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Systematic revision of the genus Solenopleura Angelin, 1854, Ptychopariida, Trilobita, Cambrian Series 3
Annales de Paléontologie 101 (2015) 185–192
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Original article
Systematic revision of the genus Solenopleura Angelin, 1854, Ptychopariida, Trilobita, Cambrian Series 3 Révision systématique du genre Solenopleura Angelin, 1854, Ptychopariida, Trilobita, Série 3 du Cambrien Jorge Esteve 1 Center of Biology, Geosciences and Environment, University of West Bohemia, Klatovska, 51, 306 14 Pilsen, Czech Republic
a r t i c l e
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Article history: Received 3 December 2014 Accepted 6 May 2015 Available online 4 June 2015 Keywords: Taxonomy Stratigraphy ISCS Middle Cambrian Sweden
a b s t r a c t The Solenopleurid trilobites comprise a very common family in East and West Gondwana. The type genus of this family, Solenopleura, has however suffered several taxonomic changes due to misunderstandings throughout the 20th century. In order to clarify and resolve all these problems, a revision is presented here that deals with both species involved in such misunderstandings, Calymene holometopa Angelin, 1851 and Calymene canaliculata Angelin, 1851. Both species are reassigned to the genus Solenopleura. The new descriptions and illustrations demonstrate that morphological features in Solenopleura holometopa are shared by other Scandinavian trilobites such as Solenopleura conifrons Westergård, 1952, which is closely related. Furthermore, the genus Gonzaloia Geyer, 1998 has been erected to include two species, G. canaliculata and G. conifrons. New descriptions herein suggest this genus is not supported by evidences and that included species should be provisionally considered, though with reservations, within the genus Solenopleura until a morphological and cladistic study of the whole genus will be able to provide significant evidence to separate both genera. © 2015 Published by Elsevier Masson SAS.
r é s u m é Mots clés : Taxonomie Stratigraphie ISCS Cambrien moyen Suède
Les trilobites Solenopleurides forment une famille de trilobites fréquente dans le Gondwana Est et Ouest. Le genre-type de cette famille, Solenopleura, a cependant souffert d’incompréhensions qui ont mené à plusieurs changements taxonomiques au cours du 20e siècle. Afin de clarifier et de résoudre tous ces problèmes, la révision des deux espèces à leur origine, Calymene holometopa Angelin, 1851 et Calymene canaliculata Angelin, 1851, est présentée ici. Les deux espèces sont replacées dans le genre Solenopleura. Les nouvelles descriptions et illustrations démontrent que les caractères morphologiques de Solenopleura holometopa sont partagés par d’autres trilobites scandinaves comme Solenopleura conifrons Westergård, 1952, qui sont proches. De plus, Geyer (1998) a érigé le genre Gonzaloia pour inclure deux espèces, G. canaliculata et G. conifrons. Les nouvelles descriptions faites ici suggèrent que ce genre n’est pas soutenu par les évidences et que les espèces inclues devraient être provisoirement considérées, bien qu’avec réserve, au sein du genre Solenopleura jusqu’à ce qu’une étude morphologique et cladistique de l’ensemble du genre fournisse les preuves nécessaires à sa division. © 2015 Publié par Elsevier Masson SAS.
1. Introduction
E-mail address: [email protected] Current address: Departamento de Paleontología, Universidad Complutense de Madrid, C/José Antonio Nováis 12, Ciudad Universitaria, 28040 Madrid, Spain. 1
http://dx.doi.org/10.1016/j.annpal.2015.05.001 0753-3969/© 2015 Published by Elsevier Masson SAS.
Solenopleurids are a family of typically “ptychopariid” trilobites from Gondwana. They have been very much studied during the last century. They are present in Cambrian strata throughout ˇ 1958; Sdzuy, 1961; the Mediterranean area (Thoral, 1947; Snajdr, Geyer, 1998; Courtessole, 1973; Álvaro and Vizcaïno, 2001; Álvaro
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Andrarum Limestone (4.10–5.65 m), and the Lejopyge laevigata Zone comprises the shales above the Andrarum Limestone but L. laevigata already appears near the base of the S.? brachymetopa Zone (Axheimer et al., 2006). These authors suggested that the L. laevigata Zone in Scandinavia should be extended to include the traditional S.? brachymetopa Zone, and its lower boundary should be defined at the first occurrence datum (FAD) of L. laevigata (Fig. 2). 2. Systematic Palaeontology Terminology. Trilobite descriptive terminology follows Whittington and Kelly in Kaesler (1997). Repositories. All the specimens described and discussed herein are housed in the collections of the Geological Survey of Sweden, Uppsala (SGU) and the Swedish Museum of Natural History (Ar). Order PTYCHOPARIIDA Swinnerton, 1915 Family SOLENOPLEURIDAE Angelin, 1854 Type genus Solenopleura holometopa by assignation of Walcott (1884). Genus Solenopleura Angelin, 1854
Fig. 1. Map showing Scania in the southern of Sweden and the distribution of Cambrian deposits in Scandinavia (Martinsson, 1974). Carte localisant la province de Scania dans le sud de la Suède et la distribution des dépôts cambriens en Scandinavie (Martinsson, 1974).
et al., 2004; Esteve et al., 2010), China (Zhang et al., 1980; Zhang and Jell, 1987; Yuan et al., 2012), UK (Cobbold and Pocock, 1934; Rushton and Berg-Madsen, 2002), Newfoundland (Fletcher, 2005) and Scandinavia (Grönwall, 1902; Westergård, 1952; Axheimer and Ahlberg, 2003; Weid and Nilsen, 2014). Thoral (1947) divided this family into two subfamilies: Solenopleurinae and Solenopleuropsinae. The main differences between the two subfamilies lie with the shape of the anterior furrow of the cranidia, symmetrical in Solenopleurinae and asymmetrical in Solenopleuropsinae, and the geometry of the anterior border, convex in Solenopleurinae and upturned in Solenopleuropsinae (Álvaro and Vizcaïno, 1997). The revision of this family lies outside the scope of the current study. Nonetheless, up to the present time, the assignation of some type species of this family has been problematic due to misunderstandings, inaccurate descriptions and poor illustrations (or even without illustrations) of the type material. In the present work, an attempt is made to resolve these misunderstandings. It focuses on the type material of two species which have been assigned to the type genus of this family: Calymene holometopa Angelin, 1851 and Calymene canaliculata Angelin, 1851. The type specimens were collected in the Andrarum limestone (Nielsen and Schovsbo, 2007) in Scania, southern Sweden (Fig. 1). These specimens belong to the Solenopleura? brachymetopa Zone (Fig. 2). According to Westergård (1952), the S.? brachymetopa Zone comprises the
Discussion. Westergård (1952) carried out a revision of the solenopleurids from Sweden, erecting the genus Parasolenopleura Westergård, 1952 and separating it from the genus Solenopleura Angelin, 1854. Both genera however have become a taxonomic wastebasket due to poor characterization of many species included within these genera (see Geyer, 1998, in press; Álvaro et al., 2004). Westergård (1952) affirmed that Miller (1889) had selected C. canaliculata as the type species of the genus instead of C. holometopa which actually had previously been selected by Walcott (1884) as the type species of Solenopleura, as was noted by Taylor and Rushton (1972) and subsequently by Chernysheva (1980), Babcock (1994), Rushton (1995), Geyer (1998) and Álvaro et al. (2004). This designation, however, was evidently unobserved by Rudolph (1994) who followed Westergård’s assumption. Rudolph (1994) studied the genus Solenopleura and restricted this genus to those forms that have a glabella with well-defined glabellar furrows, developed eye ridges, and an obsolescent preglabellar field. This means that the preocular fields are disconnected in front of the glabella. All the Scandinavian forms seem, however, to have their preocular fields connected in front of the glabella, but not at all ontogenetic stages. In large specimens of S. holometopa, the preglabellar area becomes reduced and both preocular fields are separated by a median preglabellar furrow (see Fig. 3A, D and Fig. 4A, D). Therefore, for Rudolph (1994) as well as Geyer (1998), only the species from Scandinavia, S. canaliculata (Angelin, 1851) and S. conifrons Westergård, 1952 are included in this definition. All other Scandinavian species were excluded and were assigned to ˇ the genus Jincella Snajdr, 1957, which also included the type species of the genus, S. holometopa. This classification, however, gives rise to some problems because most of the criteria that Rudolph (1994) and Geyer (1998) used to distinguish both genera, such as the width and convexity of the fixigenae or weakness of the eye ridges, are not possible or difficult to quantify and are not objectively applicable. Besides, many works illustrate the kind of variability that is common amongst Cambrian trilobites due to biological and taphonomical causes (e.g. Hughes and Rushton, 1990; Hughes, 1991, 1995; Esteve, 2014) and studies made so far have not been focused on this problem. The diagnosis of a genus should not focus only on morphological features, which are liable to suffer modifications by taphonomic processes. Rushton and Berg-Madsen (2002) noted also these difficulties and emphasized the need for further studies before agreement is possible on diagnostic features separating these genera. Álvaro et al. (2004) emended the diagnosis of Jincella
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Fig. 2. Traditional middle Cambrian biostratigraphy of Scandinavia and global zonation (from Axheimer et al., 2006) with stratigraphical distribution of the Solenopleura species studied herein. Biostratigraphie traditionnelle du Cambrien moyen de Scandinavie et zonation internationale (d’après Axheimer et al., 2006) avec la distribution stratigraphique des espèces de Solenopleura étudiées dans ce travail.
