Three durophagous mosasaur species are represented by isolated teeth in the Upper Cretaceous (Maastrichtian) phosphatic beds of Morocco. Globidens phosphaticus nov. sp. is characterised mainly by a strong heterodonty, with mid-posterior teeth being bulbous, irregularly oval in crosssection, and having an inflated posterior surface, a large eccentric located and recurved apical nubbin, vertical sulci on medial and lateral faces, no carinae and an enamel surface covered by anastomosing ridges. Teeth of Prognathodon currii are broad and tall, straight cones, slightly swollen at the base, and with two serrated carinae. These two taxa have been collected from all the phosphatic series (lower to upper Maastrichtian) in the Ganntour Basin (Morocco). Globidens phosphaticus nov. sp. is probably also represented at other Maastrichtian phosphatic sites along the southern margin of the Mediterranean Tethys. Prognathodon currii was previously known only from the Upper Cretaceous phosphates of Negev. Of the third taxon, Carinodens belgicus, only a single tooth (now lost) is known from the Oulad Abdoun Basin (Morocco); this is low, swollen, laterally compressed and bicarinate with a large apical nubbin. Previous records of this species include Europe and Brazil.

A new genus and species of primitive-limbed mosasauroid, Dallasaurus turneri, from the Middle Turonian (∼92 Ma) of north-central Texas, is described on the basis of two incomplete skeletons. The new taxon retains plesiomorphic characters such as facultatively terrestrial limbs (plesiopedal) but also exhibits certain characters shared with derived mosasaurs of the subfamily Mosasaurinae. In phylogenetic analysis, the new taxon reconstructs as the basal member of that clade. Other plesiopedal taxa previously included in the family Aigialosauridae reconstruct in basal positions within three different, major clades that include members that achieved the derived (hydropedal) fin-like limb condition. In addition, Opetiosaurus and Aigialosaurus reconstruct as successive outgroup taxa to all other mosasauroids, thereby demonstrating the paraphyletic nature of the current concept of Aigialosauridae. Interpretation of our phylogenetic analysis suggests that three different lineages of mosasauroids independently achieved the derived mosasaur body plan, including fully marine limb modifications culminating in the development of flippers or paddle-like appendages. The inclusion of plesiopedal forms within lineages of well-established hydropedal clades requires a reorganisation of our concepts of Mosasauridae to include these basal forms. In order to avoid continued use of the paraphyletic taxon ‘Aigialosauridae’ as currently defined, we recommend ‘Aigialosauridae’ as a formal taxonomic name be used only for inclusion of Aigialosaurus dalmaticus and potential members of its own independent lineage. This also avoids the implicit polyphyletic use of ‘Mosasauridae’. Additionally, the diagnosis of Mosasauridae should be modified to exclude limb characters that discriminate between more terrestrial versus more aquatic adaptations.

Recent work in the Upper Cretaceous of northeastern Mexico has produced a diversity of vertebrate remains. For specimens referable to Squamata, both old and new, an annotated catalogue is here provided, wherein are summarised the geological context and morphological features of each specimen. All specimens appear to represent marine squamates, including an aigialosaur-like reptile preserving integumentary structures, several vertebrae possibly representing mosasauroids, the first Mexican mosasaur known from significant cranial material, an isolated mosasaur mandibular fragment, and the holotype of Amphekepubis johnsoni (considered to belong to Mosasaurus). These discoveries are auspicious and should deepen our understanding of palaeobiogeographic and evolutionary patterns

The lost snout of Richard Harlan’s specimen of Mosasaurus missouriensis has been rediscovered in the vertebrate palaeontology collections of the Muséum national d’Histoire Naturelle (MNHN) in Paris, France. The specimen (MNHN 9587) bears the handwritten description, ‘Amérique du Nord. Par M. Harlan.’, which translated reads, ‘North America. By/From Mr. Harlan’. Accession information indicates the specimen was a gift to the museum prior to 1860 and was likely gifted from Harlan’s estate after his death. We examine the available history of the collection of the specimen present a description of the rediscovered snout, and demonstrate conclusively the conspecificity of M. maximiliani Goldfuss, 1845 and M. missouriensis (Harlan, 1834a) by providing a revised diagnosis of the taxon.

