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Altispinax: The Mysterious Meat-Eater of Early Cretaceous England


There are many dinosaur species which have been identified based upon very scant remains, and this article concerns one of them: a meat-eating dinosaur named Altispinax dunkeri. If you’ve never heard of this animal before, you’re not alone. It’s not exactly a name that readily springs to mind when one thinks of dinosaurs. After all, Altispinax is only known from three vertebrae that were found back in the 1850s, and nothing else has been found since then which can be positively attributed to this animal. Other isolated fossils have been found here and there, but there’s really no way to tell if all of these isolated bones, teeth, and claws all belong to the same creature. Broadly, we are reasonably sure that it was a meat-eating dinosaur, but aside from that, there’s not much else to go on.

Discovery and Description

In 1855, a British lawyer and amateur fossil hunter named Samuel H. Beckles (April 12, 1814 – September 4, 1890) was prospecting for fossils in southeastern England. Not far from the site of the Hastings battlefield, he discovered a series of three vertebrae with unusually tall dorsal spines, measuring about 14 inches (35 centimeters) from the top of the centrum disk to the top of the spine (1).

The holotype specimen of Altispinax (collections ID code: BMNH R1828, or maybe it’s NHMUK R1828). Image from “Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia” by Darren Naish and David M. Martill (2007). Journal of the Geological Society, volume 164. Page 503, Figure #7 (Pages 493-510).

The following year in 1856, the famous British paleontologist Sir Richard Owen wrote a description of this fossil in which he ascribed it to the genus Megalosaurus, which had been classified about thirty years earlier. The description of the fossil reads as follows:

“Three anterior dorsal vertebrae: p, parapophysis, or lower transverse process: t, accessory tubercle contributing some attachment to the head of the rib: d, diapophyses, or upper transverse process, fractured, which gave attachment to the tubercle of the rib: b, oblique buttress extending from the parapophysis to the diapophysis, and contributing to the support of the neural platform : z, the prozygapophysis, z’, the zygapophysis, forming the ends of the neural platform and articulating the neural arches of the vertebrae with each other, ns, the neural spine of the foremost of these vertebras, ns’, the neural spine of the second vertebra; it expands at its extremity, overhangs the anterior shorter spine, and developes a strong bony plate from its back part which fixes it to n”, the similarly developed and modified spine of the third vertebra. The extraordinary size and strength of the spines of these anterior dorsal vertebrae, indicate the great force with which the head and jaws of the Megalosaurus must have been used” (2).

This is a drawing (yes, that’s a drawing, not a photograph) of the vertebrae, made by Joseph Dinkel which accompanies Owen’s article. Public domain image, Wikimedia Commons.

The fossil vertebrae were found in the rocks of the “Wealden Supergroup”. This is a multi-layer series of geological formations consisting largely of sandstones and mudstones which are spread throughout much of southeastern England and date to the early Cretaceous Period. This geological super-formation is divided into several sub-units called “groups”, and each of these groups are divided further into “formations”. These include the “Hastings Beds Group” (dated from the Berriasian to Valanginian Stages of the early Cretaceous Period), the “Weald Clay Group” (Hauterivian and Barremian, possibly extending into the Aptian), and the “Wealden Group” (Barremian to Aptian) (3).

The vertebrae fossils were found in the rock layers of the “Hastings Beds Group”. Specifically, the fossils were found in the Wadhurst Clay Formation of East Sussex. This formation dates to the Valanginian Stage of the early Cretaceous Period, and even more specifically to the early to middle Valanginian. This would place the vertebrae’s date range at about 138-135 million years ago. During this same time, iconic early Cretaceous dinosaurs such as Iguanodon and Baryonyx had not yet evolved. Instead, Altispinax shared its habitat with the armored ankylosaur Hylaeosaurus, the sauropods Pelorosaurus and Xenoposeidon, and the small ornithopods Valdosaurus and Echinodon. Isolated fossils of Iguanodon-like animals have also been found here, as well as fossils of frogs, crocodiles, and small mammals. Since no other large carnivorous dinosaurs are known from this place and time, Altispinax might have been the top predator within its environment (4).


Altispinax is not a well-known dinosaur, but even though it is not a major star in dinosaur paleontology circles and it is not a creature well-known to the general public, largely due to the fact that the only evidence for it comes from a single fragmentary specimen found nearly 170 years ago, Altispinax has received a surprisingly high amount of academic attention. Every now and then, professional paleontologists dabble in Altispinax speculation, analyzing these three vertebrae for the umpteenth time and pondering where exactly it fits in the theropod family tree.

Unsurprisingly, because these finds are 170 years old and are known only from fragmentary remains, Altispinax’s position in the dinosaur family tree has been regularly shuffled around because nobody, it seems, can make up their minds about what sort of animal it was. When it was first discovered, Sir Richard Owen believed that these spines belonged to Megalosaurus bucklandi, one of the first dinosaurs to be discovered and named. During the 19th and 20th Centuries, the name “Megalosaurus” was considered a “wastebasket taxon” – any remains of a meat-eating dinosaur which could not be positively identified were classified as Megalosaurus. As a result, this genus name acquired a long list of species names. Indeed, early reconstructions of Megalosaurus incorporated these three tall-spined vertebrae into its anatomy. For example, the British sculptor Benjamin Waterhouse Hawkins created a statue of Megalosaurus for Crystal Palace Park in which it possessed a bison-like hump over its shoulders.

Middle 19th Century reconstruction of Megalosaurus by Benjamin Waterhouse Hawkins, on display in Crystal Palace Park. Note the prominent bison-like hump over the shoulder. Photo by C. G. P. Gray (2007). Creative Commons Attribution 3.0 Unported license.

When Megalosaurus’ appearance was further refined during the late 1800s into a definitely dinosaurian appearance, but in an incorrect upright pose as championed by people such as Joseph Leidy and Louis Dollo, this reconstruction again showed Megalosaurus with tall neural spines, forming a low ridge running down the middle of its back.

Late 19th Century reconstruction of Megalosaurus by Christian Von Meyer, in which the animal is portrayed with tall neural spines on its dorsal and sacral vertebrae. Illustration from Extinct Monsters, 5th Edition, by Reverend Henry N. Hutchinson. London: Chapman and Hall, 1897. Page 78. https://archive.org/details/extinctmonsters00hutciala.

In 1923, the famed German paleontologist Friedrich Von Huene took a look at the three spines from southern England, as well as a single tooth that was discovered in Germany which had been given the name Megalosaurus dunkeri. Von Huene lumped these fossils together in the belief that they both came from the same species, and determined that they did not, in fact, come from Megalosaurus. So he gave these spines and the solitary tooth a new name – Altispinax dunkeri, “Dunker’s high-spined ruler” (5).

Later researchers justifiably felt that Von Huene had jumped the gun by assuming that the tooth from Germany and the vertebrae from England belonged to the same species. Furthermore, new species had been discovered since then. In the late 1940s in the United States, another large theropod was discovered with a prominent ridge running down its back which looked remarkably similar to the three vertebrae found in England. In 1950, the American dinosaur was named Acrocanthosaurus atokensis, and other paleontologists began to wonder if the mysterious vertebrae found in England came from a similar animal. In the 1980s, paleontologist and paleo-artist Gregory Paul felt that the three vertebrae represented a European version of Acrocanthosaurus, so he gave it a provisional name of “Acrocanthosaurus altispinax”, though he wasn’t absolutely certain if he was correct. In 1991, George Olshevsky stated that these three spines did not belong to Acrocanthosaurus, but belonged to a new genus, and so it was named Becklespinax altispinax, named in honor of Samuel Beckles who had discovered the vertebrae in 1855 (6).

Skeleton of Acrocanthosaurus on display at the North Carolina Museum of Natural Sciences. Photo by Famille Wielosz-Caron (August 4, 2007). Creative Commons Attribution 2.0 Generic license.

Illustration of Becklespinax made by the paleo-artist James Robins in the magazine Dinosaurs!, issue #46, page 1084. Durham: Atlas Editions Partworks, Inc., 1994.

The name Becklespinax remained in place for the next twenty-five years until 2016 when it was challenged by Michael Maisch. He said that since Friedrich Von Huene recognized this animal as a distinct species back in 1923, this pre-dated George Olshevsky’s recognition of this animal as a distinct species in 1991. Therefore, the name Altispinax held priority over the more recent name Becklespinax, and therefore the name Becklespinax should be discarded. So in 2016, the old name of Altispinax dunkeri was resurrected (7).

Just as its name has been altered over the years, Altispinax’s phylogeny has also changed. In 1856, Sir Richard Owen classified this animal as a megalosaur. Then, following the discovery of Acrocanthosaurus in the late 1940s, it was believed to be an allosaur (later, Acrocanthosaurus was re-classified as a carcharodontosaurid). In 1991, George Olshevsky classified Altispinax once again as a megalosaur, specifically in the family Eustreptospondylidae. By the late 1990s, it was re-classified again as being more closely-related to a Middle Jurassic allosaur from China called Sinraptor, and was therefore placed in the allosauroidean family Metriacanthosauridae, which includes Metriacanthosaurus, Sinraptor, and Yangchuanosaurus. These species measured 20-25 feet long (which was the same size estimate commonly seen for Altispinax), had curvaceous skulls, and unusually tiny hands with stubby fingers and claws. Allosaurus, with its gigantic hands and meat hook claws, was a rough-and-tumble attacking predator (numerous injuries on fossils prove this), but its cousin Sinraptor did not have such well-developed hands. In 2003, Darren Naish classified this creature as belonging to the more evolutionarily-advanced super-family Allosauroidea, but didn’t hazard placing it into a specific allosaur family (8). In a 2007 article, Darren Naish wrote “Several other tetanurans exhibit a similar pattern of neural arch laminae to Becklespinax, including Condorraptor, Piatnitzkysaurus and Sinraptor, and Sinraptor in particular exhibits a superficially similar morphology: this could mean that Becklespinax is a sinraptorid, but there are no uniquely shared characters that might demonstrate this. For now, pending further discoveries, Becklespinax remains an indeterminate tetanuran of unknown affinities. Its combination of characters, and uniquely expanded neural spines tips, mean that it is a valid, diagnosable taxon” (9).

Skeleton of Sinraptor. Photo by Ian Armstrong (April 17, 2005). Creative Commons Attribution-Share Alike 2.0 Generic license.

Some people wondered if Altispinax might have been a spinosaur or perhaps a carcharodontosaur, since species from both groups have been found in Europe, and especially considering that carcharodontosaurs like Acrocanthosaurus and spinosaurs like Suchomimus and Ichthyovenator were known to have tall neural spines on its vertebrae forming a dorsal ridge. In a 2007 article, back when the animal was still referred to as Becklespinax, Darren Naish wrote “there are no shared derived characters that might unite Becklespinax with either spinosaurids or carcharodontosaurids, and these suggestions can’t be supported”(10). But not long after this was written, Concavenator was discovered in Spain, and old questions were resurrected regarding Altispinax’s position on the theropod family tree. It was determined that Concavenator was a carcharodontosaurid, and there were several noticeable similarities between this animal and Altispinax. Now, many people are once again changing Altispinax’s phylogeny, saying that, yes, it is a carcharodontosaur, but as to whether or not it is, it’s anybody’s guess at this point. Darren Naish re-classified Altispinax as a carcharodontosaurid in 2011, and the science website Palaeos also classifies Altispinax (identified on the web-page as Becklespinax) as a member of the family Carcharodontosauridae (11).

Skeleton of Concavenator, a 20 foot carcharodontosaurid from Spain. Photograph by Santiago Torralba (August 22, 2008). Creative Commons Attribution 2.0 Generic license.

Reconstructed skeleton of Concavenator. (May 1, 2019). Creative Commons Attribution-Share Alike 4.0 International license.


Well, time to reconstruct what the whole animal may have looked like. It is not yet clear if Altispinax was more closely related to Sinraptor or to Concavenator. Although both of these animals had different features to the structure of their skull, outwardly they would have looked very similar to each other. Both groups of animals also had short arms with small hands, and would have had an allosaur-ish body structure. One wonders if the carcharodontosaurids evolved directly from the metriacanthosaurids like Sinraptor, but this is just a guess on my part.

