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| Igai semkhu Gorscak, Lamanna, Schwarz, Díez Díaz, Salem, Sallam & Wiechmann, 2023 |
ABSTRACT
Dinosaur fossils from the latest Cretaceous (Campanian–Maastrichtian) of Africa and the Arabian Peninsula are rare. Most discoveries to date have consisted of limited fossils that have precluded detailed phylogenetic and paleobiogeographic interpretations. Fortunately, recent discoveries such as the informative Egyptian titanosaurian sauropod dinosaur Mansourasaurus shahinae are beginning to address these long-standing issues. Here we describe an associated partial postcranial skeleton of a new titanosaurian taxon from the Upper Cretaceous (Campanian) Quseir Formation of the Kharga Oasis, Western Desert of Egypt. Consisting of five dorsal vertebrae and 12 appendicular elements, Igai semkhu gen. et sp. nov. constitutes one of the most informative dinosaurs yet recovered from the latest Cretaceous of Afro-Arabia. The relatively gracile limb bones and differences in the coracoid and metatarsal I preclude referral of the new specimen to Mansourasaurus. Both model-based Bayesian tip-dating and parsimony-based phylogenetic analyses support the affinities of Igai semkhu with other Late Cretaceous Afro-Eurasian titanosaurs (e.g., Mansourasaurus, Lirainosaurus astibiae, Opisthocoelicaudia skarzynskii), a conclusion supported by posterior dorsal vertebrae that lack a postzygodiapophyseal lamina, for example. Igai semkhu strengthens the hypothesis that northern Africa and Eurasia shared closely related terrestrial tetrapod faunas at the end of the Cretaceous and further differentiates this fauna from penecontemporaneous assemblages elsewhere in Africa, such as the Galula Formation in Tanzania, that exhibit more traditional Gondwanan assemblages. At present, the specific paleobiogeographic signal appears to vary between different dinosaur groups, suggesting that Afro-Arabian Cretaceous biotas may have experienced evolutionary and paleobiogeographic histories that were more complex than previously appreciated.
DINOSAURIA Owen, 1842
SAUROPODA Marsh, 1878
TITANOSAURIA Bonaparte and Coria, 1993
LITHOSTROTIA Upchurch et al., 2004
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| Location of discovery and quarry map of Igai semkhu (Vb-621–640). A, map of Egypt showing the location of the town of Baris in the Kharga Oasis region, denoted by orange star (modified from Sallam et al., Citation2018:fig. 1a); B, satellite image from Google Earth Pro of the research area south of Baris with approximate quarry location indicated by orange star; C, quarry map showing disposition of skeletal elements in situ with currently missing and/or obliterated elements in gray, modified from Wiechmann (Citation1999b:17); and D, skeletal silhouette (reversed and modified from Sallam et al., Citation2018:fig. 1c) with elements described in the current study shown in orange. Abbreviations: cor, coracoid; dv, dorsal vertebra; fib, fibula; mtc I, metacarpal I; mtc IV, metacarpal IV; mtc V, metacarpal V; mtt I, metatarsal I; mtt II, metatarsal II; pub, pubis; tib, tibia; ul, ulna. |
IGAI SEMKHU gen. et sp. nov.
Diagnosis— Characters supporting Igai semkhu as a titanosaurian sauropod dinosaur: dorsal vertebrae lacking hyposphene-hypantrum articulations; and ulna with prominent olecranon process. Autapomorphic characters of Igai semkhu: metacarpal V with proximomedial and distomedial tubercles; reduced cnemial crest of the tibia (does not exceed anterior margin of distal end of the tibia); and distal groove along dorsal margins of metatarsals I and II.
Etymology— “Igai” is the name of the enigmatic “lord of the oasis” deity that was venerated by inhabitants of the Dakhla and Kharga oases (and surrounding regions) in Egypt from roughly the Old Kingdom to the Late Period. The species epithet “semkhu” is the perfect passive singular participle, “the forgotten,” of “semekh,” the ancient Egyptian verb “to forget.” Collectively, “the forgotten lord of the oasis” alludes to both the relatively recent emergence of latest Cretaceous non-marine vertebrate fossils from continental Africa (particularly Egypt) and the lengthy and complicated history of the holotypic specimen (see above).
Eric Gorscak, Matthew C. Lamanna, Daniela Schwarz, Verónica Díez Díaz, Belal S. Salem, Hesham M. Sallam and Marc Filip Wiechmann. 2023. A New titanosaurian (Dinosauria: Sauropoda) from the Upper Cretaceous (Campanian) Quseir Formation of the Kharga Oasis, Egypt. Journal of Vertebrate Paleontology. e2199810. DOI: 10.1080/02724634.2023.2199810
