Macginitiea gracilis

Overview

This ancient plant had leaves spreading into five lobes like a hand. Macginitiea gracilis is a relative in the plane-tree family, which includes living plane trees. Even one leaf evokes the appearance of an ancient forest.^[1][5]

Key facts

The number of leaf lobes helps distinguish names. This species generally has five clear lobes, whereas the related Macginitiea nobilis is predominantly three-lobed. Close examination of similar-looking leaves reveals different histories.^[3]

Time and place

It is known from several Paleocene and Eocene plant assemblages in North America. Republic in present-day Washington State, United States, and Horsefly in British Columbia, Canada, are localities with Eocene leaves. They guide exploration of forests around 60–50 million years ago.^[1][3][4]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

Major veins spread like fingers from the petiole toward each lobe. The outer major veins may branch above the leaf base. Examining this outline and venation before considering the tree’s overall height is more useful for reading species features.^[5][3]

Habitat and reproduction

The Horsefly plant assemblage also yielded Macginicarpa fossils with rounded fruiting heads arranged in rows alongside the leaves. Because both organs occur together at several localities, researchers investigate whether they belonged to the same plant. Connecting detached leaves and fruits helps reveal ancient forest plants.^[4]

Fossil discovery

In 1987, Wolfe and Wehr organized leaves from Republic under this name. Later research reexamined Paleocene leaves previously assigned other names. Tracing the names of old specimens connects with reading the history of plant distribution.^[1][3]

References

1. Wolfe & Wehr (1987) — USGS Bulletin 1597 · Species description of Macginitiea gracilis
2. Huegele & Correa Narvaez (2024) · Revisiting the Iconic Macginitiea Plant and Its Implications for Biogeography, Basilaminar Lobe Development, and Evolution in Platanaceae
3. Manchester 2014 — Revisions to Roland Brown’s North American Paleocene flora
4. Pigg et al. 2023 — The early Eocene flora of Horsefly, British Columbia
5. Burke Museum — Republic Macginitiea gracilis leaf
6. Wolfe & Wehr (1987) — USGS Bulletin 1597 · Species description of Macginitiea gracilis
7. Manchester 2014 — Revisions to Roland Brown’s North American Paleocene flora
8. Pigg et al. 2023 — The early Eocene flora of Horsefly, British Columbia
9. Burke Museum — Republic Macginitiea gracilis leaf
10. Wing & Hickey1984 — The Platycarya Perplex and the Evolution of the Juglandaceae
11. Wilson1977 — Eocene freshwater fishes from British Columbia
12. Wilson — Survey of the Horsefly fossil site
13. Wolfe & Wehr (1987) — USGS Bulletin 1597 · Species description of Macginitiea gracilis
14. Burke Museum — Republic Macginitiea gracilis leaf
15. Manchester 2014 — Revisions to Roland Brown’s North American Paleocene flora
16. Pigg et al. 2023 — The early Eocene flora of Horsefly, British Columbia
17. Pigg, Manchester & DeVore (2023), The early Eocene flora of Horsefly, British Columbia, Canada and its phytogeographic significance
18. Study of compound-leaved Platanaceae from North America
19. Wolfe & Wehr (1987) — USGS Bulletin 1597 · Species description of Macginitiea gracilis
20. Burke Museum — Republic Macginitiea gracilis leaf
21. Manchester 2014 — Revisions to Roland Brown’s North American Paleocene flora
22. Pigg et al. 2023 — The early Eocene flora of Horsefly, British Columbia

Research questions

Are similar leaves variations within one species or evidence of different trees? Comparing lobe number, margins, and venation alongside fruit and flower evidence makes the questions more specific. Research beginning with one leaf expands to the evolution of the whole plant.^[2][3][4]

Observation

After examining the five-lobed outline, follow the veins extending toward each tip.^[5]