“Museum Diaries” is a six-part series commissioned by TVO to celebrate the inner workings of the Royal Ontario Museum during its centennial year. “Dinos Rediscovered” embarks on a stunning journey following the ROM Vertebrate Paleontology team on a field expedition to the Alberta badlands to discover treasures from 75 million years ago. This episode also features PM Project Manager Jason French and his team as they carefully deconstruct one of the ROM’s recent dinosaur exhibits, Ultimate Dinosaurs: Giants of Gondwana, and prepares the exhibition to travel to other Museum.
Learn more here.
Check out this fun and fanciful holiday ecard from talented paleoartist Danielle Dufault, which incorporates the latest data on the mysterious theropod Deinocheirus mirificus- now revealed to have stayed enigmatic so long due to strong connections with the master of secrecy Santa himself. Awesome job Danielle!
Today we formally announced publication of a new species of a small, meat-eating dinosaur (‘raptor’) based on newly discovered fossils from Montana, USA. Acheroraptor temertyorum is based on associated upper and lower jaw fossils from the Hell Creek Formation of Montana. It was relatively large for a “raptor”, approaching Deinonychus in size, with a long-snouted skull and dagger-like ridged teeth.
Acheroraptor was one of the last non-avian dinosaurs. It lived 67 to 66 million years ago in western North America, in a community that included Tyrannosaurus rex and Triceratops. As such, Acheroraptor gives us a more complete picture of the ecosystem in North America just before the great extinction that marked the end of the Age of Dinosaurs.
The unique ridged teeth of Acheroraptor have been recognized for decades, but the lack of reasonably complete diagnostic material did not permit determination of the taxonomic affinities and evolutionary relationships of the Hell Creek dromaeosaur until now. Interestingly, the jaw bones of Acheroraptor compare more closely to those of Velociraptor and other long-snouted Asian species than those of older North American species. Dromaeosaurid evolutionary relationships and biogeography will continue to be contentious. Phylogenetic analysis based on the dataset of Longrich and Currie (2009) recovered Acheroraptor as a velociraptorine dromaeosaurid, nested within a group of Asian species. The close evolutionary relationship of Acheroraptor to a group of late-occurring Asian species that includes Velociraptor suggests that migration from Asia may have continued to shape North American dinosaur communities right up until the end of the Cretaceous period.
The research describing Acheroraptor was published in the latest issue of Naturwissenschaften:
Evans, D. C., D. Larson, and P. J. Currie. 2013. A new dromaeosaurid (Dinosauria: Theropoda) with Asian Affinities from the latest Cretaceous of North America. Naturwissenschaften 100 (11): 1041-1049. Available online here.
The Press Release from the Royal Ontario Museum can be found here.
Caleb Brown successfully defended his Ph.D. in the Department of Ecology and Evolutionary Biology at the University of Toronto last week. His thesis is entitled “Advances in Quantitative Methods in Vertebrate Palaeobiology: A Case Study in Horned Dinosaur Evolution”. His thesis explores the limits of several quantitative methods in paleobiological research and applies best practices to a pioneering study on centrosaurine ceratopsid evolution based on specimens collected in Dinosaur Provincial Park, Alberta. This study is the first to quantify cranial morphological variation at essentially the population-level (based on huge collections from successive mass-death bonebeds), and employ sophisticated model-fitting methods to assess evolutionary modes in dinosaurs. In the analysis, he finds strong support for morphological stasis in Centrosaurus and Styracosaurus, and finds no evidence for directional evolution in these lineages.
