| Bahariasaurus | |
|---|---|
 | |
| Bahariasaurus vertebra (1912 VIII 62) | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | Averostra |
| Genus: | †Bahariasaurus Stromer,1934 |
| Species: | †B. ingens |
| Binomial name | |
| †Bahariasaurus ingens Stromer, 1934 | |
| Synonyms | |
| |
Bahariasaurus (meaning "Bahariya lizard") is an enigmaticgenus of largetheropod dinosaur. The genus contains asingle species,Bahariasaurus ingens, which was found in North African rock layers dating to theCenomanian age of the Late Cretaceous. The only fossils confidently assigned toBahariasaurus were found in theBahariya Formation of theBahariya Oasis in Egypt by Ernst Stromer. This material was destroyed during aWorld War II bombing raid, with the same raid also destroying theholotypes ofSpinosaurus,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 asTyrannosaurus rex and the contemporaneousCarcharodontosaurus. The exactphylogenetic placement ofBahariasaurus has been debated. Some research has proposed close affiinities or evensynonymy ofBahariasaurus and the coevalDeltadromeus.
In early April 1914, fossils ofBahariasaurus were unearthed frommudstone strata at Gebel Ghorabi nearAin Gedid,Egypt byAustro-Hungarian paleontologistRichard Markgraf. Strata from this region derive from theCenomanian-agedBahariya Formation, around 95 million years old, one of many Cretaceous-aged sites ofNorth Africa.[1][2][3] In this formation, Markgraf did extensive collecting ofdinosaur skeletons for his employer, German paleontologistErnst Stromer of thePaläontologisches Museum München (Bavarian State Collection of Paleontology).[1] These fossils were then shipped to the Museum München, however due topolitical tensions between theGerman Empire and thenBritish-owned Egypt, these specimens took years to get to Germany. It was not until 1922 that they were transported overseas toMunich,[4]: 107–108 where they were described by Stromer in 1934.[5] Among the 1922 discoveries was a largetheropod specimen, IPHG 1922 X 47, comprising twodorsal vertebrae, a dorsalneural spine, adorsal rib fragment, threesacral vertebrae, thepubes, and an incompleteischium.[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 acervical vertebra, two dorsal vertebrae, and a pubis.[5][2][9]
All of these fossils were described by Stromer in 1934 as belonging to a newgenus andspecies of giant theropod dinosaur,Bahariasaurus ingens, with IPHG 1922 X 47 and IPHG 1922 X 48 specified astype (name-bearing) specimens, making themsyntypes. Thegeneric nameBahariasaurus is combinesBaharia, in reference to the Bahariya Formation where the fossils were unearthed, with theLatin rootsauros, meaning "lizard", while thespecific nameingens comes from the Latin word for "huge".[5] In the same work describingBahariasaurus, Stromer referred a multitude of other large theropod remains toBahariasaurus, including cervical and dorsal vertebrae, pelvic remains, ascapula,caudal vertebrae, a left and rightfemur, and a leftfibula.[5][10] An associated specimen containing was tentatively referred as well, containing: acranial fragment, nine caudal vertebrae, and ascapulocoracoid. However, the scapulacoracoid appears to be from aspinosaurid.[6] This leads to a total of 32 fossils[11][10] referred toBahariasaurus 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 toTyrannosaurus.[5][4][8] Later authors have defended Stromer's attribution of these referred specimens toBahariasaurus, with Ijouiher (2022) stating that at least the coracoid, many of the vertebrae, and the pelvis are attributable toBahariasaurus 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 aBritish bombing raid on Munich during the night of April 24/25, 1944.[12][4]: 117 Nothing but illustrations of theBahariasaurus specimens remains.[9]
Remains questionably referred toBahariasaurus have been found in theFarak Formation (Tegama Group) of Niger, consisting of a proximal caudalcentrum (65 mm), two mid caudal centra and three mid caudal centra (from different individuals), were discovered and described byAlbert-Félix de Lapparent in 1960.[13][6] However, the attribution of these fossils toBahariasaurus is questionable, with some authors stating that they could belong to acarcharodontosaurid[6][10][14] whereas Ijouiher (2022) placed it as Theropodaincertae sedis.[11]
Bahariasaurus was a notably large theropod. Estimations suggest it approached the height and length of other large-bodied theropods such asTyrannosaurus rex and the contemporaneousCarcharodontosaurus. 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 vertebralcentra are ~157% and 189% longer than they are tall and ~82% and ~95% wider than they are tall.[6] All preservedsacrals have a longitudinally elongatepleurocoel and a ventral median groove, which is unknown in anyceratosaurs. The last sacral vertebrae known fromBahariasaurus implies that there was no greater fusion of the vertebrae after that.[5]
