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Isolated mosasaur teeth and vertebrae recovered from beds of the Guadalupe Group of central Boyacá, Colombia, are reported. A partial tooth crown identified as Globidens sp., found in the Labor-Tierna Formation (Maastrichtian), represents the first report of this genus from northern South America and its most equatorial occurrence. A tooth crown recovered from the Plaeners Formation (upper Campanian–lower Maastrichtian), represents the youngest record of the subfamily Plioplatecarpinae in Colombia. These occurrences collectively constitute the youngest record of the family Mosasauridae in Colombia and expand both the taxonomic diversity and biogeography of mosasaurids in northern South America. [ABSTRACT FROM AUTHOR]

Mosasauroid squamates were abundant and had a worldwide distribution during the Late Cretaceous, but records from Sub-Saharan Africa are comparatively scanty and based mainly on fragmentary and isolated material. Here new mosasaur remains from the Maastrichtian (Upper Cretaceous) of Dakhla Oasis in the South-Western Desert of Egypt are recorded, including: a small, fragmentary right dentary of an indeterminate mosasaurine with a single tooth preserved in situ and an isolated tooth crown of the genus Globidens. This material stems from fossiliferous, calcareous sandstones with intercalated shales that form the lower portion of the Dakhla Formation, known to be an intertidal to subtidal deposit. Previously recorded mosasaur remains from the Eastern Desert in Egypt included Globidens phosphaticus , Platecarpus sp., and Igdamanosaurus aegyptiacus. In Africa, mosasaurs of the Maastrichtian age have been recorded from Morocco, Nigeria, Angola, the Democratic Republic of Congo, and Niger. The newly collected material from Dakhla Oasis currently constitutes the youngest record of mosasaurs in Egypt. [ABSTRACT FROM AUTHOR]

The Upper Maastrichtian of Morocco has produced a remarkably diverse fauna of mosasaurids, the most diverse known for any time or place. As apex predators, Mosasauridae provide a picture of the marine ecosystem just before the end-Cretaceous mass extinction. Here we describe a bizarre new plioplatecarpine mosasaurid, Khinjaria acuta , characterized by enlarged, dagger-like anterior teeth, short, robust jaws, and posterior elongation of the skull. Khinjaria is related to Goronyosaurus nigeriensis from Nigeria and Niger, and Gavialimimus almaghribensis from Morocco. These species form a distinct clade of specialized mosasaurids so far unknown outside of Africa. Mosasaurids show high endemism in the Maastrichtian, with different lineages occurring in different regions, implying that mosasaurid diversity is underestimated because of limited geographic sampling. The large size, robust jaws, akinetic skull, and bladelike teeth of Khinjaria suggest it was an apex predator, but the unusual skull and jaw differ from those of contemporary predators like Hainosaurus , Thalassotitan , and Mosasaurus , suggesting a distinct feeding strategy. Mosasaurids became increasingly specialized in the latest Cretaceous, repeatedly evolving to occupy the apex predator niche, suggesting a diverse marine ecosystem persisted up to the K/Pg boundary. Late Cretaceous marine ecosystems differ from modern marine ecosystems in the high diversity of large predators. [ABSTRACT FROM AUTHOR]

Upper Cretaceous coastal marine deposits are widespread in the Southern Urals with a number of marine vertebrates previously reported from this region. However, previous studies on the vertebrate faunas in this region often lack detailed taxonomic descriptions and illustrations, rendering comparisons to other faunal assemblages difficult. A new diverse vertebrate assemblage comprising cartilaginous and bony fishes, as well as marine reptiles, is described here from the Orenburg region near Akkermanovka (Southern Urals, Russia). Thirty five taxa are identified, including three holocephalans (Elasmodus sp., Ischyodus yans c hini , Chimaeroid indet.), two hybodontiform sharks (Meristodonoides sp., cf. Polyacrodus sp.), 17 neoselachians (Paraorthacodus cf. andersoni , Paraorthacodus sp., Synechodus sp., Cederstroemia nilsi , Acrolamna acuminata , Archaeolamna ex gr. kopingensis , Cretalamna sarcoportheta , Cretoxyrhina mantelli , Eostriatolamia segedini , E. venusta , Hispidaspis horridus , H. cf. gigas , Pseudocorax laevis , Pseudoscapanorhynchus compressidens , Scapanorhynchus rhaphiodon , Squalicorax kaupi , Ptychodus rugosus), a holostean (Lepisosteidae indet.), nine teleosts (Protosphyraena sp., Saurodontidae indet., cf. Pachyrhizodus sp., Pachyrhizodontidae indet., Enchodus petrosus , E. ferox , E. cf. gladiolus , E. spp., Alepisauroidei indet.), two plesiosaurs (Polycotylidae indet., Plesiosauria indet.), and one mosasaurid (Tylosaurinae indet.). Based on the faunal assemblage, a Santonian–?early Campanian age is proposed. Lamniform sharks are the best represented group in terms of taxic diversity and relative abundance, probably reflecting the peak in diversity this group experienced following the Cenomanian radiation in the Late Cretaceous. The faunal assemblage of Akkermanovka exhibits significant taxonomic overlaps with assemblages reported from Asia and North America, but not from Southern Hemisphere continents, indicating east–west dispersal of several marine taxa during the Late Cretaceous. [ABSTRACT FROM AUTHOR]

