 One aetosaur , Typothorax coccinarum , has been used to define the Revueltian land vertebrate <unk> . A land vertebrate <unk> ( LVF ) is a time interval that is defined by the first appearance datum ( FAD ) , or first occurrence , of a tetrapod index fossil and is commonly used to date Late Triassic and Early Jurassic terrestrial strata . Since the FAD of T. coccinarum is at the beginning of the Norian stage , the Revueltian LVF starts at the beginning of the Norian around 216 million years ago . The Revueltian ends with the next FAD , which happens to be that of the phytosaur <unk> and the start of the <unk> LVF . 
