Ichnofossils (or ichnites) are especially important for clarifying the evolution and prehistoric diversity of taxa. These cannot usually be associated with a particular genus, let alone species of bird, as hardly ever they are associated with fossil bones. But it is possible to group them into ichnotaxa based on their morphology (form). In practice, the details of shape that reveal the birds' behavior or biologic affinity are generally given more weight in ichnologic classification.