peracephalus

per·a·ceph·a·lus

(per'ă-sef'ă-lŭs), An omphalosite lacking head and upper limbs, and with a defective thorax; typically, the body consists of little more than pelvis and lower limbs. [per- + G. a- priv. + kephalē, head]

peracephalus

(pĕr″ă-sĕf′ă-lŭs) [″ + Gr. a-, not, + kephale, head] A parasitic placental twin. It does not contain a head or arms, and the thorax is malformed.