Mosasaurids were highly diverse and dominant as predators in late Cretaceous marine ecosystems. In the Maastrichtian, the Halisaurinae, a clade of relatively small-bodied mosasaurids, became common, especially in North Africa. Here, we report a new species of halisaurine from the lower Maastrichtian Dakhla Shale of the Western Desert of Egypt. Halisaurus hebae sp. nov. resembles Halisaurus platyspondylus and H. arambourgi in the shape of the frontal, suggesting close affinity with those species. A revised halisaurine phylogeny shows a cluster of species characterized by modification of the orbital bones to accommodate large eyes, suggesting a shift towards the use of visual cues to find prey, perhaps in low light conditions. The abundance and diversity of halisaurines in Africa contrasts with their relative rarity elsewhere in the world, emphasizing the regionalization of marine reptile faunas in the Maastrichtian. [ABSTRACT FROM AUTHOR]

The Mosasauridae underwent a major radiation early in the Late Cretaceous, with the subfamilies Plioplatecarpini and Tylosaurini appearing in the Turonian. Here we report an almost complete mosasaur skull assigned to the plioplatecarpine genus Yaguarasaurus. The specimen was discovered southwest of Vallecillo in the northeastern Mexico state of Nuevo Leon, about 80 km north of Monterrey, in a laminated limestone layer of the upper member of the Agua Nueva Formation (Upper Turonian - ?Lower Coniacian). The specimen is referred to as a new species, Y. regiomontanus. This is the first report of Yaguarasaurus from Mexico and the most complete of the Americas. At roughly 5 m in length, it is one of the earliest large mosasaurids. Along with Yaguarasaurus columbianus , Russellosaurus coheni , and an unnamed plioplatecarpine from Texas, it documents the rapid diversification and expansion of plioplatecarpines in the marine realm in the Turonian. • The Highlight of the paper is that is a new species of mosasaurus described for Mexico. [ABSTRACT FROM AUTHOR]

We describe and name a new mosasaur taxon, Sarabosaurus dahli gen. et sp. nov., from the lower Turonian part of the Tropic Shale in Utah, USA. The holotype specimen preserves significant portions of the skull and axial postcranial skeleton. It was found in the upper part of the Watinoceras devonense Ammonite Zone, bounded by radioisotopic dates above and below, and is thus about 93.7 Ma, the oldest mosasaurid taxon known from the Western Interior Seaway. The new taxon possesses a vascular pattern of the basisphenoid heretofore only seen in late diverging plioplatecarpine mosasaurids. Reevaluation of the morphology of the basisphenoid of previously described Turonian mosasaurs using μCT techniques reveals the derived condition is also present in Yaguasaurus and the incipient condition in Tethysaurus and Russellosaurus. In these two taxa, the canals enter the basisphenoid, but do not pass into the basioccipital. Instead, they exit only high on the posterior wall of the sella turcica, in a position similar to the basilar artery of other lizards. This vascular pattern, both in its incipient and derived states, is unique among squamates and supports inclusion of the aforementioned taxa in a monophyletic Plioplatecarpinae, for which we provide an emended diagnosis. Phylogenetic analysis recovers Sarabosaurus dahli gen. et sp. nov. as the sister taxon to Yaguarasaurus and all other later diverging plioplatecarpines, with Russellosaurus and Tethysaurus as successive sister taxa. Tylosaurine mosasaurids retain the primitive condition of the basisphenoid vascularization pattern and implies a tylosaurine-plioplatecarpine divergence in the late Cenomanian or earliest Turonian. [ABSTRACT FROM AUTHOR]

