Pteroheterochrosperma horseflyensis, Smith & Greenwalt & Manchester, 2023

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 : 65

Pteroheterochrosperma horseflyensis sp. nov.

Text-fig. 12a

P l a n t F o s s i l N a m e s R e g i s t r y. PFN003031

(for new species).

E t y m o l o g y. The specific epithet is for the Horsefly, British Columbia where the first fossils of this species were described.

H o l o t y p e. USNM PAL 722530, National Museum of

Natural History, District of Columbia, USA, Text-fig. 12a .

Ty p e h o r i z o n a n d t y p e l o c a l i t y.DakinSite in the Kishenehn Formation, ca. 44 Ma.

S p e c i f i c d i a g n o s i s. Winged structure circular; wing has thick striations (up to 0.1 mm) radiating around seed body starting from the seed body and mostly terminating at the margin of the wing, some striations bifurcating; seed body obovate with rugulate sculpture.

S i z e. Structure 2.1 mm tall, 2.7 mm wide; seed body

1.28 mm tall, 0.77 mm wide.

D e s c r i p t i o n. Roughly 27 striations radiating from the seed body, some bifurcating or trifurcating.

R e m a r k s. Similar disseminules have been found from the early Eocene Okanogan sites of Republic, WA ( Pigg and Wehr 2002), McAbee, BC and Horsefly, BC (UWBMB4131-96008, DSCN6543). Penhallow (1908) assigned specimens from Horsefly of this disseminule as Ulmus minuta GOEPP. (94–95), which was a leaf species, but he recognized that the fruit was much smaller than other known fossil and modern elms. U. minuta is a synonym for Ulmus pyramidalis (GOEPPERT) emend. ILJINSK. ( Takhtajan 1982, Traiser et al. 2019). U. pyramidalis DIPPEL was already in use for a different extant elm and was recognized as a synonym of Ulmus glabra HUDS. U. glabra ’s modern geographic range includes Europe and western Asia but its fruits lack the thick, darkened veins that appear in the fossil and possess two styles which the fossil lacks ( Thomas et al. 2018, Sherman-Broyles 2021). These tiny disseminules lack the wing venation and stylar cleft and style diagnostic for Ulmus , and thus require a new binomial.

Figures

Text-fig. 12. a: USNM PAL 722530 Pteroheterochrosperma horseflyensis gen. et sp. nov. SMITH et MANCHESTER. Scale bar 2mm. b: USNM PAL 622695 Quadrasubulaflora kishenehnensis gen. et sp. nov. SMITH et MANCHESTER showing three outer parts and two stigma. Scale bar 1mm. c: USNM PAL 625447 Q. kishenehnensis showing three outer parts. Scale bar 1mm. d: USNM PAL 624649 Q. kishenehnensis showing three outer parts. Scale bar 1mm. e: USNM PAL 622402 Q. kishenehnensis. Scale bar 2mm. f: USNM