Dipnoans (Dipnoi)

Old gypsum school model of Dipterus, maker unknown.

Biostratigraphic table of Dipnoans at Okney.

Dipterus valenciennesi Sedgwick & Murchison
Pentlandia macroptera (Traquair)

The lungfish from the Devonian Orcadian Basin are well known and described in great detail in many publications.  A new species of dipnoan, Pinalongus saxoni was recently identified from Caithness and was named after Jack Saxon the famous fossil expert from Caithness, Scotland who died in 2005.

Lungfish are fishes which have the ability to breathe air using lungs. They are still living today. Six different living species are known with some of them looking very much the same as their Devonian ancestors. Nowadays continents have their own lungfish. Australia has Neoceratodus, South America has Lipidosiren and Africa has Protopterus.

Dipterus valenciennesi is the most common lungfish found in the Devonian rocks of Orkney. They are found in the sediments indicating deep to shallow water conditions. Dipterus is almost always present in the fossiliferous rocks, although often only the scales are found. Dipterus probably could handle some of the very hostile conditions in the drying-out lakes, more than the other fishes.

Higher up in the sequence in the Eday Flags, Pentandia macroptera, a new species of lungfish appeared together with other new fish species.

Lungfish have a very specialized way of feeding which can be found in lungfish from the Devonian up to the recent lungfish. They posses large tooth plates which can be found on the palate and the lower jaw.  Most species have tooth plates with tubercles in ridges on the surface constituting the the teeth. Probably these structures in the Devonian lungfish were used to crush tiny invertebrates like arthropods or small fish. Maybe they were partly scavengers.

Formerly, the lungfish were thought to be the group that gave rise to the first amphibians and land animals (tetrapods). When more sarcopterygians (the lobbed finned fishes) were described in more detail (Gregory 1911, Jarvik and others) the osteolepids were considered the ancestor group to tetrapods. However, Jarvik and others considered that the tetrapods were diphyletic in origin with the majority of tetrapods (which includes humans) evolving from the osteolepids and the newts and salamanders evolving from the lungfish. These were grouped under the group the crossopterygians. The diphyletic origin of tetrapods has now mostly been debunked and the group, the crossopterygian also dropped as a true clade (group). Now the osteolepids are part of the group Tetrapodamorpha, with its sister group the Dipnomorpha (which includes the groups the Dipnoi and the Porolepiformes) all being lumped under the subclass, the Sarcopterygii.

Morphology and histology

Most of the Devonian lungfish had like the crossoperygians a hard cover on the outer scale surface and head plates ; cosmine, a layer composed of dentine and a thin layer of enamel on top (see also the crossoperygians and actinopterygians on this webpage). This layer probably protected the fish against predators and the often harsh environment. Because they had lungs they could leave the water for a short time to move from an almost dried up pool to another pool or river.

In recent lungfish some can burry themselves in the dry season in the mud and stay there for a year or longer until the wet season starts again, a prosess called aestivation. It could be that some of the Devonian lungfish were also able to estivate but so far fossil burrows with intact lungfish remains are not found.

Devonian lungfish scales are composed of a lamellar bone layer on the inside followed by a vascular layer with a cosmine layer on top.

Pentlandia however is an exeption in having no cosmine on the scales and head plates. To make growth possible lungfish with a cosmine cover first had to resorp the cosmine before they could enlarge the scales and headplates. Juvenile lungfish often had no cosmine at all. The cosmine started to appear on certain headplates first and some of the scales of the belly. Adult lungfish have a body completely covered with cosmine, also the scales on the fins and the fin rays are covered.

Dipterus

Head of a juvenile Dipterus showing the first cosmine patches on plates (C).

Scales of Dipterus showing the cosmine patch (C).

Head and part body without cosmine

Part body with scales with cosmine

Section of scale showing the cosmine part (C).

Pile of scales (section of body fish) with cosmine indicated (c) and ribs (r).

Scales in section showing cosmine.

Section of a toothplate showing dentine in the teeth tubercle.

