Vertebrate Paleontology
Joseph Carlin
My project focused on the luminescence of silver-bearing hydrothermal calcite veins from Batopilas, Mexico, which is in southwestern Chihuahua. Luminescence is when an external energy source excites electrons in a mineral to a higher energy state, and then as they return to ground state they emit the extra energy as visible light. I used photoluminescence (stimulus from a UV light) and cathodoluminescence (stimulus from an electron beam). There were a variety of photoluminescent colors in the calcites ranging from red-violet to pink to orange. The red-violet and pink photoluminescent samples also contained metallic minerals such as galena, sphalerite, and native silver whereas the orange samples were barren. This makes photoluminescent color a useful indicator in the field for finding metallic mineral-bearing veins.
The vestibular apparatus in bats occupies a significantly lower percentage of the petrosal cavity compared to terrestrial mammals (the mean percentage for bats is 29.9% compared to a mean percentage of 43.7% for terrestrial mammals). This finding is analogous to a reduction of the vestibular apparatus which has been well documented in whales and supports the hypothesis that moving in a three-dimensional fluid media introduces selective pressure favoring smaller vestibular structures. The difference was found to be statistically significant.