Antediluvian Beasts of the East : Hypsibema missouriense

It’s the wet season, and flocks of Ornithomimus antiquus pour down into the lowlands from the Appalachians, their feathery bodies glimmering in the sun. The flocks have been migrating through the Appalachian mountains for months, and they’re ready to rest. Predators also arrive with the rains. Pesky dromaeosaurid packs harass the Ornithomimus, picking off the weak and the vulnerable. However, the dromaeosaurs pose no threat to the largest animals of the lowlands…

Enter Hypsibema missouriense. H. missouriense is the westernmost species of Hypsibema, and the largest animal present in the lowlands. These gigantic hadrosaurs form small herds which migrate across the plains, stripping trees and shrubs of their leaves, fruits, and seeds. Their large size means H. missourense are almost immune from attacks by predators, but the wet season brings new threats to the herd, including theropods with bigger bodies and bigger appetites.

The largest predators to come with the start of the wet season are the dryptosaurs. Full grown adults can even take down a Hypsibema missouriense, and many of the gigantic hadrosaurs have scars from fights with these killers. Armed with 3-clawed hands, a mouthful of serrated teeth, and feet like those of an eagle, these dryptosaurs are well-armed carnivores.

It’s midday in the lowlands, and a juvenile dryptosaur descends from its home on an outcrop to a nearby lake. Unfortunately for the young carnivore, a herd of Hypsibema missouriense have stopped to cool off, and do not intend to share the water. The hadrosaurs spot the juvenile, and start to bellow aggressively, signaling that they’ll charge. The juvenile knows not to instigate the titanic dinosaurs, and retreats to the safety of the adult members of its pack.

Hypsibema missouriense is the better studied and more-well known of the two Hypsibema species. Designated as the State Dinosaur of Missouri in 2004 (See reference 1 for more details), this dinosaur was originally mistaken for a sauropod (Gilmore & Stewart, 1945). This attests to the size of the known bones of H. missouriense. All the fossil caudal vertebrae of this animal in the Smithsonian’s collection are almost 10 centimeters (3.9 inches) in length.

The size of H. missouriense‘s caudal vertebrae suggest an animal of similar size to H. crassicauda. However, none of the H. missourense caudal vertebrae above equate to 10 centimeters in length, whereas the caudal vertebrae of the Hypsibema crassicauda type specimen does (the H. crassicauda vertebrae is actually slightly longer then 10 centimeters. Go check out my post here for an image of the type specimen). The longest vertebrae in the image above (rightmost row, second down) comes in at approximately 9.8 centimeters in length. If we compare that with this 10 centimeter caudal vertebrae attributed to H. crassicauda, we realize that the length of the H. missouriense specimen is 96% of the H. crassicauda specimen. Using the length determined by Holtz and Rey (2007) for H. crassicauda (I should note that Holtz and Rey refer to H. missouriense as Parrosaurus, which was placed in  the genus Hypsibema by Baird & Horner (1979)), which they determined was 49.2 feet, we can make an approximate estimate of the length of the H. missouriense holotype. We find a length of 47.2113 feet (96% of 49.2 feet) for the holotype of H. missouriense. That’s slightly smaller then H. crassicauda , but still gigantic for a hadrosaur.

The caudal vertebrae above aren’t the only material we have from H. missouriense. A fragmentary dentary and predentary are known from this animal (Weishampel et. al., 2007)(Check out this page at the Bollinger County Museum’s website to see the partial dentary), as well as some phalanges (see below). From the more complete remains of H. missouriense, we can better understand how the giant hadrosaurids of Appalachia lived.

During the time of Hypsibema missouriense, Missouri was situated in the southwest of Appalachia. Here, the Appalachians gave way to lowlands, which eventually dipped into the Western Interior Seaway.

75 million years ago (Campanian Stage of the Late Cretaceous) the Appalachians were eroding away. The elements slowly chipped away at these mountains, almost flattening them into the lowlands they gave way to. H. missouriense would have been witness to the last of the Cretaceous Appalachian mountains.

