Biology

Dromaeosaurids, tyrannosauroids, and a new website: late spring and summer 2018 at an Odyssey of Time

Hello everyone! I’m sorry I haven’t posted for a while, but I’ve been researching away on some exciting new discoveries! I do, however, want to share some of the recent highlights of my work.

A giant tyrannosaur from the Cenomanian

In March, my manuscript on a huge partial theropod metatarsal from ~95 million-year-old sediments in New Jersey was published in the Bulletin of the Yale Peabody Museum of Natural History (Brownstein, 2018a). Although the find is admittedly very fragmentary, it shares many features with the metatarsals of intermediate-grade tyrannosaurs like Appalachiosaurus and clades out nearby that taxon in a phylogeny of Tyrannosauroidea. The fossil is the first bone of a tyrannosaur reported from the Potomac Formation and the oldest known eastern North American occurrence of the clade.

Even more interestingly, the fossil shows tyrannosaurid-line tyrannosaurs had already achieved sizes of 6 or more meters during the Cenomanian, contrary to research on geologically younger Asian representatives of the group which has suggested a later date for the development of gigantism (e.g., Brusatte et al. 2016).

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The Potomac tyrannosaur. Photo by the author, 2017. 

The large dromaeosaurs of North Carolina

I also published on a large theropod tooth from the little known Clifton Farm site (Brownstein, 2018b), which also produced a possible ceratopsian maxilla described by Longrich (2016). A look at the morphology of the denticles of the tooth and inclusion of the specimen in a couple principle components analyses allow for its identification as the crown of a large dromaeosaurid, perhaps one slightly larger than Deinonychus. Here’s the catch: the tooth is from the Campanian, when very few mid-sized dromaeosaurids are known. Furthermore, the tooth is unlike any dromaeosaurid crown previously described from the southeastern US, suggesting there’s evidence for the existence of at least two species in the Campanian of southern Appalachia.

Theropod bones with feeding traces.

The most publicized of my recent papers came out in early June (Brownstein, 2018c). In it, I described two interesting theropod dinosaur limb bones from New Jersey in the collections of the Yale Peabody Museum. One had a number of pits (probably made by crocodyliforms) that caught my eye upon initially seeing the bone in a drawer with other eastern North American dinosaur bones. In addition, the bone seems to show evidence of invertebrate activity on its surface. A closer look at a partial ornithomimosaur femur revealed scores likely made by sharks. Both bones demonstrate the complex ecological interactions that were happening off the coast of eastern North America during the seven million years or so before the K-Pg extinction.

Ellisdale

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A large dromaeosaurid tooth from Ellisdale. Photo by the author, 2017.

I’m very excited to share that just today my paper on theropod dinosaur material from the Ellisdale site was published in the Journal of Paleontology. Although this highly fossiliferous locality was first discovered in 1980, no comprehensive description of any dinosaur material collected from it has previously been published. I identified the presence of several theropod clades on the basis of teeth and isolated limb material. Teeth at the site are referable to a number of different animals, including a very large dromaeosaurid, a smaller maniraptoran, and tyrannosauroids similar to Dryptosaurus and Appalachiosaurus. You can read the full paper, which was kindly made freely open-access by the journal, here.

New website

Today, I also finished making the final touches on my new website (chasebrownstein.wordpress.com). Here you can view my publications, summaries of my research projects, and notes on other science-related things I’ve been up to.

Overall, it’s been a productive, exciting spring and summer. As the academic year comes on the horizon, I’ll try to start blogging more again. Some very exciting projects are in the works, so please watch this space!

References.

Brownstein, C.D. (2018). Tyrannosauroid from the lower Cenomanian of New Jersey and its evolutionary and biogeographic implications. Bulletin of the Peabody Museum of Natural History 59(1):95–104. DOI: https://doi.org/10.3374/014.058.0210

Brownstein, C.D. (2018). A large dromaeosaurid from North Carolina. Cretaceous Research 92:1—7. DOI: https://doi.org/10.1016/j.cretres.2018.07.006

Brownstein, C.D. (2018). Trace fossils on dinosaur bones reveal ecosystem dynamics along the coast of eastern North America during the latest Cretaceous. PeerJ 6:e4973 (23 pp.). DOI: https://doi.org/10.7717/peerj.4973

Brownstein, C.D. 2018. The distinctive theropod assemblage of the Ellisdale site of New Jersey and its implications for North American dinosaur ecology and evolution during the Cretaceous. Journal of Paleontology 92(5): in press. 

