Megaspores from mid Cretaceous deposits in western France and their biostratigraphic and palaeoenvironmental significance

Review of Palaeobotany and Palynology 161 (2010) 151–167

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Megaspores from mid Cretaceous deposits in western France and their biostratigraphic and palaeoenvironmental significance David J. Batten a,⁎, Jean-Paul Colin b,c, Didier Néraudeau b a School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, and Institute of Geography and Earth Sciences, Aberystwyth University, Ceredigion SY23 3DB, Wales, UK b UMR CNRS 6118, Université Rennes 1, Campus de Beaulieu, 263 avenue du Général Leclerc, 35042 Rennes, France c Universidade de Lisboa, Faculdade de Ciências, Centro de Geologia Campo Grande, C-6, 3° 1749-016 Lisboa, Portugal

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Article history: Received 30 November 2009 Received in revised form 31 March 2010 Accepted 31 March 2010 Available online 13 April 2010 Keywords: Cretaceous Albian Cenomanian megaspores palynology biostratigraphy palaeoenvironments France

a b s t r a c t Six localities in western France contain deposits of mid Cretaceous age that have yielded small assemblages of megaspores. These are Archingeay-Les Nouillers, Puy-Puy, Les Renardières, La Buzinie and Le Brouillard quarries, and Fouras tidal flat. With one exception, all are within the Charente and Charente-Maritime regions; Le Brouillard is further north in Anjou Province. The productive horizons are in sub-units of previously defined stratigraphic units A, B and C, and range in age from latest Albian or earliest Cenomanian to earliest mid Cenomanian. Owing to a scarcity of records of mid Cretaceous megaspores that can be relied upon for comparison with those recovered in this study, a cautious approach to identification has been adopted. Most forms are only compared to previously described species or referred to in open nomenclature. The most productive sample was from the lower part of sub-unit A1 at Puy-Puy. The assemblage recovered is dominated by spores referable to isoetalean Minerisporites and Paxillitriletes, with a few baculate, rugulate and other lycopsid spores and marsilealean Molaspora rugosa in association. The occurrence of the last of these in particular might indicate that this lowermost unit of the mid Cretaceous succession is earliest Cenomanian rather than latest Albian in age, but the evidence is equivocal. The composition of the assemblages from sub-unit B2 (Fouras tidal flat) and higher levels (La Buzinie, Le Brouillard) is consistent with a Cenomanian age determination and, in common with those from Puy-Puy, Archingeay-Les Nouillers and Les Renardières, indicates a bias towards parent plants that lived in and adjacent to water bodies. Among the forms recorded are species of Ariadnaesporites, Dijkstraisporites and Tenellisporites. The mixed character of the assemblages and the presence of damaged specimens and fragments in all of them lend support to previous interpretations of lacustrine to paralic environments of deposition for the sedimentary units concerned. © 2010 Elsevier B.V. All rights reserved.

1. Introduction The mid Cretaceous Cenomanian (and possibly latest Albian) deposits of the Charente and Charente-Maritime regions (collectively abbreviated in places below to “the Charentes”) in south-west France include sands, which have been commercially exploited in a number of quarries, limestones and marls. During the past 10 years important accumulations of amber containing a variety of fossils (Néraudeau et al., 2002; Nel et al., 2008) have also been recovered from several localities in this region. The first of these was discovered in a sand quarry at Archingeay-Les Nouillers, and was dated as latest Albian by Néraudeau et al. (2002). Others have since been reported from deposits considered to be early Cenomanian in age (e.g., Néraudeau et al., 2003, 2008). Although the Cenomanian age determinations are not

in doubt, the age of the oldest deposits of the Cretaceous succession, which rest unconformably on strata of late Jurassic (Kimmeridgian– Tithonian) age, are less certain, with dinoflagellate cysts recovered from marls beneath a conglomerate containing Cenomanian ostracods suggesting late Albian deposition. The aims of this paper are to (1) discuss and illustrate the megaspore assemblage recovered from units within this Cretaceous succession at several locations in the Charente and CharenteMaritime regions and one further north in Anjou Province in the context of the biostratigraphic framework of the amber-bearing deposits; (2) consider the possibility of differentiating latest Albian sediments from those of the Cenomanian; and (3) comment on the palaeoenvironmental implications of the assemblage. 2. Geological setting

⁎ Corresponding author. E-mail address: [email protected] (D.J. Batten). 0034-6667/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.revpalbo.2010.03.012

Lower Cenomanian deposits crop out widely in Charente and Charente-Maritime (Fig. 1), both in cliffs on the Atlantic coast and in

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D.J. Batten et al. / Review of Palaeobotany and Palynology 161 (2010) 151–167

Fig. 1. Geographical and geological setting of the Charentes sections sampled. The star in the inset figure indicates the approximate location of Le Brouillard quarry in Anjou Province.

several quarries inland (Moreau, 1993a,b; Néraudeau et al., 1997). They are transgressive and erosive on uppermost Jurassic strata (generally Kimmeridgian, locally Tithonian) and comprise two series of fluviatile and paralic sands and two of marine limestones and marls. The fluviatile and paralic sands contain several clay intercalations with local concentrations of plant impressions and/or lignite and amber (Néraudeau et al., 2002, 2003, 2008; Gomez et al., 2004; Perrichot, 2005; Peyrot et al., 2005; Coiffard et al., 2009; Girard et al., 2009). The older series of sand and clay were considered by Arnaud (1877), Moreau (1976, 1993a,b) and then Néraudeau et al. (1997) to represent lithological unit A, in turn subdivided into two sub-units (Fig. 2): A1 for heterogeneous sands rich in lignite and amber accumulations in the lower part (A1sl-A) and strongly cross-bedded in the upper part (A1sl-S) (Néraudeau et al., 2002); A2 for more homogeneous fine sands, mainly in horizontal beds and alternating with clays containing plant megafossils (Néraudeau et al., 2005) in the lower part (A2sm), more argillaceous but poor in plant megafossils in the upper part (A2a). These sand and clay alternations are overlain by marine limestones, corresponding to the base of lithological unit B and especially to sub-unit B1. This is a series of bioclastic (B1cs) and sandy (B1c, B1cg) limestones, with marly (B1m) and sandy (B1s) intercalations, especially rich in vertebrate remains, oysters and coastal echinoids at its base (B1cs) (Vullo et al., 2003). Calcareous sub-unit B1 is overlain by a series of estuarine to paralic sands and clay, corresponding to glauconitic sub-unit B2. These deposits are mainly argillaceous and rich in lignite (Agathoxylon), amber and vertebrates in the lower part (B2ms) (Néraudeau et al., 2003; Vullo et al., 2005), composed of sand locally rich in oysters (Rhynchostreon suborbiculatum) in the middle part (B2gl) (Videt and Néraudeau, 2003), and comprising marls or limestones with oysters (R. suborbiculatum) and echinoids (Archiacia, Catopygus, and Mecaster) in the upper part (B2m) (Néraudeau and Moreau, 1989). The highest part of the Lower Cenomanian in the Charentes is marked by the return of marine sediments that clearly accumulated in deeper conditions compared to the underlying facies. It corresponds to sub-unit B3, composed of an alternation of limestones (B3c) with rudists (Ichthyosarcolithes triangularis, Sphaerulites foliaceus) and marls with oysters (R. suborbiculatum) (Videt, 2004) and locally echinoids (Jolyclypus, Mecaster, and Micraster) (Saucède and Nérau-

