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 fifteen feet 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.

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.

Parasaurolophus: Beast of the Week

This week we will be taking a look at a very popular duck-billed dinosaur.  Say hello to Parasaurolophus!  Parasaurolophus was a plant eater that lived in what is now North America during the Late Cretaceous, about 77 to 73 million years ago.  Parasaurolophus measured about 30 feet (9.1 meters) long from beak to tail, but certain incomplete specimens show evidence of having been a bit larger.  Parasaurolophus is most well-known for its long, curved crest that grew from the back of its head, giving it one of the most iconic profiles of any dinosaur.  The name Parasaurolophus translates to "Near Crested Lizard/Reptile" and is in reference to it being compared to another duck-billed dinosaur with a smaller crest, called Saurolophus (just "crested lizard/reptile"), which was discovered earlier.  Turns out that Parasaurolophus and Saurolophus, although both hadrosaurs (duck-billed dinosaurs), weren't really that closely related.  Parasaurolophus belongs to what is called the lambeosaurine branch of hadrosaurs which had hollow crests and narrower beaks, which Saurolophus did not have.  Parasaurolophus was much more closely related to Corythosaurus, Velafrons, and Tsintaosaurus, to name a few examples.

Parasaurolophus walkeri by Christopher DiPiazza.

There are actually a few different named species of Parasaurolophus.  The most well-recognized is called Parasaurolophus walkeri, and it lived in what is now Alberta, Canada, and would have coexisted with other well-known dinosaurs like Styracosaurus, Chasmosaurus, Struthiomimus, Corythosaurus, and Eouplocephalus.  From the southwestern United States, however, there was also Parasaurolophus tubicen, which is incompletely known, but was probably the largest species, and Parasaurolophus cyrtocristatus, which had a much shorter, more curved crest, and would have coexisted with (and ran away from) Teratophoneus.  

Parasaurolophus walkeri skull on display at the American Museum of Natural History in New York City.

At one time, some paleontologists made a hypothesis that Parasaurolophus cyrtocristatus was actually a female of one of the other two species, due to its smaller crest, but further research concluded this was probably not true since they did not live during the exact same time period.  This being said, it is not unreasonable to guess that the Parasaurolophus females could have had shorter crests anyway, since we can observe similar trends of sexual dimorphism (males and females look different) in other lambeosaurine hadrosaurids that are known from a bigger pool of specimens, like Corythosaurus.

Parasaurolophus cyrtocristatus skeleton on display at the Field Museum of Natural History, in Chicago.

In 2013, a specimen of a baby Parasaurolophus was published by scientists at the Raymond M. Alf Museum of Paleontology in California, shedding more light on the growth and development of this interesting dinosaur.  The specimen, which was just under six feet long from beak to tail (small when you consider how large it could have grown), is estimated to have only been one year old when it died.  Paleontologists could tell this by looking at the cross-section of a the dinosaur's bone and counting the ring-like patterns on the inside, similar to a tree. This specimen hadn't developed any rings yet at the time of its death.  Despite this, the tiny dinosaur's crest had already started to grow from the front of  its skull, between its eyes.  At the age that it died that specimen may have still been under it's parent's care, according to the information and evidence on the fossil record about other hadrosaurid mothers.

Fossil remains of the baby Parasaurolophus published in 2013.  Photograph is from Dr. Andrew Farke's paper, cited below.

The crest of Parasaurolophus, which is actually a huge extension of its nasal bones, starting at the very front of the skull, is its most notable characteristic and what gives it its iconic profile. (I will never forget one of my students referring to it as "that pickaxe-head dinosaur")  At first some people thought that hadrosaurs, like Parasaurolophus, were amphibious, and spent a lot of their time in the water because the skin that preserved around the toes of one specimen (an Edmontosaurus) that looks like webbing at first glance (it turned out to have been more like padding for walking) and the fact that they had flat bills like ducks (which weren't really that similar to a duck bills)  To go with this incorrect idea, some proposed the crest of Parasaurolophus was a snorkeling adaptation, since it was hollow on the inside and would have connected to the animal's airways.  A more likely reason for this crest, however, is to help the animal to produce a distinctive sound.  the dinosaur would inhale through it's nose, the air would pass through the tubes inside the crest and become amplified, then released through the mouth as a loud bellow.  The mechanics would have been very similar to playing a trombone, actually.  With the help of some more modern technology, scientists were able to scan the inside of a Parasaurolophus crest and reproduce what they might have sounded like based on their findings.  According to what they came up with, the sounds of Parasaurolophus would have been pretty eerie!  Check out the audio below!

