Atlas of animals from the Late Westphalian of Writhlington, United Kingdom · 2017-11-10 · Trace...
Transcript of Atlas of animals from the Late Westphalian of Writhlington, United Kingdom · 2017-11-10 · Trace...
GEOLOGICA BALCANICA, 34. 1-2, Sofia, Jun. 2004, p. 47-50
IU S UNES 0
IGCP Project 469
Atlas of animals from the Late Westphalian of Writhlington, United Kingdom
Ed. A. Jarzembowski
Maidstone Museum & Bent/if Art Gallery, St Faith 's St, Maidstone, Kent M£14 1 LH and S.H.E.S., U11iversity of Reading, UK (E-mail: edjarzembowski@ maidstone.gov. uk)
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Abstract. Representative animals from the Writhlington assemblages are collectively illustrated for the first time with notes on palaeoecology, association and distribution. They are from a comparatively well sampled, terrestrial-fresh water fauna of nematodes, bivalves, arthropods and vertebrates from the Upper Westphalian D of the UK. The Writhlington fauna provides a baseline for comparative faunal work in the Variscan Foreland.
Jarzembowski, E.A., 2004. Atlas of animals from the Late Westphalian ofWrithlington, United Kingdom. -Geologica Bale., 34, 1-2;47-50.
Key words: Radstock, Carboniferous, Faunas.
Introduction
Writhlington Geological Nature Reserve (W.G.N.R.) lies in the Radstock Syncline of the Foreland Basin at Lower Writhlington in the Somerset Coalfield, UK (National Grid Reference ST 703 553; Latitude 51 o 17.8' North, Longitude 2° 55.6' West). W.G.N.R. is the former colliery tip of a closed deep mine and now a Site of Special Scientific Interest (S.S.S .I.) and Regionally Important Geological Site (R.I.G.S.)
Systematic collecting since 1984 has yielded a well-preserved compression flora and fauna including over 1,200 insects and other animals (Austen, 2001). The unburnt tip is composed mainly of Roof Shales (grey silt- and mudstones, occasionally sideritic) from the Farrington Formation dating from the upper part of the Westphalian D Stage (Dicksonites plueckenetii Sub-
zone). The 'shales' are mostly from above the No. 10 Coal Seam although a small amount associated with the No. 1 seam is also found. The No. 10 seam was worked jointly with the former Kilmersdon Colliery nearby (Jarzembowski, 1989; Thomas and Cleal, 1994).
Body fossils (terrestrial fauna)
The terrestrial fauna is dominated by arthropods, in particular insects (Pl. I, figs 4-6, 9, 11), arachnids (Fig. 1; Pl. 1, figs 1-2) and arthropleurids (Fig. 2). These occur mainly in the No. 4 assemblage of Proctor (1994), which is characterised by lycophyte debris. Arthropods are found less often in assemblages 5 and 6, which are dominated by sphenopsid and fern/pteridosperm remains respectively. Nos 4 and 6 are the most common
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PLATE I
Fig. 1. Phalangiotarbus sp. (extinct arachnid) body alongside Cyperites bicarinatus leaf, BMB 014846 [W 79a] coil. B. Jarzembowski. Scale line in mm. Fig. 2. Pleophrynus verrucosa (armoured spider), opisthosoma showing upper and lower surfaces (after Jarzembowski, 1989). Scale line in mm. Species also known from Cantabrian/Westphalian D of Mazon Creek, South Wales Coalfield and possibly the Central Bohemian Region (Dunlop, 1994b). Fig. 3. Phagophytichnus sp. (trace attributable to a mandibulate insect) on left side of Macroneuropteris scheuchzeri leaf; conchoidal fracture on right side (after Jarzembowski, 1992). Scale line in mm. Fig. 4. Cockroach larva (nymph) distal portion of exuvium missing. BMB 014876 [W 105] coli. P. Austen. Scale line in mm. Fig. 5. Bechlya ericrobinsoni (damselfly-like dragonfly), piece of C. bicarinatus below (after Jarzembowski and Nel, 2002). Scaleinmm. Fig. 6. Blattodean insect (mylacrid cockroach). Upper view- head shield (pronotum) with folded forewings: note fern-like wing venation (after Jarzembowski & Ross, 1993). Length 17 mm. Fig. 7. Euproops danae (horseshoe crab). BMB 014850 coli. J. Latham. 45 x 25 mm. Species also known from Mazon Creek and the South Wales Coalfield (Anderson, 1994). Fig. 8. Adelophthalmus imhofi (water scorpion) body after Proctor ( 1999). Note cuticular sculpture. Scale line in mm. Species widespread including Mazon Creek. Fig. 9. Protorthopteran (gerarid) insect, apical portion offorewing: note cross veins present. NHM In. 64605. Preserved wing length 32 mm, C. bicarinatus leaf below. Fig. 10. Palaeoxyris cf. carbonaria (shark egg case). BMB 014848 [W 467 b], counterpart ofJarzembowski (1989, fig. 17). Maximum width 6 mm. Fig. 11 . Palaeodictyopteran insect, hindwing base: note archedictyon present (after Jarzembowski, 1988). Scale line in mm. Fig. 12. Anthraconauta tenuis (fresh water bivalve) after Jarzembowski (1989). Scale line in mm. Species also present in the Sydney Coalfield and associated with Anthraconaia at Writhlington (Eagar, 1994).
