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Mosasaur

Mosasaurs were an extinct group of large marine squamate reptiles belonging to the family Mosasauridae, which dominated as apex predators in global oceans during the Late Cretaceous period, from about 98 to 66 million years ago.^[1]^[2] Characterized by their elongated, streamlined bodies, powerful laterally flattened tails for propulsion, and limbs modified into paddle-like flippers, mosasaurs ranged in size from small forms around 3 meters long to gigantic species exceeding 15 meters, such as Tylosaurus proriger and Mosasaurus hoffmannii.^[3]^[4]^[5] These secondarily aquatic lizards evolved from terrestrial ancestors within the Squamata order, rapidly diversifying into over 40 genera that adapted to a fully pelagic lifestyle, with conical or serrated teeth suited for grasping slippery prey like fish, sharks, ammonites, seabirds, and even other marine reptiles including smaller mosasaurs.^[1]^[6]^[3]^[7] Fossils of mosasaurs have been found worldwide, particularly in Late Cretaceous rock formations like the Western Interior Seaway in North America, revealing their role in complex marine food webs before their abrupt extinction during the Cretaceous-Paleogene boundary event, likely triggered by the Chicxulub asteroid impact.^[3]^[8] Paleontological research continues to uncover details of their biology, including evidence from exceptional fossils showing viviparous reproduction and possible ecomorphological convergence, where multiple lineages independently evolved similar giant sizes and adaptations.^[1]^[9]^[10]

Description

General morphology

The term "mosasaur" derives from the genus name Mosasaurus, coined in 1822 by English geologist William Daniel Conybeare, combining the Latin Mosa (referring to the Meuse River in the Netherlands, near the site of the first fossil discoveries in the late 18th century) and the Greek sauros (lizard).^[11]^[12] Mosasaurs exhibited a highly derived body plan as large, fully aquatic squamate reptiles, characterized by elongated snouts, streamlined fusiform torsos, four paddle-like limbs, and a powerful, laterally compressed tail fluke that facilitated efficient undulatory propulsion in marine environments.^[13] Their overall anatomy reflected adaptations from terrestrial varanoid lizard ancestors, with modifications emphasizing hydrodynamic efficiency and maneuverability.^[14] The skull was robust and kinetic, featuring large orbits for enhanced binocular vision, a mobile quadrate bone that allowed extensive jaw depression for prey capture, and marginal dentition consisting of conical or posteriorly recurved teeth with smooth or serrated carinae suited to grasping elusive aquatic prey.^[15] The palatal complex was tightly integrated in many taxa, providing structural stability during forceful bites. Postcranially, mosasaurs possessed an extensive vertebral column comprising 200–400 vertebrae, enabling lateral flexibility for tail-powered swimming, along with gastralia that reinforced the abdominal wall against hydrostatic pressures.^[16] The limbs were transformed into broad, flipper-like appendages with hyperphalangy—increased phalangeal count in the autopodia—to maximize thrust and steering, while the humerus and femur retained robust proximal elements for muscular attachment.^[16] Body proportions varied among major clades, reflecting ecological specializations; for instance, tylosaurines (e.g., Tylosaurus) displayed proportionally longer snouts and more slender, anguilliform bodies suited to open-water pursuits, whereas plioplatecarpines (e.g., Plioplatecarpus) had shorter snouts, deeper trunks, and more robust flippers indicative of agile, near-shore predation.^[17] Soft tissue impressions from exceptional fossils reveal scaled skin similar to modern lizards, supporting their squamate affinities.^[18]

Size and variation

Mosasauroids exhibited a wide range of body sizes, from diminutive early forms to gigantic late Cretaceous apex predators. The smallest known species, Dallasaurus turneri, reached a total length of less than 1 meter, based on the nearly complete holotype skeleton from the Middle Turonian of Texas.^[19] In contrast, the largest species, Mosasaurus hoffmannii, attained lengths of up to 17 meters and masses of 10-15 metric tons, as estimated from a partial skeleton including a massive quadrate and vertebrae from the Maastrichtian of Russia.^[20] These extremes highlight the group's evolutionary expansion in size disparity during the Late Cretaceous.^[9] Length estimates for mosasaurs are typically derived from vertebral counts and proportional scaling from skull dimensions, with complete skeletons providing baselines for incomplete specimens. Most genera feature around 7 cervical vertebrae, 50-80 dorsal vertebrae, and 40-60 caudal vertebrae, allowing approximations where total length is roughly 10-12 times the skull length for larger species like Mosasaurus.^[21] For example, a 1.5-meter skull in M. hoffmannii scales to a 15-18 meter body using these ratios, corroborated by associated postcranial elements.^[22] Morphological variations among mosasaur species included differences in snout length and body depth, reflecting adaptations to diverse niches. Short-snouted forms like Prognathodon had robust, conical snouts suited for powerful bites on hard prey, contrasting with the elongated, slender snouts of Tylosaurus, which extended well beyond the jawline for ramming or grasping. Body depth also varied; species such as Mosasaurus possessed deep, barrel-shaped rib cages that enhanced buoyancy and stability in open water, while more slender builds in genera like Platecarpus suggested greater agility in coastal environments.^[3] Evidence for sexual dimorphism comes from comparative analyses of specimens, revealing robust versus slender builds within the same species. In Pluridens serpentis, larger individuals exhibit massively reinforced dentaries, interpreted as male traits under sexual selection, while smaller, more gracile forms likely represent females.^[23] Similar patterns in vertebral robustness and limb proportions across populations indicate dimorphic differences in body mass and strength.^[24] Intraspecific variation is evident in fossil populations, with regional differences in vertebral dimensions and bone compactness. For instance, Tylosaurus specimens from the Western Interior Seaway show variations in centrum height and process length between North American and European finds, possibly reflecting local environmental influences on growth.^[1] High variability in rib histology further suggests individual or population-level adaptations in buoyancy control.^[25]

Paleobiology

Physiology and metabolism

Mosasaur physiology is inferred primarily from bone microstructure, stable isotope analysis, and rare soft-tissue preservation, revealing adaptations suited to a fully aquatic lifestyle. Bone histology of mosasaurs, such as fibrolamellar bone tissue with high vascular density and parallel-fibered matrix, indicates rapid growth rates comparable to those of extant endothermic or mesothermic vertebrates like tuna, suggesting elevated metabolic rates beyond those of typical ectothermic reptiles.^[26] Stable oxygen isotope ratios in mosasaur tooth enamel further support partial endothermy or effective thermoregulation, with body temperatures estimated 5–10°C higher than ambient seawater, enabling activity in cooler marine environments.^[27] These metabolic traits likely facilitated sustained swimming and predation in diverse oceanic habitats, though not full homeothermy as in mammals.^[28] Fossil skin impressions preserve evidence of pigmentation patterns, with melanophores indicating a dark dorsal surface and lighter ventral side for countershading camouflage in open water. In Prognathodon fossils from the Maastrichtian of Jordan, preserved eumelanosomes—spindle-shaped organelles rich in melanin—confirm this dorsoventrally countershaded coloration, similar to modern sharks and dolphins, which would have reduced visibility to prey and predators from above or below.^[29] Such pigmentation likely aided in crypsis during ambush hunting in well-lit surface waters. Soft-tissue evidence includes skin impressions showing small, overlapping, keeled scales across the body, forming a low-drag integument akin to that of varanid lizards but more streamlined for aquatic propulsion. In Plotosaurus and other taxa, these keeled scales, measuring about 1–2 mm in length, covered the flanks and tail, potentially channeling water flow to enhance hydrodynamic efficiency without the need for larger osteoderms.^[30] Possible cartilage preservation in flippers is suggested by exceptional fossils like that of Carinodens, where soft-tissue outlines imply flexible, cartilaginous elements supporting the paddle-like limbs for fine maneuvering.^[31] Viviparity is confirmed by the discovery of a near-term embryo positioned tail-first in the body cavity of a mosasauroid specimen, indicating live birth without eggshells, an adaptation preventing drowning of offspring in a marine environment.^[32] The respiratory system appears adapted for extended submersion, with inferred lung structures supporting dives lasting minutes to hours based on body size and oxygen storage capacity. Vertebral morphology, including elongated centra and possible pneumatic foramina in some taxa, hints at diverticula or air-filled extensions from the lungs that may have aided buoyancy control during prolonged underwater foraging, though direct evidence of air sacs remains elusive.^[33] Sensory physiology is evidenced by enlarged endocranial cavities in mosasaur skulls, with expanded olfactory bulbs and peduncles indicating a strong sense of smell for detecting prey in turbid or deep waters. Virtual reconstructions of Tethysaurus brains reveal optic lobes and tecta proportionally larger than in basal squamates, suggesting acute binocular vision for depth perception and targeting fast-moving fish or ammonites, compensating for the aquatic medium's distortion of light.^[34] These neural adaptations underscore mosasaurs' role as active visual and chemosensory hunters in pelagic ecosystems.

