r/Paleoblogs

https://www.tandfonline.com/doi/full/10.1080/02724634.2026.2701154

The Bahariya formation from the mid Cretaceous of Egypt was always a spot of interest. Richard Markgraf and Ernst Stromer recovered a range of large theropod bones from Bahariya in the 1910s. These include the iconic Spinosaurus aegyptiacus and recently named Tameryraptor markgrafi. Unfortunately, most of these fossils were later destroyed in the 1944 Munich bombing by allied forces during WWII. Because they're now gone, there's many mysteries with the Bahariya that will remain unsolved until new expeditions are carried out.

One of those is the controversial theropod Bahariasaurus ingens. Bahariasaurus is based primarily on axial and pelvic material (syntypes including elongate dorsal/sacral vertebrae and pubes). Stromer questionably referred additional elements, including limb material, to Bahariasaurus. However, a reliable referral is difficult because the type material of Bahariasaurus lacks any overlapping material. Despite this, many still referred these to the genus anyway. The material consists of limb elements from several different individuals. They include an incomplete left humerus IPHG 1912 VIII 193, fibula IPHG 1912 VIII 70, and the right femur IPHG 1912 VIII 69. The most noteworthy thing about them is their sheer dimensions. The femur was 122 cm in length, the fibula was 104 cm, while the humerus was about 40 cm preserved. These fossils seem distinct enough to suggest a new genus and support the evidence for a largely unrecognized group of theropods present in Gondwana.

The humerus is proportionately small and gracile. Stromer identified them as theropod and noted limited muscle attachment and mobility. This strongly matches that of abelisauroids, specifically the noasaurids as this has been reported in Deltadromeus and Gualicho. However, there are some morphological differences, such as much larger size and stouter build relative to the known Deltadromeus material that makes referral of the specimen to Deltadromeus problematic. The femur shares an expanded medial condyle with Deltadromeus, a trait seen in abelisauroids. It differs from Deltadromeus in having a proportionally stouter build, lacking a proximally directed (pointed towards the body) femoral head, and a generally shorter lateral accessory crest (short extension of bone) on the distal end. This means it lacks the adaptation to weight-bearing observed in many dinosaurs, which is a basal trait. Deltadromeus does have this feature despite coming from a much smaller animal. This is probably not ontogenetic as the Deltadromeus holotype was likely a mature animal based on fused ischial boot. The fibula very closely resembles Deltadromeus, however it too still differs due to the less-projected proximodistal end (dosen't extend out from the body) and a more extensive fibular fossa (large depression on the inner lower end of fibula), especially proximally. The specimens are all likely abelisauroid, perhaps even noasaurid, but were probably not the same genus as Deltadromeus. Based on large gracile abelisauroids like Deltadromeus, the resulting animals could reach a length of 11.5 to 12.2 meters with a possible height of 5 meters. A body mass using the femur indicates a weight of 4,600 kilograms.

Ecology is highly speculative as no complete skeleton exists, but based on other abelisauroids, it was probably an herbivore. It possibly had teeth as a juvenile, only to fall out once reaching adulthood. A greater height of 5 meters would have allowed it to possibly browse from small trees. Its imposing size alone would be a deterrent against most predators such as abelisaurids and crocodilyforms. The long, gracile hindlimbs indicate a fast-moving animal (for its size) that would allow it to out pace larger predators such as Tameryraptor. The reduced and gracile forelimbs were potentially used for display purposes and not helpful for feeding or defense.

There appears to be a giant gracile-limbed abelisauroid (possibly noasaurid) in the Bahariya formation, distinct from Deltadromeus and can not be compared to Bahariasaurus. What's bizarre is how such theropods haven't been reported almost anywhere else. Large noasaurids such as Deltadromeus, Gualicho, and an unnamed form from Maastrichtian India usually don't grow past 8 meters in length. Even the more robust abelisaurids aren't known to reach such dimensions. While the sheer size of the "Bahariya Behemoth" is highly anomalous, it wasn't the only instance of massive abelisauroid in Africa. In the Kem Kem Group in Morocco, there is a large posterior dorsal vertebra originally founded by Dale Russell in 1996. Cataloged as CMN 50403, the specimen was unidentified for years beyond being from a large theropod. It was later determined to be a sister taxon to a large noasaurid from Lybia, suggesting the specimen was probably abelisauroid. It was unusually large, with a body length of 10.68 meters despite only being a subadult. While no overlapping material exists, it's possible the "Bahariya Behemoth" and CMN 50403 belong to the same group of giant gracile abelisauroids in Gondwana. Exactly why they grew so massive is unknown

