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Maxillae. (a) IRSNB R 26 right lateral view (reflected). (b) MNHN AC 9648 right medial view and (c) the same outlined to highlight the palatine and vomer. Abbreviations: M – maxilla; Pl – palatine; Pt – pterygoid; Vo – vomer. Note: letters visible on the fossil have been painted on the specimen and bear no association with the labelling system of this study. Scale bar equals 5 cm.
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The large Late Cretaceous marine reptile
Mosasaurus
has remained poorly defined, in part owing to the unorthodox (by today's nomenclatural standards) manner in which the name was erected. The lack of a diagnosis accompanying the first use of either the genus or species names allowed the genus to become a catchall taxon, and subsequent diagnoses did...
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... lateral surface (Fig. 3a) of the maxilla is perforated by a series of foramina dorsal to the tooth row. The maxilla of MNHN AC 9648 (Fig. 3b) is blunt anteri- orly, where the maxillary/premaxillary suture ascends steeply, nearly vertically, from the tooth margin. This morphology differs in IRSNB R 26, and additionally in NHMM 006696, where the maxilla is short ...
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... lateral surface (Fig. 3a) of the maxilla is perforated by a series of foramina dorsal to the tooth row. The maxilla of MNHN AC 9648 (Fig. 3b) is blunt anteri- orly, where the maxillary/premaxillary suture ascends steeply, nearly vertically, from the tooth margin. This morphology differs in IRSNB R 26, and additionally in NHMM 006696, where the maxilla is short in height anteriorly, and the maxillary/premaxillary suture as- cends at approximately 35° (Fig. 3a). After the ...
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... maxilla of MNHN AC 9648 (Fig. 3b) is blunt anteri- orly, where the maxillary/premaxillary suture ascends steeply, nearly vertically, from the tooth margin. This morphology differs in IRSNB R 26, and additionally in NHMM 006696, where the maxilla is short in height anteriorly, and the maxillary/premaxillary suture as- cends at approximately 35° (Fig. 3a). After the suture turns posteriorly, the dorsal margin of the maxilla rises at a shallow angle until the border is even with the posterior margin of the third maxillary tooth (Fig. 3b). The dorsal margin and tooth row are each straight and the two diverge only slightly from each other, with the maxilla increasing only slightly in ...
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... IRSNB R 26, and additionally in NHMM 006696, where the maxilla is short in height anteriorly, and the maxillary/premaxillary suture as- cends at approximately 35° (Fig. 3a). After the suture turns posteriorly, the dorsal margin of the maxilla rises at a shallow angle until the border is even with the posterior margin of the third maxillary tooth (Fig. 3b). The dorsal margin and tooth row are each straight and the two diverge only slightly from each other, with the maxilla increasing only slightly in height posteriorly, until the level of the eleventh tooth, at which point the height of the element decreases rapidly to form the nar- row posterior process of the maxilla. Mosasaurus hoff- ...
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... palatine of MNHN AC 9648 is crushed against the maxilla obscuring its morphology (Fig. 3b, c). Vent- rally, the palatine is a flat plate of bone with a pos- terior triangular fossa for articulation with the anterior end of the pterygoid. A blunt ridge, most prominent medially, bounds this depression. Anteriorly there is a deep, U-shaped embayment surrounded by an anter- olateral process, which is flat, broad and articulates ...
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Citations
... Mosasaurus hoffmannii is known from a wide geographical distribution of Maastrichtian fossil sites in and around the Western Interior Seaway of North America, the North American Atlantic Coastal Plain, and the Northern Margin of the Mediterranean Tethys (Russell 1967). Its remains have been found in Belgium, Bulgaria, Denmark, Germany, Italy, Morocco, Spain, the Netherlands, Poland, Turkey, Russia, and the United States (Bardet 2012;Street and Caldwell 2017;Rempert et al. 2024). ...
During April 2022, offshore dredging for a storm damage beach renourishment project placed large quantities of Upper Cretaceous (upper Maastrichtian) Peedee Formation sediment onto the shores of Holden Beach in Brunswick County, North Carolina, USA. The Cretaceous sediment is highly fossiliferous and has yielded a rich and diversified assemblage of fossils from mosasaurid reptiles. New fossil material, namely isolated teeth, consists of several dental morphologies from the mosasaur subfamilies Halisaurinae and Mosasaurinae. Five species are recognized: Halisaurus sp., Mosasaurus cf. beaugei Arambourg, 1952, Mosasaurus cf. hoffmannii Mantell, 1829, Prognathodon cf. solvayi Dollo, 1889 and Prognathodontini indet. In this assemblage, prognathodontins predominate, being the most abundant marine reptile find, with all other species being comparatively rare. The mosasaur assemblage of North Carolina shows close affinity with the phosphates of Morocco, containing species typical of both the northern and southern margins of the Mediterranean Tethys. These new discoveries improve our knowledge of the biodiversity of mosasaur fauna from the late Maastrichtian of North Carolina and add to the known paleobiogeographical distribution of these taxa. The material described within was collected courtesy of the efforts of amateur fossil hunters and seasonal tourists combing Holden Beach for fossilized remains.
