 For example, a 2007 paper has suggested that adelospondyls are stem-tetrapods close to colosteids and a 2017 paper on "Lethiscus" has Aïstopoda in the tetrapod stem based on their primitive braincase.These studies differ in the internal and external relationships of the remaining lepospondyl taxa.The former places the remaining lepospondyls into a single clade along the amniote stem.