The Lower Permian Plocezyga (Hyphantozyga) matanensis, from Pan & Erwin (2002).

Belongs within: Hypsogastropoda.

Plocezyga was a Lower Carboniferous to Middle Permian genus of high-spired gastropods. Originally included in the genus Hemizyga, the genera had to be separated after it was established that the type species of Hemizyga was not representative of the majority of species in that genus (Hoare & Sturgeon 1980a, b). Plocezyga is a member of the family Pseudozygopleuridae which is distinguished by the form of the protoconch: smooth on the first 1.5 whorls, followed by collabral ornament on the second to fourth walls, with the ornamented whorls slightly swollen (Knight et al. 1960).

Characters (from Knight et al. 1960): Conch with both collabral and spiral ornament; labral sinus very shallow or absent.

<==Pseudozygopleuridae [Pseudozygopleurinae]
    |--Alaskozygopleura crassicosta Blodgett 1992TTE93
    |--Cyclozyga Knight 1936BR05, BR17 [Cyclozygidae]
    |    |--*C. mirabilis Knight 1930BR17
    |    `--C. sinusigeraB91
    |--Eoptychia Longstaff 1930 [Eoptychiidae]BR05
    |    `--*E. sulcata (de Koninck 1881) [=Loxonema sulcatum]BR17
    |--Stephanozyga Knight 1930 [Stephanozygidae, Stephanozyginae]BR05
    |    `--*S. nodosa (Girty 1915) [=Zygopleura nodosa, Palaeostylus (*Stephanozyga) nodosus]KC60
    |--Yaoxianospira Chen 1980C80
    |    `--*Y. yaoxianensis Chen 1980C80
    |--Helminthozyga Knight 1930KC60
    |    `--*H. vermicula Knight 1930KC60
    |--Microptychis Longstaff 1912PE02
    |    |--*M. wrighti Longstaff 1912KC60
    |    |--M. cerithiformisKC60
    |    |--M. charma Pan & Erwin 2002PE02
    |    `--M. expetendus Hoare & Sturgeon 1980PE02
    |--Pseudozygopleura Knight 1930BR05
    |    |--*P. semicostatum (Meek 1872)PE02 (see below for synonymy)
    |    |--P. convexa Batten 1985TTE93
    |    |--P. lirata Batten 1985TTE93
    |    |--P. micra Pan & Erwin 2002PE02
    |    |--P. obliqua Batten 1985TTE93
    |    `--P. pleurozyga Batten 1985TTE93
    `--Plocezyga Knight 1930BR05, HS80b
         |--P. (Plocezyga Knight 1930)PE02
         |    |--*P. (P.) corona Knight 1930 [=Hemizyga (*P.) corona]KC60
         |    |--P. (P.) acuminata (Hoare & Sturgeon 1980) [=Gamizyga (P.) acuminata]HS80a
         |    |--P. (P.) angularis (Knight 1930) [=Hemizyga angularis, Gamizyga (P.) angularis]HS80a
         |    |--P. (P.) cancellata (Mark 1912) [=Aclisina cancellata, Gamizyga (P.) cancellata]HS80a
         |    |--P. (P.) conica (Hoare & Sturgeon 1980) [=Gamizyga (P.) conica]HS80a
         |    |--P. (P.) cordiformis (Hoare & Sturgeon 1980) [=Gamizyga (P.) cordiformis]HS80a
         |    |--P. (P.) costata (Mark 1912) [=Aclisina costata, Gamizyga (P.) costata]HS80a
         |    |--P. (P.) delicata (Hoare & Sturgeon 1980) [=Gamizyga (P.) delicata]HS80a
         |    |--P. (P.) excellens (Hoare & Sturgeon 1980) [=Gamizyga (P.) excellens]HS80a
         |    |--P. (P.) intermedia (Hoare & Sturgeon 1980) [=Gamizyga (P.) intermedia]HS80a
         |    |--P. (P.) lineata (Hoare & Sturgeon 1980) [=Gamizyga (P.) lineata]HS80a
         |    |--P. (P.) lirata (Hoare & Sturgeon 1980) [=Gamizyga (P.) lirata]HS80a
         |    |--P. (P.) markae (Hoare & Sturgeon 1980) [=Gamizyga (P.) markae]HS80a
         |    |--P. (P.) obscura (Hoare & Sturgeon 1980) [=Gamizyga (P.) obscura]HS80a
         |    |--P. (P.) ornata (Mark 1912) [=Aclisina ornata, Gamizyga (P.) ornata]HS80a
         |    |--P. (P.) ornatissima (Hoare & Sturgeon 1980) [=Gamizyga (P.) ornatissima]HS80a
         |    |--P. (P.) percostata (Knight 1930) [=Hemizyga (P.) percostata, Gamizyga (P.) percostata]HS80a
         |    |    |--P. p. percostataHS80a
         |    |    `--P. p. subrotunda (Hoare & Sturgeon 1980) [=Gamizyga (Plocezyga) percostata subrotunda]HS80a
         |    |--P. (P.) perminuta (Hoare & Sturgeon 1980) [=Gamizyga (P.) perminuta]HS80a
         |    |--P. (P.) regularia (Hoare & Sturgeon 1980) [=Gamizyga (P.) regularia]HS80a
         |    |--P. (P.) subnodosa (Hoare & Sturgeon 1980) [=Gamizyga (P.) subnodosa]HS80a
         |    |--P. (P.) subquadrata (Hoare & Sturgeon 1980) [=Gamizyga (P.) subquadrata]HS80a
         |    |--P. (P.) turbinata (Hoare & Sturgeon 1980) (see below for synonymy)HS80a
         |    |--P. (P.) varica Pan & Erwin 2002PE02
         |    `--P. (P.) yunnanensis Pan & Erwin 2002PE02
         |--P. (Gamizyga Hoare & Sturgeon 1980)HS80b
         |    |--*Gamizyga’ corpulentissima (Knight 1930) [=Hemizyga corpulentissima]HS80a
         |    |--‘Gamizyga’ (G.) attenuata Hoare & Sturgeon 1980HS80a
         |    |--‘Gamizyga’ (G.) corbis (Knight 1930) [=Hemizyga corbis]HS80a
         |    |--‘Gamizyga’ (G.) expansa Hoare & Sturgeon 1980HS80a
         |    |--‘Gamizyga’ (G.) girtyi Hoare & Sturgeon 1980HS80a
         |    |--‘Gamizyga’ (G.) illineata (Knight 1930) [=Hemizyga illineata]HS80a
         |    |--‘Gamizyga’ (G.) inflata (Knight 1930) [=Hemizyga inflata]HS80a
         |    |--‘Gamizyga’ (G.) morningstarae Hoare & Sturgeon 1980HS80a
         |    `--‘Gamizyga’ (G.) nitida Hoare & Sturgeon 1980HS80a
         `--P. (Hyphantozyga Knight 1930)PE02
              |--P. (*H.) gracilis (Knight 1930)PE02 [=Hemizyga (*H.) gracilisPE02, Gamizyga (H.) gracilisHS80a]
              |--P. (H.) fenestrata (Hoare & Sturgeon 1980) [=Gamigyza (H.) fenestrata]PE02
              |--‘Gamizyga’ (H.) filicosta (Hoare 1961) [=Hemizyga (H.) filicosta]HS80a
              |--‘Gamizyga’ (H.) fusiforma Hoare & Sturgeon 1980HS80a
              |--‘Gamizyga’ (H.) grandis Hoare & Sturgeon 1980HS80a
              |--‘Gamizyga’ (H.) knighti Hoare & Sturgeon 1980HS80a
              |--P. (H.) matanensis (Pan & Yu 1993) [=Hemizyga (H.) matanensis]PE02
              |--‘Gamizyga’ (H.) perattenuata Hoare & Sturgeon 1980HS80a
              |--‘Gamizyga’ (H.) pulchra Hoare & Sturgeon 1980HS80a
              `--‘Gamizyga’ (H.) textilis Hoare & Sturgeon 1980HS80a

