Introduction
The first faunal inventory and taxonomic description of Devonian brachiopoda from the Paraná Basin (Brazil) was by Clarke (Reference Clarke1913). It included species classified at present within the order Orthotetida Waagen, Reference Waagen1884, with the occurrence of Schuchertella agassizi (Rathbun, Reference Rathbun1874), Schuchertella sulivani (Morris and Sharpe, Reference Morris and Sharpe1846), and Schuchertella sancticrucis Clarke, Reference Clarke1913. Schuchertella agassizi, the most abundant species, was identified based on ornamentation pattern similarities with specimens from the Middle Devonian Ererê Formation (Amazonas Basin, Brazil). Schuchertella sulivani was originally described from the Falkland Islands, Fox Bay Formation (Pragian-Emsian, Stone, Reference Stone2016) by Morris and Sharpe (Reference Morris and Sharpe1846) and, later, by Sharpe (Reference Sharpe1856) for the Bokkeveld Group (Emsian-Givetian, Penn-Clarke, Reference Penn-Clarke2019) in South Africa, based on growth patterns. Schuchertella sancticrucis species was named by Clarke (Reference Clarke1913) for the Santa Cruz shales, São Domingos Member (now the São Domingos Formation), Givetian (Melo, Reference Melo, McMillan, Embry and Glass1988; Grahn et al., Reference Grahn, Mauller, Bergamaschi and Bosetti2013), Paraná Basin, Brazil.
Generally orthotetide brachiopods include taxa considered broadly, a taxonomic viewpoint subsequently shown to be incorrect; e.g., “Schuchertella,” (Isaacson, Reference Isaacson1977). Schuchert (Reference Schuchert, Schuchert and LeVene1929) recognized that specimens then classified within the subfamily Orthotetinae Waagen, Reference Waagen1884 consisted of strophomenide, orthide and orthotetide fragmentary samples and considered of questionable validity.
Cooper and Grant (Reference Cooper and Grant1974) broadly revised the suborders Strophomenidina Öpik, 1934 and Orthotetidina Waagen, Reference Waagen1884. They reassigned the impunctate families Davidsoniidae King, 1850 (currently atrypides) and Fardeniidae Williams, 1965 (currently a junior synonym of Chilidiopsidae Boucot, Reference Boucot1959a) to the suborder Strophomenidina. Suborder Orthotetidina, (the pseudopunctate forms), characteristic of the post Devonian Paleozoic, were returned to the superfamily Orthotetacea Waagen, Reference Waagen1884.
“Schuchertella” misidentifications
Schuchertella was first described by Girty (Reference Girty1904), based on the type species being Streptorhynchus lens White, 1862. This included orthotetide forms of Streptorhynchus, previously assigned to Orthotetes Fisher de Waldheim, 1830, which possessed neither a median septum nor dental plates (Weller, Reference Weller1914; Easton, Reference Easton1962; Stigall Rode, Reference Stigall Rode2005).
A strong median septum in ventral valve led Fisher de Waldheim in 1850 to classify specimens as Orthotetes; however, Hall and Clarke (Reference Hall and Clarke1892) argued that these samples should probably belong to Derbyia. After a careful study of Fisher de Waldheim's figured specimens, Girty (Reference Girty1904), based on characteristics shared with the type species, agreed with their type structure as belonging to Derbyia, suggesting a synonymy between both genera. As an attempt to solve the problems related to the absence of a generic name for specimens previously assigned as Orthotetes, Girty (Reference Girty1904) erected the genus Schuchertella.
Streptorhynchus agassizi Rathbun, Reference Rathbun1874 was described from the Middle Devonian Ererê Formation, highlighting the presence of dental plates and a thin, bilobed cardinal process (Rathbun, Reference Rathbun1874). Even after Girty's description some problems remained with the new genus's description and Streptorhynchus agassizi. Nevertheless, the species was relocated to Girty's genus as Schuchertella agassizi in all three Devonian units (Ponta Grossa, Maecuru and Ererê formations), in which its occurrence was known (Rathbun, Reference Rathbun1874, Reference Rathbun1879; Clarke, Reference Clarke1913; Rezende et al., Reference Rezende, Ponciano and Brett2019a).
The common practice of ascribing Orthotetida specimens to Schuchertella led different authors to propose new taxa to include morphologies that did not fit its diagnosis. Dunbar and Condra (Reference Dunbar and Condra1932) described dental plates in specimens classified as Schuchertella, thereby defending its relocation to Schellwienella Thomas, Reference Thomas1910.
Schuchertella was considered an impunctate genus (Williams, 1965 apud Stigall Rode, Reference Stigall Rode2005). However, extropunctation was later recognized in specimens of Streptorhynchus lens (G. A. Cooper in a written commun. to J. G. Johnson, dated Dec. 28, 1965; see Boucot and Johnson, Reference Boucot and Johnson1968). Nevertheless, even recognizing this feature, Boucot and Johnson (Reference Boucot and Johnson1968) and Thomas (Reference Thomas1971) chose to keep Schuchertella's diagnosis as impunctate, but adding quotation marks until more an appropriate genus might be found. More recently, Williams and Brunton in Williams et al. (Reference Williams, Brunton, Williams, Brunton, Carlson, Boucot, Carter, Cocks, Cohen, Copper, Curry, Cusack, Dagys, Emig, Gawthorp, Gourvennec, Grant, Harper, Holmer, Hong-Fei, James, Yu-Gan, Johnson, Laurie, Stanislav, Lee, Mackay, MacKinnon, Manceñido, Mergl, Owen, Peck, Popov, Racheboueuf, Rhodes, Richardson, Jia-Yu, Rubel, Savage, Smirnova, Dong-Li, Walton, Wardlaw and Wright2000) followed by Stigall Rode (Reference Stigall Rode2005) considered Schuchertella an extropunctate genus.
