Spinosaurs
The Specialised Predatory Dinosaurs of the Spinosauridae

       Dinosaurs have been popular subjects of interest ever since the very first ones were discovered and reconstructed back in the nineteenth century,‭ ‬and out of all these it is usually the meat eating ones that get the most exposure.‭ ‬This has given rise to some genera such as Tyrannosaurus becoming household names,‭ ‬but in‭ ‬2001‭ ‬the release of a film called Jurassic Park‭ ‬3‭ ‬introduced a new favourite‭; ‬Spinosaurus.‭ ‬Cinema goers were generally impressed by the on screen arrival of‭ ‬a‭ ‬new kind of theropod dinosaur that looked radically different to anything that had been portrayed before.‭ ‬These same cinema goers were stunned when this‭ ‘‬new dinosaur‭’ ‬actually killed a T-rex in a very brief fight in the early stages of the film,‭ ‬something that had people buzzing about a dinosaur that was not only bigger than Tyrannosaurus,‭ ‬but capable of killing one too.‭ ‬This film is of course science fiction,‭ ‬a fight such as this between these two genera could never happen since Spinosaurus appeared and went extinct again many tens of millions of years before Tyrannosaurus appeared.‭ ‬It did however cement a new type of dinosaur in the public consciousness,‭ ‬though many people still do not realise that Spinosaurus is but one genus of a whole group of dinosaurs that are today referred to as the spinosaurids.

Exactly what is a spinosaurid‭?
       To briefly reference Jurassic Park‭ ‬3‭ ‬again,‭ ‬some movie goers criticised the film makers for featuring what they thought was a‭ ‘‬made up‭’ ‬dinosaur.‭ ‬With its large size,‭ ‬a very long crocodile-like mouth and huge fan shaped sail on its back,‭ ‬the Spinosaurus in the film was reminiscent of the so called‭ ‘‬slurpasaurs‭’ ‬from low budget monster flicks in the early second half of the twentieth century.‭ ‬For those not familiar with this term,‭ ‬a slurpasaur is basically where film makers take a regular lizard or baby crocodile,‭ ‬attach extra fins and spines to it and then make it move around in front of a camera on a scale set‭; ‬hey presto,‭ ‬instant‭ ‘‬dinosaur‭’‬.‭ ‬The rumours of a made up dinosaur were quickly quashed however,‭ ‬when features about the scientific history of‭ ‬Spinosaurus began to appear,‭ ‬particularly detailing how the dinosaur was reconstructed.
       Spinosaurus was first described as a dinosaur in‭ ‬1915,‭ ‬from very incomplete skeletal remains that had been discovered in Egypt in‭ ‬1912.‭ ‬Already the presence of elongated neural spines‭ (‬the upper projection of a vertebra‭) ‬was documented,‭ ‬but the genus was largely unknown to the public until it began to be included in popular science books about dinosaurs later in the twentieth century.‭ ‬During these early public appearances the skull of Spinosaurus was unknown,‭ ‬and a more‭ ‘‬standard‭’ ‬theropod skull was added for the reconstruction,‭ ‬resulting in reconstructions where Spinosaurus was simply like any other theropod dinosaur,‭ ‬but one with a huge sail on its back.
       The true nature of Spinosaurus,‭ ‬and by extension future spinosaurids,‭ ‬began to be pieced together in‭ ‬1986‭ ‬with the description of the genus Baryonyx.‭ ‬This genus does not display elongated neural spines,‭ ‬but since it is believed to be a juvenile it may have had them later in life,‭ ‬but it does have its skull.‭ ‬The snout of this skull is proportionately much longer than the snouts of other theropod genera,‭ ‬to the point where you could call it crocodile-like.‭ ‬In‭ ‬1998‭ ‬another new genus called Suchomimus was created,‭ ‬and again the long crocodile like snout was present.‭ ‬That same year a new specimen of Spinosaurus was also described and although only a partial snout‭ (‬MNHN SAM‭ ‬124‭) ‬this revealed that the long missing skull of Spinosaurus actually would have looked a lot like the skulls of Baryonyx and Suchomimus.‭

