Your Friends The Titanosaurs: Igai semkhu

This happens to be the 400th post on Equatorial Minnesota, and it's on a fitting subject, as about 15% of the posts have been on titanosaurs. In fact, this particular titanosaur has been mentioned before, as a potential coming attraction. What was referred to as MB.R.Vb-621–640 in that post now has a name: Igai semkhu. Let's have a look at what this new genus and species can tell us.

Figure 1 from Gorscak et al. (2023), including quarry map (with lost material), reconstruction, and geographic insets (CC BY-NC-ND-4.0).

Genus and Species: Igai semkhu. This name is unusual in dinosaur paleontology in being based entirely on ancient Egyptian words and concepts. "Igai" is the name of a deity, a "lord of the oasis" worshiped around the Dakhla and Kharga oases, while "semkhu" is a form of the ancient Egyptian verb meaning "to forget", referring to the post-discovery history of the specimen (Gorscak et al. 2023) (shades of Thescelosaurus neglectus). The authors rendered their combination as "the forgotten lord of the oasis".

Citation: Gorscak, E., M. C. Lamanna, D. Schwarz, V. Díez Díaz, B. S. Salem, H. M. Sallam, and M. F. 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.

Geography and Stratigraphy: I. semkhu comes from south of the Kharga Oasis, a few km south of Baris in south-central Egypt. Stratigraphically it hails from the Campanian-age Quseir Formation, as does another titanosaur, Mansourasaurus shahinae (albeit from the Dakhla Oasis) (Gorscak et al. 2023). The Quseir is becoming like the formations in South America; Gorscak et al. reference another titanosaur specimen from the Kharga Oasis area (this is the one in Salem et al. 2020), due to be described.

Holotype: Vb-621–640 ("vertebrate fossil collection of the Sonderforschungsbereiches 69 of the Technische Unversität Berlin, Germany", but held at the Museum für Naturkunde in Berlin). This includes "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)" (Gorscak et al. 2023). The specimen was found associated over a small area.

As mentioned in the "Coming Attractions" post, I. semkhu goes back to a 1977 discovery. The holotype was collected in November 1977 by K. Werner Barthel and Ronald Böttcher of the Technische Unversität Berlin. They had originally found more of the skeleton; quarry maps indicate more than 30 pieces that were never elucidated and have likely disintegrated. Apparently not enough or the wrong kind of consolidants were used during collection, although to be fair, there may not have been a correct conslidant for some of the material; Gorscak et al. report that "the ends of several limb bones are preserved essentially as loosely compacted sediment", and you can probably guess how that would be a problem. In later years, preparation, transportation (including transfers involving three institutions), and inadequate storage all took a toll on the material, with the left tibia simply vanishing at some point between 1999 and 2008. The material that remains represents the second-best late Late Cretaceous dinosaur specimen from Africa, after the Mansourasaurus type. This is more of a reflection on the current rarity of Campanian–Maastrichtian dinosaur fossils from Africa than the unalloyed greatness of the specimen, as the I. semkhu holotype underwent some enthusiastic deformation that flattened and sheared bones (Gorscak et al. 2023).

A few references to the specimen escaped over the years (Brinkmann and Buffetaut 1990; Wieschmann 1999a, 1999b), but formal description had to first wait for its third institutional change (to the Museum für Naturkunde in 2008) and finally the initiation of a collaborative effort in the late 2010s. This produced the abstracts I cited in the other post (Díez Díaz et al. 2017; Lamanna et al. 2017; Gorscak et al. 2020), and finally the present publication.

Anatomically, I. semkhu definitely falls within the "gracile" camp of titanosaurs. This is convenient for distinguishing it from robust M. shahinae, because otherwise they have very little overlap. The M. shahinae holotype is biased to the front part of the body, while the I. semkhu holotype is mostly the midsection, with only the coracoid and first metatarsal in common. (The disassociated ulna potentially belonging to M. shahinae is also robust, which is a circumstantial point in favor of it belonging to that species.) The type individual of I. semkhu appears to have been at least close to maturity based on the neural arches being fused to the vertebrae, although it is possible that the coracoid and scapula weren't fused. The ulna is rather shorter than the tibia (658 mm versus 810 mm [25.9 in versus 31.9 in]), indicating it was not among the longer-armed titanosaurs. Overall body length of the type individual is estimated in the 10–15 meter (33–49 feet) range, moderately sized for a titanosaur and slightly longer than the type individual of M. shahinae (Gorscak et al. 2023).

As one of the handful of described African titanosaurs, I. semkhu is of interest as a data point for the biogeography and evolution of the group. The phylogenetic analyses of Gorscak et al. (2023) indicate it is most closely related to several southwest European titanosaurs of similar vintage (Ampelosaurus, Lirainosaurus, and Lohuecotitan), and more distantly to Mansourasaurus, Paludititan, and Opisthocoelicaudia + Nemegtosaurus (exact configuration varies). This implies a distinct North African/European clade with deeper connections to central Asia.

References

Brinkmann, W., and E. Buffetaut. 1990. Ein Dinosaurier-Teilskelett (Sauropoda) aus der Ober-Kreide von Ägypten. Nachrichten-Deutsche Geologische Gesellschaft 43:119–120.

Díez Díaz, V., E. Gorscak, M. C. Lamanna, D. Schwarz, and I. El-Dawoudi. 2017. The metatarsus of a Late Cretaceous titanosaur (Dinosauria: Sauropoda) from the Kharga Oasis of Egypt. Zitteliana 91:31–32.

Gorscak, E., M. C. Lamanna, V. Díez Díaz, D. Schwarz, B. S. Salem, G. Abu El-Kheir, and H. Sallam. 2020. A titanosaurian sauropod from the Campanian Quseir Formation of the Kharga Oasis, Egypt, supports Afro-Eurasian dinosaur faunal connectivity during the Late Cretaceous. Journal of Vertebrate Paleontology, Program and Abstracts, 2020:no page number because in the future we just know where things are.

Gorscak, E., M. C. Lamanna, D. Schwarz, V. Díez Díaz, B. S. Salem, H. M. Sallam, and M. F. 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.

Lamanna, M. C., E. Gorscak, V. Díez Díaz, D. Schwarz, and I. El-Dawoudi. 2017. Reassessment of a partial titanosaurian sauropod dinosaur skeleton from the Upper Cretaceous (Campanian) Quseir Formation of the Kharga Oasis, Egypt. Zitteliana 91:50–51.

Salem, B. S., G. Abu El-Kheir, M. C. Lamanna, E. Gorscak, S. El-Sayed, and H. Sallam. 2020. A new titanosaurian sauropod dinosaur partial skeleton from the Late Cretaceous (Campanian) of the Kharga Oasis, Western Desert of Egypt. Journal of Vertebrate Paleontology, Program and Abstracts, 2020:no page number because in the future we just know where things are.

Wiechmann, M. F. 1999a. Ein Titanosaurier-Teilskelett aus dem Campan von Ägypten/Western Desert. Jahrestagung der Paläontologischen Gesellschaft, Zürich 69:81–82.

Wiechmann, M. F. 1999b. Ein Titanosaurier-Teilskelett aus dem Campan von Ägypten – Western Desert. Diploma thesis. Institut für Paläontologie, Freien Universität Berlin, Germany.