The adjective "most arenicolous" refers to plants or animals that thrive in sandy environments. Some synonyms for this term might include "sand-loving," "sandy-soil adapted," "psammophilic," or "dune-dwelling." Other words that could be used in a similar context might include "xerophilic" (indicating a preference for dry environments), "halophilic" (referring to organisms that thrive in salty conditions), or "thermophilic" (describing species that thrive in hot temperatures). Overall, there are many different words that could be used to describe the characteristics of organisms that are suited to sandy habitats, each of which provides slightly different nuances and shades of meaning.