A new multiple-floated Azolla from the Eocene of Britain with a brief review of the genus
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Megaspores and microspore massulae of Azolla colwellensis sp. nov. are described from the Upper Eocene, Upper Headon Beds of Colwell Bay, Isle of Wight. The megaspores possess a multifloated 'swim apparatus' with three tiers of floats. The floats are arranged in three groups of six. There is a distinct collar at the junction with the megaspore zone and hairs arising from this collar enmesh the floats. The microspore massulae possess occasionally septate, grapnel-tipped glochidia. This species is the youngest multifloated Azolla yet recorded and is the only multifloated species which possesses a collar. It further supports recent hypotheses that a number of lines of evolution have been involved in the development of extant Azolla species. A review of the sixty species recorded in the genus Azolla is presented in the form of a table showing stratigraphic ranges and features of the megaspores and massulae. Certain species are discussed in detail with relation to the morphology of A. colwellensis.
Palaeontology - Volume 23 Part 1 Pages 213-229Palaeontology - Volume 23 Part 1 Pages 213-229
Citations
COLLINSON, M. E. 1980. A new multiple-floated Azolla from the Eocene of Britain with a brief review of the genus. Palaeontology, 23, 1, 213–229.