GFF Agnostids from the Upper Cambrian of ...

3 downloads 0 Views 3MB Size Report
Dec 9, 2009 - Shergold, J.H. & Webers, G.F., 1992: Late Dresbachian (Idamean) and other trilobite faunas from the Heritage Range, Ellsworth Mountains, ...
This article was downloaded by: [Lunds Universitet] On: 18 April 2010 Access details: Access Details: [subscription number 918253869] Publisher Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 3741 Mortimer Street, London W1T 3JH, UK

GFF

Publication details, including instructions for authors and subscription information: http://www.informaworld.com/smpp/title~content=t902829199

Agnostids from the Upper Cambrian of Västergötland, Sweden

Per Ahlberg a;John Ahlgren b a Department of Geology, Historical Geology and Palaeontology, Lund, Sweden b Department of Art and Media, Skövde, Sweden Online publication date: 09 December 2009

To cite this Article Ahlberg, Per andAhlgren, John(1996) 'Agnostids from the Upper Cambrian of Västergötland, Sweden',

GFF, 118: 3, 129 — 140

To link to this Article: DOI: 10.1080/11035899609546247 URL: http://dx.doi.org/10.1080/11035899609546247

PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

GFF

Article

volume 118 (1996), pp. 129-140.

Agnostids from the Upper Cambrian of Västergötland, Sweden PER AHLBERG and JOHN AHLGREN

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

Ahlberg, P. & Ahlgren, J., 1996: Agnostids from the Upper Cambrian of Västergötland, Sweden. GFF, Vol. 118 (Pt. 3, September), pp. 129140. Stockholm. ISSN 1103-5897. Abstract: Fourteen agnostid species are described from the Upper Cambrian of Västergötland, Sweden. They are assigned to eleven genera: Agnostus, Homagnostus, Trilobagnostus, Lotagnostus, Kormagnostus, Glyptagnostus, Hypagnostus, Peratagnostus, Cristagnostus, Pseudagnostus, and Aspidagnostus. Cristagnostus and Aspidagnostus have not previously been recorded from Scandinavia. The majority of the species are from the lower part of the Upper Cambrian, i.e., the Agnostus pisiformis, the Olenus and Homagnostus obesus, and the Parabolina spinulosa Zones. Agnostids are very rare in the upper part and only three species seem to be represented, viz. Trilobagnostus rudis, T. holmi, and Lotagnostus trisectus. Keywords: Arthropoda, Agnostida, taxonomy, biostratigraphy, Upper Cambrian, Västergötland, Sweden. Per Ahlberg, Department of Geology, Historical Geology and Palaeontology, Sölvegatan 13, SE-223 62 Lund, Sweden, fax 046-121477, email [email protected]. John Ahlgren, Department of Art and Media, Högskolan i Skövde, P.O. Box 408, SE-541 28 Skövde, Sweden, fax 0500-464835. Manuscript received 11 December 1995. Revised manuscript received 4 April and accepted 16 April 1996.

The Upper Cambrian of Scandinavia consists almost exclusively of dark grey or black, kerogen-rich mudstones and shales with lenses or beds of dark grey limestone (anthraconite). A concentration of limestone lenses of considerable lateral persistence (the "Great Stinkstone Bed") occurs in the Homagnostus obesus Zone, locally extending down into the Agnostus pisiformis and up into the Parabolina spinulosa Zones. The mudstones and shales are generally parallel-laminated with a high content ( 5 20%) of organic carbon (e.g. Andersson et al. 1985), and they are referred to as alum shale. The alum shale sequences are condensed and accumulated over long periods of time under dominantly anoxic or euxinic conditions in an epicontinental sea (e.g. Thickpenny 1987). The palaeontology, stratigraphy, and geochemistry of the alum shales have been extensively studied (see, e.g., Westergârd 1922, Martinsson 1974, and Bergström & Gee 1985 for general reviews). The Upper Cambrian alum shale is characterised by intervals with very abundant, but low-diversity trilobite faunas, with brachiopods and ostracodes as minor faunal constituents. The trilobite faunas are generally dominated by olenid trilobites, except in the lowermost part of the sequence where agnostids may occur in abundance. The few documented occurrences of large trilobites and brachiopods in the Upper Cambrian are generally restricted to light-coloured limestone intercalations (Bergström 1980), and it is possible that these limestones represent regressive events (cf. Nicoll et al. 1992, pp. 387-388).

The Lower Palaeozoic of Västergötland, southern Sweden, occurs as erosional outliers resting on a Precambrian crystalline basement. The outliers constitute the geologically famous hills or mountains of Västergötland, and they have a long history of palaeontological research, extending back to the eighteenth century. The Upper Cambrian of Västergötland is well exposed in a great number of old quarries. It attains a thickness of about 15 m and is most complete on Kinnekulle and in the Billingen-Falbygden area of central Västergötland (Fig. 1). Trilobites occur frequently throughout the succession, but in general the occurrences are restricted to the concretionary limestones (Westergârd 1922). Over a number of years, the junior author has collected thousands of trilobites from the Upper Cambrian of Västergötland, particularly from Kinnekulle. The material includes several agnostid species from various stratigraphical levels. In this paper fourteen species assigned to eleven genera are described or discussed. The majority of the species are from the lower part of the Upper Cambrian, i.e., the Agnostus pisiformis, the Olenus and Homagnostus obesus, and the Parabolina spinulosa Zones (Fig. 2). Agnostids are very rare in the upper part of the sequence and only three species seem to be represented, viz. Trilobagnostus rudis, T. holmi, and Lotagnostus trisectus. Because of their abundance, wide geographic distribution, and relatively rapid evolution, agnostids afford the best means of correlating Cambrian strata, and they have been widely used for intercontinental correlations. The record of Cristagnostus papilio Rushton, 1978 and Aspidagnostus cf. stictus Öpik, 1967 in the Upper Cambrian of Västergötland is of particular interest for long-distance correlations. These species have not previously been recorded from Scandinavia. C. papilio is known from the A. pisiformis Zone of England and Newfoundland, and provides additional corroboration for correlations within the A. pisiformis Zone in the North Atlantic region (see Rushton 1978, p. 249). The record of A. cf. stictus provides further evidence for the correlation of the Glyptagnostus reticulatus Zone (lower Idamean Stage) of Australia with the lower part of the Olenus and Homagnostus obesus Zone of Scandinavia.

Systematic palaeontology Terminology. — The morphological terms used herein are those advocated by Robison (1982, pp. 134-135, text-fig. 2) and Shergold et al. (1990, pp. 8-16, figs. 1-6), except that rachis and dorsal furrow are preferred to axis and axial furrow. The pygidial rachis is taken to exclude the articulating device. Measurements. - Measurements were made with a micrometer eyepiece fitted in a binocular microscope. The accuracy of all measurements is to 0.05 mm. Estimated values and transverse

130

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian of Vastergötland

Limit of Cambrian-SMuritn cov«f — « — Limit of dolarita cov«r

Falbygden

n

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

S

V " ^

GFF 118(1996) Fig. 1. A. Map of central Västergötland showing the extent of Cambrian-Silurian rocks, and the location of Kinnekulle and the BillingenFalbygden area. B. Map of Kinnekulle showing the distribution of Middle-Upper Cambrian strata (shaded), and localities referred to in the text. 1, Hällekis; 2, Hönsäter; 3, Krokagârden; 4, Sätra; 5, Gum; 6, Backeborg; 7, Blomberg; 8, Kakeled; 9, Hjälmsäter; 10, Trolmen; 11, Rabäck.

»

»

--^'~^ \

/

measurements arrived at by doubling the width from the sagittal line are marked with a question-mark. The following symbols have been used for measured parameters: Lc = maximum length (sag.) of cephalon; Lbc = length (sag.) of cephalic border (incl. border furrow); Lac = length (sag.) of cephalic acrolobe; G = length (sag.) of glabella; N = distance (sag.) from rear of glabella to highest point of median node; We = maximum width (tr.) of cephalon; Wg = maximum width (tr.) of glabella; Lpl = length (sag.) of pygidium (incl. articulating half-ring); Lp2 = length (sag.) of pygidium (excl. articulating device); Lr = length (sag.) of pygidial rachis (excl. articulating device); Lbp = length (sag.) of posterior pygidial border (incl. border furrow); Wp = maximum width (tr.) of pygidium; Wr = maximum width (tr.) of pygidial rachis.

