An extinct plant that is intermediate between the ferns and seed-bearing plants, dying out in the Triassic period.Also called seed fern
- ‘The Pteridopsida were present, bearing spores on their leaves as they do today, but there were also fernlike seed-bearing ferns, the pteridosperms.’
- ‘In the coal swamps of North America grew pteridosperms like Medullosa, a seed plant that resembles modern tree-ferns, but which bore seeds.’
- ‘The first seeds evolved in a group of vascular plants sometimes called the pteridosperms, or ‘seed ferns.’’
- ‘The idea that cycads stem from Carboniferous so-called pteridosperms (‘seed ferns’ or seed plants with fern-like foliage) has long been popular with paleobotanists.’
- ‘Seed-ferns or pteridosperms evolved rapidly in the Carboniferous; the first conifers are known from the Upper Carboniferous.’
Early 20th century: from modern Latin pteridospermeae, from Greek pteris, pterid- fern.
We take a look at several popular, though confusing, punctuation marks.