Anomalocarid Grasping Appendage of Amplectobelua

A Terror Of The Cambrian Seas

Amplectobelua symbranchiata

Phylum Uncertain, Anomalocarididae

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

Size: 15 mm long

Fossil Site: Chengjiang Biota - Guanshan Fauna, Lower most part of Wulongqing Formation, Caijiachong Valley, Yieyatoung, Gangtoucun Village, Xiamacun Town, Kunming City, Yunnan Province, China

Amplectobelua symbranchiataDescription: This fossil comes from what has been termed the “Guanshan Fauna”, found in the Wulongqing Formation. The Guanshan Fauna shares many genera with the slightly older Chengjiang Biota, but differs at the species level. The discovery of the Chengjiang Biota by Hou Xian-guang in 1984 opened a window onto a remarkable array of lifeforms from what is termed 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. AnomalocarididaeNumerous problematic forms are known as well, some of which may have represented failed attempts at diversity that did not persist to the present day. This is the grasping arm of one of the of the “Terrors Of The Cambrian”, Amplectobelua symbranchaiata.

The members of this group of enigmatic creatures are known from Asia, Australia, Europe, and North America, and are thought by many to be closely allied with the Arthropoda, a position not held by all researchers. As of the publication of Hou’s book in 2004, some 30 examples were known, most being grasping arms like this one. The spiniferous grasping appendages are strongly suggestive of its carnivorous habits; some trilobites from Utah bear evidence of bite marks that have been attributed to its near relative Anomalocaris. The primary distinction between the 2 genera is that the spines of Anomalocaris are branched, while those on Amplectobelua are unbranched, as seen here.

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