H. missouriense itself hails from the Chronister site, a Campanian age deposit, which, in some places, constitutes as a bone bed (Fix & Darrough, 2004). During the Campanian, the Chronister site was a body of fresh water, possibly some sort of lake or wetland (Fix & Darrough, 2004). The Chronister site is very special, as it is the only locality in Missouri which produces terrestrial vertebrate remains dating to the Mesozoic (Fix & Darrough, 2004). Among the vertebrates are turtles, such as Adocus, the large amphibian Habrosaurus, and the crocodilian Leidyosuchus (Fix & Darrough, 2004). Along with H. missouriense, dromaeosaurids and tyrannosaurids make up the dinosaur fauna (Fix & Darrough, 2004). What interests me about this site, however, is its location on the western coast of Appalachia 72 million years ago.

Many Late Cretaceous localities, such as the Ellisdale site (New Jersey) and Phoebus Landing (North Carolina), have yielded the remains of not only dinosaurs, but turtles, amphibians, lizards, fish, and other vertebrates. When it comes to the fossil record from western Appalachia (I am referring to the continent), we aren’t so lucky. The Chronister site gives us the unique opportunity to study what life was like on the eastern shores of the Western Interior Seaway. Yet Chronister’s close proximity to this inland sea might have caused the downfall of its native residents. When this seaway pulled a reverse-Moses, the dinosaurs of Chronister were right there in the midst of Laramidian species, some of which may have outcompeted natives like Hypsibema missouriense. Of course, we can’t be sure what happened, as we simply do not have localities in the Central and Midwestern US which preserve Maastrichtian dinosaur bones from Appalachia. For now, the fate of western giant hadrosaurids like H. missouriense is a mystery.

Although we might never know what eventually happened to the giant hadrosaurids of western Appalachia, the future looks positive for the Chronister dig site. Excavations of this locality are currently being conducted by the Bollinger County Museum of Natural History. New specimens are constantly being unearthed, and the site’s bone bed will surely continue to yield exciting vertebrate fossils, along with those of plants and invertebrates. The secrets of Appalachia’s far west are finally being revealed.

Hypsibema missouriensis faces off against a young dryptosaur. Illustration by the author. Colored pencils on paper, 2015.

Hypsibema missouriensis faces off against a young dryptosaur. Illustration by the author. Colored pencils on paper, 2015.

For more on gigantic hadrosaurids and Appalachian localities, see these articles:

Antediluvian Beasts of the East : Hypsibema crassicauda

The Home of Some Antediluvian Beasts of the East : Ramanessin Brook 


1. The State Dinosaur”. State Symbols of Missouri. Missouri Secretary of State. URL: Accessed June 28, 2015.

2. Gilmore, C. W.; Stewart, D. R. .1945. “A New Sauropod Dinosaur from the Upper Cretaceous of Missouri”. Journal of Paleontology 19 (1): 23–29.

3. “Hypsibema missouriensis” Collections Search Center, Smithsonian Institution. Smithsonian Institution. URL: . Accessed June 28, 2015.

4. “Hypsibema crassicauda” Collections Search Center, Smithsonian Institution. Smithsonian Institution. URL: . Accessed June 28, 2015.

5. Baird, D.; Horner, J. R.  .1979. “Cretaceous dinosaurs of North Carolina”, Brimleyana 2: 1-28.

6. Weishampel, D. B.; Dodson, P.; and Osmólska, H. (eds.). 2007. The Dinosauria, 2nd Edition. Berkeley: University of California Press. p. 443.

7. “Hypsibema missouriense” Collections Search Center, Smithsonian Institution. Smithsonian Institution. URL: . Accessed June 28, 2015.

8. Fix, M. F.; Darrough, G. .2004. Dinosauria and associated vertebrate fauna of the Late Cretaceous Chronister site of southeast Missouri.” Geological Society of America Abstracts with Programs 36 (3): 14.


