| Igai Temporal range: Late Cretaceous, | |
|---|---|
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | † Sauropodomorpha |
| Clade: | † Sauropoda |
| Clade: | † Macronaria |
| Clade: | † Titanosauria |
| Family: | † Saltasauridae |
| Genus: | † Igai Gorscak et al., 2023 |
| Type species | |
| Igai semkhu Gorscak et al., 2023 | |
Igai is a genus of titanosaur from the Late Cretaceous Quseir Formation of Kharga Oasis, Egypt. The type species is Igai semkhu. [1]
The holotype specimen, VB 621–640, was originally excavated in November 1977 by Karl Werner Barthel and Ronald Böttcher of the Technical University of Berlin (TUB), and sent to Germany in 27 plaster jackets. Due to preparation choices and insufficient storage, the partial skeleton's state of preservation decreased. [1]
The specimen was first mentioned in the scientific literature in a few abstracts in the 1990s. On September 11, 2008, several dinosaur specimens from Egypt and Sudan were transferred to the Museum für Naturkunde, among them most of the Kharga specimen minus the left tibia and an isolated femur. The describers of Igai published more abstracts on it in 2017; work on the specimen was completed in September 2019. In 2023, they were named as belonging to a new genus and species of titanosaur, Igai semkhu. The generic name, "Igai", refers to a mysterious "lord of the oasis" worshipped around the Dakhla and Kharga Oases during the Old Kingdom of Egypt. The specific name, "semkhu", is Ancient Egyptian for "the forgotten", referring both to the specimen's convoluted history and the relatively recent discovery of non-marine Cretaceous vertebrates from continental Africa. [1]
Igai semkhu was relatively slender by titanosaur standards. It is distinguished from other titanosaurs by various details of its limb bones. The fifth metacarpal has two distinct tubercles on its medial side, one near the proximal end and one near the distal end, that are not seen in other titanosaurs. [1] The cnemial crest, a part of the tibia where several leg muscles attach, [2] is smaller and less projected than in other titanosaurs, with Mendozasaurus and juvenile Rapetosaurus being the most similar in this respect. [1] The first and second metatarsals show distinct grooves that are not seen in other titanosaurs. [1]
Based on comparisons with other titanosaurs, Igai has been estimated at 10–15 metres (33–49 ft) in length, larger than the sympatric Mansourasaurus which was 8–10 metres (26–33 ft) long. This reflects a trend where Late Cretaceous titanosaurs from Africa, Europe, and Arabia were small-to-medium sized; additionally, Diamantinasaurus , Epachthosaurus , and Opisthocoelicaudia approached the size of Igai. [1]
Igai was entered into a phylogenetic analysis and found to be in two possible positions: one as a close relative of the South American Saltasaurus and Neuquensaurus , and another in an Afro-Eurasian clade that includes Lirainosaurus , Opisthocoelicaudia , and the sympatric Mansourasaurus . The authors preferred the second result, since it conforms to a hypothesis that northern African taxa during the Cretaceous were more closely related to European ones while southern African taxa had more Gondwanan origins. The latter cladogram is shown below, with African taxa highlighted in red: [1]
Igai is known from the Quseir Formation, which preserves some of the few non-marine vertebrate remains known from the Late Cretaceous of North Africa. The fellow titanosaur Mansourasaurus is also known from this formation, found in nearby Dakhla Oasis. [3]
Argentinosaurus is a genus of giant sauropod dinosaur that lived during the Late Cretaceous period in what is now Argentina. Although it is only known from fragmentary remains, Argentinosaurus is one of the largest known land animals of all time, perhaps the largest, measuring 30–35 metres (98–115 ft) long and weighing 65–80 tonnes. It was a member of Titanosauria, the dominant group of sauropods during the Cretaceous. It is widely regarded by many paleontologists as the biggest dinosaur ever, and perhaps lengthwise the longest animal ever, though both claims have no concrete evidence yet.
Titanosaurs were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thriving at the time of the extinction event at the end of the Cretaceous. This group includes some of the largest land animals known to have ever existed, such as Patagotitan—estimated at 37 m (121 ft) long with a weight of 69 tonnes —and the comparably-sized Argentinosaurus and Puertasaurus from the same region.