Considering all the problems related to these classifications, new genera were proposed for morphologies that did not fit within Schuchertella (sensu stricto) definition. Consideration was given not only shell structure but also details from the cardinalia, and ornamentation. Following these criteria, Gratsianova (Reference Gratsianova1974) described the genus Eoschuchertella, while Cooper and Dutro (Reference Cooper and Dutro1982) described the genus Floweria, from the Late Devonian of New Mexico, USA. Both are impunctate, and they are distinguished by their cardinal process, in which Floweria possesses a more recurved cardinalia rather than that in Eoschuchertella.
For specimens from Brazilian sedimentary basins, Rathbun (Reference Rathbun1879) presented variations within Schuchertella agassizi from the Ererê and Maecuru formations (Rathbun, Reference Rathbun1874, Reference Rathbun1879). This species was recognized by Clarke (Reference Clarke1913) from the Ponta Grossa Formation due to similarities in ornamentation, but Clarke disregarded the problems described by Rathbun. Decades later, Melo (Reference Melo1985) suggested that these specimens may not belong to Schuchertella but did not offer any other classification.
Within South America, the species “Schuchertella” agassizi has been described from Brazil (Maecuru and Ererê formations, Amazonas Basin; Ponta Grossa Formation, Paraná Basin), South Africa (Bokkeveld Group), Argentina (Jachal – Talacasto, Porongal and Rio Pescado formations), Bolivia (Icla Formation), Paraguay (Santa Rosa Formation) and Uruguay (Cordobés Formation), from the Early to Middle Devonian (Emsian to Eifelian) (Melo, Reference Melo1985).
Few studies regarding taxonomy related to Devonian orthotetide brachiopods have been published recently, leaving many gaps of information, especially about late Paleozoic species, focusing mostly on North American specimens (Melo, Reference Melo1985, Rezende et al., Reference Rezende, Ponciano and Brett2019a).
We propose a systematic re-evaluation of the Malvinokaffric Realm (now called Malvinoxhosan Realm by Penn-Clarke and Harper, Reference Penn-Clarke and Harper2020) species “Schuchertella” agassizi through the descriptions of specimens from the Ponta Grossa and São Domingos formations, and the identification of a new species for the Lower Devonian Paraná Basin, just as for Lower and Middle Devonian Icla, Belén, Gamoneda and Huamampampa formations, Bolivia.
Geological setting
The Paraná Basin is a wide sedimentary area that encompasses parts of Brazil, eastern Paraguay, northeastern Argentina and northern Uruguay encompassing an area of approximately 1.5 million km2 (Milani et al., Reference Milani, Melo, Souza, Fernandes and França2007).
In Brazil (Fig. 1) it is distributed over the States of Mato Grosso, Mato Grosso do Sul, Goiás, São Paulo, Paraná, Santa Catarina and Rio Grande do Sul, and it is classified as an intracratonic basin. Six supersequences are recognized in the basin, with the “Paraná” corresponding to the Siluro-Devonian time span. Within this supersequence three formations are described: Furnas, Ponta Grossa and São Domingos (Milani et al., Reference Milani, Melo, Souza, Fernandes and França2007; Grahn et al., Reference Grahn, Mauller, Bergamaschi and Bosetti2013). The samples discussed here belong to the Apucarana Sub-Basin, Ponta Grossa (former Jaguariaíva Member) and São Domingos (former Tibagi and São Domingos members) formations (Fig. 2; Table 1).
Figure 1. Modified from Grahn et al., Reference Grahn, Mauller, Bergamaschi and Bosetti2013. Map of the studied area. (1) Paraná Basin distribution in Brazil; (2) Apucarana Sub-Basin formations, Outcrops: 1 – Jaguariaíva-Arapoti Railroad; 2 – Fazanda Rivadávia; 3 – Ponta Grossa Municipality; 4 -First curve of the railroad track; 5 Tibagi Municipality; 6 – Fazenda Santa Cruz, Palmeira Municipality (?).
Figure 2. Stratigraphic nomenclature and correlations of key Devonian formations in the Paraná and Amazonas basins (Brazil). Modified from Bergamaschi (Reference Bergamaschi1999), Cunha et al. (Reference Cunha, Melo and Silva2007), Grahn et al. (Reference Grahn, Mauller, Bergamaschi and Bosetti2013), Schemm-Gregory and Henriques (Reference Schemm-Gregory and Henriques2013), and Horodyski et al. (Reference Horodyski, Brett, Sedorko, Bosetti, Scheffler, Ghilardi and Iannuzzi2018). Gray bars represent no geologic record; black bars represent absence of Orthotetide brachiopods.
Table 1. Stratigraphic description of Ponta Grossa and São Domingos formations.
Material and methods
Taxonomic description and material photography
Sixty one specimens were described and analyzed with a stereoscopic microscope, measured with a caliper, and all were compared with each other and with the original description of “Schuchertella” agassizi. The diagnostic characters of Schuchertella and other taxa from the order Orthotetida were also included in the analysis in order to define which diagnostic character characterizes each taxon and provide a taxonomic (species) re-evaluation.
