[1][2] The genus is strictly used to describe leaves, but has been found in close association with other fossil platanoid organs, which collectively have been used for whole plant reconstructions.

[2][3] Macginitiea and its associated organs are important as together they comprise one of the most well-documented and ubiquitous fossil plants, particularly in the Paleogene of North America.

Macginitiea also has an inflated petiole base,[2] which in modern counterparts encloses the underlying axillary buds for the next year, indicating their deciduous nature.

[3] Macginitiea differs from modern Platanus with its often greater number of lobes and narrower angle between adjacent primary veins.

rare Frequent M. whitneyi Chalk Bluffs, California Ypresian 5-7 (7-9) very shallow, 25-35% Palinactinodromous, 15-30° Entire leaf Absent occasional M. wyomingensis Green River Formation, Western U.S. Ypresian 5 ~36% 15-30° Entire yes compound Absent Table adapted from Pigg and Stockey (1991) with updates from Huegle and Correa Narvaez (2023)[3][9] The "Clarno Plane" was established as an informal name to refer to the whole plant recognized from five fossil species: Macginitiea angustiloba (leaves), Plataninium haydenii (wood), Macginicarpa glabra (infructescences), Platananthus synandrus (staminate inflorescences), and Macginistemon mikanoides (isolated stamen clusters).

[2] The Clarno Plane is known from the west coast of North America across several states, including central California, Oregon, and northern Washington.

Platananthus synandrus is also distinctive from extant Platanus for the elongation of its connectives, extensions of filament tissue that cover or divide an anther.

[2] As of 1986, Dr. Steven Manchester said that "The Clarno Plane is currently the most completely documented fossil angiosperm species, known morphologically and anatomically from wood, leaves, pistillate and staminate inflorescences, fruits, and pollen.

"[2] Associations of multiple organs of the Clarno Plane in various combinations have been found in "more than ten localities" throughout western North America, as of 2008.

The association with Cercidiphyllum suggests that the Clarno Plane was tolerant of full sunlight and poorly developed soils.