Here’s something you don’t see too often in paleoart, Rahonavis actually hunting Falcatakely when Rahonavis is usually portrayed as not hunting something the size of Falcatakely. I decided to show Rahonavis hunt Falcatakely because with the Raptor Prey Restraint model or RPR, Rahonavis could be able to take down Falcatakely and not just be restricted to eating small vertebrates and insects.

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Spinosaurus cf aegyptiacus: A behemoth spinosaurid found in both formations mostly represented by the subadult propsed neotype FSAC KK-11888. It has been debated whether or not Spinosaurus was present in Morocco as its holotype was found in Egypt. As of now, evidence lines up more than Spinosaurus existed in Morocco unless new fossils say otherwise. The referred neotype FSAC-KK-11888 was 11.5 meters and 4 to 5 tonnes, but possible adult instances were much larger. The rostrum MSNM-V4047 and left dentary NHMUK VP r 16421 are likely from adult specimens. They indicate a body size of 14 to 15 meters long and up to 10 tonnes in weight based on unpublished findings. Juveniles were 8 meters long and 1 to 2 tonnes based on individuals such as the premaxilla FSAC-KK-7281. Spinosaurus would have been a strong-skulled semiaquatic apex predator that fed on armored fish, plesiosaurs, crocodilyforms, and other vertebrates in the vast deep river systems of Kem Kem.

Carcharodontosaurus saharicus: A large giganotosaurine carcharodontosaurid present in the Douria formation. Due to no holotype specimen, It has been questioned if Carcharodontosaurus was found in the Kem Kem group. Despite this, a neotype specimen (UCRC PV 12) had been erected in 1996 by Paleontologist Paul Sereno. It was among the largest of the Carcharodontosaurids at 12 meters in length and weighing 7 or more tonnes. It was suspected of not being fully grown based on cranial nano-sutures in the skull. Carcharodontosaurus would have been a terrestrial apex predator feeding on the limited sauropod resources in Kem Kem.

Sauroniops pachytholus: A second large carcharodontosaurid from the Gara sbaa formation. Due to a poor specimen pool, the large frontal MPM 2594 is questionable in terms of taxonomic distinction. Some sources have claimed Sauroniops was 60% the size of Carcharodontosaurus, but no evidence exists to support this. Andrea Cau, the author who described Sauroniops, states it was larger than the Carcharodontosaurus neotype with a thicker cranium and bony bosses above the eyes. I will tentatively keep it here since the census is so split. There are several non overlapping materials from the same locality that could also belong to this taxon. Sauroniops would have operated the same way as Carcharodontosaurus. With a 12 to 13 meter body length and 7 tonne mass, it was a rugged skulled apex predator feeding on large prey like sauropods, restraining them with sickle-like pedal unguals and delivering powerful cutting bites.

Abelisauroidea indet: CMN 50403 is a large posterior dorsal vertebra originally founded by Dale Russell in 1996. The fossil was found in the Gara Sbaa formation of the kem kem group in Morocco. The animal would have lived during the Cenomanian in the mid Cretaceous period. It was re-examined by Robert Smyth in a 2019 paper that overviews Moroccan abelisauroids. It was noted as resembling a large gracile abelisauroid from the Cabao formation in Lybia, possibly a sister taxon. It was estimated to have been 10.68 meters long. This could mean CMN 50403 would be the largest abelisauroid currently known. Another interesting detail is that the presence of nano-sutures indicates it was only a subadult when it died.

Spinosaurine indet: Several pieces of isolated spinosaurid material from the gara sbaa formation, including a quadrate, quadratojugal, and femur, seem to support the controversial hypothesis of two spinosaurs in the Kem Kem. The cranial material came from mature animals despite being smaller than the subadult Spinosaurus neotype and have features that are more consistent with basal spinosaurines, unlike the more derived condition of Spinosaurus. At 9.5 meters and perhaps over 2 tonnes, It likely looked and behaved closer to Irritator or Ichthyovenator. It was probably a mostly terrestrial shoreline wader that fed on small and elusive prey along the river banks or in shallow waters.

