quote: Unlike Chengjiang, where only four species of trilobites are known, 13 genera of trilobites have been recorded in the Burgess Shale, though trilobites make up a small percentage of the total fauna.
Western Utah is one of the best-known Cambrian fossil localities in the world. The Wheeler Shale and Marjum Formation, strata of Middle Cambrian age, exhibit various exposures throughout the House Range and nearby mountain ranges west of the town of Delta, Utah. The Wheeler Shale is named for a major feature in the House Range, the Wheeler Amphitheater. The Wheeler Shale contains interbeds of shaley limestone, mudstone, and thin platy limestone. Much of the Wheeler Shale is not particularly fossiliferous, but certain layers contain abundant trilobites and other shelly fossils. The Wheeler Shale also is known for a diverse biota of soft-bodied fossils, including many of the same taxa found in the Burgess Shale.
The most famous Wheeler Shale fossil is the trilobite Elrathia kingi; so common at some sites that specimens are commercially quarried and are made into novelty accessories, as well as sold to collectors and institutions all over the world. However, Elrathia is just one of about fifteen trilobite genera of the Wheeler Shale. Bathyuriscus fimbriatus is also relatively common at certain sites. Even more abundant are several species of agnostid trilobites, such a Peronopsis interstricta. These are typically less than a centimeter in length. Here are eight representative species of the Wheeler Shale:
Elrathia kingi PTYCHOPARIIDA Family Alokistocaridae
Peronopsis interstricta AGNOSTIDA Family Peronopsidae
Modocia typicalis PTYCHOPARIIDA Family Marjumiidae
Asaphiscus wheeleri PTYCHOPARIIDA Family Asaphiscidae
Bolaspidella housensis PTYCHOPARIIDA Family Menomoniidae
Jenkinsonia varga PTYCHOPARIIDA Family Alokistocaridae
Modocia laevinucha PTYCHOPARIIDA Family Marjumiidae
Bathyuriscus fimbriatus CORYNEXOCHIDA Family Dolichometopidae
It is notable that the trilobite fauna of the Wheeler Shale, being a Middle Cambrian locality, is dominated by Ptychopariida, Corynexochida, and Agnostida. In addition to trilobites, there were other species of arachnomorph (trilobite-like clade) arthropods such as Naraoia. These trilobite-like arthropods demonstrate that the group from which trilobites arose was itself successful and diverse, though being uncalcified, are only preserved under exceptional conditions, such as at exceptional lagerstätten such as the Burgess Shale and Chengjiang. Because the Burgess Shale was the first lagerstätte with such exceptional preservation, other sites with similar preservation are referred to as "Burgess Shale type" lagerstätten. This level of preservation occurs only infrequently in the Wheeler Shale.
It only took a simple google search to find this information, and this was the top of the list.
quote:Arachnomorpha is a subdivision or clade of Arthropoda, comprising the monophyletic group formed by the trilobites, other great appendage arthropods and trilobite-like families (Helmetiidae, Xandarellidae, Naraoiidae, Liwiidae, and Tegopeltidae), and a diverse sister clade including the chelicerates.[1][2] ...
And there is a lot more to the fauna and flora found in the layers with trilobites, all showing mature marine ecosystems functioning for multiple generations.
I have no idea what you are trying to say here. Both Olenellus and Glossopleura are found in the same area (the GC, for instance), but are never found in the same layer, with Olenellus always being lower.
The Time Scale illustrations make them look to be in close proximity but that is just an illusion.
Again, I have no idea what you are trying to say. Jon was discussing the map location of trilobite fossils. The relative age is always the same with Olenellus in older sediments. Just because they are close in two dimensions does not mean that they are of the same age.
You need to supply the information of where the fossils of each species have been found.
In a relative age sense, you have been told. One is older than the other.
Different species of trilobites are found in the same digs, but at different elevations
All I wanted to know was how far from each other they are horizontally. Being at different elevations could mean one group directly above another group or it could mean at a different elevation but half a mile away horizontally -- or fifty feet or whatever.
I have no idea what you are trying to say here. Both Olenellus and Glossopleura are found in the same area (the GC, for instance), but are never found in the same layer, with Olenellus always being lower
But as I just posted to RAZD, how often are they found directly above or below each other as versus some distance away horizontally?
Also although the same species is found in the same layer, how often are they found close together in their group versus scattered in the layer?
But as I just posted to RAZD, how often are they found directly above or below each other as versus some distance away horizontally?
I'm not sure what difference it makes. We are talking about the Bright Angel Shale in the Grand Canyon. I have no idea if they are stacked exactly in a vertical column. The section is what it is.
Also although the same species is found in the same layer, how often are they found close together in their group versus scattered in the layer?
Again, sounds irrelevant. I imagine both situations are common, but usually fossils are found in abundance near other fossils of the same kind. That's why fossil quarries are isolated occurrences. Not every part of a formation is productive.
Why do I get the impression you are on a hunting expedition?
All I wanted to know was how far from each other they are horizontally. Being at different elevations could mean one group directly above another group or it could mean at a different elevation but half a mile away horizontally -- or fifty feet or whatever.
™ Version 4.0 Beta
