Spinosaurus: Beast of the Week

Make way (lots of room...back up more...keep going...keep going...backbackbackback) for the mighty Spinosaurus Aegyptiacus!

Spinosaurus was a meat-eating dinosaur that lived in what is now Africa, including Egypt, Morocco, and Niger during the late Cretaceous Period, about 97-95 million years ago.  It was a massive animal, the biggest known individuals possibly measuring 49 feet (about 15m) long from snout to tail as an adult, making it the longest meat-eating dinosaur known to science.  The genus name, Spinosaurus, translates to "Spined reptile" in reference to the extremely long neural arches on it's back vertebrae. (We have neural arches too, just smaller.  If you run your finger down your spine, you can feel them.) Some of these spines were almost six feet tall, giving the animal a very striking profile in life.

Life reconstruction of a Spinosaurus aegyptiacus ambush hunting a crocodile while underwater by Christopher DiPiazza.

Spinosaurus has one of the richest histories behind its discovery.  It was first unearthed back in 1912 and published in 1915 by German Paleontologist, Ernst Stromer.  Back then all he had to work with was very fragmented remains including a part of a lower jaw, some vertebrae, and a few ribs, not enough to know for sure what the whole animal looked like, but certainly enough to tell it was something new and exciting.  For decades the remains of Spinosaurus remained in a museum in Munich, Germany, on display.  During World War II, allied forces bombed the area where this museum was.  Luckily some small fossils, including the first discovered Pterodactylus, and arguably the most valuable fossil in the world, Archaeopteryx, were able to be evacuated ahead of time but the poor bones of Spinosaurus were destroyed.  For decades the world had no real Spinosaurus fossils to study beyond the photographs and drawings left behind of the originals and small bits and pieces that didn't give any real new information found here and there every so often.  In fact, Spinosaurus teeth are actually quite common and are frequently sold in fossil and mineral stores.

Illustration of the original fossils found of Spinosaurus from Ernst Stromer's 1915 publication.  You can see three of the vertebrae with the tall neural arches on the left and the lower jaw piece on the lower right.  The straight, cone-shaped teeth are illustrated larger above the jaw.

It wasn't until the year 2005 that another big piece of Spinosaurus was found.  Italian Scientists digging in Morocco found pieces of a Spinosaurus skull, including most of the snout and the nostrils.  This showed that Spinosaurus had a much narrower snout than previously thought.  Then, this past year in 2014, paleontologist, Nizar Ibrahim, published a paper about even more material from this amazing animal, which included more of the spine and the hind legs that he and his team had uncovered in Morocco.  It was this discovery that changed Spinosaurus' image from unique to something that looks more at home in mythology. (Yes, even by dinosaur standards.)

Spinosaurus had many unique features about it that pretty much break all the rules of what we thought we knew about theropod dinosaurs.  We will start with the head and work our way back.  Spinosaurus belongs to a family of dinosaurs called spinosauridae (named after it, the first known member) which are all characterized by having very long, narrow snouts.  Their snouts are often compared to those of modern crocodiles, but this is mostly a superficial resemblance since they aren't mechanically that similar.  Spinosaurids all had pointed, cone-shaped teeth, and their nostrils were not at the tip of the snout, but higher up towards the middle.  These characteristics led scientists to believe that spinosaurids were adapted to hunting fish.  Their arms were powerful and possessed three fingers on each hand.  Digit one of each hand had an enormous, hooked claw on it, much larger than the other two.  This was probably another adaptation to hunting.

Spinosaurus skeletal mount on display at the National Geographic Museum.

