Mosasaurini Gervais 1852
Authors: Bardet, Nathalie, Desmares, Delphine, Sánchez-Pellicer, Raquel, Gardin, Silvia
Type: Taxonomic treatment
Published: 2021-05-10
Keywords: Biodiversity, Taxonomy

<p><b>Genus and species <i>incertae sedis</i></b></p><p><b><i>Jerusalem Specimen 1</i></b></p><p>MATERIAL. — MHNM.0.419.1-3, and MHNM.0.419.6-32: 30 bones including 3 vertebrae described by Répelin (1915): a dorsal (no. 1), a large median caudal (no. 2), a terminal caudal (no. 3); 27 up to now unpublished bones: 6 cranial bones including incomplete frontal (no. 6), parietal (no. 7) and postorbitofrontal (no. 8) fused and preserved in three fragments, a fragmentary left jugal (no. 9), an incomplete basicranium (no. 10) and a dentary fragment (11), as well as 21 vertebrae, including 2 dorsals (no. 12, 13), one pygal (no. 14), 6 median caudals (no. 15 to 20) and 12 terminal caudals (no. 21 to 32) (Figs 4-6; Table 1).</p><p>GEOGRAPHIC AND STRATIGRAPHIC PROVENANCES. — Lower part of the Middle Campanian, probably Mishash Formation, possibly northeastern part of Jerusalem (see Fig. 1).</p><p>DESCRIPTION</p><p><i>Cranium</i> (Fig. 4)</p><p>Several cranial bones are preserved, including an incomplete frontal-postorbitofrontal-parietal sutured complex, an incomplete occipital unit, and fragmentary jugal and dentary.</p><p><b><i>Frontal (MHNM.0.419. 6, Fig. 4A)</i></b></p><p>The frontal is incomplete but from the portions preserved on left and right sides, its complete morphology can be reconstructed.</p><p>In dorsal view it is a long, flat, triangular bone almost twice as long as wide. The anterior extremity is broken so it is impossible to know if the bone is invaded by the internarial bar of the premaxillae and by the narial openings. The lateral borders are almost straight, exhibiting only a very slight sigmoid shape and converge only slighty anteriorly, giving the bone its elongated triangular shape. The posterolateral margin is slightly concave and terminates in laterally diverging cornua</p><p>that are large and rounded tongues of bones. The dorsal midline anteriorly bears a low and blunt longitudinal crest marked only on the anterior third of the bone. Posteromedially, there are two long and thin flanges of bones embracing the parietal foramen that extend beyond it by around half its length. Lateral to these flanges, the posterior margin of the frontal is deeply excavated and concave, forming an inverted “V”. As a result, the frontal-parietal suture is very intricately undulated, precluding mesokinetic movements (LeBlanc <i>et al.</i> 2013).</p><p>In ventral view, the midline of the bone is occupied anteriorly to posteriorly by a blunt and massive ridge flanked by two large oval grooves, then a large elongated oval concave depression for the olfactory bulbs, followed by a long and narrow olfactory tract that opens posteriorly into a large triangular depression for the cerebral hemisphere. The floor of all these structures lies roughly at the same level. Laterally and raised from this median zone are very large and smooth sutural surfaces for the prefrontal anteriorly and the postorbitofrontal posteriorly. They are almost coalescent, only a thin transversal sheet of bone being present between them, showing that the prefrontal and postorbitofrontal probably almost meet. The surface occupied by the postorbitofrontal is very expanded (see below).</p><p><b><i>Parietal (MHNM.0.419. 7, Fig. 4A)</i></b></p><p>Only the right anterior part of the parietal fused to the frontal is preserved. It is a massive ala of bone contacting the frontal anterolaterally into the previously mentioned inverted V-shaped suture. The parietal foramen is of moderate size and oval, and its anterior border contacts the frontal-parietal suture. It is embraced by the long and thin tongues of the frontal. Laterally, a large vertical transversely oriented sutural zone bearing strong horizontal ridges and furrows is present. It shows that the medial wing of the postorbitofrontal was posteromedially expanded. Ventrally, the anterior part of the parietal is hidden by the expanded ala of the postorbitofrontal and the parietal foramen is surrounded laterally by two ridges that seem to converge posteriorly.