deau, 2006). The top of the sub-unit consists of marls or limestones (B3mc) with crinoids (Isocrinus cenomanensis), which mark the maximum flooding of the early Cenomanian in the northern Aquitaine Basin (Néraudeau et al., 1997). This is overlain by argillaceous deposits of unit C, which is attributed to the Middle Cenomanian here (Fig. 2). Plant compressions, lignite and amber occur in the lowermost part of this unit. The biostratigraphic attribution of the sub-units B1, B2 and B3 to the Lower Cenomanian is based on the presence of the large benthic foraminifera Orbitolina plana and O. conica (Moreau, 1993a,b). Reference of sub-unit A2 to the Lower Cenomanian is based on palynology (Moreau, 1993a). The stratigraphic age of sub-unit A1 has been a matter of some dispute. In the quarry at Archingeay-Les Nouillers, the basal lignites were thought to have accumulated during the late Albian according to the dinoflagellate cyst assemblages and especially the lack of typical basal Cenomanian species (Néraudeau et al., 2002; Dejax and Masure, 2005; Peyrot et al., 2005), but in a quarry at Cadeuil, the conglomerate overlying the basal lignites is clearly dated as early Cenomanian on the basis of the ostracod assemblages recovered (Néraudeau et al., 2008). Consequently, the upper part of A1 (A1sl-S) can be regarded as early Cenomanian but the age of lower part (A1sl-A) remains uncertain. Diachronism of the lignite-rich layers in the succession is possible, but only on a very limited stratigraphic scale. For example, it is not certain that the different lignitic facies of sub-unit B2 always reflect deposition during the same time interval (of some thousands of years) but they are always within the same third-order, sequence-stratigraphic interval between the basal hardgrounds of Ce2 and Ce3 (see Néraudeau et al., 1997). As a result, all of the deposits of this sub-unit can be regarded as sub-contemporaneous. The same applies to subunits A1 and A2, which are separated by a massive conglomerate and a clear hardground in all of the quarries where both are exposed. 3. Material and methods Sediment samples that have yielded the megaspores considered in this paper come from Archingeay-Les Nouillers, Puy-Puy and Les Renardières quarries at Tonnay-Charente, La Buzinie and Le Brouillard quarries, and Fouras tidal flat on the coast (Fig. 1). Le Brouillard is in Anjou Province to the north; the others are all within the Charente and Charente-Maritime Départements. Stratigraphic units A, sub-units A1

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Fig. 2. Synthetic stratigraphic section of the uppermost Albian–lowermost Middle Cenomanian in the Charentes, south-west France. The solid circles indicate the stratigraphic levels from which megaspores have been recovered. Owing to uncertainty of field relationships, two of these are questioned (see text).

and possibly A2; B, sub-units B2 and possibly B3; and C are represented, as listed below: A1, lower part (A1sl-A, Fig. 2), latest Albian or earliest Cenomanian: Archingeay-Les Nouillers quarry, two levels, one with amber and fossil wood and one with plant impressions but no amber; PuyPuy quarry, level with plant compressions, fossil wood and amber. A1 or A2: Les Renardières quarry, level with plant compressions, fossil wood and amber. Until recently the exposure was regarded as referable to A1, but this is now questioned, with the productive level possibly referable to A2 instead. B2, lowest part (B2ms), early Cenomanian: Fouras tidal flat, level with amber and fossil wood referred to below as Fouras Bois-Vert. B3 (lower part, B3c?) or C, late early or earliest mid Cenomanian: La Buzinie, level with fossil wood, plant compressions and amber. B3–C, latest early to earliest mid Cenomanian, Le Brouillard, level with plant compressions and amber. The extraction of megaspores involved conventional micropalaeontological processing methods, which included soaking c. 100 g of sediment in 200 ml of 10% w/v hydrogen peroxide until the sample was thoroughly disaggregated. Owing to the differences in density

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between plant material and mineral grains, following wet sieving the residues were “swirled” on a large watch glass to isolate the megaspores and “seed cuticles” from the mineral detritus. These were then picked out from the predominantly organic residues using a fine paint brush and deposited in standard micropalaeontological cellslides prior to being examined under light and scanning electron microscopes, the latter in the Muséum National d'Histoire Naturelle, Paris. As previously noted by Batten (e.g., in Batten, 1995), owing to its hierarchical nature, the formal system of megaspore taxonomy proposed by Potonié (1956 and later papers) serves little purpose and is difficult to apply. It may separate genera of similar appearance and group together others that are clearly distinct. Hence, the megaspores recorded from the levels noted above are considered in an order that accords approximately to their general morphology and degree of exine sculpture and complexity. Although the assemblages recovered contain a variety of taxa, there are insufficient examples of most of them to allow for their morphological variation to be adequately taken into account. Hence, no formal descriptions or synonymies are provided. Instead, representative specimens are illustrated with scanning electron micrographs and/or reflected light photographs and comments on their morphology and the identifications are provided. A few examples of the “seed cuticles” Costatheca Hall, 1967 and Spermatites Miner, 1935 were also recovered, along with termite faecal pellets attributable to Microcarpolithes hexagonalis Vangerow, 1954, but these are not considered here. This study highlighted a common problem with fossil megaspore studies and that is the lack of adequate descriptions and illustrations of many species. Until the availability of the scanning electron microscope during the second half of the 1960s, morphological analyses were based solely on transmitted and reflected light studies, with illustrations usually being limited to one or two photographs and/or drawings. Problems associated with, in particular, depth of focus and thick exines, coupled with often mediocre printing quality mean that morphological details in published photographs are often difficult, and sometimes impossible, to discern, and whereas some drawings are accurate representations of specimens at low magnifications (e.g., those in Harris, 1961), others are not very helpful (e.g., those in Dijkstra, 1949). Most transmitted light analyses have to rely on oxidation of the exine to “clear” spores sufficiently for light to be able to pass through them, which in the case of thick-walled forms, often means that they look very different from unoxidised specimens. The advent of scanning electron microscopy meant that the observer could examine specimens in much greater detail than previously and take the morphological features revealed into account when erecting new species, the only disadvantage being that most specimens had to be coated (e.g., with gold-palladium) to prevent charging, thus obscuring their natural colour. Despite this technological advance, together with the less common use of transmission electron microscopy for studying exine structure, identification problems have persisted. For many species, only one type of illustration was provided when they were erected. As a result, authors are commonly unable to compare like with like. More often than not the descriptions are also too superficial and based on too few specimens, which means that the full range of morphological variation is not taken into account. Hence, many subsequent records of species are suspect if not definitely incorrect, which is why, in common with some other recent papers (e.g., Lupia, 2004), most of the forms discussed in the following section are only compared with previously described species or identified in open nomenclature. These comparisons, and in some cases the lack of them, suggest that the Charentes and Anjou assemblages contain a number of taxa that are potentially of biostratigraphic value, but formal description must await the recovery of more specimens. The figured specimens will be deposited in the collections of the British Geological Survey, Keyworth, in due course.

