After a long hiatus, here's the next entry in 'Obscure Dinosaur of the Week'!

Normally, when a dinosaur is misidentified as the wrong genus or species, it is due to poorly preserved or very scrappy fossil remains confounding  the original identification. But in the case of Ruehleia bedheimensis, we have a nearly complete and well preserved fossil. So what went wrong?

It all comes down to identification and classification of specific bones.

Most animals with a backbone or spine (vertebral column) have sacral vertebrae: the part of the vertebral column that sits between the hips. Early dinosaurs had two sacral vertebrae, but some prosauropods had an extra sacral vertebrae, either being 'borrowed' from the tail end (caudosacrum - see below figure, bottom left) or from the head-end (dorsosacrum - see below figure, bottom right) of the vertebral column.

Plateosaurus had two sacral plus one caudosacral vertebrae. But on closer inspection, some fossils assigned to Plateosaurus plieningeri were found to have two sacral plus one dorsosacral vertebrae (Galton, 2001b). By definition, these fossils with dorsosacral vertebrae could not belong to Plateosaurus, and instead had to belong to another prosauropod genus. And as there were some other different features in the hip and hand bones, it was decided that the fossil belonged to a completely new prosauropod genus, Ruehleia bedheimensis (Galton, 2001a).

So, not only can you find new dinosaur species or genera by going into the field and digging up new fossils, or by scouring museum collections for unlabelled or uncategorised specimens, you can also find them as well preserved fossils already assigned to a species and hiding in plain site!

References
Galton, P. M., 2001a. Prosauropod dinosaurs from the Upper Triassic of Germany. In: Colectivo Arqueológico - Paleontológico De Salas (Eds.): Actas de las I Jornadas Internacionales Sobre Paleontología de dinosaurios y su entorno. Junta de Castilla y León, Salas de los Infantes (Burgos, España): 25-92.

Galton, P. M., 2001b. The prosauropod dinosaur Plateosaurus Meyer, 1837 (Saurischia: Sauropodomorpha; Upper Triassic). II. Notes on the referred species. Revue Paléobiologie, Genève 20(2): 435-50

Galton, P. M., Upchurch, P. 2004. Prosauropoda. In Weishampel, D. B., Dodson, P., and Osmolska, H. (eds.), The Dinosauria (second edition). University of California Press, Berkeley, pp 232-258

von Lilienstern, R., Lang, H. M., Huene, F. v., 1952. Die Saurier Thüringens. Fischer. Jena, 42 p.

I've felt too guilty for too long over the demise of my 'Obscure Dinosaur of the Week' posts, so it's time to bring them back from the brink of extinction!

You might think that a fragment of a jaw bone is not enough to describe a dinosaur. But teeth are often very distinct between dinosaur groups, due to differences in evolutionary histories including changes in diet.

For example, based on the presence of a primary ridge on the inner surface of the teeth (see images below), Rich et al. (1999) described Qantassaurus intrepidus as a hypsilophodontid, a type of ornithopod (bipedal, unarmoured, herbivorous). But closer examination by other researchers found that many types of ornithopods, not just hypsilophodontidae, have primary ridges on their teeth (Agnolin et al., 2010). They also identified secondary ridges next to the primary ridges, and with a tooth count of less than 12, decided that Q. intrepidus was not a hypsilophodontid, but a basal ornithopod (Agnolin et al., 2010).

Top left and right photos: jaw bone of Q. intrepidus in medial and lateral view respectively.
Bottom photo: close-up of jaw bone in medial view, showing the primary ridge on the lingual surface (Correction: after a kind tip-off from an expert, have replaced original image which showed secondary/subsidiary ridge on labial surface incorrectly marked as 'primary ridge').
Images courtesy of Museum Victoria (Photo: Benjamin Healley)

So why does this matter, in the grand scheme of things? Well, if we don't where a species belongs on the 'family tree' of dinosaurs (like the cladogram shown below), then we won't know what other species it's closely or distantly related too. And then we can't properly observe patterns of evolution. Which as you might know, had huge ramifications when palaeontologists started to realise that birds are actually feathery flying theropod dinosaurs.

