piranha Posted July 23, 2019 Share Posted July 23, 2019 The macropleural spines are not too long for Mesonacis fremonti. In some specimens they are truncated but usually they are quite long. Resser, C.E. 1928 Cambrian Fossils from the Mojave Desert. Smithsonian Miscellaneous Collections, 81(2):1-13 Nelson, C.A. 1976 Late Precambrian-Early Cambrian Stratigraphic and Faunal Succession of Eastern California and the Precambrian-Cambrian Boundary. pp. 31-42 In: Depositional Environments of Lower Paleozoic Rocks in the White Inyo Mountains, Inyo County, California. Pacific Coast Paleogeography Field Guide 1. Pacific Section, SEPM. Lieberman, B.S. 1999 Systematic Revision of the Olenelloidea (Trilobita, Cambrian). Peabody Museum of Natural History, Yale University, Bulletin, 45:1-150 3 Link to comment Share on other sites More sharing options...
rew Posted July 23, 2019 Author Share Posted July 23, 2019 So there's more variation in the length of the macropleural spines in Mesonacis fremonti that I thought. It looks like M. fremonti is still a contender. That species has a wide stratigraphic range. Another possibility -- Olenellus clarki. Link to comment Share on other sites More sharing options...
piranha Posted July 23, 2019 Share Posted July 23, 2019 1 hour ago, rew said: So there's more variation in the length of the macropleural spines in Mesonacis fremonti that I thought. It looks like M. fremonti is still a contender. That species has a wide stratigraphic range. Another possibility -- Olenellus clarki. Mesonacis fremonti is the correct ID. Olenellus clarki has a smaller glabella and a larger preglabellar field. 1 Link to comment Share on other sites More sharing options...
rew Posted July 24, 2019 Author Share Posted July 24, 2019 I think you're right. Unless there are any further objections, M. fremonti it is. Link to comment Share on other sites More sharing options...
rew Posted July 28, 2019 Author Share Posted July 28, 2019 It seems that this week's theme is early Cambrian Western American Redlichids found by Jake Skabelund. This trilobite, #62, is Archaeaspis macropleuron from the Campito Formation of Esmeralda County, Nevada. It is from the first half of the Atdabanian. Jake told me that this is the earliest North American trilobite found in fully articulated form (Fritzaspis is earlier but only found in bits and pieces). It is certainly the earliest trilobite in my collection. So while this is not my prettiest bug it is still a very special bug. This trilobite lived when it was still a new idea to be a trilobite. 1 Link to comment Share on other sites More sharing options...
rew Posted August 5, 2019 Author Share Posted August 5, 2019 This week's trilobite of the week, #63, is Leonaspis spinicurva, a Middle Devonian bug from Hmar Lakhdad, Morocco. The species name comes from the curved occipital spine. 4 1 Link to comment Share on other sites More sharing options...
rew Posted August 5, 2019 Author Share Posted August 5, 2019 A couple more pictures... 2 1 Link to comment Share on other sites More sharing options...
rew Posted August 11, 2019 Author Share Posted August 11, 2019 Trilobite of the week, #64 is Ceraurus pleurexanthemus, an Ordovician trilobite from the Walcott-Rust quarry in New York. The small round thing to the upper right of the trilobite is an ostracod. 2 Link to comment Share on other sites More sharing options...
Jackson g Posted August 13, 2019 Share Posted August 13, 2019 On 8/4/2019 at 10:09 PM, rew said: A couple more pictures... The eyes are very nice on this Leonaspis 2 Link to comment Share on other sites More sharing options...
rew Posted August 19, 2019 Author Share Posted August 19, 2019 Trilobite of the week #65 is the Late Middle Cambrian Norwoodia bellaspina, a dimunitive Ptychoparid from the Weeks Formation of Millard County, Utah. This bug has a very long telson. It also has an occipital spine, but it flattened against the body and overlaps with the base of the telson so isn't so easy to see. 2 Link to comment Share on other sites More sharing options...
