Nimbacinus dicksoni

Until now, life has moved at such a violent pace that I have not been able to return to this blog until now. I am nearly 26 and my life is completely different to the circumstances I was living in back in 2009. It feels like another world. In April 2008, my Mother died and my immediate family entirely fragmented. Since that point, until quite recently, I was very much alone in my struggles. At the end of 2009, I gradated with a Bachelor of Science with majors in geology and zoology from the University of Tasmania. I then relocated to Sydney to complete my Honour's year in vertebrate palaeontology, which will be the subject of this post. The course is only supposed to take a year, but due to untold dramas including assault and homelessness and the general incompetance of people and the system, I emerged, at the end of 2011, in triumph with a grade of 2nd Class 1st Division and this reconstruction of Nimbacinus dicksoni:

Nimbacinus was a 15 million year old thylacinid, which are a group of carnivorous marsupials that resembled canids because they evolved to follow similar lifestyles, not because they were closely related. They only became extinct fairly recently, in 1936, when the last Tasmanian tiger died in a zoo in Hobart, Tasmania. (I used to drive passed the remains of this zoo every time I went to university in Tasmania.) The Tasmanian tiger, (Thylacinus cynocephalus) was the largest Australian marsupial carnivore and was approximately the size of a German Shepard dog. It was called a tiger because of the dark stripes it bore on its hindquarters. Here is a photo of the late Tasmanian tiger:

The title of my thesis is Postcranial morphology of Nimbacinus dicksoni (Thylacinidae: Marsupialia) and a discussion of the functional morphology of the limbs. That may seem like a daunting mouth full but all it means is that I described all the bones of this animal except for the skull, which was already described by Steve Wroe and Anne Musser in 2001, and I discussed how it may have used its limbs when it was alive. I also did a head reconstruction of Nimbacinus based on figure 3 of Steve Wroe and Anne Musser's cranial description.

A large part of the requirements of the work was that I produce stippled drawings of all the bones of Nimbacinus and of the Tasmanian tiger and described them anatomically in the text. Here is the ventral vew of the pelvis of the Tasmanian tiger:

Overall, I had to produce nearly 60 of these such images, each bone was illustrated in anywhere from three to five different angles to demonstrate their significant features. I did an average of three drawings a day for nearly six months. I concluded that Nimbacinus was not just a miniture Tasmanian tiger. The former was about the size of a fox. Proportionately, Nimbacinus had stronger forelimbs, so whatever it did in terms of hunting, it was consuming different prey than the Tasmanian tiger and possibly doing a lot of grappling with it. The Tasmanian tiger, on the other hand, was more of a pursuit predator that chased small wallabies.

Dromornithids, "Mihirungs" or "Thunderbirds"

When I came back to Tasmania after my wonderful time at Riversleigh smashing open limestone to get fossils, I decided that my new subject for the pen and paper would be Dromornis stirtoni. After I had drawn a pair of Thylacoleo carnifex scrapping of course. (They are not anatomically sound I know but I will get better at this.) So I pulled out Tom Rich and Pat Vickers-Rich's Wildlife of Gondwana book from the shelves of the Science Library in the University of Tasmania and sketched these dromornithid legs. I saw the skull on one of Micheal Archer's powerpoint slides as he gave a lecture in the relative cool of the evening on the warm open timber awning where we took our meals. Seeing that skull sparked my interest in Dromornis stirtoni once more. I made a quick sketch in the fleeting seconds he had it on the screen...


Here it is amongst the notes I took from Mike's lecture. I really like the shape of this skull. Look at the deep upper jaw with it's beautiful curves. It has such a good solid chin. Isn't it worth swooning over?! :-D After the lecture and all the questions were asked with the lights switched back on, I did a quick reconstruction which was based more heavily on what I remembered of emus, although these Dromornithids are only distantly related to emus. (We actually don't know how these birds are related to other avian lineages but some believe that they are related to primitive anatids, hence Dromornis stirtoni has been dubbed "The Demon Duck of Doom" because of its possible carnivorous habits; others think that they are distantly related to galliforms and it was really a gigantic mutated chook).

You can see the reconstructed head of Dromornis stirtoni lower lefthand corner above. I can do something more interesting with this animal I believe and that is what my next few posts will focus on. In this picture you can also see how I have drawn Thylacoleo carnifex and Thylacinus cynocephalus. Also, I have drawn the skeletal major structures of what I hoped to be closer to the marsupial form. I had an eye opening discussion with Henk Godthelp who told me that that the shoulder structure of marsupials is unique and the scapula is orientated more vertically. The pelvis is likewise in a more vertical position as opposed to the horizontal orientation that you see in placental mammals. Also there are more vertebrae attached to the pelvis of marsupials than those of placental mammals. The marsupial posture is kind of like a kidney bean with the back arched and the limbs held rather lower than it. This is most prominantly seen in bandicoots and wombats. Actually this posture can also be observed in mustilids like otters and ferrets. Henk told me I ought to dissect a possum, but I haven't been able to lay my paws on one yet and I don't fancy going out there and shooting one like many Tasmanians do here. I haven't had time to comb the road for roadkill so far. Micheal Archer told me that the forequarters of marsupials tend to be more well-built than the hindquarters. This can be observed in the Tasmanian Devil (Sarcophilus harrisii) in particular but also in the recently extinct Thylacinus cynocephalus. This is a carry over from the fact that when a marsupial is born, it is very underdeveloped but it does have strong forearms to pull itself through the mother's fur to the pouch. We are more likely to see this feature in Thylacoleo carnifex.

The Zoology Practical Book Cover-The Back

This is the back cover of the zoology practical book. The front cover was the subject of the previous post.

At the top of the image are two dinosaurs from early Cretaceous Australia (135-107 mya, I know I made a mistake in the actual drawing). The Mesozoic fossil record in Australia is rather poor. Most of the remains exist as isolated scraps of bone and are often the preserved after travelling in a fluvial system for some time. Thus they have often been rounded and disarticulated by the actions of running water. This is true of Lightning Ridge which is a deposit that records rivers following into the sea. Hence these dinosaurs are very speculative, but hey I can dream, can't I? :-) For reference I had a look at Gregory S. Paul's Predatory Dinosaurs of the World which not only has reconstructions but good drawings of dinosaur skeletons.

Rapator ornitholestoides is known from a single metacarpel preserved in opal. It was about 9 metres long and might have looked like a lightly built Allosaurus. It's specific name, ornitholestoides, means "like Ornitholestes." Ornitholestes hermanni was described in 1903 and is still only known only from one complete skeleton found in the Bone Cabin Site of Wyoming. Ornitholestes and Rapator share an elongated posteromedial process, which is a peculiar trait suggesting that these animals could have been related. Hence, this reconstruction has been modelled on Ornitholestes. The metacarpal is not only larger than that of it's possible American relative, but is also more robust. To convey this idea I added greater depth to the head of Rapator. The nasal bones of Ornitholeste have been a source of some contention, with some people believing that they are the broken bases of a nasal crest as seen in Proceratosaurus and others thinking that the nasal bones are either displaced or the products of post-depositional deformation. For this reconstruction, Ii decided to let myself go on a flight of fancy and added a nasal horn. I have coloured it bright yellow and red because it might have been used as a sexual display . I have also given it darker skin around on the lips and around the eye because they can give better contrast to the teeth. The eyes may also look more expressive. You can see black gums on wolves in which this contrast is used to intimidated other wolves when the teeth are bared. The rest of the body is a mottled green and brown to serve as camouflage when the animals is hunting. Since no more complete remains have been recovered to date there is continued discussion as to the true lineage of this dinosaur. There are other theories suggesting that it might be a giant Alvarezsaurid and Steve Sailisbury now believes it may be related to Nqwebasaurus, a basal coelurosaur from South Africa.

Kakaru kujani is known from a single tibia preserved in opal recovered from Andamooka in South Australia. In the scientific community only a cast is available for study because the original fossil was sold by an opal dealer. The tibia is slender and resembles that of a wader bird. It is similar to Avimimus but has facets for the astragulus (ankle bone) that are unique and it could represent a completely new lineage of dinosaurs. For this reconstruction I have used Avimimus as a model and I have made the bill deep and brightly coloured as in puffins which use their deep beaks for colourful sexual displays. I put the dark ban through it to break up the contours of the beak, as in what stripes do for zebras. It might lend a bit of camouflage. On top of the head are feathers that make up a crest. These only have filaments on the tips, as in a peacock's crest.

Below is my alter-ego, Aquiline the Imperial Diallonyx with a Tasmanian Tiger (Thylacinus cynocephalus) sitting on his back. The Tasmanian Tiger has only been extinct since the 1930's and some people still believe (or want to believe) that it still roams the wilds of Tasmania. It was a remarkable case of convergent evolution and this animal took very strongly after wolves or dogs. However, it was always thought to be a solitary hunter and was the size of a German Shepard Dog. It descended from hopping ancestors and still retained the stiff back of fused vertebrae in the lower back. Note that the thylacine can see it's own reflection Aquiline's coat. The coat of the Diallonyx is has a metallic sheen to it due to silver compounds in the fur. Hence it can operate like a mirror.