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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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... States. count = 8; marginal teeth carinae asymmetric anteri- orly with lingual circumference greater than labial; cer- vical vertebra transverse processes elongate with little ventral buttressing; femur greatly expanded medially and distally with articular surfaces nearly perpendicu- lar; internal trochanter robust and offset. The premaxilla (Fig. 2) of NHMM 006696 exhibits a short, bluntly conical edentulous rostrum anterior to the first pair of premaxillary teeth. The lateral sur- faces of the anterior portion of the rostrum are perfor- ated by irregular clusters of foramina (Fig. 2a). There are also larger single or paired foramina posterodorsal to the posterior premaxillary ...
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... with articular surfaces nearly perpendicu- lar; internal trochanter robust and offset. The premaxilla (Fig. 2) of NHMM 006696 exhibits a short, bluntly conical edentulous rostrum anterior to the first pair of premaxillary teeth. The lateral sur- faces of the anterior portion of the rostrum are perfor- ated by irregular clusters of foramina (Fig. 2a). There are also larger single or paired foramina posterodorsal to the posterior premaxillary teeth. The profile of the premaxilla slopes dorsally, diverging from the plane formed by the dental margin. Of the four premaxillary teeth, the anterior pair is more gracile than the pos- terior pair. The premaxilla is widest directly posterior ...
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... projecting flanges extend from the tooth-bearing portion of the premaxilla. The premax- illa of IRSNB R 26 is more complete posteriorly, and at the posterior termination of the internarial bar for that specimen the dorsal surface dilates slightly and the ventral vertical ridge bears longitudinal grooves on each lateral surface. Ventrally (Fig. 2b), between the pairs of premaxillary teeth, there is a pair of ridges, which form a sulcus or vacuity between them along the midline. Anteriorly, this structure tapers to a point between the first pair of teeth and is separated by a groove from the roots of these teeth. Posterior to the second pair of premaxillary teeth, the ridges ...
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... logarithmic form of the suture trace between the premaxilla and the maxilla is typically 'mosasaur- ian' (Fig. 2a). However, this suture is not necessarily a smooth curve. In some cases, the vertical rise of the suture can be convex anteriorly, excavating deeper into the premaxilla, or slightly concave dorsally, excavating into the maxilla before continuing posteriorly. highlight the palatine and vomer. Abbreviations: M -maxilla; Pl -palatine; Pt ...
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... scapula should be a large, fan-shaped structure, subequal in size to the coracoid, but no complete ele- ment is known for this species. The incomplete right scapula of IRSNB R 26 does preserve the articular head and the characters thereon (Fig. 20). The head of the scapula is offset from the flat plate of the scapular blade by approximately 45°. A broad ridge separates the two articular facets on the scapular head (Fig. 20a). Facing posterolaterally is the facet that contributes to the glenoid fossa for the head of the humerus. This facet is broadly concave laterally, but where ...
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... the coracoid, but no complete ele- ment is known for this species. The incomplete right scapula of IRSNB R 26 does preserve the articular head and the characters thereon (Fig. 20). The head of the scapula is offset from the flat plate of the scapular blade by approximately 45°. A broad ridge separates the two articular facets on the scapular head (Fig. 20a). Facing posterolaterally is the facet that contributes to the glenoid fossa for the head of the humerus. This facet is broadly concave laterally, but where the facet crosses the axis formed by the scapular body it curves into a medial convexity. The outline of this facet is partially obscured by weathering to the medial side of the ...
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... development of the anterior accessory process means that while the scapular neck is constricted, it is unusually long anteroposteriorly. In lateral view (Fig. 20b), the anterior of the scapular neck is even with the plane formed by the long axis of the scap- ular head and is offset from the blade of the scap- ula. Anteriorly a broad, C-shaped canal forms between the anterior accessory process and a ridge that marks the ventral edge of the scapular blade. This ridge likely continued anteriorly, ...
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... process and a ridge that marks the ventral edge of the scapular blade. This ridge likely continued anteriorly, and its posterior termina- tion is dorsal to the ridge that separates the glenoid and coracoid articular facets on the scapular head. Intern- ally, the neck of the scapula is bowed by the medial termination of the coracoid facet (Fig. 20c). The scap- ular blade is thickest dorsal to the head of the scapula. The blade of the scapula is broken both anteriorly and posteriorly, so the degree of curvature of the dorsal margin, how far the scapular blade extended anteriorly or posteriorly, and any asymmetries of that extent are ...
