Exploring SA’s own dinosaur with CT scans
If you ask children what their favourite dinosaurs are, the answers will undoubtedly include T-Rex, triceratops and maybe brachiosaurus.
Those children answering the question in South Africa may be disappointed to discover that none of these dinosaur fossils are to be found in the country. But SA has its own, equally important dinosaurs; the most common and well known of these is massospondylus, which was first described by scientists back in 1854.
This dinosaur was approximately four to five meters long from head to tail, walked on two legs, had a long neck, a small head and ate plants. It lived in the early Jurassic time period – 200 million years ago. It was also the ancestor of the colossal creatures so many children can name today: massospondylus gave rise to giants like diplodocus.
There are fossils of these animals ranging in age from embryos still in their eggs, to adults. The oldest mature individual that has been studied reached about 25 years. The range of fossils available means that researchers can study their growth.
I am interested in the beginning of development: embryos.
One of the most famous massospondylus specimens is a clutch of seven eggs with embryos found in 1976 in the Free State. Using high-powered CT scans, I reconstructed the one centimetre-long skulls and compared them to dinosaurs’ closest living relatives: chickens, crocodiles, turtles and lizards.
I found the bones in the massospondylus embryo skulls developed in the same order as those in animals today.
This means the skulls of embryos in this group have conserved their developmental sequence for an extraordinary 250 million years of evolution.
It’s not yet known how far back this pattern goes but it could potentially appear in very early tetrapods (four-limbed animals).
Tetrapods go through a lot of changes in evolution, so having a constant feature is quite significant and indicative that you don’t mess with a good thing.