Rare Choiaella radiata Desmosponge from Chengjiang
"fossils of the Cambrian Explosion"

Name: Porifera; Desmospongia: Choiaella radiata (Chengjiang Biota)

Age: Early Cambrian (~525 million years ago)

Size (25.4mm=1 inch): 20 mm across on a 36 mm by 28 mm matrix

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

Choiaella radiataDescription: This is a rarely seen member of the Desmospongia, the most diverse of modern-day sponges. Greater than 90% of the extant 5,000 known species of sponges are desmosponges. Such a representation in the fossil record is not maintained where less than half the known genera are of this type, a consequence of the fact that the skeletons do not fossilize readily. Desmosponge skeletons are composed of spongin fibers and/or siliceous spicules. Sponges are known from the late Precambrian, with few localities contributing to the fossil record over time. The Chengjiang Biota is one such fossil lagerstatte. 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 just 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. Choiaella radiata, a rare sponge that is discoidal to shield-shaped, with the spicules arrayed radially as seen here, is envisioned as a tuft-like to brush-like sponge that emanates from a central point. Comparison with the Recent sponge Radiella suggests that both sponges shared a similar infaunal lifestyle.

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Choiaella radiata

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