(see fig. 3 of Álvaro et al., 2004). These authors argued that although compaction can modify the total convexity of the cranidium, the relative inflated character of its different parts (glabella, fixigenae, eye lobes and anterior border) can be used as diagnostic character. Thus, Jincella differs from Solenopleura in having a narrower preocular area with the margin of the fixigena close to the axial furrow which lies on the same plane that the highest peak of the glabella (genae 75–100% as broad as the glabella in a cross-section across the eye lobes), whereas the eye lobe is less convex than the fixigenae (80%), and the cranidial anterior border is slightly less convex or as convex as the eye lobes, finally the anterior branch of the facial suture between ␥ and  is divergent to the axial axis and also divergent from  to ␣. The replacement of S. canaliculata by S. holometopa for the type species of Solenopleura removes S. canaliculata, as defined by Rudolph, from the genus. Therefore, according to Geyer (1998), an appropriate generic name for S. canaliculata, based on a type species C. canaliculata Angelin, 1851, was lacking. Accordingly, Geyer (1998) erected the genus Gonzaloia with two species: G. canaliculata and G. conifrons. However, Geyer (1998, p. 392) only provided a diagnosis for the genus and he stated the following diagnosis for G. canaliculata “see above under diagnosis of the genus (because of monotypy)”. This is inadequate since he clearly included both species within this new genus. In addition, although he did carry out an appropriate description and comparison, he did not figure the holotype of this genus. To solve this trouble, I discuss, describe and figure below the type species of Gonzaloia (i.e. C. canaliculata) and the type species of Solenopleura (i.e. C. holometopa). Diagnosis. Cephalon semicircular in outline with evenly curved anterior margin, and straight posterior margin. Glabella tapering forward, anterior lobe of glabella truncated to rounded, glabellar furrows very shallow (sometimes absent in internal mould) to moderate deep furrows. Anterior border furrow well marked. Occipital ring well defined, with or without node. Palpebral lobes fairly small, central or slightly approximated to posterior margin; ocular ridges obsolete to distinct. Anterior branches of facial suture between ␥ and  subparallel to slightly convergent (ca. 20 degrees) to axial line and from  to ␣ convergent to perpendicular
to margin, posterior branches from to gently sigmoid, cutting posterior margin at a short distance within genal angles. Genal angles rounded or quite angulated, with or without genal spines, which usually are short making an angle with cheek outline, exceptionally stout and continuous. Thorax with up to 16 thoracic segments, pleural furrow well marked and anterior and posterior pleural bands well defined, fulcra distinct with rounded pleural (petaloid-like) facet. Pygidium with up to seven segments in rachis and pleural field up to 7 well-defined pleural furrows; interpleural furrows poorly developed; posterior border well defined. Solenopleura holometopa (Angelin, 1854) Figs. 1 and 2A–I *v1851 C. holometopa Angelin, p. 23, pl. 18, fig. 8.v1854 S. holometopa (Angelin), p. 26, pl. 18, fig. 8. 1878 S. holometopa, (Angelin), Brögger, p. 53, pl. 3, fig. 9. 1902 S. holometopa (Angelin), Grönwall, p. 155, pl. 4, figs 20–21, 23. 1946 S. holometopa (Angelin), Thoral, p. 14. v1952 S. holometopa (Angelin), Westergård, p. 14, pl. 4, figs. 1–8. v1952 Solenopleura holometopa humilis (Westergård, 1952), Westergård, p. 16, pl. 4, fig. 9. ˇ 1957 Jincella holometopa (Angelin), Snajdr, p. 241. ˇ 1958 J. holometopa (Angelin), Snajdr, p. 197. 1994 J. holometopa holometopa (Angelin, 1851), Rudolph, p. 202, pl. 25, figs. 8–9. 1994 Jincella holometopa humilis (Westergård, 1952), Rudolph, p. 203, pl. 25, figs. 10–11. 1998 S. holometopa (Angelin, 1851), Geyer, p. 390. v 2004 S. holometopa (Angelin, 1851), Álvaro et al., fig. 3.1. Occurrence. Cambrian Series 3, Stage 5, S.? brachymetopa Zone, Andrarum limestone; Baltica: Scania, Västergötland, Bornholm, southern Norway, and erratic boulders in northern Germany. Discussion. Westergård (1952) described the subspecies S. (holometopa) humilis on the basis of one single cranidium which differs from Solenopleura (holometopa) holometopa in having a cranidium with lower convexity, very shallow dorsal furrows, cheeks in transverse section not at all inflated and a glabella not sunk between the cheeks. However, some of these morphological
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Fig. 3. A–I Cranidia of Solenopleura holometopa (Angelin, 1854), Cambrian Series 3, Stage 5, Solenopleura? brachymetopa Zone, Andrarum limestone. A–C. Ar63472. A. Dorsal view. B. Frontal view. C. Lateral view. D–F. SGU6267. D. Dorsal view. E. Frontal view. F. Lateral view. G-I. SGU6268. G. Dorsal view. H. Frontal view. I. Lateral view. J–L. Solenopleura conifrons Westergård, 1952, Holotype, cranidium, Ar42836, Cambrian Series 3, Stage 5, Solenopleura? brachymetopa Zone, Andrarum limestone. J. Dorsal view. K. Frontal view. L. lateral view. A–I. Cranidia de Solenopleura holometopa (Angelin, 1854), Série 3 du Cambrien, Étage 5, Zone à Solenopleura? brachymetopa, Calcaire d’Andrarum. A–C. Ar63472. A. Vue dorsale. B. Vue frontale. C. Vue latérale. D–F. SGU6267. D. Vue dorsale. E. Vue frontale. F. Vue latérale. G-I. SGU6268. G. Vue dorsale. H. Vue frontale. I. Vue latérale. J–L. Solenopleura conifrons Westergård, 1952, Holotype, cranidium, Ar42836, Série 3 du Cambrien, Étage 5, Zone à Solenopleura? brachymetopa, Calcaire d’Andrarum. J. Vue dorsale. K. Vue frontale. L. Vue latérale.
features, such as the presence of shallow dorsal furrows, are not able to be quantified and may be related to the mode of preservation (see Esteve, 2014 for mode of preservation). Moreover, the analysis of the collection at the Swedish Museum of Natural History shows that the relative relief of its different parts have a distinct variability within the sample. All the specimens come from the Andrarum limestone and do not show compaction features. Thus, I suggest that both subspecies are indeed the same. Westergård (1952, p. 15) described a single thorax of this species with 11 thoracic segments but I could not find this specimen in the reposited collection. Diagnosis. Solenopleura species with inflated glabella; fixigena convexity lies under glablella and on same plane that axial furrow. Palpebral lobe at same plane that fixigena. Anterior arch of cephalic border, curving up to sagittal line. Small pygidium with 2 narrow and deep pleural furrows and between 2 and 4 axial rings.
