Geological Magazine
Middle Pennsylvanian vegetation of the San Giorgio Basin, southern Sardinia (Italy)
Christopher J. Cleal, Giovanni G. Scanu, Carla Buosi, Paola Pittau & Evelyn Kustatscher
Supplementary data
Annularia sardiniana
Description. Leafy shoots with slender stems between 0.5 mm and 6 mm wide (mean value 2.5 mm); longest preserved example 26 mm long. Leafy whorls typically occur at intervals of 10–24 mm (mean value 16 mm). Each leaf whorl has basal collar (Fig. 3b), 1.0–1.5 mm wide, attached c. 45° to stem. The basal collar produces 11–30 foliar segments (mean value 20) that seem originally to have extended away from stem at about right angles; segments within each whorl are of more or less equal length, giving the whorl a circular outline. Segments are linear-lanceolate, partly constricted at base, widest about or just above half way along segment, rather lax in appearance; segment apex acute to bluntly acute (Fig. 3c). Segment length 7–35 mm (mean 18 mm), width 0.5–2.5 mm (mean 1.6 mm). There is a statistically significant correlation between segment length and width and with the number of segments per whorl; there is also a weak statistical correlation between the number of segments per whorl and the stem width but not with whorl spacing (see Table 4 for details). A single thick vein extends along entire length of each foliar segment.
Specimens. 60 specimens: MGPDL 17101–17103, 17107, 17111, 17115, 17116, 17121, 17123, 17124, 17127, 17128, 17135, 17139, 17144, 17148, 17154, 17155, 17160, 17164, 17169, 17173, 17175, 17176, 17178–17186, 17188, 17189, 17191–17199, 17211, 17213–17215, 17217, 17226, 17389, 17392, 17393, 17397, 17399, 17402–17404.

Annularia spinulosa 
Description. Leafy shoots with slender stems between 0.5 mm and 2 mm wide (mean value 1.4 mm); longest preserved example 80 mm long. Leafy whorls typically occur at intervals of 15–20 mm (mean value 17 mm). Each whorl consists of 20–28 separate leaves, or leaves that are basally fused by a very narrow collar (Figs 3d, 6i). In a few whorls the leaves are all of the same size, but in most the size varies, giving the whorl an oval outline; in such oval whorls the leaves that lie at right angles to the stem may be up to 1.5 times longer than those that lie parallel to the stem. Leaves are linear-oblanceolate (Fig. 3e), more or less constricted at base, widest about ⅔ to ¾ of way along leaf, rather stiff in appearance; leaf apex blunt to bluntly acute, sometimes with a small mucronate tip. Leaf length 12–22 mm (mean 18 mm), width 1–2 mm wide (mean 1.5 mm), length:breadth ratio typically 11–16; there is no statistical correlation between length and width in the measured samples but this may be partly reflecting the relatively small sample size; neither is there a statistical correlation between the number of leaves per whorl and the stem width or with whorl spacing (see Table 4 for details). A single thick vein extends along entire length of each foliar segment.
Specimens. 10 specimens: MGPDL 17152, 17168, 17182, 17189, 17216, 17223, 17395, 17396, 17402, 17406.

Annularia sphenophylloides
Description. Leafy shoots with leaf whorls spaced 10 mm apart. Leaves spathulate, sometimes with a mucronate tip, 6–8 mm long, 2 mm wide (Fig. 3f).
Specimens. Two incomplete fragments on one specimen (MGPDL 17193).

Annularia galioides
Description. A single leafy shoot with small linear-lanceolate leaves, 3 mm long, c. 1 mm wide, with a bluntly acute apex (Fig. 3g). 
Specimen. MGPDL 17201.

