This widespread northern species extends rarely into the southern Appalachians and was reported from Ky. in FNA 2, but no coll. has been located. There is an erroneous record attributed to Ky. in the SERNEC database (2022 Jul): a coll. of C.W. Short from Pa. (WIS "Pennsa."). The species is known from within 50 miles of Ky. in w. Va. and s. W.Va (K). Spinulum differs from Dendrolycopodium as follows (FNA 2, W): strobili single (versus 1-7) at top of upright shoot; shoots 10-15 mm thick including leaves (versus 3-8 mm), usually branched subdichotomously 1-4 times (versus many-branched, treelike or fanlike but with a definite main axis); leaves with stiff spinule 0.4-1 mm long (versus just acute); horizontal stems on or near substrate surface (versus subterranean), with winter bud constrictions (versus without).