Phylogenetic bracketing

Phylogenetic bracketing is a method of inference used in biological sciences. It is to infer the likelihood of unknown traits in organisms based on their position in a phylogenetic tree. One of the main applications of phylogenetic bracketing is on extinct animals, known from fossils.

Extant phylogenetic bracketing is done by comparing an extinct animal to its nearest living relatives. For example, Tyrannosaurus, a theropod dinosaur, is bracketed by birds and crocodiles. A feature found in both birds and crocodiles would likely be present in Tyrannosaurus, such as the capability to lay an amniotic egg, whereas a feature both birds and crocodiles lack, such as hair, would probably not be present in Tyrannosaurus.