either smooth of faintly faceted, while the posterior surface is striated. Both pectoral and pelvic girdles are unfused in adult Tylosaurus , in contrast to other taxa (e.g., Prognathodon overtoni ). Tylosaurus
1836-406: A pit inside the roots of the original tooth called the resorption pit. This is done through a distinctively unique eight-stage process. The first stage was characterized by the mineralization of a small tooth crown developed elsewhere that descended into the resorption pit by the second stage. In the third stage, the developing crown firmly cemented itself within the resorption pit and grew in size; by
1944-424: A plesiopedal condition rather than an independent ancestral feature. The following cladograms illustrate the two views of mosasaur evolution. Topology A follows an ancestral state reconstruction from an implied weighted maximum parsimony tree by Simoes et al. (2017), which contextualizes a single marine origin with tethysaurine reversal. Topologies B and C illustrate the multiple-origins hypothesis of hydropedality;
2052-411: 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 . However, an ontogenetic study by Zietlow (2020) found that it was unclear whether this observation
2160-459: A sensitive forked tongue. A study published in 2016 by T. Lyn Harrell, Alberto Pérez-Huerta and Celina Suarez showed that mosasaurs were endothermic . The study contradicted findings published in 2010 indicating mosasaurs were ectothermic . The 2010 study did not use warm-blooded animals for comparison but analogous groups of common marine animals. Based on comparisons with modern warm-blooded animals and fossils of known cold-blooded animals from
2268-624: A slight recurve towards the back of the jaws so that the lingual (tongue-facing) side forms a U-shaped curve. From top view, they are compressed at the lingual and labial (lip-facing) sides to form an oval-like shape. Teeth of immature T. proriger are initially compressed, but become conical in adulthood. Carinae (cutting edges) are finely serrated with small denticles except in juvenile T. nepaeolicus . In T. pembinensis , they are faint. The teeth generally have both anterior and posterior carinae, but some anterior teeth may have only anterior carinae. The placement of carinae, if paired,
SECTION 20
#17327931204022376-413: A subtle point in juveniles of and becomes a distinctively broad semicircle in adults. The process is small in T. bernardi, and in T. pembinensis and T. saskatchewanensis , it is rounded. In T. saskatchewanensis , the suprastapedial process almost touches the infrastapedial process. At the bottom of the shaft is the mandibular condyle, which forms the joint between the quadrate and the lower jaw. It
2484-523: Is Bruce, a 65-70%-complete specimen of Tylosaurus pembinensis dating from the late Cretaceous Period, approximately 80 million years ago, and measuring 13.05 m (42.815 ft) from nose tip to tail tip. Bruce was discovered in 1974 north of Thornhill, Manitoba, Canada, and resides at the nearby Canadian Fossil Discovery Centre in Morden, Manitoba . Bruce was awarded the Guinness Record for
2592-641: Is a genus of russellosaurine mosasaur (an extinct group of predatory marine lizards ) that lived about 92 to 66 million years ago during the Turonian to Maastrichtian stages of the Late Cretaceous . Its fossils have been found primarily around North Atlantic Ocean including in North America , Europe , and Africa . Tylosaurus was the third new genus of mosasaur to be described from North America behind Clidastes and Platecarpus and
2700-521: Is a hook-like extension of bone that curves posteroventrally from the apex of the shaft into an incomplete loop, and it likely served as the attachment point for the depressor mandibulae muscles that opened the lower jaw. The process is slender and proportionally long in immature T. nepaeolicus and T. proriger , and thickened as the animals matured. The process is of similar length to T. proriger in T. saskatchwanensis and shorter in T. bernardi . In T. pembinensis , it abruptly turns medially at
2808-685: Is also distinguished from other mosasaurs by a scapula that is significantly smaller than the coracoid and the absence of the anterior emargination of the coracoid, as well as the absence of a well-developed pubic tubercle. Tylosaurus limbs are primitive relative to other mosasaurs; their stylopodia (humeri and femora) lack both the complex muscle attachment sites and extreme proximodistal shortening present in other derived taxa. Both carpals and tarsals in tylosaurines are mostly unossified ; while other mosasaurs typically have between three and five carpals and tarsals, adult Tylosaurus never possess more than two ossified carpal bones (usually only
