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A trigonotarbid (‘armoured spider’) from the Kent Coalfield
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A trigonotarbid ('armoured spider') from the Kent Coalfield Jason A. Dunlop
r
DUNL?P, A. 1~9~. A trigonotarbid ('annoured spider') from the Kent Coalfield. Proceedings of the Geologists ASSOClatl?n, 11~, 333-334. A new trigonotarbid find (Aracbnida: Trigonotarbida) is reported from the Chlsle~ Colliery TIP, Hersden (Upper Carboniferous: Westphalian B/C). This is the first record ?f a trigonotarbid from this coalfield. The specimen consists of a small, well preserved carapace which IS referred to Aphantomartus sp. and probably represents a juvenile. lnstitut fiir Systematische Zoologie, Museum fiir Naturkunde, lnvalidenstrafie 43, D-10 115 Berlin, Germany.
1. INTRODUCTION Trigonotarbids are an extinct order of spider-like arachnids which ranged from the Silurian to the Permian (e.g. Rossler & Dunlop, 1997). They are among the most familiar Carboniferous arachnid fossils, although they are still rare and new specimens are significant. This note reports on a trigonotarbid from the Kent Coalfield. The specimen was collected by ~r Paul Rainey from the Chislet Colliery Tip, Hersden [Gnd ref. TR 213 622] and is deposited in the Maidstone Museum & Art Gallery. The spoil heap from which this fossil was collected comprised shale tipped from the Kent No. 7 Seam of the Middle Coal Measures, similispulchra zone or even a little earlier (E. Jarzembowski, pers. comm.) which dates it to Westphalian B/C (see Gallois & Edmunds (1965) and Smart, Bisson & Worssam (1966) for
discussions of the geological setting of the Kent Coalfield). The only common animal at this site is the polycheate Spirobis, although a scorpion fossil (?Eoscorpio sp.) has been found (E. Jarzembowski, pers. comm.). The plant fossils associated with the animals are compressed, relatively abundant, but show a low diversity of species. To my knowledge, the only other arachnid described from the Kent Coalfield is Dinopilo parvus Petrunkevitch, 1953 which was described as a spider, though the specimen is not well preserved and this interpretation is questionable. This new specimen is the first trigonotarbid from the Kent Coalfield and can be referred to Aphantomartus sp. (see below). Like other trigonotarbids, and arachnids in general, ~phantomartus was probably a predator on other arthropods In the Coal Measures forests. Its dorsal tuberculation probably protected the animal against predation and, based on this, trigonotarbids have been called 'armoured spiders' (Fig. 1).
2. SYSTEMATIC PALAEONTOLOGY Order TRIGONOTARBIDA Petrunkevitch, 1949 Family APHANTOMARTIDAE Petrunkevitch, 1945 Genus APHANTOMARTUS Pocock, 1911
Aphantomartus sp. (Fig. 2) See Rossler (1998) for a full discussion and synonymy of both the family and genus.
New material Maidstone Museum & Art Gallery, no. MNEMG 1998.31, colI. Paul Rainey, from a spoil tip of the Chislet Colliery, Hersden, Kent.
Description Fig. 1. Reconstruction of the Carboniferous trigonotarbid arachnid Aphantomartus in dorsal view. .Proceedings of the Geologists' Association, 110,333-334.
The specimen is preserved in positive relief in a dark grey, unlaminated shale and represents a dorsal view of the 0016-7878/99 $15·00 © 1999 Geologists' Association
334
J. A. DUNLOP
Remarks
Fig. 2. Camera lucida drawing of the new specimen of Aphantomartus sp. Dorsal view, carapace only preserved. Scale bar equals 1 mrn.
carapace of a trigonotarbid arachnid. The carapace is small, 3.1 mm long, basal width 3.0 mm, but well preserved (Fig. 2). The carapace is subtriangular, raised medially and divided into a series of lobes, with a central eye tubercle in the middle of the carapace bearing a pair of median eyes. The carapace lobes are ornamented with large, flattened, irregular tubercles, though in places the specimen has been damaged and this tuberculation is less evident. The posterior margin of the carapace forms a broad band which lacks tuberculation. The appendages and opisthosoma are not preserved.
