Anatotitan: Prehistoric Animal 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 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

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

Zavacephale: Beast of the Week

 This week we'll be looking at a newly described little dinosaur that greatly expands our knowledge on one of the most unusual kinds of dinosaurs, the pachycephalosaurs.  Welcome Zavacephale rinpoche!

Zavacephale lived in what is now Mongolia during the early Cretaceous period, between 119 and 110 million years ago.  From snout to tail the specimen found would have only been about three feet (1 meter) in length, but it likely would have been able to grow larger.  The genus name, Zavacephale, translates to "Origin/Root Head" in reference to the fact that it is the oldest pachycephalosaur found to date.  The species name, rinpoche, is Tibetan for "precious one" because when it's skull was first discovered, it reminded the scientists who named it of a precious gem the way it was partially exposed from a sandy outcrop in the Gobi Desert.  

Life reconstruction of a young Zavacephale in watercolors by Christopher DiPiazza.  The teeth of pachycephalosaurs imply they may have been omnivores, and eaten small animals, like this crunchy beetle, in addition to plants.

Zavacephale was an early member of the pachycephalosaur family of dinosaurs.  Most famous for the latest and largest member, Pachycephalosaurus, itself, they are most well known for having thick, dome-shaped skulls surrounded by small horns.  They are historically associated with being plant-eaters, but more recently its been suggested they were more omnivorous judging by some of their teeth.  Zavacephale is extremely important because up until it's discovery, every pachycephalosaur known has been from the end of the Cretaceous, but Zavacephale lived millions of years prior in the early Cretaceous, making it the oldest member of this group by a long shot.  What makes this more interesting is the fact that despite this, Zavacephale still has a very pronounced thickened dome skull, like its later relatives, meaning this famous feature of the group evolved even earlier than Zavacephale's time, possibly back in the Jurassic period?

Photograph of Zavacephale's skull.  Note the sharp teeth in the front of the mouth.

The individual Zavacephale that was discovered was only a juvenile that wasn't done growing when it died.  Paleontologists know this because most of its bones weren't completely fused together, which is the case with more mature dinosaurs.  The one part that was fully formed, however, was its domed skull.  This is interesting since pachycephalosuars are typically thought to have used these specialized skulls for fighting within the species for dominance, which is associated with being a mature adult.  The fact that Zavacephale's dome was fully formed while the rest of its body was still growing implies the younger individuals were also using their skulls, possibly play fighting with one another?  We can only speculate as of now!

A photo taken of Zavacephale before it was fully excavated.  Note the dome skull peeking out. Photo credit: Tsogtbaatar Chinzorig

Another thing that makes Zavacephale important is the fact that in addition to be the oldest pachycephalosaur ever found, it's also the most complete skeleton of a pachycephalosaur ever found.  Most of the dome-headed dinosaurs are only known from skull material, but Zavacephale not only preserved a complete skull, but also legs, arm bones, most of the spine, the complete tail, and even hand bones, last of which were previously unknown from pachycephalosaurs.  It also had gastroliths, small stones the dinosaur swallowed to help digest its food, in its gut region.  

Zavacephale's skeleton.  Note the complete tail.

Zavacephale's actual skull was typical for pachycephalosaurs.  In addition to the dome and small horns, it had proportionally large eye sockets, implying it had good eyesight.  In the back of its mouth it had small leaf-shaped teeth that appear to have been ideal for shredding plants.  In the front of its mouth, however, it possessed pointed, fang-like teeth on both the upper and lower jaws.  Most pachycephalosaurs, and even some smaller ceratopsians, are known to have these unusual teeth.  Some believe they were an adaptation for stripping leaves, while others suggest these dinosaurs were actually more omnivorous than previously thought, possibly using those teeth to crunch small animals.  

Zavacephale had teeny tiny hand bones! Photo credit: Alessandro Chiarenza.

Zavacephale's hand bones were proportionally extremely tiny and were at the end of relatively short arms.  It's legs, however, were quite long, but as it matured it may have grown into them more, since many dinosaurs tend to have lankier builds when young.  It's tail was actually a bit shorter than one would expect for this kind of dinosaur, and had horizontal bony rods running along it, called ossified tendons, which would have made the tail stiffer in life, a trait seen in lots of other kinds of dinosaurs, like hadrosaurs and dromaeosaurs, likely for balance and stability.  

