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An international team of researchers have discovered the fossilized remains of nearly 80 extinct marine reptiles known as ichthyosaurs from a fossil quarry in south Majiashan in Chaohu City, Anhui Province, East China that date back to roughly 248 mya (end of the Early Triassic) - which is around 18 million years prior to the emergence of dinosaurs.
The ichthyosaurs belonged to the genus Chaohusaurus, which is the earliest known Mesozoic marine reptile as well as being one of the smallest ichthyosaurs, ranging from 0.7 to 1.8 meters (27.5 to 70.8") in length.
What makes this discovery especially newsworthy is that one of the specimens, which is lacking the skull, anterior trunk, and posterior tail, appears to exhibit evidence for the earliest live birth from an ancient Mesozoic marine reptile in the fossil record[1]. This new fossil of an ancient Chaohusaurus mother, that likely died due to complications while in labor delivering triplets, is associated with three embryos and newborn infants: one inside the mother, another exiting the pelvis -- with approximately half the body still inside the mother -- and the third outside of the mother.
The skulls of two embryos are visible, one still inside the mother and the other exiting her pelvis while the firstborn's bones were preserved beneath the mother's tail. The researchers think that the first baby Chaohusaurus was born dead and that because of the burial positions, it's improbable that the babies were expelled from the mother after death.
The fossils reveal that, like later ichthyosaurs, Chaohusaurus birthed its young viviparously, but, unlike later ichthyosaurs, the young exited the birth canal headfirst. The researchers also think that this headfirst birth posture indicates that live births in ichthyosaurs may have taken place on land[2], instead of in the water since caudad embryonic skull orientation is normally associated with land-dwelling animal births.
It should be noted that it may also be that this headfirst birth posture is merely a hold over from their terrestrial ancestors and that the birth took place in an aquatic environment. I would like more information on the sediments that these Chaohusaurus were found in. Basal ichthyopterygians have long been associated with coastal regions.
In addition to showing the earliest evidence for live birth of an ancient marine reptile, this new specimen is also thought to contain the oldest known fossil embryos of Mesozoic marine reptiles -- approximately 10 million years prior to the previously oldest known example
The researchers also suggest that live births in land reptiles likely appeared much earlier than was previously thought and that reptilian live birth only evolved on land.
The head of the team, Dr. Ryosuke Motani from the University of California, Davis noted that, "The study reports the oldest vertebrate fossil to capture the 'moment' of live-birth, with a baby emerging from the pelvis of its mother. The 248-million-year old fossil of an ichthyosaur suggests that live-bearing evolved on land and not in the sea."
Apparently this fossil was discovered in a laboratory while the researchers were investigating an extinct specimen of a predatory fish that resembled a modern pike known as Saurichthys
Embryos 1 and 2 are in orange and yellow, respectively, whereas neonate 1 is in red. Blue, black and green are different portions of the mother
1. The earliest fossil record of live birth belongs to a placoderm (extinct class of armored fish) found in western Australia and dating back to 380 mya (Late Devonian).
2. Similar to modern cetaceans, Ichthyosaurs were air-breathing.
Further Reading:
Terrestrial Origin of Viviparity in Mesozoic Marine Reptiles Indicated by Early Triassic Embryonic Fossils Abstract & Paper
Ancient reptile birth preserved in fossil: Ichthyosaur fossil may show oldest live reptilian birth
Fossil Shows Pre-Dino Reptile Giving Birth
Oldest Fossil of Reptile Live Birth Found
Chaohusaurus Fossil Shows Oldest Live Reptile Birth
Fossilized While Giving Birth? Ancient Reptile Preserved During Labor
248-Million-Year-Old Fossil Shows Oldest Reptile Live Birth, Chaohusaurus Was Born ‘Head First’
Ancient reptile's birth fossilised
The ichthyosaurs belonged to the genus Chaohusaurus, which is the earliest known Mesozoic marine reptile as well as being one of the smallest ichthyosaurs, ranging from 0.7 to 1.8 meters (27.5 to 70.8") in length.
What makes this discovery especially newsworthy is that one of the specimens, which is lacking the skull, anterior trunk, and posterior tail, appears to exhibit evidence for the earliest live birth from an ancient Mesozoic marine reptile in the fossil record[1]. This new fossil of an ancient Chaohusaurus mother, that likely died due to complications while in labor delivering triplets, is associated with three embryos and newborn infants: one inside the mother, another exiting the pelvis -- with approximately half the body still inside the mother -- and the third outside of the mother.
The skulls of two embryos are visible, one still inside the mother and the other exiting her pelvis while the firstborn's bones were preserved beneath the mother's tail. The researchers think that the first baby Chaohusaurus was born dead and that because of the burial positions, it's improbable that the babies were expelled from the mother after death.
The fossils reveal that, like later ichthyosaurs, Chaohusaurus birthed its young viviparously, but, unlike later ichthyosaurs, the young exited the birth canal headfirst. The researchers also think that this headfirst birth posture indicates that live births in ichthyosaurs may have taken place on land[2], instead of in the water since caudad embryonic skull orientation is normally associated with land-dwelling animal births.
It should be noted that it may also be that this headfirst birth posture is merely a hold over from their terrestrial ancestors and that the birth took place in an aquatic environment. I would like more information on the sediments that these Chaohusaurus were found in. Basal ichthyopterygians have long been associated with coastal regions.
In addition to showing the earliest evidence for live birth of an ancient marine reptile, this new specimen is also thought to contain the oldest known fossil embryos of Mesozoic marine reptiles -- approximately 10 million years prior to the previously oldest known example
The researchers also suggest that live births in land reptiles likely appeared much earlier than was previously thought and that reptilian live birth only evolved on land.
The head of the team, Dr. Ryosuke Motani from the University of California, Davis noted that, "The study reports the oldest vertebrate fossil to capture the 'moment' of live-birth, with a baby emerging from the pelvis of its mother. The 248-million-year old fossil of an ichthyosaur suggests that live-bearing evolved on land and not in the sea."
Apparently this fossil was discovered in a laboratory while the researchers were investigating an extinct specimen of a predatory fish that resembled a modern pike known as Saurichthys
Embryos 1 and 2 are in orange and yellow, respectively, whereas neonate 1 is in red. Blue, black and green are different portions of the mother
1. The earliest fossil record of live birth belongs to a placoderm (extinct class of armored fish) found in western Australia and dating back to 380 mya (Late Devonian).
2. Similar to modern cetaceans, Ichthyosaurs were air-breathing.
Further Reading:
Terrestrial Origin of Viviparity in Mesozoic Marine Reptiles Indicated by Early Triassic Embryonic Fossils Abstract & Paper
Ancient reptile birth preserved in fossil: Ichthyosaur fossil may show oldest live reptilian birth
Fossil Shows Pre-Dino Reptile Giving Birth
Oldest Fossil of Reptile Live Birth Found
Chaohusaurus Fossil Shows Oldest Live Reptile Birth
Fossilized While Giving Birth? Ancient Reptile Preserved During Labor
248-Million-Year-Old Fossil Shows Oldest Reptile Live Birth, Chaohusaurus Was Born ‘Head First’
Ancient reptile's birth fossilised
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