Baalsaurus mansillai gen. et sp. nov. a new titanosaurian sauropod (Late Cretaceous) from Neuquén, Patagonia, Argentina

We describe a dentary of a new titanosaur sauropod, Baalsaurus mansillai, gen. et sp. nov. from the Late Cretaceous of Patagonia, Argentina. The material comes from the Portezuelo Formation, Neuquén Group. Titanosaur sauropods lower jaws are scarce and only nine taxa with dentaries have been described. There are two types of morphology in titanosaur dentaries; “L” shaped or “U” shaped based on the shape, without a phylogenetic issue. In this paper; we recognize a new taxa, Baalsaurus mansillai, represented by an “L” shaped dentary with three apomorphic characters that are not present in other taxa: dentary alveoli with 10 teeth in the anterior ramus, a ventrally and anteriorly inclined symphysis and a wide ventral Meckelian groove surrounded by a thin lamina that forms a keel on the ventral border of the dentary.

Etymology: The generic name is dedicated to the dinosaur site named Baal.Baal means the fertility god, whose cult was widespread in ancient Phoenician and Canaanite lands and saurus, a reptile.
Diagnosis: As for the species.

Holotype:
The specimen is represented by an almost complete right dentary with 13 alveoli housed at the Geology and Paleontology Museum of the National University of Comahue Museum, Parque Natural Geo-Paleontológico Proyecto Dino, Barreales Lake, Neuquén Argentina.MUCPv -1460;Figs. 3-7).
Etymology: The species, mansillai, honors to Mr. Juan Eduardo Mansilla, a technician at the Geology and Paleontology Museum of the National University of Comahue, Parque Natural Geo-Paleontológico Proyecto Dino, Barreales Lake, who discovered the material.
Diagnosis: Baalsaurus differs from other titanosaurs in the following combination of features: a) dentary alveoli with 10 alveoli on the anterior ramus, b) dentary with ventrally and anteriorly inclined symphysis and c) wide ventral meckelian groove surrounded by a thin lamina that form a keel in the ventral border of the dentary.

DESCRIPTION
The material described here is an almost complete right dentary of a titanosaur (Fig. 3-7).The tooth row begins just posterior to the symphysis and thirteen alveoli are present (Fig. 3).Replacement foramina are visible on the medial margin of the tooth row as are also present in Nemegtosaurus (Nowinski 1971) and Karongasaurus (Gomani 2005).There are at least three teeth replacement in each alveolous (Fig. 7).All of the preserved teeth are pencil-like as in other titanosaurs (Fig. 3, 7).The dentary in dorsal view is L-shaped forming a strong 90 degrees angle between anterior and posterior ramus giving a square jaw morphology (different to Nemegtosaurus and Rapetosaurus but similar to Antarctosaurus).The anterior margin is straight, where, ten alveoli are placed in the rostral or anterior ramus (Fig. 3).The alveolar segment of the dentary has a large anterior ramus and short posterior ones.Another alveolus, the biggest one, is placed at the corner of the "L" shape, and the other small three ones, are placed laterally.The articulated dentaries would have formed a rectangular shape as in some titanosaurs such as Antarctosaurus wichmanianus (Huene 1929), and diplodocids (McIntosh and Berman 1975).Just in the 10 th alveoli it is possible to recognize an unworn tooth in the bottom of it.The posterior ramus of the dentary, in the lateral view, has been slightly displaced inward by postmortem deformation (Fig. 5), but this distortion is not seen in medial view (Fig. 4).Therefore, the medial side shows the real shape of the dentary in dorsal view.No dorsal and ventral rami have been preserved on the posterior part of the dentary.
The symphysis shape is subtriangular, higher than wider, and it is directed ventrally and forward.The symphyseal region is complete but the distal dentary is not well preserved.The dentary symphysis is inclined ventrally and inclines forward, a character not seen in other titanosaurs (Fig. 6).
In anterior view (Fig. 3), the dentary is deep dorsoventrally; the dorsal margin of the alveolar series is almost straight; and the ventral JORGE O. CALVO and BERNARDO GONZALEZ RIGA border is strongly convex as in Antarctosaurus wichmanianus (Huene 1929).From the symphysis, the dentary deepens backward; this expansion is well developed from the 3 rd to the 8 th alveoli.From there, the ventral border runs almost in a straight line from the anterior side to the lateral end (Fig. 4-6).The ventral border of the dentary possesses on its anterior portion a very thin lamina or keel that born at the level from the 3 rd alveoli and disappear at the level of the 8 th alveoli (Fig. 5).On the medial side, the keel is slightly curved upward, probably to enclose the Meckelian groove (Fig. 4-6).
In lingual or medial view, the dental vascular foramina of the alveolar series are well exposed (Fig. 4).The 1 st dental foramen is placed 11 mm down of the alveolar margin, dental foramen 9 th is few mm below and the thirteen dental foramen is placed close to the alveolar margin (Fig. 3, 4, 6D).The dental foramina line is almost parallel to the ventral margin of the dentary, if we do not consider the ventral keel that encloses the Meckelian groove.The Meckelian groove is wide anteriorly and surrounded by a keel that turns lingually (Fig. 4, 6D).The depth of the Meckelian canal decreases posteriorly from alveolous 2 nd to 8 th ; and then from that point, it runs below the ventral border of the dentary on an almost flat surface and.Near the symphysis, the groove rises slightly to form a prominent notch on the ventral side of the articular surface (Fig. 4).
In dorsal view (Fig. 3), the curvature of the dentary, towards the midline, begins at the level of its minimum vertical depth, the 10 th alveoli (as in Rapetosaurus).The outlines of the alveoli are subcirculars from the 1 st to 7 th , the 8 th is circular, the 9 th and 10 th are almost fused, with the 10 th the largest in the series.The 11 th to 13 th alveoli are on the lateral side of the dentary and are somewhat crushed, and very small.
A CT-Scan shows that there are at least three teeth in each alveolous, one belongs to one worn and two unworn teeth inside the dentary (Fig. 7).This is also present in a detailed study made on the Bonitasaura skull (Gallina and Apesteguia 2011), Antarctosaurus and in the fragmentary dentary of the titanosaur MCSPv−061 (García and Cerda 2010).

COMPARISONS
Dentaries with pencil-shaped teeth where used to include titanosaur + diplodocids (Coombs 1975, Dodson 1990, McIntosh 1990).However, Calvo (1994b) recognized differences in both lower jaw and tooth shape between titanosaurs and diplodocids: titanosaurs have chisel-like teeth with wear surface, among other characters, inclined 70 degrees or more with respect to the labio-lingual tooth axis.Diplodocids have peg-like teeth, with wear surface, inclined from 10 to 40 degrees with respect to the labio-lingual tooth axis.In sum, titanosaur´s teeth can easily be distinguished from diplodocid ones and therefore, it is possible to recognize dentaries from one to another clades.
Different forms of titanosaur dentaries can be identified in dorsal view.Usually, there are two types of morphology in titanosaur dentaries; "L" shaped or "U" shaped; however, we can recognize three different morphologies based on the new discovery; "L" shaped, "U" Shaped and "smoothly curved" shaped.
One of them is characterized by having a "U shape" with teeth placed both on the anterior and lateral ramus on the dentary, such as those present in the titanosaurian taxa Rapetosaurus, Nemegtosaurus, Ampelosaurus, Karongasaurus, Quaesitosaurus and Tapuiasaurus and they are associated with an elongated rostrum with cylindrical teeth exposed laterally and a tooth row that extends up to the level of the preantorbital fenestra (Wilson 2005).
The second form has a rectangular shape or "L" shaped with teeth restricted mostly to the anterior ramus of the dentary as seen in the diplodocid Diplodocus (McIntosh and Berman 1975: fig.5C), the rebacchisaurid Nigersaurus taqueti (Sereno et al. 1999) and the titanosaurs Antarctosaurus, Brasilotitan and the new taxon here described.Sauropod pencil like teeth are restricted to diplodocids and titanosaurs; however, jaw movement, tooth morphology and wear surface is different (Calvo 1994a, b).Because diplodocids belong to another clade of sauropods we are going to restrict our study only to titanosaur specimens.
The third form has a "smoothly curved" dentary and is present in Bonitasaura.Gallina and Apesteguia (2011) recognize this form as that present in Antarctosaurus but here we separate it because Bonitasaura dentary is more curved than Antarctosaurus and it is probably an intermedial morphology between the curved Nemegtosaurus and the squared outline of Antarctosaurus.
The number of teeth is difficult to know in many taxa because of missing parts.It was demonstrated    in the ventral border of the dentary, this character is considered an autopomorphy of Baalsaurus.Baalsaurus shares with Antarctosaurus wichmanianus, Brasilotitan and Bonitasaurus salgadoi "L" shaped dentary (Fig. 3).However, there are some differences that allow us to recognize it as a new taxon.
Comparing with Antarctosaurus wichmanianus the symphyseal anterior ramus is vertical but it not cants forward as in Baalsaurus.The posterior ramus and corner of the dentary of A. wichmanianus cants linguoventrally and in Baalsaurus is vertical.Unfortunately, there is not precision on the A. wichmanianus teeth number; but Huene (1929) count six on the posterior ramus and in the taxa here described there are just four.There is not a ventral keel in A. wichmanianus.The number of total teeth is eighteen different to Baalsaurus with thirteen.
Brasilotitan nemophagus has the dorsal symphyseal region of the dentary twisted medially and seven alveolous on the anterior ramus.However, in Baalsaurus, the symphysis is inclined antero-ventrally and it has ten alveolous on the anterior ramus.
The preserved mandible of Bonitasaura with "smoothly curved" shaped has 10 alveolus, some of them with teeth (Fig. 3), it should be one more and probably two disappeared (Apesteguia 2004, Gallina and Apesteguia 2011); therefore, it should have the same teeth number that Baalsaurus.
Compared with Bonitasaura dentary (Fig. 3-5); Baalsaurus has more differences; for instance, Bonitasaura has the curvature of the dentary less pronounced, and involve from alveoli 1 to 6 th then it goes straight producing a rectangular anterior ramus (Fig. 3).In Baalsaurus the curvature involves just the 10 th alveoli.Apesteguía (2004) diagnosed that "Bonitasaura differs from other titanosaurs in the following combination of features: dentary alveoli reduced in number (three in the main ramus, one in the angle, and up to seven in the anterior region)".However, we recognize in Bonitasaura the presence of three alveoli in the main ramus, three in the angle (curvature) and up to four on the anterior ramus (Fig. 3).Alveolus shape in Bonitasaura is subcuadrangular with the labial side straight different to Baalsaurus where they are mainly subcircular with the labial side circular (Fig. 4).The dental foramina are big and placed close to the alveolar margin in Bonitasaura but in Baalsaurus they are small, and they are separated from the alveolar margin (Fig. 4).The long axis of the dentary inclines strongly ventrally in Bonitasaura in such a way that the small kill present on the ventral side is placed horizontal as in Diplodocus; whereas in Baalsaurus it goes ventrally and then direct slightly forward (Fig. 5).Both labial and lingual side of the dentary is convex at the level of the 10 th alveolus in Bonitasaura but in Baalsaurus, at the level of the 10 th alveolus, the labial side is straight and then turnward labially being concave on the labial side and convex on the lingual one.In the ventral anterior side, near the symphysis there is a small keel in Bonitasaura but it is much stronger in Baalsaurus and very thin.No meckelian groove is seen in Bonitasaura but it is well developed in Baalsaurus (Fig. 4).
Apesteguia (2010) stated that the character "middle and posterior region of the dentary edentulous and forming a sharp dorsal edge" is an autopomorphy of Bonitasaura.However, it has been recently described in Brasilotitan (Machado et al. 2013).This character is not preserved in Baalsaurus; but for the shape of the preserved portion, it could have been present.
Finally, García and Cerda (2010) describe in detail a fragment of a titanosaur dentary from Anacleto Formation with seven alveoli, here considered 7 th to 13 th as it was supposed by García and Cerda (2010).The material classified as CSPv-061 shows a morphology similar to Baalsaurus in having a rectangular shape with convex lingual side dentary and a slightly straight labial side.The dental foramina are well separated from the alveolar margin as in Baalsaurus.The section of this material is relatively thin has in Baalsaurus.Alveoli in CSPv-061 are rounded similar to Barreales material.The symphysis is not well preserved but the section is subtriangular as in Baalsaurus.
According to the evidence the "L" shaped morphology of Antarctosaurus, Brasilotitan, Baalsaurus and the CSPv-061 dentary could be close relative.

CONCLUSIONS
In spite that "L" shape dentaries with teeth restricted to the anterior ramus of the dentary is shared between some titanosaur and diplodocid taxa, there are some morphological differences between them such as teeth placement and worn surface (Calvo 1994a, b).Baalsaurus mansillai is a titanosaur of medium size, with an estimated skull length of 40 cm compared con that obtained from Bonitasaura (Gallina and Apesteguia 2011).Dentary is similar to that of Antarctosaurus wichmanianus and Bonitasaura salgadoi because they share rectangular anterior snout, vertical teeth and restricted mostly to the anterior part of the dentary.Baalsaurus mansillai differs from Antarctosaurus wichmanianus and Bonitasaura salgadoi in having a vertical corner between anterior and posterior ramus.Baalsaurus mansillai is characterized by having a dentary with ventrally and forward inclination of the symphysis and a wide ventral meckelian groove surrounded by a thin lamina that form a keel in the ventral border of the dentary.

Figure 1 -
Figure 1 -Map of Neuquén Basin (Patagonia, Argentina) showing the locality where the holotype Baalsaurus mansillai gen.et sp.nov.was found.

Figure 6 -
Figure 6 -Baalsaurus mansillai n.g.n.sp.a: anterior view, b: lateral view, c: ventral view and d: lingual view.Arrows point the keel.

Figure 7 -
Figure 7 -Baalsaurus mansillai n.g.n.sp.Computed tomography-based digital visualization, a: slice in dorsal view, b: slice in lateral view.Arrows point to anterior.Scale bar: 1 cm.