Skip to main content
×
Home

An Ordovician Pycnogonid (Sea Spider) with Serially Subdivided ‘Head’ Region

  • David M. Rudkin (a1), Michael B. Cuggy (a2), Graham A. Young (a3) and Deborah P. Thompson (a3)
Abstract

The bizarre morphology of living Pycnogonida, known colloquially as sea spiders, has long fueled dissent over their status within the arthropods. Pycnogonids figure prominently in recent analyses of anterior limb homologies and ancestral crown-group euarthropod relationships, with support for the concept of Pycnogonida as sister taxon to Euchelicerata now contested by proponents of a more basal position between Radiodonta and all other arthropods. A challenge to further elucidation of their phylogenetic position is the exceptional rarity and disjunct distribution of pycnogonids in the fossil record, due largely to their fragile unmineralized exoskeletons. New fossil discoveries therefore have the potential to add significantly to knowledge of their evolution, paleoecology, and paleobiogeography. Here we report the first known occurrence of fossil pycnogonids from rocks of Ordovician age, bridging a 65 Myr gap between controversial late Cambrian larval forms and a single documented Silurian specimen. The new taxon, Palaeomarachne granulata n. gen. n. sp., from the Upper Ordovician (ca. 450 Ma) William Lake Konservat-Lagerstätte deposit in Manitoba, Canada, is also the first reported from Laurentia. It is the only record thus far of a fossil sea spider in rocks of demonstrably shallow marine origin. Four incomplete, partially disarticulated molts represent a relatively large, robust animal with a series of five segment-like elements in a ‘head’ region that does not incorporate the first of four preserved limb-bearing trunk segments. This unique pattern may reflect the plesiomorphic condition prior to complete fusion of anterior ‘head’ elements and first trunk segment to form a cephalosoma, as seen in all eupycnogonids. Palaeomarachne granulata is interpreted as occupying a basal stem-group position in the Pycnogonida.