 

 

 

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Paper Published: Appalachian Dinosaur Biogeography and Ecology

After four years of research, I am very pleased to announce that my paper reviewing all known Appalachian dinosaur faunas and analyzing Appalachian dinosaur biogeography and ecology was published in the journal Paleontologia Electronica (Brownstein, 2018). As usual, I will give an overview of the paper on this website.

In the past several years, we’ve learned a considerable amount about many aspects of Laramidian dinosaur biology, including their ecology, evolutionary relationships, and distribution. Such research has manifested in papers like Lehman (1997), Gates et al. (2010), Sampson et al. (2010), Gates et al. (2012), Sampson et al. (2013), etc. However, a major gap has persisted in the data, stemming from the poorly-documented fossil record east of the American Interior.

The new paper, which systematically reviews the dinosaurs of each fauna known from eastern North America and compares them using the Simpson similarity index, Jaccard coefficient, and Jaccard distance (e.g., Jaccard, 1902; Simpson, 1943), was written by me with the intention of helping to alleviate this issue.

My analyses seem to suggest several points about Appalachian dinosaur genera. Firstly, the data suggest that Appalachian dinosaurs represented relict forms surviving in isolation, an often-proposed hypothesis (Denton and O’Neill, 1995, 1998; Schwimmer, 1997; Kiernan and Schwimmer, 2004). Additionally, dinosaur provincialism on Appalachia seems to (maybe) be a thing, something proposed by Schwimmer (2016). Finally, competition between predatory dinosaurs and large crocodylians is also discussed, a topic that has actually attracted quite a lot of attention that has resulted in several extensive pieces of literature (e.g., Gallagher, 1995; Schwimmer, 2002; Noto et al., 2012).

I’d like to extend my utmost gratitude to all the researchers who provided me with information for this project and to everyone at PE for their helpfulness in getting this piece of research out there.

Refs.-

  1. Brownstein, CD. 2018. The biogeography and ecology of the Cretaceous non-avian dinosaurs of Appalachia. Paleontologia Electronica 21.1.5A: 1-56. DOI: https://doi.org/10.26879/801
  2. Lehman TM. 1997. Late Campanian dinosaur biogeography in the western interior of North America, p. 223-240. In: Wolberg D, Stump E, eds: Dinofest International Proceedings. Philadelphia Academy of Natural Sciences, Philadelphia,  USA.
  3. Gates TA, Sampson SD, Zanno, LE, Roberts, EM, Eaton, JG, Nydam RL, Hutchison JH, Smith JA, Loewen MA, Getty MA. 2010. Biogeography of terrestrial and freshwater vertebrates from the Late Cretaceous (Campanian) Western Interior of North America. Palaeogeography, Palaeoclimatology, Palaeoecology 291:371-387. https://doi.org/10.1016/j.palaeo.2010.03.008
  4. Sampson SD, Loewen MA, Farke AA, Roberts EM, Forster CA, Smith JA, Titus AL. 2010. New horned dinosaurs from Utah provide evidence for intracontinental dinosaur endemism. PLoS ONE 5(9):e12292.
  5. Gates TA, Prieto-Márquez A, Zanno LE. 2012. Mountain building triggered Late Cretaceous North American megaherbivore dinosaur radiation. PLoS ONE 7(8):e42135. https://doi.org/10.1371/journal.pone.0042135
  6. Sampson SD, Loewen MA, Roberts EM, Getty MA. 2013. A new macrovertebrate assemblage from the Late Cretaceous (Campanian) of southern Utah, p. 599-617. In: Titus AL, Loewen MA, eds: At the Top of the Grand Staircase: The Late Cretaceous of Southern Utah. Indiana University Press, Bloomington, USA.
  7. Jaccard P. 1902. Lois de distribution florale. Bulletin de la Socíeté Vaudoise des Sciences Naturelles 38:67-130.
  8. Simpson GG. 1943. Mammals and the nature of continents. American Journal of Science 241:1-31.
  9. Schwimmer DR. 1997. Late Cretaceous dinosaurs in Eastern USA: A taphonomic and biogeographic model of occurrences, p. 203-211. In: Wolberg E, Stump E, eds: Dinofest International Proceedings. Philadelphia Academy of Natural Sciences, Philadelphia, USA.
  10. Denton RK, O’Neill RC. 1995. Prototeius stageri, gen. et sp. nov., a new teiid lizard from the Upper Cretaceous Marshalltown Formation of New Jersey, with a preliminary phylogenetic revision of the Teiidae. Journal of Vertebrate Paleontology 15(2):235-253.
  11. Denton RK, O’Neill RC. 1998. Parrisia neocesariensis, a new batrachosauroidid salamander and other amphibians from the Campanian of eastern North America. Journal of Vertebrate Paleontology 18(3):484–494.
  12. Schwimmer DR. 2016. Was there a southeastern dinosaur province in the Late Cretaceous?. Geological Society of America Abstracts with Programs 48(3):22-23.
  13. Gallagher WB. 1995. Evidence of juvenile dinosaurs and dinosaurian growth stages in the Late Cretaceous deposits of the Atlantic Coastal Plain. Bulletin of the New Jersey Academy of Science 40:5-8.
  14. Schwimmer DR. 2002. King of the Crocodylians: The Paleobiology of Deinosuchus. Indiana University Press, Bloomington, USA.
  15. Noto CR, Main DJ, Drumheller, SK. 2012. Feeding traces and paleobiology of a Cretaceous (Cenomanian) crocodyliform: Example from the Woodbine Formation of Texas. Palaios 27(2):1-11.

