Brachiopods from the Lower-Middle Cambrian Láncara Formation of the Cantabrian Mountains, Northwest Spain

THOMAS WOTTE & MICHAL MERGL

WOTTE, T. & MERGL, M., 2007:09:03. Brachiopods from the Lower-Middle Cambrian Láncara Formation of the Cantabrian Mountains, Northwest Spain. Memoirs of the Association of Australasian Palaeontologists 33, 101-122. ISSN 0810-8889.

Micro- and macrobrachiopods from eight stratigraphic sections of the carbonate upper member of the Middle Cambrian Láncara Formation (comprising lower Beleño facies and upper Barrios facies) in the Cantabrian Mountains are analysed. They comprise ten species, two of which are new, assigned to nine genera, two of which are new. They are: Acrothele primaeva (de Verneuil & Barrande in de Prado, 1860), Acrothele sp., Eoobolidae gen. et sp. indet., Genetreta trilix gen. et sp. nov., Iberotreta sampelayoi gen. et sp. nov., Luhotreta? proclinis (Mergl & Elicki, 2004), Micromitra cf. sculptilis (Meek, 1873), Nisusia vaticina (de Verneuil & Barrande in de Prado, 1860), Trematobolus simplex (Vogel, 1962) and Yorkia zafrensis (Gil-Cid & Mélou, 1986). Stratigraphic distribution patterns of the brachiopod fauna mirror the drowning of the environment. Trematobolus simplex is exclusively found in the carbonates of the Beleño facies, whereas Nisusia vaticina and Yorkia zafrensis are typical representatives of the nodular limestones of the Barrios facies. The species of the genera Trematobolus, Nisusia and Yorkia demonstrate the affinity of the upper Láncara brachiopod association with faunas of the Siberian platform, New South Wales and some Avalonian terranes (Newfoundland, New Brunswick).

Thomas Wotte ([email protected]), Geological Institute, Freiberg University of Mining and Technology, Bernhard-von-Cotta Street 2, D-09599 Freiberg, Germany; Michal Mergl ([email protected]), Department of Biology, University of West Bohemia at Plzeň, Klatovská 51, CZ-306 19, Plzeň, Czech Republic. Received 23 April 2007.

Keywords: Brachiopoda, Middle Cambrian, Láncara Formation, Cantabrian Zone, Spain.

THE IBERIAN MASSIF (Fig. 1A) has one and fossil content allow differentiation of this of the most complete Palaeozoic sedimentary formation into two members (Zamarreño 1972): successions in Europe (Gibbons & Moreno the lower member consists of dolomites and 2002). The approximately 2700 m thick Cambrian dolomitic limestones with a rather poor fossil succession in the Cantabrian Zone consists of three content represented by algae, archaeocyaths (only formations (Fig. 2). The lowermost formation, at the eastern part of the Cantabrian Zone) (e.g., the Herrería Formation, is characterised by Debrenne & Zamarreño 1970; Perejón & Moreno- claystones, sandstones and conglomerates, Eiris 2003) and trilobites (Sdzuy 1959). The representing a ?Neoproterozoic-Early Cambrian upper member of the Láncara Formation has been age. Within this siliciclastic succession, calcareous divided into two facies (Zamarreño 1972): the intercalations are sometimes observed. The fossil lower Beleño facies is characterised by coarsely content of the Herrería Formation consists of crystalline, grey to roan dolomitic limestones ichnofossils (e.g., van der Meer Mohr & Okulitch and limestones with a high content of glauconite 1967; Palacios & Vidal 1992), acritarchs (e.g., and echinoderm debris. The overlying Barrios Palacios & Vidal 1992; Vidal et al. 1999) and facies consists of reddish to purple limestones trilobites (e.g., Sdzuy 1961; Liñán et al. 1993). and nodular limestones with a highly diverse The sedimentary environment of the Herrería fossil content. Known faunal elements of the Formation is interpreted as a shallow marine upper member of the Láncara Formation include platform with occasional intertidal deltaic and trilobites (e.g., Sdzuy 1968; Sdzuy & Liñán 1993), fluviatile episodes (e.g., Rupke 1965; Aramburu brachiopods (de Verneuil & Barrande in de Prado et al. 1992). The carbonates of the Lower-Middle 1860; Sampelayo 1935), echinoderms (Schroeder Cambrian Láncara Formation overlie the Herrería 1973; Friedrich 1993), molluscs (Geyer 1986; Formation (Fig. 2). Differences in lithology Wotte 2006), sponge and chancelloriid remains 102 AAP Memoir 33 (2007)

Fig. 1. A, simplified geological map of the Iberian Peninsula. B, generalised geological map of the Cantabrian Mountains (modified after Pérez-Estaún et al. 1988); Tr = Truebano section; Ge = Genestosa section; Ra = Rabanal section; LL = Láncara de Luna section; BL = Los Barrios de Luna section; Pe = Piedras Bermejas section; Ro = Rodiezmo section; Ve = Vegaservera section; PI = Porma section.

(Sdzuy 1969; Clausen & Álvaro 2006), and in the siliciclastic material (Wotte et al. 2004; phosphatic small shelly fossils (van den Boogaard Wotte 2005). The environment of the Láncara 1983). The faunal and lithological transition Formation is interpreted as a transition from a from the Beleño into the Barrios facies is carbonate ramp to a mixed carbonate-siliciclastic gradual, characterised by a continuous change ramp (Wotte et al. 2004; Wotte 2005), with in the fossil content, and a successive increase supralittoral-littoral conditions in its western part AAP Memoir 33 (2007) 103

Schroeder (1973), Friedrich (1993) and Sdzuy (1993); and graptolites by Sdzuy (1974). Middle Cambrian-Tremadocian acritarchs were recorded by Fombella (1978, 1979). Aramburu et al. (1992) and Aramburu & García-Ramos (1993) interpreted the siliciclastic succession of the Oville Formation as shallow platform deposits of an intertidal and braid plain deltaic environment.

BIOFACIES The upper member of the Láncara Formation contains a highly diverse fauna of trilobites, echinoderms, brachiopods, chancelloriid and sponge remains, but also molluscs and phosphatic small shelly fossils. Based on point counting analyses of thin sections, the vertical faunal distribution through the upper member of the Láncara Formation could be divided into four distinct faunal assemblages (Wotte et al. 2004; Wotte 2005; Fig. 3). For sections which were only documented but not intensively sampled, the vertical faunal succession was estimated on the basis of field data, and in comparison with the point-counted sections. The faunal assemblages of these sections are illustrated in Figure 3 as ‘assumed’. In almost all sections, the upper member of the Láncara Formation (except Genestosa; cf. Fig. 3) starts with an abrupt onset and a predominance of echinoderms, whereas trilobites and brachiopods are clearly less common. This biofacies is called faunal assemblage 1, and is equal with the Beleño facies of Zamarreño (1972). The base of faunal assemblage 2 is marked by a minimum of echinodermal remains, and characterises the base of the Barrios facies. The faunal content is either dominated by trilobites and brachiopods, or it shows nearly equal volumetric ratios of echinoderms, trilobites and brachiopods. Faunal assemblage 3 develops as part of a conformable continuum and is characterised by a further increase in the abundance of trilobites and brachiopods as well as a resurgence of Fig. 2. Simplified stratigraphic profile of the Cambrian echinoderm numbers. Faunal assemblages 1-3 of the Cantabrian Mountains (modified after Liñán et al. 1993 and Geyer & Landing 2004). also include chancelloriids, sponges, molluscs, and phosphatic small shelly fossils as minor faunal elements. In the Los Barrios de Luna section, this and shallow sublittoral environments in its eastern general faunal trend is characterised by a short region (Zamarreño 1972; Aramburu et al. 1992). and rapid decrease in echinoderms, trilobites and The overlying Middle Cambrian-Ordovician brachiopods, whereas further faunal elements Oville Formation consists of claystones and (e.g., chancelloriids, poriferids, molluscs) sandstones (Fig. 2). Sometimes quartzose beds show no distinct change. This specific portion, are observable in the uppermost part (Truyols characterised by Stromatactis-rich limestones, et al. 1990). No carbonate intercalations are represents faunal assemblage 4 (Fig. 3). present in this part of the succession. The fossil content of the Oville Formation is also relatively PREVIOUS WORK AND SAMPLE diverse: trace fossils were described by Gámez CHARACTERISTICS Vintaned et al. (2000); trilobites by Sdzuy (1961, The initial observations on brachiopods from 1968) and Gozalo et al. (2000); echinoderms by the studied area were presented by de Verneuil 104 AAP Memoir 33 (2007)

