Forget dense forests. Even roadsides could be harbouring new species that are hard to find. Scientists from the University of Delhi have discovered a new amphibian — a mysterious narrow-mouthed frog, that makes only a four-day appearance in seasonal roadside puddles every year in Kerala’s Wayanad district — according to their study published on Wednesday in Scientific Reports . The frog Mysticellus franki (named after biologist Franky Bossuyt from Brussel’s Vrije Universiteit) is not just a new species but also belongs to a completely new genus, Mysticellus (after Latin mysticus, meaning mysterious; and ellus, meaning diminutive, for the frog is just around 3 cm long). Sonali Garg, a doctoral researcher at the University of Delhi, first found tadpoles of the species — whose physical features and DNA did not match any known species — during routine field surveys in Wayanad district in 2013. Tracking the adults After a long search, the team finally found large groups of around 200 adult frogs in 2015 in a single locality in Wayanad, just metres away from vehicular movement, plantation activities and human settlements. After breeding for four days, the frogs mysteriously disappeared from the spot; a habit that earned the tiny amphibians their name. Back in the laboratory, Ms. Garg and her supervisor S.D. Biju studied multiple aspects of the species — including physical characteristics of adults and larvae, DNA and calls of adult males that they recorded on field — in detail. Physical features (such as its marble-patterned underside) and DNA studies revealed the frogs to be a completely new species. Adults have two black spots that look like eyes on their backs, a defensive feature that probably helps startle predators, write the authors. The frogs’ calls are extremely different too, resembling that of insects. ‘Genetic studies further revealed that the frog is around 40 million years old and its nearest relatives live more than 2,000 km away, in southeast Asia (including Indo-Burma, Malaysia and Vietnam). This southeast Asian connection adds strength to the theories that India and southeast Asia were connected in the past by land bridges, suggest the authors.