... The previously undescribed vertebrae GG 501, GG 502 and UHKD500005 exhibit a greater similarity to plesiosaurs than to mosasaurs and ichthyosaurs. Mosasaurs typically have procoelous vertebrae (e.g., Street and Caldwell, 2017;Sachs et al., 2018), whereas ichthyosaurs have disk-like centra throughout the axial skeleton (e.g., McGowan and Motani, 2003;Maxwell et al., 2012), with a deep concavity on their anterior and posterior articular facets, distinct but simple neurocentral and lateral articular facets and no (large and obvious) foramina. Thus, all vertebrae can most likely be referred to as plesiosaurs (for GG 422/2, GG 422/3 and the unregistered GPIH vertebrae see Stumpf, 2016 andSachs et al., 2016). ...
Mesozoic vertebrate fossils within glacially transported deposits of Pleistocene
age are rare. Here, we examine five isolated, strongly eroded vertebrae of Mesozoic
marine reptiles, most probably plesiosaurs, from glacigenic sediments of northern Germany. In addition, three consecutive plesiosaur vertebrae, having already been
described in previous publications, are briefly reconsidered. For one heavily eroded
specimen, litho- and biostratigraphical analyses of associated sediment, including thin sectioning and calcareous nannofossil investigations, confirm a mid-Cretaceous age. The internal morphology of the five isolated vertebrae in focus, investigated with the help of microCT, reveals the presence of (neuro)vascular cavities within the respective centra. Unexpectedly, we found diverse internal cavity patterns which have only one feature in common: a medial pair of foramina on the floor of the neural canal that is connected to deep-reaching canals.
... Nearly all the vertebral processes in Mosasaurus spp. cervicals are heavily "buttressed" [88], or have wide, sloping bases, but the synapophyses in NVP025 are more "discrete" in that they arise more abruptly from the sides of the centrum. NVP025 differs from Mosasaurus hoffmannii [89] in that the space between the prezygapophyses is wider in M. hoffmannii than in NVP025 (as in the space across the midline between the prezygapophyses of a single vertebra) [88]. ...
... cervicals are heavily "buttressed" [88], or have wide, sloping bases, but the synapophyses in NVP025 are more "discrete" in that they arise more abruptly from the sides of the centrum. NVP025 differs from Mosasaurus hoffmannii [89] in that the space between the prezygapophyses is wider in M. hoffmannii than in NVP025 (as in the space across the midline between the prezygapophyses of a single vertebra) [88]. The prezygapophyses and hypophyses are relatively taller in NVP025 than in M. hoffmannii. ...
Mosasaurs were diverse in the Upper Cretaceous in Africa, but relatively little is known about the mosasaur fauna of Egypt. Here, associated teeth and postcranial skeletal elements are reported for a mosasaur from the Maastrichtian Dakhla Shale of the Dakhla Oasis. The specimen includes tooth crowns, cervical, dorsal, and caudal vertebrae, and ribs. Teeth and bones exhibit features allowing referral to Prognathodontini. The teeth are relatively straight and blunt, suggesting affinities with Prognathodon overtoni or P. currii. Prognathodontins were important predators in the Maastrichtian of Africa, previously being recorded in Morocco, Congo, and Angola.
... The dorsal crest does not reach the posterior margin of the bone. A groove is present along the midline of the anterior half of the frontal; this feature was interpreted by Street and Caldwell (2017) as separate dorsal and ventral grooves that articulate with the premaxilla. Because the anterior process of NDGS 10838 is broken, and the grooves are dorsoventrally continuous, we posit that this structure may also represent incomplete fusion of separate left and right frontals. ...
... 22). It is slender and simple, as it is in Clidastes (e.g., Clidastes liodontus AMNH FARB 192) and, like Clidastes, lacks the posteroventral process present in most other mosasaurids (e.g., Tylosaurus proriger FHSM VP-3, Mosasaurus hoffmannii MNHN AC 9648; Street and Caldwell, 2017), interpreted by Russell (1967: 24) as the attachment point for the quadratomaxillary ligament. The medial surface is concave, and, while broken anteriorly, bears a deep sulcus that would have received the lateral process of the ectopterygoid. ...
