Mosasaur Pronunciation Guide

Ben Creisler

(Moved to Oceans of Kansas, July 5, 2012)

 

 


Amphekepubis Mehl 1929 "forked pubis"*

am-FEE-kee-PYOO-bis (Gr. amphekes "double-pointed" + Lat. pubis "pubis") (m) named for its distinctive "forked pubis," formed by the development of a long, slender pubic process projecting from the front of the pubic bone; known from a pelvic arch, part of a hindlimb and 9 postsacral (pygal and tail) vertebrae (Holotype: Univ. of Missouri 509VP). The type material was found in northeast Mexico near Monterrey , but the exact provenance is not known--probably the San Felipe Formation (Santonian). The slender femur makes Amphekepubis appear somewhat more primitive than Clidastes, while the transverse processes on the pygal vertebrae are much longer than in Mosasaurus. Though still incompletely known, Amphekepubis must have been a moderately large mosasaur (probably around 9 m (30 ft) long).

Type Species: Amphekepubis johnsoni [JON-suh-nie] Mehl 1930: for Carlyle D. Johnson, who collected the specimen about 40 miles east of Monterrey , Nuevo Leon, Mexico. The material was "all that could be crowded into an already over-full suit-case, the only baggage carried in a hasty trip across country" according to Johnson, who gave the fossils to the University of Missouri . Mosasaurinae Late Cretaceous (Santonian) Mexico


Amphorosteus Gibbes 1851 "amphora-boned one"

am-fo-ROS-tee-uhs (Gr. amphora, a jar with a narrow neck + Gr. osteon "bone" + -us) (m) named "from the resemblance of the vertebrae, in outline, to an ancient amphora." Late Cretaceous NA. [nomen dubium]


Angolasaurus Telles-Antunes 1964 " Angola lizard"

ang-GOH-luh-SAWR-uhs ( Angola + Gr. sauros "lizard") (m) named to indicate a mosasaur found in Angola , Africa . According to Lingham-Soliar (1994), Angolasaurus bocagei is an early species of Platecarpus. [= Platecarpus]


Ancylocentrum Schmidt 1927 "fused centrum"

AN-sil-o-SEN-truhm (Gr. agkylos "crooked, curved" [used in the applied sense "stiff, fused"] + Lat. centrum, central element of a vertrebra) (n) alluding to chevrons fused to the centrum of the tail vertebra. (To replace preoccupied Brachysaurus.) [= Prognathodon]

Baptosaurus Marsh 1870 "diving lizard"

BAP-to-SAWR-uhs (Gr. bapto "plunge" + Gr. sauros "lizard")* (m) to replace Halisaurus Marsh, supposedly preoccupied by Halosaurus Johnson 1864. Because of a one letter difference, Halisaurus is not preoccupied according to current ICZN rules. [= Halisaurus]


Baseodon Leidy 1865 "pedestal tooth"

ba-SEE-o-don (Gr. baseos (basis) "step, pedestal, base" + Gr. odon "tooth") (m) named for the enlarged base of two pterygoid teeth probably belonging to a species of Mosasaurus. Late Cretaceous NA. [nomen dubium]


Batrachiosaurus Harlan 1839 "frog-like lizard"

BAT-tra-KIE-o-SAWR-uhs (Gr. batrakheios "frog-like" + Gr. sauros "lizard") (m) named to indicate an animal that supposedly "approaches" the "batrachian reptiles" in the "form and position of the intermaxillary bones"; proposed for Mosasaurus ("Ichthyosaurus") missouriensis. [= Mosasaurus]


Brachysaurana Strand 1928 "short lizard"

BRAK-ee-saw-RAY-nuh (Gr. brachys + Gr. saura "lizard" + -ana) (f) to replace preoccupied Brachysaurus--Ancylocentrum has priority as a replacement name. [= Prognathodon]


Brachysaurus Williston 1897 "short lizard"

BRAK-ee-SAWR-uhs (Gr. brakhys "short" + Gr. sauros "lizard") (m) named for the broad and large frontal bones of the skull. (Preoccupied by Brachysaurus Hallowell 1856. See Ancylocentrum.) [= Prognathodon]

Carinodens Thurmond 1969 "keeled tooth"

kah-RIEN-o-denz (Lat. carina "keel" + Lat. dens "tooth")* (m) referring to the carina (raised cutting edge) along the teeth; new name to replace preoccupied Compressidens Dollo 1924 (proposed for "Globidens" fraasi Dollo 1913). The genus is known from a small, toothed dentary (183 mm long) (IRSNB 6571) and several isolated teeth. The teeth are broad, pointed, and laterally compressed, with carinae on the front and back edges; teeth in the front of the jaw are narrower and subcircular in cross-section. The robust blunt shape of the teeth indicates they were probably used to crush crustaceans or invertebrates with thin shells such as Nautilus--the teeth and jaws were likely too delicate to crush the more heavy-shelled mollusks preyed on by Globidens. The coarse rib- or fan-like wrinkles on the surface of the teeth are more developed than in Globidens, and would have strengthened the tooth and concentrated stress in the food item (Lingham-Soliar 1999). According to Kuypers, Jagt, Peeters and De Graaf (1998), and Lingham-Soliar (1999), the distinction between Carinodens fraasi and C. belgicus is based only on differential wear on the functioning teeth: "The tricuspid pattern on some teeth [in C. belgicus] constituted simple wear on the rounded anterior and posterior edges and on the central cusp of the more rectangular-shaped teeth. The condition presumably occurred in older teeth nearing replacement." (Lingham-Soliar 1999). Kuypers, Jagt, Peeters and De Graaf (1998) made Carinodens fraasi a junior synonym of C. belgicus. Additional material has been identified from the Netherlands (Kruytzer 1961) and Bulgaria (Tzankov 1963). A tooth belonging to Carinodens was figured by Faujas-Saint-Fond in 1799 in a monograph about teeth found at Saint Peter's Mount in Maastricht , Netherlands . One of the smallest mosasaurs known, Carinodens was probably around 3-3.5 m (10-12 ft) long.

Type Species: Carinodens belgicus [BEL-ji-kuhs] (Woodward 1891) "Belgian": originally identified as "Bottosaurus" belgicus Woodward 1891, a supposed Belgian species of the Late Cretaceous North American alligator Bottosaurus Agassiz ("(Paul-Emile) Botta's reptile"), based on teeth found in the Craie de Ciply of Belgium . The teeth are distinguished by a tricuspid shape, unique among mosasaurs. According to Kuypers, Jagt, Peeters and De Graaf (1998), the distinctive tooth shape in C. belgicus resulted from differential wear and the species is a senior synonym of Dollo's original type species C. fraasi (named for Eberhard Fraas, German paleontologist at the royal Natural History Museum in Stuttgart, who brought the original type specimen dentary to Dollo's attention and generously gave it to the Royal Museum in Brussels). Mosasaurinae Late Cretaceous (Campanian-Maastrichtian) Eur.


Clidastes Cope 1868 "(vertebrae) locker"

klie-DAS-teez (from Gr. kleidoo "to lock up" + Gr. suffix -astes "one who performs an action"; by analogy with Gr. dynastes "ruler," kolastes "punisher," etc.) (m) Cope originally proposed the name Clidastes (literally "one who locks") for a single, isolated vertebra from the Marshalltown Formation of New Jersey, with the type species Clidastes iguanavus "iguana ancestor," for its supposed similarity to the vertebrae of modern iguanas. The vertebra was notable for a zygosphene and a zygantrum--extra bony articulations that help "lock" vertebrae one to the other in the flexible backbones of lizards and snakes, and thus serve to restrict vertical bending. Cope described mosasaurs as having "the arches of the vertebral column interlocked more extensively than in other reptiles except the snakes," adding with a burst of imagination that in "Clidastes, this structure is as fully developed as in the serpents, so that we can picture to ourselves its well known consequences: their rapid progress through water by lateral undulations; their lithe motions on land; the rapid stroke; the ready coil; or the elevation of the head and vertebral column, literally a living pillar towering above waves or brush of the shore swamps." (Cope 1869). However, Clidastes' vertebrae differed "from the dorsals of known serpents in having a zygosphen on the plane of the anterior zygopophysis." (See additional comments at "Pythonomorpha.") The discovery of more complete fossils debunked Cope's vision of Clidastes and other mosasaurs as huge, coiling snakelike animals, and showed that not all mosasaurs had interlocking zygosphenes and zygantra on their vertebrae.

Clidastes was relatively small (only up to 6 m. (20 ft.)long) mosasaur with a thin elongated body and a relatively short flattened tail. The expanded neural spines toward the tip of the tail aided propulsion and suggest Clidastes was a fast swimmer-- there is no preserved fossil evidence for an additional sea- snake-like soft-tissue fin to further enlarge the end of tail as depicted in some restorations, however. In other ways, Clidastes represents a relatively primitive (less derived) type of mosasaurine, particularly in its limb structure (small number of phalanges on digits, digits widely spaced, carpus retaining primitive elements; but shapes of humerus, radius and ulna highly modified as short and broad) and in its somewhat kinetic skull (though the bones allow less intercranial movement than in most plioplatecarpines). The skull also has a distinctive short, pointed rostrum projecting beyond the front teeth, producing a v- shaped dorsal profile. The teeth are compressed and bicarinate with smooth enamel surfaces. Russell (1967) suggested that: "The long slender jaws of Clidastes were probably adapted to rapid biting." The slicing teeth "might have been effective in sawing a large object into pieces of swallowable size" when the lower jaw was moved backward and forward. Thus, unlike many other mosasaurs that probably swallowed most prey whole, the relatively small Clidastes may have been able to reduce a victim to bite-sized chunks.

