How Big was the Heart of Brachiosaurus?
In the course of Everything Dinosaur’s work with school children and young dinosaur fans we get asked lots of questions. During a school visit, one of the children asked the Everything Dinosaur team member present how big was the heart of Brachiosaurus? This was a very difficult question, one that we cannot answer with any degree of certainty as we are not aware of any soft tissue representing a heart ever being preserved in the Sauropoda fossil record.
Brachiosaurus is known from fossil material found in North America (United States). Brachiosaur fossil material found in East Africa is now more often than not assigned to another brachiosaurid genus Giraffatitan. Brachiosaurus fossils are associated with Upper Jurassic aged strata and estimates of the size of the Brachiosaur known as B. altithorax put this dinosaur around the 22 metres long mark. Brachiosaurus may have weighed 50,000 kilogrammes or more.
Picture Credit: Everything Dinosaur
We can state with confidence that the hearts of sauropods were very big, after all, these on the whole were massive animals. The hearts had to be strong enough to pump blood around the body and every time a Brachiosaurus raised its head above the position of its heart in its body (which was probably most of the time), the heart had to work extra hard against gravity to pump blood up the neck to the animal’s brain. The heart had to effectively pump blood “uphill”. With a head, in some specimens of Brachiosaurus over fourteen metres up in the air, this was no mean feat.
A fully grown Brachiosaurus would have been composed of approximately 27,000 kilgrammes of soft tissue (muscles, cartilage, internal organs and so on), plus around 2,000 kilogrammes of blood or thereabouts. The hearts of adult Giraffes can weigh more than ten kilogrammes and measure more than sixty-five centimetres long. Although, the heart of a Brachiosaurus may have been different to that of a mammal such as a giraffe, it was a very much bigger animal and therefore a larger, stronger heart would be required. When you look at extant reptiles today, snakes, crocodiles and lizards for example, nearly all living reptiles standing in a natural posture have their heads almost exactly on the same level as their hearts. Reptiles that are alive today have hearts that cannot properly separate pulmonary and systemic blood. However, many dinosaurs had heads higher than their hearts so these reptiles may have had fully divided hearts very similar to the hearts of mammals and the Dinosauria’s very near relatives – the birds.
But how big? That’s a very tough question. Based on a 50,000 kilogramme specimen the heart would have been something like the size of a dust bin, very muscular and weighing perhaps in excess of 150 kilogrammes. These are just estimates, in the absence of supporting data from the fossil record, the truth is nobody really knows.