Locomotion and sensory systems

Mosasaur locomotion relied primarily on axial undulation, with the tail serving as the main propulsive organ through lateral oscillations of a hypocercal, bilobed tail fin. Fossilized soft tissues in Prognathodon holtzwi reveal a crescent-shaped caudal fin with a downturned ventral lobe and lepidotrichia-supported rays, enabling efficient thrust generation akin to that in modern lamniform sharks, reducing drag and enhancing hydrodynamic performance during swimming.^[31] The paired limbs, evolved into flippers, provided steering, lift, and fine control rather than primary propulsion; forelimbs were typically larger and more robust than hindlimbs, functioning as hydrofoils to generate lateral forces for turning and stability, as evidenced by articulated forelimb skeletons in taxa like Platecarpus showing hyperphalangy and broadened phalanges for increased surface area. Hydrodynamic modeling of body form and tail kinematics indicates burst speeds up to 30–40 km/h for predatory pursuits, though sustained cruising was slower at around 2–3 m/s, limited by anguilliform to carangiform swimming modes in most species. Sensory adaptations complemented these locomotory capabilities, facilitating prey detection in turbid or deep-water environments. Computed tomography of the rostrum in Taniwhasaurus antarcticus uncovers a dense network of branched neurovascular canals innervated by the trigeminal nerve, suggesting a heightened sensory array possibly for electroreception or mechanoreception via ampullae-like structures, enabling detection of bioelectric fields from hidden prey similar to those in crocodilians. Orbit orientation in several taxa, notably the forward-facing eyes of Phosphorosaurus ponpetelegans with a binocular field of view estimated at 35°, implies stereoscopic vision for precise depth perception during close-range hunting, diverging from the lateral orbits typical in more basal squamates. Buoyancy control was achieved through anatomical features allowing neutral buoyancy without constant swimming effort. Body cavity dimensions in well-preserved skeletons, such as those of Mosasaurus, indicate space for an enlarged liver and paired lungs, which could be adjusted via respiratory mechanics to regulate trim and depth, akin to modern sea snakes and aiding energy-efficient hovering or diving. Locomotory strategies varied among mosasaur taxa, reflecting ecological niches. Short-bodied forms like Clidastes, with compact trunks and powerful tails, excelled as ambush predators using explosive bursts for short-distance attacks in coastal shallows. In contrast, long-bodied pursuit predators such as Tylosaurus, featuring elongated pre-caudal regions and streamlined profiles, sustained higher speeds over open-water chases, supported by enhanced axial musculature and tail depth.

Diet and feeding mechanics

Mosasaur diets were predominantly carnivorous, encompassing a range of prey from soft-bodied organisms to hard-shelled invertebrates, as evidenced by direct fossil evidence and biomechanical analyses of dental structures. Piscivorous habits dominated in many taxa, with gut contents and coprolites revealing fish scales, bones, and semi-digested remains in species like Tylosaurus and Mosasaurus, indicating frequent predation on teleosts and elasmobranchs. Teuthophagous feeding on cephalopods, such as squid and small ammonites, is supported by conical tooth punctures on belemnite guards and ammonite shells, while durophagous specialists like Globidens and Carinodens targeted bivalves, turtles, and larger ammonites, as shown by associated stomach contents including crushed shell fragments in Globidens specimens from the Pierre Shale. A newly described species, Carinodens acrodon from the Maastrichtian of Morocco (as of 2025), further exemplifies durophagous adaptations with specialized teeth for crunching hard-shelled invertebrates.^[35] Three-dimensional dental microwear texture analysis (DMTA) of Maastrichtian mosasaurs further delineates broad dietary categories: one group focused on soft prey like fish and squid (e.g., Mosasaurus hoffmannii, Tylosaurus spp.), another on harder items (e.g., Globidens dakotensis), and a mixed group (e.g., Prognathodon spp.), though without strict partitioning among co-occurring species.^[36]^[37]^[38] Tooth morphology in mosasaurs was adapted for prey capture and processing, with most taxa featuring robust, conical marginal teeth suited for piercing and holding slippery prey like fish, as seen in the recurved, serrated crowns of Tylosaurus proriger and Mosasaurus maximus. In contrast, globidensine mosasaurs evolved specialized crushing dentition, including bulbous, low-crowned molars and rounded posterior teeth in Globidens and Carinodens, capable of exerting sufficient force to fracture shells of molluscs and arthropods, as demonstrated by experimental biomechanical tests on Carinodens jaw replicas. Tooth replacement was continuous and rapid, inferred from histological sections showing incremental growth lines in dentine and resorption pits at tooth bases in Clidastes propython and Tylosaurus, with formation rates estimated at several weeks per tooth to maintain functional dentition despite wear from hard prey.^[39]^[40] Jaw mechanics facilitated versatile feeding, with a kinetic skull enabling streptostylic movement of the quadrate and intramembranous flexibility in the palate and suspensorium, allowing a wide gape for engulfing large prey relative to head size. In Plotosaurus bennisoni, this kinesis supported rapid jaw opening and closure, enhancing ambush predation on agile fish. Bite force estimates, derived from finite element analysis and lever arm models, indicate posterior forces exceeding 10,000 N in medium-sized taxa like the Miocene Zancleothys varolai, scaling to 10,000–20,000 N in larger Cretaceous species such as Mosasaurus hoffmannii based on adductor muscle reconstructions and skull robusticity. Tooth bending strength measurements from the Bearpaw Formation confirm dietary specialization, with higher resistance to lateral forces in durophagous Globidens compared to piercing-adapted Mosasaurus.^[41]^[42]^[43] Feeding strategies included opportunistic predation and scavenging, with evidence of intraspecific cannibalism from gut contents preserving partial skeletons of conspecifics and other mosasaurs. A Prognathodon kianda specimen from Angola contains three dismembered juvenile mosasaurs (including one P. kianda and two other taxa), with bite marks and partial digestion indicating active predation rather than scavenging, representing the first confirmed cannibalism in mosasaurs and highlighting tolerance for large, vertebrate prey up to 57% of body length. Niche partitioning among sympatric species is suggested by complementary dental adaptations and microwear signatures, such as Globidens exploiting benthic shellfish while Tylosaurus targeted pelagic fish, reducing competition in diverse assemblages like those of the Western Interior Seaway.^[44]^[45]^[36] Gastric digestion was highly acidic, inferred from the partial dissolution of prey remains in preserved gut contents, where smaller bones exhibit erosion pits and demineralization consistent with strong hydrochloric acid secretion. In the Prognathodon kianda specimen, ingested mosasaur bones show varying degrees of breakdown, with softer tissues fully digested and harder elements retaining structure, supporting efficient processing of diverse, high-protein meals in a marine endothermic metabolism.^[44]

Reproduction and growth

Fossil evidence indicates that mosasaurs were viviparous, giving birth to live young rather than laying eggs. The most direct proof comes from a gravid Carsosaurus specimen from the Late Cretaceous of Lebanon, which contains at least four partial embryos preserved within its body cavity, positioned tail-first relative to the mother.^[46] These embryos were in an advanced developmental stage with well-ossified skeletons, mirroring the birthing orientation in extant viviparous sea snakes to facilitate underwater delivery. Additional evidence includes a gravid Plioplatecarpus specimen from the Late Cretaceous Pierre Shale of South Dakota, apparently containing multiple embryos.^[47] The relative size of the neonates (approximately 12–15% of maternal body length) further supports viviparity, as it precludes the possibility of egg-laying in a fully aquatic lifestyle. Additional evidence for live birth derives from clusters of neonatal mosasaur fossils, including a partial Platecarpus skeleton, recovered from a single horizon in the Upper Cretaceous Niobrara Chalk of Kansas.^[48] These specimens, all around 1 m in total length, exhibit perinatal features such as open neurocentral sutures and unerupted replacement teeth, confirming their newborn status.^[48] The co-occurrence of multiple neonates in an open-ocean deposit suggests that mosasaur mothers gave birth in pelagic settings, with offspring exhibiting precocial traits like immediate swimming capability and offshore dispersal.^[48] Clutch sizes are inferred to be relatively small, with at least four offspring documented in the Carsosaurus case, though comparisons to modern viviparous squamates suggest variability up to around 20 in larger species.^[46] Mosasaurs displayed determinate growth patterns, with rapid early ontogeny transitioning to slower rates in adulthood. Histological examination of long bones from species like Clidastes and Tylosaurus reveals dense vascularization and large osteocyte lacunae, indicative of elevated metabolic rates and fast tissue deposition during juvenility.^[26] Lines of arrested growth (LAGs) are infrequent or absent in juvenile femora and humeri, pointing to near-continuous accretion without pronounced seasonal pauses, unlike many extant reptiles.^[26] Quantitative estimates from bone apposition rates show juvenile growth exceeding 1.5–1.7 μm per day, translating to substantial somatic increases—potentially up to 50 cm annually in early years—far surpassing those of modern lizards.^[49] In adults, LAGs become more prominent, marking a deceleration phase that aligns with sauropsid growth trajectories.^[24] Sexual maturity likely occurred after 5–7 years, coinciding with the onset of LAGs in limb elements and a shift to indeterminate but subdued growth.^[24] Fossil bonebeds with size-frequency clusters support this timeline, showing individuals around 4–6 m in length transitioning to adult morphologies and behaviors.^[24] Gestation periods are estimated at 6–12 months based on embryonic development stages and annual growth ring counts in related squamate analogs, though direct mosasaur data remain limited.^[46] Rare fossil structures potentially linked to mosasaur eggs, such as those associated with Carinatemys turtles in Cretaceous deposits, have been proposed but are debated as likely non-mosasaurian, given the overwhelming evidence for viviparity.^[50]

Paleoecology

Habitats and environments

Mosasauroids primarily occupied epicontinental seas and marginal marine environments during the Late Cretaceous, with the Western Interior Seaway of North America and the Tethys Ocean serving as key habitats.^[3]^[51] These settings featured shallow, warm waters, where sea surface temperatures typically ranged from 25°C to 38°C, supporting high biological productivity.^[52] High global sea levels, driven by tectonic activity and mid-ocean ridge expansion, facilitated widespread marine transgressions that expanded these shallow seas across continental interiors.^[53] Paleoceanographic conditions in these habitats were characterized by nutrient-rich upwelling zones, particularly along continental margins and within the seaways, which enhanced primary productivity and sustained diverse marine ecosystems.^[53] Mosasauroids are frequently associated with chalk and limestone formations, such as the Niobrara Chalk of the Western Interior Seaway, reflecting deposition in clear, carbonate-rich neritic waters.^[54] Their preferred depth ranges were predominantly neritic, from 0 to 200 meters, though for example, Plioplatecarpus showed affinities for shallower environments, whereas Mosasaurus and Platecarpus preferred deeper waters, based on rare earth element signatures in fossils.^[55] During the Campanian and Maastrichtian stages, mosasauroid habitats experienced dynamic shifts due to eustatic sea-level fluctuations, including regressions that occasionally constricted seaway connectivity and altered local conditions.^[53] Evidence for euryhaline tolerances comes from taxa like Pannoniasaurus inexpectatus, whose fossils occur in brackish to freshwater deposits of the Tethys region, suggesting adaptability to varying salinities.^[56] Abiotic factors, such as oxygen levels, were inferred from associated fauna like fish and invertebrates thriving in these productive but potentially stratified waters, with upwelling promoting oxygenation in surface layers while deeper zones may have been more anoxic.^[53]

Distribution and biogeography

Mosasaur fossils are known exclusively from Late Cretaceous marine deposits, spanning from the Turonian stage approximately 92 million years ago to the end of the Maastrichtian stage at 66 million years ago. Their diversity peaked during the mid- to late Maastrichtian, with the highest number of genera and species recorded in this interval, reflecting a global radiation of these marine squamates shortly before the Cretaceous-Paleogene extinction.^[23] Geographically, mosasaurs achieved a nearly cosmopolitan distribution, with remains reported from every continent, including high-latitude sites in Antarctica, though no unequivocal freshwater occurrences are known.^[57] Fossil-bearing localities are concentrated in epicontinental seas and marginal marine environments of the time, with major assemblages from North America's Western Interior Seaway, including the Niobrara Chalk of Kansas and the Eagle Ford Group of Texas, which have yielded exceptionally preserved skeletons of genera such as Tylosaurus and Platecarpus.^[58] In Europe, the Maastricht Formation of the Netherlands has produced iconic Mosasaurus specimens, while Africa's Late Cretaceous phosphates of Morocco host diverse faunas including Hainosaurus and Globidens.^[59] South American records, such as Yaguarasaurus columbianus from the Turonian Villegas Formation of Colombia, indicate early incursions into tropical western margins of the continent.^[60] Faunal provincialism is evident between the Western Interior Seaway and the Tethys Ocean, where distinct assemblages reflect geographic barriers like emerging landmasses, yet shared taxa such as Mosasaurus and Prognathodon across the Atlantic suggest episodic transoceanic dispersal via surface currents. Endemic forms highlight regional differentiation, including the high-latitude Kaikaifilu hervei from the Maastrichtian López de Bertodano Formation on Seymour Island, Antarctica, representing adaptation to polar waters.^[61] Recent discoveries, such as Jormungandr walhallaensis from the Campanian Pembina Member of the Pierre Shale in North Dakota, further illustrate localized diversity within the Western Interior.^[62] Preservation biases contribute to apparent abundance in certain regions, with lagerstätten like the Niobrara Chalk providing articulated skeletons due to rapid burial in oxygen-poor, chalky sediments that minimized disarticulation and scavenging.^[58]