Section through toothplate of Dipterus, see also for the toothplates the page on Dipterus

Pentlandia

incomplete weathered Pentlandia showing the scale surface

Close ups from the above. Scales have no cosmine.

Section of Pentlandia scales, no cosmine present

References dipnoans :

  • Alberg, P. E. and Trewin, N. H. 1995. The postcranial skeleton of the Middle Devonian lungfish Dipterus valenciennesi. Transactions of the Royal Society of Edinburgh: Earth Sciences, 85, 159-171.
  • Ahlberg P.E., Johanson Z, Daeschler EB. 2001. The late Devonian lungfish Soederberghia (Sarcopterygii, Dipnoi) from Australia and North America, and its biogeographical implications. Journal of Vertebrate Paleontology 21: 1–12
  • Ahlberg PE, Smith MM, Johanson Z. 2006. Developmental plasticity and disparity in early dipnoan (lungfish) dentitions. Evolution & Development 8: 331–349
  • Campbell, K. S. W. and Barwick, R. E. 1983. Early evolution of dipnoan dentitions and a new genus Speonesydrion. Mem. Ass. Australas. Palaeontol., 1, 17-49, 23 figs.
  • Campbell KSW, Barwick RE. 1984. Speonesydrion: an early Devonian Dipnoan with primitive toothplates, Vol. 2. München: Verlag Dr. Friedrich Pfeil.
  • Campbell KT, Barwick RE. 1986. Paleozoic lungfishes a review. Journal of Morphology 190(S1): 93–131.
  • Campbell KSW, Barwick RE. 1990. Paleozoic dipnoan phylogeny: functional complexes and evolution without parsimony. Paleobiology 16: 143–169.
  • Campbell KSW, Barwick RE. 2002. The axial postcranial structure of Griphognathus whitei from the Upper Devonian Gogo Formation of Western Australia: comparisons with other Devonian dipnoans. Records-Western Australian Museum 21: 167–202.
  • Challands TJ. 2015. The cranial endocast of the Middle Devonian dipnoan Dipterus valenciennesi and a fossilized dipnoan otoconial mass. Papers in Palaeontology 1: 289-317
  • Challands, T. and den Blaauwen, J.L. 2016. A redescription of the Middle Devonian dipnoan Pentlandia macroptera Traquair, 1889, and an assessment of the Phaneropleuridae. Zoological Journal of the Linnean Society, 1-47
  • Cloutier R. 1996b. Morphologie et variations du toit cranien de Dipneuste Scaumenacia curta (Whiteaves) (Sarcopterygii) de Devonien superieur du Quebec. Bulletin du Muséum National D’Histoire Naturelle, Section C, 4, Series 18.
  • Den Blaauwen J. L., Barwick R.E., Campbell KSW. 2005. Structure and function of the tooth plates of the Devonian lungfish Dipterus valenciennesi from Caithness and the Orkney Islands. Records of the Australian Museum 23: 91–113
  • Dollo, L. (1895) Sur la phylogénie des dipneustes. Bulletinde la Societe beige de Geologie, de Paleontologie et d’Hydrologie. 9, pp. 179-198.
  • Griphognathus whitei from the Upper Devonian Gogo Formation of Western Australia: comparisons with other Devonian dipnoans. Records-Western Australian Museum 21: 167–202.
  • Forster- Cooper, C. 1937. The Middle Devonian fish fauna of Achanarras. Roy. Soc. Edinburgh, 59, 223-239, figs. 1-10, pls. I-VIII.
  • Friedman, M. (2007) The interrelationships of Devonian lungfishes (Sarcopterygii: Dipnoi) as inferred from neurocranial evidence and new data from the genus Soederberghia Lehman, 1959. Zoological Journal of the Linnean Society, 151, 115–171.
  • Friedman M. 2007a. Cranial structure in the Devonian lungfish Soederberghia groenlandica and its implications for the interrelationships of ‘rhynchodipterids’. Earth and Environmental Science Transactions of the Royal Society of Edinburgh 98: 179–198.