All specimens consist of interior, exterior, composite molds and counter-molds of ventral and dorsal valves. Considering the available material in scientific collections, figured “UNIRIO” specimens were coated with magnesium oxide and “GP/1E” specimens were coated with ammonium chloride prior to photographing, in order to enhance the contrast between high and low surfaces in the preserved characters (Cerri, Reference Cerri2013; Zambito and Schemm-Gregory, Reference Zambito and Schemm-Gregory2013). (Note: “UNIRIO” = Universidade Federal do Estado do Rio de Janeiro; “GP/1E” = Universidade de São Paulo). The photographs were taken with a digital camera, Canon EOS50, and described according to the terms applied by Rathbun (Reference Rathbun1874, Reference Rathbun1879), Williams and Brunton in Williams et al. (Reference Williams, Brunton, Williams, Brunton, Carlson, Boucot, Carter, Cocks, Cohen, Copper, Curry, Cusack, Dagys, Emig, Gawthorp, Gourvennec, Grant, Harper, Holmer, Hong-Fei, James, Yu-Gan, Johnson, Laurie, Stanislav, Lee, Mackay, MacKinnon, Manceñido, Mergl, Owen, Peck, Popov, Racheboueuf, Rhodes, Richardson, Jia-Yu, Rubel, Savage, Smirnova, Dong-Li, Walton, Wardlaw and Wright2000), Stigall Rode (Reference Stigall Rode2005), and Bassett and Bryant (Reference Bassett and Bryant2006).
Repositories and institutional abbreviations
The studied material consists of specimens from the Ponta Grossa and São Domingos formations (Paraná Basin, Brazil; Fig. 2) included in the scientific collection “Fósseis Paleozoicos” at the Universidade Federal do Estado do Rio de Janeiro (UNIRIO), Laboratório de Estudo de Comunidades Paleozoicas (LECP). Others specimens are from the scientific collections from the Instituto de Geociências of the Universidade de São Paulo (IGeo – USP), and from the Museu de Ciências da Terra (MCTer/DGM). From Bolivia (Icla, Belén, Gamoneda and Huamampampa formations), the studied material consists of samples from the U.S. National Museum (USNM) analyzed and described by one of the authors (P. Isaacson), figured and described in Isaacson (Reference Isaacson1977, Reference Isaacson and Suárez-Soruco1993).
Systematic paleontology
Class Strophomenata Williams et al., Reference Williams, Brunton, Carlson, Holme and Popov1996
Order Orthotetida Waagen, Reference Waagen1884
Suborder Orthotetidina Waagen, Reference Waagen1884
Superfamily Orthotetoidea Waagen, Reference Waagen1884
Family Pulsiidae Cooper and Grant, Reference Cooper and Grant1974
Genus Schellwienella Thomas, Reference Thomas1910
Type species
Spirifera crenistria Phillips, 1836; lower Carboniferous (Pendleside Limestone Group, Viséan) of Bowland, Yorkshire, England.
Schellwienella clarkei new species
Figure 3–5
- Reference Sharpe1856
Strophomena baini Sharpe, p. 208, pl. 26, fig. 13.
- Reference Rathbun1874
Streptorhynchus agassizi Rathbun, p. 248, pl. 9, figs. 3, 4, 10, 16, 17, 23, 25, 26, 28-30.
- Reference Rathbun1879
Streptorhynchus agassizi Rathbun, p. 24. pl. 9, fig. 4 in Rathbun, Reference Rathbun1874.
- Reference Knod1908
Orthotetes chemungensis Knod [non Conrad], p. 541, pl. 26, figs, 13, 14, 14a; pl. 27, fig. 5.
- Reference Clarke1913
Schuchertella agassizi (Hartt) Clarke, p. 276, pl. 23, figs. 5-8, 10-13 [non 9].
- Reference Williams and Breger1916
Schuchertella woolworthana Williams and Breger [non Hall], p. 35.
- Reference Kozlowski1923
Shchuchertella agassizi (Hartt) Kozlowski, p. 85, pl. 9, fig. 30.
- Reference Reed1925
Schuchertella baini (Sharpe) Reed, p. 42.
- Reference Katzer1933
Orthotetes agassizi (Hartt and Rathbun) Katzer, p. 183, 189, 197, pl. 11, figs. 6a-c.
- Reference Méndez-Alzola1938
Schuchertella agassizi (Hartt) Méndez-Alzola, p. 22, pl. 6, fig. 1-3
- Reference Caster1939
Schellwienella agassizi (Hartt) Caster, p. 113–116.
- Reference Lange and Lange1954
Schellwienella agassizi (Hartt) Lange, p. 33, 42, 77, 81.
- Reference Carvalho1972
Streptohynchus agassizi (Hartt) Carvalho, p. 67, pl. 8, fig. 5–12.
- Reference Copper1977
Schellwienella agassizi (Hartt) Copper, p. 175-185.
- Reference Melo1985
“Schuchertella” agassizi (Hartt) Melo, appendix 1 and 2, p. 93-99.
Figure 3. Schellwienella clarkei n. sp. from Ponta Grossa and São Domingos formations, Paraná state, Brazil: (1) UNIRIO 0065 – BQ. Ventral interior mold, Lower Devonian, Ponta Grossa Formation. Scale = 10 mm; (2) UNIRIO 0051 – BQ. Ventral interior conter-mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (3) UNIRIO 0187 – BQ. Ventral interior mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (4) UNIRIO 0199 – BQ B. Ventral interior mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (5) Holotype UNIRIO 0505 – BQ A. Ventral interior conter-mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (6) Holotype UNIRIO 0505 – BQ B. Ventral interior mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (7) GP/1E 7790. Ventral interior mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (8) UNIRIO 0101- BQ A. Ventral composite mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (9) GP/1E 7790. Dorsal exterior mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (10) GP/1E 7919. Interior dorsal mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (11) UNIRIO 0186 – BQ. Interior dorsal mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (12) UNIRIO 0571 – BQ. Interior dorsal mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (13) GP/1E 7655. Interior dorsal mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (14) DGM 1804 – I. Interior ventral mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (15) DGM 1839 – I. Interior ventral mold, Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (16) DGM 1987 – I. Exterior dorsal mold, Lower/Middle Devonian. São Domingos Formation. Scale = 10 mm.
