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Praefectus

I have been reading up on Moroccan mosasaurs and one point of confusion that I have run into is differentiating teeth from Prognathodon anceps and Prognathodon giganteus. There seems to be a great deal of overlap in their descriptions and occasional contradictions in the scientific literature. 

 

 

The first issue I’ve noticed is that there seems to be a great deal of confusion over what to even call the two species.

 

Leiodon anceps (Owen, 1841-1845) was based on two tooth fragments and a section of jawbone. The genus was renamed Liodon by Agassiz (1846) because the name Leiodon was preoccupied by the pufferfish Leiodon Swainson, 1839. E.D. Cope (1869-1870) caused confusion by treating Liodon as synonymous with Tylosaurus. Further confusion was caused when the holotype material of Liodon was lost. This has resulted in authors suggesting that the Liodon is nomen dubium and all species under Liodon should be transferred to Prognathodon (Schulp et al. 2008). With regards to Moroccan specimens, Arambourg (1952) identifies prognathodontid teeth as ‘Mosasaurus’ cf. anceps. The smaller specimens identified by Arambourg have since been reclassified as teeth from Eremiasaurus heterodontus (Leblanc et al., 2012) and the larger teeth have been tentatively assigned to ‘Prognathodon anceps’. More recently, Bardet et al. 2015 suggested that the Moroccan ‘Prognathodon anceps’ may actually represent a unique species, separate from the poorly defined European M. (Leiodon) cf. anceps.

Prognathodon giganteus Dollo, 1904 (holotype IRScNB R106 / formerly 3103) was defined based on an incomplete skull and postcranial skeleton from the upper Campanian of the Ciply area, southern Belgium. Note that early mosasaurs, Lacerta gigantea and Mosasaurus giganteus both share a similar specific epithet to Prognathodon giganteus but are actually both junior synonyms of Mosasaurus hoffmannii.

 

For simplicity, I’m going to just refer to the two as Prognathodon anceps and Prognathodon giganteus.

 

In a recent thread, @pachy-pleuro-whatnot-odon made an informative post about the two prognathodontids. I have copied it below for context.

 

:bone::bone::bone::bone::bone::bone::bone::bone::bone::bone::bone::bone:Begin Quote:bone::bone::bone::bone::bone::bone::bone::bone::bone::bone::bone::bone:

 

 

…This is certainly another pair of nice teeth, even if they both belong to the most common prognathodontid species found in Morocco! I'd call them both P. giganteus from my experience, although the morphology of the top-most/first tooth conforms more with Bardet et al. (2014)'s Prognathodon nov. sp., which seems to correspond most to P. anceps as defined here. However, this is where I get confused between these two prognathodontid species, as the teeth of both species seem very similar morphologically (see below images):

 

1840452141_Prognathodonanceps.jpg.0adada5f7f46087499de0c16662a6bfc.jpg.357ad7126936b35c3e0984f97ada687d.jpg

Prognathodon (Mosasaurus) cf. anceps sensu Arambourg, figure 8 from Machalski et al., 2003. Campanian and Maastrichtian mosasaurid reptiles from central Poland

(some beautiful images of M. hoffmanni teeth in this publication too, @Praefectus)

 

322833159_Mosasauruscf.ancepssensuArambourg.jpg.c718fa0b13c7671f391b414e72309a32.thumb.jpg.c21e86f890739740b067b9d2463b229d.jpg

(Leiodon) cf. anceps, plate XXXVIII from Arambourg, 1952. Les vertébrés fossiles des gisements de phosphates (Maroc - Algérie - Tunisie)

 

506425887_PrognathodongiganteustoothfromMaastrichtianofBelgium.JPG.8a8f7b8c090b20285fce98be01d619ca.JPG

Prognathodon giganteus, figure 40 from Lingham-Soliar & Nolf, 1989. The mosasaur Prognathodon (Reptilia, Mosasauridae) from the Upper Cretaceous of Belgium

 

Amarabourg (ibid., p. 280-281) describes the teeth of Mosasaurus cf. anceps as follows:

Quote

 Ces dents appartiennent, suivant leur position sur les mâchoires, á divers types morphologiques; mais toutes sont, en général, trapues et robustes; certaines peuvent atteindre une très grande taille.

Les dents de la région symphysaire sont moins trapues que les suivantes; elles sont légèrement arquées en arrière suivant l'axe de la série dentaire; leur section, presque circulaire au niveau du collet, devient un peu ovale et irrégulière en se repprochant de la pointe. Le bord antérieur de la couronne porte une carène verticale bien marguée dans toute sa hauteur; une seconde carène, beaucoup plus obtuse naît au bord latéral externe mais ne s'étend pas, vers la bas, au delá du premier tiers de la hauteur; il en résulte, dans la partie supérieure de la dent, une section asymétrique.

Les dents latérales ont une couronne conique, un peu comprimée, et sont légèrement recourbées vers la commissure et vers le côté lingual; elles portent à chaque bord, symphysaire et commissural, une arête tranchante, finement crénelée, qui s'étend sur toute la hauteur. Cette arête sépare entre elles les faces labiale et linguale qui sont toutes deux fortement convexes; toutefois la face linguale des premières dents latérales l'est un peu plus que la face labiale. Leur section à la base est sensiblement circulaire; elle devient légèrement elliptique et anguleuse en se rapprochant de la pointe. Enfin, les dents tout á fair latérales sont comprimées avec une section symétrique nettement elliptique; leurs deux carènes sont fortement détachées.

 

 

Or, translated (mine):

Quote

These teeth belong to different morphological types according to their position along the jaw. However, all are generally stocky and robust. Some can reach a very large size.

The teeth of the symphyseal region are less stocky than the ones further along the jaw. They arch back slightly along the axis of the dental series and their cross-section, almost circular at the neck, becomes somewhat oval and irregular towards the apex. The anterior edge of the crown has a well-defined carina along its full apicobasal height. A second, more obtuse carina arises at the outer lateral edge but does not extend downwards past the first third of the height. This results in an asymmetrical section in the upper part of the tooth.

The lateral teeth have a conical crown which is somewhat compressed and curves slightly lingually and towards the commissure. They bear finely crenellated cutting edges that extend the full apicobasal height, both symphyseally and commissurally. This ridge separates labial and lingual surfaces, both of which are strongly convex. However, the lingual face of anterior lateral teeth is slightly more so than the labial face. The cross-section, circular at the base, becomes slightly elliptical and angular as it approaches the tooth apex. Lastly, the fully lateral teeth are compressed with a clearly elliptical symmetrical cross-section. Their two carinae are strongly detached.

 

Machalski et al. (ibid., p. 404-405) summarize this by stating

Quote

specimen ZPAL R. 9/3, a lateral tooth, measures 85.8 mm in height (inclusive of root), and shows well-developed anterior and posterior carinae, both with minute serrations. In cross section it is elliptical, with buccal and lingual surfaces subequal, the latter more broadly rounded. Facetting is not well developed, but is more clearly seen on the lingual surface. The crown is faintly posteriorly recurved, and more strongly so lingually. Enamel beading is present, but poorly developed. Specimen ZPAL R. 9/4 is 45 mm in height and has a subcircular cross section, with a more broadly rounded lingual surface, well-developed anterior and posterior carinae with minute serrations, faint facets on both surfaces, and depressed areas parallel to both carinae, along the entire crown height. Enamel beading is well developed.

 

 

In comparison, Lingham-Soliar & Nolf (ibid., p. 166-167) describe the teeth of Prognathodon giganteus as follows:

Quote

The teeth of P. giganteus are large, quite powerful in appearance and generally triangular in shape with somewhat posteriorly recurved tips. They are bicarinate with subequal buccal and lingual surfaces. In horizontal cross-section the tooth is subcircular and bears a close resemblance to Williston's (1897) cross-section of a tooth of P. overtoni. The teeth appear to be more or less uniform in size along most of the jaw ramus although this assessment is an inference based on an incomplete number of preserved teeth and tooth bases of the maxillae and dentaries.
Tooth surfaces are enamelled and appear to be covered in very fine vertical striae. This may on the other hand be an artifact of preservation caused by cracking of the enamel. Russell (1970, p. 374) on the other hand describes the enamel in P. giganteus as smooth but he may have based his statement on Dollo's (1904, p. 213) brief comment to that effect. Kues et al. (1985) also mention fine anastomosing striae in teeth which, however, are questionably referred to Prognathodon.

 

Overall, reading over all the slight differences in termonology used, the descriptions and images given for the teeth of both P. giganteus and P. anceps seem rather similar. However, Arambourg's definition of 'Mosasaurus' cf. anceps dates to 1952, whereas Dollo defined his P. giganteus in 1904. This would seem to suggest that P. giganteus might be the senior synonym. As Arambourg based his definition on Owen's 1841 description of Leiodon anceps, this seniority may be misleading, however, with P. anceps actually being the senior. Another reason to may be given more credence to the naming of P. anceps is that, according to Wikipedia "Prognathodon giganteus, named by Dollo in 1904, is one of species with the most brief descriptions, apparently only intended to provide a name for the skeleton of the mosasaur for exhibition in the museum hall". To my knowledge, the two prognathodontid species haven't ever been synonymized, however.

 

Quote from this thread:

 

 

:bone::bone::bone::bone::bone::bone::bone::bone::bone::bone::bone::bone:End Quote:bone::bone::bone::bone::bone::bone::bone::bone::bone::bone::bone::bone:

 

 

Below are some additional pictures and academic quotations relevant to the topic. 

 

This is the holotype skull of Prognathodon giganteus and a hypothetical sketch from Lingham-Soliar & Nolf, 1990.

holotype.JPG.a7c4c998eda8ddf55410cb490fe73368.JPG

166465494_PrognathodongiganteusLingham-SoliarNolf.thumb.JPG.1376c17cf6713ad0eec6a37cfa156bc3.JPG

 

Compare to some Prognathodon anceps skull reconstructions originating from Morocco.

471886383_Ancepsskull1.jpg.e5b973fb3cfecad3dd861ac17c3c8e90.jpg

481191092_Ancepsskull2.jpg.2a0246746f1fb83a363dd0d98c579c24.jpg

773906892_Ancepsskull3.jpg.b5aea9ff934d0cf95eb6f6a5dcbd8fb1.jpg

 

 

As far as descriptions of teeth go, Bardet and Pereda Suberbiola, 2002 describe Prognathodon giganteus in Jordan (NOT Morocco) as:

Quote

The teeth of Prognathodon giganteus are reported for the first time in Jordan. They were previously described as Mosasaurus cf. anceps by Arambourg et al. (1959). The teeth (NHM 5887; MNHN 1960-20; UD uncatalogued) have large and robust crowns with subcircular basal cross-section, subequal convex labial and lingual faces, two carinae, and anastomosing enamel especially prevalent on the blunt apical region (Fig. 2G). These teeth differ from those of Leiodon anceps  Owen, 1840 from the Campanian of England, which are laterally compressed, less robust and with a smooth enamel (Lingham-Soliar 1993). P. giganteus is known from the Maastrichtian of Belgium (Dollo 1904) and the Campanian of France (Bardet et al. 1997). This species also occurs in the Late Cretaceous Phosphates of Egypt (“mosasaur gen. et sp. indet.” of Zdansky 1935: pl. 1), Negev (pers. obs.), Syria (Bardet et al. 2000) and tentatively Angola (“Mosasauridae indet.” of Telles Antunes 1964: pl. 26 fig. 4). Moreover, isolated teeth from the Maastrichtian of Congo have been assigned to cf. Prognathodon giganteus (Lingham-Soliar 1994).

 

They include the following picture:

1953254972_PrognathodongiganteustoothGfromMaastrichtianofJordan.JPG.9058beb9639791ec97badc91a84edecf.JPG

 

Cappetta et al. 2014 described Prognathodon teeth from the Gantour basin as the following. Note that Prognathodon anceps is referred to as Prognathodon nov. sp. in this publication.

Quote

The genus Prognathodon is the largest-sized mosasaurid of the assemblage (largest tooth crowns more than 5 cm high)… It is represented by three different species. P. giganteus is the commonest species from L6 and is absent in the upper part of the succession. Its teeth are typically rounded in cross-section, poorly posteriorly recurved and without pinched carinae. The tooth crowns of P. currii are highly characteristic, being large high and straight cones with a blunt apex. It is the second rarest taxon after M. beaugei, only seven teeth have been unearthed, but having been found however in all levels. Curiously, the two largest teeth come from L5, the poorest level in vertebrate remains of the Benguerir succession. A third species of Prognathodon, here referred to as Prognathodon sp., is the commonest one in L3 and L2 but is absent in the lower part of the succession. The teeth are similar to those of an undescribed new species from Level III (Upper Maastrichtian) of the Ouled Abdoun Basin (N.B. unpublished data).

 

Bardet et al. 2015’s review of mosasaurid teeth differentiated Prognathodon teeth by the following.

Quote

Prognathodon nov. sp. (NB, unpublished data) is based on a partial skull found in the Upper CIII phosphatic level (Upper Maastrichtian) of the NE part of the Oulad Abdoun Basin. The species is otherwise very common with several well preserved specimens found in the Oulad Abdoun Basin, as well as isolated teeth in the Gantour Basin where they range through the entire Maastrichtian sequence (Cappetta et al., 2014). The teeth of Prognathodon nov. sp. correspond to the largest crowns descrbied by Arambourg (1952) as M. (Leiodon) cf. anceps Owen, 1840-1845. Other occurrences from the Southern Tethys Margin include Israel, Egypt, Brazil and Angola, and possibly also the Maastrichtian of Poland (Bardet, 2012).

Prognathodon nov. sp. is along with Prognathodon currii the largest of the Moroccan mosasaurids. Preserved skulls reach 150 cm long (NB, pers. obs. on unpublished specimens). The teeth are similar to those of P. currii and Prognathodon giganteus in being robust, large cones (5-6 cm high) with a sub-rounded to elliptical cross-section. They bear two prominent carinae extending along the entire crown height, and coarse, thick enamel that bears an anastomosed ornamentation towards the apex. These teeth. However, differ from those of the two other species of Prognathodon in their higher, sharper apex, and basal length about half the height (instead of two thirds) giving a less robust shape. Some teeth bear indistinct facets on the lingual surface…

…The teeth (of P. giganteus) are similar in their very large conical shape with subrounded basal cross-section, but differ in slight posterior curvature (instead of being straight). The apex is blunt and often worn. The enamel is thick and highly anastomosed. The base of the crown is weakly swollen. As in P. currii, the carinae are strongly marked and pinched from the main shaft with less visible serrations.

 

1523862957_MoroccanPrognathodongiganteusE.jpg.005b61d739710f2464fde3fd0e98ef44.jpg

E is Prognathodon giganteus. F is Prognathodon anceps. In my opinion, these teeth look like they come from the same mosasaur, but different parts of the jaw. 

 

 

To summarize: 

Character

Prognathodon anceps

Prognathodon giganteus

Size

Anterior teeth less stocky than lateral teeth (Arambourg, 1952)

 

Teeth robust, large cones (Bardet et al. 2015)

Large and robust in appearance (Bardet and Pereda Suberbiola, 2002)

 

The teeth appear to be more or less uniform in size along most of the jaw ramus although this assessment is an inference based on an incomplete number of preserved teeth and tooth bases of the maxillae and dentaries.
 (Lingham-Soliar & Nolf, 1992)

Recurve

Anterior teeth recurve posteriorly. Lateral teeth recurve posteriorly and slightly medially (Arambourg, 1952; Machalski et al. 2002)

Somewhat posteriorly recurved tips (Lingham-Soliar & Nolf, 1992)

Cross-section

Anterior teeth cross-section, almost circular at the neck, becomes somewhat oval and irregular towards the apex. Lateral teeth are compressed with an elliptical symmetrical cross-section (Arambourg, 1952; Machalski et al. 2002; Bardet et al. 2015)

In horizontal cross-section the tooth is subcircular and bears a close resemblance to Williston's (1897) cross-section of a tooth of P. overtoni (Lingham-Soliar & Nolf, 1992, Bardet and Pereda Suberbiola, 2002)

Carinae

Possess anterior and posterior carinae (Arambourg, 1952; Machalski et al., 2003)

They are bicarinate with subequal buccal and lingual surfaces (Lingham-Soliar & Nolf, 1992, Bardet and Pereda Suberbiola, 2002)

Labial (buccal) and lingual surfaces

Labial and lingual surfaces, both of which are strongly convex (Arambourg, 1952; Machalski et al. 2002)

Subequal convex labial and lingual faces (Bardet and Pereda Suberbiola, 2002)

 

Serrations (crenulations)

They bear finely crenellated cutting edges that extend the full apicobasal height, both symphyseally and commissurally (Arambourg, 1952; Machalski et al., 2003)

The carinae are strongly marked and pinched from the main shaft with less visible serrations (Bardet et al., 2015)

Surface features

Facetting is not well developed but is more clearly seen on the lingual surface. Enamel beading is present, but poorly developed (Machalski et al., 2002)

 

Some teeth bear indistinct facets on the lingual surface (Bardet et al., 2015)

 

Tooth surfaces are enameled and appear to be covered in very fine vertical striae. This may on the other hand be an artifact of preservation caused by cracking of the enamel. Russell (1970, p. 374) on the other hand describes the enamel in P. giganteus as smooth but he may have based his statement on Dollo's (1904, p. 213) brief comment to that effect. Kues et al. (1985) also mention fine anastomosing striae in teeth which, however, are questionably referred to Prognathodon. (Lingham-Soliar & Nolf, 1992)

 

Anastomosing enamel especially prevalent on the blunt apical region (Bardet and Pereda Suberbiola, 2002)

Pinched/unpinched carinae

Their two carinae are strongly detached (Arambourg, 1952)

Tooth crowns without pinched carinae (Cappetta et al. 2014)

 

The carinae are strongly marked and pinched from the main shaft with less visible serrations (Bardet et al 2015)

 

***Note the contradiction

Apex

Higher sharper apex (Bardet et al., 2015)

Blunt apex (Cappetta et al. 2014, Bardet et al 2015)

 

Based on all this, I think the defining differences the researchers are pointing are:

(1) P. anceps teeth are more laterally compressed than P. giganteus

(2) P. anceps teeth have “pinched” carinae while P. giganteus have unpinched carinae

(3) P. anceps teeth have a pointed apex while P. giganteus has a blunt apex

(4) P. anceps teeth are less posteriorly recurved than P. giganteus teeth

 

I’m not quite sure what to conclude. These features seem like they may fall within heterodonty or individual, ontogenetic, and sexual variation. Whether the two species can be differentiated based on cranial and postcranial elements is yet to be seen. I have not seen any attempts to synonymize the species. In my opinion, I don't think the two species are understood well enough to differentiate the them based solely on isolated teeth. I would like to hear what others have to say on the topic. 

 

 

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Firstly Prognathodon as a whole needs revising.

A number of species from Belgium,  the Netherlands and the United States are valid and some may well remain in Prognathodon.

Other valid species that have been referred to Prognathodon are going to end up in other genera; This has already happened to Gnathomortis stadtmanni and it appears "P." mosasauroides belongs in Eremiasaurus.

Species from New Zealand that have been placed in Prognathodon have been given new Genera in H. Streets PhD thesis on Mosasaurines.

There appears to be one or two species similar to Prognathodon in Morocco; these need to be described and named; they are likely not the same as the European species.

"P." kianda from Angola needs it's own genus; when it appears in cladistic analysis it never appears in a clade with Prognathodon; perhaps some of the Moroccan species will appear in the same genus as it.

Once this revision is done we will know a lot more about this group of Mosasaurs than we do at present.

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Praefectus
55 minutes ago, LeeB said:

Firstly Prognathodon as a whole needs revising.

A number of species from Belgium,  the Netherlands and the United States are valid and some may well remain in Prognathodon.

Other valid species that have been referred to Prognathodon are going to end up in other genera; This has already happened to Gnathomortis stadtmanni and it appears "P." mosasauroides belongs in Eremiasaurus.

Species from New Zealand that have been placed in Prognathodon have been given new Genera in H. Streets PhD thesis on Mosasaurines.

There appears to be one or two species similar to Prognathodon in Morocco; these need to be described and named; they are likely not the same as the European species.

"P." kianda from Angola needs it's own genus; when it appears in cladistic analysis it never appears in a clade with Prognathodon; perhaps some of the Moroccan species will appear in the same genus as it.

Once this revision is done we will know a lot more about this group of Mosasaurs than we do at present.

Prognathodon is weird because the type species, P. solvayi, does not closely resemble the other species placed under it. I predict Prognathodon currii will be the first species to be revised (and placed within globidensini). 

 

I remember reading H. P. Street's thesis. I found it really bizarre that she concluded that Mosasaurus beaugei was a junior synonym of Mosasaurus hoffmannii. If I recall correctly, one of her later publications corrected the mistake. 

 

The Moroccan species, Prognathodon cf. anceps and Prognathodon giganteus, are the two that I am curious about. The two seem extremely similar based on the dentition alone. I am unfamiliar with the cranial and postcranial elements, so there may be valid reason for keeping the two separate species. 

 

 

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As both species were named from non Moroccan material the Moroccan material will have to be compared to that material in the course of a revision.

P. sectorius may be able to be revised on the basis of some material found in the Netherlands a while back; and both P. currii and P. kianda are overdue to be revised.

M. beaugei does seem to be distinct from M. hoffmannii but they do seem to be reasonably closely related.

Much new material of M. beaugei has been found in the last decade or so; I am not sure how much would have been available to Street when she did her work for her PhD.

She does seem to agree that the two species are distinct now.

Now that she has published on what exactly M. hoffmannii is it will be interesting to see what she publishes on other Mosasaurines including Moanasaurus, various new Zealand specimens and the original "M". conodon from the eastern coast of the USA.

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Praefectus

I was reading up more on Prognathodon and stumbled across this publication on an occurrence in the Maastrichtian of Normandy, France. The authors included the following quote and images in reference to Prognathodon teeth with morphological similarities to P. giganteus and P. cf. anceps

 

Quote

They are closer to the teeth of P. giganteus DOLLO,
1904 (Campanian-Maastrichtian of Europe, Syria and Morocco)
[Lingham-Soliar and Nolf, 1989; Bardet et al., 1997;
Bardet et al., 2000, 2010), P. overtoni (WILLISTON, 1897)
(Campanian of South Dakota) [Lingham-Soliar and Nolf,

1989; Schulp, 2006], P. saturator DORTANGS et al., 2002
(Maastrichtian of The Netherlands) [Dortangs et al., 2002],
a new yet undescribed species from the Maastrichtian
of Morocco (N.B. pers. obs.)., and Dollosaurus (=
Prognathodon?) lutigini YAKOVLEV, 1901 (Campanian of
Ukraine) [Lindgren, 2005]. However, it is not possible to
determine them at the specific level so that they are here referred
to Prognathodon sp.

 

1335839747_Prognathodonsp.buffetaut20121.thumb.JPG.7a012492cb8474d737b83de37be05d0b.JPG1456905933_Prognathodonsp.buffetaut20122.JPG.995b69b455f719854e38793dae07bf1f.JPG

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Bardet is placing at least one of the Moroccan "Prognathodon" in this species group.

Perhaps P. solvayi and anything related to it will remain Prognathodon, this group could become Dollosaurus, and other species of "Prognathodon" will be split off into their own genera or in the case of "P." mosasauroides join Eremiasaurus.

We shall have to wait and see.

It would be interesting to know how close the Netherlands "P." sectorius is to "P." kianda, and if there is anything related to them in Morocco, Syria, Jordan or other parts of the Middle East. 

