 The species has an estimated adult body length of up to approximately and a width of .In contrast to "P. cristatus" which has two ribs running the length of the body on each side, only one rib is on each side of "P. tuberculatus".While both species have two rows of bumps running the width of the body between the ribs on each body segment, the front row of bumps is eleven across and the posterior row is ten across in "P. tuberculatus" rather the row and five and four in "P. cristatus".