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Fuxianhuiida is an extinct clade of
arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
s from the
Cambrian
The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...
of China. All currently known species are from
Cambrian Series 2
Cambrian Series 2 is the unnamed 2nd series of the Cambrian. It lies above the Terreneuvian series and below the Miaolingian. Series 2 has not been formally defined by the International Commission on Stratigraphy, lacking a precise lower boundary ...
aged deposits in Yunnan Province, including the
Chengjiang biota. They are generally considered to be close to the base of Euarthropoda,
but have also been considered to be early
mandibulates. Many specimens are known with exceptional soft tissue preservation, including preserved guts and neural tissue, which given their basal phylogenetic position makes them important in understanding the evolution of arthropoda as a whole. They reach a size of up to 15 cm, and are interpreted as benthic predators and scavengers.
The fuxianhuiid exoskeleton is unmineralised, and the number of
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 ...
ranges from 15 to over 40. The
cephalon is covered by a head shield and contains stalked eyes connected by the anterior sclerite,
antennae, a butterfly shaped
hyposome and a posterior facing mouth. Fuxianhuiids possess specialized post-antennal appendages with serrated edges used for food processing.
The presence of
gnathobases in members of Chengjiangocardidae suggests that they were capable of
durophagy
Durophagy is the eating behavior of animals that consume hard-shelled or exoskeleton bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including fossil tu ...
.
In most fuxianhuiids, the thorax tergites narrow posteriorly, terminating in either a swimming paddle or paired flukes with a tailspine. In members of Fuxianhuiidae the thorax is divided into two sections, the anterior wide opisthothorax and the posterior narrow limbless tail-like abdomen.
Taxonomy
Per
It has been suggested that ''Shankouia zhenghei'' is synonymous with ''Liangwangshania'' ''biloba'', with
sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
accounting for variation between specimens.
References
Arthropods
Prehistoric arthropod orders
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