Hyolitha

Belongs within: Tannuolinidae.
Contains: Circothecida, Orthothecida, Sulcavitida, Hyolithidae, Crispatellidae.

Hyoliths were a group of small shelled animals that mostly lived during the Cambrian and Ordovician (though probable hyoliths remained alive as late as the Permian—Peel & Yochelson 1984). They possessed a bilaterally symmetrical conical shell that was open at one end only and closed by an operculum (Kruse 2002). The relationship of hyoliths to other animals is uncertain—they have most often been treated as molluscs but commonly almost by default. Recent authors have preferred an affinity to brachiozoans.

Hyoliths can be divided into two main groups (Kruse 2002): Orthothecimorpha (containing Circothecida and Orthothecida), in which the aperture and conch growth lines are planar, and Hyolithomorpha (containing Sulcavitida and Hyolithida), in which the aperture has a prominent ventral ligula. Hyolithomorphs (at least) also possessed a pair of projecting struts called helens on either side of the operculum; being delicate, these are rarely preserved, so the absence to date of any records of helens in orthothecimorphs does not necessarily indicate their absence. The Middle Cambrian Globorilus globiger was separated from other hyoliths by Fisher (1962) due to its possession of a globular embryonic chamber whereas other hyoliths were supposed to lack a sharp separation between embryonic and younger parts of the shell.

<==Hyolitha [Calyptoptomatida, Hyolithoidea, Hyolithozoes]
    |--Globorilidae [Globorilida]F62
    |    |--Wyattia Taylor 1966W93, D78
    |    |    `--W. reedensis Taylor 1966W93
    |    |--Globeringa mantoensis Walcott 1905W93
    |    `--Globorilus Syssoiev 1958F62
    |         `--*G. globiger (Saito 1936) [=Hyolithes globiger]F62
    `--HyolithinaF62
         |  i. s.: PterygothecidaeF62
         |           |--Pterygotheca Novak 1891F62
         |           |    `--*P. barrandei Novak 1891F62
         |           `--Virgulaxonaria Yin 1937F62
         |                `--*V. elegans Yin 1937F62
         |--Orthothecimorpha [Orthothecomorpha]K02
         |    |--CircothecidaK02
         |    `--OrthothecidaK02
         `--HyolithomorphaK02
              |--SulcavitidaK02
              `--Hyolithida [Hyolithina]K02
                   |  i. s.: Hyptiotheca Bengtson in Bengtson et al. 1990L95
                   |           `--H. karraculum Bengtson in Bengtson et al. 1990K02
                   |         Parkula bounites Bengtson in Bengtson et al. 1990D94, K02
                   |         Nganki wumirri Kruse 1990D94
                   |         LeolitesD94
                   |           |--L. cognatusMMB05
                   |           `--L. paucicostatusMMB05
                   |         Nevadotheca Malinky 1988MB-M99
                   |           |--*N. whitei (Resser 1938) [=Hyolithes whitei]MB-M99
                   |           |--N. arenophilus (Holm 1893) (see below for synonymy)MB-M99
                   |           |--N. excellens (Billings 1872) [=Hyolithes excellens]MB-M99
                   |           |--N. heckeli Malinky 1989MB-M99
                   |           |--N. princeps (Billings 1872) [=Hyolithes princeps]MB-M99
                   |           |--N. socialis (Linnarsson 1871) (see below for synonymy)MB-M99
                   |           |--‘Hyolithes’ tenuistriatus Linnarsson 1871MB-M99
                   |           `--‘Hyolithus’ terranovicus Walcott 1891M02
                   |         Slapylites Marek 1980MB-M99
                   |           `--*S. signatulus (Novák 1891)MB-M99
                   |         Maxilites Marek 1972MB-M99
                   |           |--M. robustus (Barrande 1867)MMB05
                   |           `--M. snajdri Marek 1972MMB05
                   |         Dipterygovitus Qian 1989MB-M99
                   |--HyolithidaeK02
                   |--CrispatellidaeM02
                   `--Galicornus [Galicornidae]W93
                        |--G. anabarus Valkov 1975W93
                        `--G. lenaicus Valkov 1975W93