Preprint Published: Tyrannosaur brains from the eastern US

Hi all! Just a little update here on my research. Yesterday, a preprint of mine (Brownstein, 2018) describing the first piece of a theropod braincase known from the Late Cretaceous of New Jersey was published at PeerJ Preprints. What follows is a little summary of the research.

As you all know, the fossil record of terrestrial animals from the Cretaceous of North America is poor, especially when compared to that of the American West. Nevertheless, recent discoveries have allowed us to fill in some of the gaps regarding eastern North American dinosaurs. One such gap is our record of dinosaur cranial material from the eastern United States. Material from the skulls of dinosaurs is super rare in this area, and so any chunk can potentially tell us a lot about eastern North American dinosaur anatomy and evolution.

One such specimen is the possible partial prootic (a bone on the side of the braincase) of a juvenile tyrannosauroid dinosaur collected in the mid-1990s from the Ellisdale site of New Jersey. The bone is actually in pretty good condition. The unfused sutures on all sides of the specimen and the prootic’s small size suggest it belonged to a juvenile animal, thus representing one of the few immature dinosaur specimens from northeastern North America.

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The prootic in question.

The prootic can tell us several things about eastern North American dinosaurs, including that their braincases were similar in several ways to those of mid-Cretaceous tyrannosauroids from Asia like Timurlengia (Brusatte et al., 2016). The morphology of the prootic overall supports the notion that Appalachian tyrannosauroids were evolutionarily somewhere between the Tyrannosauridae and the basal tyrannosauroids of the Jurassic and Early Cretaceous.

Stay tuned for more, and thanks for reading!

References.

Brownstein CD. (2018Prootic anatomy of a juvenile tyrannosauroid from New Jersey and its implications for the morphology and evolution of the tyrannosauroid braincasePeerJ Preprints6:e26467v1 https://doi.org/10.7287/peerj.preprints.26467v1

Brusatte SLAverianov ASues HDMuir AButler IB. 2016. New tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies evolution of giant body sizes and advanced senses in tyrant dinosaurs. Proceedings of the National Academy of Sciences of the United States of America 113(13):34473452

 

 

Antediluvian Realms of the East: the Tar Heel and Coachman Formations

Morning, and the orange and beige of a celestial titan rising through slivers of cloud coat the swampy landscape with a buzzing, ochre light. Gently sloping mountains in the far distance, each decorated in a single shade of green trees, are the first to grasp at the brightest rays of light from the sun. Giant azhdarchid pterosaurs, drowsy and chilled by the morning air, launch off of their craggy towers in the highlands to search for food in the swamps and marshes. Within a few minutes, they reach the sky above the lowlands and sink down towards waterways beckoning with a biological buffet. The loud morning calls of ancient insects, amphibians, reptiles, and birds illuminate a scene exclusive to the Campanian. The azhdarchids land by the side of a waterhole, already taking notice of some of their company in these marshes. Nearby, a small, rough-skinned leptoceratopsid rips off leaves from some low foliage as it grunts at a small lizard picking up droppings from the dinosaur’s morning feast. This sturdy dinosaur is related to the massive ceratopsids of the west, though here it lies in the shadows of other dinosaur species. The grey and aquamarine leptoceratopsid, taking notice of the azhdarchids, sniffs and scurries into the underbrush. 