piranha Posted August 19, 2019 Share Posted August 19, 2019 12 hours ago, rew said: Trilobite of the week #65 is the Late Middle Cambrian Norwoodia bellaspina, a dimunitive Ptychoparid from the Weeks Formation of Millard County, Utah. This bug has a very long telson. It also has an occipital spine, but it flattened against the body and overlaps with the base of the telson so isn't so easy to see. The specific name "bellapsina" is invalid. It was originally described in PhD theses by Beebe 1990 and repeated by Peters 2003. It also appeared in the Italian edition of: " The Back to the Past Museum Guide to Trilobites". Because it was never formally described and published, Robison & Babcock 2011 made it nomen nudum and renamed it: Norwoodia boninoi. Additionally, there is no telson, the long spine emanates from the fourth thoracic segment. Always a challenge to keep the labels updated! Robison, R.A., Babcock, L.E. 2011 Systematics, paleobiology, and taphonomy of some exceptionally preserved trilobites from Cambrian Lagerstätten of Utah. University of Kansas, Paleontological Contributions, 5:1-47 PDF LINK Bonino, E., Kier, C. 2009 Trilobiti - il libro del Museo. [Trilobites - The book of the Museum.] Back to the Past Museum: Casa Editrice Marna. Lecco, Italy, 441 pp. Peters, S.E. 2003 Evenness, richness and the Cambrian-Paleozoic faunal transition in North America: An assemblage-level perspective. PhD Thesis, The University of Chicago, 279 pp. Beebe, M.A. 1990 Trilobite faunas and depositional environments of the Weeks Formation (Cambrian), Utah. PhD Thesis, University of Kansas, 103 pp. 2 Link to comment Share on other sites More sharing options...
rew Posted August 19, 2019 Author Share Posted August 19, 2019 Geesh, after Robison & Babcock 2011 made it nomen nuden couldn't they have kept things simple by formally naming it Norwoodia bellaspina? It's getting to the point where every time I photograph a trilobite I have to prepare a new label for it. Link to comment Share on other sites More sharing options...
piranha Posted August 19, 2019 Share Posted August 19, 2019 The rules of naming are not arbitrary, they could not keep the name even if they wanted to. 3 Link to comment Share on other sites More sharing options...
FossilDAWG Posted August 19, 2019 Share Posted August 19, 2019 This subject has been discussed several times elsewhere in the Forum so I won't belabor the point. An important function of taxonomic rules is to ensure (as much as possible) that species names are as unambiguous as possible. For that reason, discarded names cannot be reused. Otherwise, suppose you see a specimen labeled, say, "Trilobitius defuncta" and it turns out that name was used 60 years ago but was found to be invalid and it was discarded, then someone else more recently recycled it and applied it to a completely different species. How is anyone supposed to know if "Trilobitus defuncta" is being used in the original but incorrect sense or in the more recent sense? It's much less ambiguous to bury the old name and come up with something new for the new species. Of course that means people might have to make new labels. Don 3 Link to comment Share on other sites More sharing options...
rew Posted August 20, 2019 Author Share Posted August 20, 2019 But this is different. Here we'd simply be using a name that everyone has been using for this trilobite for a while and just making it official. It isn't a discarded name from some other species. Link to comment Share on other sites More sharing options...
Fossildude19 Posted August 20, 2019 Share Posted August 20, 2019 It is up to the describer's discretion as to what something is named. 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...
rew Posted August 25, 2019 Author Share Posted August 25, 2019 Trilobite of the week #66 is Amecephalus althea (= Amecephalus laticaudum) of Middle Cambrian age from the Spence Shale in Utah. Its long and broad genal spines give it something of the appearance of a Harpide trilobite, but it is a Ptychoparid within the same family as Elrathia kingi, the Alokistocaridae. The head comes very close to the edge of the rock but it is complete. 1 Link to comment Share on other sites More sharing options...
piranha Posted August 25, 2019 Share Posted August 25, 2019 40 minutes ago, rew said: Trilobite of the week #66 is Amecephalus althea (= Amecephalus laticaudum) of Middle Cambrian age from the Spence Shale in Utah. Its long and broad genal spines give it something of the appearance of a Harpide trilobite, but it is a Ptychoparid within the same family as Elrathia kingi, the Alokistocaridae. The head comes very close to the edge of the rock but it is complete. Amecephalus laticaudum is the current name. Congrats on another spectacular textbook specimen and thanks again for this great thread! Robison, R.A., Babcock, L.E., Gunther, V.G. 2015 Exceptional Cambrian fossils from Utah: A Window into the age of Trilobites. Utah Geological Survey Miscellaneous Publication, 15-1:1-97 3 Link to comment Share on other sites More sharing options...
