The Middle Ordovician of the Oslo Region, Norway, 32. Trilobites of the family Remopleurididae FRANK NIKOLAISEN Nikolaisen, F.: The Middle Ordovician of the Oslo Region, Norway, 32. Trilobites of the family Remopleurididae. Norsk Geologisk Tidsskrift, Vol. 62, pp. 231-329. Oslo 1983. ISSN 0029-196X. The Middle Ordovician remopleuridid trilobites of the Oslo Region are described in detail. From the fragmentary but very often well preserved material six genera are recognized, of which Sculptella and Sculptaspis are new. A seventh genus, Robergiella, may also be present. Eighteen new species are established; four other named species are known also from elsewhere, and one species previously described from Norway is reported. Fifteen taxa are described under open nomenclature. The Norwegian species can be compared with those occurring in the Middle and Upper Ordovician of the Swedish-Baltie area, the British Isles and even North America and China. The genus Sculptella is known with certainty only from Norway, but may be present in Ireland and China; Sculptaspis is reported from Sweden, Estonia, and may also be present in Bornholm (Denmark), Ireland, and eastern North America. A phylogenetic line from Remopleuridiella through Sculptella to Remopleurella and Amphitryon is suggest­ ed, possibly with Sculptaspis as a separate branch. The British species Remopleurides warburgae Dean, 1963 is renamed R. deani as the former name is preoccupied. Frank Nikolaisen, Paleontologisk museum, Sars gate l, Oslo 5, Norway. Contents R. sp. G ....................... 264 R. sp. H ....................... 264 Introduction . .. .. 232 R. deani n. nom. .. .. 265 Terminology . .. .. 234 Genus Sculptella n. gen. .. 265 Techniques . 234 S. scripta n. gen., n. sp. 268 Measurements . .. .. .. 235 S. aff. scripta n. gen., n. sp. 270 Repository of material . .. .. 235 S. scriptoides n. gen., n. sp. 271 Systematic palaeontology . .. .. 235 S. angustilingua n. gen., n. sp. 272 Family Remopleurididae Hawle & Corda, S. (?) nonscripta n. gen., n. sp. 274 1847................................ 235 Genus Sculptaspis n. gen. 276 Subfamily Remopleuridinae Hawle & S. cordata n. gen., n. sp. .. 278 Corda, 1847 . .. .. 235 S. erratica n. gen., n. sp. 279 Genus Remopleurides Portlock, 1843 235 S. insculpta n. gen., n. sp. 281 R. paucus n. sp. .. .. 236 S. pannucea n. gen., n. sp. .. 282 R. affluens n. sp. .. 238 S. impolita n. gen., n. sp. 283 R. aff. affluens n. sp. .. 241 S. sexlineata (Angelin, 1851) . 285 R. kullsbergensis Warburg, 1925 . 241 S. sp. .. 286 R. laevigatus n. sp. 243 Genus Robergiella Whittington, 1959 287 R. lunnerensis n. sp. .. .. 246 R. ? sp. .. .. 287 R. perspicax n. sp. .. .. 248 Genus Remopleurella Dean, 1963 . 288 R. aff. perspicax n. sp. .. 251 R. burmeisteri (Bancroft, 1949) . .. 289 R. privus n. sp. .. 251 Genus Amphitryon Hawle & Corda, R. inusitatus n. sp. .. 252 1847 . .. .. 292 R. variolaris n. sp. .. 253 A. sp. .. .. .. 292 R. aff. variolaris n. sp. .. 258 Genus Robergia Wiman, 1905 . 292 R. granensis Størmer, 1945 . .. 258 R. sparsa n. sp. .. 292 R. sp. A ....................... 261 R. microphthalma (Linnarsson, R. sp. B ....................... 262 1875) ........................ 294 R. sp. C ....................... 262 Acknowledgements .. .. 295 R. sp. D ....................... 262 References .. .. .. .. 295 R. sp. E ....................... 263 Table l . .. .. 233 R. sp. F . .. .. 263 Plates . .. .. .. 300 232 F. Nikolaisen NORSK GEOLOGISK TIDSSKRIFT 4 (1982) years. Most of the material consists of detached Introduction parts of the dorsal shield; satisfactory and com­ The present paper appears as no. 32 in a series plete dorsal shields are known in on!y four of the dealing with the Middle Ordovician palaeonto­ species. Nevertheless, it seems quite natura! to logy, stratigraphy and tectonics of the Oslo Re­ match detached parts together, because each gion. A team work on this subject was initiated species usually occurs in thin rock sequences, by the late Professor Leif Størmer in 1950, sup­ and in some cases geographically restricted ported by grants from the Norwegian Council for areas. Science and Humanities (NAVF). The remopleuridids seem to have been a fairly The term "Middle Ordovician" is here taken rapidly evolving group of trilobites, although the in the sense of Størmer (1953), i.e. from the changes are usually small. This has produced a Llanvim zone of Didymograptus bifidus to the large number of recognizable species in the Mid­ Caradoc zone of Dicranograptus clingani. dle Ordovician of the Oslo Region, and the same The stratigraphical units referred to in the text is apparently the case in the British Isles and are partly those of the traditional "etasje" classi­ North America. The differences between some fication of