The postcranial skeleton ofDiscosauriscusKuhn, a seymouriamorph tetrapod from the Lower Permian of the Boskovice Furrow (Czech Republic)
AbstractThe description of the postcranial skeleton of larval, metamorphic and early juvenile specimens of the genusDiscosauriscusis based on three-dimensional material and includes a description of the ontogeny of the swollen neural arches and the central elements of the vertebrae.Discosauriscushas 24 (or 23) presacral vertebrae. The morphology of the atlas–axis complex is similar to that inSeymouria sanjuanensis. The neural arches start to swell slightly in specimens of late larval stage; they are completely swollen immediately after metamorphosis. There are about 40 caudal vertebrae and one sacral vertebra. The atlantal pleurocentrum is paired in metamorphic individuals. In postmetamorphic individuals, the pleurocentra 2–5 are not completely closed dorsally; the pleurocentra 6–30 form complete discs. The first haemal arch is situated on the sixth caudal vertebra. The atlantal rib is present. There are six caudal ribs.Discosauriscushas an anocleithrum which is the first record of this dermal pectoral element within seymouriamorphs and Lower Permian tetrapods. The scapula and the coracoid are separate elements. The phalangeal formula of the manus is 2, 3, 4, 5, 3. The iliac blade has a massive, almost horizontally oriented posterior process; the anterior process is absent. The phalangeal formula of the pes is 2, 3, 4, 5, 3. Rounded ventral scales are present. The comparison and evaluation of the available postcranial elements ofDiscosauriscus, Utegenia, AriekanerpetonandSeymouriasupport the view thatDiscosauriscusandAriekanerpeton, forming the family Discosauriscidae, are immediately related genera.