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... humerus of Mosasaurus hoffmannii typifies the mosasaurine condition being long for its height and complexly three-dimensional (Fig. 22), differing from the more elongated, less-well-ossified humeri of Plate- carpus or Tylosaurus (Russell, 1967). Even the humeri of Clidastes and Prognathodon are not as robust as that of Mosasaurus (Russell, 1967;). Unfortunately, no complete humerus is known for M. hoffmannii, and the humerus of IRSNB R 26 is the most complete though it ...
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... medial view or lateral view, a complete hu- merus of Mosasaurus hoffmannii would likely have been as long or longer anteroposteriorly than it is tall (Fig. 22a). Proximally, the glenoid facet and the pec- toral crest contribute to the proximal width of the hu- merus, and these confluent structures form a dorsally bowed surface (Fig. 22b). Proximally (Fig. 22d), the glenoid fossa is a large, oblong facet that is slightly concave medially but convex laterally where it merges with the laterally ...
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... medial view or lateral view, a complete hu- merus of Mosasaurus hoffmannii would likely have been as long or longer anteroposteriorly than it is tall (Fig. 22a). Proximally, the glenoid facet and the pec- toral crest contribute to the proximal width of the hu- merus, and these confluent structures form a dorsally bowed surface (Fig. 22b). Proximally (Fig. 22d), the glenoid fossa is a large, oblong facet that is slightly concave medially but convex laterally where it merges with the laterally projecting pectoral crest. The post- glenoid process projects posterodorsally from the postaxial side of the glenoid fossa ( Fig. 22a-d). This structure is robust, separate from ...
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... view or lateral view, a complete hu- merus of Mosasaurus hoffmannii would likely have been as long or longer anteroposteriorly than it is tall (Fig. 22a). Proximally, the glenoid facet and the pec- toral crest contribute to the proximal width of the hu- merus, and these confluent structures form a dorsally bowed surface (Fig. 22b). Proximally (Fig. 22d), the glenoid fossa is a large, oblong facet that is slightly concave medially but convex laterally where it merges with the laterally projecting pectoral crest. The post- glenoid process projects posterodorsally from the postaxial side of the glenoid fossa ( Fig. 22a-d). This structure is robust, separate from the glenoid artic- ular ...
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... confluent structures form a dorsally bowed surface (Fig. 22b). Proximally (Fig. 22d), the glenoid fossa is a large, oblong facet that is slightly concave medially but convex laterally where it merges with the laterally projecting pectoral crest. The post- glenoid process projects posterodorsally from the postaxial side of the glenoid fossa ( Fig. 22a-d). This structure is robust, separate from the glenoid artic- ular fossa, bluntly rounded, and has parallel sides (Fig. ...
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... facet that is slightly concave medially but convex laterally where it merges with the laterally projecting pectoral crest. The post- glenoid process projects posterodorsally from the postaxial side of the glenoid fossa ( Fig. 22a-d). This structure is robust, separate from the glenoid artic- ular fossa, bluntly rounded, and has parallel sides (Fig. ...
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... the bone, and this constriction forms a U-shaped embayment in the preaxial surface of the element. Distal to the constriction the ectepicondyle extends further anteriorly than the glenoid facet. The ectepicondyle is bluntly tapered, and its distal surface is the straight articular facet for the radius, which faces anterodistally. In distal view (Fig. 22e), the ar- ticular facet for the radius is flat and ovoid in out- line, being slightly more convex medially than later- ally and narrowest at the anterior termination of the ectepicondyle. The radial facet appears to be separ- ated from the ulnar facet by a medial notch, as is seen in other mosasaurines such as Plotosaurus (Russell, ...
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... to the preaxial constriction, the pectoral crest arises from the medial surface of the humerus. It is confluent with the medial extent of the glenoid facet, where it is most prominent, and tapers into the surface of the element distally (Fig. 22a, b). The distal termina- tion of the pectoral crest is even with the ectepicondyle. The entepicondyle is not ...
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... lateral view of the humerus (Fig. 22c) is similar in outline to the medial side, but the lateral surface is flatter without such prominent elaborations for muscle attachments, though there is a rugose patch around the distal-most portion of the element. The surface of the humerus proximal to the apex formed between the ra- dial and ulnar facets is also slightly roughened ...
