The tadpoles of this class of showy frog were the last tadpole mystery left in the frog and toad world, say the scientists - belonging to the only class whose tadpoles had not yet been documented.
Of course, that makes a certain amount of sense, in hindsight: It's hard to see things that like to stay buried.
"These tadpoles probably remained unnoticed all these years because of their fossorial [ burrowing ] nature, which in itself is a rare occurrence in the amphibian world," said University of Delhi researcher S.D. Biju, in a press release.
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As is clear in the photo at the top, the tadpoles have an eel-like look and boast well-muscled tails, the better for underground maneuvering.
Another key finding about the tadpoles was the presence of ribs, grown very early on in their tadpole lives.
"Only four families of frogs are reported to have ribs," said study co-author Madhava Meegaskumbura, of the University of Peradeniya, "but we show that at least some of Micrixalidae also have ribs, even as tadpoles."
"This adaptation may provide for greater muscle attachment, helping them wriggle through sand," Meegaskumbura added.