Azolla nova

Name

Azolla nova

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

52

Year

2013

Parent Taxon

[Genus] Azolla

Fossil Status

sporae dispersae (megaspores & microspores)

Stratigraphy

Ypresian

Location

Sandpiper Well 3570–3600 cm, western Arctic Ocean

Paleoregion

Arctic

Data for Holotypus

Repository

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

Repository Number

U23536

Num

pl. 1, 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 pear-shaped to globular (typically b330 μm diameter) with rounded distal pole and obtuse proximal pole. Megaspore inferred to be spherical to sub-spherical when uncompressed, trilete mark on the proximal pole, laesurae extending up to one third of spore radius, lying in a field bordered by a triangular collar. Entire megaspore apparatus covered by a thick mat of intertwined hairs (>0.9 μm wide) arising almost entirely from the proximal region of the megaspore. Remnants of megasporocarp wall present on the proximal pole of the megaspore apparatus. Megaspore wall with distinct regularly arranged small excrescences. Megaspore surface finely rugulate under LM and SEM; rugulae usually branching and frequently topped by small papillae. Under TEM megaspore wall consisting of a thin exine and a twice as thick two-layered perine; inner surface of the exine forming a more or less continuous layer beneath a more open structure with radially elongated irregular spaces. Endoperine similar to exine with more equidimensional spaces and granular appearance and an undulating surface lacking ornamentation. Excrescences formed by expansion of the endoperine. Exoperine with contorted nodular masses in the inner part and tabular masses on the outerpart giving an undulating exoperine surface. Collar formed from granular endoperine, triangular, linking ends of the laesurae on the proximal pole; modified exoperine on the collar giving rise to hairs (suprafilosum). Float system a compact dome-shaped structure, occupying the proximal third to one quarter of the megaspore apparatus, slightly overlapping the proximal part of the megaspore; floats not numerous, most likely arranged in one tier, and enmeshed by hairs of the suprafilosum. Microspore massulae with undulating wavy irregular outline resulting from microspores bulging out from within the massula, microspores filling the massula, touching one another with clearly visible outlines. Massulae containing 1–8 smooth walled triradiate microspores, laesurae extending about half the radius of the spore. Outer surface of microspore massulae with a limited number of strap-shaped aseptate glochidia up to 85 μm long, with very broad basal attachment, narrower lower stalk grading into a wider upper stalk, with a distal dilation and a distinct constriction below an anchor-shaped tip. Flukes long, narrowing gradually, predominantly with recurved hooks. Surface of the microspore massula and glochidia bases covered by long (3–4 μm) hairs.