A brief summary of the recent study concerning the brain-case scan for Carnotaurus sastrei

Probably the first ever study dedicated to brain and inner ear reconstructions for this particular theropod is out, revealing a fair deal of information about the animal's sensory prowesses. Rather riveting information if I say so myself.

•  instance, the notable olfactory capabilities. (But more about that later on)

By the way, for initial context on any vagueness on the precise dimensions in the study, (especially around the prefrontal region in between the horns) please note that the specimen was a very difficult one to permeate through scan. With a very controversial origin story and near indistinguishable features on site. I believe I talked about the nature of said specimen in one of my previous answers with respect to the presence of facial tissue encased in ferric concretions on this particular dinosaur.

• How is that relevant? Well, these very ferric concretions on the skull and the lack of contrast between the actual fossil matter and sediment yet again proved to be a major pain in the arse, affecting the quality of scans for the specimen.

Anyhow,

First and foremost, the study study finds that Carnotaurus for the most part shares the overall confirmation of the brain and inner ear with the rest of the known abelisaurid endocasts. However, some anatomical features are distinct to the South American members of abelisauridae.

These distinguishing features encompass:

• Curved loop like olfactory tracts and bulbs oriented in an anteroventral fashion.
• Forebrain and hindbrain positioned ever so slightly differently compared to other abelisaurids like majungasaurus, aucasaurus and vevanator.

While on the other hand considering similarities;

The forebrain, midbrain, hindbrain and inner ear labyrinth's size, shape and angles (overall respective dimensions) not only closely resemble that of other abelisaurids but also other mid sized theropods, namely Ceratosaurus and certain Allosauroids.

Image representing the inner ear labyrinth of carnotaurus

Therefore one can say that the hearing capacity for Carnotaurus was on par/similar to aforementioned theropods.

Now for the exciting part.

So one of the main points of interest in the study is the Encephalization quotient calculation, a measure of relative brain sizes among theropods.

As per the chart, the total volume of the cranial endocaust for carnotaurus is 169.8cm^3. It is easily observed that the minimum REQs (another abbreviation for Reptile Encephalization Quotient) of carnotaurus are much higher than those calculated for majungasaurus and even far, far larger theropods like sinraptor and giganotosaurus but not as high as tyrannosaurus.

The reconstructed cranial endocast along with the inner ear

A larger brain size relative to body. Potentially a more fine tuned animal as far as sensory abilities go?

Speaking of sensory abilities, the study also claims a presence of large and elongated olfactory bulbs and olfactory tracts in carnotaurus which clearly state that the animal was more reliant on it's sense of smell. So much so that the olfactory sense probably over-rode the sense of sight given the reduced and less prominent size of optic lobes.

I should probably add that the olfactory sense for carnotaurus is slightly higher than it's brethren but still represents the primitive condition for theropods. Carnotaurus, although had an acute sense of smell as far as abelisaurid standards go, was not exceptionally keen with it. It was simply more reliant on it.

Also, the increased gaze stabilization among South American abelisaurids suggest a better coordination of the head, neck and body compared to other abelisaurids.

To conclude:

It is safe to take from this study that carnotaurus was more of a scent driven animal than a sight driven one, had fine head and neck coordination and a larger cranial volume compared to most abelisaurids and allosaurids with relation to body size.

Here’s the link to the study:

https://www.sciencedirect.com/science/article/pii/S1631068319301824