New Multituberculate fossil shows keys to their success

Reconstruction of Rugosodon eurasiaticus.

Multituberculates are a highly successful group of early mammals and they were surprisingly long lived having evolved in the Jurassic, survived the KT extinction event before disappearing during the Oligocene period. They are in fact the most long-lasting group of mammals, having survived at least 130 million years, more than any other group of mammals either alive or extinct. A new mostly complete fossil discovered in China, Rugosodon eurasiaticus, greatly help clarify the origin of the group. It shows that some of the key characteristics of the multituberculates, such as highly flexible spine and mobile ankle joints, evolved very early, and were probable the reasons of their success.

Reference:

Ref: Yuan C.-X., Ji Q., Meng Q.-J., Tabrum A. R., Luo Z.-X. 2013. Earliest evolution of multituberculate mammals revealed by a new Jurassic fossil. Science 341 (6147): 779–783. 

Abstract: Multituberculates were successful herbivorous mammals and were more diverse and numerically abundant than any other mammal groups in Mesozoic ecosystems. The clade also developed diverse locomotor adaptations in the Cretaceous and Paleogene. We report a new fossil skeleton from the Late Jurassic of China that belongs to the basalmost multituberculate family. Dental features of this new Jurassic multituberculate show omnivorous adaptation, and its well-preserved skeleton sheds light on ancestral skeletal features of all multituberculates, especially the highly mobile joints of the ankle, crucial for later evolutionary success of multituberculates in the Cretaceous and Paleogene. 


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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.

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 II

 Middle Jurassic Theropods of the British Isles

The Middle Jurassic of England was dominated by Megalosaurids, a family of large primitive tetanuran theropods, now believed to be closely related to the fish-eating Spinosaurids, early representatives of groups that will thrive during the Cretaceous, the tyrannosauroids and the maniraptorans were also present.

Fig 1.- Duriavenator hesperis

The Aalenian-Bajocian stages: Magnosaurus and Duriavenator

The Inferior Oolite formation of Aalenian-Bajocian age (~ 172 MYA) has given a few fragmentary remains of a theropod named Magnosaurus nethercombensis (von Huene, 1923) (originally ‘Megalosaurus’ nethercombensis) and described from partial dentaries, vertebrae, partial ilium, pubis and hindlimb (OUM J12143) found in Nethercomb, Dorset. Various others bits from the same formation in southern England were also referred to this rather obscure tetanuran. The fossil of M. nethercombensis has recently been reevaluated (Benson, 2010) and established to be a valid taxon. This megalosaurid is the oldest known tetanuran.

From the Upper Inferior Oolite Formation of Bajocian age (~ 170 MYA) comes Duriavenator hesperis (Waldman, 1974) (originally Megalosaurus hesperis), known from cranial bones (BMNH R332) found near Sherbourne in Dorset. This is another megalosaurid.

Fig 2.- Megalosaurus bucklandii

The Bathonian stage: Megalosaurus  and Proceratosaurus

The Bathonian age  (~166 MYA) of the British Isles is represented by a handful of theropods. The most famous of them is Megalosaurus, a name coined by William Buckland in 1824 to describe various remains including a lower jaw, vertebrae and partial hindlimbs uncovered at the Stonesfield quarry (Taynton Limestone Formation) that he thought belonged to a giant lizard-like creature. As many of the names from the early days of paleontology, Megalosaurus became a formidable wastebasket taxon, given to an assortment of miscellaneous theropod bones found around the world. Nowadays, only one species, Megalosaurus bucklandii Mantell, 1827 is considered valid and corresponds to the original material described by Buckland. Megalosaurus was a large 9 meter long theropod that was probably the top land predator of its time.

Cruxicheiros newmanorum Benson & Bradley, 2010 from the Chipping Norton Limestone Formation of lower Bathonian age, is based on scant materials, including a partial right femur (WARMS G15770) and other bits found on the same location near Little Crompton, Warwickshire. This one was a basal tetanuran of some sort. A single damaged vertebra found in the same formation but now lost, was named Streptospondylus cuvieri Owen, 1842.

Iliosuchus incognitus von Huene, 1932 from the Taynton Limestone Formation (Bathonian) of Stonesfield, Oxfordshire is known from three small ilia (BMNH R83, OUM J29780 and OUM J28971) found alongside remains of Megalosaurus. It is unclear what it was, either a small megalosaurid or the earliest known tyrannosauroid as some have suggested. A fragmentary small tibia found in the same formation was referred to Iliosuchus as well.

