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Mickwitzia

Mickwitziids are a Cambrian group of shelly fossils with originally phosphatic valves, belonging to the Brachiopod stem group, and exemplified by the genus Mickwitzia – the other genera are Heliomedusa (a possible junior synonym of Mickwitzia?) and Setatella.[2] The family Mickwitziidae is conceivably paraphyletic with respect to certain crown-group brachiopods.[3]

Mickwitzia
Temporal range: Terreneuvian–mid Cambrian
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Clade: Brachiozoa
Stem group: Brachiopoda
Family: Mickwitziidae
Goryanskii, 1969
Genus: Mickwitzia
Schmidt, 1888
Species
  • M. monilifera (type) (Linnarsson, 1869)[1]
  • M. formosa (Wiman, 1902)
  • M. muralensis Walcott, 1913
  • M. lochmanae McMenamin, 1992
  • M. multipunctata McMenamin, 1992

Shell microstructure edit

Punctae or tubes penetrate through multiple shell wall layers, and individual punctae often develop a single, axial phosphatic tube. The shell comprises multiple phosphatic laminae; the region closest to the edge of the shell was presumably more organic-walled than phosphatized as it tends to be more flimsily preserved.[2]

Members of the genus appear to share characteristic shell microstructure in common with Tommotiids such as Micrina,[4] and like this taxon, mickwitziids may not have been able to enclose their entire body within a bivalved shell.[5]

The shells are punctuated with inward-directed hollow cones, conceivably associated with setae – though intact setae are exceptionally preserved along the margin of mickwitziid shells yet not found emanating from the cones, which have no evidence of ever incorporating setae.[2]

Included taxa edit

  • Mickwitzia
  • Oymurania[6]
  • Setatella

Micrina edit

Heliomedusa edit

Heliomedusa orienta was first interpreted as a jellyfish - hence its name - but is now affiliated with Mickwitzia, as well as Craniopsids and Disciniids.

A craniid affinity has long been on the cards, and was the position of the Treatise.[7]

In 2007 a new interpretation reconstructed Heliomedusa as being the other way up - swapping the identity of the dorsal and ventral valves. On this view it was interpreted as a disciniid.[8]

This met with a mixed reception in the updated treatise[9] and was rejected by Zhang et al. 2009[10]

Zhang et al. (2009) state without argument that the ventral valve is larger than the dorsal valve, and argue that the ventral valve was situated downwards in living Heliomedusa. They argue that the pedicle identified by Chen et al. (2007), and central to their "ventral valve as dorsal" argument, was instead an internal structure corresponding to an infilled gut.

Affinity edit

Mickwitziids are stem-group brachiopods, with links to the tommotiid grade. Mickwitzia itself is conceivably synonymous with Heliomedusa.[2]

Distribution edit

The oldest mickwitziid dates to the Terreneuvian.[11]

