by Staff Writers
Pittsburgh PA (SPX) Feb 11, 2013
This is an artist's rendering of the hypothetical placental ancestor, a small insect-eating animal. The research team reconstructed the anatomy of the animal by mapping traits onto the evolutionary tree most strongly supported by the combined phenomic and genomic data and comparing the features in placental mammals with those seen in their closest relatives. Credit: Carl Buell.
Today's article reveals the final results of the six-year ATOL project. The study began with two teams organizing data from two distinct approaches to evolutionary research: molecular data (DNA), and morphological data (anatomical features).
Thanks to the incredible amount of anatomical information collected, the researchers were able to predict the appearance of the most recent common ancestor of all placental mammals. Explains Spaulding, "We have all these placentals alive today, from elephants to shrews, from things that fly to things that swim. What could the common ancestor of these things that are so different possibly look like?"
"We focused our study on the time around the Cretaceous-Tertiary (KT) boundary, 65 million years ago," states Spaulding, "Molecular and morphological based studies differ on the age when placentals first appeared. Molecular studies place the origin in the mid-Cretaceous, when dinosaurs still dominated. On the other hand, morphological studies have routinely found no evidence of any placental fossils in this time period, and instead place the placental origin after the mass extinction at the close of the Cretaceous that ended dinosaur dominance."
The study was conducted utilizing the web application Morphobank (www.morphobank.org). The matrix is freely available online and provides a road map to the Tree of Life team's findings by precisely outlining how the team defined each of the more than 4,500 characters in the dataset. Proving that a picture is worth a thousand words, the majority of characters include illustrations.