The Upper and Lower Fezouata formations of Morocco

Morocco

Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...

 are Burgess shale-type deposits

Burgess shale type preservation

The Burgess Shale of British Columbia is famous for its exceptional preservation of mid-Cambrian organisms. Around 40 other sites have been discovered of a similar age, with soft tissues preserved in a similar, though not identical, fashion...

 dating to the Lower Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

, filling an important preservational window between the common Cambrian lagerstätten and the Late Ordovician Soom shale

Soom Shale

The Soom Shale is a member of the Late Ordovician Cedarberg Formation in South Africa, renowned for its remarkable preservation of soft-tissue in fossil material....

. In the fossilized fauna

Fauna

Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...

 were numerous organisms previously thought to have died out after the mid-Cambrian.

Biota

Over 1500 non-mineralized specimens, representing 50 distinct taxa that have a composition similar to earlier Burgess Shale type biota

Burgess Shale

The Burgess Shale Formation, located in the Canadian Rockies of British Columbia, is one of the world's most celebrated fossil fields, and the best of its kind. It is famous for the exceptional preservation of the soft parts of its fossils...

s, have been recovered from the formations in addition to a less abundant shelly fauna. The make-up of the community varies significantly through the stratigraphic sequence, with both abundances and faunal composition changing as time progresses. Small (1–3 mm wide) burrows are present in the sediment, but major burrowing is absent; this may suggest a paucity of oxygen in the water or sediment. Particularly notable is the presence of bryozoa

Bryozoa

The Bryozoa, also known as Ectoprocta or commonly as moss animals, are a phylum of aquatic invertebrate animals. Typically about long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia...

 and graptolite

Graptolite

Graptolithina is a class in the animal phylum Hemichordata, the members of which are known as Graptolites. Graptolites are fossil colonial animals known chiefly from the Upper Cambrian through the Lower Carboniferous...

s, forms that are absent in the Cambrian period. Diverse echinoderm

Echinoderm

Echinoderms are a phylum of marine animals. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone....

s indicate a normal range of salinity, and the overall shelly assemblage is not significantly different from the normal shelly fauna expected in open Ordovician waters. The non-mineralized cohort contains a range of forms familiar from the Burgess Shale: Desmosponges, lobopods, barnacle

Barnacle

A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...

s, annelid

Annelid

The annelids , formally called Annelida , are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches...

s, possible halkieriids, marrellomorph

Marrellomorph

The Marrellomorphs are a clade of stem-group arthropods known from the Cambrian to the early Devonian. They lacked mineralised hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution....

s, paleoscolecid worms, naraoiid

Naraoia

Naraoia is a genus of trilobites found in Cambrian strata of the Burgess Shale and the Maotianshan shales Lagerstätte. They were flattened, oval-shaped animals, with an uncalcified shield that was divided into two regions, a smaller region covering the head, and a larger section covering the...

s, skaniid

Skania

Skania is a Cambrian fossil arthropod that may be related to the Ediacaran organism Parvancorina, and bears a strong, albeit superficial resemblance to the Vendiamorphans Vendia, Praecambridium and Onega...

s as well as the expected problematica. Other Ordovician oddballs are also present, including mitrate

Mitrate

Mitrates are a group of stem group Echinoderms, which may be closely related to the hemichordates.-Morphology:The organisms were a few millimetres long. Like the echinoderms, they are covered in armour plates, each of which comprises a single crystal of calcite...

s, machaeridia, cheloniellids and horseshoe crabs in abundance.

Depositional setting

The fossiliferous strata were deposited in quiet, deep waters, below the influence of wave action in all but the fiercest of storms. Such storms, or similar high-energy events, would have mobilized sediment that could be quickly deposited, trapping animals and leading to their preservation. Consequently, the assemblage is dominated by benthic organisms.

Preservation

Fossils of the Fezouata formation, which are usually squashed flat (although some do retain some degree of their original three-dimensionality) are often coated with a dusting of pyrite

Pyrite

The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...

, and tin??; this aspect of the fossil preservation is very similar to that at Chengjiang. Non-mineralized appendages are often preserved.

Location

The fossils occur within an area of 500 km², in southeast Morocco's Draa Valley, north of Zagora

Zagora

Zagora may refer to:*Zagora, Morocco*Zagora Province, Morocco*Zagora, Greece* The region Zagore in north-eastern Bulgaria*The city of Stara Zagora*The city of Nova Zagora*Zagora , a region in inland Dalmatia...

. Stratigraphically productive layers are found through a 1.1 km-thick column of rock that spans the Tremadocian and Floian epochs.

History

The lagerstätten were first identified in the late 1990s when a local fossil collector, Ben Moula, showed some of the finds to a PhD student who was then working in the area.

External links

• Images of fossils from the Fezouata. Note: This link does not provide...