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Notes on Mississippian echinoderms from Hurdlow, Derbyshire, central England
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Notes on Mississippian echinoderms from Hurdlow, Derbyshire, central England Stephen K. Donovana,b,* , A.J. (Ton) de Wintera a b
Taxonomy and Systematics Group, Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, the Netherlands Department of Earth Sciences, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada
A R T I C L E I N F O
A B S T R A C T
Article history: Received 21 August 2018 Received in revised form 25 September 2018 Accepted 2 October 2018 Available online xxx
The fossil echinoderms of the Lower Carboniferous (Mississippian) of Derbyshire remain understudied, principally due to the nature of the preservation rather than any lack of biodiversity. Echinoids and crinoids are described in float blocks of limestone from near Hurdlow, Derbyshire, which have been etched naturally after many years of being washed by weakly acidic rain. Surface detail is variable, commonly poor, but rare specimens retain enough features for tentative identification. Two species of echinoids are identified from rare disarticulated plates, namely Melonechinus? sp. (ambulacral plates) and archaeocidarid sp. (interambulacral plate); more and superior material will be necessary to confirm this division. Crinoids include a cladid brachial ossicle sp. with a distinctive sculpture; a columnal of a monobathrid camerate platycrinitid sp.; Annulocolumnus (col.) sp. cf. A. annulus Donovan, a columnal morphotaxon with an unusually broad axial canal; and Cyclocyclicus (col.) spp. This is the tenth echinoid site to be recognized from the Mississippian of the White Peak. Examination of etched float blocks provides a further method of investigation of the echinoderm fauna of this and other limestone areas. © 2018 The Geologists' Association. Published by Elsevier Ltd. All rights reserved.
Keywords: Field guides Monsal Dale Limestone Formation Brigantian Crinoids Echinoids
1. Introduction Beware of old field guides. When S.K.D. became interested in palaeontology over 40 years ago, one of the first books that he bought was ‘British Fossiliferous Localities’ (Arkell, 1954) which was over 20 years old at the time. It listed sites that were already familiar to him such as Folkestone (Gault Formation), but it also included many more, providing a host of possibilities. For two years it supported S.K.D.’s fieldwork as an amateur palaeontologist at weekends. Fieldwork was planned by reference to Arkell (1954) and the relevant Ordnance Survey topographic sheets. This led to a succession of excursions to all points of the compass and radiating from North London. It was this period of S.K.D.’s life, before he went to university, which taught him a fact that is only too obvious after brief contemplation; old field guides never die, but they do fade away. Former quarries are filled in, become overgrown, are landscaped or are occupied by industrial estates; access is denied by new owners; coastal exposures are buried by mudslides or are
otherwise inaccessible; and sometimes the information given is just wrong. This is a tale of a potentially ‘wrong’ locality that turned out right, as part of a programme of fieldwork by S.K.D. to find new echinoderm-rich sites in the Carboniferous limestones of Derbyshire. Simpson (1982, pp. 102–107) is a guide to Mississippian (Lower Carboniferous) localities around Parsley Hay, on the closed Buxton to Ashbourne railway line in Derbyshire, now a cycle path. This is an old field guide, obviously, but the former railway south of Parsley Hay, now part of the Pennine Bridleway, was known to provide some excellent fossiliferous exposures (Donovan, 2018). However, to the north, this is no longer the case in all instances. Simpson’s localities 5 and 6 are very overgrown, although some poorly exposed limestones are still apparent. Locality 7 is better exposed (Fig. 1), albeit still not rich in collectable crinoid debris. Simpson (1982, p. 107) described the palaeontology of locality 7 in the broadest terms: “ . . . profusion of shell and crinoid fossils”. But there are some rare echinoderm fragments of interest. 2. Locality and horizon
* Corresponding author at: Taxonomy and Systematics Group, Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, the Netherlands. E-mail address: [email protected] (S.K. Donovan).
Simpson’s most northerly site in this chapter, ‘Parsley Hay, the High Peak and Tissington Trails’ (1982, pp. 102–107), was his locality 7, exposed on the Pennine Bridleway south of the bridge over the minor road from Endmoor on the A515 south-west
https://doi.org/10.1016/j.pgeola.2018.10.001 0016-7878/© 2018 The Geologists' Association. Published by Elsevier Ltd. All rights reserved.
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Fig. 1. Monsal Dale Limestones Formation (lower Brigantian, Visean), south of site of former Hurdlow railway station, Derbyshire. (A, B) Silicified gigantoproductid brachiopods exposed in limestones on west side of cutting (D.A.T. Harper, research in progress). Scale in cm. (C) View of the exposure looking south towards Parsley Hey.
Fig. 2. Locality map of the Parsley Hay – Hurdlow area, south-west of Buxton, Derbyshire. Key: solid lines = roads; dashed line = Pennine Bridleway; H = site of Hurdlow railway station (closed); PH = site of Parsley Hay railway station (closed), now a cycle hire centre and café; * = fossil locality discussed herein (but see also Simpson, 1982, fig. 70). For the position of the study area within the British Isles, see Figure 6.
towards Pilsbury (Simpson, 1982, fig. 70; Fig. 2 herein). This site is a long cutting centred at about [NGR SK 130 652] (Fig. 1C) in an area of typical “ . . . distinctive upland of gently rolling hills . . . ” (Dalton et al., 1999, p. 13). In situ limestone beds are exposed on both sides of the cutting, but particularly on the west face. Specimens discussed herein came from float blocks of limestone in the grasses and other vegetation below this west face. Simpson’s map (and that of Harrison and Adlam, 1985) placed the locality in the Monsal Dale Limestone Formation (D2); lower Brigantian, Visean (George et al., 1976, table 2; Aitkenhead et al., 1985, pp. 25– 39; Aitkenhead et al., 2002, table 6). 3. Materials and methods The massive Mississippian limestones of the Derbyshire White Peak are rich in crinoid debris (Cope, 1998, fig. 62; Thomas, 2008, fig. 14), but they do not favour easy collection (Donovan, 2013). The echinoderm remains discussed herein were all collected from float, most particularly cobbles that showed the effects of many years of etching by slightly acidic rainwater (Liljestrand, 1985). Most of
these specimens were soaked in diluted domestic bleach overnight to remove recent organic matter, thoroughly washed in tap water and dried by a gentle heat by a sunny window. Examination was initially by eye and hand lens, and ossicles of interest indicated by a circle of black or red ink. Rare columnals were ‘popped off’ of the large cobbles in the field. In the laboratory they were examined by binocular microscope. Photography was by taking a series of photographs with a Leica DFC240 digital camera attached to a Leica M165c stereomicroscope with Leica LAS V4.4 software. The photographs were subsequently stacked using Helicon Focus 6.7.1 software. Terminology of the crinoid endoskeleton follows Ubaghs (1978) and Moore et al. (1978); terminology of the echinoid endoskeleton follows Melville and Durham (1966) and Durham and Wagner (1966). The specimens discussed herein are deposited in the Naturalis Biodiversity Center, Leiden (prefix RGM). 4. Systematic palaeontology Class Echinoidea Leske, 1778
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Family Palaechinidae M’Coy, 1849 Genus Melonechinus Meek and Worthen, 1861 Type species: Melonites multipora Norwood and Owen, 1846, p. 225, by original designation (Kier, 1966, p. 309), from the Mississippian of Missouri. Diagnosis: (Modified after Donovan and Lewis, 2017, pp. 170171.) “Large, globular test with thick, tesselate plates. Apical disc small, monocyclic; genital plates large, pentagonal, three or four gonopores per plate. Ambulacra more or less straight, as wide as ambulacral zones; multiserial throughout; outer and inner series of plates in each half ambulacrum with a further three or four intermediate columns; each plate with a small pore-pair; porepairs form a broad band on either side of ambulacrum; innermost series of plates largest with wide perradial zone; finely granulated with no primary tubercles. Interambulacra wide, composed of nine regular columns of polygonal plates; like ambulacra, finely granulated with no primary tubercles. Spines small and sulcate. Peristome small.” Remarks: One nominal species of Melonechinus is known from the White Peak of Derbyshire (Donovan and Lewis, 2017), namely Melonechinus etheridgi (Keeping, 1876), which ranges into the lower Brigantian. The disarticulated ambulacral plates documented below are too lacking in diagnostic features to permit little more than a tentative identification to the level of genus. The
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peristomial plating and lantern were figured by Jackson, (1912, pl. 56) (J.R. Thompson, written comm., September 2018). Range: Lower Carboniferous (Mississippian) of the USA, Europe and China (Kier, 1966, p. U309; Smith and Kroh, 2011; J.R. Thompson, written comm., September 2018). Melonechinus? sp. (Fig. 3B, C) Material: Two ambulacral plates, RGM.1332282, 1332283 (Fig. 3B, C, respectively). Remarks: Each of these specimens bears a prominent pore pair, hence they are ambulacral test plates. Further, they are both thick and a palaechinid, probably Melonechinus. However, Dr. Jeffery R. Thompson has noted that RGM.1332283 may be derived from Lepidocidaris (see below). The former are the more common (or, at least, more well-known) and these specimens are provisionally assigned to Melonechinus? sp., while noting that superior specimens may lead to a systematic reassessment. Family ArchaeocidaridaeM’Coy, 1844 Archaeocidarid sp. (Fig. 3A) Material: A single interambulacral plate, RGM.1332281 (Fig. 3A). Description: Plate hexagonal, wider than high. Central tubercle rounded, moderately broad, crenulate(?), with a low parapet, cylindrical mamelon and central, rounded ligament pit. Other features poorly preserved.
Fig. 3. Echinoids of the Monsal Dale Limestones Formation (lower Brigantian, Visean), south of site of former Hurdlow railway station, Derbyshire. (A) Archaeocidarid sp., RGM.1332281, oblique view of interambulacral plate. (B, C) Melonechinus? sp., ambulacral plates exposing pore pairs. (B) RGM.1332282. (C) RGM.1332283. Specimens uncoated.
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Remarks: This interambulacral plate, with a prominent and central tubercle, is undoubtedly derived from an archaeocidarid. If the interambulacral plates discussed as Melonechinus? sp. are actually derived from Lepidocidaris, then the three specimens RGM.1332281 to 1332283 may represent one species. However, RGM.1332282, 1332283 are so close in thickness to a Melonechinus? sp. test that separation from RGM.1332281 is considered wellfounded. Two genera of archaeocidarid are known from the White Peak, Archaeocidaris M’Coy, 1844, and Lepidocidaris Meek and Worthen, 1873. The specimen RGM.1332281 is only distinctive to the level of family: “Interambulacral plates [of Lepidocidaris] are similar to those of Archaeocidaris and can only be identified with some confidence to either genus if preserved in close association with typical primary radioles” (Donovan and Lewis, 2017, p. 176). RGM.1332281 is thus left in open nomenclature. Melonechinus and archaeocidarids have been found together at other localities in this region (Donovan and Lewis, 2017). Class Crinoidea J.S. Miller, 1821 Remarks: The crinoids described herein (Figs. 4 and 5) are a selection from a huge diversity of ossicles seen at this site. They have been chosen to demonstrate something of the preservation and variety seen in Simpson’s locality 7, while recognising that a
comprehensive study would require a major monographic treatment using multiple techniques. However, many ossicles have lost diagnostic features due to etching and remain as crinoid spp. indet. Subclass Cladida Moore and Laudon, 1943 Incerti ordinis Brachial ossicle sp. (Fig. 4A) Material: A single brachial ossicle, RGM.1332284. Description: A uniserial brachial ossicle with a broad, rounded articular facet, depressed close to the broad, open V-shaped adoral groove. The latus has a sculpture of parallel ridges arrayed along the long axis of the arm. Remarks: The distinctive ridged sculpture of this ossicle was misidentified in the field as a fragment of echinoid spine. Comparison with monographs of the British Carboniferous crinoids (Wright, 1950-1960; Ausich and Sevastopulo, 2001) failed to reveal any close match. Features suggesting that this ossicle is a cladid include it being uniserial and the geometry of the articular facet. Subclass Camerata Wachsmuth and Springer, 1885 Order Monobathrida Moore and Laudon, 1943 Family Platycrinitidae Austin and Austin, 1842 Platycrinitid sp. indet. (Fig. 4B)
Fig. 4. Crinoids of Monsal Dale Limestones Formation (lower Brigantian, Visean), south of site of former Hurdlow railway station, Derbyshire. (A) Cladid brachial ossicle sp., RGM.1332284, with a distinctive, ridged aboral latus and wide, V-shaped adoral groove. (B) Platycrinitid sp., RGM.1332285, articular facet of elliptical columnal with figure-ofeight lumen. (C–E) Cyclocyclicus (col.) spp. (C) RGM.1332287, articular facet. (D) RGM.1332288, oblique lateral view showing narrow articulum and barrel-like latus. (E) RGM.1332289, articular facet. (F, G) Annulocolumnus (col.) sp. cf. A. annulus Donovan, RGM.1332286, oblique (F) and facetal views (G). Specimens uncoated.
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Fig. 5. Annulocolumnus (col.) sp., field photograph of pluricolumnal, in section showing axial canal towards top. Scale bar represents 10 mm.
Material: A single columnal, RGM.1332285. Description: Incomplete elliptical(?) columnal with depressed articular facet. Lumen central, small, shaped like a figure-of-eight. Latus unsculptured, convex. Remarks: The platycrinitid monobathrids, with their distinctive elliptical columnals and simple cups with commonly low bases, are known from the limestones of the White Peak (Donovan et al., 2003b), but are rare compared to other sites in northern England such as Clitheroe, Lancashire (Donovan et al., 2003a). This difference is probably due to different palaeoenvironments, platycrinitids preferring the more reefal setting of the Clitheroe limestones. RGM.1332285 shows many typical features of a platycrinitid columnal, such as an elliptical, sunken facet and central lumen. However, the specimen is poorly preserved and no synarthrial ridge is apparent. Further, the figure-of-eight lumen is rotated through 90 when compared with the morphologically similar columnals of extant bathycrinids (Donovan, 1997). An alternative identification for this columnal may be a crinoid radice at the point of bifurcation of the ‘root’. Incertae sedis Morphogenus Annulocolumnus (col.) Donovan, 1989 Type morphospecies: Annulocolumnus (col.) annulus Donovan, 1989, p. 100, text-fig. 35C, pl. 11, figs 4 and 5, by original designation, from the Lower Ordovician (Arenig, Fennian) Treiorwerth Formation at Ffynnon-y-nab, Anglesey, North Wales. Diagnosis: (After Donovan, 1989, p. 98.) “A morphogenus of low cyclocyclic columnal with a broad lumen greater than two thirds of the facet diameter; radial crenularium of short, unbranched crenulae. No areola.” Remarks: These unusual columnals have a ring-like appearance and a radial symplectial articulation. Range: Lower Ordovician (Arenig) to Mississippian (lower Brigantian); only reported from the British Isles.