       The conclusion was a simple one,‭ ‬all three of these genera were somehow related to one another,‭ ‬and that together they represented a previously unknown group of dinosaurs.‭ ‬Although Baryonyx was the first to have its skull studied,‭ ‬Spinosaurus was named first,‭ ‬and under standard procedures governing the naming of animals,‭ ‬Spinosaurus had priority over the naming of this group of dinosaurs which became known as the Spinosauridae,‭ ‬with member genera of this group being known as spinosaurids.‭ ‬The Spinosauridae had actually been established as a family group back in‭ ‬1915‭ ‬by the German palaeontologist Ernst Stromer as a home for the genus Spinosaurus which he also named in‭ ‬1915,‭ ‬but again the full nature of these dinosaurs was not appreciated until the closing years of the twentieth century.‭ ‬In addition to these three,‭ ‬another genus named irritator that was named in‭ ‬1996‭ ‬from skull material was also included into the group.
       The history of the spinosaurids may actually go all the way back to‭ ‬1841‭ ‬when the British palaeontologist Richard Owen named Suchosaurus based upon a description of isolated teeth.‭ ‬Again,‭ ‬because the oldest named genus usually comes first,‭ ‬it could be said that the Spinosauridae should be named the Suchosauridae.‭ ‬But here a special case is made because‭ ‬since‭ ‬Suchosaurus is only named from isolated teeth,‭ ‬it is near impossible to attribute skeletal remains to this genus.‭ ‬This is both why this genus is considered dubious,‭ ‬and also why the Spinosauridae will stay named the Spinosauridae,‭ ‬because Spinosaurus at least has some skeletal material with which further remains can be identified by.‭ ‬However a well-known exception to the above involves the genus Troodon,‭ ‬a small predatory theropod that was described from teeth long before skeletal remains were added to the genus.
       Fossils of this group have been found in frustratingly incomplete states,‭ ‬with usually no more than teeth and bone fragments to go on,‭ ‬but we do know a few identifying features of the group.‭ ‬One is that most spinosaurids had teeth similar to one another which were long and thin so that they were conical in form,‭ ‬not great for cutting,‭ ‬but perfect for spearing and holding.‭ ‬Spinosaurid genera where the skull or parts of is known all reconstruct to the same elongated crocodile-like snout.‭ ‬The tips of these snouts also seem to have had pressure sensitive receptors.‭ ‬Some such as Spinosaurus,‭ ‬Suchomimus and later Ichthyovenator are known to have had enlarged neural spines for growths on their backs.‭ ‬Other genera do not have these parts preserved,‭ ‬or in the case of Baryonyx,‭ ‬may have been too young to have them.‭ ‬Finally‭ ‬where the hands of‭ ‬spinosaurids are‭ ‬preserved‭ ‬they‭ ‬display enlarged claws on the ends of the fingers.

How are spinosaurids related to other dinosaurs‭?
       How spinosaurids evolved is‭ ‬still a mystery at the time of writing,‭ ‬but they must have evolved from other more standard theropod dinosaurs that appeared earlier in the Mesozoic.‭ ‬Usually the Spinosauridae is placed below the Megalosauroidea,‭ ‬a group which contains some of the earliest large theropod predators of the Mesozoic,‭ ‬with origins in the Jurassic.‭ ‬Spinosaurids may be related to members of the‭ ‬Megalosauroidea sometimes‭ ‬classed under the Megaraptora such as Megaraptor and Fukuiraptor.‭ ‬These more‭ ‘‬standard‭’ ‬theropods seem to have enlarged claws on their fingers,‭ ‬though this could be a case of convergent evolution with the same feature simply repeating it itself in two distantly related family groups.
       A more general classification for spinosaurids is that they are tetanuran theropods.‭ ‬This means that they were bipedal dinosaurs that walked around on two highly developed rear legs,‭ ‬while having‭ ‬two smaller but‭ ‬still‭ ‬quite functional fore arms.‭ ‬The body would have been supported so that the spine was horizontally level to the ground while the tail was carried high off the ground and kept fairly stiff‭ (‬tetanuran theropods are often just described as‭ ‘‬stiff-tailed‭’ ‬theropods‭)‬.‭ ‬Because of this spinosaurids would have been at least distantly related to other tetanuran theropods,‭ ‬which would actually be most of the other known theropod genera of the Jurassic and Cretaceous periods.‭ ‬At the time of writing the lack of really good skeletal‭ (‬and transitional‭) ‬remains across several genera make it hard to definitively establish a closer family association with other theropod groups.‭
       After the theropods,‭ ‬the spinosaurids would of course have been related to other types of dinosaur since they are after all identified as dinosaurs,‭ ‬and the dinosaurs would in turn be related to other reptiles,‭ ‬and then even after this chordates‭ (‬back boned animals‭)‬.

Geographical and temporal distribution.
       In‭ ‬the early days of the Spinosauridae,‭ ‬spinosaurids were identified as mostly from North Africa‭ (‬Spinosaurus and Suchomimus‭)‬,‭ ‬Europe‭ (‬Baryonyx‭) ‬and South America‭ (‬Irritator‭)‬.‭ ‬Newer genera have now been named as coming from North Africa and South America,‭ ‬but now new genera have been named from Asia,‭ ‬with the best represented genus from here so far being Ichthyovenator.‭ ‬Spinosaurid remains have also been considered to have been found in Australia,‭ ‬where a single cervical‭ (‬neck‭) ‬vertebra has been described‭ (‬Barrett et al,‭ ‬2011‭)‬.

