Gleichenia-like Korallipteris alineae sp. nov. macrofossils (Polypodiophyta) from the Miocene Landslip Hill silcrete, New Zealand

ABSTRACT

Partial fossil frond impressions of a Gleichenia-like fern are described and figured from specimens recovered from the early Miocene Landslip Hill silcrete deposit, Gore Lignite Measures, Southland, New Zealand. The fronds are at least bipinnate, with the pinnae (β costae) bearing opposite pairs of ultimate leaflets; ultimate segments opposite to alternate, laterally directed, ovate, slightly recurved, apices rounded obtuse. The sori are solitary per ultimate segment and there are 5–16 sporangial base scars per sorus. However, because of the difficulty of assigning Gleichenia-like partial fronds to genus, or even to Gleicheniaceae, the fossils are assigned to the fossil fern genus Korallipteris as a new species, K. alineae. Comparison with living and Cenozoic Gleichenia-like macrofossils suggests that the fossil shows morphological resemblance to the extant species G. inclusisora and G. microphylla. The macrofossils are discussed in terms of their possible palaeoenvironmental setting, together with abundant, potentially associated dispersed Gleicheniaceae fossil spores recovered from interbedded lignites. Assuming K. alineae is gleicheniaceous, it probably grew as a pioneer coloniser species in a periodically flooded/disturbed open deltaic riverine environment.

KEYWORDS:

• Foliage
• fossil fern
• Gleicheniaceae
• Korallipteris
• Landslip Hill silcrete
• Miocene
• paleoecology

Introduction

Ferns are conspicuous elements of modern New Zealand forests (Brownsey & Smith-Dodsworth 2000), with 198 species in 28 families comprising c. 7.5% of the flora (Lehmann et al. 2002; Brownsey & Perrie 2013). They also have a long fossil history in New Zealand over the last 200 Ma (Hector 1886; von Ettingshausen 1887, 1891; Mildenhall 1980; Rees 1993; Tidwell & Ash 1994; Skog 2001; Pole 2012), with Cieraad (2003) and Cieraad & Lee (2006) listing 24 fern families from Cretaceous and Cenozoic localities. However, despite early fossil records for many groups, Brownsey (2001) argued that most living New Zealand pteridophytes arrived through relatively recent long-distance dispersal, an hypothesis apparently supported by molecular evidence (Perrie et al. 2003; Perrie & Brownsey 2007, 2015).

The majority of New Zealand Cenozoic pteridophyte fossils are preserved as dispersed miospores, or occasional frond impressions, but since spores can often be dispersed widely and easily recycled, clear evidence for ferns growing locally requires macrofossils. However, as most senescent fern fronds remain attached, breaking up in situ (Drake & Burrows 1980), identifiable macrofossils are relatively uncommon in New Zealand and when compared to the very diverse miospore flora, anatomically-preserved and/or fertile fronds are rare (Cieraad 2003; Cieraad & Lee 2006; Conran et al. 2010; Pole 2012; Homes et al. 2015).

As part of a study of the fossil flora of the silcretes of early Miocene age at Landslip Hill, Southland associated with the Gore Lignite Measures (Jackson 2015), two silcrete blocks housed in the Southland Museum bearing partial fern fronds with pinnae and pinnules (ultimate segments) were examined. These blocks had been mentioned previously by Holden (1983), where they were associated with tangle fern (Gleichenia Sm.: Gleicheniaceae) as part of the Landslip Hill silcrete flora. This paleoflora is extensive, although mostly undescribed, with several conifers, a palm, and leaves, fruits and seeds of more than 20 dicot angiosperm taxa present in addition to the fern fronds (Lindqvist 1990; Campbell 2002; Jackson 2015).

Accordingly, this article describes, illustrates and formally names the Landslip Hill fern fronds and their possible affinities, discusses the possible paleoenvironment in which these ferns grew and briefly summarises the Cenozoic fossil history of New Zealand Gleicheniaceae spores.

Material and methods

Geology and age of the site

The Landslip Hill silcrete in Southland, New Zealand (Figure 1) belongs to the Upper Gore Lignite Measures (Wood 1956) and consists of silica-cemented quartzose sandstone and conglomerate forming resistant hilltop exposures and boulder accumulations (Lindqvist 1990; Lee et al. 2003). These rocks were apparently cemented soon after burial and are thus classifiable as silcrete deposits (Holden 1983). The silcrete is bedded subhorizontally and persists along strike for 2–3 km in the Charters Road scarp and at Landslip Hill to the south, possibly forming a single alluvial channel belt. There are five sedimentary facies: pebble conglomerate; trough cross-stratified coarse grained sandstone; planar and ripple-laminated fine- to medium-grained sandstone; mottled sandstone pervaded by root structures; and silicified mudstone intra-clast conglomerate (Lindqvist 1990). The Upper Gore Lignite Measures in which the Landslip Hill silcrete beds occur is dated to the early Miocene Spinitricolpites latispinosus Zone (23–16 Ma; Pocknall & Mildenhall 1984; Mildenhall & Pocknall 1989).

