Reg. Charity No. 1168330
Diverse assemblages of dispersed spores have been recovered from Middle Devonian rocks in northern Spain, revealing a significant endemism in the flora. Middle Devonian Iberia was part of a relatively isolated island complex (Armorican Terrane Assemblage), separated by considerable tracts of ocean from Laurussia to the north‐west and Gondwana to the south‐east. The Middle Devonian deposits of the Cantabrian Zone of northern Spain are entirely marine and comprise a thick clastic unit sandwiched between extensive carbonate units. The clastic unit, the laterally equivalent Naranco, Huergas and Gustalapiedra formations of Asturias, León and Palencia provinces, represents a nearshore‐offshore transect across a marine shelf. This unit is also believed to encompass the Kačák Event, an important global extinction event. The recovered palynomorphs include marine (phytoplankton, chitinozoans, scolecodonts) and terrestrial (spores) assemblages. These are abundant and well preserved, although of variable thermal maturity. Here, we describe the dispersed spores and consider their significance as regards biostratigraphy, palaeophytogeography and Kačák Event interpretation. The dispersed spores represent a single assemblage assignable to the lemurata–langii Assemblage Zone (lemurata Subzone) indicating a probable early (but not earliest) Givetian age. Signs of endemism include various taxa known only from this region, some taxa appearing to have discordant ranges compared with elsewhere, and the absence from Iberia of certain prominent taxa characteristic of coeval assemblages elsewhere, such as those with grapnel‐tipped processes. The abrupt interruption of carbonate deposition, with a change to rapid deposition of thick clastic deposits, provides support for a monsoonal cause of the Kačák Event.
Dispersed spore assemblages from Middle Devonian deposits of northern Spain have previously been relatively neglected and briefly considered in only three publications (Cramer 1966, 1969; Fombella Blanco 1988). This is unfortunate as these deposits are otherwise well studied and exhibit a number of extremely interesting features. They represent an entirely marine onshore–offshore transect, represented by a clastic unit sandwiched between thick carbonate sequences, securely age‐constrained by conodonts and sedimentologically/palaeontologically well characterized. The sequence is of particular interest because: (1) it accumulated around a small group of islands in a palaeogeographically isolated location situated between the large continents of Laurussia and Gondwana (Torsvik & Cocks 2013); and (2) the clastic unit is believed to incorporate the Kačák Event (García‐Alcalde 1998). This extinction event has been identified globally (House 2002) although its characteristics and causes remain the subject of much debate (Marshall et al. 2007; Becker et al. 2016). The aim of this study is to describe the composition and distribution of dispersed spore assemblages from throughout this sequence and use them to test and refine previously erected spore biostratigraphical schemes, identify palaeophytogeographical differentiation on this isolated island group, and shed light on the nature of the Kačák Event.
Geological settingDevonian sediments crop out in the Cantabrian Zone in northern Spain in a large partial arc from the northern coast near Gijón, south through Asturias and in an east–west orientation across León and Palencia provinces (García‐Alcalde et al. 2002). They are interpreted as having been deposited in a transect across the shelf from nearshore (Asturias) to offshore (Palencia) (García‐Alcalde et al. 2002). Details of the stratigraphic sequence are given in Figure 1. The sedimentary sequence broadly alternates between calcareous and clastic in character. This paper concerns the Middle Devonian clastic unit classified as the laterally equivalent Naranco, Huergas and Gustalapiedra formations located in Asturias, León and Palencia, respectively. They are bounded by thick limestone sequences below (the laterally equivalent Moniello, Santa Lucía and Polentinos formations) and above (the laterally equivalent Candás, Portilla and Cardaño formations).
Figure 1 Open in figure viewerPowerPoint Age and correlation of Devonian units in several Iberian areas. Dashed lines indicate uncertainly placed boundaries. Diagram not to scale. Abbreviations for uppermost Famennian units: B, Baleas; C, Candamo; LE, Las Ermitas; V, Vegamián. Redrawn from García‐Alcalde et al. (2002).The age of the Naranco, Huergas and Gustalapiedra formations is Eifelian–Givetian, supported directly by biostratigraphical analysis based on various marine macrofaunal groups (García‐López et al. 2002). Conodonts from the bounding limestone formations provide a refined age constraint. Those from the underlying Santa Lucía Formation (and possibly lowermost Huergas and Naranco formations) belong to the Polygnathus costatus costatus Zone of middle Eifelian age (c. 391–392 Ma based on Becker et al. 2012). Those from the overlying Portilla and Candás formations belong to the lower Polygnathus varcus zone of early, but not earliest, Givetian age (c. 386–387 Ma based on Becker et al. 2012) (García‐López & Sanz‐López 2002; García‐López et al. 2002).
The sediments of the Naranco, Huergas and Gustalapiedra formations are in excess of 500 m in thickness in Asturias but reduced to only 50 m in thickness in Palencia. The deposits are characterized by a lower and an upper unit. The lower unit is coarser in character, dominated by thick sandstone layers, and represents a more abundant terrigenous clastic supply. The upper unit has a more mixed character, with rapid alternations between sandstones and siltstones (and occasional limestones) and represents a combination of course terrigenous and finer basinal deposits. In León, it includes euxinic nodular black shales that are pelagic‐like in character. García‐Ramos (1978) details the wide range of facies present in the Naranco Formation and its equivalents that represent varied marine and transitional depositional environments associated with large deltas (García‐Alcalde et al. 2002).
For this project, 30 localities were examined and samples collected for palynological analysis. The location of each site is indicated in Figure 2. Details of the sites’ location and precise geological setting, as well as samples taken, are provided in Askew & Wellman (2018).
Figure 2 Open in figure viewerPowerPoint Outline map of northern Spain. Sites surveyed in this study are marked with crosses. Outlined areas marked with dots indicate the outcrop area of Devonian sediments. Previous palynological studiesPrevious palynological studies of the Naranco and Huergas formations are limited to three papers. Cramer (1966) described an assemblage from one sampled site of the Naranco Formation, believed to be the ‘120’ site of Cramer (1969) and this study. Cramer (1969) expanded the earlier work with four additional sites from the same general area. These studies described a spore assemblage containing many new species, with others mostly showing an affinity with Russian and European floras known at the time, relatively early in the history of Devonian spore studies. Cramer interpreted the spore assemblage as supporting the Eifelian–Givetian age the Naranco Formation had previously been assigned based on invertebrate macrofossil evidence. Fombella Blanco (1988) described an assemblage of spores (including one newly described species) and phytoplankton from a single site in the Huergas Formation, relocated during the present study and described in Askew & Wellman (2018), but made no comment on the formation's age. Table 1 lists the species named in these studies, along with a correlation with the species identified and taxonomy utilized in the present study.