The Upper Cretaceous of Africa has produced a diverse fauna of mosasaurs, including the highly specialized, long-jawed Pluridens. The type of Pluridens walkeri comes from the Maastrichtian Farin-Doutchi Formation of Niger, with a second, referred specimen coming from the Campanian section of the Campanian-Maastrichtian Nkporo Shale near Calabar, in southern Nigeria. Comparisons of this referred specimen with the holotype suggest that it represents a distinct and more primitive species. The Calabar jaw resembles P. walkeri in being long and narrow anteriorly with a shallow subdental shelf, and in having small, numerous, recurved teeth with medially positioned replacement pits. However, it lacks many of the derived features that characterize Pluridens walkeri , such as the extremely long and straight jaw, the extreme lateral protrusion and subcircular section of the dentary, strong transverse expansion of the dental thecae, and extreme reduction and increase in number of the teeth. The Calabar Pluridens is therefore referred to a new species, Pluridens calabaria. Following recent studies, Pluridens is considered to represent a highly derived member of the Halisaurinae. The marked differences between the Campanian and Maastrichtian species of the genus underscore the rapid pace of mosasaur evolution during the Cretaceous. [ABSTRACT FROM AUTHOR]

The Cretaceous–Paleogene (K–Pg) transition saw mass extinctions in terrestrial and marine ecosystems. Terrestrial vertebrate diversity patterns across the K–Pg boundary have seen extensive study, but less is known about marine vertebrates. We describe a new mosasaurid from the latest Maastrichtian phosphatic beds of Morocco, showing how mosasaurids evolved to become apex predators in the latest Cretaceous. Thalassotitan atrox gen. et sp. nov., from the Oulad Abdoun Basin of Khouribga Province, Morocco is characterized by large size, a broad skull, massive jaws, and reduced cranial kinesis, suggesting it was highly adapted for carnivory. Teeth resemble those of killer whales in their robust, conical shape, and show heavy wear and damage. Phylogenetic analysis recovers Thalassotitan as a close relative of Prognathodon currii and P. saturator within the Prognathodontini. Among the associated fauna, three genera of mosasaurids, elasmosaurid plesiosaur, chelonioid turtle, and enchodontid fish show acid damage, and could be prey ingested by mosasaurids, likely Thalassotitan. Thalassotitan shows mosasaurids evolved to fill the marine apex predator niche, a niche occupied by orcas and white sharks today. Mosasaurs continued to diversify and fill new niches until their extinction at the end of the Cretaceous. [ABSTRACT FROM AUTHOR]

Mosasaurid squamates are the most numerically abundant, and taxonomically/ecologically diverse clade of marine amniotes represented in the Maastrichtian Phosphates of Morocco. With few exceptions, they are faunally typical of the Southern Mediterranean Tethys Margin (around palaeolatitude 25°N) and range from the base to the top of the stage. The Moroccan assemblages include at least 7 genera and 10 species representing a broad spectrum of sizes and morphologies that illustrate several ecological trends. Noteworthy is the predominance of Mosasaurinae which are widespread in contemporaneous outcrops worldwide and constitute 80% and 70% of the total genus/species number respectively. In contrast, Halisauromorpha and Russellosaurina (plioplatecarpines) are scarce and tylosaurines are presently unknown. All of the Moroccan mosasaurids exhibit characteristic tooth morphologies and can be placed into resource partitioning morphoguilds indicative of adaptations for piercing, crushing or cutting. Medium to large predators are found to distribute along the ‘Crush’–‘Cut’ axis of the morphoguild projection, and a new ‘Crush–Cut’ guild, previously unrecognised amongst Mesozoic marine amniotes, accommodates several Prognathodon species. Also of importance is the lack of mosasaurids along the ‘Pierce’–‘Crush’ axis, potentially inferring that these ecological niches were occupied by other marine vertebrates such as selachians and plesiosaurians. In addition, the relative abundance of mosasaurids throughout the Maastrichtian series of the Gantour Basin evidences direct ecological competition or predation phenomena. [ABSTRACT FROM AUTHOR]

