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 weren't separated by an ocean back then, remember).  From head 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 most 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 striking and 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 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 carnivorous dinosaur embryos known.  

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 it lived alongside Allosaurus (different 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.

Pachycephalosaurus: Beast of the Week

This week we shall be checking out a well-known dinosaur with an iconic skull.  This dinosaur is one of my personal all time favorites.  I will never forget seeing it's awesome representation in The Lost World: Jurassic Park in the movie theater when I was only eight years old.  The way it smashed that truck...it changed me.  Say hello to Pachycephalosaurus wyomingensis!

Pachycephalosaurus was the largest known member of the pachycephalosaur family at about 15 feet (4.5m) long from beak to tail.  In life, it was most likely a plant-eater, but some have suggested it may have supplemented its diet with meat in the form of small animals and possibly carrion.  The genus name, Pachycephalosaurus, translates to "Thick Head Lizard" in reference to the dinosaur's skull, which is almost ten inches thick in the biggest specimens.  Pachycephalosaurus lived during the very end of the Cretaceous period, between 70 and 66 million years ago, in what is now the Western United States, specifically Montana, South Dakota, and Wyoming.  In fact, its full genus and species name is Pachycephalosaurus wyomingensis, in reference to this.  When alive Pachycephalosaurus would have shared its environment with Tyrannosaurus, Anzu, Quetzalcoatlus, Edmontosaurus, Ankylosaurus, Triceratops, Pectinodon, Stygimiloch, and Dracorex.

Pachycephalosaurus life reconstruction in watercolor by Christopher DiPiazza.

Sadly, none of Pachycephalosaurus' body beyond the skull has ever been discovered.  However, we can guess what the rest of the body looked like thanks to more complete skeletons of other kinds of Pachycephalosaurids it was closely related to.  It was most likely a biped, with short front arms, each ending in a five-fingered hand.  The hips were probably relatively wide with a thick tail base.  The end of the tail would have been stiffened with ossified tendons. (bony rod-like structures found in the tails of many dinosaurs)

Pachycephalosaurus' head was its trademark feature, however.  Like I said earlier, its skull was extremely thick, and made of solid bone, encasing a relatively small brain, forming a round, dome-shaped cranium.  Around the back of the head, over the eyes, and on the top of the snout, were a series of short horns.  The mouth was tipped with a short beak and the jaws were lined teeth were small and leaf-shaped, most likely for shredding tough plants.  There were also a set of unusual pointed teeth in the front of the jaws which experts are still about the use of, but are the main reason why some have suggested an omnivorous diet.  The eye sockets of Pachycephalosaurus skulls are large, and face partially forward.  This indicates that this dinosaur would have had good vision and also had a sense of depth perception in life.  The heavy skull would have been held up by a short, muscular neck.

Pachycephalosurus skull on display at the American Museum of Natural History in New York.

The exact purpose of Pachycephalosaurus' thick skull has been debated much over the years.  The most common idea, especially in the beginning, was that rival Pachycephalosaurus would have ran into each other, head first, like modern day rams do, to establish dominance.  This idea became so popular, that you would be hard pressed to find imagery of Pachycephalosaurusdoing anything other than running with its head down about to ram something in every bit of media it was included in.  More recently, however, there have been paleontologists who have challenged this, saying the shape of Pachycephalosaurus' skull would not have allowed it to have sustained crashing into other hard objects at a high force without causing serious injury.  Many believed that the large domes of 

Pachycephalosaurus were mostly for display within the species instead.  Was it really possible that those thick skulls were just for show, though?  It seems unlikely considering how thick they were.  (Something that isn't entirely visual.)  Finally in 2013, a study on the skulls of pachycephalosaurs discovered evidence of injuries that had healed over on the skulls of many individual specimens.  In fact, the kind of bone that the skulls of pachycephalosaurs were made of seems to have been especially good at healing and repairing itself after damage was inflicted on them.  This supported the idea, once again, that Pachycephalosaurus and its kin were indeed using their skulls as weapons.  That being said, they may have swung their heads into each other at close quarters, instead of charging into each other from a running distance.  You can observe modern giraffes (like in the video below), and many other animals that sport weapons on their heads, combating each other in the same way.  If this indeed was the method used for Pachycephalosaurus fighting, the small horns on the sides of the head could have been utilized as painful weapons backed up be the force caused by the mass of the thick skull. 

Some still argue that using their heads as weapons would have injured Pachycephalosaurus in life too much and was thus, is still an unrealistic idea or real life.  These folks need to remember, however, that many animals do get injured quite a lot when fighting rivals.  In fact, many species of animals become permanently maimed, or even die fighting peers for dominance.  If a Pachycephalosaurus did hurt itself or die in combat with another back in the Cretaceous, it would have just been another example of natural selection in the works. Evolution is never perfect.  If it was nothing would ever go extinct!

Pachycephalosaurus is believed to have changed its form drastically as it matured into an adult by certain paleontologists.  The other two, slightly smaller, pachycephalosaurs, Dracorex (sported lots of horns but no dome) and Stygimoloch (long horns and a smaller dome), are believed by some to have actually been juvenile and subadult forms, respectively, of Pachycephalosaurus, which would have been the mature adult.  If this is the case, Pachycephalosaurus would have had no dome at all when young, and its horns would have become shorter, being absorbed into the growing thickness of the skull as it matured.  In contrast to this, the more recently discovered close relative, Zavacephale, was a juvenile when it died and had a fully formed dome.  This doesn't necessarily disprove the idea about Pachycephalosaurus' juvenile state (different kinds of animals grow can grow differently) but it is definitely worth noting. Since the number of pachycephalosaur specimens on the fossil record is still very limited, this hypothesis still needs a more evidence to be verified.