Copyright
References
Hide All
Arango C. P. 2002. Morphological phylogenetics of the sea spiders (Arthropoda: Pycnogonida). Organisms Diversity and Evolution, 2:107125.
Arango C. P. 2003. Sea spiders (Pycnogonida, Arthropoda) from the Great Barrier Reef, Australia: New species, new records and ecological considerations. Journal of Natural History, 37:27232772.
Arango C. P. and Wheeler W. C. 2007. Phylogeny of the sea spiders (Arthropoda, Pycnogonida) based on direct optimization of six loci and morphology. Cladistics, 23:255293.
Arnaud F. and Bamber R. N. 1987. The biology of Pycnogonida. Advances in Marine Biology, 24:196.
Bamber R. N. 2007. A holistic re-interpretation of the phylogeny of the Pycnogonida Latreille, 1810 (Arthropoda). Zootaxa, 1668:295312.
Bell T. 1853. Account of the Crustacea, p. 400410. InThe Last of the Arctic Voyages: Being a Narrative of the Expedition in H.M.S. Assistance, Under the Command of Captain Sir Edward Belcher, C. B., In search of Sir John Franklin, During the Years 1852-53-54. With notes on the Natural History by SirRichardson John, Professor Owen, Bell Thomas, Salter J. W., and Reeve Lovell, Volume 2, London, 1855, 419 p.
Bergström J., Stürmer W., and Winter G. 1980. Palaeoisopus, Palaeopantopus and Palaeothea, pycnogonid arthropods from the Lower Devonian Hunsrück Slate, West Germany. Paläontologische Zeitschrift, 54:754.
Bitsch J. and Bitsch C. 2007. The segmental organization of the head region in Chelicerata: A critical review of recent studies and hypotheses. Acta Zoologica, 88:317335.
Brenneis G., Ungerer P., and Scholtz G. 2008. The chelifores of sea spiders (Arthropoda, Pycnogonida) are the appendages of the deutocerebral segment. Evolution and Development, 10:717724.
Briggs D. E. G., Siveter D. J., Siveter D. J., Sutton M. D., Garwood R. J., and Legg D. A. 2012. Silurian horseshoe crab illuminates the evolution of arthropod limbs. Prceedings of the National Academy of Sciences, 109:1570215705.
Broili F. 1928. Crustaceenfunde aus dem rheinischen Unterdevon. Sitzungsberichte der Bayerischen Akademie der Wissenschaften, 1928:197204.
Charbonnier S., Vannier J., and Riou B. 2007. New sea spiders from the Jurassic La Voulte-sur-Rhône Lagerstätte. Proceedings of the Royal Society B: Biological Sciences, 274:25552561.
Dunlop J. A. 2010. Geological history and phylogeny of Chelicerata. Arthropod Structure and Development, 39:124142.
Dunlop J. A. and Arango C. P. 2005. Pycnogonid affinities: A review. Journal of Zoological Systematics and Evolutionary Research, 43:821.
Dunlop J. A. and Selden P. A. 2009. Calibrating the chelicerate clock: A paleontological reply to Jeyaprakash and Hoy. Experimental and Applied Acarology, 48:183197.
Dunn C. W., Hejnol A., Matus D. Q., Pang K., Browne W. E., Smith S. A., Seaver E., Rouse G. W., Obst M., Edgecombe G. D., Sorensen M. V., Haddock S. H. D., Schmidt-Rhaesa A., Okusu A., Kristensen R. M., Wheeler W. C., Martindale M. Q., and Giribet G. 2008. Broad phylogenomic sampling improves resolution of the animal tree of life. Nature, 452:745749.
Giribet G., Edgecombe G. D., and Wheeler W. C. 2001. Arthropod phylogeny based on eight molecular loci and morphology. Nature, 413:157161.
Heymons R. 1901. Die Entwicklungsgescichte der Scolopender. Zoologica, 13:1244.
Jager M., Murienne J., Clabaut C., Deutsch J., Le Guyader H., and Manuel M. 2006. Homology of arthropod anterior appendages revealed by Hox gene expression in a sea spider. Nature, 441:506508.
King P. E. 1973. Pycnogonids. Hutchinson and Co., London, U.K., 114p.
Latreille P. A. 1810. Considérations générales sur l'Ordre Naturel des Animaux composant les Classes des Crustacés, des Arachnides et des Insectes, Paris, 446p.
Legg D. A., Sutton M. D., Edgecombe G. D., and Caron J.-B. 2012. Cambrian bivalved arthropod reveals origin of arthrodization. Proceedings of the Royal Society B: Biological Sciences. doi: 10.1098/rspb.2012.1958
Lotz G. and Bückmann D. 1968. Die Hautung und die Exuvie von Pycnogonum litorale (Strom.) (Pantopoda). Zoologische Jahrbuecher (Anatomie und Ontogenie der Tiere), 85:529536.
Machner J. and Scholtz G. 2010. A scanning electron microscopy study of the embryonic development of Pycnogonum litorale (Arthropoda, Pycnogonida). Journal of Morphology, 271:13061318.
