Bahariasaurus Ingens, Like Megaraptora

''Bahariasaurus'' (meaning "Bahariya lizard") is an enigmatic genus of large theropod dinosaur. The genus contains a single species, ''Bahariasaurus ingens'', which was found in North African rock layers dating to the Cenomanian age of the Late Cretaceous. The only fossils confidently assigned to ''Bahariasaurus'' were found in the Bahariya Formation of the Bahariya Oasis in Egypt by Ernst Stromer. This material was destroyed during a World War II bombing raid, with the same raid also destroying the holotypes of ''Spinosaurus'', '' Aegyptosaurus'', and other other animals found in the Bahariya Formation.

''Bahariasaurus'' is among the largest known theropods, estimated at long and around in weight. This approaches the size of other large theropods such as ''Tyrannosaurus rex'' and the contemporaneous ''Carcharodontosaurus''. The exact phylogenetic placement of ''Bahariasaurus'' has been debated. Some research has proposed close affiinities or even synonymy of ''Bahariasaurus'' and the coeval ''Deltadromeus''.

History and status

In early April of 1914, fossils of ''Bahariasaurus'' were unearthed from mudstone strata at Gebel Ghorabi near Ain Gedid, Egypt in 1922 by Austro-Hungarian paleontologist Richard Markgraf. Strata from this region derive from the Cenomanian-aged Bahariya Formation, around 95 million years old, one of many Cretaceous-aged sites of North Africa. In this formation, Markgraf did extensive collecting of dinosaur skeletons for his employer, German paleontologist Ernst Stromer of the Paläontologisches Museum München (Bavarian State Collection of Paleontology). These fossils were then shipped to the Museum München, however due to political tensions between the German Empire and then British-owned Egypt, these specimens took years to get to Germany. It was not until 1922 that they were transported overseas to Munich, where they were described by Stromer in 1934. Of the 1922 discoveries, these included a large theropod specimen, deposited under specimen number IPHG 1922 X 47, was made up of; two dorsal vertebrae, a dorsal neural spine, a dorsal rib fragment, three sacral vertebrae, the pubes, and an incomplete ischium. Motta ''et al'' (2016) stated that the dorsal vertebrae of IPHG 1922 X 47 were actually caudal vertebrae, though few authors have followed this interpretation. Another associated skeleton (IPHG 1922 X 48) was found in 1922 consisting of: a cervical vertebra, two dorsal vertebrae, and a pubis.

All of these fossils were described by Stromer in 1934 as belonging to a new genus and species of giant theropod dinosaur, ''Bahariasaurus ingens'', with IPHG 1922 X 47 and IPHG 1922 X 48 specified as type (name-bearing) specimens, making them syntypes. The generic name ''Bahariasaurus'' is combines Baharia, in reference to the Bahariya Formation where the fossils were unearthed, with the Latin root ''sauros'', meaning "lizard", while the specific name ''ingens'' comes from the Latin word for "huge". In the same work describing ''Bahariasaurus'', Stromer referred a multitude of other large theropod remains to ''Bahariasaurus'', including cervical and dorsal vertebrae, pelvic remains, a scapula, caudal vertebrae, a left and right femur, and a left fibula. An associated specimen containing was tentatively referred as well, containing: a cranial fragment, nine caudal vertebrae, and a scapulocoracoid. However, the scapulacoracoid appears to be from a spinosaurid. This leads to a total of 32 fossils referred to ''Bahariasaurus'' known from several different localities, with 18 of them being tentatively referred fossils whereas the syntypes make up the rest. These fossils, due to their differing origins to the syntypes, were noted by Stromer as possibly belonging to one or more species or even genus. The most notable of these remains was a large, long right femur (IPHG 1912 VIII 69) that Stromer noted as belonging to a theropod comparable in size to ''Tyrannosaurus''. Later authors have defended Stromer's attribution of these referred specimens to ''Bahariasaurus'', with Ijouiher (2022) stating that at least the coracoid, many of the vertebrae, and the pelvis are attributable to ''Bahariasaurus'' and distinct from other theropods. World War II broke out in 1939, leading to IPHG 1922 X 47 and other Bahariya material to be destroyed during a British bombing raid on Munich during the night of April 24/25, 1944. Nothing but illustrations of the ''Bahariasaurus'' specimens remains.

Remains questionably referred to ''Bahariasaurus'' have been found in the Farak Formation (Tegama Group) of Niger, consisting of a proximal caudal centrum (65 mm), two mid caudal centra and three mid caudal centra (from different individuals), were discovered and described by Albert-Félix de Lapparent in 1960. However, the attribution of these fossils to ''Bahariasaurus'' is questionable, with some authors stating that they could belong to a carcharodontosaurid whereas Ijouiher (2022) placed it as Theropoda ''incertae sedis''.

Description

''Bahariasaurus'' was a notably large theropod. Estimations suggest it approached the height and length of other large-bodied theropods such as ''Tyrannosaurus rex'' and the contemporaneous ''Carcharodontosaurus''. It has been estimated at in length and in weight.

''Bahariasaurus'' is only known from postcranial material. The two posterior dorsal vertebral centra are ~157% and 189% longer than they are tall and ~82% and ~95% wider than they are tall. All preserved sacrals have a longitudinally elongate pleurocoel and a ventral median groove, which is unknown in any ceratosaurs. The last sacral vertebrae known from ''Bahariasaurus'' implies that there was no greater fusion of the vertebrae after that.Stromer, E. (1934). "Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman)." 13. Dinosauria. Abhandlungen der Bayerischen Akademie der Wissenschaften, Mathematisch-naturwissenschaftliche Abteilung n.f., 22: 1–79.

