Achistrum  je idile kokumba okun ti a ko ri mo sugbon ti a ti ri tele ni Poland ni igba Triassic, ati ni  United States  Igba Eleeedu.. 
Wọ́n ti ṣàpèjúwe àwọn àmì tí ó jọ BV nínú ìtàn, akosile àkọ́kọ́ wáyé ní ọdún 1894.Àwọn àmì àti àpẹẹrẹ àwọn ààmì àrùn yìí tí a maa ń sábà rí ní kí omi maa jáde ní ojú òbò tí ó sì maa ń run bí ẹja.. 