hemipagus

hemipagus

 [hem-ip´ah-gus]
twin fetuses joined laterally at the thorax.

hem·ip·a·gus

(hem-ip'ă-gŭs),
Conjoined twins that are united laterally at the thorax; the zone of union may also involve the neck and jaws. See: conjoined twins.
[hemi- + G. pagos, something fixed]