Monday, 28 January 2013

J is for Juravenator

Continuing on with our alphabet, we come to J. Unfortunately, there are no dinosaurs from Alberta that start with the letter 'J', so we bring you 'J is for Juravenator', which is a small theropod from Germany.

Juravenator is known from a single specimen found in southern Germany, and lived during the Late Jurassic, approximately 151 million years ago. Although it is only known from one specimen, this specimen is extremely well preserved and almost entirely complete. First discovered in 1998, it had an interesting past. It was very difficult to prepare, as the surrounding rocks are very tough and the bones are fragile, and at one point it was abandoned, thought to not be worth it. After gaining press from 1999-2001, it was finally looked at again in 2003 when they discovered a nearly complete dinosaur, which was named in 2006 [1]. The name means 'Jura-hunter', where Jura signifies that it was found in the Bavarian Jura mountains. The fossil was found in layered limestone from the Solnhofen region of Germany, typified by very fine-grained sediments. This area is known for the beautiful preservation of fossils due to the quiet lagoon-type setting these animals died in. 
Image of Juravenator from Goehlich and Chiappe [1]

The single specimen of Juravenator is a juvenile, known by the lack of fusion between bones and still-open sutures in the vertebrae [1]. Like other small theropods, it was a bipedal carnivore, and was less than a metre in length (but remember, it's just a juvenile!). The initial description found that Juravenator had no evidence of feathers or integumentary covering, which was interesting considering it was thought to be closely related and nested within many dinosaurs known to have filamentous coverings [1]. However, a re-examination of the fossil in 2010 revealed (through the use of ultra-violet light) that the animal actually had many small filaments covering various parts of the body, which is similar to other closely related coelurosaurs like Sinosauropteryx [2]. These filaments are thought to be 'primitive feathers' and can be found in many theropod dinosaurs. Another interesting thing about Juravenator is that it also shows evidence of scales, which is highly unusual as scales and filaments are rarely found together [2]. Of further interest, it happens to be one of the most complete non-avian (as in not a bird) theropod skeletons to be found in Europe!

Hopefully you enjoyed learning about the small theropod Juravenator. You can learn more about this little dino from Brian Switek's post, since we independently came up with the same guy for our features! Next week, we'll be back to dinosaurs from Alberta for our dinosaurian alphabet, with the letter 'K'!

1. Goehlich, U.B., and Chiappe, L.M. 2006. A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago. Nature 440: 329-332.
2. Chiappe, L.M., and Goehlich, U.B. 2010. Anatomy of Juravenator starki (Theropoda: Coelurosauria) from the Late Jurassic of Germany. Neues Jahrbuch fuer Geologie und Palaeontologie - Abhandlungen 258: 257-296.

Monday, 21 January 2013

I is for Irenesauripus and Ichnofossils!

This week we are going to do something a little bit different for the Alberta Dinosaurian Alphabet. This week, we have 'I is for Irenesauripus, and ichnofossils!

Irenesauripus is a type of ichnogenus, also known as a trace fossil or ichnofossil. Specifically, it is a kind of dinosaur footprint from the Cretaceous of North America. It was first discovered in the 1930's in Peace River, British Columbia, but has since been recorded in Alberta, the Yukon, and Texas. Albertan Irenesauripus tracks are typically found in the area of Grand Cache. These fossils are all three-toed and found in trackways. They represent an animal that walked on two legs (bipedal), walked on its toes (digits) rather than flat-footed, and had widely spaced impressions of the toes. They have evenly distributed weight, and show evidence of claws on each toe. In the original description, it was described as a theropod, and several studies have since agreed [1-3] while one has even gone further in declaring it a member of the Megalosauroidea [4]. These prints represent large theropods, as they are typically 28-40 cm in length. 
Example of Irenesauripus from Richard McCrea
As mentioned before, 'I' is also for ichnofossils, and ichnology. Ichnology is the study of trace fossils, which includes anything other than actual remains of animals, but rather they show behaviour. These include trackways or footprints, burrows, or even coprolites (fossilised feces). The great thing about trace fossils is that they can give us direct evidence of behaviour, which traditional fossils (like bones) typically do not. For example, a large number of trackways showing several different kinds of tracks can show a herbivore being attacked by carnivores. Or, a number of tracks from the same type of animal can show that they travelled in a herd or pack. Fossilised burrows can show us how an extinct animal made its burrow and how it lived. Unfortunately, more often than not, it is very difficult to associate a trace fossil with a specific animal. We can make assumptions based on the size of fossil and the animals that we know were around at the right time, but there is often no way we know for sure what animal made the tracks. This is why trace fossils are called ichnospecies rather than species, because they do not necessarily represent an entirely new species. Irenesauripus was a theropodian ichnogenus that would have represented a large theropod because of the size of print as well as stride (about 1 m in length). 

That's it for this week. Hopefully we introduced you to another side of palaeontology that you may not have thought about before, as well as a new area in Alberta where dinosaur fossils can be found! Stay tuned for 'J' next week, which unfortunately will be from outside of Alberta. 

Other 'I' dinosaurs from Alberta:
Ichthyornis - a bird (remember, birds technically are dinosaurs!)