Holotype
UNIRIO 0505-BQ A and B (Mold and Counter-mold) illustrated in Figure 3.5–3.6
Diagnosis
Ventral valve with pseudopunctae in an apparently random pattern; short dental plates; triangular muscle field separated by a median septum that extends until approximately ½ the length of the valve. Costae increase by bifurcation and intercalation.
Occurrence
Ponta Grossa Formation (Pragian-Emsian); São Domingos Formation (Emsian-Frasnian) (Brazil); Icla, Belén, Gamoneda and Huamampampa formations (late Pragian-mid Eifelian) (Bolivia).
Type horizon
Ponta Grossa Formation
Type locality
Railroad section, railway branch of Jaguariaíva-Arapoti between km 2.2 and 6.6, Jaguariaíva Municipality (SIGEP 65). Geological and paleobiological site has typical Devonian Malvinoxhosan Realm fossils, microfossils, trace fossils and plant debris of great paleobiogeographic importance. Difined by SIGEP (Comissão Brasileira de Sítios Geológicos e Paleontológicos), a Brazilian commission responsible for identifing geological and paleobiological sites of exceptional scientific value.
Description
Shell with subcircular to circular outline. Moderate size, length varying from 4 to 27 mm and width varying from 5 to 38 mm. Biconvex to plano-convex. Hinge line straight, ventral beak small, erect and pointed, when compared to a more concave and broadened as is the one on the dorsal valve. Costellae by intercalation and bifurcation or exclusively by one or another, which are separated by a reduced interspace. Proportions of length to width about as 0.65 to 0.75. Pseudopunctate shell.
Ventral interior
Delthyrium completely closed by the pseudodeltidium (large, convex); triangular-shaped stout hinge teeth, wider in the base and narrowing towards the apex, supported by short and posteriorly divergent dental plates. The latter, in juvenile specimens can be less developed, with greater angle of divergence (120-110°), becoming smaller in ontogeny (100-70°). Wide triangular muscle field, reaching about one-third to half the length of the valve, with both adductor and diductor scars anteriorly striated with a sub-circular shape narrowing anteriorly, completely surrounding the flabellate adductor scars. These are well impressed lanceolate scars, separated by a low median septum that extends about half the length of the valve. Fimbriate micro-ornamentation next to the anterior commisure. Pseudopunctation, in random pattern.
Dorsal interior
Bilobed cardinal process with stout, triangular lobes and a median groove facing each lobe, delimited by a small chilidium. Notothyrium anteriorly open, in order to expose the attachment of cardinal process lobes. Dental sockets triangular in shape supported by short and weakly curved socket plates. Well impressed lanceolate adductor muscle scar, posteriorly striated. Median septum dividing adductor scar, that extends half the length of the valve. (Figs. 4 and 5)
Figure 4. Schellwienella clarkei n.sp. from Ponta Grossa Formation. (1) Ventral interior counter-mold (cast in modeling clay). UNIRIO 017-BQ. Scale = 10 mm.; (2) Ventral interior counter-mold (cast in modeling clay). UNIRIO 0065-BQ. Scale = 10 mm.
Figure 5. Schellwienella clarkei n.sp. from Ponta Grossa Formation. (1) Ventral interior counter-mold highlighting the presence of pseudopunctae in the surface. UNIRIO 0051-BQ B. Scale = 1 μm.; (2) Ventral interior mold highlighting the presence of pseudopunctae in the surface. UNIRIO 0505-BQ A. Scale = 1 mm.; (3) Ventral interior counter-mold highlighting the presence of pseudopunctae in the surface. UNIRIO 0505-BQ B. Scale = 1 mm.
Etymology
Species dedicated to John Mason Clarke, pioneer paleontologist with extensive studies of Devonian invertebrates from the Paraná Basin.
Materials
Sixty one specimens (molds, exclusively) collected in different outcrops in Brazil and Bolivia; see Table 2 for details.
Table 2. Sample numbers, stratigraphic position and outcrops.
Dimensions
Figure 6. Scatter diagram plotting length to width of Schellwienella clarkei from Paraná Basin, Brazil; Schellwienella clarkei from Bolivian formations; Schuchertella agassizi from Ererê Formation, Amazonas Basin, Brazil.
Table 3. Measurements (in mm) of the species Schellwienella clarkei and Schuchertella agassizi Rathbun. ML = Mean length; MW = Mean width; MdL = Median length; MdW = Median width; MnL = Minimum length; MnW = Minimum width; MxL = Maximum length; MxW = Maximum width; SDL = Standard deviation length; SDLW = Standard deviation width.
Remarks
This species was included in the genus Schuchertella by Clarke (Reference Clarke1913) on the basis of similarities between exterior molds, as are mostly preserved in Orthotetida genera from South America. This kind of preservation makes generic assignment problematic regarding this group (Williams and Brunton, Reference Williams and Brunton1993). The present authors include it in the genus Schellwienella on the basis of interior molds containing important diagnostic features such as shell's microstructure (pseudopunctation), cardinalia, and dental plates. The recognition of these features also helps to differentiate many “Schuchertella” agassizi records in Brazil by the erection of a new species for the Paraná Basin. The new species Schellwienella clarkei resembles Schuchertella agassizi in ornamentation, but differs in shell's microstructure and between the divergence angle of the dental plates. Regarding the species Schellwienella sulivani, the Brazilian specimens possess larger and heavier shells (varying from 27 to 35 mm in length to 40–55 mm in width), and more ovate adductor scars when compared to S. clarkei. Meanwhile, Schellwienella sancticrucis is the most different one, with rounded outline, coarser ornamentation and bigger muscle field when compared to S. clarkei.
Discussion
Taxonomic history: ornament, microstructure and cardinalia
Classification of specimens from the Ponta Grossa Formation as “Schuchertella” agassizi (Clarke, Reference Clarke1913) is based on ornamentation pattern, which develops from the beak to the anterior margin, with primary and secondary costae gradually originating through bifurcation. This feature is also present on the original description of the species from the Ererê Formation. However, it is not the most significant diagnostic character, and therefore Clarke's classification needs to be reconsidered.
