oilshale Posted September 17, 2010 Share Posted September 17, 2010 (edited) The Marrellomorphs are a clade of strange looking stem-group arthropods known from the from the Cambrian Burgess Shale and the slightly older Kaili Fauna in China (Marrella), the Silurian Herefordshire Lagerstätte in England (Xylokorys), the Ordovician Basal Upper Fezouata Formation (lower Arenig, or lower Floian), north of Zagora in southeastern Morocco and the Caradoc (Upper Ordovician) in Bohemia (Furca) and the Devonian Bundenbach Shale in Germany (Mimetaster and Vachonisia). They lacked mineralized hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution.The oldest known Marrellomorph is Marrella sp. from the Cambrian Burgess Shale and the even slightly older Kaili Fauna in China. Marrella splendens is an unusual arthropod known only from a single bed in the Middle Cambrian Burgess Shale of British Columbia. Nevertheless, Marrella is the most abundant genus in the Burgess Shale. Informally, Marrella was described by Walcott as a "lace crab". It is a small animal, 2 cm or less in length. Whittington did a thorough redescription of the animal in 1971, concluding on the basis of its legs, gills and the appendages on the head that it was not a trilobite, not a chelicerate ,and not a crustacean. The head shield has two pairs of long rearward directed spikes. Marrella possessed two pairs of antennae, one long and sweeping, the second shorter and stouter. The two dozen segments each have a pair of six segmented leg / feathery gill structures. There is a tiny, button like telson at the end of the thorax. The best modern guess is that Marrella is a moderately evolved primitive arthropod descended from a common ancestor of the major later arthropod groups.The overall form of Marrella and other Marrellomorphs suggests that it was a soft-bottom dweller. The wide carapace border would have prevented sinking into unconsolidated sediment. A thorough re-investigation of Marrella splendens based on over 1000 specimens was recently published by D. García-Bellido and D. Collins: "A new study of Marrella splendens (Arthropoda, Marrellomorpha) from the Middle Cambrian Burgess Shale, British Columbia, Canada" in Can. J. Earth Sci. 43(6): 721742 (2006).A slightly younger Marrellomorph is from the Silurian Herefordshire Lagerstätte in England.A silurian marrellomorph arthropod from Herefordshire.pdf The Ordovician Marrellomorph Furca is known from only about 50 specimens. Very recently, the discovery of numerous diverse soft-bodied assemblages in the Lower and Upper Fezouata Formations (Lower Ordovician) of Morocco yielded important new material. The fossils itself were once pyritized, but are now oxidized to iron oxy-hydroxides. An overview of the fauna and its significance is available in a paper by Peter van Roy and colleagues (Nature 465). There is a very nice photo in Ru's Palaeo Galleries:http://rusmithsgalle.../p49701348.htmlAnother strange looking Marrellomorph is Mimetaster from the Lower Devonian Hunsrück Slate (Bundenbach slate) in Germany. Mimetaster hexagonalis is the most abundant non-trilobite arthropod from this Lagerstätte. They are considered to live in groups of several individuals; two, three or even more species on one slab are not uncommon. A thorough re-investigation of Mimetaster based on 123 specimens was recently published by G. Kühl and J. Rust in Paläontologische Zeitschrift, volume 84, number 3, 397-411. Edited June 25, 2013 by oilshale 1 Be not ashamed of mistakes and thus make them crimes (Confucius, 551 BC - 479 BC). Link to comment Share on other sites More sharing options...
Auspex Posted September 17, 2010 Share Posted September 17, 2010 Wondrous creatures...so strange, so ancient. How amazing that we know anything about them at all! "There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant “Try to learn something about everything and everything about something.” - Thomas Henry Huxley >Paleontology is an evolving science. >May your wonders never cease! Link to comment Share on other sites More sharing options...
Fossildude19 Posted September 17, 2010 Share Posted September 17, 2010 The preservation of the Mimetaster pictured is AMAZING!!! Thank you for posting this, Thomas! I've always been a huge fan of the Burgess Shale and similar lagerstatte fauna! Regards, Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
JimB88 Posted September 17, 2010 Share Posted September 17, 2010 wow, this is very interesting. I like seeing how a group of creatures began. Link to comment Share on other sites More sharing options...
dsalles Posted January 27, 2011 Share Posted January 27, 2011 Hi, is it still possible to find fossils in Bundenbach? Did you prep the Mimetaster yourself? Daniel Link to comment Share on other sites More sharing options...
oilshale Posted January 28, 2011 Author Share Posted January 28, 2011 Hi, is it still possible to find fossils in Bundenbach? Did you prep the Mimetaster yourself? Daniel The quarry isn't operated anymore. But you can still search the heaps. I prefer to prep my Bundenbach fossils myself whenever possible. Normally I am using a sandblaster with 150 micron soft iron pearls. Not for this Mimetaster here. For these delicate structures it is better to use a needle. And of course do an X-ray before. Thomas Be not ashamed of mistakes and thus make them crimes (Confucius, 551 BC - 479 BC). Link to comment Share on other sites More sharing options...