The fact that Parasaurolophus probably used its crest to make sounds, combined with the fact that we know the young had short crests, leads us to the undeniable fact that the young and adults must have sounded different.  (young would have been higher pitched)  This makes sense for communication reasons.  A mom would have an easier time finding her babies by their calls if they ever became separated.  You can actually observe very similar baby to parent vocalizations in modern birds(dinosaurs) and crocodilians.  The sounds were also probably a good way for adults to attract mates and establish dominance, which can also be seen in a myriad of modern animals.

There was more to Parasaurolophus than just the crest, remember.  In the front of its mouth, it had a flat, and relatively narrow beak, which would have been good for selectively foraging its favorite plants to eat.  This is different from the widened, bills of other hadrosaurs, like Edmontosaurus', which were probably more adapted for a generalist plant diet.  Like all hadrosaurs, Parasaurolophus had hundreds of tiny teeth in the back of its mouth, which were tightly packed together to form what is called a dental battery.  these structures were perfect for chewing tough plants much like molars.

Parasaurolophus had relatively long arms and could have walked on four or two limbs depending on how fast it wanted to move.  Its vertebrae had tall neural arches, especially on its back, which would have given it a hump-like profile in life.  Like all hadrosaurs, Parasaurolophus' tail was especially thick, and also pretty rigid.  The tail would have probably been its weapon of choice if it needed to defend itself.

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

References

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

Currie, Phillip J.; Koppelhus, Eva, eds. (2005). Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Bloomington: Indiana University Press. pp. 312–348. ISBN 0-253-34595-2.

Evans, David C. "Nasal Cavity Homologies and Cranial Crest Function in Lambeosaurine Dinosaurs." Paleobiology 32.1 (2006): 109-25. Web.

Farke, Andrew A., Derek J. Chok, Annisa Herrero, Brandon Scolieri, and Sarah Werning. "Ontogeny in the Tube-crested Dinosaur(Hadrosauridae) and Heterochrony in Hadrosaurids." PeerJ 1 (2013): E182.

Sullivan, R.M.; Lucas, S.G. (2006). "The Kirtlandian Land-Vertebrate "Age"-Faunal Composition, Temporal Position, and Biostratigraphic Correlation in the Nonmarine Upper Cretaceous of Western North America". In Lucas, S.G.; Sullivan, R.M. Late Cretaceous vertebrates from the Western Inter(PDF). New Mexico Museum of Natural History and Science Bulletin 35. pp. 7–23.

Weishampel, D.B. "Acoustic Analysis of Vocalization of Lambeosaurine Dinosaurs." Paleobiology 7.2 (1981): 252-61. 

Wilfarth, Martin (1947). "Russeltragende Dinosaurier". Orion (Munich) (in German) 2: 525–532.

Anurognathus: Beast of the Week

This week we will be checking out a unique little pterosaur, Anurognathus ammoni!  Anurognathus lived in what is now Germany during the late Jurassic period, about 150 million years ago.  It was tiny, sporting a 14 inch (35.5 cm) wingspan, and would have likely eaten insects.  It's genus name translates to "Frog Jaw" since its skull was similar looking to a frog's, being extremely blunt with a wide mouth.  

Watercolor reconstruction of Anurognathus ammoni by Christopher DiPiazza.

Anurognathus' skull was unusually short and broad for a pterosaur, being wider than it was long. It had huge eye sockets, suggesting it had strong vision, and needle-like teeth.  Experts think it was likely hunting flying insects, possibly at night, by flying into them with its mouth open.  This is similar to the hunting strategies of some modern birds, like swifts and swallows, which also independently evolved extremely wide jaws to do the same thing.  There were even some small bumps found lining the mouth of Anurognathus' jaws, suggesting there were whiskers growing there in life, another trait that could have possibly helped it capture fling prey in the air.  

