 Originally , all aetosaurs were considered members of the family Stagonolepididae . Early phylogenetic analyses split aetosaurs into two subfamilies , Aetosaurinae and Desmatosuchinae . <unk> are characterized by projections called eminences on the dorsal paramedian osteoderms that are close to the midline of the back . <unk> have a few more distinguishing characteristics , including grooves on the dorsal paramedians that help them lock to the lateral plates in a tight articulation . Many <unk> have long spikes projecting from the lateral plates . These spikes are especially prominent in Desmatosuchus . <unk> , on the other hand , tend to have less spikes . Many <unk> , such as Aetosaurus and Neoaetosauroides , have smooth carapaces and lack spikes altogether . More recent studies ( see below have favored a third group , <unk> , which like Desmatosuchinae has long spikes , but differs in having more sharply angled joints between osteoderms . Moreover , the genus Aetosauroides is now often classified outside Stagonolepididae as a non @-@ stagonolepidid aetosaur , making the names Aetosauria and Stagonolepididae no longer synonymous . 