Fig 3.- Proceratosaurus bradleyi

Proceratosaurus bradleyi (Woodward, 1910) from the Great Oolite Group (White Limestone Formation) of Minchinhampon, Gloucestershire (Bathonian) is known from a partial skull exhibiting a nasal horn (which was possibly part of a larger crest), thus the name. This is an early tyrannosauroid, a member of this group of coelurosaurs, which will culminate into the North American Tyrannosaurus rex at the end of the Cretaceous period. Proceratosaurus perhaps measured about 3 meters in length.

From the Forest Marble Formation of Bathonian age, famous for its fossils of the sauropod Cetiosaurus, some troodont-like and dromaeosaur-like teeth have been unearthed, making it the earliest occurrence of this group in the fossil record (Evans & Milner, 1994).

The Callovian stage: Eustreptospondylus

Later in the Middle Jurassic (Callovian stage, ~163 MYA), lived another Megalosaurid named Eustreptospondylus oxoniensis Walker, 1964. This one is known from a partial skull (OUM J13558) and a partial skeleton from a juvenile individual found in Wolvercote, Oxfordshire, at the bottom of the Oxford Clay Formation. This rather obscure species was popularized in one episode of the BBC Series “walking with dinosaurs”. It probably measured something like 5 m in length.

References:

R. B. J. Benson. 2008. A redescription of 'Megalosaurus' hesperis (Dinosauria, Theropoda) from the Inferior Oolite (Bajocian, Middle Jurassic) of Dorset, United Kingdom. Zootaxa 1931:57-67

R. B. J. Benson, 2010, The osteology of Magnosaurus nethercombensis (Dinosauria, Theropoda) from the Bajocian (Middle Jurassic) of the United Kingdom and a re examination of the oldest records of tetanurans, Journal of Systematic Palaeontology, 8(1): 131-146.

S. E. Evans and A. R. Milner. 1994. Middle Jurassic microvertebrate assemblages from the British Isles. In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods, N. C. Fraser and H.-D. Sues (eds.), Cambridge University Press 303-321

F. von Huene, F. 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.

R. Sadleir, P. M. Barrett, and H. P. Powell. 2008. The anatomy and systematics of Eustreptospondylus oxoniensis, a theropod dinosaur from the Middle Jurassic of Oxfordshire, England. Monograph of the Palaeontographical Society, London 160(627):1-82

M. Waldman. 1974. Megalosaurids from the Bajocian (Middle Jurassic) of Dorset. Palaeontology 17(2):325-339.

A. D. Walker. 1964. Triassic reptiles from the Elgin area: Ornithosuchus and the origin of carnosaurs. Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 248:53-134

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.

Ankylosaurs of the British Isles

Fig 1.- Hyleosaurus armatus.

The Ankylosaurs form a group of heavily armored ornithischian dinosaurs best known by its North American cretaceous representatives, Ankylosaurus and Euoplocephalus. Ankylosaurs and Stegosaurs together form the Thyreophorans characterized by a body covered with an armor consisting of scutes, spikes and plates, that are highly derived osteoderms (ossified scales commonly found in various groups of vertebrates such as the crocodilians).

The Ankylosaurs are divided into two or three families. The Nodosaurids have a narrow skull, a club-less tail and large spikes while the Ankylosaurids have a distinct bony club at the end of their tails and a wider body. In addition, some authors detach some Nodosaurids, into a third family, the more lightly built Polacanthids.

Scelidosaurus harrisonii from the Early Jurassic of Dorset, is an early thyreophoran close to the ancestral stock of both stegosaurs and ankylosaurs. There is however a large gap in the fossil record between the first definite ankylosaur in the United Kingdom and Scelidosaurus. Jurassic ankylosaur remains are so fragmentary that not much definite can be said about them.

In the Middle Jurassic (Bajocian, 170 MYA), an incomplete radius and ulna (forearm bones) from the Isle of Skye in Scotland, described by Clark in 2001, possibly belongs to an ankylosaur, unless it is a stegosaur.

A bit younger (Middle Jurassic, Callovian, 163 MYA), Sarcolestes leedsi is known from an incomplete lower jaw from the Oxford Clay Formation in Cambridgeshire. Three osteoderms recovered from the same formation have been attributed to it (Galton, 1994). It was originally thought to be a theropod (thus its name meaning “flesh robber”), before being classified as a stegosaur, then an ankylosaur of some sort.

From the Late Jurassic period (Oxfordian, 160 MYA), a right femur found in the Ampthill Clay Formation of Cambridgeshire was named Cryptosaurus eumerus and first attributed to an ornithopod, until Peter Galton placed it among the ankylosaurs (1983). A maxilla of the same age named Priodontognathus phillipsi was found in Yorkshire. This also was first attributed to an ornithopod before Galton classified it as a nodosaurid ankylosaur (1980).

