In snakes, the paraventral scales are the longitudinal rows of dorsal scales that contact the ventral scales. These are the first rows of dorsal scales on either side of the body and are usually slightly larger than the scales located more dorsally. In species that have mostly keeled scales, the paraventrals are usually smooth or only weakly keeled.[1]
The term paraventral may also refer to the area on either side of the ventral scales.[1]
Well, that’s interesting to know that Psilotum nudum are known as whisk ferns. Psilotum nudum is the commoner species of the two. While the P. flaccidum is a rare species and is found in the tropical islands. Both the species are usually epiphytic in habit and grow upon tree ferns. These species may also be terrestrial and grow in humus or in the crevices of the rocks.
View the detailed Guide of Psilotum nudum: Detailed Study Of Psilotum Nudum (Whisk Fern), Classification, Anatomy, Reproduction