Description. Cephalon: Cranidium moderately large, up to 19 mm long (n = 185), subpentagonal in outline, anterior margin evenly curved and posterior margin straight. Anterior branch of facial suture slightly convergent to anterior border, ca. 15 degrees to exsagittal line up to the anterior border furrow, and very divergent after it, ca. 40 degrees. Glabella inflated along longitudinal axis with frontal lobe bluntly rounded, glabella tapers anteriorly, glabellar furrows barely visible on external surface and absent on internal mould. Axial furrow moderately deep and straight in outline. Preglabellar furrow moderately deep. Occipital ring lies under glabella and moderately convex, length ca. 16 percent glabellar length, without spine, although some specimens show larger node; posterior margin convex. SO (sulcus occipital) is curved and deeper exsagitally. Frontal area unequally divided, length varies
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Fig. 4. A–H. Solenopleura holometopa (Angelin, 1854), Cambrian Series 3, Stage 5, Solenopleura? brachymetopa Zone, Andrarum limestone. A–C. Lectotype, cranidium, Ar46650. A. Dorsal view. B. Frontal view. C. Lateral view. D–F. Cranidim, Ar2073. D. Dorsal view. E. Frontal view. F. Lateral view. G–H. Pygidium, Ar46429. G. Dorsal view. H. Posterior view. I–Q. Solenopleura? canaliculata (Angelin, 1851), Cambrian Series 3, Stage 5, Solenopleura? brachymetopa Zone, Andrarum limestone. I–K. Cranidium Ar1630. I. Dorsal view. J. Frontal view. K. Lateral view. L–N. Lectotype, cranidium Ar46145. L. Dorsal view. M. Frontal view. N. Lateral view. P–Q. Pygidium Ar1785g. P. Dorsal view. Q. Lateral view. A–H. Solenopleura holometopa (Angelin, 1854), Série 3 du Cambrien, Étage 5, Zone à Solenopleura? brachymetopa, Calcaire d’Andrarum. A–C. Lectotype, cranidium, Ar46650. A. Vue dorsale. B. Vue frontale. C. Vue latérale. D–F. Cranidium, Ar2073. D. Vue dorsale. E. Vue frontale. F. Vue latérale. G–H. Pygidium, Ar46429. G. Vue dorsale. H. Vue postérieure. I–Q. Solenopleura? canaliculata (Angelin, 1851), Série 3 du Cambrien, Étage 5, Zone à Solenopleura? brachymetopa, Calcaire d’Andrarum. I–K. Cranidium Ar1630. I. Vue dorsale. J. Vue frontale. K. Vue latérale. L–N. Lectotype, cranidium Ar46145. L. Vue dorsale. M. Vue frontale. N. Vue latérale. P–Q. Pygidium Ar1785g. P. Vue dorsale. Q. Vue frontale.
between 6 percent cranidial length in larger specimens (> 15 mm) and 11 percent in smaller specimens (< 10 mm). Preglabellar field slightly concave. Anterior border (on average 10 percent cranidial length) concave and moderately upturned. Margin straight. Palpebral lobe upturned, wide and moderately long, length on average ca. 40 percent glabellar length. Anterior margin of palpebral lobe opposite, approximately, to anterior part of glabella and palpebral furrow moderately shallow. Ocular ridge very narrow and straight, development weak on external mould and well marked
on internal mould. Librigena small, maximum size 5 mm long, very narrow, lateral margin curved and downward. Genal field slightly sunken (width ca. 72 percent librigenal length). Lateral border very concave, of uniform width (width ca. 30 percent librigena width), lateral border furrow shallow and narrow. Pygidium: Small, on average length ca 15 mm and width ca 20 mm; subelliptical in outline, anterior margin slightly curved, lateral margin evenly curved. Axial mid-width is ca. 20 percent axial anterior width, axial anterior width ca. 30 percent pygidial
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Fig. 5. Solenopleura? canaliculata (Angelin, 1851), Cambrian Series 3, Stage 5, Solenopleura? brachymetopa Zone, Andrarum limestone. A–C. Cranidium Ar1786a. A. Dorsal view. B. Frontal view. C. Lateral view. D–F. Cranidium, Ar1786b. D. Frontal view. E. Dorsal view. F. Lateral view. G–I. Cranidia, Ar1630. G. Dorsal view. H. Frontal view. I. Lateral view. J–L. Cranidium, SGU6269. J. Frontal view. K. Dorsal view. L. Lateral view. Solenopleura? canaliculata (Angelin, 1851), Série 3 du Cambrien, Étage 5, Zone à Solenopleura? brachymetopa, Calcaire d’Andrarum. A–C. Cranidium, Ar1786a. A. Vue dorsale. B. Vue frontale. C. Vue latérale. D–F. Cranidium Ar1786b. D. Vue frontale. E. Vue dorsale. F. Vue latérale. G–I. Cranidia, Ar1630. G. Vue dorsale. H. Vue frontale. I. Vue latérale. J–L. Cranidium, SGU6269. J. Vue frontale. K. Vue dorsale. L. Vue latérale.
width, and axial length ca. 90 percent of pygidium length. Between 2 and 4 axial rings. Pleural region well defined, 2 narrow and deep pleural furrows. Posterior border evenly curved in posterior view. Solenopleura conifrons Westergård, 1952 Fig. 4J–L v 1952 S. conifrons sp. nov. Westergård, p. 17. pl. 4, figs. 10a–d. 1998 G. conifrons (Westergård). Geyer, p. 392. 2002 Solenopleura aff. conifrons Rushton and Berg-Madsen, figs. 5a–c. Discussion. Geyer (1998) included this species within the new genus Gonzaloia. However, he did not provide any discussion or figures. He stated “Solenopleura conifrons Westergård, 1952 is very similar to S. canaliculata. It has a well-developed preglabellar field, but this results from a sagittally narrow rather than swollen and posteriorly swinging anterior border that deviates from the border furrow to meet the axial furrow in front of the glabella” and included within the issue of “species included” within Gonzaloia but without yielding any diagnosis. The conical glabella, shallow glabellar furrows, weak eye ridge and the shape of the anterior border furrow and anterior border are similar to those of S. holometopa; this form only differs from the latter in having a wider preglabellar field. The study of the type material, housed at the Swedish Museum of the Natural History, suggests that this species is more similar to S. holometopa rather than S. canaliculata as Geyer (1998)
suggested and Westergård (1952) had already noted. S. canaliculata shows a well-marked glabellar furrow, distinct eye ridge, wider fixigena, narrower preglabellar area and a wider anterior border with a plectrum. These features, especially the presence of the plectrum, allow a proper differentiation from S. canaliculata, S. holometopa and S. conifrons. Therefore, the assignation of S. conifrons to the genus Gonzaloia cannot be supported by fails through lack of evidence. Nevertheless, the differences with S. holometopa may be related to different ontogenetic stages or intraspecific variation, but the lack of a large set of specimens [only three in Sweden and one in England (Rushton and Berg-Madsen, 2002)] prevent a study of variation. Despite this, it seems more appropriate to keep S. conifrons as a valid species and wait until more material becomes available. Occurrence. Cambrian Series 3, Stage 5, S.? brachymetopa Zone, Andrarum limestone; Baltica: Scania, Västergötland, Bornholm, southern Norway, erratic boulders in northern Germany. Paradoxides forchhammeri Zone, Rushton Brook Bed of the Upper Comley Sandstone, in England and Wales. Diagnosis. Solenopleura species with palpebral area at middle plane of glabella and in transverse section across palpebral lobes as wide as glabella and nearly horizontal or somewhat arched. Description. Cranidium small up to 15 mm long (n = 3), subpentagonal in outline, anterior margin posterior margins straight. Anterior branch of facial suture slightly convergent to anterior border, ca. 20 degrees to exsagittal line up to the anterior border
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furrow and ca. 40 degrees from anterior border furrow. Glabella inflated along longitudinal axis with rounded frontal lobe, glabella tapers anteriorly, and glabellar furrows are barely visible on the internal mould, and not impressed on external surfaces. Axial furrow is moderately deep and straight in outline. Preglabellar furrow moderately shallow. Occipital ring lies under glabella, moderately convex, length ca. 15 percent glabellar length, without node or spine on internal mould, external surface unknown. SO shallow, slightly curved and deeper exsagitally. Frontal area unequally divided, length 20 percent of cranidial length. Preglabellar field slightly concave. Anterior border (ca 8 percent cranidial length) concave. Palpebral lobe upturned and short. Anterior margin of palpebral lobe opposite of approximately to L3. Ocular ridge barely visible. Fixigena with anterior area slightly convex, sloping, with ca. 55 percent of glabellar width. Posterior border moderately convex, expanding distally, border furrow shallow and straight. Thorax and pygidium unkown. Solenopleura? canaliculata (Angelin, 1851) Figs. 4L–Q and Fig. 5 v. 1852 C. canaliculata Angelin, 1851, p. 23, pl. 18, figs. 9, 9a. v. 1854 S. canaliculata (Angelin, 1851), p. 27, pl. 18, figs. 9, 9a. 1902 S. canaliculata (Angelin), Grönwall, p. 151, pl. 4, figs. 16, 17. 1994 S. canaliculata (Angelin), Rudolph, p. 201, pl. 25, figs. 4–5. 