This species belongs to a diverse group of long-necked plant-eating dinosaurs called Titanosauria.
The group is known for large body sizes, long necks and wide stance, and includes species ranging from the largest known terrestrial vertebrates to ‘dwarfs’ no bigger than elephants.
“Igai semkhu constitutes one of the most informative dinosaurs yet recovered from the latest Cretaceous of Afro-Arabia,” Dr. Gorscak and co-authors said.
The partial postcranial skeleton of Igai semkhu — five dorsal vertebrae and 12 appendicular elements – was found in the deposits of the Quseir Formation, east of Maks El-Bahari, Kharga Oasis, Western Desert of Egypt.
“Igai semkhu is the second titanosaurian species to be described from the uppermost Cretaceous Quseir Formation of the Western Desert oases of Egypt,” the paleontologists said.
Comparisons of the dimensions of known limb elements of Igai semkhu to more complete titanosaurs suggest that the individual was relatively medium-sized for the clade, perhaps 10-15 m (33-49 feet) in estimated total body length.
Igai semkhu was probably slightly larger than Mansourasaurus shahinae, the other named titanosaur species from the Quseir Formation and nearby the Dakhla Oasis, the total body length of which is estimated at 8-10 m (26-33 feet).
“Interestingly, and perhaps not coincidentally, all known titanosaurians from Campanian-Maastrichtian deposits in northern Africa (i.e., Igai, Mansourasaurus, and an unidentified form from Morocco) and the then-conjoined Arabian Peninsula were small to medium-sized for sauropod dinosaurs,” the researchers said.
“The same is true for most Campanian-Maastrichtian titanosaurs from southern Europe.”
“By contrast, some Campanian-Maastrichtian titanosaurians from the Americas reached much greater body dimensions, and similarly large-bodied species occurred at more southerly latitudes in Africa during a roughly equivalent geologic period such as reported yet-undescribed giant titanosaur bones from the Maastrichtian Lapur Sandstone of northwestern Kenya.”
Importantly, Igai semkhu reinforces the hypothesis of an Afro-Eurasian clade of latest Cretaceous titanosaurians, with the African representatives of this group being presently known only from the northeastern region of the continent, specifically, Egypt.
“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,” the scientists said.
“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.”
The findings were published in the Journal of Vertebrate Paleontology.