       Before drawing conclusions about the exact distribution of spinosaurids,‭ ‬it needs to be firmly established that before you go looking for certain examples of prehistoric animals,‭ ‬you need to identify age appropriate rock formations for those kinds of animals.‭ ‬For example,‭ ‬so far the dinosaurs disappear from the fossil record at the end of the Cretaceous about sixty-five million years ago,‭ ‬so it would be foolish to look for dinosaurs by digging into a rock formation that was laid down‭ ‬five million years later during the‭ ‬Pliocene.‭ ‬Spinosaurids for their part are mostly known from early Cretaceous deposits,‭ ‬especially from the Hauterivian to Albian stages.‭ ‬Looking in parts of the world which have rocks that go back to this age,‭ ‬which to no surprise to geologists cover large areas of South America,‭ ‬North Africa and Asia,‭ ‬would be to make an informed start when looking for remains of spinosaurids.
       However in‭ ‬2012‭ ‬a new genus of spinosaurid named Ostafrikasaurus has raised the notion that spinosaurids may have started appearing as far back as the late Jurassic‭ (‬mid Tithonian‭)‬.‭ ‬Ostafrikasaurus is based upon the description of teeth that appear spinosaurid,‭ ‬but are also similar to other theropod forms,‭ ‬such as the higher number of denticles on the teeth.‭ ‬Unfortunately the lack of skeletal remains make any further association with spinosaurids speculative,‭ ‬but it still needs to be remembered that the spinosaurids had to start somewhere.‭ ‬Also given their somewhat radical appearance to other theropod forms,‭ ‬they would have needed some time to develop their features,‭ ‬and the late Jurassic is as good as place as any to start looking for earlier spinosaurids.
       To summarise this segment,‭ ‬spinosaurids seem to appear in the late Jurassic,‭ ‬and proliferate in the Early Cretaceous.‭ ‬To date only Spinosaurus and Oxalaia are thought to have made it into the late Cretaceous,‭ ‬specifically the Cenomanian,‭ ‬which is the first stage of the late Cretaceous.‭ ‬Caution must be established however before assuming that this was the end for the spinosaurids.‭ ‬An isolated tooth from Henan province in China has been speculated to possibly be from a spinosaurid dinosaur,‭ ‬and is significant because it was recovered from a Santonian age deposit,‭ ‬beyond halfway into the late Cretaceous‭ (‬Hone,‭ ‬Xu‭ & ‬Wang‭ ‬-‭ ‬2010‭)‬.‭ ‬Just because other remains are lacking,‭ ‬it does not mean that no spinosaurids survived into the late Cretaceous,‭ ‬just that we don‭’‬t have the fossil evidence to prove that.‭ ‬Likewise,‭ ‬just because spinosaurids are currently mostly known from North Africa,‭ ‬South America,‭ ‬south-east Asia and Western Europe,‭ ‬it does not mean that they never lived anywhere else,‭ ‬just that there is no evidence for that either.‭ ‬The range of a particular type of animal is usually dictated by the amount of suitable habitat combined with an animals ability to reach it,‭ ‬but prehistoric animals also need to fossilise to leave evidence for us to find,‭ ‬and this only happens rarely.