As for the sail, that was a bit difficult. For years, paleo-artists depicted sail-backed bipedal dinosaurs, like the old renditions of Spinosaurus, with a sail located on the back between the arms and the legs. But the best position for a theropod’s sail is directly over the hips, not between the front limbs and hind limbs as is often seen. Animals that have their sails positioned between the front legs and back legs are quadrupedal animals, like Dimetrodon, and also what we now know Spinosaurus to be like. In a four-legged animal, the body is held off of the ground in an arch, braced by the four legs, and as such the main body has the structural support necessary to carry a sail over the back. However, in a bipedal animal, the hips form a fulcrum which balances the animal. If a bipedal animal had a sail located in a Dimetrodon-like way, positioned between the arms and legs, it would make the animal front-heavy. Therefore, a sail would be better positioned over the hips. Of course, this discounts the possibility that the animal had an unusually long tail to counter-balance the weight in the front. This is with the assumption that Becklespinax’s sail was short, extending only a small distance along the length of its back. It’s possible that it may have had a skeleton similar to Acrocanthosaurus, which had raised dorsal spines running all along its back, from the base of the skull, and extending down to the tip of the tail. However, this cannot be definitively stated to be the case until more of this animal is discovered.

The drawing that you see below was made with No. 2 pencil.

Altispinax dunkeri. © Jason R. Abdale (May 3, 2021).

Source Citations:

  1. Everything Dinosaur. “Remembering Samuel Husbands Beckles (1814-1890)”, by Mike Walley (August 24, 2014).; I Know Dino podcast. Episode 54 – “Becklespinax” (December 8, 2015).
  2. Richard Owen (1856). “Monograph on the fossil Reptilia of the Wealden Formation. Part IV”. Palaeontographical Society Monographs, volume 10.
  3. Darren Naish, “Pneumaticity, the early years: Wealden Supergroup dinosaurs and the hypothesis of saurian pneumaticity”. In Richard T. J. Moody, E. Buffetaut, Darren Naish, and David M. Martill, eds., Geological Society Special Publication No. 343 – Dinosaurs and Other Extinct Saurians: A Historical Perspective. London: The Geological Society, 2010. Pages 229-230.
  4. David B. Weishampel, ‎Peter Dodson, ‎Halszka Osmólska, eds., The Dinosauria, Second Edition. Berkeley: University of California Press, 2004. Page 73; Darren Naish, “Pneumaticity, the early years: Wealden Supergroup dinosaurs and the hypothesis of saurian pneumaticity”. In Richard T. J. Moody, E. Buffetaut, Darren Naish, and David M. Martill, eds., Geological Society Special Publication No. 343 – Dinosaurs and Other Extinct Saurians: A Historical Perspective. London: The Geological Society, 2010. Page 230; Mindat. “Becklespinax”; British Geological Survey. “Wadhurst Clay Formation”; Oladapo Odunayo Akinlotan (October 2015), The Sedimentolody of the Ashdown Formation and the Wadhurst Clay Formation, Southeast England. PhD Thesis, University of Brighton. Page 1.
  5. Smithsonian Magazine. “B is for Becklespinax”, by Riley Black (October 22, 2012).
  6. Smithsonian Magazine. “B is for Becklespinax”, by Riley Black (October 22, 2012).
  7. Michael W. Maisch (2016), “The nomenclatural status of the carnivorous dinosaur genus Altispinax v. Huene, 1923 (Saurischia, Theropoda) from the Lower Cretaceous of England”. Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen, volume 280, issue 2. Pages 215-219.
  8. George Olshevsky (1991). “A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia”. Mesozoic Meanderings, volume 2. Pages 22-23 (1-196); Theropod Database. “Carnosauria”; Dinosaur Mailing List. “Re: Becklespinax” (February 18, 1997); Darren Naish (2003), “A definitive allosauroid (Dinosauria; Theropoda) from the Lower Cretaceous of East Sussex”. Proceedings of the Geologists’ Association, volume 114. Pages 319-326; Darren Naish and David M. Martill (2007), “Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia”. Journal of the Geological Society, volume 164. Pages 502-503, Figure #7 (Pages 493-510).
  9. Tetrapod Zoology. “Of Becklespinax and Valdoraptor”, by Darren Naish (October 2, 2007).
  10. Tetrapod Zoology. “Of Becklespinax and Valdoraptor”, by Darren Naish (October 2, 2007).
  11. Theropod Database. “Carnosauria”; Naish, Darren (2011). “Theropod Dinosaurs”. In Batten, ed., English Wealden Fossils. The Palaeontological Association. Pages 526-559; Smithsonian Magazine. “B is for Becklespinax”, by Riley Black (October 22, 2012); Palaeos. “Theropoda: Avetheropoda: Carcharodontosauridae”.



There are some dinosaurs that everybody thinks of when they hear the word “dinosaur”. Among these is a very large sauropod which was the reptilian analog of a giraffe. I am, of course, talking about Brachiosaurus.

Brachiosaurus is one of the more famous dinosaurs. This animal was the iconic “giraffe of the Jurassic”, and for a while it held the record of being the largest dinosaur known. It has been featured in countless books and TV documentaries about dinosaurs, and got a major role in the 1993 movie Jurassic Park. But how much do we really know about it?

Brachiosaurus makes its debut appearance in Jurassic Park (1993).

Considering that Brachiosaurus is one of the more familiar dinosaur names, we actually know surprisingly little about it. This largely has to do with the fact that fossils of this animal are extremely rare. Our total knowledge about this animal’s anatomy comes from bits and pieces of several skeletons that were found here and there across much of the Rocky Mountains within the states of Wyoming, Utah, and Colorado, as well as one location in the extreme westernmost parts of the Oklahoma pan-handle. That’s it.