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... radius is robust and distally expanded, as is typical in mosasaurines (Fig. 23). The proximal articular facet of the radius is D-shaped with the bowed side medial and the flatter surface lateral (Fig. 23a). Distal to the articular head, the radius is asymmetrically waisted, with the constriction of the preaxial margin located more proximally than the constriction of the postaxial margin (Fig. 23b, c). The ...
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... radius is robust and distally expanded, as is typical in mosasaurines (Fig. 23). The proximal articular facet of the radius is D-shaped with the bowed side medial and the flatter surface lateral (Fig. 23a). Distal to the articular head, the radius is asymmetrically waisted, with the constriction of the preaxial margin located more proximally than the constriction of the postaxial margin (Fig. 23b, c). The concavity to the preaxial mar- gin is shallower and broader than that to the postaxial margin, which is more deeply U-shaped. Distal ...
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... is typical in mosasaurines (Fig. 23). The proximal articular facet of the radius is D-shaped with the bowed side medial and the flatter surface lateral (Fig. 23a). Distal to the articular head, the radius is asymmetrically waisted, with the constriction of the preaxial margin located more proximally than the constriction of the postaxial margin (Fig. 23b, c). The concavity to the preaxial mar- gin is shallower and broader than that to the postaxial margin, which is more deeply U-shaped. Distal to the constriction of the radial shaft, the element expands and thins anteriorly and posteriorly. The distal articulation for the radiale is approximately parallel to the proximal articular surface ...
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... gin is shallower and broader than that to the postaxial margin, which is more deeply U-shaped. Distal to the constriction of the radial shaft, the element expands and thins anteriorly and posteriorly. The distal articulation for the radiale is approximately parallel to the proximal articular surface but much thinner and lenticular in out- line (Fig. 23d). As is typical of mosasaurines, a wing of bone extends anteriorly forming an anterodistal flange. In IRSNB R 299 the truncation of this flange forms a nearly right angle between the preaxial margin and the distal articular facet, but in life the preaxial margin was likely curved. Significant distal expansion of the radius is seen in ...
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... ex- cept Tylosaurus, but the distal end of the radius of M. hoffmannii most closely resembles that of Clidastes. However, the proximal end of the radius in Clidastes is narrower (Russell, 1967). Postaxial to the articular fa- cet for the radiale is a secondary articular facet oriented at an obtuse angle to the main distal articular surface ( Fig. 23e). This smaller facet is triangular in postaxial view and most likely articulated with the ...
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... ilium of NHMM 006696 is the longest of the three pelvic bones (Fig. 24). As is the case for all fully mar- ine, hydropelvic mosasaurs (Caldwell & Palci, 2007), the ilium is comprised of a slender dorsal shaft that broadens into a ventral head bearing the articular fa- cets for the pubis, ischium and femur. The shaft is compressed and blade-like. Proximal to the acetabu- lum the ilium angles slightly ...
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... the acetabu- lum the ilium angles slightly anteriorly, but the distal end extends dorsally, giving the anterior border of the element a faintly recurved outline. The posterior bor- der of the shaft is more nearly straight. The head is the most robust region of the element. Medially, the head of the ilium is rugose dorsal to the articular fa- cets (Fig. 24a), which are borne laterally and ventrally (Fig. 24b). The facet for the pubis is ventral, that for the ischium is posteroventral, and the facet that con- tributes to the acetabulum is lateral and dorsally convex (Fig. ...
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... but the distal end extends dorsally, giving the anterior border of the element a faintly recurved outline. The posterior bor- der of the shaft is more nearly straight. The head is the most robust region of the element. Medially, the head of the ilium is rugose dorsal to the articular fa- cets (Fig. 24a), which are borne laterally and ventrally (Fig. 24b). The facet for the pubis is ventral, that for the ischium is posteroventral, and the facet that con- tributes to the acetabulum is lateral and dorsally convex (Fig. ...
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... The head is the most robust region of the element. Medially, the head of the ilium is rugose dorsal to the articular fa- cets (Fig. 24a), which are borne laterally and ventrally (Fig. 24b). The facet for the pubis is ventral, that for the ischium is posteroventral, and the facet that con- tributes to the acetabulum is lateral and dorsally convex (Fig. ...
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... pubis and the ischium of NHMM 006696 are sube- qual in length with the pubis being slightly longer and more robust than the ischium (Fig. 24). The shaft of the pubis is sub-circular to sub-triangular in cross-section and straight. The distal end of the shaft is striated or rugose on all sides; these structures are presumably the scars from muscle attachments. The anteroprox- imal edge of the shaft pinches out into a pubic tubercle or process, which is large and anteriorly ...
