The Norwegian Upper illaenid

DA VID L. BRUTON & ALAN W. OWEN

Bruton, D. L. & Owen, A. W.: The Norwegian Upper Ordovician illaenid trilobites. Norsk Geologisk Tidsskrift, Vol. 68, pp. 241-258. Oslo 1988. ISSN 0029-196X.

New camera lucida techniques used in the measurement of illaenid trilobites are described and allow quantification of convexity of cephala and pygidia. Application of these techniques has demonstrated that previously identified dimorphs of Stenopareia glaber are only end members of continuous variation and that the species ranges from the upper Caradoc well into the Ashgill. A quantitative and qualitative distinction between S. glaber and S. linnarssoni is presented toget,her with descriptions of Il/aenus ( Paril/aenus) roemeri and specimens termed /. (P.) cf. da/ecarlicus. The latter throws light on the possible relationship between Octillaenus and other illaenids. Comparative material from Sweden is discussed and figured as is new material of Panderia from Norway.

D. L. Bruton, PaleontologiskMuseum, Sars gate I, N-{)562 Oslo 5, Norway; A. W. Owen, Department of Geology, The University, Dundee DDJ 4HN, Scotland.

In a previous paper (Owen & Bruton 1980) we shape are made becomes critical. To overcome described Caradoc and earliest Ashgill illaenid this, Bruton (1968, pp. 2-3) distinguished trilobites from Norway and Sweden. In doing so, between the dorsal view in which the plane pass­ we noted the occurrence of other illaenids in ing through the posterior margin of the cranidium the overlying Ordovician formations of the Oslo is vertical and the palpebral view in which the Region. These were described in an unpublished palpebral lobes are in the horizontal plane. A thesis (Owen 1977) and subsequently listed by longitudinally convex cranidium/cephalon would Owen (1981, table l) who summarized the Ashgill appear proportionally shorter in dorsal than in lithostratigraphy of the region (1981, fig. l; Fig. palpebral view. The sagittal length of convex cran­ l herein). The main purpose of the present paper idia or pygidia is especially difficult to assess is to describe these Ashgill species whose distri­ (Bruton 1971), but a technique to overcome some bution is summarized in Fig. 2. In doing so we of these problems is described here. have developed quantitative techniques which may have wider application in the and other groups. Measurement As with other smooth trilobites, the virtually featureless exoskeleton of illaenids makes taxo­ Cephala, cranidia and pygidia were orientated in nomic differentiation very difficult. Terrace line lateral view under a binocular microscope and the and muscle scar patterns, eye position, thoracic sagittal profile drawn using a camera lucida (Fig. segment number and shape of the rostral plate, 3A). The chord connecting the ends of the profile rostral flange, hypostoma and pygidial doublure was drawn and measured (12) as was the per­ are usefulin some illaenids but many species have pendicular from the chord to the highest part of been distinguished largely in terms of pro­ the profile(h). The distance along the chord from portional differences. The work of Jaanusson the perpendicular to the posterior end of the (1957) on Scandinavian Lower Ordovician illa­ cranidium or anterior end of the pygidium (11) enids exemplifies the usefulness of a quantitative was also measured. The percentage ratio h: 12 analysis of such differences, but most diagnoses gives a measure of convexity and 11:12 a measure have been essentially qualitative. The problem is of the shape of the profile.In more weakly convex compounded by the convexity of many cephala material the precise position of the perpendicular and pygidia. Not only is this prone to diagenetic and hence the value of 11 is difficult to define and and tectonic distortion, but also the orientation thus 11:12 becomes no more than a general guide in which measurements of assessments of overall to shape. The use of ratios in this analysis over- 242 D. L. Bruton & A. W. Owen NORSK GEOLOGISK TIDSSKRIFT 68 (1988)

series Oslo-Asker Ringerike Hadeland & stages E Vv W E NW � SE ou t hern �,..._...... , \ Norway i

-- ·.? HADELAND ,...., \ .i NGERIKE .' Kjorrven .l � � OSG,LO-A SKER-- ; -·_:Fm. � "'V i 'l>� ø� -'-r' l .,. -i''� �Sk ogerholmen _Grina � \=_Sha l�� �'l> -.--.- Mbr. r _ 200k m ��Gagnu m Lfi Limestone dominant litho log ies Fm. Sorbakk en � _L u nner � Skjaerholmen p;:Fm. Fm.= sandstone Fm. -�

limestone ): & siltstone �� msoya Fm.

Lunner Kirke -Gagnu m shale/mudstone = Mbr . � Venstop Fm . Sha le '\ Mbr . 1111111111 hiatus lllllillill Onnian � limestone Solvang Fm. Actonian

Fig. l. The la test Caradoc and Ashgill stratigraphy of the Oslo--Asker, Ringerike and Hadeland districts of the Oslo Region (based on Owen (1981), fig. 1-see Williams & Bruton (1983) for the Caradoc-Ashgill boundary hiatus in Oslo--Asker).

U> Ashgill ei ti a O> "'U> _.:"- ·c: _.: ei spee ies E (J u; ,.,dl o "' >- "- Pusgillian Cautleyan Rawtheyan Hirnantian (J o s - � 2 .s l [ 1 11/aenus (Pari llaenus) roe meri A,R,H -- - 1 1 27 5 1 1 26

l. (P.) fa/lax - R,H all. 2 1 1 1 1

l. (P.) dalecarlicus cf. 1 1 1 -- H

1/laenus ---- o sp. 1 1

Stenopareia glaber .. R,H 3 1 47 11 1 1 2 31

S. linnar ssoni R,O-A-- -· 42 4 22

Panderia hadelandica 1 4 13 1 1 34 ---H

P. megalopthalm a aff. 2 2 -H

P. insulana --· R 1

Fig. 2. The ranges of Ashgill illaenids in Oslo--Asker (O-A), Ringerike (R) and Hadeland (H), and the number of sclerites of each species examined in the present study. Note that the specimens of Il/aenus (Parillaenus) aff. fal/ax itemized here are from Hadeland; specimens from the lowest Ashgill Høgberg Mbr. of the Solvang Fm. in Ringerike were described by Owen & Bruton (1980). Both I. (P.) aff. fallax and Stenopareia glaber are also known from the latest Caradoc of the Oslo Region. NORSK GEOLOGISK TIDSSKRIFT 68 (1988) Upper Ordovician illaenid trilobites 243

A Sagittal Profile B Palpebral View

poster ior CRANIDIUM/CEPHALON anter ior

anter ior PYGIDIUM posterior

Fig. 3. Length (!), height (h) and width (w) measurements made h herein on: A, the sagittal profile of the illaenid cephalon/cranidium ! and pygidium and B, palpebral ----11---· l.__ ___.l orientation of the cranidium. ------12------w 1

comes the need to calculate the absolute value of on the posterior cranidial width are very scarce. the camera lucida enlargement. However, various Nevertheless, other transverse measurements are measurements of the cranidium were made using easily obtainable; namely the posterior glabellar vemier calipers and four of these proved useful width (w1), the width of the glabella at the inner in some of our analyses - 12 and three width edges of the lunettes (w2), the maximum anterior variates (Fig. 3B). width of the cranidium (w3, Fig. 3B) and the As a prerequisite for our work on the Ashgill maximum pygidial width. species of Stenopareia and as a test of the use­ Length:width and width:width plots of pairs fulness of the measurement techniques, a quanti­ of data (Fig. 4A, B, F, G) show a scatter around tative analysis of S. glaber from the la test Caradoc single growth lines which are isometric (Fig. 4A) was undertaken. This enabled the earlier hypoth­ or slightly anisometric (Fig. 4B, F, G). Percentage esis that this species is dimorphic to be tested and ratios from the camera lucida profiles(Fig. 4C-E) established a firm basis for the discrimination of also show a wide scatter but without any clustering Ashgill species. into two distinct groups. A Principal Component Analysis of 12 and the cranidial width measure­ ments also failed to show separation into clusters Stenopareia glaber (Fig. 5). The 'typical' long and short specimens 'Dimorphs' in illustrated by Owen & Bruton (1980, pl. 3, figs. (Kjerulf) 9-13) represent no more than conditions near the Owen & Bruton (1980, p. 16) suggested that extremes in length: width (Fig. 4A) and longi­ dimorphism is present in S. glaber with 'long' and tudinal profile shape and convexity (Fig. 4C, E) 'short' morphs defined on the ratio of the sagittal with a full range of intermediates present in the length to posterior width of the cranidium or sample. In width:width plots (Fig. 4F, G) these maximum pygidial width. The 'short' form was 'long' and 'short' cranidia plot almost at the same also considered to be more convex longitudinally. point. It is clear therefore that dimorphism is Similar dimorphism was suggested by Warburg not present. No clustering of points into distinct (1925, p. 126) for Swedish material which Owen instars is present on any of the plots, probably & Bruton included in S. glaber. In order to test reflecting a large amount of overlap in variation whether dimorphism is really present, all avail­ between successive moult stages, as suggested by able sufficiently complete material (60 cranidia, Hughes (1969, p. 49) for other trilobites. 13 pygidia) from the type unit, the latest Caradoc Solvang Formation in the Oslo-Asker district of the Oslo Region, was examined. In addition to the data from camera lucida profiles other Systematic palaeontology measurements were made using vemier calipers, Illaenids are known from several formations in including an accurate value of 12• Very few speci­ the Ashgill successions in the Oslo Region (Figs. mens have the narrow (exsag.) posterior parts of l, 2) and whilst those from the Hadeland district the fixedcheeks perfectly preserved and thus data are distorted to some extent, specimens from 244 D. L. Bruton & A. W. Owen NORSK GEOLOGISK TIDSSKRIFT 68 (1988)

A 15 23 8 <11 ·"' E Q) -;;·� .o ::> <11 'typical short' "O 20 Cl 10 .\ ,·.... -": Ol n-51 · .s= . ,;. r >- ' . c. "O · · .s= 3: ''typical long' 5 · 15 �· K "O · · - : lectotype 3: IJJ .".. o n-8 c. � . 0.9551 E 10 o correlation coefficient

5 sag.10 length 15cra nidium20 25 30 (12) correlation coefficient c 0.9830 45 5+------.------,------,1 o \ 5 sag. length pygidium1 5 20 'typical lectotype short' , • 1 1 , 40 " . · . ... 'typical short' 1 typ ca ong : lectotype .. 35 DF;=l=r��-r�n- T -• T - T - & __ � 1- 0 l �� - 27 30 cranidium35 40 45 E · -r ,-. , , , .- ;-, ::> .. . -·typical long' ��h/12% "O 30 c: n-60 ...<11 (.) E : lectotypel /f\ o l 2 5 ----r----. 1 ..,f-p-o s ---li-· 'typical long' n-60 a " ' · -r 'typical short'l - 1 -1 - 1 l r 1 sagittal profile -- 2-- n n 20 - 45 -r50cranidiu- _ _ _ 55m 60 65 45� 50cr anidium55 60 64 11/12% 11/12% F G 16 / 16 / <11 14 14 � n-45 /. n-47 ./� 12 Q) 12 : •:: � .o Cl <11 ,.·• / . , . o /'. Cl . .s= 1 •• 10 ::f- - • • : '-.... �� \ : :' yp1ca, l "O .. .s= lectotype . 1 .>· Jt 3: 8 :- 't ypical short' "O 8 · ong lectotype ·"' 3: ,.;,: 'typical ; .,,,� ,. , . . ". - ; : short' IJJ 6 . 6 " o ":- - c. . � 4 c. 4 correlation coefficient7 2 2- 0.803 0.9822 _./.'<'correlation coefficient 0,_-r--r--.-�--,-� 6 8 1(J max.12 14 ant. 16 wi 18dth 20cranidium 22 24 26 28 30 distance2 4 6between 8 10 lunettes12 14

Fig. 4. Quantitative analysis of Stenopareia glaber (Kjerulf, 1865) based on 60 cranidia and 13 pygidia from the latest Caradoc Solvang Fm. in Oslo--Asker and Ringerike. The dimensions of the lectotype and specimens considered by Owen & Bruton (1980) as being representative of possible long and short dimorphs are indicated. All measurements in mm. NORSK GEOLOGISK TIDSSKRIFT 68 (1988) Upper Ordovician illaenid trilobites 245

Second Eigenvector -1.200 -1.000 -0.800 -0.600 -0.400 -0.200 0.200 0.400 0.600 l 0.000 6.000 - l l l l l l l l l l l

9.500 - •

• S. llnnarssonl Sweden n-8 5.000 - o S. llnnarssonl Norway n-12 S. glaber Ashgill n-18 4.500 - o • S. glaber Solvang Fm. n-42 4.000 - D

• • 3.500 - •

3.000 - . D D .... 2.500 - • -o o 2.000 - D Q) D > c: 1.500- Q) Cl w - - 1.000 ....(/) 0.500 - u: D 0.000

-0.500- D

-1.000- 'typical short' 'typical long' -1.500 - D

-2.000-

-2.500- lectotype -3.000 - D

Fig. 5. Plot of first and second eigenvectors in the Principal Component Analysis of cranidial length (12) and width (w1_3) measurements in Stenopareia g/aber (Kjerulf, 1865) and S. linnarssoni (Holm, 1882). These two eigenvectors account for 99.17% of the variation in the sample.

limestone units in Oslo-Asker and Ringerike are tral cephalic features may also require breakage commonly well preserved although most Jack the of the exoskeleton. exoskeleton. They were analysed both quanti­ tatively and qualitatively along with comparative Family ILLAENIDAE Hawle & Corda, 1847 material for the Boda Limestone (Ashgill) of Genus Dalman, 1827 Siljan, Sweden, including topotypes of Sten­ Subgenus Parillaenus Jaanusson, 1954 opareia linnarssoni (Holm) . Many of the quali­ tative criteria for distinguishing between illaenids Type species. - By original designation, Illaenus are based on surface features of the exoskeleton fallax Holm, 1882, p. 82, pl. 2, figs. 11-13, 15- (e. g. terrace line patterns) and the shape and 20; pl. 5, figs. 15-24; pl. 6, fig. ?16, from the convexity of the pygidial doublure. Thus internal Chasmops (probably Dalby) Limestone and moulds of cranidia can be of little use and partial Kullsberg Limestone (Caradoc) in Sweden. See destruction of the pygidial exoskeleton is needed Owen & Bruton (1980: 15) for discussion of the to reveal the doublure. The investigation of ven- taxonomic status of the subgenus. 246 D. L. Bruton & A. W. Owen NORSK GEOLOGISK TIDSSKRIFT 68 (1988)

26 A 24 Swedish S. llnnarssonl (•) 22 n-8 correlation coefficient 0.9625 20 � 18 /�� · � 16 Cl� Q) / .t:l Ol 14 �· r.· Ol Norwegian S. llnnarssonl (o) J::- 12 • " n-12 Ashgill S. glaber (•) -� 10 correlation coefficient 0.9945 • n-20 ;ii,!correlation .coefficient 0.9293 - o ,o "' 8 o a. 6 ...... ·:. . 4 •:": � ... ::(.'/··.::••. :;:nge in Solvang Fm. S. g/aber 2- n-45 o�--.---.--,---.---.---.--.---�--·�---.--.---·�----�--·��-----.---.--,---�--r--,.. o 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 max. ant. width cranidium

45

C -.range- 40 •• • l

• mean__ '# o l l "' L :::: • J:: Yr"\ s. o o ls standard deviation E 35 rofile n-2 1-----i sag. p 5 ;!�:::' '6::J • nt. po -r1 ·c: __-- , __ � o n 8 � 2 - o 30 • S. llnnarssonl Sweden n-7 1-4•...-tl•n-15 o S. /innarssonl Norway n-1 O Solvang Fm. • Ashgill S. glaber n-17 141•---tls. glaber n-13 25;---�-----.------�-----.------,------, 40 45 50 55 6�0 65 10 20 30 40 post. width glabella/ max. ant. width cra m% pygidium h/12%

o S. llnnarssonl Norway n-5 nyNo D sag. profile " 30 • Ashgill S n-14 / . g/aber st. a --11- o S. ovlformls (/?. 12-- -- Sweden ....."' J:: E 20 ::J ·c;," >- a. 10 ,_�r-�-.--,--.-,.-.--,--.-.--.,--.-,--,--.-,--r--,4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 max. width pygidium .. Fig. 6. Plots of the size ranges and selected variates in Stenopareia glaber (Kjerulf, 1865) from the Solvang Fm. (stippled area) and Ashgill (dots) of Norway and S. linnarssoni (Holm 1882) from the Ashgill of Norway (open squares) and Sweden (black squares). Pygidia of S. oviformis (Warburg 1925) from Sweden (triangles) are also compared. All measurements in mm. NORSK GEOLOGISK TIDSSKRIFT 68 (1988) Upper Ordovician illaenid trilobites 247

Illaenus (Parillaenus) roemeri Volborth, 1864 coarse terrace lines. Rostral flange poorly pre­ Fig. 7A-M; Fig. 8C-D; Fig. lOH, N. served in one Norwegian specimen (Fig. lON) but axe-shaped in Swedish specimen prepared and ( ) 01864 Illaenus Roemeri Volborth p. 7, pl. 2, figs. figured by Owen & Bruton 1980 pl. l, fig. 19 . 12-15 (?non 16= Stenopareialinnarssoni). 01882 Thorax not known from Norway but illustrated Illaenus vivax Holm, pp. 74-78, pl. 6, figs. 1-7. in an enrolled Swedish specimen by Owen & ( ) 01886 Illaenus Roemeri Volborth; Holm, Bruton 1980, pl. 5, figs. 1-3 . Pygidium (Fig. 8C­ pp. 125--130, pl. 9, figs. 4-14, ?15. 01887 Illaenus D; Fig. lOH) almost semicircular in outline, very conf. Rømeri Volb.: Brøgger, p. 32. 01897 Illa­ convex (tr. sag.). Axis broad, only defined on enus Roemeri Volb.: Kiær, pp. 6, 33, 35, 74. external surface near anterior margin where it 01925 Illaenus Roemeri Volborth Warburg, pp. curves strongly forwards. On internal moulds it 108-111, pl. l, figs. 26-29. 01954 Illaenus is seen as a short triangular area differentiated Roemeri Volborth: Jaanusson, p. 574. 0?1970 from the pleural areas by a gentle break in slope. Illaenus (Parillaenus) cf. roemeri Volborth: Ing­ Anterior edge of pygidium transversely directed ham, pp. 2�21, pl. 3, figs. 2-14. 01978 l/laenus from the axis before being deflected downwards (Paril/aenus): Owen, p. 17, (non Il= I. (P.) aff. and obliquely rearwards at the lateral facet. Broad fallax). 01979 Illaenus (Parillaenus) cf. roemeri furrow extends abaxially rearwards from the an­ Volborth: Owen, Fig. 8. 01980 l/laenus (Paril­ terolateral edge of the axis to the mid part of laenus) cf., roemeri Volborth: Owen & Bruton, the facet. Remainder of pleural area featureless. p. 15, pl. l, fig. 19, pl. 5, figs. 1-3. 01981 lllaenus Surface of pygidium bears a dense pitting com­ (Paril/aenus) cf. roemeri Volborth: Owen, table prising two distinct sizes of pit. Discontinuous l (pars) (non Gagnum Limestone = I. (P) aff. terrace lines are present on the facets and on the pleural area mesially and laterally; they do not fallax). 01981 Panderia sp.; Owen, table l. cross the axis anteriorly, however, and are absent posteriorly. Doublure (Fig. 7D, F, G, H; Fig. Material, localities and horizons. - Disarticulated 8C-D) concave in dorsal view. Inner margin very sclerites are rare in the Langåra Fm. in Asker and steeply declined posteriorly, slightly less so lat­ Kjørrven and Kalvsjø formations in Hadeland, erally towards facets. Very slight median groove but are very much more abundant in the upper visible in dorsal view. Terrace lines continuous part of the Sørbakken Fm. in Ringerike. A com­ except behind facet where there is an additional plete specimen is also known from the last of series of short lines. these units. The following description is based on

this Norwegian material. Discussion. - l/laenus (Parillaenus) roemeri was described originally from the Lykholm Group Description. - Cranidum (Fig. 7 A-C) strongly (latest Caradoc-Ashgill) in the Baltic area and convex longitudinally, weakly so transversely. subsequently from the Boda Limestone and Glabella broad, very weakly convex (tr.). Dorsal Upper Jonstorp Formation (both Ashgill) in furrows shallow, deeper on internal mould, par­ Sweden. In 1980 we illustrated Swedish specimens allel, extending to leve! of anterior edge of in order to compare l. (P. ) aff.fallax from around palpebral lobe. Median glabellar node barely the Caradoc-Ashgill boundary in the Oslo discernible. Cranidium anterior to palpebral lobes Region. Our present study confirms that these sloping steeply downwards, more than twice as forms are very clearly related and can only be long as posterior part of cranidium. Posterior reliably distinguished on features of the pygidial branches of facial suture diverging very gently doublure. That of l. (P.) roemeri is very much rearwards from behind large palpebral lobe. narrower in dorsal view with a steeper inner mar­ Anterior branches diverge very slightly outwards gin than tht of l. (P.) fallax (compare Fig. 7D; before curving gently adaxially. Free cheek (Fig. Fig. 8D with Fig. 8F herein) with/. (P.) aff. fallax 71) with broadly rounded genal angle, inner part (Fig. 8A-B) having an intermediate morphology. flat-lying, outer part steeply declined. Surface of Specimens from the lower part of the Lunner Fm. cephalon bears a fine dense pitting with terrace and the Gagnum Limestone Fm. in Hadeland lines along the anterior and lateral margins as (Owen 1978, pp. ll, 17, fig. 8A, B herein) are well a on posterior part of glabella. Rostral plate closest to l. (P.) aff. fallax but there is over1ap (Fig. 7K-L) with distinct, median tongue and between the two, and whilst small specimens of 248 D. L. Bruton & A. W. Owen NORSK GEOLOGISK TIDSSKRIFT 68 (1988) the former species have a proportionally broader pygidium from the uppermost part of the cranidium, there is no difference in larger ones. Kjørrven Fm. near Bjellum, Hadeland. We concur with Ingham's (1970) identification of I. (P.) cf. roemeri from Cautleyan Zone 2 in Description. - Cranidium (Fig. 8M; Fig. 9A-C) northem England (lower than its occurrence in gen tiy convex (tr., sag.) but this has been Norway) where it replaced I. (P.) cf. fallax. We enhanced by compression, widest anteriorly. also consider that the material figured as I. (P.) Maximum width of glabella at occipital ring. Axial cf. fallax by Price (1980, pp. 846--847, pl. 108, furrows narrow (tr.) and shallow, converging figs. l, 2) from the Sholeshook Limestone (Caut­ fowards to opposite mid parts of palpebral lobes leyan to lowest Rawtheyan) of South Wales is the then diverging from this glabellar constriction and same as Ingham's I. (P.) cf.fallax. Both, together dying out at about two-thirds of cranidial length. with our I. (P.) aff.fallax, have a shorter pygidial Furrows smooth with no obvious lunettes al­ doublure than does the nominal species. A though an adjacent smooth area on the fixed pygidium ascribed to 'I. roemeri' by Modlinski & cheek of the !argest cranidium and a slight swell­ Pokorski (1969, p. 788, pl. 3, fig.17) from Ashgill ing in this area on the small er one might represent strata in Poland is insufficiently diagnostic for such features. Semicircular palpebral lobes large, confident specific assignment. I. (P.) davisii situated well back on cranidium. Short posterior Salter, 1849 from the Rhiwlas Limestone (Raw­ branches of facial suture diverge abaxially rear­ theyan) of North Wales was redescribed by Whit­ wards, anterior branches diverge forwards over tington (1966, pp. 67, 69, pl. 20, figs. 16--23, most of their length, curving sharply adaxially pl. 21, figs. 1-4, 6--9) and differs from I. (P.) anteriorly. Anteriormost part of cranidium roemeri in its much broader pygidial doublure. slightly tumed under (Fig. 9B). lndeterminate specimens of Illaenusare known Surface sculpture of cranidium consisting of from the Grimsøya Fm. in Oslo-Asker (/? sp. of minute pits between well-defined terrace lines Owen 1981, table 1). A rostral plate from this which are arched very gently forwards and are horizon (Fig. 7L) is identical to that of I. (P.) complete in front of axial furrows but curve roemeri, but the pygidium from here (Fig. 7N) sharply rearwards into, and are broken at, these shows an unusual concentric terrace line pattem. furrows. Terrace lines do not cut across the Indeterminate fragments from the highest Ordo­ smooth area on the fixed cheek of the !argest vician units in Oslo-Asker and Ringerike were specimen nor are they present on an adjacent listed by Owen (1981, table l) as Illaenus (s.l.) smooth area on the glabella. sp. and are too incomplete to warrant illustration. Free check (Fig. 8N) triangular in outline with pointed genal angle. Terrace lines cover the entire Illaenus (Parillaenus) cf. dalecarlicus Warburg, cheek surface. Those on the posterior half curve 1925 forwards from the genal angle in broad arcs back Fig. 8M-N; Fig. 9A-C. to the posterior margin. Those on the anterior 01981 illaenid? gen. nov. Owen, table l. half, from mid-cheek forwards, essentially straight, directed slightly obliquely to the lateral Material, locality and horizon. - A large, incom­ margin. plete cranidium, a very small heavily distorted Thorax of small moult stage consisting of at cranidium and a small cranidium with associated !east eight segments, only the first of which is seen free cheek, thoracic segments and incomplete in dorsal view. Axis convex (tr.), occupying a

