Acer ningmingensis Y.F.Chen & W.O.Wong, 2017

Chen, Yunfa, Wong, William Oki, Hu, Qian, Liufu, Yongqing & Xie, Zhiming, 2017, A new fossil-species of Acer (Sapindaceae) from the Ningming Basin in Guangxi, South China, Phytotaxa 298 (2), pp. 158-164 : 160

Acer ningmingensis Y.F.Chen & W.O.Wong , sp. nov. ( Fig.3 )

Holotype: NHMG 032584 ( Figs. 3 , A, B)

Paratypes: NHMG 032585, 032586, 033717, 033718 ( Figs.3 , C, D, E, F)

Repository: Guangxi Museum of Natural History ( NHMG), Guangxi, China

Type locality: Ningming County, Guangxi, China (22°07 ′ 41.96 ″ N, 107°02 ′ 30.65 ″ E)

Stratigraphic horizon: Ningming Formation, Oligocene

Etymology: Species name referring to the occurrence of the fossils in Ningming County

Diagnosis:Asymmetric samara, containing a nutlet and a wing. Nutlet flattened or very thin, nutlet outline elliptic; attachment angle 30°to 45°; wing apex narrowly rounded and conspicuously inclining to proximal side; proximal margin broadly concave, distal margin broadly rounded—broadly convex, forming a broadly shallowly V-shaped sulcus with nutlet; wing size relatively small; veins in wing body diverging from proximal margin at angles of 20° to 40°, dichotomizing 2 to 4 times.

Description: Fruits are samara with the nutlet at basal end. Nutlets are 0.7–0.8 cm long, 0.4–0.5cm wide, with an elliptic outline and are flattened or very thin ( Fig. 3A, B, E ). The attachment scar (where the two resulting fruits in the schizocarpic samara would be attached) is 0.4–0.5cm long, with an attachment angle 30°–45°, nutlet angle 20°–25° (in relation to the wing); veins on nutlet are obscure, and the nutlet surface is nearly smooth; the proximal margin of nutlet is either not or only slightly expanded beyond proximal margin of wing. The wing is 3.0– 3.4cm long, 0.9–1cm wide, and the wing apex is narrowly rounded and conspicuously inclining to proximal side; the proximal margin is broadly concave, and the distal margin is broadly rounded—broadly convex, forming a broadly shallowly V-shaped sulcus with nutlet; five prominent veins are coalesced along the wing proximal margin, extending from apical margin of nutlet; wing veins diverge from proximal margin at angles of 20° to 40°, nearly straightly extending toward distal margin, dichotomizing 2 to 4 times, few anastomoses, and the diverging angles increase from the apex to the base.

Comparison: The winged fruits described in this paper are similar to the fossils of Acer stewarti Wolfe & Tanai in the North America ( Wolfe & Tanai, 1987), in fruit size and attachment angle. However, the nutlet outline of Acer stewarti is circular, concave-convex, and proximal wing margin is straight, veins in wing body dichotomizing more (5 to 6 times). Acer washingtonense Wolfe & Tanai has moderately inflated nutlet, with veins in wing body dichotomizing more times (5–6). Acer palaeodiabolicum Endo has globular–subglobular, thick nutlet, with much smaller attachment angle (8 o –17 o). Acer miofranchetii Hu & Chaney has moderately inflated nutlet, with bigger attachment angle (50 o – 65 o).The present fossil differs from modern Acer laxiflorum fruit in Guangxi, South China which is characterized by straight proximal margin and much bigger attachment angle (>70°). Acer sino-oblongum Metc. living in South China today has very inflated nutlet. The present fossil species is distinguished from all other extinct and extant Acer samaras by its characters of the wing shape, venation in wing body and nutlet (Table 1). Considering the unique features of our specimens, we assign the fossils to a new species Acer ningmingensis sp. nov.

Figures

FIGURE 3. Acer ningmingensis. A. Holotype (NHMG032584), B. Line drawing of Holotype lobe showing the venation details. C. Paratype (NHMG032585). D. Paratype (NHMG032586). E. Paratype (NHMG033717). F. Paratpe (NHMG033718). Scale bar = 1 cm.