the Lower Palaeozoic sequences in the forms may appear small, but the present author Oslo Region. In other cases, the author has re­ considers them to merit specific, rather than sub­ ferred to lithostratigraphical units with names in specific or varietal differentiation. accordance with the recommendations of the In­ In previous publications dealing with Remo­ ternational Stratigraphic Guide (1976). Such pleurides, authors have mainly based the specific units have been established for parts of the Mid­ characters on features of the cranidium and/or dle Ordovician in several of the Oslo Region the pygidium. The present study has shown that districts, especially in recent years as steps to­ librigenae and thoracic segments are of equal, or wards achieving a complete coverage of these in some cases even greater, value in specific dif­ Lower Palaeozoic sequences (cf. Owen 1978, ferentiation. The presence or absence of lateral 1979, Bruton & Owen 1979). A correlation chart glabellar furrows has previously been given con­ partly used in the present work (Tab le l) will be siderable taxonomic weight. The present materi­ published by Bockelie (1983 in press). al includes many smooth specimens with the test Remopleuridid trilobites are some of the most preserved. In these specimens the lateral glabel­ widespread and common trilobites in the Middle lar furrows ar discemible only as differences in Ordovician sequences of the eleven districts of colour, caused by the thinner test at these fur­ the Oslo Region (Størmer 1953, Fig. 1). Remo­ rows (cf. pl. 3, fig. 7). Occasionally, the lateral pleuridids are reported herein from all the dis­ glabellar furrows are recognized as extremely tricts except Feiring and Holmestrand, yet none shallowly elevated areas (cf. Pl. 8, figs. 11 and has been described previously except the pygi­ 14), or as thin remains of the test fixed to the dium assigned to Lichas 4-spinus by Angelin intemal mould on exfoliated specimens (cf. Pl. 2, (1854) and Remopleurides latus granensis fig. 7, Pl. 9, fig. 1). It is therefore apparent that Størmer, 1945. Angelin's specimen cannot be the num ber of lateral glabellar furrows in species traced in the collections, whereas the latter spe­ of the remopleuridid genera dealt with in the eies was redescribed by Owen (1981) in his present paper is only a result of preservation; monograph on the Upper Ordovician trilobites they all have three pairs. Similarly, the occipital of the Oslo Region, where he also described tubercle seems to be present in all species in several other remopleuridids. question. The Middle Ordovician material is fragmen­ The remopleuridid material of the Middle Or­ tary, but the preservation is predominantly good, dovician of the Oslo Region is distributed and thus merits detailed description. In the amongst six genera; Remopleurides, Remopleur­ course of the study all available museum sped­ ella, Amphitryon, Robergia, and the two new mens were examined. On larger blocks, the fossil genera Sculptella and Sculptaspis. The two latter was sawn out, and the residue was cracked and appear somewhat lower in the succession in Nor­ thoroughly examined. This has produced a larger way than does the type genus of the family. The number of assorted detached parts of the exoske­ sculpture on the cranidium of these two genera is leton of the different species; very often small critical for specific determination. Species with a parts that are easily overlooked in the field. Col­ wide distribution may prove to be excellent stra­ lecting has been done over a period of about ten tigraphical guide fossils (cf. p. 277). A single 4 (1982) NORSK GEOLOGISK TIDSSKRIFr Middle Ordovician trilobites 233 ASH- LLANVIRN LLANDEILO CARADOC GILL Table 1. The stratigra- phic distribution of the c c c "' c c :.;;: c c Q) "' o � � � "' "' >- � "' c remopleuridid trilobite Q) Q) Q; :;::; Q) ·c: c;, Q) ·c: � � Cl. 'C Cl. ·s: e "' Cl. ;;:: Cl. .s "' :;::; C> ..c o ·c: ·c;, .2 :::> .2 tJ) :::> c ..c: c tJ) :::> o E o t> .E "' o � <( o ::l species discussed in c..:> :c en --' "' a... ::::;: !his paper. Correlation chart based Ortho- Ven- cera- 4a 4 stop on Bockelie 1983. tite O<,_, a'i. 4ap 4b()( 4b� 4bt Solvang Fm. Lmst. Fm. Remopleurides paucus • R. affluens - R. aff. affluens • R. ku/lsbergensis Ill- R. laevigatlls 11-111 R. lunnerensis - R. perspicax ���-· R. aff. perspicax l R. privus R. inusitatlls R. variolaris ...•• R. aff. variolaris l R. granensis - R. sp.A • R. sp. B l R. sp.C R. sp.D • R. sp.E • R. sp. F • R. sp.G •mmm• R. sp.H l Sculpte/la scripta n• S. a ff. scripta • S. scriptoides - S. angustilingua • S.(?) nonscripta - Sculptaspi.1· cordata - S. erratica S. insculpta := S. pannucea - S. impolita S. sexlineata • - s. sp. •• Robergie/la? sp. • Remopleure/la burmeisteri