Time: Early Cambrian (~525 million years ago)
Site: Chengjiang Maotianshan Shales, Quiongzhusi Section, Yu’anshan
Member, Heilinpu Formation, Maotianshan, Yuxi, Chengjiang County, Yunnan
This unusual arthropod is known as Alalcomenaeus. The taxon is known
from a number of examples, with this one from the most famous location
of all, Maotianshan (Mao Tian Hill), site of the discovery of the
Chengjiang Biota by Hou Xian-guang in 1984. 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.
specimen is a member of the “great appendage arthropods”
known as the opabinids after Opabinia from the Burgess Shale Fauna.
Other members from Chengjiang are Jianfengia and Leanchoilia (see
my other offerings for examples). The exceptional detail of the
appendages are readily apparent in this fine specimen. The taxon
is unknown outside the Chengjiang Biota. This is a truly exceptional
specimen, one that is sure to become a cornerstone of any collection
of material from the Cambrian Explosion.
Biota List Chengjiang