A revision of the upper Ordovician trilobite genus Erratencrinurus with a description of a new species from Hadeland ALAN W. OWEN & RACHEL A. HEATH Owen, A. W. & Heath, R. A.: A revision of the upper Ordovician trilobite genus Erratencrinurus with a description of a new species from Hadeland. Norsk Geologisk Tidsskrift, Vol. 69, pp. 225--233. Oslo 1989. ISSN 0029-196X. Two subgenera are recognized in Erratencrinurus: E. (Erratencrinurus) and E. (Ce/tencrinurus) each containing two species groups. A third group of taxa here termed E. (sensu lato) comprises a mid­ Caradoc to late Ashgill stock which retains many of the characters of the oldest known species of Erratencrinurus, E. (s.l.) spicatus (Tripp). This species is also closest to the probably ancestral Encri­ nuroides torulatus-Encrinuroides uncatus line age. Erratencrinurus ( Erratencrinurus) inopinatus sp. nov. is described from a newly discovered, unusually diverse fauna in the upper Ashgill (probably Rawtheyan) Kalvsjø Fm. in the Hadeland district of the Oslo Region. A. W. Owen, Department of Geology and App lied Geology, The University, Glasgow G/2 BQQ, Scotland; R. A. Heath, Department of Geo/ogy, The University, Dundee DDI 4HN, Scot/and. The upper Ordovician (?Rawtheyan) Kalvsjø Fm. the recognition of species groups and subgenera in Hadeland is largely a limestone unit and has within Erratencrinurus. This pa per addresses hitherto yielded few trilobites. This is in marked these problems and is undertaken in conjuction contrast to the underlying, more argillaceous, with Owen's revision of the Encrinuridae for the Kjørrven Fm. which contains at least 26 trilobite Treatise on Invertebrate Paleontology and · species (Owen 1978; 1981 Table 1). However, Heath's study of the latest Ordovician-early Silu­ road widening excavations north of Sverigetjern rian stratigraphy and sedimentology in Hadeland. [NM80908620] in 1988 exposed several metres of fossiliferous shales, siltstones and impure lime­ stones containing species of the trilobites Bra­ chyaspis, Stygina, Prionocheilus, Toxochasmops, Systematic palaeontology an indeterminate lichid and Erratencrinurus. Other elements of the fauna comprise at least The encrinurine terminology used herein is essen­ nine brachiopod species, streptelasmatid corals, tially that of Evitt & Tripp (1977) but the glabellar crinoids and stick bryozoans. Most of the genera tubercle notation is Iargely that of Strusz (1980, in this fauna are also known from the underlying pp. 3-5) with the minor modifications suggested Kjørrven Fm. suggesting a localized, brief, return by Owen (1981, pp. 47--48). Thus rows of to similar environmental conditions. Whilst the tubercles are numbered O, l, 2, 3 etc. away from other trilobites are too incompletely known for the sagittal line. Each row of tubercles on the specific identification, it is clear that the Erra­ posterior part of the glabella is related to the pair tencrinurus species is new and is not E. ( E.) of lo bes or furrows which it links. Longitudinally brutoni which occurs abundantly in the underlying paired tubercles are indicated by a pair of formation. asterisks, e.g. 2L-O;. As noted by Edgecombe & Erratencrinurus is known from the mid-Cara­ Chatterton (1987, p. 344) this tubercle ter­ doc to late Ashgill of Laurentia, Baltica and the minology is descriptive, not necessarily based on Anglo-Welsh area. Specificdifferentiation is rela­ precise homologies, and is essentially based on tively easy as it is largely based on semi-quanti­ the condition in adult specimens. It is accepted, tative criteria such as cephalic tuberculation and however, that a degree of variation, including pygidial segmentation. However, analysis of the ontogenetic migration of tubercle position may Kalvsjø Fm. material has highlighted problems of be present in a species. The specimens from Hade- 226 A. W. Owen & R. A. Heath NORSK GEOLOGISK TIDSSKRIFT 69 (1989) land are housed in the Paleontologisk Museum, vector. Temple & Tripp (1979, p. 244) suggested Oslo (PMO). that this might best be expressed at subgeneric level; a view supported in principle by Strusz (1980, p. 9) who none the less maintained separate genera. Owen (1981, p. 48) formally recognized Family ENCRINURIDAE Angelin, 1854. the two groups as subgenera and described three Subfamily ENCRINURINAE Angelin, 1854 new species from the Ashgill of the Oslo Region: Genus Erratencrinurus Krueger, 1971 E. (E.) imperfectus, E. (E.) brutoni andE. (C.) Type species. - Subsequently designated Krueger kiaeri. Lesperance & Tripp (1985) also adopted (1972), Erratencrinurus capricornu Krueger, this taxonomic position but restricted the concept 1971, pp. 1147-1149, pl. 6, figs. l, 2; pl. 7, figs. of Erratencrinurus (Celtencrinurus) to exclude 1-3; text-figs. l, 3G, 13, 