Palaeostachya sp. 
Description. Numerous detached cone fragments, 6–10 mm wide (probably depending on maturity) (Fig. 3h); longest fragment 55 mm long. Cones parallel-sided or slightly tapered for most of length, also slightly basally tapered in most proximal part. Cone apex blunt with a short tuft of segments protruding distally. Cone axis 1–1.5 mm wide, sometimes with 3–4 longitudinal ribs. Whorls of bracts attached to cone axis at 3–4 mm intervals, sometimes appearing trifid. Bracts emitted from cone axis at acute angle (c. 30°) but then bend so that they often appear to be attached at right angle to the cone axis. Bracts straight for c. 1 mm and then curve along rest of their length so their distal end usually is at 40–45° to the cone axis; in one example the distal end of the bract is almost parallel to cone axis, possibly representing the immature condition. Between the bracts, whorls are ovoid to ob-pyriform carbonised masses, 3–4 mm long, 2–3 mm wide. In few cases these masses can be resolved into a “T”-shaped structure with down-turned arms to the cross-bar when viewed laterally, attached to the axil between the bract and cone axis; at least 3 (presumably originally 4) elongate, ovoid sporangia with an acute tip borne on the underside of the cross-bar of the “T”; in a few cases these structures are preserved showing these structures to be peltate with a round distal head. Number of sporangiophores or bracts per whorl are impossible to determine due to compression of the fossils.
One specimen (Fig. 5c) yielded circular spores with a trilete aperture, and a smooth, laevigate outer exospore. The amb is circular to oval, 35–47 µm in diameter. The small trilete mark reaches 1/5–2/5 of the spore diameter. The sporoderm is rough, yellow and dense.
Specimens. 23 specimens: MGPDL 17113, 17140, 17122–17124, 17126, 17134, 17135, 17138, 17145, 17146, 17148, 17150, 17151, 17153, 17156, 17158, 17160, 17177, 17184, 17202, 17222, 17394.

Calamites sp.
Description. Stem fragments 6–75 mm wide pith casts (most typically 30 mm wide) with regular, longitudinal ribbing (Fig. 7a). Rib density across stem 4.5–18 per cm; there is a weak statistical correlation with pith cast width (r2 = 0.363, puncorr. = 0.018; reduced major axis regression rib density = -0.16 x pith cast width + 14.55). Many pith cast fragments show no nodes indicating inter-node spacing of at least 125 mm, whilst others show nodes at 23–50 mm intervals; no statistical difference could be found in the widths of these two sets of pith casts (t = -1.02, psame mean = 0.332). Mostly preservation was insufficient to show the shape of the rib terminations at the nodes, but some appeared to be rounded (Fig. 7b).
Specimens. 19 specimens: MGPDL 17101, 17105, 17112, 17119, 17126, 17131, 17162, 17203–17205, 17207–17210, 17214, 17136, 17399. 17401, 17407.

Pinnularia sp.
Description. Slender axes, c. 0.5 mm wide with even more slender lateral branches lying at right angles. Other than fine longitudinal striae, no other structure was visible.
Specimen. MGPDL 17135.

Sphenophyllum cf. emarginatum
Description. A leafy shoot with 1.5 mm wide stem with longitudinal ribs. Four incomplete leaf whorls spaced 9 mm apart, although only one has reasonably preserved leaves. Leaves cuneate, more or less entire, 11 mm long, 6 mm wide, lateral margins slightly curved, distal margin curved and smooth; dense veins forking several times.
Specimen. MGPDL 17408.

Cyathocarpus sp.
Description. Frond segments at least tripinnately divided. Antepenultimate rachis 11 mm wide, longitudinally striate with some irregular punctae. Penultimate rachises emitted oppositely at 60–80° (subjected to some taphonomic distortion and probably in life nearer to 80°). Penultimate rachises 2.5–3.5 mm wide, up to at least 60 mm long, irregularly longitudinally striate. Sub-opposite ultimate rachises spaced at 8–10 mm intervals, attached at 60–90° Last order pinnae at least 30 mm long, typically 8 mm wide, parallel-sided for most of length, tapering towards distal end (but no actual pinna terminal preserved). Alternately arranged pinnules attached at angles varying from 60–90° to rachis, spaced 3 mm apart (Fig. 5e). Pinnules linguaeform to sub-linguaeform, with rounded or slightly tapered distal part; pinnule length typically 3–6 mm (rarely 7–8 mm), width 2 mm (rarely 5 mm). Prominent midvein runs along most of pinnule length. Lateral veins thin, consistently once forked at a moderate angle, meeting pinnule margin at c. 80°. Many pinnules are densely covered with sori consisting of four ovate sporangia in a stellate arrangement.
Specimens. Five specimens: MGPDL 17121, 17163, 17206, 17390, 17405.

