Archosaur Air Conditioning

Today on DrNeurosaurus I want to talk about a [study] that came out in July of this year, but has recently been going around the media. This isn’t the typical study I talk about where some new fossil is discovered and described and celebrated for its novelty (new-ness) and scientific value. This is a different kind of study.

The authors wanted to take a closer look at a structure in the head of many archosaurs. You might remember archosaurs from other posts – they’re a group of animals that include the living crocodylians and birds, their ancestor, and all of its descendants:

This tree is modified from the one found [here], on Archosaur Musings.

All of these animals have openings in the top of the skull, that previous scientists thought were home to jaw muscles. The authors looked at these openings in over 100 specimens of lizards, turtles, crocodylians, and birds using CT, MRI, dissection, and other methods.

A crocodylian skull with the openings labeled. in the top of the skull. Source unknown.

They found that in many cases, the openings didn’t have muscles all the way through. Instead, the openings contained blood vessels just under the skin. When the authors looked at extinct animals like non-avian dinosaurs and extinct crocodylians, they did not find any evidence of muscles in those locations. Using comparison to living animals, they suggest that these openings housed blood vessels instead. But for what purpose?

Well, that depends on the animal. In animals with display structures like frills, those blood vessels could provide nutrients to the structure. 

A Triceratops. Its frill is a display structure – a structure that is used to communicate with other members of its species. From the Natural History Museum, London.

In animals without those structures, the blood vessels would act as a way to regulate their body temperature. To test this, the authors used thermal imaging cameras to take photos of living crocodylians. They found that those openings were cooler than the body in hot temperatures, and hotter than the body in cool temperatures. This suggests that their hypothesis (idea) has support!

Figure 11 from the paper: an artist rendition of thermal images of Daspletosaurus, Deinonychus, and two croc-line archosaurs. By Brian Engh.

Using lots of specimens and imaging methods, the authors were able to discover something completely new about animals we’ve known for a long time, including ones living today!

The Largest Land Animals Ever

This post will start out a bit differently because I want you to understand how amazing titanosaurs are before getting into the news about them.

The titanosaurs were the largest land animals ever to have lived (around 100 tons). Blue whales are heavier (around 180 tons) than the titanosaurs were, but the whale’s weight is supported by the ocean they live in. Titanosaurs had to support their weight all on their own. For comparison, an African elephant (the largest land animal alive today) weight 7 tons. So a titanosaur weighs the same as 14 elephants.

titanosaur whale comparison

They are huge.

Titanosaurs belong to the group of sauropod (long-necked) dinosaurs, which are found throughout the Mesozoic. The titanosaurs were the last group of sauropods, from 90-66 million years ago. So the largest dinosaurs were around at the very end of the Mesozoic. Stomping around and causing a big rumpus everywhere they went.

How did they get so big?? Good question! Saurischian dinosaurs, including the sauropods and theropods, developed a system of air-sacs in their body. We know this because when the air sacs were big enough, they started invading near by bone and leaving hollow spaces. These air sacs connected to the lungs and created a one-way system of respiration that is super efficient. Birds still rely on this system today.

air sacs simple

Simple animation of how a bird breathes. Take from here.


Compared to a mammal breathing. Taken from here.

Ok, so, titanosaurs are: 1) from the Cretaceous, 2) incredibly large, 3) can breathe really efficiently (probably true for all sauropods). A couple of other cool things about sauropods: some of them had [whip tails], some of them had [armor], some of them became dwarf-sized on [islands].

In short, titanosaurs are really amazing.

This week (April 2016), two articles were published about titanosaurs!

First, a wee baby Rapetosaurus krausei from Madagascar was [described]. This little baby shows that titanosaurs grow isometrically. Isometric growth is when your shape does not change as you get bigger. This is in contrast to allometric growth, where shape does change as you get bigger. Humans, among many examples, grow allometrically, so our baby shape is very different from our adult shape:


Our bodies change shape as we get bigger. Taken from here.

Titanosaurs are adult-shaped from when they hatch:

Fig 1 A

Figure 1A from the paper showing how the baby bones (yellow, green, blue) have the same shape as the adult bone (black). The smallest grey titanosaur is just hatched, the colored one is the size of the specimen they had for the paper.

Second, an almost complete skull of the new titanosaur (from Argentina!) Sarmientosaurus musacchioi was [described]. It was found near the town of Sarmiento, Chubut.

Fig 3c

Look at it! It’s beautiful. (This is figure 3c from the paper.)

It’s so well preserved that the authors were able to CT scan it and create an endocast (a representation of the brain and surrounding structures).

Fig 9A

Figure 9a from the paper – a reconstructed 3d brain (front is to the left) showing all the structures.

They were also able to use it to analyze the evolutionary relationships of titanosaurs. They ran the analysis several ways and found the same result each time: that Sarmientosaurus is an early member of the most derived titanosaurs, the Lithostrotia. The age of the rocks where Sarmientosaurus is found is older than other members of this group and makes their evolution older than what we had previously thought.

The age, evolutionary position, and great preservation of this new titanosaur helps answer many questions about the evolution of the most derived titanosaurs. It’s a spectacular discovery and addition to our knowledge of the largest land animals that ever lived.

PS: If you want to see one fully reconstructed, the American Museum of Natural History recently unveiled [one]:

titanosaur amnh

The AMNH titanosaur in all its glory.

The Mysterious Sea Bear

Sometimes we find fossils that we can’t quite compare to living animals. We can get a rough idea of what kind of animal they are and maybe what they might have eaten, but the details are unknown. Sometimes it’s because we don’t have enough of the animal’s body parts, but sometimes it’s because they are different from anything alive today.

The animal Kolponomos is like that. From the shape of its head, we knew it was related to the group Carnivora. Carnivorans include dogs, foxes, cats, bears, seals, sea lions, walruses, weasels, skunks, otters, hyenas, mongooses, and a few other animals, that eat other animals.

kolpy skull

Drawing of a Kolponomos skull done by C. Tarka and L. Meeker at the AMNH.

The odd thing about Kolponomos is that it might be a close relative of bears, but it had molars (those are the teeth in the back that grind up our food) like an otter. Otters eat hard-shelled animals using their molars, but they use tools to crush the shells open if they are too big:

Walruses also eat hard-shelled ocean creatures like clams by sucking the shell until it opens and eating the delicious insides.

walrusxi         walrus skull
“The walrus has the longest canines of all Carnivorans.” (says Jack Tseng, lead author on the paper)

Scientists couldn’t figure out how Kolponomos was eating these things, until this article came out in Proceedings of the Royal Society B. The authors tested how strong the skull was and how it moved while it bit down.

They found that Kolponomos would dive into the ocean, support its head using its lower front teeth, clamp down on the clam, and twist it off the rock using its strong neck muscles. Then it would move the clam to its molars where it would be crushed open.


Figure 1 from the article.

An interesting point about this is that sabre-tooth cats, like Smilodon would use the same method of supporting its head using its lower front teeth to drive its sabres into its prey.



© Disney

So Kolponomos is a bear-relative, with a diet like an otter or walrus, with a bite like a sabre-tooth, that lived by the ocean. Probably not in a pineapple though.