Synonymy. — • 1818 Entomostracites pisiformis — Wahlenberg, p. 42, pi. 1, fig. 5. «1922 Agnostus pisiformis (L.) - Westergârd, pp. 115-116, pi. 1, figs. 1-3 [synonymy to date]. »1923 Agnostus pisiformis Linné - Poulsen, pp. 21-22, pi. 1, fig. 1 [synonymy to date]. »1958 Agnostus (Agnostus) pisiformis Linnaeus 1757 Henningsmoen, pp. 181-182, pi. 5, figs. 1-12 [further synonymy]. «1973 Agnostus (Agnostus) pisiformis (Linnaeus, 1757) Schrank, pp. 88-89, pi. 2, figs. 6-7. »1976 Agnostus pisiformis (Wahlenberg) - Reyment, p. 3, fig. 3a-b. »1977 Agnostus pisiformis (Linné) - Pek, pi. 12, fig. 3. »1978 Agnostus pisiformis pisiformis (Wahlenberg, 1818) - Rushton, p. 258, pi. 24, figs. 15-19 [further synonymy]. »1987 Agnostus pisiformis (Linnaeus 1757) - Müller & Walossek, pp. 1-124, pis. 1-33. »1988 Agnostus pisiformis (L.) - Walossek & Müller, pp. 11-35, figs. 1-11. •1989 Agnostus pisiformis (Wahlenberg, 1818) - Ahlberg, pp. Repositories. - Illustrated and cited specimens are deposited in 142-143, fig. 5A-C. »1990 Agnostus (Agnostus) pisiformis the type collections of the Geological Survey of Sweden, Upp- (Wahlenberg, 1818) - Shergold et al., p. 32, fig. 9:la-b. »1992 sala (SGU), and the Dept. of Geology, University of Lund (LO). Agnostus pisiformis (Linnaeus, 1757) - Rudolph, pp. 159-162, pi. 1, figs. 1-6, pi. 2, figs. 1-5.

Order Agnostida Salter, 1864 Family Agnostidae M'Coy, 1849 Genus Agnostus Brongniart, 1822 Type species. - Entomostracites pisiformis Wahlenberg, 1818 (p. 42, pi. 1, fig. 5) from the Agnostus pisiformis Zone of Västergötland, Sweden; by subsequent designation of Jaekel (1909, p. 399). Remarks. - The genus was recently discussed by Robison (1994, pp. 29-31) and his generic concept is followed here.

Agnostus pisiformis (Wahlenberg, 1818) (not figured)

Lectotype. - A cephalon from Hönsäter, Kinnekulle, Västergötland, illustrated by Wahlenberg (1818, pi. 1, fig. 5) and Reyment (1976, fig. 3a-b); selected by Shergold et al. (1990). It is deposited in the type collections of the Palaeontological Museum, University of Uppsala, as no. Vg. 819. Material. - Thousands of specimens from many localities. Remarks. - Agnostus pisiformis is widely distributed in Scandinavia, and in general it occurs in abundance wherever the Agnostus pisiformis Zone is developed. It has been described and discussed extensively in the literature, and with the publication of Müller & Walossek's (1987) comprehensive monograph on its morphology, ontogeny, and life habit, A. pisiformis must rank as one of the best known fossil arthropods. Cephala and pygidia of

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

GFF118 (1996)

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian of Vastergötland

A. pisiformis were illustrated already by Bromell (1729, p. 527; cf. Regnéll 1949, p. 19, fig. 11). Later, Linnaeus (1747, p. 24 and 1751, p. 122; not 1757 as erroneously stated by many authors) noted the presence of the species at Gössäter in Västergötland and at Andrarum in Scania (cf. Nathorst 1907, p. 46). In these travel accounts Linnaeus briefly described but did not name the species, and, as shown by Rushton (1978, p. 258), the earliest valid reference to the specific name pisiformis seems to be that of Wahlenberg (1818). Agnostus pisiformis spiniger (Dalman, 1828) differs from the nominal subspecies in having distinct posterolateral spines on the cephalon (see Westergârd 1946, p. 86, pi. 13, fig. 15; Rudolph 1992, pi. 1, fig. 4). In Västergötland the former subspecies is fairly common in the lower part of the Agnostus pisiformis Zone, and on Kinnekulle (e.g. at Hällekis, Blomberg, Kakeled, and Norra Krokagârden) it is associated with Schmalenseeia amphionura Moberg, 1903. This species seems to be restricted to the lowermost part of the A. pisiformis Zone in Sweden (Westergârd 1948, p. 3). Thus, A. pisiformis spiniger appears to be indicative of the lower part of the A. pisiformis Zone, and it may be regarded as a chronosubspecies. Material collected on Billingen, Västergötland, shows that A. pisiformis pisiformis ranges upwards into the lower part of the Zone of Olenus and Homagnostus obesus.

131

Peltura scarabaeoides

a

Peltura minor Protopeltura praecursor S o.

Leploplastus

= s- « '2

Parabolina spinulosa

5

2

a

a

2

I

1

|

I

3

i8 Ig

Homagnostus obesus Apnostus pisiformis

1

t

I

1 I I t I I I I

Ml'

Fig. 2. Occurrences of agnostids in the Upper Cambrian of Västergötland.

Lectotype. - A nearly complete specimen illustrated by Belt (1867, pi. 12, fig. 4a); re-illustrated and selected by Rushton in Allen et al. (1981, pi. 16, fig. 2). Material. — Thousands of specimens.

Remarks. - Pratt (1992, pp. 27-28) discussed the intraspecific morphological variability and expanded the concept of this Genus Homagnostus Ho well, 1935 species. If Pratt's flexible taxonomic approach is accepted, a Type species. - Agnostus pisiformis var. obesus Belt, 1867 (p. number of species names can be regarded as junior subjective 295, pi. 12, fig. 4) from the Olenus Zone of North Wales; by synonyms of Homagnostus obesus. These include, for instance, Agnostus tumidosus Hall & Whitfield, 1877, Homagnostus original designation. ultraobesus Lermontova, 1940, and H. alaskensis Palmer, 1968. Although H. obesus seems to be a variable species, two speciRemarks. — The concept of Homagnostus has been discussed exmens figured and discussed by Westergârd (1922, pi. 1, figs. 5 tensively in the literature (e.g. Westergârd 1947, p. 4; Palmer 6) seem to fall outside the range of variation seen in H. obesus. 1960, p. 62,1962, p. F-12; Rushton 1978, p. 259; Shergold 1982, The specimens are from the lower Parabolina spinulosa Zone p. 17; Shergold & Cooper 1985, p. 95; Shergold & Webers 1992, (P. brevispina Subzone), and Westergârd (1947, p. 4) assigned p. 131; Jago & Brown 1992, pp. 60-61). Its characteristics are them to a ne w subspecies H. obesus laevis. One of the specimens well shown and summarized by Palmer (1960). Robison (1988, (Westergârd 1922, pi. 1, fig. 5; SGU 123) was discussed by Sherp. 33) emended the generic diagnosis to include species having a gold & Cooper (1985, p. 95) and Shergold & Webers (1992, p. uniformly developed preglabellar median furrow and a pygidial 131). It lacks a median preglabellar furrow, and Shergold & Werachis that extends to the posterior border furrow. Recently, bers (1992) suggested that it may belong to H. ultraobesus LerShergold et al. (1990) reverted to Westergârd's (1947) concept montova, 1940. The other specimen (Westergârd 1922, pi. 1, fig. and treated Homagnostus as a subgenus of Agnostus. Although it is difficult to adequately diagnose and delimit Homagnostus 6; SGU 124) is flattened and fairly poorly preserved, but differs from Agnostus and other closely related genera, such as Onc- from the type and other material of H. obesus in having a naragnostus and Trilobagnostus, we follow Rushton (1978) and rower and shorter pygidial rachis. Pratt (1992, p. 27) and consider Homagnostus as a separate Occurrence. - Homagnostus obesus is widely distributed in the genus. Zone of H. obesus and Olenus of Scandinavia, and generally it occurs in abundance. In Västergötland, it occurs throughout the Homagnostus obesus (Belt, 1867) zone at many localities. At Gum on southern Kinnekulle, it Fig. 3A-G. ranges upwards into the Parabolina spinulosa Zone. Synonymy. - »1867 Agnostus pisiformis, Lin., var. obesus - Belt, p. 295, pi. 12, fig. 4. »1922 Agnostus pisiformis obesus Belt Westergârd, p. 116 (partim), pi. 1, fig. 4a-b only. »1992 Homagnostus obesus (Belt, 1867) - Pratt, pp. 27-28, pi. 1, figs. 2638 [see for synonymy]. »1992 Homagnostus obesus (Belt, 1867) - Shergold & Webers, p. 131.