Classification

Historically, the exact taxonomic placement of ''Bahariasaurus'' has been uncertain and debated; it has been variously assigned to several theropod groups, including the CarcharodontosauridaeRauhut, (1995). "Zur systematischen Stellung der afrikanischen Theropoden ''Carcharodontosaurus'' Stromer 1931 und ''Bahariasaurus'' Stromer 1934." ''Berliner geowissenschaftliche Abhandlungen'', E16 (Gundolf-Ernst-Festschrift): 357-375. and the superfamily Tyrannosauroidea.Chure, (2000). "A new species of ''Allosaurus'' from the Morrison Formation of Dinosaur National Monument (Utah-Colorado) and a revision of the theropod family Allosauridae." Ph.D. dissertation, Columbia University, 1-964.

Relationship to ''Deltadromeus''

During the 1990s, renewed interest in the Cretaceous dinosaur fauna of North Africa resulted in the conduction of many expeditions to fossil formations in Niger, Morocco, and Algeria. In a 1995 during a joint expedition by the University of Chicago and Service Géologique du Maroc to unexplored outcrops of the Kem Kem Beds, American paleontologist Paul Sereno found an incomplete postcranial skeleton of a theropod. This skeleton (UCRC PV11; = SGM-Din 2) was unearthed from Cenomanian-aged sandstones belonging to the upper part of the Gara Sbaa Formation at a locality known as Aferdou N’Chaft located in Errachidia, Morocco. The skeleton was found preserved in articulation, one of the few articulated dinosaur skeletons known from the Kem Kem Beds, and consists of: two dorsal ribs, two gastralia, several caudal vertebrae, eight chevrons, an incomplete scapulocoracoid, incomplete forelimbs, a partial pelvis, two partial hindlimbs, incomplete peses, and several additional fragments. In 1996, the specimen was described by Sereno and colleagues in the journal ''Science'' as a new genus and species of coelurosaurian theropod named ''Deltadromeus agilis''. In the same description, Sereno and colleagues reassigned the referred material, including the giant femur, of ''Bahariasaurus'' that had been unearthed in 1911 and 1912 to ''Deltadromeus''. However, Sereno and colleagues maintained that ''Bahariasaurus'' is a separate genus from ''Deltadromeus''.

In their 2016 description of ''Aoniraptor'', Motta et al. discussed the possibility that ''Bahariasaurus'', along with ''Deltadromeus'', ''Gualicho'', and ''Aoniraptor'', could form a clade ('Bahariasauridae') of megaraptorans distinct from megaraptorids. They did not perform a phylogenetic analysis to test these claims.

The roughly contemporaneous theropod ''Deltadromeus'', to which bones initially referred to ''Bahariasaurus'' have been referred, has been suggested to be synonymous with the latter taxon.Holtz, Thomas R. Jr. (2008) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages'
Supplementary Information
/ref> In a 2010 analysis of the Ceratosauria, Carrano and Sampson noted that the differences between ''Deltadromeus'' and ''Bahariasaurus'' were partily due to misidentified bones in the former, and that other distinctions were subtle and insufficient to distinguish the two. In 2020, Ibrahim and colleagues acknowledged similarities between the two genera, but considered it unlikely that ''Deltadromeus'' represents a specimen of ''Bahariasaurus'' due to perceived differences in the pelvic bones. They further regarded ''Bahariasaurus'' as a ''nomen dubium'' without explanation.

In 2024, Andrea Cau published a comprehensive theropod phylogenetic framework that could be used to identify immature specimens of other taxa. He included the ''Bahariasaurus'' type specimen in his analyses and recovered it within the ceratosaur clade Abelisauroidea in a polytomy including ''Deltadromeus''. The following year, Cau and Paterna used an updated version of this dataset to reanalyze the relationships of ''Bahariasaurus'', ''Deltadromeus'', and other Cretaceous theropods from Africa. They determined that the variation observed between specimens of ''Deltadromeus'' and ''Bahariasaurus'' was the result of individual and ontogenetic variation, as the former is known from immature remains. They further reidentified specimen SNSB-BSPG1912VIII82—incorrectly recognized as a indeterminate theropod pubis by Stromer in his 1934 description of ''Bahariasaurus''—as a complete . The authors observed anatomical characters that the bone shares with the less complete ischia of the holotypes of both ''Bahariasaurus'' and ''Deltadromeus'', which they used to strengthen their argument. They concluded that ''Deltadromeus'' should be regarded as a junior synonym of ''Bahariasaurus''. The results of their phylogenetic analysis are displayed in the cladogram below, with ''Bahariasaurus'' (including ''Deltadromeus'') indicated in the so-called "abelisauroid clade 1".

Paleobiology

''Bahariasaurus'' was one of four giant theropods known from the Bahariya Formation, the other three being the carcharodontosaurid ''Tameryraptor'' (originally assigned to ''Carcharodontosaurus'') and the spinosaurids ''Spinosaurus'' and ''Sigilmassasaurus'', though the validity of ''Sigilmassasaurus'' has been debated. The predators in the Bahariya Formation would have exhibited niche-partitioning to avoid competition. If ''Bahariasaurus'' is indeed an abelisauroid, it would have been related to taxa interpreted as being herbivorous or omnivorous, implying minimal resource competition with the coeval faunivorous theropods.

References

{{Taxonbar, from=Q133070

Ceratosauria
Dinosaur genera
Cenomanian dinosaurs
Dinosaurs of Egypt
Dinosaurs of Niger
Fossil taxa described in 1934
Taxa named by Ernst Stromer
Taxa with lost type specimens