Stepwise formation of autostyly in lungfishes revealed by comparative analysis of palatoquadrate
Received date: 2026-01-13
Online published: 2026-04-08
Autostyly, defined by fusion of the palatoquadrate to the neurocranium and loss of the hyomandibula as a suspensory element, is a hallmark of lungfish cranial organization among sarcopterygians, yet its evolutionary origin remains incompletely understood. This study elucidates this transition through a detailed comparative analysis of the palatoquadrate and its articulations in three sequentially diverging stem dipnoans: Youngolepis, Diabolepis, and the earliest eudipnoan Paleolophus. Youngolepis exhibits a reoriented palatoquadrate, indicating functional reorganization of jaw mechanics prior to autostyly. In Diabolepis, reduction of the pars autopalatina and retention of a primitive suborbital articulation suggest further modification of jaw suspension. Paleolophus documents the earliest unambiguous autostyly, with direct palatoquadrate-neurocranial integration preceding complete fusion with the lateral commissure, along with an enlarged adductor fossa. Comparison with Middle and Late Devonian lungfishes indicates that full autostyly was achieved only after the development of a robust, integrated otic process. These results demonstrate that lungfish autostyly evolved stepwise, driven by increasing biomechanical demands associated with durophagous feeding.
Key words： Devonian; lungfish; autostyly; palatoquadrate; evolution
QIAO Tuo , LIU Cheng-Xi , CUI Xin-Dong , ZHU Min . Stepwise formation of autostyly in lungfishes revealed by comparative analysis of palatoquadrate[J]. Vertebrata Palasiatica, 2026 , 64(2) : 167 -182 . DOI: 10.19615/j.cnki.2096-9899.260408
| [1] | Ahlberg P E, Smith M M, Johanson Z, 2006. Developmental plasticity and disparity in early dipnoan (lungfish) dentitions. Evol Dev, 8: 331-349 |
| [2] | Bartsch P, 1994. Development of the cranium of Neoceratodus forsteri, with a discussion of the suspensorium and the opercular apparatus in Dipnoi. Zoomorphology, 114(1): 1-31 |
| [3] | Bemis W E, Lauder G V, 1986. Morphology and function of the feeding apparatus of the lungfish, Lepidosiren paradoxa (Dipnoi). J Morphol, 187(1): 81-108 |
| [4] | Bernacsek G M, 1977. A lungfish cranium from the Middle Devonian of the Yukon Territory, Canada. Palaeontogr Abt A, 157: 175-200 |
| [5] | Brazeau M D, 2009. The braincase and jaws of a Devonian ‘acanthodian’ and modern gnathostome origins. Nature, 457: 305-308 |
| [6] | Campbell K S W, Barwick R E, 1982. The neurocranium of the primitive dipnoan Dipnorhynchus sussmilchi (Etheridge). J Vert Paleont, 2(3): 286-327 |
| [7] | Campbell K S W, Barwick R E, 1987. Paleozoic lungfishes - a review. In: Bemis WB, Burggren WW,Kemp N F eds. The Biology and Evolution of Lungfishes. J Morphol (Suppl 1, 1986). New York: Alan R Liss. 93-131 |
| [8] | Chang M M, 1982. The braincase of Youngolepis, a Lower Devonian Crossopterygian from Yunnan, south-western China. Ph. D thesis. Stockholm: Department of Geology, University of Stockholm. 1-113 |
| [9] | Chang M M, 1991a. Head exoskeleton and shoulder girdle of Youngolepis. In: Chang MM, Liu YH, Zhang G R eds. Early Vertebrates and Related Problems of Evolutionary Biology. Beijing: Science Press. 355-378 |
