Chapter 24.6, Problem 2SB

Summary Introduction

To review:

Whether birds are more closely related to non-avian dinosaurs or to crocodilian dinosaurs.

Introduction:

Non-avian dinosaurs are extinct terrestrial dinosaurs that are not included in the bird clade. These, along with birds and crocodiles, are included within Archosauria (a group of diapsid amniotes whose living representatives include birds and crocodiles). The other clades of Archosauria became extinct in the early Mesozoic era. The similarity that exists in the characteristics of birds, crocodiles, and non-avian dinosaurs is truly a synapomorphy. Whether birds are more closely related to the non-avian dinosaurs or the crocodiles can be depicted by drawing a phylogenetic tree.