Fig. 3. Distribution of the faunal assemblages within the studied sections. For sections not point-counted, acceptance of the faunal assemblages and definition of their boundaries are problematic (see text), and thus illustrated as ‘assumed’. Genestosa is the only locality where the faunal succession starts with faunal assemblage 2. Faunal assemblage 4 was only recorded at the Los Barrios de Luna section. For abbreviations of the sections see caption to Figure 1.

& Barrande (in de Prado 1860), who discussed for the repository was not successful. Walcott and illustrated five brachiopod species. The type (1912) revised all species described by de material was not available to Walcott (1908, Verneuil & Barrande (in de Prado 1860). Finally, 1912) and has probably been lost; a recent search Sampelayo (1935) figured and commented on AAP Memoir 33 (2007) 105

section latitude longitude altitude [m] Truebano 42° 56´09. 9´´ N 006° 00´28. 4´´ W 1253 Genestosa 43° 00´22. 2´´ N 006° 00´41. 1´´ W 1265 Rabanal 42° 55´51. 4´´ N 005° 58´25. 3´´ W 1175 Láncara de Luna 42° 54´34. 8´´ N 005° 55´26. 5´´ W 1123 Los Barrios de Luna 42° 50´37. 0´´ N 005° 52´00. 0´´ W 1072 Piedras Bermejas 42° 54´47. 0´´ N 005° 49´30. 2´´ W 1485 Rodiezmo 42° 55´20. 0´´ N 005° 41´44. 2´´ W 1265 Vegaservera 42° 53´56. 3´´ N 005° 32´20. 6´´ W 1055 Porma 42° 55´13. 3´´ N 005° 18´13. 2´´ W 1040 Table 1. Latitude, longitude and altitude of the various sections discussed in the text. some brachiopods from the area, but without any Luna section, sample BL m, Barrios facies, upper accurate stratigraphic or geographic data. member of the Láncara Formation. All the material described here comes from eight stratigraphic sections measured through the Remarks. The incomplete, 1.7 mm long (estimated) Somiedo-Correcilla unit and the La Sobia-Bodon dorsal valve is strongly convex, thin-shelled and unit, western Cantabrian Zone (Fig. 1B). From has an ornament of irregular, wavy, concentric west to east, these sections include: Genestosa lines and broad pustules. Some of these pustules (Ge), Truebano (Tr), Rabanal (Ra), Láncara de have spinose edges (Fig. 4C), indicating affinity Luna (LL), Los Barrios de Luna (BL), Piedras to the family Eoobolidae. Bermejas (Pe), Rodiezmo (Ro), Vegaservera (Ve), and Porma (PI) (Fig. 1B). The exact location of Superfamily ACROTHELOIDEA Walcott & each section (based on U.T.M. projection on Schuchert in Walcott, 1908 the International Ellipsoid) is shown in Table Family ACROTHELIDAE Walcott & Schuchert 1. All microscopic specimens were extracted in Walcott, 1908 from carbonates using 10% formic or acetic acid Subfamily ACROTHELINAE Walcott & without any buffering. Samples were decanted Schuchert in Walcott, 1908 and acid renewed daily. Macrobrachiopods were found mostly on bedding planes during intensive Acrothele Linnarsson, 1876 sampling in the field. In Yorkia, calcareous shells have been removed by hydrochloric acid to obtain Type species. Acrothele coriacea Linnarsson, 1876, internal moulds. Middle Cambrian (Paradoxides forchhammeri Because of deformation and fragmentary Biozone), Sweden. preservation of most specimens, no measurements were evaluated statistically. Only general sizes are Acrothele primaeva (de Verneuil & Barrande in noted in the descriptions. de Prado, 1860) (Fig. 4D-J) All specimens are housed in the collection of the Geological Institute, Freiberg University 1860 Discina (Orbicula) primaeva s. n.; de of Mining and Technology under the prefix: Verneuil & Barrande in de Prado, p. 532, pl. FG 544/locality/microscopic or macroscopic/ 8, figs 2-2a. brachiopod/sample. 1912 Acrothele primaeva (de Verneuil & Barrande); Walcott, p. 654, pl. 57, fig. 6. SYSTEMATIC PALAEONTOLOGY Neotype. FG 544/Ge/mic/brach/18 A, almost Class LINGULATA Gorjansky & Popov, 1985 complete ventral valve (Fig. 4 F). Discina Order LINGULIDA Waagen, 1885 (Orbicula) primaeva was described by de Verneuil Superfamily LINGULOIDEA Menke, 1828 & Barrande (in de Prado 1860). However, Walcott Family EOOBOLIDAE Holmer, Popov & Wrona, (1912) did not know the whereabouts of the 1996 type specimen, which has probably been lost. The specimen selected here as the neotype was Eoobolidae gen. et. sp. indet. (Fig. 4A-C) collected from the upper member of the Láncara Formation at the Genestosa section in relative Material. One shell fragment from Los Barrios de proximity of the type area, and corresponds well 106 AAP Memoir 33 (2007)