Figure 1. Landslip Hill fossil locality. Source: Google Earth.

Previous work on the Landslip Hill flora

Plant fossils have been observed or collected from Landslip Hill since at least 1862, with collections held in the Geology Department, University of Otago, the Otago Museum, Southland Museum, Victoria University, Wellington, GNS Science, Lower Hutt and elsewhere in New Zealand. Most of the plant macrofossils are preserved as moulds or impressions in hard, well-cemented silcrete (silica-cemented quartz sandstone), generally obtained by fracturing fossiliferous boulders with a sledge hammer. They include uncompressed three-dimensional external moulds of large logs, stems, roots, rootlets, numerous leaf impressions and a variety of fruits and/or seeds (Holden 1983; Campbell & Holden 1984, Lindqvist 1990; Campbell 2002; Jackson 2015).

The earliest scientific observations of Landslip Hill plant fossils were made by the Otago Provincial Geologist, James Hector on 12 May 1862. In his unpublished field notebook held in the Hocken Library, University of Otago (Hector 1862), he mentioned silicified wood and leaves in the ‘quartzose cementstone’ at Landslip Hill, and apparently collected samples as several silcrete leaf impressions now in the Otago Museum were described by von Ettingshausen (1887) as Dryophyllum dubium Ettings., Apocynophyllum elegans Ettings., A. affine Ettings. and Elaeodendron rigidum Ettings., and annotated as ‘Ex Coll. Geol. Surv. Otago, 1862; Hector.’ in von Ettinghausen (1891, pp. 268, 276–277, 281). Hector collected further silcrete fossils in 1869 which are now held at GNS Science, Lower Hutt (NZGS B149; G45/f8497).

A few of the Landslip Hill plant fossils, including fruits resembling Corynocarpus J.R.Forst. and G.Forst. (Corynocarpaceae) and the mangrove Avicennia L. (Acanthaceae), as well as leaves similar to Pomaderris Labill. (Rhamnaceae), Nothofagus Blume (Nothofagaceae) and Planchonella Pierre (Sapotaceae, as ?Pouteria Aubl.), were described by Campbell (2002). Fruiting cones of Casuarina stellata J.D.Campb. and A.M.Holden (Casuarinaceae) with affinities to Gymnostoma L.A.S.Johnson are also abundant (Campbell & Holden 1984).

Studies of plant macrofossils at the site by Holden (1983) and Jackson (2015) found a diverse floral assemblage including one fern, at least three conifers, several monocots, > 25 eudicot or magnoliid leaf morphotypes and at least eight different fruit or seed types. These include fossils with possible affinities to Araucariaceae, Podocarpaceae, Casuarinaceae, Cunoniaceae, Elaeocarpaceae, Lauraceae, Nothofagaceae and Sapotaceae. Quantitative paleoclimate estimates suggest a much warmer and more humid climate than occurs in present day Southland, with moderate mean annual precipitation, relatively little seasonal variation and a year-round growing season (Jackson 2015).

Although palynomorphs are not preserved in the silcretes, the palynoflora of the Upper Gore Lignite Measures, in which the silcretes are interbedded, is dominated by pollen of Nothofagidites cranwellae (Couper) Mildenh. and Pocknall (Nothofagus subg. Brassospora Philipson and M.N.Philipson) and Haloragacidites harrisii (Couper) W.H.Harris in Mildenh. and W.H.Harris (Casuarinaceae). Other abundant palynomorphs include the conifer families Araucariaceae and Podocarpaceae and angiosperm families Arecaceae, Chloranthaceae, Ericaceae (subfam. Epacridoideae), Euphorbiaceae, Gunneraceae, Leguminosae: Caesalpinioideae, Loranthaceae, Myrtaceae and Proteaceae, diverse asparagoid monocots, and fern spores from the families Cyatheaceae, Gleicheniaceae, Hymenophyllaceae, Osmundaceae and Polypodiaceae (Pocknall 1982).

Fossil ferns

Among the numerous samples collected from the site are many overlapping fern fronds preserved in what was originally a single block that has since been split in two. Both pieces are housed at the Southland Museum, Invercargill (accession number G76.469.6; 119), but without collection details.

