sign in sign up
<<
Home , Diaphanopterodea, Megasecoptera, Monura, Palaeodictyoptera, Protorthoptera

Journal of the Geological Sociev, London, Vol. 144, 1987, pp. 5W-511, 3 figs. Printed in Northern Ireland

The occurrence and diversity of Coal Measure

E. A. JARZEMBOWSKI Booth Museum of Natural Hktory, Dyke Road, Brighton BN1 5AA, UK

Abslrnd Insects are generally considered to be rare in the Upper Coal Measures. However, recent work in the Westphalian D of SW England suggests that many have been overlooked in the past. This is because wings, which are the most characteristic fossils, may be mistaken for detached ‘fern’ pinnules, which are much more common. The resemblance may be functional convergence rather than leaf-mimicry. The earliest members of the class Insecta in the strict sense occur in the Upper Carboniferous. Eleven major divisions or orders are represented in the Coal Measures of which only four are still living. Primitively wingless insects () are present, relatives of familiar living insects such as the silverfish. There are numerous winged insects, some ofwhich couldfold their wings () and others which could not (). Palaeopterous insects were more diverse than today. They include three extinct orders (, , ) which were probably plant suckers like present clay bugs. Other extinct palaeopterous insects (order Protodonata) were probably aerial predators like modem , and included some of the largest insects of all time (‘giant dragonflies’). By far the most common neopterous insects were () which outnumber all other insects in theUpper Carboniferous. This abundance is perhaps less surprising when one considers the general picture of the coal forests as warm, humid, and rich in organic matter. Another important neopterous group was the extinct order , which is probably related only in part to extant (grasshoppers, crickets and locusts). There is no evidence at this time of higher insects such as , , , moths and butterflies, ants, bees and wasps.

If diversity is expressed as the total number of species, then enormous colliery tips in mining areas. Recently, systematic insects are the most successful classof organisms of all time. collecting on one such tip at LowerWrithlington, near Insects are also abundant , and it has been estimated Radstock in SW England, yielded over 300 specimens and that the current global population totals about 1 X 10” doubled the entire national collection of Carboniferous individuals(Wigglesworth 1964). The earliest evidence of fossil insects. This work suggests that the less spectacular true insects ( and Thysanura auctt.) isfrom the insect fossils from ‘roof shales’ may havebeen overlooked in Upper Carboniferous, and mainlyis from the Coal the past. There are severalreasons why this may be so. Measures. This is probably because the Coal Measures, like Dissociated insect remains are often small and not easy to insects, are essentially non-marine, and coal-bearing strata distinguish on beddingplanes crowded with dissociated are some of the most extensively mined sedimentary rocks plant remains. A detached wing bears a superficial in the geological record. Terrestrial plantremains are resemblance to certain types ofleaf on account of its extremely abundant in these deposits, andfossil evidence elongate shape and branchingvenation. Eight out of ten shows that the vegetation supported a considerable variety Carboniferous insects are cockroaches (Carpenter & of life. Burnham1985), the wingsofwhich are particularly pinnule-like. Diagenetic changes often impart a similar blackcolour to wings and plants in the CoalMeasures, Occurrence heightening the resemblance. Insect fossils are never abundant in the Coal Measures, and Jarzembowski(in press) lists criteria for distinguishing well-preserved (articulated) specimens have only been found insect wings of which the symmetry ‘rule’ has most general in quantity at a small number of localities. North (1931) application. If an imaginary line is drawn fromthe wing base attributed the scarcity of insect bodies to the feeding tothe wing apex (or lengthwise down the middle of an activities of other animals. This would account for the incomplete wing),then the venational pattern in the two preponderance ofwings over other parts found, because halves of the wing so produced is quite different, whereas in there is much more edible tissue in a body than in the wing a pinnule it is more or less the same (Janembowski 1985, of an insect. figs1-2). Wings, or evenfragments ofwings, may be A general examination of a representative insect identified by the exact configuration of the veins and, where collection from the Euramerican Carboniferous, such as in developed, an intricate network (archedictyon) between the the BritishMuseum (Natural History), shows that insects veins. The variety is considerable, but Jarzembowski (1985) have been found traditionally in small ferruginous nodules. gives somegeneral pointers, and Carpenter (1954)has However, the total number of specimens is not great, provided a keyin English to many extinct families; more possiblybecause the area of bedding plane exposedin recent papers are reviewed by Wootton (1981).Specific nodules is comparatively small. Much larger areas may be identification of Coal Measure insects is complicated by the examined by splitting blocks of ‘roof shale’, of which there is comparativelysmall samples available: newly collected a plentifulsupply because it makesup the bulk of the specimens often represent new records, variants, or new