2916-614: 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 premaxillary rostrum that does not bear teeth. The closest relatives of the Tylosaurinae include the Plioplatecarpinae and
3024-423: Is flattened into multiple sides to form a prism-like geometry. Bardet et al. (2006) classified Tylosaurus species into two morphological groups based on marginal dentition. The North American ' proriger group ' includes T. proriger and T. nepaeolicus and is characterized by teeth with smooth or faint facets, less prominent carinae, and a vein-like network of primitive striations extending to near
3132-456: Is in reference to the specimen's unique prow-like elongated rostrum and is derived from the Latin word prōra (prow) and suffix -gero (I bear). In 1870, Cope published a more thorough description of MCZ 4374. Without explanation, he moved the species into another European genus Liodon and declared his original Macrosaurus proriger a synonym. In 1872, Marsh argued that Liodon proriger
3240-402: Is known of its teeth other than having striations and no facets. The distinction of an ' ivoensis group ' is contentious. Caldwell et al. (2008) argued that T. pembinensis cannot be compared with T. ivoensis as the former's teeth are not fluted, and that T. ivoensis is more allied with the distinctively fluted teeth of Taniwhasaurus . Jiménez-Huidobro and Caldwell (2019) listed
3348-445: Is not always equal; in at least T. proriger , T. ivoensis , T. gaudryi , and T. pembinensis , they are positioned such that the surface area of the tooth's lingual side is greater than the labial side. Both sides are always balanced in area in T. bernardi . The enamel surface is lined with thin fine ridges called striations that run vertically from the tooth's base. The surface is also either smooth or faintly faceted, in which it
Bentiaba River - Misplaced Pages Continue
3456-523: Is not consistent with previous phylogenetic analyses. In the Western Interior Seaway , two species— T. nepaeolicus and T. proriger —may represent a chronospecies , in which they make up a single lineage that continuously evolves without branching 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
3564-625: Is now North America. Mosasaur fossils have been found in the Netherlands , Belgium , Denmark , Portugal , Sweden , South Africa , Spain , France , Germany , Poland , the Czech Republic , Italy Bulgaria , the United Kingdom , Russia , Ukraine , Kazakhstan , Azerbaijan , Japan , Egypt , Israel , Jordan , Syria , Turkey , Niger , Angola , Morocco , Australia , New Zealand , and on Vega Island off
3672-427: Is proportionally short in T. proriger (20-27% skull length ) , T. bernardi (24% skull length ) , and T. gaudryi (25-27% skull length), and long in T. pembinensis (28-31% skull length). The nasal bones were either free-floating or lightly articulated to the internarial bar, did not contact the frontal, and were not fused to each other as they are in extant varanid lizards . The nasals' loose association with
3780-404: Is rounded in shape in adults. On the medial surface of the bone, a thick, pillar-like vertical ridge often protrudes beyond the dorsal margin of the quadrate so that it is visible in lateral view. The upper jaws include the premaxilla and maxilla , and the lower jaws include the dentary , splenial , coronoid , angular , surangular , and prearticluar-articular (like other squamates ,
3888-483: 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
3996-526: Is taxonomically distinct from the European genus and must be assigned a new one. For this, he erected the genus Rhinosaurus , which means "nose lizard" and is a portmanteau derived from the Ancient Greek words ῥίς ( rhī́s , meaning "nose") and σαῦρος ( saûros , meaning "lizard"). Marsh also described a third species based on a partial skeleton he collected near the southern portion of
4104-451: Is unclear. Tylosaurus had 29 to 30 presacral vertebrae , 6 to 7 pygal vertebrae, and 89 to 112 caudal vertebrae; due to the lack of a bony articulation between the ilium and vertebral column, it is unclear whether any mosasaurs possessed true sacral vertebrae. In all tylosaurines, like in plioplatecarpines , the chevrons articulate to the caudal vertebrae, and are not fused to them, as they are in mosasaurines . The tail possesses
4212-702: The Harvard Museum of Comparative Zoology . The fossil, which remains in the same museum under the catalog number MCZ 4374, was recovered from a deposit of the Niobrara Formation located in the vicinity of Monument Rocks near the Union Pacific Railroad at Fort Hays , Kansas. Cope's first publication of the fossil was very brief and was named Macrosaurus proriger , the genus being a preexisting European mosasaur taxon. The specific epithet proriger means "prow-bearing", which