1998 G. canaliculata (Angelin, 1851). Geyer, p. 302 Discussion. Geyer (1998) erected a new genus using this species and provided a diagnosis but no figures. Beside all the criteria he used to diagnose this new genus, such as the convexity of the glabella and fixigenae, the fixigenae separated by a depression in front of the glabella, three pairs of well-defined glabellar furrows, occipital ring with median node or a short palpebral lobe conspicuously upturned, are not properly quantified and share features with other species of Solenopleura. The unique distinctive morphological characters are the presence of a plectrum and a wider pleural field in the pygidium. Therefore, in view of these characters and the inappropriate erection of the genus Gonzaloia, a generic distinction between Gonzaloia and Solenopleura is still in need of better argumentation, and for that reason, I take a wider view of Solenopleura and allocate this species within the genus Solenopleura, though with some reservations based on its general morphology, pending an analysis of all characters of these species. Diagnosis. Suspected Solenopleura species with plectrum; pygidium with pleural field twice wider than pygidial axis. Occurrence. Cambrian Series 3, Stage 5, S.? brachymetopa Zone, Andrarum limestone; Baltica: Scania, Västergötland, Bornholm, southern Norway, erratic boulders in northern Germany Description. Cephalon: Cranidium up to 17 mm long (n = 82), trapezoidal in shape, anterior margin straight and slightly curved toward anterior sutures, posterior margin straight. Anterior branch of facial suture convergent to anterior border furrow (ca. 14 degrees to exsagittal line) and subtends same angle from anterior border furrow to anterior margin. Glabella inflated along longitudinal axis with frontal lobe rounded to flat, glabella tapers anteriorly, glabellar furrows are well marked on external and internal moulds. Axial furrow deep and straight in outline. Preglabellar furrow moderately deep. Occipital ring convex lying under glabellar relief, length on average ca. 15 percent of glabellar length, with node, posterior margin convex. SO straight and shallow, deeper exsagitally. Frontal area unequally divided, length ca. 25 percent cranidial length. Preglabellar field sunken and connected with wide anterior border furrow. Anterior border (on average ca 16 percent cranidial length) concave and moderately upturned and with plectrum. Palpebral lobe upturned and very short. Anterior margin of the palpebral lobe approximately opposite to S2 and palpebral furrow very shallow. Ocular ridge very narrow and slightly curved, well developed on external
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mould and weak on the internal mould. Fixigena with anterior area very convex, sloping, on average ca. 20% wider than glabellar width. Posterior border moderately convex, expanding somewhat distally, border furrow shallow and straight. Cranidium covered by granules of different sizes and also pits, granules absent in furrows but pits present. Pygidium: Pygidium relatively large, average length ca 10 mm and wide ca 20 mm; subelliptical, anterior margin slightly curved, whereas lateral margins evenly curved. Axial mid-width ca. 20 percent axial anterior width, axial anterior width ca. 30 percent pygidial width, and axial length ca. 90 percent of pygidial length. Pygidium with 7–8 axial rings. Pleural region well defined, wide pleural furrows and moderately deep, posterior border evenly curved in posterior view. Ribs between furrows covered with granulations and whole pygidium with pits. Thorax unknown. 3. Conclusions The study and illustration of the type material support the following conclusions: 1. S. holometopa is the type species of the genus Solenopleura. This species shows a variability in the preglabellar area since the preocular fields are separated by a median preglabellar furrow in larger specimens, but connected in smaller individuals. 2. The cranidium of S. (holometopa) humilis shows the same variability of the relative relief than the rest of the specimens of S. holometopa. Thus, the subspecies S. (holometopa) humilis is suggested as a synonym of S. holometopa. 3. Assignment of S. conifrons to the genus Gonzaloia is rejected. Its glabellar shape, shallow glabellar furrows, weak eye ridge and shape of the anterior border furrow and anterior border point out to be closely related to S. holometopa rather than S.? canaliculata. 4. S.? canaliculata differs from known species of Solenopleura in having a plectrum and a rather larger pygidium, which may suggest generic differences. It seems, however, premature to remove this form from Solenopleura before a complete study of its morphological variability, and it is here still provisionally accommodated within Solenopleura, though with some reservations. Acknowledgments JE is supported by European Social fund and Ministry of Education Youth and Sport, Czech Republic (Ref. CZ. 1.07/2.3.00/30.0013) and by Spanish MINECO (Ref. FPDI-2013-17337). This research was supported by the Synthesys program (SE-TAF-2083) and it is a contribution to the project CGL2013-48877 from Spanish MINECO and EU–FEDER. I am grateful to Isabel Pérez (MEC-FSE, Universidad de Zaragoza, Spain) for her technical support with the pictures of manuscript. I also thank Linda Wickström (Geological Survey of Sweden) for the loan of the type material housed at Uppsala and Christian Skovsted and Jonas Hagström (Swedish Museum of the Natural History) for kind access to collections in their care. I am grateful to Euan Clarkson and J. Javier Álvaro who critically reviewed the manuscript and suggested valuable improvements. References Angelin, N.P., 1851. Palæontologica Svecica. Pars I; Iconographia crustaceorum formationis transitionis. Academie Regiae Scientarium Suecanae, Holmiae (Stockolm) 1, 1–24. Angelin, N.P., 1854. Palæontologia Scandinavica. I. Iconographia Crustacea Formationis Transitionis, Fasc. II. Berlingska and Leipzig, Wiegel, Lund (41 pl.). Álvaro, J.J., Vizcaïno, D., 1997. Révision des Trilobites Solenopleuropsinae du Cambrien Moyen de la Montagne Noire (France). Geobioscience 30, 541–561.
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Álvaro, J.J., Vizcaïno, D., 2001. Evolutionary trends in the ornamentation of Cambrian Solenopleuropsinae Trilobites. Palaeontology 44, 131–141. Álvaro, J.J., Vizcaïno, D., Kordule, V., Fatka, O., Pillola, G.L., 2004. Some solenopleurine trilobites from the Languedocian (Late Mid Cambrian) of Western Europe. Geobioscience 34, 135–147. Axheimer, N., Ahlberg, P., 2003. A core drilling through Cambrian strata at Almbacken, Scania, S. Sweden: trilobites and stratigraphical assessment. Geologiska Föreningens i Stockholm Förhandlingar 125, 139–156. Axheimer, N., Eriksson, M.E., Ahlberg, P., Bengtsson, A., 2006. The middle Cambrian cosmopolitan key species Lejopyge laevigata and its biozone: new data from Sweden. Geological Magazine 143, 447–455. Babcock, L.E., 1994. Systematics and phylogenetics of polymeroid trilobites from the Henson Gletscher and Kap Stanton formations (Middle Cambrian), North Greenland. Bulletin Grùnlands Geologiske Undersùgelse 169, 79– 127. Chernysheva, N.J., 1980. [The genus Solenopleura (Trilobita)]. Paleontologichesky Zhurnal 3, 65–73 ([in Russian]; English translation: Paleontological Journal 3, 72–80). Cobbold, E.S., Pocock, R.W., 1934. The Cambrian area of Rushton (Shropshire). Philosophical Transactions of the Royal Society of London B223, 305–409. Courtessole, R., 1973. Le Cambrien Moyen de la Montagne Noire. Biostratigraphie. Imprimerrie d’Oc. Esteve, J., 2014. Intraspecific variability in paradoxidid trilobites from the Purujosa trilobite assemblage (middle Cambrian, northeast Spain). Acta Palaeontologica Polonica 59, 215–250. ˜ Esteve, J., Zamora, S., Gozalo, R., Linán, E., 2010. Sphaeroidal enrolment in middle Cambrian solenopleuropsine trilobites. Lethaia 43, 478–493. Fletcher, T.P., 2005. Holaspid variation in the Solenopleurid Trilobite Parasolenopleura gregaria (Billings, 1865) from the Cambrian of Newfounland. Palaeontology 48, 1075–1089. Geyer, G., 1998. Intercontinental, trilobite-based correlation of the Moroccan early Middle Cambrian. Canadian Journal of Earth Sciences 35, 374–400. Geyer, G., in press. Exotic trilobites from the Lower–Middle Cambrian boundary interval in Morocco and their bearing on the Cambrian Series 3 lower boundary. Paläontologische Zeitchrift. DOI 10.1007/s12542-014-0254-0. Grönwall, K.A., 1902. Bornholms Paradoxideslag og deres fauna. Danmarks geologiske Undersùgelse 2 (13), 1–230. Hughes, N.C., 1991. Morphological plasticity and genetic exibility in a Cambrian trilobite. Geology 19, 913–916. Hughes, N.C., 1995. Trilobite Taphonomy and Taxonomy: A Problem and Some Implications. Palaios 10, 283–285. Hughes, N.C., Rushton, A.W.A., 1990. Computer-aided restoration of late Cambrian Ceratopygid trilobite from Wales, and its phylogenetic implications. Palaeontology 33, 429–445.
