Triceratops - Mammal or Reptile?

We must rethink what we think we know: mammal or reptile? Researchers think the Triceratops had forelimbs with a more mammal-like posture resembling that shown in the top images, versus the more reptile-like forelimb posture shown below. The three-horned animal, Triceratops, may have had a more upright, athletic posture than thought, new anatomical evidence suggests. Researchers say Triceratops' forelimbs may have resembled those of a large mammal, kept closer to its body than the forelimbs of reptiles and amphibians that typically have a lower, more sprawling posture.

The key is in the elbow, according to the researchers, Shin-ichi Fujiwara from the University of Tokyo and John Hutchinson from the Royal Veterinary College of the University of London. [LiveScience]

Furthermore, a study with extant mammals refutes the hypothesis on which the assumption that dinosaurs were reptilian ectotherms. This study analyzes the lines of arrested growth (LAG) in the bones of around a hundred ruminants, representative of the specific and ecological diversity of that group of mammals. The results show that the presence of these lines is not an indicator of an ectothermic physiology (does not generate internal heat), as had previously been thought, since all warm-blooded mammals have them. The study therefore dismantles the key argument of the hypothesis that dinosaurs could have been cold-blooded reptiles. More can be read about this here.