4320-603: The Royal Saskatchewan Museum estimated a total length of over 9.75 meters (32.0 ft). A mounted skeleton of T. pembinensis, nicknamed "Bruce," at the Canadian Fossil Discovery Centre measures at 13.05 meters (42.8 ft) long and was awarded a Guinness World Records for "Largest mosasaur on display" in 2014. However, the skeleton was assembled for display prior to Bullard and Caldwell (2010)'s reassessment that found
4428-540: The Smoky Hill River that is now in the Yale Peabody Museum as YPM 1268, which Marsh named Rhinosaurus micromus . Cope responded by arguing that Rhinosaurus was already a preoccupied synonym of Liodon . He disagreed with Marsh's arguments but proposed that in case Marsh was indeed correct, the genus name Rhamphosaurus should be used. Marsh later discovered that the taxon Rhamphosaurus
Bentiaba River - Misplaced Pages Continue
4536-492: The Sternberg Museum of Natural History (FHSM VP-2496) may be from an even larger individual; Everhart estimated the specimen to come from a 14 meters (46 ft) individual compared to his 12 meters (39 ft) estimate for Bunker. 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
4644-849: 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). Everhart speculated that because mosasaurs continuously grew throughout their lifetime, it would have been possible for some extremely old Tylosaurus individuals to reach 20 meters (66 ft) in absolute maximum length. However, he stressed
4752-562: The Tylosaurus specimen is anywhere between the first and sixth cervical vertebrae. In Platecarpus , the bronchi probably diverged below the sixth cervical into near-parallel pairs, while in Mosasaurus the organ is dislocated. A bifurcation point's position ahead of the forelimbs would be unlike terrestrial lizards, whose point is within the chest region, but similar to the short trachea and parallel bronchi of whales. Tylosaurus
4860-459: The external nares , or body nostril openings; unlike other mosasaurs, the prefrontal bones are excluded from the border of the nares by a long posterodorsal process of the maxilla. The nares open above the fourth maxillary tooth anteriorly in T. proriger and T. pembinensis, between the third and fourth tooth in T. nepaeolicus , and posterior to the fourth tooth in T. bernardi. Nare length relative to skull length varied between species: it
4968-588: The ulnare , sometimes the ulnare and distal carpal four) and two ossified tarsal bones (usually only the astragalus, sometimes the astragalus and distal tarsal four). Hyperphalangy (increased number of phalanges relative to the ancestral condition) is present in both fore- and hindlimbs, and the phalanges are spindle -shaped, unlike the short, blocky hourglass -shaped phalanges possessed by mosasaurines . The pisiform appears to be either unossified or absent in tylosaurines. The functional consequences of differences in limb anatomy across different mosasaur clades
5076-596: The Cretaceous seaway: Texas , southwest Arkansas , New Mexico , Kansas , Colorado , Nebraska , South Dakota , Montana , Wyoming , and the Pierre Shale / Fox Hills formations of North Dakota . Lastly, mosasaur bones and teeth are also known from California , Mexico , Colombia , Brazil , Peru , and Chile . Many of the so-called 'dinosaur' remains found on New Zealand are actually mosasaurs and plesiosaurs , both being Mesozoic predatory marine reptiles. The largest mosasaur currently on public display
5184-758: The Mosasaurinae than other mosasaurs. Bell and Polycn (2005) grouped these outside mosasaurs into two clades: the Russellosaurina, whose basal members include plesiopedal genera (Tethysaurinae) of their own and derived members consisting of the Plioplatecarpinae and Tylosaurinae; and the Halisauromorpha, containing the Halisaurinae. The placement of Dallasaurus suggested that the Russellosaurina and Halisauromorpha may have evolved
5292-495: The Upper Cretaceous to explore factors that may have influenced their evolution. No single factor unambiguously accounts for all radiations, diversification, and extinctions; however, the broader patterns of taxonomic diversification and morphological disparity point to niche differentiation in a "fishing up" scenario under the influence of "bottom-up" selective pressures. The most likely driving force in mosasaur evolution
5400-447: The absence of marginal fluting as a diagnostic (taxon-identifying) trait that differentiates Tylosaurus from Taniwhasaurus . The pterygoid teeth may have enabled ratchet feeding, in which the upper teeth held prey in place as the lower jaw slides back and forth via a streoptostylic jaw joint. The bases of the pterygoid teeth are nearly circular, and each tooth is divided into front and back-facing sides of near-equal surface area via