Better ankylosaur material appears in the Early Cretaceous with Hylaeosaurus and Polacanthus. Hylaeosaurus armatus is one of the original three animals (the others being Iguanodon and Megalosaurus) used by Sir Richard Owen to define the then new group he called Dinosauria in 1842. This 6 meter long polacanthid nodosaur is known from the Turnbridge Wells Sand Formation (Grinstead Clay member) of Valanginian age (~138 MYA) and its remains have been discovered in West Sussex. The holotype found in the Tilgate Forest area by Gideon Mantell in 1832 consists of the anterior portion of an articulated skeleton including a small portion of the skull. A second specimen from Bolney was partially destroyed by workers before Mantell could salvage a few bits including a left scapula, a fragment of the right scapula and a left tibia. A third specimen found by Mantell in 1827 from the Tilgate Forest quarry consists of an incomplete caudal series with armor (originally named H. oweni).  From Mantell’s Bolney material combined with remains found in the Isle of Wight, Nopsca erected the new genus and species Polacanthoides ponderosus in 1928. Today, the Bolney material is attributed to Hylaeosaurus armatus while the Isle of Wight material is considered to belong to Polacanthus foxii, making Polacanthoides an invalid name. Hylaeosaurus is still a quite obscure animal despite being one of the earliest described dinosaurs. It was probably closely related to Polacanthus.

Fig 2.- Polacanthus foxii.

Polacanthus foxii, which was for some times being considered to be the same animal as Hylaeosaurus, is nowadays generally thought to be distinct. Stratigraphically, it is slightly younger, appearing only in the Wessex and Vectis Formations of the Isle of Wight of Upper Barremian age (~ 125 MYA). The generic name appears first in a anonymous field note from 1865 attributing the paternity of the name to Richard Owen. The holotype collected by the reverend William Fox consists of the rear end of the animal. A second specimen described by W. T. Blows in 1979 consists of neck vertebrae and anterior armor. A third specimen is currently in private ownership. A portion of a pelvis and some dermal armor, originally named Polacanthus becklesi by Hennig in 1924 is now considered to belong to P. foxii. Many other various bits attributed to P. foxii have been found including the now lost Isle of Wight parts used to define Polacanthoides ponderosus described above and the single spine named Vectensia by Delair, 1982.  Polacanthus foxii was a 4-5 meter long nodosaur, serving as the type to the polacanthid family.

Blows has erected a second species of Polacanthus, P. rudgwickensis, in 1996 out of a partial skeleton from the mainland found near Rudgwick, Sussex. This species appears to be slightly larger and more robust than P. foxii but its validity has been disputed.

Fig 3.- Anoplosaurus curtonotus. 

From the mainland Upper Greensand Formation of Albian age (~110 MYA), a number of fragments were attributed to ankylosaurs and named into several genera including Anoplosaurus, Acanthopholis, Eucercosaurus, Syngonosaurus and Macrurosaurus and a plethora of species. All of them, save perhaps Anoplosaurus curtonotus are dubious in the sense that from such fragmentary remains there are no unique characters to define each of the species.  Anoplosaurus curtonotus has been described from various fragments from a juvenile individual and probably belong to a nodosaurid of some sort. The second species, A. major is probably chimeric. The genus Acanthopholis was often illustrated in dinosaur books but all the 7-9 species described, including the type A. horrida, were determined to be dubious by a review by Pereda-Superbiola and Barrett (1999).

This concludes our tour of the British Isles Ornithischians. Now to the Saurischians.

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


References:

Blows, W. T.  1982. A preliminary account of a new specimen of Polacanthus foxi (Ankylosauria, Reptilia) from the Wealden of the Isle of Wight. Proceedings of the Isle of Wight Natural History and Archaeological Society 1980 pt. 5(7):303-306.

Clark, N.D.L. 2001. A thyreophoran dinosaur from the early Bajocian (Middle Jurassic) of the Isle of Skye, Scotland. Scottish Journal of Geology, 37, 19–26.

Fox. W. 1866. On a new Wealden saurian named Polacanthus. Report of the British Association for the Advancement of Science, Birmingham 1865:56.

Fox. W.1866. Another new Wealden reptile. Geological Magazine 3:383.

Galton, P.M. 1980. Priodontognathus phillipsii (Seeley), an ankylosaurian dinosaur from the Upper Jurassic (or possibly Lower Cretaceous) of England. Neues Jahrbuch für Geologie und Paläontologie Monatshefte 1980(8):477-489.

Galton, P.M. 1983. Armored dinosaurs (Ornithischia: Ankylosauria) from the Middle and Upper Jurassic of Europe, Palaeontographica Abteilung A 182(1-3): 1-25.

Galton, P. M.  1994. Dermal scutes of Sarcolestes, an ankylosaurian dinosaur from the Middle Jurassic of England. Neues Jahrbuch für Geologie und Paläontologie Monatshefte 1994(12):726-732

Naish, D.; and Martill, D. M. 2008. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: Ornithischia. Journal of the Geological Society, London 165 (3): 613–623.