Genus Trilobagnostus Harrington, 1938 Type species. - Agnostus innocens Clark, 1923 (p. 122, fig. 7 only) from the Levis Formation of Quebec, Canada; by original designation. The holotype (a pygidium) was recently re-illustrated by Ludvigsen et al. (1989, pi. 1, fig. 25).

132

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian ofVästergötland

GFF118(1996)

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

WS¥;

Fig. 3. A-G. Homagnostus obesus (Belt, 1867); Zone of//, obesus and Olenus at Andrarum, Scania (E-G), or transition beds between the Zone of H. obesus and Olenus and the Parabolina spinulosa Zone at Gudhem in the Falbygden area, Västergötland (A-D). A, cephalon; LO 7316t; xl3. B, cephalon; LO 7317t; xl2. C, cephalon; LO 7318t; xl4. D, pygidium; LO 7319t; x l l . E, cephalon; original of Westergârd (1947, pi. 1, fig. lOa-b); coll. A.H. Westergârd 1913; SGU 6433; xl2. F, pygidium; original of Westergârd (1947, pi. 1, fig. 1 la-b); coll. A.H. Westergârd 1913; SGU 6434; xl 1. G, complete specimen; original of Westergârd (1922, pi. 1, fig. 4a-b); coll. A.H. Westergârd 1913; SGU 122a; x9. H-J. Trilobagnostus rudis (Salter, 1864); Peltura minor Zone. H, pygidium; Hönsäter, Kinnekulle; LO 7320t; xl4.1, cephalon; Hönsäter; LO 7321t; xl 1. J, pygidium; Sätra, Kinnekulle; original of Westergârd (1947, pi. 1, fig. 13a-b); coll. A.H. Westergârd 1919; SGU 6436; xl4. K-P. Trilobagnostus holmi (Westergârd, 1922); Peltura scarabaeoides Zone. K, cephalon; Blomberg, Kinnekulle; original of Westergârd (1922, pi. 1, fig. 13); coll. G. Holm 1896; SGU 129; xl6. L, cephalon; eastern slope of Kinnekulle; LO 7322t; xl4. M, pygidium; eastern slope of Kinnekulle; LO 7323t; xl6. N, pygidium; Blomberg; original of Westergârd (1922, pi. 1, fig. 14); coll. G. Holm 1896; SGU 130; x l 4 . 0 , pygidium; lectotype; Rabäck, Kinnekulle; original of Westergârd (1922, pi. 1, fig. 15a-b); coll. A.H. Westergârd 1918; SGU 131; xl6. P, cephalon; eastern slope of Kinnekulle; LO 7324t; xl7.

GFF118 (1996)

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian ofVästergötland

Remarks. - Ludvigsen et al. (1989, p. 12) showed that Trilobagnostus should not be referred to and regarded as a subgenus of Lotagnostus, and, following Shergold et al. (1990), it is here given generic status.

133

Lectotype. - A complete pygidium (SGU 131; Fig. 30) illustrated by Westergârd (1922, pi. 1, fig. 15a-b); selected by Henningsmoen (1958, p. 184). Material. - 14 cephala and 8 pygidia.

Trilobagnostus rudis (Salter, 1864) Remarks. - This species was originally described as a variety of Trilobagnostus rudis (Salter, 1864) by Westergârd (1922), but it is here considered a separate species. It may be distinguished Synonymy. - »1864 Agnostus princeps, ß. rudis - Salter, p. 4, pi. from T. rudis because the cephalon is more subcircular in out1, fig. 3 only. «1906 Agnostus rudis, Salter-Lake, pp. 21-22, pi. line, the cephalic border is narrower, and because the glabella is 2, figs. 13-16. *!922Agnostus rudis Salter-Westergârd, p. 118, wider and distinctly tapered forward. The glabella of T. holmi is pi. 1, fig. 17. »1947 Agnostus (Homagnostus) rudis Salter(?) - broadly rounded anteriorly and provided with a deeply impresWestergârd, pp. 4-5, pi. 1, figs. 13a-b. »1972 Rudagnostus rudis sed transglabellar furrow (F3), which is curved slightly back(Salter) - Shergold, pp. 20-21. »1988 Rudagnostus rudis (Salter, wards medially. The posteroglabella is strongly convex and pro1864)-Morris, p. 205. vided with a sagittally elongated node slightly anterior to the midpoint. The lateral furrow (F2) is nearly obsolete. The border Type data. - See Shergold (1972, p. 20), Morris (1988, p. 205). is downsloping anteriorly and laterally. There is no indication of a median preglabellar furrow. Material. - Three pygidia and one cephalon. The pygidia of T. holmi resemble those of T. rudis, but differ in having a considerably narrower border and more posteriorly Remarks. — The specimens from Västergötland closely resemble situated spines. Trilobagnostus rudis, as described by Salter (1864) and Lake (1906) from the Dolgelly Beds of North Wales. The Swedish Occurrence. - The species has been collected from the Peltura material exhibits variation in the shape of the pygidial rachis. scarabaeoides Zone (probably upper part only) at various localMuch of this variation is due to variation in the shape and length ities on Kinnekulle (e.g. Blomberg and Rabäck). of the terminal lobe of the rachis. The anterior rachial furrow (Fl) is only impressed laterally and curved forwards to isolate lateral lobes. This means that the structure of the anterior part of Genus Lotagnostus Whitehouse, 1936 the pygidial rachis is like that of Homagnostus obesus (see Rushton 1983, p. 116, text-fig. 4e). The posterior rachial furrow (F2) Type species. —Agnostus trisectus Salter, 1864 (p. 10, pi. 1, fig. is transverse and straight. The terminal rachial lobe (M3 or pos- 11) from the White-Leaved-Oak Shales (Peltura scarabaeoides teroaxis) is rounded posteriorly and longer (sag.) than Ml and Zone) in the Malvern area, England; by original designation. M2 combined. The cephalon assigned to the species (Fig. 31) has a nearly parallel-sided glabella and an obsolete median pre- Remarks. - Brief notes on the concept of Lotagnostus have been glabellar furrow. The anterior glabellar furrow (F3) is deep and given by Öpik (1963, pp. 53-54), Shergold (1975, pp. 48^9), curved backwards medially. F2 is only impressed laterally and Ludvigsen et al. (1989, pp. 11-12), and Peng (1992, p. 15). curved forwards. The anterior glabellar lobe is rounded anteriorly. Lotagnostus trisectus (Salter, 1864)

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

Fig. 3H-J.

Occurrence. - The species has been found in the Peltura minor Zone at Storeklev on the southern end of Hunneberg, at Sätra on the eastern slope of Kinnekulle (cf. Westergârd 1922, pp. 5455), and from loose boulders about 200 m north of the chapel of Hönsäter, northern Kinnekulle.

Trilobagnostus holmi (Westergârd, 1922) Fig. 3K-P. Synonymy. — »1922 Agnostus rudis Holmi n. van - Westergârd, pp. 118-119, pi. 1, figs. 13-16. »1947 Agnostus (Homagnostus) rudis holmi Wgârd - Westergârd, pp. 5 and 22. »1958 Agnostus (Homagnostus) rudis holmi Westergârd 1922 - Henningsmoen, p. 184. »1982 Micragnostus rudis holmi - Rushton, text-fig. 2. •1988 Micragnostus rudis holmi (Westergârd, 1922) -Morris, p. 139. «1991 Trilobagnostus rudis holmi (Westergârd 1922) Shergold & Sdzuy, p. 205.