5508-434: The actual size of the animal was likely smaller. Mosasaurs had a body shape similar to that of modern-day monitor lizards (varanids), but were more elongated and streamlined for swimming. Their limb bones were reduced in length and their paddles were formed by webbing between their long finger and toe bones. Their tails were broad, and supplied their locomotive power. Until recently, mosasaurs were assumed to have swum in
SECTION 50
#17327931204025616-525: The animal to maintain elevated body temperatures in colder environments. Possession of this trait during infancy would in turn facilitate fast growth rates. Unreflective dark coloring and countershading would have provided the mosasaur with increased camouflage . Additional speculative functions includes increased tolerance to solar ultraviolet radiation , strengthened integuments. The study remarked that certain melanism -coding genes are pleiotropic for increased aggression . AMNH FR 221 preserves parts of
5724-551: The atlas vertebra but is not preserved afterwards. The respiratory tract reappears below the fifth rib as a pair of bronchi and extends to just behind the as-preserved coracoids where preservation is lost. The pairing is suggestive of two functional lungs like modern limbed lizards but unlike snakes. Similar branching is also found in Platecarpus and putatively Mosasaurus , the only two other derived mosasaurs with their respiratory systems documented. The bifurcation point for
5832-463: The body in type and size. In Harrana specimens, two types of scales were observed on a single specimen: keeled scales covering the upper regions of the body and smooth scales covering the lower. As ambush predators, lurking and quickly capturing prey using stealth tactics, they may have benefited from the nonreflective, keeled scales. Additionally, mosasaurs had large pectoral girdles, and such genera as Plotosaurus may have used their front flippers in
5940-457: The carefully hidden fossil was uncovered, after a reward, it is said, of 600 bottles of wine, and transported to Paris. After it had been earlier interpreted as a fish, a crocodile, and a sperm whale, the first to understand its lizard affinities was the Dutch scientist Adriaan Gilles Camper in 1799. In 1808, Georges Cuvier confirmed this conclusion, although le Grand Animal fossile de Maëstricht
6048-428: The cartilaginous respiratory system . This includes parts of the larynx (voice box), trachea (windpipe), and bronchi (lung airways). They were however only briefly described in the preserved position by Osborn (1899). The larynx is poorly preserved; a piece of its cartilage first appears below just between the pterygoid and quadrate and extends to behind the latter. This connects to the trachea, which appears below
6156-630: The coast of Antarctica . Tooth taxon Globidens timorensis is known from the island of Timor ; however, the phylogenetic placement of this species is uncertain and it might not even be a mosasaur. Mosasaurs have been found in Canada in Manitoba and Saskatchewan and in much of the contiguous United States. Complete or partial specimens have been found in Alabama , Mississippi , New Jersey , Tennessee , and Georgia , as well as in states covered by
6264-547: The delicate nature of the scales, which nearly eliminates the possibility of preservation, in addition to the preservation sediment types and the marine conditions under which the preservation occurred. Until the discovery of several mosasaur specimens with remarkably well-preserved scale imprints from late Maastrichtian deposits of the Muwaqqar Chalk Marl Formation of Harrana in Jordan , knowledge of
6372-440: The dentary ranges from straight to slightly concave. A small dorsal ridge appears anterior to the first dentary tooth in mature individuals of T. proriger . The marginal dentition of most species is adapted for cutting large marine vertebrates, while those in T. ivoensis and T. gaudryi appear more optimized for piercing or smashing prey, and T. "borealis" in both piercing and cutting. Marginal teeth are triangular with
6480-563: The dominant marine predators. They themselves became extinct as a result of the K-Pg event at the end of the Cretaceous period, about 66 million years ago. Mosasaurs breathed air, were powerful swimmers, and were well-adapted to living in the warm, shallow inland seas prevalent during the Late Cretaceous period. Mosasaurs were so well adapted to this environment that they most likely gave birth to live young , rather than returning to
