Sciurumimus albersdoerferi: Is it a girl? Is it a boy? No, it’s a Megalosauroid…

Remember the perfectly preserved complete articulated skeleton of a young dinosaur that was presented to the press last year? Well, the paper describing it has finally been published in the Proceedings of the National Academy of Science. ‘Otto’, also known as the Kelheim theropod,  has now a proper scientific name, Sciurumimus albersdoerferi, the generic name meaning “Squirrel mimic” (in reference to its bushy tail) and the specific name honors Raimund Albersdörfer, who made the specimen available for study.  The fossil was found near Painten, Bavaria (Germany) and dates from the upper Kimmeridgian. Besides the exquisite state of preservation of the fossil that shows evidence of proto-feathers covering at least part of the body, the importance of Sciurumimus stems from its phylogenetic position on the dinosaur evolutionary tree.  It is a megalosauroid, sister taxon to the likes of Megalosaurus, Torvosaurus and Eustreptospondylus, therefore representing the most basal theropod showing direct evidence of feathers, and the most complete megalosauroid remain yet discovered. This raises the interesting possibility that feathers might be a common inherited trait to all theropods and even to all dinosaurs if indeed the feather-like structures found on Tianyulong (an heterodontosaur) and quills on the tail of Psittacosaurus (a Ceratopsian) are analogous structures.

References:

Oliver W. M. Rauhut, Christian Foth, Helmut Tischlinger, and Mark A. Norell (2012) Exceptionally preserved juvenile megalosauroid theropod dinosaur with filamentous integument from the Late Jurassic of Germany, PNAS, Advanced online publication.

Bicentenaria argentina, a new theropod dinosaur from Argentina

Bicentenaria argentina, a new theropod dinosaur from Argentina

Argentina has commemorated the 200th anniversary of its May revolution that led to the country independence on May 25, 2010. Two years later, paleontologists from that country announced the discovery of a new dinosaur and named it after the event, perhaps because the remains were unearthed on that day.  Bicentenaria argentina was unveiled to the public on Tuesday June 26, 2012 through a short press release  with pictures of the mounted skeletons of two fighting individuals (from which my illustration is based on). It is a small theropod that measured about 2.5 meters in length. The paragraph quoted from an interview with lead paleontologist Fernando Novas simply says that Bicentenaria is part of a group of dinosaurs that contain tyrannosaurs and Velociraptor and a distant ancestor to birds. This hints that Bicentenaria is a coelurosaur. The pictures of the mounted skeletons do not tell how much of it is actually known, as people tend nowadays to reconstruct entire skeletons from rather incomplete material. The actual remains consist of some 130 bones from at least 3 adults and several juveniles. The mounts look like those of a generic small size theropod, which probably means that Bicentenaria was a rather basal coelurosaurian, neither a tyrannosauroid, nor a dromaeosaur. However, the press release says the fossil is 90 million year old, thus Late Cretaceous, which seems a bit of a young age for a basal coelurosaur. I could guess the remains were found in the Portezuelo Formation of Turonian age in the Rio Negro Province, which means that Bicentenaria was a contemporary of the fabled Megaraptor, the dromaeosaurs Neuquenraptor and Unenlagia, as well as the alverezsaur Patagonykus. But let’s wait for the formal  publication of the description of this intriguing animal.

Correction: I was just told that Bicentenaria is from the Candeleros Formation of Cenomanian age, therefore a contemporary of Giganotosaurus and Buitreraptor.
 
Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com)

Theropods of the British Isles Part III

Fig 1.- Juratyrant langhami

Late Jurassic Theropods of the British Isles

From the Oxfordian stage (~ 158 MYA), Metriacanthosaurus parkeri (von Huene, 1923) is another obscure tetanuran theropod, known from vertebrae, pelvic and hindlimbs elements (OUM J.12144) found near Weymouth, Dorset in the Oxford Clay Formation. Originally thought to be a megalosaurid, there is a possibility that it actually belongs to a group called sinraptorid, better known by its Chinese representatives such as Sinraptor and Yangchuanosaurus. Metriacanthosaurus probably measured about 8 meters in length.