Pereda-Suberbiola, J. 1993. Hylaeosaurus, Polacanthus, and the systematics and stratigraphy of Wealden armoured dinosaurs. Geological Magazine, 130, 767-781.

Pereda-Suberbiola, J. 1994. Polacanthus (Ornithischia, Ankylosauria), a transatlantic armoured dinosaur from the Early Cretaceous of Europe and North America. Palaeontographica Abteilung A 232(4-6):133-159.

Pereda-Suberbiola, J. & Barrett. P.M., 1999. A systematic review of ankylosaurian dinosaur remains from the Albian-Cenomanian of England, Special Papers in Palaeontology, 60: 177-208.

Cuspicephalus scarfi

Fig 1.- Reconstruction of Cuspicephalus scarfi.

In the series of British prehistoric animals, let me this time introduce you to a pterosaur. Cuspicephalus is known from a partial skull unearthed in the Kimmeridge Clay Formation (Late Jurassic) of Dorset. This critter is possibly  related to the Chinese Darwinopterus.

A new monofenestratan pterosaur from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Dorset, England, David M. Martill and Steve Etches, Acta Palaeontologica Polonica (2011)  in press


Abstract: A new specimen of slender skulled monofenestratan pterosaur from the Late Jurassic Kimmeridge Clay Formation of Dorset, UK, is referred to the new genus and species Cuspicephalus scarfi. The dentition and posterior skull morphology suggest affinities with Darwinopterus, but a close relationship cannot be proved. There are also some similarities with the pterodactyloid Germanodactylus cristatus, but the presence of teeth on the distal rostrum excludes it from that genus. Pterosaur remains are rare in the Upper Jurassic of the UK and this specimen represents the first significant cranial remains of a pterosaur from the Kimmeridge Clay Formation, and possibly the first non-pterodactyloid monofenestratan outside China.

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

References:

David M. Martill and Steve Etches. 2011. A new monofenestratan pterosaur from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Dorset, England. Acta Palaeontologica Polonica in press.

Stegosaurs of the British Isles

Fig 1.- Lexovisaurus durobrivensis (= Loricatosaurus priscus)

Compared to the Stegosaurs of North America, restricted to the sole Morrison Formation and represented only by 1 or 2 genera and a handful of species, all from the Kimmeridgian-Tithonian age of the Late Jurassic, the plated dinosaurs from England appear comparatively more diversified with up to 6 genera spanning from the Middle Jurassic to the Early Cretaceous. Unfortunately, the fossils there are for the most part quite scrappy, consisting of teeth, bits of plates and other bones, making their identification difficult or even dubious.  Susannah Maidment and colleagues in their 2008 general revision of the Stegosauria, have recognized only 2 valid species to the United Kingdom, Dacentrurus armatus and the newly erected Loricatosaurus priscus, but this is certainly an underestimation. Let’s make a quick overview of stegosaurian materials found in England.

Middle Jurassic Stegosaurs

The most ancient British stegosaurs date from the Bathonian stage (165-168 MYA) of the Middle Jurassic and consist of a few isolated bones, including a massive right femur of a juvenile individual from the Cornbrah formation of Oxfordshire (Upper Batthonian), two incomplete vertebrae from the Sharp’s Hill Formation of Oxfordshire and two large dermal plates from the Chipping Norton Formation of Gloucestershire. These bones were all referred to “Lexovisaurus” vetustus (= “Omosaurus” vetustus). All that can be said is that they are the oldest recorded Stegosaurids in the world (the family to which all the most derived stegosaurs such as Stegosaurus and Kentrosaurus belong) and that a least one large species was present in Europe at that time.

Next, from the Middle Callovian (161-165 MYA) Oxford Clay Formation came Lexovisaurus durobrivensis, known from two partial skeletons. Maidment et al, 2008 have invalidated the name Lexovisaurus, on the basis that no unique character could be found in the holotype specimen. In its stead, a new genus, Loricatosaurus, was erected for the second partial skeleton that includes vertebrae, various pelvic and limb elements, and a piece of dermal armor, and folded into the species Loricatosaurus priscus. A large dermal plate named ‘Omosaurus leedsi’ from the same locality may be from the same animal. A third partial skeleton from a contemporary formation in Normandy, France is also referred to Loricatosaurus priscus. However there is no real indication that Lexovisaurus durobrivensis and Loricatosaurus priscus represent different taxa and the two might well be the same. Loricatosaurus probably measured about 5-6 meters in length. It is characterized by relatively short limbs and narrow plates and spines on the back. Shoulder spines may or may not have been present (A previously reported shoulder spine in the skeleton turns out to be a tail spine instead).