PLATE II
Fig. 1. Diplichnites cf. cuithensis (giant millipede trackway). W 901, Manchester Museum, coli. E. Jarzembowski. Width of trackway (external) 88 mm. Fig. 2. Kouphichnium aff. variabilis (walking trackways of horseshoe crabs). BMB 014878 [W 75a], counterpart of Jarzembowski (1989, fig. 6). Scale line in mm. Fig. 3. cf. Pseudobradypus sp. (pelycosaur (mammal-like) reptile trace) associated with unnamed ostracod ichnofossils (PL. II, fig. 4). Footprint 63 x 29 mm (after Milner, 1994). Fig. 4. Ostracod (seed shrimp) trails and resting traces after Jarzembowski (1989). Illustrated area is a 17 x 30 mm area of the bedding plane. Fig. 5. Arthropod coprolites. BMB 014872 [W 186c] coli. P. Hardy. Scale in mm. Fig. 6. Cochlichnus sp. (nematode (roundworm) burrow after J arzembowski, 1989). Scale in mm. Rare, larger forms are cf. Lunichnium (Pollard & Hardy, 1991).
plant assemblages. No. 4 represents minimally transported material from low-lying forest (dominated by Lepidodendron aculeatum) and growing in a back-basin mire. In contrast, No. 6 is more travelled material from drier, higher diversity levee forest. Animals are absent from the coal seams.
Body fossils (aquatic fauna)
Remains of aquatic animals include horseshoe crabs (Pl. I, fig. 7), water scorpions (Pl. I, fig. 8), conchostracans (Fig. 3), shark egg capsules (Pl. I, fig. 10) and non-marine bivalves (Pl. I, fig. 12). Animals are rare in river channel sandstones. The shelly lacustrine mudstone associated with the No. 1 seam is a distinctive facies.
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Trace fossils
In addition .to body fossils in the above plant-rich crevasse splay depositional environments, there are animal trace fossils from the margins of a floodplain lake (Pl. II). Diverse ethological as well as morphological data are thus available (see below).
Interpretation
A numerical breakdown of the fauna is shown graphically (Fig. 4) to give a visual impression of relative abundances. More animals have been found since the last published census but the overall asymptotic 'curve' is unchanged for the
PLATE I
Ed. A. Jarzembowski, Atlas of animals from the Late Westphalian ... Geologica Balcanica, 34, l-2, 2004
-12: • • • lj = .,..
PLATE II
·"'· /:'.'-.~: . ·.' ~ ,
Fig. 1. Protophrynus carbonarius? (whipspider) restored by Proctor and Jarzembowski (1999) on lycophyte bark, based on Dunlop (1994a)
r~. 2. Arthropleu.ra armata (giant millipede) body segwents. BRSMG Cd 4057. Drawing by C. Proctor, scale line
em. Species widespread in Westphalian D
- Geologica Balcanica, 1-2/2004
Fig. 3. Anomalonema reumau.xi (conchostracan or spinicaudate) carapace after B. Jarzembowski (1985). Length 5 rnm. Also known from northern France
lower 'shale' (i .e. excluding shell counts for the upper ' shale' ). The main change is an increase in accessory taxa suggesting that W.G.N.R. has been well sampled. Thus we now know that the 'indet.' (indeterminate) category includes unique examples of a protozygopteran odonate, an amblypygid, and a eurypterid (Fig. 1; Pl. I, fig. 5; 8). Phagophytichnus seems confirmed and an unnamed seed-piercing ichnofossil (possibly the work of palaeodictyopteroids) has been added (Fig. 5; Pl. I, 3). There have been some inevitable taxonomic changes and Eophrynus is now known as Pleophrynus (Pl. I, fig. 2).
The general palaeoenvironment at W.G.N.R. is a forested 'upper delta plain' with fresh water wetland and waterways as summarised above. The fauna is divided here into land and aquatic elements. Representative taxa are illustrated in ascending systematic order. More information and reconstructions are available in primary sourct?s, and work is continuing on a number of groups, e.g. the Araneida (true spiders) are being investigated separately at the University of Manchester. Some of the photographed specimens have been enhanced with ammonium chloride (e.g. Pl. I, fig. 5) or polarised light (e.g. Pl. I, fig. 9). The specimens illustrated are from the lower 'shales' at Writhlington except PL. I, fig. 12 from the upper 'shales' and PL. I, fig. 11 from Kilmersdon colliery tip. Specimen registration numbers for newly figured material have their depository prefixed as follows: BMB, Booth Museum Brighton; BR, Bristol City Museum; LL, Manchester University Musem; NHM, Natural History Museum, London.
It is hoped that this atlas will aid Carboniferous geologists and palaeobotanists undertaking comparative studies and, moreover, encourage the recognition and recovery of faunas which must exist on the numerous colliery tips across Euramerica. Chance finds may be the first indicator of untapped potential.
Acknowledgements. This is a contribution to IGCP 469 's Sofia meeting gratefully supported by the Royal Society. Thanks to Dr J. Pollard (Manchester) for comment on Textfig. 13.
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400
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Fig. 4. Numbers (y-axis) of animals (x-axis) at W.G.N.R. to show relative abundances (from Jarzembowski, 1989)
Fig. 5. Seed hole (attributable to a palaeodictyopteroid insect) in Trigonocar- ---1 pus sp. Left, after Jarzembowski (2001). Scale line in mm
References
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