Two new species of the Cambrian genus<i>Mickwitzia</i>

McMenamin, Mark A. S.

doi:10.1017/s0022336000033680

Cited by 19 publications

(28 citation statements)

References 21 publications

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“…the inward pointing cones with central tubes in M. muralensis, would be poorly designed for chemical interaction with the external environment. It therefore is unlikely that the tubes helped to deter encrusting or endolithic organisms as proposed by McMenamin (1992).…”

Section: Function Of Tubesmentioning

confidence: 99%

“…later studies failed to appreciate the effects of early diagenesis on the microstructure (Gorjansky 1969;McMenamin 1992;Laurie 2000). Due to its preservation, internal features, the shell microstructure and the nature of the`punctae' could not be resolved, leaving the overall de®nition of the genus vague.…”

Section: Af®nitiesmentioning

confidence: 99%

“…The multiple tubes that penetrate the Mickwitzia shell are at ®rst sight reminiscent of punctae, and the shell of Mickwitzia has been described as punctate in most studies (Walcott 1912(Walcott , 1913Rowell 1977;McMenamin 1992). Such a term, however, is deeply misleading, as the tubes of Mickwitzia are entirely distinct from the brachiopod punctae.…”

Section: Function Of Tubesmentioning

confidence: 99%

“…poor preservation. Previous interpretations of the shell microstructure as consisting of three principal layers (Walcott 1912;Rowell 1965;McMenamin 1992) failed to take into account early diagenetic alterations and have contributed to the dif®culties in establishing a sound phylogenetic placement for the genus (Laurie 2000).…”

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confidence: 99%

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Shell structure, ontogeny and affinities of the Lower Cambrian bivalved problematic fossilMickwitzia muralensisWalcott, 1913

Balthasar

2004

LET

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Shell structure, ontogeny and af®nities of the Lower Cambrian bivalved problematic fossil Mickwitzia muralensis Walcott, 1913 UWE BALTHASAR Balthasar, U. 2004 12 01: Shell structure, ontogeny and af®nities of the Lower Cambrian bivalved problematic fossil Mickwitzia muralensis Walcott, 1913. Lethaia, Vol. 37, pp. 381±400. Oslo. ISSN 0024-1164.Exceptionally preserved carbonate-and shale-hosted Mickwitzia muralensis from the Lower Cambrian Mural Formation, southern Canadian Rocky Mountains, complement one another to yield an unusually complete account of its ontogeny, ecology and phylogenetic relationships. The shell of M. muralensis is composed of dense phosphatic layers interspersed with porous organic-rich layers. At the insertion of shell-penetrating tubes, shell layers de¯ect inwards to produce inwardly pointing cones. The tubes are interpreted as having hosted setae that were secreted by outer-epithelial follicles. Follicular setae also occurred at the mantle margin, where they were oriented within the plane of the shell as in modern brachiopods. During ontogeny, the initial setae oriented in the plane of the shell occurred before the ®rst shell-penetrative setae. In the juvenile and early-mature stages of shell secretion, a posterior opening was present between both valves and was used for the protrusion of an attachment structure. In the latemature shell, this opening became ®xed in the ventral valve. Based on the posterior margin and the shell microstructure, a close relationship between Mickwitzia and the paterinids is proposed with differences interpreted as heterochronic. The shell-penetrative setal apparatus of M. muralensis is distinct from that previously described of Micrina, though both types are conceivably homologous to adult and juvenile setae of modern brachiopods. & Brachiopods, chloriti®cation, Mickwitzia, Micrina, preservation, setae.Uwe Balthasar [ubal01@esc.cam.ac.uk],

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Section: Function Of Tubesmentioning

confidence: 99%

Section: Af®nitiesmentioning

confidence: 99%

Section: Function Of Tubesmentioning

confidence: 99%

mentioning

confidence: 99%

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Shell structure, ontogeny and affinities of the Lower Cambrian bivalved problematic fossilMickwitzia muralensisWalcott, 1913

Balthasar

2004

LET

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“…The code for the 1° by 2° quadrangles is as follows: AP, Agua Prieta CB, Caborca CN, Cananea, H, Hermosillo (H12-8) IA, Isla Angel de la Guarda (H12-7) M, 1 0 2000). The Puerto Blanco Formation contains trilobites (McMenamin, 1983(McMenamin, , 1987McMenamin and others, 1994), archeocyathids (Debrenne and others, 1989), brachiopods (McMenamin, 1987;McMenamin and others, 1994), and rare other fossils (McMenamin, 1992), McMenamin and others, 1994). Chemostratigraphic studies (Rowland and others, 1993) of the Sierra Rajón section support, in general, previous correlations (Stewart and others, 1984) of stratigraphic units from Sierra Rajón to the western United States.…”

Section: Introductionmentioning

confidence: 99%

Inventory of Neoproterozoic and Paleozoic strata in Sonora, Mexico

Stewart¹,

Poole²

2002

Open-File Report

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Small shelly fossils and carbon isotopes from the early Cambrian (Stages 3–4) Mural Formation of western Laurentia

Skovsted

Balthasar

Vinther

et al. 2020

Papers in Palaeontology

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The extraordinary window of phosphatized and phosphatic small shelly fossils (SSF) during the early and middle Cambrian is an important testament to the radiation of biomineralizing metazoans. While SSF are well known from most Cambrian palaeocontinents during this time interval, western Laurentia has relatively few SSF faunas.Here we describe a diverse SSF fauna from the early Cambrian (Stages 3-4) Mural Formation at three localities in Alberta and British Columbia, Canada, complemented by carbon isotope measurements to aid in a potential future bio-chemostratigraphic framework. The fauna expands the recorded SSF assemblage diversity in western Laurentia and includes several brachiopods, four bradoriids, three chancelloriids, two hyoliths, a tommotiid and a helcionellid mollusc as well as echinoderm ossicles and specimens of Microdictyon, Volborthella and Hyolithellus. New taxa include the tommotiid genus Canadiella gen. nov., the new bradoriid species Hipponicharion perforata sp. nov. and Pseudobeyrichona taurata sp. nov. Compared with contemporaneous faunas from western Laurentia, the fauna is relatively diverse, particularly in taxa with originally phosphatic shells, which appear to be associated with archaeocyathid build-ups. This suggests that the generally low faunal diversity in western Laurentia may be at least partly a consequence of poor sampling of suitable archaeocyathan reef environments. In addition, the tommotiid Canadiella filigrana appears to be of biostratigraphical significance in Cambrian Stage 3 strata of western Laurentia, and the unexpected high diversity of bradoriid arthropods in the fauna also suggests that this group may prove useful for biostratigraphical resolution in the region.

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Two new species of the Cambrian genusMickwitzia

Cited by 19 publications

References 21 publications

Shell structure, ontogeny and affinities of the Lower Cambrian bivalved problematic fossilMickwitzia muralensisWalcott, 1913

Shell structure, ontogeny and affinities of the Lower Cambrian bivalved problematic fossilMickwitzia muralensisWalcott, 1913

Inventory of Neoproterozoic and Paleozoic strata in Sonora, Mexico

Small shelly fossils and carbon isotopes from the early Cambrian (Stages 3–4) Mural Formation of western Laurentia

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