rugosan vs rugose

rugosan

adj
  • Synonym of rugose: describing an extinct coral of the order †Rugosa. 

noun
  • A coral from that order. 

rugose

adj
  • Describing a fossil coral of the extinct order †Rugosa (also called Tetracoralla), this order has horn-shaped corals with surfaces covered with ridges. 

  • Rugged, rough, unrefined. 

  • Used when combined with another adjective, for example, rugose-reticulate or rugose-punctate. 

  • Having rugae or wrinkles, creases, ridges, or corrugation. 

  • Having a rough, wrinkled, or wavy surface; commonly in parasynthetic usage e.g. rugose-veined or rugose-leaved. 

How often have the words rugosan and rugose occurred in a corpus of books? (source: Google Ngram Viewer )