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{{Taxobox
{{Notability|date=March 2020}}
| name = ''Pterotheca attenuata''

| fossil_range = [[Ordovician|Early-Late Ordovician]]<br>~{{fossil range|480|450}}
{{Automatic taxobox
|name = Pterotheca attenuata
| image = Pterotheca attenuata.jpg
| image_caption = Pterotheca attenuata from the [[Milwaukee Public Museum]]
| fossil_range = Early [[Ordovician]] – Late [[Ordovician]],

|image = File:Pterotheca attenuata.jpg
|image_caption = Pterotheca attenuata from the [[Milwaukee Public Museum]]

| taxon = Monoplacophora
| taxon = Monoplacophora
| authority = [[Nils Hjalmar Odhner|Odhner]], 1940
| authority = [[Nils Hjalmar Odhner|Odhner]] 1940
| genus = ''[[Pterotheca]]''
| genus = ''[[Pterotheca]]''
| species = '''''P. attenuata'''''
| species = '''''P. attenuata'''''
| binomial = ''Pterotheca attenuata''
| binomial = ''Pterotheca attenuata''
| binomial_authority = (Ulrich, 1895)
| binomial_authority = (Ulrich 1895)
}}
}}


'''Pterotheca attenuata''' is a fossil from the Ordovician [[Upper Midwest|upper Midwestern United States]]. It has been variously classified as a [[monoplacophora|monoplacophoran]], [[bellerophontida|bellerophont]], or some other [[Gastropoda|gastropod]].<ref>{{cite web |title=Pterotheca Salter 1853 (snail) |url=http://fossilworks.org/?a=taxonInfo&taxon_no=8368 |website=Fossil Works |publisher=The Paleobiology Database |accessdate=20 March 2020 |ref=Fossilworks}}</ref><ref name=":0">{{cite book |last1=Ulrich |last2=Scofield |last3=Clarke |last4=Winchell |title=The Geology of Minnesota |date=1895 |publisher=Geological and Natural History Survey of Minnesota |location=Minneapolis |edition=3}}</ref> It lived in shallow marine waters and is a part of the [[Decorah Shale]] and [[Platteville Limestone]] fossil communities. It is often misclassified in museum collections because of its unusual morphology and therefore documentation of its range and abundance is poor.<ref name=":1">{{cite web |last1=Tweet |first1=Justin |title=Decorah gastropods (and some things that look like gastropods) |url=https://equatorialminnesota.blogspot.com/2018/11/decorah-gastropods.html |website=Equatorial Minnesota |accessdate=24 March 2020}}</ref>
'''''Pterotheca attenuata''''' is a fossil species from the [[Ordovician]] [[Upper Midwest|upper Midwestern United States]]. It has been variously classified as a [[monoplacophora|monoplacophoran]], [[bellerophontida|bellerophont]], or another type of [[Gastropoda|gastropod]].<ref name=PBDB>''Pterotheca'' at [[Fossilworks]].org</ref><ref name=":0">Ulrich et al., 1895</ref>


Remains of the animal were found in deposits laid down in shallow marine waters, as the [[Decorah Shale]] and [[Platteville Limestone]] of the United States Midwest. It is often misclassified in museum collections because of its unusual morphology and therefore documentation of its range and abundance is poor.<ref name=":1">Tweet, 2018</ref>
==Preservation and morphology==

== Preservation and morphology ==
[[File:Pterotheca attenuata painting.jpg|thumb|left|Pterotheca attenuata life restoration]]
[[File:Pterotheca attenuata painting.jpg|thumb|left|Pterotheca attenuata life restoration]]
The shell is composed of two slightly concave sub-triangular layers that connect along the anterior most side. The dorsal layer has a ridge that extends perpendicularly from the rest of shell along the median plane. The underside of the ventral most layer is effaced and smooth, but the top of the ventral layer and the bottom of the dorsal layer both show a slight medial ridge.<ref name=":0" />
The shell is composed of two slightly concave sub-triangular layers that connect along the anterior most side. The dorsal layer has a ridge that extends perpendicularly from the rest of shell along the median plane. The underside of the ventral most layer is effaced and smooth, but the top of the ventral layer and the bottom of the dorsal layer both show a slight medial ridge.<ref name=":0" />