Agnolin, F. L., Ezcurra, M. D., Pais, D. F., & Salisbury, S. W. 2010. A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: evidence for their Gondwanan affinities. Journal of Systematic Palaeontology, 8 (2), 257-300.

Rich, T. H., Vickers-Rich, P. 1999. The Hypsilophodontidae from southeastern Australia. Proceedings of the Second Gondwanan Dinosaur Symposium, National Science Museum Monographs 15:167-180

The remains of the basal sauropodomorph P. caducus were first discovered in 1952, and first described as belonging to Thecodontosaurus by Kermack (1984). (Interesting side note: The genus Thecodontosaurus was first described from fossils found in Wales in 1834, and was the fourth dinosaur genera ever named (Riley and Stutchbury, 1836 vide Owen, 1842). It was described 6 years before the term Dinosauria was coined (in 1842), and furthermore wasn't recognised as a dinosaur (instead of a crocodile or other 'saurian') until 1870!) (Benton, 2012).

Closer examination of these fossils, specifically several articulated partial skeletons of juveniles, by Yates (2003) suggested that they could not be ascribed to Thecodontosaurus antiquus (Morris, 1843), and were described as a new species, Thecodontosaurus caducus. But upon further examination of fossils and cladistic analysis, Yates found more and more differences between T. antiquus and T. caducus, enough to suggest that T. caducus wasn't a Thecodontosaurus at all! This problem was solved by assigning the 'T'. caducus material to a new genus, Pantydraco (Galton et al., 2007).

As for the taphonomic history of the P. caducus remains: they were found in underground limestone cave fissure fill – yellow marl that filtered down via large cracks or solution tunnels in a limestone outcrop. Articulated dinosaur skeletons including juvenile sauropodomorphs such as P. caducus have been found fossilised in this marl. It has been postulated that "flash" storms and flooding during the Late Triassic killed these dinosaurs, drowning them and washing their bodies down the fissures into the limestone caves (Galton et al., 2010). The higher percentage of juvenile sauropodomorphs preserved may have been due to size sorting: larger carcasses could not fit down these fissures, and instead decayed and eroded on the land surface.

Benton, M. J., 2012. Naming the Bristol dinosaur, Thecodontosaurus: politics and science in the 1830s. Proceedings of the Geologists’ Association. 123: 766-778

Galton, P. M., Yates, A. M., Kermack, D. M. 2007. Pantydraco n. gen. for Thecodontosaurus caducus Yates, 2003, a basal sauropodomorph dinosaur from the Upper Triassic or Lower Jurassic of South Wales, UK. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 243(1): 119-125

Galton, P. M., Kermack, D. 2010. The anatomy of Pantydraco caducus, a very basal sauropodomorph dinosaur from the Rhaetian (Upper Triassic) of South Wales, UK. Revue de Paléobiologie, Genève. 29 (2): 341-404

Kermack, D. 1984. New prosauropod material from South Wales. Linnean Society of London, Proceedings, 82: 101-117

Owen, R. 1842. Report on British fossil reptiles. Part II. Annual Report of the Association for the Advancement of Science, 1841, London, 9: 60-204

Riley, H., Stutchbury, S. 1836. A description of various remains of three distinct saurian animals discovered in the autumn of 1834, in the Magnesian Conglomerate on Durdham Down, near Bristol. Geological Society of London, Proceedings, 2: 397-399

Yates, A. M., 2003. A new species of the primitive dinosaur Thecodontosaurus (Saurischia: Sauropodomorpha) and its implications for the systematics of early dinosaurs. Journal of Systematic Palaeontology. 1(1): 1-42

When asked, "What's your favourite dinosaur?", I must admit that although I can't choose just one species or genus, I do often think of lambeosaurine dinosaurs. Their wonderful and puzzling nasal and cranial ornamentation has always been the draw card for me. So with great nostalgic pleasure, let me introduce a Late Cretaceous lambeosaurine, Olorotitan arharensis.

So, do you want to know the magical words that definitely help getting research published? 