</p><p><b><i>Postorbitofrontal (MHNM.0.419. 8, Fig. 4A)</i></b></p><p>Both incomplete postorbitofrontals are preserved, the right one being better preserved both in dorsal and ventral views. It surrounds the posterolateral corner of the frontal in a regularly convex suture. The anterior branch is dorsally narrow, tapers anteriorly and disappears just before the orbit. Though the postorbitofrontal almost meet the prefrontal ventrally on the frontal, this dorsal morphology indicates however that these two bones do not form a continuous band of bone laterally to the frontal. Ventrally, this branch expands into a wide thin ala of bone that covers most of the posteromedial ventral surface of the frontal into a sigmoid suture, more than half the distance from the corner of the frontal to the midline. This indicates that the postorbitofrontal was firmly attached to the frontal, limiting also mesokinetic movements. The posterior branch is short and narrow, transversely oriented, and medially contacts the parietal into a simple interdigitating suture. The posterolateral corner is broken but judging from the part</p><p>preserved it was probably sharp and expanded laterally. The descending branch for the jugal as well as the posterior one for the squamosal are not preserved.</p><p><b><i>Jugal (MHNM.0.419. 9, Fig. 4B)</i></b></p><p>An incomplete left jugal bearing a typical L-shape is preserved. Both horizontal and vertical rami are broken distally. The dorsal ramus is stout and elliptical in cross-section whereas the ventral one is laterally flattened. The angle between these two rami is notably very open, about 120°. A well-marked posteroventral process is present. In medial view, there is a shallow ventral surface just anterior to the tuberosity, possibly for loose contact with the ectopterygoid.</p><p><b><i>Basicranium (MHNM.0.419.10, Fig. 4C)</i></b></p><p>The incomplete occipital unit preserved most of the basioccipital and basisphenoid, as well as some ventral parapets of the exoccipital-opisthotic and prootic surrounding the foramen magnum. All bones are fused and because this complex is eroded, most of the sutures are not visible. This complex is thus described as a whole, with highlighting of the visible structures in each view.</p><p>In dorsal view, the medular canal is relatively wide and deep. At the median part of the complex, probably around the basioccipital-basisphenoid suture, it is laterally constricted. The medial internal suture with the exoccipital-opisthotic is elongated and slightly curved whereas the transverse basioccipital-basisphenoid suture is visible on the floor and lateral sides of the medullary canal. There is no trace of a basilar artery foramen.</p><p>In ventral view, the basal tubera are mostly broken but their preserved bases indicate they were probably large. Just anteriorly to them, the posteroexternal tongues of the basisphenoid are not preserved. The suture between the two bones is V-shaped and located in the bottom of an also V-shaped bowl, the tip of the V facing forward for both. Laterally, this V-shaped depression is flanked by two elongated oval depressions. Anteriorly, the basipterygoid processes are not preserved.</p><p>In posterior view, the basioccipital condyle is reniform, regularly convex ventrally and excavated dorsally by both the almost flat exoccipital articulations and the concave foramen magnum floor. This condyle is separated from the shaft of the bone by a large convex neck. Its dorsolateral corners are lateroventrally oriented and articulate with the exoccipitals (only the condyle of the left one is preserved). This view shows that the basal tubera of the basioccipital were lateroventrally oriented, with an angle of about 30° from the horizontal axis.</p><p>The anterior view reveals the V-shaped morphology of the basisphenoid and the suture with the ventro-anterior part of the prootic. None of the foramina present normally on this anterior surface of the basisphenoid are preserved.</p><p>The lateral views are abraded so that the lateral flanges of both the exoccipital-opisthotic and prootic, especially the areas bearing the otosphenoidal crest and all the nerve foramina, are not preserved. The sulcus is only visible in left lateral view below the partly broken ala of the basisphenoid where the jugular vein must pass.</p><p><i>Dentary (MHNM.0.419. 11, Fig. 4D).</i></p><p>A small fragment of the dentary (L × W × H = 6.9 / 2.7 / 3.3 cm) is preserved. It is broken both anteriorly and posteriorly. Its longitudinal axis is straight. In occlusal view, it bears three oval dental alveoli as well as smaller round ones for replacement teeth located, as usual, posteromedially to the main ones. The main teeth are all broken at the base of the crown and no tooth apices are visible in the replacement alveoli, so the morphology of the teeth remains unknown. The roots are firmly anchored in the dentary as usual in mosasaurids. Both medial and lateral parapets are of similar height. The lateral one exhibits a small rounded and shallow interdental pit for the accommodation of the corresponding upper jaw tooth apex during occlusion. The lateral surface is gently concave and bears a median row of nutritive foramina – the best preserved being a long narrow oval – and a second ventral one in which only one foramen is observable, due to the poor preservation of the ventral surface of the bone. The medial surface is eroded; it bears a long and narrow ventrally located horizontal Meckelian canal (about 8 mm wide) that slightly narrows anteriorly. Because of the occurrence of a narrow Meckelian canal and of two rows of nutritive foramina, this fragment probably belongs to the anterior third of the dentary.</p><p><b><i>Axial skeleton (Figs 4; 5)</i></b></p><p>All the vertebrae are procoelous. The preserved vertebral series, though admittedly incomplete, probably represents the posteriormost part of the dorsal series and an incomplete tail (including pygal, median caudal and terminal caudal vertebrae) of a single individual.</p><p><b><i>Dorsal vertebrae (MHNM.0.419. 1, 12, 13, Fig. 4 E-G)</i></b></p><p>Three dorsal vertebrae are preserved,including the one numbered no. 1 originally described by Répelin (1915) (Fig.4F). They are of similar size, morphology and proportions (L~ 2 × W-H), indicating that they probably come from the same portion of the vertebral column and were possibly adjacent. They are slightly distorted, being laterally compressed. The neural arches and transverse processes are broken, only their bases are preserved. In anterior and posterior views, the articular surfaces are vertically oriented and markedly concave/convex,the cotyle being slightly larger than the condyle. Both are roughly circular in axial view, being slightly higher than wide, but this could be due to the lateral compression above mentioned. The dorsal surface is excavated by the floor of the foramen magnum, which bears a median sharp ridge bordered by two lateral furrows and numerous foramina.The lateral surface bears anteriorly at mid-height large dorsoventrally compressed ovoid transverse processes with large bases that occupy almost half the length of this surface.The ventral surface is gently convex and bears two symmetrical foramina located anteriorly, just ventral to the transverse processes, as well as one median, located approximately ventral to the posterior border of the base of the transverse processes. The base of the neural arch preserved on vertebra no. 1 is fused to the centrum. It shows that its anterior and posterior peduncles are large and lenticular but does not allow us to determine if zygapophyses</p><p>were present, nor the shape and orientation of the neural spine. The anteromedian position of the transverse processes permits to identify these vertebrae as posterior dorsals (or lumbars), as defined by Russell (1967: 77). As such, we can hypothesize that the longest of these three vertebrae is the anteriormost and the shortest is the posteriormost, and that these vertebrae could represent some of the last lumbars.</p><p><b><i>Pygal vertebrae (MHNM.0.419.14, Fig. 4H)</i></b></p><p>One pygal is preserved. It is much shorter than the dorsals (about one-third), showing that a gap probably exists between them. It is slightly distorted and slightly longer than high and wide. Its articular surfaces are subtriangular. As for the dorsals, the cotyle is slightly larger than the condyle and both are poorly concave/convex, almost flat. In dorsal view, the neural canal is deep and narrow. The ventral surface is gently convex, and bears a median longitudinal low ridge bordered on each side by two shallow depressions. The lateral surface bears large dorsoventrally compressed transverse processes forming narrow alae located ventroanteriorly and projecting ventrally, making an angle of 35-38° from the horizontal. The roughly triangular shape of the articular surface and the ventrally located transverse processes indicate that this pygal was probably an anterior one.</p><p><b><i>Median caudal vertebrae</i></b></p><p><i>(MHNM.0.419. 2, 15-20, Fig. 4 I-O)</i></p><p>Seven median caudal vertebrae are preserved, including the no. 2 originally described by Répelin (1915) (Fig. 4J). They all have the same shape, size and proportions with L~H = W (around 35 × 34 × 34 mm), indicating that they were possibly adjacent or near-adjacent vertebrae from the same portion of the tail. The articular surfaces, as on the pygal, are only slightly concave/convex, and the cotyles are slightly larger and flatter than the condyles. Both are sub-hexagonal and the lateral margins are larger than the dorsal and ventral ones. In dorsal view the neural canal is narrow and deep. The neural arches are not preserved but their base shows that they were probably straight narrow blades, with no indication of postzygapophyses. The lateral surfaces are large and almost flat. Anteroventrally, they bear transverse processes that are large, dorsoventrally compressed and posteriorly oriented alae that occupy about 2⁄ of the surface 3</p><p>length. They also project ventrally with an angle comparable to that observed on the pygal vertebra.The ventral surface is almost flat and bear nutritive foramina.Posteroventrally, these vertebrae bear large fused haemal arches. Though all are broken, their oval or round basal sections show that they were only slightly posteriorly oriented. Because of their subhexagonal articular surfaces and their large transverse processes, these vertebrae are interpreted as anterior median caudals. Their size and proportion are consistent with those of the previously described dorsal and pygal vertebrae, suggesting that they probably belong to the same individual (see also “Anatomical and nomenclatural comments on the material”).</p><p><i>Terminal caudal vertebrae (MHNM.0.419.3, 21-32, Fig. 5)</i> Thirteen terminal caudals are preserved, including the no. 3 originally described by Répelin (1915) (Fig. 5I). As for the median caudals, they show <i>grosso modo</i> the same shape and proportion and their size gradually decreases, so they could also represent near adjacent vertebrae from the same portion of the tail, though some gaps are obviously present, especially between the first ten and the three posteriormost. The vertebra interpreted as the anteriormost of this series are longer and wide than high (about 35 × 34 × 32 mm), then they exhibit the same proportions (about 30 × 30 × 25 mm), and finally are as long as high but laterally compressed (about 20 x 20 x 18 mm). As a result, their articular surfaces are first vertically oval with reminiscences of the subhexagonal shape of the previous median caudals, then become horizontally oval to subrectangular, and finally vertically oval.These articular surfaces as a whole are only slightly concave/convex, almost flat as in the previous median caudals. The neural canal is very narrow and deep. None of the neural arches is preserved but from their bases as for the median caudals, it can be deduced they were narrow vertical blades. The lateral surfaces of the centra are regularly convex from side to side and no longer bear transverse processes. The ventral surface is flat to concave and small, being limited to a reduced area between the chevrons, which are fused to the centrum. All are broken proximally but bear a round. Strongly posteriorly oriented basal cross-section, making an angle of less than 10° to the horizontal. The smallest vertebra of this terminal caudal series shows on its cotyle, and especially on its condyle, typical traces of selachian scavenger activity (e.g. Corral <i>et al.</i> 2004). Because of the occurrence of haemal arches and the lack of transverse processes, these vertebrae are interpreted as terminal caudals. They are however probably not the posteriormost of the tail, and a gap exists also with more anterior caudals as no posterior median caudals have been identified.</p><p>COMPARISON</p><p>As a whole, the “ Jerusalem Specimen 1” exhibits a mosasaurine suite of characters including the invasion of the parietal by posteromedian flanges of the frontal, no basal artery canal on the basioccipital floor, vertical vertebral condyles, long trunk vertebrae and fused chevrons (Russell 1967; Bell & Polcyn 2005). These characters, however, have also been reported in the basal taxon <i>Dallasaurus</i> Bell & Polcyn, 2005; they could be plesiomorphic for mosasaurines instead of synapomorphies as usually considered (Bell & Polcyn 2005). The specimen has been compared to mosasaurines in which homologous bones are known, such as <i>Clidastes</i> Cope, 1868, <i>Kourisodon</i> Nicholls & Meckert, 2002, <i>Moanasaurus</i> Wiffen, 1980, <i>Eremiasaurus</i> LeBlanc <i>et al.</i>, 2012, <i>Prognathodon</i> Dollo, 1889, <i>Globidens</i> Gilmore, 1912, <i>Plesiotylosaurus</i> Camp, 1942, <i>Mosasaurus</i> Conybeare, 1822 and <i>Plotosaurus</i> Camp, 1951.</p><p>The “ Jerusalem Specimen 1” differs from: 1) <i>Clidastes,</i> which has a narrow frontal with nearly straight lateral margins that converged anteriorly and a weak median dorsal ridge, a straight fronto-parietal suture, a small parietal foramen located entirely on the parietal,prefrontal and postorbitofrontal widely separated above the orbit, and a jugal without any ventroposterior process (Russell 1967); 2) <i>Kourisodon,</i> which has basal tubera of the basioccipital that are oriented at 45° from the horizontal, and circular to pentagonal articular surfaces on the pygal vertebrae (Nicholls & Meckert 2002); 3) <i>Moanasaurus,</i> in which the frontal is a large triangular bone and the parietal foramen is small, circular and located on the parietal (Wiffen 1980, 1990); 4) <i>Eremiasaurus,</i> in which the frontal is a large and short triangle with a median ridge developed on the anterior two-thirds of the bone, and the jugal bears branches oriented at 90° (LeBlanc <i>et al.</i> 2012); 5) <i>Prognathodon,</i> which has a large, short triangular frontal with a straight suture with the parietal, a parietal foramen only on the parietal, a jugal with branches forming an angle of 75º and no posteroventral process, basioccipital with a small foramen on its floor, posterior dorsal vertebrae with vertical, long, oval articular surfaces, pygals with round articular surfaces, and other caudals with articular surfaces passing from horizontally oval to circular (Dollo 1889; Russell 1967; Lingham-Soliar & Nolf 1989; Schulp <i>et al.</i> 2008; Konishi <i>et al.</i> 2011); 6) <i>Globidens,</i> which has a massive triangular frontal with strongly diverging lateral margins, several dorsal ridges, a strong prefrontal-postorbitofrontal contact above the orbits, a suture with the parietal that is straight on its median part without no invading tongues and that runs strongly anteriorly, a parietal foramen on the parietal, a basioccipital with no distinct neck anterior to the condyle, so that it does not extend farther posteriorly than the basal tubera, which make a shallow angle in posterior view relative to other mosasaurines, a jugal with an extremely small posteroventral process, and a bowed and wide dentary (Russell 1975; Polcyn <i>et al.</i> 2010; LeBlanc <i>et al.