Fig. 7. A-K, M. ll/aenus (Parillaenus) roemeri Volborth, 1864. A, B, C, Cranidium, internat mould, dorsal, frontal and left lateral view. PMO 10703, xl. 3. Upper Sørbakken Fm., Frognøya, Ringerike. Coll. unknown. D, F, G, Pygidium, dorsal, anterior, oblique lateral view, prepared to show doublure. PMO 10526, x2. Upper Sørbakken Fm., Frognøya, Ringerike. Coll. W. C. Brøgger 1881. E, l, Left free cheek. PMO 35464, Ka1vsjø Fm., Stadum, Gran, Hadeland. Coll. Th. Munster 1892. E, detail of pitted poste ro lateral margin, x2.5, I, dorsal view, x1. 2. H, Pygidium, internat mould, left lateral view. PMO 80415, x 1. 5. Langåra Fm., Holmenskjæret, Asker. Coll. J. F. Bockelie 1965. J, Cranidium, palpebral view. PMO 116. 828, xl.6. Upper Sørbakken Fm., 14 m below beds with Palaeoporella, W. Frognøya, Ringerike. Coll. A. W. Owen 1974. K, Rostral plate. PMO 10625, x2. Upper Sørbakken Fm., Frognøya, east shore. Coll. J. Kiær 1914. M, Pygidium, dorsal view. PMO 10501, x3. Upper Sørbakken Fm., Frognøya, Ringerike. Coll. J. Kiær 1914. Note finepitting along posterolateral areas. L,N. Illaenus sp. indet., Rostral plate. PMO 8883, X2. Grimsøya Fm., Husbergøya, Oslo. Specimen on same block as Atractopyge cf. progemma Owen 1981, pl. 13, fig. 16. N, Incomplete pygidium, dorsal view. PMO 100.611, x2. Grimsøya Fm., Grønnsund, Asker. coll. J. F. Bockelie 1966. Specimen on same block as Lonchodomas aff. depressus (Angelin), Owen 1981, pl. 9, fig. 3. NORSK GEOLOGISK TIDSSKRIFf 68 (1988) Upper Ordovician illaenid trilobites 249 250 D. L. Bruton & A. W. Owen NORSK GEOLOGISK TIDSSKRIFf 68 (1988) third of the width of each segment. Proximal part preservation of the Boda Limestone material is of each pleura gently inclined from narrow (tr.) insufficient to show such strength of detail. More­ axial furrow, outer part (somewhat less than half) over, the posterior branches of the facial su ture declined and deftected gently rearwards at a diverge rearwards, as in the Norwegian form. distinct fulcrum. Pygidium incomplete but with Professor Valdar Jaanusson has kindly sent us short, faint, triangular axis. two pygidia (RM Ar 34268-69) collected by Holm in 1884 and identified as masckei from the Nabala Discussion. - Although the Hadeland specimens Stage (P. linearis Zone) at Odulema, Estonia. are less well preserved, they show many simi­ These specimens are very much larger than larities to l. (P.) dalecarlicus Warburg (1925, pp. material of dalecarlicus we have available and 114--:117, pl. 2, figs. 10-13, ?8) from the Boda they have a longer (sag.) pygidial doublure. Judg­ Limestone (Ashgill) of the Siljan district, type ing from Holm's illustrations and two incomplete and topotype material of which are illustrated topotype pygidia, it is possible that despite its here (Fig. 8G-H; J-L, 0). Most notable simi­ larger maximum size, l. (P.) masckei may be larities include the low transverse convexity of insufficiently different from l. (P.) dalecarlicus to the cranidium, the marked constriction of the warrant specific separation: it would then be the glabella, the large palpebral lobes, and the tri­ senior synonym. angular free cheek with pointed genal angle and However, lacking modem description and illus­ characteristic terrace line pattern. Our material, tration of Holm's species, the Hadeland material (P.) however, has marked! y divergent rather than par­ is tentatively referred to I. dalecarlicus. alle! posterior branches of the facial suture. The Dean (1978, pp. 99-100, pl. 46, figs. 6--8, 10; more strongly developed surface sculpture of the pl. 50, figs. 5, 10, 12; pl. 45, figs. l, 2, 6, 8, 14) Norwegian material may simply refiect pres­ ascribed pygidia and (tentatively) hypostomes ervational differences from the pure limestone in from the Ashgill Chair of Kildare Limestone of which the Swedish specimens occur. Nonetheless, eastern Ireland to l. (P.) dalecarlicus. A cran­ there is a small swelling on the fixed cheek of the idium termed I. (P.) sp. A. by Dean (1978, p. 101, Boda Limestone cranidia and also a broadening pl. 48; figs. 6, 10, 12) may also belong here for of the axial furrow at the glabellar constriction. although as Dean noted the minimum width of If this is a lunette, it is unusual in having a con­ the glabella seems to be very forwardly placed, a siderable length of axial furrow in front of it. topotype specimen of Warburg's species figured Both l. (P.) dalecarlicus and the Norwegian here (Fig. 8L) shows a similarly long posterior material here compared with it are very similar part of the glabella. to I. (P.) masckei Holm (1886, pp. 139-142, The anteriorly divergent axial furrows, large pl. 12, figs. 1-5) from erratic blocks and in situ eyes, pointed genal angle and poorly definedpygi­ horizons of the latest Caradoc-Ashgill Lykholm dial axis of l. (P.) dalecarlicus and J. (P.) masckei Group (F 1) in the Baltie area. Of particular note are sirnilar to the type, and only, species of Octil­ are the terrace line patterns of the cranidium and laenus, O. hisingeri(Barrande, 1846) fromAshgill free cheek illustrated by Holm (1886, pl. 12, figs. units in Bohemia and possibly Sweden, northern la, 3) which are identical to those of the England and Scotland (see Jaanusson 1954, Norwegian specimens (Fig. 8N; Fig. 9A-C) -the PP· 568-569; Snajdr 1957, pp. 155-159, pl. 7, figs. .