Table 1. Comparison of the spore taxa found in this study with those previously reported Identifications used in this study and comments on previously identified species not synonymized here Species reported in previous studies Acinosporites acanthomammillatus? A. lindlarensis Ambitisporites avitus A. dilutus A. sp. A A. sp. B A. sp. C Anapiculatisporites abrepunius A. carminaeAnapiculatisporites carminae (Cramer 1966)
A. carminae Cramer (Cramer 1969)
A. picantus Apiculatasporites perpusillus Apiculatisporis cf. elegans Apiculiretusispora cf. brandtii cf. Apiculiretusispora cf. brandtii Streel (Fombella Blanco 1988) A. plicataCyclogranisporites plicatus Allen (Cramer 1969)
? Aneurospora gregsii Clayton et al. (Fombella Blanco 1988)
? Apiculiretusispora arenorugosa McGregor (Fombella Blanco 1988)
A. sp. A A.? sp. B Brochotriletes foveolatus? Camarozonotriletes? concavus C. parvus Concavisporites? sp. A Corystisporites cf. sp. Deltoidospora priddyi Devonomonoletes cf. sp. 1 Diatomozonotriletes cf. franklinii Dibolisporites tuberculatus ? Dibolisporites echinaceous (Eisenack) Richardson (Fombella Blanco 1988) D. sp. A Dictyotriletes cf. hemeri ? Cymatiosphaera magnata Pilchler (Fombella Blanco 1988) D. gorgoneus Emphanisporites annulatusEmphanisporites annulatus McGregor (Cramer 1966)
E. annulatus McGregor (Cramer 1969)
E. cf. anulatus McGregor (Fombella Blanco 1988)
E. cf. annulatus E. annulatus? E. augusta E. cf. laticostatus E. mcgregorii Emphanisporites McGregorii Cramer (Cramer 1969) E. micrornatus E. orbicularis ? Emphanisporites erraticus (Eisenack) (Cramer 1966) E. cf. orbicularis E. protoannulatus E. rotatusEmphanisporites rotatus McGregor (Cramer 1966)
E. obscurus McGregor (Cramer 1969)
E. robustus McGregor (Cramer 1969)
E. rotatus McGregor (Cramer 1969)
E. rotatus McGregor (Fombella Blanco 1988)
E. cf. rotatus E. sp. A Geminospora lemurata G. cf. svalbardiae ? Geminospora cf. tuberculata (Kedo) Allen (Fombella Blanco 1988) Grandispora argutusHymenozonotriletes argutus ‘II’ Naumova (Cramer 1966)
p. Calyptosporites cf. deliquescens (Naumova) New Combination (Cramer 1969)
G. douglastownensis?? Hymenozonotriletes cf. eximius? Naumova (Cramer 1966)
H. cf. deliquescens? Naumova (Cramer 1966)
? Calyptosporites argutus (Naumova) New Combination (Cramer 1969)
p. C. cf. deliquescens (Naumova) New Combination (Cramer 1969)
G. cf. inculta? Hymenozonotriletes argutus ‘I’ Naumova (Cramer 1966)
H. narancae Cramer (Cramer 1966)
p. Calyptosporites microspinosus (Richardson) Richardson (Cramer 1966)
cf. C. optivus (Chibrikova) Allen; (Cramer 1969)
p. C. (?) narancae (Cramer) New Combination (Cramer 1969)
? Grandispora sp.C Paris et al. (Fombella Blanco 1988)
G. permulta Grandispora sp. A, Paris et al. (Fombella Blanco 1988) G. protea ? Calyptosporites cf. domanicus (Naumova) New Combination (Cramer 1969) G. cf. stolidota G. velatap. Calyptosporites microspinosus (Richardson) Richardson (Cramer 1969)
C. velatus (Eisenack) Richardson (Cramer 1969)
Granulatisporites concavus ? Leiotriletes bonitus Cramer (Cramer 1969) G. cf. muninensis Latosporites sp. 1 Planisporites cf. minimusCyclogranisporites rosendae Cramer (Cramer 1966)
Rhabdosporites prosperus (Cramer) New Combination (Cramer 1969)
? Acanthotriletes sp. (Fombella Blanco 1988)
Retusotriletes atratus R. goensis R. rotundusRetusotriletes barbutus Cramer (Cramer 1969)
R. rotundus (Streel) Streel (Cramer 1969)
Retusotriletes pychovii Naumova major Naumova (Cramer 1969)
R. semizonalis R. triangulatus ? Retusotriletes triangulatus (Streel) Streel (Fombella Blanco 1988) R. sp. A R. spp. Rhabdosporites minutus Samarisporites cf. praetervisus Verrucosisporites scurrus Raistrickia aratra Allen (Fombella Blanco 1988) V. tumulentus Zonotriletes armillatus Z. simplicissimus Spore type A A phytoplankton specimen Acanthotriletes espinositus Cramer (Cramer 1969) Too poorly figured to identify A. heterodontus (Fombella Blanco 1988) A phytoplankton specimen A. tenuispinosus tenuispinosus Naumova (Cramer 1969) Too poorly figured to identify; probably Dictyotriletes Camptotriletes araneosus Cramer (Cramer 1966) Too poorly figured to identify Grandispora sp. B Paris et al. (Fombella Blanco 1988) Too poorly figured to identify; potentially Apiculiretusispora G. sp. B (Fombella Blanco 1988) Too poorly figured to identify; potentially Apiculiretusispora cf. Hymenozonotriletes discors Chibrikova (Fombella Blanco 1988) Not described or figured Hystrichosporites delectabilis McGregor (Cramer 1969) Too poorly figured to identify; probably Apiculiretusispora Retusotriletes sp. Paris et al. (Fombella Blanco 1988) Not described or figured Rhabdosporites butifarrus (Cramer) New Combination (Cramer 1969) Too poorly figured to identify Samarisporites sp. B Paris et al. (Fombella Blanco 1988) Poorly figured; possibly a megaspore Verrucosisporites cf. tuberosus (Loose) Smith & Butterworth (Fombella Blanco 1988)A total of 130 samples were collected for palynological analysis from across the outcrop area of the Naranco, Huergas and Gustalapiedra formations during two fieldtrips in January and August–September 2015. Sampling focused on beds of dark, fine‐grained material, predominantly mudstones and siltstones, interspersed within the mostly sandstone formations (Fig. 3). As outlined in Askew & Wellman (2018), three relatively long sections, two incomplete and one nearly complete, were sampled with the remaining localities representing either spot samples or relatively short sections. It is important to note that during the extensive folding and thrusting of the Spanish sequence the clastic sediments of the Naranco, Huergas and Gustalapiedra formations often acted as a slip plane between the more rigid limestone formations above and below. Furthermore, compared to the bounding limestones they are often deeply weathered, with surface exposures vegetated. As a consequence: (1) long sections are rare (see above); (2) good upper and lower boundary sections are rare and difficult to identify; and (3) short exposed sections are difficult to place in stratigraphical context.
Figure 3 Open in figure viewerPowerPoint Stratigraphic log of the Playa del Tranqueru (3) site, including locations of samples taken (see Askew & Wellman (2018, chart S1) for detailed information on sample positions). Colour online.Rock samples were processed at the University of Sheffield using standard HCl–HF–HCl acid maceration, followed by sieving using a 15 μm mesh to remove the finest mineral matter. Remaining mineral residue was removed using heavy liquid centrifugation with ZnCl2. The organic residue was then assessed, with three barren samples and one with very poor preservation not being processed further. The remaining kerogen samples were evaluated by strew mounting on microscope slides and viewing using a light microscope.
