Surfaces of InP(100) were bombarded by 2.1 keV Ar+ ions under normal incidence. The total accumulated ion fluence the samples were exposed to was varied roughly from 1 x 10(17) cm(-2) to 3 x 10(18) cm(-2) while ion fluxes in the range of (0.1-2) x 10(14) cm(-2) s(-1) were used. The surface morphology resulting from these ion irradiations was examined by scanning electron microscopy (SEM). For a specific range of ion fluxes and fluences, regular closely-spaced nanocone arrays are found to form, with the cones having typical base diameters of about 100 nm. Around their outer peripheries, they commonly exhibit rather distinct protrusions, an observation not reported in previous investigations. The inspection of the initial stages of nanocone formation indicates that the growth of adatom islands, first on the pristine surface and later on previously formed islands, may lead to these 3D nanostructures. This finding would imply that surface diffusion processes of adatoms constitute an important mechanism in the evolution of the observed topography. (C) 2015 Published by Elsevier B.V.