... 23). In dorsal and ventral views, they approximate a curved arrow, with a triangular body and long, slightly curved anterior ramus; overall, the squamosal is more slender in NDGS 10838 than in Mosasaurus hoffmannii (Street and Caldwell, 2017). The ventral margin is recurved and medially inset posteriorly, producing a pointed, anteriorly oriented process that marks the beginning of the quadrate facet, which is narrow and triangular in ventral view. ...
Mosasaurs are large, carnivorous aquatic lizards with a global distribution that lived during the Late Cretaceous. After 200 years of scientific study, new mosasaur species are still being discovered as new localities are explored and specimens collected long ago are reevaluated using modern standards of species delimitation. Even so, the phylogenetic positions of many key taxa are unresolved and therefore our understanding of mosasaur macroevolution is muddled. Here, we describe a new genus and species of mosasaurine mosasaur comprising a partial skull and skeleton from the Pembina Member of the Pierre Shale Formation in Cavalier County, North Dakota. The lower bound on the age of the specimen is 80.04 ±0.11 Ma, provided by the underlying bentonite bed. Its skull and jaws are nearly complete, and the postcranial skeleton preserves seven cervical vertebrae with three hypapophyseal peduncles, 11 ribs, and five anterior dorsal vertebrae. The new specimen was scored into a modified version of an existing phylogenetic matrix of Mosasauroidea and was recovered in a polytomy with Clidastes; however, given that its morphology is significantly different from that of Clidastes, we refer it to a new genus and species, Jormungandr walhallaensis. Notably, this new taxon shares a mosaic of features seen in both basal (e.g., Clidastes; high dental counts) and derived (e.g., Mosasaurus; subrectangular quadrate) mosasaurines, in addition to possessing its own unique suite of autapomorphies. Given that it possesses morphology intermediate between Clidastes and Plotosaurini, we suspect that future analyses of mosasaur phylogeny, following the addition of new characters and taxa, will recover Jormungandr as transitional between them. Its occurrence increases the known diversity of mosasaurs from the Pembina Member and is the earliest mosasaur to possess autapomorphies of Plotosaurini. Finally, we also analyzed the matrix using different outgroups to test their effect on tree topology and resolution, and found that including multiple nonmosasauroid anguimorphs increased resolution, but not support, of mosasaurid ingroup relationships.
... Both these muscles would abducted and protracted the humerus as in extant turtles and lizards (e.g., Walker 1973, Pereyra et al. 2019. Notably, the M. latissimus dorsi scar in IAA-Pv 819 is also more extensive than in other mosasaurines (e.g., Russell 1967, Street & Caldwell 2017, Ikejiri & Lucas 2015. ...
... The dorsal vertebra of M. hoffmannii figured by Street and Caldwell, (2017, figure 18, p.545) shares some similarities with the vertebra from St Lucia although, the posterior zygapophyses are larger and extend far more laterally in the St Lucia vertebra than in M. hoffmannii. The zygantra at the base of the neural spine in the M. hoffmannii dorsal vertebra (Street and Caldwell, 2017) do not look like those triangular concavities suggested to be zygantra in the St Lucia vertebra. However, the difference in the shape of the zygosphenes and zygantra depends on the vertebral position. ...
Until recently, only one mosasaur was identified in South Africa based on disarticulated skull bones including two dentary fragments and a frontal with articulated elements. These were discovered in 1901 in Pondoland, Eastern Cape and were initially described by Broom in 1912 when he assigned them to Tylosaurus capensis. Aside from this specimen, two other mosasaur remains are known but have remained undescribed and include an isolated muzzle unit and an isolated vertebra. The current study provides a morphological description and taxonomic interpretation of all the mosasaur remains discovered in South Africa. It is suggested that the specimen originally assigned to Tylosaurus is a mosaic of two taxa: A dentary fragment and frontoparietal show affinities with Prognathodon, while a second dentary fragment shows features similar to those of Taniwhasaurus. The muzzle unit presents Prognathodon-like features, and a more recently discovered incomplete vertebra is referred to as an indeterminate Plioplatecarpine. We therefore recognize at least three mosasaur taxa from the Late Cretaceous deposits of South Africa, which we tentatively refer to cf. Prognathodon, cf. Taniwhasaurus, and cf. Plioplatecarpinae. A shark tooth that was embedded in the matrix around the Prognathodon muzzle unit was identified as a Squalicorax pristodontus (Late Campanian to Late Maastrichtian). Strontium analysis of the mosasaur tooth enamel from the same muzzle unit of the cf. Prognathodon material was dated to Late Maastrichtian (⁸⁷Sr/⁸⁶Sr = 0.707817; age = 66.85Ma).