The mosasaurine Clidastes sp. is recognised from cranial and post-cranial remains collected at four localities in NW Germany. Cranial material was found in pelagic turbiditic marls which crop out near the village of Beckum, while post-cranial skeletal elements were collected from sandy limestones exposed near the villages of Schöppingen, Coesfeld and Billerbeck. In stratigraphic order, the units producing these specimens of Clidastes are the Coesfeld, Baumberge and Beckum formations of late Campanian (Late Cretaceous) age. The cranial material comprises the anterior part of a skull and a single isolated tooth, while post-cranial bones comprise a few isolated vertebrae and a partial skeleton including forelimb bones and an articulated vertebral column. Clidastes is known to date from the western North Sea Basin (England), southern Sweden, as well as from North America (Western Interior Seaway and Gulf Coast).

Aigialosaurs have been recognised as a group of semi-aquatic marine reptiles for over one hundred years. While the taxonomic status of aigialosaurs has changed little in the past century, the interfamilial relationships have been modified considerably making the phylogenetic relationships between aigialosaurs, mosasaurs, dolichosaurs, coniasaurs, varanids and other squamates a topic of much debate. The monophyly of the family Aigialosauridae has been contested by recent studies and remains highly questionable. The higher-level relationships of mosasauroids within Squamata remain problematic with studies placing mosasauroids outside of Varanidae, Varanoidea and even Anguimorpha. These findings conflict with earlier views that aigialosaurs (and by association mosasaurs) were closely related to Varanus. This study concludes that further descriptions of aigialosaur taxa are needed, and several key flaws need to be addressed in the data matrices that have been used in previous studies. This should facilitate the clarification of aigialosaur systematic relationships both within Mosasauroidea and Squamata.

Tylosaurus kansasensis sp. nov. is described herein on the basis of thirteen specimens collected from the Smoky Hill Chalk (upper Coniacian) of western Kansas, USA. The new species, originally designated Tylosaurus n. sp., co-occurred with T. nepaeolicus and exhibits a number of primitive characters that place it in a basal position in the mosasaur phylogeny. Among the key differences separating this species from other tylosaurines are a shortened, more rounded pre-dental process of the premaxilla, a distinctive quadrate lacking an infrastapedial process, and a parietal foramen located adjacent to the frontal-parietal suture.

The Upper Cretaceous deposits of New Jersey and Delaware produced the first mosasaur specimens collected in North America. Recent recovery of mosasaur specimens from streambank exposures and new excavation sites has increased our knowledge of the stratigraphic distribution of these animals in the northern Atlantic coastal plain. Reassessment of the source and age of mosasaur specimens from the Big Brook site and other localities in Monmouth County (NJ) has greatly increased the number of known Campanian mosasaur specimens from this region. Two main taphonomic occurrence modes are noted: 1 - single, worn and broken bones and isolated teeth in mixed faunal deposits probably accumulated due to current action in nearshore environments; 2 - partial skeletons, skulls and single bones in deeper-water settings were the aftermath of biological modification of carcasses and deadfalls. The mosasaurs of the New Egypt Formation represent some of the last (i.e., stratigraphically highest) mosasaur fossils in North America. Mosasaur extinction was due to the collapse of the rich Late Cretaceous marine food web at the K/T boundary. Subsequently in the early Paleocene, with the disappearance of the mosasaurs, crocodilians became the apical predators of the marine environment in this area.

We describe a new marine varanoid, Judeasaurus tchernovi gen. et sp. nov., on the basis of a partial skull recovered from the Middle Cenomanian of the Judean Hills. The new taxon possesses a unique suite of characters exhibited in terrestrial varanoid lizards on the one hand and derived mosasauroids on the other. The characters that relate it to terrestrial varanoid lizards include broad premaxilla, anteriorly depressed maxillae underlying the nasal capsule, extensive postorbitofrontal-parietal contact and vertically oriented parietal rami. Derived mosasauroid characters include a question-mark shaped quadrate, fused frontals, intricate fronto-parietal suture and moderately retracted nares. The shape of the supratemporal and its syndesmotic articulation with the parietal distinguishes the new taxon from any other known specimen. The dentition exhibits elongate and narrow cylindrical roots lacking resorption pits, a condition reminiscent of Coniasaurus, but crowns are small, slightly recurved and conical. Taken together, the new taxon possesses a suite of characters suggesting dolichosaurid affinities.