How did spinosaurids live‭?
       As recently as the late twentieth/early twenty-first century,‭ ‬spinosaurids had been popularly envisioned as terrifying predators that would rip small plant eating dinosaurs to pieces.‭ ‬However this concept is more born out of early reconstructions of Spinosaurus way back when it was still thought to have had a more typical theropod skull.‭ ‬To get a more complete picture of how spinosaurids lived,‭ ‬you need to look at a number of elements and from there piece them together into a coherent form.
       Spinosaurids like most theropods had mouths that were full of sharp teeth,‭ ‬hinting at a predatory existence.‭ ‬The study of predators usually starts with the teeth because teeth are formed to work in certain ways.‭ ‬Most large Jurassic and early Cretaceous theropods had laterally compressed‭ (‬flattened from the sides‭) ‬teeth that were blade like with serrated edges,‭ ‬the perfect tools for slicing the flesh of large animals.‭ ‬Spinosaurids however have teeth that are unserrated,‭ ‬long,‭ ‬and relatively thin but round and end in a point,‭ ‬more like a nail than a blade.‭ ‬These teeth can’t slice flesh,‭ ‬but they are great for puncturing into flesh because the small point focuses pressure.‭ ‬These teeth are usually seen on animals that are fish eaters‭ (‬piscivores‭)‬,‭ ‬such as elasmosaurid plesiosaurs,‭ ‬ornithocheirid pterosaurs,‭ ‬fish eating crocodiles,‭ ‬to even fish that prey on other fish.
       The principal for how these teeth work is really very simple.‭ ‬If you hold a fish in your hands it will squirm and thrash about as it tries to wriggle out to escape back into the water and would do the same if it was caught in the mouth of a predator.‭ ‬A predator with serrated blade like teeth could catch a fish in its mouth,‭ ‬but the fish could cuts itself free as it thrashed about because the teeth can’t effectively hold flesh,‭ ‬only cut it.‭ ‬The fish will likely be injured and it could‭ ‬still die from its wounds,‭ ‬but what‭’‬s important here is the predator still goes hungry.‭ ‬Long thin teeth like those of spinosaurids act like pins,‭ ‬they can punch through the scales and dig into the flesh,‭ ‬and because the fish can’t thrash against the teeth to free itself,‭ ‬it ends up getting speared and held in place.‭ ‬The predator can then carry the fish away from the water and on‭ ‬to‭ ‬land where if it is still alive and thrashing about,‭ ‬the fish still has no chance of escaping into the water,‭ ‬meaning a predator that does not go hungry.
       The next part of the anatomy that hints at how predators ate are the large claws of the hands which are attached to well-developed fore-arms.‭ ‬Claws can and often are killing weapons in their own right,‭ ‬but on spinosaurids they can just be as easily explained as‭ ‬a‭ ‬reaction to the teeth.‭ ‬Teeth that are long,‭ ‬thin and unserrated are incapable of slicing flesh into bite sized chunks,‭ ‬and if they were used to tear off flesh,‭ ‬the individual in question may experience a greater than usual amount of tooth loss through excessive wear.‭ ‬In the long‭ ‬term this is not a problem since all dinosaurs‭ (‬or at least those that had teeth‭) ‬are known to have constantly replaced their teeth throughout their lives.‭ ‬Short term however such tooth‭ ‬loss could be detrimental to that individual’s ability to catch prey,‭ ‬meaning greater occurrences of unsuccessful hunting,‭ ‬and a higher likelihood of starving,‭ ‬or related conditions from said starvation.‭ ‬Having very large claws that would have been sharpened by a covering of keratin in life means however that spinosaurids were perfectly capable of rending flesh without putting too much stress on their teeth.
       One of the most specialised features seen in spinosaurids,‭ ‬which is particularly associated with the fossil remains of Spinosaurus in a‭ ‬2009‭ ‬study‭ (‬MSNM V4047‭) ‬is the snout.‭ ‬In depth study of the snout has revealed the presence of tiny pores in the bone which all link up to a space within the snout.‭ ‬Current thinking is that this was the housing for a pressure sensitive organ in the snout that was so sensitive it could detect changes in water pressure when submerged below the surface.‭ ‬This is an incredibly advanced way of detecting submerged prey but one that works by a very simple principal.‭ ‬Water at a specific depth is at a constant pressure level‭; ‬the only background differential is that the deeper you go down the weight of the water above presses down upon the water where you are,‭ ‬compacting it into a smaller space,‭ ‬increasing its pressure in the process.‭ ‬Now as a fish swims through the water its tail‭ ‬(and to an extent the body‭) ‬is pressing against the water as it flaps from side to side,‭ ‬and its head presses against the water in front as it swims forward.‭ ‬The pressing of the water from this motion causes subtle changes in the water pressure which essentially act as waves that pass through the surrounding body of water.‭ ‬This is the same principle to how you see ripples on a water surface when you drop something into a body of water.‭ ‬A spinosaurid,‭ ‬equipped with a pressure sensitive organ that was linked to multiple receptors on the snout would be able to detect these pressure waves and with practice not only would it be able to detect where the fish was,‭ ‬but how fast it was going and in what direction.‭ ‬From this point all a spinosaurid would have to do is gauge where the fish was going to,‭ ‬and then snap its jaws shut on that spot just as the fish was passing through.‭ ‬As long a spinosaurid stayed perfectly still until it‭ ‬struck,‭ ‬the fish would probably never know what was coming until it was already caught it the jaws.
       Even more evidence for spinosaurids being fish hunters comes from even more scientific analysis of fossil deposits and the fossils themselves.‭ ‬Spinosaurid fossils are mostly associated with what are called fluvial deposits.‭ ‬Basically these deposits are built up by the deposit of sediment from river systems,‭ ‬which means that spinosaurids were living in association to such geographic features such as rivers,‭ ‬deltas and floodplains.‭ ‬Oxygen isotope analysis of spinosaurid teeth‭ (‬Amiot et al,‭ ‬2010‭) ‬has also confirmed that spinosaurids were living in wetland environments such as river systems.
       Studies of spinosaurid skulls and just as importantly their neck mechanics,‭ ‬has also indicated that spinosaurids were best adapted for quick up and down motions of the head.‭ ‬This is exactly the type of motion that a sit and wait predator uses when striking into the water to snatch prey below the surface.‭ ‬Spinosaurids however do not seem to have been capable of strong side to side movements like other theropods,‭ ‬though this was unlikely to have been a hindrance given their supposed preferred mode of hunting.
       However,‭ ‬it should be remembered that a specialised predator of a type of creature is not necessarily an obligate predator of said animals.‭ ‬There are at least two occasions which counter the idea that spinosaurids only ate fish.‭ ‬These are the discovery of juvenile bones of the dinosaur Iguanodon that were found in association with the spinosaurid Baryonyx in a fashion that suggests they were consumed by the individual,‭ ‬and there is a vertebra of a pterosaur which has a spinosaurid tooth embedded into it.‭ ‬Both of these cases indicate that spinosaurids would eat other types of animal other than fish,‭ ‬giving rise to the suggestion that spinosaurids were generalists.‭
       It is also quite possible however that both of these instances may have been cases of opportunistic scavenging.‭ ‬Spinosaurids would not have been the only predators in their environments and would likely come across the carcasses left behind by these other predators after that had eaten their fills.‭ ‬After all an animal,‭ ‬any animal,‭ ‬can only eat so much to fill its stomach,‭ ‬and would have to stop eating after it had achieved this.‭ ‬All predators are known to scavenge the remains of other animals because it is a free meal that does not require the energy expenditure in the form of calories to acquire.‭ ‬When faced with the prospect of getting a few mouthfuls from a left over carcass,‭ ‬or standing on the side of a river and waiting for a fish to swim by,‭ ‬a spinosaurid will probably take the easy option.
       It should also be pointed out at this point that as well as bones of Iguanodon,‭ ‬fish scales were also found with the same specimen of Baryonyx,‭ ‬something that confirms that fish were an important part of a spinosaurid diet.

Did all spinosaurids have sails humps‭?
       The problem with answering this question is that out of all the current spinosaurid genera,‭ ‬named by‭ ‬2012‭ ‬only four have vertebrae described for them.‭ ‬From these Spinosaurus,‭ ‬Suchomimus and Ichthyovenator are all known to have had growths along their backs.‭ ‬The size and robust build of these spines however have led to popular thinking that they supported a form of fatty hump rather than a thin sail of skin.‭ ‬Baryonyx for its part does not have elongated neural spines,‭ ‬but it has also been speculated to have been an immature animal at the time of its death.‭ ‬This has not only led to further speculation that‭ ‬Baryonyx may have developed a hump in later life,‭ ‬but that Suchomimus may actually be the adult form,‭ ‬meaning that it may in fact be a synonym of Baryonyx.
       It should be said at this point that the spinosaurids were not the only dinosaurs to have had enlarged neural spines to support a growth on the back.‭ ‬The predatory carcharodontosaur theropods Acrocanthosaurus and Concavenator both had enlarged neural spines,‭ ‬and even the ornithopod Ouranosaurus,‭ ‬an ornithischian dinosaur even more distantly related than the other two previous genera also had a well-developed hump growth on its back.