I'm not saying that you're not allowed to advertise these qualities, just that it certainly helps to have the 'first', or 'longest', or 'tallest', or yes, 'most complete' fossil to write about. And that is exactly what Godefroit et al. (2003) had. Take a look!

Godefroit et al. (2012) suggested that the disarticulated nature of the O. arharensis holotype (including limbs and missing hands and feet) suggests partial decomposition before burial. Whether due to internal bacteria breaking down muscle and fat with loose elements washing away, or through hunting/ scavenging has not been vigorously examined: the authors did note what appeared to be tooth marks on the skull surface, and "tyrannosaurid" teeth have been found in the same formation, and so tentatively hypothesized that carnivorous dinosaurs had a role to play in either the death or decay of this O. arharensis.

References
Godefroit, P., Bolotsky, Y., Alifanov, V. 2003. A remarkable hollow-crested hadrosaur from Russia: an Asian origin for lambeosaurines. Comptes Rendus Palevol 2:143-151

Godefroit, P., Bolotsky, Y., Bolotsky, I. Y. 2012.  Osteology and Relationships of Olorotitan arharensis, A Hollow-Crested Hadrosaurid Dinosaur from the Latest Cretaceous of Far Eastern Russia. Acta Palaeontologica Polonica. 57(3): 527-560


PBDB, n.d. Olorotitan arharensis Godefroit et al. 2003 (lambeosurine). From the Paleobiology Database. Accessed 03/02/2013. URL: http://paleodb.org/cgi-bin/bridge.pl?a=checkTaxonInfo&taxon_no=72095&is_real_ user=1 and http://paleodb.org/cgi-bin/bridge.pl?a=checkTaxonInfo&taxon_no=72095&is_real_user=1

Smooth stones were found in the abdominal region of this specimen of this ground dwelling carnivorous coelurosaur, Nqwebasaurus thwazi, stones that are not common to the geological formation in which the fossil was preserved. So how did they get there? de Klerk et al. (2000) thought these stones were most likely gastroliths: swallowed by animals to aid in breaking down food in the stomach. 

Modern day herbivorous avian dinosaurs (birds) use gastroliths to help in the digestion of plant matter, and aquatic carnivorous animals such as crocodiles, alligators, seals, and sea lions use them  for ballast or stability. However, some doubt still surrounds these theories for gastrolith use, especially as to the true function of gastroliths in non-avian dinosaurs (see the UCMP Berkeley page on gastroliths for an overall summary). Wings (2007, pp 1) provides an even more detailed review of gastrolith use, and lists the following possible reasons for swallowing rocks:

This little guy is also import for two other reasons. First, the occurence of N. thwazi in Early Cretaceous strata pre-dates the known North American taxa by approximately 50 million years (de Klerk et al., 2000). And second, N. thwazi is the oldest Gondwanan coelurosaurian (de Klerk et al., 2000). The authors cite paucity of fossil material in southern Africa as the reason for misinterpretations concerning faunal radiations: whether this clade originated in Laurasia or Gondwana. Lets hope that more discoveries like this help clear things up!

References
Charig, A. J., Milner, A. C. 1986. Baryonyx, a remarkable new theropod dinosaur. Nature 324: 359-361.

de Klerk, W. J., Forster, C. A., Sampson, S. D., Chinsamy, A., Ross, C. F. 2000. A new coelurosaurian dinosaur from the Early Cretaceous of South Africa. Journal of Vertebrate Paleontology 20 (2): 324-332

Ji, Q., Currie, P.J., Norell, M.A., Ji, S. (1998). Two feathered dinosaurs from northeastern China. Nature 393 (6687): 753–761

Wings, O. 2007. A review of gastrolith function with implications for fossil vertebrates and a revised classification. Acta Palaeontologica Polonica 52 (1): 1–16

The original description for this genus/species included "incipient nasal horn cores" (the lumps of bone over the eyes seen in the photo below) and a large rostrum (beak). However, there is some debate over whether the orbital horn cores which characterise this species were actually present in life, or were in fact a result of preservation as other bones around the eyes were 'squashed' down leaving the tougher "horn cores" poking up (Makovicky et al., 2006). Taphonomy strikes again!  Variation in rostrum size has been noted in other protoceratopsid genera, so the large rostrum has also been called into doubt as a defining characteristic of M. dodsoni. It has been suggested by Makovicky et al. (1996) that M. dodsoni might actually be a species of Bagaceratops, another Cretaceous Mongolian protoceratopsid.

