Sunday, 7 December 2014

Ornithomimosaurs - bird mimicking dinosaurs

Ornithomimosaurs, literally bird-mimic-lizards, are a group of dinosaurs (if you hadn't guessed from the post's title) that I spent my PhD working on. They belong to the theropod lineage, the group of dinosaurs associated with meat eaters like T. rex and Velociraptor that eventually give rise to birds. Worth remembering at this point that dinosaurs are not extinct, the non-avian ones are, the avian dinosaurs (birds) are still going and remain more diverse than mammals. The ornithomimosaurs got their names when the first specimens were found back in the late 1800s around the end of the "Bone Wars" between Edward Drinker Cope and Othniel Charles Marsh. It was Marsh who got there first, describing Ornithomimus velox in 1890 based on the remains of a partial fore- and hindlimb from North America. Marsh went on to name several other species of which most are no longer considered valid and are believed to be tyrannosaurid (a common issue) or alvarezsaurid. The reason for this recurring issue is the bird-like nature of the metatarsus in many theropods which were grouped into Arctometatarsalia. This is now a defunct group as it was realised to be a convergent characteristic in theropods.

Holotype of Ornithomimus velox showing the arctometatarsalian condition of the third metatarsal being pinched between II and IV (Marsh 1890).

It was Marsh who thought that Ornithomimus were first ornithopods, until the discovery of a more complete skeleton. A new discovery by Lambe (the ornithomimosaur record is basically a who's who of palaeontologists) in 1902 lead to the naming of Ornithomimus altus which by 1916 would become Struthiomimus altus (Osborne) and the second genera in the clade. As with Ornithomimus there have been many species added into the Struthiomimus genus, although most have been grouped into S. altus. There was to be one more major addition to the Ornithomimus that would stick being Ornithomimus edmontonicus which was named in 1933 by Charles Sternberg from the famous fairly complete skeleton now found in the Canadian Museum of Nature. Between Struthiomimus and Ornithomimus there exist many complete (or as close as you can often get in palaeontology) skeletons giving a very good insight into their anatomy. There may be several additional species from North America: Dromeciomimus (which still appears in some literature, but studies suggest it is probably a junior synonym for Ornithomimus); an unnamed large ornithomimosaur which was discovered in the Royal Tyrell collections as pieces originally (and currently) within the tyrannosaur collections; and several more specimens previously described and lumped in with others that may be split back out.

In 1933, the first ornithomimosaurs from outside of North America were discovered. Archaeornithomimus (originally Ornithomimus) was described from Mongolia. It was to take many years before its reclassification as a separate genus (Russell, 1972 in fact), and until that decade no other new genera were described. The 1970s marked the reinvigoration of ornithomimosaur finds with joint Soviet expeditions to Mongolia. Deinocheirus first came to light in 1970 as a massive pair of arms (which no-one was certain what they belonged to), and with recent excavations has turned out to be one of the craziest looking dinosaurs (let alone ornithomimosaurs) found. The massive arms partner with a large body with a small sail over its pelvis, and a relatively small and very hadrosaur/duck-billed skull (Lee et al., 2014).

Deinocheirus with is massive arms, and its pelvic sail by Michael Skrepnick

Following on from Deinocheirus, Gallimimus was described in 1972 providing complete skeletal material from a range of different sized/aged animals. Following on from those taxa, the 1980s added more Mongolian taxa: Garudimimus; Harypmimus; Anserimimus.In 1990 the first European ornithomimosaur was discovered, Pelecanimimus, which wasn't only the most basal of known ornithomimosaurs, it also possessed the most teeth of any known theropod, and preserved with the remains of soft tissue including a gular (throat) pouch from which it derived its pelican-mimic name.

Map of ornithomimosaur fossil locales. Each colour represents a different taxa. The specimen in Australia is almost certainly not ornithomimosaurian, but the presence of ornithomimosaurs in South Africa suggests there should be members in the other Gondwanan continents (S. America, Australia and Antarctica). From Palaeobiology Database.

