''Emeraldella'' is a genus of

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...

known from the

Middle Cambrian Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek ...

of North America. The type species ''E. brocki'' was described in 1912 from the

Burgess Shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest fo ...

. 21 specimens of ''Emeraldella'' are known from the Greater

Phyllopod bed The Phyllopod bed, designated by USNM locality number 35k, is the most famous fossil-bearing member of the Burgess Shale fossil ''Lagerstätte''. It was quarried by Charles Walcott from 1911–1917 (and later named Walcott Quarry), and was t ...

, where they comprise < 0.1% of the community. A re-study on the species was done in 2012. A second species ''E. brutoni'' is known from the

Wheeler Shale The Wheeler Shale (named by Charles Walcott) is a Cambrian ( 507 Ma) fossil locality world-famous for prolific agnostid and '' Elrathia kingii'' trilobite remains (even though many areas are barren of fossils) and represents a Konzen ...

, which was described in 2011. An additional specimen of ''E. brutoni'' was described in 2019, which revealed more of the anatomy. It has been placed as part of the

Artiopoda The Artiopoda is a grouping of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilo ...

, a group of arthropods containing

trilobites Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

and their relatives.

Description

Caudal flaps are present on the terminal tergite, alongside an elongated spine.

''Emeraldella'' ''brocki''

''E. brocki'' is at least 60 mm in length, it possesses 12

tergites A ''tergum'' (Latin for "the back"; plural ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'mar ...

in the trunk section, with an extended telson. The attenula are long and can reach the length of the body, and are composed of more than 80 segments.

Ocular structure This glossary of entomology describes terms used in the formal study of insect species by entomologists. A–C A synthetic chlorinated hydrocarbon insecticide, toxic to vertebrates. Though i ...

s appear to be absent in this species.

''Emeraldella'' ''brutoni''

''E. brutoni'' is up to 50 mm in length, it possesses 10 trunk tergites, and possesses clear ocellii, unlike ''E. brocki'', the antennae are not preserved well enough to tell true length.

References

External links

* * http://www.fossilmuseum.net/Cambrian-Explosion/Emeraldella/Emeraldella.htm {{Taxonbar, from=Q3052157 Burgess Shale fossils Artiopoda Prehistoric arthropod genera Cambrian genus extinctions Wheeler Shale