Orthothecida

Ventral, dorsal and right lateral views of Trapezotheca aemula, from Malinky (2002).

Belongs within: Hyolitha.

The Orthothecida are a group of hyoliths defined by Kruse (2002) as including those species in which the dorsum and venter were clearly differentiated, but without a ligula along the venter. Families of Orthothecida are primarily distinguished by the shape of the cross-section. Orthothecidae have the transverse section triangular or subtriangular with a planar venter (Kruse 2002).

<==Orthothecida
    |  i. s.: ‘Hyolithes’ glabra Walcott 1911 M90
    |--Gracilitheca L95 [Gracilithecidae K02]
    |    `--G. bayonet (Matthew 1899) L95
    |--Lentitheca Syssoiev 1958 F62 [Istithecidae K02, Lentithecidae, Nikathecidae]
    |    `--*L. peracuta (Holm 1893) [=Hyolithes peracutus] F62
    |--Allathecidae (see below for synonymy) K02
    |    |--Mooritheca Val’kov 1975 K02
    |    `--Allatheca KB09
    |         |--A. cana KB09
    |         `--A. degeeri L95
    |--Quadrotheca Syssoiev 1958 [Quadrothecidae] M02
    |    |--*Q. quadrangularis (Holm 1893) (see below for synonymy) M02
    |    |--Q. rediviva Marek 1967 M02
    |    `--Q. shipaiensis Qian, Cheng & Chen 1979 M02
    |--Orthothecidae F62
    |    |--Bactrotheca Novák 1891 F62
    |    |    `--*B. teres (Barrande 1867) [=Hyolithes teres] F62
    |    |--Cryptocaris Barrande 1872 F62
    |    |    `--*C. suavis Barrande 1872 F62
    |    |--Semielliptotheca Syssoiev 1958 F62
    |    |    `--*S. rosmara (Holm 1893) (see below for synonymy) M02
    |    `--Orthotheca Novak 1886 M90
    |         |--*O. intermedia Novak 1886 F62
    |         |--O. bayonet Metthew 1899 M90
    |         |--O. pugio Matthew 1899 M90
    |         |--O. sica Matthew 1899 M90
    |         `--O. stiletto Matthew 1899 M90
    `--Novitatidae M02
         |--Novitatus Syssoiev 1968 M02
         |--Panitheca Marek 1967 K02
         |--Tcharatheca Syssoiev 1972 M02
         |--Eonovitatus Syssoiev 1968 M02
         |--Contitheca Syssoiev 1972 M02
         |--Devoniotheca Malinky 1987 M02
         |--Nephrotheca Marek 1966 K02
         |--Decoritheca Syssoiev 1972 [Decorithecidae] M02
         |    `--D. lineatula M02
         |--Foersteotheca Malinky 1987 M02
         |    |--*F. newsomensis (Foerste 1903) [=Hyolithes newsomensis] K02
         |    `--F. dubecensis (Marek 1967) [=Nephrotheca dubecensis] K02
         |--Holmitheca Syssoiev 1968 M02
         |    |--*H. obvia Syssoiev 1968 K02
         |    `--‘Hyolithes’ quadricostatus Shaler & Foerste 1888 M02
         `--Trapezotheca Syssoiev 1958 M02
              |--*T. aemula (Holm 1893) [=Hyolithus (Orthotheca) aemulus] M02
              |--T. aldanica Syssoiev 1960 M02
              |--T. dens (Holm 1893) [=Hyolithus (Orthotheca) dens, Bactrotheca dens, Semielliptotheca dens] M02
              |--‘Hyolithes’ hexagonus Barrande 1867 M02
              `--T. novaki Syssoiev 1960 [=Hyolithes quadricostatus Novák 1891 non Shaler & Foerste 1888] M02

Allathecidae [Aldanothecidae, Chelsonellidae, Curtithecidae, Exilithecidae, Fistulosithecidae, Tchuranithecidae] K02

*Quadrotheca quadrangularis (Holm 1893) [=Hyolithes (Orthotheca) quadrangularis, Bactrotheca quadrangularis, Hyolithus (l. c.) (O.) quadrangularis] M02

*Semielliptotheca rosmara (Holm 1893) [=Hyolithes (Orthotheca) rosmarus, Bactrotheca rosmarus, Hyolithus (l. c.) rosmarus, Semielliptotheca (Hyolithes) rosmarus (l. c.)] M02

*Type species of generic name indicated

REFERENCES

[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.

[KB09] Kouchinsky, A., S. Bengtson, W. Feng, R. Kutygin & A. Val’kov. 2009. The Lower Cambrian fossil anabaritids: affinities, occurrences and systematics. Journal of Systematic Palaeontology 7 (3): 241–298.

[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.