Fig. 4A-B. Synonymy. - »1864 Agnostus trisectus - Salter, p. 10, pi. 1, fig. 11. «1922 Agnostus trisectus Salter - Westergârd, p. 117, pi. 1, figs. 11-12 [synonymy to date]. «1981 Lotagnostus trisectus (Salter) - Allen et al., pp. 314-315, pi. 17, figs. 1-2. »1988 Lotagnostus trisectus (Salter, 1864) - Morris, p. 133. »1990 Lotagnostus (Lotagnostus) trisectus Salter, 1864 - Shergold et al., p. 34, fig. 9:7a-b. »1995 Lotagnostus (Lotagnostus) trisectus (Salter, 1864) - Shergold et al., p. 246, pi. 1, fig. 12. Material. — One complete cephalon and one complete pygidium. Dimensions of cephalon (mm; LO 7326t). — Lc = 1.90; Lbc = 0.15; Lac = 1.75; G = 1.35; N = 0.40; We = 1.85; Wg = 0.60. Dimensions of pygidium (mm; LO 7325t). - Lpl = 4.35; Lp2 = 4.00; Lr = 3.25; Lbp = 0.30; Wp = 4.35; Wr = 2.20.

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian of Vastergötland

GFF118 (1996)

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

134

^PS^Hg' -nf/" ^'f-Jftagnostus trisectus (Salter, 1864); lower Pe/íura minorZone at Hönsäter, KinnekuUe. A, pygidium; LO 7325t; XlO. B, cephalon; LO vin p X -A- Kormagnostusi sp.; Agnostuspisiformis Zone at Hjälmsäter, KinnekuUe. C, cephalon; LO 7327t; x l l . D, cephalon; LO 7328t; nelmll¡-PTyn 7 ^ , I]?*?11 " ¥ HyPaS^stus aff. correctus Öpik, 1967; cephalon; Zone ofHomagnostus obesus and Olenus at Hällekis, Kinob^mr áními , - ? ' I T • V w ' ^ " O f t o S P" G - c e P h a l °n; transition beds between the Agnostus pisiformis Zone and the Zone ofHomagnostus I P c i f r Krokagarden, KinnekuUe; LO 7331t; xl4. H, small cephalon; Agnostus pisiformis Zone at Gum, Kinnekulle; LO 7332t; xl6. 7333?x9 J c e X o n W ^ C l d a f t t l ( A n 8 e l i n ' 1 8 5 1 >; ^ ^ of Homagnostus obesus and Olenus at Krokagârden, KinnekuUe. I, cephalon, LO

7336 : xi5 M SS^lo^ST^nT ^

'

Pygldlum

'

L O 7337t

" ^

L

? ?334t; Xl0"K'Cephalon: L 0 7335t; ^

L

- cephalon, latex cast from external mould; LO

: xi«- N, p ygl dium; LO 7338t; XlO. O, pygidium; LO 7339t; x8. P; pygidium; LO 7340t; x l 3 .

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

GFF118 (1996)

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian of Vastergötland

Remarks. - Lotagnostus trisectus is closely comparable to L. americanus (Billings, 1860), a scrobiculate species from the Levis Formation of Quebec, Canada. The latter species was revised by Rasetti (1944, p. 233, pi. 36, figs. 1-2) and Ludvigsen et al. (1989, p. 12, pi. 1, figs. 15-17). It differs from L. trisectus mainly in being partially effaced with a weakly developed median ridge on the posterior lobe of the pygidial rachis. However, slight differences in the degree of effacement appear to be of minor taxonomic importance, and L. trisectus may eventually prove to be a subjective junior synonym of L. americanus. The holotype (by monotypy) of L trisectus cannot be found (Morris 1988, p. 133), and the species is in need of revision based on topotype material from Malvern. The material from Västergötland agrees in all essential features with Salter's (1864), Linnarsson's (1880), and Tullberg's (1880) brief descriptions of Lotagnostus trisectus horn England and Scania, southern Sweden. The cephalon from Västergötland is relatively small with weakly developed, radiating scrobicules, a well defined median preglabellar furrow, and a prominent median node. The anterior and middle glabellar furrows (F2 and F3) are well developed. This cephalon differs from cephala illustrated by Westergârd (1922, pi. 1, fig. 11), Allen et al. (1981, pi. 17, fig. 1), and Shergold et al. (1990, fig. 9:7a) in being less scrobiculate. The pygidium from Västergötland is very weakly scrobiculate, and provided with very small posterolateral spines and a distinctly trilobate terminal rachial lobe (posteroaxis). The pleural field is weakly pitted. It is similar to a well-preserved pygidium illustrated by Westergârd (1922, pi. 1, fig. 12), but differs in having a proportionately wider and shorter terminal rachial lobe.

135

Remarks. - The pygidia are strongly convex and slightly longer (sag.) than they are wide. The acrolobe is unconstricted. The pygidial border is fairly wide, sagittally occupying about 12% of the total pygidial length, and lacks distinct posterolateral spines. The rachis is effaced and poorly defined, but it is long, wide, and nearly parallel-sided. The posterior end of the rachis is completely effaced and lacks a terminal node. In the length, width, and shape of the rachis, the pygidia resemble those of species assigned to the genus Kormagnostus. The generic assignment of the pygidia to hand is uncertain because species of Kormagnostus (see Pratt 1992, pp. 30-33) have a terminal node on the pygidial rachis and a pair of distinct posterolateral spines. In addition, the rachis appears to terminate slightly in front of the border furrow in the pygidia under discussion. The pygidia are associated with three cephala, which may be conspecific. The cephala have an unconstricted acrolobe and lack a median preglabellar furrow. The anterior lobe of the glabella is of low convexity and rounded anteriorly. The anterior glabellar furrow (F3) is well defined and transverse. The posteroglabella is provided with a distinct node, located well in front of the mid-point. The general morphology of the cephala is similar to that of Micragnostus Howell, 1935 and closely related genera, such as Oncagnostus Whitehouse, 1936 and Trilobagnostus Harrington, 1938. Occurrence. - Agnostus pisiformis Zone (loose boulder) at Hjälmsäter, western Kinnekulle. The species is found with abundant specimens of Agnostus pisiformis, and also with Cristagnostus papilio Rushton, 1978.

Occurrence. — The specimens were collected from loose boul- Genus Glyptagnostus Whitehouse, 1936 ders about 200 m north of the chapel of Hönsäter, Kinnekulle. Type species. - Glyptagnostus toreuma Whitehouse, 1936 (pp. Associated olenid trilobites (Ctenopyge angusta, C. modesta, 101-103, pi. 9, figs. 17-20; = Agnostus reticulatus Angelin, and Peltura sp.) are indicative of the lower Peltura minor Zone. 1851, p. 8, pi. 6, fig. 10) from the Georgina Limestone (lower Idamean Stage) of western Queensland, Australia; by original designation.

Genus Kormagnostus Resser, 1938

Type species. — Kormagnostus simplex Resser, 1938 (p. 49, pi. 9, Glyptagnostus reticulatus reticulatus (Angelin, 1851) figs. 11-13; = Agnostus seclusus Walcott, 1884, p. 25, pi. 9, fig. Fig. 4I-P. 14) from the lower Upper Cambrian of Tennessee, U.S.A; by original designation. Synonymy. - »1851 Agnostus reticulatus n. sp. - Angelin, p. 8, pi. 6, fig. 10. »1947 Glyptagnostus reticulatus (Angelin, 1851) Remarks. — The concept of Kormagnostus has recently been disWestergârd, pp. 5-7, pi. 1, figs. 1-6 [see for synonymy]. »1962 cussed by Robison (1988, pp. 43, 45) and Pratt (1992, pp. 30Glyptagnostus reticulatus (Angelin) - Palmer, pp. 16-18, pi. 2, 31). Robison (1988) assigned the genus to the family Peronopsfigs. 1,3,8 [see for synonymy]. *1982 Glyptagnostus reticulatus idae Westergârd, 1936, but following Shergold et al. (1990) and reticulatus (Angelin, 1851) - Shergold, pp. 23-24, pi. 4, figs. 1Pratt (1992) we consider it a genus within the family Agnostidae. 12 [see for synonymy]. »1992 Glyptagnostus reticulatus (Angelin, 1851) - Pratt, p. 41, pi. 6, figs. 26-35 [see for synonymy]. Kormagnostus? sp. •1992 Glyptagnostus reticulatus Angelin (1851) sensu lato Shergold & Webers, pp. 132-133, pi. 2, figs. 13-16. «1992 Fig. 4C-E. Glyptagnostus reticulatus reticulatus (Angelin, 1851) — Peng, p. 22, fig. 10A-F. »1992 Glyptagnostus reticulatus reticulatus Material. — Two pygidia and three cephala. (Angelin, 1851)-Jago & Brown, p. 61, pi. 1, fig. T. »1993 GlyptDimensions of pygidium (mm; LO 7329t). — Lpl = 3.45; Lp2 = agnostus reticulatus (Angelin, 1851) - Rudolph, pp. 51-52, fig. 1A-B. »1995 Glyptagnostus reticulatus (Angelin, 1851) sensu 3.10; Lr = 2.40?; Lbp = 0.40; Wp = 3.35; Wr = 1.65. lato - Shergold et al., p. 250, pi. 1, figs. 13-15.