The cemented nature of the Landslip Hill silcrete matrix, and the manner of its formation, precludes both further preparation of the specimens and also the preservation of spores or pollen. Nevertheless, abundant trilete spores attributed to Gleicheniaceae have been retrieved from several late Oligocene and early Miocene sites in the Gore Lignite Measures (Pocknall 1982; Pocknall & Mildenhall 1984), within which the Landslip Hill deposit is interbedded, as well as from many hundreds of palynological samples across New Zealand (Raine et al. 2011; GNS Science 2014).

Comparisons with other ferns

The fern macrofossils were compared with New Zealand and exotic Gleicheniales specimens at the Otago Regional Herbarium (OTA) and Te Papa, Wellington (WELT), living plants of Gleichenia species growing in Northland, Southland, Fiordland, Wellington and Manawatu-Wanganui districts and Sticherus from the Wellington district, published descriptions and keys of living and fossil Gleicheniales families, and genera and other Gleichenia-like fossils. Nomenclature for extant taxa follows Christenhusz & Chase (2014) and the frond terminology for Gleicheniaceae established by Shaw & Ranker (2011) and followed by Perrie & Brownsey (2015) is used. Nomenclature and taxon concepts for the fossils follow Nagalingum & Cantrill (2006) and Vera & Passalia (2012).

The fossil fronds and modern fern specimens were photographed using a Nikon D70 digital SLR or a Canon Powershot A480 digital camera. Some photographs were taken after pretreatment of the sample by coating with sublimated ammonium chloride vapour to enhance the contrast, following the methods of Teichert (1948).

Results

Systematic paleontology

Macrofossils

Class. Polypodiopsida (=Filicopsida) Cronquist, Takhtajan and Zimmerman ex. Reveal, 1995

Order. Uncertain

Family. Uncertain

Genus. Korallipteris E.I.Vera and Passalia 2012

Type species. Korallipteris argentinica (Berry) emend. R.Herbst, 1962

Species. Korallipteris alineae Conran, J.A.Jacks., D.E.Lee and E.M.Kenn. sp. nov.

Figures 2–3

Figure 2. Fossil Gleichenia-like Korallipteris alineae foliage (Southland Museum accession number G76.469.6) from the Miocene Landslip Hill silcrete deposit. Photographs: J. G. Conran unless indicated. a, Holotype; b, same after pretreatment of the sample by coating with sublimated ammonium chloride. Photograph: R. E. Fordyce; c, drawing of holotype. Image from Holden 1983, used with permission; d, paratype; e, same after pretreatment of the sample by coating with sublimated ammonium chloride. Photograph: R. E. Fordyce; f, reverse side of holotype showing additional frond material; g–i, details of lateral pinnae; i, detail of holotype pinnae after pretreatment of the sample by coating with sublimated ammonium chloride. Photograph: R. E. Fordyce. Scale bars: a–f = 20 mm; g–h = 5 mm.

Figure 3. Fossil Gleichenia-like Korallipteris alineae foliage (Southland Museum accession number G76.469.6) from the Miocene Landslip Hill silcrete deposit. Photographs: J. G. Conran. a–d, Details of lateral pinnae; e–h, details of ultimate segments; f–g, arrows indicate midveins, some with branching; h, arrows indicate sori receptacles with remnant base scars of sporangia; i, extant Gleichenia microphylla R.Br. ultimate segments, arrows showing remnant bases of sori. Scale bars: a–b = 10 mm; c = 5 mm; d–f = 2 mm; g–i = 0.5 mm.

= Gleichenia southlandica A.Holden, Studies in N.Z. Oligocene and Miocene plant macrofossils, 154 (1983) nomen nudum

Holotype (Figure 2a–c, f–i). Collection of the Southland Museum & Art Gallery, Niho o te Taniwha, Invercargill (accession number G76.469.6); Landslip Hill silcrete member, Gore Lignite Measures.

Paratype (Figure 2d–e). Collection of the Southland Museum & Art Gallery, Niho o te Taniwha, Invercargill, (Ath. No. 119); Landslip Hill silcrete member, Gore Lignite Measures. Collector unknown.

Diagnosis. Pinnae (β costae) bearing opposite pairs of ultimate leaflets; ultimate segments opposite to alternate, laterally directed, ovate, slightly recurved, apices rounded obtuse. Sori solitary per ultimate segment, sporangial base scars 5–16 per sorus.