A subtriangular carapace with large tubercules is characteristic of the trigonotarbid family Aphantomartidae Petrunkevitch, 1945. Aphantomartids can be distinguished from the similarly tuberculate family Eophrynidae Karsch, 1882 as the latter family have the anterior carapace margin produced into a long spine, a spine not observed in this fossil. Aphantomartids are a relatively common and widespread family throughout the Westphalian and Stephanian Coal Measures of Europe and North America (e.g. Rossler, 1998). This new specimen is considerably smaller than most other aphantomartid fossils and its eye tubercle is quite large in relation to the rest of the carapace. Both these facts suggest that this new specimen is probably a juvenile. Aphantomartidae previously comprised a large number of species (e.g. Petrunkevitch, 1945, 1949, 1953), many of which appear to be defined on differences in preservation rather than morphology. Selden & Romano (1983) suggested that many aphantomartid species were probably junior synonyms. Based in part on this, Rossler (1998) recently published a major revision of the Aphantomartidae in which the family was reduced to a single genus, Aphantomartus Pocock, 1911, comprising two species, A. areolatus Pocock, 1911 and A. pustulatus Scudder, 1884, differentiated on their opisthosomal tuberculation. In light of this, it seems best to refer this new fossil, in which the opisthosoma is unknown, to Aphantomartus sp., pending more material. It is hoped that more fieldwork in the Kent Coalfield will help tie down the species.
ACKNOWLEDGEMENTS I thank Dr Ed Jarzembowski (Maidstone Museum & Art Gallery) for bringing this specimen to my attention, providing infomation on the geological setting of the Kent Coalfield and commenting on the manuscript.
REFERENCES GALLOIS, R. W. & EDMUNDS, F. H. 1965. The Wealdon District. British Regional Geology, HMSO. KARSCH, F. 1882. Ueber ein neues Spinnenthier aus der Schlesischen Steinkhole und die Arachnoiden der Steinkohlenformation iiberhaupt. Zeitschrift der Deutschen Geologischen Gesellschajt, 34, 556-561. PETRUNKEVITCH, A. I. 1945. Palaeozoic Arachnida of lIIinois. An inquiry into their evolutionary trends. Scientific Papers of Illinois, 3, 1-72. - - 1949. A study of Palaeozoic Arachnida. Transactions of the Connecticut Academy ofArts and Sciences, 37, 69-315. - - 1953. Paleozoic and Mesozoic Arachnida of Europe. Geological Society of America, Memoirs, 53, 1-128. POCOCK, R. I. 1911. A monograph of the terrestrial Carboniferous Arachnida of Great Britain. Monograph of the Palaeontographical Society, London. ROSSLER, R. 1998. Arachniden-Neufunde im mitteleuropaischen
Unterkarbon bis Perm-Beitrag zur Revision der Familie Aphantomartidae Petrunkevitch 1945 (Arachnida, Trigonotrabida). Paldontologische Zeitschrift, 72, 67-88. - - & DUNLOP, J. A. 1997. Redescription of the largest trigonotrabid arachnid - Kreischeria wiedei Geinitz 1882 from the Upper Carboniferous of Zwickau, Germany. Paldontologische Zeitschrift, 71, 237-245. SCUDDER, S. 1884. A contribution to our knowledge of Palaeozoic Arachnida. Proceedings ofthe American Academy of Arts and Sciences, 20, 15-22. SELDEN, P. A. & ROMANO, M. 1983. First Palaeozoic Arachnida from Iberia: Aphantomartus areolatus Pocock (basal Stephanian; provo Leon, N. W. Spain), with remarks on aphantomartid taxonomy. Boletin Geologico y Minero, 94, 106-112. SMART, 1. G. 0., BISSON, G. & WORSSAM, B. C. 1966. Geology of the country around Canterbury and Folkestone. Geological Survey of Great Britain, Sheet 289, pp. 305-306.
