Messel pit

The Messel site.

The Messel pit fossil site is a disused quarry near the village of Messel,(Landkreis Darmstadt-Dieburg, Hesse ) about 35 km southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its plethora of fossils, it has significant geological and scientific importance. The Messel Pit was declared a UNESCO World Heritage site on December 9, 1995.

History of the Messel pit

The oil shale was actively mined from 1859. The pit first became known for its wealth of fossils around 1900, but serious scientific excavation only started around the 1970's, when falling oil prices made the quarry uneconomical. Commercial oil shale mining ceased in 1971. The land was slotted for use as a landfill, but the plans came to nought, and the [[Hessian stat bought the site in 1991 to secure scientific access. In the few years between the end of mining and 1974, when the state started preparing the site for garbage disposal, amateur collectors where allowed to collect fossils. The amateurs developed the "transfer technique" that enabled them to preserve the fine details of small fossils, the method still employed in preserving the fossils today.

Due to the extraordinary fossils, the pit was declared a UNSCO world heritage site in 1995.

Many of the known specimens from the site have come from amateur collectors, and in 1996, an amnesty on previously collected fossils was put in effect, in the hope of getting privately owned collections back into public ownership and available to science.

Depositional characteristics

Inset map shows the location of the town and fossil locality of Messel near Frankfurt in the centralwestern part of Germany. Larger map shows the locations of Messel primates 1–7 (Table 1) within the Messel oil shale excavation.

A fossil of the primitive mammal Kopidodon', showing outline of fur.

The current surface of the Messel pit is roughly 60 m below the local land and is about 0.7 km² in area. The oil-shale bed originally extended to a depth of 190 m. 47 million years ago in the Eocene when the Messel deposits formed, the area was 10° further south than it is now. The period was very close to the Paleocene–Eocene Thermal Maximum, and the climate and ecology of the site were very different. A large series of lakes, surrounded by lush sub-tropical forests supported an incredible diversity of life. The Messel lake bed was probably a center point for drainage from nearby rivers and creeks.

The pit deposits were formed during the Geiseltalian, about 47 million years ago, based on dating of basalt fragments underlying fossil-bearing strata. Oil shale, formed by the slow anoxic deposition of mud and dead vegetation on the lake bed, is the primary rock at the site. Its sediments extend 130 m downward and lie atop an older sandstone foundation. The fossils within the shale show a remarkable clarity and preservation due to the unique depositional characteristics of the lake. The upper stratifications of the lake most certainly supported a variety of organisms, but the bottom was subject to little disturbance by current, spawning a very anoxic environment. This prevented many epifaunal and infaunal species from inhabiting this niche, and thus bioturbation was kept at a minimum. Overturn of the lake layers (caused by seasonal variations) lowered oxygen content near the surface and led to a periodic "die-off" of aquatic species. Combined with a relatively low rate of deposition (0.1 mm/yr), this provided a prime environment for the preservation of fauna and flora.

Volcanic gas releases

The area around the Messel Pit is believed to have been geologically and tectonically active during the Eocene. Leading scientists hypothesize that events much like 1986 volcanic gas releases at Lake Nyos, Africa could account for the large deposition of non-aquatic species. Periodic subsurface shifts possibly released large concentrations of reactive gases (such as carbon dioxide and hydrogen sulfide) into the lake and adjoining ecosystems, killing susceptible organisms. During these releases, birds and bats might have fallen in if near the lake surface, and terrestrials could be overwhelmed when near the lake shore.

Fossils

Darwinius masillae, holotype, showing the remarkable preservation at Messel.

The Messel Pit provides the best preserved evidence of Geiseltalian flora and fauna so far discovered. Most other sites are lucky to contain partial skeletons, but Messel boasts extensive preservation of structural integrity, even going so far as to preserve the fur, feathers, and "skin shadows" of some species, and the diversity of species is no less astonishing (thanks in part, perhaps, to the hypothesized periodic gas releases). A brief summary of some of the fossils found at the site follows:

• Early primate fossil with anthropoid (i.e. non-lemuroid) characteristics (discovery made public May 2009), see Darwinius masillae
• Over 10,000 fossilized fish of numerous species.
• Thousands of aquatic and terrestrial insects, some with distinct coloration still preserved.
• A plethora of small mammals including pygmy horses, large mice, primates, ground dwellers (hedgehogs, marsupials, pangolins), aardvark relatives, and bats.
• Large numbers of birds, particularly predatory species.
• Crocodiles, frogs, turtles, salamanders, and other reptiles or amphibians.
• Remains of over 30 distinct plant species, including palm leaves, fruits, pollen, wood, walnuts, and grapevines.

Mammals

Masillamys at the Senckenberg collection.

• Darwinius masillae, identified in 2009 as a basal primate
• Kopidodon, an extinct arboreal mammal
• Leptictidium, an extinct omnivorous hopping mammal (of the leptictid family)
• Propalaeotherium, an early relative of horses
• Ailuravus, a rodent
• Peradectes, a marsupial
• Palaeochiropteryx, a bat
• Lesmesodon, a small Creodont
• Eomanis, an early pangolin
• Eurotamandua, a scaleless, anteater-like pangolin
• Europolemur, a primate
• Paroodectes, a primitive carnivorous mammal
• Pholidocercus, an early hedgehog
• Masillamys, an early rodent [[File:Masillamys Senckenberg 2007-01.JPG|thumb|right|240px|Masillamys at the
• Senckenberg collection
• Messelobunodon, an early artiodactyl
• Godinotia, a prehistoric lemur or lemur-like prosimian

Birds

• Palaeotis, a "proto-ostrich"
• Strigogyps sapea (formerly Aenigmavis)
• Messelornis, the Messel-bird; a relative of the sunbittern
• Masillastega, a freshwater booby
• The Messelasturidae, enigmatic carnivorous birds that looked like a mix between owls and hawks
• Palaeoglaux, a primitive owl with enigmatic breast feathers
• Palaeotis, a possible ostrich relative
• Paraprefica, an early potoo
• Masillaraptor, a primitive falcon
• Parargornis, related to the hummingbirds' ancestors
• Messelirrisor, tiny hoopoe-like birds
• Selmes (an anagram of "Messel"), a coliiform with stubby toes
• Gastornis (formerly Diatryma), a large, flightless predatory bird

Reptiles

• Asiatosuchus, a large crocodile
• Diplocynodon, an alligator
• Hassiacosuchus, a durophagous crocodile
• Palaeopython, a snake
• turtles

Fish

[[File:Paleoperca proxima.jpg|thumb|The primitive perch Paleoperca proxima.]]

• bowfin
• perch
• gar
• eel

Insects

Fossil jewel betle, stil showing colour of the exoskeleton.

• Messel giant ant, a giant species of ant
• jewel beetle
• stag beetle
• rove beetle

Access

Observation point

Exhibits from the pit may be seen in the Messel town museum, the Museum of Hessen in Darmstadt (5 km from Messel) and also the Senckenberg Museum in Frankfurt (some 30 km from Messel). Casual visitors can park close to the pit and walk around 300 m to a viewing platform overlooking the pit. Entrance to the pit is only possible as part of a specially organized tour.

See also

• List of fossil sites (with link directory)
• Lagerstätte

External links

• Messel Fossils
• Missing Link Found at Messel Pit?

Template:World Heritage Sites in Germany