conducted in the 1980s and 1990s often maintained the idea that lepospondyls were paraphyletic, with nectrideans close to colosteids and microsaurs close to temnospondyls, which were considered to be ancestral to modern amphibians. However, a 1995 paper by Robert Carroll argued that lepospondyls were actually a monophyletic group closer to reptiles. Carroll considered them closer to reptiles than the seymouriamorphs, but not as close as the diadectomorphs. Many phylogenetic analyses since Carroll (1995) agreed with his interpretation, including Laurin & Reisz (1997), Anderson (2001), and Ruta et al. (2003). A few have still considered lepospondyls ancestral to amphibians, but came to this conclusion without changing the position of lepospondyls compared to seymouriamorphs and diadectomorphs. Lepospondyl and tetrapod classification is still controversial, and even recent studies have had doubts about lepospondyl monophyly. 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. The latter does not treat the relationships of nectrideans or adelospondyls, but finds microsaurs to be early amniotes, and places lysorophians within microsaurs. Interrelationships Five main groups of lepospondyls are often recognized: Microsauria, a superficially lizard- or salamander-like and species-rich group; Lysorophia, a group with elongated bodies and very small limbs; Aïstopoda, a group of limbless, extremely elongated snake-like forms; Adelospondyli, a group of presumably aquatic forms that resemble aïstopods, but have more solidly built skulls; and Nectridea, another diverse group that includes terrestrial and aquatic newt-like forms. Microsauria is generally considered paraphyletic; rather than being a monophyletic group, it has been considered an evolutionary grade of basal ("primitive") lepospondyls, although there is growing consensus that a large subset of fossorially-adapted microsaurs, the Recumbirostra, is monophyletic. Lysorophia may belong within the Recumbirostran clade, distinct from other derived lepospondyls. Nectridea may also be paraphyletic, consisting of a range of more anatomically-specialized lepospondyls. The name Holospondyli has been proposed for a clade including aïstopods, and nectrideans, and possibly adelospondyls, although not all recent phylogenetic analyses support the grouping. The following cladogram, simplified, is after an analysis of tetrapods and stem-tetrapods presented by Ruta et al. in 2003: Position within Tetrapoda The "lepospondyl hypothesis" of modern amphibian origins proposes that lissamphibians are monophyletic