Ecological roles and interactions

Mosasaurids occupied the apex predator niche in Late Cretaceous marine ecosystems, preying on a diverse array of organisms including fish, turtles, seabirds, smaller marine reptiles, and cephalopods such as ammonites and nautiloids.^[3]^[63] Evidence for this role includes fossilized stomach contents and coprolites containing remains of fish and shelled cephalopods, as well as bite marks on turtle shells and ammonite body chambers that match the conical teeth of mosasaurs like Tylosaurus and Mosasaurus.^[64]^[65]^[66] These interactions positioned mosasaurs at the top of food chains, where they regulated prey populations and exerted top-down control on community structure.^[67] Competition with other large marine vertebrates shaped mosasaur ecology, particularly with contemporaneous plesiosaurs and sharks, while earlier overlap with declining ichthyosaurs likely influenced initial diversification.^[68] Niche partitioning occurred through differences in body size, prey preferences, and foraging strategies; for instance, larger mosasaurs like Tylosaurus targeted high-mobility prey such as fish and smaller reptiles, whereas some plesiosaurs specialized in cephalopods or benthic organisms, reducing direct overlap.^[69] Sharks, including Cretoxyrhina, competed for similar mid-to-upper trophic prey like fish and smaller tetrapods, but mosasaurs' versatility in coastal and open-ocean habitats allowed them to dominate as ichthyosaurs and many pliosaurids waned.^[70] This competitive dynamic contributed to rapid mosasaur ecomorphological disparity during the Campanian stage.^[69] Stable isotope analyses of mosasaur tooth enamel confirm their occupation of high trophic levels as carnivores, with δ¹³C values often depleted in larger taxa (ranging from -12‰ to -18‰) indicating offshore foraging on lipid-rich prey.^[71]^[72]^[73] These signatures align with those of modern apex predators like killer whales, underscoring mosasaurs' role in sustaining ecosystem balance via predation pressure.^[63] Bonebed accumulations of mosasaur remains suggest locally high population densities, potentially from gregarious schooling behavior or catastrophic mass mortalities due to environmental events like storms. Traumatic pathologies on cranial elements, including healed fractures and bite scars, further indicate intraspecific agonism consistent with social interactions in dense groups.^[74] Indirect interactions included bioerosion of shells through feeding activities, where shell-crushing mosasaurs like Globidens fragmented ammonite and bivalve exoskeletons, contributing to post-mortem shell degradation and nutrient cycling in benthic environments.^[64]^[75] Such damage, observed as puncture and shear marks on cephalopod shells, enhanced decomposition rates and influenced shell accumulation in sedimentary records.^[65]

Evolutionary history

Origins and early evolution

Mosasauroids originated from semi-aquatic squamate ancestors within the Aigialosauridae, a group of basal anguimorph lizards that exhibited transitional morphologies between terrestrial varanoids and fully aquatic forms during the early Late Cretaceous.^[76] Aigialosaurs, such as Aigialosaurus bucchichi, possessed elongated bodies, shortened limbs with webbed digits, and adaptations for near-shore marine life, marking the initial shift from terrestrial habitats around 90 million years ago in the Turonian stage.^[77] These basal forms represent the ancestral lineage to mosasaurs, with phylogenetic analyses placing them as the sister group to more derived mosasauroids.^[78] The earliest known mosasauroids appear in the fossil record during the Cenomanian-Turonian boundary, approximately 98-92 million years ago, with transitional taxa like Haasiasaurus gittelmani from Israel documenting the initial aquatic invasion.^[79] Haasiasaurus, dated to about 98 Ma, features primitive cranial features and limb structures indicative of semi-aquatic locomotion, bridging aigialosaurs and later mosasaurs.^[79] Subsequent early Turonian forms, such as Tethysaurus nopscai from Morocco (~92 Ma), exhibit key innovations including further limb reduction toward paddle-like appendages, enhanced tail flukes for propulsion, and body elongation for streamlined swimming.^[80] In North America, Dallasaurus turneri from Texas (~92 Ma) represents another basal mosasauroid with retained terrestrial limb capabilities, such as functional claws and joint mobility, highlighting a mosaic evolution where swimming adaptations coexisted with partial land affinity.^[19] Evolutionary drivers for this transition included widespread marine transgressions during the mid-Cretaceous, which expanded shallow coastal and epicontinental seaways, creating unoccupied niches following the decline of ichthyosaurs after the Cenomanian-Turonian oceanic anoxic event.^[81] This event, around 94-90 Ma, disrupted marine ecosystems and facilitated the rapid radiation of mosasauroids into these environments.^[82] Basal taxa like Tethysaurus and Dallasaurus had less specialized skulls compared to later mosasaurs, with shorter snouts, conical teeth for grasping fish and soft-bodied prey, and robust quadrates suited for versatile feeding in near-shore habitats.^[80]^[19] The early evolutionary record of mosasaurs remains incomplete due to preservation biases, as Cenomanian-Turonian deposits are often anoxic and favor soft-tissue decay over skeletal fossilization, resulting in few articulated specimens from this interval.^[78] Gaps in the fossil sequence, particularly between aigialosaurs and definitive mosasaurs, underscore the challenges in tracing fine-scale transitions, though available evidence points to a rapid adaptation phase in Tethyan and Western Interior seaways.^[83]

Diversification and adaptations

Mosasaurid diversity reached its zenith during the Maastrichtian stage of the Late Cretaceous, with over 40 genera recognized across global marine deposits, reflecting a profound adaptive radiation that filled a wide array of ecological niches in the world's oceans.^[84] This peak in generic richness, building from earlier Campanian expansions, saw mosasaurs dominate as apex predators in epicontinental seas and open oceans, with subclades exhibiting specialized traits that partitioned resources. Within the Mosasaurinae, genera such as Globidens evolved durophagous dentition characterized by robust, bulbous teeth adapted for crushing hard-shelled prey like turtles and ammonites, enabling exploitation of benthic and shelly faunas unavailable to other marine reptiles.^[64] In contrast, the Tylosaurinae, including Tylosaurus, featured slender snouts and conical, recurved teeth suited to piscivory, targeting schools of fish and softer-bodied cephalopods in pelagic environments.^[85] Morphological adaptations among mosasaurs showed remarkable convergence with earlier marine reptiles like ichthyosaurs, particularly in the evolution of a fusiform body plan with a streamlined torso, reduced limbs transformed into flippers, and a powerful, vertically oriented tail fluke for efficient thunniform swimming.^[1] This hydrodynamic form, achieved independently by squamates, facilitated high-speed pursuits across vast oceanic distances, mirroring the body architecture of Mesozoic ichthyosaurs despite their distant phylogenetic origins. Ecomorphological disparity was pronounced in cranial and appendicular features; snout shapes varied from elongate and narrow in offshore predators to robust and short in nearshore ambush hunters, while limb proportions ranged from elongate paddles in basal forms to compact, high-aspect-ratio flippers in advanced taxa, correlating with habitat-specific locomotor demands and foraging strategies.^[86] Such variations underscore the clade's versatility in partitioning trophic levels, from durophagous benthic feeding to piscivorous open-water hunting. Recent phylogenetic studies as of 2024, including the description of Jormungandr walhallaensis, further support convergent evolution of gigantism across mosasaur lineages.^[62] The drivers of this diversification included eustatic sea-level fluctuations that expanded shallow epicontinental seaways, creating fragmented habitats conducive to allopatric speciation as populations were isolated by emerging land barriers and oceanic currents.^[53] Enhanced prey availability, fueled by high marine productivity from nutrient upwelling in these dynamic basins, further promoted niche specialization, with cooling climates and tectonic activity amplifying regional endemism across Tethyan and proto-Atlantic seaways.^[87] Key evolutionary events marked this radiation, including the invasion of high-latitude polar regions during the late Campanian and Maastrichtian, evidenced by diverse mosasaur assemblages from Arctic localities like Axel Heiberg Island in Canada, where taxa adapted to prolonged twilight and cooler waters through inferred ectothermic or regional endothermic strategies.^[88] Body size trends followed Cope's rule, with lineages exhibiting directional increase in maximum length—from less than 1 meter in the smallest basal forms to around 3 meters in early Turonian taxa, increasing to over 15 meters in Maastrichtian giants like Mosasaurus and Tylosaurus—driven by competitive pressures and abundant resources that favored larger body plans for enhanced predatory efficiency.^[85] Despite these advances, mosasaur faunas from South America and the Indo-Pacific remain understudied, with fragmentary records from Patagonian formations and sparse Indo-Pacific sites like those in India and New Zealand hinting at untapped endemic diversity that could reveal additional adaptive innovations in isolated marginal seas.^[63]