What were the sails/humps used for‭?
       This is the question that has caused even more debate than ideas about how spinosaurids actually lived,‭ ‬but to keep things short we’ll run through this in sequence.‭ ‬The neural spines of spinosaurids were much stronger than they needed to be to support a sail made up of mostly skin.‭ ‬Comparison to other animals that have similar developments leads most palaeontologists to agree that neural spines were probably the support for a hump.‭ ‬Out of three current genera where the humps can be reconstructed,‭ ‬they are all found to have been a specific shape for each genus.
       One of the early ideas is that‭ ‬the humps were there for thermoregulation‭ (‬body temperature control‭)‬.‭ ‬Assuming a spinosaurid had to enter the water to reach the deeper depths where the fish were,‭ ‬it may have experienced heat loss through body surfaces exposed to the cooling water.‭ ‬A hump along the back could be angled to catch more of the sun’s rays,‭ ‬warming blood that was in the hump,‭ ‬which could then be pumped to the cooler areas of the body that had been chilled by the water.‭ ‬This scenario is plausible,‭ ‬but it fails to explain why the humps took different forms in each genus.
       An alternative theory is that the hump was there for fat storage.‭ ‬This is a very interesting theory that can tie in to the actual hunting lifestyle of the dinosaur.‭ ‬Certain species of fish will live in rivers all year round,‭ ‬and some of the largest rivers in the world today such as the Amazon river contain fish that are so huge it is hard to appreciate just how big they are until you actually seen one.‭ ‬But,‭ ‬if rivers saw the arrival of fish from the sea that were headed upstream for spawning,‭ ‬just like salmon do today,‭ ‬then the survival of spinosaurids might have depending in part upon these times of bounty when the river was suddenly but briefly filled with higher than usual numbers of fish.‭ ‬These numbers of fish may have been beyond that need for a spinosaurid to live for that day,‭ ‬but by gorging itself during this period a spinosaurid could put on a lot of weight as fat,‭ ‬and by having a special feature to store fat,‭ ‬a spinosaurid could store a greater amount of fat.‭ ‬Then when times were lean,‭ ‬a spinosaurid could rely upon its fat reserve to see it through to the next occasion when the rivers were full of migratory fish again.‭ ‬This would also work in situations where rivers would flood and fill with fish in the wet season,‭ ‬but be reduced to little more than an empty trickle in the dry season meaning that spinosaurids could not feed upon their preferred food.‭ ‬While this does allow for occasional feeding upon other types of animals such as dinosaurs and pterosaurs,‭ ‬it still does not explain why humps varied in form across genera.
       The one theory that comfortably explains the difference is display.‭ ‬By having species specific humps and looking different to one another,‭ ‬Spinosaurus could not confuse an Ichthyovenator for a member of its own species‭ (‬this is not to infer the two lived together,‭ ‬just to make an example‭)‬.‭ ‬In life the humps may have had a different colouration to the rest of the body,‭ ‬or even became more vivid when an individual spinosaurid wanted to attract a mate.‭
       It is quite possibly that there may also be more than just one reason why spinosaurids had humps and ridges down their backs.‭ ‬For example,‭ ‬the theory of display also connects well with the theory of fat storage.‭ ‬A particularly well fed spinosaurid would have a much fatter hump/ridge than a spinosaurid that had not been feeding well.‭ ‬This would allow the spinosaurid with the fatter hump to signal to potential mates that it had the skills and health to be more successful than its thinner humped counterpart,‭ ‬and was therefore more worthy of passing its genes down to the next generation.