Map of locations where Brachiosaurus fossils have been found, as of 2020:
1) KU Quarry, Wyoming (KUVP 129724; KUVP 133862; KUVP 142200; KUVP 144767)
2) Freeze-out Hills, Wyoming (one caudal vertebra, undescribed)
3) Reed’s Quarry 13, Wyoming (undescribed specimen)
4) Jensen/Jensen Quarry, Utah (FHPR 17108)
5) Fruita, Colorado (undescribed specimen)
6) Riggs’ Quarry 13, Colorado (FMNH P 25107) (this is the holotype)
7) Dry Mesa Quarry, Colorado (BYU 9462; BYU 12866; BYU 12867; BYU 13023)
8) Potter Creek, Colorado (BYU 4744; USNM 21903)
9) Felch Quarry 1, Garden Park, Colorado (USNM 5730)
10) Kenton Pit 1, Oklahoma (OMNH 01138)

The discovery of Brachiosaurus dates back to the very beginning of the 20th Century. In 1900, a few very large bones were discovered in western Colorado near the small town of Fruita, located only a short distance away from the Utah-Colorado border. There wasn’t much to go on: some vertebrae, one hip bone, one femur, one humerus, and part of the shoulder. Still, the bones were distinctive enough from other sauropod dinosaurs known from the Morrison Formation to warrant classifying it as a new genus. In 1903, the creature was officially named Brachiosaurus altithorax, “arm lizard with a wide chest” by Elmer Riggs.

In 1909, a German paleontological expedition led by Wilhelm von Branca were exploring in the German colony of Tanzania when they discovered some large bones near a site called Tendaguru, meaning “steep hill” in the Mwera language. Excavations revealed that it was a partial skeleton, and similarities were soon observed between these bones and the bones that had been unearthed by Elmer Rigg’s team in Colorado several years earlier. In 1914, these bones were classified as another species of Brachiosaurus, named Brachiosaurus brancai. It helped that there was a lot more of the skeleton in this specimen, and for decades afterwards, the African species of Brachiosaurus served as the model for the North American species. However, beginning in the 1980s, doubts arose whether these animals were, in fact, two species of the same genus. A thorough compare-and-contrast analysis showed that there were actually more differences noted in each bone than similarities. Consequently in 1988, the African species was re-named as Giraffatitan brancai.

Both genera had similarities. Both Brachiosaurus and Giraffatitan were very large animals, both of them belonged to the sauropod group known as “Macronaria”, both of them had necks which could be held vertically or near-vertically rather than the horizontally-oriented necks of many other sauropods, both of them had arms which were longer than their legs (hence Brachiosaurus‘ name) which resulted in high shoulders and the back sloping downwards towards the hips, and the neck was longer than the tail. Now that we have established what they had in common with each other, how different was Brachiosaurus from Giraffatitan? Since neither skeleton is complete, and in fact Brachiosaurus is known from scant remains, it is impossible to do a comprehensive 100% compare-and-contrast analysis of both of their skeletons. However, based upon the remains which we do have, we can draw a few conclusions.

First, it appears that either A) Giraffatitan was larger, or B) Both animals were the exact same length but Giraffatitan was more physically massive. Brachiosaurus is estimated to have reached a length of 70 feet long or thereabouts with a 30 foot neck. By contrast, Giraffatitan may be the same length, but differences in body proportions (which I will describe later) meant that it was bulkier than its North American counterpart. Other estimates state that Giraffatitan exceeded Brachiosaurus in size, measuring 75 to 85 feet long.

Second, the skull shape was different. When most people imagine what the head of a Brachiosaurus looked like, they are actually imagining the head of a Giraffatitan, with its high firefighter-helmet crest. Only one partial skull of a Brachiosaurus has been found near Garden Park, Colorado; it was found in 1883, but it wasn’t identified as belonging to a Brachiosaurus until decades later. Although the skull is not complete, enough of it was preserved to indicate that it was not as tall as the skull of Giraffatitan. It appears to have had a much lower crest, sort of in-between the low curvaceous skull of an Apatosaurus and the tall crested skull of a Giraffatitan.

Skulls of Brachiosaurus altithorax (A) and Giraffatitan brancai (B). Carpenter, Kenneth; Tidwell, Virginia (1998). “Preliminary description of a Brachiosaurus skull from Felch Quarry 1, Garden Park, Colorado”. Modern Geology, volume 23. Page 73 (Pages 69–84).

Third, Brachiosaurus had larger and bulkier shoulders compared to Giraffatitan, despite the fact that Giraffatitan seems on the whole to have been larger and more robustly-built than Brachiosaurus. However, Brachiosaurus might (emphasis on “might”) have had a wider chest than its African counterpart.

Fourth, Brachiosaurus may have had a longer chest compared to Giraffatitan. This cannot be stated with 100% certainty because we have not yet found a complete vertebral column or a complete ribcage of Brachiosaurus which could give us a clear picture of the animal’s body proportions. However, if it is true that Brachiosaurus had a longer torso, it would mean that its back would have had a much gentler slope than its African counterpart.

Fifth, Brachiosaurus might have had a longer tail. Only one tail vertebra of Brachiosaurus has been found so far. However, based upon its features, it has been hypothesized that the tail would have been substantially longer than that of Giraffatitan.

The scarcity of remains hints that Brachiosaurus might have been a rare animal out on the Jurassic plains. Other sauropods such as Camarasaurus were far more common.

Like Camarasaurus, Brachiosaurus was a member of a group of sauropod dinosaurs called the “macronarians”, meaning “the large nostrils”. The skull likely acted as a resonating chamber, able to produce loud low frequency long-range noises, which would be very helpful for communicating over the vast expanses of the Morrison Formation plains. If it is true that Brachiosaurus was rare, or perhaps even a solitary animal by nature, it would still need to communicate with other members of its kind, especially during the mating season. Being able to produce such sound, which could travel over long distances, would help these animals to communicate with each other even if individuals were located miles apart from one another.

Unlike the diplodocid sauropods of the Morrison Formation such as Apatosaurus, Barosaurus, and Diplodocus, Brachiosaurus did not hold its neck in a horizontal position. Instead, it held its neck either vertically or at a diagonal angle. The act of the head sticking far above the ground would minimize the chance that the sounds that it produced would be broken up and dissipated due to ground clutter, such as rocks, trees, and even other dinosaurs. This head attached to a long vertical neck would act like a submarine’s periscope, enabling it to see for long distances, and also enabling other members of its kind to spot it from a long distance away. To make sure that it could be seen from long distances away, it is possible that the head and the neck were very brightly and vividly colored while the rest of the body was comparatively drab. It’s also possible that the head might have sported some type of decoration to further ensure that it could be spotted from miles away by other members of its species – perhaps a frill or a mane of quills or baleen-like bristles. However, color and adornment are only hypothetical conjecture and should not be taken as fact.

