Pregnant T. rex Found, May Contain DNA

Pregnant T. rex Found, May Contain DNA

kacimo samy   4:56 ص

Pregnant T. rex Found, May Contain DNA

This illustration shows a pregnant T. rex next to another female.

A pregnant Tyrannosaurus rex has been found, shedding light on the evolution of egg-laying as well as on gender differences in the dinosaur. The remains also could contain the holy grail of all dinosaur fossils: DNA.

"Yes, it's possible," Lindsay Zanno told Discovery News, referring to genetic material that may be present in this as well as similar dinosaur finds. "We have some evidence that fragments of DNA may be preserved in dinosaur fossils, but this remains to be tested further."

What has been confirmed so far is that the T. rex, which was found in Montana and dates to 68 million years ago, retained medullary bone that reveals the individual was pregnant. Medullary bone is only present in female living dinosaurs, i.e. birds, just before and during egg laying. It's this type of bone that could retain preserved DNA.

Zanno is an assistant research professor of biological sciences at North Carolina State University, where she is also head of the North Carolina Museum of Natural Sciences' Paleontology Research Lab and is curator of paleontology. She explained that medullary bone lines the marrow cavity of the long bones of birds.

"It's a special tissue that is built up as easily mobilized calcium storage just before egg laying," she said. "The outcome is that birds do not have to pull calcium from the main part of their bones in order to shell eggs, weakening their bones the way crocodiles do."

Crocodiles, she said, are the closest living relatives of dinosaurs.

"Medullary bone is thus present just before and during egg laying, but is entirely gone after the female has finished laying eggs," she said.

Early on, Mary Schweitzer suspected that medullary bone was present in the tyrannosaur remains, and was able to confirm her suspicions after she, Zanno and their team conducted a chemical analysis of the T. rex's femur.

The material, found to be consistent with known medullary tissues from ostriches and chickens, contained karatan sulfate, a substance not present in any other bone types.

"This analysis allows us to determine the gender of this fossil, and gives us a window into the evolution of egg laying in modern birds," Schweitzer said.

Credits: Discovery news

Homo naledi, new specie of Homo

Homo naledi, new specie of Homo

kacimo samy   4:48 ص

Homo naledi, new specie of the genus Homo from the Dinaledi Chamber, South Africa

Dinaledi skeletal specimens.

A team of scientists have discovered Homo naledi which is a new specie of extinct homonin within Dinaledi chamber of the rising star cave system, Cradle of human kind, South Africa. The Dinaledi chamber is located approximately 30 meters underground, within the Rising Star cave system at about 26°1′13′′ S; 27°42′43′′ E. The system lies within the Malmani dolomites, approximately 800 meters southwest of the well-known site of Swartkrans in the Cradle of Humankind World Heritage Site, Gauteng Province, South Africa. Modern humans, or Homo sapiens, are now the only living species in their genus. But as recently as 100,000 years ago, there were several other species that belonged to the genus Homo. Together with modern humans, these extinct human species, our immediate ancestors and their close relatives, are collectively referred to as ‘hominins’. 

Fossil hominins were first recognized in the Dinaledi Chamber in the Rising Star cave system in October 2013. During a relatively short excavation, our team recovered an extensive collection of 1550 hominin specimens, representing nearly every element of the skeleton multiple times, including many complete elements and morphologically informative fragments, some in articulation, as well as smaller fragments many of which could be refit into more complete elements. The collection is a morphologically homogeneous sample that can be attributed to no previously-known hominin species. Here we describe this new species, Homo naledi. We have not defined H. naledi narrowly based on a single jaw or skull because the entire body of material has informed our understanding of its biology.

Now Berger et al. report the recent discovery of an extinct species from the genus Homo that was unearthed from deep underground in what has been named the Dinaledi Chamber, in the Rising Star cave system in South Africa. The species was named Homo naledi; ‘naledi’ means ‘star’ in Sotho (also called Sesotho), which is one of the languages spoken in South Africa.

The unearthed fossils were from at least 15 individuals and include multiple examples of most of the bones in the skeleton. Based on this wide range of specimens from a single site, Berger et al. describe Homo naledi as being similar in size and weight to a small modern human, with human-like hands and feet. Furthermore, while the skull had several unique features, it had a small braincase that was most similar in size to other early hominin species that lived between four million and two million years ago. Homo naledi's ribcage, shoulders and pelvis also more closely resembled those of earlier hominin species than those of modern humans.

The Homo naledi fossils are the largest collection of a single species of hominin that has been discovered in Africa so far and, in a related study, Dirks et al. describe the setting and context for these fossils. However, since the age of the fossils remains unclear, one of the next challenges will be to date the remains to provide more information about the early evolution of humans and their close relatives.