Quick sketch of Dracorex, Stygimoloch, and Pachycephalosaurus, which are thought by many to be different growth stages of the same species.  This might not be true, or maybe true for two of the three.  More fossils and research may tell in the future.

That is all for this week!  As always feel free to comment below or on our facebook page!

References

Carpenter, Kenneth (1 December 1997). "Agonistic behavior in pachycephalosaurs (Ornithischia: Dinosauria): a new look at head-butting behavior" (PDF). Contributions to Geology 32 (1): 19–25.

Chinzorig, Tsogtbaatar; Takasaki, Ryuji; Yoshida, Junki; Tucker, Ryan T.; Buyantegsh, Batsaikhan; Mainbayar, Buuvei; Tsogtbaatar, Khishigjav; Zanno, Lindsay E. (2025-09-17). "A domed pachycephalosaur from the early Cretaceous of Mongolia". Nature: 1–8.

Horner J.R. and Goodwin, M.B. (2009). "Extreme cranial ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus." PLoS ONE, 4(10): e7626.

Peterson, J. E.; Vittore, C. P. (2012). Farke, Andrew A, ed. "Cranial Pathologies in a Specimen of Pachycephalosaurus". PLoS ONE 7 (4): e36227.

Peterson JE, Dischler C, Longrich NR (2013) Distributions of Cranial Pathologies Provide Evidence for Head-Butting in Dome-Headed Dinosaurs (Pachycephalosauridae). PLoS ONE 8(7): e68620. doi:10.1371/journal.pone.0068620

Sullivan, Robert M. (2006). "A taxonomic review of the Pachycephalosauridae (Dinosauria:Ornithischia)" (PDF). Late Cretaceous vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35: 347–366.

Ajkaceratops: Beast of the Week

This week we will be checking out a unique dinosaur that lived in an even more unique environment.  Let's talk about Ajkaceratops kozmai!

Ajkaceratops was a small plant-eating dinosaur that lived in what is now Hungary during the late Cretaceous period, about 85 million years ago.  From beak to tail it likely measured a little over 3 feet (1m) long.  The genus name translates to "Ajka Horned Face", referencing the town in Hungary near where its fossils were found.  

Watercolor of Ajkaceratops by Christopher DiPiazza.

Ajkaceratops was initially published in 2010 from the front of the beak. The beak itself was curved and pointed, much like a ceratopsian, the "horned dinosaurs", like Triceratops, so it was placed in that family alongside dinosaurs like Protoceratops.  Later on, the beak was re-examined and many unique traits were noted about it compared to other ceratopsians, like the fact that it has a more rounded cross-section and its pitted texture.  It also appears to be completely fused to the rest of the jaw, which is only seen in mature members of the larger members of the ceratopsian group, like Triceratops.  Based on this it was deemed not a ceratopsian at all, but rather an unusual kind of ornithithopod dinosaur, related to Zalmoxes, which was also found in Europe.  Then most recently more fossils from Ajkaceratops were found, including a more complete skull, and in 2026 they were published on.  Based on this new material it was found to be a ceratopsian after all.  Not only that but a few members of the ornithopod group it was previously grouped with, called the rhabdodontids, were also thought to be unusual ceratopsians as well.  This is an important determination since prior to this, ceratopsians were only ever found in North America and Asia, and it was odd that they wouldn't be in Europe.  Ajkaceratops proves they were.  

Ajkaceratops' skull.  Image from the most recent paper by Czepinski et al. referenced below.

It's not surprising the identity of Ajkaceratops was not clear since it is indeed unusual for a ceratopsian.  As mentioned, it beak is extremely long, narrow, and curved, even for a ceratopsian, which are known for having curved beaks.  In fact, its whole skull is pretty elongated, and almost rectangular in profile.  As mentioned, the beak was completely fused to the rest of the jaw, and not a separate bone as it is in vast majority of other ceratopsians, called a rostral bone.  Lastly its extremely small size is also unusual especially for living in the late Cretaceous.  The teeth were more typical and appear to be ideal for shredding plants.  They show a high amount of wear on them, suggesting Ajkaceratops could have been regularly chomping through tougher plant material like twigs and pine needles.  

Teeth of Ajkaceratops.  Image from paper by Osi et at. referenced below.

The part of Hungary that Ajkaceratops was found in was actually an island when it was alive.  That part of Europe was known to be a series of island chains during that time, and paleontologists think the ancestors of Ajkaceratops may have actually have swam there from either Asia or North America. (since ceratopsians were living on both those continents already before Ajkaceratops' time) 

References

Czepiński, Łukasz; Madzia, Daniel (2024). "Osteology, phylogenetic affinities, and palaeobiogeographic significance of the bizarre ornithischian dinosaur Ajkaceratops kozmai from the Late Cretaceous European archipelago". Zoological Journal. 202 (4).

Ősi, Attila; Butler, R.J.; Weishampel, David B. (2010-05-27). "A Late Cretaceous ceratopsian dinosaur from Europe with Asian affinities". Nature. 465 (7297): 466–468.

Maidment, Susannah C. R.; Butler, Richard J.; Brusatte, Stephen L.; Meade, Luke E.; Augustin, Felix J.; Csiki-Sava, Zoltán; Ősi, Attila (2026-01-07). "A hidden diversity of ceratopsian dinosaurs in Late Cretaceous Europe". Nature: 1–7.