Abstract: Taxonomy and stratigraphic distribution of the Upper Cretaceous marine reptiles from Japan are reviewed. Remains of the Chelonioidea (sea turtles), Mosasauridae, and Plesiosauria are known in various parts of Japan, including the holotypes of the dermochelyid Mesodermochelys undulatus, mosasaurine Mosasaurus hobetsuensis and M. prismaticus, tylosaurine Taniwhasaurus mikasaensis, and elasmosaurid Futabasaurus suzukii. Less diagnostic materials of other groups such as protostegiids, plioplatecarpines, polycotylids, pliosauroids, were also collected. Mesodermochelys dominates the chelonioid fauna, and in comparison with European and North American faunas, suggests a rather restricted geographical distribution of chelonioid species during the Late Cretaceous. The mosasaurid records support the world-wide trend of increasingly mosasaurine-dominated post-Santonian assemblages, and demonstrate suprageneric-level compositional changes in the northwestern Pacific through time. Elasmosaurid fossils are known from all stages of the Upper Cretaceous in Japan and indicate their continuous presence in the northwestern Pacific. Polycotylid remains are fewer in number and limited to the lower Upper Cretaceous. Pliosauroid specimens are even rarer but raise the upper limit of the stratigraphic range of the group in Northern Pacific to the Turonian. [Copyright &y& Elsevier]

Abstract: The Antarctic tylosaurine mosasaur Taniwhasaurus antarcticus (Upper Cretaceous, Campanian) is redescribed and rediagnosed based on the holotype. The reexamination of this specimen reveals that T. antarcticus is clearly distinguishable by a set of skull features from other species of the genus, including an almost straight fronto-parietal suture, the extreme reduction of the infrastapedial process of the quadrate, and the L-shaped coronoid. Phylogenetic analysis indicates that T. antarcticus and T. oweni are sister taxa, confirming their assignment to the same generic entity. The most striking feature of T. antarcticus is the configuration of the posterior terminus of the skull and its articulation with the quadrate. The posteroventral expansion of the supratemporal embraces medially the ventral half of the posterior border of the paroccipital process, preventing the quadrate head from extended posterior displacement. Although in T. oweni this region of the skull has not been preserved in natural position, the same configuration of the quadrate-supratemporal-squamosal and paroccipital process complex can be inferred based on the quadrate morphology. [Copyright &y& Elsevier]

Rare earth elements were analyzed from fossil marine reptile (Mosasauridae) bones collected from five superposed members (Sharon Springs, Gregory, Crow Creek, DeGrey, and Verendrye) of the upper Cretaceous Pierre Shale at localities along the Missouri River in Brule, Buffalo, Hughes, and Hyde counties in central South Dakota. Fossil bones from each member of the Pierre Shale have different rare earth element (REE) signatures that may be distinctive over wide geographic areas. Fossils from the Sharon Springs Member have distinctive REE signatures that may be further subdivided into three superposed groups that correspond with the upper, middle, and lower Sharon Springs Member. REE signatures are distinctive from each stratigraphic unit; therefore, fossils eroded from their stratigraphic context may be assigned to their proper depositional unit based on REE signature comparisons.Differences in REE compositions of bones among members appear to result from differential mixing of oxygenated and anoxic seawaters. If differences in mixing are interpreted as depth differences, the lower Sharon Springs Member was deposited in deep, anoxic water; water depths decrease in the middle and upper Sharon Springs, and the overlying Gregory and Crow Creek Members were deposited in even more shallow water. Finally, according to this interpretation, the overlying DeGrey and Verendrye members were deposited in progressively deeper marine waters, but not as deep as the lower Sharon Springs. These interpretations are generally consistent with those based on faunal diversity and eustatic sea level curves. [Copyright &y& Elsevier]

Mosasaurus beaugei Arambourg, 1952 was based on isolated teeth from the Maastrichtian phosphatic deposits of Morocco. The recent discovery of new material, including skull and mandibular remains, improves our knowledge of this species. M. beaugei shares the following synapomorphies with the genus Mosasaurus: large teeth bearing two prominent carinae and with asymmetrical labial and lingual surfaces, the labial one being flattened and strongly facetted and the lingual one being convex; premaxillae with a small pointed rostrum and dentary without rostrum; palatal elements closely united; coronoid with very large ventromedial process overlying the prearticular. M. beaugei is characterised by the following autapomorphies: 12-13 maxillary teeth; marginal teeth bearing 3-5 prisms on the labial surface and 8-9 on the lingual one; palatine with posterior border concave and perpendicular to the long axis of the skull; splenial visible laterally on half of the dentary ventral surface; coronoid with anterior wing well developed and bearing two notches. M. beaugei is only known to date in the Maastrichtian phosphates of Morocco. [Copyright &y& Elsevier]

