Azolla primaeva

Lore & Background

The species was first described from poorly preserved material collected in the Similkameen River area near Princeton, British Columbia, and later noted from outcrops at Stump Lake northeast of Princeton. The fossils were described by David P. Penhallow in the 1890 volume 'On Fossil Plants from the Smilkameen Valley and Other Places in the Southern Interior of British Columbia.' Though the volume only lists John William Dawson as author, Dawson notes that the A. primaevum description had been written by Penhallow. Due to the poor nature of the type specimen, the species was placed in the form genus Azollophyllum as Azollophyllum primaevum, indicating its similarity to the modern genus but acknowledging the lack of detail needed to confirm its placement.

Placement of the species was formally changed with the publication of a paper written by Chester A. Arnold based on new fossil specimens collected near the former mining camp of Ashnola, British Columbia, approximately 8 miles south of Princeton along the Similkameen River. The fossils were recovered from strata of the Allenby Formation, at the time considered Oligocene age, but now known to be of the Early Middle Eocene. Arnold noted the new specimens to consist of leafy vegetation and roots often forming mats in the rock, accompanied by microspore massulae and megasporangia. After comparing the new fossil specimens to both modern and fossil species, Arnold noted A. primaeva to be close in morphology to the living A. filiculoides and the Eocene A. intertrappea of India.

Reader's Guide

Azolla primaeva holds significance as the earliest fossil species of Azolla described from the fossil record, though its initial 1890 description was under the form genus Azollophyllum due to poor preservation. The 1955 redescription by Chester A. Arnold, based on better-preserved specimens from the Allenby Formation, confirmed its placement in the genus Azolla. At the time of Arnold's paper, four fossil Azolla species had been described: A. intertrappea from Eocene India (1934), A. berryi from the Middle Eocene Green River Formation (1934), A. prisca from Oligocene London Clays of England (1926), and A. tertiaria from Pliocene Nevada (1927). Arnold noted that with the placement of A. primaeva into Azolla, its 1890 description was actually the earliest species described from the fossil record. The species is morphologically close to the living A. filiculoides and the Eocene A. intertrappea. Fossil specimens of Azolla have been recovered from the closely related strata of the Klondike Mountain Formation around Republic, Washington, but have not been described to species. The species thus provides an important early Eocene record of the genus in North America.

Did You Know?

• Azolla primaeva was first described in 1890 by David P. Penhallow, though the volume only listed John William Dawson as author.
• The species was initially placed in the form genus Azollophyllum due to the poor preservation of the type specimen.
• Chester A. Arnold redescribed the species in 1955 based on new fossils from the Allenby Formation near Ashnola, British Columbia.
• Arnold noted that A. primaeva is morphologically close to the living species Azolla filiculoides.