Attenborough and the Giant Dinosaur – BBC (2016)

On February 19th 2016, a replica of the massive Titanosaurus dinosaur discovered in Argentinian Patagonia was unveiled at the American Museum of Natural History in New York. It is continuing to send strong waves of excitement to all natural history enthusiasts worldwide. Based on accurate dating of the volcanic ash surrounding the fossil we now know that the animal lived 100.6 million years ago during the Cretaceous. It belongs to the Sauropod group and yet is the largest ever found. Before this discovery Sauropod dinosaurs were known from a few bones. The finding provided more than 200 bone parts which added a whopping 10 times of what we knew before. Just a side note: This 37.2 m (122 ft) colossal individual was still growing and had not reached its adult size when it was killed with six other dinosaurs all separate species in the area found.

Sauropod gigantism has always fascinated people who have been exposed to dinosaurs in one way or another. Dinosaurs originated in the Late Triassic (about 210 million years ago). Sauropods evolved into about 120 known genera. They ruled ecosystems for more than 100 million years from the Middle Jurassic to the end of the Cretaceous. They were so well adapted that only a giant meteorite that created a global catastrophe could erase them from the face of the Earth. Living conditions and selective pressures of the Mesozoic Earth lead to the evolution of such giants that perhaps life on our planet will never achieve such a climax again (but life as usual is always full of surprises). How and why they got so big?

A scrutiny of their body provides many clues about their success. Let’s start from the head.

Finding the skull of a fossil is a huge-mega-big deal among paleontologists for it possesses so much information on the biology. In 2012, based on a detailed analysis of therapod dinosaur skulls a group of scientists concluded that birds living today are neotenized version of dinosaurs. The concept of neoteny (retention of juvenile characters) also extends into human evolution. Biologists are now accumulating more evidence that human evolution is shaped for quite a bit based on retention of juvenile characteristics such as ability to digest milk (lactose tolerance) in adulthood or having larger brains by prolonged childhood period (leaving more time for brain to develop).

Skulls of carnivores and herbivores living on land today are quite big and heavy since they have to accommodate teeth and muscles for chewing. A tiny head with small incisor teeth and just enough muscle power to nip and swallow enabled evolution of a very long neck in Sauropods. Long neck might have been a sexually desired trait which enabled high reproductive success and feeding efficiency reaching tall coniferous trees like the monkey puzzle tree (Araucaria araucana). All plant material was being swallowed whole and entire digestion took place withing the massive abdomen providing sufficiently long tract. They resembled vacuum cleaners of the 70s. Long neck enabled minimal movement but maximal feeding radius but posed another problem: Gas exchange from lungs.

Explore the panorama below:

If you have snorkeled in the sea you will quickly realize that a long snorkel makes breathing rather inefficient due to increasing residual volume. This is a common problem for all mammals who breath in and out using the diaphragm beneath the lungs. Thus it is expected that the ridiculously long dinosaur neck would lead to a larger residual volume. So large that if it was a mammal it would collapse instantly due to respiratory malfunction. Obviously this didn’t happen.

Dinosaurs and their bird descendants have a marvelous respiratory adaptation that is superior to that of the mammals. Their lungs can carry out circular breathing and the problem of residual volume was never and still is not a problem. This is the reason why birds can still afford to have extremely long necks. As the documentary wonderfully illustrates the lungs are made up of multiple air sacks that circulate air continuously and unidirectionally. This is in a way a much efficient version of a didgeridoo or zurna player who inhales air into the lungs while blowing the air stored in the cheeks. Perhaps the most famous circular breather of all is the flutist James Galway who can give long uninterrupted performances.

One subject that never gets mentioned in the documentary is that large animals face an overheating problem. Geometrically, a sphere has the maximal volume with minimal surface. Sauropods had massive bellies that are close to the definition of a sphere. Moreover, fermentation involves exothermic reactions. Elephants for example have the same problem and they dissipate heat through their large flapping ears laced with veins like a car radiator. How did the dinosaurs solved the overheating problem? Circular breathing (oh yes again)!

Animating dinosaurs on big screens is one thing, building a one to one scale exact life-size replica is another. Casts of fossils provide excellent opportunities for research and outreach. Replicas of many rare fossils are displayed in natural history museums all over the World. For example a cast of the famous Brontosaurus parvus specimen UWGM 15556 (formerly Apatosaurus excelsus) whose original is residing in the University of Wyoming Museum can be seen on display in Tellus Science Museum of Georgia, USA. This specimen is quite special since digestion stones called gastroliths were also found next to where the stomach of the animal was expected to be. Another original Brontosaurus fossil (YPM1980) is also on display in Yale Peabody Museum. Its replica casts are on display all over the World. In 1905 the genus name Brontosaurus was abandoned in favor of Apatosaurus. A study in 2015 resurrected the name.

The expertise accumulated by the company Research Casting International (RCI) playes a central role in the documentary. The Canadian company based in Ontario is specialized in building replicas of biological specimens including many other dinosaurs that have been unearthed from many different fossil sites around the World.

As mentioned earlier the site where the Titanosaur was found was a special place. In addition to this one six more dinosaur fossils were found. All are different species. Museo paleontológico Egidio Feruglio (MEF) is now working intensely to create a permanent exhibition big enough to display all. For this they have started a founding campaign calling for contributions from the curious citizens of the World.

The exhibition most certainly will be an eye opener to the past of our planet. It will help us understand how the largest terrestial plant eaters (Sauropods) became so successful but only the bird-hipped (Therapods) left descendants which evolved into birds. If you want to dig further into nesting behavior of Sauropods check out this extensive review comparing nesting sites around the World with those of modern day Megapodes.

 

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