Anyklosaurs The Forgotten Successes

In most Dinosaur books and media we’re presented with a strict timeline of when different Dinosaurs did and didn’t exist. In many ways there is nothing wrong with it. If one is to learn something about Dinosaurs a good thing to come out of it with is that most of them did not live at the same time as others (So could we please stop getting books of T-Rex fighting Stegosaurus already!), that alone in the same region.

The problem is that often by setting up these timelines the authors of the books set up a false history of Dinosaurs. One that can lead to some surprising shocks for people who later dig deeper. An example I found in one of my books published in 2002 (which shall remain nameless because it is an OTHERWISE great book) was on long necked plant eating Dinosaurs. According to this book the Prosauropods lived during the Triassic, only to be replaced by the Sauropods in the Jurassic who themselves perished in the Cretaceous.

Not a single one of these facts is true. The Prosauropods flourished well into the early Jurassic, the Sauropods themselves appeared in the Triassic and continued well into the Cretaceous (a fact this book points out later talking about the Titanosaurs of South America… yet earlier in its overview of Sauropods it was stated the Sauropds went extinct in the Jurassic).

I have always wondered why this seems to come up all the time in books (and documentaries)?

One obvious answer is lack of research. It is really easy to just read someone elses older book and rewrite what they have stated, than do the research yourself. Through this cycle the same sterotypes and false facts keep circulating again and again. The other reason I think is that we want things to be in a nice, easy, and organizable history. The way human history is. The Romans for example didn’t coexist with Napleaeon nor he with the Mongols, and thus it can be very easy to talk about and organize human history. In a similar way, wouldn’t it be nice when discussing Dinosaurs that when you mentioned say Prosauropods, everyone would automatically know you were discussing the Triassic and not the Jurassic or Cretaceous.

Sadly in the realm of Palaeontology and natural history, unlike proper history, things aren’t ever this simple…

One very clear example of this forced timelining, is this rather heavily armoured family here, the Ankylosaurs.

In most books you come across, the Ankylosaurs are presented as the invincilbe tank-like Cretaceous replacements for the Jurassic’s pseudo-armoured Stegosaurs… Right away this makes for a great narrative! The Stegosaurs being less protected and more vulenerable than the Ankylosaurs, suddenly become something of a pioneer group of Ornithischians.

Afterall if this were the case, when Stegosaurs appeared on the Mesozoic scene they’d have been “underdogs”. They had to tough out the Jurassic, a time when the Ornithischians were trying to elbow their way into a Saurischian dominated world. The Sauropods were the immense plant eating champions, and the Stegosaurs were left eating what these giants didn’t want. All the while a whole array of big scary meat eating Theropods stalked around eating anything smaller than a fully grown sauropod, most often Ornithischians according to the books. Finally at last the brave Stegosaurs endured this harsh time period to make it long enough to pass on the torch of theropod proofness to the tougher Ankylosaurs, who with their armoured hides would slug this role right through to the end of the era of Dinosaurs.

Like I said it makes for an awesome story. I’m feeling the Stegosaurs hardcoreness. The Ankylosaurs recieve a hint of solitary dignity, picking up where those weaker, but plucky Stegosaurs left off.

The thing is it isn’t even remotely true!

One of the most overglossed details in popular Dinosaur palaeontology is that the Ankylosaurs are one of the longest last/surviving groups of ALL Dinosaurs!  

(Scelidosaurus by Prehistoric Insanity)

Immediately the narrative of Jurassic Stegosaurs and Cretaceous Ankylosuars breaks down when you look at how both these families originated. Granted the EXACT nature of their origins is a bit hazy, but we DO know that the Stegosaurs and Ankylosaurs had to have had a common ancestor. An animal similar to Scutellosaurus or Scelidosaurus, was most likely the basal form for BOTH groups. This evolution and split would have probably happened sometime after Scelidosaurus‘ time of 203 million years ago, but we’re not entirely sure exactly when due to a lack of fossils from just after this era. 

Still based on fossils, the common ancestoriary has long been known about for a long time. The remains of both Scutellosaurus or Scelidosaurus have enough in common with Stegosaurs and Ankylosaurs to show that at some point these two families were once one in the very early Jurassic. Sometime there after they split. Some experts argue before Scelidosaurus (again 203 million years old) others argue after.

Either way the first fossil Stegosaurs are found around 40 million years later in the mid Jurassic. Showing in solid fossil form that the Stegosaurs were around for at least 170 million years ago in the mid Jurassic (though almost certainly earlier than this), until their demise in the early Cretaceous.

However Jurassic Ankylosaurs could be easily glossed over. There was no compelling fossil evidence to show they existed. For a long time the earliest known Ankylosaurs were from 130 million years ago in the early Cretaceous. Concievablely a primitive Scelidosaur like lineage could have carried on until the Cretaceous where it finally developed into the more advanced heavily armoured Ankylosaurs.

You could tell this story till 1993 and get away with it. However in 93 a new Ankylosaur was described that destroyed the late blossuming tankosaur theroy. Tianchisaurus was a Chinese Ankylsoaur that hailed from 170 million years ago. That is same age as the first known Stegosaurs! Meaning that these two lineages more than likely evolved alongside each other.  

The important difference being that the Ankylosaurs, unlike the Stegosaurs, continued to thrive and evolve right up till the end of the Dinosaurs era at the end of the Cretaceous.

(Graphic by Prehistoric Insanity)

Putting this into presepective let us look at the overall run of the Dinosaurs. They appeared around 235 million years ago, and went extinct around 65 million years ago. If we count the appearance of Scelidosaurus * as the beginning marker of the Ankylosuar group than they start at 203 million years ago and run right up to the extinction event in the form of Ankylosaurus itelf. That is a mere 30ish million absence from the whole 170 million year history of the Dinosaurs. Let that sink in, the Ankylosaurs lasted 140 million years. This is far from being a late entry into Dinosaur lineages most books present. Rather the Ankylosaurs are among THE longest lasting and thus in some ways most successful of all Dinosaurs! 

* Keeping in mind there is debate as to what Scelidosaurus is. Is it a basal Stegosaur? Is it actually a primitive Ankylosaur? Or is it in fact a common ancestoral form for both? I personal would weigh in on it being either the common ancestor or an Ankylosaur based on its armour, but again I’m not an expert (skeletal features are more important for figuring this out). However no matter which way it turns out, I’m confident it’ll be found that the Ankylosaurs origin lies within 5 million years before or after the 203 million mark. 

(Picture by Prehistoric Insanity) 

So let that sink in. Rather than some random oddball group that turns up towards the end of the Dinosaurs run, that they’re commonly presented as (the Cretaceous is more like half the Mesozoic anyway… I never did get how books tend to treat it like a mere 1/3!), the Ankylosaurs were running around roughly 80% of the time the rest of their fellow Dinosaurs were. There are few other overall groups of Dinosaurs that enjoy that degree of success…

Of course the Ankylosaurs were a diverse group, and hardly remained constant throughout that time. Just like the similarly long run (but recognized for their temproal success)Ornithipods, the Ankylosaurs broke down into a vast array of different families including the Polacanthids, Nodosaurids, and Ankylosaurids. Perhaps one could argue the Theropods out did both these Ornithischian groups, but I’d personal argue, for the most part, theropod families tend to be a lot more variable and dynamic temporally. The Ankylosaurs on the other hand, in particular the Nodosaurids remained fairly constantly designed throughout their history.

In any case the Ankylosaurs were remarkably longer run and successful than the average book presents them to be.

 A Paleo FACT! brought to you by Traumador the Tyrannosaur of The Tyrannosaur Chronicles