The Kimmeridge Clay Formation has yielded a few theropod remains: one incomplete tooth from Wiltshire referred to “Megalosaurus” insignis (Eudes-Delongchamps and Lennier vide Lennier, 1870) is from a indeterminate theropod. A tibia (OUM J13568) is possibly from a megalosaur or a tetanuran. Two pedal phalanges of Fleet, Dorset are from a tetanuran.

Fig 2.- Metriacanthosaurus parkeri may have been related to Sinraptor.

Tyrannosauroids are represented by Juratyrant langhami (Benson, 2008) from the Kimmeridge Clay of Tithonian age (~149 MYA). This one is known from a single partial skeleton including a pelvis, partial leg and vertebrae (OUMNH J.3311-1—J.3311-30) found in Dorset. Juratyrant is more closely related to the British Early Cretaceous Eotyrannus than to the North American Stokesosaurus to which the animal was originally referred. Juratyrant measured about 5 meters in length.

References:

R. B. J. Benson. 2008. New information on Stokesosaurus, a tyrannosauroid (Dinosauria: Theropoda) from North America and the United Kingdom. Journal of Vertebrate Paleontology 28(3):732-750

Brusatte, S.L. and Benson, R.B.J. (In press). "The systematics of Late Jurassic tyrannosauroids (Dinosauria: Theropoda) from Europe and North America." Acta Palaeontologica Polonica, (in press).

F. v. Huene. 1923. Carnivorous Saurischia in Europe since the Triassic. Bulletin of the Geological Society of America 34:449-458.

D. Naish and D. M. Martill. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London 164:493-510.

Theropods of the British Isles Part I

The bipedal theropods represent the most diverse group of dinosaurs including all the meat-eating ones as well as some omnivorous and herbivorous forms. Primitive theropods include the coelophysoids (small, slender and lightly built dinosaurs that thrived worldwide during the Late Triassic, and for which the best known representative is the North American Coelophysis), the ceratosaurs (including forms such as Ceratosaurus and Carnotaurus) and the tetanurans. The last group contains the vast majority of the theropods and its members are characterized among other things by a rigid tail and the total loss of the fourth and fifth digits in their hands. Megalosaurs (i.e. Megalosaurus) are early tetanurans while Spinosaurs (i.e. Spinosaurus and co) are possibly related to them. Later tetanurans are the allosauroids (large predators such as Allosaurus and Carcharodontosaurus) and the coelurosaurians, which in turn include the tyrannosauroids (such as Tyrannosaurus), the ornithomimosaurs (the ostrich-mimic forms such as Struthiomimus and Ornithomimus) and the maniraptorans. The maniraptorans with their modified wrist and generally large hands are represented by the birds (where the hands became wings) and all their closest relatives, such as the oviraptosaurs (Oviraptor and co), the deinonychosaurs (Velociraptor and co).

Fig 1.- Small coelophysoids lived during the Late Triassic in Great Britain.

Late Triassic Theropods

During the Upper Carnian (~ 220 MYA) of Scotland lived Saltopus elginensis Huene 1910, known from a poorly preserved partial skeleton including dorsal, sacral and caudal vertebrae and fragments of fore and hind limbs (BMNH R3915) found in the Lossiemouth Sandstone Formation, near Elgin, Morayshire. The exact affinities of the animal have been debated. It was either a primitive theropod or a more ancestral dinosauriform.

Theropods were definitely present during the Late Triassic period in the British Isles as proven by the discovery of fragments in the fissure fills of southern Wales. A pelvis, femur and dorsal vertebrae (BMNH PV RU P77/1 and RUP 76/1) from Pant-y-ffynon, Wales of Norian age (~210 MYA), were possibly from a coelophysoid.

The dubious ‘Zanclodon’ cambrensis Newton, 1899 of Rhaetian age (~200 MYA) is known from the mold of a large left dentary with teeth (BGS 6532/BMNH R2912) from Glamorganshire, Wales (Lilstock Fm). This one might be another coelophysoid.

Fig 2.- Larger coelophysoid such as Sarcosaurus roamed the Early Jurassic of England.