Manuscript received 16 July 1998; revised typescript accepted 28 September 1998
A trigonotarbid ('armoured spider') from the Kent Coalfield Jason A. Dunlop
r
DUNL?P, A. 1~9~. A trigonotarbid ('annoured spider') from the Kent Coalfield. Proceedings of the Geologists ASSOClatl?n, 11~, 333-334. A new trigonotarbid find (Aracbnida: Trigonotarbida) is reported from the Chlsle~ Colliery TIP, Hersden (Upper Carboniferous: Westphalian B/C). This is the first record ?f a trigonotarbid from this coalfield. The specimen consists of a small, well preserved carapace which IS referred to Aphantomartus sp. and probably represents a juvenile. lnstitut fiir Systematische Zoologie, Museum fiir Naturkunde, lnvalidenstrafie 43, D-10 115 Berlin, Germany.
1. INTRODUCTION Trigonotarbids are an extinct order of spider-like arachnids which ranged from the Silurian to the Permian (e.g. Rossler & Dunlop, 1997). They are among the most familiar Carboniferous arachnid fossils, although they are still rare and new specimens are significant. This note reports on a trigonotarbid from the Kent Coalfield. The specimen was collected by ~r Paul Rainey from the Chislet Colliery Tip, Hersden [Gnd ref. TR 213 622] and is deposited in the Maidstone Museum & Art Gallery. The spoil heap from which this fossil was collected comprised shale tipped from the Kent No. 7 Seam of the Middle Coal Measures, similispulchra zone or even a little earlier (E. Jarzembowski, pers. comm.) which dates it to Westphalian B/C (see Gallois & Edmunds (1965) and Smart, Bisson & Worssam (1966) for
discussions of the geological setting of the Kent Coalfield). The only common animal at this site is the polycheate Spirobis, although a scorpion fossil (?Eoscorpio sp.) has been found (E. Jarzembowski, pers. comm.). The plant fossils associated with the animals are compressed, relatively abundant, but show a low diversity of species. To my knowledge, the only other arachnid described from the Kent Coalfield is Dinopilo parvus Petrunkevitch, 1953 which was described as a spider, though the specimen is not well preserved and this interpretation is questionable. This new specimen is the first trigonotarbid from the Kent Coalfield and can be referred to Aphantomartus sp. (see below). Like other trigonotarbids, and arachnids in general, ~phantomartus was probably a predator on other arthropods In the Coal Measures forests. Its dorsal tuberculation probably protected the animal against predation and, based on this, trigonotarbids have been called 'armoured spiders' (Fig. 1).
2. SYSTEMATIC PALAEONTOLOGY Order TRIGONOTARBIDA Petrunkevitch, 1949 Family APHANTOMARTIDAE Petrunkevitch, 1945 Genus APHANTOMARTUS Pocock, 1911
Aphantomartus sp. (Fig. 2) See Rossler (1998) for a full discussion and synonymy of both the family and genus.
New material Maidstone Museum & Art Gallery, no. MNEMG 1998.31, colI. Paul Rainey, from a spoil tip of the Chislet Colliery, Hersden, Kent.
Description Fig. 1. Reconstruction of the Carboniferous trigonotarbid arachnid Aphantomartus in dorsal view. .Proceedings of the Geologists' Association, 110,333-334.
The specimen is preserved in positive relief in a dark grey, unlaminated shale and represents a dorsal view of the 0016-7878/99 $15·00 © 1999 Geologists' Association
334
J. A. DUNLOP
Remarks
Fig. 2. Camera lucida drawing of the new specimen of Aphantomartus sp. Dorsal view, carapace only preserved. Scale bar equals 1 mrn.
carapace of a trigonotarbid arachnid. The carapace is small, 3.1 mm long, basal width 3.0 mm, but well preserved (Fig. 2). The carapace is subtriangular, raised medially and divided into a series of lobes, with a central eye tubercle in the middle of the carapace bearing a pair of median eyes. The carapace lobes are ornamented with large, flattened, irregular tubercles, though in places the specimen has been damaged and this tuberculation is less evident. The posterior margin of the carapace forms a broad band which lacks tuberculation. The appendages and opisthosoma are not preserved.