Fig. 4. A-C, Eoobolidae gen. at sp. indet., FG 544/BL/mic/brach/m from sample BL m of the Los Barrios de Luna section; Barrios facies; A, incomplete dorsal? valve; B, ornament; C, detail of ornament. D-J, Acrothele primaeva (de Verneuil & Barrande in de Prado, 1860) from samples Ge 16 D, Ge 18 A, Ge 18 E of the Genestosa section; Barrios facies. D-E, FG 544/Ge/mic/brach/16 D; D, incomplete dorsal valve; E, detail of larval shell. F, FG 544/Ge/mic/brach/18 A (1); almost complete ventral valve. G, FG 544/Ge/mic/brach/18 E; incomplete ventral valve. H-J, FG 544/Ge/mic/brach/18 A (2); H, incomplete ventral valve; I, oblique view to larval shell; J, detail of postlarval ornament. K-L, Acrothele sp., FG 544/Ge/mic/brach/17 D (1) from sample Ge 17 D of the Genestosa section; Barrios facies; K, incomplete ventral valve; L, oblique view of larval shell. to the original illustration and description by de 18 A, Ge 18 B, Ge 18 C, Ge 18 E, Ge 18 F, Ge Verneuil & Barrande (in de Prado 1860). The 18 K, Ge 20, Ge 21, and Porma section, samples brachiopod fauna associated with the neotype is PI 21, PI 27, Barrios facies, upper member of the essentially the same as that associated with the Láncara Formation. type specimen of de Verneuil & Barrande (in de Prado 1860); this suggests that the lost type Diagnosis. Acrothele with mound-like elevations specimen and the neotype have the same age and on tubercles of larval shell, with few wavy, come from the same biofacies. somewhat irregular concentric ridges in an early post-larval shell and remaining post-larval shell Type horizon and locality. Barrios facies, upper without distinct concentric ornament; a ventral member of the Láncara Formation, Middle pseudointerarea arched along the axis. Cambrian; Genestosa section, Cantabrian Mountains, Spain. Description. Shell subcircular, plano-convex, thick-walled. Dorsal valve with marginal apex Material. Twenty apical parts of valves with that is weakly curved below commissural plane. preserved larval shell, numerous small fragments, Dorsal larval shell well defined, subcircular, Genestosa section, samples Ge 10 D, Ge 10 H, Ge about 500 µm in diameter, with a diverging pair 11, Ge 13, Ge 15, Ge 16 D, Ge 17 C, Ge 17 G, Ge of large and weak, low tubercles. Both posterior AAP Memoir 33 (2007) 107 and anterior portions of each tubercle mound- fig. 1i). The tubercles of A. coriacea are extended like, slightly raised but not extended into spines. into two pairs of distinct spines in dorsal shells Border of larval shell distinctly defined, lower and into one pair in ventral larval shells (Holmer than adjacent surface of postlarval shell, with & Popov 2000) and its larval shell outline is swollen edge. Surface of larval shell with shallow, transversely ovoid. Concentric ornament is less circular, larval pits 4-5 µm across. Early postlarval distinct in A. primaeva than in A. coriacea. The ornament of few wavy, somewhat irregular larval shell spines are also absent in other early concentric ridges that are more clearly defined Middle Cambrian species (e.g., Acrothele sp. of posterolaterally than anteriorly. Concentric ridges Holmer et al. 2001, pl. 12, figs 14-16). The early essentially absent anteriorly and anterolaterally. Middle Cambrian A. primaeva stratigraphically Surface between concentric ridges and postlarval precedes A. coriacea and considering shell ornament consists of irregular network of low similarity, it might be ancestral to the latter wavy ridges, with small knob-like pustules at species. their junctions. Dorsal valve interior with low De Verneuil & Barrande (in de Prado 1860) median ridge. erected Discina (Orbicula) primaeva on a Ventral valve low, asymmetrically conical, single ventral valve from Middle Cambrian red subcircular in outline with less rounded posterior limestone from Adrados (north-eastern of Boñar, margin. Apex situated in one-third to one-fourth León Province, Cantabrian Mountains). The shell length (estimated from growth lines). sampling areas for our specimens are located Ventral pseudointerarea narrowly triangular, about 5 km north (Porma section), and about 60 less than 30% of shell width, low procline. Its km north-west (Genestosa section) of the type surface lacks pustulose ornament, bearing only locality described in de Prado (1860) (Fig. 1B). low concentric growth lines of uneven size. Red limestone with Paradoxides pradoanus (de Pseudointerarea weakly arched along the axis. Prado 1860, p. 522) is a probable equivalent of the Ventral larval shell is subcircular, weakly elevated upper member of the Láncara Formation. Without above adjacent postlarval shell. Border of larval access to the original material, Linnarsson shell depressed. Paired tubercles of larval shell (1876) and Walcott (1912) referred the species anteriorly converging. Each tubercle consists of a to Acrothele. larger, mound-shaped anterior elevation and half- De Verneuil & Barrande (in Prado 1860) sized lower posterior elevation. Pedicle foramen described Discina (Orbicula) primaeva, with elongate oval, with its larger part confined to larval emphasis on its circular outline and the presence shell, only its posterior third is in contact with of three radial plications (“stries filiformes” in post-larval shell. Foramen externally bordered by original spelling) on its exterior. Our mostly a collar-like, elevated surface of median tubercle incomplete specimens with preserved juvenile of larval shell. Internal pedicle opening broadly parts of the shell lack distinct radial fila or elongate, lacking swollen periphery. Interior of plications. The only incomplete dorsal valve ventral valve without median ridge. (Fig. 4D-E) has weakly developed plications, indicating at least a pair of plications on the Remarks. The type species Acrothele coriacea dorsal valve. The development of radial fila is a Linnarsson is fairly well known (Rowell 1980; highly variable feature of the genus (e.g., Mergl Holmer & Popov 2000). Many authors (Rowell & Šlehoferová 1990; Liñán & Mergl 2001) and 1980; Henderson & MacKinnon 1981; Holmer should not be used in discriminating particular et al. 2001; González-Gómez 2005) have left species of Acrothele. Liñán & Mergl (2001) acrothelid material under open nomenclature. Data reported Acrothele cf. bohemica (Barrande, 1879) from the last decade indicate a broad variety of from the Middle Cambrian of the Iberian Chains, larval shell morphology, with tubercles extended but this species differs from A. primaeva by its into long spines (Henderson & MacKinnon more posteriorly situated ventral apex. Details 1981; Holmer & Popov 2000), short acute spines of the larval shell of Acrothele cf. bohemica (Rowell 1980; Holmer et al. 2001) to obtuse, (Barrande, 1879) are unknown due to different mound-like tubercles as in A. primaeva (Holmer and less favourable preservation. et al. 2001). The genus comprises numerous closely related species having unique larval shell Acrothele sp. (Fig. 4K-L) morphology, but having a very uniform ornament in the postlarval shell. Acrothele primaeva differs Material. Two small fragments of ventral valves, from A. coriacea in its mound-like elevations of Genestosa section, sample Ge 17 D, Barrios facies, larval shell tubercles, subcircular larval shell and upper member of the Láncara Formation. arched axial part of the ventral pseudointerarea, which is flattened (Holmer & Popov 2000, pl. 45, Remarks. The fragments have a thick-walled shell 108 AAP Memoir 33 (2007)

Luhotreta Mergl & Šlehoferová, 1990

Type species. Luhotreta pompeckji Mergl & Šlehoferová, 1990, Jince Formation, Middle Cambrian, Bohemia.

Species included. Luhotreta pompeckji Mergl & Šlehoferová, 1990; ?Vandalotreta proclinis Mergl & Elicki, 2004.

Remarks. The generic diagnosis is based on the macroscopic features. All specimens of the genus are gathered from crack-out material. Hence, fine morphological characters (e.g., nature of the pedicle opening) were not observable, and are still unknown. This led some subsequent authors (e.g., Holmer et al. 2001) to compare Luhotreta with the earlier described genus Vandalotreta Mergl, 1988. However, other features in the original diagnosis of Luhotreta (presence of intertrough, strong median buttress, absence of median ridge, and coarse, lamellose external ornament) indicate close affinity of Luhotreta pompeckji to Vandalotreta proclinis. The nature of the larval shell is known in Vandalotreta proclinis. Because there are significant differences in its position compared with those in the genus Vandalotreta, it is highly probable that Luhotreta is a valid genus. This should be confirmed by a new revision of Luhotreta. In summary, Vandalotreta proclinis is tentatively assigned to Luhotreta, although the nature of the shell opening remains unknown in the latter genus.

Luhotreta? proclinis (Mergl & Elicki, 2004) (Figs 5A-B, 6A-Q).