1. Kuhn, O. 1963. Pars 101. Ichnia Tetrapodorum. In F. Westphal (ed.), Fossilium Catalogus. I: Animalia. Ysel Press, Deventer, Netherlands. 176 pages
2. M. G. Lockley. 1992. Cretaceous dinosaur-dominated footprints assemblages: their stratigraphic and palaeoecological potential. In N.J. Mateer & P.-J. Chen (eds.) Aspects of Cretaceous Geology. China Ocean Press, Beijing, 269-282.
3. Gangloff, R. A., et al. 2004. An early Late Cretaceous dinosaur tracksite in central Yukon Territory, Canada. Ichnos 11: 299-309.
4. Haubold, H. 1971. In O. Kuhn (ed.) Handbuch der Palaeoherpetologie. Part 18. Ichnia Amphibiorum et Reptiliorum Fossilium. Gistav Fischer Verlag, Stuttgart. 1-124.

Monday, 14 January 2013

H is for Hesperonychus

Next up in our Alberta dinosaurian alphabet is Hesperonychus, a small theropod. Its name means 'western claw', in reference to the sickle-shaped claw it has on both hindlimbs. This claw tells us that it was a dromaeosaur, commonly referred to in popular media as the 'raptors' like Velociraptor or Deinonychus. It lived during the Late Cretaceous period of southern Alberta, approximately 75 million years ago. These fossils were collected in 1982, and were left undescribed and virtually ignored until they were re-discovered by Nick Longrich and Phil Currie in 2009 [1].
Artists impression of Hesperonychus by Nobu Tamura
Although known from only a few bones, the estimated total length of Hesperonychus is less than 1 m, and it weighed as little as 1.9 kg [1]. Due to the degree of fusion in the bones, it's likely this is in fact a full-grown adult individual, making it one of the smallest theropod dinosaurs found in North America, second only to Albertonykus

Hesperonychus is the first microraptorine dinosaur found in North America, and it is also one of the few small theropods, which is significant ecologically. Previously, the ecosystems of the Late Cretaceous of North America lacked small theropods (we couldn't find their fossils), while similarly aged environments in Europe and Asia had several. This find helped to fill this gap rather than having to develop an explanation for why these small animals didn't exist in North America. We now understand that carnivorous dinosaurs in North America ranged from very tiny (Hesperonychus) to very large (e.g. Tyrannosaurus rex) [1]. It is even likely that this small theropod was very common throughout Cretaceous Alberta. Although few bones are easily distinguishable as Hesperonychus, there are several small claws within collections of museums that likely represent claws from this animal. Unfortunately, claws are not very distinct between species and it can be hard to determine exactly what animal it comes from. For a bit more about this find, you can view articles from CBC and BBC

That's really all that is known from this small carnivorous theropod. Next week, we're going to talk about something a little bit different: dinosaur trackways!

Other dinosaurs from Alberta that start with 'H':
"Hadrosaurus" - although this isn't necessarily considered to be a valid name by all palaeontologists
"Hanssuesia" - synonym of the pachycephalosaur Stegoceras

1 Longrich, NR, and Currie, PJ. 2009. A microraptorine (Dinosauria-Dromaeosauridae) from the Late Cretaceous of North America. PNAS 106: 5002-5007. Not open access but can be viewed here.

Monday, 7 January 2013

G is for Gryposaurus

Now that the holidays are over, we're back to our current feature: the Albertan dinosaur alphabet. Back before the holidays started, you'll remember we talked about the strange dinosaur Falcarius, which is not from Alberta. Now, we're back with a duck-billed dinosaur from Alberta called Gryposaurus.

Gryposaurus (pronounced 'GRYE-puh-SAWR-us') means 'hooked-nose lizard' and was a duck-billed (hadrosaur) dinosaur that lived 83-75 million years ago in North America. Its remains have been found in Montana, Utah, and Alberta. Its most distinctive feature is its large, arching, humped nose which distinguishes it from other hadrosaurs. It was 8-9 m long, which is pretty typical for duck-billed dinosaurs. Almost the entire skeleton is known, making it a good dinosaur to use in comparison to other lesser-known animals. 
The head of Gryposaurus showing the nasal hump. Image by Wikimedia Commons user ArthurWeasley.
The first specimen of Gryposaurus was collected along the Red Deer River in Alberta in 1913, and it has been controversial ever since. Several people have suggested that it is the same as another dinosaur called Kritosaurus (which we will discuss for the letter K), and also the very poorly known Hadrosaurus. These three dinosaurs are considered to be distinct animals, at least for now. Three species of Gryposaurus are recognised: G. notabilis (the original species named by Lambe in 1914), G. latidens (named by Jack Horner in 1992), and G. monumentensis (named in 2007).

Like other hadrosaurs, Gryposaurus was capable of walking on 2 or 4 legs, and was a herbivore. It used its hundreds of flat teeth to grind tough vegetation, and had a cheek to allow for chewing. The function of the nasal hump is not entirely known, but was likely used for social functions like sex recognition. Many hadrosaurs have nasal or cranial ornamentation for a variety of functions, and Gryposaurus is no different! 

Stay tuned next week when we move on to 'H' and a small theropod dinosaur!

Other 'G' Dinosaurs from Alberta: