Sagenopteris
| Sagenopteris Temporal range: Middle Triassic-Late Cretaceous
| |
|---|---|
| |
| Illustration showing change in leaf shape of Sagenopteris acuminata during growth, and mature leaves attached to woody stem | |
Scientific classification 
| |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Division: | †Pteridospermatophyta |
| Order: | †Caytoniales |
| Family: | †Caytoniaceae |
| Genus: | † Presl 1838 |
| Species | |
|
See text | |
Sagenopteris is a form genus of leaves belonging to the extinct seed plant order Caytoniales, spanning from the Middle Triassic to Late Cretaceous.[1][2][3]
Description
Sagenopteris has two pairs (making four in total) of palmately arranged leaflets with anastomosing venation and a prominent midrib, which are all attached to the apex of a petiole. Mature leaves are generally lanceolate to oblanceolate, the edges are generally entire (smooth), slightly undulating, and occasionally lobed or dentate (toothed), the cuticle is somewhat thick, and the stomata are only present on the underside (abaxial surface) of the leaflets. According to Xu et al. 2024, the stomata are characterised by "guard cells with a flat surface and a sunken region around the aperture; guard cells typically surrounded by a single ring of weakly modified neighbouring cells in an anomocytic arrangement".[1]
Different organs attributed to the same original plant can be reconstructed from co-occurrence at the same locality and from similarities in the stomatal apparatus and other anatomical peculiarities of fossilized cuticles.
- Sagenopteris phillipsii may have been produced by the same plant as Caytonia nathorstii (ovulate organs) and Caytonanthus arberi (pollen organs).[4]
Species
The following species have been described:[2]
- Sagenopteris colpodes
- Sagenopteris elliptica
- Sagenopteris mclearni
- Sagenopteris nilssoniana
- Sagenopteris oregonensis
- Sagenopteris phillipsii
- Sagenopteris trapialensis[3]
- Sagenopteris variabilis
- Sagenopteris williamsii[5]
In a 2024 review, only 5 species, Sagenopteris acuminata (which was designated the lectotype species), S. colpodes, S. hallei, S. phillipsii and S. pualensis were considered valid.[1]
Distribution
Fossils of Sagenopteris have been registered in:[2]
- Triassic
Argentina, China, Germany, Greenland, Italy, Japan, Kyrgyzstan, the Russian Federation, Sweden, Tajikistan, Ukraine, United States (Virginia, Virginia/North Carolina).
- Jurassic (to Cretaceous)
Afghanistan, Antarctica, Argentina, Azerbaijan, Belarus, Canada (British Columbia, Yukon), China, Colombia (Valle Alto Formation, Caldas), Georgia, Germany, Greenland, India, Iran, Italy, Japan, Kazakhstan, Kyrgyzstan, Mexico, Peru, Poland, Romania, the Russian Federation, Tajikistan, Turkmenistan, Ukraine, the United Kingdom, United States (Alaska, Montana, Oregon/Idaho), and Uzbekistan.
- Cretaceous
Spain, Belgium, Canada (British Columbia and Alberta),[5] Greenland, the Russian Federation, and the United States (Montana).
References
- ^ a b c Xu, Yuanyuan; Barbacka, Maria; Kapusta, Paweł; Jarzynka, Agata; Wang, Yongdong; McLoughlin, Stephen (November 2024). "Revision of Sagenopteris (Caytoniales): a major lineage of the Mesozoic seed plants". Papers in Palaeontology. 10 (6). doi:10.1002/spp2.1607. ISSN 2056-2799.
- ^ a b c Sagenopteris at Fossilworks.org
- ^ a b Elgorriaga, A.; Escapa, I. H.; Cúneo, R. (2019). "Southern Hemisphere Caytoniales: vegetative and reproductive remains from the Lonco Trapial Formation (Lower Jurassic), Patagonia". Journal of Systematic Palaeontology. 17 (17): 1477–1495. Bibcode:2019JSPal..17.1477E. doi:10.1080/14772019.2018.1535456. S2CID 92287804.
- ^ Retallack, G.J. & Dilcher, D.L. (1988). "Reconstructions of selected seed ferns". Missouri Botanical Garden Annals. 75 (3): 1010–1057. doi:10.2307/2399379. JSTOR 2399379.
- ^ a b Bell, W.A. 1956. Lower Cretaceous floras of western Canada; Geological Survey of Canada, Memoir 285, p. 80-81 and plates 31, 33, 34, and 36.