Fig. 5. Interior (A, C, E) and longitudinal cross- 2004 Vandalotreta proclinis n. sp.; Mergl & sections (B, D, F) of the ventral valve of (A-B) Elicki, p. 588, pl. 2, figs 1-9. Luhotreta? proclinis (Mergl & Elicki, 2004), (C-D) Iberotreta sampelayoi gen. et sp. nov., and (E-F) Material. Hundreds of valves and many fragments, Genetreta trilix gen. et sp. nov. Genestosa section, samples Ge 10 B, Ge 16 C, Ge 16 D, Ge 16 F, Ge 17 C, Ge 17 D, Ge 18 A, Ge and steeply procline ventral pseudointerarea. A 18 C, Ge 18 F, Ge 18 G, Ge 18 H, Ge 18 I, Ge 18 large pedicle foramen continues internally with J, Ge 18 K, Ge 20, Ge 21, Ge 23, Barrios facies, a robust pedicle tube. General morphology of upper member of the Láncara Formation. the valve is consistent with Acrothele granulata (Linnarsson, 1876). Fragments differ from A. Description. See Mergl & Elicki (2004, p. 588). primaeva in having a seemingly steeper ventral Favourable preservation of the Spanish material pseudointerarea and a thicker shell with robust reveals previously unknown morphological pedicle tube. Specimens are left under open features. Larval shell is densely and evenly nomenclature due to the limited material. covered by deep, 1.0-1.5 µm sized pits (Fig. 6 K). Pedicle foramen enclosed within larval shell, Order ACROTRETIDA Kuhn, 1949 perforating the top of a short, posteroventrally Superfamily ACROTRETOIDEA Schuchert, directed, broadly conical tubercle of the larval 1893 shell. Shallow transverse depression separates Family ACROTRETIDAE Schuchert, 1893 tubercle with foramen from anterior transverse tubercle of ventral larval shell. Dorsal larval shell AAP Memoir 33 (2007) 109

Fig. 6. Luhotreta? proclinis (Mergl & Elicki, 2004). A, FG 544/Ge/mic/brach/18 F (8); dorsal valve. B-C, FG 544/Ge/mic/brach/18 F (9); B, dorsal valve in anterior view; C, dorsal valve in dorsal view. D, FG 544/Ge/ mic/brach/18 F (10); dorsal valve in lateral view. E, FG 544/Ge/mic/brach/18 F (11); dorsal valve in oblique view. F-G, FG 544/Ge/mic/brach/18 F (12); F, dorsal valve in lateral view; G, detail of larval shell. H, FG 544/Ge/mic/brach/18 F (13); ventral valve in anterior view. I, FG 544/Ge/mic/brach/18 F (14); ventral valve in apical view. J-K, FG 544/Ge/mic/brach/21; J, juvenile ventral valve in lateral view; K, detail of larval shell. L, FG 544/Ge/mic/brach/18 F (15); ventral valve in oblique view. M, FG 544/Ge/mic/brach/18 F (16); dorsal valve interior in oblique view. N-O, FG 544/Ge/mic/brach/17 D (2); N, bored ventral valve; O, detail of its pseudointerarea. P-Q, FG 544/Ge/mic/brach/18 K; P, ventral valve interior in dorsal view; Q, ventral valve interior in oblique view. has one subcentral tubercle encircled by depressed Lamellae are more densely spaced in later growth periphery. Border of larval shell is weakly defined stages, somewhat overlapping one another. Large by disappearance of larval pitting, and by the shells have typically ten to eleven lamellae in each first fine concentric fila of postlarval ornament. valve, but the number of lamellae fluctuates. Concentric fila are interrupted by prominent concentric lamellae. Lamellae are very coarse, of Remarks. These specimens are identical to uniform size, highly raised above shell surface. those from the Middle Cambrian Campo Pisano 110 AAP Memoir 33 (2007)

Formation of Sardinia (Mergl & Elicki 2004) deep. Proximal ventral vascula lateralia arcuate, in shell size, outline, convexity and details of deeply impressed. Postlarval ornament of internal morphology. The straight to weakly uniform, distinct concentric fila. concave anterior slope of ventral valve (Fig. 5A-B) distinguishes this species from other Discussion. Iberotreta gen. nov. differs from acrotretids in our samples from the Cantabrian numerous acrotretid genera by the combination Mountains. Tectonic deformation of some shells of a highly conical ventral valve, a weak dorsal prevents evaluation of shell outline and convexity median ridge, and a pedicle foramen enclosed variability. within the larval shell; the last feature distinguishes Procline ventral pseudointerarea and coarse the new genus from otherwise similar genera growth lamellae suggest placing L. proclinis such as Anelotreta, Dicondylotreta, Hadrotreta, in Anabolotreta Rowell & Henderson, 1978, Linnarssonia, Prototreta and Vandalotreta. In with A. lepida Koneva, 1986 from the Middle contrast to the morphologically similar genus Cambrian of Central Asia. Anabolotreta differs Tingitanella, the new genus possesses a procline by having the apical pedicle foramen not enclosed ventral pseudointerarea and a raised anterior part within larval shell, and despite their variation of the dorsal median ridge forming a low septum. in Luhotreta, growth lamellae of Anabolotreta Iberotreta can be distinguished from Neotreta by are more variable in their strength and shape. its short conical pedicle tube. Unlike the uniform The type species, Anabolotreta tegula Rowell & pitting of Araktina and Vandalotreta, the new Henderson, 1978, has a much lower ventral valve genus has larval pits of two different sizes. than in L. proclinis. Circular cylindrical borings (some aborted) Iberotreta sampelayoi sp. nov. (Figs 5C-D, are commonly present on shells in our collection. 7A-R) Some have one (Fig. 6H) to as many as five (Fig. 6N) borings in the same valve. Boreholes are Holotype. FG 544/Ge/mic/brach/18 F (1), dorsal observable in ventral and dorsal valves and they valve (Fig. 7A-C). have a uniform size. Some boreholes are located at hidden places below growth lamellae (Fig. 6 B-C) Paratype. FG 544/Ge/mic/brach/18 F (5), ventral indicating a flexibility of boring apparatus of an valve (Fig. 7J-M). unknown predator. Similarly shaped borings were described in Cambrian acrotretids by Conway Type horizon and locality. Barrios facies, upper Morris & Bengtson (1994) and Streng (1999), but member of the Láncara Formation, Middle our sample is too small for statistical evaluation Cambrian; Genestosa section, Cantabrian of the bored specimens. Mountains, Spain.

Iberotreta gen. nov. Etymology. After the Spanish geologist P.H. Sampelayo, the author of the first review of Type species. Iberotreta sampelayoi gen. et sp. the Cambrian brachiopods from the Cantabrian nov., upper member of the Láncara Formation, Mountains. Middle Cambrian, Spain. Material. Fifty valves and many fragments, Los Etymology. After the Iberian Peninsula. Barrios de Luna section, samples BL a, BL n; Genestosa section, samples Ge 7, Ge 8, Ge 9, Ge Diagnosis. Acrotretid genus with small, thin- 10 B, Ge 10 C, Ge 10 D, Ge 10 E, Ge 10 F, Ge shelled, ventribiconvex shell with weakly and 10 I, Ge 16 E, Ge 17 D, Ge 18 B, Ge 18 D, Ge broadly unisulcate commissure. Shell covered 18 E, Ge 18 F, Ge 18 K, Ge 20, Ge 21; Porma by closely arranged, fine, regular, concentric filae section, sample PI 27; Rodiezmo section, sample without distinct growth lamellae. Dorsal median Ro 13; Vegaservera section, samples Ve 2, Ve septum low and short, separated from median 4, Barrios facies, upper member of the Láncara buttress. Larval shell shows two different sized Formation. pits: large circular flat-bottomed pits, and smaller circular hemispherical pits. Ventral valve highly Diagnosis. As for genus. conical. Ventral pseudointerarea poorly defined laterally, steeply procline, depressed, narrowly Description. Shell small and thin, ventribiconvex, triangular with distinct intertrough. Pedicle about 1.1 mm wide in adults, with convex dorsal foramen enclosed within larval shell. Apical valve, bluntly conical ventral valve and feebly process boss-like, prominent, transverse, with unisulcate anterior commissure. convex surface; apical pits lateral to foramen, Dorsal valve subcircular, 90% as long as wide, AAP Memoir 33 (2007) 111

