Teeth hold clues to dinosaur migrations

Fig 1.- A migrating herd of Camarasaurus. 

The teeth shape and wear pattern could already tell a lot about the diet of long gone creatures. New scientific methods applied to fossil teeth allow deciphering even more subtle behavioral habits. Last year, oxygen isotope analysis performed on Spinosaurus teeth has already shown that the popular back-sailed theropod dinosaur had a semiaquatic lifestyle. More recently, a detailed distribution analysis of ¹³C and ¹⁸O isotopes in the teeth of several sauropod dinosaurs was used to measure their body temperature. Now, in a new paper by Henry C. Fricke, Justin Hencecroth and Marie E. Hoerner published in the journal Nature, variations in the ¹⁸O isotope content measured in the teeth of the common Morrison formation sauropod Camarasaurus, lead strong support to the migratory behavior of those dinosaurs. The ratio of isotopes varies with the water the dinosaur drank and is recorded in the teeth enamel. Water from low elevation wetlands have higher ratio of ¹⁸O than those coming from surface water and precipitations at higher altitude. Comparisons of the teeth isotope ratio with those of ancient soils and their variations show that Camarasaurus was seasonally migrating for food, traveling as much as several hundreds of kilometers. During the wet months, they were staying in the lowland basin, but during the dry seasons when drought was quite possible, they moved uplands in search of vegetation. Pretty neat…

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com)


References:

Amiot, R., Buffetaut, E., Lecuyer, C., Wang, X., Boudad, L., Ding, Z., Fourel, F., Hutt, S., Martineau, F., Medeiros, M., Mo, J., Simon, L., Suteethorn, V., Sweetman, S., Tong, H., Zhang, F., & Zhou, Z. (2010). Oxygen isotope evidence for semi-aquatic habits among spinosaurid theropods Geology, 38 (2), 139-142

Robert A. Eagle, Thomas Tütken, Taylor S. Martin, Aradhna K. Tripati, Henry C. Fricke, Melissa Connely, Richard L. Cifelli, and John M. Eiler, 2011, “Dinosaur Body Temperatures Determined from Isotopic (13C-18O) Ordering in Fossil Biominerals” Science. 333(6041):443-5.

H. C. Fricke, J.Hencecroth, M.E. Hoerner. 2011. Lowland–upland migration of sauropod dinosaurs during the Late Jurassic epoch. Nature. Advanced online publication.

A New Rebbachisaurid Sauropod from the Isle of Wight.

Fig 1.- Reconstruction of Rebbachisaurus. 

Rebbachisaurids are a rather obscure and poorly understood group of sauropod dinosaurs so far known only from the Early Cretaceous period of Africa, South America and Europe. A new find described in an article by Philip D. Mannion, Paul Upchurch and Stephen Hutt in this month issue of Cretaceous Research confirms the presence of this group on the Isle of Wight during the Early Cretaceous. The paper reports of a an anterior caudal vertebra from the Wessex Formation of Barremian age, discovered at Brightstone Bay on the Southwest coast of this little Island of the English Channel. No species name has been assigned to the fossil.

The type genus of the Rebbachisaurids, Rebbachisaurus was a sauropod, big plant-eating dinosaur similar to the famed Diplodocus, and member of the Diplodocoidea superfamily. It lived during the Early Cretaceous in what is now North Africa. It was first described in 1954 by R. Lavocat from fragmentary remains, consisting of a tail vertebra, a humerus (upper arm bone), a scapula (shoulder blade) and a sacrum, and collected from the Tegana Formation of Morocco. The species name is Rebbachisaurus garasbae. In 1960, A.F. de Lapparent described a second species, R. tamesnensis from various fragments of the Farak Formation of Niger, but this one is a bit dubious and can well belong to a completely different sauropod. More complete material from the Rio Limay Formation of Argentina including a partial skull has been referred to a third species, R. tessonei (Calvo & Salgado, 1995), and was used as proof of a land connection between Africa and South America in the Early Cretaceous, but the species has since been transferred to its own genus, Limaysaurus. So as today, the only species referable with certainty to the genus Rebbachisaurus is the Moroccan one described by Lavocat.

Fig 2.- Nigersaurus taqueti.