Extinction

Mosasaurus and other mosasaurs abruptly disappeared approximately 66 million years ago at the Cretaceous-Paleogene (K-Pg) boundary, marking the end of the Maastrichtian stage of the Late Cretaceous. This extinction event coincided with the Chicxulub asteroid impact in the Yucatán Peninsula and the ongoing massive eruptions of the Deccan Traps in present-day India, which together triggered profound global environmental changes.^[89]^[90] Fossil evidence indicates that mosasaurs persisted until the very latest Maastrichtian, with well-preserved specimens from formations such as the New Egypt Formation in New Jersey representing some of the stratigraphically highest records in North America. No mosasaur fossils have been confirmed in Danian (early Paleocene) strata worldwide, confirming their complete extinction at the boundary. While direct associations of mosasaur bonebeds with the iridium-enriched clay layer— a hallmark of the K-Pg impact—are rare, the abrupt termination of mosasaur-bearing horizons below this layer in multiple global sites underscores the synchrony of their demise with the broader mass extinction.^[91]^[59] The primary causal factors for mosasaur extinction involved the catastrophic disruption of marine ecosystems, driven by global cooling from sulfate aerosols and dust lofted by the impact, as well as sulfate emissions from Deccan volcanism. This induced an "impact winter" lasting months to years, severely inhibiting sunlight penetration and causing a collapse in phytoplankton productivity—the base of the oceanic food web. As plankton declined, so did populations of planktivorous fish and invertebrates, triggering a trophic cascade that starved higher-level predators like mosasaurs, which depended on this rich food chain for sustenance.^[89]^[92]^[93] Larger mosasaur species appear to have been disproportionately affected, likely owing to their elevated energy requirements and specialization as apex predators in a productivity-starved ocean; smaller-bodied taxa may have fared marginally better but still succumbed. Hypotheses proposing survival in deep-sea refugia, where conditions might have been less perturbed, remain untested due to limited sampling in such environments.^[10]^[94] In the aftermath, the disappearance of mosasaurs created an ecological vacuum at the top of marine food webs, with no immediate replacements among reptiles. This niche was gradually filled by archaic whales, such as Basilosaurus, emerging as dominant predators in the late Paleocene and Eocene, alongside the radiation of modern shark lineages that diversified to exploit the vacated roles.^[59]^[95]

Classification

Higher-level relationships

Mosasauria represents a derived clade within the order Squamata, the group encompassing modern lizards and snakes, with its higher-level phylogenetic relationships remaining a subject of ongoing debate among paleontologists.^[96] Morphological analyses frequently position Mosasauria as basal members of Anguimorpha, a major squamate subgroup that includes anguids (such as slow worms and glass lizards) and varanids (monitor lizards), rather than as close relatives of snakes (Serpentes).^[97] Alternative hypotheses, based on combined morphological and molecular data, suggest Mosasauria as the sister group to snakes, implying a shared aquatic ancestry for these lineages, though this view has been challenged by evidence favoring terrestrial origins for serpents.^[98] Molecular clock estimates indicate that the divergence of Mosasauria from other squamate lineages occurred approximately 100–120 million years ago during the Early Cretaceous, aligning with the emergence of stem-mosasauroid forms in marine environments.^[99] Within Anguimorpha, Mosasauria has been allied with Varanoidea, a superfamily that includes extant monitor lizards (genus Varanus), based on shared osteological features such as robust cranial kinesis and elongated body plans adapted for predatory lifestyles.^[100] These affinities are supported by similarities in sensory structures, including potential evidence for forked tongues— a trait prominent in varanids for chemosensory detection via the vomeronasal organ—though direct fossil preservation of soft tissues in mosasaurs remains elusive, leading to inferences from skeletal correlates like expanded choanal regions.^[101] Additionally, both groups exhibit traits suggestive of venom delivery potential, such as grooved marginal teeth, which may have facilitated envenomation in a manner akin to modern venomous monitors, though unequivocal evidence for functional venom glands in mosasaurs is lacking.^[102] The aquatic adaptations of mosasaurs parallel those seen in the evolutionary transition to snakes, particularly in the progressive limb reduction and elongation of the axial skeleton that facilitated undulatory swimming.^[98] This convergence is exemplified by dolichosaurs, a group of semi-aquatic squamates from the Late Cretaceous, which mirrored early stages of mosasaur limb loss and body streamlining, suggesting repeated selective pressures for marine lifestyles within Squamata.^[98] A key controversy surrounds the Toxicofera hypothesis, which posits that mosasaurs, along with anguimorphs and advanced snakes (such as colubroids and viperids), belong to a monophyletic clade characterized by ancestral venom systems derived from modified salivary glands.^[102] Proponents argue that morphological signals linking Mosasauria to these venomous lineages support inclusion in Toxicofera, potentially explaining shared dental specializations, while critics highlight inconsistencies with molecular phylogenies that place mosasaurs outside this group, emphasizing instead their anguimorph affinities.^[96] Fossil evidence bolstering these squamate origins includes transitional taxa like Adriosaurus, a small, lizard-like reptile from the Late Cretaceous of Italy, which exhibits a mosaic of primitive squamate features (such as well-developed limbs) and derived traits (like an elongated trunk) that bridge terrestrial lizards to fully aquatic mosasaurs.^[98] Phylogenetic analyses of Adriosaurus and related dolichosaurs consistently recover them as successive outgroups to snakes, with Mosasauria positioned as their sister taxon, reinforcing a stepwise aquatic radiation within basal anguimorphs.^[98]

Genera and species

Mosasauridae encompasses approximately 47 recognized valid genera and over 100 species, reflecting a diverse radiation of Late Cretaceous marine squamates, though taxonomic revisions continue to refine these counts. The family is traditionally divided into four principal subfamilies: Halisaurinae, Mosasaurinae, Plioplatecarpinae, and Tylosaurinae, each characterized by distinct cranial and dental features adapted to varied predatory niches.^[84] Mosasaurinae, the most speciose subfamily, includes about 11 genera such as Mosasaurus, Prognathodon, and Globidens, often featuring robust skulls and conical teeth suited for grasping prey.^[103] Tylosaurinae comprises roughly 4 genera, exemplified by Tylosaurus and Taniwhasaurus, notable for their elongate snouts and piercing, slender teeth indicative of a piscivorous lifestyle.^[104] Halisaurinae and Plioplatecarpinae are comparatively less diverse, with Halisaurinae encompassing genera like Halisaurus and Pluridens that exhibit primitive traits such as shorter rostra, while Plioplatecarpinae includes Plioplatecarpus, Platecarpus, and Yaguarasaurus, marked by more derived, blade-like marginal teeth for slicing flesh.^[103] The type species of Mosasauridae is Mosasaurus hoffmannii, originally described from a partial rostrum discovered in the Maastrichtian of the Netherlands, serving as the benchmark for the genus and family.^[21] Recent taxonomic work has clarified or synonymized several taxa; for instance, in 2022, South African Maastrichtian material previously assigned to Mosasaurus (Leiodon) cf. anceps was reclassified as a junior synonym of the new genus Thalassotitan atrox, a durophagous mosasaurine with specialized crushing dentition.^[105] Other post-2020 emendations include revisions to Yaguarasaurus species boundaries in South America, incorporating new cranial material to distinguish valid taxa from synonyms.^[105] Several historical names remain invalid or dubious due to inadequate diagnostic fossils. Macrosaurus, for example, is a nomen dubium based on fragmentary vertebrae from the Campanian of England, lacking unique features to warrant generic status and often considered indeterminate within Mosasauridae.^[106] Junior synonyms abound in the literature, such as early referrals of Prognathodon material to Liodon, which have been systematically resolved through phylogenetic analyses emphasizing dental and quadrate morphology. Notable recent additions highlight ongoing discoveries. In 2023, Ectenosaurus shannoni was erected for a partial skeleton from the Mooreville Chalk of Alabama, representing the ninth species in the plioplatecarpine genus Ectenosaurus and extending its known diversity in the Western Interior Seaway equivalents.^[107] Similarly, Yaguarasaurus regiomontanus was described that year from a nearly complete skull in Mexico's Agua Nueva Formation, bolstering Plioplatecarpinae representation in southern Gondwanan assemblages.^[84] In 2024, the genus Khinjaria was described from Morocco, and in 2025, Oneirosaurus caballeroi was erected from Colombia, further illustrating ongoing taxonomic refinements.^[108] These findings underscore the persistent refinement of mosasaur taxonomy through integrated morphological and stratigraphic data.