ABSTRACT: Discerning modes and rates of biological evolution and speciation are some of the primary objectives of evolutionary biology. Much palaeobiological work has focused on developing robust methods for testing and fitting evolutionary models to samples of fossils across a stratigraphic or temporal axis, with most analyses centering on marine invertebrates. Recent extensive sampling of dinosaur deposits now allows for testing of evolutionary modes in this clade, a first for large-bodied terrestrial vertebrates. Within dinosaur palaeobiology, the relative roles of anagenesis and cladogenesis in diversification, particularly for horned dinosaurs, are hotly debated. Due to their large sample sizes, well-documented stratigraphic positions, highly diagnostic ornamentation, and monodominant bonebeds (representing populations), centrosaurine dinosaurs from the Belly River Group of Alberta make an ideal model system for testing the predictions of these two divergent evolutionary modes. Despite this unparalleled fossil record, it (as well as most fossil records) is limited by missing data, small sample size, taphonomic biases, and stratigraphic error. In this thesis, I present case studies that attempt to quantify and better understand these limitations, and inform best practices for overcoming them. The first four chapters, utilizing data sets for crocodilians (extant archosaurs) and a model geological system (upper Belly River Group), allow for a better- constrained quantitative evolutionary analysis of the Belly River Group centrosaurines in chapter five. Correlations and time-series analyses of morphology and stratigraphic position of Centrosaurus apertus and Styracosaurus albertensis are used to test for directional trends and evolutionary model fitting. Evolutionary results are robust to multiple simulations of stratigraphic uncertainty, and overlap between the taxa depends on a single locality. Results find no support for anagenesis, and rather are consistent with taxonomic turnover due to punctuated evolutionary events or, more likely, ecological replacement due to habitat tracking.”
Congrats to Caleb on completion of his degree, and I also want to thank him for all of his help in the lab and in the field over the last four years. Caleb is moving on to the position of Elizabeth Nichols Postdoctoral Fellow at the Royal Tyrrell Museum of Paleontology starting in December.
Congrats to Nic Campione for successfully defending his PhD thesis, which he handed in last week. Nic’s thesis was entitled “Inferring Body Mass in Extinct Terrestrial Vertebrates and the Evolution of Body Size in a Model-Clade of Dinosaurs (Ornithopoda)” (see abstract below).
ABSTRACT– Organismal body size correlates with almost all aspects of ecology and physiology. As a result, the ability to infer body size in the fossil record offers an opportunity to interpret extinct species within a biological, rather than simply a systematic, context. Various methods have been proposed by which to estimate body mass (the standard measure of body size) centering on two main methods: volumetric reconstructions and extant scaling models. The latter models are particularly contentious when applied to extinct terrestrial vertebrates, particularly stem-based taxa for which living relatives are difficult to constrain, such as non-avian dinosaurs and non- therapsid synapsids, resulting in the use of volumetric models that are highly influenced by researcher bias. However, criticisms of scaling models have not been tested within a comprehensive extant dataset. Based on limb measurements of 200 mammals and 47 reptiles, linear models were generated between limb measurements (length and circumference) and body mass to test the hypotheses that phylogenetic history, limb posture, and gait drive the relationship between stylopodial circumference and body mass as critics suggest. Results reject these and instead recover a highly conserved relationship that provides a robust method to estimate body mass in extinct quadrupedal tetrapods. The constrained model is then used to derive a mathematical correction that permits the body mass of bipedal taxa to be estimated from the quadrupedal-based equation. These equations thus form the empirical baseline dataset with which to assess the accuracy of mass estimates derived from volumetric reconstructions, which, although subjective, are crucial for interpreting biomechanical and physiological attributes in extinct forms. The models developed through this research provide accurate and consistent estimates of body size in terrestrial vertebrates, with important implications for generating large datasets aimed at reconstructing macroevolutionary patterns of body size in association with changing Earth systems.
Nic has already accepted a postdoctoral post at Uppsala University in Sweden, where he will be working with Drs. Ben Kear and Per Alhberg on Palaeozoic fish diversity and evolutionary dynamics- as well as dinosaur work. All of us in the lab wish him the very best in his new post!
Yesterday, a team of palaeontologists from the University of Toronto, Royal Ontario Museum, Cleveland Museum of Natural History and University of Calgary announced another new dinosaur, Albertadromeus syntarsus, the smallest plant-eating dinosaur species known from Canada. Albertadromeus was identified from a partial hind leg, and other skeletal elements, found in the Oldman Formation near the town of Manyberries in southern Alberta.
Albertadromeus lived in what is now southern Alberta in the Late Cretaceous, about 77 million years ago. Albertadromeus syntarsus means “Alberta runner with fused foot bones”. Unlike its much larger ornithopod cousins, the duckbilled dinosaurs, its two fused lower leg bones would have made it a fast, agile two-legged runner. Approximately 1.6 m (5 ft) long, it weighed about 16 kg (30 lbs), comparable to a large turkey.