The palynomorph assemblages are mostly well preserved but of variable thermal maturity, between 2− and 4 on the TAI scale (Traverse 2008). All samples were oxidized in Schulze's solution for between 5 and 60 min, except for four extremely mature samples that were oxidized for around 19 h. At this stage, the samples were spiked with Lycopodium tablets at a ratio of one tablet per millilitre of solid yield. Two to four strew mounts were made of these final preparations. From these, 113 samples were counted to 200 identifiable palynomorph specimens or the end of the slide in the occasional samples with less than 200 palynomorphs per slide. A note was kept of the number of modern Lycopodium spores encountered to enable quantitative assessment of the fossil material using an equation derived from one given by Stockmarr (1971). Slides were examined using standard light microscopy techniques and photographed using a Meiji Techno Infinity 1‐5C camera mounted on a Meiji Techno MT5300H transmitted light microscope.
Systematic palaeontologyTaxa are organized alphabetically by genera and species. Species with an uncertain identification are signified cf. or ?, after Matthews (1973). A limited synonymy is provided for species previously recorded from the Naranco and Huergas formations. Dimensions are given for each species as diameters and where three numbers are given these correspond to the minimum value (arithmetic mean) and maximum values. Species occurrences are given as locality code characters for brevity (for an explanation see Askew & Wellman 2018). Previous records are taken from consultation of the John Williams Index of Palaeopalynology (for details see Riding et al. 2012). Materials (rock samples, residues and slides) are housed in the collections of the Centre for Palynology, Department of Animal and Plant Sciences, University of Sheffield, UK. Figured specimens are located using an England Finder.
Acinosporites acanthomammillatus Richardson, 1965.
Acinosporites acanthomammillatus? Richardson, 1965Figure 4A, L Figure 4 Open in figure viewerPowerPoint Each figured specimen is identified by slide including the sample code, followed by its England Finder reference. A, L, Acinosporites acanthomammillatus?; AJA2‐GZ‐O1, R31; L, detail of ornament. B, Ambitisporites avitus; AJA3A‐O1; X34/3. C, Ambitisporites dilutus; AJA2‐PC‐O1; G46/3 (open trilete form). D, Ambitisporites sp. A; AJA598C‐O1; N39/1 (open trilete form). E, Anapiculatisporites carminae; AJA598C‐O1; D46/4. F, Camarozonotriletes parvus; AJA2‐7G‐O1; W30/2 (open trilete form). G, Ambitisporites sp. C; AJA11A‐O1; M33/1. H, Ambitisporites sp. B; AJA3A‐O1; Y34/2. I, Anapiculatisporites picantus; AJA598C‐O1; D26. J, Concavisporites? sp. A; AJA7A‐O1; Y37/2. K, Deltoidospora priddyi; AJA2‐7B‐O1; V44/4. Scale bars represent: 10 μm (A–K); 10 μm (L). Colour online.Amb shape uncertain. Laesurae not observed. Exine appears quite thick, ornamented with biform processes. Sculptural elements are rounded, up to 6 μm wide, often joined to form ridges and surmounted by apical spines up to 4 μm high.
55 (70) 85 μm (5 specimens measured).
Identification is highly questionable, as it is based entirely on the characteristic ornament of rounded ridges topped by spines, in a low number of incomplete and very poorly preserved specimens.
Sites 3, 11, G.
Reported from Eifelian–Frasnian strata with a worldwide distribution (Breuer & Steemans 2013).
Acinosporites lindlarensis Riegel, 1968Figure 5A Figure 5 Open in figure viewerPowerPoint Each figured specimen is identified by slide including the sample code, followed by its England Finder reference. A, Acinosporites lindlarensis; AJA2‐7A‐O1; W40/4. B, Apiculatasporites perpusillus; AJA3A‐O1; R34/2. C, Apiculatisporis cf. elegans; AJA598C‐O1; L33/1 (open trilete form). D, Apiculiretusispora plicata; AJA10B‐O1; V37/4. E, Apiculiretusispora cf. brandtii; AJA7A‐O1; C33/3. F, Anapiculatisporites abrepunius; AJA598C‐O1; J27 (open trilete form). G, Brochotriletes foveolatus?; AJA2‐7E‐O1; O33. H, Devonomonoletes cf. sp. 1; AJA2‐7E‐O1; H46/3. Scale bar represents 10 μm. Colour online.Amb circular to subcircular. Laesurae straight, extending one‐half to the whole amb radius. Equatorial thickening of 2–4 μm observed, with some minor separation of the exoexine from a possible inner body. Proximal surface laevigate. Distal surface bears an ornament of microgranulae, large conate elements up to 3 μm high and wide as well as more irregular, parallel sided, sometimes biform elements up to 5 μm high.
49 (79) 153 μm (8 specimens measured).
This genus is distinguished by bearing its ornament atop anastomosing ridges. These ridges are not visible in these specimens except for some small joining of ornament bases. However, this species has been repeatedly recorded as having an extremely variable morphology, including a lack of obvious ridges (McGregor & Camfield 1976; Richardson et al. 1993).
Sites 3, 7, G.
Reported from Emsian to Frasnian strata and with an almost worldwide distribution (although absent from Australia) (Breuer & Steemans 2013; Xu et al. 2014), as well as an unusual specimen from the Lochkovian of Belgium (Steemans 1989).
Genus AMBITISPORITES Hoffmeister, 1959Ambitisporites avitus Hoffmeister, 1959.
Ambitisporites avitus Hoffmeister, 1959Figure 4B26 (37) 67 μm (10 specimens measured).
Sites 2, 3, 7, 11, 19, 120, 598, G.
Reported from Lower Silurian to Lower Devonian strata and with a worldwide distribution (Breuer & Steemans 2013).
Ambitisporites dilutus (Hoffmeister) Richardson & Lister, 1969Figure 4C21 (35) 54 μm (43 specimens measured).
Sites 2, 3, 4, 7, 10, 11, 13, 15, 19, 22, 120, 598, 599, G, P.
Reported from Upper Ordovician to Eifelian strata and with an almost worldwide distribution (although absent from Australia).
Ambitisporites sp. AFigure 4DAmb circular to subcircular. Laesurae straight, extending from one‐third to five‐sixths of the amb radius. Tips of the laesurae may be slightly spatulate. Wall 1–2 μm thick. Surface laevigate.
18 (36) 65 μm (142 specimens measured).
This taxon is distinguished from A. dilutus by its shorter laesurae.
Sites 2, 3, 4, 5, 7, 10, 11, 15, 19, 120, 598, 599, G, P.
Ambitisporites sp. BFigure 4HAmb circular to subcircular. Laesurae straight, accompanied by narrow labra along their length, extending from one‐half to two‐thirds of the amb radius. Wall c. 1 μm thick. Surface laevigate.
24 (35) 55 μm (35 specimens measured).
This taxon is distinguished from A. sp. A by its possession of labra.
Sites 2, 3, 4, 5, 7, 10, 11, 22, 120, 598, 599, G, P.
Ambitisporites sp. CFigure 4GAmb circular to subcircular. Laesurae straight, accompanied by narrow labra along their length, extending from three‐quarters to the whole amb radius. Wall c. 1 μm thick. Surface laevigate to occasionally scabrate.
22 (35) 48 μm (26 specimens measured).
This taxon is distinguished from A. sp. B by its longer laesurae and from A. dilutus by its distal ornament.
Sites 2, 3, 5, 7, 10, 11, 13, 19, 20, 22, 120, 598, 599, G, P.
Genus ANAPICULATISPORITES Potonié & Kremp, 1954Anapiculatisporites isselburgensis Potonié & Kremp, 1954.
Anapiculatisporites abrepunius Cramer, 1966Figure 5FAmb circular to subcircular. Laesurae straight, extending from one‐half to the whole amb radius. Equatorial thickening of 1–4 μm observed. Proximal surface laevigate. Distal surface bears a sparse ornament of microgranulae and small spines separated by at least 2 μm.
25 (38) 61 μm (9 specimens measured).
Some of the specimens have shorter trilete rays than specified in the original description, though this was considered to be insufficient to justify an alternative identification.
Sites 2, 3, 4, 5, 7, 10, 15, 120, 598.
Reported from the Pragian–Emsian of Spain (Cramer 1966).
Anapiculatisporites carminae Cramer, 1966Figure 4E
Amb circular to subcircular. Laesurae straight, extending from three‐quarters to the whole amb radius. Equatorial thickening of 1–4 μm observed. Proximal surface laevigate. Distal surface bears an ornament of microgranulae and granulae above 1 μm in size.
21 (36) 65 μm (26 specimens measured).
The specimens reported by Cramer (1966) from the Naranco Formation are often larger than the specimens seen here.
Sites 2, 3, 4, 5, 7, 10, 11, 13, 14, 19, 20, 22, G.
Reported from the upper Eifelian to lower Frasnian of Spain (Cramer 1966, 1969).
Anapiculatisporites picantus Cramer, 1966Figure 4IAmb circular to subcircular. Laesurae straight, extending from two‐fifths to the whole amb radius. Equatorial thickening of 1–3 μm observed. Proximal surface laevigate. Distal surface bears an ornament of microgranulae.
25 (39) 83 μm (25 specimens measured).
Distinguished from A. abrepunius by its denser ornament. Specimens seen here may have shorter laesurae than originally described.
Sites 2, 3, 4, 5, 7, 10, 11, 13, 14, 16, 19, 20, 22, 120, 598, G.
Reported from the Pragian of Belgium (Steemans 1989) and the Pragian–Emsian of Spain (Cramer 1966).
Genus APICULATASPORITES Potonié & Kremp, 1956Apiculatasporites spinulistratus (Loose) Ibrahim, 1933.
Apiculatasporites perpusillus (Naumova ex Chibrikova) McGregor, 1973Figure 5B25 (38) 55 μm (12 specimens measured).
Sites 3, 7, 13, 19, 22, G.
Reported from Upper Silurian to Famennian strata and with an almost worldwide distribution (although absent from Australia).
Genus APICULATISPORIS Potonié & Kremp, 1956Apiculatisporis aculeatus (Ibrahim) Potonié, 1956.
Apiculatisporis cf. elegans McGregor, 1960Figure 5CAmb circular to subcircular. Laesurae straight, usually open, extending from one‐half to three‐quarters of the amb radius. Proximal surface laevigate. Distal surface bears a dense ornament of large microgranulae up to 1 μm in size.
34 (48) 63 μm (6 specimens measured).
The species as originally described has a less variable trilete size and slightly larger ornament than the specimens found here. Owens (1971) considered A. elegans to be one end member of a morphological series, with Planisporites minimus McGregor, 1960 as the other extreme. This series shows an increase in ornament size with amb dimensions. This study recovered both end members of the series but no intermediate forms. The decision was taken to preserve them as separate, tentatively assigned species, as P. minimus is not formally included under synonymy with A. elegans by Owens (1971) or McGregor (1964) and A. elegans has only ever been synonymized with a tentatively identified assemblage of Apiculatasporites dilucidus (McGregor) McGregor, 1964 (Owens 1971), which does not resemble the specimens found here.
Sites 3, 7, G.
Reported from the upper Eifelian to lower Givetian of the USA (Urban 1968), the middle to upper Givetian of Greenland (Friend et al. 1983), the Frasnian of Canada (McGregor 1960) and the Upper Devonian of Romania (Venkatachala et al. 1968).
Genus APICULIRETUSISPORA (Streel) Streel, 1967Apiculiretusispora brandtii Streel, 1964.
Apiculiretusispora cf. brandtii Streel, 1964Figure 5E
32 (46) 61 μm (15 specimens measured).
The species as originally described is markedly larger than the specimens described here, while the ornament seen here occasionally exceeds 1 μm in height, hence the uncertain identification.
Sites 2, 3, 4, 5, 7, 10, 11, 13, 14, 20, 22, 598, G.
Reported from Pragian–Givetian strata and with a worldwide distribution (Breuer & Steemans 2013).
Apiculiretusispora plicata (Allen) Streel, 1967Figure 5D
20 (52) 100 μm (45 specimens measured).
Sites 2, 3, 4, 5, 7, 10, 11, 13, 14, 15, 19, 20, 22, 120, 598, G, P.
Reported from Lower–Middle Devonian strata with a worldwide distribution (Breuer & Steemans 2013).
Apiculiretusispora? sp. AFigure 6G–H Figure 6 Open in figure viewerPowerPoint Each figured specimen is identified by slide including the sample code, followed by its England Finder reference. A, cf. Apiculiretusispora sp. B; AJA2‐GP‐O2; S37. B–C, Dibolisporites tuberculatus: B, AJA3A‐O1, P40; C, AJA3A‐O1, V28. D–E, I, Camarozonotriletes? concavus: D, AJA2‐7Q‐O1, W41/2; E, AJA2‐7J‐O1, W43/3; I, AJA2‐7B‐O1, X35/3. F, Dictyotriletes gorgoneus; AJA2‐3R‐O1; X41/4. G–H, Apiculiretusispora? sp. A: G, AJA2‐GZ‐O1, U44; H, AJA2‐GA‐O1, X33. J, Diatomozonotriletes cf. franklinii; AJA598C‐O1; J33/1. Scale bars represent: 20 μm (A); 10 μm (B–J). Colour online.Amb circular to subcircular. Laesurae straight, extending to the equator. Possible 2–3 μm wide equatorial thickening observed. Proximal face bears subcircular thickened region extending from two‐thirds to three‐quarters of the distance to the equator. Distal surface bears an ornament of microgranulae.
50 (61) 92 μm (4 specimens measured).
These specimens are doubtfully assigned to this genus owing to their lack of obvious curvaturae, although these could be incorporated in the thickened wall. Some previously figured specimens of Apiculiretusispora do not show obvious curvaturae, such as Breuer & Steemans (2013, fig. 10F). This species’ interradial thickenings are reminiscent of the structures seen in A. arabensis Al‐Ghazi, 2009 although they are not of such a clear rounded shape.