Upper Jurassic Stegosaurs

Fig 2.- Dacentrurus armatus.

From the Coralline Oolite Formation, Yorkshire, of Middle Oxfordian age (156-161 MYA), came a poorly preserved femur of a juvenile individual that has been named ‘Omosaurus phillipsi’ (= ‘Dacentrurus phillipsi’). There is no real indication that it was a stegosaur at all and the name is considered a nomen dubium (dubious name).

From the Kimmeridge Clay Formation of Wiltshire, of Lower Kimmeridgian age (151-156 MYA), came Dacentrurus armatus, a partial skeleton preserved in a large slab on exhibit at the Natural History Museum of London. Some fragmentary materials from France, Spain and Portugal were also referred to Dacentrurus. It was a large stegosaur with an estimated length of some 8 meters. Its aspect is not well known, but it probably resembled the African Kentrosaurus. From the Kimmeridge Clay also came a few dermal spines named “Omosaurus hastiger” that might belong to the same animal than Dacentrurus. 

Fig 3.- Dacentrurus armatus holotype on display at the Natural History Museum in London (Credit: Emőke Dénes, via Wikipedia)

Early Cretaceous Stegosaurs

From the Lower Cretaceous Wealden Beds, Sussex of Valanginian age (136-140 MYA), came a partial right mandible, Regnosaurus northamptoni, that was variously attributed to the Ornithopod Iguanodon (Mantell, 1841), the ankylosaur Hylaeosaurus (Owen, 1858), a scelidosaur (Lydekker, 1888), and even a sauropod (Ostrom, 1970) until it was discarded as a nomen dubium (Coombs, 1971). However, more recently, Barrett & Upchurch, 1995, resuscitated Regnosaurus as a stegosaur and found it to be a relict of the old stegosaurian lineage that included the Chinese Huayangosaurus. The dubious Craterosaurus pottonensis, known from a single incomplete and poorly preserved dorsal vertebra, has been described as a stegosaur, but that is probably more wishful thinking. Interestingly Craterosaurus from Bedfordshire is probably also of Valanginian age.

Fig 4.- Regnosaurus northamtoni was a close relative of Huayangosaurus taibaii.

This concludes our tour of the stegosaurian remains of England.

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

References:

P. M. Barret & P. Upchurch. 1995. Regnosaurus northamptoni, a stegosaurian dinosaur from the Lower Cretaceous of Southern England. Geological Magazine 132: 213–222.

P. M. Galton and H.P. Powell, H. P. 1983. Stegosaurian dinosaurs from the Bathonian (Middle Jurassic) of England, the earliest record of the Family Stegosauridae. Geobios 16: 219-229.

P. M. Galton. 1985. British plated dinosaurs (Ornithischia, Stegosauridae). Journal of Vertebrate Paleontology 5(3):211-254.

S. C. R. Maidment, D. B. Norman, P. M. Barrett and P. Upchurch. 2008. Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia). Journal of Systematic Palaeontology 6(4):367-407.

Xiaotingia zhengi or is Archaeopteryx still a bird?

Fig 1.- A reconstruction of Xiaotingia zhengi.

Xiaotingia zhengi is a new small carnivorous theropod dinosaur discovered in the Late Jurassic Tiaojishan Formation of the western Liaoning province of China. It is known from a single articulated skeleton missing the tail and part of the left leg, and preserved in a slab that also contains some feather impressions.

Fig 2.- Anchiornis huxleyi, a taxon previously described as a troodont, is closely related to Xiaotingia and Archaeopteryx.

The intriguing part of the story published last month in the journal Nature is less the description of the new fossil itself than the resulting cladistic analysis that followed. Xiaotingia was found to be closely related to the famous dinosaur-bird transitional fossil Archaeopteryx lithographica from Bavaria, Germany, and to another taxon described in 2009, Anchiornis huxleyi. Anchiornis had its share of fame last year when it became the first dinosaur to reveal its true colors from the examination of fossilized pigments found in the feather impressions. But Anchiornis was at that time classified as a flying dinosaur belonging to the troodontid family.

Fig 3.- Archaeopteryx lithographica, the "ancestral" bird, was actually a deinonychosaurian dinosaur related to Velociraptor. Note, the position of the wings is too high in this reconstruction.