Fig. 8. A,B, l. 11/aenus (Parillaenus) aff. fallax (Holm, 1882). A,B, Dorsal and left lateral view of partly exfoliated thorax and pygidium prepared to show sloping pygidial doublure. PMO 68522, xl. Gagnum Lmst. Fm., Øyskogtjem, north of Øystad, Hadeland. Coll. L. Størmer 1951. l, Cranidium, dorsal view. PMO 3550, x2. Gagnum Lmst. Fm.,beach south of Gjøvik, Gran, Hadeland. Coll. Th. Munster 1892. E,F, ll/aenus (Paril/aenus) fallax(Holm, 1882). Right lateral and dorsal view of partly enrolled individual with pygidium prepared to show doublure. RM Ar10273, xt. ?Dalby Limestone (Caradoc), Siljan district, Sweden, Iocality unknown. G, H,J-L, O,1llaenus (Parillaenus) da/ecarlicus Warburg, 1925. G, H,J, Dorsal and right lateral view (x1) and ventral view of cephalon (x2) of complete individual. SGU Coll. Original of Warburg 1925,pl. 2, figs.1(}.. 11,Boda Limestone, Kallholn, Siljan district, Sweden. K,L, Cranidium, anterior and palpebral view. RM 10043,X2. O,Small cranidium, palpebral view. RM 10045,X4. Boda Lmst., Osmundsberg, Siljan district, Sweden. Coll. G. Holm 1880. M,N, lllaenus (Parillaenus) cf. dalecar/icus Warburg, 1925. M, Dorsal view of small cranidium with left free cheek, eight thoracic segments and incomplete pygidium, x2. N, Detail of terrace line pattern on free cheek, x8. PMO 101.297. Uppermost Kjørrven Fm., near Bjellum, Hadeland. Coll. A. W. & G. Owen 1978. C, D,11/aenus (Parillaenus) roemeri Volborth, 1864. Exfoliated pygidium, dorsal and anterior view. PMO 103.839, xt.5. Langåra Fm.,s-10 mi n section, Holmen, Asker. Coll. P. J. Brenchley & G. Newall 1979. Note near vertical inner margin of doublure cf. l. (P.) fallax. NORSK GEOLOGISK TIDSSKRIFT 68 (1988) Upper Ordovician illaenid trilobites 251 252 D. L. Bruton & A. W. Owen NORSK GEOLOGISK TIDSSKRIFT 68 (1988)

1-2, text-fig. 6, 1983; Piibyl & Vanek 1980, 01979 Stenopareia sp.; Owen, p. 253. 01979 pp. 270-271, p1. 2, figs. 3-5; Ingham 1970, pp. 22- Stenopareia aff. glaber (Kjerulf); Owen, text-fig. 23, pl. 3, figs.15-25). Octillaenusis characterized 8. 01980 Stenopareia glaber (Kjerulf); Owen & by its thorax of eight segments - the number Bruton, pp. 15-18, pl. 2, figs. 13, 14; pl. 3; pl. 4; preserved in the more complete of our specimens pl. 5, figs. 1-3; text-fig. 3. 01981 Stenopareia aff. of l. (P.) cf. dalecarlicus which is of comparable glaber (Kjerulf); Owen, table l. 0?1981 Steno­ overall size to the illustrated material of O. pareia aff. bowmanni (Salter); Owen, table l. hisingeri.The type material of l. (P.) dalecarlicus 01984 Stenopareia glaber (Kjerulf); Owen in and l. (P.) masckei both include specimens with Harper & Owen, pp. 32-33, pl. 5, figs. 13-18. lO thoracic segments. It is possible therefore that Octillaenus hisingerideveloped paedomorphically Material, localities and horizons. - In addition to from species such as l. (P.) dalecarlicus and l. the late Caradoc material described by Owen & (P.) masckei, and the restricted number of seg­ Bruton (1980) and Owen in Harper & Owen ments and smaller overall size may be the only (1984, see also Harper et al. 1985, Fig. 4), disar­ significant generic-level differences. l. dalecar­ ticulated sclerites of S. glaber are common in the licus and l. masckei were ascribed to lllaenus Frognøya Shale Mbr. of the Venstøp Fm. and (Parillaenus) by Jaanusson on the basis of the throughout the overlying Sørbakken Fm. in simple curvature of the inner edge of the pygidial Ringerike. A few complete specimens are also doublure (1954, p. 574, text-fig. lOD)- a feature known. Poorly preserved specimens from the also shared with O. hisingeri (see Snajdr 1957, Kjørrven Fm. and Grina Shale Mbr of the Lunner pl. 7, fig. 2). Moreover, all the species discussed Fm. in Hadeland previously termed S. aff. bow­ here have several styginid (sensu Lane & Thomas manni by Owen (1981) also probably belong in S. 1983) features, most notably the low sagittal con­ glaber. vexity of the cranidium and the anteriorly diver­ gent axial furrows. Such affinities to 'Bronteus' Discussion. - A full description of S. glaber was were noted from l. (P.) masckei by Holm (1886, given by Owen & Bruton (1980) on the basis p. 142), Raymond (1916) and Warburg (1925, of type, topotype and other material from the pp. 98-100) and the familial affinities of all these Solvang Fm. (see also above for discussion of taxa must remain in doubt. 'dimorphism'). Specimens from the Ashgill of Ringerike show a narrower range of variation and Genus Stenopareia Holm, 1886 include larger specimens than the sample of S. glaber from the Solvang Fm. Nevertheless, most Type species. - By original designation, Illaenus specimens fall within the range of variation of S. Linnarssonii Holm, 1882 (see synonymy below glaber (Figs. 5, 6) and thus the Ashgill material for full citation), from the Boda Limestone (Ash­ is assigned to Kjerulf's species. gill) of Siljan, Sweden. Amongst material figured as S. bowmanni (Salter, 1848) by Price (1974, pl. 112, figs. 1-8; Stenopareia glaber (Kjerulf, 1865) pl. 108, fig. 15) from the Sholeshook Limestone Fig. 9D-K; Fig. lOM, P. of South Wales and S. cf. bowmanni (Ingham 01865 lllaenus glaber Kjerulf, p. 14, fig. 28. 1970, pl. 4, figs. 1-7) from the Cautleyan Zone 2-

Fig. 9. A-C, Il/aenus (Paril/aenus) cf. dalecarlicus Warburg, 1925. Dorsal, frontal and teft lateral view of partly crushed cranidium. PMO 101.295, x2. Locality and collection as Fig. 8M, N. D-K, Stenopareia glaber (Kjerulf, 1865). D, Incomplete pygidium prepared to reveal cuspate doublure. PMO 116.830, x2. Upper Sørbakken Fm., 14 m below beds with Palaeoporel/a, W. Frognøya, Ringerike. Colt. A. W. Owen 1974. E, F, Pygidium, dorsal and right lateral view. PMO 106.485, x2. Same horizon as Fig. 90. Coll. D. L. Bruton 1974. G, Cephalon, part thorax and pygidium prepared to reveal cuspate doublure. PMO 106.473, X l. Upper Sørbakken Fm., Frognøya, Ringerike. Colt. W. C. Brøgger 1881. H, Cranidium, dorsal view. PMO 106.486, x3. Same horizon as Fig. 9D. I, J,K. Slightly distorted cephalon, internat mould, dorsal, ventral and teft lateral view. PMO 116.838, x2. Kjørrven Fm., 200 m ESE of Valborgtjern, Hadeland. Coll. A. W. Owen. L-r',Stenopareia linnarssoni (Holm, 1882). L, Cranidium, internat mould, dorsal view. PMO 100.677, xl. Langåra Fm., Holmenskjæret, Asker. Colt. J. F. Bockelie 1965. M, N, O, Incomplete cephalon, internat mould, teft lateral and dorsal view, xl; detail of glabellar muscle scars, x2. PMO 116.839. Same horizon as Fig. 9L. P, Cranidium, oblique dorsal view to show glabellarmuscle scars. PMO 17609, x2. Bønsnes Fm., Stavenestangen

( = Stamnestangen), Ringerike. Colt. J. Kiær 1914. Note layering in test: l= true internat mould; 2 = thin layer with weak pitting;

3 = layer with dense pitting on fixed cheek, fine pitting between muscle scars and around glabellar node; 4 = fragment of dorsal exoskeleton. NORSK GEOLOGISK TIDSSKRIFT 68 (1988) Upper Ordovician illaenid trilobites 253 254 D. L. Bruton & A. W. Owen NORSK GEOLOGISK TIDSSKRIFf 68 (1988)