References

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.

Madzia, Daniel; Arbour, Victoria M.; Boyd, Clint A.; Farke, Andrew A.; Cruzado-Caballero, Penélope; Evans, David C. (2021-12-09). "The phylogenetic nomenclature of ornithischian dinosaurs". PeerJ. 

Pentaceratops: Beast of the Week

This week we will be checking out yet another awesome ceratopsian dinosaur.  Enter Pentaceratops sternbergii!

Pentaceratops was a plant-eating dinosaur that measured about twenty feet long from beak to tail. As a ceratopsian (horns, beaks, and frills) it was member of the chasmosaurine group, and was closely related to Chasmosaurus and Coahuilaceratops to name a few.  It lived in what is now New Mexico, USA, during the late Cretaceous Period, between 76 and 73 million years ago.  The genus name, Pentaceratops, translates to "Five Horned Face" in reference to the single horn on the snout, two over the eye sockets, and two on the jugals (cheek bone).  I personally feel the name is a bit misleading since many ceratopsians, including ones that are named for having specifically fewer horns, have "horns" on their jugals also.  When I hear "Five Horned Face" I expect two extra horns growing out over the eyes or something...oh well.

 

Watercolor reconstruction of Pentaceratops by Christopher DiPiazza.

Pentaceratops had one of the largest skulls of any land animal.  From beak to the end of its frill, its skull measured almost eight feet long.  Most of this was frill, which was basically a light frame of bone around two large holes, called fenestre.  Large fenestre are common in most ceratopsians (Triceratops being an exception) to make sure their skulls weren't too heavy.  Pentaceratops' frill was lined with small horn-like structures called epoccipitals.  At the top of the frill, there is a "U" shaped dip in the middle, and the middle-most two epoccipitals actually face downwards, like the collar of a shirt.  As is the case with all of its relatives, the frill and horns of Pentaceratops may have served as display adaptations for within the species, possibly attracting mates and/or intimidating rivals.  They also could have aided in deterring potential predators, like the tyrannosaurid, Bistahieversor, which it coexisted with in life.

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

Unlike many ceratopsians, of which paleontologists more often than not only find the skulls of, most of Pentaceratops' body is known, as well.  What is interesting is that the neural arches in the middle of the back are relatively tall.  This suggests that there may have been muscles attaching there that led to the back of the skull, to help hold up the giant frill.

Most recently, in 2011, the remains of a juvenile Pentaceratops were discovered in New Mexico by a team of paleontologists from the New Mexico Museum of Natural History and Science.  It took years to finally get the big baby out of the rock until it was finally airlifted, via helicopter, to the museum in 2015 to be worked on further in a lab.  This awesome find will be on display in the years to come when it is fully excavated and prepped!

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

References

H.F. Osborn, 1923, "A new genus and species of Ceratopsia from New Mexico, Pentaceratops sternbergii, American Museum Novitates 93: 1-3

Lehman, T.M., 1998, "A gigantic skull and skeleton of the horned dinosaur Pentaceratops sternbergi from New Mexico: Journal of Paleontology, 72(5): 894-906Rowe, T., Colbert, E.H. and Nations, J.D., 1981, "The occurrence of Pentaceratops with a description of its frill", In: Lucas, S.G., Rigby, J.K. and Kues, B.S. (eds.) Advances in San Juan Basin Paleontology, University of New Mexico Press, Alburquerque p. 29-4

"National Guard Airlifts Baby Pentaceratops Fossil out of New Mexico Badlands." UPI. N.p., n.d. Web.

Irritator: Beast of the Week

This week's beast is a special dinosaur that helps us understand more about the appearance and lifestyle of its family.  Check out Irritator challengeri!

Irritator life reconstruction in watercolor by Christopher DiPiazza.

