The cover shows an artist’s impression of Gaiasia jennyae, a large, salamander-like creature that lived around 280 million years ago. Unveiled in this week’s issue by Claudia Marsicano and colleagues, Gaiasia fills a gap in the early evolutionary history of four-legged vertebrates. The researchers identified Gaiasia from at least four incomplete fossils found in Namibia, including skull fragments and a nearly complete backbone. Gaiasia was unusually large, probably clocking in at around 2.5 metres in length, and had a powerful bite for capturing prey. Not only are the remains among the largest for early tetrapods, they were also found much farther south than previous species, indicating that such creatures had a much wider range than was previously thought.

The fungal disease chytridiomycosis has spread rapidly worldwide and has driven at least 90 species of amphibian to extinction. Although successful work has been done treating amphibians in captivity, managing the disease in the wild remains a challenge. In this week’s issue, Anthony Waddle and colleagues present a simple approach that could help amphibians overcome the disease in the wild. The key is temperature — the fungus that causes chytridiomycosis cannot tolerate environments above 28 °C. So, the researchers built a microhabitat using bricks piled inside a small greenhouse warmed by the sun. Testing it using Australian green and golden bell frogs (Ranoidea aurea), the team found that the amphibians preferred to sit in the hotspots (as seen on the cover). The warmth of these frog saunas lifted body temperatures high enough for the animals to reduce and clear fungal infections. Frogs cleared in this way subsequently showed resistance to chytridiomycosis, even in cool conditions optimal for fungal growth.

Whether it is used to help find prey or to avoid predators, sound is key to survival for many vertebrates. On land, the direction from which a sound originates can readily be determined by gauging the time delay and intensity variation between each ear. Underwater, that is much harder. In this week’s issue, Benjamin Judkewitz and colleagues affirm how fish achieve this feat. Working with the small, transparent fish Danionella cerebrum (a stained specimen of which is pictured on the cover), the researchers carefully controlled pressure and particle motion in the water, and imaged sound-induced vibration inside the fish. The team found that, in line with one of several considered hypotheses, the fish compare pressure and particle motion signals to detect the direction of sound sources.