Specimens of Hyolithes bisulcatus, from Malinky (2002). Figs 10, 13 and 14 are dorsal views; figs 11 and 15 are lateral; figs 12 and 16 are ventral.

Belongs within: Hyolitha.

The Hyolithidae were a family of hyoliths found during the Cambrian and Ordovician. Though the circumscription of the family has varied widely over the years (and the type genus, Hyolithes, seems to have long been the default repository for almost any hyolith), it was defined by Kruse (2002) as including those species in which a ligula is present on the venter, and the dorsoventral transition is decoupled from the lateral transition such that the venter perimeter is greater than the dorsal perimeter. Malinky (2002) indicated that Hyolithes should be restricted to species possessing a lateral furrow near each edge of the dorsum. He also classified the genera Diplotheca and Camerotheca within the Hyolithidae (the latter as a synonym of Hyolithes). These two genera had previously been classified separately on the basis of the structure of the shell apex, which was supposed to be cylindrical and septate rather than simply conical as in Hyolithidae, but Malinky (1990) demonstrated that these supposed characters were not visible in the original specimens.

<==Hyolithidae [Camerothecida, Camerothecidae, Camerothecina, Diplothecida, Diplothecidae, Diplothecina]
    |--Novakotheca Malinky 1990 M02
    |--Raitilites Marek 1989 K02
    |--Hallotheca Malinky, Linsely & Yochelson 1987 M02
    |--Korilithes Missarzhevsky 1969 M02
    |--Joachimilites Marek 1967 K02
    |    `--J. modestus MB05
    |--Yalarrnga Kruse 2002 K02
    |    `--*Y. mara Kruse 2002 K02
    |--Diplotheca Matthew 1885 M90
    |    `--*D. hyattiana Matthew 1885 (see below for synonymy) M90
    |--Helenia Walcott 1889 F62
    |    `--*H. bella Walcott 1889 F62
    |--Sololites Marek 1967 K02
    |    |--*S. ferrigenus Marek 1967 K02
    |    `--S. kankari Kruse 2002 K02
    |--Nitoricornus Syssoiev 1973 M90
    |    |--N. communis (Billings 1872) M90
    |    |--N. danianum (Matthew in Walcott 1884) [=Hyolithes danianus, Camerotheca daniana] M90
    |    `--N. impar (Ford 1872) M90
    |--Carinolithes Syssoiev 1958 M02
    |    |--*C. pennatulus (Holm 1893) [=Hyolithus pennatulus] M02
    |    |--C. hospes (Holm 1893) [=Hyolithes hospes, Hyolithes hospe (l. c.), Hyolithus (l. c.) hospes] M02
    |    |--‘Hyolithus’ pennatuloides Cobbold & Pocock 1934 M02
    |    |--C. tantulus Marek 1967 M02
    |    |--C. tjikilirri Kruse 2002 K02
    |    `--C. triumvir (Holm 1893) [=Hyolithes triumvir, Hyolithus (l. c.) triumvir] M02
    `--Hyolithes Eichwald 1840 M02 (see below for synonymy)
         |--*H. acutus Eichwald 1840 M02
         |--H. acadica Hartt in Walcott 1884 (see below for synonymy) M90
         |--H. angustus M02
         |--H. ardmillanensis M02
         |--H. arenophilus Holm 1893 M02
         |--H. attenuatus Walcott 1890 M02
         |--H. bicostatus Novák 1891 M02
         |--H. bisulcatus Holm 1893 [=Hyolithus (l. c.) bisulcatus] M02
         |--H. communis Tate 1892 K02
         |--H. concinnus Holm 1893 [=Hyolithus (l. c.) concinnus] M02
         |--H. conularoides Tate 1892 K02
         |--H. costatus Matthew 1901 M90
         |--H. costulatus Barrande 1867 M02
         |--H. degeeri Holm 1893 M02
         |--H. giganteus MB05
         |--H. gracilior Matthew 1895 M90
         |--H. gracilis Matthew 1885 [=Hyolithes (*Camerotheca) gracilis] M90
         |--H. gracillimus Matthew 1901 M90
         |--H. gregaria W77
         |--H. hathewayi F62
         |--H. incurvatus Novák 1891 M02
         |--H. innotatus Holm 1893 [=Hyolithus (l. c.) innotatus] M02
         |--H. lanceolatus (Morris 1845) [=Theca lanceolatus] F62
         |--H. latus Eichwald 1860 [incl. H. latus var. recidivus] M02
         |--H. lineatus Kjerulf 1865 M02
         |--H. lineolatus Salter in Salter & Blandford 1865 M02
         |--H. magnificus F62
         |--H. micmac Matthew in Walcott 1884 [=H. (Camerotheca) micmac, H. (Orthotheca) micmac] M90
         |--H. norvegicus Kjerulf 1865 [incl. Theca elegantula Kjerulf 1865] M02
         |--H. obesus (n. d.) M02
         |--H. orientalis Waagen 1880 PY84
         |--H. poulseni Resser 1938 M02
         |--H. primordialis (Hall 1861) [=Theca primordialis] W77
         |--H. princeps F62
         |--H. tenuistriatus L95
         |--H. triangularis Portlock 1843 M02
         `--H. tricarinatus F62

Nomen nudum: Camerotheca snajdri Syssoiev 1962 M90

*Diplotheca hyattiana Matthew 1885 [=Hyolithes hyattianus; incl. D. hyattiana var. caudata Matthew 1885, H. caudatus] M90

Hyolithes Eichwald 1840 M02 [=Hyolithus (l. c.) M02; incl. Camerotheca Matthew 1885 M90, Centrotheca Salter 1866 F62, Cleidotheca Salter 1866 F62, Cleodora Ludwig 1864 nec Péron & Lesueur 1810 nec Mulsant 1850 F62, Orthoceras Münster 1840 non Bruguière 1789 F62, Pugiunculus Barrande 1847 F62, Vaginella d’Orbigny 1850 F62]

Hyolithes acadica Hartt in Walcott 1884 [=Diplotheca acadica, Theca acadica; incl. D. a. var. crassa Matthew 1885, Hyolithes crassus, D. a. var. obtusa Matthew 1886, D. a. var. sericea Matthew 1886, Hyolithes sericeus] M90

*Type species of generic name indicated


[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.

[M90] Malinky, J. M. 1990. Cambrian Hyolitha from northeast Canada: reappraisal of the hyolith orders Camerothecida and Diplothecida. Journal of Paleontology 64 (4): 587–595.

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

[MB05] Mus, M. 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.

[W77] White, C. A. 1877. Report upon the invertebrate fossils collected in portions of Nevada, Utah, Colorado, New Mexico, and Arizona, by parties of the expeditions of 1871, 1872, 1873, and 1874. U.S. Geographical Surveys West of the One Hundredth Meridian 4 (1): 1–219, pls 1–21.

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