|White Spruce leaves (needles)|
They have naked seeds, in contrast to the seeds or ovules of flowering plants (angiosperms) which are enclosed during pollination. Gymnosperm seeds develop either on the surface of scale- or leaf-like appendages of cones, or at the end of short stalks (Ginkgo).
The gymnosperms and angiosperms together make up the spermatophytes or seed plants. By far the largest group of living gymnosperms are the conifers (pines, cypresses, and relatives), followed by cycads, Gnetales (Gnetum, Ephedra and Welwitschia), and Ginkgo (a single living species).
Fossil gymnosperms include many that do not belong to the four modern groups, including the so-called "seed ferns" (Pteridosperms) and the "cycadeoids" (Bennettitales). Most of the Gymnosperms became extinct in the Cenozoic era (from 65 million years ago to present day).
- The term comes from the Greek word (γυμνός) for "naked seed", gymnospermos.
- Crisp, M.D.; Cook, L.G. (2011). "Cenozoic extinctions account for the low diversity of extant gymnosperms compared with angiosperms". New Phytologist. 192 (4): 997–1009. doi:10.1111/j.1469-8137.2011.03862.x.CS1 maint: multiple names: authors list (link)
- Chung-Shien Wu, Ya-Nan Wang, Shu-Mei Liu and Shu-Miaw Chaw (2007). "Chloroplast Genome (cpDNA) of Cycas taitungensis and 56 cp protein-coding genes of Gnetum parvifolium: insights into cpDNA evolution and phylogeny of extant seed plants". Molecular Biology and Evolution. 24 (6): 1366–1379. doi:10.1093/molbev/msm059.CS1 maint: multiple names: authors list (link)