507

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/144/3/507/4889131/gsjgs.144.3.0507.pdf by guest on 02 October 2021 508 E.A. JARZEMBOWSKI

Fig.- 1. Lithomantis carbonarius Woodward, Coal Measures, near Ayr, Strathclyde, Scotland (r, rostrum; p, prothoraciclobe). Scale in mm.

taxa.Wings distinguish insects from all other , 1973). There is no evidence of higher Neoptera in the Coal but body parts have fewer diagnostic characters. However, Measures ( or Holometabola auctt. : common wings found in the same beds provide valuable clues, and insects with a pupal stage or chrysalis during development some parts have a distinctmorphology, such as the and including nine extant orders). Other notable absentees head-shield or pronotum (Bolton 1930, p1 111, fig. at this time are the hemipteroid orders (five extant) which

2) * belong tothe exopterygote Neoptera or Hemimetabola auctt., insects whichlack the pupal stage. (Laurentiaux Vieira & Laurentiaux (1985) consider that are Diversity uniquely represented in the Namurian of Belgium). The Coal Measure insects can be considered as representing However, the blattoid-orthopteroid orders of exopterygote three grades of insect evolution (Carpenter & Burnham Neoptera are well represented, and the forewings in these 1985). In descending order, they are insects commonly serve as tegmina. The order Blattodea, or (i) wingedinsects which habituallyfold their wings cockroaches, (Figs 2 & 3) comprises 80%of all insects found when at rest (Neoptera); in the Upper Carboniferous (Carpenter & Burnham 1985). (ii) winged insects which usually do not fold their wings About loo0 specieshave been describedfrom the late (Palaeoptera); Palaeozoic (Schneider 1983). This predominance cannot be (iii) primitively wingless insects ( auctt). attributed to selective preservation becausenumerous Wings are important because, apart from being common hindwingsand whole bodies are knownin addition to insect fossils, they provide insects with a mode of dispersal detached tegmina; extant cockroaches are often foundin unique amongst the invertebrates. Insects which canfold warm, humid, well vegetated situations and perhaps their their wingswhen not flying enjoy additional advantages, abundance in the Coal Measures reflects the suitability of such as avoiding being blownabout, and being able to enter the coal swamp environment. Fossil cockroaches also show confined spaces. In the latter case, the forewings are often promise as biostratigraphical tools (Schneider 1983; Durden modified as hard wing covers (tegmina or elytra) whilst the 1984). The order Orthoptera (grasshoppers,crickets and hindwings remain membraneous and flexible to provide locusts) is scarce in the Coal Measures and it may be noted propulsion in flight. This specialization has palaeontological that crickets and locusts are not known to occurin the significance because the tougher forewings are more likely Palaeozoic, nor are any of the several extant families of the to survive transport in a recognizable form. suborder Ensifera which are referred to generallyas There are 11 orders of insects found in the Coal grasshopppers.However, the Carboniferous Orthoptera Measures compared with about 27 at the present day (see (Oedischiidae)were certainly grasshopper-like (Sharov proposed Treatise classification by F. M. Carpenter in Tasch 1971). Related to the Blattodea and Orthoptera, and found

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/144/3/507/4889131/gsjgs.144.3.0507.pdf by guest on 02 October 2021 COAL MEASURES INSECIX 509

Fig. 3. Blattodea nymph, Upper Coal Series, Lower Writhlington, 2. Archimylacris eggintoni (Bolton): Middle Coal Fig. eggintoni Avon, England (ST 703553) Note wing pads are contiguous with of Measures, Coseley, Staffordshire, England. Negative impression terga showing that a metamorphic instar was presentin cockroaches adult cockroach showing dorsal aspect. The arrow indicates the by Westphalian D times. Scale lines arein mm; specimens were The wings in rest pronotum or head-shield. are folded the position. coated with ammonium chloride.