Its lifestyle is still debated. Williston (1898) intrepreted Clidastes as an apparent surface feeder. Martin and Rothschild (1989) concurred, noting that Clidastes' bones do not show evidence of "the bends" or decompression syndrome (avascular necrosis), indicating to them that it "lived near shore" and "did not regularly engage in deep diving." However, Sheldon (1997) analyzed the microstructure of ribs from Clidastes and discovered low bone density (osteoporosis)--the porous bones would have been filled with lipids, providing neutral bouyancy over a greater range of depths. Based on comparisons with living marine vertebrates, Sheldon concluded that Clidastes was in fact built to be a deep diver--its "thorax construction was conducive to lung compression," which would have decreased diffusion of gases into the bloodstream and thus would have prevented the avascular necrosis found in the bones of mosasaurs such as Platecarpus that were adapted to live in shallower depths.

The single type specimen vertebra (Clidastes iguanavus) that inspired the generic name is no longer considered diagnostic and probably belongs to Mosasaurus; the generic name Clidastes was conserved with a new type species (Clidastes propython) and new holotype specimen (ANSP 10193) by ICZN Opinion # 1750 (1993), based on a nearly complete skeleton and skull from the Selma Formation of Alabama that Cope had identified as Clidastes from the presence of a zygosphene and a zygantrum on the dorsal vertebrae.

Vertebrae: 42 presacrals / 7 pygals/ 26 intermediate caudals with chevrons and transverse processes / 46 terminal caudals
Length: up to 6.2 m. (21 ft.); skull: 65.8 cm (2.2 ft.)

Type Species: Clidastes propython [proh-PIE-thon] Cope 1869 "before-python": referring to what Cope saw as "ophidian affinities" in mosasaurs, especially in the vertebrae and certain parts of the skull--he classified mosasaurs in a separate order of reptiles called the Pythonomorpha "python forms" (see Pythonomorpha). Based on a nearly complete skeleton and skull (Holotype: ANSP 10193) found in the Selma Formation (Rotten Limestone), near Uniontown, Alabama; made the type species in place of Clidastes iguanavus ("iguana ancestor") by ICZN Opinion 1750 (1993).

Additional Species: Clidastes liodontus [lie-o-DON-tuhs] Merriam 1894 "smooth-toothed": "All the teeth on the maxillary, premaxillary and dentary bones are completely smooth and can be compared with those of Liodon Owen, from which they are almost, if not totally, indistinguishable." (Merriam 1894); originally based on maxillae, premaxilla and dentaries--now known from a number of nearly complete skeletons.

NOTE: "Clidastes moorevillensis," from the Mooreville Chalk of Alabama , is a distinct species of Clidastes yet to be formally described (Gorden Bell, personal communication); another new species also awaits description. "Clidastes" sternbergii Wiman 1920 was transferred to Halisaurus by Russell (1970). More recently, a number of other researchers have suggested that the species "Clidastes" sternbergii represents a genus of primitive mosasaur distinct from both Clidastes and Halisaurus, and is in need of redescription. See comments below under Halisaurus (Additional Species: Halisaurus ("Clidastes") sternbergii). Mosasaurinae Late Cretaceous (Coniacian-Campanian) NA.


Compressidens Dollo 1924 "compressed tooth"

com-PRES-i-denz (Lat. compressus "compressed" (from comprimo "press together) + Lat. dens "tooth") (m) named for the laterally compressed shape of teeth, unlike the rounded teeth of Globidens (preoccupied by Compressidens Pilsbury & Sharp 1897. See Carinodens) [= Carinodens]

Dollosaurus Yakovlev 1901

DOL-o-SAWR-uhs (Dollo + Gr. sauros "lizard") (m) named to honor Louis Dollo (1857-1931), noted Belgian paleontologist who studied mosasaurs; known from a partial skull and skeleton from the Donetz Basin of southern European Russia. The functional zygosphenes and zygantra, the fused chevrons on the tail vertebrae, and the reduced number of large pterygoid teeth show a close relationship to Prognathodon and Plesiotylosaurus. Lingham- Soliar (1989) determined Dollosaurus was a form of Prognathodon, but some other researchers still accept separate generic status.

Type Species: Dollosaurus lutugini [loo-TOO-gee-nie] Yakovlev 1901: for Leonid Ivanovich Lutugin (1864-1915), Russian geologist and cartographer, who studied the Donetz Basin where the fossils were found. Plioplatecarpinae Late Cretaceous (Campanian) EEur. [= ?Prognathodon]


Drepanodon Leidy 1856 "sickle tooth"

dre-PAN-o-don (Gr. drepane "sickle, scythe" + Gr. odon "tooth") (m) for the sharp blade-like shape of the tooth. Late Cretaceous NA. [nomen dubium]

Ectenosaurus Russell 1967 "drawn-out (snout) lizard"

EK-ten-o-SAWR-uhs (Gr. ektenes "drawn-out" + Gr. sauros "lizard")* (m) referring to the thin, elongated form of the muzzle; for "Platecarpus" clidastoides Merriam 1894. Ectenosaurus is closely related to Platecarpus, with a similar, highly kinetic skull, but differs in the narrow, elongated shape of its snout, and in certain features of the skull bones and of the forelimbs. The original type material at the Bayerische Staatssammlung fuer Palaeontologie in Munich , Germany , appears to have been destroyed in WWII. Additional specimens include skulls and partial skeletons in the Yale Peabody Museum and the Fort Hays Kansas Museum . Known from the Niobrara Formation, Smoky Hill, Kansas .

Length: (estimated) 6 m. (20 ft.); skull: .65 m. (2.2 ft.)

Type Species: Ectenosaurus clidastoides [klie-das-TOY-deez] (Merriam 1894) "Clidastes-like"; for a resemblance to Clidastes in the shape of the back of the skull. Plioplatecarpinae Late Cretaceous (Santonian-Campanian) NA.


Edestosaurus Marsh 1871 "devourer lizard"

e-DES-to-SAWR-uhs (Gr. edestes "devourer" + Gr. sauros "lizard")* (m) named for its carnivorous nature. [= Clidastes]


Elliptonodon Emmons 1858 "elliptical tooth"

e-lip-TON-o-don (from Gr. elleiptikos "elliptical" + Gr. odon "tooth") (m) based on a single tooth from North Carolina with a crown "circular at the base, becoming elliptical, and finally sub-elliptical"; resembling a tooth of Prognathodon but with strongly striated enamel. Late Cretaceous NA. [nomen dubium]

Globidens Gilmore 1912 "globular tooth"

GLOB-i-denz (Lat. globus "globe, sphere" + Lat. dens "tooth") (m) named for the rounded globular shape of its teeth, designed for crushing hard-shelled mollusks (more likely ammonites rather than clams or gastropods) and possibly the shells of turtles. Globidens is a fairly small, specialized mosasaur with a short, massive head, and jaws containing bulbous to blunt-tipped teeth with strongly constricted bases and a covering of wrinkles; pterygoid teeth on the palate are absent or very rudimentary (unlike in other mosasaurs, which have functional pterygoid teeth). The vertebrae have weakly developed zygapophyses. The skull and vertebrae show a close relationship to Clidastes (Russell 1975). New North American material (not yet described) includes a nearly complete skeleton. Similar-looking tooth material from Africa, Europe, Middle East and South America may belong to the genus.

Length: (estimated) 5.5-6 m. (18-20 ft.); skull: (estimated) .47 m. (19 in.))

Type Species: Globidens alabamaensis [AL-uh-bam-uh-EN-sis] Gilmore 1912 "from Alabama ": found in the Selma Chalk of Alabama; known from parts of skull and one vertebra (Holotype: USNM 6527).

Additional Species:

Globidens dakotensis [dak-o-TEN-sis] Russell 1975 "from (South) Dakota": found in the Sharon Springs Member of Pierre Shale, in Custer County , South Dakota ; based on a complete skull and 11 presacral vertebrae (Holotype: FMNH PR 846). The skull roof "is more firmly knitted together, the muzzle shorter, and the teeth lower and broader" than in the earlier species Globidens alabamaensis. Mosasaurinae Globidentini Late Cretaceous (Campanian- Maastrichtian) NA., Eur., NAfr., WAfr. , Israel , Brazil , Timor


Goronyosaurus Azzaroli, de Guili, Ficcarelli & Torre 1972 "Goronyo ( Nigeria ) lizard"

goh-RON-yo-SAWR-uhs (Goronyo + Gr. sauros "lizard") (m) named for the Goronyo district of Sokoto State , Nigeria , where the type matieral was found; for "Mosasaurus" nigeriensis Swinton 1930. Goronyosaurus is a "bizarre" form with deep interdental pits in the upper and lower jaws for the tips of the long pointed teeth (only about 10 in each jaw), so that the exceptionally long jaws fitted tightly together when closed with the teeth overlapping from above and below. The long snout with jaw muscles relatively far back on the robust temple bones indicates a "snapping" bite similar to some fossil marine crocodiles, for rapidly impaling fast-moving, moderately small prey. Lingham-Soliar (1989) has suggested that its small eyes, tactile snout and probably enhanced sense of smell indicate the animal "may have subsisted in darker estruarine conditions feeding on the highly evasive and slippery young of other marine animals, perhaps even other mosasaurs." Further material has been discovered since that adds to the unique characters of Goronyosaurus and that may justify creation of a separate subfamily for the genus (Lingham-Soliar 1998).

Length: (estimated) 7 m. (24 ft.); skull: (estimated) .62 m. (2 ft.); lower jaw: (estimated) .7 m. (2.3 ft.).

Type Species: Goronyosaurus nigeriensis [nie-jeer-ee-EN-sis] (Swinton 1930) "from Nigeria " (Holotype: IGF 14750) Mosasauridae i.s. Late Cretaceous (Maastrichtian) Afr.