Fig. 7. Iberotreta sampelayoi gen. et sp. nov. A–C, holotype FG 544/Ge/mic/brach/18 F (1); A, dorsal valve; B, oblique view showing ornament; C, posterolateral view to larval shell. D–E, FG 544/Ge/mic/brach/18 F (2); D, dorsal valve in posterolateral view; E, detail of larval shell. F, FG 544/Ge/mic/brach/18 F (3); incomplete dorsal valve interior. G–I, FG 544/Ge/mic/brach/18 F (4); G, dorsal valve interior; H, dorsal valve in oblique view; I, dorsal larval shell in lateral view. J–M, FG 544/Ge/mic/brach/18 F (5); J, ventral valve in apical view; K, ventral valve in posterior view; L, ventral valve in posterolateral view; M, detail of larval shell. N–Q, FG 544/Ge/mic/brach/18 F (6); N, ventral valve in lateral view; O, ventral valve in anterior view; P, ventral larval shell; Q, detail of larval shell. R. FG 544/Ge/mic/brach/18 F (7); ventral valve larval shell in lateral view. widest at midlength, with less rounded posterior by larger circular pits and smaller, less regular and anterior margins than lateral margins. Valve pits in between (Fig. 7Q). Circular pits shallow, moderately convex in transverse profile with flat-bottomed, with diameter from 2-8 µm. Size weakly depressed median sector. Convexity of circular pits decreases towards the periphery prominent near dorsal apex, but decreasing of the larval shell. Dorsal pseudointerarea anteriorly. Dorsal larval shell transversely oval, orthocline, with a broadly triangular, weakly 180 µm wide, with central raised tubercle, clearly concave median groove, slightly overhanging bordered by swollen margin; larval shell covered posterior margin. Sides of median groove subtend 112 AAP Memoir 33 (2007) an angle of 80-100°. Anterior edge of median anterior part of the median ridge is unknown in groove straight. Propareas small. Dorsal median Vandalotreta. ridge with prominent median buttress, almost disappearing at posterior third, but continues as Genetreta gen. nov. short, triangular septum anteriorly. Thickened concentric brim along the periphery of the valve Type species. Genetreta trilix gen. et sp. nov., weakly defined. Cardinal muscle scars large, upper member of the Láncara Formation, Middle elongate-oval, almost parallel, located at midway Cambrian, Spain. between median ridge and lateral margin. Pallial markings obscure. Etymology. After the type locality Genestosa. Ventral valve is highly conical, with apex in posterior quarter (Fig. 5C-D). Valve about Diagnosis. Acrotretid with small, moderate to 50% as high as long with a high, narrowly thick-shelled, ventribiconvex shell with weakly triangular pseudointerarea. Steeply procline and broadly unisulcate commissure; shell covered interarea occupies about 30% of valve width, by less regular low concentric fila and weak with weakly defined sides and depressed surface. growth lamellae. Median buttress present. Dorsal Pseudointerarea medially divided by distinct, valve with very low, long median ridge branching narrow and deep intertrough. Anterior slope of into two oblique low ridges near valve centre valve weakly convex, especially in early growth and with gently swollen anterior termination. stages. Lateral slopes almost straight. Pedicle Larval shell covered with circular pits of foramen enclosed within larval shell. Foramen uniform size. Ventral valve conical with procline circular, 25 µm in diameter, piercing top of pseudointerarea divided by weak intertrough. short, posteroventrally directed, broadly conical Pedicle foramen enclosed within larval shell. tubercle. Low, transverse tubercle located in Apical process prominent, subcircular. Apical anterior half of larval shell. Apical chamber of pits deep, posterolateral to internal pedicle ventral valve filled by low, transverse apical opening. Ventral vascula lateralia arcuate, weakly process with a weak anterior slope. Internal impressed. pedicle foramen circular at the ventral termination of internal convex surface of intertrough, laterally Remarks. The new genus differs from most bordered by very deep apical pits. Cardinal acrotretids in having a low, stout and distinct scars large, obliquely oval, with weakly convex dorsal median ridge. The dorsal median ridge surfaces, situated at the posterolateral part of trifurcates in the middle of the valve and the inner surface of pseudointerarea. Vascula lateralia median buttress has a prominent bifurcation. This with curved deeply impressed proximal parts, but feature, together with a rather high conical ventral obscure distal parts. valve, a pedicle foramen enclosed within the larval Postlarval ornament of fine, distinct, rounded shell, a prominent pair of tubercles on the dorsal concentric fila of uniform size arranged with larval shell, and uniform fine pitting of the larval regular spacing (Fig. 5C-D). Some fila are shell characterises the new genus. Kostjubella wavy with numerous, short, drape-like folds. is similar in most characters, but Genetreta has Growth lamellae absent externally but distinct a foramen enclosed within the larval shell and concentric bands of a different coloured material possesses a low dorsal median ridge. in otherwise transparent shells indicate cessation of the growth. Genetreta trilix gen. et sp. nov. (Figs 5E-F, 8A-M) Remarks. The new species is externally similar to Vandalotreta vafra Mergl, 1988, but differs in Holotype. FG 544/Ge/mic/brach/18 G (1), dorsal having a pedicle foramen that is enclosed within valve figured (Fig. 8A-B). the larval shell and a posteroventrally directed short pedicle tube. In V. vafra and other species Paratype. FG 544/Ge/mic/brach/10 F (1), ventral referred to Vandalotreta (Holmer et al. 1996; valve figured (Fig. 8C-E). Streng 1999), the foramen cuts the posterodorsal border of the ventral larval shell and is directed Type horizon and locality. Barrios facies, upper posteriorly. The exterior of the dorsal valve is member of the Láncara Formation, Middle almost indistinguishable from that of Vandalotreta Cambrian; Genestosa, Cantabrian Mountains, except for a more transverse shell outline and Spain. a depressed median sector that forms a weakly unisulcate anterior commissure, while in V. Etymology. After Latin trilix, -icis, referring to vafra the commisure is rectimarginate. A raised the triradiate appearance of the dorsal median AAP Memoir 33 (2007) 113

