Everything about Marrella totally explained
Marrella splendens is an unusual
arthropod known from
fossils found in only a single
stratum of the Middle
Cambrian Burgess Shale of
British Columbia. It is, however, the most common fossil in the Burgess Shale, with over 15,000 specimens catalogued.
Marrella was the first fossil collected by
Charles Walcott from the Burgess Shale. Walcott described
Marrella informally as a "lace crab" and described it more formally as an odd
trilobite. It was later reassigned to the now defunct
class Trilobitoidea in the
Treatise on Invertebrate Paleontology. In
1971,
Whittington did a thorough redescription of the animal and, on the basis of its legs,
gills and head appendages, concluded that it was neither a trilobite, nor a
chelicerate, nor a
crustacean.
Marrella itself is a small animal, 2 cm or less in length. The head shield has two pairs of long rearward directed spikes. On the underside of the head are two pairs of
antennae, one long and sweeping, the second shorter and stouter.
Marrella has a body composed of 24–26 body segments, each with a pair of branched appendages. The lower branch of each appendage is a leg for walking, while the upper branch is a long, feathery gill. There is a tiny, button-like
telson at the end of the
thorax. It also contains eyes under its head. It is unclear how the unmineralized head and
spines were stiffened.
Marrella has too many antennae, too few cephalic legs, and too few segments per leg to be a trilobite. It lacks the three pairs of legs behind the mouth that are characteristic of
crustacea. The legs are also quite different from those of crustaceans. The identification of a
diffraction grating pattern on well-preserved
Marrella specimens proves that it would have harboured an iridescent sheen — and thus would have appeared colourful.
It is currently accepted that
Marrella is a stem group arthropod — that is, it's descended from a common ancestor common to it and most or all of the major later arthropod groups. It is thought to have been a
benthic (bottom-dwelling) marine
scavenger living on
detrital and particulate material.
Marrella had a hard shell-like head that wasn't only hollow but like the shell of a
crab.
Taken with two other unexpectedly unique arthropods,
Opabinia and
Yohoia,
Marrella has demonstrated that the soft bodied Burgess fauna were much more complex and diverse than anyone had previously suspected.
Further Information
Get more info on 'Marrella'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://marrella.totallyexplained.com">Marrella Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