Kaesler, R.L., (Ed) 1997. Treatise on Invertebrate Paleontology. Part O. Arthropoda 1. Trilobita, Revised. Geological Society of America, Boulder, and University of Kansas, Lawrence. Martinsson, A., 1974. The Cambrian of Norden. In: Holland, C.H. (Ed.), Lower Palaeozoic Rocks of the World. 2, Cambrian of the British Isles, Norden, and Spitsbergen. John Wiley & Sons, London, UK, pp. 185–283. Miller, S.A., 1889. North American Geology and Palaeontology. Cincinnati, Ohio. Western Methodist Book Concern. Nielsen, A.T., Schovsbo, N.H., 2007. Cambrian to basal Ordovician lithostratigraphy in southern Scandinavia. Bulletin of the Geological Society of Denmark 53, 47–92. Rudolph, F., 1994. Die Trilobiten der mittelkambrischen Geschiebe. Systematik Morphologie und OÈkologie. Verlag Frank Rudolph, Wankendorf. Rushton, A.W.A., Berg-Madsen, V., 2002. The age of the Middle Cambrian ‘Paradoxides forchhammeri Grit’ of the Wrekin district, 92. Shropshire, England, pp. 335–346. Sdzuy, K., 1961. Das Kambrium Spaniens. Teil II: Trilobiten. Akademie der Wissenschaften und der Literatur Abhandlungen der MathematischNaturwissenschaftililichen Klasse 1961 (7–8), 217–408. ˇ ´ Snajdr, M., 1957. O novych trilobitech z cˇ eského kambria, 32., pp. 235–246. ˇ Snajdr, M., 1958. Trilobiti Ceského Stredního Kambria. Rozpravy ústredního ústavu geologického 24. Swinnerton, H.H., 1915. Suggestions for a revised classification of trilobites. Geological Magazine New Series 6, 487–496, 538–545. Taylor, K., Rushton, A.W.A., 1972. The pre-Westphalian geology of the Warwickshire Coalfield. Bulletin of the Geological Survey of Great Britain 35, 1–150. Thoral, M., 1947. Trois nouveaux genres de trilobites acadiens du Languedoc et de l’Espagne. Comptes Rendus des Séances de l’Académie des Sciences, Paris 244, 59–60. Walcott, C.D., 1884. On the Cambrian faunas of North America. U.S. Geological Survey Bulletin 10, 289–355. Weid, T., Nilsen, A.T., 2014. A highly diverse trilobite fauna with Avalonian affinities from the Middle Cambrian Acidusus atavus Zone (Drumian Stage) of Bornholm, Denmark. Journal of Systematic Palaeontology 12, 23–92. Westergård, A.H., 1952. Non-Agnostidean trilobites of the Middle Cambrian of Sweden. III. Sveriges Geologiska UndersoÈkning C526. Yuan, J.L., Li, Y., Mu, X.N., Lin, J.P., Zhu, X.J., 2012. Trilobite fauna of the Changhia Formation (Cambrian Series 3) from Shandong and adjacent area, North China. Palaeontologia Sinica New Series B 35, 1–785 (in Chinese with English summary). Zhang, W.T., Jell, P.A., 1987. Cambrian Trilobites of North China. Chinese Cambrian Trilobites Housed in the Smithsonian Institution. Science Press, Beijing. Zhang, W.T., Lu, Y.H., Zhu, Z.L., Qian, Y.Y., Lin, H.L., Zhou, Z.Y., Zhang, S.G., Yuan, J.L., 1980. Cambrian trilobite faunas of southwestern China. Palaeontologica Sinica New Series B 159, 1–497 (in Chinese with English summary).
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Original article
Systematic revision of the genus Solenopleura Angelin, 1854, Ptychopariida, Trilobita, Cambrian Series 3 Révision systématique du genre Solenopleura Angelin, 1854, Ptychopariida, Trilobita, Série 3 du Cambrien Jorge Esteve 1 Center of Biology, Geosciences and Environment, University of West Bohemia, Klatovska, 51, 306 14 Pilsen, Czech Republic
a r t i c l e
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Article history: Received 3 December 2014 Accepted 6 May 2015 Available online 4 June 2015 Keywords: Taxonomy Stratigraphy ISCS Middle Cambrian Sweden
a b s t r a c t The Solenopleurid trilobites comprise a very common family in East and West Gondwana. The type genus of this family, Solenopleura, has however suffered several taxonomic changes due to misunderstandings throughout the 20th century. In order to clarify and resolve all these problems, a revision is presented here that deals with both species involved in such misunderstandings, Calymene holometopa Angelin, 1851 and Calymene canaliculata Angelin, 1851. Both species are reassigned to the genus Solenopleura. The new descriptions and illustrations demonstrate that morphological features in Solenopleura holometopa are shared by other Scandinavian trilobites such as Solenopleura conifrons Westergård, 1952, which is closely related. Furthermore, the genus Gonzaloia Geyer, 1998 has been erected to include two species, G. canaliculata and G. conifrons. New descriptions herein suggest this genus is not supported by evidences and that included species should be provisionally considered, though with reservations, within the genus Solenopleura until a morphological and cladistic study of the whole genus will be able to provide significant evidence to separate both genera. © 2015 Published by Elsevier Masson SAS.
r é s u m é Mots clés : Taxonomie Stratigraphie ISCS Cambrien moyen Suède
Les trilobites Solenopleurides forment une famille de trilobites fréquente dans le Gondwana Est et Ouest. Le genre-type de cette famille, Solenopleura, a cependant souffert d’incompréhensions qui ont mené à plusieurs changements taxonomiques au cours du 20e siècle. Afin de clarifier et de résoudre tous ces problèmes, la révision des deux espèces à leur origine, Calymene holometopa Angelin, 1851 et Calymene canaliculata Angelin, 1851, est présentée ici. Les deux espèces sont replacées dans le genre Solenopleura. Les nouvelles descriptions et illustrations démontrent que les caractères morphologiques de Solenopleura holometopa sont partagés par d’autres trilobites scandinaves comme Solenopleura conifrons Westergård, 1952, qui sont proches. De plus, Geyer (1998) a érigé le genre Gonzaloia pour inclure deux espèces, G. canaliculata et G. conifrons. Les nouvelles descriptions faites ici suggèrent que ce genre n’est pas soutenu par les évidences et que les espèces inclues devraient être provisoirement considérées, bien qu’avec réserve, au sein du genre Solenopleura jusqu’à ce qu’une étude morphologique et cladistique de l’ensemble du genre fournisse les preuves nécessaires à sa division. © 2015 Publié par Elsevier Masson SAS.
1. Introduction
E-mail address: [email protected] Current address: Departamento de Paleontología, Universidad Complutense de Madrid, C/José Antonio Nováis 12, Ciudad Universitaria, 28040 Madrid, Spain. 1
http://dx.doi.org/10.1016/j.annpal.2015.05.001 0753-3969/© 2015 Published by Elsevier Masson SAS.
Solenopleurids are a family of typically “ptychopariid” trilobites from Gondwana. They have been very much studied during the last century. They are present in Cambrian strata throughout ˇ 1958; Sdzuy, 1961; the Mediterranean area (Thoral, 1947; Snajdr, Geyer, 1998; Courtessole, 1973; Álvaro and Vizcaïno, 2001; Álvaro
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Andrarum Limestone (4.10–5.65 m), and the Lejopyge laevigata Zone comprises the shales above the Andrarum Limestone but L. laevigata already appears near the base of the S.? brachymetopa Zone (Axheimer et al., 2006). These authors suggested that the L. laevigata Zone in Scandinavia should be extended to include the traditional S.? brachymetopa Zone, and its lower boundary should be defined at the first occurrence datum (FAD) of L. laevigata (Fig. 2). 2. Systematic Palaeontology Terminology. Trilobite descriptive terminology follows Whittington and Kelly in Kaesler (1997). Repositories. All the specimens described and discussed herein are housed in the collections of the Geological Survey of Sweden, Uppsala (SGU) and the Swedish Museum of Natural History (Ar). Order PTYCHOPARIIDA Swinnerton, 1915 Family SOLENOPLEURIDAE Angelin, 1854 Type genus Solenopleura holometopa by assignation of Walcott (1884). Genus Solenopleura Angelin, 1854
Fig. 1. Map showing Scania in the southern of Sweden and the distribution of Cambrian deposits in Scandinavia (Martinsson, 1974). Carte localisant la province de Scania dans le sud de la Suède et la distribution des dépôts cambriens en Scandinavie (Martinsson, 1974).
