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Evidence of evolution


All modern birds are descended from a group of dinosaurs called theropods. Theropods first appear in the fossil record during the late Triassic to early Jurassic period, roughly 200 million years ago. In contrast, fossils of taxa similar to modern birds can be found in the fossil record by the end of the Cretaceous period, roughly 66 million years ago.
The following table provides information about the presence of certain traits in theropods and modern birds. The presence of a trait is indicated by a checkmark.
TraitTheropodsModern birds
Hollow bones
Long, bony tail
Fused clavicle
Jaws with sharp teeth
Reversed first toe
Each answer choice below describes a specific fossil. Which fossil provides the strongest evidence for the discovery of a transitional species between theropods and modern birds?
Choose 1 answer: