''Kangacaris'' is an
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
genus of soft-shelled
trilobite-like
arthropod of the
nektaspid
Nektaspida (also called Naraoiida, Nektaspia and Nectaspida) is an extinct order (biology), order of non-Mineralized tissues, mineralised artiopodan arthropods. They are known from the mid-Cambrian to the upper Silurian. Originally classified as t ...
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
from the
Lower Cambrian (Botomian). ''K. zhangi'' is known from
South Australia,
and ''K. shui'' from South-West China.
Etymology
The generic name is derived from "Kanga", a contraction of Kangaroo Island, and
Latin ' ("shrimp"). The specific name of the type species honors the Chinese
palaeontologist Xingliang Zhang.
Description
The
dorsal exoskeleton of ''Kangacaris'' is inverted egg-shaped, about long and wide. The axis is ⅓× 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., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont Company. Baldino s ...
) is about ⅔× as long as the tailshield (
pygidium), and in between them three short
thoracic body segments (
somites). 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 ¼× as long (axially) as the thoracal somites, and the border of the pygidium is about ½× 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
''Emucaris fava'' is an extinct species of soft-shelled trilobite-like arthropod of the nektaspid order from the Lower Cambrian (Cambrian Stage 4) of South Australia. It is the only species classified under the genus ''Emucaris''.
Etymology
...
'' 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 ⅓ 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 of
Kangaroo Island, South Australia.
Remains of ''K. shui'' have been found at the
Maotianshan Shales,
Yunnan, South-West China.
References
{{Taxonbar, from=Q16983865
Nektaspida
Prehistoric arthropod genera
Prehistoric arthropods of Australia
Emu Bay Shale