Schuchertella was erected by Girty (Reference Girty1904), type species Streptorhynchus lens, for specimens that lacked a median septum and dental plates (Weller, Reference Weller1914; Easton, Reference Easton1962; Stigall Rode, Reference Stigall Rode2005). The recognition of extropunctation in Streptorhynchus lens, previously described as impunctate, resulted in a modification of Shuchertella's diagnosis, restricting it to extropunctate forms (Thomas, Reference Thomas1971; Stigall Rode, Reference Stigall Rode2005). The identification of shell structure is essential in Orthotetidina's taxonomic hierarchy. According to Williams and Brunton (Reference Williams and Brunton1993) the details of microstructure can be synapomorphies of certain groups. Also, the articulation apparatus and muscle field are considered just as essential to ensure a precise taxonomic identification. Three groups of microstructure are recognized, impunctate (e.g. Chilidiopsidae, Areostrophiidae), pseudopunctate (e.g Pulsiidae), extropunctate (e.g Schuchertellidae) (William and Brunton, Reference Williams and Brunton1993; Long and Brunton, Reference Long and Brunton2005).
Small dental plates supporting hinge teeth in Schuchertella specimens were discussed by Boucot (Reference Boucot1959b), who disagreed with this classification, mentioning that such plates are present in Schellwienella and not in Schuchertella. Details from the cardinalia were used by Cooper and Grant (Reference Cooper and Grant1974), Bassett and Bryant (Reference Bassett and Bryant2006) and Sun and Baliński (Reference Sun and Baliński2008) to justify the inclusion of Schuchertella and Schellwienella within Orthotetacea. They assigned two subfamilies, Pulsinae and Schuchertellinae to this superfamily. The Pulsinae would include Schuchertellidae specimens with dental plates (e.g. Pulsia and Schellwienella) and the Schuchertellinae would not have dental plates (e.g Schuchertella). Another important structure from the cardinalia to be considered when ascribing brachiopods to Schellwienella is the presence and size of a pseudodeltidium (Isaacson, Reference Isaacson1977, Reference Isaacson and Suárez-Soruco1993), in which specimens possess a large and convex pseudodeltidium (Halamski and Baliński, Reference Halamski and Baliński2009; Mottequin and Simon, Reference Mottequin and Simon2017).
The main reasons that warrant familial separation are details from shell microstructure, which according to Williams and Brunton (Reference Williams and Brunton1993) would have priority during taxonomic classification of Orthotetacea, along with structures from the articulation apparatus and presence or absence of dental plates (as discussed by Cooper and Grant, Reference Cooper and Grant1974; Bassett and Bryant, Reference Bassett and Bryant2006). The Pulsiidae are described as possessing pseudopunctae and dental plates variable in angle and length, and Schuchertellidae as possessing extropunctae and bearing hinge teeth unsupported by dental plates (Williams and Brunton, Reference Williams and Brunton1993; Williams and Brunton in Williams et al., Reference Williams, Brunton, Williams, Brunton, Carlson, Boucot, Carter, Cocks, Cohen, Copper, Curry, Cusack, Dagys, Emig, Gawthorp, Gourvennec, Grant, Harper, Holmer, Hong-Fei, James, Yu-Gan, Johnson, Laurie, Stanislav, Lee, Mackay, MacKinnon, Manceñido, Mergl, Owen, Peck, Popov, Racheboueuf, Rhodes, Richardson, Jia-Yu, Rubel, Savage, Smirnova, Dong-Li, Walton, Wardlaw and Wright2000; Long and Brunton, Reference Long and Brunton2005), therefore it is inappropriate to keep Pulsiinae as a subfamily within Schuchertellidae.
Shell microstructure
Pseudopunctation was already reported for Schellwienella by Boucot (Reference Boucot1959a) in juvenile specimens and was used by Brice et al. (Reference Brice, Nicollin and Mottequin2013) as a criterion of differentiation from Schuchertella.
Microstructure preservation is complex, which sometimes enables a precise identification within a taxonomic group. Studied molds’ preservation can provide equivocal information (presence or absence) of this structure (Cerri, Reference Cerri2013). However, differentiating pseudopunctae and extropunctae is a taphonomic-related issue (Williams and Brunton, Reference Williams and Brunton1993). Pseudopunctation consists of inwardly directed conical deflections, which may or may not possess calcite rods (taleolae). These can appear as tubercles on the valve interiors. Extropunctae occur as a depression on the interior of the valve. During fossilization, these features are often filled by fine sediment or diagenetic precipitates. When the extropunctae are filled, pseudopunctate microstructure can be misidentified. Here, microstructure is considered as pseudopunctate, since similar tubercles are found, along with its origin as discussed herein. In association with other diagnostic characters that fit Schellwienella, the diagenetic precipitation hypothesis is currently discarded.
The recognition of extropunctae in Schuchertella lens led Cooper and Dutro (Reference Cooper and Dutro1982) to create a new genus Floweria, which resembles Schuchertella in outline and ornamentation, but with a reduced interarea and impunctate fabric. This genus also resembles Eoschuchertella, also impunctate, but bearing differences in the cardinalia and the ornamentation pattern (Cooper and Dutro, Reference Cooper and Dutro1982; Mottequin, Reference Mottequin2008).