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Macrophyseter
On 5/11/2021 at 8:58 PM, Praefectus said:

I remember reading H. P. Street's thesis. I found it really bizarre that she concluded that Mosasaurus beaugei was a junior synonym of Mosasaurus hoffmannii. If I recall correctly, one of her later publications corrected the mistake. 

 

Out of curiosity, what's your opinion on Street's other proposition that WIS M. conodon should be reidentified as M. missouriensis and EC M. conodon should be a distinct genus?

 

 

On 5/13/2021 at 1:33 AM, LeeB said:

Much new material of M. beaugei has been found in the last decade or so

 

It's surprising how well-preserved and complete some of these material are, like the complete skeleton Nick Longrich posted in his blog, and yet remain unpublished. Perhaps maybe there's a long-term study underway that sheds light to them?

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pachy-pleuro-whatnot-odon
2 hours ago, Macrophyseter said:

It's surprising how well-preserved and complete some of these material are, like the complete skeleton Nick Longrich posted in his blog, and yet remain unpublished. Perhaps maybe there's a long-term study underway that sheds light to them?

 

I doubt it, to be honest. I mean, there were never that many researchers working on Moroccan mosasaur material to start with, and many of those are francophone. This is, to me, the outcome of the long standing cultural relationship between France and Morocco on the one hand and the linguistic barrier for researchers from other countries on the other. But it does mean there are less academics active in Morocco than might otherwise have been the case. It probably also means that that which is published gets published in french - and if palaeontological publication is in anyway similar to anthropological and archaeological literature, this means that there may exist entire parallel schools and data sets. Also, keep in mind that only a fraction of palaeontologists actually active in Morocco would be working on vertebrate material, and that mosasaur material is even just a fragment of that. There's also a lot of mosasaur palaeontologists that work in different countries, rather than Morocco, which might be due to things like political climate, the abundance of fakes and lack of stratigraphical context in Morocco. Certainly, there's a wealth of information there, but it's politically sensitive, not very well grounded and therefore a bit of a hot potato to work on - and that's not even considering the fact that by now so much data has accumulated that to properly describe material you'd need years to sort through the mess. I think that most scientists, for this reason, prefer to stay away from Moroccan material... Just my 2cts...

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  • 2 weeks later...
On 7/16/2021 at 11:39 AM, Macrophyseter said:

 

Out of curiosity, what's your opinion on Street's other proposition that WIS M. conodon should be reidentified as M. missouriensis and EC M. conodon should be a distinct genus?

 

 

 

It's surprising how well-preserved and complete some of these material are, like the complete skeleton Nick Longrich posted in his blog, and yet remain unpublished. Perhaps maybe there's a long-term study underway that sheds light to them?

Bear in mind that very few specimens of Mosasaurus missouriensis were known when the monograph by Russell (1967) was published. Now that more complete specimens of Mosasaurus missouriensis have been found in the Western Interior Seaway, Street's conclusion about the WIS specimens being missouriensis rather than conodon makes sense because they are older than the M. conodon holotype.  

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Praefectus
Posted (edited)
On 7/16/2021 at 1:39 PM, Macrophyseter said:

Out of curiosity, what's your opinion on Street's other proposition that WIS M. conodon should be reidentified as M. missouriensis and EC M. conodon should be a distinct genus?

Hello Macrophyster. Sorry for the slow response. I currently view the two as distinct genera and differentiable based on tooth morphology and enamel ornamentation. M. conodon is known from Upper Campanian through Lower Maastrichtian sediments and bears slender teeth with flat enamel faces (no lingual or labial facets). M. missouriensis is known from Upper Campanian rocks and has teeth with 4-6 labial facets, 8 lingual facets. I can't recall currently, but I think there are also some cranial differences between the two. 

 

Edit because I know Pachy-pleuro is gonna grill me for this: Crown facetting within Mosasaurus is sometimes variable depending on tooth size and should not be used as the sole means of differentiating species. 

Edited by Praefectus
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