Irritator was a meat-eating dinosaur that lived in what is now Brazil during the early Cretaceous period, between 113 and 110 million years ago. From snout to tail it would have measured between 20 and 26 feet (6 and 8 meters) and was a meat-eater when alive.  The genus name, Irritator, is certainly an unusual name for a dinosaur, and is in reference to the fact that the skull, which was originally found by a fossil dealer who attached fake bones to the end of it in an attempt to make it look cooler.  When paleontologists actually got hold of the specimen they found it extremely irritating to undo all the damage to the specimen the dealer had done, so much so, they literally named it that.  The species name is after the fictional character, Professor George Edward Challenger, from the novel by famous author, Sir Arthur Conan Doyle, The Lost World. (which takes place in Brazil and features dinosaurs)

Irritator was a theropod that belonged to the spinosaurid family, which also includes other dinosaurs, like Baryonyx and the gigantic and extremely popular Spinosaurus, itself.  Most spinosaurs were relatively large theropods, Spinosaurus being arguably the largest theropod ever in some ways, but Irritator, at only 26 feet at the high end was a relatively smaller exception to this trend.  Like all spinosaurs, Irritator possessed a long, narrow snout, lined with pointed cone-shaped teeth.  Its nostrils were midway up the snout, instead of at the tip like those of most dinosaurs.  It also possessed a thin bony crest in the midline of the top of its skull.  Sadly only the skull of Irritator was ever oficially found.  There are other spinosaur bones known from the same time and relative area as Irritator, but because there are no overlapping parts between these bones and the Irritator skull, it is impossible to positively say they are all from the same kind of dinosaur.  That being said, if it was anything like other members of its family, it would have possessed strong arms with three curved claws on each hand, with the first finger of each hand possessing the largest claw.  Irritator may have also possessed proportionally shorter legs, a sail of some sort on the back comprised of extended neural spines, and a flattened tail.  These are all traits seen in Spinosaurus, which is thought to be closely related to Irritator even within the spinosaurid family.  

Left and right sideviews of Irritator's skull.

Irritator lived in an environment that would have been tropical in climate and abundant with large lagoons.  It had a long snout lined with pointed teeth, plus  possessed an extra bony palate on the roof of its mouth which would have helped the skull withstand pressure from twisting, an adaptation helpful if it was grabbing large struggling prey.  A study published in 2023 suggested that Irritator's lower jaws would have actually been somewhat flexible and were able to slightly bow outwards to the sides, expanding he gape of the mouth.  It also pointed out that Irritator's eyes were positioned facing forward, giving it particularly good binocular vision.  All these traits suggest Irritator was adapted to hunting fish, and it probably was, however we also know that Irrirator ate pterosaurs at least some of the time.  This is thanks to an Irrirator tooth found embedded into a pterosaur spine.  We don't know if Irritator was actively hunting the flying reptiles or scavenging them, however.  

When the skull of Irritator was first found by German and English scientists in the early 1990s, it was in the hands of a fossil dealer.  The scientists bought the skull from the dealer and brought it back to Germany where it resides to this day.  Current law in Brazil states that fossils found there must stay there unless given explicit permission by the government.  Many believe, including many paleontologists, that Irritaor's skull should be returned to and housed in a museum in Brazil.  

References

Cisneros, Juan C.; Ghilardi, Aline M.; Raja, Nussaïbah B.; Stewens, Paul P. (November 15, 2021). "The moral and legal imperative to return illegally exported fossils". Nature Ecology & Evolution. 6 (1): 1–3.

Machado, E.B.; Kellner, A.W.A. (2005). "Notas Sobre Spinosauridae (Theropoda, Dinosauria)". Anuário do Instituto de Geociências (in Portuguese). 28 (1): 158–173.

Machado, E.B.; Kellner, A.W.A.; Campos, D.A. (2005). "Preliminary information on a dinosaur (Theropoda, Spinosauridae) pelvis from the Cretaceous Santana Formation (Romualdo Member) Brazil". Congresso Latino-Americano de Paleontologia de Vertebrados. 2 (Boletim de resumos): 161–162.

Martill, D.M.; Cruickshank, A.R.I.; Frey, E.; Small, P.G.; Clarke, M. (1996). "A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil" (PDF). Journal of the Geological Society. 153 (1): 5–8.

