Sclerocephalus

Abstract: The early larval development of the temnospondyl Sclerocephalus sp. is analyzed, based on 38 specimens from the Lower Rotliegend (Permo-Carboniferous boundary) of the Saar-Nahe Basin (south-west Germany). The study focuses on the smallest larval specimens, which exemplify changes in both proportions and ossification patterns. In comparison with dissorophoid larvae, the skull ossifies more fully and at a much faster rate; the smallest specimens already have completely formed circumorbital bones that are sutured throughout. Sculpturing undergoes two marked changes, first from uniformly pitted to pits of variable size and regional differentiation, and finally to the origin of ridges. The palate of small larvae differs from that of larger specimens in patterns of dentition, having more teeth including a denticle field on the cultriform process. The mandible of small larvae is described for the first time, being narrower than in adults and having three dentigerous coronoid elements. The smallest specimens have poorly ossified neural arches, lack vertebral centra, and have faintly ossified humeri, femora, and very poorly developed distal elements. The posterior ribs, metapodia, and phalanges appeared after the dermal elements of the pectoral girdle, whereas the scapulocoracoid and ischium are absent throughout the larval period. Early growth and differentiation of the limbs and the ilium illustrates the developmental patterning of the appendages, which proceeded from proximal to distal. Dermal squamation is uniform in small stages, consisting of round or oval osteoderms with pronounced growth rings; in large larvae, they start to differentiate in certain body regions.

Abstract: A new species of the temnospondyl tetrapod, Sclerocephalus stambergi n. sp., is described from the early Permian deposits of the Boskovice Basin in Moravia (Czech Republic). The length of the skull of the only known specimen is about 50 mm. Characters including the well-ossified quadrate, septomaxilla and scapulocoracoid, presence of the maxilla-nasal suture and a free posterolateral margin of the supratemporal suggest an early adult age. This new species of Sclerocephalus is distinguished from the others on the basis of the following characters: nasal and maxillary processes of the premaxilla of equal width; absence of the alary process of the premaxilla; distinct pointed process on the lacrimal between the maxilla and jugal; narrow interclavicle; and very peculiar tabular presenting a quadrangular, plate-like process extending from its posterolateral portion, an almost right angle between its lateral and posterior margins, and a long posteromedial process. The new species represents the smallest and possibly the most basal Sclerocephalus species. The specimen described here sheds new light on the anatomy and taxonomy of Sclerocephalus. It completes the biodiversity of the tetrapod fauna from the Boskovice Basin, and our knowledge on the evolution of the European Paleozoic temnospondyls.