As stated before, Spinosaurus had extremely long neural arches on its back that would have been covered in skin and other living tissue when the dinosaur was alive, giving it a sail-like appearance.  This is not completely unlike the sail of the also famous mammal-like reptile (and totally not a dinosaur), Dimetrodon, which lived millions of years earlier.  Despite the similarities, these two animals are not directly related to each other and is just another beautiful example of convergent evolution.  The function of the sail on Spinosaurus is something nobody can quite agree on.  There are always those who will say an adaptation like that was for display within the species.  Others believe it was to help regulate the animal's body temperature, having possibly been rich in blood vessels in life and easier to heat up in the sun.  This is a good hypothesis especially if Spinosaurus was spending a lot of its time near or in the water to hunt.  Bodies of water always cool an area down, conducting warmth more slowly than land does, and being in or near it can lower an animal's body temperature to the point where it needs to leave the area to warm up again.  Those that don't leave the water would need adaptations to help them stay warmer longer.  Think about ducks and geese (which produce their own heat, being endothermic) and how they have a layer down feathers against their bodies.  Also think about modern Marine Iguanas (cannot produce their own body heat as ectothermic) and how they can only stay in the ocean for a few minutes at a time until they need to haul out on shore to absorb more warmth from the sun.  A good way to experience this is going out on a boat during the summer, it may be hot on the land but the farther out the boat goes, the more everyone wishes they brought a jacket.  The sail on Spinosaurus may have been a way for it to increase its surface area to warm itself up in the sun as efficiently as possible while still being able to hang out in places with lots of water for long periods of time. 

For decades, everyone just assumed Spinosaurus' legs were the same as those of its close relatives like Suchomimus and Baryonyx, fellow spinosaurids which scientists had more complete skeletons of and were relatively typical for theropods, long and powerful, supporting an obligatory bipedal posture.  A discovery of more Spinosaurus bones that was published in 2014 changed all that, however.  According to what was unearthed,  Spinosaurus had short legs...like really short legs.  Initially some people proposed Spinosaurus may have been a quadroped, possibly walking on its knuckles to keep its claws sharp, making it the only known quadrupedal theropod known in history.  (which is mostly not accepted.)  Right after this publication was released many people thought that perhaps the paleontologists suggesting these odd proportions had not considered maybe their new leg material was from a juvenile specimen and was not scaled up to the other already-known material which was from adults.  The problem with that argument is that the new leg material was found with other bones that were almost certainly all from the same individual, including some of the long spine vertebrae, which were big just like the other adult-sized material already on the fossil record from Spinosaurus.  The mighty Spinosaurus really did have the proportions close to that of a dachshund mythical Asian Dragon!

Despite its proportionally small legs, assuming its front limbs were similarly built to those of any other theropod's, Spinosaurus still almost certainly only walked on its hind legs.  It was likely slower and clumsy on land, possibly dragging its tail for extra support.

The 2014 discoveries didn't end with the legs, however.  Spinosaurus' feet were unique in that the toes were flatter and wider than what is typically seen in theropod dinosaurs, except for certain birds that have webbed toes for paddling, like penguins and ducks, suggesting Spinosaurus had webbed toes as well.   Spinosaurus' bones were also not hollow like those of most other theropods.  Instead they were dense and solid.  Penguins are another kind of theropod with solid bones so that they can swim under water more easily.  These two amazing discoveries, combined with what we already knew about Spinosaurus' snout and teeth, lead us to believe that this dinosaur was specially adapted for a life in the water.  Even having short legs makes more sense.  Think of the legs of hippos and otters.  These are animals that, although capable getting around on land, really move best when under the water.  Also, if Spinosaurus was under the water a lot, having a large sail on its back which may have been more often poking above the surface to soak up some warmth from the sun, it would have been able to help prevent its body from getting too cold.  All of these strange adaptations which confused scientists for many years all start to come together a little more with the help of just a few more new (yet strange) discoveries!

In 2020 yet another previously absent part of Spinosaurus was published on, the tail, which was also unique.  The neural arches and chevrons (bony protrusions on the top and bottom of the vertebra) on the tail bones were greatly extended, implying Spinosaurus had a broad, paddle-shaped tail, like a gigantic newt! This actually makes sense since by this point scientists already had reason to think Spinosaurus was spending most of its time in the water.  This tail would have only helped Spinosaurus to move around in its environment better.

Photograph of Spinosaurus' newly published tail bones from Ibrahim's 2020 paper.

