The headword is aorist active participle, nominative plural masculine, of the verb swmatopoie/w. (For other forms of the same verb, which literally means 'give bodily existence to', see sigma 839, sigma 840, sigma 842.) It is presumably extracted from a literary source (but not from the quotation given, where the participle occurs in the genitive singular). The few extant possibilities include Diogenes Laertius 2.138 and the Epistle of Aristeas to Philocrates 166.
[1] Polybius fr. 229 Büttner-Wobst; derived, according to Adler, from the Excerpta of Constantine Porphyrogenitus.