The Sella Formation is a

Dapingian The Dapingian is the third stage of the Ordovician system and the first stage of the Middle Ordovician series. It is preceded by the Floian and succeeded by the Darriwilian. The base of the Dapingian (and the top of the Floian) is defined as t ...

Darriwilian The Darriwilian is the upper stage of the Middle Ordovician. It is preceded by the Dapingian and succeeded by the Upper Ordovician Sandbian Stage. The lower boundary of the Darriwilian is defined as the first appearance of the graptolite species ' ...

geologic formation of southern Bolivia. The grey to green bioturbated

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

s interbedded with thin

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

layers bear lenticular shell beds. Other parts of the formation contain yellow-green limy

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

s and grey sandy

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

Coquina Coquina () is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of mollusks, trilobites, brachiopods, or other invertebrates. The term ''coquina'' comes from the S ...

s often fill gutter casts and included

brachiopod Brachiopods (), phylum (biology), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear e ...

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

s and

nautiloid Nautiloids are a group of cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and species rich, with over 2,500 recorded species. Th ...

s. The sediments were deposited in an open marine environment.Sella Bed 4
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org The species '' Coxiconchia sellaensis'' was named after the formation.

Fossil content

The formation has provided the following fossils: * '' Baltograptus minutus''Suárez Riglos et al., 2018, p.64 * '' Coxiconchia sellaensis'' * '' Desmorthis segnis'' * '' Glyptorthis imbrex'' * '' Hemiprionodonta lusitanica'' * '' Lingulocystis boliviensis'' * '' Natasia boliviensis'' * '' Pliomeridius sulcatus'' * '' Redonia riojana'' * '' Ribeiria spinosa'' * '' Peelerophon cf. oehlerti'' * '' Ampyx sp.'' * '' Boeckaspis sp.'' * '' Branisaspis sp.'' * '' Bucania sp.'' * '' Colpocoryphe sp.'' * '' Cosmogoniophorina sp.'' * '' Ctenodonta sp.'' * '' Cyptendoceras sp.'' * '' Didymograptus sp.'' * '' Endoceras sp.'' * '' Eothinoceras sp.'' * '' Famatinolithus sp.'' * '' Haploprimitia sp.'' * '' Hoekaspis sp.'' * '' Lecanospira sp.'' * '' Lonchodomas sp.'' * '' Maclurites sp.'' * '' Quadrilobella sp.'' * '' Parapyxion sp.'' * '' Protocycloceras sp.'' * '' Sibiritella sp.'' * '' Suriaspis sp.'' * '' Synhomalonotus sp.'' * '' Technophorus sp.'' * '' Trinucleus sp.''

References

Bibliography

* {{citation , last=Suárez Riglos , first=Mario , last2=Dalenz Farjat , first2=Alejandra , last3=Pérez Leyton , first3=Miguel Ángel , year=2018 , title=Fósiles y Facies de Bolivia , url=https://www.igeo.ufrj.br/ismar/1/1_64.pdf , publisher=Sincronía Diseño & Publicidad, Santa Cruz de la Sierra , pages=1–146 , accessdate=2019-03-03 , isbn=978-99974-79-68-6

Fossil content

See also

References

Bibliography

Further reading