Hainosaurus Dollo 1885 "Haine (River) lizard"

EN-o-SAWR-uhs (Haine + Gr. sauros "lizard") (m) named for the Haine River (in imitation of Mosasaurus "Meuse (River) lizard"), geographic feature in southern Hainaut Province , Belgium , where the type material (Holotype: IRSNB R23) was found (Craie de Ciply (Maastrichtian)). Hainosaurus is a gigantic mosasaur related to Tylosaurus, with a similar toothless rostrum at the tip of the snout, but with longer nostril openings and more elongated trunk proportions. Hainosaurus has up to 53 vertebrae between the head and the beginning of chevron-bearing tail bones compared to 35 vertebrae in the same region of the vertebral column in Tylosaurus; Hainosaurus also has a shorter tail, with fewer chevron-bearing tail vertebrae than in Tylosaurus. As in Tylosaurus, the chevrons are not fused to the centra. Documented stomach contents include turtle parts. Taniwhasaurus from the Maastrichtian of New Zealand appears to be closely related to Hainosaurus.

Vertebrae: 40 presacrals / 9+ pygals / 30-35 intermediate caudals / 33+ terminals
Length: (estimated) 12-15+ m. (40-50+ ft.); skull: 1.5+ m. (5+ ft.)).

Type Species: Hainosaurus bernardi [ber-NAR-die] Dollo 1885: for Leopold Bernard, a Belgian industrialist who permitted the excavation of the holotype fossils on his phosphate mining concession at Mesvin-Ciply , Belgium . (Maastrichtian of Belgium and France ).

Additional Species: Hainosaurus pembinensis [pem-bi-NEN-sis] Nicholls 1988 "from Pembina": for the Pembina Member of the Pierre Shale (early Campanian), Mantiboa, Canada ), where the type material was found (Holotype: MT 2 ( Miami Museum ( Manitoba )).

Hainosaurus gaudryi [goh-DREE-ie] (Thevennin 1896): for Jean Albert Gaudry (1827-1908), French paleontologist; originally as "Mosasaurus" gaudryi Thevennin 1896--the teeth are typically tylosaurine with a deep cross-section and striations on the buccal and lingual sides. (Santonian of France ) Tylosaurinae Late Cretaceous (Santonian-Maastrichtian) Eur., NA.


Halisaurus Marsh 1869 "sea lizard"

HAL-i-SAWR-uhs (Gr. halis (hals) "sea" + Gr. sauros "lizard")* (m) named to indicate a marine reptile. Marsh later assumed the name was preoccupied by Halosaurus Johnson 1864 (a fish) and provided the unnecessary replacement name Baptosaurus for his Halisaurus. (A one-letter spelling difference is adequate to distinguish two generic names under modern rules of nomenclature.)

Halisaurus remains a problematic taxon. It appears to have been a small mosasaur with primitive-looking vertebrae and a highly kinetic skull. Fragmentary fossils identified as Halisaurus indicate a wide geographic range (North America, South America, Europe, Africa) and a surprisingly long stratigraphic occurrence (ten million years from Upper Santonian to Upper Maastrichtian). The cervical vertebrae are distinguished by their compressed shape, with very broad central articulations ("This genus is especially characterized by the great depression of the centra of the vertebrae, which gives the articular ball and cup a very transverse elliptical outline, exceeding in this respect apparently those of any other Reptilia." (Marsh 1869)), and lack of zygosphenes and zygantra. Crucial to accurately diagnosing and classifying Halisaurus is whether or not the nearly complete specimen originally called Clidastes sternbergii Wiman 1920 should be included in the genus.

Marsh's type species Halisaurus platyspondylus is based on an angular bone, braincase fragments, and two vertebrae (cervical and dorsal) that lack a zygosphen and a zygantrum (Holotype: YPM 444), found in the New Egypt Formation (Maastrichtian) in New Jersey: Merriam added the species Halisaurus onchognathus (as Baptosaurus onchognathus) in 1894, based on a partial skull and lower jaw, associated with Halisaurus-like vertebrae found in the Niobrara (Santonian-Campanian) of Kansas and sent to a German collection (destroyed in WWII). Russell (1967) accepted the two species in the same genus, even though they are widely separated in time. Baird and Case (1966) identified a frontal bone from New Jersey as Halisaurus platyspondylus, based on Russell's discovery of similar frontals associated with typical Halisaurus vertebrae in the Selma Chalk of Alabama. The fragmentary nature of known Halisaurus material seemed largely remedied when Russell (1970) transferred the species Clidastes sternbergii Wiman (known from a nearly complete skeleton and skull found in the Niobrara of Kansas) to Halisaurus. Russell made the taxonomic switch based on newly described but incomplete material from Alabama --frontal bones resembling those in "Clidastes" sternbergii associated with vertebrae closely matching the morphology of Marsh's type material. However, DeBraga and Carroll (1993) questioned whether "Clidastes" sternbergii (a form retaining many strikingly primitive characteristics in its skull, limbs, and skeleton) really belongs in Halisaurus. (See additional comments under Halisaurus ("Clidastes") sternbergii below.) Also disputing Russell, Lingham-Soliar (1996) redefined Halisaurus to include Phosphorosaurus ortliebi Dollo (known only from a fragmentary skull lacking any associated vertebrae), citing the unique, extremely narrow frontal bone. Because of differences in the skulls of "Phosphorosaurus" ortliebi and "Clidastes" sternbergii such as the size of the parietal openings, Lingham-Soliar excluded "Clidastes" sternbergii from the genus Halisaurus. (See additional comments under Halisaurus ("Clidastes") sternbergii below.) If "Clidastes" sternbergii is removed from the diagnosis of the genus, Halisaurus appears to be a plioplatecarpine mosasaur that shares several important characters with Plioplatecarpus--Halisaurus thus would not be a uniquely primitive form outside the recognized subfamilies. In contrast, Gordon Bell (1997) supports Russell's position and has classified Halisaurus, with the species "Clidastes" sternbergii included, as a sister taxon to all other mosasaurs, distinguished by its primitive features. Bell has also recognized at least one additional species of Halisaurus yet to described.

Length: (estimated based on H. ortliebi): up to 4.5 m. (15 ft.); skull: 40 cm (16 in).

Type Species: Halisaurus platyspondylus [plat-ee-SPON-di-luhs] Marsh 1869 "broad vertebrae": for the broadened, compressed shape of the vertebrae.

Additional Species:

Halisaurus onchognathus [ong-KOG-na-thuhs] (Merriam 1894) "hook- jaw": "the hind end of the lower jaw has a hook-like appearance"; type specimen in the Munich museum destroyed in WWII.

Halisaurus ortliebi [ort-LEE-bie] (Dollo 1889); for Jean Ortlieb, Belgian geologist and director of the research laboratory of the Society Solvay and Cie; originally described as Phosphorosaurus ortliebi Dollo 1889. The species is only known from a fragmentary skull (IRSNB R34); Lingham-Soliar (1996) identified it as a form of Halisaurus based on the narrow frontal bone in the skull, even though no associated vertebrae (the usual diagnostic feature of Halisaurus) are currently known.

Halisaurus ("Clidastes") sternbergii [stuhrn-BUHR-gee-ie] (Wiman 1920): for Levi Sternberg (1894-1976), who discovered the type specimen in Logan County , Kansas (Smoky Hill Member of the Niobrara ). Founded on a nearly complete skeleton and skull sold to the Uppsala University Museum in Stockholm , Sweden (Holotype: UPI R163 (Uppsala Palaeontological Institute)), representing a small adult animal (total length: 2.65 m (8.8 ft.); skull (as reconstructed by deBraga and Carroll): 25 cm (10 in.) (nose to occiput)). Wiman (1920) originally identified the specimen as a new species of Clidastes (Clidastes sternbergii), based on the fusion of the chevrons to the centra of the tail bones. Some details of the skull and limbs had been restored in plaster, complicating the diagnosis. Wiman pointed out in particular the "primitive condition of the extemities," with slender limb bones more like those of terrestrial lizards. He was unable to determine the condition of the zygosphene and zygantrum because of poor preservation of the cervical vertebrae. Russell (1967) suggested that "Clidastes" sternbergii (which he respelled "sternbergi") might belong in a new genus distinct from Clidastes because of its reduced number of thoracic vertebrae and its small scapula and slender limb bones. But after more study, Russell (1970) transferred the species to the existing, poorly known genus Halisaurus, relying on similarities between Wiman's specimen and new material found in Alabama that associated similar looking skull bones with Halisaurus-like vertebrae. DeBraga and Carroll (1993) used new photographs to reevaluate Wiman's type specimen and confirmed numerous primitive features that set "Clidastes" sternbergii apart from other known mosasaurs. The skull in particular showed "the most primitive cranial anatomy known within the Mosasauridae," retaining "an unspecialized mode of cranial kinesis relative to all other mosasaurs." They also questioned whether the species belongs in Halisaurus. Lingham-Soliar (1996) cited the parietal openings in the skull to distinguish "Clidastes" sternbergii from Halisaurus (which he defined mainly based on Halisaurus ("Phosphorosaurus") ortliebi)--the openings in "Clidastes" sternbergii are relatively small and placed further back on the skull than in other mosasaurs. Other researchers such as Gordon Bell (1997) accept Russell's conclusions and continue to include "Clidastes" sternbergii in the genus Halisaurus. Russell (1967) attributed a relatively complete specimen in the Smithsonian (USNMNH 3777) to the species as well; other more fragmentary remains have been recognized. NOTE: Under the ICZN rules (Art. 33.4 (4th Edition)), Wiman's original spelling "sternbergii" should be retained. ?Plioplatecarpinae Late Cretaceous (Santonian-Maastrichtian) NA., SA., Eur., Afr.