However, several closely related taxa have been described since then, mostly from South America, and a family, the Rebbachisauridae, has been erected by P. Sereno and co-workers in 1999 to regroup them. Although only known from Cretaceous strata, they appear to be basal members of the Diplodocoidea and therefore more primitive than the earlier Diplodocus and Apatosaurus from the late Jurassic period, indicating "a ghost lineage" from the Middle to Late Jurassic. Besides Rebbachisaurus and Limaysaurus, the Rebbachisaurids include the odd sauropod Nigersaurus taqueti, known from several well-preserved skeletons from the “Middle” (Aptian-Albian) Cretaceous of Niger, and described in the media as the “dinosaur with a vacuum cleaner mouth”. From the ten or so Rebbachisaurid taxa named so far, only Limaysaurus and Nigersaurus are known from relatively complete materials. All the others are very fragmentary so it is difficult to get a complete picture of this enigmatic family. One characteristic and common trait of this clade is the paddle-shaped scapular blade.

Besides Africa and South America, Rebbachisaurids were also living in Europe. The species Histriasaurus boscarottii, has been erected based on a few vertebrae from the Early Cretaceous (Hauterivian-Barremian) of Croatia (Dalla Vecchia, 1998), the most ancient member of the family so far and some materials from the Castrillo de la Reina Formation (Barremian-Aptian) of Spain have been reported by Pereda Superbiola et al. in 2003 and recently described in details under the name Demandasaurus darwini by Fernández-Baldor et al., in 2011. Finally, rebbachisaurids are also known from the Isle of Wight of England. A characteristic scapula (shoulder blade) collected by Nick Case in 1989 from the Wessex Formation on the southwest coast of the Isle of Wight has been described by Philip Mannion in 2009. In a recent cladistic analysis by Carballido et al., (2010), this British scapula comes, oddly, as a sister taxon of the South American Limaysausus tessonei. It is possible that the newly described caudal vertebra does belong to the same animal, even if the phylogenetic analysis placed it in a close kinship with the Spanish Demandasaurus and the African Nigersaurus, rather than with Limaysaurus. However, conclusions based on single incomplete bones are probably not to be entirely trusted until new discoveries are added to the analysis.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com)

References:

J. O. Calvo and L. Salgado. 1995. Rebbachisaurus tessonei sp. nov. a new Sauropoda from the Albian-Cenomanian of Argentina; new evidence on the origin of the Diplodocidae. GAIA 11:13-33.

J. L. Carballido, A. C. Garrido, J. L. Canudo and L. Salgado. 2010. Redescription of Rayososaurus agrioensis Bonaparte (Sauropoda, Diplodocoidea), a rebbachisaurid from the early Late Cretaceous of Neuquén. Geobios 43:493-503.

F. M. Dalla Vecchia. 1998. Remains of Sauropoda (Reptilia, Saurischia) in the Lower Cretaceous (Upper Hauterivian/Lower Barremian) limestones of SW Istria (Croatia). Geologica Croatica 51(2):105-134.

F. Torcida Fernández-Baldor, J. I. Canudo, P. Huerta, D. Montero, X. Pereda Suberbiola and L. Salgado. 2011. Demandasaurus darwini, a new rebbachisaurid sauropod from the Early Cretaceous of the Iberian Peninsula. Acta Palaeontologica Polonica 56(3):535-552

A. F. d. Lapparent. 1960. Les Dinosauriens du "Continental intercalaire" du Saharal central [The dinosaurs of the "Continental Intercalaire" of the central Sahara]. Mémoires de la Société géologique de France, nouvelle série 39(88A):1-57

R. Lavocat. 1954. Sur les dinosauriens du Continental Intercalaire des Kem-Kem de la Daoura [On the dinosaurs from the Continental Intercalaire of the Kem Kem of the Doura]. Comptes Rendus 19th Intenational Geological Congress, 1952 1:65-68.

P. D. Mannion. 2009. A rebbachisaurid sauropod from the Lower Cretaceous of the Isle of Wight, England. Cretaceous Research 30:521-526.

P. D. Mannion, P. Upchurch, and S. Hutt. 2011. New rebbachisaurid (Dinosauria: Sauropoda) material from the Wessex Formation (Barremian, Early Cretaceous), Isle of Wight, United Kingdom. Cretaceous Research 32:774-780

X. Pereda Suberbiola, F. Torcida, L. A. Izquierdo, P. Huerta, D. Montero and G. Pérez. 2003. First rebbachisaurid dinosaur (Sauropoda, Diplodocoidea) from the early Cretaceous of Spain: palaeobiogeographical implications. Bulletin de la Societé Géologique de France 2003(5):471-479

L. Salgado, A. Garrido, S. E. Cocca and J. R. Cocca. 2004. Lower Cretaceous rebbachisaurid sauropods from Cerro Aguada del León (Lohan Cura Formation), Neuquén province, northwestern Patagonia, Argentina. Journal of Vertebrate Paleontology 24(4):903-912.

P. C. Sereno, A. L. Beck, D. B. Dutheil, H. C. E. Larsson, G. H. Lyon, B. Moussa, R. W. Sadleir, C. A. Sidor, D. J. Varricchio, G. P. Wilson, and J. A. Wilson. 1999. Cretaceous sauropods from the Sahara and the uneven rate of skeletal evolution among dinosaurs. Science 286:1342-1347.

Scelidosaurus harrisoni, a basal thyreophoran from southern England

Fig 1.- A reconstruction of Scelidosaurus harrisonii.

The Black Ven cliff between Charmouth and Lyme Regis, in Dorset, southern England is world famous for its Early Jurassic fossils of marine animals such as ammonites and ichthyosaurs. It is also known for a single species of dinosaur that has only been found there, Scelidosaurus harrisoni. How this fully terrestrial animal ended up preserved in marine deposits is somewhat a mystery (carcasses were presumably washed to sea after death and quickly buried by layers of sand) but it allows getting a rare glimpse of the fauna that lived during the Early Jurassic period on the islands of Europe (Most of Western Europe was under a shallow sea at that time).

Scelidosaurus was known from quite some time having been described in 1861 by Sir Richard Owen based on a skull and various non-associated postcranial bits discovered near the village of Charmouth. The original material contains a right knee joint, a femur fragment and a phalanx (finger bone) that proved later to belong to one or several type of megalosaurs (theropod dinosaurs) (Newman, 1968). Some other elements described by Owen as belonging to a juvenile Scelidosaurus proved later to be from a hypsilophodont.  In the meantime, the postcranial skeleton associated to the original skull was uncovered and described by Owen in 1862. He named the species Scelidosaurus harrisonii, in honor of its discoverer, James Harrison.

Fig 2.- Original skull of Scelidosaurus in Owen's 1861 description of the genus. This skull is presently the lectotype as the holotype (a femur fragment) turned out to belong to a megalosaur.

These were the only fossils of the animal known for over a century and the exact affinities of the new dinosaur remained uncertain until fairly recently. The characteristic dermal scutes that make a kind of armor covering the body pointed to a close relationship with others armored ornithischians such as the stegosaurs, the ankylosaurs or the fabrosaurs. It was in turn considered a primitive stegosaur (von Zittel, 1902, Romer, 1956), an ankylosaur (Romer, 1968), a basal ornithopod (Thurlborn, 1977) and then generally considered a primitive ornithischian of some sort. A second skull previously described as a juvenile Scelidosaurus (Rixon, 1968) might actually belong to a hypsilophodont. Scutes from the Kayenta formation in Arizona were attributed to Scelidosaurus, which would indicate a large geographical range for the genus (Padian, 1989), but this identification has been questioned.

The uncertainty has dwindled in the last decade or so thanks in part to the fact that the original specimen described by Owen has been acid prepared so that it can be studied more thoroughly (Norman, 1996).  Also, new specimens of Scelidosaurus began to turn up in the 1990s. Dave Martill described two of them in 1991 and 2000. The first is a rather complete articulated skeleton including skull fragments.  It was found in 1985 near Charmouth in the Black Ven marls of Upper Sinemurian age. The second consists of a set of 8 articulated tail vertebrae and was acquired in 1998 from a private collection at the death of his owner, Prof. John Challinor. It unfortunately misses information about its provenance. A palynological analysis however indicates an Early Jurassic age from the same period as the Owen specimen (Late Hettangian- Sinemurian). Interestingly, both specimens show kerogenized traces of soft tissues indicating that the scutes (osteoderms) were covered by a horny sheath.  A third specimen was collected in the same area between Charmouth and Lyme Regis in 2000 by a local fossil collector, David Sole. It has been described as the most complete skeleton of a dinosaur ever found in the UK.

