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Spinosaurus aegyptiacus

Spinosaurus Dinoasur showing the Aquatic Posture

Fast Facts about Spinosaurus

Picture of the Illustration of Spinosaurus aegyptiacus at the National Geographic Museum in Washington, D.C. The illustration is by Davide Bonadonna

Name: Spinosaurus aegypaticus (pronunciation: "SPINE-oh-SAW-rus") - The name means "Spine lizard of Egypt"

Taxonomy: Dinosauria (Dinosaur) - Saurischia (Lizard Hipped) - Theropoda (Beast Footed) - Spinosauroidea aka Megalosauroidea (Superfamily) - Spinosauroidea (Family) - Spinosaurus (Genus) - S. aegyptiacus (species)

Age: Mid Cretaceous
Spinosaurus lived during the Cenomanian and Albain ages 94-110 million years ago.
Spinosaurus became extinct 30 million years before T-rex appeared.

Discovery: Stromer, 1915
In 1912, Richard Markgraf found a partial specimen in the Baharia Oasis of Egypt. He sent the fossils to Ernst Stromer in Germany for study, and in 1915 this dinosaur was named Spinosaurus.

Distribution: North Africa:
Other Spinosaurid dinosaurs have been found globally, from Brazil, Asia, Europe, to Australia, but S. aegyptiacus is only found in Northern Africa. Fossil locations include Egypt, Morocco, Algeria, Tunisia, Lybia, and even Kenya.

Body Size: The Biggest! 15 meters (49 feet)!
With a skull of over 4 feet in length, Spinosaurus a. wins the record as the longest theropod. It was a full 10 feet longer than T. rex, and about 7 feet longer than Carcharodontosaurus, a T. rex like theropod that lived alongside Spinosaurus.
However, Spinosaurus had a very long tail and a long neck, so Carcharodontosaurus and T. rex would have been bulkier!

Diet: Fish
Spinosaurs teeth and jaws were designed for eating fish

Designed For the Water: Unlike other theropods, this dinosaur is very specialized.

Some of the specializations that Ibrahim's paper discusses (Ibrahim, et al. 2014) include:

* A crocodile like head with a long, slender snout that had many interlocking pointy teeth for grasping large fish
* Pressure sensors in the snout to detect moving prey in the water, just like crocodiles
* A long tail that moved from side to side for propulsion in water
* Possible webbed back feet
* Hind legs that were better at a paddling motion (for swimming) than a walking motion
* Front arms that were very robust with rigid hands; probably to support its weight when walking, since it had to walk on all four legs.
* Nostrils that were positioned further up on the skull, enabling it to breathe while mostly submerged
* A dense bone structure, just like cetaceans (whales) and other aquatic mammals, for better buoyancy for swimming and diving

Spinosaurus aegyptiacus fossils have been found in the following formations:

Mid-Late Cretaceous Formations Locations
Bahariya Formation Egypt
Aoufous Formation (Kem Kem Beds) Morocco
Tegana Formation (Kem Kem Beds) Morocco
Chenini Formation Tunisia
Cabao Formation Libya
Turkana Grits Formation Kenya
"Gara Samani" Algeria

A reconstructed Spinosaurus that was on display at the National Geographic Musuem in Washington D.C. This is the new, corrected mount, showing its aquatic posture, as it could not have walked on two legs.

Discovery / Paleontological History of Spionosaurus

Ernst Stromer on the expedition in Egypt in either 1911 or 1912

Ernst Stromer on the expedition in Egypt in either 1911 or 1912

Richard Markgraf on an earlier expedition with Osborn of the AMNH in 1907

Richard Markgraf on an earlier expedition with Osborn of the AMNH in 1907.

1911: Stromer and Markgraf: The Spine Lizard of Egypt

The story begins in 1911, when Ernst Stromer, a Bavarian paleontologist, launched an expedition to collect mammal fossils in the little explored deserts of Egypt. Stromer met up with Richard Markgraf, an Austrian fossil collector who lived near Cairo.