Taxa comparison
Schuchertella, Floweria, Eoschuchertella, Schellwienella are similar regarding its external morphology, which led Stigall Rode (Reference Stigall Rode2005) to give greater evolutionary importance to shell microstructure and to species chronostratigraphy, as presented in Table 4. Cooper and Grant (Reference Cooper and Grant1974) described a single species, Schuchertella subvexa which occurred from latest Devonian (Famennian) to Upper Permian. They did not consider the divergences between the generic description and the morphology observed in typical Devonian specimens. More recently, Schuchertella bassa by Grant (Reference Grant1995), also studied by Shen and Claphan (Reference Shen and Clapham2008), recognized the cemented life habit in this species. This is similar to what is observed in orthotetoids from the late Paleozoic (Brett and Walker, Reference Brett and Walker2002). Pedicle atrophy during the early stages of life led to an unattached stock and, consequently, an epibenthic (lying on the sea floor) mode of life, was found in genera such as Pulsia, Schellwienella and Orthotetes, in the lower Paleozoic (Williams, Reference Williams1953; Williams and Brunton, Reference Williams and Brunton1993). This questioned the viability of the genus's presence in for a wider stratigraphic distribution. For these reasons, it is not possible to attribute the Paraná specimens to any Schuchertella species, due to not only its chronostratigraphic distribution, but also the microstructure details and paleoecological characteristics.
Table 4. Comparative morpho-anatomic data of each Late Paleozoic Orthotetida genera. Pr = Profile, Int = Interarea, CP = Cardinal Process, DPl = Dental Plates, MS = Median Septum, MF = Muscle Field, SF = Shell's Fabric, Chronostrat = Chronostratigraphy, References.
Generic evolutionary relations
Even though Williams (Reference Williams1956) was not able to identify pseudopunctae in Silurian orthotetacid specimens, Boucot (Reference Boucot1959a), through written communication with Williams in 1957, highlighted its presence in juvenile specimens of Schellwienella. The ‘schuchertellid’ brachiopods lack dental plates, having their first known occurrence for the Lochkovian, possibly from a schellwienellid ancestor. The older Schellwienella-like species is known from England's upper Silurian (Boucot, Reference Boucot1959a). Girty (Reference Girty1904, Reference Girty1908) and Campbell (Reference Campbell1957) suggested that its origin was in the Silurian, becoming pseudopunctate in the Lower Devonian (Williams et al., Reference Williams1970), with greater development during the Late Devonian/Early Mississipian.
The ancestral relationships within Orthotetacea were also debated by Campbell (Reference Campbell1957), following the criteria also used by Girty (Reference Girty1908) and Dunbar and Condra (Reference Dunbar and Condra1932), without including the reduction and development of dental plates. Evolutionary relationships of shell microstructure could have been responsible for the outwardly directed extropunctae to be derived from the inwardly directed pseudopunctae, due to a change in its organic components (Williams and Brunton, Reference Williams and Brunton1993). Considering a recent taxonomic classification, the single extropunctate family is Schuchertellidae, which had its origin in the lower Paleozoic, followed by greater diversification during the Carboniferous and Permian.
Schellwienella clarkei n. sp. distribution
The occurrence of Schellwienella in the Paraná Basin had already been mentioned by Copper (Reference Copper1977) with no description of its diagnostic characters. The specimens found in the Ponta Grossa and São Domingos formations belong to Schellwienella, given the presence of pseudopunctae, dental plates supporting hinge teeth, a median septum in the ventral valve, and a triangular muscle field. Therefore, it is impractical to retain the name Schuchertella agassizi, a species from the Ererê Formation (Rathbun, Reference Rathbun1874), which has divergences between the descriptions, especially regarding the absence of a median septum and pseudopunctation. Hence, it is here described as a new species named Schellwienella clarkei n. sp.
Considering that the origin of the first ‘Schellwienellid’ occurrence is from the late Early Silurian (Boucot, Reference Boucot1959a), the occurrence of Schellwienella in southern Brazil supports the origin of pseudopunctate Schellwienella in Lower Devonian (Williams et al., Reference Williams1970). Based on samples described herein from the Ponta Grossa strata (Pragian-Emsian), it is possible to infer that the origin of pseudopunctate orthotetoids could be in the Southern Hemisphere (southwestern Gondwana).
A large number of specimens studied by Clarke (Reference Clarke1913) were assigned to the species Schuchertella agassizi, originally from the Amazonas Basin, based strictly on the similarity of exterior molds, which show both intercalation and bifurcation. The original description of the species by Rathbun (Reference Rathbun1874) indicates differences between the material from the Amazonas and Paraná Basin. According to Rathbun (Reference Rathbun1874) the ornamentation pattern occurs by intercalation, which is different than S. clarkei n. sp.
Besides the difference of exterior molds, features of the interior are diagnostic, such as the divergence between the angle of the dental plates in Schuchertella agassizi and Schellwienella clarkei n. sp., of 135 degrees in the former and of 70 to 110 degrees in the latter. Even considering that this angle in juvenile specimens becomes smaller in ontogeny, the greatest angle measured so far was of 120 degrees, maintaining the difference between Schuchertella agassizi and Schellwienella clarkei. Another internal feature that separates the Amazonian S. agassizi from the southern S. clarkei pertains to the kind of microstructure, which not only differentiates species, but also supports in generic differences between Schuchertella and Schellwienella. Even though Rathbun (Reference Rathbun1874) did not describe the texture of Amazonian specimens, some samples from the Ererê Formation have been seen by the first author, in which no punctation or pseudopunctation were observed. Meanwhile, the pseudopunctae occur in Paraná specimens, establishing the difference between both species. Another distinguishing feature seen in samples is regarding the absence of a dorsal septum in S. agassizi, (not specified in Rathbun, Reference Rathbun1874), however present in S. clarkei n. sp. specimens.
