Eocene Introduction

The Eocene epoch extends from 55.8 to 33.9 million years ago. Eocene is derived from Greek and means "dawn of the modern". This name is well chosen as representatives of most modern orders of birds and mammals appear during this epoch.

Primary Producers & Reefs

Coccolithophorids experienced a mass extinction at the K/T boundary. Diatoms and dinoflagellates were less affected. By the Eocene all three groups had recovered; however, from then on dinoflagellate and coccolithophore diversity declined. Diatoms, on the other hand, have increased in diversity. Today, diatoms are the most diverse group in the plankton.

Interestingly, the success of diatoms may be tied to the evolution of grasses. Grasses sequester silica into their tissues in the form of phytoliths. Phytoliths add structural support to the plant. Phytoliths may also produce a gritty texture making the plant distateful to herbivores. The Silica released from phytoliths during plant decay is easily dissolved in water and washed in rivers and seas. The influx of phytolith silica into the oceans would benefit diatoms as they construct their frustules from silica. Increase in diatom diversity and abundance is correlated with the appearance of phytoliths during the Late Cretaceous and with the expansion of grasses in the Eocene, Oligocene and Middle Miocene (Kooistra, Gersonde, Medlin & Mann, 2007, pp. 228 & 229). Diatoms, dinoflagellates, and coccolithophores make up the dominant primary producers in todays oceans.

Marine Invertebrates

Fish

Amphibians

Reptiles

Mammals

Birds

Insects

Plants

Grube Messel

Grube Messel or the Messel Pit is a Fossil Laggerstaten near the town of Messel, Germany that was declared a UNESCO World Heritage Site in 1995. From 1875 to the 1960's the site was developed as an open pit oil shale mine. Over the years many fossils were found during the mining operations. The sediments that formed Grube Messel were layed down in a restricted lake basin within the Rhine Rift Valley during the Early Eocene 49 million years ago. Faulting and volcanic activiey were common within this rift valley. The Grube Messel stratigraphy and biota suggest the basin was part of a lush subtropical environment with extensive rivers and lakes. Some interpret the deposit as representing a crater lake. The flora and fauna preserved in the Messel shale represent a number of environments that surrounded the lake including: open water, swamp, bank-side, damp forest and drier elevated regions.

Among plants angiosperms or the flowering plants are the most common at Messel; although, gymnosperms and ferns are also present. Ferns, swamp cypresses, grasses (such as rushes and sedges), lilies, palms, laurels, tea, grapevines, citrus, and walnut represent environments that were inundated with water or moist. Pines, beeches, chestnuts, and oak grew in drier conditions farther from the lake.

Among arthropods beetles are the most common and beautiful in the Messel shale. Click beetles, weevils, jewel, dung, stag, water, longhorn, rove and leaf beetles are represented. The larvae of a particular genus of water beetle Eubrianax are interesting because extant forms live in waterfalls were oxygen levels are high. The elytra or wing cases of some beetle specimens exhibit a colorful iridescence.

Baltic Amber

Green River Formation

Florissant

Bibliography

Kooistra, W.H.C.F., Gersonde, R., Medlin, L. K. & Mann, D.G. (2007). The Origin and Evolution of the Diatoms: Their Adaptation to a Planktonic Existence. In Falkowski, P.G. Knoll, A.H. [Eds] Evolution of Primary Producers in the Sea. (pp. 133-163). China: Elsevier Academic Press.