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Bahariasaurus
Extinct genus of theropod dinosaurs From Wikipedia, the free encyclopedia
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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 animals found in the Bahariya Formation.
Bahariasaurus is among the largest known theropods, estimated at 11–12 metres (36–39 ft) long and around 4 tonnes (3.9 long tons; 4.4 short tons) 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.
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History and status
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In early April 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.[1][2][3] 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).[1] 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,[4]: 107–108 where they were described by Stromer in 1934.[5] 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.[5][6] Motta et al (2016) stated that the dorsal vertebrae of IPHG 1922 X 47 were actually caudal vertebrae,[7] though few authors have followed this interpretation.[8][6] Another associated skeleton (IPHG 1922 X 48) was found in 1922 consisting of: a cervical vertebra, two dorsal vertebrae, and a pubis.[5][2][9]
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".[5] 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.[5][10] 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.[6] This leads to a total of 32 fossils[11][10] 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.[5][8] The most notable of these remains was a large, 1.22 metres (4.0 ft) long right femur (IPHG 1912 VIII 69) that Stromer noted as belonging to a theropod comparable in size to Tyrannosaurus.[5][4][8] 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.[11] 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.[12][4]: 117 Nothing but illustrations of the Bahariasaurus specimens remains.[9]
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.[13][6] However, the attribution of these fossils to Bahariasaurus is questionable, with some authors stating that they could belong to a carcharodontosaurid[6][10][14] whereas Ijouiher (2022) placed it as Theropoda incertae sedis.[11]
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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 11–12.2 metres (36–40 ft) in length and 4–4.6 tonnes (3.9–4.5 long tons; 4.4–5.1 short tons) in weight.[15][16][17]
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.[6] 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.[5]
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Classification
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Historically, the exact taxonomic placement of Bahariasaurus has been uncertain and debated; it has been variously assigned to several theropod groups, including the Carcharodontosauridae[10] and the superfamily Tyrannosauroidea.[18]
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.[19][20][21] 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.[22][2] 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.[2][22]
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.[23]
The roughly contemporaneous theropod Deltadromeus, to which bones initially referred to Bahariasaurus have been referred,[22] has been suggested to be synonymous with the latter taxon.[15] 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.[24] 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.[2]
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.[25] 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 an indeterminate theropod pubis by Stromer in his 1934 description of Bahariasaurus—as a complete ischium. 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".[26]
| Abelisauroidea |
| ||||||||||||||||||||||||||||||||||||||||||||||||
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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.[29] 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.[26]
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References
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