Paleontology: Early Vertebrate Evolution

In this lesson we take you back to the beginning of the Phanerozoic Eon to learn what it truly means to have backbone, as we encounter the key anatomical features of vertebrates and their closest chordate relatives. We’ll also introduce the language of evolution – phylogenetics – as we examine some of the contenders for the title of ‘The Earliest Vertebrate’, and give you a crash course in sedimentology, so you can begin to piece together the spectacular environments that were home to our early aquatic ancestors. Just a quick note before you get started: 'Palaios' is the Greek word for 'ancient', so palaeontology or paleontology is the study of ancient life. Both spellings are correct, with palaeontology used in Britain, and paleontology more common in the US.

The old problem of the comparative anatomist was exactly how to compare two animals that appeared, at first glance, to look nothing alike. How, do you compare cows and lobsters? Well, in this lesson you’ll not only learn how to compare crustaceans and cattle, but you’ll also quickly learn that there’s more to a vertebrate than just a backbone as we delve into basic vertebrate anatomy. We’ll cover all the need-to-know anatomical terms and directions, as well as specialist features like the lateral line system, which not only helped early fish avoid predation, but is also the main reason why you find it very difficult to catch fish with your bare hands today! We will also explore the immense diversity of the jawless vertebrates including the tenacious Cyclostomata, the elusive Conodonta, and, long before Ankylosaurus, a group of heavily armoured jawless fishes – the ostracoderms.

The Ordovician, Silurian and Devonian Periods were times of great continental, oceanic and climactic change that brought about the Earth’s first mass extinction events. With environmental catastrophes opening up new ecological niches, a trait evolved in early vertebrates that would prove so successful that over 99% of modern vertebrates still retain it: jaws. In this lesson we will try to understand the geographical and temporal background of early vertebrate diversity, as well as the impact and origin of the evolution of jaws on vertebrate life. Introducing huge predators such as Dunkleosteus along the way, we’ll explore the incredible diversity of the Gnathostoma (the jawed fishes), mainly from fossils known from the spectacular Late Devonian site of Miguasha in Quebec. So get ready for a lesson you can really sink your teeth into!

Although this lesson marks the end of the beginning of the vertebrate story, we still have some bones left to pick! In this last lesson we’ll look at the features of the Osteichthyes (the bony fishes) and examine the differences between two immensely successful vertebrate groups; one that conquered the water: the Actinopterygii (ray-finned fishes), and one that eventually conquered the land: the Sarcopterygii (lobe-finned fishes). We’ll investigate how the sarcopterygians gave rise to the tetrapods, meet our very first tetrapod ancestors like Acanthostega, and introduce the features that were essential in making the leap from water to land. Along the way we’ll meet some living fossils, see some incredible evolutionary adaptations, and learn about our earliest terrestrial origins – it’s time to step up and finish the tale of ‘Early Vertebrate Evolution’!