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4. Systematic palaeontology Trileites Erdtman, 1947 ex Potonié, 1956 Type species: Trileites spurius (Dijkstra, 1951) Potonié, 1956 Trileites sp. cf. T. persimilis (Harris, 1935) Potonié, 1956 (Plate I, 1) Locality: Fouras Bois-Vert, B2. Remarks: Smooth-walled megaspores are generally difficult to identify at species level owing to the lack of morphological characters on which to distinguish them coupled with the fact that several of the taxa that have been described are not clearly differentiated from each other. In addition, as with all spores, variations in the quality of preservation, which include deformation, shrinkage and fracturing of exines, can also cause problems. The description of specimens recorded by Floquet and Lachkar (1979) as Trileites persimilis from late Cenomanian deposits in Spain and the accompanying illustration (Floquet and Lachkar, 1979, pl. 1, fig. 1) suggest that their material is comparable but not identical to the smooth-walled specimen shown here (Plate I, 1). It is also a possible candidate for inclusion in Trileites subrotundus (Miner, 1932) Potonié, 1956, a species that was erected on the basis of spores recovered from the Atane Formation of West Greenland, originally dated as late Turonian–Coniacian but more recently considered to be late Albian– Cenomanian, with the youngest deposits possibly of Turonian age (Koppelhus and Pedersen, 1993); however, it has not been reported again since then. Trileites persimilis was originally described from Rhaetian deposits of the Kap Stewart Formation of East Greenland (now Kap Stewart Group: e.g., Surlyk, 2003), but most of the several attributions to this species subsequently have been of Cretaceous age. Other smooth-walled spores of similar general appearance include some from Rhaetian deposits in southern Denmark referred by Bertelsen and Michelsen (1970) to Trileites sp. cf. T. pedinacron (Harris, 1935) Potonié, 1956. Jux and Kempf (1971) thin-sectioned and examined a few of these under a transmission electron microscope. They regarded the wall structure of this morphotype to be sufficiently distinctive to merit erecting a new genus, Tasmanitriletes, to accommodate it. Bacutriletes van der Hammen, 1955 ex Potonié, 1956 emend. Banerji et al., 1984 Type species. Bacutriletes tylotus (Harris, 1935) Potonié, 1956 Bacutriletes colinii Lachkar, in Floquet and Lachkar, 1979 (Plate I, 4–10; Plate VI, 5, 6) Localities. Archingeay-Les Nouillers, A1; Puy-Puy, A1; Fouras BoisVert, B2; Le Brouillard, B3–C. Remarks. The description of specimens recorded by Floquet and Lachkar (1979) as Bacutriletes colinii from late Cenomanian deposits in Spain and the accompanying illustrations (Floquet and Lachkar, 1979, pl. 1, figs. 2, 3) suggest that their material is closely similar to more or less identical to some of the verrucate to baculate specimens encountered in this study (e.g., that illustrated in Plate I, 6). Their description does not clearly take into account specimens that are rather more obviously baculate (e.g., those in Plate I, 4, 7–9 herein), but since these are not undoubtedly separable from this species, they are considered to be referable to it. Bacutriletes sp. of Colin (1975), reported from the Cenomanian Salardais lignites of the Dordogne region of south-west France, was placed in synonymy by Floquet and

Lachkar, although the specimen illustrated (Colin, 1975, pl. 1, fig. 3) seems to be rather more robustly and perhaps also more densely sculptured. Of other baculate species that have been reported from Cretaceous deposits, Bacutriletes greenlandicus (Miner, 1932) Potonié, 1956, originally described from the Atane Formation of West Greenland (late Albian–Cenomanian or possibly Turonian in age: see above), is most closely comparable. Their size ranges overlap, with the mean diameter, the mean width and height of the bacula and triradiate ridge, and the thickness of the wall of B. greenlandicus all being somewhat greater according to the data presented by Singh (1983), although the mean diameter of the three specimens recorded by Kovach and Dilcher (1988) as 495 μm is well within the range of 450– 650 μm noted by Floquet and Lachkar. The specimens of B. greenlandicus illustrated by Miner (1932, figs. 10, 11) and Singh (1983, pl. 32, figs. 4–7) and that recorded as B. cf. B. greenlandicus by Sweet (1979, pl. 3, fig. 6) are all more distinctly baculate than B. colinii and some of the specimens figured here. A further characteristic of B. greenlandicus is that there are striations on the bacula (Singh, 1983; Kovach and Dilcher, 1988). Other similar taxa include: (1) Bacutriletes nanus (Dijkstra, 1949) Potonié, 1956, which is much smaller than B. colinii and, according to Batten (1988), has a sculpture that is dominated by coni rather than bacula; (2) some of the specimens from earliest Aptian deposits of northern Germany identified as Verrutriletes dasyplocoides Schultz and Noll, 1987 by Batten (1995, pl. 4, figs. 3, 4, 6), which are also smaller; (3) specimens from early Cretaceous (Valanginian–Hauterivian) deposits of the lower Strzelecki Group in the Gippsland Basin of Victoria, Australia, referred by McLoughlin et al. (2002) to Verrutriletes sp. cf. V. dubius (Dijkstra, 1949) Potonié, 1956, the diameter of the largest being equal to that of the smallest B. colinii; and (4) B. tylotus, the type species of the genus, all positive identifications of which are from late Triassic–early Jurassic (late Norian–Hettangian) deposits. Bacutriletes sp. (Plate VI, 1, 2) Locality. Puy-Puy, A1. Remarks. This baculate spore is smaller than Bacutriletes colinii (c. 380 μm as opposed to c. 450–650 μm) and has less convex sides, a more prominent triradiate ridge and more tightly packed verrucate to mostly baculate, but also a few more or less clavate, elements over the entire surface. Its colour in reflected light also differs from that of B. colinii in being a more uniformly darker brownish red. It bears some resemblance to Bacutriletes ferulus Koppelhus and Batten, 1989, recovered from deposits in southern Sweden that are either late Santonian or early Campanian in age, but is slightly smaller and the sculpture of the distal face is more tightly and uniformly distributed. Bacutriletes triangulatus Taylor and Taylor, 1988, from early Aptian beds near the base of the Baqueró Formation of Santa Cruz Province, Argentina, is sculptured with similarly densely packed baculate to clavate elements but it is larger and convexly triangular to subcircular in polar view. Verrutriletes van der Hammen, 1955 ex Potonié, 1956 emend. Binda and Srivastava, 1968 Type species. Verrutriletes compositipunctatus (Dijkstra, 1949) Potonié, 1956 Verrutriletes sp. cf. V. dubius (Dijkstra, 1949) Potonié, 1956 (Plate I, 3)

Plate I. Megaspores from mid Cretaceous deposits in western France. Scale bars represent 100 μm. 1. 2. 3. 4–10.

Trileites sp. cf. T. persimilis Harris (1935) Potonié, 1956: Fouras Bois-Vert, B2. Verrutriletes sp. 1: Archingeay-Les Nouillers, A1. Verrutriletes sp. cf. V. dubius (Dijkstra, 1949) Potonié, 1956: Archingeay-Les Nouillers, A1. Bacutriletes colinii Lachkar, in Floquet and Lachkar, 1979: 4, 5, Puy-Puy, A1; 6, Archingeay-Les Nouillers, A1; 7, 9, same specimen, the latter showing detail of sculpture around triradiate ridge, Fouras Bois-Vert, B2; 8, 10, Le Brouillard, B3–C.

