The oldest known amniotic embryos suggest viviparity in mesosaurs

  title={The oldest known amniotic embryos suggest viviparity in mesosaurs},
  author={Graciela Pi{\~n}eiro and Jorge Ferigolo and Melitta D. Meneghel and Michel Laurin},
  journal={Historical Biology},
  pages={620 - 630}
The earliest undisputed crown-group amniotes date back to the Late Carboniferous, but the fossil record of amniotic eggs and embryos is very sparse, with the oldest described examples being from the Triassic. Here, we report exceptional, well-preserved amniotic mesosaur embryos from the Early Permian of Uruguay and Brazil. These embryos provide the earliest direct evidence of reproductive biology in Paleozoic amniotes. The absence of a recognisable eggshell and the occurrence of a partially… 
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.
Reproduction in Early Amniotes
Exceptional insights into early amniote reproduction are offered by recent fossil discoveries, and the fact that these fossils come from ancient seas and lakes and not from dry land helps to explain the paradox that there is an older fossil record for live-bearing amniotes than for egg laying in ammiotes.
Viviparity in a Triassic marine archosauromorph reptile
Eggs or embryos have been reported in various groups of fossil reptiles, where viviparity is a common mode of reproduction in aquatic taxa such as the ichthyopterygians, some groups of
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.
Integrating developmental biology and the fossil record of reptiles.
Fossil forms often display developmental traits absent or rare among modern ones such as polydactyly, hyperphalangy, the presence of ribcage armour, reduction of head ornamentation during ontogeny, extreme modifications of vertebral count or a wide range of feather-like structures, which provide an empirical background for many morphogenetic considerations.
A case study of developmental palaeontology in Stereosternum tumidum (Mesosauridae, Parareptilia)
The accelerated growth rate or earlier onset of ossification to be a potential developmental pathway generating limb element variation in the adult present in 280 million year old mesosaurs, which are known for their fully aquatic lifestyle, in which the hind limbs play a more prominent role than the forelimbs.
Live birth in an archosauromorph reptile
The discovery of a pregnant long-necked marine reptile (Dinocephalosaurus) from the Middle Triassic of southwest China shows live birth in archosauromorphs, and phylogenetic models indicate that Dinocephalosaurus determined the sex of their offspring by sex chromosomes rather than by environmental temperature like crocodilians.
The Feeding Habits of Mesosauridae
Exquisitely preserved articulated mesosaur skeletons from the Brazilian Irati Formation indicate excellent conditions of preservation, extending the Konservat-Lagerstatte designation to both units in the Parana Basin and suggest casual necrophagy on the dead bodies of small mesosaurs and large pygocephalomorphs might have been an alternative alimentary behavior adopted for survival in mesosaurs.
An Oviraptorosaur Adult-Egg Association from the Cretaceous of Jiangxi Province, China
Histological tissues and open neurocentral sutures indicate that this reproductively active individual was several years old but still growing at the time of death, a pattern observed in other non-avian maniraptorans.


First record of live birth in Cretaceous ichthyosaurs: closing an 80 million year gap
  • E. Maxwell, M. Caldwell
  • Environmental Science, Geography
    Proceedings of the Royal Society of London. Series B: Biological Sciences
  • 2003
New fossils of embryonic ichthyosaurs are both the geologically youngest and the physically smallest known ichysosaur embryos, and are located within the body cavity of an adult, presumably the mother.
Caecilian viviparity and amniote origins: a reply to Wilkinson and Nussbaum
The presence of a significant amount of intrauterine development in the earliest amniotes remains as parsimonious as the alternative, despite recent claims to the contrary.
Palaeontology: Pterosaur embryo from the Early Cretaceous
A Chinese fossil from the Early Cretaceous period containing an embryo that is unambiguously a pterosaur is described, confirming that pterosaurs were egg-layers and sheds new light on the understanding of pterOSaur development.
A review of the available data indicates that the widespread view that a majority of caecilians are viviparous is mistaken, and the most parsimonious inference is that the ancestral amniotes did not practice extended embryo retention.
Embryos of an Early Jurassic Prosauropod Dinosaur and Their Evolutionary Significance
Embryonic body proportions and an absence of well-developed teeth suggest that hatchlings of this dinosaur may have required parental care and suggests that the quadrupedal gait of giant sauropods may have evolved by retardation of postnatal negative allometry of the forelimbs.
The First Fossil Soft-shell Eggs with Embryos from Late Mesozoic Jehol Biota of Western Liaoning, China
  • Ji Qiang
  • Geography, Environmental Science
  • 2004
Two kinds of fossil reptilian eggs are reported in this paper.Both of them are from the Late Mesozoic beds in Yixian County of Jinzhou City, Western Liaoning, China, which is famous of producing
Viviparity and K-Selected Life History in a Mesozoic Marine Plesiosaur (Reptilia, Sauropterygia)
Quantitative analysis indicates that plesiosaurs gave birth to large, probably single progeny, and the combination of viviparity, large offspring size, and small brood number differs markedly from the pattern seen in other marine reptiles but does resemble the K-selected strategy of all extant marine mammals and a few extant lizards.
The Choristodera is a poorly known clade, but very a distinctive group of aquatic reptiles, which has been found from the Late Triassic to the Late Oligocene in Asia, North America and Europe.
A mixed-age classed ‘pelycosaur’ aggregation from South Africa: earliest evidence of parental care in amniotes?
The Late Middle Permian age of the varanopid family predates the previously known oldest fossil evidence of parental care in terrestrial vertebrates by 140 Myr.
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.