Placentarele are those mammals in which the embryo is housed in the uterus until full development, as fed during interauterine life through the placenta, a specialized organ that connects the vascular system of the mother and the baby. Nutrients from the mother’s body passes directly into the blood as chicken. Afarpă year of this feature, placentarele have certain skeletal particuarităţi which differ from other groups of mammals – monotremele and marsupials.
Ancestor of all placental mammals looked like and when they occurred are issues that have long concerned scientists.
Within the frameworks of this new study, whose results were published in the journal Science, scientists have “drawn” in the most detailed way so far failed, phylogenetic tree of placental mammals using data both anatomical and genetic, to reconstruct ancestral form, the ancestor of all placentarelor.
The results – which contradicts a widely accepted theory – shows that the group began to diversify after the extinction of the dinosaurs 65 million years ago. The new information could help scientists better understand how mammals survived past climate change and the impact it might have on their future environmental changes.
In the international study, a group of researchers from the University of Florida, USA, analyzed the anatomy of primate fossils and present, including lemurs, monkeys and humans, as well as that of the closest relatives of primates, arboreal and chiţcanii colugo (arboreal mammals of the order Dermoptera living in Asia and are able to glide from one tree to another, thanks to a membrane stretched between its forelegs and hind. known only two species are present.)
The results provide a new perspective on how major changes may influence the creatures, for example, dinosaur extinction, which was such a major change created conditions for diversification probably all mammals, including our ancestors removed,
Reconstitution appearance placental mammal ancestors – some small insectivorous animals – was made possible by a large database, publicly accessible, called MorphoBank.
Unlike other restorations, it creates a clearer picture of the phylogenetic tree, combining two types of data: data phenomena (including observational features, such as those related to anatomy and behavior) and genomic data, encoded in DNA.
Combining all this evidence, scientists can create the most documented reconstruction of past events, explained study leader, Professor Maureen O’Leary, Universităţiii working at Stony Brook and the American Museum of Natural History and compared the reconstruction tree with phylogenetic reconstruction of a crime – an event in the past can not be relived.
Researchers have been observational characteristics of 86 species of mammals placenatre, including 40 fossil species. The resulting database contains over 12,000 images over 4,500 corresponding to features such as the presence or absence of wings, teeth or certain bones, hairs covering the body type, certain brain structures. Dataset is about 10 times higher than those used in previous studies of the relationship between mammalian species.
Other researchers in the team compared the characteristics of people with each other 7 species and one fossil current Euarchonta group (which includes primates, arboreal and colugo chiţcanii) and the results contradict previous conception widespread.
The evolution of placental mammals was interpreted over time, in very different ways, depending on the data set analyzed. Thus, previously, an analysis based only on genomic data indicate that a number of “branches” of the late Cretaceous placental mammals exist and that Cretaceous-Paleogene extinction have survived (the one that killed the dinosaurs). This hypothesis suggests that primates were separated from other mammals long before the extinction of the dinosaurs, but the new study, based on data and analysis directly from fossils, paints a different picture, showing that placental mammals began to diversify only after dinosaur extinction , about 65 million years.
Researchers have reconstructed common ancestor placentarelor anatomy, using the best supported by evidence, resulting in the fact that it had a horned uterus, a brain whose presence convolution cortex and placenta in which maternal blood came into contact with the membrane surrounding the fetus as happens today in humans.