| [10] | Chang M M, 1991b. “Rhipidistians”, dipnoans, and tetrapods. In: Schultze HP, Trueb L eds. Origins of the Higher Groups of Tetrapods:Controversy and Consensus. New York: Cornell University Press. 3-28 |
| [11] | Chang M M, 1995. Diabolepis and its bearing on the relationships between porolepiforms and dipnoans. Bull Mus Natl Hist Nat, Sect C, 17(1-4): 235-268 |
| [12] | Chang M M, 2004. Synapomorphies and scenarios - more characters of Youngolepis betraying its affinity to the Dipnoi. In: ArratiaG, Wilson M VH, Cloutier R eds. Recent Advances in the Origin and Early Radiation of Vertebrates. München: Verlag Dr. Friedrich Pfeil. 665-686 |
| [13] | Chang M M, Smith M M, 1992. Is Youngolepis a porolepiform? J Vert Paleont, 12(3): 294-312 |
| [14] | Chang M M, Yu X B, 1981. A new crossopterygian, Youngolepis praecursor, gen. et sp. nov., from Lower Devonian of eastern Yunnan, China. Sci Sin, 24(1): 89-99 |
| [15] | Chang M M, Yu X B, 1984. Structure and phylogenetic significance of Diabolichthys speratus gen. et sp. nov., a new dipnoan-like form from the Lower Devonian of eastern Yunnan, China. Proc Linn Soc NSW, 107(3): 171-184 |
| [16] | Chang M M, Yu X B, 1987. A nomen novum for Diabolichthys Chang et Yu, 1984. Vert PalAsiat, 25: 79 |
| [17] | Clément G, Janvier P, 2004. Powichthys spitsbergensis sp. nov., a new member of the Dipnomorpha (Sarcopterygii, lobe-finned fishes) from the Lower Devonian of Spitsbergen, with remarks on basal dipnomorph anatomy. Foss Strata, 50: 92-112 |
| [18] | Cloutier R, Ahlberg P E, 1996. Morphology, characters, and the interrelationships of basal sarcopterygians. In: Stiasnny M LJ, Parenti LR, Johnson G D eds. Interrelationships of Fishes. San Diego: Academic Press. 445-479 |
| [19] | Cui X D, Friedman M, Qiao T et al., 2022. The rapid evolution of lungfish durophagy. Nat Commun, 13(1): 2390 |
| [20] | Denison R H, 1968a. Early Devonian lungfishes from Wyoming, Utah, and Idaho. Fieldiana Geol, 17(4): 353-413 |
| [21] | Denison R H, 1968b. The evolutionary significance of the earliest known lungfish Uranolophus. In: ?rvig T ed. Current Problems of Lower Vertebrate Phylogeney. Nobel Symposium 4. Stockholm: Almqvist and Wiksell.247-257 |
| [22] | Edgeworth F H, 1925. On the autostyly of dipnoi and amphibia. J Anat, 59: 225-264 |
| [23] | Forey P L, Gardiner B G, Patterson C, 1991. The lungfish, the coelacanth and the cow revisited. In: Schultze HP, Trueb L eds. Origins of the Higher Groups of Tetrapods:Controversy and Consensus. Ithaca: Cornell Publishing Associates. 145-172 |
| [24] | Fox H, 1965. Early development of the head and pharynx of Neoceratodus with a consideration of its phylogeny. J Zool, 146: 470-554 |
| [25] | Gardiner B G, 1984a. The relationship of placoderms. J Vert Paleont, 4(3): 379-395 |
| [26] | Gardiner B G, 1984b. The relationships of the palaeoniscid fishes, a review based on new specimens of Mimia and Moythomasia from the Upper Devonian of Western Australia. Bull Br Mus (Nat Hist) Geol, 37(4): 173-428 |
| [27] | Holmgren N, 1943. Studies on the head of fishes, Part IV. Acta Zool, 24: 1-188 |
| [28] | Janvier P, 1996. Early Vertebrates. Oxford: Clarendon Press. 1-393 |
| [29] | Jarvik E, 1952. On the fish-like tail in the ichthyostegid stegocephalians with descriptions of a new stegocephalian and a new crossopterygian from the Upper Devonian of East Greenland. Medd Gr?nl, 114(12): 1-90 |
