The last three decades have seen a great improvement in our understanding of the Dinosaurs, and other terrestrial Animals, inhabiting the Gondwana supercontinent during the Latest Cretaceous (Campanian–Maastrichtian). A large number of new Dinosaur species have been described from South America, India, Pakistan, Madagascar, and even Antarctica. However, two significant regions of Gondwana, Africa and Australia, still have very poor fossil records from this time, making it hard to understand the biogeographical connections between the faunas of these regions and that of other parts of the world. The Campanian–Maastrichtian Dinosaur record of mainland Africa is exceptionally poor, with a very limited amount of material known and most of that comprising of very fragmentary material and isolated skeletal elements, of limited use for morphological or phylogenetic studies.
The most complete Dinosaur fossil from the Latest Cretaceous of Africa is the Titanosaurian Sauropod Mansourasaurus shahinae, from the Campanian Quseir Formation of the Dakhla Oasis in the Western Desert of Egypt. This is a partial skeleton comprising the craniomandibular, postcranial axial, appendicular, and possible dermal elements, though many of the bones are significantly deformed, which makes interpreting these remains challenging. The partial hind limb of another Titanosauriform Sauropod has been reported from Maastrichtian phosphatic deposits in the Ouled Abdoun Basin of Morocco, and Sauropod fossils from the Latest Cretaceous of Kenya and Jordan (which lies on the Arabian Peninsula, still part of Africa in the Cretaceous). Furthermore, two species of Titanosaur, Rukwatitan bisepultus and Shingopana songwensis, have been described on the basis of partial skeletons from the Upper Cretaceous Namba Member of the Galula Formation of southwestern Tanzania, which may be Campanian or a little older. Numerous isolated Sauropod bones have also been reported from the Namba Member.
Most of these fossils were discovered in the first two decades of the twenty first century, however, another, as yet undescribed, Titanosaur is known from a partial skeleton recovered from the Quseir Formation of the Kharga Oasis in 1977, by a field team from the Technische Universität Berlin. Although briefly mentioned in several publications in the 1990s, no formal description of this skeleton or attempt to place it within a broader phylogenetic analysis has ever been published. Although this specimen is fragmentary, and many of the elements are distorted, it is the second-most complete Dinosaur skeleton from the Latest Cretaceous of Africa.
In a paper published in the Journal of Vertebrate Paleontology on 20 July 2023, Eric Gorscak of the Department of Anatomy at Midwestern University, Matthew Lamanna of the Section of Vertebrate Paleontology at the Carnegie Museum of Natural History, Daniela Swartz and Verónica Díez Díaz of the Museum für Naturkunde at the Leibniz-Institut für Evolutions-und Biodiversitätsforschung, Belal Salem of the Department of Geology at Benha University, the Mansoura University Vertebrate Paleontology Center, and the Department of Biological Sciences and Ohio Center for Ecological and Evolutionary Studies at Ohio University, Hesham Sallam, also of the Mansoura University Vertebrate Paleontology Center, and of the Institute of Global Health and Human Ecology at the American University in Cairo, and Marc Filip Weichmann of the Bundesanstalt für Geowissenschaften und Rohstoffe, present a formal description of the Kharga Oasis Titanosaur.
The skeleton was discovered by Werner Barthel and Ronald Böttcher of the Technische Universität Berlin in November 1977, collected in 27 plaster jackets, and returned to Berlin, where it remained overlooked for the next two decades. Barthel's records of the excavation show that the skeleton was damaged during the process, due to insufficient use of preservatives. In the 1990s the skeleton was transferred to the Institut für Paläontologie of the Freie Universität Berlin (where it was studied by Marc Filip Weichmann as the subject of his diploma thesis, as part of a wider transfer of palaeontological material collected in the Western Desert. In 2008, the Freie Universität Berlin abandoned its vertebrate palaeontology program, and the specimen was tranferred to the collection of the Museum für Naturkunde, along with a large number of other fossils from the Cretaceous of Egypt and Sudan. Gorscak et al. re-examined the specimen in 2017, finding that most of the material observed by Weichmann in the 1990s was still present, although some skeletal elements had received further damage, most of which has since been repaired, using photogrammetric records made by Weichmann during his study, and the left tibia had gone missing, although the records made of this bone by Weichmann during his study still exist.
Based upon the available material, Gorscak et al. describe the specimen as a new species, Igai semkhu, where 'Igai' was a deity worshipped in the region around the Dakhla and Kharga oases from at least the Old Kingdom to the Pharaonic Late Period, whose name is thought to mean something like 'Lord of the Oasis', and 'semkhu' means 'the forgotten', making 'Igai semkhu' 'the forgotten Lord of the Oasis', a reference both to its place of origin and the long period it sat overlooked in the collections of various institutions.
The skeleton comprises five fragmentary dorsal vertebrae, partial left coracoid, partial left ulna, three left metacarpals (I, IV, and V), the proximal part of the left pubis, both tibiae (a partial right and the complete and well-documented but currently missing left, Vb-634), the left fibula, and three metatarsals (left I, left and right II). Numerous other elements were apparently present when the skeleton was discovered, but are not missing and have not been observed by any members of the team.
The dorsal vertebrae of Igai semkhu lack hyposphene-hypantrum articulations, and its ulna has a prominent olecranon process, both of which mark it out as a Titanosaur. The fragmentary nature of the material, combined with the fact that many of the elements are distorted, prevent a very detailed reconstruction of the specimen, but it is estimated to have been about 10-15 m in length in life, and either mature or very close to maturity. This makes it slightly larger than Mansourasaurus shahinae, which is estimated to have been 8-10 m in length.
A phylogenetic study recovered both Igai semkhu and Mansourasaurus shahinae as Saltosaurids. This is interesting, as Saltosaurids are otherwise absent from Africa, while in Europe almost all Titanosaurs from the Latest Cretaceous are Saltosaurids, and of similar size to Igai semkhu and Mansourasaurus shahinae, implying a link between the Sauropod fauna of Egypt and that of Europe in the Latest Cretaceous. In sub-Saharan Africa and Madagascar, in contrast, there appears to have been a wider range of Titanosaur groups, matching the more diverse faunas of the Americas, and many species appear to have grown far larger than their Egyptian and European relatives.
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