Smilodon fatalis canine and alveolus junction gap: Using MicroCT scans and 3D Slicer

Abstract The cranium of the sabertooth cat Smilodon fatalis from Rancho La Brea, now called La Brea Tar Pits and Museum (LBTPM), has been extensively studied; however, little research has been done on the placement and depth of the canines in the alveolus (tooth socket). During sample preparation, 110 years ago, canines often fell into the cleaning vats, so it is important to revisit and check these samples. Over the last fifty years, Computerized Tomography (CT) scans, including MicroCT and NanoCT scans, have moved from studying living humans to studying fossils. MicroCT scans can verify external observations such as misalignment of teeth. The reliance on 19th and 20th-century curations has always been fraught with complications. This study uses one of the largest collections of CT/MicroCT scans of this California sabertooth cat and demonstrates details that cannot be seen externally. A gap at the apical root would make the canine appear longer than in life. Results of our data set show that some of the specimens have improperly fitted canines, which can create errors in modelling. Finally, we demonstrate the use of 3D Slicer to virtually insert the canines and help determine whether a specific canine belongs to a specific cranium.