</i> 2019); and 7) <i>Plesiotylosaurus,</i> which has a very robust triangular frontal with a weak anterior dorsal ridge, a prefrontal-postorbitofrontal strongly in contact laterally with the frontal above the orbit, a stout and wide postorbitofrontal dorsal surface, and a very small parietal foramen (Camp 1942; Lindgren 2009).To sum up, the “ Jerusalem Specimen 1” greatly differs from basal Mosasaurinae such as <i>Clidastes</i> and from Globidensini.</p><p>On the contrary, it shares several similarities with Mosasaurini (= Plotosaurini of Bell (1997) – see LeBlanc et al (2012) and Madzia & Cau 2017 for nomenclatural details) that include an intricately undulated frontal-parietal suture with posteromedian flanges of the frontal embracing the parietal foramen, a frontal with strongly developed posterolateral alae,laterally and ventrally expanded postorbitofrontal (at least in <i>Mosasaurus</i>, see Street & Caldwell 2017). All these characters imply a loss of movements along the mesokinetic axis (Russell 1967; LeBlanc <i>et al.</i> 2013). It shares also no basal artery canal on the basioccipital, dorsal vertebrae with circular articular surfaces, triangular pygals and fused chevrons. Some similarities and differences with both <i>Mosasaurus</i> and <i>Plotosaurus</i> have been observed, making the “ Jerusalem Specimen 1” intermediate between these two taxa.</p><p>The “Jerusalem Specimen 1” has a fronto-parietal suture comparable to that of <i>Mosasaurus</i>, with thin and sharp posteromedian flanges of the frontal embracing the parietal foramen and no extensive prefrontal-postorbitofrontal contact above the orbit, at least in “gracile” species like <i>M. lemonnieri</i> Dollo, 1889 and <i>M. conodon</i> (Cope, 1881); the contact is broader in larger species like <i>M. hoffmanni</i> Mantell, 1829 and <i>M. missouriensis</i> (Harlan, 1834), forming a robust bar of bone lateral to the frontal (Lingham-Soliar 2000; Caldwell & Bell 2005; Konishi <i>et al.</i> 2014; Harrell & Martin 2015; Ikejiri & Lucas 2015; Street & Caldwell 2017). Unfortunately, the frontal-parietal complex and postcranial skeleton of <i>Mosasaurus beaugei</i> Arambourg, 1952 from the latest Cretaceous southern Tethys Margin (Middle-East, northwestern Africa and Brazil) (see Bardet <i>et al.</i> 2004; Bardet 2012a; see “Discussion”) is currently unknown, precluding any comparison. It differs in general from the genus <i>Mosasaurus,</i> which has a wide triangular frontal with strongly converging margins ending in a rectangular anterior part, a strongly developed dorsal median ridge, and only slightly emarginated posterolateral margins lateral to the median flanges, which are more developed posterior to the parietal foramen (a distance at least its length), a generally circular parietal foramen located on the parietal at some distance from the frontal-parietal suture, branches of the jugal that form an angle of 90°, and basioccipital basal tubera that form an angle of 80% to the horizontal.</p><p>The “ Jerusalem Specimen 1” shares with <i>Plotosaurus</i> a narrow and long frontal bearing very emarginated concave posterolateral margins lateral to the median flanges (Camp 1942; Lindgren <i>et al.</i> 2008; LeBlanc <i>et al.</i> 2013). However, it differs from this genus, which has less anteriorly converging lateral margins (as a result the frontal remains broad anteriorly), no median dorsal ridge, stout rectangular posteromedian flanges, a very large parietal foramen located very near but not in contact with the suture, a broad prefrontal-postorbitofrontal lateral contact above the orbit, the ventroposterior process of jugal nearly absent, very short posterior dorsal vertebrae (L =W = H), and median caudals triangular to subhexagonal with H>W (Camp 1942; Lindgren <i>et al.</i> 2008; LeBlanc <i>et al.</i> 2013). It should be noted that <i>P. bennisoni</i> Camp 1942, the only currently recognized species of the genus, is probably a juvenile specimen (LeBlanc <i>et al.</i> 2013).In the largest probably adult specimens of the genus, previously referred to <i>P. tuckeri</i> Camp 1942 (now considered a synonym of <i>P. bennisoni</i>, Lindgren <i>et al.