Description. Rhizomes not preserved. Partial fronds at least bipinnate, stipe not preserved. Pinnae (β costae) at least 110 mm long and 70 mm wide, rachis 1–2 mm wide (Figure 2a–f), with at least 10–39 opposite pairs of ultimate leaflets divergent at 70–90°. Ultimate leaflets at least 40–70 mm long, with at least 6–25 pairs of opposite to alternate ultimate segments. Ultimate segments oblong, isodromous, attachment adnate (possibly decurrent), laterally directed,1–2 mm long, 0.7–1.3 mm wide, ovate and apparently slightly recurved, apices rounded-obtuse; margins entire, without sinuses (Figures 2g–i, 3a–g), showing indentations at right angles to pinna; midvein directed towards ultimate segment apex (Figure 3g), vein branches few, obscure (Figure 3f–g). Sorus solitary per ultimate segment, base of sorus (receptacle) round (Figure 3i), sporangial base scars 5–16 per sorus, sporangia and spores not preserved. Hairs or scales not observed.

Etymology. Named after Dr Aline Homes (formerly Holden) who first mentioned these Landslip Hill specimens in her unpublished PhD thesis (Holden 1983).

Age. Early Miocene.

Material examined. Southland Museum (G76.469.6 and Ath. No. 119). Many partial fronds on several bedding surfaces on a single original block that was broken subsequently into two smaller blocks.

Discussion

The fossils comprise several incomplete frond pieces (Figure 2a–f). These specimens were named informally by Holden (1983, p. 288) in her unpublished PhD thesis as ‘Gleichenia southlandica’ but that name was not published validly.

Gleichenia-like fossil fern fronds are common globally, especially in Mesozoic floras (see review in Vera & Passalia 2012) and include simple or 1–2-forked pinnately divided fronds with numerous small pinnules with a midvein and few lateral veins. Many of these were assigned historically to Gleichenites Goeppert and associated with Gleicheniaceae, but Cretaceous Gleichenia-like fronds with fertile structures from other families are known, such as Dicksoniaceae (Cantrill 1998) and Cyatheaceae (Césari 2006), suggesting that morphology alone is not enough to place Gleichenia-like fossils to family.

Arber (1917) noted further that the type of Gleichenites was a seed fern and proposed that the fossil genus Microphyllopteris Arber be used instead. However, Cantrill (1998) observed that there were still nomenclatural issues and Nagalingum & Cantrill (2006) proposed using Microphyllopteris for Gleichenia-like fossils with unknown or pseudo-dichotomous branching without resting buds, whereas Gleicheniaceaephyllum Crabtree emend. Nagalingum and Cantrill should be used for gleicheniaceous material that has a resting bud among two to four primary branches. Unfortunately, the type species of Microphyllopteris is also a seed fern, so Vera & Passalia (2012) proposed Korallipteris Vera and Passalia as the new name for fertile or sterile fern fronds with Gleichenia-like morphology (e.g. pinnate fronds with small pecopteroid pinnules) but without a resting bud or enough diagnostic features to allow family-level placement.

Korallipteris was proposed principally as a fossil genus for Mesozoic fossils, but Vera & Passalia (2012) observed that korallipteroid fossils fitting this taxon extended from the Triassic into the Paleogene. However, we consider that as this represents a fossil genus, and not necessarily a phylogenetic lineage, it cannot reasonably be time-limited, so that Neogene Gleichenia-like fossils meeting the criteria for assignment should also be placed into Korallipteris, hence the approach followed here.

Comparison with fossil Gleicheniaceae and Gleichenia-like fossils

When the fossil is compared with extant Gleicheniaceae genera (Figure 4), the fossil frond pieces from Landslip Hill match closely to Gleichenia, although the absence of a preserved pinna bud precludes placement into the extant genus (or even family). Short, rounded ultimate segments are found only in some species of Gleichenia (Figure 4a–d) and the monotypic New Caledonian Stromatopteris moniliformis Mett. (Figure 4i); however, the latter genus has simple fronds, whereas those of the fossil are at least bipinnate. The dichotomously branched, indeterminately-growing frond structure in Gleichenia and related genera such as Dicranopteris Bernh. (Figure 4e), Diplopterygium (Diels) Nakai (Figure 4f) and Gleichenella Ching (Figure 4g) often results in scrambling colonial plants that climb over surrounding vegetation (Kramer 1990b; Moran 2004; Vasco et al. 2013). Nevertheless the ultimate pinnae in these taxa, as well as the related, non-climbing umbrella fern (Sticherus C.Presl.) are elongate and have more complex venation than occurs in the fossil (Kramer 1990b; Perrie & Brownsey 2015), ruling them out as likely candidates. Similarly, frond dissection and ultimate pinnule structure also rules out other families in the order Gleicheniales (Kramer 1990a, 1990b, 1990c).

