Azolla nuda

Name

Azolla nuda

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

56

Year

2013

Parent Taxon

[Genus] Azolla

Fossil Status

sporae dispersae (megaspores & microspores)

Stratigraphy

Ypresian

Location

ODP 913B 48R 2W 70–72, Arctic Ocean

Paleoregion

Arctic

Data for Holotypus

Repository

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

Repository Number

U23539

Num

pl. 3, 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 ovoid to pear-shaped (up to 440 μm long), broader distally. Megaspore inferred to be spherical to sub-spherical when uncompressed, trilete, laesurae extending about half of the radius of the spore. Entire megaspore apparatus covered by a thick mat of intertwined hairs, which arise almost entirely from the proximal region of the megaspore (hence suprafilosum). Collar not visible under transmitted light. Remnants of megasporocarp wall present on the proximal pole of the megaspore apparatus. Megaspore wall lacking excrescences. Under LM megaspore surface with small-scale ornamentation, combining rugulae and small papillae. Under SEM exoperine surface finely rugulate, rugulae usually branching and consistently topped by small papillae to baculae. Under TEM megaspore-wall consisting of an exine and a two-layered perine; inner surface of the exine forming a more or less continuous layer beneath a more open structure with a small number of radially elongated irregular spaces. Endoperine similar to exine but with more equidimensional spaces, granular appearance and an undulating surface lacking ornamentation. Exoperine with contorted nodular masses in the outer part supported by nodular baculae giving a strongly undulating exoperine surface. Collar formed from endoperine, slightly spongy and pseudovacuolate, modified exoperine on the collar gives rise to hairs (suprafilosum). Modified exoperine also forming a columella extending proximally through the float system. Float system compact dome-shaped, occupying at least the proximal two-fifths of the megaspore apparatus; floats spongy pseudovacuolate, probably numerous, arranged in at least two, probably three, tiers. Floats enmeshed by hairs of the suprafilosum. Microspore massulae with slightly irregular outline and granular appearance, internally spongy, vacuolated in structure, obscuring the spore outlines. Massulae containing up to 20 smooth-walled trilete microspores, laesurae extending about half the radius of the spore. Outer surface of the microspore massulae with a number of aseptate glochidia up to 75 μm long, with broad basal attachment, a narrow lower stalk grading into a broader upper stalk with a distal dilation and a distinct constriction below an anchor shaped tip. Flukes mostly lacking recurved hooks. Surface of the microspore massulae and glochidia bases lacking hairs.