Posts Tagged ‘fossils’

Remains of oldest horned dinosaur in North America found

December 11, 2014 Leave a comment
This artist's conception shows Aquilops americanus in its early Cretaceous period ecosystem. Image courtesy Raymond M. Alf Museum of Paleontology, copyright Brian Engh.

This artist’s conception shows Aquilops americanus in its early Cretaceous period ecosystem. Image courtesy Raymond M. Alf Museum of Paleontology, copyright Brian Engh.

Paleontologists have identified a species of horned dinosaur that lived in Montana more than 100 million years ago, the oldest known ceratopsian in North America.

The two foot-long animal – about as long as a crow or a raven – was an ancestor much larger horned and frilled creatures that roamed Cretaceous period landscapes on the continent.

Known as Aquilops americanus, the animal is a clue to a pattern of dinosaur migration from Asia to North America.

“Aquilops lived nearly 20 million years before the next oldest horned dinosaur named from North America,” Andrew A. Farke, a paleontologist at the Raymond A. Alf Museum of Paleontology in Claremont, Calif. and lead author of a paper documenting the discovery. “Even so, we were surprised that it was more closely related to Asian animals than those from North America.”

Those relatives included Liaoceratops yanzigouensis, another tiny predecessor of Triceratops, Styracosaurus, and other ceratopsian dinosaurs whose fossils were discovered in China and described in 2002.

Researchers found only the remnants of one, probably adolescent, Aquilops’ skull, about 84 millimeters long. But those bones are distinctive enough to set the fossils apart as a holotype. Among the most distinctive features of the skull is a downward-curving, bumped beak.

The Aquilops americanus fossils were found in 1997. The name means “American eagle face.”

The paper documenting the discovery was published in the Dec. 10 edition of PLOS One.

Fossil showing birth of early Triassic ichthyosaur shows viviparity may have evolved on land

February 16, 2014 Leave a comment


This photograph shows the locations of two embryos and one neonate, along with the female ichthyosaur, documented in a new study that indicates marine reptile viviparity may have evolved on land. Image courtesy Ryosuke Motani.

Scientists have discovered a fossil that preserves an infant prehistoric marine reptile in the process of being born, a find that indicates live birth may have first evolved among land-dwelling organisms.

The specimen dates to about 248 million years ago, during the early Triassic period, and is of a female ichthyosaur, along with two embryos and one neonatal individual.

One of the embryos was still inside its mother when death came, another was partially outside the adult individual’s pelvis, and a third was entirely outside its mother.

The position of the embryo that is half-way out of its mother’s body indicates that head-first birth occurred among ichthyosaurs. If so, then the birth may have occurred on land and not in the water, as has generally been presumed by scientists to be likely in the case of early Mesozoic animals.

Viviparity, as live birth of infants is known, has independently evolved across a wide variety of organisms. It is known in fishes, amphibians, reptiles, and mammals and, even among ichthyosaurs, the phenomenon has been observed in fossils dating from the middle Triassic period to the Cretaceous period.

Mosasaurs and plesiosaurs are other Mesozoic era marine organisms that were viviparous. Those reptiles lived during the Cretaceous period.

The fossil preserved individuals of the genus Chaohusaurus would have plied seas near present-day Chaohu and Yuanan, China. The adult specimen was about 100 centimeters long, while the embryos and neonate were about 18 centimeters long.

A paper documenting the fossil discovery appears in the Feb. 14, 2014 edition of PLOS One.

The fossils documented in it are at the Anhui Geological Museum in Hefei City, China.

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