We are going to begin our fact file journey in the Triassic period but, for now, we are going to withhold from looking at dinosaurs. Instead, I want to investigate some of the other creatures that flourished during this particular time era.
The first of these is the placodonts (temporal range: 245-200 Mya). The placodonts were an intriguing group of marine reptiles (measuring between 1-3 metres in length) that first appeared during the Middle Triassic period, but became extinct at the Triassic/Jurassic boundary. The first specimen was discovered in 1830, but the order Placodontia was not developed until 1871, when Edward Drinker Cope classified the placodonts within the Sauropterygia (the group which includes the plesiosaurs).
The earliest placodonts were characterised by their heavy, barrel-shaped bodies, similar in appearance to that of the modern day iguana. However, as the number of marine predators began to increase as the Triassic period progressed, the placodonts developed bony plates on their backs. By the end of the Triassic era these bony plates had grown to cover the animal’s entire body, meaning the final placodonts resembled creatures similar to the modern day sea turtle. It is widely thought that this armour plating served a predominantly defensive purpose, protecting the animal’s fleshy body, although it has also been suggested that the armour may have helped to improve hydrodynamic efficiency.
It is believed, that due to their dense bone structure and heavy armour plating, that the placodonts would have been far too weighty to have floated in the ocean and would have had to expend a great deal of energy to swim to the waters surface. This had led researchers to suggest that the placodonts would have lived in shallow waters and not in deep oceans. In addition, it is thought that the placodonts would not have been confined to water and would have had the ability to travel on land, possibly to breed or nest.
The placodont diet consisted mainly of marine molluscs and brachipodods, so their teeth were tough and extremely thick, specifically designed to crush the shells of small, aquatic invertebrates.
Picture: Placodus, one of the first placodonts.