Reconstruction of Gotlandochiton interplicatus, from Smith (1960).

Belongs within: Sachitida.
Contains: Chelodina, Neoloricata, Solenogastres, Caudofoveata.

The Polyplacophora includes the chitons, molluscs in which the test is comprised of a series of separate overlapping valves surrounded by a spicular girdle. Living chitons had eight valves, but varying numbers are found in stem-group chitons. In the Ordovician to Cretaceous Chelodina, the test contained eight generally thick and massive valves that lacked an articulamentum layer at the junction between valves (Smith 1960).

Aculifera [Chelodida, Eoplacophora, Mattheva, Mattheviidae, Matthevina, Paleoloricata]SB12
    |  i. s.: SpicuchelodesJB12
    |         Preacanthochiton [Preacanthochitonidae]BE93
    |           |--P. cooperi Bergenhayn 1960BE93
    |           |--P. depressus Bergenhayn 1960BE93
    |           `--P. productus Bergenhayn 1960BE93
    |         HemithecellaCRF04
    |         ConodiaCRF04
    |         CalceochitonCRF04
    |--Polyplacophora (see below for synonymy)SB12
    |    |  i. s.: ArctoplaxSB01
    |    |         Cobcrephora Bischoff 1981 [Cobcrephoridae, Phosphatoloricata, Phosphatoloricatida]SHC01
    |    |           |--C. corrugataBRW98
    |    |           `--C. silurica Bischoff 1981BE93
    |    |         Acanthopleurus echinatus (Barne 1842)Y08
    |    |         Ocruranus Liu 1979BR17
    |    |           |--O. finialP08
    |    |           `--O. trulliformisP08
    |    |         Eohalobia diandongensisEL11, P08
    |    |         Sinuconus Yu 1979 [Sinuconidae]BR17
    |    |           `--*S. clypeus Yu 1979BR17
    |    |--ChelodinaVWR04
    |    `--+--NeoloricataVWR04
    |       `--+--Echinochiton dufoeiVWR04
    |          `--+--Rhombichiton DeKoninck 1883SB12, S60 [=Rhombochiton (l. c.) non Berry 1919S60]
    |             `--Multiplacophora [Hercolepadida]VWR04
    |                  |  i. s.: Diadeloplax paragrapsimaVWR04
    |                  |         AenigmatectusVWR04
    |                  |         Deltaplax Puchalski et al. 2009SB12
    |                  |         Polysacos Vendrasco, Wood & Runnegar 2004VWR04
    |                  |           `--*P. vickersianum Vendrasco, Wood & Runnegar 2004VWR04
    |                  |         Strobilepis Clarke 1888VWR04
    |                  |           `--S. spinigera Clarke 1888VWR04
    |                  `--HercolepadidaeWS93
    |                       |--Hercolepas signata (Aurivillius 1892)VWR04, WS93
    |                       `--ProtobalanusWS93
    |                            |--P. hamiltonensis Hall & Clarke 1888WS93
    |                            `--P. spinicoronatusVP17
    `--Aplacophora [Scolecomorpha, Telobranchia]SB12
         |  i. s.: Crystallophrisson nitensI96
         |    |--Acutichiton etheridgei Smith & Hoare 1987SB12, BE93
         |    |--Elachychiton juxtaterminus Hoare & Mapes 1985BE93
         |    `--SoleachitonBE93
         |         |--S. soleaformis (Etheridge 1882)BE93
         |         `--S. yochelsoni Hoare & Smith 1984BE93
         |--Septemchitonidae [Septemchitonida, Septemchitonina]BE93
         |    |--+--Bursata santacrucensis Dzik 1994D94
         |    |  `--Solenocaris Young & Young 1868D94, S60
         |    |       |--*S. solenoides Young & Young 1868S60
         |    |       `--S. elongata (Hadding 1913)BE93
         |    `--+--Sarkachiton kielcensis Dzik 1994D94
         |       |--Carnicoleus gazdzickii Dzik 1986D94
         |       `--Septemchiton Bergenhayn 1955SB12, S60
         |            |--*S. vermiformis Bergenhayn 1955S60
         |            |--S. grayiae (Woodward 1885)BE93
         |            `--S. thraivensis (Reed 1911)BE93
            |  `--GenitoconiaVP17
            `--+--Phthipodochiton thraivensis [=Helminthochiton thraivensis]SB12
               `--+--Kulindroplax Sutton, Briggs et al. 2012SB12
                  |    `--*K. perissokomos Sutton, Briggs et al. 2012SB12
                  `--+--Matthevia Walcott 1885SB12, S60
                     |    |--*M. variabilis Walcott 1885F62
                     |    |--M. wahwahensisVP17
                     |    `--M. walcotti Runnegar et al. 1979BE93
                        `--Acaenoplax Sutton, Briggs et al. 2001SB12, SB01
                             `--*A. hayae Sutton, Briggs et al. 2001SB01