The 2000s have led to many more discoveries of ornithomimosaurs, not least driven by the opening up of many sites within China. Hexing, Shenzhousaurus, Sinornithomimus, Qiupalong, Beishanlong all quickly joined the literature, as have ornithomimosaurs from Africa (Nqwebasaurus - with the Nq actually being a click sound from the Xhosa language in South Africa and thus being one of my favourite dinosaur names) and Thailand. Other unnamed taxa have been found in Bulgaria, Japan, France and Kazakhstan and await further description/material.

Barsbold, 1976
Nqweba =Kirkwood Fm. in Xhosa
de Klerk et al., 2000
N. thwazi
Xhosa for fast funner
Choiniere et al., 2012 assigns to ornithomimosaurs
Pérez-Mereno et al.,1994
P. polyodon
Many teeth
Pérez-Mereno et al.,1994
Ancient name for China-lizard
Ji et al., 2003
S. orientalis
Of the orient
Ji et al., 2003
“Like a crane” in Chinese
Liyong et al., 2012
H. qingyi
“with slender wings” in Chinese
Liyong et al., 2012
Harpy – Greek mythology
Barsbold and Perle, 1984
H. okladnikovi
Named after AP Okladnikov
Barsbold and Perle, 1984
Being from Thai mythology
Buffetaut et al., 2009
K. khonkaenensis
From Khon Kaen
Buffetaut et al., 2009


Lee et al. 2014
White Mountain Dragon
Makovicky et al., 2010
B. grandis
Makovicky et al., 2010
Garuda (Mongolian mythology)-mimic
Barsbold, 1981
G. brevipes
Short foot
Barsbold, 1981
Osmόlska and Roniewicz, 1970
D. mirificus
Osmόlska and Roniewicz, 1970


Marsh, 1890
Marsh, 1890 (including Dromiceiomimus Russell, 1972)
O. velox
Marsh, 1890
O. edmontonicus
From Edmonton
Stemberg, 1933 (including Struthiomimus currelli Parks, 1933; S. brevitertius Parks, 1926; S. ingens Parks, 1933; S. samueli Parks, 1928)
Osborn, 1917
S. altus
Lambe, 1902 (Ornithomimus altus Lambe, 1902)
Russell, 1972
A. asiaticus
From Asia
Gilmore, 1933 (= O. asiatcus Gilmore, 1933)
Osmόlska et al., 1972
G. bullatus
From Latin bulla – ref to parasphenoid
Osmόlska et al., 1972
Kobayashi and Lü, 2003
S. dongi
Discoverer = Dong
Kobayashi and Lü, 2003
Barsbold, 1988
A. planinychus
Flat claw
Barsbold, 1988
Quipa Formation, long = dragon
Xu et al., 2011
Q. henanensis
Henan Province
Xu et al., 2011


Unnamed specimen from Alberta

Longrich, 2008
Bulgarian ornithomimid

Mateus et al., 2010
Ornithomimidae indet

Alifanov and Averianov, 2006
Ornithomimidae indet

Averianov, 2006
French ornithomimosaur

Néraudeau et al., 2012
Japanese ornithomimosaur

Hasegawa et al., 1999

Phylogeny and Phylogenetic Positions
So I've said all about ornithomimosaur discoveries, but how do they all relate?

Cuff 2014. Composite tree of Ornithomimosauria (Based on phylogenies from: Lee et al., 2013 SVP; Makovicky et al., 2004; Xu et al., 2011; Choiniere et al., 2012; Makovicky et al., 2010; Buffetaut et al., 2009. Ornithomimosauria - 1, Ornithomimidae - 2, Deinocheiridae - 3.

I based that tree on a composite of all known phylogenies up until my hand-in, and what I could remember of the Deinocheiridae from the Lee et al. 2013 SVP talk. Since then, the overall topology is roughly the same with better resolution within the Deinocheiridae:

Modified from Lee et al., 2014

The phylogeny does suggest that we have some big gaps to fill in the ornithomimosaur fossil record based on the ghost lineages (the length of time between the known appearance of taxa, and where they separate from their relatives), particularly for Harpymimus and Deinocheirus.