Finally, if Spinosaurus was an aquatic dinosaur, it would also make more sense of what we know about its environment.  The areas that Spinosaurus bones have been discovered in have a lot of other fossils in them too, most notably lots of other species of meat-eating dinosaur, and also lots of aquatic creatures like fish, turtles, and crocodiles.  Before this year, it was assumed that Spinosaurus was so large because it was competing with other predatory dinosaurs, like the slightly smaller allosauroid, called Carcharadontosaurus, and various ceratosaurs.  Despite this, it still always seemed strange to have that many predators but not so many plant-eating dinosaurs in the community.  Now we know that Spinosaurus probably evolved in a completely different direction to avoid competition altogether.  It was more likely an aquatic predator, spending more of its time in the water hunting fish and other aquatic prey.  This way it wasn't occupying the same space, nor was it competing for the same food as its fellow theropods.  Since it was the only dinosaur to exploit such a unique niche, it could have evolved to be extremely large without any competition.

Spinosaurus running under the water like a boss...or a hippo.  I have my doubts if this dinosaur was actually good at swimming, through the water like a crocodile, but walking/running around under it, sure, given its anatomy.

Note I haven't specifically said Spinosaurus would have been swimming underwater.  That's because despite how there is much evidence that suggests it spent time in and near the water, there is evidence that without contradicting any of this, suggests it was a poor swimmer.  That sounds contradictory at first but consider the fact that hippos don't really swim, despite spending most of their time in the water.  Birds, like herons, storks, and cranes also don't swim well, while spending lots of time in and around the water.  A paper published in 2021 investigated Spinosaurus' body proportions to test how well it would actually be able to swim in deep water, and found that because of its sail and upright dinosaurian posture (having its legs directly underneath the body) it would have been very top heavy and therefore at best a very clumsy swimmer.  That being said, it still appears to be adapted for living near and in the water, it was just more likely wading or walking around in it, not openly swimming.

Image of the skull of Spinosaurus mirabilis by Daniel Vidal.  Areas highlighted in red are what was actually found.  Gray areas are based on other spinosaurs to fill the gaps.

Finally, in 2026, a completely new species of Spinosaurus was published on!  The new species, called Spinosaurus mirabilis, was discovered in what is now Niger, Africa.  It was the younger of the two Spinosaurus species, living 95 million years ago, and its environment would have been more inland, farther away from the ocean.  It is only known from a skull, a few vertebra, and a leg bone, which is enough to identify it as a new species.  It's jaws were skinner than those of its older, Egyptian cousins'.  It also would have had proportionally slightly longer legs. (not a high bar just sayin) Most interesting, however, is probably the huge crescent-shaped bony crest growing out of the middle of the forehead.  The texture of the bone of this crest is highly vascularized, which means there was likely a layer of keratin over it in life and could have been much longer than what the bone core alone shows.  

sketches of both species of Spinosaurus known to science.

Spinosaurus holds many titles as a dinosaur.  Not only was it the longest known meat-eater, it was also the first known non-avian dinosaur to have actually been at least somewhat aquatic.  This long-snouted, short-legged, webbed-footed, sail-backed, paddle-tailed beastie would have truly been a sight to behold!

References

dal Sasso, C.; Maganuco, S.; Buffetaut, E.; Mendez, M.A. (2005). "New information on the skull of the enigmatic theropod Spinosaurus, with remarks on its sizes and affinities". Journal of Vertebrate Paleontology 25 (4): 888–896. 

Hone; Holtz, Thomas R. Jr. (2021). "Evaluating the ecology of Spinosaurus: Shoreline generalist or aquatic pursuit specialist?". Palaeontologia Electronica. 24

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.

Ibrahim, Nizar; Maganuco, Simone; Dal Sasso, Cristiano; Fabbri, Matteo; Auditore, Marco; Bindellini, Gabriele; Martill, David M.; Zouhri, Samir; Mattarelli, Diego A.; Unwin, David M.; Wiemann, Jasmina (2020). "Tail-propelled aquatic locomotion in a theropod dinosaur". Nature. 581: 1–4. 

Sereno et al (2026) "Scimitar-crested Spinosaurus species from the Sahara caps stepwise spinosaurid radiation" Science. vo391 issue6787: 

Smith, J.B.; Lamanna, M.C.; Mayr, H.; and Lacovara, K.J. (2006). "New information regarding the holotype of Spinosaurus aegyptiacus Stromer, 1915". Journal of Paleontology 80 (2): 400–406. 