6588-528: The exception of the pterygoid teeth, which are smaller and more recurved than the marginal teeth. Tylosaurine dentaries were elongate; the dentary is between 56 and 60% of total length of the entire lower jaw in adult T. nepaeolicus and T. proriger , about 55% in T. pembinensis , and 62% in T. saskatchwanensis . The dentary is robust, though not as strongly built as it is in Mosasaurus , Prognathodon , or Plesiotylosaurus . The ventral margin of
SECTION 60
#17327931204026696-497: The existence of fossilized animals that were different from any known living creatures. When the specimen was discovered between 1770 and 1774, Johann Leonard Hoffmann , a surgeon and fossil collector, corresponded about it with the most influential scientists of his day, making the fossil famous. The original owner, though, was Godding, a canon of Maastricht cathedral. When the French revolutionary forces occupied Maastricht in 1794,
6804-510: 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
6912-535: The family Mosasauridae that lived during the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. They belong to the order Squamata , which includes lizards and snakes . During the last 20 million years of the Cretaceous period ( Turonian – Maastrichtian ages), with the extinction of the ichthyosaurs and pliosaurs , mosasaurids became
7020-524: The first in Kansas . The early history of the genus as a taxon was subject to complications spurred by the infamous rivalry between American paleontologists Edward Drinker Cope and Othniel Charles Marsh during the Bone Wars . The type specimen was described by Cope in 1869 based on a fragmentary skull measuring nearly 5 feet (1.5 m) in length and thirteen vertebrae lent to him by Louis Agassiz of
7128-425: The food items of mosasaurs were ammonites , molluscs with shells similar to those of Nautilus , which were abundant in the Cretaceous seas. Holes have been found in fossil shells of some ammonites, mainly Pachydiscus and Placenticeras . These were once interpreted as a result of limpets attaching themselves to the ammonites, but the triangular shape of the holes, their size, and their presence on both sides of
7236-818: The former follows Makádi et al. (2012), while the latter follows a PhD dissertation by Mekarski (2017) that experimentally includes dolichosaur and poorly-represented aigialosaur taxa. Placement of major group names follow definitions by Madzia and Cau (2017). Adriosaurus suessi Dolichosaurus longicollis Komensaurus carrolli Pontosaurus kornhuberi Aigialosaurus dalmaticus Opetiosaurus bucchichi Halisaurinae Yaguarasaurus columbianus Russellosaurus coheni Romeosaurus fumanensis Tethysaurus nopcsai Pannoniasaurus inexpectatus Tylosaurinae Plioplatecarpinae Dallasaurus turneri Clidastes Derived mosasaurines Tylosaurus Tylosaurus ( / ˌ t aɪ ˈ l oʊ ˈ s ɔːr ə s / ; "knob lizard" )
7344-410: The fourth stage, it would be of the same size as the crown in the original tooth. Stages five and six were characterized by the development of the replacement tooth's root: in stage five the root developed vertically, and in stage six the root expanded in all directions to the point that the replacement tooth became exposed and actively pushed on the original tooth. In the seventh stage, the original tooth
7452-531: The genus is a premaxilla ( TMM 40092-27) recovered from Middle Turonian deposits of the Arcadia Park Shale in Texas , which is dated between 92.1 and 91.4 million years old based on correlations with index fossils. Although formally referred to as Tylosaurinae incertae sedis during its first description, it was remarked to probably belong to T. kansasensis . The specimen was later listed within
7560-433: 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
7668-407: The kidneys is farther forward in the abdomen than it is in monitor lizards, and is more similar to those of cetaceans . As in cetaceans, the bronchi leading to the lungs run parallel to each other instead of splitting apart from one another as in monitors and other terrestrial reptiles. In mosasaurs, these features may be internal adaptations to fully marine lifestyles. In 2011, collagen protein
7776-407: The lack of fossil evidence suggesting such sizes and the odds against any being preserved. Other Campanian- Maastrichtian species were similarly large. The most recent maximum estimate for T. bernardi is 12.2 meters (40 ft) by Lindgren (2005); historically the species was erroneously estimated at even larger sizes of 15–17 meters (49–56 ft). A reconstruction of T. saskatchewanensis by