et al., 2004; Esteve et al., 2010), China (Zhang et al., 1980; Zhang and Jell, 1987; Yuan et al., 2012), UK (Cobbold and Pocock, 1934; Rushton and Berg-Madsen, 2002), Newfoundland (Fletcher, 2005) and Scandinavia (Grönwall, 1902; Westergård, 1952; Axheimer and Ahlberg, 2003; Weid and Nilsen, 2014). Thoral (1947) divided this family into two subfamilies: Solenopleurinae and Solenopleuropsinae. The main differences between the two subfamilies lie with the shape of the anterior furrow of the cranidia, symmetrical in Solenopleurinae and asymmetrical in Solenopleuropsinae, and the geometry of the anterior border, convex in Solenopleurinae and upturned in Solenopleuropsinae (Álvaro and Vizcaïno, 1997). The revision of this family lies outside the scope of the current study. Nonetheless, up to the present time, the assignation of some type species of this family has been problematic due to misunderstandings, inaccurate descriptions and poor illustrations (or even without illustrations) of the type material. In the present work, an attempt is made to resolve these misunderstandings. It focuses on the type material of two species which have been assigned to the type genus of this family: Calymene holometopa Angelin, 1851 and Calymene canaliculata Angelin, 1851. The type specimens were collected in the Andrarum limestone (Nielsen and Schovsbo, 2007) in Scania, southern Sweden (Fig. 1). These specimens belong to the Solenopleura? brachymetopa Zone (Fig. 2). According to Westergård (1952), the S.? brachymetopa Zone comprises the
Discussion. Westergård (1952) carried out a revision of the solenopleurids from Sweden, erecting the genus Parasolenopleura Westergård, 1952 and separating it from the genus Solenopleura Angelin, 1854. Both genera however have become a taxonomic wastebasket due to poor characterization of many species included within these genera (see Geyer, 1998, in press; Álvaro et al., 2004). Westergård (1952) affirmed that Miller (1889) had selected C. canaliculata as the type species of the genus instead of C. holometopa which actually had previously been selected by Walcott (1884) as the type species of Solenopleura, as was noted by Taylor and Rushton (1972) and subsequently by Chernysheva (1980), Babcock (1994), Rushton (1995), Geyer (1998) and Álvaro et al. (2004). This designation, however, was evidently unobserved by Rudolph (1994) who followed Westergård’s assumption. Rudolph (1994) studied the genus Solenopleura and restricted this genus to those forms that have a glabella with well-defined glabellar furrows, developed eye ridges, and an obsolescent preglabellar field. This means that the preocular fields are disconnected in front of the glabella. All the Scandinavian forms seem, however, to have their preocular fields connected in front of the glabella, but not at all ontogenetic stages. In large specimens of S. holometopa, the preglabellar area becomes reduced and both preocular fields are separated by a median preglabellar furrow (see Fig. 3A, D and Fig. 4A, D). Therefore, for Rudolph (1994) as well as Geyer (1998), only the species from Scandinavia, S. canaliculata (Angelin, 1851) and S. conifrons Westergård, 1952 are included in this definition. All other Scandinavian species were excluded and were assigned to ˇ the genus Jincella Snajdr, 1957, which also included the type species of the genus, S. holometopa. This classification, however, gives rise to some problems because most of the criteria that Rudolph (1994) and Geyer (1998) used to distinguish both genera, such as the width and convexity of the fixigenae or weakness of the eye ridges, are not possible or difficult to quantify and are not objectively applicable. Besides, many works illustrate the kind of variability that is common amongst Cambrian trilobites due to biological and taphonomical causes (e.g. Hughes and Rushton, 1990; Hughes, 1991, 1995; Esteve, 2014) and studies made so far have not been focused on this problem. The diagnosis of a genus should not focus only on morphological features, which are liable to suffer modifications by taphonomic processes. Rushton and Berg-Madsen (2002) noted also these difficulties and emphasized the need for further studies before agreement is possible on diagnostic features separating these genera. Álvaro et al. (2004) emended the diagnosis of Jincella
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Fig. 2. Traditional middle Cambrian biostratigraphy of Scandinavia and global zonation (from Axheimer et al., 2006) with stratigraphical distribution of the Solenopleura species studied herein. Biostratigraphie traditionnelle du Cambrien moyen de Scandinavie et zonation internationale (d’après Axheimer et al., 2006) avec la distribution stratigraphique des espèces de Solenopleura étudiées dans ce travail.
(see fig. 3 of Álvaro et al., 2004). These authors argued that although compaction can modify the total convexity of the cranidium, the relative inflated character of its different parts (glabella, fixigenae, eye lobes and anterior border) can be used as diagnostic character. Thus, Jincella differs from Solenopleura in having a narrower preocular area with the margin of the fixigena close to the axial furrow which lies on the same plane that the highest peak of the glabella (genae 75–100% as broad as the glabella in a cross-section across the eye lobes), whereas the eye lobe is less convex than the fixigenae (80%), and the cranidial anterior border is slightly less convex or as convex as the eye lobes, finally the anterior branch of the facial suture between ␥ and  is divergent to the axial axis and also divergent from  to ␣. The replacement of S. canaliculata by S. holometopa for the type species of Solenopleura removes S. canaliculata, as defined by Rudolph, from the genus. Therefore, according to Geyer (1998), an appropriate generic name for S. canaliculata, based on a type species C. canaliculata Angelin, 1851, was lacking. Accordingly, Geyer (1998) erected the genus Gonzaloia with two species: G. canaliculata and G. conifrons. However, Geyer (1998, p. 392) only provided a diagnosis for the genus and he stated the following diagnosis for G. canaliculata “see above under diagnosis of the genus (because of monotypy)”. This is inadequate since he clearly included both species within this new genus. In addition, although he did carry out an appropriate description and comparison, he did not figure the holotype of this genus. To solve this trouble, I discuss, describe and figure below the type species of Gonzaloia (i.e. C. canaliculata) and the type species of Solenopleura (i.e. C. holometopa). Diagnosis. Cephalon semicircular in outline with evenly curved anterior margin, and straight posterior margin. Glabella tapering forward, anterior lobe of glabella truncated to rounded, glabellar furrows very shallow (sometimes absent in internal mould) to moderate deep furrows. Anterior border furrow well marked. Occipital ring well defined, with or without node. Palpebral lobes fairly small, central or slightly approximated to posterior margin; ocular ridges obsolete to distinct. Anterior branches of facial suture between ␥ and  subparallel to slightly convergent (ca. 20 degrees) to axial line and from  to ␣ convergent to perpendicular
to margin, posterior branches from to gently sigmoid, cutting posterior margin at a short distance within genal angles. Genal angles rounded or quite angulated, with or without genal spines, which usually are short making an angle with cheek outline, exceptionally stout and continuous. Thorax with up to 16 thoracic segments, pleural furrow well marked and anterior and posterior pleural bands well defined, fulcra distinct with rounded pleural (petaloid-like) facet. Pygidium with up to seven segments in rachis and pleural field up to 7 well-defined pleural furrows; interpleural furrows poorly developed; posterior border well defined. Solenopleura holometopa (Angelin, 1854) Figs. 1 and 2A–I *v1851 C. holometopa Angelin, p. 23, pl. 18, fig. 8.v1854 S. holometopa (Angelin), p. 26, pl. 18, fig. 8. 1878 S. holometopa, (Angelin), Brögger, p. 53, pl. 3, fig. 9. 1902 S. holometopa (Angelin), Grönwall, p. 155, pl. 4, figs 20–21, 23. 1946 S. holometopa (Angelin), Thoral, p. 14. v1952 S. holometopa (Angelin), Westergård, p. 14, pl. 4, figs. 1–8. v1952 Solenopleura holometopa humilis (Westergård, 1952), Westergård, p. 16, pl. 4, fig. 9. ˇ 1957 Jincella holometopa (Angelin), Snajdr, p. 241. ˇ 1958 J. holometopa (Angelin), Snajdr, p. 197. 1994 J. holometopa holometopa (Angelin, 1851), Rudolph, p. 202, pl. 25, figs. 8–9. 1994 Jincella holometopa humilis (Westergård, 1952), Rudolph, p. 203, pl. 25, figs. 10–11. 1998 S. holometopa (Angelin, 1851), Geyer, p. 390. v 2004 S. holometopa (Angelin, 1851), Álvaro et al., fig. 3.1. Occurrence. Cambrian Series 3, Stage 5, S.? brachymetopa Zone, Andrarum limestone; Baltica: Scania, Västergötland, Bornholm, southern Norway, and erratic boulders in northern Germany. Discussion. Westergård (1952) described the subspecies S. (holometopa) humilis on the basis of one single cranidium which differs from Solenopleura (holometopa) holometopa in having a cranidium with lower convexity, very shallow dorsal furrows, cheeks in transverse section not at all inflated and a glabella not sunk between the cheeks. However, some of these morphological
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Fig. 3. A–I Cranidia of Solenopleura holometopa (Angelin, 1854), Cambrian Series 3, Stage 5, Solenopleura? brachymetopa Zone, Andrarum limestone. A–C. Ar63472. A. Dorsal view. B. Frontal view. C. Lateral view. D–F. SGU6267. D. Dorsal view. E. Frontal view. F. Lateral view. G-I. SGU6268. G. Dorsal view. H. Frontal view. I. Lateral view. J–L. Solenopleura conifrons Westergård, 1952, Holotype, cranidium, Ar42836, Cambrian Series 3, Stage 5, Solenopleura? brachymetopa Zone, Andrarum limestone. J. Dorsal view. K. Frontal view. L. lateral view. A–I. Cranidia de Solenopleura holometopa (Angelin, 1854), Série 3 du Cambrien, Étage 5, Zone à Solenopleura? brachymetopa, Calcaire d’Andrarum. A–C. Ar63472. A. Vue dorsale. B. Vue frontale. C. Vue latérale. D–F. SGU6267. D. Vue dorsale. E. Vue frontale. F. Vue latérale. G-I. SGU6268. G. Vue dorsale. H. Vue frontale. I. Vue latérale. J–L. Solenopleura conifrons Westergård, 1952, Holotype, cranidium, Ar42836, Série 3 du Cambrien, Étage 5, Zone à Solenopleura? brachymetopa, Calcaire d’Andrarum. J. Vue dorsale. K. Vue frontale. L. Vue latérale.