Phylogeny

Mosasauroid phylogeny is characterized by a basal grade of aquatic squamates including aigialosaurs, followed by the monophyletic Mosasauridae, which splits early into the sister clades Russellosaurina and Mosasaurinae. Russellosaurina encompasses subfamilies such as Tylosaurinae and Plioplatecarpinae, defined by synapomorphies including an elongated retroarticular process on the mandible for improved gape and a reduced temporal bar. Mosasaurinae, in contrast, features taxa with more robust skulls and specialized dentition for durophagy in some lineages. This topology is recovered consistently in cladistic analyses using morphological datasets of 100-150 characters scored across 30-50 taxa.^[78] Major phylogenetic analyses have employed parsimony, maximum likelihood, and Bayesian methods to test relationships, revealing robust support for the core clades. For instance, Simões et al. (2017) analyzed 111 characters and 40 taxa, yielding bootstrap values above 70% for the Russellosaurina-Mosasaurinae divergence and posterior probabilities exceeding 0.95 in Bayesian runs, highlighting the stability of the tree despite methodological differences.^[78] More recent work by Polcyn et al. (2025) updates these frameworks by incorporating additional taxa and stable isotope data to refine plioplatecarpine interrelationships within Russellosaurina and achieving bootstrap support over 60% for subclades previously unresolved.^[71] The placement of aigialosaurs remains controversial, with most analyses positioning them as stem-mosasaurs based on shared features like flattened skulls and paddle-like limbs, though alternative trees suggest they form a grade closer to dolichosaurs outside crown Mosasauridae.^[109] Temporal calibration of phylogenies using first appearance dates from Cenomanian (~100 Ma) to Maastrichtian (~66 Ma) strata indicates diversification rates peaking at ~5-10 new lineages per million years during the Turonian-Coniacian interval, reflecting rapid radiation into marine niches.^[68] Sampling gaps persist in the early phylogeny, particularly for Cenomanian and Turonian forms, where fragmentary fossils limit resolution of basal nodes and underestimate initial diversity.^[110]

History of discovery

Early discoveries

The earliest recorded discovery of mosasaur fossils occurred in 1764, when quarry workers unearthed a partial jawbone from Late Cretaceous chalk deposits in the St. Pietersberg hill near Maastricht, Netherlands. This specimen was acquired by Swiss-born army surgeon and naturalist Johann Leonhard Hoffmann (1710–1782), who initially interpreted it as the jaw of a large crocodile and referred to it as the "crocodile of the Meuse" after the nearby river. The fossil, now known as part of Mosasaurus hoffmanni, sparked early interest but was not formally studied until later.^[111]^[17] Between 1770 and 1774, a second, more complete skull was discovered in the same Maastricht quarry, further fueling scientific curiosity. Early interpretations of these fossils varied widely, with some scholars proposing they belonged to a crocodile, a sperm whale, or even a gigantic iguana, reflecting the limited understanding of extinct marine reptiles at the time. In 1798, Dutch anatomist Adriaan Gilles Camper, son of Pieter Camper, reexamined descriptions of the Maastricht specimens and concluded they represented a giant monitor lizard, a view later supported by French naturalist Georges Cuvier, who in 1808 affirmed their reptilian nature based on comparative anatomy. However, it was not until 1822 that English geologist William Conybeare formally named the genus Mosasaurus, combining "Meuse" (Latinized as Mosa) with "sauros" (lizard), honoring its discovery site and lizard-like features. Cuvier adopted this name in his 1824 work, solidifying its taxonomic status.^[112]^[111] American discoveries began in the early 19th century, with the first reported mosasaur remains from North America coming from the Navesink Formation in Monmouth County, New Jersey, noted in 1818 by physician and naturalist Samuel L. Mitchill. In 1825, Richard Harlan, an American physician and paleontologist, described fragmentary mosasaur bones from New Jersey greensand deposits, contributing to the growing recognition of these reptiles on the continent. Joseph Leidy, another key figure, expanded on these finds in the 1850s and 1860s, describing multiple specimens from New Jersey and establishing mosasaurs as significant components of the Cretaceous fauna. A notable early specimen was Harlan's Mosasaurus missouriensis from 1834, based on material from the Midwest, though its type snout was later rediscovered in European collections.^[113]^[114] The 19th century saw intensified exploration during the so-called "Bone Wars," a fierce rivalry between paleontologists Edward Drinker Cope and Othniel Charles Marsh from the 1870s onward. Their expeditions in the Western Interior Seaway deposits, particularly in Kansas chalk beds, yielded dozens of mosasaur specimens, leading to the naming of numerous species such as Tylosaurus proriger by Marsh in 1872 and various Clidastes taxa by Cope. Marsh's collections from the 1870s, including well-preserved skulls and skeletons from the Niobrara Formation, provided critical insights into mosasaur diversity and propelled the field forward, despite the acrimonious competition that sometimes prioritized quantity over careful analysis. These efforts resulted in over 20 new mosasaur species attributed to the rivals, transforming early understandings of these extinct predators.^[113]