What can be expected for spinosaurids in the future‭?
       The golden age of the study of spinosaurids began in the final two decades of the twentieth century,‭ ‬and especially in the‭ ‬1990s,‭ ‬with the naming of new genera and the discovery of new fossils for existing genera taking place for the first time since the naming of Spinosaurus in‭ ‬1915.‭ ‬In the first decade of the twenty-first century,‭ ‬even more new fossils and genera were found,‭ ‬allowing for enough fossils to be widely studied to begin to figure out the inner workings of spinosaurids.‭ ‬Now that palaeontologists have a much larger history of study to base their own theories on,‭ ‬the search for new spinosaurids can be focused upon areas where discoveries of these dinosaurs are more likely to happen.‭ ‬The increase in paleontological study in areas of the world such as Asia will likely yield more new discoveries just like they have already begun to.
       Future problems however may come from the creation of dubious genera on the basis of remains that are geographically and temporally isolated from existing finds.‭ ‬A recent tooth taxon called Ostafrikasaurus has shed insight into the possible evolution of spinosaurids,‭ ‬but unless further teeth actually attached to a skull are found,‭ ‬it will be near impossible to attribute further remains to this genus.‭ ‬The fragmentary nature of most spinosaurid fossils is also problematic,‭ ‬such as with the South American genus Oxalaia,‭ ‬which at the time of writing only has a tip of a snout attributed to the genus.‭ ‬In fact out of all the new fossils and genera named since Suchomimus in‭ ‬1998,‭ ‬the only genus to reveal a radically new and never before seen feature was Ichthyovenator in‭ ‬2012,‭ ‬with its distinctive notch.‭
       It is hard to predict further finds of fossils because not only does a fossil have to be found,‭ ‬but it needs to have fossilised in the first place.‭ ‬It also needs to be remembered that the larger the animal,‭ ‬the less likely it is that a complete specimen will be found,‭ ‬simply because bones only fossilise after they have been buried and protected from the elements,‭ ‬scavengers,‭ ‬bacteria,‭ ‬etc.,‭ ‬and this would obviously take longer with a large animal rather than a small one.‭ ‬But with that said,‭ ‬spinosaurids do seem to have lived in wetland ecosystems near rivers and on floodplains,‭ ‬and there is a higher chance with this happening in these ecosystems because rivers can flood,‭ ‬burying the surrounding area as well as remains of any dead animals under a layer of sediment.‭ ‬Another troublesome factor to consider is that the climate of some rock formations,‭ ‬particularly those in places like North Africa,‭ ‬is very harsh,‭ ‬and fossils that become exposed to the elements can be quickly damaged by such processes as wind erosion.
       The prospect of future fossil discoveries of spinosaurids is as much a certainty as any other kind of dinosaur,‭ ‬but in all likelihood fossils are likely to be fragmentary and incomplete.‭ ‬This does not mean that an almost complete spinosaurid will never be found,‭ ‬but this is never likely for any kind of animal,‭ ‬and complete individuals of any large vertebrate are rarely found.‭ ‬It’s possible that we may see a greater abundance of spinosaurid remains in late Cretaceous era rocks since this trend does seem to be happening right now.‭ ‬Primitive forms might be discovered in late Jurassic deposits also.‭ ‬Out of all the known spinosaurid fossils,‭ ‬teeth will probably continue to be the most numerous,‭ ‬in part due to the fact that dinosaurs would shed teeth that were worn and/or damaged so that a new one could grow to replace it.
       Geographically,‭ ‬Asia,‭ ‬North Africa,‭ ‬South America and Western Europe are likely to yield more remains,‭ ‬but we may see discoveries being made further afield.‭ ‬Expeditions in other parts of Africa may yield further remains,‭ ‬and discoveries in Thailand and Laos hint at a broad distribution of Asian spinosaurids.‭ ‬The fossil formations of China in particularly may hold untold numbers of spinosaurids yet to be discovered.‭ ‬Australia is also an interesting proposition since many of the rock Formations there are age appropriate for early Cretaceous spinosaurids,‭ ‬as well as the presence of a shallow sea‭ (‬Eromanga sea‭) ‬over much of modern inland Australia would allow for the presence of a large number of river deltas that could have been home to spinosaurids.
       The only continents left out so far are Antarctica and North America.‭ ‬Antarctica was much closer to Australia during the Mesozoic,‭ ‬and many dinosaur genera are known to have lived there.‭ ‬If spinosaurids were able to colonise what is now Australia,‭ ‬Antarctica would not be too far away for them to colonise,‭ ‬especially if they found suitable habitat there.‭ ‬Again however,‭ ‬without fossils to prove this,‭ ‬no one can say for certain.‭ ‬A further thing to consider is that while Antarctica was not covered by a sheet of ice in the Cretaceous,‭ ‬it would have had a greater seasonal change in temperature,‭ ‬and if spinosaurids ventured this far,‭ ‬they may have had to have been seasonal visitors that migrated back towards the equator when it got cooler.
       North America however is a little uncertain for a number of reasons.‭ ‬One and most obvious is the fact that the fossil bearing rock formations of North America,‭ ‬particularly those of Canada and the United States have been studied for longer and more extensively than most others in the world,‭ ‬and so far no spinosaurid remains have been found.‭ ‬Additionally North America was effectively split during the middle for much of the Cretaceous by the Western Interior Seaway,‭ ‬something that hampered faunal interchange.‭
       So far though there would have been three ways for spinosaurids to possibly reach North America,‭ ‬the first in the late Jurassic to Early Cretaceous.‭ ‬All of the continents used to be much closer together than they were today and there seems to have been a connection between North America and Western Europe,‭ ‬specifically Portugal as recently as the Early Cretaceous.‭ ‬The best evidence for this comes from many dinosaurs discovered in Portugal,‭ ‬including a specimen of Stegosaurus,‭ ‬being almost identical to some of the dinosaurs living in North America during the late Jurassic.‭ ‬Western European genera like Baryonyx are known from the earliest stages of the Cretaceous,‭ ‬and these just might have had enough time to cross over into North America.‭ ‬Baryonyx is of particular interest since although it was first discovered in England,‭ ‬fossils for this genus are also known from Spain which is on the Eastern border of Portugal.
       The other two ways rely upon spinosaurids surviving into the late Cretaceous.‭ ‬Like with Europe and North America,‭ ‬Africa and South America are believed to have still been joined well into the Cretaceous period,‭ ‬something that explains the presence of spinosaurids on both continents,‭ ‬as well as some other kinds of dinosaurs.‭ ‬During the late Cretaceous it is now believed that South America and North America were at one point if only briefly connected.‭ ‬Evidence for this comes from the seemingly sudden presence of saurolophine hadrosaurids like the genus Willinakaqe,‭ ‬a type of dinosaur usually seen in North America and Asia,‭ ‬and‭ ‬previously‭ ‬thought to have not possibly been able to reach South America because of a long severed connection with Africa.‭ ‬Again,‭ ‬if spinosaurids were still around in South America by the latest stages of the Cretaceous,‭ ‬it is remotely possible that they may have been able to cross over too.
       The final path of approach for late Cretaceous spinosaurids would‭ ‬be through Asia and across the Bering land bridge into upper North America.‭ ‬This seems to have been the route taken by many other types of dinosaurs,‭ ‬and one that was stable and open throughout the Mesozoic.‭ ‬If spinosaurids were indeed living in China during the Santonian stage of the late Cretaceous,‭ ‬it is an outside possibility that they may have had the opportunity to cross over.
       As it keeps being said,‭ ‬all of the above depends upon future fossil discoveries to prove them,‭ ‬and if these are not made then it would be just as easy to say that spinosaurids did not live in these areas.‭ ‬But for the above reasons stated,‭ ‬future discoveries in South America‭ (‬especially Brazil‭)‬,‭ ‬Africa,‭ ‬Western Europe,‭ ‬South East Asia and all of the areas that connect them are possible as long as there‭ ‬are late Jurassic to Cretaceous‭ (‬especially early‭) ‬sedimentary rocks to study.‭ ‬Australia and parts of Asia that are further north and east from existing south east Asian finds are possibilities.‭ ‬Antarctica and North America are not impossibilities,‭ ‬but the chances of finding spinosaurids on these continents are far more remote.‭

