and most show evidence of functional internal gills throughout life, and probably only occasionally ventured onto land. Their polydactylous feet had more than the usual five digits for tetrapods and were paddle-like. The tail bore true fin rays like those found in fish. The vertebrae were complex and rather weak. At the close of the Devonian, forms with progressively stronger legs and vertebrae evolved, and the later groups lacked functional gills as adults. All were however predominantly aquatic and some spent all or nearly all their lives in water. Reptile-like amphibians An early branch was the terrestrial reptile-like amphibians, variously called Anthracosauria or Reptiliomorpha. Tulerpeton has been suggested as the earliest member of the line, indicating the split may have happened before the Devonian-Carboniferous transition. Their skulls were relatively deep and narrow compared to other labyrinthodonts. Front and hind feet bore five digits on most forms. Several of the early groups are known from brackish or even marine environments, having returned to a more or less fully aquatic mode of living. With the exception of the diadectomorphs, the terrestrial forms were moderately sized creatures that appeared in the early Carboniferous. The vertebrae of the group foreshadowed that of primitive reptiles, with small pleurocentra, which grew and fused to become the true centrum in later vertebrates. The most well known genus is Seymouria. Some members of the most advanced group, the Diadectomorpha, were herbivorous and grew to several meters in length, with great, barrel-shaped bodies. Small relatives of the diadectomorphs gave rise to the first reptiles in the Late Carboniferous. Temnospondyli The most diverse group of labyrinthodonts was the Temnospondyli. Temnospondyls appeared in the early Carboniferous and came in all sizes, from small salamander-like Stereospondyli that scurried along the waters edge and undergrowth, to giant, well armoured Archegosauroidea that looked more like crocodiles. Prionosuchus was an exceptionally large member of the Archegosauridae, estimated to have been up to 9 meters long, it is the largest amphibian ever known to have lived. Temnospondyls typically had large heads and heavy shoulder girdles with moderately long tails. A fossil trackway from Lesotho shows larger forms dragged themselves by the front limbs over slippery surfaces with limited sideways movement of the body, very unlike modern salamanders. A temnospondyl's fore-foot had only four toes, and the hind-foot five, similar to the pattern seen in modern amphibians. Temnospondyls had a conservative vertebral column in which the pleurocentra