at this time, arethree extinct orders: Protorthoptera, lacked the freedom of movement of Recent insects which Caloneurodea and (Carpenter & Burnham use their rostra for blood-sucking, e.g. cimicid Hemiptera, 1985).Of these last three, theorder Protorthoptera is culicid Diptera. The prothoracic lobes of Palaeozoic insects comparativelycommon and is evidently related to the have received much attention in theoretical work on wing Orthoptera (Oedischiidae: Sharov 1971) but is probably evolution (Kingsolver & Koehl 1985). Wootton (1976) has paraphyletic and possibly polyphyletic. Foreleg adaptations suggested that the lobes could have been actually involved in a few Protorthoptera show that some specieswere in flight. The rostrum is forward pointing in L. carbonarius, specialized predators, more like prayingmantids than as in other Palaeodictyoptera, but unlike the Hemiptera grasshoppers (Carpenter 1971). where it is normally pointed posteriorly beneath the body in The Upper Carboniferous palaeopterous insectswere fossils. Perhaps the cup-shaped prothoracic lobes in L. comparativelydiverse and five orders are represented, carbonarius provided lift in flight for the elongate, forward compared with only two in the Recent fauna (Carpenter & pointed head, or even acted as air brakes to stop the insect Burnham 1985). With one exception (order Ephemeroptera from impaling itself when landing, because the wings were or ,which is rare in the Carboniferous) the apparently permanently outstretched in Palaeodictyoptera. Palaeozoic orders are extinct, and three (Palaeodictyoptera, The Diaphanopterodea differed from other Palaeoptera in Megasecoptera and Diaphanopterodea) form a distinct that their wingscould be folded, but the mechanism group characterized by beak-like or rostrate mouthparts of involved was unlike that of any Neoptera (KukalovCPeck variablelength (Palaeodictyopteroids: Wootton 1981). 1974). Typical megasecopteran wing specializations may be Lithornantiscurbonurius (Woodward 1876) from the Coal seen on specimens of Brodiu from the Coal Measures of the Measures of Scotland(Fig. l), is a typical palaeodictyop EnglishMidlands in the BM(NH)collection, and include teran with a rostrum (r), broad fore- and hindwings and a narrow wingswith petiolate basesand a comparatively pair of wing-like lobes on the prothorax (p). It is commonly reduced venation comparedwith Lithomantis: Bolton supposed that palaeodictyopteroids used their rostra to feed 1921-2, pl. 111. The wing shapes of Brodiu and Lithomantis on plant juices (Carpenter 1971). An enlarged ‘clypeus’ has resemble those of extant palaeopteran (odonatan) genera been described in Palaeodictyoptera which suggests that a such as Ischnuru and Aeshnu respectively.However, the rostra1 pump was present as in Recent sucking Hemiptera similarity does not extend to important body parts. Extant (KukalovB1970). The comparatively large size of L. possess spiny legs and well-developed mandibles carbonarius and broad, palaeopterous wings suggest that it associated with their specialized mode of insect predation,

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/144/3/507/4889131/gsjgs.144.3.0507.pdf by guest on 02 October 2021 510 E. A. JARZEMBOWSKI