Fig. 8. Genetreta trilix gen. et sp. nov. A–B, holotype FG 544/Ge/mic/brach/18 G (1); A, dorsal valve in posterolateral view; B, dorsal valve in apical view. C–E, FG 544/Ge/mic/brach/10 F (1); C, detail of ventral valve in apical view; D, detail of larval shell; E, detail of larval shell. F–G, FG 544/Ge/mic/brach/10 F (2); F, dorsal valve in posterolateral view; G, detail of larval shell. H–I, FG 544/Ge/mic/brach/18 G (2); H, dorsal valve interior; I, detail of dorsal valve interior. J–K, FG 544/Ge/mic/brach/10 I; J, detail of larval shell of the ventral valve; K, detail of larval shell of the ventral valve. L–M, FG 544/Ge/mic/brach/10 F (3); L, larval shell of the dorsal valve; M, detail of larval shell. ridge. dorsal valve and bluntly conical ventral valve, rather thick shelled, with weakly unisulcate Material. Thirty valves and many fragments, anterior commissure. Dorsal valve subcircular, Genestosa section, samples Ge 10 I, Ge10 F, Ge 85% as long as wide, widest at midlength, with 18 F, Ge18 G, Barrios facies, upper member of less rounded posterior and anterior margins the Láncara Formation, Middle Cambrian. than lateral ones. Valve moderately convex transversely, with slightly depressed median Diagnosis. As for genus. sector. Convexity prominent near posterior margin and evenly decreasing anteriorly. Dorsal Description. Shell small, ventribiconvex, about larval shell distinct, with a pair of high, elongate 1.1 mm wide in adult specimens with convex tubercles. Larval shell transversely oval, 220 µm 114 AAP Memoir 33 (2007) wide in measured specimens. Periphery of larval 8, Ge 10 A, Ge 10 E, Ge 10 F, Ge 10 D, Ge 10 H, shell flat. Larval shell covered by circular pits, 1-2 Ge 10 I, Ge 11, Ge 15, Ge 16 C, Ge 16 F, Ge 17 µm in diameter (Fig. 8D). Dorsal pseudointerarea G, Ge 18 A, Ge 18 F, Los Barrios de Luna section, orthocline, with broadly triangular, weakly sample BL i, Porma section, samples PI 21, PI 25, concave median groove. Sides of median groove PI 26, PI 28, PI B 1, Rodiezmo section, samples subtend an angle of 130-140°. Anterior edge of Ro 13, Ro 14, Ro 15, Vegaservera section, sample median groove weakly arched, supported by base Ve 2, Piedras Bermejas section, sample Pe B 1, of median ridge. Propareas very small. Visceral Barrios facies, upper member of the Láncara area defined by a broad, posteriorly horizontal and Formation. anteriorly sloping brim. Median ridge with large median buttress extended into low, anteriorly Description. Shell inequivalved, strongly ventri- swollen median ridge, which disappears at two- biconvex, thin-shelled and 5.2 mm wide in the thirds of valve length. Short and low diverging largest observed specimen. Anterior commissure ridges extend from the base of median buttress rectimarginate, cardinal extremities obtuse. near centre of valve, posterolaterally bordering Dorsal valve weakly arched transversely and small anterocentral scars. Cardinal scars large, poorly convex in a lateral profile. Pseudointerarea elongate-oval, about 30% as long and 30% as low, marked by a distinct edge from rest of wide as the valve, with convex surface. Visceral surface. Notothyrium broadly triangular, open. area posterior with remarkably coarse and deeply Edges of notothyrium collar-like, thickened, but impressed epithelian cell moulds. a homeochilidium has not been observed. Dorsal Ventral valve shell asymmetrically conical, larval shell depressed with four distinct lobes, with with convex anterior slope (Fig. 5E-F). Pedicle posterior edge extending over notothyrium. opening directed posteriorly, enclosed within Ventral valve transversely suboval to larval shell. Ventral pseudointerarea steeply semicircular, 65-70% as long as wide, strongly procline, high, with intertrough. Ventral convex in apical part, with maximum width interior with high, knob-like, anteriorly steeply posterior to mid-length. Hinge line equal to 60% of sloping apical process bordered by moderately shell width. Adult valve triangular in anterior view, converging, proximal vascula lateralia. Internal with straight flanks; young shells strongly convex pedicle opening circular, with thickened walls of in both profiles, with tumid beak. Convexity pedicle tube. Small and deep apical pits situated of valve decreases anteriorly. Anterior part of laterally to pedicle opening (Fig. 5E-F). Cardinal adult valve almost flat. Ventral pseudointerarea muscle scars large, with raised surface. The shell sharply defined laterally, steeply apsacline, with is ornamented by less regular concentric fila. widely triangular delthyrium largely covered by thin, highly arched homeodeltidium. Surface of Class PATERINATA Williams, Carlson, Brunton, pseudointerarea covered by distinct growth lines. Holmer & Popov, 1996 Ventral larval shell almost circular, remarkably Order PATERINIDA Rowell, 1965 variable in size (from 0.5 mm to almost 1 mm), Superfamily PATERINOIDEA Schuchert, 1893 with distinct boundaries. Larval shell with axial Family PATERINIDAE Schuchert, 1893 lobe extended over apical part of homeodeltidium. Two pairs of lateral lobes weakly defined, but Micromitra Meek, 1873 shallow axial groove between them is distinct. Ornament of postlarval shell is a combination Type species. Iphidea? sculptilis Meek, 1873, of radial costellae and concentric fila. Costellae Middle Cambrian, Montana, USA. appear immediately at the earliest growth line of postlarval shell, with new ones originating by Micromitra cf. sculptilis (Meek, 1873) (Fig. bifurcation of the primary costellae. However, 9A-M) some costellae disappear with growth, leaving broad interspaces. Concentric filose ornament Material. Two ventral valves in limestone and is more prominent on interspaces than the crests hundreds of shell fragments and juvenile shells of costellae; this results in a net-like ornament from acid residue, Genestosa section, samples Ge in juvenile shells, but as concentric ornament Fig. 9. A-M, Micromitra cf. sculptilis (Meek, 1873). A–C, FG 544/PI/mac/brach/B 1; A, ventral valve in apical view; B, ventral valve in anterolateral view; C, ventral valve in posteroventral view. D–G, FG 544/Ge/mic/ brach/10 F (4); D, ventral valve in apical view; E, ventral valve in lateral view; F, ventral valve in anterior view; G, detail of pseudointerea. H, FG 544/Ge/mic/brach/10 F (5); detail of ornament of the ventral valve. I, FG 544/ Ge/mic/brach/18 A (3); ventral valve in oblique view. J, FG 544/Ge/mic/brach/18 F (17); dorsal valve larval shell. K, FG 544/Ge/mic/brach/10 F (4); ventral valve interior. L, FG 544/BL/mic/brach/i; pseudointerarea of dorsal valve. M, FG 544/Ge/mic/brach/18 A (4); fragment of ventral valve showing (continued opposite) AAP Memoir 33 (2007) 115