Stromer had hired Markgraf in previous expeditions, enjoyed his expertise and company, and hired him again as his fossil collector and expedition guide for this trip.

The expedition set out to three locations in the Egyptian desert. For the most part, the expedition was a bust for mammal fossils; however, in the Baharia Oasis of Egypt, he discovered large creatacous dinosaurs, including several carnivores. By 1912, Stromer returned to Germany and had Markgraf stay to continue the excavations. In late 1912, Markgraf came across a partial skeleton of a large and bizarre shaped dinosaur (Smith, et al. 2006). He shipped the material back to Stromer for study, and in 1915 Stromer published a paper describing the specimen. He coined this new dinosaur: Spinosaurus aegyptiacus, the "Spine Lizard of Egypt."

1936: The First Reconstruction

Spinosaurus Fossil Illustrations from Stromers first spinosaurus publication in 1915. This is plate 2 from his publication.

As time went by, more and more fragmentary fossils of Spinosaurus were discovered and sent to Stromer. By 1936 Stromer had enough material to make a reconstruction. He published the reconstruction of Spinosaurus in an additional publication. Spinosaurus was reconstructed into a huge, lumbering, bipedal carnivore with a giant sail on its back.

1944: The Complete Destruction

The Author looking at casts of Stromers original Spinosaurus fossils. These were on display at the National Geographic Museum.

The Spinosaurus material had been on display at the Bavarian State Collection in Munich. When WWII began, Stromer tried desperately (but unsuccessfully) to get his specimens moved out of Munich and away from Allied bombings. Unfortunately, in 1944, an Allied bombing run obliterated the museum and all of Stromer's fossils.

This dinosaur was lost for years. Fragments of this dinosaur and its relatives would be found from time to time. Based on these fragmentary findings, paleontologists concluded Spinosaurus had a crocodile-like snout, ate mainly fish, probably spent its time in or near the water, and had unusually robust forearms for a theropod. Some proposed the giant sail should be a hump, like on a buffalo. However, nothing substantial enough had been found to do a more accurate analysis and reconstruction. Thus, Spinosaurus remained enigmatic for over 50 years.

2008: Enter Nizar Ibrahim - The New Specimen

The Baharia Oasis in Egypt where the first Spinosaurus was Discovered.

In 2008, Ibrahim was doing fieldwork in the Cretaceous Kem Kem beds near Erfoud, Morocco. While there, he bought a small box that contained unusual looking dinosaur bones. They were in an odd purple colored matrix with yellow streaks. The fossil also had an unusual looking cross-section. When at the Natural History Museum in Milan, Italy a year later, Ibrahim was shown a partial dinosaur specimen from Morocco. He immediately realized it was a very rare partial Spinosaurus and that the specimen looked identical to his small unusual fossil with the purple/yellow matrix he purchased in 2008. Realizing that it might be the same specimen, he thought he may be able to find the exact location and uncover more of it.

Now, Ibrahim had to track down the fossil dealer in Erfoud that excavated the finds. He returned to Morocco four years later and began to track down the dealer. With many false leads he was about to give up. On his last day in Morocco, Ibrahim was sitting at a cafe and miraculously recognized the fossil dealer as he happened to walk by. The dealer eventually brought Ibrahim to the dig site, showing where the Spinosaurus was unearthed. Ibrahim, with the help of Paul Sereno (an expert on Spinosaurus), returned to the dig site with a team and uncovered more of the associated partial specimen. Ibrahim and Sereno then took digital measurements of their new specimen, measurements from Stromer's pictures, and digital measurements of other fragmentary finds in North Africa. They did an in depth analysis of all these fossils and came up with the most accurate reconstruction of Spinosaurus to date. In 2014 they published their findings: a highly specialized, sail-backed, semi-aquatic dinosaur that was designed for swimming!