Carpenter (2001) places Scelidosaurus as a basal ankylosaur. However, most of the recent phylogenetical analysis including the latest comprehensive one on the Ankylosauria (Thompson et al., 2011) points toward an ancestral position of Scelidosaurus relatively to both the stegosaurs and ankylosaurs, as a basal member of the thyreophorans. Other genera probably related to it include the gracile Scutellosaurus lawleri from the Kayenta formation in Arizona (Sinemurian-Plienbaschian), and the rather enigmatic Emausaurus ernsti from the Toarcian of Germany. Tatisaurus oeheleri from the Lufeng formation of Yunnan might be another relative, although the remains are so fragmentary that it is difficult to be sure. The same can be said of Bienosaurus lufengensis from the same formation known from fragments of a skull, and Lusitanosaurus liasicus from the Early Jurassic of Portugal, also known from a few skull fragments and teeth.

 

 Fig 3.- Cast of a nearly complete skeleton of Scelidosaurus harrisonii found in 2000 and on display at the Charmouth Heritage Coast Center (photo by User:Ballista via wikipedia, CC3.0 licensed).

Scelidosaurus was a 4-meter long herbivorous dinosaur that probably walked on all fours although it was possibly able to stand on its hind legs from time to time. The body was covered with bony scutes called osteoderms as a protection against predators. Contrary to earlier depictions of the animal as a bulky quadruped, Scelidosaurus was probably more gracile in appearance with a relatively long neck compared to stegosaurs and ankylosaurs.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com)

References:

K. Carpenter. 2001. Phylogenetic analysis of the Ankylosauria. In K. Carpenter (ed.), The Armored Dinosaurs. Indiana University Press, Bloomington 455-483a

D.M. Martill, 1991. Organically preserved dinosaur skin: taphonomic and biological implications. Modern Geology, 16, 61±68.

B. H. Newman. 1968. The Jurassic dinosaur Scelidosaurus harrisoni, Owen. Palaeontology 11(1):40-43

R. Owen. 1861. A monograph of a fossil dinosaur (Scelidosaurus harrisonii, Owen) of the Lower Lias, part I. Monographs on the British fossil Reptilia from the Oolitic Formations 1:1-14

R. Owen. 1862. A monograph of a fossil dinosaur (Scelidosaurus harrisonii, Owen) of the Lower Lias, part II. Monographs on the British fossil Reptilia from the Oolitic Formations 2:1-26.

K. Padian, 1989. Presence of the dinosaur Scelidosaurus indicates Jurassic age for the Kayenta Formation (Glen Canyon Group, northern Arizona). Geology. May 1989, v. 17; no. 5; p. 438-441

A.E. Rixon, 1968. The development of the remains of a small Scelidosaurus from a Lias
nodule. Mus. J. 67:315-321.

A. S. Romer. 1956. Osteology of the Reptiles, University of Chicago Press 1-772

A.S. Romer. 1968. Notes and Comments on Vertebrate Paleontology. Chicago Univ. Press, Chicago, 304 p.

R. S. Thompson, J.C. Parish, S. C. R. Maidment & P. M. Barrett, 2011.  Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora), Journal of Systematic Palaeontology, in press.

R. A. Thulborn. 1977. Relationships of the Lower Jurassic dinosaur Scelidosaurus harrisonii. Journal of Paleontology 51(4):725-739.

K. A. von Zittel, 1902. Text-book of Palaeontology, V. II. (Transl. C. R. Eastman). Macmillan, London and New York, 283 p.

Two extraordinary paleontology finds this week: one good, one bad...

Fig 1.- Speed painting of the giant prehistoric kraken.

