Aristolochia mortua
Green River Formation
Parachute Creek Member
Middle Eocene
Uintah County, Utah

This is a splendid specimen of the rare fossil leaf of Aristolochia. The leaf is 5 cm tall and displays remarkable venation. The slab also has a very good leaf of Oreopanax elongatum.

Aristolochia is a genus of evergreen and deciduous woody vines and herbaceous perennials. The smooth stem is erect or somewhat twining. The simple leaves are alternate and cordate, membranous, growing on leaf stalks. There are no stipules.
The flowers grow in the leaf axils. They are inflated and globose at the base, continuing as a long perianth tube, ending in a tongue-shaped, brightly colored lobe. There is no corolla. The calyx is one to three whorled, and three to six toothed. The sepals are united (gamosepalous). There are six to 40 stamens in one whorl. They are united with the style, forming a gynostemium. The ovary is inferior and is four to six locular.
These flowers have a specialized pollination mechanism. The plants are aromatic and their strong scent attracts insects. The inner part of the perianth tube is covered with hairs, acting as a fly-trap. These hairs then wither to release the fly, covered with pollen.
The fruit is dehiscent capsule with many endospermic seeds.