Trilobite Tip of the Month:


February 2001:

Kainops raymondi eye, Haragan Formation, Lower Devonian, Arbuckle Mts., Okla.

Paciphacops campbelli eye, Haragan Formation, Lower Devonian, Arbuckle Mts., Okla.

Differences between Paciphacops Maksimova, 1972 and Kainops Ramsköld and Werdelin, 1991

     Both genera occur in the Haragan Formation, Lower Devonian of Oklahoma (as well as elsewhere in North America, Czech Republic, Australia, and possibly Russia). From the Haragan Formation, Campbell (1977) described 1 species, Paciphacops raymondi, with 2 morphs: large-eyed and small-eyed morphs. These 2 morphs (as well as some of those previously assigned to other Paciphacops species) were determined by Ramsköld and Werdelin (1991) to actually belong to separate species, indeed even separate genera. The large-eyed morph of P. raymondi was assigned to the genus Kainops and the small-eyed morph was called Paciphacops campbelli Ramsköld and Werdelin, 1991.
     Differences between Kainops raymondi and Paciphacops campbelli are mainly in the eyes. K. raymondi has larger eyes with 6-7 lenses in a dorsoventral file, while P. campbelli has smaller eyes with 3-4 lenses in a dorsoventral file. The sclera in the eyes of Paciphacops is strongly thickened, while Kainops have “normal” sclera (which are thickened dorsally only). Also, the pygidial axis of P. raymondi is is considerably wider than that of K. raymondi.
     These, plus a few other character differences proved sufficient (in the phylogenetic analysis of Ramsköld and Werdelin) to separate these species into separate genera. Kainops was erected for a clade of 6 species formerly assigned to some Paciphacops and Ananaspis species (K. microps, K. ekphymus, K. guttulus, K. invius, K. raymondi, and K. veles), while Paciphacops was generically restricted to include about 9 species (P. birdsongensis, P. campbelli, P. crosslei, P. eldredgei, P. hudsonicus, P. latigenalis, P. logani, P. serratus, and P. sp. nov. Ramsköld and Werdelin, 1991). Ananaspis was restricted to 5 species in a monophyletic clade, with a few species formerly assigned treated as inncertae cedis (“Ananaspis”).
     If anyone has any other information regarding this topic, please contact Kevin.

References:

Campbell, K.S.W. (1977)  Trilobites of the Haragan, Bois d’Arc and Frisco Formations (Early Devonian), Arbuckle Mountains region, Oklahoma. Bull. Okla. Geol. Surv. 123:i-iv, 1-227

Ramsköld, L. and Werdelin, L. (1991)  The Phylogeny and Evolution of some Phacopid Trilobites. Cladistics 7:29-74