Aquatic Adaptations of Spinosaurus: Designed for Water

Members of the Spinosauroid family had some aquatic adaptations, but it appears Spinosaurus took those adaptations much further. Changes in the skull, legs, feet, neck, tail, and even the bone density made Spinosaurus look more like a crocodile or an early cetacean (whale) than a theropod dinosaur. Below are details on the aquatic adaptations:

Short 3 minute Video about Spinosaurus from National Geographic/NOVA with Nizar Ibrahima and Paul Sereno

The Teeth: Ideal for Grasping onto Fish

Spinosaurus aegyptiacus teeth are relatively common in the Bahariya Formation and the Kem Kem beds of Morocco. They are odd for a theropod. Even Stromer realized they were unlike any other theropod's teeth. Instead of teeth with the typical serrated knife-like blade, Spinosaurus teeth were long, round, and pointy, more like crocodile or odontocete (toothed whale) teeth.

Since the teeth are not blade like with serrations, they would do a horrible job at slicing and cutting through flesh and bone. However, the peg-like teeth, like those of crocodiles, toothed whales, and even the sand-tiger shark, are ideal for grasping and holding onto fish.

The image below shows a peg-like Spinosaurus tooth and a similar sized Carcharodontosaurus tooth (T. rex of Africa). Notice the tooth designs are completely different. The Spinosaurus tooth is similar to a Crocodile tooth; where they are ideal for grasping and holding onto prey, but not for chewing. The Carcharodontosaurus tooth is blade like with serrations, like a steak knife; ideal for cutting and slicing through meat and bone.

This image shows a peg-like Spinosaurus tooth and a similar sized Carcharodontosaurus tooth (T. rex of Africa). Notice the tooth designs are completely different. The Spinosaurus tooth is idealy suited for grasping, while the Carcharodontosaurus tooth is idealy suited for slicing and cutting.

The Skull: Like a Crocodile

Like the teeth, the jaws of Spinosaurus are suited for capturing fish. They are very similar to jaws of the Gavial, a type of fish eating crocodile with very narrow jaws. These narrow jaws are clearly much weaker than other large theropods, like T. rex and Carcharodontosaurus. They lack the huge muscle attachment areas. This means they are not suitable for clamping onto large struggling prey and tearing chunks of flesh from them. Just like the Gavail, they are more suitable for grasping onto smaller prey, like fish. Although, for the huge Spinosaurus, they were giant fish (over 10 feet coelacanths, and over 20 feet sawfish).

The front of the snout contains has an array of small openings. In the 2014 publication, Ibrahim, et al. states these are very similar to the foramina in crocodiles. These foramina contain pressure receptors that can detect moving prey under water.

One difference between Spinosaurus skulls and crocodile skulls is the nasal openings. Ibrahim also states that the nostril of Spinosaurus is positioned toward the posterior end of the skull. This would help keep water out, and allow Spinosaurus to better breathe when mostly submerged. A similar design can be seen on early cetaceans (whales); as time goes on, the nasal openings migrate toward the back of the skull.

This image shows a comparison between an American Alligator skull and a Spinosaurus skull. Notice the striking similarities. American Alligators mainly eat fish. Image of the American Alligator by: By Didier Descouens (Own work). CC BY 3.0, via Wikimedia Commons

The Limbs and Tail: Made for Swimming

The Tail:

The tail is unique in Spinosaurus. By looking at the model, it's obviously unusually long. However, there is another big difference. All theropods tails are rigid, and are used as a counterbalance. Spinosaurus tail is designed to bend laterally. In the paper, Ibrahim states the vertebra centra are short, and the neural arches are reduced. These features enable the tail to bend laterally. The same design is seen in bony fish and in crocodiles. This means Spinosaurus' tail was probably used for propulsion when swimming and diving.

