Wolffiella HEGELM.

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 Wolffiella HEGELM.

Text-fig. 4f

M a t e r i a l. USNM PAL 622956, 626140.

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

D e s c r i p t i o n. Frond triangular, 4.4–4.7 mm long, 0.3–0.7 mm wide at base, base flat to curved, budding pouch triangular, 0.9–1.2 mm tall, 0.3–0.7 mm wide, aerenchyma present.

R e m a r k s. The slender triangular fronds with aerenchyma and budding pouches are diagnostic of Wolffiella ( Armstrong 2021) . This specimen is not the dispersal hair of a Typha fruit because it is a multicellular frond. Wolffiella plants can exhibit a variety of morphologies including ovate, “tongue” and sickle shaped ( Acosta et al. 2021) ( Text-fig. 4g ). The size range of these specimens also fits the size range of modern North American Wolffiella fronds (4.4– 4.7 mm for the fossils, 1–9 mm for the modern) ( Landolt 2020). Ours would fit in the “tongue” category, which does not occur in the other genera of Lemnoideae. These are the first reported Wolffiella fossils. Today there are 10 species of this floating aquatic plant across the Americas and Africa ( Landolt 2020). Species in the US are concentrated in the Southwest and Southeast ( Landolt 2020).

Figures

Text-fig. 4. Lemnoideae from the Kishenehn Formation. a: USNM PAL 625611 Spirodela sp. showing fronds, prophyllum and daughter plant with brown pigment cells. Scale bar 2mm. b: Close up of USNM PAL 625611 prophyllum and brown pigment cells. Scale bar 1mm. c: USNM PAL 768304 Spirodela sp. showing fronds, prophyllum and daughter plant with brown pigment cells. Scale bar 2.5mm. d: Close up of USNM PAL 768304 daughter plant with brown pigment cells. Scale bar 2.5mm. e: USNM PAL 620300 Lemna sp. showing fronds with aerenchyma and pseudoroot. Scale bar 1mm. f: USNM PAL 626140 Wolffiella sp. “tongueshaped” multicellular frond with brood pouch at the base. Scale bar 2mm. g: Modern Wolffiella caudata frond with brood pouch and daughter plant from Pagliuso et al. 2018. Scale bar 1 mm.