So that's the inter-relationships of the ornithomimosaurs, but where do they fit within the theropods as a whole?
Cuff 2014 SVP talk. Modified from Choiniere et al., 2013 and Lee et al., 2014.

The ornithomimosaurs consistently fall out close to the compsognathids (the little dinosaurs in Jurassic Park that chirp and attack the girl in the beginning of the second film) and close to the tyrannosaurs. This phylogenetic closeness, and convergence within the metatarsals (foot bones) means that the feet of small tyrannosaurs and large ornithomimosaurs look very similar and sometimes cause confusion as with the large North American ornithomimosaur. The ornithomimomsaur position in theropods is within Coelurosauria, but just below the Maniraptora. For most laypeople that means nothing, but it helps us define the position easily, and is important for studying patterns of character change (and diet which I will come back to later).

Soft tissues
So I mentioned Pelecanimimus possessed a gular pouch, but it also seems to have possessed some form of soft tissue crest too. It, however, does not seem to possess feathers (or at least they aren't preserved). This is a bit strange as it is known feathers are found throughout theropods, as well as it seems in some of the Ornithischia. It is even more strange that Ornithomimus has feathers (Zelenitsky et al., 2012). Ornithomimus feathers are interesting because they appear to change through growth (ontogenetically) with small members being fluffy, with large individuals having large pennaceous feathers. This discovery has been suggested that wings may have first developed for sexual display.

Feathered Ornithomimus reconstructions based on Zelenitsky et al. (2012) showing the ontogenetic differences in feathering. Artwork by Julius Csotoyni (a great palaeoartist - check out his other work)

Feathers had been suggested to be also sexual display within oviraptorosaurs with pygostyles, so this fits nicely (and explains the Nature paper for what otherwise is a boring story as we already knew tyrannosaurs had feathers by 2012, so expected ornithomimosaurs to have them). An interesting find on orrnithomimosaurs (or at least two specimens) is the preserved keratinous rhamphothecae (beak - although technically that is the keratin layer and bone, but I will talk beaks from now on when I mean rhamphothecae). Indeed it is these beaks (or equally lack of teeth) that has led to many discussions on what ornithomimosaurs ate.

The two ornithomimosaur specimens preserving the keratinous rhamphothecae. Top is Ornithomimus edmontonicus (RTMP 95.110.1), Middle is Gallimimus bullatus (IGM100/1133), with the bottom an enlargement of the premaxilla from the same G. bullatus specimen (Norell et al. 2001).

In ornithomimosaur crania the loss of teeth and the preservation of soft tissue remnants of rhamphothecae has drawn more specific focus (Norell et al., 2001; Barrett, 2005). The remnants of columnar structures in the rhamphotheca in a specimen of Gallimimus (GIN 100/1133) led to comparisons with lamellae in the beaks of anseriforms, particularly a filter-feeding straining species, Anas clypeata (Norell et al., 2001). A re-examination of the fossil showed that these structures are the keratinous rods vital for the structure of a rhamphotheca and found in many other taxa (Barrett, 2005). In addition, the lack of retracted nares, a small depressor mandibulae, a potentially wide gape (Barsbold and Osmólska, 1990) and a calculation of energetics required for filtering suggest this was not a possible ecological niche for ornithomimosaurs (Barrett, 2005).

Interestingly the filtering/predating on freshwater invertebrates was not a new idea (Osborn, 1917), and was one of many hypotheses for ornithomimid feeding. In addition, the following have all been suggested at some time or another: a browsing, herbivorous lifestyle (Osborn, 1917); myrmecophagous (anteater-like) habits (Osborn, 1917); omnivorous but limited to soft food – eggs, fruits, invertebrates and small vertebrates (Barsbold and Osmόlska, 1990); or predatory, but restricted to small vertebrates, insects and possibly eggs (Osmόlska et al., 1972; Russell, 1972). All of these suggestions were based upon cranial morphology, but have never been tested. Indeed, Paul (1988) noted that many of the assumptions of weak skulls with limited adductor musculature overlooked similarities to dinornithid birds (such as bracing in the quadrate and jaw joints) and ornithomimosaurs may in fact have skulls stronger than previously suggested. I spent my PhD reconstructing skulls of several taxa and carrying out functional tests upon the skulls under different feeding regimes to finally test some hypotheses.

