Onto those teeth... and thumbs... and noses

©H. Kyoht Luterman

Muttaburrasaurus is, as stated, an interesting animal with an interesting name. Unfortunately, it has also become the butt end of a few incorrect beliefs about its anatomy as well as the relinquisher of interesting facts that are correct about its anatomy. Let us start with incorrect fact number one by studying the following image:

Bipedal capabilities, but probably wouldn't stand
like it was confused all the time.

Now, technically, this anatomical faux pas is debatable depending upon the source you consider. Muttaburrasaurus is, after all, a rhabdodontid or iguanodontid (depending, again, on your source) and therefore the way you feel about thumbs may be affected in either direction. Myself, I tend to agree with Ralph Molnar in the idea that the thumbs of Muttaburrasaurus were most likely not held out at angles like railroad spikes despite their placement in the iguanodont group. I suppose there may be some who believe that all iguanodonts held their thumbs out in this way, but I, myself, am not among them. Gregory Paul also shows the thumb held like a spike but he doesn't place Muttaburrasaurus in either group previously mentioned; he lists them as Ankylopollexia Miscellanea which are iguanodontians with thumb spikes that are not clearly related to Camptosaurs or other iguanodonts. The problem is, mainly, that the thumbs of these animals have not been reliably recovered as undeniably the first digit of the manus and that leads to some speculation which can then be segregated into two camps; those that believe there are thumb spikes and those that believe there are not thumb spikes. If I am wrong then the illustration above has a wonderfully accurate foreleg and manus. If I am right, it is wrong. I'll tell you know why I believe as I do that there are no thumb spikes.

Look at those teeth!

The teeth of a Muttaburrasaurus are totally out of whack when compared other iguanodonts. That doesn't mean it isn't an iguanodont, so much as it means that it is much more basal in its dental battery than other iguanodonts. Iguanodonts have a battery of teeth which are set up to be replaced over and over again. This is true with Muttaburrasaurus as well. However, the teeth of Muttaburrasaurus, while possessing this and a number of other traits akin to other later iguanodonts, the teeth replacement system was strangely different. Other ornithopods replace teeth at constant rate it is believed, allowing for multiple generations of teeth to exist in the mouth at any point in time. It was found in Muttaburrasaurus that the replacement teeth grew directly under the exposed teeth in such a way that only one generation of teeth was exposed at any given time. This system made chewing nearly impossible for Muttaburrasaurus. In continuing its strangeness, Muttaburrasaurus lacked a primary ridge that its cousins had on their teeth. This led Ralph Molnar, and Gregory Paul still describes it this way, to state that he believed Muttaburrasaurus may have scavenged corpses by shearing off meat. He later changed his mind and stated that he believed it more likely that the teeth acted like those in ceratopsian dental batteries which shear off vegetation and chop it up.

No one scares a Sage Grouse!

The reason I said before that this makes me believe there would be no thumb spike is that these are basal iguanodontid traits. The thumb spike was a basal iguanodontid trait in North America, but we have little to no proof that iguanodontids living in the Southern Hemisphere were developing or carrying on the development of thumb spikes (the exception being Lurdusaurus of Niger which dates from the same era as Muttaburrasaurus approximately but lived in Africa, an area completely separated from Australia at the time by an ocean thus negating travel between the two as far as we know meaning that Muttaburrasaurus probably did not evolve directly from Lurdusaurus). Looking at it as a characteristic taken from known iguanodontids prior to the isolation of Australia and Antarctica it is feasible to say that the thumb spike may exist, however, I feel that the Muttaburrasaurus would have either relied on its large size and herd practices, like zebra and wildebeest, or intimidation (like the Sage Grouse) to scare away predators. To intimidate we would have to look at that nose, in addition to their sheer body size, and what kind of fleshy thing could have covered it.

Walking with Dinosaurs covered the nose in a way you wouldn't really expect. I've seen trunks and all kinds of other things placed on dinosaur heads during the course of my personal research into dinosaur anatomy and biology. Eventually you think you've seen it all then something as unassuming and peaceful looking as the WwD Muttaburrasaurus comes along and frightens the life out of you. First of all, while I'm not a fan of the thumb spike thing I also don't believe in the grappling hook scenario that's off to our right here. I acknowledge the idea that the hands had limited motility, like a thumb spiked hand would have, but I don't believe they were hoofed either. I think my mental image is somewhere near four toes lightly on the ground with the ability to pull vegetation. This hand has five fingers and looks like it could reach out and grab you by the ear delicately if it needed to. I think there's too much articulation. Anyhow, back to that nose, WwD had a big surprise for us stored on the nostrils of its Muttaburrasaurus which, in all honesty, could be accurate. I don't like to debate skin flaps, as anything within reason could be acceptable and therefore not worth arguing over, so if anyone has any ideas on the subject they're welcome to pitch an idea for conversation purposes.

Here's what Walking with Dinosaurs did for their Muttaburrasaurus skin flap over the nostril idea (which is also where the intimidation idea comes in):