Holcodus Gibbes 1851 "striated tooth"

HOL-ko-duhs (Gr. holkos "furrow, track" + Gr. odous "tooth") (m) named for "teeth...peculiarly striated toward the base." Late Cretaceous NA. [nomen dubium]

Holosaurus Marsh 1880 "complete lizard"

HOL-o-SAWR-uhs (Gr. holos "entire" + Gr. sauros "lizard")* (m) named for the completeness of the type specimen: "based on one of the most complete skeletons of the Mosasauroid reptiles yet discovered." [= Platecarpus]

Igdamanosaurus Lingham-Soliar 1991 "Igdaman ( Niger ) lizard"

EEG-dah-MAHN-o-SAWR-uhs (Igdaman + Gr. sauros "lizard") (m) named for the village of Igdaman, near where the type specimen material was found in Niger, west Africa; known from a fragmentary jaw (Holotype: BMNH R11898) and isolated teeth. Igdamanosaurus was apparently a shell-crushing form that evolved in the plioplatecarpine line of mosasaurs, independently of the mosasaurine Globidens. Notable for a massive dentary (lower jaw) with broad domed teeth but marked by fine striations and unconstricted at the base, unlike the teeth of Globidens. Igdamanosaurus fits the tooth morphotype of Massare's "crunch" guild and probably fed on moderately soft-shelled invertebrates (cephalopods), in constrast to Globidens (a member of the "crush" guild with very broad bulbous teeth to process hard-shelled invertebrates and turtles). Igdamanosaurus is a small mosasaur, probably around 3.6 m (12 ft.) long.

Type Species: Igdamanosaurus aegyptiacus [ee-jip-TIE-a-kuhs] (Zdansky 1935) "Egyptian": after teeth found in Egypt , named Globidens aegyptiacus by Zdansky in 1935. Lingham-Soliar used the old species name for his new genus Igdamanosaurus because Zdansky's mosasaur teeth were so similar, and unlike those of Globidens: "The sharing of such an unusual tooth morphology by R 11898 [Holotype of Igdamanosaurus] and 'G[lobidens]' aegyptiacus suggests that they should be included in the same genus." (Lingham-Soliar 1991). Note that the type material for Igdamanosaurus described by Lingham-Soliar comes from Niger , not Egypt . Plioplatecarpinae Late Cretaceous (Campanian-Maastrichtian) WAfr., ?SWAs.

Kolposaurus Camp 1942 "bay lizard"

KOL-po-SAWR-uhs (Gr. kolpos "bay, estruary, gulf" + Gr. sauros "lizard")* (m) named to indicate a form that may have frequented the near-shore. (Preoccupied by Kolposaurus Skuphos 1893. See Plotosaurus) [= Plotosaurus]

Leiodon Owen 1841 "smooth tooth"

LIE-o-don (Gr. leios "smooth" + Gr. odon "tooth")* (m) named "in reference to the smooth and polished surface of the teeth." Owen's original spelling Leiodon is preoccupied by Leiodon Swainson 1839 (Pisces: Tetraodontidae) (See Hay (1903), Bibliography of North American Fossil Vertebrates and Eschmeyer (1990), The Genera of Recent Fishes) and therefore is NOT valid as a generic name, contrary to Lingham-Soliar 1993 ("The Mosasaur Leiodon Bares its Teeth" Modern Geology 1993 18: 443-458.) See Liodon. [= Liodon]


Liodon Agassiz 1846 "smooth tooth"

LIE-o-don (Gr. leios "smooth" + Gr. odon "tooth")* (m) named "in reference to the smooth and polished surface of the teeth" (Owen 1840); valid name for Leiodon Owen 1841 (preoccupied by Leiodon Swainson 1839); based on a jaw fragment with large blade-like, somewhat recurved teeth having smooth enamel (Holotype: BMNH 41639), found in Essex, England. The genus has a confused taxonomic history, but Lingham-Soliar ("The Mosasaur Leiodon Bares its Teeth" Modern Geology 1993 18: 443-458) has argued that the genus is distinct and definable. Liodon was a large mosasaur with "powerful, highly specialised teeth...probably the most efficient in the Mosasauridae for tearing off chunks of soft bodied prey such as fishes and other marine reptiles...[Liodon] was a formidable predator, the nearest mosasaur analogue to sharks." (Lingham-Soliar 1993). The postcranial skeleton has not been described--Lingham-Soliar (1993) suggests that a skeleton from Japan identified as Mosasaurus hobetsuensis Suzuki 1985 may be a specimen of Liodon.

Owen's original spelling Leiodon is preoccupied by the fish name Leiodon Swainson 1839 (Pisces: Tetraodontidae). Agassiz 's emended spelling Liodon Agassiz 1846 was proposed to "correct" Leiodon Owen according to standard rules for latinizing the Greek diphthong ei as i, and is the earliest replacement name under ICZN rules. Lingham-Soliar (1993) overlooked the preoccupied status of the name Leiodon when he accepted Owen's original spelling as valid. Note that Cope used the name Liodon for forms now identified as Tylosaurus--Liodon and Tylosaurus are completely distinct taxa that are not closely related.

Length: (estimated) up to 12+ m. (40+ ft.)); skull: 1.2 m. (4 ft.)

Type Species: Liodon anceps [AN-seps] (Owen 1840) "two-edged": referring to the carinae or cutting edges (front and back) on the teeth: "the anterior edge is most produced"; known mainly from jaw fragments and isolated teeth.

Additional Species:

Liodon mosasauroides [moh-suh-saw-ROY-deez] Gaudry 1892 "Mosasaurus-like" the largest known species (estimated 12+ m. (40+ ft.), with the most laterally compressed teeth; found in SW France in the Pyrenean Basin .

Liodon sectorius [sek-TOR-ee-uhs] Cope 1871 "cutting": referring to its double-edged teeth; a small species (estimated around 25- 30 ft. long) known from jaws (including a nearly complete dentary) from the Navesink Formation, New Jersey and the Netherlands . Mosasaurinae Late Cretaceous (Campanian-Maastrichtian) NA., SA., Eur., NAfr. , New Zealand , ? Japan


Lesticodus Leidy 1859 "predatory tooth"

les-TIK-o-duhs (Gr. lestikos "predatory, piratical" + Gr. odous "tooth") (m) based on an isolated pterygoid tooth. Late Creteceous NA. [nomen dubium]


Lestosaurus Marsh 1872 "pirate lizard"

LES-to-SAWR-uhs (Gr. lestes "pirate, robber" + Gr. sauros "lizard")* (m) named to indicate a fierce, predatory marine reptile. [= Platecarpus]

Macrosaurus Owen 1849 "long lizard"

MAK-ro-SAWR-uhs (Gr. makros "long" + Gr. sauros "lizard") (m) named "from the length of the body indicated by the proportions of the vertebrae"; based on two vertebrae from New Jersey . Late Cretaceous NA. [nomen dubium (?Mosasaurus)]


Moanasaurus Wiffen 1980 "sea lizard"

maw-UH-nuh-SAWR-uhs (Maori moana "sea" + Gr. sauros "lizard")* (m) named to indicate a marine mosasaur found in New Zealand . Moanasaurus is a very large mosasaurine known originally from a disarticulated skull, vertebrae, ribs and paddle bones (Holotype: NZGS CD43); notable for a broad and robust skull, with long conical striated teeth with bulbous roots, and a short and massive humerus. Wiffen identified an additional juvenile specimen in 1990. Bell , Caldwell , Holmes, Wiffen & McKee (1999) confirm that Moanasaurus is distinct from Mosasaurus, and identify Rikkisaurus and Mosasaurus flemingi as junior synonyms.

Length: (estimated) 12 m. (40 ft.); skull: (estimated) 78 m. (2.5 ft.))

Type Species: Moanasaurus mangahouangae [MUHNG-uh-haw-WUHNG-ee] (Wiffen 1980) from the Mangahouanga Stream, North Island, New Zealand (Synonyms: Rikkisaurus tehoensis, Mosasaurus flemingi) NOTE: A second species may be described based on material from New Zealand previously attributed to Prognathodon overtoni (Gorden Bell, personal communication). Mosasaurinae Late Cretaceous (Campanian-Maastrichtian) New Zealand


Mosasaurinae (Gervais 1853) Williston 1897 "Mosasaurus subfamily"

moh-suh-saw-RIE-nee (Mosasaurus + -inae) (fem. plural) subfamily of the Mosasauridae containing long-bodied mosasaurs with a long trunk section (usually 42-45 presacral vertebrae); zygosphenes and zygantra present on the vertebrae in most taxa; haemal arches on the underside of the tail fused with the centra; enlarged vertebrae form a fin at the end of the tail in some forms (Clidastes, Plotosaurus). Limb structure often highly modified (compact, elongated paddles with extra phalanges; radius and ulna broad and short). Skull is akinetic in more advanced forms (Mosasaurus, Plotosaurus, Globidens). Includes some of the most derived and specialized forms of mosasaurs, as well as the most gigantic (Mosasaurus).

Members: Mosasaurus (type genus); Amphekepubis, Carinodens, Clidastes, Globidens, Liodon, Moanasaurus, Plotosaurus

(NOTE: Bell (1997) includes Prognathodon and Plesiotylosaurus in the Mosasaurinae.)


Mosasaurus Conybeare 1822 " Meuse (River) lizard"

MOH-suh-SAWR-uhs (Mosa, Latin name for the Meuse River + Gr. sauros "lizard") (m) Latinized version of Cuvier's term "great lizard of the Meuse," after the Meuse River near Maastricht, Netherlands (Holland), where the type skull (Holotype: NMHN AC. 9648) was found in 1780. Mosasaurus was one of the last, most advanced, and largest of all mosasaurs. It had a robustly constructed skull and lower jaw (more tightly united than in other mosasaurs), with relatively immobile bony parts and modified musculature (unlike the kinetic skulls, expandable jaws and lizard-like musculature found in earlier mosasaurs). The powerful backward curving jaw teeth were capable of both crushing and cutting; the pterygoid teeth on the palate were small (reduced in importance in rachet feeding). The parietal foramen for the pineal eye is the smallest of any mosasaur. According to Lingham-Soliar (1995), the moderately large orbits and relatively low level of binocular vision, along with poorly developed olfactory organs, suggest Mosasaurus hoffmanni was a surface- swimming animal adapted to an open, relatively uncomplicated habitat in nearshore waters 40-50 m. in depth. The skeleton had around 46 presacral vertebrae and 80 tail vertebrae, with a deep, barrel-shaped trunk. The compact and elongated ichthyosaur-like limb fins had extra phalanges. Healed injuries to the mandible in a number of specimens indicate a violent lifestyle, likely including fighting with members of its own species. A number of species have been distinguished, some based mainly on differences in tooth shape. Gorden Bell (1997) considers the genus paraphyletic.

