A fossil groundcherry, Physalis infinemundi.
A fossil groundcherry, Physalis infinemundi. Ignacio Escapa, Museo Paleontológico Egidio Feruglio

Among the world’s plants, the nightshade family is one of most prolific and most useful. Among its 2,500 species are some of the humanity’s favorite foods (potatoes, peppers, eggplants, tomatoes) and distractions (petunias, tobacco). This family of plants was thought to have diverged from the morning glory family somewhere between 49 and 67 million years ago, but that was something of an educated guess: their delicate fruits rarely fossilize, and archaeologists had only ever found a few seeds linking the present-day plants to the past.

In a new paper in Science, though, a team of scientists reports on the discovery of two small fossils of ancient nightshades of the physalis genus, which includes tomatillos, ground cherries, and husk tomatoes. These two specimens, with their delicate husks preserved around them, are about 52 million years old and show that the nightshade family is much, much older than previously realized.

In this specimen, the berry turned to coal.
In this specimen, the berry turned to coal. Peter Wilf, Penn State

The fossils were found in Laguna del Hunco in Patagonia, Argentina, an area that scientists have been studying for about a decade. Of the more than 6,000 fossils found there, these are the only ones from the physalis genus and, according to Peter Wilf, the lead author of the Science paper, “the only two fossils known of the entire nightshade family that preserved enough information to be assigned to a genus within the family.”

The scientists identified features on the fossils that clearly placed them in the same genus as today’s tomatillos: they named the ancient species Physalis infinemundi, after its place “at the end of the world,” in Patagonia.

Before this discovery, molecular dating had indicated the the physalis genus was only about 9 to 11 million years old. The fossil indicates that it evolved about 40 million years earlier than that. Since these husky plants are on the recent end of nightshade evolution, the discovery also indicates that nightshades as a family are likely older than anyone had imagined.

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