paleozoicfish Posted January 31, 2011 Share Posted January 31, 2011 The quarry isn't operated anymore. But you can still search the heaps. I prefer to prep my Bundenbach fossils myself whenever possible. Normally I am using a sandblaster with 150 micron soft iron pearls. Not for this Mimetaster here. For these delicate structures it is better to use a needle. And of course do an X-ray before. Thomas Thomas, Beautiful pieces especially the Mimetaster. I love marella-morphs; they are so bizarre. I also felt not enough forum members marveled at these fossils enough. Let's get more chatter going on these! Do you have any furca? I have one, but I am not satisfied with it. I have been looking for a perfect one. cheers, PzF Link to comment Share on other sites More sharing options...
palaeopix Posted January 31, 2011 Share Posted January 31, 2011 I don't currently own any Marrellamorphs, but they sure are weird looking beasts! Maybe one day I'll own a Marrella or Mimetaster or Furca, but until then I'll just have to look at this photo that I took at the Burgess Shale back in 1993. Marrella splendens. Marrella isn't nearly as scary looking as Mimetaster!! If they were alive today we'd probably keep them in Aquaria, like sea monkeys! Dan Link to comment Share on other sites More sharing options...
Wrangellian Posted February 1, 2011 Share Posted February 1, 2011 I think they are fascinating but I don't know much about them and have no specimens to show (I'm too poor to afford one apparently and you can't take them from the Burgess refuse heap but that's another discussion). I think you're right about sea monkeys.. they look like they were quite delicate, so unless that were poisonous or something they must have been quite harmless - no more so than a shrimp. I wonder what that black stain at the rear of the Marella was, they say it occurs in just about every specimen from Burgess.... maybe there was an ink sac link in an octopus? Link to comment Share on other sites More sharing options...
palaeopix Posted February 1, 2011 Share Posted February 1, 2011 I think they are fascinating but I don't know much about them and have no specimens to show (I'm too poor to afford one apparently and you can't take them from the Burgess refuse heap but that's another discussion). I think you're right about sea monkeys.. they look like they were quite delicate, so unless that were poisonous or something they must have been quite harmless - no more so than a shrimp. I wonder what that black stain at the rear of the Marella was, they say it occurs in just about every specimen from Burgess.... maybe there was an ink sac link in an octopus? It has been suggested that the black stain seen at the rear of the specimen, is the result of decay products that have leaked out of the body cavity into the surrounding sediment. The black colour is the result of the organic material being altered during diagenesis into kerogen. Link to comment Share on other sites More sharing options...
Scylla Posted February 1, 2011 Share Posted February 1, 2011 Thomas, Beautiful pieces especially the Mimetaster. I love marella-morphs; they are so bizarre. I also felt not enough forum members marveled at these fossils enough. Let's get more chatter going on these! Do you have any furca? I have one, but I am not satisfied with it. I have been looking for a perfect one. cheers, PzF Didn't know marella had descendants, great post, thanks Link to comment Share on other sites More sharing options...
oilshale Posted February 1, 2011 Author Share Posted February 1, 2011 (edited) It has been suggested that the black stain seen at the rear of the specimen, is the result of decay products that have leaked out of the body cavity into the surrounding sediment. The black colour is the result of the organic material being altered during diagenesis into kerogen. Didn't know that - sounds reasonable! Malek is offering a couple of exceptionally preserved Burgess Shale-type organisms from the Early Ordovician Fezouata biota. Have you seen the article he posted about Ordovician soft-bodied fossils from Morocco? Beside other strange creatures, there is the picture of a Furca in this article. Very attractive fossils with stunning preservation. The Furca is a real beauty. I guess I have to persuade my wife to spend our next holiday in Morocco. She can go swimming… Thomas article1.pdf Edited February 1, 2011 by oilshale Be not ashamed of mistakes and thus make them crimes (Confucius, 551 BC - 479 BC). Link to comment Share on other sites More sharing options...
Frank Menser Posted February 1, 2011 Share Posted February 1, 2011 (edited) Truly beautiful creatures :wub: Edited February 1, 2011 by Frank Menser Be true to the reality you create. Link to comment Share on other sites More sharing options...
Wrangellian Posted February 1, 2011 Share Posted February 1, 2011 Didn't know that - sounds reasonable! Malek is offering a couple of exceptionally preserved Burgess Shale-type organisms from the Early Ordovician Fezouata biota. Have you seen the article he posted about Ordovician soft-bodied fossils from Morocco? Beside other strange creatures, there is the picture of a Furca in this article. Very attractive fossils with stunning preservation. The Furca is a real beauty. I guess I have to persuade my wife to spend our next holiday in Morocco. She can go swimming… Thomas article1.pdf Yes I saw the article and the for-sale items - still too pricey for me! Would be nice to go there to collect if you have the luxury, and if they haven't closed it off to the public already... Be sure to post what you find, if you go! Link to comment Share on other sites More sharing options...
pleecan Posted February 2, 2011 Share Posted February 2, 2011 Great thread Thomas! Some how I missed this thread... but am glad I found it.... Marrella type creatures may also extend into the Silurian Lagerstatte... I will be on the look out for these creatures.... Link to comment Share on other sites More sharing options...
paleozoicfish Posted February 2, 2011 Share Posted February 2, 2011 Great thread Thomas! Some how I missed this thread... but am glad I found it.... Marrella type creatures may also extend into the Silurian Lagerstatte... I will be on the look out for these creatures.... Seeing as they are found as late as the Devonian, it should be possible. -PzF Link to comment Share on other sites More sharing options...
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