The lungfish (Class Dipnoi, Superclass Sarcopterygii) are air-breathing fishes whose extant crown group comprises six living species. These fall into two orders, the Ceratodontiformes (now represented by the Australian lungfish) and the Lepidosireniformes (the South American lungfish - illustrated in the header above - and the African lungfish).
Many fossil lungfishes have been assigned to the stem-Dipnoi, and several phylogenetic trees have been published (e.g. Ahlberg et al, 2006; Qiao and Zhu, 2009; Pardo et al, 2014; Kemp et al, 2017; Challands et al, 2019; Cui et al, 2022). However, these trees show significant differences and it appears that the phylogeny of the stem-Dipnoi remains uncertain. A simplified version of one of these trees, by Challands et al (2019), is shown below:
Many fossil lungfishes have been assigned to the stem-Dipnoi, and several phylogenetic trees have been published (e.g. Ahlberg et al, 2006; Qiao and Zhu, 2009; Pardo et al, 2014; Kemp et al, 2017; Challands et al, 2019; Cui et al, 2022). However, these trees show significant differences and it appears that the phylogeny of the stem-Dipnoi remains uncertain. A simplified version of one of these trees, by Challands et al (2019), is shown below:
Figure 1. Time tree of the stem-Dipnoi
The earliest known representative of the stem-Dipnoi is Youngolepis sp., from the Early Devonian (Early Lochkovian) Xishancun Formation of Qujing, Yunnan, China (Zhu and Fan, 1995; Friedman and Brazeau, 2010). No public-domain image of this genus is available, but some members of the basal clade known as the Porolepiformes are illustrated below (for a larger view, click on image):
Figure 2. Images of Porolepiformes (basal stem-group dipnoans)
For the stem-Dipnoi crownward of the Porolepiformes (see Figure 1), images in the public domain are available for only the few fossils shown below (click on image to see a larger view):
Figure 3. Images of stem-Dipnoi crownward of Porolepiformes
The fossils shown above (Figure 3) are ordered from the most basal to those closest to the crown group, but no obvious trends can be seen in this limited set of images. However, these fossils do generally appear more like extant lungfishes than do the Porolepiformes (Figure 2). This similarity is seen particularly in the pectoral girdle and fin of Pentlandia macroptera, which have several features also seen in the extant lungfish genus Neoceratodus, although other aspects are primitive with respect to Neoceratodus (Jude et al, 2014).
The oldest known representative of the crown-Dipnoi is Gosfordia truncata, a member of the stem-Lepidosireniformes from the Early Triassic (Olenekian) Terrigal Formation at Gosford Quarry, New South Wales, Australia (Woodward, 1890; Longrich, 2017). No image is available in the public domain.
The stem-to-crown transition of the Dipnoi appears to have lasted at least 163 million years, from the Early Devonian to the Early Triassic (Figure 1).
The oldest known representative of the crown-Dipnoi is Gosfordia truncata, a member of the stem-Lepidosireniformes from the Early Triassic (Olenekian) Terrigal Formation at Gosford Quarry, New South Wales, Australia (Woodward, 1890; Longrich, 2017). No image is available in the public domain.
The stem-to-crown transition of the Dipnoi appears to have lasted at least 163 million years, from the Early Devonian to the Early Triassic (Figure 1).
References
Benton, M. J. (2015). Vertebrate Palaeontology - Fourth edition. John Wiley & Sons, 468 pages.
Ahlberg, P. E., Smith, M. M., & Johanson, Z. (2006). Developmental plasticity and disparity in early dipnoan (lungfish) dentitions. Evolution & Development, 8(4), 331-349.
Challands, T. J., Smithson, T. R., Clack, J. A., Bennett, C. E., Marshall, J. E., Wallace-Johnson, S. M., & Hill, H. (2019). A lungfish survivor of the end-Devonian extinction and an Early Carboniferous dipnoan radiation. Journal of Systematic Palaeontology, 1-22.
Cui, X., Friedman, M., Qiao, T., Yu, Y., & Zhu, M. (2022). The rapid evolution of lungfish durophagy. Nature communications, 13(1), 1-9.
Friedman, M., & Brazeau, M. D. (2010). A reappraisal of the origin and basal radiation of the Osteichthyes. Journal of Vertebrate Paleontology, 30(1), 36-56.
