Fossil vertebrates from the phosphate Basins of Morocco

 Geographical and geological contexts

 The phosphate deposits of Morocco are known since 1908, and are exploited as an economical resource since the 1920's (Office Chérifien des Phosphates, 1989). They are part of the Mediterranean Tethyan phosphogenic province which extends from North Africa to Middle-East (Lucas & Prévôt-Lucas, 1996). The Moroccan phosphate deposits outcrop in four basins, which are from NE to SW: Ouled Abdoun, Ganntour, Meskala, and Bou-Craa in the Sahara. Stratigraphically, they extend from the Late Cretaceous (Maastrichtian) to the Early/Middle Eocene, that is about 25 Ma, spanning the largest interval of time of all Tethyan phosphate deposits (Lucas & Prévôt-Lucas, 1996).

The fossiliferous phosphate series from the Ouled Abdoun Basin is characterized by the exceptional association of the following remarkable features :

• the fossils are plentiful, remarkably diversified, and well preserved;
• they document key periods of vertebrate evolution;
• the fossiliferous sites and outcrops are of very wide scale, with long time perspectives for excavations;
• the discovered fossil material is of both scientific (see works in references), patrimonial and museologic value, with complete and spectacular specimens (skulls and articulated skeletons, especially among mosasaurs and crocodilians).

The vertebrate faunas

 The phosphates of Morocco have yielded one of the richest known vertebrate marine fauna of the world, including various selachians, bony fishes and reptiles. Our recent research has yielded new and unexpected taxa from the continental fauna, including dinosaurs and pterosaurs in the Late Cretaceous levels and land mammals and seabirds in the Palaeogene ones. Our fieldworks since 1997 have yielded (1) new material enhancing considerably knowledge of taxa described by Arambourg (1952), and (2) regular discoveries of important new taxa. Fossil discoveries concern
the whole Maastrichtian-Ypresian phosphate series. The following tetrapod taxa have been recovered in association with the rich selachian and bony fish faunas:

Squamata: Varanoids, palaeophids, mosasaurids;

Crocodyliformes : Eusuchians and dyrosaurids;


Plesiosauria : Elasmosaurids;


Pterosauria : Azhdarchids;


Dinosauria : Saurischian titanosauriforms and ceratosaurians;


Aves : Odontopterygiforms, prophaethontids, and phaethontids


Chelonia : Bothremydids, chelonioids;


Mammalia (Placentals) : Hyaenodontid "creodonts", proboscideans, hyracoids and "condylarths".

Importance of the vertebrate collection from Moroccan Phosphate Basins

 The collection of the Ouled Abdoun fossils housed by the OCP is a major reference for the studies on the evolution of the vertebrate fauna during the key-period of the Mesozoic-Cenozoic transition. Mosasaurs and crocodyliforms from the Ouled Abdoun collection are among the most diversified and the best known from this period, and they illustrate respectively in situ K/T extinction and recovery events. The avian collection includes the oldest known modern birds (Neornithes) from Africa and it shed new light on the early evolution of the Neornithes. Mammals are among the oldest known African placentals, and among the oldest known representatives of modern orders of ungulates. The accurate biostatigraphy of the phosphate series is based on the selachian systematic associations and successions. It allows useful datations for the study of the evolution of recognized lineages and faunal associations. Ongoing chemo- and magnetostratigraphical studies will help to refine the stratigraphy and correlation of the phosphate series. The fossil collection provides data on the in situ evolution during an exceptionally large time span of ca. 25 Myr, in remarkable homogeneous sedimentological and paleoenvironmental contexts. It documents two periods of major faunal turnover: (1) the K/T transition, noteworthy illustrated by selachian and large marine reptile extinction followed by crocodilian and placental mammals radiations, and (2) the P/E transition, characterized by the selachian and crocodilian extinction and the replacement of primitive mammal taxa such as "condylarths" by more modern lineages such as proboscideans.

References

 Arambourg C. (1935). Note préliminaire sur les vertébrés fossiles des phosphates du Maroc. Bulletin de la Société Géologique de France, 5: 413-439, 2 fig., 2 pl.

Arambourg C. (1952). Les vertébrés fossiles des gisements de phosphates (Maroc-Algérie-Tunisie). Notes et Mémoires du Service Géologique du Maroc (Rabat), 92: 1-372.

Bardet (2004), Bardet et al. (2004a et b, 2005a et b) : see publications list of the team.

Bourdon (2005), Bourdon et al. (2005 a et b) : see publications list of the team.

Cavin et al. (2000) : see publications list of the team.

El Houssaini Darif (2007): see publications list of the team.

Gheerbrant (2001), Gheerbrant et al. (1996, 1998, 2001, 2002, 2003, 2005, 2006) : see publications list of the team.
Hua & Jouve (2004) : see publications list of the team.

Jouve (2004, 2005), Jouve et al. (2005a et b) : see publications list of the team.

Lucas J and Prévôt-Lucas L. (1996). Tethyan phosphates and bioproductites. In: Nairn AEM et al., eds.The Ocean Basins and Margins, The Tethys Ocean. New-York: Plenum Press, 8: 367-391.

Noubhani A, Cappetta H. (1997) : see publications list of the team.

Office Chérifien des Phosphates (1989). The phosphates basins of Morocco. In: Notholt AJG, Sheldon RP, Davidson DF, eds. Phosphates deposits of the world, Phosphate rock resources. Cambridge: Cambridge University Press, 2: 301-311.

Pereda Suberbiola et al. (2003, 2004) : see publications list of the team.