''Igdamanosaurus'', meaning "lizard from Igdaman", is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

marine lizard belonging to the

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on ...

family. It is classified as part of the

Globidensini The Globidensini or Globidentatini are a tribe of mosasaurine mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the tribe, known as "globidensins" or "globidensine mosasaurs", have been recovered from North America, Eu ...

tribe (within the

Mosasaurinae The Mosasaurinae are a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "mosasaurines" and their fossils have been recovered from every continent excep ...

), and is like the other members of the tribe recognised by its rounded and knob-like teeth. These teeth indicate a highly specialized lifestyle, likely including a durophagous diet. The genus contains a single species, ''Igdamanosaurus aegyptiacus'', from

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval ...

-aged marine environments of

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

. Its fragmentary fossil remains have been recovered from the Duwi Formation of

Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Medit ...

Ouled Abdoun Basin The Oulad Abdoun Basin (also known as the Ouled Abdoun Basin or Khouribga Basin) is a phosphate sedimentary basin located in Morocco, near the city of Khouribga. It is the largest in Morocco, comprising 44% of Morocco's phosphate reserves, and a ...

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria t ...

, and the Dukamaje Formation of

Niger ) , official_languages = , languages_type = National languagesglobidensin ''

Carinodens ''Carinodens'' is an extinct genus of Cretaceous marine lizard belonging to the mosasaur family. "''Carinodens''" means "keel teeth" and was named in 1969 as a replacement name for ''Compressidens'', "compressed teeth", which was already in use ...

.'' Its fossils preserve blunt, rounded teeth similar to those of the other members of the

. These teeth were better suited for crushing armored prey like

molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...

and

turtles Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tur ...

, rather than

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

or other reptiles normally preyed on by other mosasaurs. The type specimen, BMNH R11898, is fragmentary and consists of three poorly preserved jaw fragments, two almost complete finely striated teeth, three tooth bases and fragments from at least five broken teeth. Though it is difficult to tell, these remains likely come from the same individual.T. Lingham-Soliar. 1991. Mosasaurs from the Upper Cretaceous of Niger. ''Palaeontology'' 34(3):653-670 The dentary is noted as being of massive proportions, similar to the massive and robust dentaries found in ''Globidens'' and ''

Prognathodon ''Prognathodon'' is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like ''Mosasaurus'' and ''Clidastes''. ''Prognathodon'' has been recovered from depo ...

''. A medially located shallow recess on the dentary indicates the groove for the splenial.

Dentition

The type specimen preserves seven teeth in various degrees of preservation which increase in size in an anteroposterior direction, except for the last tooth which is slightly smaller than the penultimate of the preserved teeth. The teeth are straight, broad cones with rounded and domed tips. In cross-section the teeth are subcircular. Tooth crowns possess unwaisted bases and are covered in fine parallel ribbing or ''striae'', numbering at approximately 65 to 70 per tooth. The teeth are more or less uniform across the dentary and the largest one measures approximately 27 mm high and 22 mm wide.

Classification

Originally named as '' Globidens aegyptiacus'' by Zdansky (1935),Zdansky, O. 1935. The occurrence of mosasaurs in Egypt and in Africa in general. ''Bulletin de l’Institut d’Egypte'' 17:83-94 the species was first recognised as sufficiently distinct to be separated into its own genus by Lingham-Soliar (1991), who named it ''Igdamanosaurus'' after the village of Igdaman (sometimes called In Dama), which was near to where the type specimen was found. Though undoubtedly similar to ''Globidens'' in its dental adaptations and similar to ''G. alabamaensis'' in possessing unusually small foramina for exits of the mandibular nerve on the lower lateral surface of the dentary, Lingham-Soliar (1991) noted that the vertical striae present in ''Igdamanosaurus'' would suggest that it represented a completely new type of durophagous mosasaur that was derived from a ''

Platecarpus ''Platecarpus'' ("flat wrist") is an extinct genus of aquatic lizards belonging to the mosasaur family, living around 84–81 million years ago during the middle Santonian to early Campanian, of the Late Cretaceous period. Fossils have been fo ...

''-like ancestor rather than a ''

Clidastes ''Clidastes'' is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like ''Mosasaurus'' and ''Prognathodon''. ''Clidastes'' is known from deposits ranging i ...

''-like one and thus classified it as part of the

Plioplatecarpinae Plioplatecarpinae is a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "plioplatecarpines" and have been recovered from all continents, though the occu ...

. The latest analyses all place ''Igdamanosaurus'' within the

however, within the

tribe as a close relative of ''

'' and ''Globidens''.

References

* ''Fossil Vertebrates - Fauna and Concepts'' by W. Sargeant and William A.S. Sargeant (page 41) * ''Ancient Marine Reptiles'' by Jack M. Callaway and Elizabeth L. Nicholls (page 287) * ''Vertebrate Fossils and the Evolution of Scientific Concepts'' by W. Sargeant (page 547) {{Taxonbar, from=Q5991623 Mosasaurids Mosasaurs of Africa Fossil taxa described in 1991 Mosasaurines