In the Triassic period, giant squids were roaming the oceans to pray on large ichthyosaurs the size of a school bus.  Mark McMenamin, a professor of Geology at Mount Holyoke College, MA, presented this claim at the last Geological Society of America conference in Minneapolis (October 10, 2011). The proof lays in the curious arrangement of vertebral disks observed in the remains of the ichthyosaur Shonisaurus. According to McMenamin, this can only be the work of some giant artsy prehistoric cephalopods portraying themselves on the sand with the bones of their hapless victims! This is probably the most ludicrous paleontological claim made since the treeosaur. Amazingly, some major news outlets took the bait (see for instance here).

 Fig 2.- Reconstruction of the Kelheim theropod.

The second extraordinary announcement of the week is the discovery of a 98% complete articulated skeleton of a young theropod dinosaur in Germany, the most complete ever found in Europe. The discovery has been unveiled by Oliver Rauhut, conservator of the Bavarian Paleontological and Geological collections in Munich. The press release unfortunately gave very little details about it. The fossil has been uncovered near Kelheim in Bavaria, and is, I would guess in view of the geology of the region, of Late Jurassic age (and not 135 MYA i.e. Early Cretaceous as said in the news). Judging from the photo of the skeleton that came with the release, it looks to be a compsognathid with a very long tail. General proportions of the skull and limbs are strikingly similar to Juravenator. But what do I know about this amazing yet unnamed theropod? Let’s wait for the full description of the fossil that will hopefully be published in the upcoming months.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com)

Talos sampsoni, a new troodontid from Utah

After the Chinese Linhevenator, yet, another troodontid, Talos sampsoni, has just been described in the current issue of PLoS ONE. This one is from the distinct and quite specific fauna of the Kaiparowits formation of Utah, which included the unique ceratopsians Kosmoceratops, Utahceratops and Nasutuceratops, the tyrannosaurid Teratophoneus, the hadrosaur Gryposaurus and the Oviraptosaur Hagryphus. Talos is essentially known from remains of the hindlimbs plus a few other bits such as some  vertebrae, and a left ulna. It was probably similar in shape to the other derived troodonts with short forelimbs, long legs and had a sickle claw on each foot.

 

References:
Lindsay E. Zanno, David J. Varricchio, Patrick M. O'Connor, Alan L. Titus and Michael J. Knell. 2011. A new troodontid theropod, Talos sampsoni gen. et sp. nov., from the Upper Cretaceous Western Interior Basin of North America. PLoS ONE 9 (6): e24487.

Pachyrhinosaurus perotorum, new boreal dinosaur from Alaska

Fig 1.- Pachyrhinosaurus perotorum.

 

Anthony R. Fiorillo, and Ronald S. Tykoski, from the Museum of Nature and Science, Dallas, TX, have just described a new species of Ceratopsian (Horned dinosaur), Pachyrhinosaurus perotorum from the Prince Creek formation of the North Slope in the northernmost region of Alaska. The species is based on two fragments of parietals (which in Ceratopsians are the bones that formed the frill) and a partial skull.



What makes P. perotorum special is that it was a boreal dinosaur. During the Late Cretaceous, Alaska was situated at latitudes similar or higher than its current geographical position, meaning that its northern inhabitants experienced, as of today, a yearly 6 month long winter night with freezing temperature. Polar dinosaurs are also known from the southern hemisphere with representatives of the early Cretaceous period such as the hypsilophodont Leallynasaura amicagraphica from Australia featured in WWD. The Late Cretaceous Prince Creek formation of Alaska, however, appears to be the richest trove of polar dinosaur bones from either hemisphere. The Kikak-Tegoseak Quarry where the P. perotorum remains were unearthed, also include bones of the raptors Dromaeosaurus albertensis and Troodon formosus as well as remains attributed to the tyrannosaur Gorgosaurus libratus, some hadrosaurs and the Pachycephalosaur Alaskacephale gangloffi.

Fig 2.- Pachyrhinosaurus canadensis.

P. perotorum is the third named species of the genus Pachyrhinosaurus which contains Ceratopsians with massive flattened bosses in place of the usual horns on the nose and above the eyes. The larger 6 meter long P. canadensis was described in 1950. It is known from the St Mary River (Upper Campanian-Lower Maastrichtian) and Horseshoe Canyon Formations (Lower Maastrichtian) of Alberta, Canada. The smaller 5 meter long P. lakustai, described in 2008 from the Wapiti Formation (Late Campanian) of Alberta, differs from P. canadensis by well-separated nasal and supraorbital bosses and by the presence of a comb of horns on the parietal bone just behind the eyes.

