Shark skin may act as an exotendon altering swimming performance among species with varying ecologies. Shark skin is a material composed of dermal denticles embedded in the stratum compactum of the dermis, where an elastic network is formed between denticles and collagen fibers. This network stretches in two distinct orientations of uniaxial stress (longitudinal and hoop), transmitting muscular and controlling tensile forces during swimming. Previous work on shark skin showed that denticles and collagen fiber networks impact mechanical properties. Our goal is to quantify the anisotropic properties of shark skin and the impacts of the collagen fiber network and dermal denticle density among four shark species. We dissected skin between the two dorsal fins and created a grid around the body. We imaged each grid cell (5x5cm) using a stereoscopic microscope and quantified denticle density on the external and collagen fiber angle on the internal skin surface using ImageJ. Four dog-bone shaped samples, 2 at each orientation (longitudinal and hoop), were tested in tension until failure at a 2 mm/s strain rate on an Instron E1000. We generated a stress-strain curve for each sample and calculated the tensile properties: ultimate strength (MPa), maximum strain (mm-2), toughness (MPa), and Young’s Modulus (MPa). We found significant differences among species for all mechanical properties, and testing orientation was significant for all mechanical properties except toughness. As collagen fiber angle and denticle density increase, toughness decreases. These data improve our understanding of the role of shark skin in swimming mechanics for energy reduction and meeting demands in various habitats, thereby potentially acting as an exotendon.