Below are a pair of drawings that I made of Brachiosaurus altithorax. I have adorned the top part of the neck with a series of long quills forming a mane, and I also made its head bright red in order to stand out amidst the Morrison landscape. As to the remaining colors of grey with blue stripes, I based this on the Brachiosaurus model made for the Carnegie Collection in the 1980s. The drawings were made with No. 2 pencil, No. 3 pencil, and assorted Crayola and Prismacolor colored pencils.

Brachiosaurus altithorax. © Jason R. Abdale (April 26, 2021).

Keep your pencils sharp, everyone.

List of Articles about the Morrison Formation

The Morrison Formation of western North America is my favorite geological / paleontological formation to study. Within these rock layers, which are dated to the late Jurassic Period from approximately 155 to 145 million years ago, are found the fossils of some of the most famous dinosaurs known, such as Allosaurus, Brachiosaurus, Stegosaurus, and Diplodocus. However, dinosaurs were not the only animals which lived here. This was a vibrant ecosystem home to all kinds of fish, amphibians, reptiles, and mammals.

Since I set up this website in 2013, I have written several articles concerning the animals which lived in the Morrison Formation. It can be a bit difficult for me to keep track of what I’ve already written about and what I haven’t yet, so I’ve decided to compile all of my articles here into a comprehensive list. That way, it’s easy for myself and indeed anybody to quickly use this as a reference guide to look up info about the animals of late Jurassic North America.






Saurosuchus was a 20-foot pseudosuchian (a distant ancestor of crocodiles) which lived in Argentina during the middle Triassic Period about 230 million years ago. It was the largest carnivorous animal in its environment in terms of both length and weight, and it was likely the top predator within the Ischigualasto Formation, but that was before the dinosaurs arrived. Saurosuchus lived side-by-side with the meat-eating dinosaurs, but eventually carnivorous dinosaurs like Herrerasaurus, which were faster, more agile, and possibly more intelligent, drove these creatures to extinction.

Skull of Saurosuchus. Drawn in Crayola black marker. © Jason R. Abdale. March 11, 2021.


Panphagia, the Oldest-Known Sauropodomorph Dinosaur

For decades, South America has been regarded by paleontologists as the place where dinosaurs originated. It is here that we have our clearest record of what the oldest dinosaurs looked like. Specifically, Brazil and Argentina hold the record for the countries that possess the oldest-known dinosaur fossils. Based upon the fossils that have been uncovered in Brazil’s Santa Maria Formation and Argentina’s Ischigualasto Formation (in particular a locality known as “the Valley of the Moon”), dinosaurs are believed to have appeared during the middle of the Triassic Period about 235-230 million years ago.

Prior to the appearance of dinosaurs in the middle Triassic, smaller dinosaur-like animals scurried about within the jungles of South America. These proto-dinosaurs are known as “dinosauromorphs”. They first appeared during the early Triassic Period, and continued into the late Triassic, well after dinosaurs had appeared and established themselves. Probably the most well-known of these early dinosauromorphs is Lagosuchus, a small reptile about the size of a chicken. What made Lagosuchus and its kind different from the other reptiles which were around at the time was the fact that Lagosuchus and its close relatives ran around on two legs instead of four. This would be a major innovation which would be exploited by the earliest dinosaurs.


The skeleton of Marasuchus, an advanced “dinosauromorph” from Argentina, dated to the middle Triassic Period about 235 MYA. It has been hypothesized that Marasuchus and Lagosuchus are in fact the same animal. Photograph by Michelle Reback (July 28, 2008). Public domain image, Wikimedia Commons.

For a long time, our idea of what the earliest dinosaurs looked like was shrouded in mystery. However, it seemed that the first dinosaurs were carnivores. From the 1950s until the very early 1990s, creatures like Staurikosaurus of Brazil and Herrerasaurus of Argentina were the oldest-known dinosaurs, and they were also believed to be the most evolutionarily primitive. Still, despite their supposedly archaic nature, these were fairly large animals – Staurikosaurus reached 6 to 8 feet long, and Herrerasaurus was even bigger, reaching 12 feet long. Both of these animals, and Herrerasaurus in particular, clearly would have been formidable competitors to the other carnivorous four-legged reptiles which were alive at the time. This was quite an upgrade from small chicken-sized creatures like Lagosuchus, which had existed only a short time earlier. Considering the very short time difference between the appearance of small creatures like Lagosuchus and the subsequent appearance of large meat-eating dinosaurs like Herrerasaurus, it appeared as though one of two options applied here: either dinosaurs managed to evolve into a large size within a very short length of time, or there was some intermediate species which hadn’t been discovered yet. Was it possible that there was another dinosaur, as yet undiscovered, which could fill the gap between the primitive dinosauromorphs and creatures like Herrerasaurus?

In 1991, the skeleton of a new dinosaur was discovered in Argentina by Dr. Ricardo Martinez, a paleontologist from the University of San Juan. This animal was far smaller, and it seemed more primitive, than Herrerasaurus. It measured only 3 feet long, and it appeared to have an anatomy which was less advanced than either Staurikosaurus or Herrerasaurus. In 1993, the animal was named Eoraptor, “the dawn thief”. For nearly two decades, this little animal held the title of being the oldest-known dinosaur.

However, complications arose. A closer examination of the skeletons of both Herrerasaurus and Eoraptor created doubts as to whether or not Eoraptor really was the oldest and most primitive dinosaur ever found. For example, the fewer sacral vertebrae an animal has, the more primitive it’s believed to be. Eoraptor possessed three sacral vertebrae, but Herrerasaurus had only two. This indicated that Herrerasaurus, despite being five times larger, was actually more primitive than Eoraptor. Another point of contention was the structure of the lower jaw. When Eoraptor was first discovered and described, it was believed that it possessed a less-evolved jaw structure than Herrerasaurus, but this turned out to be false. Gradually, concerns began to be raised that Eoraptor, despite its small size, was actually not as primitive as it first appeared to be. Special attention was given to the skull and the teeth. Eoraptor possessed different kinds of teeth in its mouth, indicating that it was an omnivore. A close examination of both the skull structure and the teeth made some wonder if Eoraptor was as primitive as we initially believed. In fact, there were some aspects of its anatomy that bore a bit of a resemblance to the sauropodomorph dinosaurs – the long-necked long-tailed creatures that we typically associate with the word “dinosaur” – rather than the fleet-footed meat-eating theropod dinosaurs.

In 2011, Dr. Ricardo Martinez (the same man who had found Eoraptor’s skeleton in 1991) re-classified Eoraptor as a primitive sauropodomorph. This claim was met with skepticism by the scientific community. In a subsequent study, Martinez changed his mind again and stated that Eoraptor was so archaic that it could not be placed into any definite group of saurischian dinosaurs and ought to be placed at the very base of Saurischia. However in 2013, Dr. Paul Sereno did his own evaluation of Eoraptor’s skeleton and concluded that indeed it was a primitive sauropodomorph, distantly related to other prosauropods like Plateosaurus and Anchisaurus. Even so, the overwhelming majority of the scientific community has refuted this claim. Numerous studies have been conducted on Eoraptor since it was discovered and named, and most of them state that Eoraptor is either a very primitive theropod dinosaur or else it is the earliest saurischian, appearing before the saurischians split into theropods and sauropodomorphs.

All of this raises an interesting question. If Eoraptor was not the earliest sauropodomorph, then what was?

In 2006, Dr. Ricardo Martinez was once again exploring the middle Triassic rock layers of the Ischigualasto Formation, dated to 228.3 million years ago, when he found another skeleton. It looked similar to Eoraptor, but it was noticeably larger, measuring 4.25 feet (1.3 meters) in length; Martinez thought that the skeleton was of a juvenile, and that the adult would be larger, say perhaps 6 feet long. The skeleton was incomplete, including only a partial skull. Teeth were only found in the lower jaw. The skull was clearly similar to Eoraptor’s, but it also showed some features which can be seen in very primitive sauropodomorphs like Plateosaurus. For example, the lower jaw curves downwards towards the front, which is a tell-tale feature of that group. The teeth were also very similar to those seen in prosauropods. Based upon the skull structure and the shape of the teeth, this animal seemed to be more closely related to sauropods than theropods. In 2009, the animal was named Panphagia, which is ancient Greek for “eats everything” in reference to its supposedly omnivorous diet.

Reconstruction of the skeleton of Panphagia protos. Photograph by Eva Kröcher (December 5, 2010). Creative Commons “Attribution Non-Commercial Non-Derivative 3.0 (US)”, GNU Free Documentation License (GFDL), and Free Art License. https://commons.wikimedia.org/wiki/File:Panphagia_fossil_DSC_6168.jpg.

A complete skull was not found with the skeleton, but we have enough of the bones to give us an idea of the skull’s outline. Below is an illustration that I made of what the complete skull of Panphagia might look like, based upon what was seen in the photograph that you see above. The drawing was made with a black Crayola marker.

Skull of Panphagia protos. © Jason R. Abdale (February 9, 2021).

Based upon this skeleton and the description that Ricardo Martinez and Oscar A. Alcober gave in their paper on this animal, I have reconstructed what the entire animal might look like. The creature bears a slight resemblance to prosauropods like Plateosaurus and Anchisaurus. No hands were found with the specimen. However, the illustration which accompanied Martinez and Alcober’s paper showed Panphagia sporting hands with four fingers, although the fourth digit was so small that it was probably incorporated into the wrist and wasn’t seen on the outside. The fingers themselves were longer the more distal they were to the body (in other words, the middle finger was longer than the thumb, and the pinky was even longer than the middle finger), and this was repeated in the skeletal reconstruction seen above. Since this was the reconstruction seen in both sources, I incorporated it into my own illustration.

I think that there are two issues with the illustrated reconstruction of Panphagia’s skeleton seen in the scientific paper and in the physical reconstruction seen in the photo above. Firstly, I think that the tail is too short. The animal looks conspicuously front-heavy, and the tail ought to be longer to give it better balance. Secondly, I believe that the hand structure is incorrect. Prosauropods like Plateosaurus, Massospondylus, and Anchisaurus had hands with five fingers and large thumb claws. However, it must be noted that all three of those species came from the late Triassic and early Jurassic Periods, nearly twenty to thirty million years after Panphagia’s appearance, and their hand structure may have been more evolved than that seen in archaic animals like Panphagia. However, until a more complete specimen of this animal is found, I think my reconstruction is going to remain as it is.

My drawing was made with No. 2 pencil on printer paper.

Panphagia protos. © Jason R. Abdale (February 14, 2021).


For more information, please read Martinez’ and Alcober’s paper on this animal, which you can see here:

Martínez, Ricardo N.; Alcober, Oscar A. (February 16, 2009). “A basal sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the early evolution of Sauropodomorpha”. PLoS ONE, volume 4, issue 2. Pages 1-12. doi:10.1371/journal.pone.0004397.



Keep your pencils sharp, everyone.


Ceratodus: The Iconic Lungfish of the Mesozoic Era

Ceratodus was a genus of prehistoric lungfish which existed on Earth for a surprisingly long time, from the middle of the Triassic Period approximately 227 million years ago to the beginning of the Eocene Epoch of the Tertiary Period about 55 million years ago – a jaw-dropping span of 172 million years! That’s impressive by ANYBODY’S standards!

Lungfish as a whole are a primitive group of fish. They first appeared during the early Devonian Period about 416 million years ago (MYA), and it’s believed that they represent an evolutionary “missing link” between fish and amphibians. The closest relatives of the lungfish are the coelacanths, meaning “hollow spines”. That’s not surprising, considering that both lungfish and coelacanths have prehistoric origins as well as that both groups are classified as “lobe-finned fish”.

Lungfish do not have individual teeth like many fish today. Instead, they have four large bone plates (two in its upper jaw, and another two in its lower jaw) that were ridged in texture and crowned with thick triangular projections, and were used for crushing and cracking. Many species of modern lungfish feed on worms, freshwater snails, crustaceans, small fish, and amphibians.

Today, there are only six surviving species of lungfish, and all of them are found in hot tropical environments. With the exception of one species found in the Amazon Jungle and another species found in northern Australia, the remaining lungfish species are found in Africa.

  1. The South American Lungfish (Lepidosiren paradoxa), found in the Amazon River.
  2. The Marbled Lungfish (Protopterus aethiopicus), which is found throughout much of eastern and central Africa.
  3. The Gilled Lungfish (Protopterus amphibius), which is also found in eastern Africa.
  4. The West African Lungfish (Protopterus annectens), which is found, not surprisingly, in western Africa.
  5. The Spotted Lungfish (Protopterus dolloi), which inhabits the Congo Jungle of central Africa.
  6. The Australian Lungfish, also called the Queensland Lungfish (Neoceratodus forsteri), found in northeastern Australia. Of all of the extant lungfish species, this one is believed to be the most primitive.

Special attention must be given to the Australian Lungfish (Neoceratodus forsteri), for not only is this species regarded as the most archaic of all of the extant lungfish, but it was once believed to be the sole surviving member of the prehistoric lungfish genus Ceratodus alive in modern times.

Skeleton of Neoceratodus forsteri. From Günther, Albert. “Description of Ceratodus, a Genus of Ganoid Fishes, Recently Discovered in Rivers of Queensland, Australia”. Philosophical Transactions of the Royal Society of London, volume 161 (1871). Plate XXX. https://www.jstor.org/stable/pdf/109041.pdf.

The lower jaw of Neoceratodus forsteri, seen from above. From Krefft, Gerard. “Description of a gigantic amphibian allied to the genus Lepidosiren from the Wide-Bay district, Queensland”. Proceedings of the Zoological Society, volume 16 (April 28, 1870). Page 222. https://ia800405.us.archive.org/16/items/biostor-107043/biostor-107043.pdf.

The genus Ceratodus was established in 1837 by the famed Swiss ichthyologist Louis Agassiz based upon teeth which were found in European rock layers dated to the Triassic and Jurassic Periods. Most Ceratodus fossils that are found consist of isolated tooth plates, and different species have been named based largely upon difference in tooth morphology. Twenty-two species of Ceratodus have been named since the genus was first described in 1837. For a long time, Ceratodus was what is known as a “waste basket taxon” – all North American lungfish fossils were ascribed to this genus, regardless of how different they were from each other. Recently, a careful re-examination of lungfish fossils have revealed that these animals are remarkably different from each other and may constitute numerous genera, not just one. If that’s the case, then the overall lifespan of Ceratodus as a genus may be dramatically shorter than was previously supposed (Günther, Albert. “Description of Ceratodus, a Genus of Ganoid Fishes, Recently Discovered in Rivers of Queensland, Australia”. Philosophical Transactions of the Royal Society of London, volume 161 (1871). Page 512).


Ceratodus, painted by Heinrich Harder. From Animals of the Prehistoric World (1916). Public domain image, Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Ceratodus.jpg.

Ceratodus’ length varied depending on the species. Most sources which I have seen give an average length of 3 feet long. However, one species of Ceratodus may have reached truly gigantic proportions, possibly reaching 10 to 12 feet long. This estimate is based upon a single bone plate, which is the largest-known of any lungfish. The tooth plate was found in central Nebraska in rocks dated to the Miocene or Pliocene Epochs of the Tertiary Period. Shimada and Kirkland hypothesized that the tooth had been carried into central Nebraska by river from older rock layers that were located further to the west within Wyoming, in rocks dated to either the late Jurassic or early Cretaceous Periods. However, the tooth isn’t as banged up as you would expect from such a long journey. It’s possible that the tooth is endemic to central Nebraska, and if that is the case, 1) Ceratodus was alive in North America for a much longer geologic time span than previously supposed, or 2) This species is mis-identified and belongs to a new un-described genus of giant lungfish which lived in central North America about 5 million years ago, or 3) This was a species which happened to have unusually large teeth within its jaws, and the overall length of the animal was much smaller than the 4 meter estimate given by Shimada and Kirkland. Unfortunately, only one tooth plate has been discovered. Until more specimens are found, everything that we have to say about this specimen needs to be taken with a great degree of skepticism. (Kenshu Shimada and James I. Kirkland, “A Mysterious King-Sized Mesozoic Lungfish from North America”. Transactions of the Kansas Academy of Science, volume 114, issue 1 (2011). Pages 135-141. https://www.researchgate.net/publication/261964060_A_Mysterious_King-Sized_Mesozoic_Lungfish_from_North_America).

For the artwork accompanying this article, I decided to change up my style. For this drawing, I chose to evoke the whimsical style of the paleo-art of Patricia Bujard. If you don’t know who Patricia Bujard is, then I highly recommend that you check out her work. She is a children’s author and illustrator with a love for prehistoric life, and I find her artwork adorable. There aren’t too many people who can make an Allosaurus “cute”, but dag-nabbit, she somehow manages to pull it off. You can see her artwork on her WordPress page, Pete’s Paleo Petshop. My own drawing, which you can see below, was made with an ordinary Crayola black marker.

Ceratodus © Jason R. Abdale. February 9, 2021.

Keep your pencils sharp, and in this case, also keep your markers properly stored so they don’t dry out.


This is Promastodonsaurus, literally meaning “before Mastodonsaurus”. Despite its saurian name, it was not a dinosaur, or even a reptile – it was actually a large amphibian. Fossils of Promastodonsaurus were found in Argentina within the rocks of the Ischigualasto Formation, dated to the middle Triassic Period approximately 230 million years ago. The species was officially named in 1963 by the famed South American paleontologist José Bonaparté, in reference to another large amphibian named Mastodonsaurus which lived in Europe during a slightly later time.