References edit

  1. ^ Linnarsson, J. G. O. (1869). "IV.—On some Fossils found in the Eophyton Sandstone, at Lugnås, in Sweden" (PDF). Geological Magazine. 6 (63): 393–406. Bibcode:1869GeoM....6..393L. doi:10.1017/S0016756800162910. S2CID 129861881.
  2. ^ a b c d Butler, A.D.; Streng, M.; Holmer, L.E.; Babcock, L.E. (2016). "Exceptionally preserved Mickwitzia from the Indian Springs Lagerstätte (Cambrian Stage 3), Nevada". Journal of Paleontology. 89 (6): 933–955. doi:10.1017/jpa.2016.8. S2CID 81646340.
  3. ^ "Organophosphatic bivalve stem-group brachiopods". {{cite journal}}: Cite journal requires |journal= (help)
  4. ^ McMenamin, M. A. S. (1992). "Two new species of the Cambrian genus Mickwitzia". Journal of Paleontology. 66 (2): 173–182. Bibcode:1992JPal...66..173M. doi:10.1017/S0022336000033680. JSTOR 1305903. S2CID 132405917.
  5. ^ Holmer, L. E.; Skovsted, C. B.; Williams, A. (2002). "A stem group brachiopod from the Lower Cambrian: Support for a Micrina (halkieriid) ancestry". Palaeontology. 45 (5): 875–882. Bibcode:2002Palgy..45..875H. doi:10.1111/1475-4983.00265. S2CID 85069340.
  6. ^ "The new stem-group brachiopod Oymurania from the lower Cambrian of Siberia". {{cite journal}}: Cite journal requires |journal= (help)
  7. ^ Williams, Alwyn; Brunton, C.H.C.; Carlson, S.J.; et al. (1997–2007). Kaesler, Roger L.; Selden, Paul (eds.). Part H, Brachiopoda (Revised). Treatise on Invertebrate Paleontology. Boulder, Colorado; Lawrence, Kansas: Geological Society of America; University of Kansas.
  8. ^ Chen, J.-Y., Huang, D.-Y., and Chuang, S.-H. (2007). Reinterpretation of the Lower Cambrian brachiopod Heliomedusa orienta Sun and Hou, 1987a as a discinid. J. Paleontol. 81, 38–47.
  9. ^ Williams, A., Racheboeuf, P.R., Savage, N.M., Lee, D.E., Popov, L.E., Carlson, S.J., Logan, A., Lüter, C., Cusack, M., Curry, G.B., et al. (2007). "Part H, Brachiopoda (Revised)". In Treatise on Invertebrate Paleontology, pp. 2321–3226.
  10. ^ Zhang, Z., Li, G., Emig, C.C., Han, J., Holmer, L.E., and Shu, D. (2009). Architecture and function of the lophophore in the problematic brachiopod Heliomedusa orienta (Early Cambrian, South China). Geobios 42, 649–661.
  11. ^ Devaere, Léa; Holmer, Lars; Clausen, Sébastien; Vachard, Daniel (2014). "Oldest mickwitziid brachiopod from the Terreneuvian of southern France". Acta Palaeontologica Polonica. doi:10.4202/app.00021.2013.

mickwitzia, mickwitziids, cambrian, group, shelly, fossils, with, originally, phosphatic, valves, belonging, brachiopod, stem, group, exemplified, genus, other, genera, heliomedusa, possible, junior, synonym, setatella, family, mickwitziidae, conceivably, para. Mickwitziids are a Cambrian group of shelly fossils with originally phosphatic valves belonging to the Brachiopod stem group and exemplified by the genus Mickwitzia the other genera are Heliomedusa a possible junior synonym of Mickwitzia and Setatella 2 The family Mickwitziidae is conceivably paraphyletic with respect to certain crown group brachiopods 3 MickwitziaTemporal range Terreneuvian mid Cambrian PreꞒ Ꞓ O S D C P T J K Pg NScientific classificationDomain EukaryotaKingdom AnimaliaClade BrachiozoaStem group BrachiopodaFamily MickwitziidaeGoryanskii 1969Genus MickwitziaSchmidt 1888SpeciesM monilifera type Linnarsson 1869 1 M formosa Wiman 1902 M muralensis Walcott 1913M lochmanae McMenamin 1992M multipunctata McMenamin 1992 Contents 1 Shell microstructure 2 Included taxa 2 1 Micrina 2 2 Heliomedusa 3 Affinity 4 Distribution 5 ReferencesShell microstructure editPunctae or tubes penetrate through multiple shell wall layers and individual punctae often develop a single axial phosphatic tube The shell comprises multiple phosphatic laminae the region closest to the edge of the shell was presumably more organic walled than phosphatized as it tends to be more flimsily preserved 2 Members of the genus appear to share characteristic shell microstructure in common with Tommotiids such as Micrina 4 and like this taxon mickwitziids may not have been able to enclose their entire body within a bivalved shell 5 The shells are punctuated with inward directed hollow cones conceivably associated with setae though intact setae are exceptionally preserved along the margin of mickwitziid shells yet not found emanating from the cones which have no evidence of ever incorporating setae 2 Included taxa editMickwitzia Oymurania 6 SetatellaMicrina edit Main article Micrina Heliomedusa edit Heliomedusa orienta was first interpreted as a jellyfish hence its name but is now affiliated with Mickwitzia as well as Craniopsids and Disciniids A craniid affinity has long been on the cards and was the position of the Treatise 7 In 2007 a new interpretation reconstructed Heliomedusa as being the other way up swapping the identity of the dorsal and ventral valves On this view it was interpreted as a disciniid 8 This met with a mixed reception in the updated treatise 9 and was rejected by Zhang et al 2009 10 Zhang et al 2009 state without argument that the ventral valve is larger than the dorsal valve and argue that the ventral valve was situated downwards in living Heliomedusa They argue that the pedicle identified by Chen et al 2007 and central to their ventral valve as dorsal argument was instead an internal structure corresponding to an infilled gut Affinity editMickwitziids are stem group brachiopods with links to the tommotiid grade Mickwitzia itself is conceivably synonymous with Heliomedusa 2 Distribution editThe oldest mickwitziid dates to the Terreneuvian 11 References edit Linnarsson J G O 1869 IV On some Fossils found in the Eophyton Sandstone at Lugnas in Sweden PDF Geological Magazine 6 63 393 406 Bibcode 1869GeoM 6 393L doi 10 1017 S0016756800162910 S2CID 129861881 a b c d Butler A D Streng M Holmer L E Babcock L E 2016 Exceptionally preserved Mickwitzia from the Indian Springs Lagerstatte Cambrian Stage 3 Nevada Journal of Paleontology 89 6 933 955 doi 10 1017 jpa 2016 8 S2CID 81646340 Organophosphatic bivalve stem group brachiopods a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help McMenamin M A S 1992 Two new species of the Cambrian genus Mickwitzia Journal of Paleontology 66 2 173 182 Bibcode 1992JPal 66 173M doi 10 1017 S0022336000033680 JSTOR 1305903 S2CID 132405917 Holmer L E Skovsted C B Williams A 2002 A stem group brachiopod from the Lower Cambrian Support for a Micrina halkieriid ancestry Palaeontology 45 5 875 882 Bibcode 2002Palgy 45 875H doi 10 1111 1475 4983 00265 S2CID 85069340 The new stem group brachiopod Oymurania from the lower Cambrian of Siberia a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help Williams Alwyn Brunton C H C Carlson S J et al 1997 2007 Kaesler Roger L Selden Paul eds Part H Brachiopoda Revised Treatise on Invertebrate Paleontology Boulder Colorado Lawrence Kansas Geological Society of America University of Kansas Chen J Y Huang D Y and Chuang S H 2007 Reinterpretation of the Lower Cambrian brachiopod Heliomedusa orienta Sun and Hou 1987a as a discinid J Paleontol 81 38 47 Williams A Racheboeuf P R Savage N M Lee D E Popov L E Carlson S J Logan A Luter C Cusack M Curry G B et al 2007 Part H Brachiopoda Revised In Treatise on Invertebrate Paleontology pp 2321 3226 Zhang Z Li G Emig C C Han J Holmer L E and Shu D 2009 Architecture and function of the lophophore in the problematic brachiopod Heliomedusa orienta Early Cambrian South China Geobios 42 649 661 Devaere Lea Holmer Lars Clausen Sebastien Vachard Daniel 2014 Oldest mickwitziid brachiopod from the Terreneuvian of southern France Acta Palaeontologica Polonica doi 10 4202 app 00021 2013 Retrieved from https en wikipedia org w index php title Mickwitzia amp oldid 1188435764, wikipedia, wiki, book, books, library,

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