features, such as the presence of shallow dorsal furrows, are not able to be quantified and may be related to the mode of preservation (see Esteve, 2014 for mode of preservation). Moreover, the analysis of the collection at the Swedish Museum of Natural History shows that the relative relief of its different parts have a distinct variability within the sample. All the specimens come from the Andrarum limestone and do not show compaction features. Thus, I suggest that both subspecies are indeed the same. Westergård (1952, p. 15) described a single thorax of this species with 11 thoracic segments but I could not find this specimen in the reposited collection. Diagnosis. Solenopleura species with inflated glabella; fixigena convexity lies under glablella and on same plane that axial furrow. Palpebral lobe at same plane that fixigena. Anterior arch of cephalic border, curving up to sagittal line. Small pygidium with 2 narrow and deep pleural furrows and between 2 and 4 axial rings.
Description. Cephalon: Cranidium moderately large, up to 19 mm long (n = 185), subpentagonal in outline, anterior margin evenly curved and posterior margin straight. Anterior branch of facial suture slightly convergent to anterior border, ca. 15 degrees to exsagittal line up to the anterior border furrow, and very divergent after it, ca. 40 degrees. Glabella inflated along longitudinal axis with frontal lobe bluntly rounded, glabella tapers anteriorly, glabellar furrows barely visible on external surface and absent on internal mould. Axial furrow moderately deep and straight in outline. Preglabellar furrow moderately deep. Occipital ring lies under glabella and moderately convex, length ca. 16 percent glabellar length, without spine, although some specimens show larger node; posterior margin convex. SO (sulcus occipital) is curved and deeper exsagitally. Frontal area unequally divided, length varies
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Fig. 4. A–H. Solenopleura holometopa (Angelin, 1854), Cambrian Series 3, Stage 5, Solenopleura? brachymetopa Zone, Andrarum limestone. A–C. Lectotype, cranidium, Ar46650. A. Dorsal view. B. Frontal view. C. Lateral view. D–F. Cranidim, Ar2073. D. Dorsal view. E. Frontal view. F. Lateral view. G–H. Pygidium, Ar46429. G. Dorsal view. H. Posterior view. I–Q. Solenopleura? canaliculata (Angelin, 1851), Cambrian Series 3, Stage 5, Solenopleura? brachymetopa Zone, Andrarum limestone. I–K. Cranidium Ar1630. I. Dorsal view. J. Frontal view. K. Lateral view. L–N. Lectotype, cranidium Ar46145. L. Dorsal view. M. Frontal view. N. Lateral view. P–Q. Pygidium Ar1785g. P. Dorsal view. Q. Lateral view. A–H. Solenopleura holometopa (Angelin, 1854), Série 3 du Cambrien, Étage 5, Zone à Solenopleura? brachymetopa, Calcaire d’Andrarum. A–C. Lectotype, cranidium, Ar46650. A. Vue dorsale. B. Vue frontale. C. Vue latérale. D–F. Cranidium, Ar2073. D. Vue dorsale. E. Vue frontale. F. Vue latérale. G–H. Pygidium, Ar46429. G. Vue dorsale. H. Vue postérieure. I–Q. Solenopleura? canaliculata (Angelin, 1851), Série 3 du Cambrien, Étage 5, Zone à Solenopleura? brachymetopa, Calcaire d’Andrarum. I–K. Cranidium Ar1630. I. Vue dorsale. J. Vue frontale. K. Vue latérale. L–N. Lectotype, cranidium Ar46145. L. Vue dorsale. M. Vue frontale. N. Vue latérale. P–Q. Pygidium Ar1785g. P. Vue dorsale. Q. Vue frontale.
between 6 percent cranidial length in larger specimens (> 15 mm) and 11 percent in smaller specimens (< 10 mm). Preglabellar field slightly concave. Anterior border (on average 10 percent cranidial length) concave and moderately upturned. Margin straight. Palpebral lobe upturned, wide and moderately long, length on average ca. 40 percent glabellar length. Anterior margin of palpebral lobe opposite, approximately, to anterior part of glabella and palpebral furrow moderately shallow. Ocular ridge very narrow and straight, development weak on external mould and well marked
on internal mould. Librigena small, maximum size 5 mm long, very narrow, lateral margin curved and downward. Genal field slightly sunken (width ca. 72 percent librigenal length). Lateral border very concave, of uniform width (width ca. 30 percent librigena width), lateral border furrow shallow and narrow. Pygidium: Small, on average length ca 15 mm and width ca 20 mm; subelliptical in outline, anterior margin slightly curved, lateral margin evenly curved. Axial mid-width is ca. 20 percent axial anterior width, axial anterior width ca. 30 percent pygidial
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Fig. 5. Solenopleura? canaliculata (Angelin, 1851), Cambrian Series 3, Stage 5, Solenopleura? brachymetopa Zone, Andrarum limestone. A–C. Cranidium Ar1786a. A. Dorsal view. B. Frontal view. C. Lateral view. D–F. Cranidium, Ar1786b. D. Frontal view. E. Dorsal view. F. Lateral view. G–I. Cranidia, Ar1630. G. Dorsal view. H. Frontal view. I. Lateral view. J–L. Cranidium, SGU6269. J. Frontal view. K. Dorsal view. L. Lateral view. Solenopleura? canaliculata (Angelin, 1851), Série 3 du Cambrien, Étage 5, Zone à Solenopleura? brachymetopa, Calcaire d’Andrarum. A–C. Cranidium, Ar1786a. A. Vue dorsale. B. Vue frontale. C. Vue latérale. D–F. Cranidium Ar1786b. D. Vue frontale. E. Vue dorsale. F. Vue latérale. G–I. Cranidia, Ar1630. G. Vue dorsale. H. Vue frontale. I. Vue latérale. J–L. Cranidium, SGU6269. J. Vue frontale. K. Vue dorsale. L. Vue latérale.
