A Dinosaur Skull in Amber? Maybe Not

On March 11^th, paleontologists working out of Myanmar’s vast amber quarries announced the discovery of a dinosaur skull encased in Amber. The dinosaur—named Oculudentavis—was tiny, with a skull measuring just 1.5 centimeters long. The authors of its initial Nature paper described Oculudentavis as a dinosaur complete with almost two dozen teeth used for catching insects that was fully capable of flight like birds. The idea of Oculudentavis as a species right on the middle of the evolutionary tree between dinosaurs and birds seemed miraculous. This seemed too good to be true, and indeed it may have been. In the following days, while media outlets from CNN to national geographic made headlines of the “smallest dinosaur ever”, paleontologists the world over became highly skeptical of this find. Within less than a week, new research was released that challenged the taxonomy of Oculudentavis, proposing it as a species of lepidosaur (lizards, snakes) as opposed to a dinosaur. With this in mind, the question must be asked: What is the amber skull? A lizard, or an avian dinosaur?

Why was it Considered as a Dinosaur?

To come to a definitive conclusion, we must first understand why the skull was presumed to be that of a dinosaur. According to head paleontologist Lida Xing, the connection was established as the appearance of the skull, specifically the large eyes and a thin, lengthy snout are similar to that of birds (Greshko). Aside from these physical traits and the age of the fossil, there really isn’t anything connecting the skull to dinosaurs, especially as the skull lacks feathers and has skin patches instead. According to some reports, feathers were discovered on an accompanying block of Amber. However, this block is now missing and thus it cannot be used as evidence.

The Evidence Against:

The first major issue with the dinosaur argument is with the skull shape. While the skull appears to be similar to some bird species, this is not a conclusive means to identify an animal’s taxonomy. In fact, some small reptiles also have similar skull shapes and as such the simple appearance of the head is far from reliable in making a proper diagnosis of the animal’s taxonomy.

The major reason why this identification seems to be incorrect is due to a quirk in the skull itself. Archosaurs (the group inclusive of dinosaurs, birds and crocodylomorphs) possess skeletal openings on the middle of their snouts called the antorbital fenestra. The fenestra, which typically house a sinus cavity to weigh down the skull, are unique to Archosauria and are typically used as a defining trait for the group. With this in mind, the skull of Oculudentavis lacks the presence of the fenestra, a telltale sign that it may not have been a dinosaur. Further, the close relatives of Oculudentavis, such as the early birds Archaeopteryx and Jeholornis all possess these skeletal openings, meaning it would be highly unlikely that Oculudentavis managed to lose the fenestra in a relatively short amount of time.

Lastly, the teeth of Oculudentavis are unlike those of other Archosaurs. While Archosaurs such as crocodiles and carnivorous dinosaurs have sockets in their jaw which house their teeth, this trait is absent in Oculudentavis. Instead of sockets, its teeth are directly attached to the sides of its jaw, which is a defining trait for the group of reptiles that encompass lizards and snakes, known as squamates. This fusion, which is unheard of amongst other dinosaur and bird species, may just be the final nail in the coffin for the “world’s smallest dinosaur”.

With these facts in mind, it would seem as though Oculudentavis was not a dinosaur, but rather a small species of lizard that lived in the mid-cretaceous period of Myanmar. Having said this, it is entirely possible that it was a highly distinct dinosaur, complete with its own specialized adaptations. Until more fossil material is described, it is impossible to confirm whether or not the world’s smallest dinosaur has officially been discovered.

While finds like this are awesome, the mines of Myanmar are notoriously inhumane; I do not endorse their use and will discuss their ethics in a later article.

Really concept cool art of lizard Oculudentavis can be found here: credit Mette Aumala.

Bibliography: 

I do not take credit for any images in this article.

Bird Oculudentavis: Credit to Han Xhixin, Viewed Here.

Ichthyosaur: Credit to Andreas T. Matzke, found Here

Oculudentavis in amber found Here

Archaeopteryx skull found Here

Oculudentavis 3D skull found Here

Greshko, Michael. “Smallest-Ever Fossil Dinosaur Found Trapped in Amber.” National Geographic, 12 Mar. 2020, http://www.nationalgeographic.com/science/2020/03/smallest-ever-fossil-dinosaur-found-trapped-in-amber/.

Li, Zhiheng, et al. “Is Oculudentavis a Bird or Even Archosaur?” BioRxiv, Cold Spring Harbor Laboratory, 18 Mar. 2020, http://www.biorxiv.org/content/10.1101/2020.03.16.993949v1.full.