u/DifficultDiet4900

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

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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.

https://onlinelibrary.wiley.com/doi/10.1002/spp2.70115

https://www.science.org/doi/10.1126/sciadv.aeb7528

(Austronaga minuta by Gabriel Ugueto)

https://www.science.org/doi/10.1126/sciadv.aeb7528

(Austronaga minuta. by Gabriel Ugueto)

The name is Musango matusadonaensis, it is an unaysaurid sauropodmorph from the Late Triassic (Norian). It is known from a partial skeleton, found in the Pebbly Arkose Formation, located in Zimbabwe.

The generic name (name of the genus), on this case "Musango" both refers to the Musango Concession Area, the type locality of the genus, and is a word that means "living in the bush". The specific name (name of the species) on the other hand, on this case, "matusadonaensis", refers to the Matusadona National Park, also located near its type locality.

Here's a link to a article with more information on it: https://www.tandfonline.com/doi/full/10.1080/14772019.2026.2678610

Credits to Mark Witton for the illustration

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Model of Spinosaurus based on Nizar Ibrahim's unpublished data. The flesh models of Spinosaurus are available publicly on the Shanghai National History Museum channel on Bilibili. A deep and relatively broad torso does seem to suggest a front heavy animal. The somewhat short arms probably wouldn't be of help for locomotion. The reduced hindlimbs holding up a 10 tonne frame are highly inefficient for shoreline wading. This indicates that Spinosaurus would have had limited terrestrial capabilities, which supports a highly aquatic lifestyle. However, Ibrahim has yet to publish any studies on the topic and won't for a long time. His data may or may not hold up to scrutiny when it gets peer reviewed.

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In January 2026, Nizar Ibrahim held a talk at the Shanghai National History Museum in China. Since it was broadcast on the video platform Bilibili, it flew by the radar of Western viewers. I was told about this livestream a few days ago, so I downloaded the Bilibili app to watch it. There's several new pieces of information on Spinosaurus that were previously not public that should be noted.

Here are the noteworthy highlights:

Largest Spinosaurus specimens are 15 meters (1:02:29)

Largest Spinosaurus specimens weighed 10 tonnes, same as Tyrannosaurus (1:02:13)

PHD student working on Spinosaurus neck biomechanics (1:01:29)

Fsac-kk-11888 is now 70% complete (53:14)

New material of a giant unnamed theropod (1:06:08)

More Deltadromeus material (1:05:02)

All seems to point that Ibrahim considers Spinosaurus a 10 tonne highly aquatic river monster. Of course, none of this has been peer reviewed and might not hold up to scrutiny. However, this is the only real look at what Ibrahim and his colleagues are working on with this animal as of 2026.

Anteosaurus was a large dinocephalian from the Tapinocephalus Assemblage Zone in the Abrahamskraal Formation in mid-permian Southern Africa. It belongs to the Dinocephalians, a group of non-mammalian synapsids that were the most abundant terrestrial vertebrates during the permian. Essentially, they're "proto mammals." In a way, Anteosaurus was a bear before bears existed. But unfortunately, it became obscure, in the shadows of the gorgonopsid Inostrancevia alexandri and pelycosaur Dimetrodon.

Anteosaurus was perhaps the largest terrestrial predator of the Permian, with a body length of up to 5 to 6 meters. Previous weight estimates suggest the largest specimens where anywhere from 500 to 600 kg. However, these are possibly underestimated as older models used a more gracile body plan. A more likely weight range based on more modern models is 1000 to 2000 kg. Excluding dinosaurs, the only terrestrial predators that grew larger than Anteosaurus were the triassic rauisuchians, such as Fasolasuchus.

The skull of Anteosaurus could have reached a length of 80 centimeters (30+ inches). It was massively constructed with a deep, robust snout and extreme pachyostosis (thickened bone). Most distinctively, Anteosaurus possessed a long bony boss on its head and pronounced horn like bumps above the eyes. Interestingly, there's extreme variation between individuals. Some have both the "horns," and the boss massively thickened, while others have more prominent "horns" but a weaker or nonexistent boss, and others had both weakly developed "horns" and bosses. Juveniles lacked these features and the robust skull, but they would have developed them as they matured. These structures were probably used for infraspecific conflict, with individuals participating in shoving matches and maybe even head butting similar to modern bison.

The dentition of Anteosaurus was quite formidable. Near the front on the jaws, there's typically five upper and four lower incisors the interlock. They were conical and used more for peircing prey. Then there's four fang like canines, 2 giant ones on the upper jaws, and 2 smaller ones on the lower jaws. They were probably for stabbing the vitals of prey similar to other saber toothed carnivores. Behind the canines, Anteosaurus had 4 to 8 small postcanines on the upper jaw. These were more weakly developed but could still have aided in pulverising flesh and bone. If that wasn't enough, Anteosaurus also possessed small, gripping teeth on the palate (roof of the mouth). These palatal teeth were for additional gripping strength to restrain struggling prey. All these plus the large jaw muscles suggest a deadly bite that could tear apart flesh and crush bone.

