Unique growth pattern of Metoposaurus diagnosticus krasiejowensis (Amphibia, Temnospondyli) from the Upper Triassic of Krasiejów, Poland

► Histology of Metoposaurus diagnosticus femora reveals unique growth pattern. ► Slow growth phases are interpreted as annuli, fast growth phases as zones. ► Annuli are always untypically broad and contain several non-annual resting lines. ► Metoposaurus from Krasiejów stayed active during the long unfavorable season. ► Dutuitosaurus from Argana aestivated during the unfavorable season.