Xylabion

Xylabion sp., from the American Museum of Natural History.

Belongs within: Cheirurinae.

Xylabion is an Ordovician genus of trilobites bearing three pairs of spines on the pygidium, with the outer pair curved backwards.

Characters (from Ludvigsen 1977): Glabella quadrate, anterolateral corners rounded; glabellar furrows long (exsag.), nearly transverse; cephalic borders flat. Pygidium with three pairs of spines, graduated in length; anterior pair longest, curving outwards and backwards.

<==Xylabion Lane 1971 PVP85
    |--*X. gelasinosum (Portlock 1843) PVP85
    |--X. biformis (Maksimova 1955) PVP85
    |--X. craigense (Tripp 1954) PVP85
    |--X. elongatum (Cooper 1930) PVP85
    |--X. frequens (Chugaeva 1968) PVP85
    |--X. gilvum (Koroleva 1959) PVP85
    |--X. helgoeyense (Nikolaisen 1961) PVP85
    |--X. jakovlevi (Chugaeva 1958) PVP85
    |--X. kasachstanicum (Chugaeva 1958) PVP85
    |--X. kassini (Chugaeva 1958) PVP85
    |--X. kluevkaensis (Balashova 1959) PVP85
    |--X. longisulcatum (Chugaeva 1975) PVP85
    |--X. meekanum (Miller 1889) PVP85
    |--X. nordicum (Balashova 1959) PVP85
    |--X. sexermis (Öpik 1937) PVP85
    |--X. susceptum (Reed 1931) PVP85
    `--X. taimyricum (Balashova 1959) PVP85

*Type species of generic name indicated

REFERENCES

Ludvigsen, R. 1977. The Ordovician trilobite Ceraurinus Barton in North America. Journal of Paleontology 51 (5): 959-972.

[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.