What core difficulty in classification does the contrasting anatomy of Xiaotingia force researchers to confront?
Deciding whether classification is based on the most derived or the most ancestral features
The conflicting characteristics displayed by Xiaotingia zhengi—possessing the extensible toe typical of Deinonychosaurs while simultaneously having long forelimbs suggesting flapping potential—exemplify a fundamental ambiguity in systematics. The difficulty lies in determining which set of traits should take precedence when drawing lines between clades. Classification can swing dramatically depending on whether researchers prioritize traits deemed evolutionarily advanced or 'derived' (like flight adaptations) versus those deemed primitive or 'ancestral' traits that were retained from a common ancestor (like the predatory toe). The interpretation of the fossil record thus becomes highly dependent on the mathematical model prioritizing one set of features over the other.