Site G.
cf. Apiculiretusispora sp. BFigure 6AAmb circular to subcircular. Laesurae straight, extending almost to the equator. Laesurae connected by curvaturae perfectae delimiting obvious proximal contact areas, up to 15 μm away from the equator. Distal surface bears an ornament of microgranulae and granulae together with a prominent, 10 μm wide annulus, positioned one‐half of the distance of the equator.
147 (198) 268 μm (2 specimens measured).
This taxon could be accommodated by the genus Apiculiretusispora except that it is outside the normal size range for the genus, with the larger specimen being of megaspore size.
Site G.
Genus BROCHOTRILETES Naumova ex Ishchenko, 1952Brochotriletes magnus Ishchenko, 1952.
Brochotriletes foveolatus? Naumova, 1953Figure 5G39 (51) 64 μm (3 specimens measured).
The identification of this species is doubtful for similar reasons cited in McGregor (1973); the original description and figures are inadequate for confident identification of modern material. In addition, the specimens seen here have slightly larger luminae than the specimens in McGregor (1973).
Sites 3, 7, G.
Reported from Upper Silurian to upper Famennian strata with a worldwide distribution.
Genus CAMAROZONOTRILETES Naumova ex Naumova, 1953Camarozonotriletes devonicus Naumova, 1953.
Camarozonotriletes? concavus Loboziak & Streel, 1989Figure 6D–E, IAmb subtriangular with slightly concave to slightly convex interradial margins. Laesurae straight, may be accompanied by narrow labra along their length, extending from two‐thirds to the whole amb radius. Equatorial thickening of 1–4 μm observed, wider in the interradial areas though this is not always obvious. Proximal surface laevigate. Distal surface bears an ornament of microgranulae.
24 (31) 39 μm (11 specimens measured).
The generic assignment of this species is dubious owing to only a slight thinning of the equatorial thickening opposite the laesurae (Breuer & Steemans 2013). Distinguished from C. parvus by its concave interradial margins.
Sites 3, 7, G.
Reported from the middle Eifelian to lower Frasnian of Tunisia (Breuer & Steemans 2013), the upper Eifelian to Frasnian of Brazil (Loboziak et al. 1988; Melo & Loboziak 2003; Breuer & Grahn 2011), the lower–middle Givetian of Libya and the lower–upper Givetian of Saudi Arabia (Breuer & Steemans 2013).
Camarozonotriletes parvus Owens, 1971Figure 4F24 (32) 41 μm (5 specimens measured).
Sites 7, G.
Reported from the lower Eifelian to upper Frasnian of Libya (Moreau‐Benoit 1989), the upper Eifelian to Frasnian of Canada (McGregor & Owens 1966; Owens 1971; McGregor & Uyeno 1972; McGregor & Camfield 1982), the lower Givetian of Saudi Arabia (Breuer & Steemans 2013), the Givetian of Morocco (Rahmani‐Antari & Lachkar 2001), Algeria (Moreau‐Benoit et al. 1993), Brazil (Breuer & Grahn 2011) and Libya (Breuer & Steemans 2013), and the Frasnian of Tunisia (Breuer & Steemans 2013).
Genus CONCAVISPORITES Pflug in Thomson & Pflug, 1953Concavisporites rugulatus Pflug in Thomson & Pflug, 1953.
Concavisporites? sp. AFigure 4JAmb subtriangular with straight to slightly convex interradial margins. Laesurae straight, simple or accompanied by narrow labra along their length, extending from one‐half to two‐thirds of the amb radius. Proximal surface bears thickened kyrtomes in the interradial areas, reaching the tips of the laesurae. Surface otherwise laevigate.
29 (31) 33 μm (3 specimens measured).
This species meets the generic criteria for Concavisporites, although this genus has not previously been used in the Palaeozoic.
Site 7.
Genus CORYSTISPORITES Richardson, 1965Corystisporites multispinosus Richardson, 1965.
Corystisporites cf. sp. Turnau, 1996Figure 7A Figure 7 Open in figure viewerPowerPoint Each figured specimen is identified by slide including the sample code, followed by its England Finder reference. A, Corystisporites cf. sp.; AJA2‐GD‐O1; R45/3. B, Emphanisporites annulatus; AJA2‐20B‐2‐O2; O42/4. C, Emphanisporites cf. annulatus; AJA7A‐O1; X42/4. D, Emphanisporites annulatus?; AJA598C‐O1; L32/1. E, Emphanisporites cf. orbicularis; AJA2‐PC‐O1; N41. F, Dibolisporites sp. A; AJA10B‐O2; W42/3. G–H, Dictyotriletes cf. hemeri: G, AJA2‐7D‐O1, W33/2 (open trilete form); H, AJA598C‐O1, H31/4 (open trilete form). Scale bar represents 10 μm. Colour online.Amb subcircular to vaguely subtriangular. Laesurae not easily discerned, believed to extend to the equator. Proximal surface presumed to be laevigate. Distal surface bears an ornament of densely packed, tapering spines up to 19 μm high. Spines often have wide bases with marked shoulders at around one‐third to one‐half of their height, before a thinner tapering portion begins. Large, rounded granulae are also seen, though these are probably broken spine bases.
70 (98) 139 μm (5 specimens measured).
The specimens seen here are sometimes smaller than those of Turnau (1996) and with less variation in the length of the spines. Aside from this we draw similar conclusions: the species resembles Acinosporites macrospinosus Richardson, 1965 except for having more densely distributed spines not clearly superimposed on convolute ridges.
Site G.
The study of Turnau (1996) was carried out on Middle Devonian strata from Poland. A. macrospinosus, which the species has been compared to, is reported from upper Pragian to Lower Carboniferous strata and has a worldwide distribution.
Genus DELTOIDOSPORA Miner, 1935Deltoidospora hallii Miner, 1935.
Deltoidospora priddyi (Berry) McGregor, 1973Figure 4K23 (32) 48 μm (8 specimens measured).
Sites 3, 7, 11, 599.
Reported from the upper Pragian to lower Emsian of France (Le Hérissé 1983), the Emsian to lower Eifelian of Bolivia (McGregor 1984), the Emsian to middle Eifelian of Canada (McGregor 1973), the Eifelian of Russia (Chibrikova & Olli 1992) and the Emsian–Eifelian (Andrews et al. 1977) and Pennsylvanian of the USA (Ravn 1986; Willard 1992; Gennett & Ravn 1993; Peppers 1993; Eble 1996).
Genus DEVONOMONOLETES Arkhangelskaya, 1985Devonomonoletes microtuberculatus (Chibrikova) Arkhangelskaya, 1985.
Devonomonoletes cf. sp. 1 Breuer & Steemans, 2013Figure 5HAmb circular to subcircular. Monolete mark observed, extending from one‐half to the whole amb radius. Curvaturae perfectae may be observed at the laesurae tips. Equatorial thickening of 1–2 μm observed. Proximal surface laevigate. Distal surface bears an ornament of microgranulae.