Modern research and recent finds

In the mid-20th century, paleontologist Dale A. Russell advanced mosasaur classification through his 1967 monograph, Systematics and Morphology of American Mosasaurs, which provided a comprehensive framework for understanding their taxonomy and anatomy based on North American specimens.^[14] This work established key morphological distinctions among genera and influenced subsequent research by emphasizing skeletal features for phylogenetic placement. By the 1990s, advancements in imaging technology, including early applications of computed tomography (CT) scanning, began revealing internal skull structures and traces of soft tissues in well-preserved specimens, enhancing interpretations of sensory capabilities and cranial mechanics. Recent fossil discoveries have continued to refine our understanding of mosasaur diversity and distribution. In 2023, paleontologists described Jormungandr walhallaensis, a new mosasaurine species from the Late Cretaceous Pierre Shale near Walhalla, North Dakota, based on a partial skeleton exhibiting unique vertebral morphology suggestive of enhanced flexibility.^[115] That same year, Ectenosaurus shannoni, a plioplatecarpine mosasaur, was identified from fragmentary remains in Alabama's Mooreville Chalk Formation, highlighting regional endemism in the Western Interior Seaway.^[107] In 2025, a significant mosasaur specimen dubbed "Walt"—named after the Texas teenager who discovered it during a dig—was unearthed in southern Manitoba, Canada, representing one of the largest articulated skeletons from the region's Cretaceous deposits.^[116] Additional finds that year included multiple mosasaur fossils from the newly opened Edelman Fossil Park quarry in Sewell, New Jersey, where excavations exposed a rich Cretaceous bonebed yielding vertebrae and limb elements from the Atlantic Coastal Plain.^[117] Also in 2025, geologists in Mississippi discovered a massive vertebra attributed to Mosasaurus hoffmannii near Starkville, estimated to belong to an individual over 30 feet long, marking the largest such fossil from the state.^[118] Methodological innovations have driven deeper insights into mosasaur biology. Since the 2010s, stable isotope analysis of tooth enamel and bone has elucidated dietary preferences, revealing niche partitioning among species—such as piscivory in Platecarpus versus durophagy in Globidens—through carbon and nitrogen ratios indicating marine trophic levels.^[119] Three-dimensional modeling, often derived from CT scans and laser scanning, has enabled biomechanical simulations of jaw function and locomotion, demonstrating powerful bite forces in genera like Tylosaurus exceeding 8,000 Newtons.^[120] In 2024, Michael J. Polcyn's comprehensive paleoecological study integrated fossil distributions with environmental data to reconstruct mosasaur habitats, showing correlations between sea-level changes and clade radiations in the Western Interior Seaway.^[121] Despite these advances, challenges persist in mosasaur research due to biases in the fossil record. Analyses of specimen completeness across 4,083 mosasaur fossils indicate that preservation quality varies significantly by lithology and formation, with offshore marine deposits yielding more articulated skeletons than nearshore ones, potentially skewing diversity estimates.^[122] Squamate "megafilters"—geochemical and taphonomic processes that preferentially preserve robust bones while destroying delicate ones—further distort the record, as evidenced by the underrepresentation of small-bodied or juvenile squamates, including early mosasaurs.^[123] Ongoing debates surround the attribution of fossil eggs to mosasaurs; while viviparity is confirmed by embryonic fossils, a 2020 analysis of a large soft-shelled egg from Antarctica has sparked discussion on possible oviparity in some species, though its mosasaur origin remains tentative and most evidence supports live birth in open water.^[124]^[125] Mosasaur research has also intersected with popular culture, notably through portrayals in the Jurassic World franchise, where Mosasaurus is depicted as a massive apex predator, boosting public interest but often exaggerating sizes and behaviors. Scientific outreach efforts, such as those by the Canadian Fossil Discovery Centre, have countered these inaccuracies by highlighting real specimens like "Bruce" the mosasaur to educate on accurate paleobiology and conservation of fossil sites.^[126]

