Science Advances On

Thoughts from Steven: Science Marches On, Mosasaurs

Mosasaurs 1 (2)

The phrase “science marches on” is often used to denote a topic, idea, or concept that was accurate back when it was made but has become incorrect with new scientific information. For instance, Jurassic Park portrayed its Velociraptors very well for 1993, but science marched on, so when Jurassic World came out, its Velociraptors were horribly dated, even though they were portrayed exactly the same.

I want to address a couple of examples of science marching on, one in this post and one in the next. Today, I want to look at mosasaurs.

Mosasauridae is a group of extinct marine lizards. They are commonly referred to as mosasaurs. Unlike many of the other extinct groups of reptiles, the mosasaurs are actual lizards. Matter of fact, they are put in the same broad group that includes the monitor lizards, which includes the famous Komodo dragon. While several types of lizards are semiaquatic, the mosasaurs were exclusively aquatic. The majority of them were marine: there are a couple species that are thought to have lived in freshwater environments, but the rest were sea dwellers.

Above is a picture of Mosasaurus, one of the classic examples of mosasaurs. This is a picture of a model from the Carnegie Collection. This particular model is from 1991.

Next is a picture of Tylosaurus. This model is also from the Carnegie Collection except it is from 2008.

Mosasaur 2 (2)

Mosasaurus and Tylosaurus would have looked very similar to one another. They were similarly sized mosasaurs with similar builds. If they were similar, why do these two models look so different? Because of when they were made, mosasaurs were once thought to have a serrated frill running down their backs, as the Mosasaurus model illustrates. This frill was a misinterpretation of preserved traces of skin in the neck region. It is now known that mosasaurs had little ornamentation and had a more torpedo-shaped body, much like the Tylosaurus illustrates.

The scales on the Mosasaur are large and noticeable. While the Tylosaurus appears smooth and scaleless, it is known from skin impressions that mosasaurs had fine, keeled scales covering their bodies. The smoothness of the model highlights the small and fine nature of these scales.

Finally, the Mosasaurus model shows the nostrils perched right on top of the snout and actually projecting above the skull a little bit. This is a misinterpretation of the aquatic nature of the mosasaurs. Yes, they had to surface in order to breath and yes, their nostrils were still on top of the snout, but that does not warrant portraying their nostrils like whale blowholes. The Tylosaurus model corrects this by reducing the nostrils.

Even though the Tylosaurus model is much more up to date, it also has a few errors. The biggest is that the tail probably should have an upper lobe on it making it slightly forked, kind of like the tails of some sharks. This information did not become known until just a couple of years ago when a mosasaur was found with good traces of its outline. Before then, the exact structure of the tails was not known for certain.

These models should illustrate how science advances and old ideas are replaced by new ones. One must always take care in science and not hold onto cherished ideas too strongly. While some people may have grown up with old models (such as the 1991 Mosasaurus), new information changes our understanding and creates new models (such as the 2008 Tylosaurus).

Leave a Reply

%d bloggers like this: