Haikouichthys

Taxobox
name = Haikouichthys
fossil_range = Early Cambrian


image_width = 190px
image_caption = Artists concept of "Haikouichthys ercaicunensis"
regnum = Animalia
phylum = Chordata
unranked_classis = Craniata
superclass = Agnatha
genus = "Haikouichthys"
species = "Haikouichthys ercaicunensis"
species_authority = Luo, Hu & Shu.

Haikouichthys is an extinct genus of craniate believed to have lived c. 530 million years ago, during the Cambrian explosion. "Haikouichthys" had a defined skull and other characteristics that have led paleontologists to label it a true craniate.

Description

Cladistic analysis indicates that the animal is probably a primitive agnathan fish or fishlike chordate most closely related to the Lampreys. It is about 2.5cm long and is narrower than the Myllokunmingia, another primitive fish that comes from the same beds. The holotype was found in the Yuansshan member of the Qiongzhusi Formation in the 'Eoredlichia' Zone near Haikou at Ercaicun, Kunming City, Yunnan, China.

The animal has a distinct head and tail. The head has at least six and perhaps nine probable gills. There are a number of segments (myomeres) with rear directed chevrons in the tail. There is probably a notochord although only a short segment is preserved in the single known specimen. There is a prominent dorsal fin with fin radials. The fin radials seem to angle "forward" toward the end thought on the basis of internal structures to be the head. This happens with a few modern fish but is an uncommon arrangement. There is a ventral fin fold. There are 13 circular structures along the bottom that may be gonads, slime organs, or something else entirely.

A similar creature from these shales is known as "Myllokunmingia".

Popular Culture

In the first episode of the BBC series "Walking With Monsters", "Haikouichthys" is portrayed as a kind of early fish. In that episode, a school of them attack a wounded "Anomalocaris". Later, "Haikouichthys" is depicted allegedly evolving into the Early Devonian "Cephalaspis".

See also

* Ostracoderm

External links

* See the following web sites for more information and pictures:
** http://www.sciencenews.org/sn_arc99/11_6_99/fob1.htm
** http://news.bbc.co.uk/1/hi/sci/tech/504776.stm

References

* cite book
author = CAMPBELL, NEIL A. & REECE, JANE B.
title = Biology, Seventh Edition
location = San Francisco CA | publisher = Benjamin Cummings
year = 2005