| [30] | Jarvik E, 1963. The fossil vertebrates from East Greenland and their zoological importance. Experientia, 19: 1-6 |
| [31] | Jarvik E, 1972. Middle and Upper Devonian Porolepiformes from East Greenland with special reference to Glyptolepis groenlandica n. sp. and a discussion on the structure of the head in the Porolepiformes. Medd Gr?nl, 187(2): 1-307 |
| [32] | Jarvik E, 1980. Basic Structure and Evolution of Vertebrates, Vol. 1. London: Academic Press. 1-575 |
| [33] | Jessen H L, 1980. Lower Devonian Porolepiformes from the Canadian Arctic with special reference to Powichthys thorsteinssoni Jessen. Palaeontogr Abt A, 167: 180-214 |
| [34] | Maisey J G, 1980. An evaluation of jaw suspension in sharks. Am Mus Novit, 2706: 1-17 |
| [35] | Maisey J G, 2005. Braincase of the Upper Devonian shark Cladodoides wildungensis (Chondrichthyes, Elasmobranchii), with observations on the braincase in early chondrichthyans. Bull Am Mus Nat Hist, 288: 1-103 |
| [36] | Miles R S, 1965. Some features in the cranial morphology of acanthodians and the relationships of the Acanthodii. Acta Zool, 46: 233-255 |
| [37] | Miles R S, 1973. Relationships of acanthodians. In: Greenwood PH, Miles RS, Patterson C eds. Interrelationships of Fishes. London: Academic Press. 63-103 |
| [38] | Miles R S, 1977. Dipnoan (lungfish) skulls and the relationships of the group: a study based on new species from the Devonian of Australia. Zool J Linn Soc, 61(1-3): 1-328 |
| [39] | Panchen A L, Smithson T R, 1987. Character diagnosis, fossils and the origin of tetrapods. Biol Rev Camb Philos Soc, 62: 341-438 |
| [40] | Qiao T, Zhu M, 2010. Cranial morphology of the Silurian sarcopterygian Guiyu oneiros (Gnathostomata: Osteichthyes). Sci China-Earth Sci, 53(12): 1836-1848 |
| [41] | Qiao T, Cui X D, Zhao W J et al., 2026. A new fossil fish sheds light on the rapid evolution of early lungfishes. Curr Biol, 36: 1-9 |
| [42] | Reisz R R, Smith M M, 2001. Lungfish dental pattern conserved for 360 Myr. Nature, 411: 548 |
| [43] | Schaeffer B, 1981. The xenacanth shark neurocranium, with comments on elasmobranch monophyly. Bull Am Mus Nat Hist, 169(1): 1-66 |
| [44] | Schultze H P, 1987. Dipnoans as sarcopterygians. In:Bemis W E, Burggren W W, Kemp N E eds. The Biology and Evolution of Lungfishes. J Morphol (Suppl 1, 1986). New York: Alan R Liss. 39-74 |
| [45] | Schultze H P, Campbell K S W, 1987. Characterization of the Dipnoi, a monophyletic group. In: Bemis WE, Burggren WW,Kemp N E eds. The Biology and Evolution of Lungfishes. J Morphol (Suppl 1, 1986). New York: Alan R Liss. 25-37 |
| [46] | Thomson K S, Campbell K S W, 1971. The structure and relationships of the primitive Devonian lungfish - Dipnorhynchus sussmilchi (Etheridge). Bull Peabody Mus Nat Hist, 38: 1-109 |
| [47] | Yu X B, 1998. A new porolepiform-like fish, Psarolepis romeri, gen. et sp. nov. (Sarcopterygii, Osteichthyes) from the Lower Devonian of Yunnan, China. J Vert Paleont, 18(2): 261-274 |
| [48] | Zhu M, Schultze H P, 1997. The oldest sarcopterygian fish. Lethaia, 30(4): 293-304 |
| [49] | Zhu M, Yu X B, Janvier P, 1999. A primitive fossil fish sheds light on the origin of bony fishes. Nature, 397: 607-610 |
| [50] | Zhu M, Yu X B, Ahlberg P E, 2001. A primitive sarcopterygian fish with an eyestalk. Nature, 410: 81-84 |
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