Early Jurassic Theropods

In the early Jurassic, coelophysoids are represented by the shadowy Sarcosaurus. The type species, Sarcosaurus woodi Andrews, 1921 is known from a partial pelvis, femur and vertebra (BMNH 4840/1) from Leicestershire (Lias Fm) of Early Sinemurian age (which probably is actually of earlier Late Rhaetian or Hettangian age, ~198-200 MYA). A second species, Sarcosaurus andrewsi Huene, 1932 (= Magnosaurus woodwardi) is based on a partial right tibia (BMNH R3542), originally reported by Woodward in 1908 from Warwickshire of Hettangian age (~198 MYA). Sarcosaurus was a quite large coelophysoid with an estimated length of about 3.5 m.

From the Sinemurian (~192 MYA) Upper Broadford Beds Formation of the Isle of Skye (Scotland) came an incomplete right tibia (NMS.G.1994.10.1), interpreted as belonging to a small theropod, probably another coelophysoid (Benton et al., 1995).

A partial hindlimb from Charmouth, Dorset  (BMNH 39496) that was described by Owen (1861) alongside remains of the ornithischian Scelidosaurus harrisonii was reported from the Lower Lias (Hettangian-Sinemurian). This one was found to be comparable to a megalosaur and would therefore be an early member of this group of large theropods that will dominate the Middle Jurassic period.

Finally, a tooth (BMNH 41352) from the Lias group of Lyme Regis, named ‘Megalosaurus’ lydekkeri von Huene, 1926 (= Magnosaurus lydekkeri), is from an indeterminate theropod.

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


References:

C. W. Andrews. 1921. On some remains of a theropodous dinosaur from the Lower Lias of Barrow-on-Soar. Annals and Magazine of Natural History, series 9 8:570-576

M.J. Benton, D.M. Martill & M.A. Taylor, 1995. The first Lower Jurassic dinosaur from Scotland: limb bone of a ceratosaur theropod from Skye. Scottish Journal of Geology, 31, 177–182.

F. v. Huene. 1910. Ein primitiver Dinosaurier aus der mittleren Trias von Elgin [A primitive dinosaur from the Middle Trias of Elgin]. Geologie und Paläontologie Abhandlungen (n.s.) 8(6):317-322.

D. Naish and D. M. Martill. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London 164:493-510.

O. W. M. Rauhut and A. Hungerbühler. 2000. A review of European Triassic theropods. GAIA 15:75-88.

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.

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)

Daemonosaurus chauliodus

Daemonosaurus chauliodus

The Evil Spirit lizard haunts theropod phylogeny

Meet Daemonosaurus chauliodus, a newly discovered theropod dinosaur from the Chinle Formation of the “Coelophysis Quarry” at Ghost Ranch in New Mexico. Its description by Hans-Dieter Sues, Sterling J. Nesbitt, David S.  Berman and Amy C. Henrici, has just been published in the Proceedings of the Royal Society B (Sues et al., 2011).

Fig 1.- A reconstruction of the head of Daemonosaurus. The fur is speculative.

The media has readily dubbed this little critter as the “Bucked-toothed Demon Lizard” but there is actually nothing devilish about the look of the 

animal. The intended meaning of the generic name is in fact a bit different: the authors used the Greek word daimon in its original sense of ‘evil spirit’ and allude to legends about evil spirits haunting Ghost Ranch, the place of discovery. The specific name, derived from the Greek chauliodous and which means ‘with prominent teeth’ is shared with the scientific name of the deep-sea viperfish (Chauliodus sloani). Like the viperfish, Daemonosaurus is indeed characterized by a set of much enlarged fang-like front teeth. Such teeth might be an indication of a specialized diet, but at this point, we don’t have a clue of what it was.