Anurognathus skeleton that was described in 2007.

Thanks to a well preserved skeleton known of Anurognathus, we not only know about its bones, but also some of its other softer body parts that usually disappear before fossilization.  Paleontologists were able to see some of its limb muscles as well as the membrane of skin that made up its wing.  Perhaps most interesting, is we even know that Anurognathus would have had fuzzy feathers covering most of its body, including its wings! 

Pterosaurs are basically divided into two major groups.  The pterodactyloids are known for their long skulls, longer necks, and short tails.  This includes famous pterosaurs, like Pteranodon, Pterodactylus, and Quetzalcoatlus. The rhamphorhynchoids are characterized by smaller skulls, shorter necks, long tails, and an elongated fifth toe on each foot, which a membrane between their legs, used for maneuvering in the air, anchored to.  This group includes Rhamphorhynchus and Dimorphodon.  Anurognathus, despite having a proportionally short tail, has been found to be more closely associated to the rhamphorhynchoid branch of pterosaurs, due to its shorter neck and large fifth toe.  

References

Bennett, S. C. (2007). "A second specimen of the pterosaur Anurognathus ammoni", Paläontologische Zeitschrift, 81: 376-398

Döderlein, L. (1923). "Anurognathus Ammoni, ein neuer Flugsaurier". Sitzungsberichte der Mathematisch-Naturwissenschaftlichen Abteilung der Bayerischen Akademie der Wissenschaften zu München, 1923, 306-307.

Witton, M.P. (2008) "A new approach to determining pterosaur body mass and its implications for pterosaur flight". Zitteliania B28: 143-159

Edmontosaurus: Beast of the Week

Today we are checking out one of the largest and most well studied of the duck-billed dinosaurs.  Enter Edmontosaurus!  

Edmontosaurus annectens in watercolors by Christopher DiPiazza.

Edmontosaurus was a hadrosaur ("duck-billed") dinosaur that could grow to at least 39 feet (12 meters) long from beak to tail that lived during the late Cretaceous period in what is now western North America.  There are currently two recognized species within the genus, Edmontosaurus regalis and Edmontosaurus annectens.  E. regalis lived between 73 and 70 million years ago in what is now Alaska, Colorado, and Alberta, and had a more robust snout. Edmontosaurus annectens lived between 68 and 66 million years ago in what is now Montana, South Dakota, and Wyoming, and had a longer, lower snout.  The genus name translates to "Edmonton Reptile/Lizard" in reference to Edmonton, Alberta, where the first specimen was found.  Edmontosaurus also includes the dinosaurs that used to be called Anatosaurus and Anatotitan, which were initially thought to be distinct taxa.  (Part of me wishes Anatotitan, which translates to "Duck Titan" was still valid because the name "duck titan" brings me joy.)

Skeletons on display at the American Museum of Natural History in New York City.

Before we go further, describing this dinosaur, I think it's important to mention that one thing that makes Edmontosaurus particularly special, is the fact that we know an incredible amount about it compared to other dinosaurs.  This is because in addition to skeletons, we have not one, but SEVERAL mummified specimens that have been unearthed over the years.  Thanks to this we know more about Edmontosaurus' life appearance than almost any other prehistoric dinosaur.  So as you read the rest of this post if you notice I am able to describe Edmontosaurus in much more detail than normal, this is why.

Image from Sereno's recent paper (referenced below) showcasing the fleshy sail and lizard-like spines down the midline of a recently described Edmontosaurus mummy.