Polyplacophora [Crepipoda, Lamellata, Lepidoglossa, Loricata, Placophora, Polybranchiata, Polyplaciphora, Polyplakiphora, Polyplaxiphora, Polyplaxiphorae]SB12

*Type species of generic name indicated


[BRW98] Beesley, P. L., G. J. B. Ross & A. Wells (eds) 1998. Fauna of Australia vol. 5. Mollusca: The Southern Synthesis. Part A. Australian Biological Resources Study: Canberra.

[BE93] Benton, M. J., & D. H. Erwin. 1993. Mollusca: Amphineura and ‘Monoplacophora’. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 125–130. Chapman & Hall: London.

[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.

[CRF04] Cherns, L., D. M. Rohr & J. Frýda. 2004. Polyplacophoran and symmetrical univalve mollusks. In: Webby, B. D., F. Paris, M. L. Droser & I. G. Percival (eds) The Great Ordovician Biodiversification Event pp. 179–183. Columbia University Press.

[D94] Dzik, J. 1994. Evolution of ‘small shelly fossils’ assemblages of the early Paleozoic. Acta Palaeontologica Polonica 39 (3): 247–313.

[EL11] Erwin, D. H., M. Laflamme, S. M. Tweedt, E. A. Sperling, D. Pisani & K. J. Peterson. 2011. The Cambrian conundrum: early divergence and later ecological success in the early history of animals. Science 334: 1091–1097.

[F62] Fisher, D. W. 1962. Small conoidal shells of uncertain affinities. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt W. Miscellanea: Conodonts, Conoidal Shells of Uncertain Affinities, Worms, Trace Fossils and Problematica pp. W98–W143. Geological Society of America, and University of Kansas Press.

[I96] Ivanov, D. L. 1996. Origin of Aculifera and problems of monophyly of higher taxa in molluscs. In: Taylor, J. D. (ed.) Origin and Evolutionary Radiation of the Mollusca pp. 59–65. Oxford University Press: Oxford.

[JB12] Johnson, M. E., & B. G. Baarli. 2012. Development of intertidal biotas through Phanerozoic time. In: Talent, J. A. (ed.) Earth and Life: Global biodiversity, extinction intervals and biogeographic perturbations through time pp. 63–128. Springer.

[P08] Parkhaev, P. Y. 2008. The Early Cambrian radiation of Mollusca. In: Ponder, W. F., & D. R. Lindberg (eds) Phylogeny and Evolution of the Mollusca pp. 33–69. University of California Press: Berkeley.

[S60] Smith, A. G. 1960. Amphineura. 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. I41–I76. Geological Society of America, and University of Kansas Press.

[SB01] Sutton, M. D., D. E. G. Briggs, D. J. Siveter & D. J. Siveter. 2001. An exceptionally preserved vermiform mollusc from the Silurian of England. Nature 410: 461–463.

[SB12] Sutton, M. D., D. E. G. Briggs, D. J. Siveter, D. J. Siveter & J. D. Sigwart. 2012. A Silurian armoured aplacophoran and implications for molluscan phylogeny. Nature 490: 94–97.

[SHC01] Sutton, M. D., L E. Holmer & L Cherns. 2001. Small problematic phosphatic sclerites from the Ordovician of Iapetus. Journal of Paleontology 75 (1): 1–8.

[VWR04] Vendrasco, M. J., T. E. Wood & B. N. Runnegar. 2004. Articulated Palaeozoic fossil with 17 plates greatly expands disparity of early chitons. Nature 429: 288–291.

[VP17] Vinther, J., L. Parry, D. E. G. Briggs & P. Van Roy. 2017. Ancestral morphology of crown-group molluscs revealed by a new Ordovician stem aculiferan. Nature 542: 471–474.

[WS93] Wills, M. A., & J. J. Sepkoski Jr. 1993. Problematica. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 543–554. Chapman & Hall: London.

[Y08] Yu W. 2008. On the genus Yangtzemerisma and related genera (Mollusca: Merismoconchia). Records of the Western Australian Museum 24 (2): 181–194.

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