A gravid lizard from the Cretaceous of China and the early history of squamate viviparity

  title={A gravid lizard from the Cretaceous of China and the early history of squamate viviparity},
  author={Yuan Wang and Susan E. Evans},
Although viviparity is most often associated with mammals, roughly one fifth of extant squamate reptiles give birth to live young. Phylogenetic analyses indicate that the trait evolved more than 100 times within Squamata, a frequency greater than that of all other vertebrate clades combined. However, there is debate as to the antiquity of the trait and, until now, the only direct fossil evidence of squamate viviparity was in Late Cretaceous mosasauroids, specialised marine lizards without… 

Terrestrial Origin of Viviparity in Mesozoic Marine Reptiles Indicated by Early Triassic Embryonic Fossils

The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records and strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view.

An exceptionally preserved Jurassic skink suggests lizard diversification preceded fragmentation of Pangaea

The present distribution of lizards is usually explained as a result of relatively recent global events, i.e. faunal turnovers or exchanges within and between particular continents mostly connected

Early origin of viviparity and multiple reversions to oviparity in squamate reptiles.

This work reconstructs ancestral parity modes accounting for state-dependent diversification in a large-scale phylogenetic analysis and finds strong support for an early origin of viviparity at the base of Squamata, and a complex pattern of subsequent transitions.

Live birth in a 47-million-year-old snake

Viviparity is a widespread reproductive trait in snakes, although fossil evidence bearing on its evolution is extremely sparse. Here, we report an exceptional specimen of the minute booid snake

Evolution of viviparous reproduction in Paleozoic and Mesozoic reptiles.

P paleontological evidence indicates that extinct viviparous reptiles had internal fertilization, amniotic fetal membranes, and placentas that sustained developing embryos via provision of respiratory gases, water, calcium, and possibly organic nutrients.

Evolution of viviparity in squamate reptiles: Reversibility reconsidered.

  • D. G. Blackburn
  • Biology
    Journal of experimental zoology. Part B, Molecular and developmental evolution
  • 2015
Evidence derived from studies of anatomy, physiology, and developmental biology strongly supports the inference that oviparity is ancestral for squamates and has given rise to viviparity on numerous occasions.

Life‐history strategies indicate live‐bearing in Nothosaurus (Sauropterygia)

In Sauropterygia, a diverse group of Mesozoic marine reptiles, fossil evidence of viviparity (live‐bearing) only exists for Pachypleurosauria and Plesiosauria, and was assumed to also be the case for



Live birth in Cretaceous marine lizards (mosasauroids)

  • M. CaldwellM. S. Lee
  • Environmental Science, Geography
    Proceedings of the Royal Society of London. Series B: Biological Sciences
  • 2001
Viviparity in early medium-sized amphibious aigialosaurs may have freed them from the need to return to land to deposit eggs, and permitted the subsequent evolution of gigantic totally marine mosasaurs.

Triassic marine reptiles gave birth to live young

Two gravid specimens of Keichousaurus hui Young from the Middle Triassic of China provide the first unequivocal evidence of reproductive mode and sexual dimorphism in sauropterygians and indicate that viviparity could have been expedited by the evolution of a movable pelvis in pachypleurosaurs.

Cretaceous choristoderan reptiles gave birth to live young

This exquisitely preserved specimen of the Early Cretaceous Hyphalosaurus baitaigouensis contains up to 18 embryos arranged in pairs, and size comparison with small free-living individuals and the straight posture of the posterior-most pair suggest that those embryos were at term and had probably reached parturition.


The value of the squamate model ultimately may lie in insights it provides into physiological problems rather than in universality of specific mechanisms that have evolved to meet those problems, given the diverse mechanisms by which they achieve viviparity.

Phylogeny And Systematics Of Squamata (Reptilia) Based On Morphology

This study examines squamate relationships using 222 ingroup taxa scored for 363 morphological characters and confirms the monophyly of the clades Scleroglossa (extant squamates exclusive of Iguania), Gekkota, Scincomorpha, Lacertoidea,ScincoideA, Anguimorpha and Varanoidea.

Cretaceous age for the feathered dinosaurs of Liaoning, China

The results of this dating study indicate that the lower Yixian fossil horizons are not Jurassic but rather are at least 20 Myr younger, placing them within middle Early Cretaceous time.


Four additional nothosaurid embryos found in the Monte San Giorgio area strongly support the hypothesis that nothosaurs were viviparous, particularly since three of the four embryos are clustered together in close association, excluding the possibility that they derive from isolated eggs washed into the coastal basin prior to fossilization.

Live birth among Iguanian lizards predates Pliocene–Pleistocene glaciations

Divergence-dating analysis on a 733-species tree of Iguanian lizards recovers 20 independent lineages that have evolved viviparity, of which 13 multispecies groups derived live birth prior to glacial advances (8–66 Myr ago).


Using available data on reproductive modes and phylogenetic relationships within reptiles, the numbers and directions of evolutionary transitions between oviparity and viviparity are measured.

A new Lower Cretaceous bird from China and tooth reduction in early avian evolution

Phylogenetic analysis indicates that Zhongjianornis is phylogenetically basal to Confuciusornis and the dominant Mesozoic avian groups, Enantiornithes and Ornithurae, and therefore provides significant new information regarding the diversification of birds in the Early Cretaceous.