... Mosasaurus had a complex taxonomic history, with at least 50 species referred to it but several of them are junior synonyms of former species or have been assigned to other genera. Currently, there are ten species recognized within Mosasaurus but some of them are under revision (Street and Caldwell, 2017). Some of the better-known taxa include the type species M. hoffmannii Mantell, Bardet et al., 2000;Konishi et al., 2014;Ikejiri and Lucas, 2015;Street and Caldwell, 2017). ...
... Currently, there are ten species recognized within Mosasaurus but some of them are under revision (Street and Caldwell, 2017). Some of the better-known taxa include the type species M. hoffmannii Mantell, Bardet et al., 2000;Konishi et al., 2014;Ikejiri and Lucas, 2015;Street and Caldwell, 2017). The number and size of facets formed by the enamel of the marginal teeth are often used to diagnose species of Mosasaurus (Sakurai et al., 1999;Bardet et al., 2004). ...
... Mosasaurus hoffmannii has two to three facets on the labial side of the crown and no facets on the lingual side, M. missouriensis has four to six labial facets and eight lingual facets, M. lemonnieri has eight to ten labial facets, and M. beaugei has three to five labial facets and eight to nine lingual facets (Bardet et al., 2004). With the exception of M. conodon, most species of Mosasaurus display some sort of enamel ornamentation, but it can be highly variable from individual to individual, along the tooth row, or even with tooth ontogeny (Street and Caldwell, 2017). ...
Remains of Cretaceous vertebrates have been scarce in the fossil record of Cuba, but recent exploration of Upper Cretaceous outcrops in the central part of the island has led to the discovery of new fossil-bearing deposits from nearshore depositional environments. Here, we report upon two isolated marginal teeth, which we identified as belonging to the genus Mosasaurus. The specimens described here, recovered from two upper Campanian – lower Maastrichtian outcrops in central Cuba, represent the first record of mosasaurs from the West Indies, and along with other marine fossils suggest that the Caribbean played an important role in the faunal interconnection across seaways and oceans in the region.
... choteauensis, 5) Spinaptychus sternbergi, and 6) Hesperornis; and Carpenter (2008) added a seventh zone, Dolichorhynchops, to represent the overlying Sharon Springs Member. Previously described stratigraphic species ranges of particular vertebrate taxa useful for defining assemblage zones include those of the shark Squalicorax of the North American Western Interior (Underwood and Cumbaa, 2010;Shimada and Cicimurri, 2005;Bice and Shimada, 2016), the fish Enchodus of the North American Western Interior (Parris et al., 2007), the turtle Toxochelys of SD (Carrino, 2007), hesperornithiform birds of southwestern MB (Aotsuka and Sato, 2016), polycotylid marine reptiles of KS (Everhart, 2003) and the North American Western Interior (McKean, 2012), mosasauroid marine reptiles of TX (Bell Jr. et al., 2013), plioplatecarpine mosasaurs worldwide (Konishi and Caldwell, 2011), mosasaurine mosasaurs worldwide (Street and Caldwell, 2017), and tylosaurine mosasaurs worldwide (Jiménez-Huidobro and Caldwell, 2019). Since Ludvigsen et al. (1986) recommend using a single taxon to define zones based on species-range data, taxa with the longest and most continuous stratigraphic ranges, as well as high abundance of fossil remains, were considered for definition of assemblage zones. ...
Community zonation of the Late Cretaceous Western Interior Seaway (WIS) has been suggested for bivalves, cephalopods, foraminifera, gastropods, and tetrapods. Most proposed WIS community zones consist of a northern and southern subprovince with a gradational boundary across central or south-central North America. Since it has been over three decades since the WIS community zonation hypothesis has been investigated for vertebrates, recent radiometric age determinations, taxonomic revisions, additional specimen discoveries, and recently available online museum specimen catalogues allow for an updated description of Manitoba (MB) escarpment faunal assemblages and testing of the community zonation hypothesis. Nine time bins were used to represent nine Upper Cretaceous lithostratigraphic units of the MB escarpment to test the zonation hypothesis consistency for nearly the entire Late Cretaceous (~71–95 Ma). Relatively high genus-level community similarity values (25–50%) of south-central WIS localities and low values (<20%) of localities furthest north and south support the existence of a central subprovince during late Cenomanian to early Turonian and late Coniacian to early Campanian times, when the gradational subprovincial boundary would have been furthest south between Kansas and Texas localities. Comparatively low genus-level community similarity values (<25%) of all localities south of MB during mid-Cenomanian and early to mid-Campanian times indicate the southern subprovincial boundary was farthest north between MB and South Dakota localities during these time intervals and had migrated throughout the Late Cretaceous. This work highlights significant fluctuations in vertebrate community zonation throughout the WIS through time and space and offers insight into the magnitude of compositional and palaeoecological changes that can occur in shallow marine vertebrate communities over an approximately 25 million year interval.