Cladistically-speaking, this animal belonged to a large group of amphibians called the “labyrinthodonts”, so-named because a cross-section of their teeth looked like a maze. Within this broad group is a sub-division called the “temnospondyls”, “the cut vertebrae” because each of their backbones is divided into several parts. The temnospondyls were a diverse group of labyrinthodont amphibians which first appeared during the Carboniferous Period and lasted into the Cretaceous Period – a span of nearly 200 million years. Within the order Temnospondyli is the sub-order “Stereospondyli”, and within this is a division called the “capitosaurians”, “the head lizards”, so-named due to their freakishly huge heads; Promastodonsaurus was a member of this group. It was essentially a giant meat-eating salamander with the head of an alligator.

The only evidence that we have of this animal is a single partial skull. Based upon its similarity to the skulls of other temnospondyl amphibians within its family, it is believed that the animal’s head measured 45 centimeters long (Hans-Dieter Sues and Nicholas C. Fraser, Triassic Life on Land: The Great Transition. New York: Columbia University Press, 2010. Page 69). This in turn would make the entire animal somewhere in the vicinity of 6 feet long, as big as a medium-sized alligator.

Promastodonsaurus bellmani. © Jason R. Abdale. February 9, 2021.

During the middle Triassic Period, crocodilians did not exist, so the capitosaurians like Mastodonsaurus and Promastodonsaurus essentially filled in that ecological niche as crocodilian analogs. Large amphibians like these would continue to dominate freshwater environments until they were replaced by the phytosaurus during the late Triassic Period, who in turn would be replaced by crocodilians during the Jurassic Period.

Fruitachampsa, the crocodile-bear-cat of the Morrison Formation

Meet the Jurassic Period’s analog of the common house cat. This is Fruitachampsa callisoni, a prehistoric reptile which inhabited western North America during the late Jurassic Period. However, this was not a dinosaur. In fact, Fruitachampsa was a distant relative of crocodiles.

The fossils of this animal were discovered by James M. Clark and George Callison near Fruita, Colorado during the middle and late 1970s within the rocks of the Morrison Formation dated to about 150 million years ago (MYA). By the late 1980s, this creature was unofficially known by the name “Fruitachampsa”, but since it had not been officially named or described in any scientific research article, this name could not yet be used. It wasn’t until 2011 that the animal was officially classified under the name Fruitachampsa callisoni, “George Callison’s Crocodile from Fruita”.

Clark, James M. “A new shartegosuchid crocodyliform from the Upper Jurassic Morrison Formation of western Colorado”. Zoological Journal of the Linnean Society, volume 163, issue supplement 1 (December 2011): S152–S172.

Fruitachampsa belonged to a group of reptiles which were related to crocodiles known as the “shartegosuchids”. These reptiles are known from the late Jurassic and early Cretaceous Periods, and all known specimens have been found in North America, Europe, and Asia. Shartegosuchids have distinctive skull features, including:

  1. A lack of anteorbital fenestrae (the hole between the nostril and the eye socket) in the upper jaw.
  2. Within the upper jaw’s palate, the choanae (the holes that connect the nostril to the inside of the mouth) are set within a deep depression in the center of the palate.
  3. The palatal bones, which form most of the inside of the mouth of the upper jaw, are joined together medially.
  4. The teeth in the lower jaw never extend posteriorly past the mandibular fenestrae.
  5. The edges of the teeth in both the upper and lower jaws are ridged with serrations – quite unlike the smooth cone-shaped teeth that are often associated with crocodilians.

The shartegosuchids are visibly similar to earlier primitive crocodyliforms such as Protosuchus, and have even been ascribed to the same family as that genus. However, they appear to be slightly more advanced than Protosuchus and other members of Protosuchidae, and may represent the next evolutionary development of crocodilians.

Fruitachampsa measured three feet long, and its body was more-or-less about the same size as a cat. Like a cat, it also had large eyes, and was therefore possibly nocturnal, preying upon the small rodent-like mammals which inhabited the Morrison Formation.

Fruitachampsa also possessed unusually long legs in proportion with the rest of its body. However, like a crocodile, it walked in a “plantigrade” style, walking on the flats of its feet like a human or a bear, rather than walking “digitigrade”, on its toes, like a cat. So perhaps we should think of Fruitachampsa less like a cat and more like a pygmy-sized long-legged bear.

Fruitachampsa possessed a double-row of rectangular osteoderms which ran down the middle of its back, in which the row in front slightly overlapped the row behind, like roof shingles or an ancient Roman legionnaire’s body armor.

Fruitachampsa callisoni. © Jason R. Abdale. December 19, 2020.

Keep your pencils sharp, everybody.

More photos of Allosaurus from the AMNH

Greetings friends. In an earlier post from 2014, I put up some photographs which I took of the two Allosaurus skeletons that are on public display in the American Museum of Natural History (or AMNH for short) in New York City. I’ve recently uncovered some other photos which I took during a visit there in March 2019, and so I’m posting them here. Enjoy!




This is Caturus, a prehistoric fish which swam in the oceans during the Mesozoic Era. Fossils of this saltwater fish have been found in North America, Europe, northern Africa, and as far as China within rocks spanning from the beginning of the Triassic Period about 250 million years ago (MYA) up to the middle of the Cretaceous Period, about 100 MYA. However, most Caturus fossils have been found in Europe within rock layers dated to the middle and late Jurassic Period, about 170-150 MYA.

Despite a superficial resemblance to a salmon, Caturus was actually more closely related to a bowfin (Amia calva), which is a rather primitive ray-finned fish.

So far, paleontologists have identified fourteen species of Caturus. The largest species, Caturus furcatus, which lived in the Tethys Sea (the shallow sea that covered much of Europe during the middle Jurassic to the middle Cretaceous Period), reached three feet long; other species were much smaller. One species, Caturus dartoni, is known from North America in rocks dated to the middle Jurassic Period, about 165 MYA. Only two skeletons of this particular species have been found, the largest measuring 15 inches long.

Caturus. © Jason R. Abdale. September 5, 2020.

This drawing was made on printer paper with No. 2 pencil, No. 3 pencil, Crayola colored pencils, Prismacolor colored pencils, and Artist’s Loft colored pencils.