Annulocolumnus (col.) sp. cf. A. annulus Donovan, 1989 (Figs. 4F, G, 5) Material: One columnal, RGM.1332286 (Fig. 4F, G). The specimen illustrated in Figure 5 was in a block of limestone too big to collect. Description: Circular columnal with a broad, central, circular lumen. No areola. Articulation radial symplectial. Latus planar, unsculptured. Remarks: The palaeobiological questions posed by these columnals with such wide axial canals were discussed by Donovan (2016). They are so different from all modern crinoids, with their narrow axial canals, as to defy confident interpretation. Morphogenus Cyclocyclicus (col.) Yeltysheva, 1955 Type morphospecies: Cyclocyclicus tenuis Yeltysheva, 1955, pp. 46–47, pl. 54, fig. 6, from the Silurian (Llandovery) of the Siberian Platform (after Donovan, 1989, p. 101). Diagnosis: (After Donovan, 1989, p. 103.) “A morphogenus of pelmatozoan columnal in which both the lumen and the articular facet are circular in outline. Columnal outline also commonly circular. Lumen diameter less than two-thirds that of articular facet. Articulation commonly symplectial, rarely synostosial, but never synarthrial. Columnals usually wider than high, columnal height is commonly 0.4 times columnal diameter or less.” Remarks: “Cyclocyclic columnals are amongst the most common and widespread in the Palaeozoic globally, but are also the most difficult to assign to a nominal species with confidence because the morphology is both conservative and convergent in many lineages. Their simplicity makes Cyclocyclicus (col.) a 'bucket' morphotaxon.” (Bouman and Donovan, 2015, p. 296). Range Ordovician to Permian, worldwide (Jeffords, 1978, p. T933), numerous morphospecies including those in open nomenclature (Donovan, 1989, pp. 101–103; Webster and Webster, 2014). Cyclocyclicus (col.) spp. (Fig. 4C-E)
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Fig. 6. (A) Outline map of the outcrop of Mississippian limestones in the Peak District showing the distribution of echinoid localities (based on Harrison and Adlam, 1985, map; modified after Donovan and Lewis, 2017,Fig. 1a). Principal towns in black; edge of main limestone outcrop stippled; outliers (Ashover, Crich) not shown. Key: * = echinoid locality; Hurdlow = locality 7 of Simpson (1982, pp. 102–107). (B) Simplified palaeogeography and tectonic framework of northern England based on a map in Waters et al. (2009) and provided by Dr. S.G. Molyneux (after Donovan and Lewis, 2017, Fig. 1b). Key: CBF = Cronkston-Bonsall Fault; DH = Derbyshire High. The inset map shows the position of (B) in the British Isles.
Material: Three figured columnals, RGM.1332287–1332289 (Fig. 4C-E, respectively). Description: RGM.1332287. Small, circular columnal. Lumen (and areola?) obscured by limestone, assumed circular. Articulation marginal, radial symplectial and composed of short, tapering, peg-like, unbranched crenulae. Latus unsculptured, weakly convex. RGM.1332288. Small, circular, barrel-like columnal. Much of the articular facet is a circular depression, but lumen and areola not discernible. Articulation marginal, symplectial, forming a narrow rim to depression; crenulae short and peg-like. Latus unsculptured, convex. RGM.1332289. Circular columnal with a small, central, circular (?) lumen. Areola circular. Marginal symplectial articulation, crenulae numerous and unbranched. Remarks: The majority of columnals from this site are circular with a circular lumen and are thus assignable to Cyclocyclicus (col.)
Yeltysheva. Higher classification is difficult; columnals similar to these columnals are found in all major groups of crinoids. The three columnals described above were chosen for their differences, not their similarities, to demonstrate something of the range of forms attained by Cyclocyclicus (col.) in the Brigantian. Many larger cyclocyclic columnals are apparent on fresh limestone faces (S.K.D., research in progress). 5. Discussion That this site has not been recognized as an echinoderm locality of some interest is hardly surprising. Although the exposure is extensive (Fig. 1C), it is not appealing to the collector. Even the better preserved fossils are poor (Figs. 1A, B, 3–5). But it was the mode of preservation that suggested the way forward. Surface etching of limestones enhances the exposure of tiny invertebrates and, if caught before the surface detail is lost, may expose
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identifiable specimens. In short, the best specimens were found in float blacks which have had many (probably 100+) years to be etched to just the right depth. Echinoid localities are rare in the Mississippian of the Peak District and this is only the tenth site to be recorded. Figure 6shows the position of the new site near Hurdlow with respect to others in this region (for further details of other sites, see Donovan and Lewis, 2017). Archaeocidaris has been recorded from two other sites that may be in the Monsal Dale Limestone Formation. Nominal fossil crinoids from the Mississippian of the White Peak of Derbyshire and Staffordshire remain few (reviewed in Bouman and Donovan, 2015, table 1). A start has been made to assigning distinctive columnals to morphogenera (Bouman and Donovan, 2015), but this is a large project that will take many tens of years. To these, there are at least five potential sources of new data on the biodiversity of the crinoids of this area that may be recognized. 5.1. Species described from cups These are obviously the best source of data. Recollecting the sites from which known specimens were found offers the potential to duplicate known taxa and, with luck, find new ones, but many provide no more detailed field data than ‘Derbyshire’ (Bouman and Donovan, 2015, table 1). In short, identification of new taxa by recollecting old crinoid localities is not as promising as might be hoped. Discovery of new cups is likely to be rare and serendipitous. 5.2. In situ limestone beds These contain so many crinoids, so much raw data, yet are difficult to collect from, at best, and intractable in the laboratory. That is, calcitic fossils in a well-cemented limestone will remain so – the techniques do not exist to easily liberate them. A chance cross section in the right orientation can be informative. For example, Donovan et al. (2003b) recorded a basal circlet of a platycrinitid monobathrid camerate in a stile, where it had been polished by walkers’ boots over many years. But vigilance is necessary to find and document such rare occurrences. Again, serendipity will play a major roll. 5.3. Silicification and Derbyshire screws Screwstones are cherts in which crinoid ossicles or pluricolumnals are preserved as natural moulds. These have an undoubted advantage over massive limestones because the moulds can be used to manufacture latex casts from which their morphology can be examined ‘in the round’. The one Derbyshire screwstone deposit to be examined in detail has yielded columnals of a diplobathrid camerate, Gilbertsocrinus? fionae Donovan, 2006, and more than six crinoid columnal morphotaxa (Bouman and Donovan, 2015). These results are encouraging and further screwstones need to be examined in similar detail. This approach is likely to reproduce more worthwhile data than either of the two methodologies discussed above. 5.4. Mudrock horizons These promise riches in the form of disarticulated ossicles that can be picked from bulk samples after processing using micropalaeontological techniques (Brasier, 1980). Donovan (2018, research in progress) has already obtained worthy data using this methodology from a thin mudrock bed near Alsop en le Dale (either Hopedale Limestone Formation (Asbian-lower Brigantian) or, less confidently, Widmerpool Formation (Brigantian)). It is this and similar horizons that are likely to yield identifiable ossicles by
