NAME: Jimbacrinus Bostocki
LOCALITY: Cundlego Formation, Gasgoyne Junction, Jimba Jimba Station, Carnarvon, Western Australia.
The Jimbacrinus bostocki is a crinoid. Crinoids are marine animals (not plants), with this particular species inhabiting the deep-sea seafloor. As the crinoids belong to the Echinoderm phylum, it is related to starfish, brittle stars and sea urchins. Crinoids have kept the same basic body shape throughout time.
The Jimbacrinus bostocki fossils are described as having two parts. The stalk and the crown.
As they are seafloor animals, the Jimbacrinus bostocki had a stalk to attach itself to the seafloor substrate. These stalks are made up of flexible, porous columnal “discs” connected by soft tissue. The stalk is also hollow, like an internal tube and this is where the nervous system is located. Oxygen is absorbed through thin walled tube feet.
The crown is made up of a calyx and the arms.
The calyx is the body of the crinoid, where the organs such as the mouth and anus are located. The mouth is located on the upper surface of the calyx surrounded by the 5 feeding arms.
The 5 arms are lined with fine feathery tentacle like structures called pinnules. It unfurls its arms to filter feed on planktonic particles and detritus in the surrounding moving sea water. The feathery pinnules are very well preserved in the Jimbacrinus bostocki specimens. The picture below shows where the stalk attaches to the underside of the 5 segments of the calyx.
Specimens of Jimbacrinus bostocki are relatively large and are found to be up to 22cm long. They are available on the open market, with permits required for export from Australia. Lengthy preparation of the well preserved specimens reveals stunning detail and are considered to be of museum quality.
The alien looking Jimbacrinus bostocki crinoid fossils were first discovered in 1949 by the manager of the Jimba Jimba cattle station in Western Australia. As you can see the genus name is derived from the property name where they are located. The Jimba Jimba station managers name was Mr J Bostock, who the fossil species has been named after. These fossils were then further collected by fieldwork geologists from the Bureau of Geology, and transported to Melbourne. A paper first describing these fossils was published in the Journal of Palaeontology in January 1954. This paper was authored by Curt Teichert of the University of Melbourne, Victoria, Australia.
The Cundlego Formation where these fossils are found, is a sandstone formation that was created by flooding and storm event deposition during the Early PERMIAN – approximately 275 million years ago. This deposit was found along a dry creek bed and is filled with the fossilized remains of the abundant bottom dwelling species of the time. These fossils are often found complete and have not been found elsewhere.
This fossil deposit also gives us a snapshot into the extinction events of the Permian Period. The geological boundary between the end of the Permian and the beginning of the Triassic is known as the “Great Dying” and is the largest and most severe of the one of 5 recorded great Extinction events over recorded geological time. More than 90% of all marine species have not been found in the fossil record after this time. It is said that as global temperatures were rising, the warmer waters became increasingly acidic, methane and metals levels also increased and the waters were just unable to hold enough oxygen for the marine animals to survive. A small percentage of crinoids survived this extinction event and there are over 600 species alive today.
FUN FACT: Crinoid fossils were the inspiration for the Sentinels in the Matrix Movies. The Sentinels had many purposes early on, but eventually became the robotic killing machines that serve the Matrix by patrolling the underground cities searching for humans and Zion vessels.
Written by Lucinda Hook
Jimbacrinus bostocki fossil photos by Crystal World
Sentinels illustration by PIDJY – 2003