Mosasaurus was first large Mesozoic reptile identified. The type specimen skull in the National Museum of Natural History in Paris has a colorful history--it was looted from the Netherlands by Napoleon's troops in 1795. (See http://www.nhmmaastricht.nl/1exp_tk31.htm).

Vertebrae: 45-46 presacrals / 8 pygals / 21 intermediate caudals with chevrons / 54+ terminal caudals
Length: (estimated) 12.5-17.6 m. (40-59 ft.); skull: 1.5+ m. (5+ ft.) jaw: 1.6+ m. (5.2+ ft.))

Type Species: Mosasaurus hoffmanni [HOF-muh-nie] Mantell 1829: for Dr. C.K. Hoffmann, a retired military surgeon who originally collected the type specimen from the chalk quarry at Saint Peters Mount, Maastricht, Netherlands around 1780; the largest known species, probably reaching close to 18 m. (60 ft.) in length (Lingham-Soliar 1995). The species "shows the most advanced form of tooth facetting in marine reptiles; each crown providing numerous cutting or breaking edges." (Lingham-Soliar 1995).

Additional Species:

Mosasaurus conodon [KOH-no-don] (Cope 1881) "cone tooth": for smoothly surfaced conical teeth; originally based on skull and jaw parts, 12 vertebrae, scapula, coracoid, humerus and pectoral limb elements from the Navesink Formation of Monmouth County, New Jersey as "Clidastes" conodon. Russell (1967) referred a large, nearly complete specimen (with a badly eroded cranium) from South Dakota to the species, permitting a full description; however, a new description of the specimen at the South Dakota School of Mines and Technology is in preparation, and it may be referred to another taxon. (See http://www.oceansofkansas.com). Russell (1967) also suggested Mosasaurus lemonnieri was a junior synonym of M. conodon.

Mosasaurus dekayi [de-KAY-ie] Bronn 1838: for James Ellsworth De Kay (1792-1851), American zoologist, who first described the type material; originally known from teeth and a few vertebrae from the Navesink Formation of New Jersey. Bell, Martin, Paris & Grandstaff (1994) cite the discovery of a new specimen (partial skull) found along the Missouri River in South Dakota (Late Maastrichtian), identified by its highly distinctive assymetrically bicarinate, extremely prismatic teeth.

Mosasaurus ivoensis [ee-voh-EN-sis] Persson 1963: for Ivo parish in the Scania region of southern Sweden , where the type specimen (crown of a tooth) was found; originally proposed as the subspecies Mosasaurus hoffmanni ivoensis. Russell (1967) identified a more complete specimen from the Niobrara of North America as the belonging to the same taxon, which he raised to species level.

Mosasaurus lemonnieri [luh-mon-YAYR-ie] Dollo 1889: for Alfred Lemonnier, a Belgian industrialist who presented the type fossil (a nearly complete skull with parts of the atlas/axis vertebrae) to the Royal Museum of Natural History at Brussels; known from a number of skeletons--the number of vertebrae with functional zygosphenes extend further back along the backbone toward the posterior trunk section than is recorded in other species of Mosasaurus (Lingham-Soliar 1991).

Mosasaurus maximus [MAK-si-muhs] Cope 1869: "largest"--"The remains indicate an animal of the largest size, perhaps seventy- five feet in length." (Cope 1869); for a very large species (now estimated at 40.66 ft long) from the Navesink Formation of New Jersey; additional material has been identified from Texas . The species is still incompletely known and is possibly the same as Mosasaurus hoffmanni (per Jagt, Mulder, Gallagher, Schulp 1999).

Mosasaurus missouriensis [mi-soor-ee-EN-sis] (Harlan 1834) "from Missouri ": for "Ichthyosaurus" missouriensis Harlan 1834, based on the anterior portion of a snout found on the Big Bend of the Missouri River, near modern Pierre , South Dakota (Pierre Shale). Harlan later gave it the new generic name Batrachiosaurus "frog- like lizard," for the supposed amphibian-like "form and position of the intermaxillary bones." The rest of same specimen (a nearly complete skull, most of the vertebrae, and parts of the limb girdle) was later described as Mosasaurus maximiliani by Goldfuss in 1845, in turn given the new generic name Pterycollosaurus by Dollo (1882).

Mosasaurus mokoroa [maw-kaw-RAW-uh] Gregg & Welles 1971 "long lizard": "From the Maori moko -lizard and roa -long, a name suggested by Dr. Roger Duff, Director of the Canterbury Museum"; for a species from New Zealand (skull: .7 m. long) Mosasaurinae Late Cretaceous (Santonian-Maastrichtian) NA., Eur., Afr., New Zealand, Ant., ?Japan

Nectoportheus Cope 1868 "swimming destroyer"

NEK-to-POR-thee-uhs (Gr. nekto "swim" + Gr. portheus "destroyer") (m) for a single large vertebra from Medford , New Jersey . Mosasaurinae Late Cretaceous NA. [nomen dubium (?Mosasaurus)]

Oterognathus Dollo 1889 "different jaw"

o-te-ROG-na-thuhs (for Gr. hoteros "the other" + Gr. gnathos "jaw" + -us) (m) According to Dollo, "its mandible, absolutely unique in the suborder Mosasauria...extremely gracile, indicating a weak ability to chew" [= Plioplatecarpus]

Phosphorosaurus Dollo 1889 "phosphate lizard"

FOS-for-o-SAWR-uhs (Gr. phosphoros "light-giving" + Gr. sauros "lizard") (m) named for the phosphated brown chalk at Hainaut, near Mons , Belgium , where the fragmentary fossil skull was found. Lingham-Soliar (1996) has transferred the type species (Phosphorosaurus ortliebi) to Halisaurus. [= Halisaurus]


Platecarpus Cope 1869 "oar wrist"

PLAT-ee-KAHR-puhs (Gr. plate "oar" + Gr. karpos "wrist, carpus")* (m) named for the flattened paddle-like construction of the limb bones in mosasaurs: "The anterior limbs are fins, with all the elements in a single plane, the radius incapable of rotation. The humerus broad and flat." (Cope 1869) (The name is sometimes misspelled "Platycarpus" ("flat wrist")--Cope gave the etymology as Greek plate "an oar.") Platecarpus was a medium-sized mosasaur with a highly kinetic skull and unspecialized post-cranial anatomy. The body is relatively short and stout, while the tail is fairly elongated. Teeth are long, slender and circular in cross-section. Documented stomach contents include remains of small fish. Preserved scales//////

Platecarpus now appears to have been adapted to life in shallow water as an ambush predator, although this proposed ecological niche contradicts some earlier speculation. Williston (1898) thought Platecarpus might have been a deep diver, based on its ossified external ear (a feature found in many types of mosasaurs), its relatively short and thick body, and its almost smooth scales, making the animal slick and free of drag. Martin and Rothschild (1989) found evidence of decompression syndrome (avascular necrosis) in a high percentage of Platecarpus bones sampled, which seemed to support Williston's idea about deep diving. However, Sheldon (1997) found pachyostosis in the bone microstructure of its ribs and concluded Platecarpus was in fact adapted to life in shallow water much like a modern beluga whale, perhaps lying in ambush on bottom sediments. If it was forced to dive deeply, it could not compress is rigid, thickened rib cage and would have suffered the "bends" (decompression syndrome).

Artists have often depicted mosasaurs incorrectly with an iguana- like nuchal fringe running from the neck along the back to the end of the tail. This error can be traced to a paper by Williston (1899) describing a specimen of Platecarpus--he misidentified preserved tracheal rings from the throat as impressions of a dermal crest along the top of the neck. Williston (1902) later corrected his mistake, but many artists have overlooked his retraction and continue to add the dermal fringe to mosasaurs, often embellishing the crests to fantastic dimensions. There is currently NO preserved soft-tissue evidence for either a dorsal frill or an enlarged fleshy tail-fin on any known mosasaur specimen--mosasaurs appear to have had a sleek, hydrodynamic body outline.

Vertebrae: 29 presacrals / 5 pygals / 26-31 caudals with chevrons and transverse processes / 65 terminal caudals
Length: 7.5 m. (25 ft.); skull: .7 m. (2.3 ft.))

Type Species: Platecarpus tympaniticus [tim-pa-NIT-i-kuhs] Cope 1869 "about tympanic bones": alluding to the "marked differences" in the construction of the quadrate bone compared to Mosasaurus: "broad as long, meatus larger." Leidy (1865) called the quadrate a "tympanic bone" (a term now reserved for mammal anatomy) in his original illustration of the type material found by William Spillman near Columbus , Mississippi . The quadrate has "a delicate tympanic ala" (Russell 1967). (Holotype: ANSP 8484, 8487, 8488, 8491, 8558-9, 8562). Gorden Bell (1997) considers the genus Platecarpus paraphyletic and in need of revision.

Additional Species:

Platecarpus coryphaeus [kor-i-FEE-uhs] (Cope 1872) "leader": alluding to the type specimen: "a fine relic...one that leads its genus in size and explains its structure" (Cope 1875); originally called Holcodus coryphaeus Cope 1872. Cope endured considerable misery to excavate the type specimen from a high bluff in Kansas : "One of the gales, so common in that region, sprang up, and striking the bluff fairly, reflected it upward. So soon as the pick pulverized the rock, the limestone-dust was carried into the eyes, nose, and every available opening in the clothing. I was speedily blinded, and my aid disappeared in the canyon, and was seen no more while the work lasted. A handkerchief tied over the face, and pierced by minute holes opposite the eyes, kept me form total blindness, though dirt in abundance penetrated the mask." (Cope 1875) (Holotype: AMNH 1566). (NOTE: This species is very likely a junior synonym of Platecarpus tympaniticus.)