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Locality. Archingeay-Les Nouillers, A1. Remarks. The spore illustrated on Plate I, 3 is similar but somewhat smaller than the specimens from the Cenomanian and late Turonian lignites and lignite-rich clays of the Dordogne region of south-west France referred by Colin (1975, p. 17, pl. 1, figs. 4, 5) to Verrutriletes sp. cf. V. dubius. It is also not very well preserved and barely within the size range given for the species by Dijkstra (1949: 400–750 μm) and Batten (1988: 390–750 μm). Although none of the sculptural elements is flat-topped and therefore baculate, the possibility that it is a degraded specimen of Bacutriletes colinii cannot be dismissed. Verrutriletes sp. 1 (Plate I, 2) Locality. Archingeay-Les Nouillers, A1. Remarks. The sculpture of the specimen illustrated here consists of both verrucae and rugulae. Being the only example of this form encountered, it is unclear to which species it is most closely similar; hence the identification in open nomenclature. Verrutriletes sp. 2 (Plate II, 7) Locality. Puy-Puy, A1. Remarks. This specimen with its triangular shape, prominent triradiate ridge and verrucate sculpture in which the dimensions of the verrucae become smaller towards the proximal pole, is not clearly attributable to any previously described verrucate species. In general aspect it is superficially similar to the late Cretaceous spore in the collection of Dijkstra (1949) referred by Batten (1988, p. 6, pl. 5, fig. 4) to Bacutriletes sp., but is considerably larger (400 μm as opposed to 276 μm). Both this size difference and the sculpture distinguish it from the type species, Verrutriletes compositipunctatus. The specimen compared by Koppelhus and Batten (1989, p. 102, pl. 5, fig. 8) to V. compositipunctatus has more similar sculpture but it is also much smaller (224 μm). Verrutrilete minutus Yang and Sun, 1982, from early Jurassic deposits in the Junggar Basin, Xinjiang, China, bears some resemblance to the spore illustrated here, but the single specimen on which this species is based is again much smaller (314 μm). Rugotriletes van der Hammen, 1955 ex Potonié, 1956 Type species. Rugotriletes diktyotus van der Hammen, 1955 ex Potonié, 1956 Rugotriletes sp. cf. R. diktyotus van der Hammen, 1955 ex Potonié, 1956 (Plate II, 2) Locality. Archingeay-Les Nouillers, A1. Remarks. The sculpture of the specimen illustrated is similar to that of the type species of Rugotriletes, but the muri are proportionally a little more delicate and the spore lacks an irregular, coarsely reticulate to spongiose mass of exine around the proximal pole, although the rather ragged triradiate ridge in this region may be evidence of its former presence. Rugotriletes sp. cf. R. comptus Singh, 1983 (Plate VII, 7, 8) Locality. Fouras Bois-Vert, B2. Remarks. The single specimen encountered is very similar to the type material of Rugotriletes comptus (mistakenly referred to Rugutriletes by Singh, 1983), which was described from the Dunvegan and lower Kaskapau formations of the Peace River area of Alberta (Canada), dated as middle–late Cenomanian. Minor differences appear to be

somewhat lower irregular muri and a more spongiose neck (described by Singh as a gula) around the triradiate suture in the CharenteMaritime specimen. Erlansonisporites Potonié, 1956 Type species. Erlansonisporites erlansonii (Miner, 1932) Potonié, 1956 Erlansonisporites sp. cf. E. sparassis (Plate VI, 7, 8) Locality. Puy-Puy, A1. Remarks. The most widely reported species of Erlansonisporites is E. sparassis (Murray, 1939) Potonié, 1956 and, probably partly as a result of this, it also has the longest stratigraphic range, having been reported from Pliensbachian–Maastrichtian deposits (e.g., Kendall, 1942; Harris, 1961; Gunther and Hills, 1972; Marcinkiewicz, 1981; Waksmundzka, 1983; Schultz and Noll, 1987; Munk and Granzow, 1992; Villar de Seoane and Archangelsky, 2008). Harris (1961) remarked that it is a difficult species to study because of its very variable size and form. He found it necessary to emend its diagnosis to accommodate a wider morphological range than Murray (1939) allowed in his description of Middle Jurassic material from the East Midlands of England. Despite this, attributions to the species by some authors seem to be rather at variance with the broader circumscription. Apart from the spore shown in Plate VI, 7, 8, which displays characters that more or less agree with those of E. sparassis, the other specimens of Erlansonisporites illustrated here do not belong in this species. The proximal face has been compressed obliquely; nevertheless, there is no evidence of significantly elevated flanges bordering the trilete suture. Erlansonisporites erlansonii (Miner, 1932) Potonié, 1956, which was erected on the basis of specimens from late Cretaceous coals in East Greenland, is similar but has a more reticulate sculpture, the surface of E. sparassis being covered with ridges that form only a very imperfect network. Records of this species are confined to Cretaceous deposits (e.g., Hueber, 1982; Singh, 1983; Kovach and Dilcher, 1988). Erlansonisporites indicus Banerji, Jana and Maheshwari, 1984, from the early Cretaceous Bhuj Formation in the Kachchh District of India (see also Jana, 2004), is another very similar taxon. Erlansonisporites sp. 1 (Plate VII, 1, 2) Locality. Fouras Bois-Vert, B2. Remarks. This spore is similar in size to Erlansonisporites sp. cf. E. sparassis but more finely murornate. Erlansonisporites sp. 2 (Plate II, 3; Plate VI, 13, 14; Plate VII, 3, 4) Localities. Fouras Bois-Vert, B2; Le Brouillard, B3–C. Remarks. The specimens illustrated here suggest the occurrence of a species similar to some of the spore-types that have previously been included by authors in both Erlansonisporites sparassis and E. erlansonii, but which have atypically more prominent triradiate flanges. Illustrations of these may be found in, for example, Kovach and Dilcher (1988, pl. 1, fig. 12, which they considered to be an immature or abortive form of E. erlansonii), and Waksmundzka (1983, pl. 51, fig. 2, recorded as E. sparassis). A tendency for the muri of some specimens to radiate away from the triradiate flange on the proximal face, as shown in Plate II, 3, has led some authors to refer similar forms to Striatriletes van der Hammen, 1955 ex Potonié, 1956. An example of this is Striatriletes aureus Huckreide, 1982, erected on the basis of spores of Aptian age from Sauerland, Germany.

Plate II. Megaspores from mid Cretaceous deposits in western France. Scale bars represent 100 μm. 1. 2. 3. 4–6, 8. 7. 9–11.

Erlansonisporites sp. 4?: Puy-Puy, A1. Rugotriletes sp. cf. R. diktyotus van der Hammen, 1955 ex Potonié, 1956: Archingeay-Les Nouillers, A1. Erlansonisporites sp. 2: Le Brouillard, B3–C. Echitriletes sp. 1: 4, 5, same specimen, the latter showing detail of sculpture of proximal surface near and at equator, Fouras Bois-Vert, B2; 6, La Buzinie, B3 or C; 8, Le Brouillard, B3–C. Verrutriletes sp. 2: Puy-Puy, A1. Minerisporites sp. 1: 9, La Buzinie, B3 or C; 10, 11, Puy-Puy, A1.