The most widely accepted hypothesis for ornithomimosaur diets is that they were herbivorous (or at least mainly herbivorous). A series of papers by Lindsay Zanno and colleagues (Zanno et al., 2009; Zanno and Makovicky, 2011) suggested that there were a series of characters found throughout dinosaurian lineages that could be correlated with herbivory e.g. loss of teeth in upper and lower jaws, presence of gastroliths etc. etc. Zanno and colleagues posit that around the base of the mainraptoriformes there is a transititon from carnivory to herbivory based on the acquisition of these correlates within many of the dinosaurs belonging to this group. Ornithomimosaurs possess all the correlates so are expected to be herbivorous. Despite the presence of many specimens containing gastroliths (granted most are Sinornithomimus [Kobayashi et al., 2001; Kobayashi and Lü, 2003], there had been no evidence of any food remains in the stomach cavities/within the gastrolith masses until the discovery (perhaps unsurprising as plant material often doesn't preserve as well as bones) and description of Deinocheirus (Lee et al., 2014) where some fish bones were found in the stomach area with gastroliths. The authors suggest that Deinocheirus was probably omnivorous consuming fish and plant material as its diet.

Deinocheirus stomach contents (Lee et al. 2014).

Group living
Jurassic Park first showed ornithomimsaurs (or at least Gallimimus) running around in flocks like birds. To give Jurassic Park credit on this, there is a fair amount of evidence that ornithomimosaurs were indeed group living (or at least several species were).

Two clips from Jurassic Park (1993) showing Gallimimus flocking. The bottom clip is entertaining as one of the other Gallimimus in the background (arrowed) actually stops to watch the unlucky one get munched by the T. rex. I can't decide if it's supposed to show some level of bonding/care between individuals, but do look out for it next time you watch!

There have been findings of ornithomimosaurs skeletons in relatively close association with each other relatively early on, however very little is written about their group living until the discovery of Sinornithomimus (Kobayashi et al., 2001; Kobayashi and Lü, 2003) where 14 skeletons were found in very close association, and a further expedition found another 13 in another association. In both of these groups there are a small number of sub-adults to adults with the majority being juvenile individuals and it has been suggested they got trapped in a drying mudhole.

Block containing  8 individuals of Sinornithomimus dongi (Kobayashi and Lü, 2003).

Since then, a description of three North American ornithomimids found together by Sternberg in 1926 has appeared in the literature (Cullen et al., 2013). In addition there is a large ornithomimosaur bone-bed from France that may suggest that more primitive ornithomimosaurs (and not just ornithomimids) also lived in groups (Néraudeau et al., 2012).

Since the discovery of the first ornithomimosaur foot, it was realised they were very bird like, and indeed with the naming of Struthiomimus the convergence with the ostrich (Struthio) was laid bare. All ornithomimosaurs, except the screwy Deinocheirus, have elongate legs and are believed to be relatively rapid runner. They have adapted so much to high speed running that their claws on their feet have all become very flat (very similar to that of the ostrich). Muscle reconstruction of the hindlimb in Dromeciomimus(Ornithomimus) suggests that the hindlimb muscle moment arms were comparable to those of the ostrich, the fastest of the terrestrial avians presently alive, whilst Struthiomimus had smaller muscle forces and might not have been quite as quick (Russell, 1972). The construction and articulation of the limb bones as well as ontogenetic scaling suggest that ornithomimosaurs of all sizes were probably using a combination of endurance and speed to outrun predators (Paul, 1998). Of importance seems to be the arctometatarsalian foot. Such morphology appears to have evolved to evenly transmit forces to the metatarsals, this hypothesis being tested using finite element modelling (Snively and Russell, 2002) principal component and thin-plate spline analyses (Snively et al., 2004).