Nearby, a flock of ornithomimosaurs stops to drink in the early morning sun. Brilliantly adorned in gleaming black, blue, and grey feathers, the ostrich-mimic dinosaurs huddle close together as they hydrate for the day ahead. Two males, both decked out in feathers designed to impress the females of the crowd, start to kick and peck at each other while displaying the brilliant patterns that spur from their forelimbs. Both males are soon driven off when a mixed heard of Lophorhothon and Hadrosaurus arrive by the side of the waterhole. At 8-9 meters in length, these are all medium-sized hadrosaurs, the Lophorhothon representing a more ancient lineage of duckbills than their Hadrosaurus companions. As the large herbivores lower their heads to drink, Saurornitholestes dromaeosaurs scamper out from their feet. These small predators would do well to mind the size and temper of the hadrosaurs. 

On the opposite side of the waterhole, a herd of true giants triumphantly marches out from the surrounding swamps and bayous. These are Hypsibema crassicauda, 15 meters long and 15 tons in weight, the largest animals of these lands. The herd of hadrosaurs, thirteen strong, lumbers toward the edge of the waterhole to drink. The massive skulls of the titans slowly gulp up the water as smaller dinosaurs and crocodylomorphs flee the scene. A large female Dryptosaurus, 9 meters from head to tail, is also deterred from a quick stop for water by the Hypsibema herd. Several fresh water turtles push themselves back into the murky water. 

Back on the other side of the waterhole, a disturbance spooks the hadrosaurs. Suddenly, an ornithomimosaur is pulled underneath the water. Just off of shore, the head a giant Deinosuchus crocodyliform emerges as the massive predator tries to gulp down the dead ornithomimosaur whole. The azhdarchids take off. They’ve had enough of the lowlands. 

For the majority of the 19th and 20th centuries, the Cretaceous animals of the Carolinas have remained obscure, with decades lacking in finds punctuated by tantalizing glimpses of Cretaceous Carolinian ecosystems by means of fragmentary specimens. Ebenezer Emmons, namer of the Adirondack mountains, described isolated teeth that would later be identified as those of the massive crocodylian Deinosuchus rugosus (e.g., Emmons, 1858; Schwimmer, 2002), an noted paleontologist Edward Drinker Cope designated hadrosaur remains from a marl pit in North Carolina as the type of Hypsibema crassicauda 11 years later (Cope, 1869).

However, the past forty years have seen revelations in our understanding of the Cretaceous species of these states, including the publication of several Cretaceous-age faunas from sites within them. New discoveries of terrestrial and aquatic vertebrates from the Carolinas have illuminated several biogeographic trends from the Cretaceous of North America, supporting the notion that Appalachia was a refugium for certain vertebrate groups like as non-tyrannosaurid tyrannosauroid and basal hadrosauroid dinosaurs.

In North Carolina, perhaps the most important (in terms of terrestrial fossils) site is Phoebus Landing, a tidal-estuarine deposit located near Elizabethtown (e.g., Miller, 1967; Baird and Horner, 1979; Weishampel and Young, 1996). This site, bearing sediments of the middle-late Campanian Tar Heel Formation (e.g., Baird and Horner, 1979; Weishampel and Young, 1996; Weishampel et al., 2004; Self-Trail et al., 2004; Schwimmer et al., 2015), has not only produced skeletal elements from at least four different dinosaur species, but has also preserved teeth and bones from the massive crocodylian Deinosuchus. Among the dinosaur remains discovered here are the morphologically odd (NB: distinct from adult H. foulkii) massively constructed vertebrae of the giant (12+ meter long) hadrosauroid Hypsibema crassicauda (e.g., Baird and Horner, 1979; Weishampel and Young, 1996). Additional evidence of supermassive hadrosauroids in the Tar Heel Formation ecosystem comes in the form of a massive partial humerus only outsized by that of Magnapaulia from Phoebus Landing (Baird and Horner, 1979). Unfortunately, the fragmentary nature of these specimens means that, for now, only tantalizing glimpses of the Cretaceous giants that must have once roamed the Carolinas have been afforded by the marls. Specimens comparable to the corresponding elements in Hadrosaurus foulkii have also been recovered from the sediments at Phoebus Landing (e.g., Baird and Horner, 1979; Weishampel and Young, 1996), and Miller (1967) suggested the presence of “Hadrosaurus minor” (a dubious species of New Jersey hadrosaur possibly representative of juveniles of indeterminate genera) in the fauna present at the site. Finally, specimens comparable to the hadrosauroid Lophorhothon atopus have been recovered (e.g., Baird and Horner, 1979; Weishampel and Young, 1996). From all of this, it seems safe to conclude that two to three species of hadrosaurid were present in the Tar Heel fauna at Phoebus Landing. Importantly, a partial jawbone from a site nearby Phoebus Landing was recently described as Appalachia’s first neoceratopsian (Longrich, 2016).