The new cladistic tree proposed by Xing Xu and colleagues places Archaeopteryx, Anchiornis and the novel taxon Xiaotingia within the same family, the Archaeopterygidae and nests them at the base of the Deinonychosaurians, the group that contains such celebrities as Velociraptor, Deinonychus, Troodon and Utahraptor, and away from the ‘sister” branch (the Avialae) that lead to the modern birds. Archaeopterygidae is then a third and the most basal family that constitutes the Deinonychosaurians, along with the more derived Troodontids (Troodon and friends) and Dromaeosaurs (Velociraptor and friends). The real story behind the discovery of Xiaotingia is therefore that it knocks Archaeopteryx out of the genealogical tree that lead to the modern birds, a position that it held for a century and half! The true ancestors of birds, were more closely related to such oddities as the strange Scansoriopteryids and perhaps other dinosaurs such as the beaked Oviraptosaurs. This leads to the interesting possibility that an herbivorous rather than a carnivorous diet was an ancestral trait for birds.

Fig 4.- Phylogenetic tree of the ancestor of birds and their closest relatives (After Xu et al., 2011). Archaeopteryx does no longer belongs to Aves (Birds in the traditional sense).

As a matter of fact, the position of Archaeopteryx as the ancestor of all birds was precarious for some times now. The close relationship of Archaeopteryx with the Deinonychosaurians has been suspected for quite a while, with such discoveries as the four-winged flying sensation called Microraptor and other small “dromies”. The new cladistic analysis is just confirming a trend that started some two decades ago. Overall the new analysis by Xu and colleagues is making perfect sense: a number of traits that Archaeopteryx possesses are more akin to Deinonychosaurians than to Avialians. Archaeopteryx for instance has a slender shallow snout like the Deinonychosaurians and quite unlike basal avialians such as Epidexipteryx and Sapeornis and Oviraptosaurs who tend to have short and blunt snouts. Many details of the skeletal anatomy, such as the dimension and shape of the different openings in the skull (antorbital fenestra, premaxillary fenestra, …) shape and proportions of different bones (such as the lacrimal in the skull, the pubis, metatarsals, etc…) all point to Deinonychosaurian affinities for the Archaeopterygids.

Now to the vexed question as whether Archaeopteryx could still be considered a bird or not, the most we can say is that it all depends on how you define “bird”. In the traditional sense (as “birds”=Aves), Archaeopteryx is not a bird anymore. But using a broader definition (for instance, “birds”= Paraves (Avialae+ Deinonychosauria)), Archaeopteryx would still be considered a bird, but so should be all Archaeopteryx closest relatives, Velociraptor, Microraptor, Deinonychus and co. Anyway, the fact that a small feathered dinosaur related to Velociraptor could have been mistaken for the  “Urvogel”, the ancestral bird for well more than a century, tellingly shows how intimate the connection between the two groups is. Birds really are the last surviving group of dinosaurs, so get over it and move on, folks!


References:
Xing Xu, Hailu You, Kai Du and Fenglu Han. 2011. An Archaeopteryx-like theropod from China and the origin of Avialae. Nature 475: 465–470.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission.

Ornithopods of the British Isles, Part I

Fig 1.- Callovosaurus leedsi might have look like Dryosaurus although it is hard to tell from a single bone.

If you were asked to cite one dinosaur that lived in the British Isles, chances are that you will mention Iguanodon. Since Mary Ann Mantell discovered the first teeth of this animal while going for a walk in Sussex in the year 1822, countless bones have been unearthed and attributed to Iguanodon extending the geographical presence of this genus from Europe to North America, Africa and Asia and its temporal range from the Middle Jurassic to the Late Cretaceous. In effect, Iguanodon became a so-called wastebasket taxon. Most of the Ornithopods (the group of bird-hipped dinosaurs to which Iguanodon belongs) remains from the British Isles were originally described as “Iguanodon”.  In recent years, scientists have started going through this mess resulting in the naming of a number of new genera and restricting the use of the generic name to a single species, I. bernissartensis from the Barremian-Aptian of England and Belgium. One notable consequence of this exercise is that Ornithopod dinosaurs of the British Isles now look way more diversified than previously thought (instead of 3 genera, we now have a dozen or more). This is the first of a two-part post on the Ornithopod dinosaurs of the United Kingdom.

The herbivorous Ornithopods can be classified into a few types or families: the lightly built bipedal Hypsilophodonts and Dryosaurs, the medium sized Rhabdodonts, the more heavily built and mostly quadrupedal Camptosaurs and Iguanodonts, and the variously crested and non crested “Duck-billed” dinosaurs (the Hadrosaurs). Except for the Rhabdodonts, all are represented in the British Isles, although the remains of Hadrosaurs are to date very scrappy and questionable.

Fig 2.- Cumnoria prestwichii.

The most geologically ancient Ornithopod of the UK is known from a single isolated femur:  Callovosaurus leedsi (originally “Camptosaurus leedsi”) is from the Oxford Clay Formation, near Peterborough, Cambridgeshire, dating from the Middle Jurassic (Callovian, ~163 MYA). It is hard to say much from a single bone but the animal is either a Camptosaur (Galton, 1980) or a Dryosaur as recently proposed (Ruiz-Omeñaca et al., 2007). Either way, it is the earliest recorded of its kind worldwide. It probably measured something like 2.5 m in length.

