The conifers (Class Pinopsida, subphylum Spermatophytina) have needle-shaped leaves, usually evergreen, and seeds attached to the scales of a woody cone. They are most abundant in cool temperate and boreal regions, but they are most diverse in warmer areas, including tropical mountains (Encyclopaedia Britannica). The conifers comprise the pines, cypresses, araucarians and gnetophytes (Yang et al, 2022).
The time tree below illustrates the most complete recent phylogeny of the conifer stem group:
The time tree below illustrates the most complete recent phylogeny of the conifer stem group:
Figure 1. Summarized phylogenetic tree of the stem-Pinopsida
Note that the species Swedenborgia cryptomerioides, Krassilovia mongolica, Cycadocarpidium erdmanni and Telemachus elongatus shown in the above time tree represent cones that are thought to be associated with leaves that were assigned different names in the past: the leaf genus Podozamites for Swedenborgia, Krassilovia and Cycadocarpidium, and the leaf genus Heidiphyllum for Telemachus (see Figure 5 of Herrera et al, 2020).
The oldest known member of the stem-group conifers is Cordaixylon iowensis, which belongs to the extinct order Cordaitales. It is described from coal balls in the Late Carboniferous (Moscovian) Laddsdale Coal near the town of What Cheer, Iowa, USA (Trivett, 1992; Morris et al, 2018). Unfortunately, no photographs of this fossil are available in the public domain, but other stem-group fossils for which public-domain images are available are shown below (click on image for a larger view):
The oldest known member of the stem-group conifers is Cordaixylon iowensis, which belongs to the extinct order Cordaitales. It is described from coal balls in the Late Carboniferous (Moscovian) Laddsdale Coal near the town of What Cheer, Iowa, USA (Trivett, 1992; Morris et al, 2018). Unfortunately, no photographs of this fossil are available in the public domain, but other stem-group fossils for which public-domain images are available are shown below (click on image for a larger view):
Names in red indicate that the fossil is younger than the oldest known crown-group fossil.
Figure 2. Images of stem-Pinopsida
The above images are ordered from most basal to most crownward, and there appears to be a trend in leaf shape from needle-like (e.g. Otovicia hypnoides) to blade-like (e.g. Cycadocarpidium erdmanni). This is interesting because many extant conifers have needle-like leaves.
As indicated in Figure 1, the conifer stem-to-crown transition took place over a period of between 104 and 111 million years, from Late Carboniferous to Late Triassic time.
As indicated in Figure 1, the conifer stem-to-crown transition took place over a period of between 104 and 111 million years, from Late Carboniferous to Late Triassic time.
References
Castillo, G. R. H. (2006). Systematics of the most ancient conifers. Ph.D. thesis, University of Alberta.
Doyle, J. A. (2006). Seed ferns and the origin of angiosperms. The Journal of the Torrey Botanical Society, 133(1), 169-209.
Herrera, F., Shi, G., Mays, C., Ichinnorov, N., Takahashi, M., Bevitt, J. J., ... & Crane, P. R. (2020). Reconstructing Krassilovia mongolica supports recognition of a new and unusual group of Mesozoic conifers. PLoS One, 15(1), e0226779.
Morris, J. L., Puttick, M. N., Clark, J. W., Edwards, D., Kenrick, P., Pressel, S., ... & Donoghue, P. C. (2018). The timescale of early land plant evolution. Proceedings of the National Academy of Sciences, 115(10), E2274-E2283.
Rothwell, G. W., Stockey, R. A., Mapes, G., & Hilton, J. (2011). Structure and relationships of the Jurassic conifer seed cone Hughmillerites juddii gen. et comb. nov.: implications for the origin and evolution of Cupressaceae. Review of Palaeobotany and Palynology, 164(1-2), 45-59.
Trivett, M. L. (1992). Growth architecture, structure, and relationships of Cordaixylon iowensis nov. comb.(Cordaitales). International Journal of Plant Sciences, 153(2), 273-287.
Yang, Y., Ferguson, D. K., Liu, B., Mao, K. S., Gao, L. M., Zhang, S. Z., ... & Zhang, Z. X. (2022). Recent advances on phylogenomics of gymnosperms and a new classification. Plant Diversity, 44(4), 340-350.
Doyle, J. A. (2006). Seed ferns and the origin of angiosperms. The Journal of the Torrey Botanical Society, 133(1), 169-209.
Herrera, F., Shi, G., Mays, C., Ichinnorov, N., Takahashi, M., Bevitt, J. J., ... & Crane, P. R. (2020). Reconstructing Krassilovia mongolica supports recognition of a new and unusual group of Mesozoic conifers. PLoS One, 15(1), e0226779.
Morris, J. L., Puttick, M. N., Clark, J. W., Edwards, D., Kenrick, P., Pressel, S., ... & Donoghue, P. C. (2018). The timescale of early land plant evolution. Proceedings of the National Academy of Sciences, 115(10), E2274-E2283.
Rothwell, G. W., Stockey, R. A., Mapes, G., & Hilton, J. (2011). Structure and relationships of the Jurassic conifer seed cone Hughmillerites juddii gen. et comb. nov.: implications for the origin and evolution of Cupressaceae. Review of Palaeobotany and Palynology, 164(1-2), 45-59.
Trivett, M. L. (1992). Growth architecture, structure, and relationships of Cordaixylon iowensis nov. comb.(Cordaitales). International Journal of Plant Sciences, 153(2), 273-287.
Yang, Y., Ferguson, D. K., Liu, B., Mao, K. S., Gao, L. M., Zhang, S. Z., ... & Zhang, Z. X. (2022). Recent advances on phylogenomics of gymnosperms and a new classification. Plant Diversity, 44(4), 340-350.
Image credits – stem- Pinopsida
- Figure 2 (Ferugliocladus riojanus): Wiki Paleobotánica, under Creative Commons licence 3.0 (Unported) (CC-BY-SA).
- Figure 2 (Dicranophyllum hallei): CC BY-NC-SA @ Museum für Naturkunde Chemnitz
- Figure 2 (Otovicia hypnoides): By permission of Hans Steur (https://steurh.home.xs4all.nl/engplant/ewalchid.html)
- Figure 2 (Ernestiodendron flliciforme): Ghedoghedo, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
- Figure 2 (Ortiseia sp.): Museo delle Scienze (MUSE), Trento, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
- Figure 2 (Voltzia hexagona): Photo by Yvonne Arremo, by permission of Swedish Museum of Natural History
- Figure 2 (Pseudovoltzia liebeana): Photo Yvonne Arremo, by permission of Swedish Museum of Natural History
- Figure 2 (Cycadocarpidium erdmanni): ): Photo Yvonne Arremo, by permission of Swedish Museum of Natural History
- Figure 2 (Krassilovia mongolica & Podozamites harrisii, fossils): from Open Access article Herrera, F., Shi, G., Mays, C., Ichinnorov, N., Takahashi, M., Bevitt, J. J., ... & Crane, P. R. (2020). Reconstructing Krassilovia mongolica supports recognition of a new and unusual group of Mesozoic conifers. PLoS One, 15(1), e0226779.
- Figure 2 (Krassilovia mongolica & Podozamites harrisii, life restoration): from Open Access article Herrera, F., Shi, G., Mays, C., Ichinnorov, N., Takahashi, M., Bevitt, J. J., ... & Crane, P. R. (2020). Reconstructing Krassilovia mongolica supports recognition of a new and unusual group of Mesozoic conifers. PLoS One, 15(1), e0226779.