New data on the bone histology of Araripesuchus buitreraensis (Crocodylomorpha: Notosuchia) from the Late Cretaceous of Argentinean Patagonia

Abstract

Araripesuchus is a genus of Notosuchia from the Upper Cretaceous of southern continents. A previous paleohistological study performed in individuals assigned to one of the South American the species (Araripesuchus buitreraensis) has revealed, among other palaeobiological inferences, cyclical and slow growth dynamics. To increase the knowledge about the growth dynamics and intraskeletal and interspecific histological variation, here we analyse the microstructure of femur, tibia, fibula, metatarsal (II, III and IV) and two osteoderms of an individual referred to Araripesuchus cf.buitreraensis (MPCA-Pv 263) from the Late Cretaceous of Argentina. All elements present a cortex formed by both parallel fibred and lamellar bone tissues interrupted by lines of arrested growth (LAGs), revealing a general slow growth rate annually interrupted. A similar growthstrategy has been inferred for other notosuchians, as Iberosuchus macrodon, but an important variation regarding this parameter is evident in the clade. Although the bone tissue suggests that the individual reached the sexual maturity (i.e. increasing in the intrinsic fibre arrangement in the outer cortex), the absence of an external fundamental system indicates that somatic maturation has not been attained. MPCA-Pv 263 exhibit discrete layer of WFB in the cortical bone whose origin is still unambiguous.