  1. It is nice to see our Missouri dinosaur getting some recognition. Thank you for throwing a spotlight on it.
    However, there are a few things in your blog that need to be revised. First of all, the species name should be “missouriense,” not “missouriensis.” The wrong species name was given to the state legislator (not by me) that drew up the bill to make it the state dinosaur. Back when it was Parrosaurus, missouriensis was correct, but when Horner and Baird transferred it to Hypsibema, then the species name had to be changed to the feminine form missouriense. A dinosaur specialist friend of mine thinks that it should be put back into Parrosaurus, so who knows, it could end up being missouriensis again.
    Second, in your photo of Missouri specimens from the Smithsonian (these are all casts by the way), you have labeled one of the specimens as a “skin impression.” It is a piece of the plastron of a beaded turtle, “Naomichelys speciosa.” No skin impressions are known from our site.
    Third, our listing of an ornithomimid in the 2004 talk, turns out to be incorrect. That fossil turned out to be a finger bone from the hand of Hypsibema.
    Finally, I have noticed that you have a habit of using the word “then” when you should be using the word “than.” “Then” indicates sequential timing of events, such as The dinosaur lifted its head and then ran away,” or time conditional situations such as, “When I am old enough, then I can vote. When you are comparing one thing to another, that is when you use the word “than,” such as “Hypisbema is bigger than Edmontosaurus.” A minor point perhaps, but it will add a little polish to your very nice blog.


    1. Thank you so much for commenting! The grammatical error you mentioned is something that often slips my mind, but recently I’ve tried to make time to further proofread these posts. Thank you for the information on the correct nomenclature of the Chronister hadrosaur. I had thought that missouriense pertained to the now defunct name “Parrosaurus”, and therefore Hypsibema missouriensis was the correct name of this taxon. In regards to the validity of the placement of the Chronister hadrosaur into Hypsibema, from what I have seen, it seems rather trivial to assign the Missouri material to the genus Hypsibema, as the holotype of the type species H. crassicauda consists of nothing more than bone fragments and a caudal centrum. I am sure that more complete specimens and further phylogenetic analyses will clear up the nomenclature.
      The information you provided on the “skin impression” is really helpful. I couldn’t find any papers reporting skin impressions from H. missouriense, and the only picture I could find of the specimen was the one shown above. I was suspicious of the fossil’s identity but I didn’t have anything better to rely on than the information on the Smithsonian’s collections database to rely on, so shame on me for not checking with someone working at the Chronister site prior to writing this post. I couldn’t find any more sources on the ornithomimid bone, so shame on me again. In the coming months I plan to rewrite this post, as well as those on H. crassicauda and O. immanis, and I will factor in this new information while writing the former of these three.

      I must ask if you and your colleagues at the Chronister site have found any more H. missouriense fossils. The prospect of a bone bed at the Chronister site is certainly an exciting one, especially since there is a dearth of information on the inhabitants of the western coast of Appalachia.

      I also want to inquire about the tyrannosaur remains you all found at the site. If you have found more than teeth, I would really appreciate it if you told me, especially since there is a chance the remains could belong to dryptosaurs.


      1. In answer to your questions, there has not been any excavation at the site since the Fall of 2008 when a film crew from “Flight 33 Productions” came to film a segment for a documentary titled “Prehistoric Chicago.” The reasojn for this is because in February 2009 a massive ice storm caused most of the greenhouse that covered the excavation to collapse. Guy has obtained a new greenhouse and this will be erected to replace the one that was destroyed.
        During this hiatus I have continued to prep specimens already excavated and have also been mapping a partial Hypsibema skeleton in a plaster jacket. There is a photo on the Bollinger County Museum website of me using a custom built device that uses meter sticks with laser pointers to map points on the specimen. You have a link on this page to that exact page. Normally, I would have mapped it insitu, but Guy was concerned for the safety of the specimen because of a break-in in which another specimen, cranial material, was damaged and some rib pieces were stolen. So, we put three marker points in the matrix and mapped them as references, so that the rest of the mapping could be done in the museum. This has proved to be quite a challenge and prompted me to have the mapping device built. This has sped up the mapping, but it is still the most tedious and mentally exhausting project that I have ever undertaken. However, the end is in sight. I have now mapped about 90% of it and should complete the mapping by year’s end. Once that is done, then I will begin the job of removing the bones from the matrix and reassembling the pieces. This partial skeleton appears to be from the same individual as the cranial material which was found next to it. It includes the scapula, corocoid, cervical vertebrae and processes, partial radius and ulna, cervical and dorsal rib pieces and other bones not yet identified.
        As to your other question regarding theropod remains. We have one tooth which Phil Currie has identified as Tyrannosaurid and some fragments of as yet unidentified limb bones. These limb fragments are identified as theropod based on the great thickness of lamellar bone. I hope that we find more bones from this beast, so that a better identification can be made. I have wondered if they could be from Appalachiosaurus.


