Azolla coloniensis Ben. et Zamaloa in Benedetti, Zamaloa, Gandolfo & Cúneo

Plant Fossil Names Registry Number: PFN000763

Act LSID: urn:lsid:plantfossilnames.org:act:763

Authors: F. D. Benedetti & M. C. Zamaloa

Rank: species

Reference: Benedetti, F. D., Zamaloa, M. C., Gandolfo, M. A. & Cúneo, N. R. (2018): Heterosporous Ferns From Patagonia: The Case of Azolla. in Krings, M., Harper, C. J., Cúneo, N. R., Rothwell, G. W. (eds): Transformative Paleobotany. Papers to commemorate the life and legacy of Thomas N. Taylor. Academic Press: 361–373.

Page of description: 363

Illustrations or figures: pls 1, 2

Types

Original diagnosis/description

Megaspore apparatus is ovoid, c. 360 (400) 520 μm long and c. 260 (270) 360 μm wide, partially covered by a thick mat of intertwined hairs. Megaspore trilete, spherical to sub-spherical, c. 250–320 μm in diameter. Megaspore wall is formed by exine and a much thicker two-layered perine. In LM, exine and endoperine appear homogeneous, whereas exoperine is columellate and has a reticulate surface. In thin section under TEM, exine is relatively homogeneous with dispersed small irregular cavities; endoperine is of granular appearance and spongy structure; exoperine consists of contorted nodular or clavate to tabular partially fused masses. Under SEM, exoperine surface consists of muri linked to form a reticulum with rounded
lumina. Hairs emerge from the exoperine surface and cover completely the megaspore forming the infrafilosum. Float system is thimble shaped, occupying at least the upper twofifths of the megaspore apparatus. Floats spongy pseudovacuolate, 18–21 or more, arranged in three (exceptionally four) tiers. Lower level with 9–12 small spherical, elliptical, or rhomboidal floats that extend over the proximal surface of the megaspore. Middle level with 6 or more larger floats, rhombic-shaped or irregular, often with a large invagination. Upper level with three large rhombic floats with deep invaginations. Modified perine forms a proximal dome-shaped columella. Hairs arise from the reticulate surface of the floats and from the columella. Microspore massulae are irregular, elliptical or triangular in shape, with a granular appearance and spongy vacuolated structure. Microspores trilete, psilate, c. 14–30 μm in equatorial diameter. Surface of the microspore massulae with numerous aseptate glochidia of up to 35 μm long, with a stalk of uniform width and distally broadening and then constricted below an anchor-shaped tip. Flukes narrow gradually and with recurved hooks.

Etymology

From the stratigraphic unit La Colonia Formation.

Stratigraphy

Cretaceous, Upper Cretaceous
La Colonia Formation

Locality

Argentina
Cañadón del Irupé, NE Chubut Province