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comparison with similar lithologies in, for example, the Clitheroe area (Donovan et al., 2003a), although in contrasting palaeoenvironmental settings. 5.5. Etched float blocks The specimens described above are a first attempt to derive worthwhile data by examining etched float blocks from Derbyshire. The Cromford and High Peak Railway from Cromford to Hurdlow opened in 1830 (Rimmer, 1998), so the cobbles and pebbles documented herein were presumably part of the float since then, at least. They have been etched by mildly acidic rain to leave disarticulated ossicles standing proud of the surface. In this state they are more conducive to microscopical examination than a ‘clean’ surface from a fresh rock face. Acknowledgements The companionship in the field provided by his son, Pelham, is gratefully acknowledged by S.K.D. Dr. Jeffery R. Thompson (formerly University of Southern California, Los Angeles) and Professor William I. Ausich (The Ohio State University, Columbus) are thanked for their informed comments on certain of these specimens. We thank our referees, Dr. Jeffrey R. Thompson (Baylor University, Texas) and a second, anonymous reviewer, for their considered and balanced comments. References Aitkenhead, N., Chisholm, J.I., Stevenson, I.P., 1985. Geology of the Country around Buxton, Leek and Bakewell. Memoir of the British Geological Survey. England and Wales, Sheet, pp. 111. Aitkenhead, N., Barclay, W.J., Brandon, A., Chadwick, R.A., Chisholm, J.I., Cooper, A.H., Johnson, E.W., 2002. British Regional Geology. The Pennines and Adjacent Areas, fourth edition British Geological Survey, Nottingham. Arkell, W.J., and 71 others, 1954. Directory of British Fossiliferous Localities. Palaeontographical Society, London. Ausich, W.I., Sevastopulo, G.D., 2001. The Lower Carboniferous (Tournaisian) crinoids from Hook Head, County Wexford, Ireland. Monograph of the Palaeontographical Society, London, pp. 1–137 155 (no. 617). Austin, T., Austin Jr, T., 1842. XVIII – Proposed arrangement of the Echinodermata, particularly as regards the Crinoidea, and a subdivision of the class Adelostella (Echinidae). Annals and Magazine of Natural History 10 (series 1), 106–113. Bouman, R.W., Donovan, S.K., 2015. Biodiversity of Mississippian (Lower Carboniferous) crinoids from Bradford Dale, Derbyshire, U.K. Proceedings of the Yorkshire Geological Society 60, 293–302. Brasier, M.D., 1980. Microfossils. HarperCollins, London. Cope, F.W., 1998. Geology explained in the Peak District. Scarthin Books, Cromford. . Dalton, R., Fox, H., Jones, P., 1999. Classic Landforms of the White Peak. Geographical Association, Sheffield. Donovan, S.K., 1989. Pelmatozoan columnals from the Ordovician of the British Isles. Part 2. Monographs of the Palaeontographical Society, London, pp. 69–114 142 (no. 580). Donovan, S.K., 1997. [for 1996]. Comparative morphology of the stems of the extant bathycrinid Democrinus Perrier and the Upper Palaeozoic platycrinitids (Echinodermata, Crinoidea). Bulletin of the Mizunami Fossil Museum 23, 1–27. Donovan, S.K., 2006. ‘Screwstones’ from the Lower Carboniferous (Mississippian; Visean, Brigantian) at Bradford Dale, Youlgrave, Derbyshire, and a new species of Gilbertsocrinus Phillips (Echinodermata, Crinoidea). Proceedings of the Yorkshire Geological Society 56, 87–90. Donovan, S.K., 2013. Where are all the crinoids? An enigma of the Lower Carboniferous (Mississippian) White Peak of midland England. Geology Today 29, 108–112. Donovan, S.K., 2016. Problematic aspects of the form and function of the stem in Palaeozoic crinoids. Earth-Science Reviews 154, 174–182. Donovan, S.K., 2018. Taphonomy of a Mississippian crinoid pluricolumnal, Newton Grange, Derbyshire, UK. Proceedings of the Yorkshire Geological Society 62, 59–63. Donovan, S.K., Lewis, D.N., 2017. Echinoids (Mississippian, Visean) of the Peak District, Derbyshire and Staffordshire, UK. Proceedings of the Yorkshire Geological Society 61, 169–178. Donovan, S.K., Lewis, D.N., Crabb, P., 2003a. Lower Carboniferous echinoderms of northwest England. Palaeontological Association Fold-Out Fossils 1, 1–12. Donovan, S.K., Lewis, D.N., Tilsley, J.W., 2003b. Platycrinitid crinoid cups from the Lower Carboniferous of Yorkshire and Derbyshire. Proceedings of the Yorkshire Geological Society 54, 253–256.
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Durham, J.W., Wagner, C.D., 1966. Glossary of morphological terms applied to echinoids. In: Moore, R.C. (Ed.), Treatise on Invertebrate Paleontology. Part U, Echinodermata 3, vol. 1. Geological Society of America and University of Kansas, New York and Lawrence pp. U251, U253-U256. George, T.N., Johnson, G.A.L., Mitchell, M., Prentice, J.E., Ramsbottom, W.H.C., Sevastopulo, G.D., Wilson, R.B., 1976. A correlation of the Dinantian rocks in the British Isles. Geological Society of London, Special Report 7, 1–87. Harrison, D.J., Adlam, K.A.Mc L., 1985. Limestones of the Peak: A guide to the limestone and dolomite resources of the Peak District of Derbyshire and Staffordshire. British Geological Survey, Mineral Assessment Report 144, 1–40. Jackson, R.T., 1912. Phylogeny of the Echini, with a revision of Palaeozoic species. Memoirs of the Boston Society of Natural History 7, 1–491. Jeffords, R.M., 1978. Dissociated crinoid skeletal elements. In: Moore, R.C., Teichert, C. (Eds.), Treatise on Invertebrate Paleontology, Part T, Echinodermata 2, vol. 3. Geological Society of America and University of Kansas, Boulder and Lawrence, pp. T928–T937. Keeping, W., 1876. On the discovery of Melonites in Britain. Quarterly Journal of the Geological Society, London 32, 395–399. Kier, P.M., 1966. Noncidaroid Paleozoic echinoids. In: Moore, R.C. (Ed.), Treatise on Invertebrate Paleontology. Part U, Echinodermata 3, vol. 1. Geological Society of America and University of Kansas, New York and Lawrence, pp. U298–U312. Leske, N.G., 1778. Iacobi Theodori Klein Naturalis disposito Echinodermatum. Edita et aucta a N.G. Leske, Lipsiae. Liljestrand, H.M., 1985. Average rainwater pH, concepts of atmospheric acidity, and buffering in open systems. Atmospheric Environment 19 (1967), 487–499. M’Coy, F., Griffith, R., 1844. A Synopsis of the Characters of the Carboniferous Limestone fossils of Ireland. University Press, Dublin. M’Coy, F., 1849. On some new Palaeozoic Echinodermata. Annals & Magazine of Natural History 3 (series 2), 244–254. Meek, F.B., Worthen, A.H., 1861. Descriptions of new species of Crinoidea and Echinoidea from the Carboniferous rocks of Illinois, and other western states. Proceedings of the Academy of Natural Sciences of Philadelphia 1860, 379–397 Not seen.. Meek, F.B., Worthen, A.H., 1873. Palaeontology, descriptions of invertebrates from Carboniferous System. Illinois Geological Survey 5, 323–619. Melville, R.V., Durham, J.W., 1966. Skeletal morphology. In: Moore, R.C. (Ed.), Treatise on Invertebrate Paleontology, Part U, Echinodermata 3, vol. 1. Geological Society of America and University of Kansas, New York and Lawrence, pp. U220–U251. Miller, J.S., 1821. A natural history of the Crinoidea or lily-shaped animals, with observations on the genera Asteria, Eurayle, Comatula and Marsupites. C. Frost, Bristol.
Moore, R.C., Laudon, L.R., 1943. Evolution and classification of Paleozoic crinoids. Geological Society of America Special Paper 46, 1–153. Moore, R.C., with additions by Ubaghs, G., Rasmussen, H.W., Breimer, A., Lane, N.G., 1978. Glossary of crinoid morphological terms. In: Moore, R.C., Teichert, C., Treatise on Invertebrate Paleontology, Part T, Echinodermata 2, vol. 1. Geological Society of America and University of Kansas, Boulder and Lawrence, pp. T229, T231, T233–T242. Norwood, J.G., Owen, D.D., 1846. Description of a remarkable fossil echinoderm, from the Limestone Formation of St. Louis, Missouri. American Journal of Science 2 (series 2), 225–228. Rimmer, A., 1998. The Cromford & High Peak Railway, second edition Oakwood Press, Usk. Simpson, I.M., 1982. The Peak District. Rocks and Fossils, volume 3. Unwin Paperbacks, London. Smith, A.B., Kroh, A., 2011. The Echinoid Directory. World Wide Web electronic publication. . Accessed August 2018 http://www.nhm.ac.uk/research-curation/ projects/echinoid-directory. Thomas, I.A., 2008. Hopton Wood Stone – England’s premier decorative stome. In: Doyle, P. (Ed.), England’s Heritage in Stone. English Stone Forum, Folkestone, , pp. 90–104. Ubaghs, G., 1978. Skeletal morphology of fossil crinoids. In: Moore, R.C., Teichert, C. (Eds.), Treatise on Invertebrate Paleontology, Part T, Echinodermata 2, vol. 1. Geological Society of America and University of Kansas, Boulder and Lawrence, pp. T58–T216. Wachsmuth, C., Springer, F., 1885. Revision of the Palaeocrinoidea, part III, section 1. Discussion of the classification and relations of the brachiate crinoids, and conclusion of the generic descriptions. Proceedings of the Academy of Natural Sciences of Philadelphia for 1885 223–364. Waters, C.N., Waters, R.A., Barclay, W.J., Davies, J.R., 2009. A lithostratigraphical framework for the Carboniferous successions of southern Great Britain (Onshore). British Geological Survey Research Report RR/09/01. Webster, G.D., Webster, D.W., 2014. Bibliography and Index of Palaeozoic Crinoids: Paleozoic Crinoids, Coronates, and Hemistreptocrinoids, 1758-2012. . Accessed May, 2018 http://crinoids.azurewebsites.net/. Wright, J., 1950-1960. A monograph of the British Carboniferous Crinoidea. Monograph of the Palaeontographical Society. London vol. 1, pt. 1, i-xxx+ 1-24 [1950]; pt. 2, 25-46 [1951a]; pt. 3, 47-102 [1951b]; pt. 4, 103-148 [1952]; pt. 5, 149-190 [1954]: vol. 2, pt. 1, 191-254 [1955a]; pt. 2, 255-272 [1955b]; pt. 3, 273306 [1956]; pt. 4, 307-328 [1958]; pt. 5, 329-347 [1960].. . Yeltysheva, R.S., 1955. Class Crinoidea - sea lilies - stems of sea lilies.. In: Nikiforova, O.I. (Ed.), Field Atlas of Ordovician and Silurian Faunas of the Siberian Platform, , pp. 40–47 Leningrad. [In Russian.].
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Notes on Mississippian echinoderms from Hurdlow, Derbyshire, central England Stephen K. Donovana,b,* , A.J. (Ton) de Wintera a b
Taxonomy and Systematics Group, Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, the Netherlands Department of Earth Sciences, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada
A R T I C L E I N F O
A B S T R A C T
Article history: Received 21 August 2018 Received in revised form 25 September 2018 Accepted 2 October 2018 Available online xxx
The fossil echinoderms of the Lower Carboniferous (Mississippian) of Derbyshire remain understudied, principally due to the nature of the preservation rather than any lack of biodiversity. Echinoids and crinoids are described in float blocks of limestone from near Hurdlow, Derbyshire, which have been etched naturally after many years of being washed by weakly acidic rain. Surface detail is variable, commonly poor, but rare specimens retain enough features for tentative identification. Two species of echinoids are identified from rare disarticulated plates, namely Melonechinus? sp. (ambulacral plates) and archaeocidarid sp. (interambulacral plate); more and superior material will be necessary to confirm this division. Crinoids include a cladid brachial ossicle sp. with a distinctive sculpture; a columnal of a monobathrid camerate platycrinitid sp.; Annulocolumnus (col.) sp. cf. A. annulus Donovan, a columnal morphotaxon with an unusually broad axial canal; and Cyclocyclicus (col.) spp. This is the tenth echinoid site to be recognized from the Mississippian of the White Peak. Examination of etched float blocks provides a further method of investigation of the echinoderm fauna of this and other limestone areas. © 2018 The Geologists' Association. Published by Elsevier Ltd. All rights reserved.
Keywords: Field guides Monsal Dale Limestone Formation Brigantian Crinoids Echinoids
1. Introduction Beware of old field guides. When S.K.D. became interested in palaeontology over 40 years ago, one of the first books that he bought was ‘British Fossiliferous Localities’ (Arkell, 1954) which was over 20 years old at the time. It listed sites that were already familiar to him such as Folkestone (Gault Formation), but it also included many more, providing a host of possibilities. For two years it supported S.K.D.’s fieldwork as an amateur palaeontologist at weekends. Fieldwork was planned by reference to Arkell (1954) and the relevant Ordnance Survey topographic sheets. This led to a succession of excursions to all points of the compass and radiating from North London. It was this period of S.K.D.’s life, before he went to university, which taught him a fact that is only too obvious after brief contemplation; old field guides never die, but they do fade away. Former quarries are filled in, become overgrown, are landscaped or are occupied by industrial estates; access is denied by new owners; coastal exposures are buried by mudslides or are
otherwise inaccessible; and sometimes the information given is just wrong. This is a tale of a potentially ‘wrong’ locality that turned out right, as part of a programme of fieldwork by S.K.D. to find new echinoderm-rich sites in the Carboniferous limestones of Derbyshire. Simpson (1982, pp. 102–107) is a guide to Mississippian (Lower Carboniferous) localities around Parsley Hay, on the closed Buxton to Ashbourne railway line in Derbyshire, now a cycle path. This is an old field guide, obviously, but the former railway south of Parsley Hay, now part of the Pennine Bridleway, was known to provide some excellent fossiliferous exposures (Donovan, 2018). However, to the north, this is no longer the case in all instances. Simpson’s localities 5 and 6 are very overgrown, although some poorly exposed limestones are still apparent. Locality 7 is better exposed (Fig. 1), albeit still not rich in collectable crinoid debris. Simpson (1982, p. 107) described the palaeontology of locality 7 in the broadest terms: “ . . . profusion of shell and crinoid fossils”. But there are some rare echinoderm fragments of interest. 2. Locality and horizon
* Corresponding author at: Taxonomy and Systematics Group, Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, the Netherlands. E-mail address: [email protected] (S.K. Donovan).
Simpson’s most northerly site in this chapter, ‘Parsley Hay, the High Peak and Tissington Trails’ (1982, pp. 102–107), was his locality 7, exposed on the Pennine Bridleway south of the bridge over the minor road from Endmoor on the A515 south-west
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Fig. 1. Monsal Dale Limestones Formation (lower Brigantian, Visean), south of site of former Hurdlow railway station, Derbyshire. (A, B) Silicified gigantoproductid brachiopods exposed in limestones on west side of cutting (D.A.T. Harper, research in progress). Scale in cm. (C) View of the exposure looking south towards Parsley Hey.
Fig. 2. Locality map of the Parsley Hay – Hurdlow area, south-west of Buxton, Derbyshire. Key: solid lines = roads; dashed line = Pennine Bridleway; H = site of Hurdlow railway station (closed); PH = site of Parsley Hay railway station (closed), now a cycle hire centre and café; * = fossil locality discussed herein (but see also Simpson, 1982, fig. 70). For the position of the study area within the British Isles, see Figure 6.
towards Pilsbury (Simpson, 1982, fig. 70; Fig. 2 herein). This site is a long cutting centred at about [NGR SK 130 652] (Fig. 1C) in an area of typical “ . . . distinctive upland of gently rolling hills . . . ” (Dalton et al., 1999, p. 13). In situ limestone beds are exposed on both sides of the cutting, but particularly on the west face. Specimens discussed herein came from float blocks of limestone in the grasses and other vegetation below this west face. Simpson’s map (and that of Harrison and Adlam, 1985) placed the locality in the Monsal Dale Limestone Formation (D2); lower Brigantian, Visean (George et al., 1976, table 2; Aitkenhead et al., 1985, pp. 25– 39; Aitkenhead et al., 2002, table 6). 3. Materials and methods The massive Mississippian limestones of the Derbyshire White Peak are rich in crinoid debris (Cope, 1998, fig. 62; Thomas, 2008, fig. 14), but they do not favour easy collection (Donovan, 2013). The echinoderm remains discussed herein were all collected from float, most particularly cobbles that showed the effects of many years of etching by slightly acidic rainwater (Liljestrand, 1985). Most of
these specimens were soaked in diluted domestic bleach overnight to remove recent organic matter, thoroughly washed in tap water and dried by a gentle heat by a sunny window. Examination was initially by eye and hand lens, and ossicles of interest indicated by a circle of black or red ink. Rare columnals were ‘popped off’ of the large cobbles in the field. In the laboratory they were examined by binocular microscope. Photography was by taking a series of photographs with a Leica DFC240 digital camera attached to a Leica M165c stereomicroscope with Leica LAS V4.4 software. The photographs were subsequently stacked using Helicon Focus 6.7.1 software. Terminology of the crinoid endoskeleton follows Ubaghs (1978) and Moore et al. (1978); terminology of the echinoid endoskeleton follows Melville and Durham (1966) and Durham and Wagner (1966). The specimens discussed herein are deposited in the Naturalis Biodiversity Center, Leiden (prefix RGM). 4. Systematic palaeontology Class Echinoidea Leske, 1778
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Family Palaechinidae M’Coy, 1849 Genus Melonechinus Meek and Worthen, 1861 Type species: Melonites multipora Norwood and Owen, 1846, p. 225, by original designation (Kier, 1966, p. 309), from the Mississippian of Missouri. Diagnosis: (Modified after Donovan and Lewis, 2017, pp. 170171.) “Large, globular test with thick, tesselate plates. Apical disc small, monocyclic; genital plates large, pentagonal, three or four gonopores per plate. Ambulacra more or less straight, as wide as ambulacral zones; multiserial throughout; outer and inner series of plates in each half ambulacrum with a further three or four intermediate columns; each plate with a small pore-pair; porepairs form a broad band on either side of ambulacrum; innermost series of plates largest with wide perradial zone; finely granulated with no primary tubercles. Interambulacra wide, composed of nine regular columns of polygonal plates; like ambulacra, finely granulated with no primary tubercles. Spines small and sulcate. Peristome small.” Remarks: One nominal species of Melonechinus is known from the White Peak of Derbyshire (Donovan and Lewis, 2017), namely Melonechinus etheridgi (Keeping, 1876), which ranges into the lower Brigantian. The disarticulated ambulacral plates documented below are too lacking in diagnostic features to permit little more than a tentative identification to the level of genus. The
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peristomial plating and lantern were figured by Jackson, (1912, pl. 56) (J.R. Thompson, written comm., September 2018). Range: Lower Carboniferous (Mississippian) of the USA, Europe and China (Kier, 1966, p. U309; Smith and Kroh, 2011; J.R. Thompson, written comm., September 2018). Melonechinus? sp. (Fig. 3B, C) Material: Two ambulacral plates, RGM.1332282, 1332283 (Fig. 3B, C, respectively). Remarks: Each of these specimens bears a prominent pore pair, hence they are ambulacral test plates. Further, they are both thick and a palaechinid, probably Melonechinus. However, Dr. Jeffery R. Thompson has noted that RGM.1332283 may be derived from Lepidocidaris (see below). The former are the more common (or, at least, more well-known) and these specimens are provisionally assigned to Melonechinus? sp., while noting that superior specimens may lead to a systematic reassessment. Family ArchaeocidaridaeM’Coy, 1844 Archaeocidarid sp. (Fig. 3A) Material: A single interambulacral plate, RGM.1332281 (Fig. 3A). Description: Plate hexagonal, wider than high. Central tubercle rounded, moderately broad, crenulate(?), with a low parapet, cylindrical mamelon and central, rounded ligament pit. Other features poorly preserved.
Fig. 3. Echinoids of the Monsal Dale Limestones Formation (lower Brigantian, Visean), south of site of former Hurdlow railway station, Derbyshire. (A) Archaeocidarid sp., RGM.1332281, oblique view of interambulacral plate. (B, C) Melonechinus? sp., ambulacral plates exposing pore pairs. (B) RGM.1332282. (C) RGM.1332283. Specimens uncoated.
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Remarks: This interambulacral plate, with a prominent and central tubercle, is undoubtedly derived from an archaeocidarid. If the interambulacral plates discussed as Melonechinus? sp. are actually derived from Lepidocidaris, then the three specimens RGM.1332281 to 1332283 may represent one species. However, RGM.1332282, 1332283 are so close in thickness to a Melonechinus? sp. test that separation from RGM.1332281 is considered wellfounded. Two genera of archaeocidarid are known from the White Peak, Archaeocidaris M’Coy, 1844, and Lepidocidaris Meek and Worthen, 1873. The specimen RGM.1332281 is only distinctive to the level of family: “Interambulacral plates [of Lepidocidaris] are similar to those of Archaeocidaris and can only be identified with some confidence to either genus if preserved in close association with typical primary radioles” (Donovan and Lewis, 2017, p. 176). RGM.1332281 is thus left in open nomenclature. Melonechinus and archaeocidarids have been found together at other localities in this region (Donovan and Lewis, 2017). Class Crinoidea J.S. Miller, 1821 Remarks: The crinoids described herein (Figs. 4 and 5) are a selection from a huge diversity of ossicles seen at this site. They have been chosen to demonstrate something of the preservation and variety seen in Simpson’s locality 7, while recognising that a
comprehensive study would require a major monographic treatment using multiple techniques. However, many ossicles have lost diagnostic features due to etching and remain as crinoid spp. indet. Subclass Cladida Moore and Laudon, 1943 Incerti ordinis Brachial ossicle sp. (Fig. 4A) Material: A single brachial ossicle, RGM.1332284. Description: A uniserial brachial ossicle with a broad, rounded articular facet, depressed close to the broad, open V-shaped adoral groove. The latus has a sculpture of parallel ridges arrayed along the long axis of the arm. Remarks: The distinctive ridged sculpture of this ossicle was misidentified in the field as a fragment of echinoid spine. Comparison with monographs of the British Carboniferous crinoids (Wright, 1950-1960; Ausich and Sevastopulo, 2001) failed to reveal any close match. Features suggesting that this ossicle is a cladid include it being uniserial and the geometry of the articular facet. Subclass Camerata Wachsmuth and Springer, 1885 Order Monobathrida Moore and Laudon, 1943 Family Platycrinitidae Austin and Austin, 1842 Platycrinitid sp. indet. (Fig. 4B)
Fig. 4. Crinoids of Monsal Dale Limestones Formation (lower Brigantian, Visean), south of site of former Hurdlow railway station, Derbyshire. (A) Cladid brachial ossicle sp., RGM.1332284, with a distinctive, ridged aboral latus and wide, V-shaped adoral groove. (B) Platycrinitid sp., RGM.1332285, articular facet of elliptical columnal with figure-ofeight lumen. (C–E) Cyclocyclicus (col.) spp. (C) RGM.1332287, articular facet. (D) RGM.1332288, oblique lateral view showing narrow articulum and barrel-like latus. (E) RGM.1332289, articular facet. (F, G) Annulocolumnus (col.) sp. cf. A. annulus Donovan, RGM.1332286, oblique (F) and facetal views (G). Specimens uncoated.
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Fig. 5. Annulocolumnus (col.) sp., field photograph of pluricolumnal, in section showing axial canal towards top. Scale bar represents 10 mm.
Material: A single columnal, RGM.1332285. Description: Incomplete elliptical(?) columnal with depressed articular facet. Lumen central, small, shaped like a figure-of-eight. Latus unsculptured, convex. Remarks: The platycrinitid monobathrids, with their distinctive elliptical columnals and simple cups with commonly low bases, are known from the limestones of the White Peak (Donovan et al., 2003b), but are rare compared to other sites in northern England such as Clitheroe, Lancashire (Donovan et al., 2003a). This difference is probably due to different palaeoenvironments, platycrinitids preferring the more reefal setting of the Clitheroe limestones. RGM.1332285 shows many typical features of a platycrinitid columnal, such as an elliptical, sunken facet and central lumen. However, the specimen is poorly preserved and no synarthrial ridge is apparent. Further, the figure-of-eight lumen is rotated through 90 when compared with the morphologically similar columnals of extant bathycrinids (Donovan, 1997). An alternative identification for this columnal may be a crinoid radice at the point of bifurcation of the ‘root’. Incertae sedis Morphogenus Annulocolumnus (col.) Donovan, 1989 Type morphospecies: Annulocolumnus (col.) annulus Donovan, 1989, p. 100, text-fig. 35C, pl. 11, figs 4 and 5, by original designation, from the Lower Ordovician (Arenig, Fennian) Treiorwerth Formation at Ffynnon-y-nab, Anglesey, North Wales. Diagnosis: (After Donovan, 1989, p. 98.) “A morphogenus of low cyclocyclic columnal with a broad lumen greater than two thirds of the facet diameter; radial crenularium of short, unbranched crenulae. No areola.” Remarks: These unusual columnals have a ring-like appearance and a radial symplectial articulation. Range: Lower Ordovician (Arenig) to Mississippian (lower Brigantian); only reported from the British Isles.
Annulocolumnus (col.) sp. cf. A. annulus Donovan, 1989 (Figs. 4F, G, 5) Material: One columnal, RGM.1332286 (Fig. 4F, G). The specimen illustrated in Figure 5 was in a block of limestone too big to collect. Description: Circular columnal with a broad, central, circular lumen. No areola. Articulation radial symplectial. Latus planar, unsculptured. Remarks: The palaeobiological questions posed by these columnals with such wide axial canals were discussed by Donovan (2016). They are so different from all modern crinoids, with their narrow axial canals, as to defy confident interpretation. Morphogenus Cyclocyclicus (col.) Yeltysheva, 1955 Type morphospecies: Cyclocyclicus tenuis Yeltysheva, 1955, pp. 46–47, pl. 54, fig. 6, from the Silurian (Llandovery) of the Siberian Platform (after Donovan, 1989, p. 101). Diagnosis: (After Donovan, 1989, p. 103.) “A morphogenus of pelmatozoan columnal in which both the lumen and the articular facet are circular in outline. Columnal outline also commonly circular. Lumen diameter less than two-thirds that of articular facet. Articulation commonly symplectial, rarely synostosial, but never synarthrial. Columnals usually wider than high, columnal height is commonly 0.4 times columnal diameter or less.” Remarks: “Cyclocyclic columnals are amongst the most common and widespread in the Palaeozoic globally, but are also the most difficult to assign to a nominal species with confidence because the morphology is both conservative and convergent in many lineages. Their simplicity makes Cyclocyclicus (col.) a 'bucket' morphotaxon.” (Bouman and Donovan, 2015, p. 296). Range Ordovician to Permian, worldwide (Jeffords, 1978, p. T933), numerous morphospecies including those in open nomenclature (Donovan, 1989, pp. 101–103; Webster and Webster, 2014). Cyclocyclicus (col.) spp. (Fig. 4C-E)
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Fig. 6. (A) Outline map of the outcrop of Mississippian limestones in the Peak District showing the distribution of echinoid localities (based on Harrison and Adlam, 1985, map; modified after Donovan and Lewis, 2017,Fig. 1a). Principal towns in black; edge of main limestone outcrop stippled; outliers (Ashover, Crich) not shown. Key: * = echinoid locality; Hurdlow = locality 7 of Simpson (1982, pp. 102–107). (B) Simplified palaeogeography and tectonic framework of northern England based on a map in Waters et al. (2009) and provided by Dr. S.G. Molyneux (after Donovan and Lewis, 2017, Fig. 1b). Key: CBF = Cronkston-Bonsall Fault; DH = Derbyshire High. The inset map shows the position of (B) in the British Isles.
Material: Three figured columnals, RGM.1332287–1332289 (Fig. 4C-E, respectively). Description: RGM.1332287. Small, circular columnal. Lumen (and areola?) obscured by limestone, assumed circular. Articulation marginal, radial symplectial and composed of short, tapering, peg-like, unbranched crenulae. Latus unsculptured, weakly convex. RGM.1332288. Small, circular, barrel-like columnal. Much of the articular facet is a circular depression, but lumen and areola not discernible. Articulation marginal, symplectial, forming a narrow rim to depression; crenulae short and peg-like. Latus unsculptured, convex. RGM.1332289. Circular columnal with a small, central, circular (?) lumen. Areola circular. Marginal symplectial articulation, crenulae numerous and unbranched. Remarks: The majority of columnals from this site are circular with a circular lumen and are thus assignable to Cyclocyclicus (col.)