There isn't much known on the limbs, but they should still be noted. Anteosaurus had a semi sprawling gait with flexible joints. Based on close relatives, Anteosaurus probably had well-developed claws and massively built forelimbs, allowing it to actively wrestle and restrain prey. The hindlimbs were proportionately shorter and less robust than the forelimbs. The femur possesses a fourth trochanter that is notably reduced. It probably wasn't particularly agile. Anteosaurus likely relied heavily on its forelimbs to restrain prey, perhaps in a similar fashion to bear and certain large felids.

Above all of these, one terrifying thing you wouldn't expect from this animal was its agility. Recent studies analyzing the internal structure of the braincase indicate that Anteosaurus was actually a highly agile and active predator (for its size). The inner ear structure is closer to modern mammalian predators than to reptiles. These findings indicate that it possessed the neurological adaptations necessary for relatively fast and calculated movements. Even scarier, the inner ear is similar in structure to its relative Titanophoneus, which hunted in the deep cover of night and dusk rather than in broad daylight. Anteosaurus' speed is unknown, but based on the broad body build and stocky limbs, it probably could have run like a bear. Short yet powerful bursts of speed to overwhelm prey.

All these findings suggest that Anteosaurus is an active ambush predator that hunted in low light conditions. The forelimbs would have wrestled prey to the ground, and the robust jaws would have dispatched it with powerful bites. Given the swampy environment Anteosaurus lived in, it was probably an efficient swimmer. The large and extremely rotund prey animals, such as the 3 tonne Jokeria and 2 tonne Tapinocephalus, would have required a robust build and large size to hunt. Despite the many unique adaptations this taxon had, it died out after a mid-permian extinction event that wiped out the dinocephalians.

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The skeletal reconstruction of Mastodonsaurus I used was heavily outdated. The tail was much longer, and the torso was proportionally shorter. There is a composite skeleton and flesh model with proper proprtions available at the Natural History Museum in Stuttgart. This indicates that Mastodonsaurus looked less like an elongated frog and more a tusked crocodile that lacked a neck. The long tail and shorter body makes Mastodonsaurus more streamlined and thus more efficient when ambushing prey. The jaw length was also too short. The study that estimated Mastodonsaurus had a 110 cm mandible length seems to have underestimated the largest known specimen's size. The scale bar in one of the figures from this study (figure 7) was too large, making the specimen look much smaller than it actually was. The largest known individual of Mastodonsaurus, SMNS 81310, would have had a mandible length of 140 cm. With the new proportions and 140 cm mandible, the resulting animal was over 7 meters long! This length is speculative as there are no modern skeletal reconstructions of Mastodonsaurus in literature. Regardless, the longer tail suggests Mastodonsaurus could have exceeded 6 meters.

The debate over the ecology of Spinosaurus has spanned over a decade, with no signs of slowing down. Spinosaurus is a highly enigmatic creature with curious anatomy, some not seen in any other dinosaur. Learning how this animal lived has always been a topic of interest. However, direct testing of the material has been uncommon. Only a single decent specimen exists (Fsac-kk-11888), and more material from it is still being uncovered. These gaps in information lead in interpretation, some plausible others not. The most popular theory today is that Spinosaurus was a shoreline predator, not unlike herons.

However, based on the current evidence from the skeleton, Spinosaurus was more likely to be a semi-aquatic subaqueous forager not unlike that of cormorants and some crocodilians. A lean body with a deep, robust tail is perfect for launching forwards. Its slim jaws were well adapted for relatively fast and powerful biting. The long neck would have had well developed muscle attachments for quick movement and high flexibility. The giant sail, while could cause drag, would do little to slow it down if Spinosaurus dived to certain depths, swam along the surface, or counteract it with sheer body size alone. Diving is possible thanks to the heavy bone frame consistent throughout the body. Spinosaurus would have fed on large, hard bodied prey items such as armored fish, crocodilyforms, turtles, and crustaceans in the low light conditions of deep and wide fluvial channels. Plesiosaurs and terrestrial animals could still be an option if in range. There is still more to be learned about Spinosaurus. The fossils don't lie. The problem is it takes time to describe such finds, which can lead to long periods of confusion and disagreements as interpretation is used to fill in the gaps.

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https://www.biorxiv.org/content/10.1101/2022.05.05.490811v1.full

Ashame this never saw peer review. It's a decent counter to Mvyhold et al. (2024)

The debate over the ecology of Spinosaurus has spanned over a decade, with no signs of slowing down. Spinosaurus is a highly enigmatic creature with curious anatomy, some not seen in any other dinosaur. Learning how this animal lived has always been a topic of interest. However, direct testing of the material has been uncommon. Only a single decent specimen exists (Fsac-kk-11888), and more material from it is still being uncovered. These gaps in information lead in interpretation, some plausible others not. The most popular theory today is that Spinosaurus was a shoreline predator, not unlike herons. However, existing data from the fossils suggest a more semiaquatic lifestyle.