I unfortunately don't know enough about ceratopsian anatomy to determine the validity of this myself, so until an official name change is published, it's still a valid taxon in my mind. Good luck, M. dodsoni!

References
Makovicky, P. J., Norell, M. A. 2006. Yamaceratops dorngobiensis, a new primitive ceratopsian (Dinosauria: Ornithischia) from the Cretaceous of Mongolia. American Museum Novitates 3530, 1-42.

You, H., Dong, Z. 2003. A new protoceratopsid (Dinosauria: Neoceratopsia) from the Late Cretaceous of Inner Mongolia, China. Acta Geologica Sinica 77(3):299-303

Although Lophorhothon atopus was a terrestrial hadrosaurid, its remains were found in a marine chalk deposit (the Mooreville Chalk Formation). Various taphonomic scenarios have been suggested for how it ended up in the middle of the ocean,  including the bloat-and-float model. This model suggests that:

• As a carcass undergoes initial decay, internal bacteria in the digestive tract produce gases which cause the carcass to swell up and  'bloat'. 
  
• If the carcass is laying at the bottom of a lake, river, or ocean, the gases causing bloating overcome the carcass's weight and negative buoyancy in water, and will therefore allow it to 'float' to the surface. 
  
• The carcass may then drift for some time until decay advances enough for the internal gases to escape, resulting in the carcass sinking. 
  

So the idea behind the location of L. atopus in marine sediment is that after it died, it was washed into the ocean, floated for a period of time, and then sank onto, and was buried by, marine chalk sediments. It would be difficult to tell whether it was washed out to sea while still alive, or whether it had already died. Although modern experiments involving carcasses lying on the ocean floor suggest that if had died at sea, it would likely be completely obliterated before it had a chance to float! (As per this pig decay experiment - WARNING - some may find these images disturbing). And the paucity of fossil material recovered from this specimen and others preserved in the eastern United States marine formations suggests that these oceans were very taphonomically active zones (TAZ),  with lots of micro- and macro-scavengers consuming soft and hard tissue.

This float-and-bloat model is exactly what I've been testing for my PhD: looking at the buoyancy of juvenile salt-water crocodiles and native fish in fresh water. This will help add to the body of knowledge regarding what sort of time frame different animals bloat-and-float over, and the potential distances they could travel in that time, including floating into the middle of an ocean! 

References
Langston, W. Jr. 1960. The vertebrate fauna of the Selma Formation of Alabama. Part VI. The dinosaurs . Fieldiana: Geology Memoirs  3(6): 315-361

Schwimmer, D. R.,  Dent Williams, G., Dobie, J. L., and Siesser, W. G., 1993. Late Cretaceous Dinosaurs from the Blufftown Formation in Western Georgia and Eastern Alabama. Journal of Paleontology  67(2): 288-296

Schwimmer, D. R. 2010. Lophorhothon. The Encyclopedia of Alabama TM & © 2012, accessed 7 December 2012.

Apart from the first paper by Zhao (1993) describing K. gobiensis, it is difficult to locate detailed descriptions or investigations regarding this sauropod. This is likely due to the preparation and preservation of the fossil skeleton, or lack thereof. Apparently, after the fossilised remains of K. gobiensis were excavated and transported back to Beijing in 1985, "... extreme fluctuation in ambient temperature and humidity" (Zhao, 1993, pg 1) started to disintegrate the remains . I wonder how much of it, if any, now still exists.