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., Cavin, L., & Guinot, G. (2017). Evolutionary history of lungfishes with a new phylogeny of post-Devonian genera. Palaeogeography, Palaeoclimatology, Palaeoecology, 471, 209-219.
Longrich, N. R. (2017). A stem lepidosireniform lungfish (Sarcopterygia: Dipnoi) from the Upper Eocene of Libya, North Africa and implications for Cenozoic lungfish evolution. Gondwana Research, 42, 140-150.
Pardo, J. D., Huttenlocker, A. K., & Small, B. J. (2014). An exceptionally preserved transitional lungfish from the Lower Permian of Nebraska, USA, and the origin of modern lungfishes. PloS One, 9(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.
Woodward, A. S. (1890). The fossil fishes of the Hawkesbury Series at Gosford. Memoirs of the Geological Survey of New South Wales. Palaeontology 4:1-57.
Zhu, M., & Fan, J. (1995). Youngolepis from the Xishancun Formation (Early Lochkovian) of Qujing; China. Geobios, 28, 293-299.
Ahlberg, P. E., Smith, M. M., & Johanson, Z. (2006). Developmental plasticity and disparity in early dipnoan (lungfish) dentitions. Evolution & Development, 8(4), 331-349.
Challands, T. J., Smithson, T. R., Clack, J. A., Bennett, C. E., Marshall, J. E., Wallace-Johnson, S. M., & Hill, H. (2019). A lungfish survivor of the end-Devonian extinction and an Early Carboniferous dipnoan radiation. Journal of Systematic Palaeontology, 1-22.
Cui, X., Friedman, M., Qiao, T., Yu, Y., & Zhu, M. (2022). The rapid evolution of lungfish durophagy. Nature communications, 13(1), 1-9.
Friedman, M., & Brazeau, M. D. (2010). A reappraisal of the origin and basal radiation of the Osteichthyes. Journal of Vertebrate Paleontology, 30(1), 36-56.
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., Cavin, L., & Guinot, G. (2017). Evolutionary history of lungfishes with a new phylogeny of post-Devonian genera. Palaeogeography, Palaeoclimatology, Palaeoecology, 471, 209-219.
Longrich, N. R. (2017). A stem lepidosireniform lungfish (Sarcopterygia: Dipnoi) from the Upper Eocene of Libya, North Africa and implications for Cenozoic lungfish evolution. Gondwana Research, 42, 140-150.
Pardo, J. D., Huttenlocker, A. K., & Small, B. J. (2014). An exceptionally preserved transitional lungfish from the Lower Permian of Nebraska, USA, and the origin of modern lungfishes. PloS One, 9(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.
Woodward, A. S. (1890). The fossil fishes of the Hawkesbury Series at Gosford. Memoirs of the Geological Survey of New South Wales. Palaeontology 4:1-57.
Zhu, M., & Fan, J. (1995). Youngolepis from the Xishancun Formation (Early Lochkovian) of Qujing; China. Geobios, 28, 293-299.
Image credits – stem-Dipnoi
- Header (South American lungfish Lepidosiren paradoxa, in the tropical aquarium of the Palais de la Porte Dorée, in Paris): Vassil, CC0, via Wikimedia Commons
- Figure 2 (Porolepis sp.): Dmitry Bogdanov, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
- Figure 2 (Glyptolepis paucidens, fossil): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
- Figure 2 (Glyptolepis paucidens, life restoration): Nobu Tamura under Creative Commons Attribution- ShareAlike (CC BY-SA) license
- Figure 2 (Holoptychius quebecensis): Smokeybjb, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
- Figure 2 (Holoptychius nobilissimus): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
- Figure 2 (Laccognathus embryi): Obsidi♠nSoulbackground from: Sea_floor_sand.jpg: Dimitris Siskopoulos from Alexandroupolis, Greece, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
- Figure 3 (Chirodipterus australis): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
- Figure 3 (Dipterus valenciennesi, fossil): Photographed by Bob James (owner of website) at American Museum of Natural History, New York, May 2024
- Figure 3 (Dipterus valenciennesi, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
- Figure 3 (Phaneropleuron andersoni): Lankester Edwin Ray, Public domain, via Wikimedia Commons
- Figure 3 (Pentlandia macroptera): Open Access article 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.
- Figure 3 (Conchopoma gadiforme): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
- Figure 3 (Gnathorhiza sp.): DiBgd, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons