Ancient Brachipod with Hyolithid from Chengjiang
"fossils of the Cambrian Explosion"

Diandongia pista - Phylum Brachiopoda

Ambrolievitus (Chengjiang) - Phylum Hyolitha

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

Size: Diandongia: 9 mm by 7 mm Hyolithid: 12 mm long on a 25 mm by 23 mm and an 18 mm by 23 mm matrix

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

Diandongia pistaDescription: This small brachiopod is known as Diandongia pista. The species is a relatively common member of the biota, with most preserved with some 3-dimensional detail. The discovery of the Chengjiang Biota by Hou Xian-guang in 1984 brought to light an exceptional largerstatte of the time known as the Cambrian Explosion. 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.

It is thought that this species lived epifaunally, attached by a short pedicle. The elongated structure seen on the positive example is a member of the Hyolitha, a phylum with problematic affinities, thought to be related to the mollusks. They are thought to have lived on the substrate, resting on the flatter side of the shell for stability. The two stabilizing structures are termed the Helens. While Hyolthiods are a common fossil of the Chengjiang Biota, many have not been described. This one most looks like a member of the genus Ambrolinevitus. The linear structure is thought to be the result of collapse of the shell postmortem. Obviously, the brachiopod had greater structural integrity, leaving you the fine specimen seen here.

Also see: Chengjiang Biota List Chengjiang Fossils

click to enlarge


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