References
Upchurch, P., Barrett, P. M., and Dodson, P. 2004. Sauropoda. IN: Weishampel, D. B., Osmolska, H., and Dodson, P. (eds.), The Dinosauria (2nd edition). University of California Press, Berkeley, pp 259-322

Zhao, X., 1993. A new mid-Jurassic sauropod (Klamelisaurus gobiensis gen. et sp. nov.) from Xinjiang, China. Vertebrata PalAsiatica 31(2): 132-138

Although the average person may not have heard of Juravenator starki, it's certainly well known to palaeontologists, due to its near perfect preservation. All the skeletal elements are present, except for the last third of the tail. There's even soft tissue preservation, along the tibiae (lower leg) and between the 8th and 22nd caudal vertebrae (part of the tail) (Göhlich et al., 2006). Because of this fantastic preservation it has been included in numerous papers, including those focusing on its anatomy (Chiappe et al., 2010), estimated body size (Therrien et al., 2007), eye function and possible nocturnality (Schmitz et al., 2011), phylogenetic relationships (Butler et al., 2007), and of course, taphonomy (Reisdorf et al., 2012).

A number of coelurosaurs  have been found possessing fossilised feathers or feather-like structures. J. starki is also a coelurosaur, however the authors found an, "...absence of feathers or feather-like structures..." in this specimen, including no evidence of structures that would support feathers in the preserved soft tissue. You might expect that in an almost perfectly preserved specimen such as this, if there were any feathers present then they would have been fossilised. But absence of evidence is not necessarily evidence of absence. And quite rightly, the authors point out that changes in season or growth stages may influence the presence or absence of feathers.

Look at this beautifully preserved holotype! Everything is in place, except for the tip of the tail. Soft tissue imprints around the tail are labelled 'st'.

References
Butler, R. J., Upchurch, P. 2007. Highly incomplete taxa and the phylogenetic relationships of the     theropod dinosaur Juravenator starki. Journal of Vertebrate Paleontology 27(1), 253-256.

Chiappe, L. M., Göhlich, U. B. 2010. Anatomy of Juravenator starki (Theropoda: Coelurosauria)         from the Late Jurassic of Germany. Neues Jahrbuch für Geologie und Paläontologie -                 Abhandlungen 258(3), 257-296.

Göhlich, U. B., Chiappe, L. M. 2006. A new carnivorous dinosaur from the Late Jurassic Solnhofen     archipelago. Nature 440, 329-332.

Reisdorf, A. G., Wuttke, M. (2012). Re-evaluating Moodie’s Opisthotonic-Posture Hypothesis in         Fossil Vertebrates Part I : Reptiles — the taphonomy of the bipedal dinosaurs Compsognathus     longipes and Juravenator starki from the Solnhofen Archipelago (Jurassic, Germany).                 Palaeobiodiversity and Palaeoenvironments 92 (1), 119-168.

Schmitz, L., Motani, R. 2011. Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit             Morphology. Science 332 (6030), 705-708.

Therrien, F., Henderson, D. M. 2007. My theropod is bigger than yours … or not: estimating body     size from skull length in theropods. Journal of Vertebrate Paleontology 27(1),  108-115.

I feel sorry for this spinosaurid, now forever known as an irritating challenge because some idiot fossil poachers wanted to 'enhance' the length of the skull to make an extra buck. The authors discovered this after conducting a CAT scan:

Sacrilege! But there was at least some good news, as I. challengeri was the first ever the non-avian maniraptoran described from the Cretaceous of South America, and the most complete spinosaurid skull ever found (even sans car body filler). As Cretaceous non-avian maniraptorans had only previously been found in North America and Asia, this suggested that there was an ancient land link between these regions and South America, possibly through Africa. So the irritation was well worth it, in the end!

References
Martill, D. M., Cruickshank, A. R. I., Frey, E., Small, P. G., and Clarke, M. 1996. A new crested         maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil. Journal of         the Geological Society, London 153:5-8

Sues, H. D., Frey, E., Martill, D. and Scott, D. 2002. Irritator challengeri, a spinosaurid                     (Dinosauria; Theropoda) from the early Cretaceous of Brazil. Journal of Vertebrate      Paleontology 22 (3): 535 - 547