Yeltysheva. Higher classification is difficult; columnals similar to these columnals are found in all major groups of crinoids. The three columnals described above were chosen for their differences, not their similarities, to demonstrate something of the range of forms attained by Cyclocyclicus (col.) in the Brigantian. Many larger cyclocyclic columnals are apparent on fresh limestone faces (S.K.D., research in progress). 5. Discussion That this site has not been recognized as an echinoderm locality of some interest is hardly surprising. Although the exposure is extensive (Fig. 1C), it is not appealing to the collector. Even the better preserved fossils are poor (Figs. 1A, B, 3–5). But it was the mode of preservation that suggested the way forward. Surface etching of limestones enhances the exposure of tiny invertebrates and, if caught before the surface detail is lost, may expose
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identifiable specimens. In short, the best specimens were found in float blacks which have had many (probably 100+) years to be etched to just the right depth. Echinoid localities are rare in the Mississippian of the Peak District and this is only the tenth site to be recorded. Figure 6shows the position of the new site near Hurdlow with respect to others in this region (for further details of other sites, see Donovan and Lewis, 2017). Archaeocidaris has been recorded from two other sites that may be in the Monsal Dale Limestone Formation. Nominal fossil crinoids from the Mississippian of the White Peak of Derbyshire and Staffordshire remain few (reviewed in Bouman and Donovan, 2015, table 1). A start has been made to assigning distinctive columnals to morphogenera (Bouman and Donovan, 2015), but this is a large project that will take many tens of years. To these, there are at least five potential sources of new data on the biodiversity of the crinoids of this area that may be recognized. 5.1. Species described from cups These are obviously the best source of data. Recollecting the sites from which known specimens were found offers the potential to duplicate known taxa and, with luck, find new ones, but many provide no more detailed field data than ‘Derbyshire’ (Bouman and Donovan, 2015, table 1). In short, identification of new taxa by recollecting old crinoid localities is not as promising as might be hoped. Discovery of new cups is likely to be rare and serendipitous. 5.2. In situ limestone beds These contain so many crinoids, so much raw data, yet are difficult to collect from, at best, and intractable in the laboratory. That is, calcitic fossils in a well-cemented limestone will remain so – the techniques do not exist to easily liberate them. A chance cross section in the right orientation can be informative. For example, Donovan et al. (2003b) recorded a basal circlet of a platycrinitid monobathrid camerate in a stile, where it had been polished by walkers’ boots over many years. But vigilance is necessary to find and document such rare occurrences. Again, serendipity will play a major roll. 5.3. Silicification and Derbyshire screws Screwstones are cherts in which crinoid ossicles or pluricolumnals are preserved as natural moulds. These have an undoubted advantage over massive limestones because the moulds can be used to manufacture latex casts from which their morphology can be examined ‘in the round’. The one Derbyshire screwstone deposit to be examined in detail has yielded columnals of a diplobathrid camerate, Gilbertsocrinus? fionae Donovan, 2006, and more than six crinoid columnal morphotaxa (Bouman and Donovan, 2015). These results are encouraging and further screwstones need to be examined in similar detail. This approach is likely to reproduce more worthwhile data than either of the two methodologies discussed above. 5.4. Mudrock horizons These promise riches in the form of disarticulated ossicles that can be picked from bulk samples after processing using micropalaeontological techniques (Brasier, 1980). Donovan (2018, research in progress) has already obtained worthy data using this methodology from a thin mudrock bed near Alsop en le Dale (either Hopedale Limestone Formation (Asbian-lower Brigantian) or, less confidently, Widmerpool Formation (Brigantian)). It is this and similar horizons that are likely to yield identifiable ossicles by
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comparison with similar lithologies in, for example, the Clitheroe area (Donovan et al., 2003a), although in contrasting palaeoenvironmental settings. 5.5. Etched float blocks The specimens described above are a first attempt to derive worthwhile data by examining etched float blocks from Derbyshire. The Cromford and High Peak Railway from Cromford to Hurdlow opened in 1830 (Rimmer, 1998), so the cobbles and pebbles documented herein were presumably part of the float since then, at least. They have been etched by mildly acidic rain to leave disarticulated ossicles standing proud of the surface. In this state they are more conducive to microscopical examination than a ‘clean’ surface from a fresh rock face. Acknowledgements The companionship in the field provided by his son, Pelham, is gratefully acknowledged by S.K.D. Dr. Jeffery R. Thompson (formerly University of Southern California, Los Angeles) and Professor William I. Ausich (The Ohio State University, Columbus) are thanked for their informed comments on certain of these specimens. We thank our referees, Dr. Jeffrey R. Thompson (Baylor University, Texas) and a second, anonymous reviewer, for their considered and balanced comments. References Aitkenhead, N., Chisholm, J.I., Stevenson, I.P., 1985. Geology of the Country around Buxton, Leek and Bakewell. Memoir of the British Geological Survey. England and Wales, Sheet, pp. 111. Aitkenhead, N., Barclay, W.J., Brandon, A., Chadwick, R.A., Chisholm, J.I., Cooper, A.H., Johnson, E.W., 2002. British Regional Geology. The Pennines and Adjacent Areas, fourth edition British Geological Survey, Nottingham. Arkell, W.J., and 71 others, 1954. Directory of British Fossiliferous Localities. Palaeontographical Society, London. Ausich, W.I., Sevastopulo, G.D., 2001. The Lower Carboniferous (Tournaisian) crinoids from Hook Head, County Wexford, Ireland. Monograph of the Palaeontographical Society, London, pp. 1–137 155 (no. 617). Austin, T., Austin Jr, T., 1842. XVIII – Proposed arrangement of the Echinodermata, particularly as regards the Crinoidea, and a subdivision of the class Adelostella (Echinidae). Annals and Magazine of Natural History 10 (series 1), 106–113. Bouman, R.W., Donovan, S.K., 2015. Biodiversity of Mississippian (Lower Carboniferous) crinoids from Bradford Dale, Derbyshire, U.K. Proceedings of the Yorkshire Geological Society 60, 293–302. Brasier, M.D., 1980. Microfossils. HarperCollins, London. Cope, F.W., 1998. Geology explained in the Peak District. Scarthin Books, Cromford. . Dalton, R., Fox, H., Jones, P., 1999. Classic Landforms of the White Peak. Geographical Association, Sheffield. Donovan, S.K., 1989. Pelmatozoan columnals from the Ordovician of the British Isles. Part 2. Monographs of the Palaeontographical Society, London, pp. 69–114 142 (no. 580). Donovan, S.K., 1997. [for 1996]. Comparative morphology of the stems of the extant bathycrinid Democrinus Perrier and the Upper Palaeozoic platycrinitids (Echinodermata, Crinoidea). Bulletin of the Mizunami Fossil Museum 23, 1–27. Donovan, S.K., 2006. ‘Screwstones’ from the Lower Carboniferous (Mississippian; Visean, Brigantian) at Bradford Dale, Youlgrave, Derbyshire, and a new species of Gilbertsocrinus Phillips (Echinodermata, Crinoidea). Proceedings of the Yorkshire Geological Society 56, 87–90. Donovan, S.K., 2013. Where are all the crinoids? An enigma of the Lower Carboniferous (Mississippian) White Peak of midland England. Geology Today 29, 108–112. Donovan, S.K., 2016. Problematic aspects of the form and function of the stem in Palaeozoic crinoids. Earth-Science Reviews 154, 174–182. Donovan, S.K., 2018. Taphonomy of a Mississippian crinoid pluricolumnal, Newton Grange, Derbyshire, UK. Proceedings of the Yorkshire Geological Society 62, 59–63. Donovan, S.K., Lewis, D.N., 2017. Echinoids (Mississippian, Visean) of the Peak District, Derbyshire and Staffordshire, UK. Proceedings of the Yorkshire Geological Society 61, 169–178. Donovan, S.K., Lewis, D.N., Crabb, P., 2003a. Lower Carboniferous echinoderms of northwest England. Palaeontological Association Fold-Out Fossils 1, 1–12. Donovan, S.K., Lewis, D.N., Tilsley, J.W., 2003b. Platycrinitid crinoid cups from the Lower Carboniferous of Yorkshire and Derbyshire. Proceedings of the Yorkshire Geological Society 54, 253–256.
Please cite this article in press as: S.K. Donovan, A.J.T. de Winter, Notes on Mississippian echinoderms from Hurdlow, Derbyshire, central England, Proc. Geol. Assoc. (2018), https://doi.org/10.1016/j.pgeola.2018.10.001
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Please cite this article in press as: S.K. Donovan, A.J.T. de Winter, Notes on Mississippian echinoderms from Hurdlow, Derbyshire, central England, Proc. Geol. Assoc. (2018), https://doi.org/10.1016/j.pgeola.2018.10.001