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

136

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian of Västergötland

GFF118 (1996)

Material. - Numerous specimens from various localities on Kinnekulle.

is angulate in the cephalon to hand, whereas it is broadly rounded in H. correctus.

Remarks. - Glyptagnostus reticulatus and its subspecies are discussed extensively in the literature (e.g. Westergârd 1947, pp. 5 7; Palmer 1962, pp. F16-F18; Jago 1974, pp. 120-122; Rushton 1983, pp. 117-118; Peng 1992, p. 22; Pratt 1992, p. 41; Shergold & Webers 1992, pp. 132-133; Rudolph 1993, pp. 51-52). Palmer (1962) discussed the evolutionary development of the pygidium of Glyptagnostus, and regarded G. reticulatus angelini (Resser, 1938) as a valid subspecies. Pratt (1992) concluded, however, that the characteristics of this subspecies intergrade with those of the nominal subspecies, and he considered G. reticulatus angelini to be an invalid subspecies.

Occurrence. — Zone of Homagnostus obesus and Olenus in an old quarry at Hàllekis, Kinnekulle (c. 600 m WNW of the chapel of Hönsäter). Associated trilobites include, e.g., Aspidagnostus cf. stictus Öpik, 1967, Homagnostus obesus (Belt, 1867), Hypagnostusl sp., and Olenus cf. gibbosus (Wahlenberg, 1818).

Occurrence. — Glyptagnostus reticulatus reticulatus is widely distributed in the lower part (Olenus gibbosus and O. truncatus Subzones) of the Zone of Homagnostus obesus and Olenus in Scandinavia (Westergârd 1947, p. 7). In Västergötland it has been recorded from a great number of localities on Kinnekulle. The specimens figured herein (Fig. 4I-P) are from the Olenus gibbosus Subzone at Krokagàrden, eastern Kinnekulle.

Family Spinagnostidae Howell, 1935 Genus Hypagnostus Jaekel, 1909 Type species. - Agnostus parvifrons Linnarsson 1869 (p. 82, pi. 2, figs. 56-57) from the Hypagnostus parvifrons Zone ofVästergötland, Sweden; by original designation.

Hypagnostus äff. correctus Öpik, 1967 Fig. 4F. Material. — One complete cephalon. Dimensions (mm, LO 7330t). - Lc = 2.30; Lbc = 0.20; Lac = 2.10; G = 1.30; N = 0.80; We = 2.55; Wg = 0.95. Description. - The cephalon is highly convex and 1.1 times as wide as it is long. The glabella, occupying about 57% of the total cephalic length, is slightly tapered forward, broadly rounded posteriorly, angulate in front, and about 1.4 times as long as its maximum width. A faint median node is situated in the anterior part. The basal lobes are simple and separated from the glabella and the genae by well-impressed furrows. The acrolobe is unconstricted with strongly down-sloping genae. The preglabellar field is longer (sag.) than the width (tr.) of the posterior part of the gena. The border is of almost uniform width and non-deliquiate. Sagittally, the border and border furrow combined occupy about 9% of the total cephalic length. Remarks. - The cephalon most closely resembles that of Hypagnostus correctus Öpik, 1967 from the basal Mindyallan Stage of northwestern Queensland, Australia. It differs from the latter in lacking a node at the posterior end of the glabella ('tgn' of Öpik 1967, fig. 16). Furthermore, the anterior end of the glabella

Hypagnostus sp. Fig. 4G-H. Material. - One moderately large cephalon (LO 733It) and two small cephala, 0.7 and 0.9 mm long. Dimensions (mm, LO 7331t). - Lc = 2.45; Lbc = 0.20; Lac = 2.25; G = 1.35; N = 0.90; We = 2.65; Wg = 0.95. Remarks. - The cephala are non-scrobiculate and unconstricted. The glabella is slightly longer than half that of the total cephalic length and widest at about mid-length. It is obtusely angulate anteriorly and broadly rounded posteriorly. The large specimen has a distinct node in the anterior half of the glabella and a faint median depression in the anterior part of the preglabellar field. The cephalic border is widest anteriorly and antero-laterally. The small cephala are subcircular in outline and provided with a uniformly wide border. Occurrence. - The small cephala were collected from the Agnostus pisiformis Zone (loose boulders) in a quarry at Gum, c. 3.3 km WNW of Husaby church, southern Kinnekulle. The large cephalon (Fig. 4G) is from a loose boulder in a quarry at Krokagârden, eastern Kinnekulle. It was probably recovered from the transition beds between the Agnostus pisiformis Zone and the Zone of Homagnostus obesus and Olenus. Hypagnostus? sp. Fig. 5A-D. Material. - Five pygidia, ranging in length from 1.6 to 2.9 mm. Remarks. -The pygidia are non-scrobiculate, wider than they are long, and provided with distinct posterolateral spines. The rachis is ogival and long, reaching the border furrow. It is constricted at F2 and provided with a distinct median node and a faint terminal node. The posterior lobe is more than twice as long as the anterior lobe (Ml and M2 combined) and one specimen (Fig. 5A) shows that it has four pairs of muscle impression areas. The length and shape of the rachis may suggest that the pygidia belong to a species of Hypagnostus. They differ, however, from most species of Hypagnostus in having distinct posterolateral spines and in lacking a median postrachial furrow. Acmarhachis Resser, 1938 is another genus with a long rachis reaching the border furrow, but it has a broad and tumid posterior lobe. Occurrence. - Zone of Olenus and Homagnostus obesus at Häl-

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

GFF118 (1996)

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian ofVästergötland

137

Fig. 5. A-D. Hypagnostust sp.; Zone of Homagnostus obesus and Olenus. A, pygidium; Hönsäter, Kinnekulle; LO 7341t; xl 1. B, pygidium; Hällekis, Kinnekulle; LO 7342t; x l l . C, pygidium; Hällekis, Kinnekulle; LO 7343t; xl6. D, pygidium; Hällekis, Kinnekulle; LO 7344t; xl5. E-G. Peratagnostus falanensis (Westergârd, 1947). E, pygidium; holotype by monotypy; original of Westergârd (1947, pi. 1, fig. 14) and Rushton (1978, pi. 24, figs. 10-12); Agnostus pisiformis Zone at Djupadalen, 5 km east of Falköping in the Billingen-Falbygden area; SGU 6437; xl0.5. F, pygidium; Parabolina spinulosa Zone at Gum, Kinnekulle; LO 7345t; x9. G, small pygidium; Agnostus pisiformis Zone at Trolmen, Kinnekulle; LO 7346t; xl6. H. Pseudagnostus cf. cyclopyge (Tullberg, 1880); pygidium; transition beds between the Zone of Olenus and Homagnostus obesus and the Parabolina spinulosa Zone at Gudhem in the Falbygden area; LO 7347t; xl3.1-L. Aspidagnostus cf. stictus Öpik, 1967; Zone of Olenus and Homagnostus obesus at Hällekis, Kinnekulle. I, pygidium; LO 7348t; xl3. J, cephalon; LO 7349t; xl3. K, cephalon; LO 7350t; xlO. L, pygidium; LO 7351t; xlO.

lekis and Hönsäter, Kinnekulle. Associated trilobites include, e.g., Aspidagnostus cf. stictus Öpik, 1967, Hypagnostus aff. correctus Öpik, 1967, and Proceratopyge cf. nathorsti Westergârd, 1922.

geographically widespread and characterized by advanced effacement of the furrows and lobes.