Much has been made of ornithomimosaur brains, with all of the literature suggesting that they have relatively large brains:

REQ (reptile encephalisation quotient - a measure of relative brain size to body mass for reptiles) for various archosaur groups. Dromecieomimus (Ornithomimus) is shown here having brains comparabale to the low end of Troodon (considered the relatively biggest brained of non-avian dinosaurs). From Lautenschlager et al., 2012.

However, I have done some reconstructions on three taxa using the same metrics, and come up with far smaller REQs (comparable to Erlikosaurus [Lautenschlager et al., 2012), and indeed work presented at SVP this year showed that Deinocheirus has an REQ similar to that of Brachiosaurus in the above image. Wait for official publications to confirm these findings, but it perhaps shouldn't be surprising seeing that ornithomimosaurs have relatively small heads (probably associated with their relatively long necks). This isn't to say they weren't smart; group living does involve a reasonable level of social interaction and cognition

Ignoring their brains (which have limited description to date so I don't want to say much on inferring the sense of smell) the other major sense for ornithomimosaurs is their vision. Ornithomimosaurs have quite large orbits.

Ornithomimus edmontonicus (RTMP 95.110.1) showing off its large circular orbits. 

The large orbits of ornithomimosaurs (Makovicky et al., 2004) would likely have hosted large eyes, Within the eyes of many dinosaurs are sclerotic rings, which are rings of bones that all articulate much like a camera diaphragm, and help keep shape and potentially help adjust the amount of light coming in. Ornithomimosaurs indeed possess relatively large sclerotic rings too (Schmitz and Motani, 2011). This suggests that vision played a large, if not the largest factor in ornithomimosaurian habits. The enhanced visual abilities may have been for locating edible plants or flowers and undoubtedly played a vital role in escaping predators by early detection (Russell, 1972). It has also been suggested that their enlarged orbits allowed mesopic behaviour (in all light levels: Schmitz and Motani, 2011) at least in Ornithomimus, furthered by some potential ornithomimosaurian finds from polar regions where it is dark for many months in winter (Watanabe et al., 2013).

Hopefully that gives you all an insight into the group of dinosaurs that I spent 3 and a bit years of my life working on. They are truly a cool group of dinosaurs and it's not because of big teeth and curved sharp claws, but because they have beaks, massive eyes, crazy feathers, ran around in groups at high speed, and if you trust Jurassic Park they stop to watch their flock-mates get eaten.

References (if you care)
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Averianov AO, 2006. On an ornithomimid dinosaur (Saurischia, Ornithomimosauria) from the Cenomanian of Fergana. Paleontological Journal 40, 323-327.

Barrett PM, 2005. The diet of ostrich dinosaurs (Theropoda: Ornithomimosauria). Palaeontology 48, 347-358.

Barsbold R, 1976. K evolyutsii i sistematike pozdnemezozoyskikh khishchnykh dinozavrov [The evolution and systematics of late Mesozoic carnivorous dinosaurs]. In N. N. Kramarenko, B. Luvsandansan, Y. I. Voronin, R. Barsbold, A. K. Rozhdestvensky, B. A. Trofimov & V. Y. Reshetov (eds.), Paleontology and Biostratigraphy of Mongolia. The Joint Soviet-Mongolian Paleontological Expedition, Transactions 3, 68-75.

Barsbold R, 1981. Bezzubyye khishchnyye dinozavry Mongolii. Sovmestnaia Sovetsko-Mongol’skaia Paleontologicheskaia Ekspeditsiia Trudy 15, 28-39.

Barsbold R, 1988. A new Late Cretaceous ornithomimid from the Mongolian People's Republic. Paleontological Journal 22, 124-127.

Barsbold R, Osmόlska H, 1990. Ornithomimosauria. 225-244. in Weishampel DB, Dodson P, and 
Osmólska H, (eds.) The Dinosauria. University of California Press, Berkley, Los Angeles, Oxford, 1990, xvi-733.