different juvenile and adult ornament. N–S, Yorkia zafrensis Gil-Cid & Mélou, 1986. N–O, FG 544/LL/ mac/brach/B 8; N, ventral valve in apical view; O, detail of the apex. P. FG 544/LL/mac/brach/B 4; ventral valve in apical view. Q–R, FG 544/LL/mac/brach/B 1; Q, ventral valve in lateral view, internal mould shows pedicle tube; R, ventral valve in ventral view. S, FG 544/Ra/mac/brach/Ra; dorsal valve, internal mould shows pseudointerea. T–W, Nisusia vaticina (de Verneuil & Barrande in de Prado, 1860); T, FG 544/Ro/mac/brach/B 1; ventral valve in apical view. U–V, FG 544/LL/mac/brach/B 23; U, dorsal valve in apical view; V, dorsal valve in anterior view. W, FG 544/LL/mac/brach/B 9; ventral valve in posterior view. X–Y, Trematobolus simplex (Vogel, 1962). X. FG 544/Tr/mac/brach/B 4; ventral valve in apical view. Y. FG 544/Tr/mac/brach/B 1; ventral valve in apical view. 116 AAP Memoir 33 (2007) becomes more prominent with growth, the adult Canada. shells have dominant, finely lamellose, concentric ornament. Trematobolus simplex (Vogel, 1962) (Fig. The interior of the ventral valve bears a weak 9X-Y) radial striation, muscle scars have not been observed. Two vertical ridges bordering a laterally 1962 Trematobolus sp.; Vogel, pl. 1, figs 2-4. concave chamber below the homeodeltidium are 1962 Lamellodonta simplex n. g. n. sp.; Vogel, p. distinct on interior of posterior shell wall. 216, pl. 1, figs 1, 5-9, pl. 2, figs 1-4, 7-9, pl. 3, figs. 1-2, 4-5, pl. 4, fig. 2. Remarks. Paterinids are commonly documented, 1969 Lamellodonta simplex Vogel, 1962; Newell, but there are few well defined species and most N 400, D 8.4. occurrences are referred to the type species 1975 Lamellodonta simplex Vogel, 1962; Pojeta, Micromitra sculptilis (Meek, 1873), to M. pl. 1, fig. 5-7, pl. 4, fig. 7. modesta (Lochman, 1940) or they are left under 1978 Trematobolus simplex (Vogel, 1962); open nomenclature (e.g., Bell 1944; Lochman & Havlíček & Kříž 1978, p. 974, pl. 1, figs 1- Hu 1960; Henderson & MacKinnon 1981; Zell & 16. Rowell 1988; Holmer et al. 2001). Our specimens 1986 Trematobolus simplex (Vogel, 1962); Mergl are very similar to the type species, with an & Liñán, p. 170, pl. 2, fig. 1-5. apsacline ventral pseudointerarea, identical shell 1995 Trematobolus simplex (Vogel, 1962); Geyer outline, convexity and ornament, although the type & Mergl, p. 208. specimen of M. sculptilis (Meek, 1873) differs in 2001 Trematobolus simplex (Vogel, 1962); Liñán its distinctly coarser radial ornament. Because Bell & Mergl, pp. 328-329, figs 7, 8a-i. (1941) noted a great variability of the ornament with shell age, we assign our specimens to M. Material. Numerous ventral valves, Rodiezmo cf. sculptilis. Several other species of the genus section, sample Ro 2 e B 5, Piedras Bermejas have been described from the Middle Cambrian section, samples Pe B 2, Pe B 3, Pe B 4, Pe B 6, of Europe. Cobbold (1921) noted Micromitra and Truebano section, samples Tr B 1, Tr B 2, Tr sp. from the Middle Cambrian of England and B 3, Tr B 4, Beleño facies, upper member of the compared it with the Scandinavian M. ornatella Láncara Formation. (Linnarsson, 1876). Both species are poorly illustrated and their affinity is difficult to assess. Remarks. Our specimens are indistinguishable Spanish specimens described as Micromitra sp. from the shells described from the early Middle (Liñán & Mergl 2001) cannot be referred to M. Cambrian (Valdemiedes Formation) from the cf. sculptilis because they have a less prominent Iberian Chains (Vogel 1962; Liñán & Mergl radial ornamentation; they also come from the 2001). They have a very narrow, long and almost early Middle Cambrian (Mansilla and Murero parallel pedicle track, coarse growth lamellae, Formations) of the Iberian Chains. The Australian and a weakly developed pair of radial plications taxon M. nerranubawu Kruse, 1990 differs in bordering a depressed median sector are present its less transverse outline, a depressed ventral in the specimens from the upper member of the pseudointerarea and a very large homeodeltidium. Láncara Formation. Micromitra semicircularis Imanaliev & Pelman, 1988 from Central Asia (Holmer et al. 2001) Class KUTORGINATA Williams, Carlson, differs from our specimens in having a more Brunton, Holmer & Popov, 1996 prominent concentric ornament and an open Order KUTORGINIDA Kuhn, 1949 delthyrium with vestigial homeodeltidium. Superfamily KUTORGINOIDEA Schuchert, 1893 Class OBOLELLATA Williams, Carlson, Family YORKIIDAE Rowell, 1962 Brunton, Holmer & Popov, 1996 Order OBOLELLIDA Rowell, 1965 Yorkia Rowell, 1962 Superfamily OBOLLELOIDEA Walcott & Schuchert in Walcott, 1908 Type species. Yorkia wanneri Walcott, 1897, Family TREMATOBOLIDAE Popov & Holmer, Lower Cambrian, Pennsylvania, USA. 2000 Yorkia zafrensis Gil-Cid & Mélou, 1986 (Fig. Trematobolus Matthew, 1893 9N-S)

Type species. Trematobolus insignis Matthew, ?1860 Brachiopode, nouv. gen.; de Verneuil & 1893, Lower Cambrian, New Brunswick, Barrande in de Prado, p. 536, pl. 8, figs 5, AAP Memoir 33 (2007) 117

5a-e. solely on the illustrations of de Verneuil & ?1896 Acrothele; Pompeckj, p. 603. Barrande (in de Prado 1860) is probably lost, as ?1908 Botsfordia? barrandei sp. n.; Walcott, figs stated by Walcott (1912), and because we have 77-78. no topotypic material, it is impossible to elucidate ?1912 Botsfordia? barrandei; Walcott, pp. 602- its taxonomic position. However, a calcareous 603, pl. 57, figs 7, 7a-b. shell, noted already by de Verneuil & Barrande ?1935 Siphonotreta barrandei Walcott (E) Samp.; (in de Prado 1860, p. 536) has an apical foramen Sampelayo, p. 483, pl. 9. and an apsacline interarea indicating affinity to ?1935 Obolus barrandei Walcott (E) Samp.; kutorginides, probably Yorkia Walcott, 1897. Sampelayo, p. 487, pls. 9-10. Yorkia is known from the Lower Cambrian ?1935 Obolus leonensis Walcott (E) Samp.; of North America (Pennsylvania and eastern Sampelayo, p. 487, pl. 11. Canada) (Walcott 1897, 1912), the lower Middle 1986 Yorkia zafrensis n.sp.; Gil-Cid & Mélou, p. Cambrian of Spain (Sierra Morena) (Gil Cid 198, pl. 1, figs 1-5, text-figs 4-5. & Mélou 1986), from the Middle Cambrian of Australia (New South Wales) (Brock 1998), and Material. Four ventral valves, one dorsal valve, probably also from New Zealand (MacKinnon Láncara de Luna section, samples LL B 1, LL B 1983; Brock 1998). Yorkia wanneri Walcott, 1897 4, LL B 8, Barrios facies, upper member of the has a more transverse shell and a less extended Láncara Formation. ventral beak than our specimens. Gil Cid & Mélou (1986) described Y. zafrensis from the Description. Shell subequally biconvex, thick- lower Middle Cambrian near Bajadoz, SW Spain. walled, with rectimarginate commissure, 14 mm Although our specimens are more transverse long. and less triangular in outline, we refer them to Dorsal valve subpentagonal, as long as Y. zafrensis. The relationship of Y. zafrensis to wide, gently convex in transverse profile and specimens figured by de Verneuil & Barrande more convex anteriorly than posteriorly. Dorsal (in de Prado 1860) and by Sampelayo (1935) is interarea low, orthocline, occupying less than half outside the scope of our paper due to the lack of of shell width. Notothyrium broadly triangular, topotypic material. apically bordered by short and poorly convex chilidium. The interior with a thickened posterior Family NISUSIIDAE Walcott & Schuchert in platform, but muscle scars and pallial markings Walcott, 1908 are obscure. Ventral valve evenly convex, subtrigonal to Nisusia Walcott, 1905 elongate oval, 110% as long as wide, gently convex, with rather thick shell, especially in Type species. Orthisina festinata Billings, 1861, posterior part. Maximum width in anterior third. Lower Cambrian, Vermont, USA. Ventral apex slightly tumid. Beak angular, with apical angle 100°. Ventral interarea low, apsacline, Nisusia vaticina (de Verneuil & Barrande in de with narrowly triangular delthyrium entirely Prado, 1860) (Fig. 9T-W) covered by a weakly convex pseudodeltidium. External pedicle foramen is circular, 0.2-0.3 mm 1860 Orthisina vaticina s. n.; de Verneuil & in diameter, directed posteriorly, and located at the Barrande in de Prado, p. 533, pl. 8, figs 8, top of the apex. Foramen internally continues to a 8a-d. long, rapidly expanding tube opened at the bottom 1860 Orthisina pellico s. n.; de Verneuil & of a thickened platform. Pallial markings and Barrande in de Prado, p. 535, pl. 8, figs 7, muscle scars have not been observed indicating 7a-b. their weak impressions on valve interior. Shell 1912 Nisusia? vaticina (de Verneuil & Barrande); ornament of smooth growth bands, separated by Walcott, p. 730, pl. 97, figs 3, 3a-b. weak growth lamellae. 1912 Nisusia (Jamesella) pellico (de Verneuil & Barrande); Walcott, p. 735, pl. 97, figs 2, Remarks. Two specimens which probably belong 2a-b. to Yorkia zafrensis were described and illustrated 1935 Nisusia vaticina (de Verneuil & Barrande); without any formal name by de Verneuil & Sampelayo, p. 493, pl. 13, figs 3-5, pl. 14. Barrande (in de Prado 1860). Walcott (1908, 1935 Nisusia pellicoi (de Verneuil & Barrande); 1912) referred them to Botsfordia; Sampelayo Sampelayo, p. 494, pl. 14. (1935) compared this species with Siphonotreta and Obolus. The type material of Botsfordia Material. Fourteen, mostly poorly preserved barrandei Walcott, 1908, which was erected (deformed, broken) ventral and five dorsal valves, 118 AAP Memoir 33 (2007)

