running animals in general. One specimen is known to have had a bone pathology, with the long bones of the right foot fused at their tops, hindering swift movement. Examinations of the teeth of Thescelosaurus and comparisons with the contemporary pachycephalosaur Stegoceras suggest that Thescelosaurus was a selective feeder, while Stegoceras was a more indiscriminate feeder, allowing both animals to share the same environment without competing for food. Supposed fossilized heart In 2000, a skeleton of this genus (specimen NCSM 15728) informally known as "Willo", now on display at the North Carolina Museum of Natural Sciences, was described as including the remnants of a four-chambered heart and an aorta. It had been originally unearthed in 1993 in northwestern South Dakota. The authors had found the internal detail through computed tomography (CT) imagery. They suggested that the heart had been saponified (turned to grave wax) under airless burial conditions, and then changed to goethite, an iron mineral, by replacement of the original material. The authors interpreted the structure of the heart as indicating an elevated metabolic rate for Thescelosaurus, not reptilian cold-bloodedness. Their conclusions have been disputed; soon after the initial description, other researchers published a paper where they asserted that the heart is really a concretion. As they noted, the anatomy given for the object is incorrect (for example, the "aorta" narrows coming into the "heart" and lacks arteries coming from it), it partially engulfs one of the ribs and has an internal structure of concentric layers in some places, and another concretion is preserved behind the right leg. The original authors defended their position; they agreed that it was a type of concretion, but one that had formed around and partially preserved the more muscular portions of the heart and aorta. A study published in 2011 applied multiple lines of inquiry to the question of the object's identity, including more advanced CT scanning, histology, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. From these methods, the authors found the following: the object's internal structure does not include chambers but is made up of three unconnected areas of lower density material, and is not comparable to the structure of an ostrich's heart; the "walls" are composed of sedimentary minerals not known to be produced in biological systems, such as goethite, feldspar minerals, quartz, and gypsum, as well as some plant fragments; carbon, nitrogen, and phosphorus, chemical elements important to