Pygidia of Cydonocephalus cf. torulus, from Tremblay & Westrop (1991).

Belongs within: Phacopida.
Contains: Acanthoparyphinae, Heliomera, Sphaerexochus.

The Sphaerexochinae are a group of trilobites known from the Upper Cambrian to the Upper Silurian. Mature sphaerexochines may have spent much of their time buried in the substrate with the head at the surface (Přibyl et al. 1985) and were possibly ambush predators.

Characters (from Přibyl et al. 1985): Exoskeleton compact, arched, mostly thick-walled; glabella large and spherically inflated; genae without marked scrobiculation; genal spines present in juveniles but absent at maturity; pygidium with leaf-like or lobate pleural spines and rounded pleural margins.

<==Sphaerexochinae [Heliomerinae]
    |  i. s.: Pompeckia Warburg 1925PVP85
    |           |--*P. wegelini (Angelin 1854)PVP85
    |           |--P. minor Warburg 1925PVP85
    |           `--P. repentina Petrunina 1975PVP85
    |  |--Parasphaerexochus Chugaeva 1973PVP85
    |  |    |--*P. galeatus Chugaeva 1973PVP85
    |  |    `--P. confragosus Chugaeva 1973PVP85
    |  `--Xystocrania Whittington 1965 [incl. Xialiangshania Chen 1975]PVP85
    |       |--*X. perforata (Billings 1865)PVP85
    |       |--X. glauca (Billings 1865)PVP85
    |       |--X. rara (Chien 1975) [=*Xialiangshania rara]PVP85
    |       `--X. unicornica (Hintze 1953)PVP85
    `--+--Emsurina Sivov 1955PVP85
       |    |--*E. sibirica Sivov 1955PVP85
       |    |--E. fulita Rosova 1960PVP85
       |    `--E. minuta Rosova 1960PVP85
       |  `--Kolymella Chugaeva 1973PVP85
       |       `--*K. plana (Chugaeva 1964)PVP85
       `--+--Forteyops Přibyl & Vaněk in Přibyl, Vaněk & Pek 1985PVP85
          |    |--*F. sexapugius (Ross 1951) [=Kawina sexapugia]PVP85
          |    |--F. approximus (Raymond 1905)PVP85
          |    |--F. divergens (Reed 1945)PVP85
          |    `--F. spinigenus (Ancygin 1977)PVP85
          |--Kawina Barton 1916PVP85
          |    |--*K. vulcanus (Billings 1865)PVP85
          |    |--K. arnoldi Whittington 1963PVP85
          |    |--K. billingsi (Raymond 1905)PVP85
          |    |--K. chazyensis (Raymond 1905)PVP85
          |    |--K. limbata Whittington 1963PVP85
          |    |--K. raripustulata (Weber 1948)PVP85
          |    `--K. webbi Hintze 1953PVP85
             `--Cydonocephalus Whittington 1963PVP85
                  |--*C. griphus Whittington 1963PVP85
                  |--C. mercurius (Billings 1865)PVP85
                  |--C. prolificus (Billings 1865)PVP85
                  |--C. prominulus Whittington 1963PVP85
                  |--C. scrobiculatus Whittington 1963PVP85
                  |--C. torulus Whittington 1963PVP85
                  |--C. trisulcatus (Chugaeva 1973)PVP85
                  `--C. wilsoni (Ross 1972)PVP85

*Type species of generic name indicated


[PVP85] Přibyl, A., J. Vaněk & I. Pek. 1985. Phylogeny and taxonomy of family Cheiruridae (Trilobita). Acta Universitatis Palackianae Olomucensis Facultas Rerum Naturalium Geographica-Geologica XXIV 83: 107–193.

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