Azolla astroborealis

Name

Azolla astroborealis

Rank

Species

Generic Name

[Genus] Azolla

Authors (Pub.)

van der Burgh J. Collinson M. E. van Konijnenburg-van Cittert J. H. A. Barke J. Brinkhuis H.  

Publication

The freshwater fern Azolla (Azollaceae) from Eocene Arctic and Nordic Sea sediments: new species and their stratigraphic distribution [2013/3]

Journal

Review of Palaeobotany and Palynology

Volume

194

Page number

58

Year

2013

Parent Taxon

[Genus] Azolla

Fossil Status

sporae dispersae (megaspores)

Stratigraphy

Ypresian

Location

Northstar 1 Well (Amerada) western Arctic sea along the north coast of Alaska, Arctic ocean

Latitude/Longitude

70:31′42.02″N

149:5′48.82″W

Paleoregion

Arctic

Data for Holotypus

Repository

Utrecht University, Laboratory of Palaeobotany and Palynology, Utrecht, The Netherlands

Repository Number

U23541

Num

pl. 5, figs 1, 5, 8, pl. 6, fig. 1

Pub.

The freshwater fern Azolla (Azollaceae) from Eocene Arctic and Nordic Sea sediments: new species and their stratigraphic distribution [2013/3]

Diagnosis

Megaspore apparatus truncated oviform (up to 450 μm long), wider distally, proximal pole slightly flattened. Filosum lacking over megaspore, apart from rare hairs associated with excresences. Remnants of megasporocarp wall, firmly attached over the proximal pole of the megaspore apparatus. Under SEM megaspore exoperine surface finely reticulate, muri formed by rugulae, rugulae regularly topped by small papillae. Distinct excrescences, formed from exoperine, occurring near the distal pole. Under TEM megaspore wall consisting of a thin exine and a much thicker two-layered perine. Inner surface of the exine forming a more or less continuous membrane beneath a more open structure, with small irregular radially elongate cavities; endoperine with open spongy porous appearance, granular in the inner part, variable larger spaces in the outer part; endoperine surface slightly undulating, lacking ornamentation; exoperine variable from solid contorted nodular masses to large alveolae bounded by thin elongate strands. Endoperine expanded in thickness and becoming spongy vacuolated in structure near the proximal pole, forming a collar encircling the megaspore, and a narrow columella extending distally through the center of the float system. Modified exoperine of the collar and columella gives rise to hairs (suprafilosum) occurring between the floats and in a thick mat at the proximal pole of the megaspore apparatus beneath the remnant of megasporocarp wall. Float system dome-shaped, proximal pole slightly flattened, extending over slightly less than one half of the megaspore apparatus. Floats nine, in two tiers, upper tier of three large floats, lower tier of six small floats, one large and two small floats in each third of the float system overlying one contact face of the megaspore. Microspore massulae not known.