List of some known spinosaurid genera

Angaturama‭ (‬widely regarded as a synonym to Irritator‭)
Baryonyx
Cristatusaurus
Ichthyovenator
Irritator
Ostafrikasaurus‭
Oxalaia
Siamosaurus
"Sinopliosaurus‭"
Spinosaurus
Suchomimus

Further reading
-‭ ‬A neurovascular cavity within the snout of the predatory dinosaur Spinosaurus,‭ ‬C.‭ ‬Del Sasso,‭ ‬S.‭ ‬Maganuco,‭ ‬A.‭ ‬Cioffi‭ ‬-‭ ‬2009.

-‭ ‬Oxygen isotope evidence for semi-aquatic habits among spinosaurid theropods,‭ ‬R.‭ ‬Amiot,‭ ‬E.‭ ‬Buffetaut,‭ ‬C.‭ ‬Lecuyer,‭ ‬X.‭ ‬Wang,‭ ‬L,‭ ‬Boudad,‭ ‬Z.‭ ‬Ding,‭ ‬F.‭ ‬Fourel,‭ ‬S.‭ ‬Hutt,‭ ‬F.‭ ‬Martineau,‭ ‬A.‭ ‬Medeiros,‭ ‬J.‭ ‬Mo,‭ ‬L.‭ ‬Simon,‭ ‬V.‭ ‬Suteethorn,‭ ‬C.‭ ‬Sweetman,‭ ‬H.‭ ‬Tong,‭ ‬F.‭ ‬Zhang‭ & ‬Z.‭ ‬Zhou‭ ‬-‭ ‬2010.

-‭ ‬New data on spinosaurid dinosaurs from the Early Cretaceous of the Sahara,‭ ‬P.‭ ‬Taquet‭ & ‬D.‭ ‬A.‭ ‬Russel‭ ‬-‭ ‬1998.
-‭ ‬A new specimen of Spinosaurus‭ (‬Dinosauria,‭ ‬Theropoda‭) ‬from the Lower Cretaceous of Tunisia,‭ ‬with remarks on the evolutionary history of the Spinosauridae,‭ ‬E.‭ ‬Buffetaut‭ & ‬M.‭ ‬Ouaja‭ ‬-‭ ‬2002.
-‭ ‬Fine sculptures on a tooth of Spinosaurus‭ (‬Dinosauria,‭ ‬Theropoda‭) ‬from Morocco,‭ ‬Y.‭ ‬Hasegawa,‭ ‬G.‭ ‬Tanaka,‭ ‬Y.‭ ‬Takakuwa‭ & ‬S.‭ ‬Koike‭ ‬-‭ ‬2010.

-‭ ‬Pterosaurs as part of a spinosaur diet,‭ ‬E.‭ ‬Buffetaut,‭ ‬D.‭ ‬Martill‭ & ‬F.‭ ‬Escuillie‭ ‬-‭ ‬2004.

-‭ ‬Neural spine elongation in dinosaurs:‭ ‬sailbacks or buffalo-backs‭?‬,‭ ‬J.‭ ‬B.‭ ‬Bailey‭ ‬-‭ ‬1997.

-‭ ‬New information on the skull of the enigmatic theropod Spinosaurus,‭ ‬with remarks on its sizes and affinities,‭ ‬C.‭ ‬Del Sasso,‭ ‬S.‭ ‬Maganuco,‭ ‬E.‭ ‬Buffetaut‭ & ‬M.‭ ‬A.‭ ‬Mendez‭ ‬-‭ ‬2005.

-‭ ‬A new crested maniraptoran dinosaur from the Santana Formation‭ (‬Lower Cretaceous‭) ‬of Brazil,‭ ‬D.‭ ‬M.‭ ‬Martill,‭ ‬A.‭ ‬R.‭ ‬I.‭ ‬Cruickshank,‭ ‬E.‭ ‬Frey,‭ ‬P.‭ ‬G.‭ ‬Small‭ & ‬M.‭ ‬Clarke‭ ‬-‭ ‬1996.