Figure 4. Extant Gleicheniaceae exemplars for comparison with the fossil foliage at Landslip Hill. Photographs: J. G. Conran unless indicated. a–b, Gleichenia microphylla R.Br.; c, Gleichenia dicarpa R.Br.; d, Gleichenia alpina R.Br.; e, Dicranopteris linearis (Burm.f.) Underw. Photograph: F. Xaver, https://en.wikipedia.org/wiki/Dicranopteris#/media/File:Dicranopteris_linearis_1.jpg (CC BY-SA 3.0); f, Diplopterygium pinnatum (Kunze) Nakai. Photograph: Kenpei, https://en.wikipedia.org/wiki/Gleicheniaceae#/media/File:Diplopterygium_pinnatum1.jpg, GFDL,Creative Commons Attribution ShareAlike 2.1 Japan License (CC BY-SA 3.0); g, Gleichenella pectinata (Willd.) Ching. Photograph: Acuaa, https://commons.wikimedia.org/wiki/File:Gleichenella_pectinata_amr-1874_%286%29.JPG, Creative Commons Attribution-Share Alike 3.0 Unported; h, Sticherus cunninghamii (Heward ex Hook.) Ching; i, Stromatopteris moniliformis. Photograph: G. Gâteblé, used with permission. Scale bars: a, I = 5 cm; b–c = 5 mm; d = 2 cm; e–h = 10 cm.

Gleicheniales are a widespread, largely pantropical order of leptosporangiate ferns characterised by root steles with 3–5 protoxylem poles and antheridia with 6–12 narrow, twisted or curved cells in their walls (Smith et al. 2006). The order is ancient and proximal within the leptosporangiate ferns and appears to have diverged from its sister lineage (the filmy ferns) in the Permian, just over 270 Ma (Pryer et al. 2004).

There are three extant families in the order: Dipteridaceae (two genera) from India, South East Asia and northern Australia; the pantropical to southern temperate Gleicheniaceae (six genera); and the tropical Matoniaceae (two genera) from South East Asia (Christenhusz et al. 2011; Christenhusz & Chase 2014). Of these families, only three of the six extant genera of Gleicheniaceae are present in the modern New Zealand flora (Perrie et al. 2012; Brownsey et al. 2013; Perrie & Brownsey 2015): Dicranopteris (one species); Gleichenia Sm. (four species and a natural hybrid); and Sticherus (four species). Australia has four extant genera (Chinnock & Bell 1998; Short et al. 2003): Dicranopteris (one species); Diplopterygium (one species); Gleichenia (seven species); and Sticherus (five species).

Gleicheniaceae macrofossils are widespread from the Mesozoic onwards (Taylor et al. 2009; Vera & Passalia 2012), with Gleichenia-like fossils from the Mesozoic to the Paleogene of North America (Litwin 1985; Gandolfo et al. 1997; Mindell et al. 2006), the Early Cretaceous of Antarctica (Nagalingum & Cantrill 2006), Japan (Kimura 1975) and the Eocene of Europe (Collinson 1996; Herendeen & Skog 1998). There are also macrofossils from the Oligocene sediments at Cethana, Tasmania (Carpenter 1991; Carpenter et al. 2004), the Oligocene to the mid–late Miocene of Lightning Ridge, New South Wales (Carpenter et al. 2011) and the mid-Cenozoic Yallourn and Morwell coals in Victoria (Cookson 1953; Blackburn 1985). There are also Australian Sticherus fossils from the Oligocene Cethana deposit of Tasmania (Carpenter 1991; Carpenter et al. 2004) and possibly the middle Eocene Nerriga deposit of New South Wales (Hill 1982).

The only validly published pre-Quaternary Gleicheniaceae macrofossil from New Zealand is Gleichenia obscura Ettingsh. from the Late Cretaceous/early Paleocene (Haumurian to Teurian stages; 83.6–56.0 Ma) rocks collected at Pākawau, northwest Nelson (von Ettingshausen 1887), which is now seen as being possibly more closely allied to Sticherus (Oliver 1950; Pole 2012). A fossil fern frond of Triassic age from Eighty-Eight Valley, Nelson named informally by Hector (1886) as ‘Gleichenia waitai’ is a nomen nudum. There are also undescribed Gleichenia-like frond impressions preserved in Late Cretaceous (Haumurian) Pākawau Group sediments reported by Kennedy (1993) and these Mesozoic fossils are the subject of ongoing research.