The prominent teeth are not the only things remarkable about this critter. Daemonosaurus is also one of the most primitive theropod which makes him all the more important as the early history of this particular group of dinosaurs is somewhat sketchy. We know that by the Late Triassic Carnian age (216.5-228 MYA) , the three principal lineages of dinosaurs, i.e. the theropods, the sauropodomorphs and the ornithischians were already well differentiated. A sample of the earliest theropods, i.e. Herrerasaurus, Staurikosaurus, Eoraptor and the recently described Eodromaeus (Martinez et al., 2011) and Sanjuansaurus (Alcober et al., 2010) were found in South America in the Ischigualasto Formation of Argentina and the Santa Maria Formation of Brazil. These primitive theropods still retained five digits on both their hands and feet (albeit greatly reduced fifth digits), while the Neotheropoda, a group that contains all the most advanced theropods including Tyrannosaurus, Velociraptor and the birds, had only three digits in their hands (with sometimes a vestigial fourth as in Coelophysis; in T. rex the 3rd digit is also vestigial), and three functional digits per feet (the fifth is vestigial and the first, is reduced to a “dew claw” on the inside or back of the foot).

Until recently, the later Norian and Rhaetian stages of the Late Triassic (199.6 to 216.5 MYA) have only yielded Neotheropods belonging to a single group called Coelophysoidea (some examples include Coelophysis of WWD fame, Segisaurus, Lilensternus and most probably Zupaysaurus), with the sole exception of the enigmatic Chindesaurus from Arizona which is difficult to classify due to the fragmentary nature of its remains (Nesbitt et al., 2007) but which is now generally considered a late survivor of the Herrerasaurus tribe. The evolutionary gap between the early theropods and the neotheropods started to be filled a couple of years ago with the description of a new species, Tawa hallae (Nesbitt et al., 2009), also from the Ghost Ranch locality of New Mexico and that has been shown to be intermediate between the herrerasaurs and the neotheropods. And this year, we have Daemonosaurus.

Fig 2.- Reconstructed skulls of Daemonosaurus chauliodus (top) and Tawa hallae (bottom). Based after Nesbitt et al., 2009 & Sues et al., 2010. Note the shorter snout and proportionally longer front teeth and larger orbital fenestrae of Daemonosaurus.

Daemonosaurus appears to be even more primitive than Tawa. The holotype consists of a crushed skull, vertebrae and ribs, found in the so-called Coelophysis quarry of Rhaetian age (Stewart et al., 1972). The fossil was indeed extracted from a large block containing remains of several Coelophysis bauri, and there is a chance that more postcranial remains of Daemonosaurus will turn up after completion of the preparation of the block. With its short and deep skull equipped with pointy teeth, Daemonosaurus look is surprising, unlike any of the other basal theropods. The structure of the cervical vertebrae indicates that it probably had a long neck like Tawa or Coelophysis. Like most of the other theropods of the Late Triassic, it was pretty small, measuring perhaps no more than 1.5 meters.

It now appears that the theropod fauna of the Late Triassic was far more diverse than originally thought. Due to its unusual skull shape and teeth, Daemonosaurus was however probably not a transitional form to the new theropods but an evolutionary dead-end that left no descendant.

References:

Alcober, O. A.; and Martinez, R. N. 2010. A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina. ZooKeys 63: 55–81.

Martinez, R. N., Sereno, P. C., Alcober, O. A., Colombi, C. E., Renne, P. R., Montan˜ ez, I. P. & Currie, B. S. 2011. A basal dinosaur from the dawn of the dinosaur era in southwestern Pangaea. Science 331, 206–210.

Nesbitt, S. J., Irmis, R. B. & Parker,W. G. 2007 A critical re-evaluation of the Late Triassic dinosaur taxa of North America. J. Syst. Palaeontol. 5, 209–243.

Nesbitt, S. J., Smith, N. D., Irmis, R. B., Turner, A. H., Downs, A. & Norell, M. A. 2009 A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs. Science 326, 1530–1533.

Stewart, J. H., Poole, F. G. & Wilson, R. F. 1972 Stratigraphy and origin of the Chinle Formation and related Upper Triassic strata in the Colorado Plateau region. US Geol. Surv. Prof. Pap. 690, 1–336.

Sues, H.-D.; Nesbitt, S.J.; Berman, D.S.; and Henrici, A.C. 2011. A late-surviving basal theropod dinosaur from the latest Triassic of North America. Proceedings of the Royal Society B in press