32 (42) 49 μm (4 specimens measured).
The specimens described here do not show obvious curvaturae as seen in the original figured specimens. These specimens resemble Latosporites sp. B Owens, 1971, though Latosporites is a laevigate genus.
Sites 2, 3, 4, 5, 7, 10, 13, 14, G.
Reported from the Pragian to middle Emsian of Saudi Arabia (Breuer & Steemans 2013).
Genus DIATOMOZONOTRILETES (Naumova) emend. Playford, 1963Diatomozonotriletes saetosus (Hacquebard & Barss) Hughes & Playford, 1961.
Diatomozonotriletes cf. franklinii McGregor & Camfield, 1982Figure 6JAmb subtriangular with straight to slightly convex interradial margins. Laesurae straight, extending from two‐thirds to the whole amb radius. Proximal surface laevigate. Distal surface bears an ornament of microgranulae, with a prominent row of spines around 1 μm high in the interradial regions. The areas opposite the laesurae are laevigate to very finely scabrate.
26 (29) 30 μm (3 specimens measured).
The specimens seen here have shorter interradial spines than the species as originally described, possibly attributable to damage.
Sites 3, 7, G.
Reported from the Emsian–Eifelian of Morocco (Rahmani‐Antari & Lachkar 2001), the middle Emsian of Saudi Arabia (Breuer & Steemans 2013), the upper Emsian to lower Eifelian of Algeria (Moreau‐Benoit et al. 1993), the upper Emsian to Givetian of Brazil (Loboziak et al. 1988; Melo & Loboziak 2003), the upper Emsian to middle Givetian of Libya (Breuer & Steemans 2013), the upper Emsian to lower Frasnian of Tunisia (Breuer & Steemans 2013), the upper Eifelian of Russia (Avkhimovitch et al. 1993) and the upper Eifelian to lower Givetian of Canada (McGregor & Uyeno 1972).
Genus DIBOLISPORITES Richardson, 1965Dibolisporites echinaceus (Eisenack) Richardson, 1965.
Dibolisporites tuberculatus Breuer & Steemans, 2013Figure 6B–C
Amb circular to subcircular. Laesurae straight, extending from three‐quarters to the whole amb radius. An equatorial thickening up to 4 μm is sometimes observed. Curvaturae perfectae joining the tips of the laesurae are sometimes observed, often coincident with equator. Proximal surface laevigate. Distal surface bears an ornament of rounded granules and pointed spines. Well‐preserved specimens may show slightly bulbous tips on the spines. These ornamental units are 2–3 μm high and separated by at least 1–2 μm.
35 (46) 77 μm (18 specimens measured).
This species is distinguished from D. eifeliensis by its original authors by having a coarser ornament. The stated ornament dimensions in the original descriptions of the two species are almost identical, however, and we consider this species’ much greater wall thickness to be a more useful diagnostic feature.
Sites 2, 3, 7, 11, 20, 120, 598.
Reported from the Emsian–Eifelian of the USA (Ravn & Benson 1988), the Emsian to lower Givetian of Saudi Arabia (Breuer & Steemans 2013; Breuer et al. 2015), the upper Eifelian of Brazil (Breuer & Grahn 2011) and Tunisia (Breuer & Steemans 2013) and the Givetian of Libya (Breuer & Steemans 2013).
Dibolisporites sp. AFigure 7FAmb circular to subcircular. Laesurae not observed. Equatorial thickening of 5 μm observed. Surface (probably distal) bears a dense ornament of clavate elements, with narrow bases c. 1 μm wide and widened heads up to 3 μm wide. Elements have rounded tips and are up to 10 μm high.
70 μm (one specimen measured).
The sculptural elements on this species closely resemble those of D. pilatus Breuer et al., 2007, except for being slightly narrower, often taller and distributed much more densely, in contrast to the sparse, irregular ornament of D. pilatus. The specimen also resembles a small example of the megaspore Jhariatriletes emsiensis Moreau‐Benoit, 1979. Only a single specimen was found.
Site 10.
Genus DICTYOTRILETES Naumova ex Ishchenko, 1952Dictyotriletes bireticulatus (Ibrahim) Potonié & Kremp, 1955.
Dictyotriletes gorgoneus Cramer, 1966Figure 6F40 μm (one specimen measured).
Distinguished from D. cf. hemeri in this study by its rather more substantial looking muri and more irregularly shaped luminae. The figured specimen could be interpreted as having an interradially thickened wall, in the fashion of Camarozonotriletes, but we interpret this specimen as having a widely opened trilete mark, leaving the proximal exine gathered around the margins. Though known primarily from earlier sediments this species is known from the Givetian, through a taxon known from the Givetian of Spitsbergen and placed in open nomenclature by Allen (1965), later referred to D. gorgoneus by Breuer & Steemans (2013). Only a single specimen was found in this study.
Site 3.
Reported from the upper Lochkovian to upper Emsian of Belgium (Lessuise et al. 1979; Steemans 1989), the lower Pragian to Emsian of Germany (Steemans 1989), the Pragian–Emsian of Spain (Cramer 1966) and Saudi Arabia (Breuer & Steemans 2013), the Emsian of Canada (McGregor & Owens 1966; McGregor 1973) and the Emsian–Givetian of Spitsbergen (Allen 1965).
Dictyotriletes cf. hemeri Breuer & Steemans, 2013Figure 7G–H
Amb circular to subcircular or ovoid. Laesurae straight, sometimes accompanied by narrow labra along their length, extending from one‐half to the whole amb radius. Proximal surface laevigate. Distal surface bears a reticulate ornament with muri, c. 1–2 μm high and wide, enclosing mostly polygonal luminae 2–6 μm wide. Small projections may occur at muri junctions.
33 (43) 53 μm (4 specimens measured).
The species as originally described is rather larger and with larger sculptural elements than the specimens described here. In addition, the biform elements at muri junction are not obvious in these specimens, though this is also the case on some of the original figured specimens.
Sites 3, 7, 11, 598, G, P.
Reported from the Eifelian–Givetian of Spain (Cramer 1969) and the upper Eifelian to middle Givetian of Saudi Arabia (Breuer & Steemans 2013).
Genus EMPHANISPORITES McGregor, 1961Emphanisporites rotatus McGregor emend. McGregor, 1973.
Emphanisporites annulatus McGregor, 1961Figure 7B
28 (38) 62 μm (15 specimens measured).
Sites 3, 7, 10, 19, 20, 22, G.
Specimens questionably assigned to E. annulatus owing to their poor state of preservation are called E. annulatus? (e.g. Fig. 7D).
Reported from Emsian–Tournaisian strata with a worldwide distribution (Taylor et al. 2011).
Emphanisporites cf. annulatus McGregor, 1961Figure 7CAmb circular to subcircular. Monolete mark observed, extending to the equator. Equatorial thickening of 3 μm observed. Proximal face bears interradial muri, six in each half. Distal surface bears an annulus, otherwise laevigate.
35 (40) 51 μm (3 specimens measured).