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Fossils from Phoebus Landing were probably deposited in a tidal or estuarine setting. Photo by the author, 2017. 

 

Theropods also left an important record at Phoebus Landing. Teeth and hindlimb elements possibly referable to Dryptosaurus aquilunguis have been recovered and described from the site, as have ornithomimosaur bones and dromaeosaurid teeth (e.g., Miller, 1967; Baird and Horner, 1979; Weishampel and Young, 1996; Kiernan and Schwimmer, 2004). Along with the data from ornithischian remains, the Tar Heel supported at least seven different dinosaur genera.

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Lophorhothon and other hadrosauroids from the Tar Heel Formation were probably similar in form to Claosaurus (above). Photo by the author, 2017. 

Of overlapping time and geographically adjacent to the Tar Heel Formation is Coachman Formation, which in South Carolina has recently been found to contain several species of dinosaur. Schwimmer et al. (2015), in their extensive review of several sites with Coachman Formation outcrops, described remains assignable to the tyrannosauroid Appalachiosaurus montgomeriensis, the dromaeosaurid Saurornitholestes langstoni, at least one additional dromaeosaurid represented by teeth, indeterminate ornithomimosaurs, indeterminate maniraptorans, specimens comparable to “hadrosaurines”, and indeterminate hadrosauroid and ornithischian material. In addition, many species of turtles, fish, and crocodylians (including Deinosuchus) were described by Schwimmer et al. (2015) from Coachman Formation sediments, further bettering our understanding of that ecosystem.

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The dromaeosaurid Saurornitholestes would have been similar to Velociraptor (skull imaged above). Photo by the author, 2015. 

 

The Tar Heel and Coachman Formations represent important glimpses of Cretaceous life in the Carolinas that are becoming clearer with new research into their faunas. The formations’ geographic location, sandwiched between the historically notable fossiliferous formations of New Jersey and Delaware and the more recently recognized ones of the states of Alabama, Mississippi, Tennessee, Missouri, and Georgia, mean the faunas of the Tar Heel and Coachman are essential to our understanding of the biogeography of vertebrates on Appalachia. What remains to be discovered in these deposits will certainly reveal more and more about the life forms of the obscure landmass that sat east of the Western Interior Seaway over 68 million years ago.

For more on some of the dinosaurs of the Tar Heel and Coachman Formations, see these previous posts:

Antediluvian Beasts of the East: Hypsibema crassicauda

Antediluvian Beasts of the East: Dryptosaurus aquilunguis 

PaleoNews #18

References.

Schwimmer DR. 2002. King of the Crocodylians: the Paleobiology of Deinosuchus. Bloomington: Indiana University Press.

Cope ED. 1869. Remarks on Eschrichtius polyporusHypsibema crassicaudaHadrosaurus tripos, and Polydectes biturgidusProceedings of the Academy of Natural Sciences of Philadelphia 21:191-192.

Miller HW. 1967. Cretaceous Vertebrates from Phoebus Landing, North Carolina. Proceedings of the Academy of Natural Sciences of Philadelphia 119:219-239.

Baird D and Horner JR. 1979. Cretaceous dinosaurs of North Carolina. Brimleyana 2:1-28.

Weishampel DB and Young L. 1996. Dinosaurs of the East Coast. Baltimore: Johns Hopkins University Press. 

Weishampel DB, Barrett PM, Coria RA, Loeuff JL, Xing X, Xijin Z, Sahni A, Gomani EMP, and Noto CR. 2004. Dinosaur Distribution. In: Weishampel DB, Dodson P, and Osmólska H, eds: The Dinosauria, 2nd Edition. Berkeley: University of California Press. p. 517-617.

Self-Trail JM, Christopher RA, Prowell D, and Weems RE. 2004. The Age of Dinosaur-Bearing Strata at Phoebus Landing, Cape Fear River, North Carolina. Geological Society of America Abstracts with Programs 36(2):117.

Schwimmer DR, Sanders AE, Erickson BR, and Weems RE. 2015. A Late Cretaceous Dinosaur and Reptile Assemblage from South Carolina, USA. Transactions of the American Philosophical Society 105(2):1-157.

Longrich NR. 2016. A ceratopsian dinosaur from the Late Cretaceous of eastern North America, and implications for dinosaur biogeography. Cretaceous Research 57:199-207.

Kiernan K and Schwimmer DR. 2004. First record of a Velociraptorine theropod (Tetanurae, Dromaeosauridae) from the eastern Gulf Coastal United States. The Mosasaur 7:89-93.