''Kangacaris'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of soft-shelled

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 ...

-like

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

of the nektaspid order from the Lower Cambrian (Botomian). ''K. zhangi'' is known from

South Australia South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...

, and ''K. shui'' from South-West China.

Etymology

The generic name is derived from "Kanga", a contraction of Kangaroo Island, and

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

' ("shrimp"). The specific name of the type species honors the Chinese

palaeontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...

Xingliang Zhang.

Description

The

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

exoskeleton An exoskeleton () . is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs, in contrast to an internal endoskeleton (e.g. human skeleton, that ...

of ''Kangacaris'' is inverted egg-shaped, about long and wide. The axis is × as wide as the body and only slightly raised. The semi-circular headshield (or

cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino Jr., Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont ...

) is about × as long as the tailshield ( pygidium), and in between them three short

thoracic The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main ...

body segments (

somite The somites (outdated term: primitive segments) are a set of bilaterally paired blocks of paraxial mesoderm that form in the embryogenesis, embryonic stage of somitogenesis, along the head-to-tail axis in segmentation (biology), segmented animals. ...

s). The lateral margin of the pygidium is progressively angling towards the axis, ending in the slightest hint of a point. Twelve to thirteen furrows are most distinct on the axis, and becoming indiscernible near the border. The border of the cephalon is about × as long (axially) as the thoracal somites, and the border of the pygidium is about × as long as the somites. This border has about 17 regularly spaced ridges perpendicular to the rim. ''K. shui'' has a better defined and narrower axis, more arched posterior margin of the cephalic shield, more posterolaterally deflected pleural areas of the thoracic segments, and smaller pygidium than ''K. zhangi''.

Differences from ''Emucaris fava''

''Kangacaris'' differs from '' Emucaris fava'' in having three thorax segments, while ''Emucaris'' has four. When disregarding the border, ''Kangacaris'' has an inverted egg-shape, while the pygidium of ''Emucaris'' is a triangle with a rounded termination. The axis of the pygidium of ''Kangacaris'' is of the width of the body and clearly segmented, while in ''Emucaris'' it is one fifth and has a pattern of polygons of approximately equal area. The axis of the pygidium of ''Emucaris'' terminates in a spine that ends at the outer rim of the border, while ''Kangacaris'' lacks a terminal spine.

Distribution

Fossils of ''K. zhangi'' were collected from the

Emu Bay Shale The Emu Bay Shale is a Formation (stratigraphy), geological formation in Emu Bay, South Australia, containing a major Konservat-Lagerstätte (fossil beds with soft tissue preservation). It is one of two in the world containing Redlichiidan trilob ...

Kangaroo Island Kangaroo Island (, ) is Australia's third-largest island, after Tasmania and Melville Island, Northern Territory, Melville Island. It lies in the state of South Australia, southwest of Adelaide. Its closest point to the mainland is Snapper Poi ...

, South Australia. Remains of ''K. shui'' have been found at the

Maotianshan Shales The Maotianshan Shales () are a series of Early Cambrian sedimentary deposits in the Chiungchussu Formation or Heilinpu Formation, famous for their '' Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized orga ...

Yunnan Yunnan; is an inland Provinces of China, province in Southwestern China. The province spans approximately and has a population of 47.2 million (as of 2020). The capital of the province is Kunming. The province borders the Chinese provinces ...

, South-West China.

References

{{Taxonbar, from=Q16983865 Nektaspida Prehistoric arthropod genera Prehistoric arthropods of Australia Emu Bay Shale