Peratagnostus falanensis (Westergârd, 1947) Fig. 5E-G.

Genus Peratagnostus Öpik, 1967 Type species. - Peratagnostus nobilis Öpik, 1967 (pp. 87-90, pi. 52, figs. 10-11, pi. 53, figs. 1-11) from the Erixanium sentum Zone (Idamean Stage) of Queensland, Australia; by original designation. Remarks. - Peratagnostus was discussed comprehensively by Robison (1994, pp. 65-67), who expanded its concept to include a number of species from the Middle Cambrian. The genus is

Synonymy. - »1947 Ciceragnostusl falanensis sp.n. - Westergârd, pp. 7-8, pi. 1, fig. 14. »1978 Grandagnostus falanensis (Westergârd, 1947) - Rushton, pp. 256-258, pi. 24, figs. 6-14, text-fig. 3a [synonymy to date]. »1983 Grandagnostus falanensis (Westergârd, 1947) - Rushton, p. 117, pi. 15, figs. 2-5, 8-9. •1994 Peratagnostus falanensis (Westergârd, 1947) - Robison, pp. 66-67.

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

138

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian of Västergötland

GFF118 (1996)

Holotype by monotypy. - An incomplete pygidium (SGU 6437; Fig. 5E) from the Agnostus pisiformis Zone at Djupadalen, 5 km east of Falköping in the Billingen-Falbygden area, Västergötland; re-illustrated by Rushton (1978, pi. 24, figs. 10-12).

Holotype. - A nearly complete specimen illustrated by Rushton (1978, pi. 25, fig. 5) and Shergold et al. (1990, fig. 15:2).

Other material. - Two pygidia.

Dimensions (mm). - LO 7352t: Lpl = 4.75?, Wp = 5.15?; LO 7353t: Lp2 = 3.70, Wp = 4.75.

Remarks. - This species was described and discussed by Rushton (1978, 1983), who assigned it to Grandagnostus Howell, 1935. The holotype of the type species (G. vermontensis Howell, 1935) is poorly preserved, and Robison (1988, p. 53) proposed that application of the name Grandagnostus should be restricted to that single specimen (an incomplete cephalon re-illustrated by Robison 1988, fig. 12.7). Recently, Robison (1994, pp. 66-67) briefly discussed the generic assignment of ' Ciceragnostus' falanensis Westergârd, 1947, and showed that it can be placed in Peratagnostus Öpik, 1967. In the degree of the effacement, P. falanensis strongly resembles P. sinicus as described by Peng (1992, p. 23, fig. 11A-F). A pygidium from the Parabolina spinulosa Zone of Västergötland (Fig. 5F) closely resembles the holotype. It is slightly less effaced than the holotype and the outline of the rachis is faintly indicated. The rachis is slightly constricted in the anterior part and tapers distinctly backwards. It ends well in front of the posterior border and occupies about 70% of the total pygidial length. A distinct node is present between a quarter and one-third of the pygidial length from the front.

Material. - Two nearly complete pygidia (LO 7352t and 7353t).

Remarks. - The pygidia to hand are specifically indistinguishable from Rushton's (1978) detailed description of pygidia of C. papilio from the Agnostus pisiformis Zone of England. They are very weakly scrobiculate with a distinct median notch at the posterior margin. The median spine is hidden in the rock or broken off, but it was clearly directed downwards and backwards. The median ridge is well preserved and provided with a pair of small knobs at the anterior end. Occurrence. - Agnostus pisiformis Zone (loose boulders) at Hjälmsäter and from a locality c. 200 m north of the chapel of Hönsäter, Kinnekulle. The specimens are associated with A. pisiformis in abundance. The species has previously been described from the A. pisiformis Zone of England and southeastern Newfoundland (Rushton 1978). Furthermore, it has been recorded from the lower Upper Cambrian of western Hunan, China (Shanchi Peng, Nanjing, pers. comm. 1995).

Genus Pseudagnostus Jaekel, 1909 Occurrence. - In addition to type stratum and type locality, the species is known from the Agnostus pisiformis Zone at Trolmen, western Kinnekulle, and the Parabolina spinulosa Zone at Gum, c. 3.3 km WNW of Husaby church, southern Kinnekulle. Rushton (1978,1983) described the species from the Lejopyge laevigata, Agnostus pisiformis, and Olenus Zones of central England.

Family Diplagnostidae Whitehouse, 1936 Genus Cristagnostus Rushton, 1978

Type species. -Agnostus cyclopyge Tullberg, 1880 (p. 26, pi. 2, fig. 15a and c) from the Upper Cambrian (upper Homagnostus obesus Zone or Parabolina brevispina Subzone) at Andrarum, Scania, southern Sweden; by original designation. Remarks. - Pseudagnostus was discussed comprehensively by Shergold (1977), and his definition, classification, and discussion cover all important aspects. More recently, the concept of the genus has been discussed by Westrop (1986, pp. 25-26) and Pratt (1992, p. 33).

Type species. — Cristagnostus papilio Rushton, 1978 (pp. 265266, pi. 25, figs. 5-13) from the Outwoods Formation (Agnostus Pseudagnostus cf. cyclopyge (Tullberg, 1880) pisiformis Zone) in the Nuneaton district, England; by original Fig. 5H. designation. Remarks. - Cristagnostus appears to be restricted to the uppermost Middle Cambrian and the lowermost Upper Cambrian (Shergold et al. 1990, p. 48). Its characteristics are well shown by Rushton (1978, pp. 262-264), and his interpretation of the genus and its referral to the Diplagnostidae are followed here.

Cristagnostus papilio Rushton, 1978 Fig. 6A-B. Synonymy. - »1978 Cristagnostus papilio sp. nov. - Rushton, pp. 265-266, pi. 25, figs. 5-13 [further synonymy]. »1988 Cristagnostus papilio Rushton, 1978 - Morris, p. 57. »1990 Cristagnostus papilio Rushton, 1978 - Shergold et al., p. 48, fig. 15:2.

Material. - An internal mould of a nearly complete pygidium (LO 7347t). Dimensions (mm). - Lpl = 3.15; Lp2 = 2.85; Lbp = 0.35; Wp = 3.20. Remarks. - The syntypes figured by Tullberg (1880, pi. 2, fig. 15) cannot be located, and, as noted by Shergold (1977), the current concept of Pseudagnostus cyclopyge is based on specimens illustrated by Westergârd (1922, pi. 1, figs. 7 and 8). The latter specimens (a topotype cephalon numbered LO 3066t, and a topotype pygidium numbered LO 3067t) were collected by A.G. Nathorst and re-illustrated by Shergold (1977, pi. 15, figs. 1-2) and Shergold et al. (1990, fig. 15:5a-b).

GFF118 (1996)

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian of Västergötland

139

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

Fig. 6. Cristagnostuspapilio Rushton, 1978; Agnostus pisiformis Zone; x9. A, pygidium, latex cast from external mould; Hönsäter, Kinnekulle; LO 7352t. B, pygidium; Hjälmsäter, Kinnekulle; LO 7353t.

The pygidium from Västergötland has clearly defined accessory furrows continuing to the marginal furrow. It differs from topotype pygidia in having a faint depression at the posterior end of the deuterolobe and in lacking a terminal pygidial node. Further, the acrolobe is less constricted than in topotype pygidia. The overall morphology strongly suggests that it should be classified among the taxa of the cyclopyge species group of Shergold (1977), and it most closely resembles the nominal species. Specimens assigned to P. cyclopyge were recently described by Pratt (1992, pp. 33-34) from the uppermost Steptoean Stage of the Rabbitkettle Formation in southern Mackenzie Mountains, northwest Canada. Occurrence. - Transition beds between the Zone of Olenus and Homagnostus obesus and the Parabolina spinulosa Zone (loose boulder) in an old quarry at Gudhem in the Falbygden area. The specimen is associated with H. obesus, Olenus truncatusl, Parabolina brevispina, and numerous ungulate brachiopods.

Family Clavagnostidae Howell, 1937 Genus Aspidagnostus Whitehouse, 1936 Type species. - Aspidagnostus parmatus Whitehouse, 1936 (pi. 9, fig. 5 only) from the Glyptagnostus stolidotus or G. reticulatus Zone of Queensland, Australia; by original designation.