Monolete specimens attributed to various Emphanisporites species have been recorded previously (Breuer & Steemans 2013).
Site 7.
Emphanisporites augusta Fombella Blanco, 1988Figure 8A Figure 8 Open in figure viewerPowerPoint Each figured specimen is identified by slide including the sample code, followed by its England Finder reference. A, Emphanisporites augusta; AJA2‐7F‐O1; W39/1. B, Emphanisporites cf. laticostatus; AJA120A‐O2; L35/4. C, Emphanisporites micrornatus; AJA2‐GE‐O1; T30. D, Emphanisporites sp. A; AJA2‐7C‐O1; H29. E–F, Emphanisporites mcgregorii: E, AJA7A‐O1, S28/3; F, AJA11A‐O1, C38/2. G–H, Emphanisporites orbicularis: G, AJA3A‐O1, Q46; H, AJA2‐GE‐O1, S43/2. I, Emphanisporites protoannulatus; AJA2‐GH‐O1; S33/3. J, Emphanisporites rotatus; AJA7A‐O1; C42/3. K–L, Emphanisporites cf. rotatus: K, AJA7A‐O1, U42/1; L, AJA2‐GF‐O1, S40. M, Granulatisporites concavus; AJA10B‐O1; O38. N, Granulatisporites cf. muninensis; AJA7A‐O1; W39/2. Scale bar represents 10 μm. Colour online.Amb circular to subcircular. Laesurae straight, accompanied by narrow labra along their length, extending from one‐half to the whole amb radius. Equatorial thickening of 1–2 μm observed. Proximal face bears interradial muri, 2–3 per sector. Distal surface bears an ornament of microgranulae.
25 (38) 52 μm (32 specimens measured).
The species as originally described is larger than the specimens seen here, with a wider cingulum.
Sites 2, 4, 5, 7, 10, 11, 13, 14, 19, 20, 22, G.
Reported from the Middle Devonian of Spain (Fombella Blanco 1988).
Emphanisporites cf. laticostatus Breuer & Steemans, 2013Figure 8BAmb circular to subcircular. Laesurae straight, accompanied by narrow labra, extending from two‐thirds to three‐quarters of the amb radius. Equatorial thickening of 1–3 μm observed. Proximal face bears interradial muri, 2–4 per sector. Distal surface laevigate.
26 (37) 57 μm (5 specimens measured).
The species as originally described is larger than the specimens reported here and these specimens do not show fading muri towards the equator.
Sites 3, 7.
Reported from the middle Givetian of Brazil (Breuer & Grahn 2011) and the upper Givetian to Frasnian of Tunisia and Saudi Arabia (Breuer & Steemans 2013).
Emphanisporites mcgregorii Cramer, 1966Figure 8E–F
Amb circular to subcircular. Laesurae straight, may be accompanied by narrow labra, extending from one‐third to the whole amb radius. Equatorial thickening of 1–2 μm observed. Proximal face bears interradial muri, 4–12 per sector and arranged parallel to one another, producing a distinct herringbone pattern. Distal surface laevigate.
23 (36) 53 μm (22 specimens measured).
The description of McGregor (1961), restated by Cramer (1966), does not specify the number of interradial ridges this species should possess. We have included specimens with laesurae shorter than the radius in this species as this measurement varies in other members of the genus. The descriptions of this species and E. spinaeformis Schultz, 1968 do not differ in their important characteristics and the synonymization of the two by Breuer & Steemans (2013) is followed here. Care should be taken not to confuse this species with E. macgregorii Schultz in Lanninger, 1968, rendered a nomen nudum by McGregor (1973) as a later homonym (orthographic variant) of the species used here.
Sites 3, 5, 7, 10, 16, 19, 22, 598, G.
Reported from the Lochkovian to Eifelian of Germany (Lanninger 1968; Riegel 1968; Schultz 1968; Edalat 1974; Steemans 1989; Pflug & Prössl 1991), the upper Lochkovian to Emsian of France (Steemans 1989; Moreau‐Benoit 1994) and Belgium (Steemans 1989), the Pragian to upper Givetian of Libya (Massa & Moreau‐Benoit 1976; Moreau‐Benoit 1979, 1989; Paris et al. 1985; Moreau‐Benoit & Massa 1988; Streel et al. 1988; Breuer & Steemans 2013), the Pragian to middle Emsian of Poland (Turnau 1986; Turnau & Jakubowska 1989), the Pragian–Givetian of Spain (Cramer 1966, 1969), the upper Pragian to lower Emsian of Brazil (Mendlowicz Mauller et al. 2007), the upper Pragian to upper Givetian of Saudi Arabia (Breuer & Steemans 2013), the Emsian to lower Eifelian of Bolivia (McGregor 1984), the Emsian–Famennian of Algeria (Abdesselam‐Rouighi 1986; Moreau‐Benoit et al. 1993), the upper Emsian to lower Frasnian of Tunisia (Breuer & Steemans 2013), the lower Givetian of Egypt (Schrank 1987) and the Upper Devonian to Tournaisian of Ireland (Naylor et al. 1977; Sleeman et al. 1978).
Emphanisporites micrornatus Richardson & Lister, 1969Figure 8CAmb circular to subcircular. Laesurae straight, may be accompanied by narrow labra, extending from one‐half to the whole amb radius. Proximal face bears interradial muri, 4–8 per sector. Distal surface bears an ornament of microgranulae.
26 (37) 45 μm (23 specimens measured).
These specimens possess more interradial muri than the species as originally described.
Sites 2, 4, 7, 10, 13, 14, 19, 20, 22, G.
Reported from Lochkovian–Emsian strata with a worldwide distribution (Taylor et al. 2011).
Emphanisporites orbicularis Turnau, 1986Figure 8G–H
Amb circular to subcircular. Laesurae straight, may be accompanied by narrow labra along their length, extending from one‐third to three‐quarters of the amb radius. Equatorial thickening of 1–5 μm observed. Proximal face bears interradial muri, 3–10 per sector. Distal surface laevigate.
22 (33) 58 μm (70 specimens measured).
The original description for this species does not specify how many interradial muri it should possess and does not mention labra, though they may be visible on one of the figured specimens (pl. 4, fig. 9).
Sites 3, 7, 10, 11, 13, 19, 22, 120, 598, G, P.
Reported from the upper Lochkovian to Emsian of Poland (Turnau 1986; Turnau & Jakubowska 1989), the upper Givetian to Frasnian of Iran (Ghavidel‐Syooki 1994) and the upper Famennian to lower Tournaisian of Canada (Playford & McGregor 1993).
Emphanisporites cf. orbicularis Turnau, 1986Figure 7EAmb circular to subcircular. Monolete mark observed, extending from one‐half to three‐quarters of the amb radius. Proximal face bears interradial muri, 8–15 in each half. Distal surface laevigate.
25 (33) 40 μm (15 specimens measured).
Monolete specimens attributed to various Emphanisporites species have been recorded previously (Breuer & Steemans 2013).
Sites 3, P.
