Sagenopteris

Sagenopteris; Temporal range: Middle Triassic-Late Cretaceous Anisian–Campanian PreꞒ Ꞓ O S D C P T J K Pg N
	Illustration showing change in leaf shape of Sagenopteris acuminata during growth, and mature leaves attached to woody stem
Scientific classification
Kingdom:	Plantae
Clade:	Embryophytes
Clade:	Tracheophytes
Clade:	Spermatophytes
Division:	†Pteridospermatophyta
Order:	†Caytoniales
Family:	†Caytoniaceae
Genus:	†Sagenopteris; 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

Immature leaf of *Sagenopteris trapialensis*

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

1 2 3 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.
1 2 3 Sagenopteris at Fossilworks.org
1 2 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. hdl:11336/117441. 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.
1 2 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.

[:0-1] 1 2 3 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.

[FWSagenopteris-2] 1 2 3 Sagenopteris at Fossilworks.org

[Elgorriaga2019-3] 1 2 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. hdl:11336/117441. S2CID 92287804.

[4] 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.

[Bell-5] 1 2 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.

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