Month: October 2016

Drawing Hands

I am doing a session on drawing hands with a local arts club early next year, so decided to sit down and do some prep work.

Hands are familiar and easy to to model, but they can seem a bit daunting to draw. Their structure and movement are complex, and if the proportions are off or the gesture shown is unnatural, people tend to notice it fairly quickly.

As it turns out, hands are also tricky to photograph, at least if the ones you are planning to draw are your own. The pictures below were taken using the self timer feature on my webcam. This allowed me to press the button and still have both hands free for the photo.
hands-four-pics Read more

Linosaurs

In my foray into printmaking earlier this year, one of the things I decided to try was a lino cut of a dinosaur.

It is often hard to tell where artistic inspiration comes from, but who would not marvel knowing our world once was populated by such awesome creatures? I was never one of those children who are obsessed with dinosaurs, but I have had a soft spot for them (for most things fossil, really) all of my life.  So once I decided I wanted to show a Triceratops, I went into research mode and looked for papers and studies about them.

As it turned out, I ignored much of what I learnt when it came to the actual art. Lino is not really a medium that lends itself to photorealism, so here is my little Triceratops munching on cycad leaves.

Lino cut, 9" x 12"

 

The artist in me is all about creative expression, but the biologist tends to ask factual questions such as “What other dinosaurs were actually around at the same time as Triceratops?” The Mesozoic, or ‘age of reptiles’ lasted roughly 180 million years, and many species never co-existed. Triceratops was a latecomer. It only appeared in the late Cretaceous, shortly (relatively speaking) before dinosaurs went extinct. Research at the Hell Creek Formation in Montana that stems from this period has excavated not just individual skeletons but also looked at numbers [1]. Next to Triceratops and Tyrannosaurus, it turned up many specimens of Edmontosaurus, a hadrosaur or ‘duck-billed dinosaur’ that I chose for my next lino cut.

One of the fascinating things I learnt while reading about these animals is that both Edmontosaurus and Triceratops have undergone substantial taxonomic revision over time. Traditionally a new-found skull that looked ‘different enough’ from previous specimens (where ‘different-enough’ is a matter of expert assessment) would be assigned to a new species or even a new genus. But once there was more material and palaeontologists began to look at the whole evidence, they sometimes had to re-assess species boundaries.

Intuitively, this makes sense.  A small, duck-billed dinosaur that looks similar but lacks some of the features we associate with Edmontosaurus may indeed be a different species. Alternatively, it may just be a young Edmontosaurus. If all you have are two or three isolated skulls (or parts of skulls), this is hard to figure out. If you have quite a few of them, you can start to see patterns. For both Triceratops and Edmontosaurus, our understanding of natural variation and the way an individual’s appearance changed as it grew has improved, and some finds that palaeontologists used to think were separate species are now considered young or sub-adult individuals [2,3,4].

A question more directly relevant to my art project was food. Like Triceratops and its kin, hadrosaurs were herbivores, but what types of plants exactly did Edmontosaurus eat? Far more studies have looked into this than I could read, but based on differences in teeth and tooth wear, Triceratops ate tough, fibrous plant material, hence the cycads above. Hadrosaur diets were probably varied and included items such as leaves, fruit, and twigs [5]. One recent study concluded that Edmontosaurus was a grazer that may have eaten horsetails, [6] so here is my rather loose interpretation of that.

 

There are fossilized hadrosaur skin impressions [7,8], but actual scales seemed too small to carve, so the stripes and spots are entirely my doing.  Also, one of the two usually-recognized species of Edmontosaurus, had a fleshy ‘cock’s comb’, which was probably used for social signalling [9]. For the other,  the jury still seems to still be out, so I did not include one.

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  1. John R Horner, Mark B Goodwin & Nathan Myhrvold (2011). Dinosaur census reveals abundant Tyrannosaurus and rare ontogenetic stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA. PLos ONE 6(2): e16574. doi:10.1371/journal.pone.00016574.
  2. John H Ostrom and Peter Wellnhofer (1986). The Munich specimen of Triceratops with a revision of the genus. Zitteliana 14: 111-158.
  3. John R Horner & Mark B Goodwin (2006). Major cranial changes during Triceratops ontogeny. Proceedings of the Royal Society B: 273: 2757-2761, doi:10.1098/rspb2006.3643.
  4. Nicolás E Campione & David C Evans (2011). Cranial growth and variation in Edmontosaurs (Dinosauria: Hadrosauridae): Implications for Latest Cretaceous megaherbivore diversity in North America. PLos ONE 6(9): e25186. doi: 10.1371/journal.pone.0025186.
  5. Jordan C Mallon & Jason S Anderson (2014). The functional and palaeoecological implications of tooth morphology and wear for the megaherbivorous dinosaurs from the Dinosaur Park Formation (Upper Campanian) of Alberta, Canada. PLos ONE 9(6): e98605. doi: 10.1371/journal.pone.0098605.
  6. Vincent S Williams, Paul M Barrett & Mark A Purnell (2009). Quantitative analysis of dental micro wear in hadrosaurid dinosaurs, and the implications for hypotheses of jaw mechanics and feeding. PNAS 106(27): 11194-11199. doi: 10.1073/pnas.0812631106.
  7. Henry Fairfield Osborn (1916). Integument of the Iguanodont Dinosaur Trachodon. Memoirs of the American Museum of Natural History, New Series I: 33-54.
  8. Phil R Bell (2012). Standardized terminology and taxonomic utility for hadrosaurid skin impressions: A case study for Saurolophus from Canada and Mongolia. PLos ONE 7(2): e31295. doi: 10.1371/journal.pone.0031295.
  9. Phil R Bell, Federico Fanti, Philip J Currie & Victoria M Arbour (2014). A mummified duck-billed dinosaur with a soft-tissue cock’s comb. Current Biology 24: 70-75. doi: 10.1016/j.cub.2013.11.008.