Tuesday, May 26, 2015

What walks on four legs at dawn, on two legs mid-morning, and then on four legs again at noon?

An Iguanodon. The second dinosaur ever described in scientific literature and one of the genera known from the most specimens, this beast has arguably gone through the most dramatic makeover of any dinosaur, as this drawing from last June demonstrates.


























The first iteration of Iguanodon (standing on the left) was conceived by Sir Richard Owen — who envisioned it as an elephantine behemoth and popularized by Benjamin Waterhouse Hawkins in a series of sculptures unveiled at London's Crystal Palace Park in 1854. An isolated triangular bone was interpreted as a horn that jutted between the nostrils like a modern rhino's.

In 1878, dozens of intact Iguanodon skeletons were discovered near the Belgian town of Bernissart. These remains revealed a much more slender animal along the lines of Hadrosaurus (described in 1858), and like Hadrosaurus, the animal was reconstructed in a tripodal, kangaroo-like position (center). The horn also turned out to be a spiky, ersatz thumb. As a very young child, I remember most dinosaur books, toys, and other dinosaur media conforming to this image, even as other dinosaurs assumed a more balanced, horizontal stance. In addition, I noticed that many of these depictions had also Iguanodon drooping their skulls downward, drawing attention to the back of their heads and making them look like vultures or bald men. Some of these illustrations also gave the animal a set of scaly ridges running down the vertebrae — not completely impossible, given the presence of these structures in the iguanodonts' later relatives and successors, the hadrosaurs.

The most recent reconstruction of Iguanodon (right) was devised by David Norman, who found that it walked primarily on all fours. 

I normally am hesitant about coloring dinosaurs green, worrying it will make them look too lizard-like. For Iguanodon, however, I thought it appropriate to keep the initial, super-reptilian restoration that color. I chose to make the later restorations mostly green as well, but with starker secondary colors and markings to represent our view of dinosaurs becoming more nuanced throughout the ages.

The markings for the modern Iguanodon are actually based on the modern Fiji crested iguana, albeit in a cedar rather than emerald green and with no teal scales. Also like this iguana, I made the skin around the nostrils yellow, although I'm not sure this was the most practical or aesthetically pleasing decision.


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