A Left-Handed, Stem-Twining Plant from the Miocene Shanwang Formation of Eastern China

Twining stems of plants are very common in extant tropical and subtropical forests, and the climbing growth habit of plants may be an evolutionary innovation and ecological adaptation to either closed, shady or open, edge environments. However, the origin of handedness in climbing plants remains unclear. Here we report a Miocene (ca. 16 million years ago) macrofossil from the Shanwang Formation of Shandong Province, Eastern China, unequivocally exhibiting the first direct fossil evidence for a left-handed, stem-twining growth habit in plants. This fossil plant bears a thicker, slightly curved supporting stem (2 3.5 mm wide), which is loosely, spirally twined by a thinner stem (1.5 2 mm wide), possibly representing part of distal branches from a liana or vine.