Korallipteris alineae differs from most other Korallipteris species in the possession of a single sorus per ultimate leaflet (Vera & Passalia 2012). There are two other species in the genus with this characteristic; however, neither is a close match to the Landslip Hill fossil. The foliage of K. unisora (Cantrill and Nagalingum) E.I.Vera and Passalia from the middle Cretaceous (late Albian) of Antarctica is thought to represent a member of the Lophosoriaceae, similar to Lophosoria cupulatus Cantrill (Cantrill & Nagalingum 2005).

Herbst (1962) described two species of Gleichenites with dichotomously branching fronds broadly similar to extant Gleichenia microphylla from the middle Cretaceous (Aptian–Albian) of Patagonia and these have each been transferred subsequently to species of Korallipteris (Vera & Passalia 2012) and Gleicheniaceaephyllum (Vera & Passalia 2014), respectively. Korallipteris vegagrandensis (R.Herbst) E.I.Vera and Passalia has ultimate segments with a single sorus, each with more than 20 sporangia (Herbst 1962), whereas K. alineae has 5–16, estimated from sporangial base scars. Similarly, Gleicheniaceaephyllum san-martini (R.Herbst) E.I.Vera and Passalia, although somewhat similar in frond morphology, possesses an arrested laminar bud, hence its definite placement in Gleicheniaceae (Vera & Passalia 2014); both taxa also differ from K. alineae in having distally inclined ultimate segments (Herbst 1962). The Korallipteris-like Mesozoic fossil Microphyllopteris gleichenioides (Oldham and Morris) Walkom from the Upper Jurassic to the mid-Cretaceous of India and Australia differs in having much shorter ultimate leaflets (< 30 mm) and smaller, isodiametric (1 × 1 mm) ultimate segments (McLoughlin 1996).

Comparison of K. alineae with Cenozoic Gleichenia-like fossils from Australia (Carpenter 1991; Carpenter et al. 2004, 2011) and the four New Zealand and seven Australian living Gleichenia species (Table 1) shows that the fossil shares some features in common with the widespread G. microphylla, New Zealand endemic G. inclusisora and the Northern Territory endemic Gleichenia species ‘Victoria River’, in particular, the long β costae with numerous ultimate leaflets, each with numerous ultimate segments. However, the ovate ultimate segments with rounded apices distinguish it from these species (as well as the eastern Australian G. mendellii).

Table 1. Comparison of the Landslip Hill fossil fern fronds with extant Australian and New Zealand Gleichenia species and Gleichenia-like macrofossils.

Character	†Korallipteris alineae	Gleichenia abscida	Gleichenia alpina	Gleichenia dicarpa	Gleichenia inclusisora	Gleichenia mendellii
Pinna compound	yes	yes	yes	yes	yes	yes
Frond β costa	yes	=gamma	yes	yes	yes	yes
length (mm)	c. 40–70	15–40	11–73	29–280	25–135	10–50
leaflet pairs	c. 10–39+	15–35	4–14	7–50	5–26	10–30
Ultimate segment
pair number	c. 6–25+	8–35	11–48	17–80	15–47	10–30
shape	ovate	ovate	square	square	ovate	deltoid
length (mm)	1–2	1–1.6	0.5–0.9	0.4–1.6	0.7–1.4	1.2–1.5
width (mm)	0.7–1.3	1.2–2	0.6–1.0	0.6–1.6	0.9–1.4	1–1.2
apex	rounded	rounded	rounded	rounded	rounded	acute
pouched	recurved	yes	yes	yes	recurved	no
Sporangia/sorus	5–16*	2–4	2	1–2(–3)	3(–4)	2–3(–4)
Character	Gleichenia microphylla	Gleichenia rupestris	Gleichenia sp. Vic R	†‘Gleichenia’ sp. Tas	†‘Gleichenia’ sp. NSW	Stromatopteris moniliformis
Pinna compound	yes	yes	yes	yes	?	no
Frond β costa	yes	yes	yes	yes	?	no
length (mm)	30–390	10–40	10–750	c. 14–19+	c. 18–35+	n/a
leaflet pairs	5–38	8–45	10–20	9+	c. 12–28+	n/a
Ultimate leaflet
segment pairs	18–62	6–20	18–80	12–14+	12–30+	> 100
shape	deltoid	deltoid	deltoid	ovate	deltoid	oblong
length (mm)	1.3–2.7	1.3–3	1.5–4.5	c. 1.5	2–4	1.5–2.5
width (mm)	0.8–2.0	1–2	0.7–1.9	c. 1.5	2–3	1.5–2.5
apex	acute	acute	rounded	rounded	acute	rounded
pouched	no	no	no	?	no	yes
Sporangia/sorus	2–4(–5)	3–4	2–4	?	?	15–20

NSW, New South Wales; Tas, Tasmania; Vic R, Victoria River, Northern Territory.