? Crenulopteris sp.
Description. Pinnate fragment with robust pinnatifid pinnae (Fig. 5f). Main rachis 47 mm long, 2 mm wide. Ultimate rachises alternately inserted at c. 80°, 7 mm apart on either side of main rachis. Ultimate pinnae 20 mm long, 7 mm wide, parallel-sided for most of length, bluntly terminated by a roundly subtriangular terminal pinnule / lobe. Dentate pinnules with round apex alternately arranged ultimate rachis, 4 mm long, 2.5 mm wide, inserted at near to right angles, spaced 3 mm apart. No veins visible.
A second specimen shows a single once pinnate segment, rachis 28 mm long, with 10 pinnules alternately arranged; pinnule spacing 5 mm on either side. Pinna somewhat tapered but the preserved fragment does not reach the pinna apex. Pinnules 35 mm wide, varying between 9 mm and 16 mm in length, strongly decurrent on basiscopic side, somewhat constricted on acroscopic side. Pinnules curved acroscopically, parallel-sided for proximal half to two-thirds, then taper to a rounded apex. Midvein only slightly decurrent at base, thick, and extending almost to pinnule apex. Lateral veins arise from midvein at narrow angle, then arch in an angular manner to reach pinnule margin at c. 80°. Veins fork up to twice, once about ¼ of the way to the pinnule margin; the second fork occurs on the more distal of the two branches about ⅔ of the way to the margin.
Specimens. Two specimens: MGPDL 17212, 17219.

? Sydneia sp.
Description. Fragments of pinna segments with slender ultimate rachises, 15 mm long, covered with fine denticles or spines. Small fertile pinnules spaced at intervals of c. 1.5 mm. Each pinnule seems to consist of a midvein 4–5 mm long to which are attached two rows of 8–9 elongate sporangia c. 1 mm long. Sporangia yield trilete spores with circular to subcircular amb, diameter 44–58 µm. Leasurae simple, sometimes curved in compressed specimens, reaching ⅔ of the radius, sometimes labrum 1-2 µm wide and high. Proximal and distal surface of spore with small and regular distributed granuli. Orbicular globules are present on the surface of the specimens as well. 
Specimen. MGPDL 17200.

Renaultia cf. villosa 
Description. Several small fragments of sphenopteroid fern, most of which appear to have been partly naturally macerated so that only the veins remain. However, one better-preserved fragment shows eight ultimate pinnae positioned such that they were almost certainly from a near-terminal part of a bipinnate segment (Fig. 5f), although the penultimate rachis is not preserved. Ultimate rachis thin, c. 0.5 mm wide, straight or slightly curved, preserved to a length of up to 25 mm. Ultimate pinnae parallel-sided for most of length, but gradually tapered in their distal part; no terminal pinnule preserved. Pinnules alternate, obliquely attached to rachis (45–60°), consistently 2 mm wide, 3 mm long in distal part of segment, 4–5 mm long in more proximal positions. Pinnules subtriangular with rounded apex, basally constricted on acroscopic side, sometimes decurrent on basiscopic side. Smaller pinnules entire, larger pinnules with three lobes on either side of midvein plus an apical lobe; lobes rounded, often with somewhat flattened distal margin, and rarely more than half pinnule width.
Two fragments were found with similar oblique, subtriangular pinnules with lobed margins, in which the pinnule limb was covered by globular sporangia c. 0.5 mm in diameter.  In situ spores contained in the sporangia have circular amb and are 55–70 µm in diameter, with a cingulum that varies from narrow to wide. Laesurae simple with gently rising sutura reaching ½ of the radius. Spores show variation in the sculpturing, grading between the typical Cyclogranisporites and Puntactisporites ornamentation; the proximal and distal surface is smooth or is of a fine granulation with the base of the grains in contact all around so that the surface of the spore appears irregularly granulate or finely rugulate. Sporoderm is up to 2.5 µm thick. 
Specimens. Eight specimens: MGPDL 17125, 17141, 17147, 17149, 17167, 17218, 17187 (counterpart), 17190.

