the edge of the orbits (eye holes) due to a contact between the pre- and post-frontals which typically lie in front of and behind the orbits, respectively. Unlike lysorophians and aïstopods, which had snake-like skulls with large openings and reduced bone material, adelospondyl skulls were strongly built and covered with ridges, pits, and grooves, including lateral line sulci. They typically possessed many teeth, although such teeth differ in structure between families. Adelogyrinids, for example, had many numerous "chisel-shaped" teeth, while Acherontiscus had blunt teeth at the back of the mouth and sharp, thin teeth at the front. As is the case in other lepospondyls, the teeth of adelospondyls did not have a maze-like internal structure like those of "labyrinthodonts", nor did adelospondyls possess enlarged fang-like teeth on the roof of the mouth. Similar to various other lepospondyls, adelospondyls lost several bones in the temporal region of the skull, which is at the back of the skull between the quadratojugal bone of the jaw joint and the parietal and postparietal bones at the midline of the skull roof. Stem- and crown-tetrapods typically have three to four bones on each side of the skull in this region (from top to bottom): the tabular, supratemporal (and sometimes an adjacent intertemporal), and squamosal. The intertemporal is lost (or fused into other bones) in a variety of unrelated tetrapod groups. The same process additionally occurs to the supratemporal in several lepospondyls, namely "microsaurs" and a few "nectrideans" such as Scincosaurus and diplocaulids. Adelospondyls take this one step further. They possess only a single bone between the jaw joint and the skull roof. This bone is often believed to be a fusion between the tabular and the squamosal (termed a "tabular-squamosal" or "squamosotabular"), although it is also conceivable that the tabular disappeared completely leaving only the enlarged squamosal in its place. Postcranial bones Adelospondyls can also be characterized by their vertebrae compared to other lepospondyls. They were spool-shaped and high in number, with Acherontiscus having an estimated 64 vertebrae and an indeterminate juvenile adelogyrinid having at least 70. Most of these vertebrae lack haemal spines, indicating that the primary elongation took place in the body rather than the tail. The neural spines are not fused to the centra, a characteristic which D.M.S. Watson (1929) used to characterize the adelospondyls as a distinct order. In fact, the name "adelospondyl" is Greek for "obscure vertebra", referencing both the