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... but poor preservation of its distal end makes it un- clear whether the termination of the process would have been triangular, as in Mosasaurus conodon, or rectangular, as in Clidastes ( Russell, 1967). The pubic tubercle of Prognathodon overtoni is more gracile than that of M. hoffmannii ( ). The ob- turator foramen is wider and oval internally (Fig. 24a) and constricts as it passes through the pubis to exit as a small, sub-circular opening anterior to the ridge that extends along the external surface of the shaft from the acetabulum to its distal end (Fig. 24b). The obturator foramen pierces the concavity between that ridge and the dished pubic process. The robust pubic head bears ...
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... tubercle of Prognathodon overtoni is more gracile than that of M. hoffmannii ( ). The ob- turator foramen is wider and oval internally (Fig. 24a) and constricts as it passes through the pubis to exit as a small, sub-circular opening anterior to the ridge that extends along the external surface of the shaft from the acetabulum to its distal end (Fig. 24b). The obturator foramen pierces the concavity between that ridge and the dished pubic process. The robust pubic head bears articular facets posteriorly for the ischium, postero- dorsally for the ilium and laterally for the acetabulum. The facets for the ilium and the acetabulum are each ...
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... head of the ischium of NHMM 006696 also bears three articular facets (Fig. 24b). Those for the ilium and pubis are flat to concave, and the facet that contributes to the acetabulum is convex. Internally, the surface of the anteroposteriorly expanded medial end of the shaft is striated where it would articulate with its counter- part on the midline, and the surface around the head is rugosely striated (Fig. 24a). ...
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... facets (Fig. 24b). Those for the ilium and pubis are flat to concave, and the facet that contributes to the acetabulum is convex. Internally, the surface of the anteroposteriorly expanded medial end of the shaft is striated where it would articulate with its counter- part on the midline, and the surface around the head is rugosely striated (Fig. 24a). There is a shallow fossa along the posterior edge of the middle of the bone, medial to the ischiadic process. This process arises from the posterodorsal border of the shaft slightly me- dial to the head. There is little constriction of a neck between the ischiadic process and the head of the is- chium, with the posterior border being ...
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... of a neck between the ischiadic process and the head of the is- chium, with the posterior border being only slightly concave between the two. The borders of the shaft are more distinctly concave both posteriorly and anteriorly, and the anterior curvature of the bone is created by the anterolateral projection of the ischiadic head. Extern- ally (Fig. 24b), the medial end of the ischium is striated, though the striations are shallower than those on the in- ternal surface. The constriction of the shaft is more distinct in this view because the flange of the ischiadic process is offset from the ...
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... left femur of MNHN AC 9648 is more weathered than the cranial elements (assuming it came from the same individual), and some of the features are obscured (Fig. 25). The articular surfaces for the acetabulum and the tibia and fibula are each expanded, but the axes of expansion are oriented at nearly right angles to each other. Between the condyles, the shaft of the femur is constricted, particularly in medial and lateral views. The distal end of the femur forms two distinct ...
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... lateral aspect of the femur (Fig. 25a) bears a crest that originates proximally from the femoral head and tapers to terminate at about the midpoint of the shaft. In this view, the preaxial surface of the bone is gently concave, and the postaxial edge is deeply con- cave, giving the trailing edge a broadly U-shaped out- line. The distal end of the femur is the more expanded ...
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... preaxial view (Fig. 25b) the proximal end of the femur is fan-shaped, and the tapered region of the shaft appears very short. The fan-shaped proximal ex- pansion is formed by the rounded, oval femoral head (Fig. 25e), which is confluent with the lateral crest, and the robust internal trochanter. The internal trochanter, positioned proximomedially on the shaft ...
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... preaxial view (Fig. 25b) the proximal end of the femur is fan-shaped, and the tapered region of the shaft appears very short. The fan-shaped proximal ex- pansion is formed by the rounded, oval femoral head (Fig. 25e), which is confluent with the lateral crest, and the robust internal trochanter. The internal trochanter, positioned proximomedially on the shaft (Fig. 25b-e), does not extend as far proximally as the femoral head, and it is separated from the latter structure by a broad sulcus (Fig. 25d). A buttress supporting the internal trochanter ...
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... (Fig. 25b) the proximal end of the femur is fan-shaped, and the tapered region of the shaft appears very short. The fan-shaped proximal ex- pansion is formed by the rounded, oval femoral head (Fig. 25e), which is confluent with the lateral crest, and the robust internal trochanter. The internal trochanter, positioned proximomedially on the shaft (Fig. 25b-e), does not extend as far proximally as the femoral head, and it is separated from the latter structure by a broad sulcus (Fig. 25d). A buttress supporting the internal trochanter extends distally about halfway along the shaft (Fig. ...
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... ex- pansion is formed by the rounded, oval femoral head (Fig. 25e), which is confluent with the lateral crest, and the robust internal trochanter. The internal trochanter, positioned proximomedially on the shaft (Fig. 25b-e), does not extend as far proximally as the femoral head, and it is separated from the latter structure by a broad sulcus (Fig. 25d). A buttress supporting the internal trochanter extends distally about halfway along the shaft (Fig. ...
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... crest, and the robust internal trochanter. The internal trochanter, positioned proximomedially on the shaft (Fig. 25b-e), does not extend as far proximally as the femoral head, and it is separated from the latter structure by a broad sulcus (Fig. 25d). A buttress supporting the internal trochanter extends distally about halfway along the shaft (Fig. ...
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... facet is the larger of the two, and it is nearly perpendicular to the long axis of the femoral shaft. This facet would likely have been approximately rectangular. The fibular facet projects postaxially from the distal end of the bone, and the outline of the facet is a reflected D- shape. The fibular facet is more concave than that for the tibia (Fig. 25f). In lateral and medial views (Fig. 25a, c), the tibial and fibular facets meet in a slightly obtuse ...
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... is nearly perpendicular to the long axis of the femoral shaft. This facet would likely have been approximately rectangular. The fibular facet projects postaxially from the distal end of the bone, and the outline of the facet is a reflected D- shape. The fibular facet is more concave than that for the tibia (Fig. 25f). In lateral and medial views (Fig. 25a, c), the tibial and fibular facets meet in a slightly obtuse ...
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... tibia of NHMM 006696 is approximately as long as it is tall (likely it would have been longer than tall if complete), and bears a thin, dished convex flange on its anterior edge (Fig. 26). Some degree of anterior expansion is exhibited by the tibiae of Prognathodon and Tylosaurus (Russell, 1967;), but that expansion is greater in M. hoffmannii. The main shaft and posterior edge are considerably thicker, and the posterior edge is deeply concave (Fig. 26a, b). The proximal articular facet for the femur is concave and ...
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... tall if complete), and bears a thin, dished convex flange on its anterior edge (Fig. 26). Some degree of anterior expansion is exhibited by the tibiae of Prognathodon and Tylosaurus (Russell, 1967;), but that expansion is greater in M. hoffmannii. The main shaft and posterior edge are considerably thicker, and the posterior edge is deeply concave (Fig. 26a, b). The proximal articular facet for the femur is concave and ovoid, with the anterior end being narrower than the posterior end (Fig. 26c). The distal end bears two articular facets at a 120° degree angle to each other ( Fig. 26d). The anterior facet for the first metatarsal is slightly deeper mediolaterally and teardrop shaped, and the ...
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... the tibiae of Prognathodon and Tylosaurus (Russell, 1967;), but that expansion is greater in M. hoffmannii. The main shaft and posterior edge are considerably thicker, and the posterior edge is deeply concave (Fig. 26a, b). The proximal articular facet for the femur is concave and ovoid, with the anterior end being narrower than the posterior end (Fig. 26c). The distal end bears two articular facets at a 120° degree angle to each other ( Fig. 26d). The anterior facet for the first metatarsal is slightly deeper mediolaterally and teardrop shaped, and the posterior facet for the astragalus is shorter (both dorsoventrally and anteroposteriorly) and more deeply ...
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... M. hoffmannii. The main shaft and posterior edge are considerably thicker, and the posterior edge is deeply concave (Fig. 26a, b). The proximal articular facet for the femur is concave and ovoid, with the anterior end being narrower than the posterior end (Fig. 26c). The distal end bears two articular facets at a 120° degree angle to each other ( Fig. 26d). The anterior facet for the first metatarsal is slightly deeper mediolaterally and teardrop shaped, and the posterior facet for the astragalus is shorter (both dorsoventrally and anteroposteriorly) and more deeply ...
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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.