†Indicates an extinct taxon.

*Based on sporangial base scar numbers per receptacle.

Data for extant taxa from Jones & Clemesha (1981), Duncan & Isaac (1986), Kramer (1990b), Chinnock & Bell (1998), Short et al. (2003) and Perrie & Brownsey (2015); data for previously described extinct taxa from Blackburn & Sluiter (1994), Carpenter (1991), Carpenter et al. (2004, 2011). Frond structure terminology follows Shaw & Ranker (2011) and Perrie & Brownsey (2015).

Macrofossils attributed to Gleichenia (as two unnamed species) have also been reported variously by Cookson (1953), Blackburn (1985), Blackburn & Sluiter (1994) and Hill & Jordan (1998) from the early Oligocene–early Miocene Yallourn and early–middle Miocene Morwell coals in Victoria. One of these species was locally abundant in the early Miocene-aged Yallourn Seam, forming clear layers of foliage and rhizomes, and associated with charcoal. This taxon was related to the extant G. dicarpa by Blackburn & Sluiter (1994), but was not described in detail, nor were pinna buds mentioned for any of these fossils.

Carpenter (1991, p. 28) reported both Gleichenia and Sticherus macrofossils from the Oligocene-aged (c. 35 Ma) Cethana site in Tasmania. The Gleichenia sp. was described as:

[A] section of an alternately branched pinna 35 mm long. Pinnule branches occur at right angles to the main axis and are up to 13 mm long. The pinnules are divided into small rounded lobes, typically about 1.5 mm broad at the base and 1.5 mm long.

However, as there are no pinna buds preserved, placement into Gleichenia cannot be confirmed.

Similarly, the Gleichenia sp. described from Lightning Ridge silcretes by Carpenter et al. (2011, p. 404) has detached ultimate segments with ‘numerous ultimate lobe segments each side of costae. Lobes apically directed, 2–4 mm long. Weak venation evident within each lobe, with several lateral veins emerging at c. 45^o from a ventral vein directed towards the lobe apex’. He noted that the long ultimate segments with highly reduced lobes were very distinctive for Gleichenia and suggested that the fossils were most closely related to the extant Australian G. rupestris R.Br. or Australasian G. microphylla R.Br., but following the criteria of Nagalingum & Cantrill (2006) and Vera & Passalia (2012) these fossils should be regarded instead as ‘Gleichenia-like’.

When compared with the Landslip Hill fossils, these Gleichenia-like Australian fossils differ in a range of characteristics (Table 1); in particular, the open-spaced and alternate ultimate leaflets seen in the Cethana fossil and the acute, apically directed ultimate segments of the Lightning Ridge fossils. The association of the fossils described from the Yallourn and Morwell with G. dicarpa suggests that they are also different, as that taxon (as well as G. abscida and G. alpina) has conspicuously pouched ultimate segments.

Cenozoic Gleicheniaceae spore records from New Zealand

The family is reported widely from the New Zealand Cenozoic fossil record as spores referred to Clavifera triplex (Bolchovitina) Bolchovitina (youngest New Zealand record in the Paleocene), Gleicheniidites circinidites (Cookson) M.E.Dettmann, G. senonicus K.Ross or Gleichenia circinnata Sw. (Raine et al. 2011). Another Cenozoic spore type Dictyophyllidites arcuatus Pocknall and Mildenh. was regarded as closest to Dicranopteris in its possible modern affinity (Pocknall & Mildenhall 1984). The range in spore morphology assigned to these genera and species suggests that Gleicheniaceae were diverse and well represented throughout the Cenozoic of New Zealand. In the Gore Lignite Measures, within which the fossils are interbedded, distinctive equatorially tricrassate, trilete Gleicheniaceae spores are common at many other early Neogene sites, such as the Oligo–Miocene Newvale Mine (D. C. Mildenhall, pers. comm. 2011), forming up to 55% of the palynomorph count in some samples (Pocknall & Mildenhall 1984), clearly representing local sources. These trilete gleicheniaceous spores are considered to represent probably Gleichenia and/or Dicranopteris (Raine et al. 2011), although Diplopterygium is also possible, whereas Gleichenella, Sticherus and Stromatopteris bear monolete and ellipsoidal spores (Tryon & Lugardon 1991; Kramer 1990b).