Barsbold R, Perle A, 1984. [On first new find of a primitive orithomimosaur from the Cretaceous of the MPR]. Paleontologicheskii zhurnal 2, 121-123.

Buffetaut E, Suteethorn V, Tong H, 2009. An early 'ostrich dinosaur' (Theropoda: Ornithomimosauria) from the Early Cretaceous Sao Khua Formation of NE Thailand, pp. 229-243 IN E. Buffetaut, G. Cuny, J. Le Loeuff & V. Suteethorn (eds.), Late Palaeozoic and Mesozoic Ecosystems in SE Asia. Geological Society, London, Special Publications 315, 229-243.

Choiniere JN, Forster CA, de Klerk WJ, 2012. New information on Nqwebasaurus thwazi, a coelurosaurian theropod from the Early Cretaceous (Hauteriverian?) Kirkwood Formation in South Africa. Journal of African Earth Sciences 71-72, 1-17.

Cullen TM, Ryan MJ, Schröder-Adams C, et al., 2013. An ornithomimid (Dinosauria) bonebed from the Late Cretaceous of Alberta with implications for the behavior, classification and stratigraphy of North American ornithomimids. PLoS ONE 8(3): e58853. doi:10.1371/journal.pone.0058853

Cuff AR, 2014. Functional mechanics of ornithomimosaurs.PhD Thesis. University of Bristol, Bristol, UK.

de Klerk WJ, Forster CA, Sampson SD, et al., 2000. A new coelurosaurian dinosaur from the Early Cretaceous of South Africa. Journal of Vertebrate Paleontology 2, 324-332.

Gilmore CW, 1933. On the dinosaurian fauna of the Iren Dabasu Formation. Bulletin of the American Museum of Natural History 67, 23-78.

Hasegawa Y, Manabe M, Kase T, et al., 1999. An ornithomimid vertebra from the Early Cretaceous Sebayashi Formation, Sanchu Terrane, Gunma Prefecture, Japan. Bulletin of the Gunma Museum of Natural History 3, 1-6.

Ji Q, Norrell M, Makovicky PJ, et al., 2003. An early ostrich dinosaur and implications for ornithomimosaur phylogeny. American Museum Novitates 3420, 1-19.

Kobayashi Y, Lü J-C, 2003. A new ornithomimid dinosaur with gregarious habits from the Late Cretaceous of China. Acta Palaeontologica Polonica 48, 235-259.

Kobayashi Y, Lü J-C, Dong Z-M, et al., 1999. Herbivorous diet in an ornithomimid dinosaur. Nature 402, 480-481.

Lambe L, 1902. New genera and species from the Belly River Series (mid-Cretaceous). Geological Survey of Canada Contributions to Canadian Palaeontology 3, 25-81.

Lautenschlager S, Rayfield EJ, Alangerel P, et al., 2012.The endocranial anatomy of Therizinosauria and its implications for sensory and cognitive function. PLoS ONE 7(12): e52289.

Lee YN, Barsbold R, Currie, PJ, et al., 2014. Resolving the long-standing enigmas of a giant ornithomimosaur Deinocheirus mirificus.Nature 515 (7526), 257–260.

Liyong J, Jun C, Godefroit P, 2012. A New Basal Ornithomimosaur (Dinosauria: Theropoda) from the Early Cretaceous Yixian Formation, Northeast China. In Godefroit, P. (eds). Bernissart Dinosaurs and Early Cretaceous Terrestrial Ecosystems. Indiana University Press 467-487.

Longrich N, 2008. A new, large ornithomimid from the Cretaceous Dinosaur Park Formation of Alberta, Canada: implications for the study of dissociated dinosaur remains. Palaeontology 51, 983-997.

Makovicky PJ, Li Daqing, Gao K-Q, et al., 2010. A giant ornithomimosaur from the Early Cretaceous of China. Proceedings of the Royal Society B 277, 191-198.

