Potamogeton

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 : 49

Genus Potamogeton L.

Text-fig. 5a–c

L o c a l i t i e s. Deep Ford, Disbrow Creek, Park and

Spring.

M a t e r i a l. USNM PAL 622670, 622675, 623125,

626043, 625757, DMNH EPI.48225, 48188.

D e s c r i p t i o n. Stem 0.2–0.7 mm wide; leaves opposite; nodes thick; leaves at least 24.9 mm long, 1.2– 1.4 mm wide; 2° 1° 2° (where left to right the veins are thin, thick then thin, see fig. 1a, b in Robil et al. (2021) for comparison) parallel venation type with veins joining to the center vein near leaf apex; apex rounded; margin entire; pigment or glandular cells present; fruits flat, circular drupes, 2.24–3.10 mm tall, 1.8–2.6 mm wide, 0.6 mm thick; style pointed with persistent stigmatic region; pedicel 0.1 mm long and 0.1 mm wide; four fruits on a raceme with peduncle 9 mm long and 0.2 mm wide.

R e m a r k s. The aquatic genus, Potamogeton , is identifiable from leafy stems bearing infructescences. The genus is distinguished by its opposite narrow leaves, and circular, flat fruits with a pointed apex and persistent styles that are borne in racemes ( Manchester 2001). Fruits and leaves of Potamogeton have also been recognized from the late Eocene Florissant Formation of Colorado ( Manchester 2001) and leaves from the mid-Eocene Thunder Mountain flora of Idaho ( Axelrod 1998).

Figures

Text-fig. 5. Potamogeton sp. and Typha sp. from the Kishenehn Formation. a: USNM PAL 622670 Potamogeton sp. stem and leaves. Scale bar 1cm. b: DMNH EPI. 48225 Potamogeton sp. showing vegetative structures and fruit. Scale bar 1cm. c: USNM PAL 623125 Potamogeton sp. infructescence with leaves. Scale bar 5mm. d: USNM PAL 622997 follicle body of Typha sp. showing longitudinal opening and apical tuft/stylar remnant. Scale bar 1mm. e: USNM PAL 623087 follicle body of Typha sp. showing longitudinal opening. Scale bar 1mm. f: USNM PAL 621989 Typha sp. carpodium. Scale bar 2mm.