A Grammatical Dictionary of Botanical Latin

supinus,-a,-um (adj.A): bent backwards, backwards, lying on the back, supine; prostrate, with the face turned upward; opp. cernuus, ‘with the face down-turned;’ opp. pronus (leaning or hanging forward, prostrate); of the hands, with open palms turned upwards e.g. to heaven in prayer; of the head, ‘thrown back;’ as a chair inclined backward; of localities, inclined, sloping; syn. declivis; cf. procumbens; see prostrate; the opposite of pronus and cernuus, bent forwards) [> L. supinus,-a,-um (adj.A) backwards, lying on the back, supine (opp pronus, cernuus); lowered, opp. erectus; stretched out, extended, as the sea or a field (Lewis & Short);

NOTE: in grammar, ‘supine’ [verbum supinum]: “a Latin verbal noun [of the fourth declension] [occurring only] either in the accusative case in -um, used after verbs of motion to denote purpose (as in abiit piscatum “he’s gone fishing”) or in the ablative in -u, used as an ablative of specification (as in difficile dictu, “hard to say” (WIII). Also “an English infinitive with ‘to’” (WIII); mirabile dictu, ‘marvelous to relate;’ facilis factu, ‘easy to do.’ These verbal forms resemble nouns of the fourth declension which are derived from verbs; see ‘fourth declension.’

- posterior Astacus supina parte nigricat, prona lutescit, lateribus nigris maculis variegates (Ulysse Aldrovandi), the Astacus, behind, with the part bent back, is black, with the forward-leaning part yellowish, with the sides variegated with black marks.

Carex supina “lying back” (Fernald 1950); Gnaphalium supinum, Alpine Cudweed, ‘lying on its back’ (Fernald 1950); Potentilla supina, Sisymbrium supinum, Braya supina.