A subtriangular carapace with large tubercules is characteristic of the trigonotarbid family Aphantomartidae Petrunkevitch, 1945. Aphantomartids can be distinguished from the similarly tuberculate family Eophrynidae Karsch, 1882 as the latter family have the anterior carapace margin produced into a long spine, a spine not observed in this fossil. Aphantomartids are a relatively common and widespread family throughout the Westphalian and Stephanian Coal Measures of Europe and North America (e.g. Rossler, 1998). This new specimen is considerably smaller than most other aphantomartid fossils and its eye tubercle is quite large in relation to the rest of the carapace. Both these facts suggest that this new specimen is probably a juvenile. Aphantomartidae previously comprised a large number of species (e.g. Petrunkevitch, 1945, 1949, 1953), many of which appear to be defined on differences in preservation rather than morphology. Selden & Romano (1983) suggested that many aphantomartid species were probably junior synonyms. Based in part on this, Rossler (1998) recently published a major revision of the Aphantomartidae in which the family was reduced to a single genus, Aphantomartus Pocock, 1911, comprising two species, A. areolatus Pocock, 1911 and A. pustulatus Scudder, 1884, differentiated on their opisthosomal tuberculation. In light of this, it seems best to refer this new fossil, in which the opisthosoma is unknown, to Aphantomartus sp., pending more material. It is hoped that more fieldwork in the Kent Coalfield will help tie down the species.
ACKNOWLEDGEMENTS I thank Dr Ed Jarzembowski (Maidstone Museum & Art Gallery) for bringing this specimen to my attention, providing infomation on the geological setting of the Kent Coalfield and commenting on the manuscript.
REFERENCES GALLOIS, R. W. & EDMUNDS, F. H. 1965. The Wealdon District. British Regional Geology, HMSO. KARSCH, F. 1882. Ueber ein neues Spinnenthier aus der Schlesischen Steinkhole und die Arachnoiden der Steinkohlenformation iiberhaupt. Zeitschrift der Deutschen Geologischen Gesellschajt, 34, 556-561. PETRUNKEVITCH, A. I. 1945. Palaeozoic Arachnida of lIIinois. An inquiry into their evolutionary trends. Scientific Papers of Illinois, 3, 1-72. - - 1949. A study of Palaeozoic Arachnida. Transactions of the Connecticut Academy ofArts and Sciences, 37, 69-315. - - 1953. Paleozoic and Mesozoic Arachnida of Europe. Geological Society of America, Memoirs, 53, 1-128. POCOCK, R. I. 1911. A monograph of the terrestrial Carboniferous Arachnida of Great Britain. Monograph of the Palaeontographical Society, London. ROSSLER, R. 1998. Arachniden-Neufunde im mitteleuropaischen
Unterkarbon bis Perm-Beitrag zur Revision der Familie Aphantomartidae Petrunkevitch 1945 (Arachnida, Trigonotrabida). Paldontologische Zeitschrift, 72, 67-88. - - & DUNLOP, J. A. 1997. Redescription of the largest trigonotrabid arachnid - Kreischeria wiedei Geinitz 1882 from the Upper Carboniferous of Zwickau, Germany. Paldontologische Zeitschrift, 71, 237-245. SCUDDER, S. 1884. A contribution to our knowledge of Palaeozoic Arachnida. Proceedings ofthe American Academy of Arts and Sciences, 20, 15-22. SELDEN, P. A. & ROMANO, M. 1983. First Palaeozoic Arachnida from Iberia: Aphantomartus areolatus Pocock (basal Stephanian; provo Leon, N. W. Spain), with remarks on aphantomartid taxonomy. Boletin Geologico y Minero, 94, 106-112. SMART, 1. G. 0., BISSON, G. & WORSSAM, B. C. 1966. Geology of the country around Canterbury and Folkestone. Geological Survey of Great Britain, Sheet 289, pp. 305-306.
Manuscript received 16 July 1998; revised typescript accepted 28 September 1998