Out of all the hadrosaurs, which are characterized by having wide, flat bills in the front of their mouths, Edmontosaurus annectens had arguably the "duckiest" bill, which was particularly wide and almost squared off to a degree.  Initially hadrosaurs were believed to have been semi-aquatic, behaving like the ducks, swimming in fresh water and eating water plants.  Since then, we have found out that he bill of a hadrosaur, including Edmontosaurus, wasn't really similar to a duck's at all.  Thanks to a mummified specimen of Edmontosaurus which preserved the keratin that was growing over the skull in life, we know that the flat duck-like beak was only the shape of the skull and the whole beak would have been bigger and more downturned in life.  This appears to be more of an adaptation for clipping tough plant material, including pine needles and twigs which would the be processed in the back of the jaws by literally hundreds of small teeth that were arranged tightly together in units called dental batteries. These dental batteries were the dinosaur's way to grind food like some mammals do today with molars.  Like all reptiles, if a tooth became too worn down, it would fall out and be replaced with a fresh tooth.  Because of this hadrosaur teeth are among some of the most common fossils in locations where they lived. 

Edmontosaurus specimen on display at the American Museum of Natural History in New York.  This individual preserved soft tissue, including some of the beak's keratin.

Dental battery on the lower jaw of Edmontosaurus.

There is a mummified specimen of Edmontosaurus regalis (although it has been recently been suggested this may be a third species) which preserved the skin around the neck, which appears to have had a wide, wrinkled texture.  This same specimen also shows the animal had a fleshy crest, like a chicken's wattle, on its head.  We don't know if all members of the species had this feature or if it was just in one sex, nor do we know if it was present in Edmontosaurus annectens.  That being said there are also mummies of Edmontosaurus annectens which show us a lot about its scaly skin, including a fleshy sail-like crest that ran from the back of its neck down to the base of its tail, at which point it had a single row of triangular spines running down the midline of the tail, similar spines in some modern lizards, takes over.  Another Edmontosaurus annectens mummy, which preserved the skin on the tail, shows the mosaic-like scales are arranged in banding patterns, which may imply the dinosaur had colored stripes on its tail in life.  

Photograph and graphic showing the skin texture and fleshy crest of Edmontosaurus regalis.

Like all hadrosaurs, Edmontosaurus would had robust hind legs with three toes on each foot and slender, yet strong front limbs.  It likely would have been able to walk on all fours or on its hind legs depending on what its needs were.  Each hand had five fingers, but the middle three were fused together and ended in one large hoof-like claw.  The first finger also had a claw and jutted out to the side while the fifth also jutted out on the other end but had no claw.  When the animal was on all fours the middle three digits that formed the hoof would support most of the weight. The same mummy that showed the back crest mentioned earlier also preserved the feet, showing Edmontosaurus' nails were also extremely hoof-like and its toes were heavily padded.  

Photograph of the mummified hand of Edmontosaurus annectens.  Note the large hoof that encompasses the middle three fingers.  You an also see the fine scaly skin and folds on the wrists.  From paper by Drumheller et al. referenced below.

Edmontosaurus possessed an extremely muscular tail that was also reinforced with boney tendons running along its spine, causing the tail to be stiff and easier to hold off the ground in life.  The huge tail would have acted as a counterbalance to the dinosaur's torso as it walked or ran on its hind legs.  The tail could also have been an extremely effective weapon against potential predators or even members of its own species.  This is important to note, since I feel far too often hadrosaurs are depicted as fodder for meat-eating dinosaurs simply because they didn't have obvious weapons like horns, clubs, or spikes.  In reality they likely were probably more than capable of defending themselves and a healthy adult Edmontosaurus would have been a challenging target for even the hungriest tyrannosaur. 

Nanuqsaurus eyes a family of Edmontosaurus regalis.  The adult Edmontosaurus would have been too large and dangerous for the tyrannosaur to attempt to hunt.

That's all for this week.  As always feel free to comment below!

References

Campione, N.E.; Evans, D.C. (2011). "Cranial Growth and Variation in Edmontosaurs (Dinosauria: Hadrosauridae): Implications for Latest Cretaceous Megaherbivore Diversity in North America". PLOS ONE. 6 (9) e25186.

Bell, P. R.; Fanti, F.; Currie, P. J.; Arbour, V.M. (2013). "A Mummified Duck-Billed Dinosaur with a Soft-Tissue Cock's Comb". Current Biology. 24 (1): 70–75.

Brett-Surman, Michael K. (1979). "Phylogeny and paleobiogeography of hadrosaurian dinosaurs". Nature 277 (5697): 560–562

Campione, Nicolás E.; and Evans, David C. (2011). "Cranial growth and variation in Edmontosaurs (Dinosauria: Hadrosauridae): implications for latest Cretaceous megaherbivore diversity in North America". PLoS ONE 6 (9): e25186. 

Drumheller SK, Boyd CA, Barnes BMS, Householder ML (2022) Biostratinomic alterations of an Edmontosaurus “mummy” reveal a pathway for soft tissue preservation without invoking “exceptional conditions”. PLoS ONE 17(10): e0275240.

Lambe, Lawrence M. (1917). "A new genus and species of crestless hadrosaur from the Edmonton Formation of Alberta" (pdf (entire volume, 18 mb)). The Ottawa Naturalist 31 (7): 65–73. Retrieved 2009-03-08.

Lambe, Lawrence M. (1920). "The hadrosaur Edmontosaurus from the Upper Cretaceous of Alberta". Department of Mines, Geological Survey Memoirs 120: 1–79. 

Manning, Phillip L.; Morris, Peter M.; McMahon, Adam; Jones, Emrys; Gize, Andy; Macquaker, Joe H. S.; Wolff, G.; Thompson, Anu; Marshall, Jim; Taylor, Kevin G.; Lyson, Tyler; Gaskell, Simon; Reamtong, Onrapak; Sellers, William I.; van Dongen, Bart E.; Buckley, Mike; Wogelius, Roy A. (2009). "Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation, North Dakota (USA)". Proceedings of the Royal Society B. 276 (1672): 3429–3437.

Morris, William J. (1970). "Hadrosaurian dinosaur bills — morphology and function". Contributions in Science (Los Angeles County Museum of Natural History). 193: 1–14.

Ostrom, John H. (1964). "A reconsideration of the paleoecology of the hadrosaurian dinosaurs". American Journal of Science 262 (8): 975–997

Sereno, Paul. (2025) Duck-billed dinosaur fleshy midline and hooves reveal terrestrial clay-template "mummification". Science 0

Sharpe, H. S., Bell, P. R., Baylatry, I., Sissons, R., & Sullivan, C. (2025). Re-evaluation of a soft crested Edmontosaurin, with implications for hadrosaurid life appearance and diversity. The Anatomical Record, 1–20. 

Nanotyrannus: Beast of the Week

 This week we will be learning about a dinosaur who's identity has been the subject of a lot of debate or decades.  Check out Nanotyrannus!

Nanotyrannus was a meat-eating dinosaur that lived in what is now Montana in the United States during the latest Cretaceous period, between 67 and 66 million years ago.  From snout to tail it measured between 17 and 20 feet (6.2 meters) long as an adult. The genus name translates to "Small/Dwarf Tyrant" because it was originally believed to be a close relative of Tyrannosaurus rex, but much smaller.  

Watercolor life reconstruction of Nanotyrannus lancensus attacking a baby Tyrannosaurus rex by Christopher DiPiazza.

The first known Nanotyrannus bones were fond in the 1940s and it was initially thought to be a kind of Gorgosaurus. Then in the 1980s it was re-examined and thought by many paleontologists to be worthy of its own genus and was renamed Nanotyrannus.  Then in the 1990s it was suggested by some to be a juvenile Tyrannosaurus and the discovery of a new skeleton, nicknamed "Jane", further strengthened that stance, since that skeleton was indeed of a juvene when it died.  It also exhibited the typical traits paleontologists already knew for sure juvenile tyrannosauroids had, thanks to confirmed juvenile specimens of other taxa, like Albertosaurus.  These traits include proportionally longer arms and legs, which experts suggested allowed younger individuals to fill a different ecological niche, specializing in running down smaller faster prey, before bulking into mature adults.  For decades there was a division among experts on this possibility.  Then finally much more recently in 2025, a formal paper on an extremely complete skeleton, nicknamed "Bloody Mary", deemed Nanotyrannus a valid taxon again.  "Bloody Mary" was not a juvenile, in fact when a cross section of one of their bones was examined, it was estimated they were in their twenties when they died, which is similar to the age of some of the largest adult Tyrannosaurus rex specimens when they died.  Based on this, plus a few other key differences in its skull and limb anatomy, it appeared that Nanotyrannus was indeed it's own kind of dinosaur, and not simply a young T. rex. (although Tyrannosaurus itself still likely looked similar to Nanotyrannus it when it was a juvenile)

