Dennstaedtia christophelii
- 演化之聲
- Mar 19
- 2 min read
Age
Paleogene（Ypresian）
50 Ma
Taxonomy
Kingdom: Plantae
Class: Polypodiopsida
Order: Polypodiales
Family: Dennstaedtiaceae
Genus: Dennstaedtia
Species: Dennstaedtia christophelii
Morphological description
Dennstaedtia christophelii is currently known only from fossilized fronds, and thus the morphology of its roots, stems, and reproductive structures beyond the preserved sori remains unknown. The fronds are pinnate, measuring approximately 4.5 to 6.8 cm in length. The pinnae show a gradual transition along the frond: at the base, the pinnae are fully separated, but they progressively converge toward the apex, where they become fused. Individual pinnae are about 5 to 9 mm long and 3 to 5 mm wide. Their arrangement shifts from opposite at the base of the frond to alternate toward the distal region.
Each pinna bears 3 to 10 pinnules, which are fused at the apex. The pinnules are generally elongated and oval in shape, with margins ranging from shallowly serrated to slightly lobed. Each pinnule contains a vascular strand; the primary vein enters the pinnule and branches once or twice, terminating either at the margin or within the sori when present. The sori are spherical, measuring approximately 0.5 to 1 mm in diameter, and are enclosed within cup-shaped indusia. These sori are arranged in clusters along the margins of the pinnules and extend slightly beyond the leaf edge.
Etymology
The genus name Dennstaedtia honors the German botanist August Wilhelm Dennstedt.
The species name christophelii commemorates David C. Christophel, mentor to researchers David Greenwood and James Basinger.
Biological description
Fossils of Dennstaedtia christophelii have been discovered in northeastern Washington State, USA, and in parts of British Columbia, Canada. Based on the morphology of its indusia, it has been assigned to the genus Dennstaedtia. As of 2022, this genus comprises 55 species. The closest morphological relatives of Dennstaedtia christophelii are two species found in tropical South America, differing primarily in the shape of their sori, which are sub-spherical rather than perfectly spherical.
This species inhabited a temperate, moderately humid highland lake environment. The climate was mild, with winter temperatures rarely dropping low enough for sustained snowfall. Paleoenvironmental reconstructions suggest an annual mean temperature ranging from approximately 8 to 14 °C. The surrounding ecosystem consisted of angiosperm-dominated forests, within which Dennstaedtia christophelii likely occupied the understory layer.
(Author: Bai Leng)
References
1. Pigg, K. B., DeVore, M. L., Greenwood, D. R., Sundue, M. A., Schwartsburd, P., Basinger, J. F. (2021). Fossil Dennstaedtiaceae and Hymenophyllaceae from the Early Eocene of the Pacific Northwest. International Journal of Plant Sciences.
2. Greenwood, D.R., Archibald, S.B., Mathewes, R.W, Moss, P.T. (2005). Fossil biotas from the Okanagan Highlands, southern British Columbia and northeastern Washington State: climates and ecosystems across an Eocene landscape. Canadian Journal of Earth Sciences.
+48.7, -118.7
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