... Achieving a total body length of 14 m and exhibiting robust jaws lined with sharp, weakly prismatic teeth, M. hoffmannii would have fed at the apex trophic level of the Late Cretaceous marine ecosystem (Lingham-Soliar, 1995;Street and Caldwell, 2017). First discovered over 200 years ago in the upper Maastrichtian chalk quarries of St Pieter's Mountain, south of Maastricht, the Netherlands, the species is reported from Campanian and Maastrichtian marine deposits within a geographic belt ranging from the paleolatitudes 30-45°N (Mantell, 1829;Lingham-Soliar, 1995;Bardet and Tunoğlu, 2002;Jagt et al., 2008). ...
... The posterior carina points laterally forming strongly unequal labial and lingual surfaces. The high degree of labiolingual asymmetry indicates origin from the front of the jaw (Grigoriev, 2014) (Grigoriev, 2014;Street and Caldwell, 2017). Apical curvature is mediodistally oriented. ...
... The distally pointed carinae are minutely, but distinctly crenulated, while a faint anastomosing texture covers the enamel of the entire tooth. The number of prism faces and angle at which the carinae are offset from each other indicate that this is a premaxillary tooth(Street and Caldwell, 2017).AVM 02(Fig. 5, E)is a small marginal tooth crown 39.7 mm tall. ...
Marginal tooth crowns from the hypercarnivorous marine reptile Mosasaurus hoffmannii Mantell, 1829 are reported for the first time from the Late Cretaceous (Maastrichtian) phosphates of Morocco. Fossilized remains of this species are previously known from Campanian and Maastrichtian outcrops in Europe, North America, and western Asia at a paleolatitudinal belt of 30-45°N. New fossil material originates from the Upper Couche III layer of the Oulad Abdoun Basin, south of Oued Zem, Morocco. The discovery of M. hoffmannii in Morocco extends its paleobiogeographic range south to 25°N and into the southern margin of the Mediterranean Tethys.
... Not only have these gross anatomical characters been used in phylogenetic analyses, but some have also been used to diagnose mosasaur taxa. For example, the presence of facets diagnoses Mosasaurus (Lingham-Soliar 1995;Russell 1967;Street and Caldwell 2017), while striations are diagnostic of Plioplatecarpini (Russell 1967), Russellosaurina , or Plioplatecarpinae (Konishi and Caldwell 2011). Facets in mosasaurs have also been referred to as "prisms" (e.g., Russell 1967:64;Lingham-Soliar 1995:161). ...
Mosasaur researchers have used varieties of tooth crown ornamentation as diagnostic and phylogenetic characters for decades. Such tooth crown features include facets, flutes, striations, serrated carinae, and coarse anastomosing texture. is study investigates the relative contributions of dentine and enamel to the development of these dental characters and assesses homology statements between these structures. Histological analysis of isolated mosasaur teeth reveals that flutes and facets develop initially from the dentine, and the external enamel morphology we observe macroscopically mirrors the shape of the underlying dentine. Striations combine underlying contributions from the dentine with additional and irregular enamel deposition resulting strictly from amelogenesis. In both serrated carinae and anastomosing texture the Dentine-Enamel Junction is smooth, and these external ornamentations form exclusively through variations in enamel development. Based on these observations, we infer that flutes and facets form a morphological spectrum and should not be treated as separate phylogenetic characters. Conversely, striations develop differently than flutes and facets, and should therefore be treated as a distinct character. We recommend referring to serrations on mosasaur carinae as false denticulations to differentiate these enamel-only structures from true denticles possessing a dentine core. Anastomosing texture can also coincide with significant apical enamel thickening, both of which could be adaptations for processing harder prey, as they are in modern reptiles. Care must be taken when using tooth crown features as diagnostic or phylogenetic characters because seemingly different morphologies can have similar developmental origins, and tooth morphology can be more closely tied to diet than common ancestry.
