nov., Khoshyeilaq Formation (Upper Devonian, Famennian) of the eastern Alborz Mountains, Iran; (2) Phacops (Omegops) paiensis Farsan, 1998, late Famennian (Strunian) of Herat Province, Afghanistan; (3) Phacops (Omegops) cf.
?1998 Phacops (Omegops) accipitrinus accipitrinus (Phillips, 1841); Farsan, p.
?1998 Phacops (Omegops) accipitrinus maretiolensis Richter & Richter, 1933; Farsan, p.
Originally they were assigned by Salter to Phacops latifrons (Bronn, 1825), but subsequently included in the synonymy of Omegops accipitrinus accipitrinus by Richter & Richter (1933), which was also confirmed by Morris (1988) in his review of British trilobites.
A large trilobite (Phacops
sp.) found without a tail, has had one from another specimen skillfully grafted into the matrix.
Collections made from weathered surface exposures along the banks of drainage ditches at this location include, in descending abundance and diversity, brachiopods (e.g., Callipleura sp., Chonetes sp., Mucrospirifer prolificus, Schizoporia ferronensis), anthozoans (e.g., Aulopora sp., Heliophyllum halli bellense, Pluerodictyum cornu), bryozoans, crinoids (Gennaeocrinus variabilis), ostracods, trilobites (Phacops
rana), bivalves (?Cornellites sp.), and tentaculids (Tentaculites attenuatus).
Deeper water biofacies constituting the upper portion of the stratigraphic section are dominated by a trilobite-cephalopod-gastropod assemblage primarily defined by Phacops
sp./Greenops sp.-Stracocera sp.- Cyclonema sp.
Together, we counted rows of Phacops rana's eyes to show that the sudden increase in number demonstrated sudden speciation; while abroad, Scots working in the same formation, once joined to ours, counted ribs to prove that change was gradual.
Phacops rana usually occurred in three sections (hence tri-lobite), like a crab shell from which the crab has departed.