Platecarpus ictericus [ik-TAYR-i-kuhs] (Cope 1871) "from the yellow (chalk)"; referring to the Niobrara Formation yellow chalk at Smoky Hill River, near Fort Wallace, Kansas; originally classified as Holcodus ictericus Cope 1871. (Holotype: AMNH 1559)

Platecarpus planifrons [PLAN-i-fronz] (Cope 1874) "flat forehead"; originally as Clidastes planifrons Cope 1874: "the frontal bone is especially massive, and is plane on the superior surface."

Platecarpus bocagei [boh-KAH-zhay-ie] (Antunes 1964): named to honor Jose Vicente Barboza du Bocage (1823-1908), famous Portuguese naturalist who described the living reptiles of Angola ; originally Angolasaurus bocagei Telles-Antunes 1964, reidentified as the earliest known species of Platecarpus by Lingham-Soliar (1994). Africa ( Angola ) (Turonian). Plioplatecarpinae Late Cretaceous (Turonian-Maastrichtian) NA., Eur., Afr., ?Aus.


Plesiotylosaurus Camp 1942 "near-Tylosaurus"

PLEE-see-o-TIE-lo-SAWR-uhs (Gr. plesios "near to" + Tylosaurus "knob (snout) lizard") (m) named in reference to its large skull, described as "elongate and narrow, approaching Tylosaurus in proportions, but without an elongate, conical rostrum" (Camp 1942). Despite the overall skull shape, Plesiotylosaurus is not closely related to Tylosaurus, and researchers traditionally classify the genus in the subfamily Plioplatecarpine close to Prognathodon; however, Bell (1997) classifies Plesiotylosaurus as a close relative of Globidens in the Mosasaurinae. Plesiotylosaurus is known mainly from a skull and lower jaws (Holotype: CIT 2759) from the Moreno Formation of California. The elongated skull has greatly restricted kinesis similar to the shorter-skulled Prognathodon, indicating a crushing bite and a probable diet of large shelled mollusks such as ammonites. The teeth are relatively large and strongly recurved, with carinae toward the tip, and bases that are swollen and nearly circular. The pterygoid teeth are well developed, unlike in Globidens.

Length: (estimated) 10 m. (33 ft.); skull: .88 m. (35 in.); lower jaw: .98 m. (3 ft.))

Type Species: Plesiotylosaurus crassidens [KRAS-i-denz] Camp 1942 "thick-toothed": for its "large and heavy" mandibular teeth. Plioplatecarpinae (or Mosasaurinae) Late Cretaceous (Maastrichtian) NA.


Plioplatecarpinae (Dollo 1884) Williston 1897 "Plioplatecarpus subfamily"

PLIE-o-plat-ee-kahr-PIE-nee (Platecarpus + -inae) (fem. plural) subfamily of the Mosasauridae containing short-bodied mosasaurs, with relatively short trunk section (29 or fewer presacral vertebrae); skull is kinetic in most forms, with movable bones in both the upper and lower jaws. Skull kinesis is greatly reduced in Prognathodon and Plesiotylosaurus, forms with conical, straight teeth and a crushing bite. The haemal arches not fused to tail vertebrae except in Prognathodon.

NOTE: Bell (1997) classifies both Prognathodon and Plesiotylosaurus in the Mosasaurinae as close relatives of Globidens instead of as members of the Plioplatecarpinae.

Members: Plioplatecarpus (type genus); Ectenosaurus, ?Halisaurus, Igdamanosaurus, Platecarpus, Plesiotylosaurus, Prognathodon, Selmasaurus, Yaguarasaurus

Undescribed Members: The recently announced "Oronosaurus," found in the Negev Desert of Israel (see http://www.discovery.com/news/archive/news990914/brief4.html?ct=37dfec1a), appears to be closely related to Prognathodon, but is larger--probably in the 40 ft. range with a 5-foot-long skull. No formal description has been published yet.


Plioplatecarpus Dollo 1882 "more-Platecarpus"

PLIE-o-plat-ee-KAHR-puhs (Gr. pleion "more" + Platecarpus) (m) named to indicate that its closest affinities were to Platecarpus, based on the form of the teeth (recurved, striated), lack of zygosphenes, and unfused chevrons (free haemal arches) on the tail. The more massive humerus and compact fore-paddle set it apart. Most species are known from incomplete material. Recently much better fossils have been found for the North American species Plioplatecarpus primaevus, including a nearly complete skeleton from Canada (Holmes 1996) and embryos associated with a skeleton from South Dakota (Bell, Sheldon, Lamb & Martin 1996), providing evidence that mosasaurs gave birth to live young. Another even larger species (yet to be described) is known from a skull and skeleton about 70% complete found in North Dakota , indicating an animal about 7 m. (23 ft.) long. (See www.oceansofkansas.com/ND-Plio.html)

Plioplatecarpus appears adapted to shallow water, perhaps as a highly maneuverable ambush predator in seaweed beds or coral reefs (Lingham-Soliar 1994). The highly kinetic jaws and weakly implanted teeth would fit a diet of soft cephalopods. The teeth are sharp and strongly curved backward, suggesting it also used rachet feeding (similar to some snakes) when devouring larger prey--the curved teeth would prevent prey from escaping away from the throat. The brain appears to have been proportionately twice as large as in Mosasaurus, perhaps indicating more complex and adaptable behavior; the parietal foramen containing the pineal eye is also enormous compared to some other mosasaurs. Lingham- Soliar (1993) has suggested at least one species of Plioplatecarpus (P. marshii) could use its forelimbs to perform underwater flight similar to penguins or sealions while maneuvering in its complex marine environment, but other researchers (Nicholls & Godrey 1994; Holmes, Caldwell & Cumbaa 1999) dispute this interpretation of the animal's limb structure, at least for other species such as Plioplatecarpus primaevus. Specimens have recently been identified from Antarctica , providing evidence Plioplatecarpus could move between continents along coastlines. A specimen from Scabby Bluff (Saint Mary River Formation) in Alberta, Canada, comes from what appears to be a freshwater deltaic environment some distance inland from the sea, indicating Plioplatecarpus could enter estruaries and rivers as well (Holmes, Caldwell & Cumbaa 1999).

Vertebrae: 7 cervicals / 15 dorsals / 16 pygals / 24 intermediate caudals / 58 terminal caudals
Length (P. marshii): 6 m. (20 ft.); skull (est.) : 52 cm (21 in.)

Type Species: Plioplatecarpus marshii [MAHR-shee-ie] Dollo 1882 for O. C. Marsh (1831-1899), noted American paleontologist, who had visited the Royal Museum in Brussels and was the first to point out that the specimen (which he attributed to Liodon) differed from the genus Mosasaurus. Notable for a very slender dentary bone and a compact, well-developed forepaddle. Lingham- Soliar (1992) has interpreted the limb-structure as evidence of underwater flight similar to plesiosaurs in this species rather than typical mosasaur tail-propulsion. (Holotype: IRSNB R38) Belgium

Plioplatecarpus houzeaui [hoo-ZOH-ie] (Dollo 1889) : for M. A. Houzeau de Lehaie, member of the Chamber of Representatives and Vice President of the Belgian Society of Geology, Paleontology and Hydrology, who helped secure important fossils for the Royal Museum of Natural History in Brussels (originally Oterognathus houzeaui Dollo 1889); a smaller (around 4.5 m. (15 ft.) long) species from Belgium.

Plioplatecarpus primaevus [prie-MEE-vuhs] Russell 1967 "young": indicating the earliest recorded species of Plioplatecarpus, from the Lower Pierre Shale of South Dakota, based on a right quadrate, scapulocoracoids and three thoracic vertebrae (Holotype: USNM 18254). A new, almost complete specimen (NMC 21853) from the Bearpaw Formation of Saskatchewan, Canada, is attributed to the species (Holmes 1996), and along with other new material, including embryos (Bell, Sheldon, Lamb & Martin 1996) found in the pelvic region of an adult skeleton unearthed in South Dakota. About 3.3 m (12 ft.) long. Plioplatecarpinae Late Cretaceous (Campanian-Maastrichtian) NA., Eur., Afr., Ant.


Plotosaurus Camp 1951 "swimmer lizard"*

PLOT-o-SAWR-uhs (Gr. plotes "swimmer" + Gr. sauros "lizard") (m) named to indicate a highly adapted swimming reptile (new name to replace preoccupied Kolposaurus Camp). Plotosaurus is a very derived (advanced) mosasaur, with many similarities to ichthyosaurs: a slender and elongate skull with exceptionally large orbits and nares; narrow, elongated ichthyosaur-like paddles (notable for many extra phalanges); a deep, shortened, relatively rigid midsection; extreme reduction of chevrons and zygapophyses; and a tail with an enlarged, flattened end formed from raised neural spines. It was probably among the fastest swimming mosasaurs, with large eyes for keen eyesight. It may have hunted swift moving surface fish--fossilized stomach contents indicate a fish diet. Camp thought it frequented the near-shore (thus the original name Kolposaurus "bay lizard").

Vertebrae: 51 presacrals / 30 pygals / 5 intermediate caudals with chevrons and transverse processes / 64 terminal caudals
Length: (P. tuckeri) 13 m. (43 ft.); skull: 59 cm (24 in.)

Type Species: Plotosaurus bennisoni [ben-i-SOH-nie] (Camp 1942): for Allan Bennison, a California fossil collector who found the type specimen in 1937 in the Mount Diablo Range of California (Moreno Formation). A smaller species, known from a complete skull and partial skeleton (Holotype: UCMP 32778) indicating an animal about 65% the size of Plotosaurus tuckeri; (estimated length: 8.7 m. (29 ft.); skull: 39 cm. (15 in.))