The Hind Limb:

Ibrahim, discovered that the pelvis was reduced and the hind limbs, such as the femur, were short. However, the hind limbs have robust muscle attachments (Ibrahim, et al. 2014). Ibrahim notes this same type of design is found in early cetaceans (whales), and semiaquatic mammals today that use their hind limbs for paddling in water. This means Spinosaurus' hind legs were better designed for swimming than walking.

Ibrahim also noticed huge differences in the hind feet when compared to other large theropods. The hind feet are flattened and resemble the feet of shorebirds, Ibrahim suggests the hind feet were adapted for walking on soft substrates, or were even webbed for paddling in water (Ibrahim, et al. 2014).

Another unique finding is that Spinosaurus' center of gravity is shifted toward the rib cage, whereas all other theropods the center of gravity is over the hips. This means it would have been very difficult to walk on its short back legs. All other theropods are bipedal. Ibrahim suggests Spinosaurus was not bipedal, but needed its forelimbs to walk (Ibrahim, et al. 2014).

Image of Spinosaurus' tail and hind limbs. The hind limbs are very flattened and resemble early whale llimbs rather than dinosaur limbs. The tail is desinged like a crocodiles, to propell it foreward while swimming.

Bones like an Early Cetacean (Whale)

Another interesting finding from Ibriham's paper is the bone density of Spinosaurus. Some of the bones samples had a bone density 30-40% greater than that of other theropods, including other early spinosaurids (Ibriham, et al. 2014).

A high bone density is found in aquatic and semi-aquatic mammals. It helps with buoyancy when diving and swimming. A similar bone density is also found in early cetaceans (whales). Their bone density increased as they were adapting to the water. Clearly, Spinosaurus was adapting to life in an aquatic environment.

This is Maiacetus, an early cetacean (whale). Its bone density is much higher than land mammals.
This cast is on display at the Smithsonian Museum of Natural History in Washington, D.C.

The Sail of Spinosaurus

Spinosaurus has HUGE processes on its dorsal vertebra. They can reach lengths of over 5 feet! They are the tallest processes on any dinosaur. Stromer believed these processes formed a large sail on its back, like some reptiles. However, there was never enough fossil evidence to determine what these large processes were actually for. Later, some people proposed they formed a large hump on its back. Others thought it was for heat regulation.

Fortunately, a partial specimen in the 2014 paper has some well preserved dorsal processes. These spines are very dense and are not vascularized; this means it would not have served as a heat regulatory function. They also found the edges of the spines to have ligament scars. This means it would not have been a hump, like on a buffalo, but instead wrapped tightly in skin (Ibrahim, et al. 2014). They therefore conclude the large spines would have functioned as a sail on the dinosaur's back, possibly serving as a display structure that would have been visible while swimming (Ibrahim, et al, 2014). So, Stromers original idea was correct; it was probably a large sail.

Image of the large and dense spines of the Spinosaurus Dinosaur.


The remarkable rediscovery of this intriguing dinosaur gives scientists enough information to clearly say Spinosaurus was semi-aquatic. Spinosaurus was a theropod that was not bipedal, as it had the wrong center of gravity and short stubby hind legs. It had a crocodile-like skull and teeth for grasping onto fish, with crocodile-like water pressure sensors. It had nasal openings set away from the front of the snout with dense bones, just like early cetaceans. It had a long Mosasaur-like tail, and wide flat feet like shorebirds. Spinosaurus was truly an evolutionary masterpiece, superbly designed for the water.

Recommended Books/Videos/Fossils for Spinosaurus:

Spinosaurus (Exploring Dinosaurs)
This is a great little Childrens book about Spinosaurus! I am kind of partial to this book because a few of my pictures are used in it! If your child likes dinosaurs, this is a great bedtime read!

PBS and National Geographic always do a great job with their documentaries. This one is no exception. The DVD: Nova: Bigger Than T Rex is hands down the best documentary out there about Spinosaurus. It starts with Stromers discovery in Egypt in the early 1900's until 2014 with Ibrahim and Sereno's new aquatic model. This DVD is in depth and comprehensive, covering Spinosaurus' paleobiology and paleoecology. It also has great CGI animations of the corrected beast.