Nanotyrannus lethaeus on display at the Burpee Museum in Illinois, USA.  This specimen was thought to be a juvenile Tyrannosaurus rex by many experts.

This latest paper also was able to identify that Nanotyrannus included two species.  Nanotyrannus lethaeus, which includes the skeleton, named "Jane", and was the slightly larger of the two.  Nanotyrannus lancensus was smaller, but had proportionally longer arms, which includes the newer "Bloody Mary" individual.  Another interesting point that the newest paper suggested, was that Nanotyrannus was much less closely related to the group that contains Tyrannosaurus and Gorgosaurus, called the tyrannosaurids, than previously believed.  Even those who thought it was a distinct taxon in the past thought it to be within the tyrannosaurid family.  Thanks to the "Boody Mary" skeleton, which preserved a lot of anatomy not known prior, the new paper suggests Nanotyrannus was outside tyrannosaurids, but still a tyrannosauroid, more similar to dinosaurs like Dryptosaurus, which also had proportionally longer arms, large hand claws, and lived during the late Cretaceous.

Nanotyrannus lancensus skull. (photo: James St. John)

As stated, Nanotyrannus had proportionally long and slender legs, implying it was a fast runner when alive, likely specializing in hunting smaller faster prey, while its much larger cousin, T. rex could take larger, more heavily armored prey.  That being said, juvenile Tyrannosaurus were still almost certainly similar in build to Nanotyrannus, so they would have likely competed with each other on that level at the very least.  

Close up of the skin preserved on Nanotyrannus lancensus' leg.

Nanotyrannus had a narrow, slender snout, filled with proportionally long, bladelike teeth, ideal for slashing meat, not for crushing like adult T. rex had.  Nanotyrannus also possessed little bony crests in front of its eyes, which may have had keratin growing over them in life, forming small display structures, which is a feature common in many tyrannosaurs.  As stated earlier it's arms were proportionally long for a tyrannosaur, and were tipped with two fingers on each hand, each with a hook-shaped claw.  One specimen preserves what appears to be scaly skin on it's leg like a bird, which anyone would have assumed it had there, but is still really exciting to have proof of.  Considering it was a tyrannosauroid which are known in the fossil record to have had feathers and were closely related to birds, it probably also had feathers of some kind on other parts of its body. 

That is all for this week!  Comment below!

References

Bakker, R.T.; Williams, M.; Currie, P.J. (1988). "Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana". Hunteria. 1: 1–30.

Carr, T.D. (1999). "Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria)". Journal of Vertebrate Paleontology. 19 (3): 497–520.

Eberth, David A.; Currie, Philip J. (2010). "Stratigraphy, sedimentology, and taphonomy of the Albertosaurus bonebed (upper Horseshoe Canyon Formation; Maastrichtian), southern Alberta, Canada". Canadian Journal of Earth Sciences. 47 (9): 1119–1143.

Gilmore, C.W. (1946). "A new carnivorous dinosaur from the Lance Formation of Montana". Smithsonian Miscellaneous Collections. 106: 1–19.

Henderson (2005). "Nano No More: The death of the pygmy tyrant." In "The origin, systematics, and paleobiology of Tyrannosauridae", a symposium hosted jointly by Burpee Museum of Natural History and Northern Illinois University.

Larson, P. (2013). The validity of Nanotyrannus lancensis (Theropoda, Lancian - Upper Maastrichtian of North America (PDF). Society of Vertebrate Paleontology 73rd Annual Meeting. p. 159.