      2. Yes, I am aware of the unfortunate collapse of the protective greenhouse, and the fact that research on the site hasn’t stopped altogether puts my mind at rest. It is interesting that you mentioned the possibility of the theropod material being from Appalachiosaurus, as I know others have suggested that as well. However, Appalachiosaurus montgomeriensis is only known from a partial specimen from the Demopolis Chalk Formation (vs. the Ripley Formation), so I’m leaning toward this animal being either a new species or genus. I agree with you that there is a possibility of the Chronister material being from an Appalachiosaurus, but due to the geographical and temporal differences between the respective formations and fossil sites from which these specimens were retrieved, referral of the Chronister specimens to Appalachiosaurus is tentative to say the least. Stinchcomb (2006) referred the remains at the site to Albertosaurus sp., which I support even less due to the known presence and wide distribution of large, “intermediate” tyrannosauroids on Appalachia combined with the dearth of tyrannosaurid remains found on the landmass, save for a couple referred teeth and bone fragments. Here’s hoping for you to pull out giant, recurved hand claw from the site!

        By the way, have you heard about the Tar Heel leptoceratopsid yet? Here’s the link to the abstract if you haven’t seen it yet:


      3. Yes, I have read the paper on the leptoceratopsian. Very intriguing, and I hope that they find more of it. Andrew McDonald, who recently earned a Phd under Peter Dodson, sent me a copy of it. He asked me to keep an eye out for ceratopsian bones at our site.
        He has become very interested in Hypsibema and has examined the cranial material. He has even done a preliminary cladogram based on the cranial material. He found it to be a very basal taxon. He is the one that has been referring to the beast as Parrosaurus, rather than Hypsibema.
        The reason that I thought that our theropod might be Appalachiosaurus is that Currie said that the tooth is from a tyrannosaurid, and Appalachiosaurus is a tyrannosauroid, not the same thing, I know, but I thought it more plausible than Albertosaurus or Daspletosaurus. Also, Alabama is not all that far, and there was continuous land between our site and Alabama – no epicontinental sea blocking the way. I really don’t have any strong opinions on its affinities one way or the other. I hope we do find more remains so that a more precise classification can be made. It would be great if it is a new genus or species.
        You mentioned the Ripley formation in your comment. It is not likely that our deposit is Ripley. For one thing, the Ripley as such does not occur in Missouri. “The Stratigraphic Succession in Missouri” does not list the Ripley among the Cretaceous of our state. The reference to it in the Gilmore and Stewart paper is in error. The Ripley is a Marine sequence, whereas our deposit is not strictly marine. Based on the fauna, especially the turtles and the fish, it is more likely either a freshwater lake, bayou or wetlands that some marine fish were able to reach, or it may have been an estuary. Also, the Ripley is Maastrichtian, but the faunal analysis done by Parris and Grandstaff concluded that the Chronister sediment is Campanian.


      4. I am also keeping a lookout for ceratopsian material among our collections (a lot of the stuff I work with at the Stamford Museum is from local sites and hasn’t been examined since the 1800s).

        In response to your second comment, I plead the 5th. We simply can’t conclude the presence of a certain dinosaur at the site described on the basis of partial remains from a couple of teeth.

        Thirdly, I was wondering about the Chronister site’s referral to the Ripley, and I see now it is unlikely. Do you think it belongs to a new formation, and if so, will there be a paper published on the site’s geological affinities in the near future?


      5. With regard to your question about the stratigraphy, as far as I know, this clay is an undesignated stratigraphic unit. I tried many years ago to get a local clastic sedimentologist interested in the deposit. I even sent him images of parts of it. Much to my disappointment, he did not reply to my email.
        Now that we are in preparation for starting a new excavation, I intend to try again to find a sedimentologist to assist us. I have felt for years that this unit needs to be formally designated.


      6. Hopefully you find someone to do a sediment analysis and description. I’ll do some searching as well now that I know you are in need of a clastic sedimentologist. I might be able to ask Mark Norell if he knows of anyone. However, when I last spoke with him at the AMNH he was getting ready for a multi-month trip to the Gobi (in classic AMNH style), and so I don’t know when exactly I’ll be able to inquire. For now, good luck on your search!


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