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".

Ceratosaurus: Beast of the Week

This week we shall be looking at a popular meat-eater with some truly unique features.  Enter Ceratosaurus!

Watercolor life reconstruction of Ceratosaurus nascornis eating the ancient lungfish, Ceratodus robustus by Christopher DiPiazza.

Ceratosaurus was a meat-eating dinosaur that lived during the late Jurassic period, about 150 million years ago, in what is now the United States, specifically Utah and Colorado.  Bones thought to be from Ceratosaurus have also been unearthed in Portugal.  As an adult it would have measured about twenty feet from nose to tail but one specimen suggests it may have grown even larger in some cases.  The genus name, "Ceratosaurus" translates to "Horned reptile/lizard" and refers to the horn-like protrusions on the animal's snout and over its eyes.

Bronze cast of a Ceratosaurus skull on display at the Mesalands Dinosaur Museum in Tucumcari new Mexico.

The most notable feature about Ceratosaurus is the presence of its "horns".  These bony structures aren't really horns as much as they are crests, however, since they were extremely thin and delicate.  Whereas the horns of certain other dinosaurs, like Carnotaurus, were robust enough to have been effective weapons in life, the "horns" of Ceratosaurus would have easily broken if they were used in any sort of violent activity.  They were most likely used for display rather than for physical fighting.  Keep in mind that these crests would have had a layer of keratin growing over them, so they might have appeared even longer and possibly even a slightly different shape in life.  A juvenile Ceratosaurus skeleton that was discovered showcases proportionally smaller crests on its skull, supporting the idea that they were for display, possibly helping individuals within the species to identify others as sexually mature or not.  They may have also been for display against other species, making Ceratosaurus' head look bigger and therefore more intimidating to rival meat-eaters, like Allosaurus. 

Juvenile Ceratosaurus skull on display at the North American Museum of Ancient Life. Note the smaller crests on the nose and above the eyes. (Photo credit: Jens Lallensack)

The crests weren't Ceratosaurus' only unique feature.  This dinosaur also had a row of small bony plates, called osteoderms, running down the center of its back.  This is a feature common in certain groups of dinosaurs, like the thyreophorans, like Stegosaurus, but is extremely rare in theropods.  The exact purpose is a mystery, but we can make some educated guesses.  As with the head crests, these bony structures may have aided in display to other dinosaurs.  Perhaps males had longer plates than females?  Perhaps they were absent in juveniles?  Maybe they helped camouflage Ceratosaurus slightly by breaking up its basic body shape?  We may never know for sure.

Neck of the Ceratosaurus skeleton on display at the Smithsonian National Museum of Natural History in Washington D.C.  I circled a group of the osteoderms in yellow.

Ceratosaurus' tail was particularly deep and flattened laterally. This lead some to hypothesize that Ceratosaurus may have been a decent swimmer and specialized in hunting aquatic prey. (although there is little other evidence that suggests this)  Ceratosaurus also had short, but fully functional arms each tipped with four fingers and three claws.

Lastly, Ceratosaurus had the longest teeth proportional to its body of any known dinosaur.  The teeth were curved and serrated, like steak knives.  They look to be ideal for slashing chunks of flesh from bone, rather than crushing through armor and bone.  This is further supported by the fact that Ceratosaurus' lower jaw was rather thin, and therefore wouldn't have been capable of applying too much force or withstanding too much pressure before being injured.

Almost-complete(no arms!) Ceratosaurus skeletal mount on display at the National Museum in Washington D.C. 

Ceratosaurus bones have been found in the same formations as other, larger Jurassic meat eaters, like Allosaurus and Torvosaurus.  Most scientists agree that Ceratosaurus may have specialized in hunting a different kind of prey than its larger contemporaries, perhaps going after smaller animals, rather than giant sauropods and heavily-armed stegosaurs.  This is further supported by the fact that Ceratosaurus bones are particularly less common than most of the other dinosaurs known from the Late Jurassic of North America.  This could mean that Ceratosaurus typically dwelled in habitats slightly different from the rest of those dinosaurs where fossilization didn't take place as easily.

Sometimes I wonder what exactly prevented Ceratosaurus from existing close to the other megapredators of it's time...

They said it couldn't be done but I managed to make a cartoon merging Late Jurassic predators with Mean Girls.  It wasn't even that hard.

That's all for this week!  As always feel free to comment below!  Want to see a particular prehistoric beastie reviewed?  Let me know and I'll make it happen!

Works Cited

Carrano, M.T.; Sampson, S.D. (2008). "The Phylogeny of Ceratosauria (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 6 (2): 183–236.

Foster, John (2007). "Gargantuan to Minuscule: The Morrison Menagerie, Part II". Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 162–242. 

Gilmore, C.W. (1920). "Osteology of the carnivorous Dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) and Ceratosaurus". Bulletin of the United States National Museum 110: 1–154.

Marsh, O.C. (1884). "Principal characters of American Jurassic dinosaurs, part VIII: The order Theropoda". American Journal of Science 27 (160): 329–340.

Rowe, T.; Gauthier, J. (1990). "Ceratosauria". In Weishampel, D.B.; Dodson, P.; Osmólska, H. The Dinosauria. University of California Press. pp. 151–168. 

Lepidotes: Beast of the Week

 This wee we will look at a unique kind of prehistoric fish that swam in rivers and lakes while some of the largest dinosaurs walked on land.  Check out Lepidotes!

Watercolor reconstruction of Lepidotes gigas by Christopher DiPiazza.

Lepidotes was a genus of heavily scaled bony fish that lived in what is now Europe and North America during the early Jurassic between 180 and 175 million years ago.  The genus may have even persisted into the Early Cretaceous, as recent as 115 million years ago, but the identity of these later species has been proposed to be from a separate genus by some experts.  In life Lepidotes lived in mostly fresh water and some shallow salt water environments, and would have eaten small invertebrates.  The genus name translates to "covered with scales" in Greek.  From nose to tail most Lepidotes grew to about a foot in length (30 cm).  

Fossil of Lepidotes gigas (photo credit: Ghedo) Note the hard scales, which fossilized extra dark compared to the other parts of the fish.

Lepidotes is most known for its scales, which are by far the most commonly fount fossil from it, and were particularly hard and shiny.  Its closest living relatives are gars, which also have extremely tough armored scales.  Like Gars, the scales of Lepidotes acted as as armor against predators. Gars, however, are also known for their long bodies and snouts, lined with pointed teeth, while Lepidotes was convergently more shaped like a carp, with a taller, rounder body, and proportionally small round mouth.  

In the back of Lepidotes' mouth were rounded teeth, ideal for crushing shelled invertebrates on which it likely preyed on when alive.  Another interesting characteristic of Lepidotes was that both the upper and lower jaws were not attached directly to the rest of its skull, allowing it to have stretched its mouth out into a tube-like structure while sucking up food.  In addition to its body shape, this is another trait present in modern carp.  

References

 Agassiz, L. (1832), Untersuchungen über die fossilen Fische der Lias-Formation. Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde 

Frederickson, Joseph A.; Lipka, Thomas R.; Cifelli, Richard L. (2018-08-28). "Faunal composition and paleoenvironment of the Arundel Clay (Potomac Formation; Early Cretaceous), Maryland, USA". Palaeontologia Electronica.

Lambe, L.M. (1902). "New Genera and Species from the Belly River Series (mid cretaceous)". Geological Survey of Canada. Contributions to Canadian Palaeontology. 3: 25–81.

López-Arbarello, Adriana (2012-07-11). Steinke, Dirk (ed.). "Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterygii)". PLOS ONE. 7 (7): e39370.