There are two main hypotheses on Spinosaurus' ecology. The topic of the "aquatic" hypothesis of Spinosaurus comes from the discovery of a nearly complete pair of hindlimbs from a subadult individual (Fsac-kk-11888) in Morocco in 2014 by paleontologists Nizar Ibrahim, Paul Sereno, and colleagues. They stated Spinosaurus was incapable of bipedal locomotion and was thus more restricted to the water. The "wader" hypothesis began when the 2014 study was questioned in 2018 by Dr. Donald Henderson, who created 3d models of Spinosaurus and determined it was incapable of swimming. Instead, Spinosaurus was a competent biped and fully terrestrial animal staying on the shore of rivers. Henderson's study would later be criticized by the Ibrahim team in 2020 with the description of a tail from the same Spinosaurus individual. The tail was deep and kneeled, suggesting Spinosaurus used it to propel itself through the water. While they agreed Spinosaurus was biped, it was still very front heavy. Ibrahim et al. (2020) would later be questioned by David Hone and Thomas Holtz in the following year. They came to the same conclusion as Henderson, being that Spinosaurus was a fully terrestrial wader who was poorly suited for swimming. Then, their study was criticized in 2022 by Matteo Fabbri et al. with Ibrahim as a co-author. This paper looked into the bone density of Spinosaurus. They argued it had a consistently high density that is only seen in diving taxa that submerged themselves underwater. The wader Spinosaurus would return again in a 2023 study lead by Paul Sereno, Henderson as a co-author, and other colleges where they made a new 3d model to support their conclusions. They claimed Spinosaurus was an unstable swimmer incapable of diving. Instead, it waded in shallow water no more than 2.6 meters deep. In 2024, a paper be Nathan Mvyhold et al. with Sereno as a co-author criticized Fabbri et al. (2022) bone density study stating it's not good enough evidence for diving to be possible in Spinosaurus. Fabbri et al. did have a preprint response to the study, by it was never published. This debate is bound to continue with Nizar Ibrahim's team describing the new material of Spinosaurus. They stated that it had special adaptations for underwater feeding. On the other hand, the Sereno team planned on publishing a paper claiming Spinosaurus had adaptations for feeding above water. David Hone also has a study in the works claiming Spinosaurus didn't have webbed feet, and the feet were instead used for weight support on land. All this to say, Spinosaurus ecology is a mess.

Most of the arguments in favor of the "wader" hypothesis do not line up with the skeleton. They severely underestimate the bone density and fail to apply said bone density to the entire body, instead only adding it to the hindlimbs. The flexibility of the tail was ignored, and the impact of the large caudalfemoralis muscle was heavily understated. The ribcage of the other other models is too gracile, which could impact stability. The reduction of the hindlimbs being for weight support is implausible as other giant theropods show no sign of this reduction despite reaching similar body sizes. An 8, 9, 10 tonne animal with heavy bones and short hindlimbs standing in shallow water of a massive river system is highly unlikely. No known wading animal has these combinations of features.

However, there is one issue, the sail. There is visible drag behind the giant rigid structure. With that said, it should be noted that the sail is comparatively thin compared to a rotund body. It won't make diving or swimming impossible. While the drag will still slow it down to some extent, that won't be enough to stop Spinosaurus from being a proficient swimmer. If anything, the sail probably made Spinosaurus more stable, similar to the keel of a boat of dorsal fin of an Orca. The long and muscular tail, along with the possibly webbed feet, could counter drag when lunging at prey. Its immense size might also have rendered drag irrelevant. One study on plesiosaurs determined they too had heavy drag, but their size would have compensated for that. One final thing to mention is that the sail only causes drag under certain conditions. If Spinosaurus just swam at the surface with the sail above the waterline, those drag problems are gone. Another solution is if Spinosaurus dives down to a depth 2x the diameter of the sail, the drag will disappear. Considering the river depths in North Africa were possibly at just the right depth, the sail realistically won't be much of a hindrance.

Based on the current evidence, Spinosaurus was more likely to be a semi-aquatic subaqueous forager not unlike that of cormorants, crocodilians. A lean body with a robust tail is perfect for launching forwards. Its slim jaws were well adapted for relatively fast and powerful biting. The long neck would have had well developed muscle attachments for quick movement and high flexibility. The giant sail would do little to slow it down while Spinosaurus dived to certain depths, which is possible thanks to the heavy bone frame. Spinosaurus would have fed on large, hard bodied prey items such as armored fish, crocodilyforms, turtles, and crustaceans in the low light conditions of deep fluvial channels. Plesiosaurs and terrestrial animals could still be an option if in range to strike. There is still more to be learned about Spinosaurus. The fossils don't lie. the problem is it takes time to describe such finds, which can lead to long periods of confusion and disagreements as interpretation is used to fill in the gaps. As more material is found, however, a semiaquatic lifestyle seems to be more likely.