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The Spinosaurus is known by many as the “should be” king of dinosaurs with dinosaur enthusiasts all across the planet claiming that this ferocious carnivore rivaled the Tyrannosaurus Rex. This humongous predator may have given the Tyrannosaurus Rex a run for its money, however, due to a lack of specimens of Spinosaurus it is particularly difficult for paleontologists to ever know as much about this spiny dinosaur of the Cretaceous period, as is known about the particularly well known Tyrannosaurus Rex.
Spinosaurus: Dino Profile
The Spinosaurus roamed the Earth during the late Cretaceous period, some 98 to 95 million years ago. The name Spinosaurus translates to “spiny lizard” and refers to the large spined sail that ran down these large dinosaurs back. The Spinosaurus was most certainly a bipedal dinosaur which walked similarly to the Tyrannosaurus Rex due to its smaller arms and larger, more muscular legs. It is thought by some paleontologists that the Spinosaurus would occasionally walk on all fours similar to other dinosaurs who switched from bipedal to quadrupedal locomotion since the Spinosaurus did have longer forearms than many other Theropods. This fact remains in question but for the most part it is believed that the Spinosaurus was a bipedal carnivore.
The Spinosaurus is thought to have measured around 46 feet long and weighed about 7.4 short tons. The most impressive section of the Spinosaurus’ length is perhaps the elongated skull with crocodilian type jaws which measured in at approximately 5 feet long.
Spinosaurus vs. T-Rex
To continue the comparison of the Spinosaurus to the Tyrannosaurus Rex the Tyrannosaurus Rex measured in at approximately 42 feet long and weighed around 7.5 short tons. In terms of height it is estimated that the Spinosaurus measured in at around 14 feet tall; however, including the large spiny sail along the back it measured in at around 20 feet tall. The Tyrannosaurus is believed to have measured in at between 15 to 20 feet tall.
The Spiny Sail
The Spinosaurus spiny sail along its back is perhaps the most recognized feature of this large Cretaceous carnivore. The Spinosaurus’ sail is a particularly unusual addition to the dinosaur family; however, it was not unlike the sail of Dimetrodon, an 11 foot long Synapsid living 280 to 265 million years ago. Unlike creatures such as the Stegosaurus whose plates raised out of the skin the sail of the Spinosaurus was anchored by extensions of the vertebrae along the back of the dinosaur completely anchoring them to the skeleton. These extensions of the back vertebrae could grow as long as 5.5 feet and the sail like structure that connected the vertebrae are thought to have been thin and skin like. Towards the trips of the sail it was thought to be similar to the webbing between amphibious toes. There is some argument as to the actual composition of the sail itself. While it is understood that the spines within the sail were anchored to the vertebrae it is unknown as to what the sail was made from.
While some paleontologists believe that the sail of Spinosaurus was more like that of Dimetrodon, there are also those like Jack Boman Bailey who believed that due to the thickness of the spines within the sail, the sail itself may have been much more than a thin skin like membrane. Bailey suggests that perhaps the sail of the Spinosaurus was a particularly fatty structure skin to those of common day buffalo. The actual composition of the Spinosaurus sail is unknown at this time due to the complete lack of specimens to provide trace tissue samples.
The Spinosaurus sail is much like various features of other dinosaur genuses in that its actual function is unknown but widely speculated. Some paleontologists believe that the Spinosaurus sail played a part in thermoregulation. Thermoregulation is a common idea that is used to explain many unique structures on a variety of dinosaurs including Spinosaurus, Stegosaurus and Parasaurolophus. It is believed by these paleontologists that the sail was riddled with blood vessels which were so close to the skin that they enabled rapid absorption of heat to enable the dinosaur to stay warm during colder night temperatures. Other paleontologists suggest that the Spinosaurus spine was used to circulate blood through the blood vessels close to the skin to enable rapid cooling in warmer climates. Thermoregulation seems like a plausible explanation for the Spinosaurus sail, however, there are some other proposed explanations which also bring up interesting points.
Some paleontologists believe that the Spinosaurus sail acted much like the plumage displays of large birds today, in that they were used to attract a mate and show sexual maturity. While the colors of the Spinosaurus sail are unknown it is suggested by these paleontologists that the sails of Spinosaurus were brightly colored similar to the modern day birds that utilize this same method of attracting a mate. Lastly it is also suggested that the Spinosaurus utilized its sail to become larger when it felt threatened by predators. Extending the dorsal sail the Spinosaurus would become much larger and potentially more threatening to any predator that was considering attacking the Spinosaurus for a quick meal.
The Spinosaurus Skull
While the purpose of the Spinosaurus sail may be questioned the purpose of its large, elongated skull is certainly not brought in to question. The Spinosaurus is recognized by paleontologists for having a particularly long skull which features crocodilian type jaws which provided the majority of the length of the skull itself. The Spinosaurus skull size makes it the longest skull of any carnivorous dinosaur known to date measuring in at around 5 feet long. The large jaws which make up so much of this length contained un-serrated teeth that were conical in structure and seem particularly well suited to catching and eating fish. It is believed that the Spinosaurus had around forty teeth in both the upper and lower jaw and featured two very large teeth on each side of the jaw. The Spinosaurus jaw isn’t the only feature of this carnivore which makes it similar to the crocodile, the Spinosaurus is believed by some paleontologists to have had eyes that were elevated at the back of the skull similar to modern day crocodiles. This feature lends to the theory of some paleontologists that the Spinosaurus was at least a part time aquatic dinosaur.
Switching Between Terrestrial and Aquatic life
Recent studies by Romain Amiot and his colleagues have studied the teeth of the Spinosaurus in detail and found that the oxygen isotope ratios within the teeth of the Spinosaurus were closer to those of crocodiles than other animals. This led to the theory that the Spinosaurus was a particularly opportunistic predator that was able to switch between terrestrial and aquatic life. This idea came about due to the levels of oxygen isotope ratios being higher than other animals but not as high as full time aquatic creatures. The Spinosaurus conical teeth also led to the theory that the Spinosaurus at least fed in aquatic environments as the teeth are well suited to fishing and not as well suited to terrestrial hunting due to a lack of serration. Discovery of fish scales etched by digestive acid on the rib cage of a Spinosaurus specimen also lend to the theory that the Spinosaurus fed on fish.
Other paleontologists compare the Spinosaurus to the similar Baronyx carnivore which fed on both fish and smaller dinosaurs and suggest that perhaps the Spinosaurus fed on both fish and other terrestrial life. One specimen of Pterosaur was actually located with a Spinosaurus tooth embedded in the skeleton suggesting that the Spinosaurus was in fact an opportunistic feeder and would take what it could get when it could get it. It is doubtful, however, that the Spinosaurus attempted to feed on much larger dinosaurs due to the fact that its teeth and jaws were more suited to feeding on fish than to capturing and killing large terrestrial prey.
The Lack of Spinosaurus Specimens
Much of what is known about the Spinosaurus is unfortunately known from speculation due to the absence of complete specimens. The first remains of the Spinosaurus were located in the Bahariya Valley in Egypt in 1912 although they were not named as Spinosaurus until three years later by the German paleontologist Ernst Stromer. Further Spinosaurus bones were located in Bahariya and identified as a second species in 1934. Unfortunately due to the timing of the find some of these bones were damaged in shipment back to Munich and the rest were destroyed during Allied bombing in 1944. To date six partial Spinosaurus specimens have been located and no complete or near complete specimens have been located. While the 1915 Spinosaurus specimen was destroyed during World War II paleontologists of the time still had detailed descriptions and illustrations of the find allowing for estimations of the size of a sub adult Spinosaurus.
Another Spinosaurus specimen found in 1996 in Morocco consisted of mid-cervical vertebra, an anterior dorsal neural arch and an anterior and mid-dentary. Additionally two more specimens located in 1998 in Algeria and in 2002 in Tunisia both consisted of dentaries. Another specimen located in Morocco in 2005 consisted of significantly more skull material and the huge skull is estimated by Sasso of the Civic Natural History Museum in Milan to be around 6 feet long making this Spinosaurus specimen one of the largest to date.
Unfortunately both for the Spinosaurus and for paleontologists no complete specimens of Spinosaurus have been found, in fact no specimens have been found that are even remotely close to being complete.
This lack of complete or nearly complete specimens leads to confusion over certain factors pertaining to the physiological appearance of the Spinosaurus. No limb bones have ever been discovered to give paleontologists any idea of the actual structure of the Spinosaurus. The finding of Spinosaurus limb bones would not only give a more complete physiological structure to the Spinosaurus but they would also assist paleontologists in piecing together how this aquatic and terrestrial creature moved. It is perhaps from a lack of limb bones that the argument has arisen over whether the Spinosaurus was strictly bipedal or bipedal and quadrupedal.
So far all specimens of the Spinosaurus have been comprised of backbone and skull material which, while providing valuable information on the Spinosaurus as a species, also lacks considerable information on other important factors pertaining to the Spinosaurus.
As with most dinosaur genera that lack complete specimens paleontologists are forced to compare the species of dinosaur to similar beasts; however, with the Spinosaurus this is a slightly more difficult task. While there are dinosaurs who are thought to have had similar characteristics to the Spinosaurus there are none that distinctly resemble this unique and monstrous carnivore.
So while it is possible to infer that the Spinosaurus most probably walked bipedally like other large carnivores like the Tyrannosaurus Rex, it can never be known for certain, at least not until the discovery of a large and nearly complete Spinosaurus specimen.
So why are nearly complete specimens of the Spinosaurus so difficult to find? The Spinosaurus is believed to have lived for the most part in common day Africa and Egypt in semi aquatic lifestyles. These two factors alone perhaps lead to the fact that few specimens of the Spinosaurus have been discovered. With specimens of the Spinosaurus most likely lying underneath the Sahara desert they are unlikely to be excavated any time soon. The Spinosaurus was perhaps a dinosaur that lived in areas which are today such difficult places to excavate and that is the reason why we lack any larger or more complete specimens. The Sahara Desert has been an area of much discovery in terms of Spinosaurus specimens and while this area is particularly difficult to excavate because of weather conditions as well as its sheer mass it is also a location that is not best suited to preserving fossilized remains. It is likely that any specimens accidentally uncovered during sand storms are so sandblasted that there remain little of them to be spotted even were there someone around to spot them. So paleontologists take what they can get when it comes to the Spinosaurus in hopes that someday a more complete specimen will come their way and provide answers to many unanswered questions.