Emphanisporites protoannulatus Rodríguez, 1978Figure 8IAmb circular to subcircular. Laesurae straight, accompanied by narrow labra along their length, extending two‐thirds of the amb radius. Proximal face bears interradial muri, 3–4 per sector. Distal surface bears a 3–4 μm annulus, otherwise laevigate.
31 (35) 39 μm (3 specimens measured).
Distinguished from E. annulatus in this study by its shorter trilete rays.
Sites 3, G.
Reported from the Ludlow to Lower Devonian of Spain (Rodríguez 1978, 1983).
Emphanisporites rotatus McGregor emend. McGregor, 1973Figure 8J
21 (34) 52 μm (165 specimens measured).
Sites 2, 3, 4, 5, 7, 10, 11, 13, 14, 19, 20, 22, 120, 598, 599, G, P.
Reported from Upper Silurian to Tournaisian strata with a worldwide distribution (Taylor et al. 2011; Breuer & Steemans 2013).
Emphanisporites cf. rotatus McGregor emend. McGregor, 1973Figure 8K–LAmb circular to subcircular. Monolete mark observed, extending to the equator. Equatorial thickening of 1–3 μm observed. Proximal face bears interradial muri, 3–12 in each half. Distal surface laevigate.
23 (36) 48 μm (6 specimens measured).
Monolete specimens attributed to various Emphanisporites species have been recorded previously (Breuer & Steemans 2013).
Sites 3, 7, 11, 13, G.
Emphanisporites sp. AFigure 8DAmb circular to subcircular. Laesurae straight, extending to the equator. Equatorial thickening of 2–3 μm observed. Proximal face bears interradial muri, 5–7 per sector and arranged parallel to one another, producing a distinct herringbone pattern. Distal surface bears an ornament of microgranulae.
33 (41) 50 μm (7 specimens measured).
This species has the herringbone muri pattern of E. mcgregorii but possesses a distal ornament.
Sites 7, 10, 13, 14, G.
Genus GEMINOSPORA Balme, 1962Geminospora lemurata Balme emend. Playford, 1983.
Geminospora lemurata Balme emend. Playford, 1983Figure 9A–C, E–G Figure 9 Open in figure viewerPowerPoint Each figured specimen is identified by slide including the sample code, followed by its England Finder reference. A–C, Geminospora lemurata: A, AJA2‐3C‐O2, E43/3; B, AJA2‐GE‐O1, R49/2; C, AJA2‐7A‐O1, O49/3. D, Grandispora douglastownensis?; AJA2‐GE‐O1; M49/4. E–G, Geminospora lemurata: E, AJA2‐7Q‐O1, V50; F, AJA2‐GAB‐O2, P29/3; G, AJA2‐7A‐O1, N39/2. H–I, Latosporites sp. 1: H, AJA10B‐O1, R28; I, AJA2‐7D‐O1, P46/1 (open monolete form). J, Planisporites cf. minimus; AJA598C‐O1; K34. Scale bars represent: 10 μm (A–C, E–J); 20 μm (D). Colour online.Amb circular to subcircular. Cavate. Exoexine attached proximally, detached equatorially and distally. Intexine forms distinct inner body. Laesurae straight, extending to perimeter of intexine. Exoexine extends past intexine perimeter by one‐quarter to one‐third the radius of the intexine. Exoexine markedly thick, always over 1 μm. Proximal surface laevigate. Exoexine distally sculptured with densely distributed grana and apiculate elements up to 1 μm high.
Intexine: 23 (40) 53 μm; exoexine: 30 (52) 76 μm (10 specimens measured).
The specimens described here correspond to the specific designation in all respects. Distinguished from species of Grandispora in the thickness of the exoexine and in the laesurae not extending past the intexine.
Sites 3, 7, G.
Reported from Givetian–Frasnian strata with a worldwide distribution (Breuer & Steemans 2013).
Geminospora cf. svalbardiae (Vigran) Allen, 1965Figure 10A–D Figure 10 Open in figure viewerPowerPoint Each figured specimen is identified by slide including the sample code, followed by its England Finder reference. A–D, Geminospora cf. svalbardiae: A, AJA2A‐O1, V42; B, AJA2‐7A‐O1, U32/1; C, AJA11A‐O1, T46/4; D, AJA2‐7A‐O1, N32. E, Grandispora permulta; AJA2‐GI‐O1; U46/4. F, Grandispora cf. inculta; AJA7A‐O1; C28/4. G, Grandispora velata; AJA10B‐O1; D28/2. Scale bars represent: 10 μm (A–E); 20 μm (F–G). Colour online.
Amb circular to subcircular. Cavate. Exoexine attached proximally, detached equatorially and distally. Intexine forms distinct inner body. Laesurae straight, extending to perimeter of intexine. Exoexine extends past intexine perimeter by one‐quarter to one‐third the radius of the intexine. Exoexine markedly thick, always over 1 μm. Proximal surface laevigate. Exoexine distally sculptured with densely distributed grana and apiculate elements 1–4 μm high.
Intexine: 33 (38) 48 μm; exoexine: 39 (46) 58 μm (5 specimens measured).
The specimens described here differ from those assigned to G. lemurata primarily in having a larger ornament and sometimes a somewhat thinner exoexine, though still thicker than in Grandispora. The specimens described here are rather smaller than those originally described for the species.
Sites 2, 3, 7, 10.
Reported from Pragian to upper Famennian strata with an almost worldwide distribution (although absent from Australia).
Genus GRANDISPORA Hoffmeister et al. emend. Neves & Owens, 1966Grandispora spinosa (Hoffmeister et al. 1955).
‘Grandispora’ (Hymenozonotriletes) argutus Naumova, 1953 sensu Cramer, 1969Figure 12C
Amb subcircular to vaguely subtriangular. Cavate. Exoexine attached proximally, detached equatorially and distally. Intexine forms distinct inner body. Laesurae not obvious, may extend to the spore equator. Exoexine extends past intexine perimeter by a distance equal to the radius of the intexine. Proximal surface laevigate. Exoexine distally sculptured with an ornament of large ridges and spines up to 15 μm long. These spines have a broad base, often drawing up the exoexine around them. This produces a ‘pinched’ appearance and a prominent scalloped margin to the exoexine.
Intexine: 39 (58) 75 μm (6 specimens measured); exoexine: 75 (104) 135 μm (5 specimens measured).
This taxon has a complicated taxonomic history. Naumova (1953) described and illustrated two new species, which are very different in structure and morphology, but called both of them Hymenozonotriletes argutus sp. n. These were described as spore number 73 (p. 41) and spore number 169 (p. 67) illustrated as line figures in her plate 4, figure 10 and plate 9, figure 9, respectively. Cramer (1966) identified both species in the Spanish Middle Devonian and called them Hymenozonotriletes argutus ‘I’ Naumova, 1953 and Hymenozonotriletes argutus ‘II’ Naumova, 1953 with I referring to spore number 73 and II referring to spore number 169. Subsequently Cramer (1969) placed Hymenozonotriletes argutus ‘II’ Naumova, 1953 in the genus Calyptosporites as a new combination: Calyptosporites (Hymenozonotriletes) argutus (Naumova) Cramer,