rew Posted August 25, 2019 Author Share Posted August 25, 2019 Well, the American Museum of Natural History's trilobite gallery used to have their specimen as Amecephalus lauticaudum but later changed to to Amecephalus althea. (See https://www.amnh.org/research/paleontology/collections/fossil-invertebrate-collection/trilobite-website/gallery-of-trilobites/cambrian-period-trilobites/cambrian-trilobites-of-the-united-states-alphabetized ) So I figured that was the more up to date name. Their specimen is exactly the one you posted above. 1 Link to comment Share on other sites More sharing options...
fifbrindacier Posted August 25, 2019 Share Posted August 25, 2019 Phacops sp and Phacops (Phacops) aff. fecundus degener Devonian "On ne voit bien que par le coeur, l'essentiel est invisible pour les yeux." (Antoine de Saint-Exupéry) "We only well see with the heart, the essential is invisible for the eyes." In memory of Doren Link to comment Share on other sites More sharing options...
piranha Posted August 25, 2019 Share Posted August 25, 2019 43 minutes ago, rew said: Well, the American Museum of Natural History's trilobite gallery used to have their specimen as Amecephalus lauticaudum but later changed to to Amecephalus althea. (See https://www.amnh.org/research/paleontology/collections/fossil-invertebrate-collection/trilobite-website/gallery-of-trilobites/cambrian-period-trilobites/cambrian-trilobites-of-the-united-states-alphabetized ) So I figured that was the more up to date name. Their specimen is exactly the one you posted above. AMNH is an excellent resource, unfortunately they are off the mark on this one. Amecephalus (=Alokistocare) althea (Walcott 1916) is a different trilobite than Amecephalus (=Alokistocare) laticaudum (Resser 1939). Here are the figures from the papers that first described them as new species. Walcott, CD. 1916 Cambrian Geology and Paleontology III, No. 3 - Cambrian Trilobites. Smithsonian Miscellaneous Collections, 64(3):157-258 Resser, C.E. 1939 The Spence Shale and its Fauna. Smithsonian Miscellaneous Collections, 97(12):1-29 3 Link to comment Share on other sites More sharing options...
rew Posted August 25, 2019 Author Share Posted August 25, 2019 Apparently the trilobite expert at AMNH decided that A. althea and A. laticaudum are the same species so assigned the senior name. I don't know what the general consensus is. Certainly all specimens I've seen for sale use A. laticaudum, but fossil sellers are often a bit behind when species get renamed. Link to comment Share on other sites More sharing options...
piranha Posted August 25, 2019 Share Posted August 25, 2019 16 hours ago, rew said: Apparently the trilobite expert at AMNH decided that A. althea and A. laticaudum are the same species so assigned the senior name. I don't know what the general consensus is. Certainly all specimens I've seen for sale use A. laticaudum, but fossil sellers are often a bit behind when species get renamed. Foster 2011 synonymized A. althea and A. laticaudum but subsequently they continue to be regarded as separate species more recently by Robison et al. 2015. Another Cambrian specialist familiar with this situation said a significant difference separating the species is A. althea has a triangular swelling in the preglabellar area and A. laticaudum does not. Foster, J.R. 2011 Trilobites and other fauna from two quarries in the Bright Angel Shale (middle Cambrian, Series 3; Delamaran), Grand Canyon National Park, Arizona. pp. 99-120 In: Hollingsworth, J.S., Sundberg, F.A. & Foster, J.R. (eds) Cambrian Stratigraphy and Paleontology of Northern Arizona and Southern Nevada. Museum of Northern Arizona Bulletin, 67:1-321 LINK Robison, R.A., Babcock, L.E., Gunther, V.G. 2015 Exceptional Cambrian fossils from Utah: A Window into the age of Trilobites. Utah Geological Survey Miscellaneous Publication, 15-1:1-97 Link to comment Share on other sites More sharing options...
Scylla Posted August 25, 2019 Share Posted August 25, 2019 Just saw this thread! Wow. I mean WOW! Link to comment Share on other sites More sharing options...
rew Posted August 27, 2019 Author Share Posted August 27, 2019 Okay, I flipped a coin -- heads I go back to calling this Amecephalus laticaudum. Heads it is. (That's how I do science.) Link to comment Share on other sites More sharing options...
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