width, and axial length ca. 90 percent of pygidium length. Between 2 and 4 axial rings. Pleural region well defined, 2 narrow and deep pleural furrows. Posterior border evenly curved in posterior view. Solenopleura conifrons Westergård, 1952 Fig. 4J–L v 1952 S. conifrons sp. nov. Westergård, p. 17. pl. 4, figs. 10a–d. 1998 G. conifrons (Westergård). Geyer, p. 392. 2002 Solenopleura aff. conifrons Rushton and Berg-Madsen, figs. 5a–c. Discussion. Geyer (1998) included this species within the new genus Gonzaloia. However, he did not provide any discussion or figures. He stated “Solenopleura conifrons Westergård, 1952 is very similar to S. canaliculata. It has a well-developed preglabellar field, but this results from a sagittally narrow rather than swollen and posteriorly swinging anterior border that deviates from the border furrow to meet the axial furrow in front of the glabella” and included within the issue of “species included” within Gonzaloia but without yielding any diagnosis. The conical glabella, shallow glabellar furrows, weak eye ridge and the shape of the anterior border furrow and anterior border are similar to those of S. holometopa; this form only differs from the latter in having a wider preglabellar field. The study of the type material, housed at the Swedish Museum of the Natural History, suggests that this species is more similar to S. holometopa rather than S. canaliculata as Geyer (1998)
suggested and Westergård (1952) had already noted. S. canaliculata shows a well-marked glabellar furrow, distinct eye ridge, wider fixigena, narrower preglabellar area and a wider anterior border with a plectrum. These features, especially the presence of the plectrum, allow a proper differentiation from S. canaliculata, S. holometopa and S. conifrons. Therefore, the assignation of S. conifrons to the genus Gonzaloia cannot be supported by fails through lack of evidence. Nevertheless, the differences with S. holometopa may be related to different ontogenetic stages or intraspecific variation, but the lack of a large set of specimens [only three in Sweden and one in England (Rushton and Berg-Madsen, 2002)] prevent a study of variation. Despite this, it seems more appropriate to keep S. conifrons as a valid species and wait until more material becomes available. Occurrence. Cambrian Series 3, Stage 5, S.? brachymetopa Zone, Andrarum limestone; Baltica: Scania, Västergötland, Bornholm, southern Norway, erratic boulders in northern Germany. Paradoxides forchhammeri Zone, Rushton Brook Bed of the Upper Comley Sandstone, in England and Wales. Diagnosis. Solenopleura species with palpebral area at middle plane of glabella and in transverse section across palpebral lobes as wide as glabella and nearly horizontal or somewhat arched. Description. Cranidium small up to 15 mm long (n = 3), subpentagonal in outline, anterior margin posterior margins straight. Anterior branch of facial suture slightly convergent to anterior border, ca. 20 degrees to exsagittal line up to the anterior border
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furrow and ca. 40 degrees from anterior border furrow. Glabella inflated along longitudinal axis with rounded frontal lobe, glabella tapers anteriorly, and glabellar furrows are barely visible on the internal mould, and not impressed on external surfaces. Axial furrow is moderately deep and straight in outline. Preglabellar furrow moderately shallow. Occipital ring lies under glabella, moderately convex, length ca. 15 percent glabellar length, without node or spine on internal mould, external surface unknown. SO shallow, slightly curved and deeper exsagitally. Frontal area unequally divided, length 20 percent of cranidial length. Preglabellar field slightly concave. Anterior border (ca 8 percent cranidial length) concave. Palpebral lobe upturned and short. Anterior margin of palpebral lobe opposite of approximately to L3. Ocular ridge barely visible. Fixigena with anterior area slightly convex, sloping, with ca. 55 percent of glabellar width. Posterior border moderately convex, expanding distally, border furrow shallow and straight. Thorax and pygidium unkown. Solenopleura? canaliculata (Angelin, 1851) Figs. 4L–Q and Fig. 5 v. 1852 C. canaliculata Angelin, 1851, p. 23, pl. 18, figs. 9, 9a. v. 1854 S. canaliculata (Angelin, 1851), p. 27, pl. 18, figs. 9, 9a. 1902 S. canaliculata (Angelin), Grönwall, p. 151, pl. 4, figs. 16, 17. 1994 S. canaliculata (Angelin), Rudolph, p. 201, pl. 25, figs. 4–5. 1998 G. canaliculata (Angelin, 1851). Geyer, p. 302 Discussion. Geyer (1998) erected a new genus using this species and provided a diagnosis but no figures. Beside all the criteria he used to diagnose this new genus, such as the convexity of the glabella and fixigenae, the fixigenae separated by a depression in front of the glabella, three pairs of well-defined glabellar furrows, occipital ring with median node or a short palpebral lobe conspicuously upturned, are not properly quantified and share features with other species of Solenopleura. The unique distinctive morphological characters are the presence of a plectrum and a wider pleural field in the pygidium. Therefore, in view of these characters and the inappropriate erection of the genus Gonzaloia, a generic distinction between Gonzaloia and Solenopleura is still in need of better argumentation, and for that reason, I take a wider view of Solenopleura and allocate this species within the genus Solenopleura, though with some reservations based on its general morphology, pending an analysis of all characters of these species. Diagnosis. Suspected Solenopleura species with plectrum; pygidium with pleural field twice wider than pygidial axis. Occurrence. Cambrian Series 3, Stage 5, S.? brachymetopa Zone, Andrarum limestone; Baltica: Scania, Västergötland, Bornholm, southern Norway, erratic boulders in northern Germany Description. Cephalon: Cranidium up to 17 mm long (n = 82), trapezoidal in shape, anterior margin straight and slightly curved toward anterior sutures, posterior margin straight. Anterior branch of facial suture convergent to anterior border furrow (ca. 14 degrees to exsagittal line) and subtends same angle from anterior border furrow to anterior margin. Glabella inflated along longitudinal axis with frontal lobe rounded to flat, glabella tapers anteriorly, glabellar furrows are well marked on external and internal moulds. Axial furrow deep and straight in outline. Preglabellar furrow moderately deep. Occipital ring convex lying under glabellar relief, length on average ca. 15 percent of glabellar length, with node, posterior margin convex. SO straight and shallow, deeper exsagitally. Frontal area unequally divided, length ca. 25 percent cranidial length. Preglabellar field sunken and connected with wide anterior border furrow. Anterior border (on average ca 16 percent cranidial length) concave and moderately upturned and with plectrum. Palpebral lobe upturned and very short. Anterior margin of the palpebral lobe approximately opposite to S2 and palpebral furrow very shallow. Ocular ridge very narrow and slightly curved, well developed on external
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mould and weak on the internal mould. Fixigena with anterior area very convex, sloping, on average ca. 20% wider than glabellar width. Posterior border moderately convex, expanding somewhat distally, border furrow shallow and straight. Cranidium covered by granules of different sizes and also pits, granules absent in furrows but pits present. Pygidium: Pygidium relatively large, average length ca 10 mm and wide ca 20 mm; subelliptical, anterior margin slightly curved, whereas lateral margins evenly curved. Axial mid-width ca. 20 percent axial anterior width, axial anterior width ca. 30 percent pygidial width, and axial length ca. 90 percent of pygidial length. Pygidium with 7–8 axial rings. Pleural region well defined, wide pleural furrows and moderately deep, posterior border evenly curved in posterior view. Ribs between furrows covered with granulations and whole pygidium with pits. Thorax unknown. 3. Conclusions The study and illustration of the type material support the following conclusions: 1. S. holometopa is the type species of the genus Solenopleura. This species shows a variability in the preglabellar area since the preocular fields are separated by a median preglabellar furrow in larger specimens, but connected in smaller individuals. 2. The cranidium of S. (holometopa) humilis shows the same variability of the relative relief than the rest of the specimens of S. holometopa. Thus, the subspecies S. (holometopa) humilis is suggested as a synonym of S. holometopa. 3. Assignment of S. conifrons to the genus Gonzaloia is rejected. Its glabellar shape, shallow glabellar furrows, weak eye ridge and shape of the anterior border furrow and anterior border point out to be closely related to S. holometopa rather than S.? canaliculata. 4. S.? canaliculata differs from known species of Solenopleura in having a plectrum and a rather larger pygidium, which may suggest generic differences. It seems, however, premature to remove this form from Solenopleura before a complete study of its morphological variability, and it is here still provisionally accommodated within Solenopleura, though with some reservations. Acknowledgments JE is supported by European Social fund and Ministry of Education Youth and Sport, Czech Republic (Ref. CZ. 1.07/2.3.00/30.0013) and by Spanish MINECO (Ref. FPDI-2013-17337). This research was supported by the Synthesys program (SE-TAF-2083) and it is a contribution to the project CGL2013-48877 from Spanish MINECO and EU–FEDER. I am grateful to Isabel Pérez (MEC-FSE, Universidad de Zaragoza, Spain) for her technical support with the pictures of manuscript. I also thank Linda Wickström (Geological Survey of Sweden) for the loan of the type material housed at Uppsala and Christian Skovsted and Jonas Hagström (Swedish Museum of the Natural History) for kind access to collections in their care. I am grateful to Euan Clarkson and J. Javier Álvaro who critically reviewed the manuscript and suggested valuable improvements. References Angelin, N.P., 1851. Palæontologica Svecica. Pars I; Iconographia crustaceorum formationis transitionis. Academie Regiae Scientarium Suecanae, Holmiae (Stockolm) 1, 1–24. Angelin, N.P., 1854. Palæontologia Scandinavica. I. Iconographia Crustacea Formationis Transitionis, Fasc. II. Berlingska and Leipzig, Wiegel, Lund (41 pl.). Álvaro, J.J., Vizcaïno, D., 1997. Révision des Trilobites Solenopleuropsinae du Cambrien Moyen de la Montagne Noire (France). Geobioscience 30, 541–561.
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