Sediments in north-central Texas, ranging in age from >117 to 85 Ma, represent a variety of terrestrial and marine depositional settings. Isotopic analyses of wood fragments found throughout the section allow correlation to the standard secular marine δ13C curve because of characteristic peaks at the Aptian-Albian and Cenomanian-Turonian boundaries. Consistency of the north-central Texas δ13C curve with the marine standard facilitates correlation among non-marine and marine environments on a global scale. Radiometrically dated ammonite zones recognised in Texas provide calibration for the Cenomanian and Turonian portions of the section. Cenomanian and Turonian sediments in north-central Texas preserve the oldest (96 Ma) and the youngest (<85 Ma) well-documented Coniasaurus, a dolichosaur also known from the southern North Sea Basin during that interval. Haasiasaurus, the oldest known well-documented early mosasaur, is found at ‘Ein Yabrud, Israel (98 Ma), followed by other poorly dated Cenomanian taxa from the eastern Mediterranean region, and then by Dallasaurus turneri and Russellosaurus coheni in Texas (92 Ma) and Tethysaurus (90.5 Ma) in Morocco. Neither shifts in δ13C nor large-scale sea level change seem to have influenced dolichosaur or mosasaur evolution in substantial ways during the Cenomanian and Turonian stages.

The north-central Texas Cretaceous section and its contained fossils, as compared to sections at ‘Ein Yabrud in the eastern Mediterranean region, demonstrate that dolichosaurs and primitive mosasaurs inhabited marine environments at least from the intertidal zone to <100 m in depth. The small body size of dolichosaurs and primitive mosasaurs, and the association of Haasiasaurus with marine snakes at ‘Ein Yabrud, suggest similar temperature requirements to modern sea snakes and marine iguanas (Amblyrhynchus cristatus), specifically sea-surface temperatures between approximately 20° and 30° С The Cenomanian and Turonian stages are characterised by widespread shallow seas with relatively high sea-surface temperatures extending to at least 45° N and 65° S latitude. The distribution of dolichosaurs, mosasaurs and snakes during this interval contradicts palaeoclimate models that predict high (>30° C) equatorial sea-surface temperatures and a steep latitudinal temperature gradient in the Northern Hemisphere.

Mosasaur taxa currently known from Campanian-Maastrichtian strata in the Liège-Limburg (SE Netherlands, NE Belgium) and Mons (southern Belgium) basins are listed and briefly discussed and their stratigraphic ranges indicated. Recently published and/or ongoing work on coleoid and ammonoid cephalopods in these areas allows tie points between NW Europe and the United States (Western Interior, Gulf Coast, Atlantic Seaboard) to be established. Future studies need to refine the resultant, rather crude, scheme. The ultimate aim is a more robust picture of mosasaur taxonomy, biostratigraphy and palaeobiogeography, and a detailed evaluation of migratory patterns across the Atlantic.

Two isolated mosasaur teeth, one from the upper Campanian of Piotrawin, the other from the upper Maastrichtian at Nasilów (Wisla River valley, central Poland), recently described as Plioplatecarpinae sp. A and Plioplatecarpinae sp. B, respectively, are reassigned to the tylosaurine genus Hainosaurus Dollo, 1885. The present record thus adds to the list of Hainosaurus species known to date from elsewhere in Europe (Sweden, Belgium and England).