3 in northem England, there are cranidia which Note that some records of 'l. linnarssoni' from fall within the variation described for S. glaber. Norway were reidentified as S. glaber by Owen They differ from the lectotype of S. bowmanni & Bruton (1980, p. 16). (see Whittard 1961, pl. 31, fig. 1), which has a broader (tr.) and more convex glabella with Material, localites and horizons. - Disarticulated shorter dorsal furrows, features also shared by sclerites are common in the Bønsnes Fm. in the S. aff. bowmanni figured by Zhou & Dean Ringerike and are rare in the overlying sandstone (1986, pl. 62, figs. 8, 9, 11) from the Caradoc of and the Husbergøya, Langøyene and Langåra northwest China. formations in Oslo-Asker. In our view the Sholeshook and Cautley specimens may beS. glaber, but the material, for the most part, is of distorted intemal moulds Discussion.- Owen & Bruton (1980) gave a quali­ which makes identificationuncertain. A pygidium tative comparison between the Swedish S. lin­ (Ingham 1970, pl. 4, fig. 4) clearly shows the narssoni and material of S. glaber from the cuspate inner margin of the doublure which is Solvang Fm. They noted (1980, p. 17) that War­ characteristic for S. glaber. burg (1925, p. 117) redefinedS. linnarssoni on the basis of only a pygidium and a hypostome Stenopareia linnarssoni (Holm, 1882) from Holm's original material together with Fig. 9L-P; Fig. 10A-F. additional specimens from the Boda Limestone. Her extensive description need not be repeated 01882 Illaenus Linnarssonii Holm, pp. 103-109 here except to stress that her description of the (pars), pl. 4, figs. 21-22; pl. 5, fig. 6; pl. 6, fig. 15 pygidial doublure was incorrect. As shown by (non pl. 4, figs. 13-20; pl. 5, figs. 1-5, 7, 8 = S. Owen & Bruton (1980, p. 18, pl. 2, figs. 15, 16) glaber; pl. 4, figs. 23-27 = S. oviformis]. 01886 the inner margin of the doublure has a prominent, 1/laenus Linnarssonii Holm: Holm, pp. 146-150, tongue-like mesial projection (Fig. lOA-D). This pl. 10, figs.12, 14-23. 01897 1/laenus Linnarssoni contrasts with the median embayment with lateral Holm; Kiær, pp. 12, 74. 01925 1/laenus Lin­ cusps inS. glaber (Fig. 9D) and is also seen in the narssoni Holm: Warburg, pp. 117-123, pl. 2, figs. Norwegian material included in S. linnarssoni 14-18. 01954 Stenopareia linnarssoni .(Holm): here. The cranidial and pygidial proportions of Jaanusson, p. 570, pl. 2, figs. 4-6, text-figs. lOF, these late Ashgill Norwegian specimens (Figs. 16A, B. 01959 Stenopareia linnarssoni (Holm): 5, 6) are also indistinguishable from those of a Jaanusson in Moore p. 0374, fig. 282, 6a-d. O? topotype S. linnarssoni sample examined in the 1978 Stenopareia linnarssoni (Holm): Dean, pp. present study. 101-102 (pars)pl. 49, figs. 2, 3, 5; text-fig. 5A-E The overall size range of Swedish and (non pl. 47, figs. l, 2, 6-10; pl. 48, figs. 4, 5, 9; Norwegian specimens extends well beyond that pl. 49, figs. l, 4, 6-9, 13, 14; pl. 50, figs. 1-3, 11]. of S. glaber, but some of the smaller specimens 01980 Stenopareia linnarssoni (Holm): Owen & fall within the total range of Kjerulfs species (Fig. Bruton pl. 2, figs. l, 12, 15, 16. 01981 Stenopareia 6A). These differences in proportional glabellar sp.; Owen, table l. width are also shown in Fig. 6B, which also indi-

Fig. 10. A-F. Stenopareia linnarssoni (Holm, 1882). A, B, C, Pygidium, internal mould prepared to show median 'tongue' of doublure, dorsal, anterior and right lateral view. PMO 20761, x2. Bønsnes Fm. 35-38 m from base, Stavenestangen

( = Stamnestangen), Ringerike. Coll. J. Kiær 1894. D,Pygidium with test,right half prepared to show doublure. PMO 14377, x4. Bønsnes Fm., Vestre Svartøya, Ringerike. CoU. Th. Munster 1891. E, Immature cephalon, palpebral view. PMO 17878, x5. Bønsnes Fm., Frognøya, Ringerike. CoU. J. Kiær 1914. F,Right free cheek,frontal view. PMO 14384, x4. Same horizon as Fig. 90. G,J, L. Panderia aff.megalopthalma Linnarsson,1869. G,J, Cranidium,palpebral and dorsal view. PMO 98238, x8. Gagnum Lmst. Fm.,Gammeåsen, Hadeland. CoU. A. W. & G. Owen 1977. L,Pygidium,latex east of external mould. PMO 98235, x7. Gagnum Lmst. Fm.,between Gamme and Gamme øvre,Hadeland. Coll. A. W. & G. Owen 1977. I,K, O. Panderia hadelandica Bruton, 1968. I, Slightly distorted cephalon, internal mould, palpebral view. PMO 100.051, x4. Gagnum Shale Mbr., Lunner Fm., 350m N.W. of Espen,Hadeland. Coll. A. W. & G. Owen 1977. K, Pygidium,latex east of external mould. PMO 99400, X10. Gagnum Shale Mbr.,Lunner Fm.,200m N. of Vien Søndre,near Østtjernet,Hadeland. Coll. A. W. & G. Owen 1977. O, Pygidium, prepared to show doublure. PMO 99405, X6. Same horizon and collection as Fig. 10 K. H,N. Illaenus (Parillaenus) roemeri Volborth, 1864. H, Pygidium,dorsal view. PMO 55334, x3. Sørbakken Lmst. Fm., northeast Frognøya, Ringerike. Coll. J. Kiær. N, Rostral plate and cheek doublure of incomplete cephalon. PMO 20763, x2. Sørbakken Lmst. Fm., Vaker, Ringerike. Coll. Varlo 1881. M,P. Stenopareia glaber (Kjerulf, 1865). Left lateral view of cephalon and ventral view showing rostral plate and cheek doublure. PMO 106.473, X l. Same specimen as Fig. 9G. NORSK GEOLOGISK TIDSSKRIFT 68 (1988) Upper Ordovician illaenid trilobites 255 256 D. L. Bruton & A. W. Owen NORSK GEOLOGISK TIDSSKRIFT 68 (1988) cates that the variation in longitudinal cranidial ?Family P ANDERIIDAE Bruton, 1968 convexity (h: 12) in S. glaber completely encom­ Genus Panderia Volborth, 1863 passes that of S. linnarssoni. The longitudinal pygidial convexity (h: 12) of the Norwegian S. Type species.- By original designation, Panderia linnarssoni is consistently greater than that of triquetra Volborth, 1863, p. 32, pl. 3, figs. 13- Ashgill specimens of S. glaber, but Iies in the 17, probably from the Kunda Stage (B3) (upper upper part of the range of topotype S. glaber Arenig-lower Llanvirn), Pavlosk, Leningrad dis­ (Figs. 6C, D). The two available pygidia of S. trict, USSR (see Bruton 1968, p. 10). oviformis (Warburg) from the Boda Limestone show a greater convexity than any of these speci­ Discussion.- We follow Lane & Thomas's (1983) mens (Fig. 6C, D) and this reflects the distinct tentative proposal that the Panderiinae Bruton 'hump' in the lateral profile in Warburg's species 1968 be elevated to family rank. This means (see Owen & Bruton 1980, p. 18, pl. 2, fig. 18). that the group can no longer be referred to as Figure 6D also shows that some pygidia of both 'illaenids', but we include them here for the sake S. linnarssoni and Ashgill S. glaber are larger than of completeness. any seen in the topotype sample of S. glaber. The Scandinavian species of Panderia were Whilst the convexity remains constant with extensively revised by Bruton (1968) and although increasing size in S. linnarssoni there is a sug­ some additional material from the Ashgill of Nor­ gestion of a decrease in convexity in the Ashgill way has been discovered it adds little to the mor­ S. glaber. phological and taxonomic information given in The width of the glabella at its base (w�> Fig. the earlier pa per. It does, however, enable greater 3B) and at the lunettes (w2), the maximum stratigraphical refinement. Taking the species in anterior cranidial width (w3) and the sagittal cran­ stratigraphical order: idial length (12) in S. glaber and S. linnarssoni were analysed using Principal Component Analy­ P. hadelandica Bruton, 1968 (Fig. 101, K, 0). A sis (PCA). A plot of the first two eigenvectors considerable amount of material is now known which together account for 99.17% of the vari­ from various levels in the Gagnum Shale Mbr of ation in the sample shows the two species to be the Lunner Fm. in Hadeland (Owen 1978, p. 15, distinct (Fig. 5) with specimens of S. glaber having 1981, Table 1). The incomplete cephalon and higher scores on the second eigenvector than thorax from north of Mjørputten assigned to P. those of comparable size in S. linnarssoni. The migratoria by Bruton (1968, pl. 6, figs. 6, 8, 9) second eigenvector bas direction cosines of O.3 24, probably also comes from the Gagnum Shale and -0.403, -0.561 and 0.647 for variates 12, wb w2 is tentatively reassigned to P. hadelandica. We and w3, respectively. Since S. glaber has higher exclude from here the pygidia figured by Bruton scores on this eigenvector than S. linnarssoni, it (1968, pl. 5, fig. 3, pl. 7, fig. 7) from mid-Caradoc has a relatively narrower glabella (at its base, w1 strata in Estonia and Latvia because they are and at the lunettes, w2) relative to cranidial area slightly narrower and have a hetter defined axis. (12, w3). This is partly reflected in the slightly Thus P. hadelandica is restricted to the type unit. narrower fixed cheek of S. linnarssoni ( compare As noted by Ingham (1970, p. 26), pygidia of P. Fig. 9L, N with Fig. 9H, I). The Ashgill S. glaber aff. hadelandica from the Cautleyan stages 3 & 4 specimens plot in the same field as those from the in northern England have a more tapered axis Solvang Fm. although there is some separation which resembles more closely the condition seen amongst the larger specimens. The Norwegian in P. megalopthalma Linnarsson. material ascribed to S. linnarssoni is indis­ tinguishable from the Swedish specimens on this P. aff. megalopthalma Linnarsson (Fig. lOG, J, multivariate analysis. L). Both Størmer (1945) and Bruton (1968, pl. 10, As previously noted (Owen & Bruton 1980, figs. 4-6, 9) figured a cranidium from 2m below p. 18), material of Stenopareia figured by Dean the top of the Gagnum Shale Mbr of the Lunner (1978) from the Chair of Kildare and Keisley Fm. east of Gagnum. The counterpart to this Iimestones comprises various cranidia and specimen has come to light recently. In addition pygidia. Of the latter only one specimen (pl. 49, to this we now have a cranidium and two pygidia figs. 2, 3, 5) has the median projection of the from the lower part of the Gagnum Limestone doublure characteristic for S. linnarssoni. Fm. NORSK GEOLOGISK TIDSSKRIFT 68 (1988) Upper Ordovician il/aenid trilobites 257