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Erlansonisporites altus Li and Batten, in Li et al., 1987, described from the Damoguihe Formation in Inner Mongolia, China, tentatively dated as Barremian–Aptian, has a very pronounced triradiate flange. It differs from Erlansonisporites sp. 2 in having a rugulate sculpture that is more strongly developed on the proximal face than distally, with the rugulae increasing in height towards the triradiate flange. The triradiate flanges of two of the specimens illustrated (Plate VI, 13, 14; Plate VII, 3, 4) appear as a spongiose mass of exine at the proximal pole. A similar feature is apparent on a specimen from the late Coniacian–early Santonian Tamagawa Formation in north-eastern Japan that Takahashi et al. (2001, fig. 2A) attributed to Erlansonisporites scanicus Koppelhus and Batten, 1989. They described it (Takahashi et al., 2001, p. 432) as “constricted muri of the robust reticulum at the proximal pole”, which rendered the trilete laesurae unclear. Erlansonisporites sp. 3 (Plate VI, 9, 10) Locality. Fouras Bois-Vert, B2. Remarks. The sculpture of this spore-type consists of less clearly defined muri and rugulae than is apparent in the other forms that are attributable to Erlansonisporites, giving the whole of the surface a crumpled appearance. It is possibly comparable to the specimens identified as Verrutriletes cf. compositipunctatus (Dijkstra, 1949) Potonié, 1956 by Colin (1975, p. 17, pl. 1, fig. 6). Erlansonisporites sp. 4 (Plate VII, 5, 6) Locality. Fouras Bois-Vert, B2 (also Puy-Puy A1?, Plate II, 1) Remarks. This large, dark-walled megaspore from Fouras Bois-Vert, B2 has a slightly iridescent appearance in reflected light, suggesting that the structure of the exine is similar to that known from both fossil and extant megaspores of selaginellalean affinity. Much of the wall is sculptured with a reticulum that consists of comparatively narrow muri of low elevation surrounding lumina that are mainly between 40 and 115 μm in maximum diameter. Despite the openness of the sculpture, the triradiate flange is not clearly delineated. On the specimen illustrated here, it is probably towards the top where the muri are slightly higher and do not form a reticulum. Similar spores have not definitely been reported previously from Cretaceous deposits. Those from the Cenomanian Salardais lignites of the Dordogne region of south-west France identified by Colin (1975, p. 18, pl. 1, fig. 7) as Horstisporites sp. bear a slight resemblance. Echitriletes van der Hammen, 1955 ex Potonié, 1956 Type species. Echitriletes lanatus (Dijkstra, 1951) Potonié, 1956 Echitriletes sp. 1 (Plate II, 4–6, 8) Localities. Puy-Puy, A1, Fouras Bois-Vert, B2; La Buzinie, B3 or C; Le Brouillard, B3–C. Remarks. The sculpture of the specimens illustrated is slightly atypical for the genus in that it ranges from simple hairs or spines to spinose complexes with bifurcated, trifurcated or even more complicated tips, some of which may be recurved. The specimen from late Turonian lignite-rich clays of the Dordogne region of south-west France identified by Colin (1975, p. 18, pl. 1, fig. 9) as Echitriletes cf. lanatus (Dijkstra, 1951) Potonié, 1956 resembles them to some extent but has a simpler echinate sculpture (see below). The spore body of Echitriletes zemechensis Knobloch, 1984, described from Cenomanian deposits of the Peruc Formation in the Bohemian Cretaceous Basin, is covered with spines that may have branched tips, but these elements are proportionally larger and more widely spaced than those of the Charentes and Anjou specimens. The Czech species also differs in other ways (see under Arcellites sp.). Echitriletes sp. 2 (Plate VI, 11, 12, 15, 16) Locality. Fouras Bois-Vert, B2. Remarks. The tightly packed hairs on the surface of specimens of this megaspore-type commonly obscure the triradiate ridge making it difficult to locate. Although somewhat larger than the single specimen

referred to Echitriletes cf. lanatus by Colin (1975, see above), they are smaller than those from the English Wealden (early Cretaceous) samples on which Dijkstra (1951) based E. lanatus (see also Batten, 1975, pl. 13, fig. 4). The hairs (capilli) that cover Echitriletes lanuginosus Huckreide, 1982, are mostly branched but, like E. lanatus, this species is also much larger. The scanning electron micrograph of Colin's specimen shows that some of the hairs on the body are branched but rather less complexly than those of Echitriletes sp. 1. Recovery of additional specimens in the future might reveal whether these differences in sculpture indicate that two megaspore species are represented, as suggested here, or simply reflect the range of variation encountered in a single taxon. Echitriletes densicapillosus Singh, 1983, described from the Cenomanian Dunvegan Formation of the Peace River area of Alberta (Canada), differs in being smaller and covered with shorter, finer hairs. Tenellisporites spinatus Peake, in Hall and Peake, 1968, erected on the basis of spores extracted from Cenomanian deposits in Minnesota (USA), is smaller and covered with evenly distributed but widely spaced spines that are sometimes forked at their tips. As noted by Singh (1983), the characters of this species do not conform to those of Tenellisporites. The form of the appendages of Flabellisporites crinitus Marcinkiewicz, 1978, described from late Triassic deposits in Poland, differs from that of all of the Cretaceous taxa noted here, as does their arrangement on the spore. Henrisporites Potonié, 1956 emend. Binda and Srivastava, 1968 Type species. Henrisporites affinis (Dijkstra, 1951) Potonié, 1956 Henrisporites sp. (Plate III, 4) Locality. Archingeay-Les Nouillers, A1. Remarks. The specimen illustrated is similar in general aspect to Minerisporites sp. cf. M. dissimilis Tschudy, 1976, as reported below, but lacks a reticulate sculpture. The few small protuberances on the surface suggest that reference to Henrisporites is more appropriate. It is similar to H. levis Lachkar, in Floquet and Lachkar, 1979, which was described as not having any particular ornament (hence the specific epithet levis), although at high magnification it was reported to have a “light granulation” (Floquet and Lachkar, 1979, p. 146). Owing to its essentially smooth surface, this species was transferred to Minerisporites by Batten and Koppelhus (1993). ?Henrisporites sp. (Plate III, 5, 6) Locality. Fouras Bois-Vert, B2. Remarks. The two specimens illustrated are sculptured with a large number of small coni on the proximal face, which may be associated in part with a barely discernible fine reticulum. The rather irregular zona and triradiate flange suggest that they are degraded specimens which, were they better (more completely) preserved, might not be attributable to Henrisporites. Minerisporites Potonié, 1956 Type species. Minerisporites mirabilis (Miner, 1935) Potonié, 1956 Minerisporites mercadensis Floquet, in Floquet and Lachkar, 1979 (Plate VII, 14, 15) Locality. Puy-Puy, A1. Remarks. A few of the spores recovered seem to have the characters of Minerisporites mercadensis, which was erected on the basis of specimens recovered from late Cenomanian deposits in Spain. The spore body of this species has an ill-defined sculpture of indentations and mounds that may, in part, give it a vaguely verrucate to imperfectly reticulate surface. Minerisporites sp. 1 (Plate II, 9–11; Plate III, 1, 3) Localities. Archingeay-Les Nouillers, A1; Puy-Puy, A1; Fouras BoisVert, B2; La Buzinie, B3 or C.

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Plate III. Megaspores from mid Cretaceous deposits in western France. Scale bars represent 100 μm. 1, 3. 2. 4. 5, 6. 7. 8.

Minerisporites sp. 1: 1, Fouras Bois-Vert, B2; 3, Archingeay-Les Nouillers, A1. Minerisporites sp. 2: Le Brouillard, B3–C. Henrisporites sp.: Archingeay-Les Nouillers, A1. ?Henrisporites sp.: Fouras Bois-Vert, B2. ?Tenellisporites sp.: Fouras Bois-Vert, B2. Dijkstraisporites sp. 1: Fouras Bois-Vert, B2.

Remarks. The description of specimens recorded by Floquet and Lachkar (1979) as Minerisporites dissimilis Tschudy, 1976 from late Cenomanian deposits in Spain and the accompanying illustrations (Floquet and Lachkar, 1979, pl. 2, figs. 1–4) suggest that their material is closely similar to more or less identical to some of the specimens figured here. However, reference to M. dissimilis is inappropriate

because this species differs in having a triradiate flange that is notched at the proximal pole and a more complex reticulate sculpture. Most specimens are also much larger than those from Charente and Charente-Maritime: Tschudy (1976) gave a size range of 408–800 μm for M. dissimilis, whereas the largest specimens encountered in this study are in the region of 440 μm in maximum diameter.

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Other published species that bear some resemblance to the Charentes spores include Minerisporites delicatus and M. irregularis, both erected by Gunther and Hills (1972) from deposits in the Nordegg area of Alberta (Canada) dated as Campanian and Campanian–Maastrichtian respectively. Sweet (1979) also reported M. irregularis from beds questionably dated as Campanian in the Eureka Sound Formation on Ellef Ringnes Island, Arctic Canada. Both species are, however, smaller than the Charentes specimens. Minerisporites sp. 2 (Plate III, 2) Locality. Le Brouillard, B3–C. Remarks. The specimens referred to M. pseudorichardsonii Gunther and Hills, 1972 by Lachkar, in Floquet and Lachkar (1979, p. 145, pl. 2, figs. 5, 6) are closely similar, but the attribution to this species is not very convincing when compared with either the two illustrations provided by Gunther and Hills or the spores placed in this species by Tschudy (1976, pl. 4, figs. 1–6), who illustrated five specimens. Dijkstraisporites Potonié, 1956 Type species. Dijkstraisporites helios (Dijkstra, 1951) Potonié, 1956 Dijkstraisporites sp. 1 (Plate III, 8) Locality. Fouras Bois-Vert, B2. Remarks. The specimen illustrated has a corona that consists of comparatively wide processes extending rather unevenly from the equator giving it a crumpled appearance. The triradiate flange is similar in form but breaks down into smaller, more discrete elements towards the proximal pole. The surface of the body of the spore is uneven, scabrate to weakly reticulate. Although having the basic form of species that are attributable to Dijkstraisporites (see discussion in Batten and Koppelhus, 1993), it differs from all those that have been erected hitherto.

Localities. Archingeay-Les Nouillers, A1; Puy-Puy, A1; Les Renardières, A1 or A2; Fouras Bois-Vert, B2. Remarks. Paxillitriletes dakotaensis was based on spores recovered from the Cenomanian Dakota Formation of Iowa (USA). Although the specimens illustrated by Hall (1963, figs. 37–39) suggest that they are not morphologically identical to those figured here, most of the appendages extending from the triradiate flange apparently being somewhat wider and most of the distal projections not being hooked, the accompanying description implies that they are closely similar. The illustration of P. dakotaensis from the same formation in Kansas (USA) provided by Kovach and Dilcher (1988, pl. 4, fig. 7), the description and illustrations of specimens recovered by Tschudy (1975, p. 18, fig. 3a–g) from a sample of lignitic clay of probable Cenomanian age from Massachusetts (USA), and the measurements and illustrations of specimens from Cenomanian deposits of the Peace River area of Alberta (Canada) given by Singh (1983, p. 109, pl. 35, fig. 10; pl. 36, figs. 1–4, pl. 37, fig. 1) provide further support for this conclusion. Spores referable to Paxillitriletes midas (Dijkstra, 1951) Hall and Nicolson, 1973 and P. alatus (Batten, 1969) Hall and Nicolson, 1973, originally recorded from Wealden beds in the Netherlands and southeast England respectively, have appendages scattered over their distal faces. The former taxon is, however, smaller than P. dakotaensis and the distal projections on P. alatus are more numerous, smaller and more delicate. Although there are reticulate or spinose distal projections on some other species of the genus, these are less prominent and form part of a more uniform sculpture.

Paxillitriletes Hall and Nicolson, 1973 Type species. Paxillitriletes reticulatus (Mädler, 1954) Hall and Nicolson, 1973

?Paxillitriletes sp. (Plate VII, 9–11) Locality. Fouras Bois-Vert, B2; La Buzinie, B3 or C. Remarks. Species of Paxillitriletes may have triradiate sutures that are bordered by elevated, more or less continuous, though commonly irregularly ribbed, flanges or somewhat lower membranes from which appendages of varying length extend upwards. Additional characters are a proximal face that also bears appendages, which increase in height towards the triradiate flange, and a zona that is wider in radial than in interradial regions. By contrast, both the triradiate flange and zona of species of Minerisporites are usually fairly uniform, continuous membranes, the proximal face does not bear appendages that become higher towards the triradiate flange, and the distal face lacks prominent projections. The Charente specimens illustrated here lack proximal appendages adjacent to the triradiate flange yet display distal projections, which, although not long, clearly extend beyond the reticulate sculpture that covers the rest of the distal face. The body of the spore from La Buzinie, B3 or C (Plate VII, 9, 10) is smaller than that of Paxillitriletes sp. cf. P. dakotaensis (c. 350 μm as opposed to 400– 560 μm) and, coupled with the form of the triradiate flange and zona, suggests that is unlikely to be an immature example of this species, especially since a much larger specimen from Fouras Bois-Vert, B2 (Plate VII, 11) is morphologically similar. Paxillitriletes maheshwarii, described by Jana and Ghosh (1997, p. 154, pl. 2, figs. 4–10) from the Athgarh Formation in the Mahanadi Basin of India, which they dated as early Cretaceous, resembles the Charentes specimens to some extent in general aspect but lacks distal appendages.

Paxillitriletes sp. cf. P. dakotaensis (Hall, 1963) Hall and Nicolson, 1973 (Plate IV, 1–3, 5)

Tenellisporites Potonié, 1956 Type species. Tenellisporites tenellus (Dijkstra, 1949) Potonié, 1956

Dijkstraisporites sp. 2 (Plate VI, 3, 4) Locality. La Buzinie, B3 or C. Remarks. The specimen illustrated has an equatorial extension of the exine that ranges from being almost as wide as the radius of the spore body in interradial regions to wider than this where the pronounced triradiate flange extends onto it. The outer margin of this zona has a rather serrated appearance resulting from the presence of several ribs in each interradial segment. The triradiate flange becomes sinuous towards the proximal pole. The sculpture of the central body is weakly reticulate with a few small spinose elements. In common with Dijkstraisporites sp. 1, this form differs from all previously described species of the genus. Morphologically closest is Minerisporites pterotus, described by Singh (1983, pp. 107, 108, pl. 35, figs. 7, 8) from early–middle Cenomanian deposits in the Peace River area of Alberta (Canada). This has a very wide zona and a comparatively small central body, features that led Batten and Koppelhus (1993) to transfer it to Dijkstraisporites. The zona was described as bearing radial striations, but these are finer than in the specimen illustrated here. The species also differs in other ways.