The species Schuchertella sulivani was identified by Clarke (Reference Clarke1913) from the Ponta Grossa Formation as the same as described by Morris and Sharpe (Reference Morris and Sharpe1846) from the Falkland Islands, Fox Bay Formation, Lower Devonian (Stone, Reference Stone2010; Reference Stone2016) and by Sharpe (Reference Sharpe1856) to its equivalent unit in the Bokkeveld Group, South Africa (Penn-Clarke, Reference Penn-Clarke2019). The species S. sulivani in both Fox Bay Formation and Bokkeveld Group are described by Morris and Sharpe (Reference Morris and Sharpe1846) and by Sharpe (Reference Sharpe1856) as identical and possessing ornamentation in a bifurcation pattern; however, that assigned by Clarke (Reference Clarke1913) possesses a pattern similar to “Schuchertella” agassizi, having bifurcation and intercalation. Nevertheless, it is not the purpose herein to discuss this matter, and we accept the species Schuchertella sulivani as occurring in all three Malvinoxhosan Realm regions.
The specimens assigned by Clarke (Reference Clarke1913) as Schuchertella sulivani (Fig. 7) were described as of larger and heavier shells than “Schuchertella” agassizi (Schellwienella clarkei n. sp. herein), but also possibly different ontogenetic stages. The species Schuchertella sulivani was relocated to Schellwienella by Caster (Reference Caster1939) and followed by Lange (Reference Lange and Lange1954). Even though no formal description was offered to justify this re-assignment; following works have retained this classification without question (Aldiss and Edwards, Reference Aldiss and Edwards1999; Stone, Reference Stone2010, Reference Stone2012, Reference Stone2016; Stone and Rushton, Reference Stone and Rushton2013). Since the exterior molds possess a similar ornamentation pattern in both Schellwienella sulivani (Ponta Grossa Formation) and Schellwienella clarkei n. sp., thereby presenting a possible intraspecific variation, the main differences consist mostly on the shape of the dorsal adductor scar, which assumes a lanceolate form in S. clarkei and an ovate form in S. sulivani. However, since there are few specimens of Schellwienella sulivani a conclusion can only be tentative at this time. More specimens need to be studied in order to enumerate the differences between the new species Schellwienella clarkei, Schellwienella sulivani from Ponta Grossa Formation and Schellwienella sulivani from other Malvinoxhosan Realm areas. Meanwhile, we accept both as different species, with its main difference regarding the interior dorsal mold.
Figure 7. Brazilian Devonian orthotetides coeval with Schellwienella clarkei sp.n. (1) DGM 272 – I. “Schuchertella” agassizi. Clarke (Reference Clarke1913). Plate 23, fig. 6, 8, 12, 13. Lower Devonian. Ponta Grossa Formation. Scale = 100 mm; (2) DGM 273 – I. “Schuchertella” agassizi. Clarke (Reference Clarke1913). Plate 23, fig. 5. Lower Devonian. Ponta Grossa Formation. Scale = 50 mm; (3) DGM 270 – I. “Schuchertella” agassizi. Clarke (Reference Clarke1913). Plate 23, fig. 11. Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (4) DGM 271 – I. “Schuchertella” agassizi. Clarke (Reference Clarke1913). Plate 23, fig. 7. Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (5) DGM 274 – I. “Schuchertella” agassizi. Clarke (Reference Clarke1913). Plate 23, fig. 10. Lower Devonian. Ponta Grossa Formation. Scale = 50 mm; (6) DGM 276 – I. “Schuchertella” sulivani. Clarke (Reference Clarke1913). Plate 23, fig. 21. Lower Devonian. Ponta Grossa Formation. Scale = 50 mm; (7) DGM 277 – I. “Schuchertella” sulivani. Clarke (Reference Clarke1913). Plate 23, fig. 23. Lower Devonian. Ponta Grossa Formation. Scale = 50 mm; (8) DGM 278 – I. “Schuchertella” sulivani. Clarke (Reference Clarke1913). Plate 23, fig. 16. Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (9) DGM 279 – I. “Schuchertella” sulivani. Clarke (Reference Clarke1913). Plate 23, fig. 22. Lower Devonian. Ponta Grossa Formation. Scale = 10 mm; (10) DGM 281 – I. “Schuchertella” sancticrucis. Clarke (Reference Clarke1913). Plate 23, figs 14–15. Middle Devonian. São Domingos Formation. Scale = 50 mm.
Another species described by Clarke (Reference Clarke1913) was Schuchertella sancticrucis (Fig. 7) from the Santa Cruz shales, São Domingos Formation, Santa Rosa Member, currently São Domingos Formation, Givetian in age (Melo, Reference Melo, McMillan, Embry and Glass1988; Grahn et al., Reference Grahn, Mauller, Bergamaschi and Bosetti2013). Caster (Reference Caster1939) proposed closer similarity between Schuchertella sancticrucis and Schellwienella sulivani (from the Falkland Islands) due to internal characters, which led to the former's reassignment as Schellwienella sancticrucis. These criteria were also followed by Lange (Reference Lange and Lange1954) but without detailed taxonomic discussion. Based on elements provided by Clarke (Reference Clarke1913), Schellwienella sancticrucis possesses a coarser costa and shows little evidence of multiplication, along with a nearly circular outline. The interior is described as presenting a very large flabellate scar, however it is an ill-defined muscle field. Clarke (Reference Clarke1913) stated that such features did not allow an in-depth comparison to other species. Yet, they do offer distinctions to the new species S. clarkei, which possesses a different ornamentation pattern and a different outline. In addition, according to the analysis of Clarke's holotype, there are slight differences between Schellwienella clarkei n. sp. and Schellwienella sancticrucis muscle field, with a more prominent adductor scar in the latter. Again, the lack of sufficient specimens leads us here to agree with Clarke (Reference Clarke1913), reinforcing the need of more in-depth studies about Schellwienella sancticrucis for further comparisons.