Schade, Marco; Rauhut, Oliver; Foth, Christian; Moleman, Olof; Evers, Serjoscha (2023). "A reappraisal of the cranial and mandibular osteology of the spinosaurid Irritator challengeri (Dinosauria: Theropoda)". Palaeontologia Electronica. 26 (2). a17.

Mirasaura: Beast of the Week

 This week we will be checking out a newly published and super unique little creature, Mirasaura grouvogeli!

Watercolor life reconstruction of Mirasaura grouvogeli by Christopher DiPiazza.

Mirasaura was a reptile that lived in what is now France, during the late Triassic period, 247 million years ago.  Adults of this species may have grown to about 8-10 inches (20-25cm), The genus name translates to "Marvelous Reptile".  The species name, grouvogeli, honors Louis Grouvogel, who originally discovered the first fossils of Mirasaura and helped with its excavation. Mirisaura is known from two almost complete, likely juvenile specimens, as well as eighty specimens of isolated parts of the crest structure found on the animal's back.  Some of these isolated crests are much longer than those of the two nearly complete individuals, implying they could have grown larger than the two actual skeletons on the fossil record.  

Despite being recently published, Mirasaura was actually discovered back in the 1930s.  Its crest was initially believed to have been a disembodied fish fin and then an insect wing.  It wasn't until 2019 that it was reexamined again and realized to be the elaborate and unusual crest of a reptile.  

Photograph of one of the nearly complete, likely juvenile, Mirasaura specimens.

Mirasaura was a member of a family of interesting creatures called drepanosaurs.  Drepanosaurs were small, tree-dwelling reptiles, that lived during the Triassic period.  They all exhibit traits similar to modern lizards, in particular chameleons, but are not directly related to them.  Narrow, beaklike snouts with small teeth on the sides of the jaws and a hunched back are common to members of this group, including Mirasaura.  Some of them, like Mirisaura, sported flamboyant crests on their backs, which were made of soft, yet rigid structures that were actually extremely similar to feathers.  Thanks to Mirasaura, of which many fossil specimens preserved these soft feather-like structures, it is possible other members of this group, which only preserved bones, had similar crests.  Sadly the limbs and tail from both known skeletons of Mirasaura are missing, but other drepanosaurs had limbs and feet adapted for grasping branches and some had a single claw on the tip of the tail.  

Possibly the most interesting thing about Mirasaura's crest is the fact that the individual structures that form it are arranged slightly overlapping but in a single file down the midline of the animal, making it not symmetrical. (Best analogy I can think of is when you pose for a group photo at a wedding or something.)  So far experts do not know exactly why this is.  The exact function of the whole crest is also still a mystery.  Like modern reptiles it may have been a signal to members of its own species for impressing mates or intimidating rivals.  If they sported them before they were fully grown, however, they may have had other uses.  Perhaps they could have been for camouflage, obscuring Mirasaura's outline and making it look more like part of a tree?  We may never know for sure.

Mirasaura may have specialized in eating small insects, rooting them out of crevices in trees with its pointed snout, and then crunching them up with the teeth in the sides of its jaws.  Because it was so small, it would have needed to be weary of many of its own predators when alive, ranging from pterosaurs, to dinosaurs, to crocodilian relatives, and even early mammals, all of which were around during the late Triassic.  Because of this, living up in the trees may have been an effective way to minimize predation.  

References

Calzavara M., Muscio G. & Wild R. (1980). "Megalancosaurus preonensis, n. g., n. sp., a new reptile from the Norian of Friuli". Gortania. 2: 49–63.

Senter, P. (2004). "Phylogeny of Drepanosauridae (Reptilia: Diapsida)". Journal of Systematic Palaeontology. 2 (3): 257–268.

Spiekman, Stephan N. F.; Foth, Christian; Rossi, Valentina; Gascó Martín, Cristina; Slater, Tiffany S.; Bath Enright, Orla G.; Dollman, Kathleen N.; Serafini, Giovanni; Seegis, Dieter; Grauvogel-Stamm, Léa; McNamara, Maria E.; Sues, Hans-Dieter; Schoch, Rainer R. (2025-07-23). "Triassic diapsid shows early diversification of skin appendages in reptiles".