Aspidagnostus cf. stictus Öpik, 1967 Fig. 5I-L. Material. - Two cephala (LO 7349t and 7350t) and two pygidia (LO7348tand7351t). Dimensions of cephalon (mm; LO 7350t). — Lc = 3.00; Lbc = 0.25; Lac = 2.75; G = 1.90; N = 1.05; We = 3.20; Wg = 0.95. Dimensions of pygidium (mm; LO 7351t). - Lpl = 3.10?; Lp2 = 2.90; Lr = 2.20; Lbp = 0.60; Wp = 2.95; Wr = 1.20. Remarks. — The Västergötland specimens are closely comparable to Aspidagnostus stictus from the lower Glyptagnostus reticulatus Zone of northwestern Queensland, Australia. The holotype cephalon differs slightly from the cephala to hand in having a more parallel-sided glabella. It is worth noting, however, that the glabellar outline appears to be a variable feature in Aspidagnostus. This is evident in cephala of A. inquilinus Öpik, 1967 from western Queensland, Australia (compare the cephala figured by Öpik 1967, pi. 56, figs. 1 and 9). Specimens ascribed to A. stictus have recently been recorded from the Glyptagnostus stolidotus Zone of western Hunan, China (Shanchi Peng, Nanjing, pers. comm. 1995).

Occurrence. — Zone of Olenus and Homagnostus obesus (probably lower part) in an old quarry at Hällekis, Kinnekulle (about Remarks. — The concept oí Aspidagnostus is discussed at length 600 m WNW of the chapel of Hönsäter). Associated trilobites by Öpik (1967, pp. 113-117), who also discussed its relationship include, e.g., Olenus gibbosus (Wahlenberg, 1818), Proceratowith Clavagnostus Howell, 1937. It is characterized by a trispinose and zonate pygidium with a collar crossed by a deep median pyge cf. nathorsti Westergârd, 1922, and Hypagnostus aff. corgroove, extending from the posterior end of the rachis onto the rectus Öpik, 1967. median marginal spine. A pair of low knobs are generally present Acknowledgements. - Professor Jan Bergström, Stockholm, and Dr. Roger A. adjacent to the median groove. The posterior lobe of the pygidial Cooper, Lower Hurt, New Zealand, provided constructive comments on the Drs. Adrian W.A. Rushton, Nottingham, and John H. Shergold, Canrachis is long with a deep transverse depression at about mid- manuscript. berra, kindly supplied data and commented on some species. Dr. Tomas Nihlén length. The cephalic border is angulate, the basal lobes divided, and Mr. Robert Kristoffersson (both of Lund) skilfully carried out the dark-room For assistance with some old literature we are indebted to Professor and the median preglabellar furrow well developed. The genus is work. Gerhard Regnéll, Lund. Britt Nyberg, Lund, made the drawings. Per Ahlberg's widely distributed and has been recorded from the lower Upper work has been supported by grants from the Swedish Natural Science Research Cambrian in Australia, Siberia, Kazakhstan, North America, Council ( N n y . England, and China (e.g. Palmer 1962; Öpik 1967; Rushton 1978; Ergaliev 1980; Pratt 1992). References Ahlberg, P., 1989: Cambrian stratigraphy of the När 1 deep well, Gotland. Geologiska Föreningens i Stockholm Förhandlingar 111, 137-148.

Downloaded By: [Lunds Universitet] At: 19:27 18 April 2010

140

Ahlberg & Ahlgren: Agnostids from the Upper Cambrian of Vastergötland

GFF118 (1996)