</i> 2008), the frontal is wider and more triangular, approaching the condition observed in <i>Mosasaurus</i>. It could thus be possible that the width and length of the frontal of <i>Plotosaurus</i> is ontogenetically controlled (M. Polcyn, pers. comm.), a condition already observed in <i>M. hoffmanni</i> (Harrell & Martin 2015). This could also apply to the relative development of the prefrontal-postorbitofrontal bar above the orbit, more developed in larger than in smaller species of <i>Mosasaurus</i>. In this case, however, this character could be size – but not necessarily ontogenetically – dependent, because smaller <i>Mosasaurus</i> species are currently recognized as valid and not considered juvenile of the larger ones (Street & Caldwell 2017). However ontogenetic growth or relative size of taxa are concerned, both are related to absolute size (small <i>versus</i> large).This hypothesis however cannot be confirmed nor rejected here and is beyond the scope of this paper.</p><p>To sum up, the “ Jerusalem Specimen 1” appears to be clearly a member of the Mosasaurini clade. However, its frontal-parietal-postorbitofrontal configuration, despite being intermediate between <i>Mosasaurus</i> and <i>Plotosaurus,</i> is unique in bearing a long narrow frontal with long narrow posteromedial flanges embracing a large oval parietal foramen in contact with the fronto-parietal suture, deeply emarginated posterior margins lateral to the median flanges, broad and large posterolateral cornua, a median dorsal ridge extended only onto the anterior third of the bone, and a short anterior branch of the postorbitofrontal that probably does not contact the prefrontal anteriorly (no bar above orbit). This combination of characters also clearly indicates reduction of cranial movements on the mesokinetic axis, characteristics of derived mosasaurines (LeBlanc <i>et al.</i> 2013).</p><p>Despite this unique suite of characters that could be suitable to erect a new taxon, due to the scarcity of the material and pending: 1) the discovery of homologous skeletal elements of <i>Mosasaurus beaugei</i> (including notably the frontal-parietal complex) for comparison, and because this species is the only one known from the latest Cretaceous Southern Tethys Margin and thus potentially present in Israel; 2) a review of <i>Mosasaurus</i> that appears paraphyletic in most recent phylogenetic analyses (e.g. Bell & Polcyn 2005; Madzia & Cau 2017; Simoes <i>et al.</i> 2017); and 3) a subsequent comprehensive review of the Mosasaurini and the understanding of the <i>Mosasaurus</i> / <i>Plotosaurus</i> relationships, this specimen is conservatively referred here to Mosasaurini <i>incertae sedis</i>.</p><p>PHYLOGENETIC AFFINITIES (Fig. 6)</p><p>In order to test the systematic assignment proposed above and provide additional support to the mosasaurine affinities of the “ Jerusalem Specimen 1”, a phylogenetic analysis using the previous one of Makádi <i>et al.</i> (2012) was performed (see Part “Preparation and cladistic analysis” for methodological details and Table 4). Note that <i>Eremiasaurus</i> was not included in this analysis because the paper of LeBlanc <i>et al.</i> (2012) appeared in the same year (but it has been shown above that the “ Jerusalem Specimen 1” is clearly different from this taxon).</p><p>The analysis generated three most parsimonious trees, each having 363 steps (CI = 0.4628, RI = 0.7310, HI = 0.5372). The strict consensus tree (Fig. 6) shows the same topology – beyond the scope of this paper to comment – as that reported by Makádi <i>et al.</i> (2012).</p><p>The analysis confirms the affinities of the “ Jerusalem Specimen 1” within the Mosasaurini as the sister-group of <i>Mosasaurus hoffmanni</i>, both being sister-groups of <i>Plotosaurus</i>. As previously mentioned in the comparison part, the “ Jerusalem Specimen 1” differs from <i>Mosasaurus</i>, especially the largest species of the genus such as <i>M. hoffmanni</i>, by several characters of its frontal-parietal-postorbitofrontal configuration.</p>