Beyond Paraná State, Quadros (Reference Quadros1987) reported a possible first occurrence of “Schuchertella” specimens from the outcrops of Serra do Atimã, in Chapada dos Guimarães municipality, Mato Grosso State, northwest of the Paraná Basin (Chapada series; Alto-Garças sub-Basin). Even though the Quadros (Reference Quadros1987) specimens are described as impunctate, based on the figured fossils, interior mold structures resemble pseudopunctae (Quadros, Reference Quadros1987, pl. 3, figs. 3, 4, 9). Also, the dental plates and muscle scars are split by a median septum. Another similarity is shown in the ornamentation pattern, described by Quadros (Reference Quadros1987) as showing ontogenetic bifurcation and, more rarely, by intercalation. Therefore, the Quadros (Reference Quadros1987) specimens are here considered as belonging to Schellwienella cf S. clarkei.
Morphological similarities between the external molds of other Orthotetida were responsible for equivocal taxonomic classification of “Schuchertella.” In the Malvinoxhosan Realm, this taxon is usually designated as “Schuchertella” (Boucot et al., Reference Boucot, Rowell, Racheboeuf, Pereira, Melo and Siqueira2001; Rezende et al., Reference Rezende, Ponciano and Brett2019a). This assumption allowed Boucot (Reference Boucot1975) to suggest this genus was cosmopolitan.
In other South American localities, Méndez-Alzola (Reference Méndez-Alzola1938) described the species S. agassizi from the Devonian of Uruguay as of relatively small size, with costae increasing by bifurcation or by intercalation. Even though the Uruguayan samples diverge from the original species Schuchertella agassizi from the Ererê Formation and possess the same intraspecific variation as the new species S. clarkei, the lack of internal characters in its description do not allow inclusion into the new species.
Isaacson (Reference Isaacson1977, Reference Isaacson and Suárez-Soruco1993) described samples from the Icla, Belén, Gamoneda, and Huamampampa formations in Bolivia attributing it to “Schuchertella” sp., since no better taxon was available. This description mentions an ontogenetic change of the divergence angle of the dental plates, which tends to become smaller. The same ontogenetic change was observed in Ponta Grossa specimens (Fig. 2.1–2.5, 2.7, 2.14). Isaacson (Reference Isaacson1977, Reference Isaacson and Suárez-Soruco1993) mentioned two of the three species established by Clarke (Reference Clarke1913) (Schuchertella sulivani and Schuchertella agassizi) and criteria to distinguish both species based on size and number of costae; however, the former applied the presence or absence of dental plates as a criteria for the Bolivian fossils. In addition, Isaacson (Reference Isaacson1977, Reference Isaacson and Suárez-Soruco1993) pointed out the obsolescent chilidium as an unlikely feature in Schellwienella. Nevertheless, the presence of bilobed dental plates, cardinal process and the pseudopunctation are enough to support its generic relocation to Schellwienella.
The taxonomic classification for the Brazilian specimens applies to those of Isaacson (Reference Isaacson1977, Reference Isaacson and Suárez-Soruco1993) from the Icla, Belén, Gamoneda and Huamampampa formations in Bolivia. Occurrences of the same species in these formations supports marine connections between the Paraná Basin, the Andean (Bolivia) and Chaco (Northwestern Argentina and Paraguay) basins during lower Devonian (Barrett and Isaacson, Reference Barrett, Isaacson, Mcmillan, Embry and Glass1988; Melo, Reference Melo, McMillan, Embry and Glass1988; Grahn et al., Reference Grahn, Horodyski, Mauller, Bosetti, Ghilardi and Carbonaro2016; Penn-Clarke, Reference Penn-Clarke2019), from which the species would have migrated.
Conclusion
Brachiopods from the Ponta Grossa and São Domingos formations (Brazil) described by Clarke (Reference Clarke1913) as Schuchertella agassizi are identified herein as Schellwienella clarkei n. sp. The generic assignment is supported by the presence of pseudopunctae, dental plates supporting hinge teeth, a median septum in the ventral valve, and a triangular muscle field. This new classification is also known from coeval deposits of Bolivia.
Shell microstructure is confirmed as an important taxonomic criterion within orthotetides. Published studies on orthotetides dealt mostly with North American material and their results were applied uncritically to South American taxa; the revision of the latter seems a fruitful subject of future work.
Scarcity of information regarding Brazilian orthotetide fossils is an issue for proper, in-depth, taxonomic studies. Most of the published works are based on North American late Paleozoic specimens, possibly maintaining gaps of information and identification mistakes about this group (Melo, Reference Melo1985). Herein, the efforts are aimed at taxonomic clarifications for orthotetide systematics, a group to which varying assignments were made, and further detailed studies regarding the southern hemisphere specimens are needed.
Acknowledgments
The authors would like to acknowledge the Universidade Federal do Estado do Rio de Janeiro (UNIRIO), the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) [under grant number118716/2019-0], which awarded the first author's scholarship, and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) [under grant 8887.484101/2020-00]. The authors would also like to thank D.M.C. Machado for providing the samples from the “Fósseis Paleozoicos” scientific collection held by the Laboratório de Estudos de Comunidades Paleozoicas (LECP). We also thank J.M.L. Basso, I.C. Gonzalez and J.P.G.S. Silva for welcoming us and providing the material in the Instituto de Geociências from the Universidade de São Paulo (USP). We are also very grateful to L.E. Anelli for all his help with the photography, supervision, and suggestions during our time in USP. To R.R. Machado and R.C. Silva for providing Clarke's material, along with other specimens from Paraná Basin held in the Museu de Ciências da Terra (MCTer). We also acknowledge C. Wellman (University of Sheffield) for the help with the references, and F.M. Vasconcellos for the linguistic revision and suggestions. The authors are grateful to the associate editor C. Sproat, to A.T. Halamski and an anonymous reviewer for their kind, careful and helpful revision, which resulted in a much improved manuscript.
