Zhongyuansaurus ("Zhongyuan lizard"); pronounced ZHONG-you-ann-SORE-us
Woodlands of Asia
Early Cretaceous (130-125 million years ago)
Size and Weight
Low-slung build; armor plating; lack of tail club
During the early Cretaceous period, about 130 million years ago, the very first armored dinosaurs began to evolve from their ornithischian forebears--and they gradually split into two groups, nodosaurs (small sizes, narrow heads, lack of tail clubs) and ankylosaurs (larger sizes, more rounded heads, lethal tail clubs).
The importance of Zhongyuansaurus is that it's the most basal ankylosaur yet identified in the fossil record, so primitive, indeed, that it even lacked the tail club that would otherwise be de rigueur for classification under the ankylosaur umbrella. (Logically enough, Zhongyuansaurus was first described as an early nodosaur, albeit one with a fair number of ankylosaur characteristics.)