REVISION OF THE TRILOBITES OF THE SILURIAN HENRYHOUSE FORMATION OF OKLAHOMA

The Henryhouse Formation is a Late Silurian (basal Ludlow to end-Přídolí) unit of the Hunton Group, developed in the Southern Oklahoma Aulacogen. The formation is mainly composed of argillaceous limestones with inferred environments of deposition from shallow subtidal to supratidal. The upper member of the formation is Ludfordian (Ozarkodina snajdri conodont biozone) to late Přídolí in age and yields a prolific and moderately diverse trilobite fauna featuring common articulated exoskeletons. The environment of deposition was likely a low-energy, shallow marine carbonate ramp. The fauna was originally described by Campbell over 50 years ago. During the intervening half century, additional taxa have been discovered by vocational paleontologists, and the species described by Campbell are in need of modern revision.

Campbell's work identified 11 species of trilobites in the Henryhouse; a single new species of aulacopleurid was described in 1996, and ongoing collecting has yielded a further seven new species for a total of 19 now known from the unit. The fauna is numerically dominated by calymenids (49% of the 520 currently available specimens), followed by dalmanitids (16%) and phacopids (13%). Other groups make up 5% or less of the fauna. These proportions are based on museum collections, and hence may reflect collecting bias, for example in favor of articulated specimens.

Including the Henryhouse species, only 37 Late Silurian Laurentian trilobite species have been formally named. There are obvious faunal similarities between the Henryhouse and the coeval biotas of the Brownsville Formation, Tennessee (which is also dominated by calymenids, and which shares an encrinurid species with the Henryhouse), and the Hardwood Mountain Formation, Maine (shared genera include Proetus s.s., Fragiscutum, Dalmanites, and Kettneraspis).

New trilobite taxa from the Henryhouse include two new species of the lichid Belenopyge, and new species of the odontopleurid Kettneraspis, the phacopid Paciphacops, the cheirurid Cheirurus, the dalmanitid Dalmanites, and the harpetid Scotoharpes. All are represented by articulated individuals.