Plocezyga (Plocezyga) turbinata (Hoare & Sturgeon 1980) [=Gamizyga (P.) turbinata; incl. Hemizyga cancellata Sayre 1930 non Aclisina cancellata Mark 1912]HS80a

*Pseudozygopleura semicostatum (Meek 1872)PE02 [=Loxonema semicotatumBR17, L. attenuata semicostataKC60, Palaeostylus (*Pseudozygopleura) semicostatusKC60]

*Type species of generic name indicated


[B91] Bandel, K. 1991. Über triassische “Loxonematoidea” und ihre Beziehungen zu rezenten und paläozoischen Schnecken. Paläontologische Zeitschrift 65 (3–4): 239–268.

[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1–2): 1–397.

[BR17] Bouchet, P., J.-P. Rocroi, B. Hausdorf, A. Kaim, Y. Kano, A. Nützel, P. Parkhaev, M. Schrödl & E. E. Strong. 2017. Revised classification, nomenclator and typification of gastropod and monoplacophoran families. Malacologia 61 (1–2): 1–526.

[C80] Chen R.-Y. 1980. Yaoxianospira, a new genus of Gastropoda from the Taoqipo Formation in Yaoxian of Shaanxi. Acta Palaeontologica Sinica 19 (5): 421–422.

[HS80a] Hoare, R. D., & M. T. Sturgeon. 1980a. The Pennsylvanian pseudozygopleurid gastropod genus Gamizyga n. gen. from Ohio and West Virginia. Journal of Paleontology 54 (1): 159–187.

[HS80b] Hoare, R. D. & M. T. Sturgeon. 1980b. Gamizyga: a correction. Journal of Paleontology 54 (5): 1101.

[KC60] Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda: systematic descriptions. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1: Mollusca—General Features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—General Features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I169–I331. Geological Society of America, and University of Kansas Press.

[PE02] Pan, H.-Z., & D. H. Erwin. 2002. Gastropods from the Permian of Guangxi and Yunnan Provinces, south China. Journal of Paleontology 76 (Memoir 56): 1–49.

[TTE93] Tracey, S., J. A. Todd & D. H. Erwin. 1993. Mollusca: Gastropoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 131–167. Chapman & Hall: London.

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