Chapter Five

Were dinosaurs evolutionary failures?

Why study dinosaurs?

Despite the great affection for dinosaurs from scientists and the general public alike, they rarely feature in evolution textbooks. But dinosaurs make an ideal case study for examining the macroevolutionary processes of adaptive radiation (diversification of a lineage into many different forms and ways of life) and mass extinction (simultaneous loss of many lineages, far exceeding normal background extinction rates). Considering the rise of dinosaurs allows us to consider the role of both key adaptations and chance in diversification. And considering their fall prompts us to question our ability to resolve events and determine cause and effect in deep time.

What are the main points?

• The study of fossils gives us so much more than size and form of extinct species, but also sheds light on physiology, locomotion, behaviour, and ecology.
• The diversification of dinosaurs may have been driven by key adaptations, such as upright gait and fast metabolism, that allowed them to exploit a wide range of niches, or it may have been triggered by opportunity, through the extinction of other reptile groups.
• Given that vertebrate fossils are rare, and biased in terms of location, taxa and time period, there is some uncertainty over the timing and nature of dinosaur extinctions.

What techniques are covered?

• Temporal resolution: Qualitative and quantitative assessment of the effect of incomplete sampling on our ability to assess timing and rate of evolutionary events
• Hypothesis testing in deep time: making predictions based on proposed mechanisms and weighing up evidence for and against particular causes.

What case studies will be included?

• Testing evolutionary hypotheses with fossil evidence: Did birds outcompete pterosaurs?

 

Image:  Emily Willoughby CC4.0