-‭ ‬Irritator challengeri,‭ ‬a Spinosaurid‭ (‬Dinosauria:‭ ‬Theropoda‭) ‬from the Lower Cretaceous of Brazil,‭ ‬H.‭ ‬D.‭ ‬Sues,‭ ‬E.‭ ‬Frey,‭ ‬D.M.‭ ‬Martill‭ & ‬D.‭ ‬M Scott‭ ‬-‭ ‬2002.

-‭ ‬New remains of the enigmatic dinosaur Spinosaurus from the Cretaceous of Morocco and the affinities between Spinosaurus and Baryonyx,‭ ‬E.‭ ‬Buffetaut‭ ‬-‭ ‬1989.

-‭ ‬New information regarding the holotype of Spinosaurus aegyptiacus Stromer,‭ ‬1915,‭ ‬J.‭ ‬B.‭ ‬Smith,‭ ‬M.‭ ‬C.‭ ‬Lamanna,‭ ‬H.‭ ‬Mayr‭ & ‬K.‭ ‬J.‭ ‬Lacovara‭ ‬-‭ ‬2006.

-‭ ‬Baryonyx walkeri,‭ ‬a fish-eating dinosaur from the Wealden of Surrey,‭ ‬A.‭ ‬J.‭ ‬Charig‭ & ‬A.‭ ‬C.‭ ‬Milner‭ ‬-‭ ‬1997.

-‭ ‬The spinosaurid dinosaur Baryonyx‭ (‬Saurischia,‭ ‬Theropoda‭) ‬in the Early Cretaceous of Portugal,‭ ‬E.‭ ‬Buffetaut‭ ‬-‭ ‬2007.

-‭ ‬Unusual theropod dinosaur teeth from the Upper Jurassic of Phu Wiang,‭ ‬northeastern Thailand,‭ ‬E.‭ ‬Buffetaut‭ & ‬R.‭ ‬Ingevat‭ ‬-‭ ‬1986.

-‭ ‬An early spinosaurid dinosaur from the Late Jurassic of Tendaguru‭ (‬Tanzania‭) ‬and the evolution of the spinosaurid dentition,‭ ‬E.‭ ‬Buffetaut‭ ‬-‭ ‬2012.

-‭ ‬Spinosaurid teeth from the Late Jurassic of Tendaguru,‭ ‬Tanzania,‭ ‬with remarks on the evolutionary and biogeographical history of the Spinosauridae,‭ ‬E.‭ ‬Buffetaut‭ ‬-‭ ‬2008.

-‭ ‬The first definitive Asian spinosaurid‭ (‬Dinosauria:‭ ‬Theropoda‭) ‬from the early cretaceous of Laos,‭ ‬R.‭ ‬Allain,‭ ‬T.‭ ‬Xaisanavong,‭ ‬P.‭ ‬Richir‭ & ‬B.‭ ‬Khentavong‭ ‬-‭ ‬2012.

-‭ ‬A long-snouted predatory dinosaur from Africa and the evolution of spinosaurids,‭ ‬P.‭ ‬C.‭ ‬Sereno,‭ ‬A.‭ ‬L.‭ ‬Beck,‭ ‬D.‭ ‬B.‭ ‬Dutheil,‭ ‬B.‭ ‬Gado,‭ ‬H.‭ ‬C.‭ ‬E.‭ ‬Larsson,‭ ‬G.‭ ‬H.‭ ‬Lyon,‭ ‬J.‭ ‬D.‭ ‬Marcot,‭ ‬O.‭ ‬W.‭ ‬M.‭ ‬Rauhut,‭ ‬R.‭ ‬W.‭ ‬Sadleir,‭ ‬C.‭ ‬A.‭ ‬Sidor,‭ ‬D.‭ ‬D.‭ ‬Varrichio,‭ ‬G.‭ ‬P.‭ ‬Wilson‭ & ‬J.‭ ‬A.‭ ‬Wilson‭ ‬-‭ ‬1998.

-‭ ‬A new dinosaur‭ (‬Theropoda,‭ ‬Spinosauridae‭) ‬from the Cretaceous‭ (‬Cenomanian‭) ‬Alcantara Formation,‭ ‬Cajual Island,‭ ‬Brazil,‭ ‬Alexander W.‭ ‬A.‭ ‬Kellner,‭ ‬Sergio A.K.‭ ‬Azevedeo,‭ ‬Elaine B.‭ ‬Machado,‭ ‬Luciana B.‭ ‬Carvalho‭ & ‬Deise D.R.‭ ‬Henriques‭ ‬-‭ ‬2011.

-‭ ‬A probable baryonychine‭ (‬Theropoda:‭ ‬Spinosauridae‭) ‬tooth from the Upper Cretaceous of Henan Province,‭ ‬China,‭ ‬Hone,‭ ‬Xu‭ & ‬Wang‭ ‬-‭ ‬2010.

-‭ ‬First spinosaurid dinosaur from Australia and the cosmopolitanism of Cretaceous dinosaur faunas,‭ ‬P.‭ ‬M.‭ ‬Barrett,‭ ‬R.‭ ‬B.‭ ‬J.‭ ‬Benson,‭ ‬T.‭ ‬H.‭ ‬Rich‭ & ‬P.‭ ‬Vickers-Rich‭ ‬-‭ ‬2011.




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