7884-530: The largest mosasaur on public display in 2014. The first publicized discovery of a partial fossil mosasaur skull in 1764 by quarry workers in a subterranean gallery of a limestone quarry in Mount Saint Peter , near the Dutch city of Maastricht , preceded any major dinosaur fossil discoveries, but remained little known. However, a second find of a partial skull drew the Age of Enlightenment 's attention to
7992-415: The largest publicly exhibited mosasaur skeleton in the world is on display at the Canadian Fossil Discovery Centre in Morden , Manitoba . The specimen, nicknamed "Bruce", is just over 15 m (49 ft) long, but this might be an overestimate as 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
8100-404: The lateral sufrace of the bone within a bowl-like depression called the alar conch. The conch is shallow in T. nepaeolicus , T. proriger , and T. bernardi , and deep in T. pembinensis and T. saskatchewanensis . The alar rim is thin in T. nepaeolicus , T. proriger , and T. bernardi , and thick in T. bernardi , T. pembinensis , and T. saskatchewanensis . The suprastapedial process
8208-417: The lingual and occasionally labial sides that do not reach the tooth's tip, and facets on the labial side. The facets are gentle in T. pembinensis , while in T. ivoensis they are slightly concave. The latter feature is also known as fluting. Marginal teeth in T. gaudryi are virtually indistinguishable from those in T. ivoensis . T. iembeensis was not placed within either group; no further description
8316-442: The lower jaw to the cranium and holding the eardrums . The complex anatomy of the bone renders it extremely diagnostic, even to the species level. In lateral view, the quadrate resembles a hook in immature T. nepaeolicus and T. proriger individuals, but in adult forms for both species and in T. bernardi , T. pembinensis , and T. saskatchweanensis it takes on a robust oval-like shape. The eardrum (tympanum) attached to
8424-475: The mosasaur discovery, they have given their name to the final six-million-year epoch of the Cretaceous, the Maastrichtian . The traditional view of mosasaur evolution held that all paddle-limbed (hydropedal) mosasaurs originated from a single common ancestor with functional legs (plesiopedal). However, this was shaken with the discovery of Dallasaurus , a plesiopedal mosasauroid more closely related to
8532-517: The nature of mosasaur integument was mainly based on very few accounts describing early mosasaur fossils dating back to the upper Santonian –lower Campanian , such as the famous Tylosaurus specimen (KUVP-1075) from Gove County, Kansas. Material from Jordan has shown that the bodies of mosasaurs, as well as the membranes between their fingers and toes, were covered with small, overlapping, diamond-shaped scales resembling those of snakes. Much like those of modern reptiles, mosasaur scales varied across
8640-509: The nostrils to the throat. In Tylosaurus , they are shaped like a compressed teardrop and bordered by the vomers , palatines , and the maxilla. Anterior to the choanae, each vomer borders the fenestra for the Jacobson's organ , which is involved in the tongue-based sense of smell . It begins opposite of the fourth maxillary tooth in Tylosaurus , and also ends immediately past the fifth maxillary tooth in T. bernardi . The exit point for
8748-421: The posteroventral process. The vertical ramus is overlapped by the postorbitofrontal in most species, and the horizontal ramus overlaps the maxilla. In T. bernardi , the vertical ramus is not overlapped but joins with the postorbitofrontal by a suture, and is much thicker than the horizontal ramus. The quadrate bones (homologous to the incus in mammals) are located at the back of the skull, articulating
8856-400: The prearticular is fused to the articular). The premaxilla, maxilla, and dentary house the marginal dentition, and the pterygoids house palatal dentition. On each side of the skull, Tylosaurus had 2 premaxillary teeth, 12 to 13 maxillary teeth, 13 dentary teeth, and 10 to 11 pterygoid teeth. The dentition is homodont , meaning that all teeth are nearly identical in size and shape, with
8964-428: The prefrontal, lacrimal, postorbitofrontal, and jugal bones . A diagnostic feature of Tylosaurus is that the prefrontals and postorbitofrontals overlap above the orbits, preventing contribution of the frontal. The jugal forms the bottom of the orbit; in Tylosaurus , it is L-shaped and has a distinctive serif-like extension at the lower back corner of the junction between the horizontal and vertical rami (arms) called
9072-451: The premaxilla in the latter. The frontal crest is present but poorly developed in most T. nepaeolicus skulls, and occasionally lost in some mature individuals. The frontal overlaps the prefrontals and postorbitofrontals above the orbits (eye sockets), and the parietal posteriorly. The position of the pineal eye on the parietal is variable, either appearing close to the frontoparietal suture or contacting it. The orbits are bordered by
