Spectacular Cambrian chordate fossils from China
British Columbia's Burgess Shale contains extraordinary late Cambrian-aged (505 m.y.) fossils with remarkable preservation of soft parts, and it represents a resource of information which has changed our understanding of both the structure of the evolutionary tree, and the very process of evolution. It now looks as if the equally spectacular fossils of China's Maotianshan Shale - of early Cambrian age (530 m.y.) - could have a similar impact.
For the past decade, the site near to Kunming in Yunnan province has yielded many new treasures, and the discovery reported by a Chinese team in a recent issue of Nature is no exception. The latest find is of a little fish-like creature which may push the date of the earliest chordate organisms back by around 10 million years. The new animal, called Haikouella lanceolata, is a small (2 to 3 cm) member of the group known as Cephalochordata, animals which share many similarities with vertebrates including a dorsal nerve chord supported by a muscularized rod call a notochord. Cephalochordates do not have bones. They live today within the sand of shallow tropical marine environments(1), ingest water through a mouth and trap food particles. They have a digestive system and a circulatory system, and the sexes are separate.
There is some controversy about whether the recent discoveries in China are true chordates, but there is no question about their quality, and the remarkable preservation of soft tissues.
Some examples - taken from the Nature article - are shown below.
The various features pointed out are: G: gonad, It: intestine, Nt: notochord, Mg: midgut, M2 - M20: myosepta, Va: ventral aorta
Reference:
Jun-Yuan Chen, Di-Ying Huang and Cia-Wei Li, An early Cambrian craniate-like chordate, Nature, V. 402, p. 518-522 (December 1999)
1. At Discovery Bay in Jamaica up to 5000 amphioxus individuals have been reported per square metre of sand. In many areas cephalochordates are "fished" commercially.
Steven Earle, 2000. Return to Earth Science News