''Chuandianella ovata'' is an extinct bivalved arthropod that lived during

Cambrian Stage 3 Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approxi ...

of the

Early Cambrian The Cambrian Period ( ; sometimes symbolized 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 years ago ...

(about 520 to 516

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

). It is the only

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

classified under the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

''Chuandianella''. Its fossils were recovered from the

Chengjiang Biota The Maotianshan Shales are a series of Early Cambrian deposits in the Chiungchussu Formation, famous for their '' Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized organisms or traces. The Maotianshan Shales ...

in Yunnan, China.

Taxonomy

It was originally described in 1975 under the "

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...

"-like genus '' Mononotella'', as ''Mononotella ovata''. In 1991, the paleontologists Xian-Guang Hou and Jan Bergström reclassified it under the new genus ''Chuandianella'' when additional discoveries of more complete specimens made its resemblance to '' Waptia fieldensis'' more apparent. In 2004, paleontologist Jun-Yuan Chen tentatively transferred it to the genus ''

Waptia ''Waptia fieldensis'' is an extinct species of arthropod from the Middle Cambrian Burgess Shale ''Lagerstätte'' of Canada. It grew to a length of , and had a large bivalved carapace and a segmented body terminating into a pair of tail flaps. It ...

''. However, ''C. ovata'' had eight abdominal somites in contrast to five in ''W. fieldensis''. Its limbs were biramous and were undifferentiated, unlike those of ''W. fieldensis''. Other authors deemed these differences to be enough to separate it from ''Waptia'' to its own genus. In 2022, a detailed restudy was published, which rejected ''Chuandianella'' from

Hymenocarina Hymenocarina is an order of extinct arthropods known from the Cambrian. They possess bivalved carapaces, typically with exposed posteriors. Members of the group are morphologically diverse and had a variety of ecologies, including as filter feed ...

, the group includes ''Waptia'', because of absence of

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bon ...

s and

maxillae The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The tw ...

, and was instead considered an "upper

stem-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

arthropod" as opposed to the more derived mandibulate hymenocarines.

Description

Chuandianella diagrammatic reconstruction

Specimens of ''Chuandianella'' reach a total body length of up to . ''Chuandianella ovata'' had a bivalved carapace up to long with a medial fold line. The carapace was composed of

calcium phosphate The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are wh ...

. The head had a pair of stalked eyes. The body has at least 18 segments. The first appendage pair is elongate and antenniform with 10

podomere The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plu ...

s with each podomere bearing inward-facing

seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. T ...

e, and the second appendage is uniramous and short and has 6 podomeres. These are followed by 10 biramous appendage pairs that are all similar to each other, which have endopods each with at least 27 podomeres, which have blade-like endites projecting perpendicularly from the limb axis, which have been described as "feather like". The exopods are short and paddle-shaped. The trunk terminates with a pair of elongate caudal flukes.

Ecology

It has been suggested that it was an active swimmer and a

filter feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

, using its feathery endopod endites to capture small food particles from the water column, with the short second appendage used to help process food. Specimens of ''Chuandianella'' have been found with up to 100 eggs, each across, adhered to the inside surface of the bivalved carapace, this is thought to have been a form of

brood care Brood may refer to: Nature * Brood, a collective term for offspring * Brooding, the incubation of bird eggs by their parents * Bee brood, the young of a beehive * Individual broods of North American Periodical Cicadas: ** Brood X, the largest br ...

to protect the eggs against predators.

References

{{Taxonbar, from=Q5115205 Prehistoric arthropod genera Maotianshan shales fossils

Taxonomy

Description

Ecology

See also

References