Rodiezmo section, samples Ro B 1, Ro B 2, Ro B most similar to Kostjubella from the early Middle 3, and Láncara de Luna section, samples LL B 5, Cambrian of Kazakhstan (Popov et al. 1996). LL B 6, LL B 7, LL B 9, LL B 12, LL B 13, LL In the Middle Cambrian, the acrotretoids rapidly B 15, LL B 16, LL B 17, LL B 18, LL B 20, LL diversified as shown by the presence of twenty B 21, LL B 23, LL B 24, LL B 25, Barrios facies, genera in subequatorial regions in the late Middle upper member of the Láncara Formation. Cambrian (Ushatinskaya 1996). None of the most widespread genera (Anabolotreta, Dactylotreta, Description. Shell ventribiconvex, transversely Neotreta, Opisthotreta, Prototreta, Rhondellina, subrectangular, with gently unisulcate Stilpnotreta, Treptotreta) or the North African commissure, thick shelled, and 25 mm wide in genera Vandalotreta and Tingitanella (Mergl the largest specimen. 1988; Streng 1999) have been documented in Dorsal valve weakly convex, with shallow and the early Middle Cambrian of the Cantabrian broad sulcus, widest at hinge line with almost Mountains. The acrotretid diversity remained low rectangular cardinal extremities. Dorsal interarea in the upper member of the Láncara Formation, low and anacline. with one or two species in each sample. Ventral valve strongly convex in transverse The obolellid Trematobolus has a cosmopolitan profile, with weakly depressed cardinal extremities distribution. It is known, besides from more and prominent apex. Lateral profile straight to distant areas, from Newfoundland and eastern gently concave near apex, becoming convex from North America (Matthew 1893; Walcott 1912), posterior one-third. Ventral interarea apsacline, Morocco (Geyer & Mergl 1995), Spain (Vogel straight, with broad delthyrium, that is apically 1962) and Poland (Jendryka-Fuglewicz 2004). closed by thick, highly convex pseudodeltidium. This genus dominates in carbonate or mixed Sides of interarea form prominent acute edges siliciclastic-carbonate sequences near the Lower- above the shell surface. Ventral interior with Middle Cambrian boundary. In the upper member broadly diverging, thickened lateral margins of of the Láncara Formation it is abundant in the grey pseudodeltidium. Ornament of rounded uniform to roan, glauconitic limestone of the Beleño facies. radial costellae, 0.2-0.3 mm wide, separated by The more reddish limestone (Barrios facies) of rounded interspaces of the same size. Ten to the upper member of the Láncara Formation twelve costellae extend from the apex, with new commonly yields the nisusiid Nisusia vaticina costellae originating by implantation. Large shells associated with the kutorginid Yorkia zafrensis. with up to 40-50 costellae. Raised hollow spines While Nisusia is a widespread genus, Yorkia is extend from the crest of costellae and at the edges less common, found in late Lower Cambrian strata of concentric lamellae. Ventral valve densely of Iberia, eastern North America, the Altai-Sayan covered by rows of spines on crests of costellae, region (Aksarina & Pelman 1978) and the early while spines are less prominent and less numerous Middle Cambrian of Australia (Brock 1998). on dorsal valve. Concentric ornament of weak The low abundance of small lingulates in growth lamellae, some imbricating anteriorly. the upper member of the Láncara Formation is consistent with their suggested infaunal or Remarks. This species has been referred to Nisusia semi-infaunal mode of life. Carbonate mud with by Walcott (1912). The specimens described as abundant skeletal material was unstable and thus Orthisina pellico de Verneuil & Barrande in de less appropriate for the burrowing habit of small Prado, 1860, are only juvenile individuals of N. lingulates. Pedunculate epibenthic brachiopods vaticina, as can be judged from illustrations in de attached to skeletal debris (nisusiids, kutorginids, Prado (1860) and our material. Acrothele, Trematobolus, Micromitra) or algal mats (acrotretids) found favourable substrate CONCLUSIONS on the bottom. The relative high diversity, with Unlike the cosmopolitan genera Acrothele, the genera Trematobolus, Nisusia and Yorkia, Micromitra, Trematobolus and Nisusia (cf. demonstrates the affinity of the brachiopod Brock 1998), the acrotretid brachiopods of the association of the Láncara Formation with faunas upper member of the Láncara Formation have a of the low latitude Siberian platform (Aksarina & restricted distribution. Luhotreta is known from Pelman 1978), New South Wales (Brock 1998) the early Middle Cambrian of Sardinia (Mergl & and some Avalonian terranes (Newfoundland, Elicki 2004) from beds of the same age (Campo New Brunswick) (Walcott 1912). Pisano Formation) and also from the Middle Cambrian Jince Formation of Central Bohemia ACKNOWLEDGEMENTS (Mergl & Šlehoferová 1990). The new genera For the SEM work we are very grateful to J. Iberotreta and Genetreta are so far unknown Nebesářová, A. Polák (Czech Academy of outside the Cantabrian Mountains. The latter is Science, České Budějovice, Czech Republic), AAP Memoir 33 (2007) 119 and to A. Obst (Institute of Geology, Freiberg Paleontology 72, 604-619. University of Mining and Technology, Germany). CLAUSEN, S. & ÁLVARO, J.J., 2006. Skeletonized For rapid and uncomplicated help during the microfossils from the Lower-Middle Cambrian coating of some SEM samples, the authors are transition of the Cantabrian Mountains, northern also thankful to B. Ullrich (Institute of Ceramics, Spain. Acta Palaeontologica Polonica 51, 223- Glass and Construction Materials, Freiberg 238. University of Mining and Technology, Germany). COBBOLD, E.S., 1921. The Cambrian horizons of The authors are indebted to the reviewers G.A. Comley (Shropshire) and their Brachiopoda, Brock (Macquarie University, Sydney, Australia), Pteropoda, Gasteropoda, etc. Quarterly Journal of L.E. Popov (National Museum of Wales, Cardiff, the Geological Society, London 304, 325-386. United Kingdom), and M. Streng (Uppsala CONWAY MORRIS, S. & BENGTSON, S., 1994. Cambrian University, Uppsala, Sweden) for constructive predators: possible evidence from boreholes. discussions, criticism and linguistic help. This Journal of Paleontology 68, 1-23. work is part of the research project EL 144/12 DEBRENNE, F. & ZAMARREÑO, I., 1970. Sur le découverte “Microfauna of the Early to Middle Cambrian d’Archéocyathes dans le Cambrien du NW de Láncara Formation (Cantabrian Mountains, NW- l’Espagne. Breviore Geologica Asturia 14, 1-11. Spain): micropalaeontology, palaeobiogeography, DE PRADO, C., 1860. Sur l’existence de la faune and process dynamics at the Early-Middle primordiale dans la chaîne cantabrique. Bulletin Cambrian transition of western Gondwana” de la Société Géologique de France, 2d serie 17, supported by the German Research Foundation. 516-542. The taxonomic part was partially supported by FOMBELLA, M.A., 1978. 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