9180-543: 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. Tylosaurus was among the earliest derived mosasaurs. The oldest fossil attributable to
9288-410: The rest of the skull in Tylosaurus and other mosasaurs may be why the bones are frequently lost and therefore exceedingly rare; Tylosaurus is one of the only mosasaurs in which the nasal bones are clearly documented; the other is the holotype of Plotosaurus , although one of the bones is missing. The external nares lead to the choanae (internal nares) in the palate, which provide passage from
9396-410: The same time period, the 2016 study found mosasaurs likely had body temperatures similar to those of contemporary seabirds and were able to internally regulate their temperatures to remain warmer than the surrounding water. The coloration of mosasaurs was unknown until 2014, when the findings of Johan Lindgren of Lund University and colleagues revealed the pigment melanin in the fossilized scales of
9504-638: The shells, corresponding to upper and lower jaws, is evidence of the bite of medium-sized mosasaurs. Whether this behaviour was common across all size classes of mosasaurs is not clear. Virtually all forms were active predators of fish and ammonites; a few, such as Globidens , had blunt, spherical teeth, specialized for crushing mollusk shells. The smaller genera, such as Platecarpus and Dallasaurus , which were about 1–6 m (3.3–19.7 ft) long, probably fed on fish and other small prey. The smaller mosasaurs may have spent some time in fresh water, hunting for food. The largest mosasaur Mosasaurus hoffmannii
9612-435: The shore to lay eggs as sea turtles do. The smallest-known mosasaur was Dallasaurus turneri , which was less than 1 m (3.3 ft) long. Larger mosasaurs were more typical, with many species growing longer than 4 m (13 ft). Mosasaurus hoffmannii , the largest known species reached up to 17 m (56 ft), but it has been considered to be probably overestimated by Cleary et al. (2018). Currently,
9720-528: The skin. Microscopic analysis of scales in a T. nepaeolicus specimen by Lindgren et al. (2014) detected high traces of the pigment eumelanin indicative of a dark coloration similar to the leatherback sea turtle in life. This may have been complemented with countershading , present in many aquatic animals, though the distribution of dark and light pigments in the species remains unknown. A dark-colored form would have provided several evolutionary advantages. Dark coloration increases absorption of heat, allowing
9828-412: The snout proportionally longer than most mosasaurs, with the exception of Ectenosaurus . The most recognizable characteristic of Tylosaurus is the elongated edentulous rostrum that protrudes from its snout, for which the genus is named. This is formed by the elongation of the front end of the premaxilla and dentary. The rostrum was small and acutely angled at birth, but rapidly developed into
9936-659: The species in a 2020 reexamination. A slightly younger specimen is of a skull (SGM-M1) of an indeterminate Tylosaurus species similar to T. kansasensis from the Ojinaga Formation in Chihuahua, Mexico , dated around ~90 million years old at earliest. A tooth from a Late Maastrichtian deposit in Nasiłów, Poland dating close to the Cretaceous–Paleogene boundary has been attributed to Hainosaurus sp. With
10044-423: The species' number of vertebrae to be exaggerated. T. "borealis" is estimated at 6.5–8 meters (21–26 ft) in total length. The largest known skull of Tylosaurus is T. proriger KUVP 5033 (the "Bunker" specimen), estimated at 1.7 meters (5.6 ft) long. Depending on age and individual variation, Tylosaurus skulls were between 13 and 14% of the total skeleton length. The head was strongly conical and
10152-419: 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. The following cladogram
10260-414: 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
10368-539: The time this error was discovered, depicting mosasaurs with such crests in artwork had already become a trend. Mosasaurs had double-hinged jaws and flexible skulls (much like those of snakes ), which enabled them to gulp down their prey almost whole. A skeleton of Tylosaurus proriger from South Dakota included remains of the diving seabird Hesperornis , a marine bony fish , a possible shark , and another, smaller mosasaur ( Clidastes ). Mosasaur bones have also been found with shark teeth embedded in them. One of
