December 12th

Box #12 in our count down is Dysalotosaurus…

Days 1-5 of the count down.
Days 6-10 in the count down
Days 11-15 of the count down
Days 16-20 of the count down
Days 21-25 of the count down

Dysalotosaurus: the “Uncatchable Lizard”

Dysalotosaurus lived in late Jurassic Tanzania, Africa, and fits the generic body plan of smallish, bipedal body plan quite nicely. Thousands of individuals big and small, young and old (they’re estimated to live about 20 years) have been discovered in a massive burial site. Having so many fossils from so many growth stages provides a unique opportunity, and many studies have been done on growth stages, how their brains developed as they grew, and even various diseases suffered by members of the herd.

One such illness is known as Paget’s disease, a rare condition that causes certain areas to layer new bone rapidly. This rapid layering causes bulges and deformities in the bone, which is brittle and weak. It usually affects the pelvis or spine, causing pain like arthritis, but can also give headaches or bow-leggedness when it forms on the skull or legs. It is proposed that a virus and some genetic tendencies are the cause of this disease, so the Dysalotosaurus that suffered from it is the earliest known occurrence of viral infection.

Why was the herd so large, and what could have killed so many at once? Since the Tendaguru Formation represented a coastal area of tidal flats and lagoons, it has been proposed that the herd died during a migration across a tidal channel. The tide rose as the small dinosaurs attempted cross, and those that drowned drifted down to a curve in the river not far away and were quickly buried.

Perhaps such a death seems foolish. Keep in mind that large herds like wildebeast or zebra will gather at the edge of a river until finally there are so many that the ones closest to the edge finally have to jump or else they will simply fall in. Once the first jump in, the rest follow like the current of a river, and it cannot be stopped until all have crossed. Those that try to refuse to cross get pushed forward by the hundreds of those behind them, and so they have no choice but to brave the danger of predators or the swift currents of the incoming or outgoing tide. Or perhaps they got stuck in the soft, churned mud at low tide, drowned with the incoming tide (or got trampled), and then swept back down as the tide receded.

There are so many ways this dramatic scene could have played out. As sad as it may be for the Dysalotosaurus that died, it is good to have so many fossils from which to learn.

3 thoughts on “December 12th

  1. This is a very interesting article. I didn’t know about the presence of Paget’s disease within this species. Fascinating.

    As I’m sure you’ve read, Dysalotosaurus is very similar to the North American genus Dryosaurus, and for a while it was believed to be an African species of Dryosaurus.

    I recently overhauled my article on Dryosaurus. I’ve added more info and replaced the earlier drawings with two new ones. I’ve done much reading on basal ornithischian dinosaurs this year, and I discovered that I had made a big mistake in 2020 with my first reconstruction. I had incorrectly showed Dryosaurus with the small “dew claw” near its ankle which many small dinosaurs had. However, Dryosaurus (and Dysalotosaurus for that matter), are classified as basal iguanodontians, and these animals only have three toes on their feet, not four. Please pop over and let me know what you think about the update. Here’s the link:


    1. Thank you! I’m glad you enjoyed it. 🙂 I always like discovering new things when researching the critters for these posts, and fossil pathologies are especially fascinating. From what I read, it appears that aside from humans, apes, and perhaps a few other primates like lemurs, it is extremely rare to find Paget’s disease. The rarity makes it even more interesting to find a dinosaur with evidence of it.

      Yes, I chose Dysalotosaurus because I wanted another creature with the similar body plan to Dryosaurus. It’s always a tough call on how much information I can give in a short post like this one.

      I took a look at your post, and I think it looks good! It has been a little while since I’ve done direct research on Dryosaurus, so I did not know that about the dew claw. I’m pretty sure my illustration has the same error, since little Rosie is one of my older drawings and has never had an update. Thank you for sharing your article 🙂

      Liked by 1 person

  2. A couple errors in your presentation of this fascinating ornithopod:
    1. In this sentence, “Dysalotosaurus lived in late Jurassic Tanzania, Africa, a fits the generic body plan of smallish, bipedal body plan quite nicely”, the word “a” should be “and”.
    2. In the last paragraph, it looks like you combined “Lobolytoceras” and “Dysalotosaurus” together, when it should say “Dysalotosaurus”.

    But onto the animal itself, I am in love with this entry. I already really liked the creature itself, but I didn’t see it coming at all. I thought its history with being referred to as Dryosaurus, a creature you have officially shown in the shop (shout out to Rosie, btw), would mean you’d not cover it at least for now, but I’m glad I’m wrong in that vein.
    For today, my focus will be dedicated to Megalibgwilia, an echidna from the Miocene to the late Pleistocene of Australia. First described all the way back in 1884 with a second species described in 1896 (with this species being the oldest-known echidna and the only Miocene species of echidna), the genus is sometimes referred to as giant echidnas, although in reality, it is thought to have been similar in size with the western long-beaked echidna of New Guinea. Megalibgwalia was most likely an insect eater, similar to the short-beaked echidna of Australia. It was thought to have gone extinct due to a number of factors ultimately linked to the increasing acidification of Southern Australia.


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