Manuel M., Jager M., Murienne J., Clabaut C., and Guyader H. L. 2006. Hox genes in sea spiders (Pycnogonida) and the homology of arthropod head segments. Development Genes and Evolution, 216:481491.
Maxmen A., Browne W. E., Martindale M. Q., and Giribet G. 2005. Neuroanatomy of sea spiders implies an appendicular origin of the protocerebral segment. Nature, 437:11441148.
Meyer K. E. and Bückmann D. 1963. Die Hautungen des Pantopoden Pycnogonum litorale (Strom). Verhandlungen der Deutschen Zoologischen Gesellschaft, 26:604609.
Nakamura K. 1981. Post embryonic-development of a pycnogonid, Propallene longiceps. Journal of Natural History, 15:4962.
Nowlan G. S. and Haidl F. M. 2001. Biostratigraphy and paleoecology of Late Ordovician conodonts from a composite section in the subsurface of Saskatchewan. Saskatchewan Energy and Mines Miscellaneous Report 2001–4.1, 1431.
Poschmann M. and Dunlop J. A. 2006. A new sea spider (Arthropoda: Pycnogonida) with a flagelliform telson from the Lower Devonian Hunsrück Slate, Germany. Palaeontology, 49:983989.
Rota-Stabelli O., Campbell L., Brinkmann H., Edgecombe G. D., Longhorn S. J., Peterson K. J., Pisani D., Philippe H., and Telford M. J. 2011. A congruent solution to arthropod phylogeny: Phylogenomics, microRNAs and morphology support monophyletic Mandibulata. Proceedings of the Royal Society B: Biological Sciences, 278:298306.
Rudkin D. M., Young G. A., and Nowlan G. S. 2008. The oldest horseshoe crab: A new xiphosurid from Late Ordovician Konservat-Lagerstätten deposits, Manitoba, Canada. Palaeontology, 51:19.
Scholtz G. and Edgecombe G. D. 2005. Heads, Hox and the phylogenetic position of trilobites, p. 139165. InKoenemann S. and Jenner R. A.(eds.), Crustacean Issues 16, Crustacean and Arthropod Relationships. CRC Press, Boca Raton.
Scholtz G. and Edgecombe G. D. 2006. The evolution of arthropod heads: Reconciling morphological, developmental and palaeontological evidence. Development Genes and Evolution, 216:395415.
Siveter D. J., Sutton M. D., and Briggs D. E. G. 2004. A Silurian sea spider. Nature, 431:978980.
Staples D. A. 2007. A new species of Colossendeis (Pycnogonida: Colossendeidae) together with records from Australian and New Zealand waters. Memoirs of Museum Victoria, 64:7994.
Sutcliffe O. E., Tibbs L. E., and Briggs D. E. G. 2002. Sedimentology and environmental interpretation of fine-grained turbidites in the Kaub Formation of the Hunsrück Slate: Analysis of a section excavated for Project Nahecaris. Metalla (Bochum), 9:89104.
Tetlie O. E., Brandt D. S., and Briggs D. E. G. 2008. Ecdysis in sea scorpions (Chelicerata, Eurypterida). Palaeogeography, Palaeoclimatology, Palaeoecology, 265:182194.
Vilpoux K. and Waloszek D. 2003 . Larval development and morphogenesis of the sea spider Pycnogonum litorale (Ström, 1762) and the tagmosis of the body of Pantopoda. Arthropod Structure and Development, 32:349383.
Waloszek D. and Dunlop J. A. 2002. A larval sea spider (Arthropoda, Pycnogonida) from the upper Cambrian “Orsten” of Sweden, and the phylogenetic position of pycnogonids. Palaeontology, 45:421446.
Whittington H. B. 1997. Morphology of the exoskeleton, p. 185. InKaesler R. L.(ed.), Treatise on Invertebrate Paleontology, Pt. O, Arthropoda 1, Trilobita (revised edition).Geological Society of America and the University of Kansas Press, Boulder, Colorado and Lawrence, Kansas.
Young G. A., Rudkin D. M., Dobrzanski E. P., Robson S. P., Cuggy M. B., and Thompson D. P. 2010. Late Ordovician Lagerstätten in Manitoba, Canada: Glimpses of softbodied diversity. IPC3–Third International Palaeontological Congress, London, UK, Programme and Abstracts, 419.
Young G. A., Rudkin D. M., Dobrzanski E. P., Robson S. P., and Nowlan G. S. 2007. Exceptionally preserved Late Ordovician biotas from Manitoba, Canada. Geology, 35:883886.
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Journal of Paleontology
  • ISSN: 0022-3360
  • EISSN: 1937-2337
  • URL: /core/journals/journal-of-paleontology
Please enter your name
Please enter a valid email address
Who would you like to send this to? *
×

Metrics

Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 11 *
Loading metrics...

Abstract views

Total abstract views: 116 *
Loading metrics...

* Views captured on Cambridge Core between September 2016 - 15th December 2017. This data will be updated every 24 hours.