Plate IV. Megaspores from mid Cretaceous deposits in western France. Scale bars represent 100 μm. 1–3, 5. 4. 6. 7, 8.

Paxillitriletes sp. cf. P. dakotaensis (Hall, 1963) Hall and Nicolson, 1973: 1, Puy-Puy, A1; 2, Les Renardières, A1 or A2; 3, Fouras Bois-Vert, B2; 5, Archingeay-Les Nouillers, A1. Arcellites sp.: La Buzinie, B3 or C. Ariadnaesporites sp.: Le Brouillard, B3–C. Molaspora lobata (Dijkstra, 1949) Hall, in Hall and Peake, 1968: Puy-Puy, A1.

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Plate V. Megaspores from mid Cretaceous deposits in western France. Scale bars represent 100 μm in 1 and 10 μm in 2–4. 1–4.

Molaspora lobata (Dijkstra, 1949) Hall, in Hall and Peake, 1968: 1, 3, 4, same specimen, Le Brouillard, B3–C; 2, same specimen as in Plate IV, 8, Puy-Puy A1.

Tenellisporites spp. (Plate VII, 12, 13; ?Plate III, 7) Localities. Fouras Bois-Vert, B2; La Buzinie, B3 or C. Remarks. The separation of Tenellisporites from Dijkstraisporites can be difficult, especially when specimens are damaged, as in the case of that shown on Plate III, 7 in which flattened processes extend from wider triradiate and equatorial flanges than is typical for Tenellisporites. On the other hand, the width of the corona is substantially less than the radius of the spore, which does not favour reference to Dijkstraisporites. The specimen shown in Plate VII, 12, 13 is a more convincing example in which discrete processes on both the triradiate flange and corona are more pronounced. It is not readily referable to any of the species of this genus that have been erected. Tenellisporites brasinoviensis Knobloch, 1984, from late Cretaceous deposits of the Bohemian Basin, is perhaps the most closely similar. Arcellites Miner, 1935 emend. Ellis and Tschudy, 1964

Type species. Arcellites disciformis Miner, 1935 emend. Ellis and Tschudy, 1964 Arcellites sp. (Plate IV, 4) Locality. La Buzinie, B3 or C. Remarks. Although the single specimen found has been placed in Arcellites, it is unlike any other published species of this genus. Its neck is damaged but it appears to be leaf-like, and is the main reason for the attribution. The sculpture of the body of the spore is unusual in consisting of closely spaced cones that may have spinose tops, and in some cases are extended into hairs that may be bifurcated at their tips. Triletes squamosus Dijkstra, 1961, erected on the basis of a single specimen from subsurface Wealden deposits in the Netherlands, is superficially similar but has a reticulate sculpture. The body of Echitriletes zemechensis Knobloch, 1984, described from Cenomanian deposits of Bohemia (see under Echitriletes sp.), is covered with spines

Plate VI. Megaspores from mid Cretaceous deposits in western France. 1, 2. Bacutriletes sp., proximal and distal surfaces: Puy-Puy, A1. 3, 4. Dijkstraisporites sp. 2, proximal and distal surfaces: La Buzinie, B3 or C. 5, 6. Bacutriletes colinii Lachkar, in Floquet and Lachkar, 1979, proximal and distal surfaces: Puy-Puy, A1. 7, 8. Erlansonisporites sp. cf. E. sparassis, obliquely compressed specimen in lateral and distal views: Puy-Puy, A1. 9, 10. Erlansonisporites sp. 3, proximal and distal surfaces: Fouras Bois-Vert, B2. 11, 12, 15, 16. Echitriletes sp. 2: 11, 12, both sides of a laterally compressed specimen; 15, 16, both sides of a more or less laterally compressed specimen: Fouras Bois-Vert, B2. 13, 14. Erlansonisporites sp. 2, both sides of a more or less laterally compressed specimen: Fouras Bois-Vert, B2.

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that may have branched tips, but these elements are proportionally both rather more robust and more widely spaced, and the proximal neck, when observed, is not as strongly developed. Molaspora Schemel, 1950 emend. Hall, 1963

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Type species. Molaspora lobata (Dijkstra, 1949) Hall, in Hall and Peake, 1968 Molaspora lobata (Dijkstra, 1949) Hall, in Hall and Peake, 1968 (Plate IV, 7, 8; Plate V, 1–4)

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Plate VII. Megaspores from mid Cretaceous deposits in western France. 1, 2. 3, 4. 5, 6. 7, 8. 9, 10. 11. 12, 13. 14, 15.

Erlansonisporites sp. 1, both sides of a more or less laterally compressed specimen: Fouras Bois-Vert, B2. Erlansonisporites sp. 2, both sides of a more or less laterally compressed specimen: Fouras Bois-Vert, B2. Erlansonisporites sp. 4, both sides of a more or less laterally compressed specimen: Fouras Bois-Vert, B2. Rugotriletes sp. cf. R. comptus Singh, 1983, proximal and distal surfaces: Fouras Bois-Vert, B2. ?Paxillitriletes sp., both sides of a laterally compressed specimen: La Buzinie, B3 or C. ?Paxillitriletes sp., one side of a similar but much larger, laterally compressed specimen: Fouras Bois-Vert, B2. Tenellisporites sp., proximal and distal surfaces: La Buzinie, B3 or C. Minerisporites mercadensis Floquet, in Floquet and Lachkar, 1979, proximal and distal surfaces: Puy-Puy, A1.

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Localities. Puy-Puy A1; Le Brouillard, B3–C. Remarks. Of the five species that have been attributed to Molaspora, M. lobata has been the most commonly reported in the literature. The late Cretaceous specimens from the Netherlands on which it is based (Dijkstra, 1949) are sculptured with irregularly shaped granules and verrucate to papillate elements. The sculpture of the Charentes and Anjou spores differs somewhat in consisting of papillate rather than granulate elements, making them more closely similar to Paleocene specimens attributed to the species described by Dijkstra (1961) as Pyrobolospora lobata (Dijkstra, 1949) Hughes, 1955 (see e.g., Batten, 1988, pl. 17, fig. 2), and the dimensions of the neck are somewhat smaller. Although other records of the species, such as those of Hall (1963) and Kovach and Dilcher (1988) from the Cenomanian Dakota Formation in Iowa and Kansas (USA) respectively, and Takahashi et al. (2001) from the late Coniacian–early Santonian Tamagawa Formation in north-eastern Japan, may also show minor morphological differences from our specimens, at present there is no clear basis for attributing any of them to other species. Tosolini et al. (2002) reported four specimens of Molaspora lobata from two horizons in the upper Eumeralla Formation of the Otway Group in coastal sections of south-eastern Australia, which had been dated previously as late Albian on palynological grounds. One of the samples was from an exposure at Racecourse Steps from which Douglas (1973) recorded the unnamed specimen that Batten and Kovach (1990) suggested belonged to this species. The morphology of the Australian forms is similar to that of the late Cretaceous specimens reported by Dijkstra (1949; also Batten, 1988). Ariadnaesporites Potonié, 1956 emend. Tschudy, 1966 Type species. Ariadnaesporites ariadnae (Miner, 1932) Potonié, 1956 emend. Tschudy, 1966 Ariadnaesporites sp. (Plate IV, 6) Locality. Le Brouillard, B3–C. Remarks. The single specimen recorded is incomplete, having lost most of its appendages. Specific determination is, therefore, impos-