Mosasaurids (Mosasauridae) were specialized marine lizards that evolved and radiated in the Late Cretaceous. Their diversity peaked in the Maastrichtian, with the most diverse faunas known from Morocco. Here we describe a new species of mosasaurid from this fauna. Pluridens serpentis sp. nov. is described based on two complete skulls and referred jaws. It is referred to Pluridens based on the elongate and robust jaws, small teeth, and specialized tooth implantation. Pluridens is referred to Halisaurinae based on the posteriorly expanded premaxilla, long premaxilla-maxilla suture, broad premaxillary facet on the maxilla, closed otic notch, and small, striated, hooked teeth. The orbits are reduced relative to other halisaurines while the snout is robust and flat with a broad, rounded tip. The jaws bear numerous small, hooked, snake-like teeth. Skulls imply lengths of 5–6 m; referred material suggests lengths of ≥9 m. Pluridens' specialized morphology – especially the contrasting large size and small teeth - suggests a distinct feeding strategy. Small orbits imply that P. serpentis relied on nonvisual cues including touch and chemoreception during foraging, as in modern marine snakes. Numerous neurovascular foramina on the premaxillae are consistent with this idea. The small teeth suggest proportionately small prey. The dentary becomes massive and robust in the largest individuals, suggesting sexual selection and perhaps sexual dimorphism, with the mandibles possibly functioning for combat as in modern beaked whales and lizards. The new mosasaur emphasizes how Maastrichtian mosasaurids were characterized by high species richness, high functional diversity, and high endemism, i.e. geographic specialization. It appears mosasaurids continued diversifying until the end of the Cretaceous, just prior to the K-Pg extinction. [ABSTRACT FROM AUTHOR]

The mosasaurids (Mosasauridae) were a group of lizards that became highly specialized for marine life in the mid-Cretaceous. By the end of the Cretaceous, they had undergone an adaptive radiation, and showed a wide range of body sizes, locomotor styles, and diets. Their ranks included piscivores, apex predators, and durophages. Here, we report a new taxon, Xenodens calminechari gen. et sp. nov., from the upper Maastrichtian phosphates of Morocco, with dental specializations unlike those of any known reptile. Teeth form a unique dental battery in which short, laterally compressed and hooked teeth formed a saw-like blade. Unique features of tooth structure and implantation suggest affinities with the durophagous Carinodens. The tooth arrangement seen in Xenodens not only expands known disparity of mosasaurids, but is unique among Squamata, or even Tetrapoda. The specialized dentition implies a previously unknown feeding strategy, likely involving a cutting motion used to carve pieces out of large prey, or in scavenging. This novel dental specialization adds to the already considerable disparity and functional diversity of the late Maastrichtian mosasaurids and marine reptiles. This provides further evidence for a diverse marine fauna just prior to the K-Pg extinction. [ABSTRACT FROM AUTHOR]

Dental morphology, microstructure and chemistry provide unique insights into various aspects of the evolutionary history and ecology of extinct clades. However, most studies have focused exclusively on the morphological aspects of teeth, while there are significantly fewer detailed accounts of tooth microstructure and mineralogy. Here we provide a full description of the enamel and dentine microstructure of mosasaurid squamates based on an assessment of isolated teeth belonging to two distantly related mosasaurid taxa, i.e., a russellosaurinan and a mosasaurine, from the ?Coniacian–Santonian and Maastrichtian of Belgium. The obtained data are further explored with regard to their value for inferences of mosasaurid predatory behaviour. SEM observations have shown that the Schmelzmuster consists of columnar enamel with an outer layer of parallel crystallites; transmitted light observations have further revealed the presence of mantle dentine cushioning between enamel and orthodentine, and electron microprobe analyses have demonstrated the unaltered enamel chemistry and heterogeneous diagenetic alteration of dentine. Columnar enamel allows minute movements without rupture under bending stress, and together with the presence of shock-absorbing mantle dentine and possibly elevated Fe contents in the enamel, which increase its hardness and enhance acid resistance, it is suggestive of a good ability of the teeth to withstand severe mechanical damage. Such properties of teeth indicate adaptation to shaking and tearing large and resisting prey. [ABSTRACT FROM AUTHOR]