rarity of adelospondyls and this trait. However, Watson also included Lysorophus as an adelospondyl rather than a lysorophian "microsaur", and other studies have shown that the absence of neurocentral fusion is very common among tetrapods, and therefore useless as a distinguishing feature. However, adelospondyls do have an additional quality of the vertebrae which is unique compared to other lepospondyls. In most lepospondyls, the left and right halves of each vertebra's neural arch are separate, rather than fused as in other tetrapods. Adelospondyls retain the primitive condition of the two halves being completely fused, making their vertebrae unique among lepospondyls. Acherontiscus deviates from the norm of the subclass even more than other adelospondyls, as it possessed two separate bony components of the centra, rather than a single centrum (which is the case in adelogyrinids and other lepospondyls). These two different components (the intercentrum at the front and pleurocentrum at the back) were nearly equal in size, similar to the vertebrae of embolomeres. Although adelospondyls lost all trace of their fore- and hind-limbs, they did retain a notable remnant of their presumably limbed ancestors. This remnant is a large bony dermal shoulder girdle, comprising the plate-like interclavicle which was positioned on the midline of the chest, two clavicle bones on either side of it, and two boomerang-shaped cleithrum bones at the base of the neck. On the other hand, the bones of the endochondral shoulder girdle (i.e. the scapulae and coracoids), which supported the forelimbs, were lost along with the limbs. Adelospondyls possessed a large bony hyoid apparatus, including gill-supporting bones such as hypobranchials and ceratobranchials. Long, thin scales have been preserved in most adelospondyl specimens, and they were more abundant on the ventral (belly) side of the body rather than the dorsal (back) side. References Carroll, RL (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co. von Zittel, K.A (1932), Textbook of Paleontology, CR Eastman (transl. and ed), 2nd edition, vol.2, p. 225, Macmillan & Co. External links Adelogyrinidae - Palaeos Adelospondyls Carboniferous amphibians of Europe Mississippian first appearances Mississippian extinctions Taxa named by D. M. S. Watson Fossil taxa described in 1930 ca:Adelogirínid es:Adelogyrinidae