Hyolitha incertae sedis:
  CupitthecaK02
    |--C. clathrata (Bengtson in Bengtson et al. 1990)K02
    |--C. hemicyclata (Bengtson in Bengtson et al. 1990)K02
    `--C. holocyclata (Bengtson in Bengtson et al. 1990)K02
  ‘Salterella’ planoconvexa Tate 1892K02
  Triplicatella Conway Morris in Bengtson et al. 1990K02, CA06
    `--T. disdoma Conway Morris in Bengtson et al. 1990K02
  Globoritubulus Qian & Zhang 1985K02
  Eumorpholites bouceki Marek 1967K02
  ElegantilitesK02
    |--E. elegans (Barrande 1867)MB-M99
    `--E. tigris Marek 1967K02
  Emarites Marek, Malinky & Geyer 1997M02
  Polylopia Clark 1925M02
    `--*P. billingsi (Safford 1869) [=Salterella billingsi]F62
  Ensitheca Duan 1984M02
  Toxeumorphoridae [Toxeumorphorida]PY84
    |--Pseudotoxeuma magnifica Shimanskiy 1963PY84
    |--ToxeumorphoraPY84
    |    |--T. dombarense Shimanskiy 1963PY84
    |    `--T. langi Shimanskiy 1963PY84
    `--Macrotheca Waagen 1880PY84
         |--*M. wynnei Waagen 1880PY84
         |--M. almgreeni Peel & Yochelson 1984PY84
         `--M. timorensis Wanner 1941PY84
  Gompholites striatulus (Barrande 1847)MMB05
  Tizilites creberMMB05
  Dilytes occultusMMB05
  OboedalitesMMB05
    |--O. oboediensMMB05
    `--O. peregrinusMMB05
  Chimerolites temperatusMMB05
  Paolites obviusMMB05
  Kygmaeoceras Flower 1954F62
    `--*K. perplexum Flower 1954F62
  Pharetrella Hall 1888F62
    `--*P. tenebrosa Hall 1888F62
  Phragmotheca Barrande 1867F62
    `--*P. bohemica Barrande 1867F62
  Quinquelithes Syssoiev 1958F62
    `--*Q. pavonaceus Syssoiev 1958F62
  Hemicosmorthoceras laterculum Ristedt 1968D94
  Parahyolithes danicus Poulsen 1969MB-M99
  Insolitotheca Landing & Bartowski 1996MB-M99
  Sysoieva exilis Marek, Malinky & Geyer 1997CA06
  Neogloborilus hymenodes (Duan & Xiao in Qian et al. 2000)CA06
  Egdetheca Missarzhevsky 1969D78
  Kotuyitheca Missarzhevsky 1974D78

Nevadotheca arenophilus (Holm 1893) [=Hyolithus arenophilus, Hyolithes arenophilus, Linevitus arenophilus]^MB-M99

Nevadotheca socialis (Linnarsson 1871) [=Hyolithus socialis, Dorsolinevitus socialis, Hyolithes socialis, Linevitus socialis]^MB-M99

*Type species of generic name indicated

References

[CA06] Clausen, S., & J. J. Álvaro. 2006. Skeletonized microfossils from the Lower–Middle Cambrian transition of the Cantabrian Mountains, northern Spain. Acta Palaeontologica Polonica 51 (2): 223–238.

[D78] Durham, J. W. 1978. The probable metazoan biota of the Precambrian as indicated by the subsequent record. Ann. Rev. Earth Planet Sci. 6: 21–42.

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

[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.

[K02] Kruse, P. D. 2002. Biostratigraphic potential of Middle Cambrian hyoliths from the eastern Georgina Basin. Alcheringa 26: 353–398.

[L95] Landing, E. 1995. Upper Placentian–Branchian series of mainland Nova Scotia (middle–upper Lower Cambrian): faunas, paleoenvironments, and stratigraphic revision. Journal of Paleontology 69 (3): 475–495.

[M02] Malinky, J. M. 2002. A revision of Early to Mid Ordovician hyoliths from Sweden. Palaeontology 45: 511–555.

[MB-M99] Malinky, J. M., & V. Berg-Madsen. 1999. A revision of Holm’s Early and early Mid Cambrian hyoliths of Sweden. Palaeontology 42: 25–65.

[MMB05] Martí Mus, M., & J. Bergström. 2005. The morphology of hyolithids and its functional implications. Palaeontology 48 (6): 1139–1167.

[PY84] Peel, J. S., & E. L. Yochelson. 1984. Permian Toxeumorphorida from Greenland: an appraisal of the molluscan class Xenoconchia. Lethaia 17: 211–221.

[W93] Wills, M. A. 1993. ?Mollusca incertae sedis. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 265–270. Chapman & Hall: London.