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sible. The body of the spore is significantly larger than that of the specimens referred to Ariadnaesporites sp. by Floquet, in Floquet and Lachkar (1979) from late Cenomanian deposits in Spain. 5. Biostratigraphic and palaeoenvironmental significance Comparisons with specimens recorded from rock successions that are relatively close geographically and of similar age to those encountered in any new study of megaspore assemblages, and their biostratigraphic significance are, of course, always necessary and important. Hence, previous observations on species reported from mid Cretaceous deposits in south-west France by Colin (1975) and northern Spain by Floquet and Lachkar (1979) have received particular attention in this paper. However, the work of Busnardo and Taugourdeau (1964) on the megaspores recovered from Albian flysch in Andalousia, Spain, is not cited apart from here. This is partly because the few taxa described do not clearly resemble any of the spores recorded, but also because comparisons are hampered owing to the fact that the characters of the specimens illustrated are difficult to discern. The only papers on palynological matter from the Charente and Charente-Maritime regions to have previously reported megaspores are those by Deák and Combaz (1968) and Dejax and Masure (2005). The former studied the palynology of two samples recovered from a well drilled at Saint-Romain-de-Benêt, 6 km to the east of Saujon, Charente-Maritime, one of which was from a horizon that they dated as late Albian or more probably early Cenomanian. In the systematic section of their paper, they recorded a single megaspore, which they described as Balmeisporites sp., but they referred to it elsewhere as B. glenelgensis (Deák and Combaz, 1968, fig. 3 and pl. 3, fig. 7). Dejax and Masure (2005) also recorded B. glenelgensis Cookson and Dettmann, 1958 as well as Henrisporites sp. and Paxillitriletes dakotaensis. These were recovered from the “A1sl2 level” (A1sl-A herein) of sub-unit A1 in Archingeay-Les Nouillers quarry, which they dated as late Albian based on the associated dinoflagellate cyst assemblage. To judge from the illustration provided (Dejax and Masure, 2005, fig. 2J), their

Table 1 List of taxa in the order that they are considered in the systematic section of this paper along with their occurrence in the sedimentary units examined. Taxon

Trileites sp. cf. T. persimilis Bacutriletes colinii Bacutriletes sp. Verrutriletes sp. cf. V. dubius Verrutriletes sp. 1 Verrutriletes sp. 2 Rugotriletes sp. cf. R. diktyotus Rugotriletes sp. cf. R. comptus Erlansonisporites sp. cf. E. sparassis Erlansonisporites sp. 1 Erlansonisporites sp. 2 Erlansonisporites sp. 3 Erlansonisporites sp. 4 Echitriletes sp. 1 Echitriletes sp. 2 Henrisporites sp. ?Henrisporites sp. Minerisporites mercadensis Minerisporites sp. 1 Minerisporites sp. 2 Dijkstraisporites sp. 1 Dijkstraisporites sp. 2 Paxillitriletes sp. cf. P. dakotaensis ?Paxillitriletes sp. Tenellisporites spp. Arcellites sp. Molaspora lobata Ariadnaesporites sp.

Archingeay-Les Nouillers

Puy-Puy

Les Renardières

Fouras Bois-Vert

La Buzinie

Le Brouillard

A1

A1

A1 or A2

B2

B3 or C

B3–C

X

X X

X X

X

X X X X X X X X X X X X

X? X

X

X

X

X X X

X X

X

X X

X X X

X

X

X

X X X

X X X X X

166

D.J. Batten et al. / Review of Palaeobotany and Palynology 161 (2010) 151–167

identification of Balmeisporites glenelgensis is probably incorrect: B. holodictyus Cookson and Dettmann, 1958 is more likely. No specimens attributable to Balmeisporites were encountered in the present study, and the few spore taxa that have been recovered from sub-unit A1 in Archingeay-Les Nouillers quarry do not distinguish the assemblage from that recovered from the same sub-unit at PuyPuy, which is more diverse and includes Molaspora lobata (Table 1). Except for the occurrence of a few specimens in a very distant Albian deposit, namely in Victoria, Australia (Douglas, 1973; Batten and Kovach, 1990; Tosolini et al., 2002), all records of this species are from Cenomanian and younger Cretaceous–Paleocene formations in the Northern Hemisphere. The most common spore in the assemblages is Paxillitriletes sp. cf. P. dakotaensis. Apart from that reported by Dejax and Masure (2005), all previous definite records of this species are Cenomanian. Indeed, the composition of the assemblages as a whole (Table 1), and in particular the occurrences of Rugotriletes sp. cf. R. diktyotus in Archingeay-Les Nouillers, A1, Rugotriletes sp. cf. R. comptus in Fouras Bois-Vert, B2, Minerisporites mercadensis in Puy-Puy, A1, Tenellisporites sp. in La Buzinie, B3 or C, Ariadnaesporites in Le Brouillard, B3–C, and Minerisporites sp. 1 and Bacutriletes colinii in all samples apart from that from Les Renardières (which yielded very few specimens), seems to be consistent with a Cenomanian determination. Spores that have equatorial flanges and a distinctive wall structure, suggesting (e.g., Kovach, 1994) that their affinities lie with the Isoetales, are important components of all of the assemblages. Represented by Dijkstraisporites, Henrisporites, Minerisporites, Paxillitriletes and Tenellisporites, the parent plants probably grew near or in freshwater bodies. Arcellites, Ariadnaesporites and Molaspora were almost certainly derived from aquatic plants (e.g., Batten et al., 1994; Batten and Collinson, 2001). Some of the more numerous associated lycopsid megaspores, such as Bacutriletes and Erlansonisporites, were also probably shed by plants that lived in close proximity to the water bodies in which they were deposited and ultimately preserved. However, some representatives of most forms are broken or show other evidence of damage, which was probably inflicted, at least in part, during transport to the depositional sites that were not necessarily in fresh water. This observation supports previous interpretations (e.g., Gomez et al., 2008) that the amber- and plantbearing beds accumulated in paralic environments. 6. Conclusions Most of the spores recovered cannot be positively identified at species level owing to a scarcity of similar associations of mid Cretaceous age (cf. Kovach and Batten, 1989) with which they can be compared satisfactorily. However, the assemblage overall may well be typical of Albian/Cenomanian boundary deposits in the European region, if not also further afield, and hence of biostratigraphic value. It is hoped that the recovery of more specimens in due course will enable full descriptions of most of the forms discussed and illustrated here to be presented. Several are potentially referable to new species. This will enable the associations recorded to have greater application in biostratigraphic and palaeoenvironmental analyses of successions of similar age elsewhere. It may also lead to the determination of a basis for differentiating latest Albian from earliest Cenomanian assemblages, which at present remains equivocal. Acknowledgements We are grateful to Jean Dejax (Muséum National d'Histoire Naturelle, Paris), Peter Morris (Microstrat Services, Devon) and Richard Hartley (University of Manchester) for scanning electron microscopy, reflected light photography and digital manipulation of images on the plates, respectively. The comments of two anonymous referees were also appreciated.

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