Fig 3.- Barilium dawsoni.

The next known Ornithopod in geological order is Cumnoria prestwichii (Originally “Iguanodon prestwichii”) from the Kimmeridge Clay Formation in Oxfordshire and dating from the Late Jurassic (Kimmeridgian, ~153 MYA). This one is known from a partial skull and some postcranial elements. Cumnoria was probably bipedal, measuring about 3 to 3.5 meters in length and looked a lot like the North American Camptosaurus.

 

Fig 4.- Hypselospinus fittoni.

From the Early Cretaceous (Berriasian ~142 MYA) Purbeck Limestone formation in Dorset, there is a right dentary, which was named Owenodon hoggii (Originally “Iguanodon hoggii”), probably another Camptosaur.

The Wadhurst Clay Formation in East Sussex of Early Cretaceous (Middle Valanginian, ~138 MYA) age is home to at least two species of Iguanodonts, the large size (8 m) and heavily built Barilium dawsoni (Originally “Iguanodon dawsoni”) and the medium size (6 m) and more lightly built Hypselospinus fittoni (Originally “Iguanodon fittoni”), both known from partial postcranial remains. A large skull recovered at Henfield, West Sussex, might belong to Barilium. The two new generic names were coined by David Norman in 2010. However, Ken Carpenter and Yusuke Ishida unknowingly gave the name Torilion dawsoni and Wadhurstia fittoni the very same year to the very same fossils, but since their publication came out a few weeks later, Norman’s names for the two animals have priority and thus prevailed.  As for differences in the two studies, Carpenter and Ishida made one specimen that Norman included in Barilium, as a separate species and named it Sellacoxa pauli and considered  “Iguanodon holligtonensis” distinct from Hypselospinus.

From the Tunbridge Wells Sand Formation in West Sussex of Early Cretaceous (Middle-Upper Valanginian age, ~136 MYA), a right dentary was named Kukufeldia tilgatensis (this fossil was previously taken as a specimen of “Iguanodon anglicus”). This is probably another Iguanodont of some sort.

This is all for now, folks! Stay tuned for the second part with Hypsilophodon and Iguanodon.

References:

Carpenter, K. and Ishida, Y. 2010. Early and "Middle" Cretaceous Iguanodonts in Time and Space. Journal of Iberian Geology 36 (2): 145–164.

Galton, P. M. 1980. European Jurassic ornithopod dinosaurs of the families Hypsilophodontidae and Camptosauridae. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 160 (1): 73–95.

McDonald, A.T., Barrett, P.M. and Chapman, S.D. 2010. A new basal iguanodont (Dinosauria: Ornithischia) from the Wealden (Lower Cretaceous) of England. Zootaxa, 2569: 1–43.

Naish, D., and Martill, D. M. 2008. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: Ornithischia. Journal of the Geological Society, London 165: 613–623.

Norman, D. B. 2010. A taxonomy of iguanodontians (Dinosauria: Ornithopoda) from the lower Wealden Group (Cretaceous: Valanginian) of southern England. Zootaxa 2489: 47–66.

Ruiz-Omeñaca, J. I.; Pereda Suberbiola, X.; and Galton, P. M. 2007. Callovosaurus leedsi, the earliest dryosaurid dinosaur (Ornithischia: Euornithopoda) from the Middle Jurassic of England. In Carpenter, Kenneth (ed.). Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Bloomington and Indianapolis: Indiana University Press. pp. 3–16.

How many Stegosaurs in the Morrison Formation?

Fig 1.- Stegosaurus ungulatus.

Stegosaurus is one of the most iconic dinosaurs from the famed Late Jurassic Morrison Formation of North America. Artists have often depicted the plated “roofed lizard” as the formidable opponent to its nemesis, the fearsome theropod Allosaurus. The first remains of a stegosaur have been unearthed in Colorado during the Bone Wars and described by Othniel Charles Marsh in 1977 as Stegosaurus armatus. Since then, numerous specimens were found and described from different areas encompassing the Morrison Formation, in Colorado, Wyoming and Utah. Of the 11 or so names that were given to stegosaur remains from the United States, Marsh has described no less than 7 species.

Fig 2.- Hesperosaurus mjosi

But subtle differences seen in the bones can either be signatures of different species or simply reflect individual variations within the same species. How to define characteristics that are unique to a given species (autapomorphies) is easier said than done when the number of specimens is limited and when remains are fragmentary (i.e. statistics is lacking).

