Early Paleozoic Hyolitha from North America: reexamination of Walcott's and Resser's type specimens

Abstract

Concepts of the family Hyolithidae Nicholson fide Fisher and the genera Hyolithes Eichwald and Orthotheca Novak have been expanded through time to encompass a variety of morphologically dissimilar shells. The Hyolithidae is here considered to include only those hyolithid species which have a rounded (convex) dorsum; slopes on the dorsum are inflated, and the venter may be flat or slightly inflated. Hyolithes encompasses species which possess a low dorsum and a prominent longitudinal sulcus along each edge of the dorsum; the ligula is short and the apertural rim is flared. The emended concept of Orthotheca includes only those species of orthothecid hyoliths which have a subtriangular transverse outline and longitudinal lirae covering the shell on both dorsum and venter.Eighteen species of Hyolithes and one species of Orthotheca from the Appalachian region and Western Interior were reexamined in light of more modern taxonomic concepts and standards of quality for type material. Reexamination of type specimens of H. similis Walcott from the Lower Cambrian of Newfoundland, H. whitei Resser from the Lower Cambrian of Nevada, H. billingsi Walcott from the Lower Cambrian of Nevada, H. gallatinensis Resser from the Upper Cambrian of Wyoming, and H. partitus Resser from the Middle Cambrian of Alabama indicates that none of these species represents Hyolithes. Hyolithes similis is here included under the new genus Similotheca, in the new family Similothecidae. Hyolithes whitei is designated as the type species of the new genus Nevadotheca, to which H. billingsi may also belong. Hyolithes gallatinensis is referred to Burithes Missarzhevsky with question, and H. partitus may represent Joachimilites Marek. The type or types of H. attenuatus Walcott, H. cecrops Walcott, H. comptus Howell, H. cowanensis Resser, H. curticei Resser, H. idahoensis Resser, H. prolixus Resser, H. resseri Howell, H. shaleri Walcott, H. terranovicus Walcott, and H. wanneri Resser and Howell lack shells and/or other taxonomically important features such as a complete aperture, rendering the diagnoses of these species incomplete. Their names should only be used for the type specimens until better preserved topotypes become available for study. Morphology of the types of H.? corrugatus Walcott and “Orthotheca” sola Resser does not support placement in the Hyolitha; the affinities of these species are uncertain.

A Revision of Early To Mid Ordovician Hyoliths from Sweden

“…Terms used to describe such features as nature of ornament on the shell, cross section of the conch, and type of aperture, among others, are from Malinky and Berg-Madsen (1999). The terms left and right are used in reference to the¯anks of the dorsum and to the lateral edges when viewed from the dorsal side.…”

“…Several general items, such as literature, spelling, collecting methods and registration, together with accessibility of sites, of importance for this paper as well, have been discussed in Malinky and Berg-Madsen (1999) and Berg-Madsen and Malinky (1999). Likewise, problems surrounding translations, particularly of Russian and Chinese papers into English, have been discussed previously.…”

“…Additionally no opercula have been recorded so far from the Swedish Ordovician. Possible reasons for the scarcity of these skeletal pieces were discussed in detail by Malinky and Berg-Madsen (1999).…”

“…These occurrences were also quoted by Lindstro Èm (1888) and Moberg (1890). Hyoliths were not known from the Tremadoc except from redeposited material; recorded sandstone boulders within the Obolus conglomerate containing internal moulds of Middle Cambrian hyoliths that he referred to H. arenophilus (see Malinky and Berg-Madsen 1999). Wiman (1903) recorded and ®gured a Hyolithus sp.…”

Small shelly fossils from the Montezuman–Delamaran of the Great Basin in Nevada and California

“…1; Skovsted, 2006a). The lower Cambrian hyolith fauna originally described by Walcott (1886) and Resser (1938) from Nevada were reinvestigated by Malinky (1988).…”