Phacopidae Hawle and Corda, 1847

Crônier, Catherine, 2003, Systematic relationships of the blind phacopine trilobite Trimerocephalus, with a new species from Causses-et-Veyran, Montagne Noire, Acta Palaeontologica Polonica 48 (1), pp. 55-70 : 56

Family Phacopidae Hawle and Corda, 1847 Subfamily Phacopinae Hawle and Corda, 1847 Genus Trimerocephalus McCoy, 1849

Type species: Phacops mastophthalmus Richter, 1856 (= Trinucleus ? laevis Münster, 1842); Upper Devonian (Famennian); Thuringia.

Species.— Trimerocephalus mastophthalmus ( Richter, 1856) : Lower Famennian (do II, III?), Rhineland, Harz Mts., Thuringia, Holy Cross Mts., England, South−Western Asia, Kazakhstan; Trimerocephalus caecus ( Gürich, 1896) : Lower Famennian (do II – III), Holy Cross Mts., Harz Mts., Rhineland, Thuringia, Urals Mts., North Africa, Armorican Massif; Trimerocephalus ? steinachensis ( Richter and Richter, 1926): Famennian (do II), Thuringia, Harz Mts.; Trimerocephalus cryptophthalmoides ( Maksimova, 1955) : Lower Famennian, South Urals Mts., Kazakhstan; Trimerocephalus vodorezovi ( Maksimova, 1955) : Famennian (do II), Kazakhstan; Trimerocephalus sponsor Chlupač, 1966 : Famennian (do III), Moravia, Cantabrian Mts.; Trimerocephalus lentiginosus ( Maksimova, 1955) : Famennian (do V), South Urals Mts.; Trimerocephalus polonicus Osmólska, 1958 : Famennian (do III), Holy Cross Mts.; Trimerocephalus? trifolius ( Osmólska, 1958) : Famennian (do II, III?), Holy Cross Mts.; Trimerocephalus lacunosus ( Pfeiffer, 1959) : Famennian (do II), Thuringia; Trimerocephalus dianopsoides Osmólska, 1963 : Famennian (do II?, do III), Holy Cross Mts.; Trimerocephalus procurvus Arbizu, 1985 : Famennian (do III), Cantabrian Mts., Germany; Trimerocephalus interruptus Berkowski, 1991 : Famennian (do III), Holy Cross Mts.; Trimerocephalus lelievrei Crônier and Feist, 1997 : Famennian (do III), Tafilalt ( Morocco); Trimerocephalus tardispinosus Feist and Becker, 1997 : Famennian (do II, Palmatolepis rhomboidea Zone ), Australia; Trimerocephalus shotoriensis Feist, Yasdi, and Becker , in press: Famennian (lower P. marginifera to upper P. trachytera Zone ), Eastern Iran (Shotori−Range).

Trimerocephalus ? steinachensis displays a massive bor− der, which is not covered by the glabella in dorsal view. This is analogous to Cryphops ? latilimbatus ( Maksimova, 1955) which has well developed eyes.

The discovery of new material with a trilobed cephalic outline allows redefinition of Trimerocephalus? trifolius and creation of a new species: both are attributed to Trimerocephalus (Trifoliops) subgen. nov.

Stratigraphic and geographic distribution.—The range of all species falls within the late Upper Devonian: Famennian do II–IV (acme in Lower Famennian); Europe, South−Western Asia, Kazakhstan, North−East China, North Africa and Australia.

The diversity of Upper Devonian blind phacopids coincides with the expansion of off−shore environments of external platforms ( Chlupač 1975).

These different species are widely represented in Europe: P. rhomboidea Zone in the Montagne Noire, Upper P. crepida Zone in the Harz Mts.

Besides Trimerocephalus lelievrei , only one individual belonging to the species Trimerocephalus caecus has been cited, but not figured, from North Africa ( Alberti 1970). This species is still of problematical status.

Few studies have been undertaken in South−Western Asia and Kazakhstan. Trimerocephalus lentiginosus has been discovered from the Urals Mts., in the upper Famennian ( V); but this age has not been confirmed by conodont data.