Abelisauridae indet: A large bodied abelisaurid present in both formations of the kem kem group in Morocco. The largest specimen is OLPH 025 which was an isolated proximal femur. It was from a large animal at 7.4 meters long and 1.85 tonne. It would have rivaled Carnotaurus in size. A subadult specimen, the maxilla UCPC PV 10, was slightly larger than the Rugops holotype estimated at 5 meters long and 570 kilograms. Another individual, cervical vertebra FSAC-KK-5015, was a possible juvenile instance at around 2.7 meters long. Ibrahim et al.(2020) stated this abelisaurid cannot be referred to as Rugops, but one of his colleagues, Robert Smyth (2019), made a compelling case in favor covalence in this taxa. This abelisaurid was the truest definition of a mesopredator in a land of giants. It would have hunted small dinosaurs and crocodilymorphs on top of scavenging, not unlike the modern-day jackal.

Deltadromeus agilis: A large noasaurid from the Gara Sbaa based on the type specimen UCRC PV11. Deltadromeus was 8 meters in length and over 1 tonne in weight. Juveniles are over 2 meters in length. It was closely related to the Tanzanian Elaphrosaurs and other gracile abelisauroids. Like the Elaphrosaurs, it would have been an agile omnivore capable of speeds up to 30 miles per hour. A paper by Nizar Ibrahim and colleagues (2020) claimed the Deltadromeus type was a juvenile of Bahariasaurus, a mysterious giant theropod from Egypt. However, those claims so far have been untrue, and the two are distinct. It also can not be referred to the giant kem kem Abelisauroid CMN 50403 due to size and age. Deltadromeus was likely mature due to weight bearing adaptations in the femur and a fused ischial boot, while the much larger CMN 50403 was not at full maturity.

Noasauridae indet: One of the only small theropods in the Kem kem from the Gara sbaa formation. The first recognized specimen is a cervical vertebrate numbered FSAC-KK-5016, which can be distinguished from Deltadromeus mainly by body size. It was 1.5 meters long and weighed 20 kilograms as a subadult, its smaller than a 1 year old juvenile Deltadromeus specimen (ROM 64666) which was over 2 meters. A possible adult instance could be CMN 41873, a humerus of 2.4 meter individual. Some isolated material like teeth are also attributable to noasaurids. The taxon seems to be a close relative to Masiakasaurus, a shoreline predator that hunted small vertebrates like fish and snakes.

Unenlagiiae indet: A small parave (possibly unenlagiid) from the Gara sbaa formation of the Kem Kem Group. An isolated thoracic (lower back) vertebra cataloged NMC 50852 was noted as being “very similar” to the Madagascan Rahonavis. There were also some teeth and hand claws from the same area that strongly resembled Rahonavis as well. This likely parave was 1.7 meters long and 8.8 kilograms in weight, making it the smallest theropod from the Kem Kem. Given the possible relation to Rahonavis, it might be capable of flight or at least low gliding. It would have been a predator that hunted small animals like lizards and insects.

Theropods that may, or may not, be present in the Kem Kem Group:

Megaraptora?: Megaraptorans were hinted at before, but no smoking gun. A study published in 2024 used machine learning and phylogenetic analysis on isolated teeth from the Kem Kem Group. It ascribed a highly unusual, strongly curved, compressed tooth of a 7 meter theropod to either a megaraptoran or a non-abelisauroid ceratosaur.

Maniraptora?: An isolated manual ungual, BSPG 1993 IX 330, from an unknown locality. The bone is possibly maniraptoran and comes from an animal over 2 meters long. The shape is very peculiar, low, and elongated with a curious curve on the apex. No known theropod ungual in Kem Kem has these characteristics. In fact, nothing in Africa does, for that matter. The only specimen that shares a similar morphology is another ungual from the Marília formation of Brazil that matches the strange shape almost exactly. Both likely are from a clade of theropods currently unknown to science. All that can be said is that both are some form of non-paravian maniraptoran more derived than Ornitholestes and Alvarezsauridae.

Unknown: At the Shanghai National History Museum, Nizar Ibrahim teased the discovery of brand new fossil material belonging to a completely unnamed giant theropod. He seems to imply it's different from any confirmed theropod group in the kem kem. However, exactly what it could be is unknown.