Mosasaurs are rare in Australia with fragmentary specimens known only from the Cenomanian-lower Turonian Molecap Greensand (Perth Basin), Campanian - lower Maastrichtian Korojon Calcarenite (Carnarvon Basin), and upper Maastrichtian Miria Formation (Carnarvon Basin), Western Australia. These units were laid down during a near-continuous marine inundation of the western margin of the Australian landmass (which followed separation from India in the Valanginian and genesis of the Indian Ocean) in the Early-Late Cretaceous. The Australian mosasaur record incorporates evidence of derived mosasaurids (mainly plioplatecarpines); however, as yet no specimen can be conclusively diagnosed to genus or species level. The fragmentary nature of the remains provides little basis for direct palaeobiogeographic comparisons. However, correlation with existing data on associated vertebrates, macroinvertebrates and microfossils suggests that the Western Australian mosasaur fauna might have been transitional in nature (particularly following palaeobiogeographic separation of the northern and southern Indian Oceans during the mid-Campanian), potentially sharing elements with both northern Tethyan and austral high-latitude regions.

Presented are the first formal descriptions of mosasaur remains of Maastrichtian age from the Danish mainland (Jylland, Sjælland); just two taxa are recognised, viz. Mosasaurus cf. hoffmanni and Plioplatecarpus sp. Recent finds include an association of skeletal fragments, inclusive of a single marginal tooth crown, from within 10 metres or so of the K/T boundary near Holtug, Stevns Klint (Sjælland, eastern Denmark), here assigned to Plioplatecarpus sp. A brief review of previous records of Danish mosasaurs is added.

A new mosasaur, Russellosaurus coheni, is described from the Collignoniceras woollgari Zone (lower Middle Turonian) at Cedar Hill, Dallas County, Texas. At approximately 92 Ma, it is the oldest well-preserved mosasaur skull from North America. It possesses characters diagnostic of Plioplatecarpinae but retains numerous plesiomorphies as well. Phylogenetic analysis indicates a close relationship with Yaguarasaurus columbianus, and these two, together with Tethysaurus nopcsai, form a clade that occupies a position basal to the divergence of the subfamilies Tylosaurinae and Plioplatecarpinae. Russellosaurus coheni is proposed as the nominal taxon of a new mosasaur clade, parafamily taxon novum Russellosaurina, which includes Plioplatecarpinae, Tylosaurinae, their common ancestor and all descendants. Tethysaurus retains a plesiopedal limb and girdle morphology, and along with Russellosaurus and Yaguarasaurus, cranial plesiomorphies. Dallasaurus turneri, a temporally and geographically sympatric plesiopedal mosasaur, occupies a basal position within Mosasaurinae. This phyletic arrangement confirms that marine adaptations, such as development of paddle-like limbs, occurred independently in at least two lineages of mosasaurs, once within Mosasaurinae and once within Russellosaurina.

Shark bite marks on mosasaur bones abound in the fossil record. Here we review examples from Kansas (USA) and the Maastrichtian type area (SE Netherlands, NE Belgium), and discuss whether they represent scavenging and/or predation. Some bite marks are most likely the result of scavenging. On the other hand, evidence of healing and the presence of a shark tooth in an infected abscess confirm that sharks also actively hunted living mosasaurs.

Recognition of decompression syndrome-related pathology (in the form of avascular necrosis) reveals diving behaviour in mosasaurs. Macroscopic and radiologic examination was performed to identify linear bone death characteristic of avascular necrosis in vertebrae from the major North American and European collections. This survey of mosasaurs extends throughout most of their geographic and stratigraphic range and includes examples across their diversity.

Avascular necrosis was invariably present in Platecarpus coryphaeus and P. ictericus, Tylosaurus proriger, Mosasaurus lemonnieri and M. conodon, Plioplatecarpus houzeaui and Pl. primaevus, Prognathodon giganteus, Hainosaurus bernardi and an as yet unnamed Antarctic mosasaur. The frequency of occurrence in a given genus was independent of geography, present equally in European and North American and in the Niobara and Selma chalks. It was invariably absent from Clidastes propython and C. liodontus, Ectenosaurus, Halisaurus and Kolposaurus.

The bone pathology, avascular necrosis, has a characteristic distribution in seven genera and thirteen species of mosasaurs and is absent in five genera and seven species. It segregated according to diving habits, uniformly present in supposed deep divers and uniformly absent in the shallow-habitat group.