Dragons of my childhood – about the dinosaur that defeated the T-Rex

Spinosauridae is one of the strangest subgroups of theropods. We know of only four genera with well-preserved material – Spinosaurus, Irritator, Suchomimus and Baryonyx, but these meager fossils are enough to describe them as astonishing spacers with elongated snouts similar to those of today’s crocodiles and huge forelegs. The skull, stomach contents and isotopic analyses indicate that they were mostly fish-eating and lived along the banks of bodies of water, also unusual for theropods. One of them, Spinosaurus, may have been the largest theropod that ever existed. -Stephen Louis Brusatte, 2012, Dinosaur Paleobiology, Wiley & Sons

Dinosaurs have accompanied, at least some of the time, many a child. Sometimes a small triceratops even replaced a rocking horse. The era of reptiles reigning on Earth, shaping the imagination, often inspired future scientists. For years, many paleontologists and evolutionary biologists have wondered how powerful and aggressive theropod species fared while occupying the same ecological niches. And when did you first hear about spinosaurus? Discovered more than a century ago because of the grotesque sail of skin on their backs with the stature of a two-legged giant, they did not easily penetrate pop culture, resembling dragons more than dinosaurs.

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Spinosaurus began its media career when it was looking for a worthy opponent for… tyrannosaurus – a dinosaur of similar size and capabilities. Their duel, however, makes no sense. Spinosaurus lived in the southern part of the decaying supercontinent of Gondwana and in Laurasia, besides which they occupied their own niche, moving away from other theropods to the shores of water bodies. Tyrannosaurs lived on Laramidia, a continent that existed at the end of the Cretaceous (99.6-66 million years ago) between the Pacific Ocean, the Arctic Ocean and the North American Inner Sea.

The fight would be severely anachronistic at that. You will say: it’s chalk and it’s chalk. And you will be right. However, at best, the Turonian (93.9-89.8±0.3 million years ago) is almost 18 million years apart from the Mastrychtian (72.1±0.2-66 million years ago), the last Upper Cretaceous floor that ended with the Chicxulub bolide impact. The human race has existed some six times shorter – the genus, not the species.

The comparative analysis, based on lever mechanics, shows that Spinosaurus had relatively weak (12 kN), though very fast, bites compared to Tyrannosaurus (48.5 kN), which bit hard and deep. Yet it was the spinosaurus that defeated the tyrannosaurus… in Part III of the blockbuster film Jurrasic Park. But this is not the end of the career of the largest of the theropods. In 2020. The world circulated the news that he did not carry himself like a godzilla, but rather dived like a leviathan.

A dinosaur like never before

The modern history of Spinosaurus begins in 1915, when Ernst Freiherr Stromer von Reichenbach described the fossil of a theropod with an elongated and narrow lower jaw, resembling a crocodile, found three years earlier by Richard Markgraf in Egypt. It was as much as 1.6 meters long, however, more puzzling were the long spinous processes protruding from the spine. The find was dated to about 97 million years ago, or the Lower Cenomanian (100.5-93.9 million years ago), the beginning of the Upper Cretaceous. Unfortunately, this holotype specimen (BSP 1912 VIII 19) was destroyed in a bombing during World War II, and all that remains of it are engravings and photographs found in 2000. It was imagined that the spinosaurus must have been 15 meters long and resembled a T-Rex in stature.

In 1980. Amateur William J. Walker discovered fossils of Baryonyx walkerii in England that were similar enough to a spinosaur that the family Spinosauridae was assembled from them. Teeth and scales of the Mesozoic fish Lepidotes were found near the gut of the fossil of this holotype bararyx, but also the remains of a juvenile iguanodon. The find therefore indicated that the baryonyx hunted fish, which it could transport to shore thanks to its long paws ending in claws. Attention was then drawn to its short legs and large feet, which resemble those of modern wading birds, and the density of its bones, which may have served as a ballast system, similar to those of today’s manatees and dugongs and the basilosaurs we recently described. Perhaps it even had pressure receptors like crocodiles. However, the evolution of spinosaurus was far from over.

The intricate paths of evolution

In 1996. Dale Russel has discovered fossils of new spinosaurids in Morocco. He named one Sigilmassasaurus brevicollis, another Spinosaurus maroccanus, and disbursed both to Alb (113-100.5 years ago), with Sigilmasaurus defined on the basis of a single, isolated vertebra. In 1998. Russel found fossils of Spinosaurus aegyptiacus in Algiers, and in 2002. Eric Buffetaut and Mohamed Ouaja discovered Egyptian spinosaur teeth (also dated to Alb; specimen BM231) in Tunisia.

And yet Oliver Rauhut, analyzing images found in 2000, concluded in a monograph on theropods that Stromer had made a mistake and the Egyptian spinosaur holotype was in fact a chimera, composed of several different, quite different species. The monograph combined the families Spinosauridea (now Megalosauroidea) and Allosauroidea (now in the Avetheropoda clade) into Camosauria – an unrecognized clade of tetanurs today.

Spinosaurus was defended by Cristiano Dal Sasso’s team. In 2005. Newly found skull fragments of Spinosaura aegyptiacus from the early Cenomanian (specimens UCPC-2 and MSNM V4047) are described. Paleontologists are still unable to agree on whether Spinosaurus aegyptiacus, Spinosaurus maroccanus and Sigilmassasaurus brevicollis are synonyms or separate species, disagreeing more than two ways. In 2014. Nizar Ibrahim and his team considered both Sigilmassasaurus brevicollis and Spinosaurus marocanus to be synonyms of the following Spinosaurus aegyptiacus .

Serjoscha Eversa’s team disagreed a year later, recognizing sigilmasasaurs as a separate species that includes a Moroccan spinosaur for a change. In doing so, the neotype of the spinosaur was also questioned, as will be discussed later. This is seen even differently by Hone and Holtz or Thomas Arden and his team, who questioned the designation of the MSNM specimen V4047 as an Egyptian spinosaur, believing it to be more of a sigilmasasaurus. However, the arguments of all of them were countered in 2020. Robert Smyth and his team, ruling again that only one species of spinosaur could have lived in the same North African ecosystem at one time.

Do we know anything for sure about spinosaurids?

The oldest fossil attributed to a representative of the Spinosauridae family is the late Jurassic(148-145 million years old) baryonyx-like Ostafrikasaurus crassiserratus. It was discovered during a massive paleontological expedition by the Natural History Museum in Berlin to German colonies in East Africa between 1909 and 1912. A new species of spinosaur was identified from the only tooth found at the time only by Eric Buffetaut in 2013. These animals certainly lived in the Cretaceous, from the Albian to the Turonian, although the period of their prosperity was clearly the Cenomanian.

According to various estimates, the Egyptian spinosaurus may have grown up to 18 m long and weighed up to 9 t. However, these are estimates based on very incomplete bone material. François Therrien and Donald M. Henderson, in a text with the all-telling title My theropod is bigger than yours… estimated it at as much as 20 t with a skull length of 1.75 m. They made their assumption based on a fossil from Morocco, which since 1975. was in a private collection, and in 2002. was obtained by Cristiano Dal Sasso and his team (specimen MSNM V4047, considered by some, as mentioned above, to be a sigilmasaur). However, the latest conservative estimates give it 15 m and 7.4 t.

It is believed to have been the largest of the theropods with gigantosaurus, tyrannosaurus and carcharodontosaurus included. He also had twice as many teeth as those there and a bone comb between his eyes. The lack of a complete fan does not allow one to conclude beyond any doubt about its function and shape. So there isn’t even a consensus on whether it stretched the skin sail or supported the hump on the back. If it was a sail, it could be used to regulate body temperature, like the ears of African elephants. Reduced hip bones and short legs may indicate an earthy or aquatic lifestyle. The reconstruction of the appearance of the Egyptian Spinosaurus is based on only six certain specimens.

Divided by the ancient ocean

Fossils of Spinosaurus are known primarily from North Africa (Egypt, Algiers, Tunisia, Morocco and Niger), while Baryonyx is known from England, France, Spain (Protathlitis cinctorrensis from the Late Baremian in the Lower Cretaceous) and Portugal (a jaw fragment long mistaken for a crocodile). The split of the family into Baryonychinae and Spinosaurinae is explained by the indentation of the Tethys Ocean between Gondwana and Laurasia, but African fossils of Suchomimus tenerensis – a species closer to Baryonyx – muddles this scenario.

Slightly older representatives of the family Spinosauridaea, dating back to the Lower Cretaceous, have been found in ancient Laurasia: in Laos (Ichthyovenator laosensis From apt: 121.4±1-113.0±1 million years), Thailand (tooth fossils Siamosaurus suteethorni of barrem and aptu or albu), China (a specimen resembling a Siamosaurus suteethorni from Thailand), Japan, but also in Australia… As many as two or three species of spinosaurus have been found in Brazil. These are Irritator challengeri and Angaturama limai of albu, although the latter may be synonymous with the former. The only Cenomanian fossil from Brazil: Oxalaia quilombensis, which is probably a surprising because geographically distant synonym of Spinosaurus aegyptiacus, was described in 2011. Alexander Wilhelm Armin Kellner. The holotype reportedly burned during a museum fire in 2018.

A turning point in the modern evolution of spinosaurids

In 2014. Nizar Ibrahim, Paul C. Sereno, Cristiano Dal Sasso and Matteo Fabbri and their team described a spinosaur found in Morocco (dated to the Cenomanian specimen FSAC-KK 11888). In 2018. further elements of the same juvenile were obtained. So far, there was no complete skeleton of a spinosaurid, so they proposed a neotype on the basis of this find, later contested by Hone and Holtz or Evers’ team, considering the fossils as a conglomerate. Most interesting, however, were the nerve endings, indicating that the entire tail was finned. Based on this, it was concluded that the bone sail of the Spinosaurus extended all the way to the end of the tail. They began to seriously consider the aquatic lifestyle of the spinosaurus as an active and effective underwater predator.

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