"Lepidocephalichthys jonklaasi" is distinguished from "L. furcatus", "L. micropogon, L. manipurensis, and L. goalparensis" by rounded/truncated (vs. forked) caudal fin, from "L. irrorata and L. kranos" by absence of scales on top of head, from "L. guntea, L. hasselti, L. tomaculum, L. alkaia, and L. annandalei" by broad regularly spaced dark bars (vs. reticulations, spots, or stripe) on caudal fin, from "L. thermalis, L. arunachalensis, L. coromandelensis, and L. berdmorei" by vertically elongated, dark spots on side that form irregular, thin bars (vs. round spots that sometimes form squares or thin stripe), and from "L. lorentzi" by thinner, more irregularly spaced dark side bars, dorsal-fin origin anterior (vs. posterior) to pelvic-fin origin, and larger size (to 45 vs. 33 mm SL), (Havird & Page 2010). The two Sri Lankan species "L. jonklaasi" and L."thermalis" are not very closely related. They are easily differentiated by body shape and proportions, colour pattern, and form of sexual dimorphism that is unique to "L. jonklaasi".[Further, a mature adult "L. jonklaasi" is significantly longer than "L. thermalis". It is not easily confused with "L. thermalis" owing to its distinctive colour pattern and robust, tubular body. The sides are yellow, darkening dorsally, and are mottled with several chaotically arranged, large spots. Daraniyagala 1956, and De Silva 1963, observed that the last pectoral fin ray was ossified in some specimens, but did not consider this as a secondary sexual character. However, it is in fact present only in males and can therefore be used to differentiate between males and females. Breeding of this has not observed either in the wild or captive conditions. Very little is known of the biology of this species. It has been recorded by Pethiyagoda only from its type locality in Wilpita, Akuressa. This stream traverses through thick forest with dense undergrowth.