Marsh OC, 1890. Description of new dinosaurian reptiles. The American Journal of Science 3, 81-86.

Mateus O, Dyke GJ, Motchurova-Dekova N, et al., 2010. The first record of a dinosaur from Bulgaria. Lethaia 43, 88-94.

Néraudeau D, Allain R, Ballèvre M, et al., 2012. The Hauterivian-Barremian ligntic bone bed of Angeac (Charente, south-west France): stratigraphical, palaeobiological and palaeogeographical implications. Cretaceous Research 37, 1-14.

Norell MA, Makovicky P, Currie PJ, 2001. The beaks of ostrich dinosaurs. Nature 412, 873-874.

Osborn HF, 1917. Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus. Bulletin of the American Museum of Natural History 35, 733-771.

Osmólska H, Roniewicz E, 1970. Deinocheiridae, a new family of theropod dinosaurs. Palaeontologica Polonica 21, 5-19.

Osmólska H, Roniewicz E, Barsbold R, 1972. A new dinosaur, Gallimimus bullatus n. gen., n. sp. (Ornithomimidae) from the Upper Cretaceous of Mongolia. Palaeontologia Polonica 27, 103-143.

Parks WA, 1926. Struthiomimus brevetertius - A new species of dinosaur from the Edmonton Formation of Alberta. Transactions of the Royal Society of Canada 20, 65-70.

Parks WA, 1928. Struthiomimus samueli, a new species of Ornithomimidae from the Belly River Formation of Alberta. University of Toronto Studies, Geology Series 26, 1-24.

Parks WA, 1933. New species of dinosaurs and turtles from the Upper Cretaceous formations of Alberta. University of Toronto Studies, Geological Series 34, 1-33.

Paul GS, 1998. Limb design, function and running performance in ostrich-mimics and tyrannosaurs. Gaia 15, 257-270.

Perez-Moreno BP, Sanz JL, Buscalioni AD, et al., 1994. A unique multitoothed ornithomimosaur from the Lower Cretaceous of Spain. Nature 370, 363-367.

Russell D, 1972. Ostrich dinosaurs from the Late Cretaceous of Western Canada. Canadian Journal of Earth Sciences 9, 375-402.

Schmitz L, Motani R, 2011. Nocturnality in dinosaurs inferred from scleral ring and orbit morphology. Science 332, 705-708.

Snively E, Russell AP, 2002. The tyrannosaurid metatarsus: bone strain and inferred ligament function. Senckenbergiana lethaea 82, 35-42.

Snively E, Russell AP, Powell GL, 2004. Evolutionary morphology of the coelurosaurian arctometatarsus: descriptive, morphometric and phylogenetic approaches. Zoological Journal of the Linnean Society 142, 523-553.

Sternberg CM, 1933. A new Ornithomimus with complete abdominal cuirass. The Canadian Field-Naturalist 47, 79-83.

Watanabe A, Erickson GM, Druckenmiller PS, 2013. An ornithomimosaurian from the Upper Cretaceous Prince Creek Formation of Alaska. Journal of Vertebrate Paleontology 33, 1169-1175.

Xu L, Kobayashi Y, Lü J, et al., 2011. A new ornithomimid dinosaur with North American affinities from the Late Cretaceous Qiupa Formation in Henan Province of China. Cretaceous Research 32, 213-222.

Zanno LE, Makovicky PJ, 2011. Herbivorous ecomorphology and specialization patterns in theropod dinosaur evolution. PNAS 108, 232-237.

Zanno LE, Gillette DD, Albright LB, et al., 2009. A new North American therizinosaurid and the role of herbivory in “predatory” dinosaur evolution. Proceedings of the Royal Society B 276, 3505-3511.

Zelenitsky DK, Therrien F, Erickson GM, et al., 2012. Feathered non-avian dinosaurs from North America provide insight into wing origins. Science 338, 510-514.


  1. Wow. I tip my hat to you, give you a trophy, congratulate you, and do it all again. Very long and inclusive post.

  2. Great post on a woefully underrated dinosaur family.