Paleoecology

Modern New Zealand Gleichenia species grow from coastal to subalpine regions throughout the North and South Islands and are also present on the Stewart and Chatham Islands. Several of these species also extend to Australia, New Caledonia, South East Asia, Malesia and the Philippines (Perrie & Brownsey 2015). Gleichenia is usually found in moderately to highly productive swamps, forest margins and generally impoverished soils (Brownsey & Smith-Dodsworth 2000; Jin et al. 2013) and is particularly common in scrub, forest and swampland with high humidity and/or high rainfall where it can form dense tangled intertwining masses (A. Homes, pers. comm. 2015). The family is often regarded as indicative of disturbance and open environments (e.g. Russell et al. 1998; Clarkson et al. 2011; Kitchener & Harris 2016). It is probable that some of the Landslip Hill macrofossils were flood-transported before deposition, as evidenced by the random, three-dimensional orientation of the fossils in the rocks, the frequent damage seen on leaf fossils and the abundance of fossil wood (log cavities) that resembles a mixture of fluvial point bar assemblages and in situ vegetation, suggesting island or channel margin sand-flats that were subjected to periodic flooding (Lindqvist 1990).

Collinson (2001) suggested that Gleicheniaceae in the Miocene of Australia formed part of a fire-prone vegetation, with charcoalified foliage of several species from the Miocene brown coals of the Latrobe Valley, Victoria, Australia (Blackburn 1985; Blackburn & Sluiter 1994; Hill & Jordan 1998). Because modern Gleichenia dicarpa in Australia grows in damp open sclerophyllous forests to moors and is strongly influenced by fires, the paleoenvironment was interpreted as a fire-prone, Gleichenia–Restionaceae-dominated moor (Blackburn 1985; Blackburn & Sluiter 1994). Similarly, G. microphylla in South Australia rapidly colonises recently-burnt wet Leptospermum J.R.Forst. and G.Forst. (Myrtaceae) swamps, where it can grow to form deep peat beds under a dense 2 m thick almost monospecific fern canopy, such as in Yundi Swamp on the Fleurieu Peninsula (J. G. Conran, pers. obs.).

New Zealand Gleicheniaceae (including both G. dicarpa and G. microphylla) similarly grow in damp, open scrub and low forest, swamps, or wet, infertile heaths on poor substrates (Perrie & Brownsey 2015), but without an apparent association with fire; disturbance-related open habitat being more important for local dominance. However, abundant charcoal and burnt palynomorphs indicative of fire induced by volcanic activity was seen in the lowest samples from the 183 m long paleolake core drilled at Foulden Maar (Mildenhall et al. 2014) where trilete Gleicheniaceae spores dominated the early stages of post-eruption recovery.

This dependence by many modern and fossil Gleicheniaceae on disturbance suggests that, although there was a diversity of forest-type floristic elements present in the Landslip Hill deposit (Campbell 2002; Lee et al. 2003; Jackson 2015), the periodic flooding events and open deltaic conditions suggested by Lindqvist (1990) would have provided the types of open, disturbed habitats that would allow Gleichenia-like ferns to establish. Nevertheless, in the absence of a definitive systematic placement for K. alineae, this paleoecological association has to remain speculative.

Conclusions

This article describes a new Gleichenia-like fern species, Korallipteris alineae, from the Miocene Landslip Hill silcrete flora (Gore Lignite Measures) in southern New Zealand. The fossil shares many morphological features with living Gleichenia species, such as the (at least) bipinnate frond morphology, ultimate leaflet shape and size, and the disposition of the sori. However, the absence of a resting bud in the pinna dichotomies or in situ spores makes it impossible to place definitively into Gleicheniaceae and the fossil is therefore assigned to the fossil fern genus Korallipteris (family incertae sedis). Its affinities must also remain uncertain pending the discovery of more completely preserved material.

Acknowledgements

The Department of Geology, University of Otago is thanked for the provision of resources towards this project, which was undertaken by Joe Jackson as part of a Master of Science degree. Erin Tuhura of the Southland Museum & Art Gallery, Niho o te Taniwha, Invercargill is thanked for the loan of the fossils and Aline Homes for comments on fern biology and Miocene silcrete floras. Ewan Fordyce is thanked for help with fossil photography and Gildas Gâteblé for the photograph of Stromatopteris. Daphne Lee wishes to thank staff at the Hocken Library, University of Otago for providing access to the original field notebooks of James Hector. We thank Ezequiel Vera, Mauro Passalia and two anonymous reviewers for helpful comments on the manuscript. We also acknowledge use of information contained in the New Zealand Fossil Record File (FRED). Associate Editor: Dr Leon Perrie.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Funding was provided by a Marsden Grant [UOO1115] from the Royal Society of New Zealand.