10476-617: The tip. The group was originally defined as having slender teeth, but subsequent research has since recognized that slenderness is an ontogenetic trait in T. proriger with robust teeth appearing in adult forms. Though not formally classified within a group, the marginal teeth of T. saskatchwanensis shares a comparable morphology with T. proriger . The second is the Euro-American ' ivoensis group ' and consists of T. ivoensis , T. gaudryi , and T. pembinensis . Their teeth are robust with prominent carinae with striations on
10584-480: The veins leading to sinuses inside the palatine occur right in front of the Jacobson's organ between the vomers and maxilla. This differs from living varanids, where the exit occurs behind the organ. The frontal bone in Tylosaurus usually, but not always, possesses a low midline crest. It is most prominent in T. proriger, and is moderately developed in T. saskatchewanensis and T. bernardi , extending onto
10692-435: The water, while their tails provided strong propulsion. These animals may have lurked and pounced rapidly and powerfully on passing prey, rather than chasing after it. At least some species were also capable of aquaflight, flapping their flippers like sea lions . Early reconstructions showed mosasaurs with dorsal crests running the length of their bodies, which were based on misidentified remains of tracheal cartilage. By
10800-424: The whole body. An individual measuring 5 meters (16 ft) in total body length had dermal scales measuring 3.3 by 2.5 millimeters (0.130 in × 0.098 in), and in each square inch (2.54 cm) of the mosasaur's underside an average of ninety scales were present. Each scale was keeled in a form resembling that of a shark's denticles . This probably helped reduce underwater drag and reflection on
10908-454: 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,
11016-592: Was first done in 1873 by Joseph Leidy by transferring Rhinosaurus proriger to Tylosaurus . Rhinosaurus micromus was formally transferred to the same genus in 1894 by John Campbell Merriam . Tylosaurus was one of the largest known mosasaurs. The largest well-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. A fragmentary skeleton of another T. proriger from
11124-427: Was high productivity in the Late Cretaceous, driven by tectonically controlled sea levels and climatically controlled ocean stratification and nutrient delivery. When productivity collapsed at the end of the Cretaceous, coincident with bolide impact, mosasaurs became extinct. Sea levels were high during the Cretaceous period, causing marine transgressions in many parts of the world, and a great inland seaway in what
11232-484: Was not actually named Mosasaurus (' Meuse reptile') until 1822 and not given its full species name, Mosasaurus hoffmannii, until 1829. Several sets of mosasaur remains, which had been discovered earlier at Maastricht but were not identified as mosasaurs until the 19th century, have been on display in the Teylers Museum , Haarlem , procured from 1790. The Maastricht limestone beds were rendered so famous by
11340-480: Was preoccupied as a genus of lizard named in 1843. As a result, he suggested a move to a newly erected genus named Tylosaurus . This name means "knob lizard" in another reference to the elongated rostrum characteristic of the genus. It is derived from the Latin tylos (knob) and Ancient Greek σαῦρος . Despite coining the new genus, Marsh never formally transferred the Rhinosaurus species to Tylosaurus ; this
11448-460: Was recovered from a Prognathodon humerus dated to the Cretaceous . In 2005, a case study by A.S. Schulp, E.W.A Mulder, and K. Schwenk outlined the fact that mosasaurs had paired fenestrae in their palates. In monitor lizards and snakes, paired fenestrae are associated with a forked tongue , which is flicked in and out to detect chemical traces and provide a directional sense of smell . They therefore proposed that mosasaurs probably also had
11556-442: Was shed and the now-independent replacement tooth began to anchor itself into the vacancy. In the eighth and final stage, the replacement tooth has grown to firmly anchor itself. Mosasaur growth is not well understood, as specimens of juveniles are rare, and many were mistaken for hesperornithine birds when discovered 100 years ago. However, the discovery of several specimens of juvenile and neonate-sized mosasaurs unearthed more than
11664-420: Was the apex predator of the Late Cretaceous oceans, reaching more than 11 metres (36 ft) in length and weighing up to 10 metric tons (11 short tons) in body mass. Despite the many mosasaur remains collected worldwide, knowledge of the nature of their skin coverings remains in its early stages. Few mosasaurid specimens collected from around the world retain fossilized scale imprints. This lack may be due to
#401598