is thought by some scientists to be one of the great appendage arthropods
known as the opabinids, named after Opabinia from the Burgess Shale Fauna.
Other opabinids from Chengjiang are Jianfengia and Leanchoilia.
long antenna and exceptional detail of the appendages are readily
apparent in this fine specimen. Outside
Chengjiang Biota, fossils from Utah have been ascribed to Alalcomenaeus. Alalcomenaeus had
three eyes, with two on stalks, biramous legs, 11 segments, exoskeleton,
and a telson like a paddle.
is placed in a group called the Great Appendage arthropods that are generally
not accepted to be monophyletic. What group
have in common is “great appendages” used in hunting and feeding.
Perhaps the most famous members are the anomalocaridids that
are renowned to have been trilobite predators, and sometimes called a “terror
of the Cambrian” that may have grown to some two meters in length,
making them the largest Cambrian animals known. Tanaka et al, (2013) did
a neuroanatomical study of Chengjiang Alalcomenaeus fossils supporting
placement of Great Appendage Arthropods in Subphylum
Arachnomorpha) and new Class Megacheira. If so, it is further confirmation
of the long held belief that as part of the great
Cambrian metazoan radiation, these Chelicerates
(i.e., spiders, scorpions, ticks, horseshoe crabs, eurypterids, etc.) branched
from other arthropod lineages (i.e., insects, crustaceans and many more).
Discovered in 1984, the Chengjiang
Biota now ranks as the most diverse
faunal fossil assemblage of all the Burgess Shale like deposits. It is
also some 10 million years older than the Burgess Shale. Like the Burgess
Shale, non-mineralized soft tissue parts are often extraordinarily well
preserved with high resolution as aluminosilicate films, sometimes with
oxidized iron content. Various taphonomic processes leading extensive preservation
of soft tissue have been proposed, including rapid death by asphyxia followed
by rapid burial in anoxic sediment undisturbed by turbidity. The Chengjiang
biota is dominated by phyla Arthropoda and Porifera. There are seven lobopodians,
more than any other Lagerstätte that some scientists elevate to phylum
rank, and seven members of the extinct phylum Vetulicolia. Members or potential
members of phyla Priapulida, Nematomorpha, Hyolitha, Hemichordata, Echinodermata,
Ctenophora, Chordata, Cnidaria, Chaetognatha, and Brachiopoda are found.
A large number of enigmatic animals of uncertain affinity are found as
well, some of which may represent failed evolutionary experiments, or even
new phyla that did not persist for long in the early Cambrian, or were
rapidly replaced by more derived forms. Among the diverse Maotianshan Shales
fauna, of utmost important are the putative early chordates, particularly
Haikouella, potentially an ancestor to or the earliest craniate chordate.
Myllokunmingia and Haikouichthys are interpreted as early Craniata, and
possibly very primitive agnathids, the progenitor of the fishes and all
see: Chengjiang Biota Chengjiang