? Discinites sp.
Description. Part and counterpart of part of an elliptical to ovate cone, 59 mm long and 29 mm wide, with a proximal attachment width of 5 mm (Fig. 5i). Surface covered by helically arranged lozenge-shaped structures 3–4 mm tall and 6 mm wide; these structures become more compact towards the base of the fossil. In the proximal part of the cone there are also round protuberances, 1–2 mm in diameter, also in helical arrangement. 
Several immature masses of miospores have been obtained from each scale in the middle part of the cone. The miospores are compressed, slightly thermally altered, and brown in colour. No tetrads have been observed, but groups of numerous grains. The miospores are very variable in shape and dimensions but show a morphological transition from laevigate, thick-walled to cavate (pseudosaccus?), obovoid recalling pre-pollens in shape. The inner body is light yellow and smooth, circular to transversally oval in shape when detached from the exoexine. The outer layer is thickened in the equatorial margin up to 15 µm and thinner in the polar regions where it is cracked due to compression or the ultrasonic vibrations during preparation. The aperture is difficult to observe and may be absent; in some specimens slits of different length are observed. In some grains a hylum seems to be present at the centre of the dorsal(?) surface (Fig. 4d). The gradation in morphotypes is well visible also in the spore wall. In general it appears homogeneous, unstructured for ¾ of the thickness while sometimes it has arcuate columns departing from the inner portion towards the intexine. In some grains the exine is glossy, with mottled appearance likely due to delicate folds or thickenings of the outer layer, in other grains intra-alveolar with small rugulate internal elements. The spore wall of the polar surfaces appear thinner than that of the equator, where a structure similar to a pseudo-monosaccus is likely. Total diameter ranges from 90 to 152 µm (measured on 40 specimens). The inner body is from 70 to 130 µm (on 12 specimens). Grains show two different exine structures. 
Specimen. MGPDL 17172a, b (part and counterpart).

Eusphenopteris nummularia
Description. Pinnate segments at least bipinnately divided (Figf. 5j). Penultimate rachis 2 mm wide, longitudinally striate without cross bars. Ultimate rachises attached at c. 80° (although this has been subjected to some distortion), 1–3 mm wide, the longest rachis preserved for length of 33 mm. Ultimate pinnae parallel-sided as far as is preserved, although no pinna apex was observed. Alternately arranged lobed pinnules somewhat obliquely attached at 50–80°, spaced c. 5 mm apart along each side of rachis. Pinnules 7–14 mm long, 4–6 mm wide, usually subtriangular, except for largest pinnules that are parallel-sided proximally but tapered distally. Each pinnule mostly has 3–4 lobes on either side of main rachis plus a terminal lobe, except for the most proximal pinnules in a pinna that have only 2 lobes. Lobes vaulted, rounded, pyriform or sometimes bilobed, usually c. 2 mm in size. Venation not prominently marked but midvein lies in a medial furrow; lateral veins sometimes seen to be thick, inclined to pinnule margin and once forked.
Specimens. Seven specimens: MGPDL 17148, 17163, 17166, 17184, 17224, 17391, 17400.

Dicksonites plukenetii
Description. The most complete pinna is a bipinnate segment 85 mm long, the other is a fragment of ultimate pinna preserved for a length of 30 mm (Fig. 6a). Penultimate rachis 2 mm wide, longitudinally striate, bearing alternating ultimate rachises spaced 24 mm apart, at 80–90° (although there has been some taphonomic distortion). Ultimate rachises straight or slightly deflected at the attachment of pinnule; there is some suggestion the rachises are winged. Ultimate pinnae more than 35 mm long (none were preserved complete), but are incomplete, and are 24–26 mm wide. Pinnules inserted at c. 80° to rachis, 12 mm long, 4–7 mm wide, short, squat, parallel sided for most of length, bluntly terminated by a single lobe with a somewhat acute apex. Pinnules with 2–4 roundly angular, almost sub-rhomboidal lobes on either side of non-decurrent midvein; adjacent lobes touching or somewhat overlapping. Pinnule limb slightly vaulted. Veins mostly difficult to discern but where visible are widely spaced.
Specimen. MGPDL 2764.

Alethopteris ambigua
Description. Two short pinna fragments 20 mm wide, preserved for lengths of 30–33 mm, with 1 mm wide rachis. Pinnules alternately attached to rachis (Fig. 6b), spaced 7 mm apart on each side; pinnule insertion 60–70° on one side of rachis, 80–90° on the other. Pinnules linguaeform, basally constricted on acroscopic side, constricted or decurrent on acroscopic side, apical part slightly tapered to a round apex, 10 mm long, 3 mm wide; pinnule limb very vaulted on either side of midvein. Midvein lies in a deep furrow and runs for at least ¾ of pinnule length. Lateral veins poorly preserved but appear to be once forked and meet the pinnule margin about 80°; marginal vein density 26–30 per cm.
Specimen. MGPDL 17117.

Alethopteris sp.
Description. Two fragments of alethopterid pinnules preserved on one specimen. The most complete is part of a detached alethopterid pinnule, linguaeform with rounded apex, 16 mm long, 5 mm wide, prominent midvein for ¾ of pinnule length (Fig. 6c). Lateral veins broadly arched, broadly arch to meet the pinnule margin at near to right angles, branch usually twice at a narrow angle, marginal vein density 48 per cm. A second specimen showing just the parts of two pinnules each with a strongly confluent base.
Specimen. MGPDL 17220.

Trigonocarpus sp.
Description. Sclerotesta cast, 12 mm long, 7–8 mm wide, with at least two clear longitudinal ribs visible (the third one is presumably embedded in the matrix). 
Specimen. MGPDL 17409.

Neuropteris sp.
Description. Neuropteroid pinna fragment, rachis 25 mm long; pinna 15 mm wide. Pinnules alternately attached to rachis at 80–90° on one side of rachis, 60–70° on the other side; pinnule spacing c. 5 mm on either side. Pinnules 8 mm long, 4 mm wide, squat-linguaeform or in some cases slightly barrelled, with a round apex, and constricted base that tends to cut in more on the acroscopic side. Midvein slightly decurrent at base, strongly marked and extending for c. ⅔ of length of pinnule, where it dissolves into subsidiary veins. Subsidiary veins emitted at acute angle and then arch broadly to meet pinnule margin at about right angles. Veins fork mostly twice; vein density 42–44 per cm along pinnule margin.
Specimen. MGPDL 17221.

(?)Neuropteris sp.
Description. Two pinnules, one complete, 23 mm long by 8 mm wide, and one broken preserved for a length of 13 mm and 7 mm wide. Pinnules subfalcate with round apex; complete pinnule with weakly cordate base, broken pinnules with more markedly cordate base. Pinnule limb fairly flat. Thin midvein extends for 90% of pinnule length. Full details of lateral veins difficult to make out but appear to branch several times, arch broadly to meet the pinnule margin at 80–90°; vein density c. 50 per cm on pinnule margin.
Specimen. MGPDL 17170.

Linopteris cf. obliqua
Description. Proximal fragment of pinnule, 14 mm wide, preserved length 13 mm (but very incomplete). Pinnule with straight lateral margins, flat bottom, parallel, constricted but non-cordate base. Weakly developed midvein. Dense lateral veins formed into more or less elongated meshes that meet pinnule margin at c. 80°; margin vein density 28 per cm.
Specimen. MGPDL 17409.

Artisia approximata
Description. Pith cast 52 mm long, 20 mm wide. Outer zone of featureless tissue, 4 mm wide. Inner part with transverse plates, 6–7 per cm, some of which anastomose.
Specimen. MGPDL 17133.

Table 4. Correlation and regression analyses for sphenophyte leafy shoots: x and y – the two parameters being analysed; r2 – Pearson's correlation coefficient squared; puncorr. – probability that the parameters are not correlated; d.f. – degrees of freedom; RMA – resulting reduced major axis regression equation. Significant correlations (i.e. puncorr. < 0.05) are highlighted in bold.
Species	y-parameter	x-parameter	r2	puncorr.	d.f.	RMA	
A. sardiniana	Segment length	Segment width	0.683	<0.001	(49)	y = 13.4x – 3.1	
	Segment length	No. of segments per whorl	0.297	0.003	(28)	y = 1.8x – 19.4	
	Stem width	No. of segments per whorl	0.471	0.020	(11)	y = 0.38x – 5.8	
	Spacing between whorls	No. of segments per whorl	0.240	0.126	(11)	–	
A. stellata	Leaf length	Leaf width	0.169	0.209	(11)	–	
	Leaf length	No. of leaves per whorl	<0.001	0.991	(9)	–	
	Stem width	No. of leaves per whorl	0.0.059	0.528	(9)	–	
	Spacing between whorls	No. of leaves per whorl	0.058	0.532	(9)	–