Tomatillo fossil is oldest nightshade plant

Two tiny tomatillo fossils have kicked the origin of nightshade plants back to the age of dinosaurs.

The fossils, pressed into 52-million-year-old rock, suggest that the nightshade family originated millions of years earlier than scientists had suspected, researchers report in the Jan. 6 Science.

Nightshades include roughly 2,500 species of plants, from tomatoes to eggplants to tobacco. Previous estimates had dated the family to some 30 to 51 million years ago. And scientists had suggested that tomatillos, specifically, arose even more recently, around 10 million years ago.

Paleontologist Peter Wilf and colleagues have nixed that timeline. They uncovered the roughly 2-centimeter-tall fossils from an ancient lake in what is now Patagonia. Each fossil preserves the delicate, tissue-paper-like sheath that typically covers a tomatillo’s central berry, like a candle inside a paper lantern. In one fossil, evidence of a berry (now turned to coal) still remains.

“This is like an impossible fossil,” says Wilf, of Pennsylvania State University in University Park. “That you could preserve something this delicate — this little papery structure. It’s unheard of.”

The outer structures may keep tomatillo berries dry — and afloat. “You’ve got an umbrella and a life raft,” Wilf says. And it’s built right in.

The fossils represent a new species of tomatillo, called Physalis infinemundi, Wilf and colleagues at Cornell University and the Paleontological Museum Egidio Feruglio in Patagonia report. Infinemundi is Latin for “at the end of the world.”

Fifty-two million years ago puts these tomatillos deep in the southern hemisphere during the final days of the supercontinent Gondwana, before Antarctica split from Australia and the southern tip of South America.