Stromer, E. (1915). "Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman). 3. Das Original des Theropoden Spinosaurus aegyptiacus nov. gen., nov. spec". Abhandlungen der Königlich Bayerischen Akademie der Wissenschaften, Mathematisch-physikalische Klasse (in German) 28 (3): 1–32.

Corythosaurus: Beast of the Week

This week we will take a look at a well known duckbill dinosaur.  Enter Corythosaurus!  

Corythosaurus was a plant eater that belonged to the lambiosaurine group within the family, Hadrosauridae. (duckbills)  Lambiosaurine hadrosaurs typically had hollow crests on their heads and narrower beaks compared to other kinds hadrosaurs.  It was closely related to other lambiosaurine hadrosaurs such as Parasaurolophus, Hypacrosaurus, Lambeosaurus, and Velafrons.  It lived in what is now Alberta, Canada, during the Late Cretaceous period, between 77 and 76 million years ago.  Corythosaurus could have measured up to 30 feet (about 9m) long from beak to tail and its genus name translates to "helmet lizard/reptile" because of its tall disc-shaped crest, which in profile resembles a helmet.  

Corythosaurus cassuarius life reconstruction in watercolors by Christopher DiPiazza.

Corythosaurus actually includes two distinct species.  Corythosaurus cassuarius was had a larger crest and was found in rocks that about 1 million years older, and Corythosaurus intermedius, which had a slightly smaller crest and was found in slightly younger rocks.

There are two species of Corythosaurus currently known.

The crest of Corythosaurus, despite the name, wasn't really a helmet.  (Although another group of dinosaurs, the pachycephalosaurs, did have skulls that were more literally helmet-like.)  Its crest was semi-circular, and hollow on the inside, housing a network of tubes that likely connected the animal's nostrils to its windpipe.  Originally scientists thought this was an adaptation for a semi-aquatic lifestyle, but they were most likely for amplifying the sounds that Corythosaurus made.  Corythosaurus could inhale through its nostrils, where the air would pass through the series of tubes before being released through the mouth, thus producing a louder sound, much like the inner workings of trumpets or other brass wind instruments.  Sound was probably a very important method of communication for Corythosaurus and its relatives.  

Juvenile Corythosaurus skull on display at the Royal Ontario Museum in Canada.  Note the proportionally much smaller crest.

Thanks to a beautifully preserved specimen of Corythosaurus, paleontologists were able to discover highly developed inner ear bone, further supporting this idea.  The Corythosaurus genus used to consist of several species with similar crests of varying sizes.  It was later realized, however, that these specimens were more likely different ages and sexes of the same species since they were all found in the same area together and the largest specimens had the largest crests.  Furthermore, if adult male and female Corythosaurus also had different looking crests, they would have had different sounding calls.  We can see this today with their modern relatives, the birds and crocodilians, as well as other kinds of animals like frogs and insects.  It is possible lambiosaurid dinosaurs practiced similar behaviors, using sound to announce their age and sex over longer distances than they could with just looks.  Since more than one different kinds of these duckbills would have lived in the same place during the same time (Corythosaurus and Parasaurolophus, for instance.) it would make sense that each would have different crests to make different sounds and thus, preventing any identity confusion just like all the kinds of birds and frogs within the same community each have their unique calls today. 

Corythosaurus skeleton, which includes patches of skin and other soft tissue, on display at the American Museum of Natural History in New York.

Corythosaurus is amongst the most well-studied of the non-avian dinosaurs because one specimen that was unearthed in the early 1900s not only included nearly every single bone in the skeleton, but it also preserved skin, organs, and even the animal's last meal!  Thanks to this individual, now on display at the American Museum of Natural History in New York, we know that Corythosaurus would have had pebbly, mosaic-like scales that varied in size to form patterns on its skin.  It also had padding under its feet and hands, which scientists in the early 1900s originally thought would have been webbing for swimming, further supporting the now debunked aquatic hypothesis.  In the stomach cavity were the remains of conifer needles, sticks, and seeds.  These plant foods would have been plucked with Corythosaurus' narrow, flat beak and chewed up with its hundreds of tiny teeth lining the back of its jaws. 

When alive, Corythosaurus would have coexisted with many other well-known dinosaurs, like close relative, Parasaurolophus, the horned ceratopsian, Chasmosaurus and, the tyrannosaur, Gorgosaurus.

