Name: Princeton Chert
Location: British Columbia, North America
Age: Middle Eocene (49 mya)
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Fauna and Flora

The Princeton Chert contains an abundance of anatomically preserved fruits, seeds and vegetative structures - providing evidence of an extensive wetland biota. Although each layer does not preserve a unique flora, trends are evident throughout the outcrop. For example, taxa such as Metasequoia decline in the upper layers, whereas Pinus and monocotyledons (one embryo; narrow-leafed plants, e.g. cereals and grasses) increase in abundance through time (Stockey, 2001). Fern species also show a dramatic increase in these layers, which are also devoid of angiosperms (flowering plants; Stockey, 2001).

The Princeton Chert contains the oldest known pollen cones described for Pinus, and the only fossils of the genus for which pollen ultrastructure (developemental characters) has been described (Phipps et al., 1998). Other plants from this locality include:

Many of the plants indicate adaptations to an aquatic habitat. These include: aerenchymatous tissues (which provide aeration and buoyancy), reduced vascular and mechanical systems (due to support in water; common in aquatic plants), and protoxylem lacunae (air spaces-increase surface area; Cevallos-Ferris et al., 1991). In addition, many of the angiosperms have affinities to living aquatic flora: water lilies (Nymphaeaceae), loosestrife (Lythraceae), water plantains (Alismataceae), sedges and rushes (Cyperaceae/ Juncaceae), and aroids (Araceae) are common in the chert (Smith and Stockey, 2001). Terrestrial families like the grapes (Vitaceae) are uncommon in comparison, represented by a few seeds, which may have been transported by birds (Cevallos-Ferris et al., 1991).

Figure 5. Fossilised remains of the freshwater fish, Amyzon, in horizontal and vertical views (courtesy of M. Wilson)

Evidence for the lacustrine ecology of the Princeton Chert deposit also comes from faunal remains. A partially articulated skeleton and many separate bones of Amia, a freshwater fish, have been found over the plant beds (Wilson, 1982). Disarticulated remains of the fishes Amyzon (Figure 5), Libotonius and Eohiodon (Figure 6), and a soft-shelled turtle (found in the chert itself), add further weight to evidence of an aquatic environment (Li et al., 1997).

Figure 6. Fossilised remains of the freshwater fish, Eohiodon, in horizontal view (courtesy of M. Wilson)

Microscopic, pathogenic (disease-causing) fungi have also been found on the leaves and organs of the vascular plants in the Princeton Chert (Stockey, 2001). Uhlia palms have "tar spot" fungi present on their leaves, which are themselves being parasitised by another fungal parasite (Currah et al., 1998). This strange "parasite within a parasite" case has only ever been reported once previously in the fossil record. Mycorrhizal (symbiotic - "living together" - relationships between plant roots and fungi) associations have also been found (Currah et al., 1998). For example, roots of Pinus with external mycorrhizal associations are the first of their kind to be described in the fossil record (Phipps et al., 1998). Roots of fossilised Metasequoia have been compared to those of extant Metasequoia, suggesting that mycorrhizal associations which occurred 50 million years ago (mya) are similar to those that occur today (Stockey, 2001).

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