Panderia megalopthalma was redescribed by Ireland with P. edita and this assignment seems Bruton (1968) on the basis of topotype material well founded as does that of material from the fromthe Upper Jonstorp Formation (Rawtheyan) Sholeshook Limestone ( Cautleyan to lowest Raw­ of Vlistergotland, Sweden. Bruton also assigned theyan) of South Wales by Price (1980, pp. 847- other Swedish specimens to this species from the 848, pl. 108, figs. 3--8). Apollonov (1974) figured type unit in Ostergotland, the Jerrestad Mudstone three cranidia as Panderia sp. from Ashgill strata (late Ashgill) in Skåne and the Lower Jonstorp in Kazakhstan and whilst close comparisons can­ Formation and Ålleberg Beds (both Ashgill) in not be drawn, their great convexity probably indi­ Vlistergotland. The species has also been cates affinity with forms such as P. insulana. described from Ashgill strata in Latvia (Mlinnil Acknowledgements. - We thank Dr D. A. T. Harper for his 1966; Bruton 1968), Poland (Kielan 1960; Mod­ help and encouragement with the statistics and his helpful linski & Pokorski 1969; Tomczykowa & Tomczyk comments on an earlier draft of this paper,Professors V. Jaanus­ 1970) and, as P. cf. mega/opthalma, North Wales son (Stockholm) and R. A. Reyment (Uppsala) and Dr J. K. (Price 1981). Whilst having the characteristically lngham (Glasgow) for the loan of specimens in their care and long (sag., exsag.) frontal part of the glabella, Mrs Jenny Orr for typing the manuscipt. We also thank Dr lngham for his helpful comments on the manuscriot and for these cranidia differ from the undistorted cran­ allowing figuredspecimens forrnerlyin Owen's collection at the idium of P. mega/optha/ma figured by Bruton Hunterian Museum,Glasgow to be transferred to the Paleon­ (1968, pl. 11, fig. 5) in being more convex (tr.). tologisk Museum, Oslo. Owen's work was initiated during the This may be partially a size related feature, but tenure of NERC Research Grant GR3/4471 which is gratefully acknowledged. the smaller of the Norwegian cranidia is distinctly more convex ( tr.) than a specimen of comparable Manuscript received January 1988 size figured by Bruton (1968, pl. 11, fig. 5). The pygidia of P. aff. mega/optha/ma are more trans­ verse than those of the Swedish species. Bruton (1968, p. 28) commented on the sirnilarity in dor­ References sal view of P. aff. megalopthalma to P. lewisi Apollonov,M. K. 1974: (Ashgillian Trilobites of Kazakhstan). (Salter, 1867) from ? Ashgill strata near Oswestry, Jzdatelystvo Nauka Kazakhskoy S.S.R.,Alma Ata. 136 pp, North Wales but noted that the Welsh species has 21 pls. Barrande,J. 1846: Notice preliminaire sur le Systeme Silurien et a narrower ( tr.) glabeila in palpebral view. The les trilobites de Boheme. Leipsic. vi+ 97 pp. pygidium of P. lewisiis much more elongate than Bruton, D. L. 1968: The genus Panderia from the that of P. aff. mega/opthalma. Ordovician of Scandinavia and the Baltic Areas. Norsk Geo· logisk Tidsskrift 48, 1-53. Bruton, D. L. 1971: Middle and Upper Ordovician illaenids P. insulana Bruton. The holotype and only known Trilobite News l, 36. Univ. Oslo,Paleont. Museum,Norway. cephalon is from the upper part of the Sørbakken Brøgger,W., C. 1887: Geologisk kart over øerne ved Kristiania, Limestone Fm. on Frognøya (see Bruton 1968, Nyt Magazin for Naturvidenskaberne 31, 1-36. pp. 24-25, pl. 8, figs. 2, 5, 6, 8, 9, pl. 9, fig. 2). Dalman, J. W. 1827: Om Palaeaderna, eller de så kallade P. insulana resembles two Swedish species: P. Trilobiterna. Kongliga Svenska Vetenskaps-Academiens Hand/ingar l, 113-152. erratica Bruton, 1968 from erratic blocks of the Dean,W. T. 1978: The trilobites of the Chair of Kildare Lime­ Ostersjo Limestone and the Lower Jonstorp For­ stone (Upper Ordovician) of eastern Ireland. Palaeonto­ mation and P. edita Bruton, 1968 from the Boda graphical Society (Monographs) (3),99-129. Limestone. As Bruton (1968, p. 25, text-fig. 2B­ Harper,D. A. T. & Owen,A. W. 1984: The Caradoc brachio­ pod and trilobite fauna of the upper Kirkerud Group,Hade­ D) discussed, the position of the transverse suture land, Norway. Geologica et Palaeontologica 18, 21-51, pls. in P. insulana is intermediate between those of 1-6. the two Swedish species and he considered that Harper,D. A. T., Owen, A. W. & Williams, S. H. 1985: The the marginal migration of this su ture has tempora! Middle Ordovician of the Oslo Region,Norway, 34. The type significance. Bruton also noted that P. edita has Nakholmen Forrnation (upper Caradoc), Oslo, and its fauna! significance. Norsk Geologisk Tidsskrift 64, 239-312. a longer anterior part of the glabella than P. Hawle,I. & Corda,A. J. C. 1847: Prodrom einer Monographie insulana and that the free cheeks of P. erratica are der b6hmischen Trilobiten. Prague. 176 pp. broader and the facial sutures more convergent Holm, G. 1882: De svenske artena af Trilobitslaktet Jllaenus frontally than in the Frognøya specimen. Dean (Dalman). Kungliga Svenska Vetenskaps-Akademiens Hand­ /ingar 7, 1-148. (1978, pp. 108--109, pl. 51, figs. 7, 8; pl. 52, figs. Holm,G. in Schmidt,F. 1886: Revision der ostbaltischen silu­ 1-14, 16, 17) compared material from the Chair rischen Trilobiten. Ill,Illaeniden. Memoires de L'Akademie of Kildare Limestone (probably Rawtheyan) in Imperial des Sciences St. Petersbourg (7) 33, (8), 1-173. 258 D. L. Bruton & A. W. Owen NORSK GEOLOGISK TIDSSKRIFT 68 (1988)