Nemegtosauridae is a family of titanosaurian sauropod dinosaurs based on their diplodocid-like skulls. Only three species are known: Nemegtosaurus, Quaesitosaurus and possibly Tapuiasaurus, each from the Cretaceous.
Alamosaurus is a genus of opisthocoelicaudiine titanosaurian sauropod dinosaurs containing a single known species, Alamosaurus sanjuanensis, from the Maastrichtian age of the Late Cretaceous period in what is now southwestern North America. Isolated vertebrae and limb bones indicate that it reached sizes comparable to Argentinosaurus and Puertasaurus, which would make it the absolute largest dinosaur known from North America. Its fossils have been recovered from a variety of rock formations spanning the Maastrichtian age. Specimens of a juvenile Alamosaurus sanjuanensis have been recovered from only a few meters below the Cretaceous-Paleogene boundary in Texas, making it among the last surviving non-avian dinosaur species. Alamosaurus is the only known sauropod to have inhabited North America after their nearly 30-million year absence from the North American fossil record and probably represents an immigrant from South America.
Opisthocoelicaudia is a genus of sauropod dinosaur of the Late Cretaceous Period discovered in the Gobi Desert of Mongolia. The type species is Opisthocoelicaudia skarzynskii. A well-preserved skeleton lacking only the head and neck was unearthed in 1965 by Polish and Mongolian scientists, making Opisthocoelicaudia one of the best known sauropods from the Late Cretaceous. Tooth marks on this skeleton indicate that large carnivorous dinosaurs had fed on the carcass and possibly had carried away the now-missing parts. To date, only two additional, much less complete specimens are known, including part of a shoulder and a fragmentary tail. A relatively small sauropod, Opisthocoelicaudia measured about 11.4–13 m (37–43 ft) in length. Like other sauropods, it would have been characterised by a small head sitting on a very long neck and a barrel shaped trunk carried by four column-like legs. The name Opisthocoelicaudia means "posterior cavity tail", alluding to the unusual, opisthocoel condition of the anterior tail vertebrae that were concave on their posterior sides. This and other skeletal features lead researchers to propose that Opisthocoelicaudia was able to rear on its hindlegs.
Epachthosaurus was a genus of titanosaurian sauropod dinosaur from the Late Cretaceous. It was a basal lithostrotian titanosaur. Its fossils have been found in Central and Northern Patagonia in South America.
Trigonosaurus, is a genus of saltasaurid dinosaurs from the Maastrichtian Serra da Galga Formation of Brazil. The type species, Trigonosaurus pricei, was first described by Campos, Kellner, Bertini, and Santucci in 2005. It was based on two specimens, both consisting mainly of vertebrae. The two specimens were originally believed to have come from the same individual. However, one specimen was described as the holotype of Caieiria in 2022, while the holotype may have instead come from Baurutitan. Before its description, it was known as the "Peirópolis titanosaur", after the place it was found.
Pellegrinisaurus is a genus of titanosaurian sauropod dinosaur that lived in South America during the Late Cretaceous period. The holotype was found in the Allen Formation, Argentina.
Saltasauridae is a family of armored herbivorous sauropods from the Upper Cretaceous. They are known from fossils found in South America, Africa, Asia, North America, and Europe. They are characterized by their vertebrae and feet, which are similar to those of Saltasaurus, the first of the group to be discovered and the source of the name. The last and largest of the group and only one found in North America, Alamosaurus, was thirty-four metres in length and one of the last sauropods to go extinct.
Lithostrotia is a clade of derived titanosaur sauropods that lived during the Early Cretaceous and Late Cretaceous. The group was defined by Upchurch et al. in 2004 as the most recent common ancestor of Malawisaurus and Saltasaurus and all the descendants of that ancestor. Lithostrotia is derived from the Ancient Greek lithostros, meaning "inlaid with stones", referring to the fact that many known lithostrotians are preserved with osteoderms. However, osteoderms are not a distinguishing feature of the group, as the two noted by Unchurch et al. include caudal vertebrae with strongly concave front faces (procoely), although the farthest vertebrae are not procoelous.
