Skin morphology in fossil and living dipnoans
Anne Kemp
9 Hampton Grove, Norwood, Adelaide, SA 5067, Australia. Email: annerkemp@gmail.com
Australian Journal of Zoology 67(4) 203-209 https://doi.org/10.1071/ZO20021
Submitted: 3 April 2020 Accepted: 7 October 2020 Published: 22 October 2020
Abstract
The morphology of the skin of living dipnoans can be compared with the arrangements present in the dermis and epidermis of the snout and mandible of fossil dipnoans, but the structures that may have been present in the fossils are significantly reduced in living lungfish. One advantage of assessing the living species is that soft tissues are intact. Fossil dipnoans have cosmine in the epidermis of the snout and mandible, and the dermis is supported by several layers of structured extracellular matrix. Cosmine includes dentine elements as well as pore canals. Among the pore canals are gaps in the cosmine layer that would have housed electroreceptors in the living fish. Below the cosmine is a layer of cancellous bone, separated from the dermal tissues within by a thin, almost continuous, ossified layer. Deep to this layer is a region that lacks any ossified structure, and below this the tubules that pass through the dermis terminate in irregular bulbs. Thin branches with an ossified coat arise from the tubules in the terminal layer and enter the cancellous bone below the cosmine and the pore canals, although they are not numerous. Living dipnoans have no ossified structures in the skin, and lymphatic vessels in the snout are reduced to the plexus below the epidermis, and the lymphatic loops that emerge from the plexus and enter the epidermis. These are numerous and occur in regular layers. In the living species, the lymphatic loops are close to electroreceptors. This may have been the case in fossil lungfish as well. Parallels in fossil and living dipnoans are present.
Keywords: cosmine, dermis, electroreceptors, epidermis, lymphatic vessels, nerves, pore canals.
References
Bemis, W. E., and Northcutt, G. R. (1992). Skin and blood vessels in the snout of the Australian lungfish, Neoceratodus forsteri, and their significance in interpreting the cosmine of Devonian lungfishes. Acta Zoologica 73, 115–139.| Skin and blood vessels in the snout of the Australian lungfish, Neoceratodus forsteri, and their significance in interpreting the cosmine of Devonian lungfishes.Crossref | GoogleScholarGoogle Scholar |
Campbell, K. S. W., and Barwick, R. E. (1988). Uranolophus: a reappraisal of a primitive dipnoan. Memoirs of the Association of Australasian Palaeontologists 7, 87–144.
Campbell, K. S. W., and Barwick, R. E. (1994). Speonesydrion, an Early Devonian dipnoan with primitive tooth plates. Palaeoichthyologia 2, 1–48.
Campbell, K. S. W., and Wragg, S. (2014). Structural details of Early Devonian dipnoans. Australian Journal of Zoology 62, 18–25.
| Structural details of Early Devonian dipnoans.Crossref | GoogleScholarGoogle Scholar |
Cavin, L., Suteethorn, V., Buffetaut, V., and Tong, H. (2007). A new Thai Mesozoic lungfish (Sarcopterygii, Dipnoi) with an insight into post-Palaeozoic dipnoan evolution. Zoological Journal of the Linnean Society of London 149, 141–177.
| A new Thai Mesozoic lungfish (Sarcopterygii, Dipnoi) with an insight into post-Palaeozoic dipnoan evolution.Crossref | GoogleScholarGoogle Scholar |
Challand, T. J. (2015). The cranial endocast of the middle Devonian dipnoan Dipterus valenciennesi and a fossilized dipnoan otoconial mass. Papers in Palaeontology 2015, 1–29.
Cheng, H. (1989). On the tubuli in Devonian lungfish. Alcheringa 13, 153–166.
| On the tubuli in Devonian lungfish.Crossref | GoogleScholarGoogle Scholar |
Clement, A. M., and Long, J. (2010). Xeradipterus hatcheri, a new dipnoan from the late Devonian (Frasnian) Gogo Formation, Western Australia, and other new holodontid material. Journal of Vertebrate Paleontology 30, 681–695.
| Xeradipterus hatcheri, a new dipnoan from the late Devonian (Frasnian) Gogo Formation, Western Australia, and other new holodontid material.Crossref | GoogleScholarGoogle Scholar |
Gross, W. (1956). Ueber Crossopterygier und Dipnoer aus dem Baltischen Oberdevon im Zusammenhang einer vergliechenden Untersuchung des Porencanalsystems paläozoicher Agnathen und Fische. Kungliga Svenska Vetenskaps Akademiens Handlingar 5, 1–140.
Kemp, A. (1987). The biology of the Australian lungfish, Neoceratodus forsteri. Journal of Morphology 1, 181–198.
Kemp, A. (1999). Ontogeny of the skull of the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi). Journal of Zoology 248, 97–137.
| Ontogeny of the skull of the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).Crossref | GoogleScholarGoogle Scholar |
Kemp, A. (2014). Skin structure in the snout of the Australian lungfish, Neoceratodus forsteri, and in fossil relatives (Osteichthyes: Dipnoi). Tissue & Cell 46, 397–408.
| Skin structure in the snout of the Australian lungfish, Neoceratodus forsteri, and in fossil relatives (Osteichthyes: Dipnoi).Crossref | GoogleScholarGoogle Scholar |
Kemp, A. (2017). Cranial nerves in the Australian lungfish, Neoceratodus forsteri, and in fossil relatives (Osteichthyes: Dipnoi). Tissue & Cell 49, 45–55.
| Cranial nerves in the Australian lungfish, Neoceratodus forsteri, and in fossil relatives (Osteichthyes: Dipnoi).Crossref | GoogleScholarGoogle Scholar |
Krefft, G. (1870). Description of a gigantic amphibian allied to the genus Lepidosiren, from the Wide-Bay District, Queensland. Proceedings of the Zoological Society of London 1870, 221–224.
Miles, R. S. (1977). Dipnoan (lungfish) skulls and the relationships of the group: a study based on new species from the Devonian of Australia. Zoological Journal of the Linnean Society 61, 1–328.
| Dipnoan (lungfish) skulls and the relationships of the group: a study based on new species from the Devonian of Australia.Crossref | GoogleScholarGoogle Scholar |
Northcutt, R. G. (1987). Lungfish neural characters and their bearing on Sarcopterygian phylogeny. Journal of Morphology 1, 277–297.
Pridmore, P. A., and Barwick, R. E. (1993). Post-cranial morphologies of the Late Devonian dipnoans Griphognathus and Chirodipterus and locomotor implications. Memoirs of the Association of Australasian Palaeontologists 15, 161–182.
Stensio, E. (1963). The brain and cranial nerves in fossil lower craniate vertebrates. Skrifter Norske Videnskaps Akademi i Oslo. Mat. – Naturv. Klasse Ny Series 13, 1–20.
Zhu, M., Wang, W., and Yu, X. (2010). Meemannia eos, a basal sarcopterygian fish from the Lower Devonian of China – expanded description and significance. In ‘Morphology, Phylogeny and Paleobiogeography of Fossil Fishes’. (Eds D. K. Elliott, J. G. Maisey, and X. Yu.) pp. 199–214. (Verlag Dr Friedrich Pfeil: München, Germany.)