Additional Species:

Plotosaurus tuckeri [TUHK-uhr-ie] (Camp 1942) for W.M. Tucker of Fresno State College, who found a long series of its vertebrae (Holotype: UCMP 33913) in the Moreno Formation, Fresno County , California . The species is much larger than Plotosaurus bennisoni, differing also in the relatively large interclavicle, the form of the frontal bone in the skull, and fewer (12-13) pterygoid teeth. Mosasaurinae Late Cretaceous (Maastrichtian) NA.


Pluridens Lingham-Soliar 1998 "many teeth"*

PLOOR-i-denz (Lat. pluris (plus) "more, many" + Lat. dens "tooth") (m) named for the large number of teeth (28+) in its lower jaw, one and a half times the number recorded in any other known mosasaur; known from an isolated almost complete dentary bone (Holotype: BMNH R14153) from the Farin-Doutchi Formation near Mount Ilatarda, Niger and a referred dentary (BMNH R9804), found in the Nkporo Formation (Campanian-Maastrichtian) near Calabar, southern Nigeria, West Africa. Pluridens was a moderately large mosasaur (estimated 8-9 m (25-30 ft.) long). The unusual number of rather small, close-fitting, uniform teeth and relatively long, slender jaw suggests a diet similar to early ichthyosaurs such as Temnodontosaurus. Pluridens may have been an ambush predator adapted to a shallow sea and lagoonal environment, specialized for feeding on small fish and thin- shelled mollusks.

Type Species: Pluridens walkeri [WAW-kuhr-ie] Lingham-Soliar 1998 for Cyril A. Walker, to mark his contributions as a vertebrate paleontologist at the British Museum of Natural History. Mosasauridae i.s. Late Cretaceous (Maastrichtian) WAfr.


Prognathodon Dollo 1889 "forward-jaw tooth"

prog-NATH-o-don (Gr. pros "forward, before" + Gr. gnathos "jaw" + Gr. odon "tooth") (m) named for "its procumbant premaxillary teeth, projecting forward from the bone that contains them" in the upper jaw. The projecting teeth in some species may indicate a diet of shellfish scooped off the seafloor, similar to placodonts. The skull is akinetic, with relatively short and heavy jaws, and a broad blunt snout (unlike the pointed snout of most mosasaurs). The moderately swollen, generally straight and sometimes heavily grooved conical teeth "are better adapted to crushing than in any mosasaur except Globidens" (Russell 1967). The pterygoid teeth on the upper palate are very large (unlike the absent or rudimentary pterygoid teeth in Globidens). The vertebrae have functional zygosphenes and zygantra; haemal chevrons are fused to the caudal vertebrae. No skeletons known so far provide a relatively complete set of vertebrae. Researchers have generally classified Prognathodon in the subfamily Plioplatecarpinae; Bell (1997) considers the genus paraphyletic, consisting of forms closely related to Globidens as members of the subfamily Mosasaurinae. Lingham-Soliar (1989) includes Dollosaurus as a synonym, but some other researchers have retained Dollosaurus as a distinct genus. A very large (40 ft.) mosasaur recently discovered in Israel, originally thought to be a specimen of Prognathodon, will be described as a new genus called "Oronosaurus" after the Oron phosphate field where the specimen as found in the Negev Desert, near Be'er Sheva.

Length: 6-10.5 m. (20-34 ft.); skull: 60 cm. (2 ft.)

Type Species: Prognathodon solvayi [sol-VAY-ie] Dollo 1889: for Ernst Solvay, a Belgian technochemist who founded the Solvay Institute--most of the bones originally described (a nearly complete skull, incomplete postcranial skeleton with vertebrae, fragments of scapula and coracoid (Holotype: IRSNB R33(4672))) were found on the institute's property in Mesvin , Belgium . Teeth have heavily grooved enamel. (6 m) skull: 60 cm.

Additional Species:

Prognathodon giganteus [ji-GAN-tee-uhs or ji-gan-TEE-uhs] Dollo 1904 "gigantic"; a large European species up to 10 m. (33 ft.) long in length, with smooth enamel on its teeth. skull est. 85 cm.

Prognathodon overtoni [oh-vuhr-TOH-nie] (Williston 1897): for T. R. Overton, S. W. Williston's laboratory assistant, who collected the type specimen; originally called Brachysaurus overtoni Williston 1897; a medium to large species, with non-procumbant anterior teeth and smooth enamel, from the Pierre Shales in South Dakota; skull est. 70 cm.

Prognathodon rapax [RAP-aks] (Hay 1902) "rapacious"; an incompletely known North American species with a distinctive quadrate, which has a large tuberosity on the anteromedian edge of the shaft.

Prognathodon stadtmani [STAT-muh-nie] Kass 1999: for Kenneth Stadtman, curator of the Brigham Young University Earth Science Museum; a large species distinguished by the shape of the coronoid bone and an edentulous anterior projection of the dentary bone. Known from an incomplete skull and skeleton (Holotype: BYU 13082) found in the Mancos Shale near Cedaredge, western Colorado . The recovery site would have been far out to sea from the ancient shoreline, and along with the cancellous condition of the bones, suggests the species was a deep-diving marine form. Estimated length: 10.5 m (34.3 ft).

Prognathodon waiparaensis [WIE-puhr-uh-EN-sis] Gregg & Welles 1971 "from Waipara (River)," South Island , New Zealand ; a very large form, known from a disarticulated skull, cervical vertebrate and ribs. The skull is estimated at about 1.1 m. (3.6 ft.) long, making it possibly the largest known species (probably close to 11 m (35 ft) long). From the Haumurian (Maastrichtian), Laidmore Formation, on the right bank of the Middle Waipara River . Plioplatecarpinae (or Mosasaurinae) Late Cretaceous (Campanian- Maastrichtian) NA., Eur., Afr. , New Zealand


Prognathosaurus Dollo 1889 "forward jaw lizard"

PROG-na-tho-SAWR-uhs (Gr. pros "first, foward" + Gr. gnathos "jaw" + Gr. sauros "lizard") (m) named for "its procumbant premaxillary teeth, projecting forward from the bone that contains them"; unnecessary replacement name for Prognathodon Dollo, supposedly preoccupied by Prognathodus Edgerton. [= Prognathodon]

Pterycollosaurus Dollo 1882 "fused-pterygoid lizard" ter-i-KOL-o-SAWR-uhs (irr. ptery(goid), wing-shaped bone in the skull + Gr. kolla "glue" + Gr. sauros "lizard") (m) from Goldfuss's description of the skull of Mosasaurus maximiliani, indicating that the pterygoid bone was supposedly fused to the nasal bones, a condition not found in other mosasaurs. Goldfuss's description was in error. [= Mosasaurus]


Pythonomorpha Cope 1869 "python forms"

pie-THON-o-MOR-fuh (Gr. Python, a giant serpent killed by Apollo + Gr. morphe "form" + -a) (n) Cope rejected widely accepted ideas about the classification of mosasaurs. Cuvier thought Mosasaurus was most closely related to monitor lizards--a view still held by most modern researchers. Owen in turn supported a classification of mosasaurs among lizards, as did Marsh--although as a distinct suborder Marsh called the Mosasauria. Cope, however, recognized affinities to lizards, plesiosaurians and especially to snakes in the mosasaurs, and placed them in a separate order of reptiles, explaining: "In the mosasauroids, we almost realize the fictions of snake-like dragons and sea-serpents, in which men have been every prone to indulge. On account of the ophidian part of their affinities, I have called this order Pythonomorpha." Cope's original vision of "pythonomorphs" was highly imaginative, and inaccurate in many details--he thought that the creatures had a single "pair of powerful paddles in front," and that "the body was snake-like, with narrow chest and neck scarcely differing in diameter. They were immensely elongate...", in some cases approaching one hundred feet. In a bout of monster fever, Cope deemed it probable that: "terrestrial representatives now unknown to us, inhabited the forests and swamps of the Mesozoic continents, and strove for mastery with the huge dinosaurs"--no such land-living pythonomorphs have ever been found. On the scientifically substantiated side, discoveries of complete specimens of mosasaurs showed the animals had a pair of hind paddles, and were much less elongated and serpentine in appearance than Cope surmised. Partly in response to this better understanding of mosasaur anatomy, Cope's theory of a close affinity between snakes and mosasaurs was widely dismissed and almost universally ignored by 20th century researchers, who favored a burrowing rather than an aquatic origin for snakes. In a major taxonomic twist, however, some researchers (Lee 1997; Caldwell & Lee 1997) have revived Cope's old idea, creating fresh controversy. Although some of the features Cope used to link snakes and mosasaurs are no longer considered valid, his fundamental insight may be sound: mosasaurs and snakes appear to share unique similarities in their teeth, skulls and vertebrae that set them apart from varanoid lizards. Lee has redefined the category Pythonomorpha as "The most recent common ancestor of mosasauroids and snakes, and all its descendants," thus including Cope's original Pythonomorpha (a synonym of the Mosasauridae), the aigialosaurs, coniasaurs and the Serpentes (snakes). It seems that a number of enigmatic snake-like marine squamates from the Early Cretaceous such as Simoliophis "Cretaceous snake," could belong in the redefined Pythonomorpha as well, or even qualify as true snakes, though new formal studies have yet to be published. Other researchers (Zaher & Rieppel 1999; American Museum Novitates 3271) have recently disputed the close mosasaur- snake relationship, citing the mode of tooth-attachment to the jaw, which they see as fundamentally different in the two groups. [clade]

Rhamphosaurus Cope 1872 "beak lizard"

RAM-fo-SAWR-uhs (Gr. rhamphos "beak" + Gr. sauros "lizard") (m) proposed replacement for preoccupied Rhinosaurus Marsh; preoccupied by Rhamphosaurus Fitzinger. See Tylosaurus. [= Tylosaurus]


Rhinosaurus Marsh 1872 "snout lizard"

RIEN-o-SAWR-uhs (Gr. rhin- (rhis) "nose, snout" + Gr. sauros "lizard")* (m) alluding to "an elongate cylindrical muzzle, that projects some distance in front of the teeth" (Preoccupied by Rhinosaurus Gray 1845. See Tylosaurus) [= Tylosaurus]


Rikisaurus Wiffen 1990 "small lizard"

RIK-i-SAWR-uhs (Maori riki "small" + Gr. sauros "lizard") (m) named to indicate a "small adult mosasaurine" found in New Zealand and "representing an intermediate stage of development between Clidastes and Mosasaurus"; known from a skull and cervical vertebrae (Holotype: NZGS CD531). A slender form with a long muzzle, tapering to a point; the teeth are small, with carinae on front and back edges, 13-14 teeth in the maxilla; now considered the same as Moanasaurus (Bell, Caldwell, Holmes, Wiffen & McKee, 1999). [= Moanasaurus]

Saurochampsa Wagler 1830 "lizard crocodile"

SAWR-o-KAMP-suh (Gr. sauros "lizard" + Gr. champsa "crocodile") (f) [= Mosasaurus]


Selmasaurus Wright & Shannon 1988 " Selma lizard"

SEL-muh-SAWR-uhs ( Selma + Gr. sauros "lizard") (m) named "for the Selma Group [Formation] from the which the holotype is believed to have come"; for a specimen found "somewhere in western Alabama " and later noticed in the University of Alabama collection. Selmasaurus is based on parts of a skull (Holotype: GSATC 221) that formed a relatively rigid unit, unlike the more kinetic arrangement found in some earlier, less derived mosasaurs.

