pachycephalic (adj.)

word-forming element in science meaning "thick, large, massive," from Latinized form of Greek pakhys "thick, fat, well-fed, dense, stout,"  from PIE *bhengh- "thick, fat" (source also of Sanskrit bahu- "much, numerous;" Avestan bazah- "height, depth;" Armenian bazum "much;" Hittite pankush "large," panku- (adj.) "total;" Old Norse bingr "heap," Old High German bungo "a bulb;" Latvian biezs "thick").

word-forming element meaning "having a head" (of a specified type), from Greek kephalē "head" (see cephalo-).