Zanno, Lindsay E.; Napoli, James G. (2025-10-30). "Nanotyrannus and Tyrannosaurus coexisted at the close of the Cretaceous". Nature. doi:10.1038/s41586-025-09801-6.

Zuul: Beast of the Week

 This week we will be learning about an amazing armored dinosaur with a delightfully spooky name.  Check out Zuul crurivastator!  

Zuul was an ankylosaur dinosaur that lived in what is now Montana, USA, during the late Cretaceous period, about 75 million years ago.  It measured about 20 feet (6 meters) from beak to tail and would have eaten plants when alive.  The genus name is in direct reference to the monster from the 1984 movie, Ghostbusters, which paleontologists think resembled the dinosaur's skull.  The genus name translates to "destroyer of shins" because of how this dinosaur may have used its tail weapon defensively on the legs of predatory dinosaurs.  

Zuul watercolor life reconstruction by Christopher DiPiazza.

Zuul is especially important to paleontologists because we have an almost complete skeleton from it containing not only most of its bones, but also most of the armor still in the position on the body it would have been when the dinosaur was alive.  More commonly when armored dinosaurs are discovered all of those bits are just jumbled nearby (if they are present at all) leaving scientists guessing the best they can how they were arranged in life.  Zuul also preserved parts of its body that normally don't fossilize like the keratin that covered its armor and even some of its scaly skin!  

Zuul from Ghostbusters (top) compared to Zuul from the Cretaceous (bottom)

Zuul's skull is similar to those of most ankylosaurids, possessing a relatively low, wide snout that had a beak growing over it in life.  In the back of its jaws it had a series of serrated leaf-shaped teeth which were ideal for processing plants.  It had a bony plate-like structure growing from either side of its lower jaws and short horns growing from its cheek bones and the back of its skull.  It also had forward-facing nostrils which were lined with bony armor.  Because of their wide snouts, ankylosaurids are thought to have been more generalist feeders, essentially hoovering up large volumes of plants low to the ground.  

Photographs of Zuul's tail including its club, osteoderms, and even some skin.  Note how the portion of the tail closest to the bony club is stiffened like a rod. (image from Arbour's 2017 paper referenced below)

Zuul's tail is extremely well preserved, with sharp triangular osteoderms (bony plates that grow from the animal's skin) lining each side.  Some of these osteoderms preserve the keratin (material that horns and nails are made of) that would have been growing over them, showcasing their size and shape in life.  Like all ankylosaurids, Zuul had a bony club made of a set of fused osteoderms at the tip of its tail.  The base of Zuul's tail nearest the hips would have bee relatively flexible and muscular to allow it to swing its club around with great force. The thirteen vertebra closest to the club, however, were rigid, forming a stiff handle allowing for stability when the weapon was swung, preventing injury.  (To better understand why this is important, imagine how awful using a hammer would be if the handle was floppy.)

Photograph top view of Zuul's fossilized skull, back armor, and tail.  Below is a diagram highlighting in red the armor that is thought to have been damaged in fights with other Zuul. (photo from Arbour et al's 2022 paper referenced below)

The armor on Zuul's back was preserved in place as well as a lot of its skin, giving us a really accurate idea of what it looked like in life.  When observed more closely by paleontologists, they noticed that some of the armor plates on its back appeared to have been broken and healed over repeatedly during the course of the dinosaur's life.  These sorts of injuries don't really appear to have been inflicted by a predatory dinosaur, but they DO match up with being inflicted by the tail of another Zuul, which is exactly what experts think they were from.  This supports the idea that ankylosaurid tail weapons weren't evolved primarily for defense against predators, but also for combat within the species, possibly for dominance, territory, or access to mates.  

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

References

Arbour, Victoria M.; Evans, David C. (2017). "A new ankylosaurine dinosaur from the Judith River Formation of Montana, USA, based on an exceptional skeleton with soft tissue preservation". Royal Society Open Science. 4 (5) 161086.

Arbour, Victoria M. Lindsay Z., Evans, Daid C. (2022)."Palaeopathological evidence for intraspecific combat in ankylosaurid dinosaurs" . Royal Society Open Science. 18: 20220404