The holotype specimen was found in 2009, during a joint fieldwork project conducted by the Royal Ontario Museum and Dr. Michael Ryan of the Cleveland Museum of Natural History.
The paper not only names a new taxon, but documents the the first articulated/associated thescelosaur skeletons from the exceedingly well sampled Belly River Group of Alberta, and provides a census of all thescelosaur specimens collected from this unit to date. The conclusion- their remains are much more abundant than previously recognized, and they were probably a lot more diverse as well. This research also contributes to a growing body of data suggesting preservational biases against the delicate bones of these small dinosaurs, in that they are less likely to be preserved than larger ones because they are destroyed before being fossilized, play a major role in shaping our perceptions of dinosaur ecosystems.
The research was led by Caleb Brown, currently a Ph.D. student in my lab at the University of Toronto, but who completed much of the work as part of his MSc thesis at the University of Calgary under the supervision of Dr. Anthony Russell. The paper was published as the Feature Article in the latest issue of the Journal of Vertebrate Paleontology, which features a reconstruction of Albertadromeus by Julius Csotonyi on the cover.
See the University of Toronto Press Release here.
Brown, C. M., D. C. Evans, M. J. Ryan, and A. P. Russell. 2013. New data on the diversity and abundance of small-bodied ornithopods (Dinosauria: Ornithischia) from the Belly River Group (Campanian) of Alberta. Journal of Vertebrate Paleontology 33(3):1–26. Available for free download here.
Study of pachycephalosaur fossil record hints at higher diversity of small-bodied ornithischians
Today, my research group reported on a new species of pachycephalosaur from Alberta, Canada, in the current issue of the Nature Communications (link here). Acrotholous audeti ( Ack-RHO-tho-LUS) was identified from both newly discovered and historically collected fossils. Approximately 6 feet long and weighing about 40 kgs in life, the newly identified plant-eating dinosaur represents the oldest definitive pachycephalosaur from North America, and possibly the World. Acrotholus provides a wealth of new information on the evolution of dome-headed dinosaurs. Although it is one of the earliest known members of this group, it’s thickened skull dome is surprisingly well-developed for its geological age. More importantly, detailed study of the unique fossil record of dome-headed dinosaurs highlights biases against the preservation of small dinosaur species, and suggests they were probably far more diverse than we currently know.
Acrotholus means “tall dome,” referring to the dome-shaped skull, which is composed of solid bone over 2 inches thick. The species name honors Alberta rancher Roy Audet, on whose land the best specimen was discovered. Acrotholous walked on two legs, and had a greatly thickened domed skull above its eyes, which was used as a visual signal to other members of its species, and may have also been used in head-butting contests. Acrotholous lived about 85 million years ago. The new dinosaur is based on two skull ‘caps’ from the Milk River Formation of southern Alberta. One of these was collected by the Royal Ontario Museum over 50 years ago, but the best specimen was found in 2008 by University of Toronto graduate student Caleb Brown during a field expedition organized by myself and Dr. Michael Ryan of the Cleveland Museum of Natural History.
Small mammals and reptiles can be very diverse and abundant in modern ecosystems, but small dinosaurs (<100 kg) are considerably less common than large ones in the fossil record. Whether this pattern is a true reflection of dinosaur ecosystems, or is an artefact related to the greater potential for small bones to be destroyed by carnivores and natural decay, has been debated. The massively constructed skull domes of pachycephalosaurs are resistant to destruction, and are much more common than their relatively delicate skeletons-–which otherwise closely resemble those of other small plant-eating dinosaurs. Therefore, we argue, the pachycephalosaur fossil record might provide insight into the diversity of small, plant-eating dinosaurs as a whole.
See Acrotholus in 3D via Digimorph: http://digimorph.org/specimens/Acrotholus_audeti/
Read the Press Release here.
Evans, D. C., R. Schott, D. Larson, C. Brown, and M. J. Ryan. 2013. The oldest North American pachycephalosaurid and the hidden diversity of small-bodied ornithischian dinosaurs. Nature Communications 4:1828. doi:10.1038/ncomms2749