That is all for this week!  As always feel free to comment below!

References

Barden, Holly. "Sexual dimorphism in dinosaurs: a review of the evidence and approaches" (PDF). APS 402 Dissertation. University of Sheffield. Retrieved 13 August 2013.

Bell, P. R. (2012). "Standardized Terminology and Potential Taxonomic Utility for Hadrosaurid Skin Impressions: A Case Study for Saurolophus from Canada and Mongolia". In Farke, Andrew A. PLoS ONE 7 (2): e31295.

Dodson, P. (1975). "Taxonomic implications of relative growth in lambeosaurine dinosaurs". Systematic Zoology 24 (1): 37–54.

Torvosaurus: Beast of the Week

Today we are going to look at a huge Jurassic predatory dinosaur, Torvosaurus tanneri! 

Torvosaurus lived about 150 million years ago during the Late Jurassic period. Its bones have been unearthed in Colorado, USA, Portugal, and possibly Germany (Europe and North America were not as vastly separated back then, remember, so a lot of the dinosaurs on each of them from that time shared recent ancestors).  From nose to tail it measured up to 36 feet (about 11m) and would have been among the largest, most formidable meat eaters of its time.  The name, Torvosaurus, translates to "Fierce Reptile".
  

Torvosaurus in watercolors life reconstruction by Christopher DiPiazza.

Torvosaurus is a member of the megalosaurid family, and is closely related to the more famous, Megalosaurus.  Megalosaurids are mostly known from the middle and late Jurassic period, and are not super well known, since not many of them have ever been found compared to most other dinosaurs.  That being said they tend to have long, low skulls with large robust teeth with serrations for cutting meat.  Their arms were powerful with three fingers, tipped with proportionally large hooked claws.  Their legs also tend to be proportionally shorter.  The more popular spinosaurs are currently thought to be closely related to the megalosaurids (both are classified within the broader megalosauroid group), and it is likely that the megalosaurids gave rise to the first spinosaurs, although we currently don't have any obvious transition fossils that demonstrate this yet.

Torvosaurus, itself, currently contains two distinct species.  Torvosaurus tanneri from North America, and the slightly larger Torvosaurus gurneyi, from Europe.

Torvosaurus tanneri Skeletal mount on display at the Mesalands Dinosaur Museum in New Mexico.

Torvosaurus is especially important to paleontology because its one of the few dinosaurs paleontologists have actually found eggs from.  The nest of eggs found in Portugal, appeared to have been methodically buried in life by the parent.  They were close to hatching because the bones of embryos were also found inside, making them the oldest theropod dinosaur embryos known to science.  

When alive Torvosaurus tanneri would have coexisted with many famous dinosaurs, including the long-necked sauropods, Apatosaurus, Brontosaurus, Diplodocus, Barosaurus, Camarasaurus, and Braciosaurus, the armored Stegosaurus and Gargoyleosaurus, and the ornithopod Camptosaurus, all of which it may have hunted.  It also would have coexisted with fellow predators, Allosaurus and Ceratosaurus.  In Europe Torvosaurus gurneyi lived alongside Allosaurus (European species) and the long-necked stegosaur, Dacentrurus, to name just a few.

References

Araújo, Ricardo; Castanhinha, Rui; Martins, Rui M. S.; Mateus, Octávio; Hendrickx, Christophe; Beckmann, F.; Schell, N.; Alves, L. C. (2013). "Filling the gaps of dinosaur eggshell phylogeny: Late Jurassic Theropod clutch with embryos from Portugal". Scientific Reports. 1924 1924: 8.

Chure, Daniel J.; Litwin, Ron; Hasiotis, Stephen T.; Evanoff, Emmett; and Carpenter, Kenneth (2006). "The fauna and flora of the Morrison Formation: 2006". In Foster, John R.; and Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 233–248.

Mateus, O., Walen, A., and Antunes, M.T. (2006). "The large theropod fauna of the Lourinha Formation (Portugal) and its similarity to that of the Morrison Formation, with a description of a new species of Allosaurus." New Mexico Museum of Natural History and Science Bulletin, 36.

 Mateus, O., & Antunes, M. T. (2000). Torvosaurus sp.(Dinosauria: Theropoda) in the late Jurassic of Portugal. In I Congresso Ibérico de Paleontologia/XVI Jornadas de la Sociedad Española de Paleontología (pp. 115-117).

Ribeiro, Vasco; Mateus, Octávio; Holwerda, Femke; Araújo, Ricardo; Castanhinha, Rui (March 4, 2014). "Two new theropod egg sites from the Late Jurassic Lourinhã Formation, Portugal". Historical Biology. 26 (2): 206–217.

Hesperosuchus: Beast of the Week

This week we will be checking out a relative of modern crocodilians that has tricked scientists multiple times!  Enter Hesperosuchus agilis!

Hesperosuchus was a pseudosuchian (related to crocodilians) that lived in what is now Arizona and New Mexico, USA, during the late Triassic period, about 210 million years ago.  It would have been a meat-eater and from snout to tail the most complete skeleton measures about four feet (1.2m) but other fossils suggest it could have grown larger, up to about six feet (1.8m).  The genus name translates to "Western Crocodile" due to where it was fond and its relation to modern crocodilians, and the species name to "agile" in reference to how it was likely a swift and agile runner in life.

Hesperosuchus stealing an egg from the dinosaur, Coelophysis. Watercolor reconstruction by Christopher DiPiazza.

When Hesperosuchus was first discovered it was initially thought to be a kind of dinosaur.  This is due to the fact that it had hollow bones, a trait that at that time was not known to be in pseudosuchians.  Hesperosuchus is just one of many examples of how the group that includes modern crocodilians was extremely diverse and evolved into many different forms during the Mesozoic, especially the Triassic.  Not only did Hesperosuchus have hollow bones, but it also possessed fully erect upright posture with long slender limbs.  It may have even been able to run on its hind legs.  

Hesperosuchus also possessed a laterally compressed skull (again like most theropod dinosaurs) which is in contrast to modern crocodilians, all of which have skulls that are more flattened top to bottom, an adaptation for spending much of their time in the water.  Aquatic crocodilians had not yet evolved in the Triassic and all of their closest relatives from then, like Hesperosuchus, were actually land animals.  Hesperosuchus possessed pointed teeth that were serrated on both the front and rear edges, implying it at meat when alive, probably focusing on snatching up small animals.  Like modern crocodiles it had a slight notch in its snout where its bottom teeth interlocked with its top jaws.

Hesperosuchus skull image from the 2012 paper by Nesbitt et al., referenced below.

 Like most pseudosuchians, Hesperosuchus also had osteoderms, bony armor that exists in the skin, in the form of two rows of almost square-shaped scutes running down its back.  This was likely for defense against predators, of which there were many Hesperosuchus had to be weary of.  That being said it appears this armor may not have protected Hesperosuchuchus every time since there is a famous skeleton of the dinosaur, Coelophysis, has what appears to be bones from Hesperosuchus (which were initially thought to be from a baby Coelophysis) inside its stomach cavity. 

When alive, Hesperosuchus would have lived alongside other pseudosuchians, like the herbivorous aetosaurs and shuvosaurs, and the large  carnivore, Postosuchus.  It also would have shared its environment with the not-crocodile-but-crocodile-resembling phytosaurs, as well as the carnivorous dinosaur, Coelophysis.  

References

Clark, James M.; Sues, Hans-Dieter; Berman, David S. (19 January 2001). "A new specimen of Hesperosuchus agilis from the Upper Triassic of New Mexico and the interrelationships of basal crocodylomorph archosaurs". Journal of Vertebrate Paleontology. 20 (4): 683–704.

Colbert, E. H. 1952. A pseudosuchian reptile from Arizona. Bulletin of the American Museum of Natural History 99:561–592.

Nesbitt, Sterling J.; Turner, Alan H.; Erickson, Gregory M.; Norell, Mark A. (22 December 2006). "Prey choice and cannibalistic behaviour in the theropod Coelophysis". Proceedings of the Royal Society B. 2 (4): 611–4.

Nesbitt, Sterling J.; Turner, Alan H.; Weinbaum, Jonathan C. (September 2012). "A survey of skeletal elements in the orbit of Pseudosuchia and the origin of the crocodylian palpebral". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 103 (3–4): 365–381.