P. attenuata is most often preserved in fine grained sedimentary rock like shale and limestone, but its range likely extends outside of these [[facies]]. <ref>{{cite journal |last1=Sloan |first1=Robert |title=RI-35 Middle and Late Ordovician Lithostratigraphy and Biostratigraphy of the Upper Mississippi Valley |journal=Minnesota Geological Survey |date=1987 |url=https://conservancy.umn.edu/handle/11299/60756 |accessdate=24 March 2020}}</ref> The shell is often found broken and the two layers separated. P. attenuata's unusual shape and the fragmentary nature of many of its fossils are both causes of its frequent misclassification as a [[brachiopoda|brachiopod]].<ref name=":1" />
''P. attenuata'' is most often preserved in fine-grained sedimentary rock like [[shale]] and [[limestone]], but its range likely extends outside of these [[facies]].<ref name=Sloan1987>Sloan, 1987</ref> The shell is often found broken and the two layers separated. P. attenuata's unusual shape and the fragmentary nature of many of its fossils are both causes of its frequent misclassification as a [[brachiopoda|brachiopod]].<ref name=":1" />


== References ==
== References ==
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{{reflist}}
{{reflist}}

[[Category:Paleontology in Minnesota]]
=== Bibliography ===
[[Category:Paleozoic North America]]
<!--Most recent publications first-->
* {{cite web |last1=Tweet |first1=Justin |title=Decorah gastropods (and some things that look like gastropods) |url=https://equatorialminnesota.blogspot.com/2018/11/decorah-gastropods.html |website=Equatorial Minnesota |accessdate=24 March 2020}}
* {{cite web |title=Pterotheca Salter 1853 (snail) |url=http://fossilworks.org/?a=taxonInfo&taxon_no=8368 |website=Fossil Works |publisher=The Paleobiology Database |accessdate=20 March 2020 |ref=Fossilworks}}
* {{cite journal |last1=Sloan |first1=Robert |title=RI-35 Middle and Late Ordovician Lithostratigraphy and Biostratigraphy of the Upper Mississippi Valley |journal=Minnesota Geological Survey |date=1987 |url=https://conservancy.umn.edu/handle/11299/60756 |accessdate=24 March 2020}}
* {{cite book |last1=Ulrich |last2=Scofield |last3=Clarke |last4=Winchell |title=The Geology of Minnesota |date=1895 |publisher=Geological and Natural History Survey of Minnesota |location=Minneapolis |edition=3}}

[[Category:Paleozoic life of North America]]
[[Category:Paleozoic life of North America]]
[[Category:Prehistoric life of North America]]
[[Category:Prehistoric life of North America]]
[[Category:Paleontology]]
[[Category:Ordovician United States]]
[[Category:Paleontology in Minnesota]]

[[Category:Fossil taxa described in 1940]]

[[Category:Disputed taxa]]
{{paleo-stub}}

Revision as of 22:30, 24 March 2020

Pterotheca attenuata
Temporal range: Early-Late Ordovician
~480–450 Ma
Pterotheca attenuata from the Milwaukee Public Museum
Scientific classification
Genus:
Species:
P. attenuata
Binomial name
Pterotheca attenuata
(Ulrich 1895)

Pterotheca attenuata is a fossil species from the Ordovician upper Midwestern United States. It has been variously classified as a monoplacophoran, bellerophont, or another type of gastropod.[1][2]

Remains of the animal were found in deposits laid down in shallow marine waters, as the Decorah Shale and Platteville Limestone of the United States Midwest. It is often misclassified in museum collections because of its unusual morphology and therefore documentation of its range and abundance is poor.[3]

Preservation and morphology

File:Pterotheca attenuata painting.jpg
Pterotheca attenuata life restoration

The shell is composed of two slightly concave sub-triangular layers that connect along the anterior most side. The dorsal layer has a ridge that extends perpendicularly from the rest of shell along the median plane. The underside of the ventral most layer is effaced and smooth, but the top of the ventral layer and the bottom of the dorsal layer both show a slight medial ridge.[2]

P. attenuata is most often preserved in fine-grained sedimentary rock like shale and limestone, but its range likely extends outside of these facies.[4] The shell is often found broken and the two layers separated. P. attenuata's unusual shape and the fragmentary nature of many of its fossils are both causes of its frequent misclassification as a brachiopod.[3]

References

  1. ^ Pterotheca at Fossilworks.org
  2. ^ a b Ulrich et al., 1895
  3. ^ a b Tweet, 2018
  4. ^ Sloan, 1987

Bibliography

  • Tweet, Justin. "Decorah gastropods (and some things that look like gastropods)". Equatorial Minnesota. Retrieved 24 March 2020.
  • "Pterotheca Salter 1853 (snail)". Fossil Works. The Paleobiology Database. Retrieved 20 March 2020.
  • Sloan, Robert (1987). "RI-35 Middle and Late Ordovician Lithostratigraphy and Biostratigraphy of the Upper Mississippi Valley". Minnesota Geological Survey. Retrieved 24 March 2020.
  • Ulrich; Scofield; Clarke; Winchell (1895). The Geology of Minnesota (3 ed.). Minneapolis: Geological and Natural History Survey of Minnesota.