References

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The Evolution of Mosasaurid Foraging Behavior Through the Lens of ...
Apr 15, 2025 · A large data set of new and previously published measurements of δ¹³C values derived from tooth enamel (n = 223, of which 93 are new) are ...
[72]
and high-latitude mosasaurs and ish isotopic composition: carbon ...
The stable carbon isotope composition of vertebrate bioapatite mainly derives from ingested food (except in chondrichthyan enam- eloid as detailed in “δ13C ...
[73]
Louisiana fossils reveal mosasaur life before dinosaur-killing ...
Aug 7, 2025 · Fossils found show evidence of a thriving marine ecosystem during the last stages of the Late Cretaceous, abruptly terminated by the Chicxulub ...
[74]
https://www.researchgate.net/publication/397351977_The_social_ecology_of_mosasaurs_as_evidenced_by_traumatic_paleopathologies
[75]
[PDF] Mosasaur bites or punctured limpet home scars?
Even a superficial glance at the left side of the ammonite reveals a V-shaped set of punctures strikingly similar to that whch would have been left by the teeth ...
[76]
A review of the taxonomy and systematics of aigialosaurs
Kramberger hypothesised that the Aigialosauridae were ancestral to modern lacertilians, dolichosaurs, and pythonomorphs (snakes and mosasaurs). Kramberger's ...
[77]
A review of the taxonomy and systematics of aigialosaurs
Aug 9, 2025 · Species assigned to Aigialosaurus form the basalmost mosasauroid clade. ... Intermediate forms that led to the cruising species are known in ...
[78]
Mosasauroid phylogeny under multiple phylogenetic methods ...
May 3, 2017 · Mosasauroids were a successful lineage of squamate reptiles (lizards and snakes) that radiated during the Late Cretaceous (95–66 million ...
[79]
Cretaceous δ13C stratigraphy and the age of dolichosaurs and early ...
Sep 1, 2005 · Haasiasaurus, the oldest known well-documented early mosasaur, is found at 'Ein Yabrud, Israel (98 Ma), followed by other poorly dated ...Missing: earliest | Show results with:earliest<|separator|>
[80]
A new mosasauroid (Squamata) from the Late Cretaceous (Turonian ...
Aug 6, 2025 · Tethysaurus nopcsai gen. et sp. nov. is described on the basis of both cranial and postcranial material from the Late Cretaceous (Early ...
[81]
[PDF] Cross, SRR, Moon, BC, Stubbs, TL, Rayfield, EJ, & Benton
This study investigates the macroevolution of mosasauroid feeding and locomotory disparity, finding early shifts in morphology and later expansion of ...
[82]
The Cenomanian-Turonian (late Cretaceous) radiation of marine ...
Nov 1, 2008 · “Dolichosaurids” and mosasauroids were rather mid latitude distributed groups, found in a wide range of palaeoenvironments of both the ...
[83]
Mosasauridae) from the Turonian (Upper Cretaceous) of Kansas ...
Mosasaurs are extinct marine lizards that are commonly found in Coniacian–Maastrichtian (Late Cretaceous) deposits nearly worldwide but are rare in older rocks.
[84]
New Species of Mosasaur Identified in Mexico | Sci.News
Nov 24, 2023 · “Over 40 genera are recognized, the largest specimens reaching a length of 12 m (39.3 feet).” “The phylogenetic relationships within ...
[85]
Rapid evolution, diversification and distribution of mosasaurs (Reptilia
Mar 11, 2016 · Highly-adapted marine reptiles called mosasaurs became the apex predators of the Earth's oceans in the last 25 million years of the Late Cretaceous.Missing: bonebed accumulations gregarious
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[PDF] Charting the Late Cretaceous Seas: Mosasaur Richness and ...
Novel dental morphologies, inferred to reflect differences in feeding adaptations, appear sporadically among mosasaurs dur- ing the Late Cretaceous (Table 3).Missing: diet | Show results with:diet
[87]
[PDF] Physical drivers of mosasaur evolution - Docentes FCT NOVA
May 24, 2013 · High temperatures and high sea levels causing epicontinental seas contributed to the remarkably high productivity of the Late Cretaceous. Some ...
[88]
Arctic mosasaurs (Squamata, Mosasauridae) from the Upper ...
New mosasaur remains from circumpolar regions are currently appearing at the background of recent studies of thermoregulation of these marine reptiles ...
[89]
(PDF) Physical Drivers of Mosasaur Evolution - ResearchGate
Aug 6, 2025 · The most likely driving force in mosasaur evolution was high productivity in the Late Cretaceous, driven by tectonically controlled sea levels and climatically ...
[90]
Evolution and dispersal of snakes across the Cretaceous ... - Nature
Sep 14, 2021 · The Cretaceous-Paleogene (K-Pg) transition resulted in the loss of an estimated 76% of all species. High-resolution records of fossil pollen and ...Results · Post-Extinction... · Oligocene Extinction And...
[91]
Recent mosasaur discoveries from New Jersey and Delaware, USA
Aug 9, 2025 · The mosasaurs of the New Egypt Formation represent some of the last (i.e., stratigraphically highest) mosasaur fossils in North America.
[92]
A Bite into the Past of Extinct Marine Reptiles | CNRS News
May 25, 2017 · Plankton-eating fish—vital food sources for the plesiosaurs and mosasaurs—also dropped in number, triggering the reptiles' disappearance. Balter ...
[93]
The impact winter model - Letters from Gondwana. - WordPress.com
Jul 29, 2013 · The food webs supported by plankton were severely affected. For instance, ammonites were plankton feeder and they, like mosasaurs, plesiosaurs ...
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Greensand mosasaurs of New Jersey and the Cretaceous ...
Nov 14, 2014 · The preservational quality of the mosasaur bone itself is unlike the more dense, darkened thoroughly permineralized bone of mosasaurs found in ...Missing: bonebed accumulations gregarious
[95]
Post-Impact Changes In Earth's Ocean Ecology - Astrobiology Web
Mar 6, 2024 · Mosasaurs, plesiosaurs and giant sea turtles disappeared, along with entire families of fish. This opened the way for whales and seals, and fish ...
[96]
8 - A Review of Non-Mosasaurid (Dolichosaur and Aigialosaur ...
These tests highlight the stronger phylogenetic signal of mosasaurians as anguimorph lizards, especially close to varanoids, and not closely related to snakes ( ...
[97]
Adriosaurus and the affinities of mosasaurs, dolichosaurs, and snakes
May 20, 2016 · The analysis further reveals that up to five successive outgroups to living snakes (pachyophiids, Adriosaurus, dolichosaurs, Aphanizocnemus, and ...
[98]
Ecomorphological diversification in squamates from conserved ...
Jul 1, 2019 · Although the phylogenetic placement of Mosasauria within squamates remains ambiguous (37–39, 61), Plotosaurus was placed within the molecular ...
[99]
A challenge to categories: “What, if anything, is a mosasaur?”
Jan 1, 2012 · The secondary thesis of this paper is that mosasaurs, whatever they are, are not descended from within the platynotan lineage of anguimorph ...
[100]
Did mosasaurs have forked tongues? - ResearchGate
Aug 9, 2025 · We suggest that mosasaurs had a diploglossan tongue that remained in a relatively underived state. The form of the tongue would probably have been most like ...
[101]
THE SQUAMATE TREE OF LIFE - BioOne
May 5, 2021 · Large-scale molecular phylogeny, morphology, divergence-time estimation, and the fossil record of advanced caenophidian snakes (Squamata ...
[102]
Integrated Analyses Resolve Conflicts over Squamate Reptile ...
In summary, 42 of 46 genes support snakes and/or anguimorphs as sister to Iguania, with or without additional groups. Among the genes that did not show the ...
[103]
A new species of Yaguarasaurus (Mosasauridae: Plioplatecarpinae ...
Over 40 genera are recognized, the largest specimens reaching a length of 12 m (Grigoriev, 2014). The phylogenetic relationships within Mosasauridae are ...
[104]
Mosasaurids Bare the Teeth: An Extraordinary Ecological Disparity ...
The general morphology of the skull (or skull portions) is briefly described and is focused on characteristics allowing the inference of size, robustness ...
[105]
A New Hypothesis of the Phylogenetic Relationships of ... - Frontiers
Mar 26, 2019 · No confirmed evidence of sexual dimorphism has been found in mosasauroid lizards. Genus Taniwhasaurus (Hector, 1874). Type Species ...<|separator|>
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Unraveling the taxonomy of the South African mosasaurids - Frontiers
The current study provides a morphological description and taxonomic interpretation of all the mosasaur remains discovered in South Africa.
[107]
https://museums.ua.edu/new-mosasaur-species-from-alabama-discovered/
[108]
New mosasaur species from Alabama discovered
Nov 28, 2023 · The new mosasaur species, Ectenosaurus shannoni, was found in Greene County, Alabama, and is the ninth of its genus worldwide. It includes ...Missing: 2024 | Show results with:2024
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Mosasauroid phylogeny under multiple phylogenetic methods ... - NIH
May 3, 2017 · In this study, we present the first mosasauroid phylogenetic analysis performed under different analytical methods, including maximum likelihood ...Missing: 2024 | Show results with:2024<|control11|><|separator|>
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(PDF) Mosasauroid phylogeny under multiple phylogenetic methods ...
May 3, 2017 · In this study, we present the first mosasauroid phylogenetic analysis performed under different analytical methods, including maximum likelihood ...
[111]
A new look at Faujas de Saint-Fond's fantastic story on the ...
Jan 1, 2012 · ... Mosasaurus hoffmanni Mantell, 1829 –the first mosasaurid specimen to be named– told by the geologist B. Faujas de Saint-Fond (1741–1819) in ...
[112]
Fact or Fiction? Discovering the Mosasaur
Oct 14, 2015 · Finally, in 1822, William Daniel Conybeare gave the animal the genus name Mosasaurus, and in 1829, Gideon Mantell supplied the specific epithet ...Missing: primary source
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[PDF] Systematics and morphology of American mosasaurs (Reptilia, Sauria)
The first general review of the “grand animal fossile de Maestricht” was that of Cuvier (1808) in which the remains were redescribed and refigured, and the.
[114]
Harlan's lost mosasaur snout rediscovered
The lost snout of Richard Harlan's specimen of Mosasaurus missouriensis has been rediscovered in the vertebrate palaeontology collections of the Muséum ...
[115]
Timeline of mosasaur research - Wikipedia
Williston publicly acknowledged that the supposed fringe running down the back of a mosasaur he had reported was actually misidentified tracheal rings.
[116]
Fossil unearthed in North Dakota could help solve an evolutionary ...
Jormungandr walhallaensis — is unusual, displaying a mix of traits from other creatures of its kind.
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Meet 'Walt,' the 80-million-year-old mosasaur named after the Texas ...
Aug 2, 2025 · A man holds up a fossil. A man holds up a mosasaur fossil fragment at a dig site in southern Manitoba in July 2025. (Prabhjot Singh Lotey/CBC).
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Paleontologists Find Mosasaur Fossils in New Jersey Quarry
Sep 23, 2025 · The site, discovered by Kenneth Lacovara, Ph.D., houses so many fossils thanks to the extinction layer that stretches across the quarry.Missing: 1820s | Show results with:1820s
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MSU researchers, both MGS geologists, help unearth giant ...
May 6, 2025 · The vertebra, measuring more than seven inches across, belonged to Mosasaurus hoffmannii, one of the largest marine reptiles to roam Earth's ...
[120]
Community Structure, Population Control, and Competition
Galván Does trawl fisheries affect the diet of fishes? A stable isotope analysis approach, Isotopes in Environmental and Health Studies 55, no.44 (Jun 2019) ...
[121]
[PDF] SVP 84th ANNUAL MEETING - Society of Vertebrate Paleontology
Oct 30, 2024 · This will be the second annual meeting of the Society of Vertebrate Paleontology in the Twin Cities, and we look forward to having you here, ...
[122]
New insights into the evolution and paleoecology of Mosasaurs
Dec 13, 2024 · Palaeontologist Michael Polcyn presented the most comprehensive study to date on the early evolution and ecology of these extinct marine reptiles.Missing: analysis et
[123]
The Mosasaur Fossil Record Through the Lens of ... - ResearchGate
Apr 22, 2018 · We analyse the fossil record of mosasaurs in terms of fossil completeness as a measure of fossil quality, using three novel metrics of fossil completeness.
[124]
https://www.nature.com/articles/s41586-020-2377-7
[125]
This Giant Fossil Egg Sat In A Museum Storage For Years
May 10, 2025 · A massive egg fossil, recently identified as soft-shelled and possibly belonging to a mosasaur, may reveal that these powerful marine reptiles reproduced in ...<|control11|><|separator|>
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Mosasaurs Gave Birth to Their Offspring in Open Ocean ... - Sci.News
Apr 11, 2015 · Paleontologists say that mosasaurs did not lay eggs on beaches, and that newborn mosasaurs likely did not live in sheltered nearshore ...
[127]
Jurassic World Hype Putting Mosasaurs And Morden Museum On ...
Jul 9, 2015 · The world is catching up on what visitors to the Canadian Fossil Discovery Centre (CFDC) have known for years: mosasaurs are amazing.