CONICET | Buscador de Institutos y Recursos Humanos

Solanaceae, an economically important family with an intriguing evolutionary history, has a minimal fossil record. Roughly 50 fossil taxa have been described as belonging to Solanaceae, and among these, only some can be confidently assigned to the family. Here, we report on a recently discovered fossil lantern fruit with a suite of features characteristic of the genus Physalis within Solanaceae. The fossil comes from the early Eocene Huitrera Formation (Laguna del Hunco site, ca. 52 Ma) in Chubut, Argentina, which previously produced the only other solanaceous fruit fossils, Physalis infinemundi. The new fossil differs from P. infinemundi in its fruiting calyx with wider primary veins, longer and thinner lobes, and especially in its venation pattern with high density, transverse tertiary veins, in contrast to the low-density, reticulate tertiaries of P. infinemundi; these features support its placement in a new species. In comparison with extant physaloid genera, the calyx venation pattern and other diagnostic traits support placement of the new fossil, like P. infinemundi, within the Physalideae tribe of Solanaceae. These traits include a combination of an inflated, five-lobed and angled fruiting calyx, basally invaginated, with primary veins terminating at lobe tips, a pedicel longer than 15 mm, five secondary veins that emerge from the calyx base, and the presence of a large, round berry. Both species of fossil nightshades from Laguna del Hunco represent crown-group Solanaceae but are older than all prior age estimates of that node. Although at least 20 transoceanic long dispersals have been proposed as the driver of range expansion of Solanaceae to the Old World, these Patagonian fossils push back the diversification of the family to Gondwanan times. Thus, some of the proposed dispersals may not be necessary in light of the ancient trans-Antarctic land connections between South America and Australia.

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