Kaʾannamā introduces an imagined resemblance: the skull’s junctions appear drawn together as though fashioned towards a sharply defined rim. The verse does not assert that the animal’s skull has literally been filed or cut.
Waʿā carries an idea of holding or gathering; al-multaqā denotes a place of meeting. The construction min ... ilā defines a span from one point to another. Those grammatical relations help the comparison form a coherent physical image rather than a disconnected list of objects.