monaxonic
/ˌmɒnəkˈsɒnɪk/Zoology and (now chiefly) Palaeontology
adjective
Of a sponge spicule, coral sclerite, etc.: that has a single axis; = monaxon.
Origin
Late 19th century; earliest use found in Encyclopaedia Britannica. From ancient Greek μόνος + ἀξον-, ἄξων axis + -ic, probably after scientific Latin Monaxonida, order name, or Monaxona, former order name.