Xiphosurid traces, Kouphichnium aff. variabilis (Linck), from the Namurian Upper Haslingden Flags of Whitworth, Lancashire J. I. Chisholm CONTENTS SUMMARY Summary 37 An assemblage of trackways and trails on the base of a siltstone near the top of the Upper Haslingden Flags is at­ Introduction 37 tributed to the activities of Carboniferous xiphosurids. Description and interpretation of traces 40 Walking traces can be distinguished from half-swimming Diagnosis 40 traces by the relative lengths of the paces: the difference is Remarks 40 believed to reflect that between air-supported and water- Trace A 40 supported locomotion. Most of the traces arc probablv Trace B 40 undertracks, impressed through thin layers ol sediment, Trace C 42 rather than surface markings. The whole assemblage is Trace D 42 assigned to a single taxon in the belief that the combina­ Trace E 42 tion of behaviour patterns represented b\ the trace* may Trace F 42 indicate a particular depositional environment; the Trace G 43 assemblage more closely resembles that ot Kouphichnium variabilis (Linck) than any other so far described, and is Discussion 43 named accordingly. Types of locomotion 43 Carboniferous xiphosurid traces 43 Acknowledgements 44 INTRODUCTION References 44 The two specimens described here were found by the author during an excursion led by Dr J. D. Collinson to FIGURES Hey's Britannia Quarries, Whitworth. in 1972. Tb< 1 Fit of specimens and identification of traces larger specimen has twice been figured (Collinson and A-G 41 Banks, 1975, pi. 26: Eagar and others. 1983, pi. HE), but 2 Outline drawing of trackway C 42 withoui detailed description. The specimens were found lying loose among other PLATES fallen debris on a ledge in the quarry face, and were clear­ 1 Under-surface of specimen LZA 8874 38 ly not far out of place, having been derived from the top 2 Under-surface of specimen LZA 8875 39 part of bed 2 of the following section (located at British National Grid Reference SD 8713 2031): 4 Sandstone, verv coarse-grained, feldspatbic. pale brown; erosional base 1.5 + 3 Mudstone and siltstone. dark grey, fissile 2.5 2 Siltstone and fine-grained sandstone with silty mudstone bands, all greenish grey; :i few bivalve escape-shafts 5.0 1 Sandstone, fine-grained, with a few silt­ stone bands; all greenish-grey 10.0 The section is similar to those seen in the nearby boreholes 3 and 7 illustrated by Collinson and Banks (1975, pi. 29), bed 1 being the Upper Haslingden Flaes and bed 4 the Rough Rock. Both sandstones lie within a single late-Namurian cyclothem, that with the Gastnoceras cumbriense Marine Band at its base. The Upper Hasl­ Bibliographical reference ingden Flags are thought to represent the mouth-bar CHISHOLM, J. I. 1983. Xiphosurid traces, deposits of a delta-lobe that advanced into an area of open Kouphichnium aff. variabilis (Linck), from the Namurian water from the west (Collinson and Banks, 1975, pp. Upper Haslingden Flags of Whitworth, Lancashire, 448-451) The Rough Rock, by contrast, is believed (o Rep. Inst. Geol. Sci., No. 83/10. pp. 37-44 represent the channel deposits of a vigorous river system that flowed generally from north-east to south-west across Author the central Pennine region (Shackleton, 1962, pi. 7). J. I. Chisholm, MA The specimens are numbered LZA 8874-5 in the Institute of Geological Sciences, Ring Road Halton, Leeds. Palaeontology Collections of the Institute of Geological LSI5 8TQ_ Sciences. The better preserved specimen. 8874, is shown 37 c.\ §•'•'• K ! v :' i*vi Y c7 ? vf^«PPW5«^% ?.*Vy'v>,.r- ''•••• V---1. • •" ' "* \ ' V #v ^MmmmkMfc> >••• • ;•-<?• j^. • -1 ,v--' •' •• wPil > -'•* ^v • ' -•r."^V'';>,>V' •''•'»v-v:-- '( . •; • V,« 7 \\ r -.•• * •--:-> ,:>•• t:/..V':' •' ' ' • •••*.•>,* ••"• ' *• '. " • * ,'. 'i'V-/1 (•••'• JY •ill : ' < ' ?y ' f • '•&*' ktM'fyWv l - ' v'" W". - '' ./.! ' :•'•'[-' '••< ' , -V.' 't,(i."St':-'A. ' jij' " #l:'ljiv"'H"*'V."l!'J': '• ••>.. : ' '.' ''",.'•'• • V" • '••V-'.--'" - •'•; •• •.'?*•'v. ••'"':• ,;-,?'"•'•.-/• -V. f*,' '•' t -ZTfy l.j-i. ' r,- iff 1 "' •'; , , .-••) i*.z. ji *.s &^•*•*:/•*y$&;•»•$:: -y * • »«•• --! y-'^^m^mm^^'zy ;. ;:^ /" ;.^ ^V. ' .-...'.-' 1' A-•" „-t.\z ...J. .-..,' ': : ' '"' ' '', /—tB .-^y'tf' r '., ,;' \ •'?. (•.- .'-.•> >-' ."•' ' '• .'• ' - V . • i (r Scale Plate 1 l'in1<T-surl;m- ul •.pi'iinien I.ZA KK.4 /..,.,• ;i.in ul u.m A li: irmn .niniln-i .uml shi ».\ ile!.uK ,,'. outer tr;u k* '.(.ilr .u *idi' m niilimieirf* in Plat i !: li el.tinier <p i iinen. 8875. ;n l'laii - li.junl ;:i'li\ i.liial appenilav.'e A\\^\ l.ie lerm 'Il'.u sw a\ ;- a.iii 'id shows how ihe two til lot;ether and idcniil'ic- ihe in­ in a Miui'.Mi'ii ol ir.uks. A "trail is a more continuous dividual traies. A in (i. described below All are preserv­ trace. In description the traces arc treated a^ positive ed as positi\ e reliefs on the base of a bed "I laminated pale features innmnd-. ridcol. as the\ appear ml d'.c greenish srivv quanz-siltstone. Follow ins; the IIMCI' spii iinen-. but .ivr interpreted in terms ol the necatne l| reconinu'iulrd b\ lre\ il 7.' and Siuip^on il!'75 . die le.itii! a s i pjiv. hollows, scrat i lies I produced 1" da an'.ma! term "track i* u-ni t'1 dei;oti .•:: imprewioi, maiii :-\ •>.;•• I ..I..u» lini!- -«# .*«CT *j»rN J ,^:;vvX 7V't4&£& %**J.V- o \ I.inn _L Scale ft £&& Plate 2 Under-surface of specimen LZA 887 outermost pair being different from the inner pans), as (19/5. p. 451). A shallow-water origin is consistent with a well as tail traces, and are sufficientlv like those made b\ notable difference of pace length between two kinds of the modern Limulus (Caster. 1938} lo sutmest that tbe\ trackwav preserved on the specimens; longer paces sug­ were produced bv xiphosurids. All arc believed in have gest that the bodv w as partly supported by water, and are been made while the animals were walking on die sedi­ taken to denote a halt-walking, half-swimming mode of ment surface or swimming close above it. Caster (1938. locomotion, whereas shorter paces suggest more laborious pp. 15-22) states that the present-day Limulm ikinc, crab walking, perhaps on a surface exposed briefly to the air. or horseshoe crab) will normally burrow into the sediment I'he dilleiencc is conveniently expressed by the pace it fulh submerged: it will swim onlv il the water lx-i am•» ratio, defined here as the repeat interval of the outermost very shallow, and will walk onlv when exposed to an ( )n limb impressions divided by the width between the cen- this basis the Haslingden traces suggest very shallow con­ n cs ol each pair of these; this figure gives a rough ditions, with subaerial emergence at tunes, and this was measure of relative length of paces, and is independent of the interpretation placed on them bv Collinson and Banks the si/e ol the animal. Trackways A and B, with pace ratios of 0.44 and 0.35, are interpreted as true walking distance of 35 cm (Plates I, 2; Figure 1). The width is traces, and trackway C, with pace ratio of 1.2, as a half- 20 mm throughout. It is a heteropodous trace with an swimming trace. Trackways E and F show relatively long outer set of regularly spaced paired tracks enclosing repeat intervals (but no outer limb impressions) and are fainter marks spaced at roughly the same intervals. There also interpreted as half-swimming traces. is a well marked median ridge. The trackway closely The shallow-water interpretation is not the only resembles the walking traces of fossil and present-dav possibility, however, for the behaviour of recent Limulus is xiphosurids described by Caster (1938; 1939) and by not necessarily a guide to the behaviour of ancient forms, Goldring and Seilacher (1971). It is interpreted mainly by and Goldring and Seilacher (1971) have described fossil comparison with these. xiphosurid walking trails from a variety of formations, The outer paired tracks repeat on average at intervals some of them supposedly deposited in water of moderate of 7 mm, and the width between the centres of most pairs depth. is 16 mm: the pace ratio is thus 0.44. The long axes of the Tracks showing fine detail, like those described here, elongate-triangular tracks lie oblique to the axis of the are unlikely to be true surface traces; they are more likely trackway in a pigeon-toed arrangement, with the broad to be undertracks (Goldring and Seilacher, 1971, p. 428) ends facing inwards; this can be seen clearly (Plate 1, in­ that have been impressed through a thin layer or layers of set) in only a few places because of poor preservation of sediment on to the surface where they are preserved. The the left series of tracks. The tracks were probably made by trackways are of different ages, as shown by cross-cutting the outermost pair of appendages, which are distinguish­ relationships, and it is likely, therefore, that the surface of ed from the inner pairs by the presence of forward- the specimen harbours an accumulation of undertracks pointing 'pushers' (Caster, 1938, fig. 2). The pigeon-toed impressed at different times from slightly different overly­ arrangement allows the direction of movement to be in­ ing levels. Some true surface traces may also be included. ferred (Goldring and Seilacher, 1971, p. 426). which in this case was from bottom to top of Figure 1. The tracks made by the inner pairs of appendages are DESCRIPTION AND INTERPRETATION OF fainter than those of the outer pair and have probably also TRACES been in part overprinted by them, but one or two series are visible in places on the left side of the trackway, the Formal nomenclature of xiphosurid traces is unusually best preserved being small elongate marks, sharp at the difficult, for almost every trail or trackway is mor­ anterior ends but blunt behind.