and such appendages are found in the extinct order the wings are orientated horizontally in the rest position as Protodonata, which includes the celebrated ‘giant dragon- in Recent Blattodea. Such flattening of the wingsis flies’ of the Coal Measures (Carpenter 1971; Whalley 1980). consistent with an insect that hides in crevices like Recent The wingspan of some ‘giants’ clearly exceeded that of any cockroaches. (By contrast, Orthoptera such as locusts that extant insect and this gigantism has been regular source of livein the open on foliagecan fold their wings likean wonder. Whatever the biological reasons for this large size, inverted V.) the fossil record suggests that these insects were at least free It could be argued that Recent cockroaches are usually from competition with other large aerial predators because found near the ground, and that fossil cockroaches would the latter (pterosaurs, birds, bats) do not appear until later have been less conspicuous on leaf litter where pinnules are geological periods. likely to lie in a random arrangement. However, if this were Apterygotes are represented in the CoalMeasures by the case one might expect to find angiosperm leaf-mimics in bristletailsbelonging to the extinct suborder later geological periods, but this is not so. An alternative (Carpenter & Richardsonin press). This group is andless elaborate explanation for the superficial re- distinguished from other apterygotes by the presence of a semblance between cockroachwings and ‘fern’ pinnules may single caudal process or ‘tail’. beconvergent evolution for functionalreasons. Aninsect wing, like a leaf lamina, is a thin membrane with a large surface area and elongate shape which needssupporting. Coevolution The open (branching) and reticulate venation of Palaeozoic There is growing evidenceof insect interaction with plants in ‘ferns’ (Chaloner & Collinson 1975)may be simply the Coal Measures, especially feeding activity such as chew analogous structures to the branchingvenation and marks and coprolites (Scott & Taylor 1983). Wing markings archedictyon of Palaeozoic cockroach wings. preserved insome insects suggest interaction with other animals. Thus Carpenter (1971)gave anexample of Discussion aposematic wing markings in a Stephanian protorthopteran from northern France, andJarzembowski (inpress) The Carboniferous Coal Measures are a principal source of considers cryptic markings ina Westphalian protorthopteran information on earlyinsect life and reveal an already from southern England. complex community. However, the fauna differed in several Early workers interpreted asleaf-mimicry the re- important respects from the Recent one. Palaeodictyopter- semblance between Carboniferous cockroach wings and oid Palaeoptera evidently filled the plant-sucking niche now ‘fern’pinnules (North 1931). (The term ‘fern’ is used occupied by hemipteroid Neoptera, and endopterygote broadly here because the Palaeozoicflora included an Neoptera hadevidently not yet appeared. Exopterygote extinct major group (seed ferns) which do not belong to the Neoptera were represented by diverseBlattoid- Pteridophyta.) This idea has been revived recently by Fisher Orthopteroid species. Insects were the only flying animals, (1979). Their caseis that because the richlybranching and extinct Palaeoptera (Protodonata) would have been the venation of cockroachforewings resembles that of ‘fern’ dominant aerial predators. Four extant orders occur in the pinnules, it confers protection from predation on the insect. CoalMeasures but only one, Blattodea, iscommon and Some extant Mantodea and Orthoptera show a marked fossil blattodeans differ significantly from Recent ones inthe resemblance to leaves when restingon foliage, e.g. the structure of their egg-laying devices (Carpenter 1971). longhorn grasshopper Zabilius aridus from Ghana (Ed- The low frequency of insectremains in the Coal munds 1974, pl. 3(b)). The resemblance is not only in the Measures is somewhatpuzzling when one considers the pattern of the wing venation when the wings are folded, but general abundance of land plants amongst which the insects also in the matching green colour of the grasshopper. Such surelylived. A number of post-Palaeozoicwater-laid crypsisis unknown in Recent Blattodea (J. A. Marshall, deposits show a similar poor associationand mayreflect pers. comm.). This may be because most extant cockroaches more general factors suchas sorting (some of the best are nocturnal, hiding by day under bark, logs, or stones associations are from low energysystems such as lake (Mackerras 1970).Some extant cockroaches are diurnal, deposits). Data frommodern environments may help to including Polyzosteria viridirsima Shelfordand Ellipsidion explain the occurrence of insectfossils as ithas the magnificum Hebard. However, the former is green-coloured occurrence of fossil plant remains. but wingless(Commonwealth Scientific & Industrial Hundreds of insect species havebeen described from the Research Organization 1970: pl. 2b); the latter iswinged Coal Measures, but many are still only known from single and the forewings are well-developed and richly veined as in specimens and the description of new taxa shows no sign of fossil cockroaches, but are orange coloured, and therefore abating. The numerousspoil heaps in coal mining areas do not suggest leaf-mimicry (CSIRO 1970, pl. 2d), although provide a unique resource for regular collecting. Ellipsidion spp. are found on tree foliage (Mackerras 1970). It may be that fossil cockroaches differed in their habits I am indebted to H. Taylor for photographs, P. E. S. Whalley for from Recent ones. The leaf-mimicryidea would be reading the manuscript and all the volunteers whohave helped supported if there was lack of wing folding and widespread collect on Lower Writhlington Colliery Tip. diurnal activity on foliagein early cockroaches. Recent cockroaches are neopterous insects, folding their wings References when at rest, and thus do not resemble the regularly spaced, diverging pinnules of a fern frond. Fossils in the BM(NH) BOLTON,H. 1921-2. A monograph of the fossil insects of the British Coal collectionshow that Carboniferous cockroacheswere also Measures. Palaeontographical Society (Monograph), London, 6. BOLTON,H. 1930.Fossil insects of the South Wales Coalfield. Quarterly capable of folding their wings (Bolton 1921-2, pl. VI). The Journal of the Geological Society of London, 86, 9-49. insects are preserved uncrushed in ferruginous nodules and CARPENTER,F. M. 1954. Extinct families of insects. In: BRW, C. T.,

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/144/3/507/4889131/gsjgs.144.3.0507.pdf by guest on 02 October 2021 COAL MEASURES INSECTS 511