 

Fig 3.- Pachyrhinosaurus lakustai.

P. perotorum is the youngest (Lower Maastrichtian) of the three species, and about the same size as P. lakustai. It is characterized by the unique anterior parietal pair of horns just at the top edge of the parietal cavities (the large holes in the frill), and a narrow dome in a back portion of the nasal boss. The bizarre blunt rounded rostrum might just be an individual oddity (the partial skull is apparently from an aged individual). A recently discovered specimen numbered TMP 2002.76.1 (Housed at the Royal Tyrrel Museum), from the Dinosaur Park Formation, Alberta, which shows similarities with both Pachyrhinosaurus and Achelousaurus, might represent a fourth species.


Pachyrhinosaurus belongs to the Pachyrhinosauri tribe of the Centrosaurine Ceratopsian that also contains the basal genera with enlarged nasal horns Einiosaurus and Rubeosaurus, as well as the derived forms with nasal and supraorbital bosses, Achelousaurus.


Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com)

 

References:

 

P. J. Currie, W. Langston, and D. H. Tanke. 2008. A new species of Pachyrhinosaurus (Dinosauria, Ceratopsidae) from the Upper Cretaceous of Alberta, Canada. In P. J. Currie, W. Langston Jr., D. H. Tanke (eds.), in A New Horned Dinosaur from an Upper Cretaceous Bone Bed in Alberta. NRC Research Press, Ottawa 1-108.

A.R. Fiorillo, and R.S.T. Tykoski, R.S.T.  2011. A new species of the centrosaurine ceratopsid Pachyrhinosaurus from the North Slope (Prince Creek Formation: Maastrichtian) of Alaska. Acta Palaeontologica Polonica. In press.

Linhevenator tani, a new troodontid from China

Fig 1.- Reconstruction of Linhevenator tani.

Troodontids are a family of very bird-like small theropods with long legs and enlarged braincases.  Phylogenetically, they are placed alongside the dromaeosaurs (Velociraptor, Deinonychus and friends) among the Deinonychosaurians, a sister group to the birds. Fossils of troodonts were found in Asia, Europe and North America in sediments dating from the Upper Jurassic to the Upper Cretaceous periods. Some of the better known troodonts include the Early Cretaceous Mei long (the shortest name given to a dinosaur, and meaning “sleeping dragon” because its exceptionally preserved articulated skeleton has been found in a sleeping position) and the Late Cretaceous Troodon formosus from North America, which was originally described on the basis of a single characteristic serrated tooth, but which is now known from multiple fragmentary specimens (previously referred as "Stenonychosaurus").

Fig 2.- The holotype (LH V0021) of Linhevenator tani (Xu et al., 2011). Licensed under CC 2.5. Scale bar is 2 cm.

Xing Xu and colleagues are reporting in the September 2011 issue of the open access journal PLoS ONE, a new troodontid from the Late Cretaceous Wulansuhai Formation of Bayan Mandahu, Inner Mongolia. The Wulansuhai Formation is equivalent to the famous Mongolian dinosaur bearing Djadokhta Formation of Campanian age. This new species, Linhevenator tani is known from a partly articulated skeleton that includes the skull, several vertebrae, pelvic girdle and limb elements. Although badly weathered, the remains are of particular interest are they are to date the most complete ones from a Late Cretaceous Troodontid and therefore likely to shed new lights on the more derived members of this family. Linhevenator was a rather large species (around 2-3 meters in length) characterized by rather short arms (the humeri measured only 40% of the length of the femur) and with a sickle clawed second digit on each foot similar to those of the dromaeosaurs, although these may be in fact common traits to all derived troodontids such as Troodon and Saurornithoides.

References:
Xing Xu, Qingwei Tan, Corwin Sullivan, Fenglu Han and Dong Xiao. 2011. A Short-Armed Troodontid Dinosaur from the Upper Cretaceous of Inner Mongolia and its Implications for Troodontid Evolution. PLoS ONE 6 (9): e22916

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com)