14, from glacial erratics (inter alia) E. praecursor and E. kiaeri. These of the Rakvere Stage (F) (upper Caradoc, were reassigned to Erratencrinurus (s.J.). approximately Marshbrookian-Actonian) near The use of a weakly constrained sensu lato Binz (Rostock district), East Germany. grouping is clearly undesirable but there are some instances in trilobite taxonomy where it has been Historical background. - The genus Erraten­ a necessary, pragmatic approach. The late Ordo­ crinurus was established by Krueger (1971) for a vician species of Calymene (see lngham 1977, p. group of species bearing glabellar spines occurring 98) and some species of Harpidella (see Owen & in Pleistocene erratics of mid to late Caradoc Bruton 1980, p. 19) are notable examples. The age in the Baltic area. With the exception of E. problem in Erratencrinurus is emphasized by the seebachi (Schmidt) these species were also new, Jack of consensus in the placement of some species namely E. capricornu, E. kauschi, E. nebeni, E. even before Lesperance & Tripp's restricted diag­ ceras, E. kummerowi andE. paetzensis. Krueger nosis of E. (Celtencrinurus). Thus, for example, also described three Ashgill species from erratics 'Encrinurus' cornutus was ascribed to Celten­ which he ascribed to Encrinurus: E. melzenensis crinurus by Evitt & Tripp (1977) and Strusz Krueger, E. moe Mannil and E. striatus (1980), Erratencrinurus (Erratencrinurus) by (Angelin). The latter two had previously been Owen (1981) and plotted with other members described from in situ in Estonia and Sweden, of the latter group in Temple & Tripp's (1979) respectively. analysis. 'Encrinurus' kingi Dean was assigned Evitt & Tripp (1977, p. 120) considered that to Erratencrinurus by McNamara (1979) and E. Erratencrinurus was derived from the North (Erratencrinurus) by Owen (1981) but to Cel­ American Encrinuroides torulatus-Encrinuroides tencrinurus by Strusz (1980). uncatus Jineage as was another new genus, Cel­ The new species from Hadeland apparently tencrinurus. This genus was essentially the Encri­ Jacks glabellar spines which hitherto have been nurus punctatus group of species from the upper considered diagnostic of Erratencrinurus (Erra­ Caradoc and Ashgill of Scotland, Northern Ire­ tencrinurus) by several authors. However, it has land and E. Canada (Tripp 1957). Added to this a tubercle pattern which is much closer to mem­ was Encrinuruscornutus lngham, 1974, from the bers of that group than to species of Erra­ mid-Ashgill of Northern England. Celtencrinurus tencrinurus (Celtencrinurus). It highlights the fact was thus defined as compnsmg C. that there are no individual diagnostic criteria multisegmentatus(Portlock) (the type species), C. distinguishing groups within Erratencrinurus.The trispinosus (Reed), C. laurentinus (Twenhofel), recognition of subgenera and species groups must C. lamonti (Tripp), C. praecursor (Tripp) and C. rest on combinations of characters. An appreci­ cornutus (lngham). ation of possible phylogenies also helps greatly. The multivariate analysis of the Encrinurinae undertaken by Temple & Tripp (1979) showed Groupings within Erratencrinurus. - Fig. l shows the two gtoups of species previously assigned to features of the cranidium and pygidium shared by Erratencrinurus and Celtencrinurus were clearly groups of species within Erratencrinurus. Charac­ separated from other members of the subfamily ters common to all species (such as tuberculiform on the second eigenvector of the Principal Com­ glabellar lobes L2 and L3 and the presence of 3L- ponent Analysis. The two groups showed some 1 tubercles) are not included. Most of the features separation from each other on the third eigen- have been used in earlier diagnoses of Erra- NORSK GEOLOGISK TIDSSKRIFf 69 (1989) Ordovician trilobite from Hadeland 227 Taxa ....... inopinatus nov . .." " c. cornutus 9-11 •..• .. "o � seebachi 9-11 �"'. .. .. .. 36 11 • • ku mmerowi .. .Q .. � .. nebeni 9-11 t.i kause hi l 25 8-10 ? 1 o ' v/gl/ans 28 ..... .." c. ceras .. "o " � .-: Cl paetzensis .. " � ".. .. capricornu 8 • o .. 10 ... ".... imperfectus .. Q, �- brutoni 11-13 lli" ....... "., trispinosus 31 12 .... " -�!! /aurentinus 40 15 o:c. " 11 ..�Ila. o perceensis e.a multi- 12-13 .....<J.� .::: segmentatus .." lamonti 32 12-14 �e" kiaeri 10-13 .... .. ... " .. 31 12 !.!� .... ' � praecursor... � 32 11 � spicatus 21 6 .. A 21 8 .." � sp. "o .,_ sp. B ·� � � ... " melzens is .."' c: • Q) .. 25 11 .. _"' kingi Lu striatus 26 11-12 Fig. l. The distribution of selected cranidial and pygidial characters in species of Erratencrinurus. Horizontal shading indicates the presence of a character, dots its absence. E. (s.l.) sp. A andE. (s.l.) sp. Bare the indeterminate species described by Tripp (1974) and Lesperance & Tripp (1985)