The femur referred toBahariasaurus andDeltadromeus has a large accessory trochanter, a feature found on many theropods. This femur was noted to differ from that ofDeltadromeus in that it appears proportionally stouter, lacks a proximally (towards body) directed femoral head (proximal end of femur), and a shorter lateral accessory crest (extension of bone) on the distal end. The proximal inclination of the femoral head is an adaptation to weight-bearing observed in many dinosaurs,[10] however it is notably absent in this large femur. However, it is present in the smaller femur of theDeltadromeus holotype, suggesting they come from different taxa.[18]
Historically, the exact taxonomic placement ofBahariasaurus has been uncertain and debated; it has been variously assigned to several theropod groups, including theCarcharodontosauridae[10] and the superfamilyTyrannosauroidea.[19]
In a 1995 paper, German researcher Oliver Rauhut analyzed the systematics ofCarcharodontosaurus—though this was based on the material now referred toTameryraptor—andBahariasaurus. Rauhut theorized thatCarcharoodntosaurus andBahariasaurus were the only two named members of Carcharodontosauridae, but that the family may have originated in Tanzania.[20] This origin hypothesis was based on fossils of"Allosaurus"tendagurensis and "Megalosaurus"ingens, which are two theropods known from fragmentary remains from theLate JurassicTendaguru Formation.[21][22] However, later studies have not supported these conclusions, withCarcharodontosaurus remaining a carcharodontosaurid but is not recovered as a relative ofBahariasaurus,[23] "A."tendagurensis being an indeterminatetetanuran,[24][22][25]: 252 and"M." ingens possibly being a species ofTorvosaurus.[26][27]
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.[28][29][30] In a 1995 during a joint expedition by theUniversity of Chicago andService Géologique du Maroc to unexplored outcrops of theKem Kem Beds, American paleontologistPaul 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 theGara Sbaa Formation at a locality known asAferdou N'Chaft located inErrachidia, 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, twogastralia, several caudal vertebrae, eightchevrons, an incomplete scapulocoracoid, incompleteforelimbs, a partial pelvis, two partialhindlimbs, incompletepeses, and several additional fragments.[31][2] In 1996, the specimen was described by Sereno and colleagues in the journalScience as a new genus and species ofcoelurosaurian theropod namedDeltadromeus agilis. In the same description, Sereno and colleagues reassigned the referred material, including the giant femur, ofBahariasaurus that had been unearthed in 1911 and 1912 toDeltadromeus. However, Sereno and colleagues maintained thatBahariasaurus is a separate genus fromDeltadromeus.[2][31]
In their 2016 description ofAoniraptor, Motta et al. discussed the possibility thatBahariasaurus, along withDeltadromeus,Gualicho, andAoniraptor, could form a clade ('Bahariasauridae') ofmegaraptorans distinct frommegaraptorids. They did not perform aphylogenetic analysis to test these claims.[32]
The roughly contemporaneous theropodDeltadromeus, to which bones initially referred toBahariasaurus have been referred,[31] has been suggested to be synonymous with the latter taxon.[15] In a 2010 analysis of theCeratosauria, Carrano and Sampson noted that the differences betweenDeltadromeus andBahariasaurus were partily due to misidentified bones in the former, and that other distinctions were subtle and insufficient to distinguish the two.[33] In 2020, Ibrahim and colleagues acknowledged similarities between the two genera, but considered it unlikely thatDeltadromeus represents a specimen ofBahariasaurus due to perceived differences in the pelvic bones. They further regardedBahariasaurus as anomen dubium without explanation.[2]
In 2024,Andrea Cau published a comprehensive theropodphylogenetic framework that could be used to identify immature specimens of other taxa. He included theBahariasaurus type specimen in his analyses and recovered it within theceratosaur cladeAbelisauroidea in apolytomy includingDeltadromeus.[34] The following year, Cau and Paterna used an updated version of this dataset to reanalyze the relationships ofBahariasaurus,Deltadromeus, and other Cretaceous theropods from Africa. They determined that the variation observed between specimens ofDeltadromeus andBahariasaurus was the result of individual andontogenetic 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 ofBahariasaurus—as a completeischium. The authors observed anatomical characters that the bone shares with the less complete ischia of the holotypes of bothBahariasaurus andDeltadromeus, which they used to strengthen their argument. They concluded thatDeltadromeus should be regarded as ajunior synonym ofBahariasaurus. The results of theirphylogenetic analysis are displayed in thecladogram below, withBahariasaurus (includingDeltadromeus) indicated in the so-called "abelisauroid clade 1".[23]
| Abelisauroidea |
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Bahariasaurus was one of three giant theropod taxa known from theBahariya Formation, the other three being the carcharodontosauridTameryraptor (originally assigned toCarcharodontosaurus) and the spinosauridSpinosaurus. The predators in theBahariya Formation would have exhibitedniche-partitioning to avoid competition.[37] IfBahariasaurus 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.[23]
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