THE CONCISE DINOSAUR ENCYCLOPEDIA by Burnie, David ( Author ) on Mar-15-2004[ Hardcover ]
This is one of the better general books on dinosaurs. It is incredibly visual and goes over countless dinosaurs lifestyles, behaviors, and the habitat they lived in. It also covers dinsoaur evolution and their extinction.

Get Your Very Own Spinosaurus Tooth:

These are Authentic Spinosaurus teeth sold by Fossil Era Although Spinosaurus bones are rare, Spinosaurus teeth, like the one pictured here, are fairly common, because, like all dinosaurs, they shed their teeth regularly. They are great gifts for the fossil fanatic! Who knew you could own a real tooth from one of the largest theropods to exist! The teeth that Fossil Era sale come in many different sizes and prices, from small to large and museum quality. Check them out, they make great gifts!

References / Works Cited

Allain, R.; Xaisanavong, T.; Richir, P.; Khentavong, B. (2012). "The first definitive Asian spinosaurid (Dinosauria: Theropoda) from the early cretaceous of Laos".Naturwissenschaften 99 (5): 369-377. 99 (5)

Barrett, P.M., Benson, R.B.J, Rich, T.H., and Vickers-Rich, P. (2011). "First spinosaurid dinosaur from Australia and the cosmopolitanism of Cretaceous dinosaur faunas." Biology Letters online preprint: doi:10.1098/rsbl.2011.0466

Buffetaut, E. and M. Ouaja. (2002). "A new specimen of Spinosaurus (Dinosauria, Theropoda) from the Lower Cretaceous of Tunisia , with remarks on the evolutionary history of the Spinosauridae." Bulletin de la Societe Geologique de France 173/5:415-421. PDF file

Ibrahim, N., Sereno, P. C., Dal Sasso, C., Maganuco, S., Fabbri, M., Martill, D. M., Zouhri, S., Myhrvold, N., Iurino, D. A. (2014). "Semiaquatic adaptations in a giant predatory dinosaur". Science. PDF file

Kellner, A.; Azevedo, S.; Machado, A.; De Carvalho, L.; Henriques, D. (2011). "A new dinosaur (Theropoda, Spinosauridae) from the Cretaceous (Cenomanian) Alcantara Formation, Cajual Island, Brazil" Anais da Academia Brasileira de Ciencias, 83 (1), 99-108 PDF file

Martill, D. M., Cruickshank, A. R. I., Frey, E., Small, P. G., Clarke, M. (1996). "A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil". Journal of the Geological Society 153: 5. doi:10.1144/gsjgs.153.1.0005.

Paul C. Sereno, Allison L. Beck, Didier B. Dutheil, Boubacar Gado, Hans C. E. Larsson, Gabrielle H. Lyon, Jonathan D. Marcot, Oliver W. M. Rauhut, Rudyard W. Sadleir, Christian A. Sidor, David D. Varricchio, Gregory P. Wilson, Jeffrey A. Wilson (1998). "A Long-Snouted Predatory Dinosaur from Africa and the Evolution of Spinosaurids" Science 282, 1298; DOI: 10.1126/science.282.5392.1298

Joshua B. Smith, Matthew C. Lamanna, Helmut Mayr, and Kenneth J. Lacovara. (2006). "New Information Regarding the Holotype of Spinosaurus Aegyptiacus Stromer, 1915" The Paleontological Society; J. Paleont., 80(2), 2006, pp. 400-406 PDF file

Taquet, P., and Russell, D.A. (1998). "New data on spinosaurid dinosaurs from the Early Cretaceous of the Sahara". Comptes Rendus de l'Academie des Sciences - Series IIA - Earth & Planetary Sciences 327 (5): 347-353. PDF file

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