A trilobite fauna from the highest Shineton Shales in Shropshire, and the correlation of the latest Tremadoc

Abstract

A rich fauna dominated by trilobites and calcified chordates has been collected in Shropshire from the Arenaceous Beds, the highest member of the Tremadoc Shineton Shale Formation, and hitherto regarded as poorly fossiliferous. This fauna shows that shelf conditions persisted longer in Shropshire than has been supposed. It is likely that even younger Tremadoc is cut out at the unconformity below the Caradoc in the Shineton Inlier. The correlation of the later Tremadoc is reviewed, and the nomenclature of British Tremadoc biozones is revised. The trilobites described here are a mixture of previously known and new forms. The name Shumardia (Conophrys) salopiensis Callaway is revived for British material traditionally assigned to the Scandinavian species Shumardia pusilla (Sars), from which it is distinct. The new taxa Litagnostus meniscus sp.nov., Apatokephalus sarculum sp.nov. and Skljarella cracens sp.nov. are described. The type species of Asaphellus, A. homfrayi and Leptoplastides, L. salteri, are redescribed, and Geragnostus callavei, Pseudokainella impar, and Parapilekia sp. are recorded. New information on the ontogeny of S. (C.) salopiensis and A. homfrayi is given. Litagnostus and Skljarella are recorded from the British Isles for the first time.

Taxonomy and fossils: a critical appraisal

“…Growth stages of individual taxa have received separate names, which may spuriously increase apparent diversity. Trilobites grow from larvae a millimetre long to adults some centimetres in length, during which ontogeny most of the features Fortey & Owens (1991). The Middle Cambrian trilobite Sao acquired no less than seven synonyms in this manner.…”

Lower to Middle Ordovician trilobite faunas along the Ural border of Baltica

“…List of the trilobite genera of the Uralian border of Baltica (Weber 1948;Bondarev et al 1965;Burskiy 1966Burskiy , 1970Varganov et al 1973;Antsygin 1977Antsygin , 1978Antsygin , 1991Antsygin , 1993Antsygin , 2001Antsygin et al 1977;Klyuzhina 1985;Puchkov 1991; shown with distribution on the other terranes. Main references to the faunas reviewed from different areas are as follows: Baltoscandia (Tjernvik 1956;Henningsmoen 1957;Ebbestad 1999;Żylińska 2002;Terfelt et al 2011;Pärnaste et al 2009, Argentina plus Bolivia (Robison & Pantoja-Alor 1968;Přibyl & Vaněk 1980;Waisfeld & Vaccari 2003;Tortello & Esteban 2007;Balseiro & Marengo 2008;Vaccari & Waisfeld 2008), Avalonia (Owens et al 1982;Fortey & Owens 1991), Armorica: Iberia (Álvaro et al 2007(Álvaro et al , Hammann et al 2008, Montagne Noir (Vizcaïno et al 2001, Vizcaïno & Álvaro 2003, Shergold et al 2007, Bavaria (Sdzuy et al 2001), Perunica (Mergl 2006), Turkey (Shergold & Sdzuy 1984, Dean 2006, Alborz, Iran (Ghobadi Pour 2006, Ghobadi Pour et al 2007, Bruton et al 2004, South China (Lu 1975;Peng 1990aPeng , 1990bPeng , 1...…”

Late Late Cambrian Trilobites From Near Birch Inlet, South‐Western Tasmania

“…Onchonotellus has been discussed in some detail by O È pik (1967O È pik ( ), Shergold (1980 and Shergold and Sdzuy (1984). Shergold (1980) and Shergold and Sdzuy (1984) listed the species of Onchonotellus. In addition to these species Zhang (1981, p. 169, pl.…”

“…Shergold and Sdzuy went on to suggest that the inclusion within the Eulominae of the Late Cambrian genera (i.e. Duplora Shergold, 1972, Plecteuloma Shergold, 1975and Iveria Shergold, 1980 described by Shergold (1972Shergold ( , 1975Shergold ( , 1980) from Australia, is questionable.…”

“…bexelli Zone, Mictosaukia striata-Fatocephalus Zone, Leiostegium (Leiostegium) constrictum-Shanjiawania brevica Zone (top). The presence of Saukia, Shergoldia and Mictosaukia in the Shenjiawan Formation indicates correlation with the Payntonian and early Datsonian of western Queensland (Shergold 1991). The occurrence of Lotagnostus, Charchaqia, Hedinaspis, Onchotellus and Skljarella in both the Birch Inlet fauna and the Shenjiawan Formation indicates that they are correlatives (Text-®g.…”