Type Species: Selmasaurus russelli [RUH-sel-ie] Wright & Shannon 1988: for Dale A. Russell "for his extensive work on the Mosasauridae." Plioplatecarpinae Late Cretaceous (Campanian) NA.

See also Selmasaurus johnsoni Polcyn and Everhart 2008


Sironectes Cope 1874 "rope swimmer"

SIE-ro-NEK-teez (Gr. seira "rope, chain" + Gr. nektes "swimmer") (m) alluding to the supposed "elongate snake-like form" of mosasaurs; Cope greatly exaggerated the sinuous shape of mosasaurs in his inaccurate early conceptions; based on a partial specimen of Platecarpus. [= Platecarpus]

Taniwhasaurus Hector 1874 "Taniwha lizard" ("water-monster lizard")

TUHN-i-fuh-SAWR-uhs (Maori taniwha, a dragon-like water monster + Gr. sauros "lizard") (m) named for Taniwha, a dragon-like sea- monster in Maori mythology, to indicate a mosasaur found in New Zealand. Welles and Gregg (1971) revised the material and designated a lectotype (Lectotype: DM R1536): a well-preserved partial skull from Haumuri Bluff, North Island , New Zealand . Incompletely known but a large tylosaurine with a small toothless ram at the tip of its lower jaw (Welles and Gregg 1971). Pterygoid teeth are very small; jaw teeth have a sharp cutting along the front and back. Bell , Caldwell , Holmes, Wiffen & McKee (1999) include Tylosaurus haumuriensis Welles & Gregg 1971 as a junior synonym, and indicate that Taniwhasaurus shows important similiarities to Hainosaurus bernardi Dollo; the exact relationship of Tylosaurus, Taniwhasaurus and Hainosaurus needs additional study. The type specimen skull (est. 50 cm long ) indicates an animal about 6+ m. (20+ ft.) long; the skull formerly called "Tylosaurus haumuriensis" is estimated at about 1.1 m (3.7 ft.) long, indicating an animal in the 12+ m. (40+ ft.) range.

Type Species: Taniwhasaurus oweni [OH-wen-ie] Hector 1874: for Sir Richard Owen (1804-1892), British paleontologist and comparative anatomist, who first described Mesozoic marine reptiles from New Zealand . (Synonyms: Tylosaurus haumuriensis) Tylosaurinae Late Cretaceous (Maastrichtian) New Zealand


Tylosaurinae Williston 1897 "Tylosaurus subfamily"

tie-lo-saw-RIE-nee (Tylosaurus + -inae) (fem. plural) subfamily of the Mosasauridae containing large, highly predatory short- bodied mosasaurs notable for a "ram" snout--a toothless bony extension of the upper and lower jaws. Zygosphenes and zygantra are rudimentary or absent on vertebrae. The tail is relatively long, without a fin; the haemal arches on the underside of the tail are not fused with the centra. The humerus, radius and ulna are long (a primitive trait) but the carpal elements are reduced and the number of phalanges greatly increased. Lingham-Soliar (1992) saw evidence that tylosaurines were neither the fastest swimmers nor the physically strongest mosasaurs--instead, they were lightly built, with a massive reduction in body weight, relatively small limb girdles and paddles, and highly cancellous bones (probably impregnated with fat in life for buoyancy). Such features suggest tylosaurines relied on shark-like stealth and ambush, using a sudden, short burst of speed to strike at prey rather than long pursuits.

Members: Tylosaurus (type genus); Hainosaurus, Taniwhasaurus


Tylosaurus Marsh 1872 "knob (snout) lizard"

TIE-lo-SAWR-uhs (Gr. tylos "protuberance, knob" + Gr. sauros "lizard")* (m) named for "an elongated cylindrical muzzle," or rostrum, projecting beyond the frontmost teeth in the upper jaw; new generic name to replace preoccupied Rhinosaurus Marsh. The tip of the snout was similar in function to the "ram" or "beak" (Gr. embolon or proembolos; Lat. rostrum) that the ancient Greeks and Romans mounted on the prow of warships to ram and sink enemy vessels--older paleontological literature often referred to Tylosaurus as the "ram-nosed lizard" based on the analogy. Tylosaurus likely used its "ram" snout to stun prey, defend against sharks or other predators, and probably to battle rivals of its own species. One specimen has the tip of the snout deformed into a mushroom shape as a result of injury and infection.

Tylosaurus is a very large, highly predatory mosasaur known from a number of complete skeletons and skulls, though the holotype skull from the Museum of Comparative Zoology appears to be lost. The teeth lack strong carinae and have a somewhat flattened outer labial side and more rounded lingual side with striated enamel on the internal faces. Preserved scales have well developed keels and ridges. Tylosaurus was evidently capable of deep diving. Curiously, its bones show both osteoporosis and decompression syndrome (avascular necrosis) (Sheldon 1997). Stomach contents recorded in a single specimen (Martin & Bjork 1987) include a shark, teleost fish, the bird Hesperornis and the mosasaur Clidastes. It may also have fed on giant squid that lived in the depths (Martin & Rothschild 1989). Material that may be referrable to Tylosaurus has been found in South Africa and Angola , as well as Japan .

Vertebrae: 29-30 presacrals/ 6-7 pygals/ 33-34 caudals with chevrons / 56-78 terminal caudals
Length: (T. proriger) 10-12.3 m. (33-40 ft.); skull:1-1.3 m (3.3- 3.5 ft.)

Type Species: Tylosaurus proriger [PROHR-i-jer] (Cope 1869) "prow-bearing": referring to "the cylindrical prolongation of the premaxillary bone beyond the teeth and a similar flat prolongation of the extremity of the dentary" (Cope 1869), as Macrosaurus proriger Cope 1869; based on a partial skull and vertebrae from western Kansas "in the Museum of Comparative Zoology, Cambridge, Mass., brought by Prof. Agassiz from the Cretaceous beds in the neighborhood of Monument, Kansas, and near the line of the Kansas Pacific Railroad." (Cope 1875) The holotype specimen is apparently lost. (Santonian-Campanian)

Additional Species: Tylosaurus nepaeolicus [nep-ee-OL-i-kuhs] (Cope 1874) "from the Nepaholla River": derived from an alternate spelling of Nepaholla, an old name for the Solomon River in north central Kansas, near where the type fossils were found (Niobrara Formation); an earlier (Coniacian), smaller, more primitive species differing from Tylosaurus proriger in some features of the skull (Holotype: AMNH 1565). (estimated length: 7 m. (24 ft.); skull: 63 cm. (2.1 ft.)) (Coniacian). A much larger specimen has been found but not yet described (Mike Everhart, personal communication).

See also Tylosaurus kansasensis Everhart 2005

NOTE: A new species of Tylosaurus from the Late Coniacian of North America will be described soon. "Tylosaurus haumuriensis" from the Maastrichtian of New Zealand is a now considered a synonym of Taniwhasaurus oweni . Tylosaurinae Late Cretaceous (Coniacian-Campanian) NA., Afr., Eur., ? Japan

Yaguarasaurus Paramo 1994 "Yaguara (people) lizard"

yah-GWAHR-uh-SAWR-uhs (Yaguara (a Native American people) + Gr. sauros "lizard") (m) named for the Native American Yaguara people, who inhabited the region in western central Colombia where the specimen was found (Villeta Formation limestone (Upper Turonian), near the village of Yaguara, Huila Department). Yaguarasaurus is a small plioplatecarpine, known from a nearly complete skull and mandible, plus the atlas, axis and first cervical vertebra, two anterior dorsal vertebrae and rib fragments (Holotype: BRV-68 (Paleontological Collections of the Department of Geosciences of the National University of Colombia, Bogota)); additional parts of the skeleton may be lie unexposed at the site at an angle difficult to excavate. It has a highly kinetic skull, but differs from other plioplatecarpines in the proportions and form of the frontals and other cranial bones. The vertebrae have well developed zygantra and zyosphenes. The recurved and striated teeth suggest a diet of both vertebrates (fish) and invertebrates (ammonites) of similar size. Yaguarasaurus is the first mosasaur found in Colombia and one of the oldest plioplatecarpines known (Turonian).

Length: (estimated) 4.7-5 m. (16-16.6 ft.); skull: 47 cm. (to occiput)/ 54.5 cm. (to squamosal).

Type Species: Yaguarasaurus colombianus [ko-LOM-bee-AY-nuhs] Parano 1994; for Colombia , the country in which the specimen was found in South America . Plioplatecarpinae Late Cretaceous (Turonian) SA.