The halkieriids are a group of fossil organisms from the Lower to Middle Cambrian. Their eponymous genus is Halkieria, which has been found on almost every continent in Lower to Mid Cambrian deposits, forming a large component of the small shelly fossil assemblages. The best known species is Halkieria evangelista, from the North Greenland Sirius Passet Lagerstätte, in which complete specimens were collected on an expedition in 1989. The fossils were described by Simon Conway Morris and John Peel in a short paper in 1990 in the journal Nature. Later a more thorough description was undertaken in 1995 in the journal Philosophical Transactions of the Royal Society of London and wider evolutionary implications were posed.
Halkieriid
Comparison of Orthrozanclus (left) and Halkieria (right)
The Cambrian is the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran period 538.8 Ma to the beginning of the Ordovician Period 485.4 Ma.
Archeocyathids from the Poleta formation in the Death Valley area
Stromatolites of the Pika Formation (Middle Cambrian) near Helen Lake, Banff National Park, Canada
Trilobites, like these Elrathia kingii were very common arthropods during this time
Pikaia was a stem-chordate from the Middle Cambrian
