The growth of the skull roof plates in Arabosteus variabilis (Acanthothoraci, Placodermi) from the Early Devonian Jauf Formation (Saudi Arabia): Preliminary results

The skull roof growth of Arabosteus variabilis (Acanthothoraci), from the Pragian-Early Emsian of Saudi Arabia is studied on the basis of well-preserved growth lines on the dermal plates. A clear tendency towards growth in length, i.e. allometry in length, can be observed for all studied skull roof plates of Arabosteus variabilis as well as for the skull roof in general. Each studied plate displays particular growth shaping the skull roof according to its position in the skull roof pattern, e.g., the preorbital plate controls the shape of the part of the orbit and the nuchal plate retains the relative proportions in the skull roof during growth.