IMMENSE Kuamaia Chengjiang Biota Arthropod

Kuamaia lata

Phylum Arthropoda

Geological Time: Early Cambrian (~525 million years ago)

Size: 150 mm long and 110 mm across

Fossil Site: Chengjiang Maotianshan Shales - Quiongzhusi Section, Yu’anshan Member, Heilinpu Formation, Mafang Village, Anning, Kunming, Yunnan Province, China

Kuamaia lataDescription: This unusual arthropod is known as Kuamaia lata, and at 150 by 100 mm, represents a huge specimen compared to others that have been found. The species is known from some 100 examples as of Kuamaia2004, some of which show many exquisite details.

With the discovery of the Chengjiang Biota in 1984 a window on the Cambrain Explosion in China was opened. The diversity of soft-tissue fossils is astonishing: algae, medusiforms, sponges, priapulids, annelid like worms, echinoderms, arthropods (including trilobites), hemichordates, chordates, and the first agnathan fish make up Kuamaia picturejust a small fraction of the total. Numerous problematic forms are known as well, some of which may have represented failed attempts at diversity that did not persist to the present day.

The taxon has a relatively wide and flat dorsal exoskeleton (hence the generic name) which is differentiated into a cephalic shield (CS), a thorax (T1-T8), and a pygidium (Py). Note also the eyes, hypostome (H), and central gut as highlighted in the interpretive drawing. It bears some resemblance to the younger Burgess Shale genus Hemetia, which has led some to place them in the Helmetidae along with several other similar arthropods. The body shape suggests that Kuamaia was a benthic animal which was possibly carnivorous. The species is only known from the Chengjiang Biota.

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