Betula sp.

Smith, MacKenzie A., Greenwalt, Dale E. & Manchester, Steven R., 2023, Diverse Fruits And Seeds Of The Mid-Eocene Kishenehn Formation, Northwestern Montana, Usa, And Their Implications For Biogeography, Fossil Imprint 79 (1), pp. 37-88 : 58

Betula sp.

Text-fig. 8g

M a t e r i a l. USNM PAL 624925.

L o c a l i t y. Dakin.

D e s c r i p t i o n. Samara obovate 4.0 mm long, 2.2 mm wide; seed body in center of wing, fusiform 3.0 mm long, 0.8 mm wide; style splits near margin of wing 1.3 mm long, curled; wing 0.6 mm wide and tapers at base.

R e m a r k s. The thin wing that is differentiated from the seed body and long styles of the seed distinguish this specimen as Betula and can be contrasted with the nondifferentiated wing and short styles in Alnus . Betula fossils are known from the early Eocene McAbee, One Mile Creek, Quilchena and Falkland floras of British Columbia ( Crane and Stockey 1987, Lowe et al. 2018, Mathewes et al. 2016, Smith et al. 2012), Republic flora of Washington ( Wolfe and Wehr 1987, Pigg et al. 2011) and late Eocene Bull Run flora of Nevada ( Wing 1987). Alnus appears to be more common in Paleogene deposits compared to Betula , which may be due to temperature or its proximity to the water (pers. obs.).

Figures

Text-fig. 8. Betulaceae and Juglandaceae from the Kishenehn Formation. a: DMNH L6933 Alnus sp. L1 leaves. Scale bar 2cm. b: DMNH EPI.48179 Alnus sp. leaf. Scale bar 2cm. c: DMNH EPI.48136b Alnus sp. leaf. Scale bar 2cm. d: USNM PAL 622756 Alnus sp. I1 infructescence attached to branch. Scale bar 1cm. e: USNM PAL 623160 Betuloideae showing wing, seed body and two persistent styles. Scale bar 1mm. f: USNM PAL 622732 Alnus sp. F1 samara showing two persistent styles. Scale bar 1mm. g: USNM PAL 624925 Betula sp. samara showing wing, seed body and two persistent styles. Scale bar 1mm. h: USNM PAL 623147 Alnus sp. F2 samara showing. Scale bar 1mm. i: USNM PAL 622690 Palaeocarya sp. samara showing three wings with reticulate venation and hairs at base. Scale bar 1cm.