Hughes, C. P. 1969: The Ordovician trilobite faunas of the Trilobiten aus dem bohmischen Ordovizium. Casopis pro Builth-Llandrindod Inlier, Central Wales. Part l. Bulletin of Mineralogii a Geologii 25, 264-274. the British Museum Natura/ History (Geology) 18 (3), 39-- Price, D. 1974: Trilobites from the Sholeshook Limestone 103. (Ashgill) of South Wales. Palaeontology 17, 841-868. Ingham, J. K. 1970: A monograph of the upper Ordovician Price, D. 1980: The Ordovician trilobite fauna of the Sholeshook trilobites from the Cautley and Dent districts of Westmorland Limes tone Formation of South Wales. Palaeontology 23, 839-- and Yorkshire. Palaeontographical Society (Monographs) 887. (1), 1-58. Price, D. 1981: Ashgill trilobite faunasfrom the Llyn Peninsula, Jaanusson, V. 1954: Zur Morphologie und Taxonomie der North Wales, U.K. Geological Journa/ 16, 201-216. lllaeniden. Arkiv for Mineralogi och Geologi l, 545-583. Raymond, P. E. 1916: New and old trilobites from Jaanusson, V. 1957: Unterordovizicshe lllaeniden aus south-eastern Wisconsin, with notes on the genera of the Skandinavien. Bulletin of the Geological lnstitutions of the lllaenidae. Bulletin of the Museum of Comparative Zoology University of Uppsala 38, 79--165. Harvard College 60, 1-41. Jaanusson, V. 1959: Family lllaenidae Hawle & Corda 1847. Jn Salter, J. W. 1849. Figures and descriptions illustrative of British Moore, R. C. (ed.): Treatise on Jnvertebrate Paleontology, organic remains. Memoir of the Geological Survey of the Part O, Anhropoda l, pp. 0372-0375. Geological Society of United Kingdom, Decade 2; 35 pp. , pls. 1-9. America aned University of Kansas Press. Salter, J. W. 1867. The Trilobites of the Silurian, , Kielan, Z. 1960: Upper Ordovician trilobites from Poland and etc., Formations, Part IV (Silurian). Palaeontographica/ some related forms from Bohemia and Scandinavia. Palae­ Society (Monographs), 177-214, pls. 25-30. ontologia Polonica 11, i-vi, 1-198. Snajdr, M. 1957: Classificationof the Family lllaenidae (Hawle Kiær, J. 1897: Faunistische Uebersicht der Etage 5 des nor­ et Corda) in the Lower Paleozoic of Bohemia. Sbornik vegischen Silursystems. Skrifter utgitt uv Det Norske Vid­ Ostfedniho Ostavu Geologickeho 23, 125-284. enskaps-Akademie i Oslo. Matematisk-Naturvidenskapelig Snajdr, M. 1983: O statuta Alceste Hawle et Corda, 1847 Klasse, 1897, No. 3, 1-76. (Trilobita). Casopis Narodniho Muzea 152, 9--11. Kjerulf, T. 1865: Veiviser ved geologische Excursioner i Chris­ Størmer, L. 1945: Remarks on the Tretaspis (Trinucleus) Shales tiania Omegn. Universitets-perogram sem. 2, iv + 43 pp. of Hadeland with descriptions of trilobite faunas. Norsk Geol­ Lane, P. D. & Thomas, A. T. 1983. A review of the trilobite ogisk Tidsskrift 25, 379-425. suborder Scutelluina. Special Papers in Palaeontology 30, Tomczykowa, E. & Tomczyk, H. 1970: Stratigraphy: the 141-160. Ordovician. In Sokalowski, S. (ed.): The Geology of Poland. Modlinski, z. & Pokorski, J. 1969: Stratygrafia ordowiku w Vol. l. Stratigraphy Pan I. Pre- and Palaeozoic. wiercenice Jezioro Okragle l (Stratigraphy of Ordovician in Wydawnictwa Geologiczne, Warsaw. borehole Jezioro Okragle). Kwartalnik geologiczny 12, 777- Volborth, A. von. 1863: Uber die mit glatten Rumpfgliedern 793 (in Polish with Russian and English summaries). versehenen russischen Trilobiten, nebst einem Anhange iiber Miinnil, R. 1966: (Evolution of the Baltic Basin during the die Bewegungorgane und iiberdas Herz derselben. Memoires Ordovician). Publications of the Geological Institute of the de L'Akademie Imperial des Sciences St. Petersbourg, Serie Estonian Academy of Science Tallinn (in Russian with 7, 6 (2), 1-47. Estonian resume and English summary), 199 pp. + maps. Volborth, A. von. 1864: Uber einige neue esthlandische Owen, A. W. 1977: Upper Ordovician stratigraphy and trilobite lllaenen. Memoires de L'Academie Imperial des Sciences St faunas of the Oslo Region, with special reference to Hadeland Petersbourg, Serie 7, 8, (9), 1-11. and Ringerike. Unpublished PhD thesis, Univ. of Glasgow. Warburg, E. 1925: The trilobites of the Leptaena limestone in Vol. l,512 pp., Vol. 2, i-xvi + 34 plates. Dalarna. Bulletin of the Geological Jnstitutions of the Uni­ Owen, A. W. 1978: The Ordovician and silurian stratigraphy versity of Uppsala 17, 1-446. of Central Hadeland, South Norway. Norges geologiske Whittard, W. F. 1961: The Ordovician trilobites of the Shelve undersøkelse 338, 1-23. Inlier, West Shropshire. Palaeontographical Society (Mono­ Owen, A. W. 1979: The upper Ordovician succession at Nor­ graphs), (6), 197-228. derhov and on Frognøya in Ringerike, Norway. Norsk Geol­ Whittington, H. B. 1966: A monograph of the Ordovician ogisk Tidsskrift 58, 245-258. trilobites of the Bala area, Merioneth. Palaeontographical Owen, A. W. 1981: The Ashgill trilobites of the Oslo Region, Society (Monographs) (3), 63-92 Norway. Palaeontographica Abteilung A 175, 88 pp. + 17 pl. Williams, S. H. & Bruton, D. L. 1983: The Caradoc-Ashgill Owen, A. W. & Bruton, D. L. 1980: Late Caradoc-early Ashgill boundary in the central Oslo Region and associated graptolite trilobites of the central Oslo Region, Norway. Palae­ faunas. Norsk Geologisk Tidsskrift 63, 147-191. ontological Contributionsfrom the University of Oslo, Num­ Zhou, Z. & Dean, W. T. 1986: Ordovician Trilobites from ber 245, 42 pp. Paleontologisk Museum, Oslo, Norway. Chedao, Gansu Province, north-west China. Palaeontology Pfibyl, A. & Vanek, J. 1980. Neue Erkenntnisse iiber einige 29, 743-786.