  • Jarvik E. 1967. On the structure of the lower jaw in dipnoans: with a description of an early Devonian dipnoan from Canada, Melanognathus canadenis gen. et sp. nov. Journal of the Linnean Society of London, Zoology 47: 155–183.
  • Jude E, Johanson Z, Kearsley A, Friedman M. 2014. Early evolution of the lungfish pectoral-fin endoskeleton: evidence from the Middle Devonian (Givetian) Pentlandia macroptera. Frontiers in Earth Science 2: 18.
  • Kemp A. 1977. The pattern of tooth plate formation in the Australian lungfish, Neoceratodus forsteri Krefft. Zoological Journal of the Linnean Society 60: 223–258.
  • Lehman J-P. 1959. Les dipnuestes du Devonien superieur du Groenland. Meddelelser om Grønland 160: 1–58.
  • Lehman J-P. 1966. Dipnoi. In: Pivetau J, ed. Traite de Paleontologie, Vol. 4. Paris: Mason & Cie, 243–300.
  • Long JA. 1987. A redescription of the lungfish Eoctenodus Hills 1929, with reassessment of other Australian records of the genus Dipterus, Sedgwick and Murchison 1828. Records of the Western Australian Museum 13: 297–314.
  • Marshall CR. 1986a. A list of fossil and extant dipnoans. Journal of Morphology 190(S1): 15–23.
  • Miles, R. S. 1977. Dipnoan (lungfish) skulls and the relationships of the group: a study based on new species from the Devonian of Australia. Journal Linnean Soc. London, 1-328, figs. 1-158.
  • Smith, M. M. 1976. The microstructure of the dentition and dermal ornament of three dipnoans from the Devonian of western Australia: A contribution towards dipnoan inter-relations, and morphogenesis, growth and adaption of the skeletal tissues. Phil. Trans. R. Soc. Lond. B281, 29-72, figs. 1-18, pls. 1-10.
  • Newman, M. J. and den Blaauwen, J.L. 2007a. A new dipnoan fish from the Middle Devonian (Eifelian) of Scotland. Palaeontology, 50, 1403-1419.
  • Newman, M. J. and den Blaauwen, J.L. 2010. Developmental anomalies on the skull of the Scottish Middle Devonian lungfish Pinnalongus saxoni. Scottish Journal of Geology, 46, 85-87.
  • Pardo JD, Huttenlocker AK, Small BJ. 2014. An exceptionally preserved transitional lungfish from the Lower Permian of Nebraska, USA, and the origin of modern
    lungfishes. PLoS ONE 9: e108542.
  • Qiao T, Zhu M. 2009. A new tooth-plated lungfish from the Middle Devonian of Yunnan, China, and its phylogenetic relationships. Acta Zoologica 90: 236–252.
  • Qiao T, Zhu M. 2015. A new Early Devonian lungfish from Guangxi, China, and its palaeogeographic significance. Alcheringa: An Australasian Journal of Palaeontology 39: 428–437.
  • Romer AS. 1936. The dipnoan cranial roof. American Journal of Science 190: 241–256.
  • Traquair, R. H. 1878. On the genera Dipterus And Murch., Palaedaphus Van Beneden and De Koninck, Holodus Pander, and Cheirodus M’Coy. Ann. Mag. Nat. His., (5) II, 1-17, pl. III.
  • Traquair, R. H. 1889. On a new species of Dipterus. Geological Magazine, Decade 3, 6, 97-99.
  • White, E. I. 1965. The head of Dipterus valenciennesi. Bulletin of the British Museum, Natural History (Geology), 11, 1-45.
  • White, E. I. 1966. Presidential address: A little on Lung-fishes. Linn. Soc. London, 177, 1-10, figs. 1-5, pls. 1, 2.
  • Westoll, T. S. 1949. On the evolution of the Dipnoi.121-184. In: Jepsen, G. L., Simpson, G. G. And Mayr, E. (eds). Genetics, paleontology and evolution. Princeton University Press. 474 pp.

Dipnoans (Dipnoi)