Regnéll, G., 1949: On the position of palaeontology and historical geology in Allen, P.M., Jackson, A.A. & Rushton, A.W.A., 1981: The stratigraphy of the Sweden before 1800. Arkiv for Mineralogi och Geologi 1, 1-64. Mawddach Group in the Cambrian succession of North Wales. Proceedings of the Yorkshire Geological Society 43, 295-329. Resser, C.E., 1938: Cambrian System (restricted) of the Southern Appalachians. Geological Society of America, Special Papers 15, 1-140. Andersson, A., Dahlman, B., Gee, D.G. & Snäll, S., 1985: The Scandinavian alum shales. Sveriges Geologiska Undersökning Ca 56, 1-50. Reyment, R.A., 1976: Göran Wahlenberg's collection. De rebus in Palaeontologico Museo Upsaliensi collectis 3, 2-11. Angelin, N.P., 1851: Palaeontologia Svecica. I: Iconographia crustaceorum formationis transitionis. Fasc. 1, 1-24. Lund. Robison, R.A., 1982: Some Middle Cambrian agnostoid trilobites from western North America. Journal of Paleontology 56, 132-160. Belt, T., 1867: On some new trilobites from the Upper Cambrian rocks of North Wales. Geological Magazine 4, 294-295. Robison, R.A., 1988: Trilobites of the Hohn Dal Formation Gate Middle Cambrian), central North Greenland. Meddelelser om Grønland, Geoscience 20, Bergström, J., 1980: Middle and Upper Cambrian biostratigraphy and sedimen23-103. tation in south central Jämtland, Sweden. Geologiska Föreningens i Stockholm Förhandlingar 102, 373-376. Robison, R.A., 1994: Agnostoid trilobites from the Henson Gletscher and Kap Stanton formations (Middle Cambrian), North Greenland. Bulletin Grønlands Bergström, J. & Gee, D.G., 1985: The Cambrian in Scandinavia. In D.G. Gee & geologiske Undersøgelse 169, 25-77. B.A. Sturt (eds.): The Caledonide Orogen—Scandinavia and Related Areas, 247-271. John Wiley & Sons. Rudolph, F., 1992: Bestimmungshilfen für Geschiebesammler: Trilobiten. 17. Agnostus pisiformis (Linnaeus, 1757). Geschiebekunde aktuell 8(3), 159-163. Bromell, M. von, 1729: Lithographia Svecana. Acta Literaria (et Scientiarum) Sveciae Upsaliae publicata, 2, continens annos 1725—29. Upsaliae & Stock- Rudolph, F., 1993: Bestimmungshilfen für Geschiebesammler: Trilobiten. 19. holmiae s.a. Glyptagnostus reticulatus (Angelin, 1851). Geschiebekunde aktuell9(2), 51-52. Rushton, A.W.A., 1978: Fossils from the Middle-Upper Cambrian transition in Clark, T.H., 1923: A group of new species of Agnostus from Levis, Quebec. the Nuneaton district. Palaeontology 21, 245-283. Canadian Field Naturalist 37, 121-125. Ergaliev, G.Kh., 1980: Trilobity srednego i verkhnego kembriya Malogo Karatau. Rushton, A.W.A., 1982: The biostratigraphy and correlation of the Merioneth[Trilobites of the Middle and Upper Cambrian of Malyi Karatau.] 211 pp. Tremadoc Series boundary in North Wales. In M.G. Bassett & W.T. Dean Akad. Nauk Kazakh. SSR, Alma-Ata. [In Russian.] (eds.): The Cambrian-Ordovician boundary: sections, fossil distributions, and correlations, 41-59. National Museum of Wales, Geological Series 3. Henningsmoen, G., 1958: The Upper Cambrian faunas of Norway with descriptions of non-olenid invertebrate fossils. Norsk Geologisk Tidsskrift 38, 179-196. Rushton, A.W.A., 1983: Trilobites from the Upper Cambrian Olenus Zone in central England. Special Papers in Palaeontology 30, 107-139. Jaekel, O., 1909: Über die Agnostiden. Zeitschrift der Deutschen Geologischen Gesellschaft 61, 380-401. Salter, J.W., 1864: Trilobites (chiefly Silurian). Figures and descriptions illustrative of British organic remains. Decade 11,10 pls. Memoirs of the Geological Jago, J.B., 1974: Glyptagnostus reticulatus from the Huskisson River, Tasmania. Survey of the United Kingdom. London. Papers and Proceedings of the Royal Society of Tasmania 107, 117-127. Jago, J.B. & Brown, A.V., 1992: Early Idamean (Late Cambrian) agnostoid triloSchrank, E., 1973: Fauna und Kontakt Mittelkambrium/Oberkambrium in einem bites from the Huskisson River, Tasmania. Papers and Proceedings of the Geschiebe. Zeitschrift für Geologische Wissenschaften 22, 85-99. Royal Society of Tasmania 126, 59-65. Shergold, J.H., 1972: Late Upper Cambrian trilobites from the Gola Beds, western Queensland. Bureau of Mineral Resources, Geology and Geophysics, BulLake, P., 1906: A monograph of the British Cambrian trilobites. Part 1. Palaeletin 112, 1-127. ontographical Society Monographs, 1-28 (part of volume for 1906). Linnaeus, C., 1747: Wästgöta-Resa, pâ Riksens högloflige Ständers befallning Shergold, J.H., 1975: Late Cambrian and Early Ordovician trilobites from the förrättad år 1746. Med anmärkningar uti oeconomien, naturkunnogheten, Burke River Structural Belt, western Queensland, Australia. Bureau of Minantiquiteter, inwånames seder och lefnads-sätt. Lars Salvius, Stockholm. eral Resources, Geology and Geophysics, Bulletin 153,1-251. (12)+284+(20) pp. [Several later eds.] Shergold, J.H., 1977: Classification of the trilobite Pseudagnostus. Palaeontology 20, 69-100. Linnaeus, C., 1751: Skånska resa, på höga öfwerhetens befallning förrättad år Shergold, J.H., 1982: Idamean (Late Cambrian) trilobites, Burke River Structural 1749. Med rön och anmärkningar uti oeconomien, naturalier, antiquiteter, Belt, western Queensland. Bureau of Mineral Resources, Geology and Geoseder, lefnadssätt. Lars Salvius, Stockholm. (10)+xiv+434+(34) pp. [Several physics, Bulletin 187, 1-69. later eds.] Shergold, J.H. & Cooper, R.A., 1985: Late Cambrian trilobites from the Mariner Linnarsson, J.G.O., 1869: Om Vestergötlands cambriska och siluriska aflagringar. Group, northern Victoria Land, Antarctica. Journal of Australian Geology & Kongliga Svenska Vetenskaps-Akademiens Handlingar 8(2), 1-89. Geophysics 9, 91-106. Linnarsson, J.G.O., 1880: Om försteningame i de svenska lagren med Peltura och Sphaerophthalmus. Geologiska Föreningens i Stockholm Förhandlingar 5, 132-161.Shergold, J.H. & Sdzuy, K., 1984: Cambrian and early Tremadocian trilobites from Sultan Dag, central Turkey. Senckenbergiana lethaea 65, 51-135. Ludvigsen, R., Westrop, S.R. & Kindle, C.H., 1989: Sunwaptan (Upper Cambrian) trilobites of the Cow Head Group, western Newfoundland, Canada. Shergold, J.H. & Sdzuy, K., 1991 : Late Cambrian trilobites from the Iberian MounPalaeontographica Canadiana 6, 1-175. tains, Zaragoza Province, Spain. Beringeria 4, 193-235. Martinsson, A., 1974: The Cambrian of Norden. In C.H. Holland (ed.): Lower Shergold, J.H. & Webers, G.F., 1992: Late Dresbachian (Idamean) and other Palaeozoic Rocks of the World. 2. Cambrian of the British Isles, Norden, and trilobite faunas from the Heritage Range, Ellsworth Mountains, West AntarcSpitsbergen, 185-283. John Wiley & Sons. tica. In G.F. Webers, C. Craddock & J.F. Splettstoesser: Geology and PaleonMorris, S.F., 1988: A review of British trilobites, including a synoptic revision of tology of the Ellsworth Mountains, West Antarctica, 125-168. Geological SoSalter' s monograph. Palaeontographical Society Monographs 574, 1-316. ciety of America Memoir 170. Müller, K.J. & Walossek, D., 1987: Morphology, ontogeny, and life habit of Agnostus Shergold, J.H., Laurie, J.R. & Sun Xiaowen, 1990: Classification and review of pisiformis from the Upper Cambrian of Sweden. Fossils and Strata 19, 1-124. the trilobite order Agnostida Salter, 1864: an Australian perspective. Bureau Nathorst, A.G., 1907: Carl von Linné såsom geolog. In: Carl von Linnés betyof Mineral Resources, Geology and Geophysics, Report 296, 1-93. delse såsom naturforskare och läkare. Skildringar utgifna af Kungl. VetenShergold, J.H., Bordonaro, O. & Liñán, E., 1995: Late Cambrian agnostoid triloskapsakademien i anledning af tvåhundraårsdagen of Linnés födelse. 80 pp. bites from Argentina. Palaeontology 38, 241-257. Almqvist & Wiksell. Thickpenny, A., 1987: Palaeo-oceanography and depositional environment of Nicoll, R.S., Laurie, J.R., Shergold, J.H. & Nielsen, A.T., 1992: Preliminary corthe Scandinavian alum shales: sedimentological and geochemical evidence. In relation of latest Cambrian to Early Ordovician sea level events in Australia J.K. Leggett & G.G. Zuffa (eds.): Marine Clastic Sedimentology - Concepts and Scandinavia. In B.D. Webby & J.R. Laurie (eds.): Global Perspectives on and Case Studies, 156-171. Graham & Trotman. Ordovician Geology, 381-394. A.A. Balkema. Tullberg, S.A., 1880: Om Agnostus-artema i de kambriska aflagringarne vid Öpik, A.A., 1963: Early Upper Cambrian fossils from Queensland. Bureau of Andrarum. Sveriges Geologiska Undersökning C 42, 1-38. Mineral Resources, Geology and Geophysics, Bulletin 64, 1-133. Wahlenberg, G., 1818: Petrificata telluris svecanae. Nova Acta Regiae Societatis Öpik, A.A., 1967: The Mindyallan fauna of north-western Queensland. Bureau Scientiarum Upsaliensis 8, 1-116. [The title page of the volume is dated 1821, of Mineral Resources, Geology and Geophysics, Bulletin 74, 1-404. but Wahlenberg's memoir was printed 1818, as stated on p. 293 in the same Palmer, A.R., 1960: Trilobites of the Upper Cambrian Dunderberg Shale, Eureka volume.] district, Nevada. United States Geological Survey Professional Paper 334-C, Walcott, C.D., 1884: The paleontology of the Eureka district, Nevada. United 53-105. States Geological Survey Monographs 8, 1-298. Palmer, A.R., 1962: Glyptagnostus and associated trilobites in the United States. Walossek, D. & Müller, K.J., 1988: Über die Ventralmorphologie und Ökologie United States Geological Survey Professional Paper 374-F, 1-49. von Agnostus. Der Geschiebesammler 22, 11-38. Pek, I., 1977: Agnostid trilobites of the central Bohemian Ordovician. Sbornik Westergård, A.H., 1922: Sveriges olenidskiffer. Sveriges Geologiska Undersökgeologickych véd, paleontologie 19, 7-44. ning Ca 18, 1-205. Peng Shanchi, 1992: Upper Cambrian biostratigraphy and trilobite faunas of the Westergård, A.H., 1946: Agnostidea of the Middle Cambrian of Sweden. Sveriges Cili-Taoyuan area, northwestern Hunan, China. Association of Australasian Geologiska Undersökning C477, 1-140. Palaeontologists Memoir 13, 1-119. Westergård, A.H., 1947: Supplementary notes on the Upper Cambrian trilobites of Sweden. Sveriges Geologiska Undersökning C489, 1-34. Poulsen, C., 1923 olenuslag og deres fauna. Danmarks geologiske Westergård, A.H., 1948: Non-agnostidean trilobites of the Middle Cambrian of Undersøgelse 2(40), 1-83 Sweden. I. Sveriges Geologiska Undersökning C 498, 1-32. Pratt, B.R., 1992: Trilobites of the Marjuman and Steptoean stages (Upper CamWestrop, S.R., 1986: Trilobites of the Upper Cambrian Sunwaptan Stage, southern brian), Rabbitkettle Formation, southern Mackenzie Mountains northwest Canadian Rocky Mountains, Alberta. Palaeontographica Canadiana 3, 1-179. Canada. Palaeontographica Canadiana 9, 1-179. Whitehouse, F.W., 1936: The Cambrian faunas of north-eastern Australia. Parts Rasetti, F., 1944: Upper Cambrian trilobites from the Lévis Conglomerate Jour1 and 2. Memoirs of the Queensland Museum 11(1), 59-112 nal of Paleontology 18, 229-258.