Diamantinasaurus is a genus of titanosaurian sauropod from Australia that lived during the early Late Cretaceous, about 94 million years ago. The type species of the genus is D. matildae, first described and named in 2009 by Scott Hocknull and colleagues based on fossil finds in the Winton Formation. Meaning "Diamantina lizard", the name is derived from the location of the nearby Diamantina River and the Greek word sauros, "lizard". The specific epithet is from the Australian song Waltzing Matilda, also the locality of the holotype and paratype. The known skeleton includes most of the forelimb, shoulder girdle, pelvis, hindlimb and ribs of the holotype, and one shoulder bone, a radius and some vertebrae of the paratype.
Angolatitan is a genus of titanosauriform sauropod dinosaur from the Upper Cretaceous. It is also the first non-avian dinosaur discovered in Angola. The genus contains a single species, Angolatitan adamastor, known from a partial right forelimb. Angolatitan was a relict form of its time; it was a Late Cretaceous basal titanosauriform, when more derived titanosaurs were far more common.
Aeolosaurini is an extinct clade of titanosaurian dinosaurs known from the Cretaceous period of Argentina and Brazil. Rodrigo M. Santucci and Antonio C. de Arruda-Campos (2011) in their cladistic analysis found Aeolosaurus, Gondwanatitan, Maxakalisaurus, Panamericansaurus and Rinconsaurus to be aeolosaurids.
Rukwatitan is a genus of titanosaur sauropod dinosaur from the Galula Formation in Tanzania. It lived around 100 million years ago, during the middle Cretaceous. The species, which shared features with another southern African species, Malawisaurus dixeyi, measured 30 feet (9.1 m) from the head to the tip of the tail, and had forelimbs that were estimated around 6.5 feet (2.0 m) long. Its fossils were found embedded in a cliff face near Lake Rukwa in the Rukwa Valley, from which it gets its name.
Shingopana is a genus of titanosaurian sauropod from the Upper Cretaceous Galula Formation of Tanzania. It is known from only the type species, S. songwensis. Gorscak & O'Connor's phylogenetic testing suggest Shingopana is more closely related to the South American titanosaur family of Aeolosaurini than any of the titanosaurs found so far in North & South Africa.
Mansourasaurus is a genus of herbivorous lithostrotian sauropod dinosaur from the Quseir Formation of Egypt. The type and only species is Mansourasaurus shahinae.
Hesham Sallam is an Egyptian paleontologist and the founder of the Mansoura University Vertebrate Paleontology Center (MUVP-C), the first vertebrate paleontology program in the Middle East. He works as an associate professor at the American University in Cairo and Mansoura University. Sallam led the discovery and description of Mansourasaurus shahinae, a species of sauropod dinosaur from Egypt, which has improved understanding of the prehistory of Africa during the latest Cretaceous period. His work has helped popularize paleontology in Egypt.
The Quseir Formation is a geological formation in the vicinity of the Kharga Oasis in Egypt. It is Campanian In age. The lithology largely consists of soft shale with hard bands of sandstone, siltstone and phosphorite. The environment of deposition was nearshore to freshwater fluvio-lacustrine characterized by moist and aquatic habitats with a tropical warm-humid climate. It is conformably overlain by the marine late Campanian-Maastrichtian Duwi Formation, and unconformably overlies the Turonian Taref Formation. The sauropod dinosaurs Mansourasaurus and Igai are known from the formation, as well as the proximal fibula of an indeterminate theropod. Additionally the lungfish genera Lavocatodus and Protopterus, the crocodyliform Wahasuchus and the bothremydid turtle Khargachelys are also known.
Abditosaurus is an extinct genus of titanosaurian sauropod dinosaur from the Late Cretaceous (Maastrichtian) Tremp Group of Catalonia, Spain. The type and only species is Abditosaurus kuehnei. Phylogenetic analyses recover it within a clade of South American and African saltasaurines, distinct from other insular dwarf sauropods from the European archipelago. Abditosaurus inhabited the Ibero-Armorican Island, a prehistoric island made up of what is now Spain, Portugal, and southern France, and would have been the largest titanosaur species in its environment.
