We know a lot about how dinosaurs’ bodies worked because birds are dinosaurs. We can examine birds and how they function to better understand dinosaurs. This idea not only helps us understand how their bodies moved and behaved, but also how illness affected them.
That is what this [article] is about. Birds can get respiratory diseases (sickness in their lungs, throats, noses, and air sac system). One of the differences between birds and humans is that bird lungs are not just connected to their throats. Birds have a complicated set of other sacs connected to their lungs. The air flow through those sacs and into their lungs happens in a single direction, so every time the bird breaths in and out, fresh air is brought to the lungs. That’s not like what we, as mammals, have. Our air goes in and out of our lungs through the same passage, so every time we breath in, we have to breath in some air that was already in our lungs. Bird lungs are much more efficient than mammal lungs.
The flip side to this is that birds have more organ related to their breathing systems that can get sick. They can have illnesses in their lungs and air sacs. And as the air sacs carve spaces for themselves in the nearby bone, many illnesses in the air sacs can create illness in the bone. Sauropods, the long-necked dinosaurs, had the same system of air sacs invading bone in their bodies.
The authors describe a diplodocine (specimen MOR 7029) that had a deformation in the bones of the neck. Because those bones would have surrounded an air sac, it is likely that the dinosaur had an infection in the air sacs that caused the surrounding bone to react. The authors describe many respiratory diseases in birds that could have been the cause of this infection.
But because we are only able to analyze the bones, the authors tell us that it is hard to know exactly which disease caused this. They also say that the most likely cause was an infection from a fungus known from similar environments. We have fossils of that fungus from the Eocene, so it’s not too much of a stretch to assume it was around in the Mesozoic as well. The better understanding we have of birds, the more we can understand their extinct relatives.
This week, a new [paper] was published that described the largest sauropod footprint ever found from the Early Cretaceous (146-100 millions of years ago) of Korea. The footprint is more than 50cm (20 inches) in diameter!
The authors found something very rare inside the footprint: a dinosaur skin impression. That’s the equivalent of leaving a palm print on wet cement, like on the Hollywood Walk of Fame.
Mickey Mouse’s hand and footprints on the Hollywood Walk of Fame. From Pinterest.
The impression preserves interlocked hexagons that have a range of sizes. They seem to get smaller on the outsides of the impression.
Figure 2A from the paper showing the footprint on the left and a close up of the skin impression on the right.
The authors analyzed the sediment around the footprint to try and understand why skin impressions are so rare. They found that these impressions were left in on a muddy surface that had dried enough to preserve the impression. That muddy surface had to stay dry afterwards, and not get covered over by water. If more flooding had occurred, the print would have disappeared. The muddy surface also had to be covered by a thin layer of bacteria in order to hold the mud together. The combination of these conditions allowed the footprint and skin impression to stay preserved. These conditions can be hard to find in the same place and time, meaning that more dinosaur skin impressions could still be rare in the future.
I’ve talked about [Titanosaurs] before on this blog, but I’ll briefly describe Titanosaurs for those just tuning in. Titanosaurs are amazing because of their size. They are the largest animals that ever walked on Earth.
(From the American Museum of Natural History)
Being that big requires a lot of physical changes in order to keep their bodies working. Their limbs were like giant columns to support their weight, they developed a one-way breathing system to not re-inhale the stale air in their long necks, and some of them even had armor!
This week’s post comes from a report of the largest dinosaur footprint ever found. The print was found in the Gobi Desert of Mongolia (from the Cretaceous), on a joint expedition between the Okayama University in Japan and researchers from the Mongolian Academy of Sciences. The print is 1 meter long and 0.77 meters wide.
The dinosaur footprint with discoverer for scale.
Not only is this the largest footprint ever found, it also preserves nail prints, which are rarely fossilized! Because of this, we can understand a little more about titanosaur walking patterns.
Continuing with sauropods this week, another [article] was published that re-examined a trackway site in Sichuan, China that’s Early Jurassic in age. Because of that, it’s the oldest trackway known for sauropods. It also preserves something interesting – the sauropod turned! Animals turn while they walk all the time, so this shouldn’t be surprising. The cool thing is, we have it preserved in the fossil record. And for an animal as big as a sauropod, the turn is actually quite sharp. This means that despite their large size, sauropods were still pretty agile.
The trackway showing a sharp turn. Supplementary figure from the article.