This Eremiasaurus tooth is preserved in natural matriz in exceptional way, inside his own matrix.
To read more about this type of Mosasaur (which was recently described), you can read the following reference from its authors: A. R. H. LeBlanc, M. W. Caldwell, and N. Bardet. 2012. A new mosasaurine from the Maastrichtian (Upper Cretaceous) phosphates of Morocco and its implications for mosasaurine systematics. Journal of Vertebrate Paleontology 32(1):82-104
In the international market is very common to find Mosasaurus rests coming from the phosphate quarries of the Upper Cretaceous of the Ouled Abdoun Basin (Morocco). This quarries have been exploited since the beginning of the past century. Many sellers that sell this fossils do not make a good precise taxonomic identification work. In these sites there are numerous different species of Mosasaurus described in the enormous assemblage of giant marine reptiles that reigned the seas during the Cretaceous. The main rich levels in these paleontological taxons are in the deeper stratigraphic levels of the sedimentarian filling of the Ouled Abdoun Basin. The age of these correspond to the Maastrichtian stage, 66 million years ago. Most of the research carried out on these marine reptiles from Morocco have been performed by French researchers.
Next we list the different Mosasaur species which have been recognised in the phosphate rocks in North Africa:
-Halisaurus aramborgi (Bardet et al., 2005)
-Halisaurus walkeri (Lingham-Solier, 1998)
-Prognathodon sp (Dollo, 1889)
-Prognathodon anceps (Leiodon anceps)
-Prognathodon solvay (Dollo, 1889)
-Prognathodon currii (Christiansen & Bonde, 2002)
-Eremiasaurus heterodontus (LeBlanc et al., 2012)
-Mosasaurus beaugei (Arambourg, 1952)
-Mosasaurus hoffmanni (Mantell, 1829)
-Tylosaurus (Marsh, 1872)
-Platecarpus ptychodon (Arambourg, 1954)
-Globidens phosphaticus (Bardet et al., 2005)
-Carinodens belgicus (Bardet et al., 2005)
The Ouled Abdoun Basin (or Khouribga Basin), located in the central sector of Morocco, is an enormous sedimentarian basin represented mostly by a vast filling of phosphate sediments. Apart from having a relevant raw material to be extracted, it has a series of very important paleontological sites in which amazing assemblages from big and small marine vertebrates are present. The basin has a so great continuity in its stratigraphic record that both the Upper Cretaceous as well as the two first epochs of the Paleogene (Paleocene and Eocene) can be studied. The main assemblage of vertebrate fossils of the Paleogene sector present there is composed by sharks, fish, turtles, marine snakes, rays, crocodiles, other types of reptiles and even marine birds. In the Cretaceous part we can add Mosasaurs, Pterosaurs and Plesiosaurs. Next you can visit a link with very interesting information about this sedimentarian basin rich in fossil vertebrates: Ouled Abdoun Basin
REPTILIA Linnaeus, 1758
SQUAMATA Oppel, 1811
MOSASAURIDAE Gervais, 1853
MOSASAURINAE Gervais, 1853
EREMIASAURUS, gen. nov.
Etymology—From the Greek eremia (masc., desert) and sauros (masc., lizard), referring to the arid climate in present day Morocco where this marine reptile was recovered.
LeBlanc, A.R.H., Caldwell, M.W. and Bardet, N. 2012. A new mosasaurine from the Maastrichtian (Upper Cretaceous) Phosphates of Morocco and its implications for mosasaurine systematics. Journal of Vertebrate Paleontology 32(1):82-104.
Diagnosis—Apomorphies of taxon: pterygoid teeth become increasingly curved posteriorly; pronounced heterodonty, anterior marginal teeth straight and conical, middle dentition composed of laterally compressed blade-like teeth with anterior and posterior serrated carinae, posterior teeth asymmetrically expanded anteriorly, producing highly convex anterior surfaces in lateral view; tooth enamel surfaces smooth; upper and lower teeth interdigitate tightly in anterior region of the snout, leaving interdental pitting of the bone between adjacent tooth crowns; interdental spaces decrease posteriorly in maxillae and dentaries.
13 teeth on a maxillary 16 teeth on a dentary .
Sources: The Fossil Forum - Moroccan Mosasaurs - General Fossil Discussion