MELANDER,A. L. & CARPENTER,F. M. Classification of insects. Bulletin KUKALQVA-PECK,J. 1974. Wing-foldingin the Palaeozoicinsect order of the Museum of Comparative Zoology, Harvard College, 108,777-821. Diaphanopterodea (Paleoptera), with a description ofnew repre- CARPENTER,F. M. 1971. Adaptations amongPaleozoic insects. In: sentatives of the family Elmoidae. Psyche, 81, 315-33. Proceedings of theNorth American Palaeontological Convention, LAURENTIAUXVIEIRA, F. & LAWRENTTALK,D. 1985. Les insectes Chicago, 1969, 1, 1236-51. CarboniRres: revue sommaire. Compte Rendu: Congr2s International de CARPENER,F. M. & BURNHAM,L. 1985. The geological record of insects. Srrntigraphie et de G6ologie du CarbonifPre, Madrid 1983, 2, 449-54. Annual Review of Earth and Planetary Sciences, W, 297-314. ~CKERRAS,M. J. 1970. Blattodea. In: CSIRO TheInsects of Australia, CARPENTER,F. M. & RICHARDSON, E. S. Jr. Inpress. Archaeognatha Melbourne University Press, Carlton, Victoria, 262-74. (Insecta) from the Upper Carboniferous of Illinois. Psyche. NORTH, F. J. 1931. Insect-life in the coal forests, with special reference to CHALONER,W. G. & COLLINSON,M. E. 1975. An illustrated key to the South Wales. Transactions of the Cardiff Naturalbts’ Society, 62, 16-44. commonerBritish Upper Carboniferous plantcompression fossils. SC~,A. C. & TAYLOR,T. N. 1983. Plant/animal interactions during the Proceedings of the Geologists’ Association, 86, 1-44. Upper Carboniferous. Botanical Review, 49,259-307. COMMONWEALTH SCIENTIFIC & INDUSTRIAL RESEARCHORGANIZATION. 1970. SHAROV, A.G. 1971. Phylogeny of the Orthopteroidea. Israel Programme for The insects of Australia. Melbourne University Press, Carlton, Victoria. Scientific Translations, JeNSakm. DURDEN,C. J. 1984. North Americanprovincial insect ages for the SCHNEIDER, 3. 1983. Die Blattodea (Insecta) des Palaozoikums.Teil 1: continental last half of the Carboniferous and first half of the . Systematik, Okologie und Biostratigraphie. FreibergerForschungshefte, Compte Rendu. Congr2s International de Stratigraphie et de Giologie du c382,106-46. CarbonifPre,Warhington & Champaign-Urbana (1979), 2, Southern TASCH,P. 1973. Arthropoda I11 (Insecta) In: TASCH,P. (ed.) Paleobiology of Illinois University Press, Carbondale & Edwardsville, 606-612. the Invertebrares. J. Wiley & Sons, New York, 609-30. EDMUNDS, M.1974. Defence in AnimaLr. Longman, Harlow. WHALLEY,P. E. S. 1980. Tupus diluculum sp. nov. (Protodonata), a giant FISHER,D. C. 1979. Evidence for subaerial activity of Euproops danae dragody from the Upper Carboniferous of Britain. Bullerinof the (Merostomata, Xiphosurida). In: NITECKI,M. H. (ed.) Maron Creek British Museum (Natural History), Geology, 34, 285-87. Fossils. Academic Press, New York, 379-447. WIGGLEWORTH,V. B. 1964. The Life ofInsects. Weidenfeld & Nicholson, JARZEMBOWSKI,E. A. 1985. On the track of giant dragonflies. Antenna, 9, London. 126-7. WOODWARD,H. 1876. On an orthopterous insect from the Coal-Measures of -(In press). Prospecting for early insects. West Sussex GeologicalJou~M~. Scotland. QuarterlyJournal of the Geological Society of London, 32, KINGSOLVER, J. G. & KOEHL,M. A. R. 1985. Aerodynamics, 60-64. thermoregulation, and the evolution of insect wings: differential scaling WOOITON,R. J. 1976. The fossil record and insect flight. In: RAINEY, R. C. and evolutionary change. Evolution, 39, 488-504. (ed.) InsectFlight. Symposia of the Royal EntomologicalSociety of KUKALOVA,J. 1970. Revisional study of the Order Palaeodictyoptera in the London, 7,235-54. Upper Carboniferous shales of Commentry, France. Part 111. Psyche, 77, -1981. Palaeozoic insects. Annual Review of , 26, 319-44. 1-44.

Received 10 April 1986; revised typescript accepted 14 July 1986.

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/144/3/507/4889131/gsjgs.144.3.0507.pdf by guest on 02 October 2021