Sigmurethra is a taxonomic category of air-breathing land snails and slugs, terrestrial pulmonate gastropod molluscs.
 This is an informal group which includes the majority of land snails and slugs.
Aptera is an obsolete taxonomic category, which included the Apterygota along with various other wingless arthropods.
Sapium is a genus of flowering plants in the family Euphorbiaceae.
 It is widespread across most of Latin America and the West Indies.
 Many Old World species were formerly included in the genus, but recent authors have redistributed all the Old World species into other genera.
Heterostropha was a previously used taxonomic category, an order of sea snails, within the superorder Heterobranchia.
 In the most current gastropod taxonomy, that of Bouchet & Rocroi, this taxon is no longer in use.
Eogastropoda was a previously used taxonomic category of snails or gastropods, a subclass which was erected by Ponder and Lindberg in 1997.
 It was one of two great divisions (subclasses) of the class Gastropoda, the snails.
 The other subclass of gastropods was the Orthogastropoda.
Gammaridae is a family of amphipods.
 In North America they are included among the folk taxonomic category of "scuds", and otherwise gammarids is usually used as a common name.
Cladorhiza inversa is a species of sponge in the taxonomic category of Demospongiae.
 The body of the sponge consists of a spicule and fibers and is water absorbent.
Cladorhiza segonzaci is a species of sponge in the taxonomic category of Demospongiae.
 The body of the sponge consists of a spicule and fibers and is water absorbent.
Helleborine is the common name for a number of species of orchid.
 It does not correspond to any currently used taxonomic category.
 Some of the plants called helleborines are classified in the genus "Epipactis", some in genus "Cephalanthera".
 A genus "Helleborine" was formerly recognised but has now been absorbed into the Grass pink genus "Calapogon".
Polygonum is a genus of about 220 species of flowering plant in the buckwheat and knotweed family Polygonaceae.
 Common names include knotweed, knotgrass, bistort, tearthumb, mile-a-minute, smartweed and several others.
 In the Middle English glossary of herbs "Alphita" ( 1400-1425), it was known as ars-smerte.
 There have been various opinions about how broadly the genus should be defined.
 For example, Buckwheat ("Fagopyrum esculentum") has sometimes been included in the genus as "Polygonum fagopyrum".

Question: To which taxonomic category do both Polygonum and Sapium belong?
Answer: genus