Fig 3.- Stegosaurus stenops

In a 2008 review of all stegosaurs, Susannah Maidment and colleagues made some very drastic cuts in the number of species present in the Morrison formation, recognizing only two valid ones: Stegosaurus armatus and Hesperosaurus mjosi that they renamed Stegosaurus mjosi. The other species are either junior synonyms of S. armatus or dubious (nomen dubium). However in another case of the now classic opposition between “splitters” (scientists who think there is only a narrow range of variation inside a species, thus considering more species as valid) and “lumpers” (scientists who think that there are few species with large individual variations), Peter Galton and colleagues in a 2010 paper had a closer look on the various remains from the Morrison formation and found that up to 7 species must be considered valid. To add a little twist to the story, they infer that the type species, Stegosaurus armatus, is a nomen dubium due to the fragmentary nature of the holotype that does not allow defining any autapomorphy. But if S. armatus were unvalidated, so would be the genus name, Stegosaurus. Consequently, a petition to the ICZN (International Commission of Zoological Nomenclature) was filed to make the best-known species, Stegosaurus stenops as the new type for the genus (good choice, nobody really wants our favorite plated lizard to be renamed Hypsirophus or Diracodon !).

Fig 4.- Stegosaurus longispinus, here depicted as a Kentrosaurus grade species

In view of the diversity of Ornithopods and Sauropods in the Morrison formation, it is not that surprising to see more than one species of stegosaurs living at the same time there. If we discard the species that are either too fragmentary or not properly described, we end up with some 4 or 5 different stegosaurs in North America. Among them, Hesperosaurus mjosi is the oldest, having been found close to the base of the formation. It is easily distinguishable by the plates, which are longer than taller. Stegosaurus stenops is the best known with several almost complete skeletons.  It is characterized by three unpaired alternating dermal plates just before the spikes while Stegosaurus ungulatus has three pairs of small dermal plates there. Interestingly, remains of a stegosaur from Portugal have tentatively been assigned to this particular species. Stegosaurus sulcatus with its large based tail spikes might also be another valid species.

Stegosaurus longispinus, characterized by longer tail spines or “thagomizer” is only known from materials from the rear of the animal, which were unfortunately mostly destroyed in the early 1920s. Because of the longer tail spines, some have argued that S. longispinus might have been a Kentrosaurus-like stegosaur, which would need to be redescribed as a new genus.

Note: as I am writing this, I realized this story was already covered much more eloquently and in depth by paleontologist Darren Naish a few months earlier (see his post here)…



References:

S. C. R. Maidment, D. B. Norman, P. M. Barrett and P. Upchurch. 2008. Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia). Journal of Systematic Palaeontology 6(4):367-407.

P. M. Galton, 2010. Species of plated dinosaur Stegosaurus (Morrison Formation, Late Jurassic) of western USA: new type species designation needed. Swiss Journal of Geosciences 103, 187-198.

Arcusaurus pereirabdalorum, a new sauropodomorph dinosaur from the Early Jurassic of South Africa

Sauropodomorphs form a group of bipedal and quadrupedal herbivorous dinosaurs that reached gigantic proportions in the Jurassic and Cretaceous periods with the likes of Diplodocus, Argentinosaurus and Brachiosaurus. The Upper Elliot Formation of Early Jurassic age in South Africa is home of at least three species of sauropodomorphs. The best known is Massospondylus carinatus, with several specimens uncovered. The two other species are Massospondylus kaarae and Aardonyx celestae, both named very recently, while the status of Gryponyx africanus is unclear, and of Ignavusaurus rachelis, dubious.

Yet, another species, Arcusaurus pereirabdalorum, the smallest of them all, has been added to the list. Scattered remains of at least two individuals, probably juveniles, have been unearthed.
The generic name, which means “Rainbow lizard”, honors the people of South Africa, the “rainbow nation”. Interestingly, Arcusaurus, albeit its Plateosaurus-like deep snout, in the analysis looks very basal and came as a sister taxon of the triassic sauropodomorphs such as Thecodontosaurus and Efraasia. If this were the case, Arcusaurus would be a relict of the primitive Triassic sauropodomorphs that somehow made it to the Jurassic.

Adam M. Yates, Matthew F. Bonnan, and Johann Neveling have described the species in the May 2011 issue of the Journal of Vertebrate Paleontology.

References:

Barrett, P. M. 2009. A new basal sauropodomorph dinosaur from the upper Elliot Formation (Lower Jurassic) of South Africa. Journal of Vertebrate Paleontology 29:1032–1045.

Yates, A. M., M. F. Bonnan, J. Neveling, A. Chinsamy, and M. G. Blackbeard. 2010. A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism. Proceedings of the Royal Society B 277:787–794.

Yates, A.M.,  M. F. Bonnan, and J. Neveling. 2011. A New Basal Sauropodomorph Dinosaur from the Early Jurassic of South Africa. Journal of Vertebrate Paleontology, 31(3):610-625.