Snakes are the most diverse group of lizards1, but their origins and early evolution remain poorly understood owing to a lack of transitional forms. Several major issues remain outstanding, such as whether snakes originated in a marine2, 3, 4 or terrestrial5, 6 environment and how their unique feeding mechanism evolved1, 7, 8. The Cretaceous Coniophis precedens was among the first Mesozoic snakes discovered9, but until now only an isolated vertebra has been described9, 10 and it has therefore been overlooked in discussions of snake evolution. Here we report on previously undescribed material11 from this ancient snake, including the maxilla, dentary and additional vertebrae. Coniophis is not an anilioid as previously thought11; a revised phylogenetic analysis of Ophidia shows that it instead represents the most primitive known snake. Accordingly, its morphology and ecology are critical to understanding snake evolution. Coniophis occurs in a continental floodplain environment, consistent with a terrestrial rather than a marine origin; furthermore, its small size and reduced neural spines indicate fossorial habits, suggesting that snakes evolved from burrowing lizards. The skull is intermediate between that of lizards and snakes. Hooked teeth and an intramandibular joint indicate that Coniophis fed on relatively large, soft-bodied prey. However, the maxilla is firmly united with the skull, indicating an akinetic rostrum. Coniophis therefore represents a transitional snake, combining a snake-like body and a lizard-like head. Subsequent to the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull, which was followed by a major adaptive radiation in the Early Cretaceous period. This pattern suggests that the kinetic skull was a key innovation that permitted the diversification of snakes.
At a glance
- 1997) Snakes: the Evolution of Mystery in Nature (Univ. California Press,
- A snake with legs from the marine Cretaceous of the Middle East. Nature 386, 705–709 (1997) &
- On the reptilian orders Pythonomorpha and Streptosauria. Proc. Bost. Soc. Nat. Hist. 12, 250–267 (1869)
- Molecular evidence and marine snake origins. Biol. Lett. 1, 227–230 (2005)
- A Cretaceous terrestrial snake with robust hindlimbs and a sacrum. Nature 440, 1037–1040 (2006) &
- Molecular evidence for a terrestrial origin of snakes. Proc. R. Soc. Lond. B 271, S226–S229 (2004) &
- The origin of snake feeding. Nature 400, 655–659 (1999) , &
- 293–333 (Academic, 2000) & in Feeding: Form, Function, and Evolution in Terrestrial Vertebrates (ed. )
- Notice of new reptiles from the Laramie Formation. Am. J. Sci. 43, 449–453 (1892)
- Fossil snakes of North America. Geol. Soc. Am. Bull. 9, 1–96 (1938)
- Fossil Vertebrates from the Late Cretaceous Lance Formation, Eastern Wyoming. Univ. Calif. Publ. Geol. Sci. 49, 140–141 (1964)
- The anatomy of the Upper Cretaceous snake Najash rionegrina Apesteguía & Zaher, 2006, and the evolution of limblessness in snakes. Zool. J. Linn. Soc. 156, 801–826 (2009) , &
- 349–692 (Society for the Study of Amphibians and Reptiles, 2008) & in Biology of the Reptilia Vol. 20 (eds , & )
- 606–662 (Maison et Cie, 1955) in Traité de Paléontologie (ed. )
- Squamate reptiles from the middle Eocene of Lissieu (France). Geobios 43, 253–268 (2010) &
- Varanoid-like dentition in primitive snakes (Madtsoiidae). J. Herpetol. 36, 100–106 (2002) &
- Feeding behavior in Cylindrophis and its bearing on the evolution of alethinophidian snakes. J. Zool. 237, 353–376 (1995)
- Predation upon hatchling dinosaurs by a new snake from the Late Cretaceous of India. PLoS Biol. 8, e1000322 (2010) , , &
- The skull of the Upper Cretaceous snake Dinilysia patagonica Smith-Woodward 1901, and its phylogenetic position revisited. Zool. J. Linn. Soc. 164, 194–238 (2012) &
- The Pleistocene serpent Wonambi and the early evolution of snakes. Nature 403, 416–420 (2000) &
- Skull of the large non-macrostomatan snake Yurlunggur from the Australian Oligocene. Nature 439, 839–842 (2006)
- Dinilysia patagonica (Reptilia, Serpentes): matériel vertébral additionel du Crétacé supérieur d’Argentine. Étude complémentaire des vertèbres, variations intraspécifiques etintracolumnaires. Neues Jahrb. Geol. Paläontol. Monatsh. 1989, 433–447 (1989) &
- Vertebrae and ribs of modern reptiles.. in Biology of the Reptilia Vol. 1 (ed. ) 201–310 (Academic, 1969). &
- Amphibians and squamates from the Maastrichtian of Naskal, India. Cretac. Res. 16, 95–107 (1995)
- Palaeoenvironment and palaeoecology of three Cretaceous snakes: Pachyophis, Pachyrhachis, and Dinilysia. Acta Palaeontol. Pol. 46, 203–218 (2001) &
- Systematics of the Amphisbaenia (Lepidosauria: Squamata) based on morphological evidence from recent and fossil forms. Herpetological Monogr. 17, 1–74 (2003)
- The Cenomanian: stage of hindlimbed snakes. Carnets Géol. 2003, 2003/01. (2003) &
- Mid-Cretaceous (Cenomanian) snakes from Wadi Abu Hashim, Sudan: the earliest snake assemblage. Palaeontol. Afr. 35, 85–110 (1999) &
- A primitive snake from the Cretaceous of Utah. Spec. Pap. Palaeontol. 60, 87–100 (1999) &
- Supplementary Information 1 (554K)
This file contains Supplementary Text and Data 1-2, Supplementary Figures 1-2 and additional references.
- Supplementary Information 2 (1.1M)
This file contains Supplementary Text and Data, Supplementary Materials, Supplementary Results, a Supplementary Discussion and additional references.
- Supplementary Information 3 (3M)
This file contains the Supplementary Character illustrations 155-228.
- Supplementary Information 4 (8.5K)
This file contains the Supplementary Character-taxon matrix.