Equisetum yenbaiense A.T.Aung, T.Su, T.V.Do & Z.K.Zhou, 2020

Equisetum yenbaiense A.T.Aung, T.Su, T.V.Do & Z.K.Zhou sp. nov.

Holotype.

XTBGVNMN4001 (Fig. 2D View Figure 2 ).

Paratypes.

XTBGVNMN4002-4004 (Fig. 2C, E-F View Figure 2 ).

Locality.

Hop Thanh Village, Tuy Loc Commune, Yen Bai Province, northern Vietnam ( 21.725N, 104.849E).

Age.

The late Miocene.

Repository.

Paleoecology Collections, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences and Vietnam National Museum of Nature, Vietnam Academy of Science and Technology.

Etymology.

The species name ' yenbaiense ' means that fossils are from Yen Bai Province, northern Vietnam.

Diagnosis.

Rhizomes with internodes and nodes, node round; Four bunches of tubers arranged in a whorl on a node (Fig. 2D View Figure 2 ); most tubers elongate in shape, with one to two tubers in each bunch (Fig. 2C-D View Figure 2 ); longitudinal ridges on the surface of tuber; the tip of tuber mucronate (Fig. 2F View Figure 2 ).

Description.

Rhizomes have both internodes and nodes (Fig. 2D View Figure 2 ). The internode is ~0.2-0.3 cm in width, the length could not be observed, three longitudinal ridges are on the surface of the internode (Fig. 2D View Figure 2 ). The node is round and ~0.2 cm in diameter (Fig. 2D View Figure 2 ). Four bunches of tubers attach to one node and arrange in a whorl (Fig. 2D View Figure 2 ). Only one tuber is preserved on each bunch, but it is likely that there are more than one tuber on each bunch (Fig. 2E-F View Figure 2 ). Most tubers are elongate (Fig. 2D View Figure 2 ); few are elliptical (Fig. 2F View Figure 2 ), being~ 0.8 to 3.0 cm long and 0.4 to 1.0 cm wide. Two to four ridges are on the surface of each tuber (Fig. 2D View Figure 2 ). The tip of tuber is mucronate (Fig. 2F View Figure 2 ).