Mesonacidæ of Comley in Shropshire, with a discussion of Classification within the Family

Abstract

The trilobite family Mesonacidae was erected by Walcott (1890 b ) in his “Fauna of the Lower Cambrian or Olenellus Zone” for the genera Olenellus, Mesonacis , and their relatives, which especially characterize that rock series. The first discovery of a Mesonacid in Britain was made by C. Lapworth at Comley in Shropshire; and was recorded in 1888 in the Geological Magazine and in Nature , the species being named Olenellus callavei . In 1890 a short characterization of this species by him appeared in Walcott's above-mentioned monograph (p. 640), and Lapworth himself in 1891 described and figured the species under the name Olenellus ( Holmia ) callavei . In 1910 appeared Walcott's monograph on “Olenellus and other genera of the Mesonacidæ”. In this, Lapworth's species was illustrated and was referred to Matthew's genus Callavia , to which also was referred a new species from Comley, the characteristics of which were furnished by Raw, described below (p. 274) under Nevadia (Walcott, 1910, pp. 282–3, pl. 42, figs. 1–4). In this monograph were brought under review all the known examples of the family, many of them discovered and described by Walcott himself; and to it as well as to his previous and later papers all students of the family are indebted. Earlier than this Dr. E. S. Cobbold had commenced his intensive study of the Cambrian rocks and fauna of Shropshire, furnished not only in natural exposures and in quarries, but also by about sixty special excavations made by him, about half of which exposed Lower Cambrian rocks. In a

Phylogenetic analysis of some basal early Cambrian trilobites, the biogeographic origins of the Eutrilobita, and the timing of the Cambrian radiation

“…However, if so, that generic assignment is not correct because Paranevadella is characterized by having the ocular lobes contacting the entire lateral margin of the frontal lobe, and by having the posterior border of the cephalon deflected much further posteriorly near the genal spine than near L0. The genera the two partial cephala from the Fallotaspis Zone share the most features with are Nevadia or Nevadella Raw, 1936. The one character that suggests these speci mens have a closer relationship with Nevadia is the condition of SO, which is straight in the two specimens and in Nevadia whereas SO is typically convex in Nevadella.…”

Through a glass darkly: taxonomy, phylogeny, and biostratigraphy of the Olenellina

“…6,3), which permits this genus, originally described from badly distorted material in Spain by Sdzuy (1961), to be placed in context with the other Olenellina of the western sector of Gondwana/ peri-Gondwana. Repina (1986) (Raw, 1936) from pre-Callavia beds at Comley is a fallotaspid, a suggestion that we tentatively accept. The ranges of Olenellina within Baltica have been synthesized from scattered occurrences in Norway, Sweden, Estonia, and southern Poland and integrated into the regional lithostratigraphy by Ahlberg et al (1986) andAhlberg (1991).…”

New discoveries of the oldest trilobites Profallotaspis and Nevadella in the northeastern Siberian Platform, Russia

“…New findings of trilobites Profallotaspis (in Khomentovskiy & Repina 1965, Nevadella Raw, 1936 andParanevadella Palmer &Repina, 1993 in the north-eastern Siberian Platform have extended their distribution area and are of great importance for regional and international correlation. For now, Profallotaspis tyusserica sp.…”

“…Family Nevadiidae Hupé, 1953 Genus Nevadella Raw, 1936 Type species. -Nevadella eucharis Walcott, 1913, Cambrian Stage 3, upper "Nevadella" Zone, Canada (Cordilleran region).…”