Illustration of Notobatrachus degiustoi by Gabriel Lio from https://www.newscientist.com/article/2454031-oldest-tadpole-fossil-known-to-science-dates-back-161-million-years/

Dear Readers, frogs are amongst my favourite animals, and I’m not sure why. Partly it’s because they make the work of looking after my pond so worthwhile – their eager faces peering up from the water is often the first sign of spring, and the sound of their half-hearted singing as I toddle out to the shed always cheers me up. Then there are the masses of tadpoles, and then the tiny frogs, and then they seem to disappear, although there’s often the tell tale ‘plop’ of a late frog diving for cover as the days lengthen. Plus, they have such terrible habits, what with mating with anything that stands still long enough although female frogs have come up with a variety of ways to deal with all that testosterone-fuelled nonsense. Well, this week New Scientist reports the finding of the oldest fossil tadpole in the world, dating back some 161 million years. The scientists involved were searching a rock formation in Argentina for feathered dinosaurs, but I hope they were just as delighted with the world’s oldest fossil tadpole.

Fossil of Notobatrachus degiustoi tadpole (Photo by Mariana Chuliver et al, from Notobatrachus degiustoi)

The tadpole measures about 16 centimetres/6 inches long (comparable with the largest tadpoles found today), and it is so beautifully preserved that scientists can tell that it was just about to undergo metamorphosis when it met its untimely end. There are lots of adult frog fossils in this particular rock formation too (the La Matilde Formation of the Deseado Massif in southern Patagonia) , so it’s unclear exactly what happened to cause the tadpole’s demise.  However, the climate was warmer, wetter, and there were few other frog species or fish around to act as predators, so you could describe it as ‘frog heaven’.

Artist’s impression of adult frog By Nobu Tamura (http://spinops.blogspot.com) – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19461181

What’s interesting is that the frog’s form of metamorphosis hasn’t changed in all these millions of years – it’s proved to be a robust method of reproduction despite all the changes that the Earth has gone through. When the frogs gather in spring we’re watching something that has been happening for time immemorial, which I find strangely comforting. And how adaptable these creatures are, from frogs that lay their eggs in pitcher plants in tropical forests, to desert frogs that bury themselves for most of their lives, only emerging during the wet season. They are truly extraordinary animals, and I always feel so privileged to live alongside them.

Frogs in my pond 2023

You can read the New Scientist article here, and the research paper is here.