VARIATION IN SCALE MORPHOLOGY OF HYNERIA LINDAE (SARCOPTERYGII, TRISTICHOPTERIDAE) FROM THE RED HILL SITE, PENNSYLVANIA, U.S.A

Scale morphology among extinct sarcopterygian fish is highly variable. Scales among lobe-finned fishes range from cosmine-covered rhombic scales in more primitive Osteolepids to thin rounded scales in Tristichopterids. Evolution of squamation patterns among lobe-finned fish is most likely related to a change from a less agile type of existence among more primitive taxa to a more fast swimming, predatory type of lifestyle among more advanced types of sarcopterygians. Scale morphology can also vary within an individual fish based on the body position of the scale. Scales from the main body axis of an individual are usually different in size and shape compared to those from other regions of the body. Several recent studies on extinct bony fish have analyzed the size and shape of isolated scales so as to assign these scales to specific body regions. Hyneria lindae was a large (up to 3m in length) predatory species of tristichopterid sarcopterygian fish described from the Upper Devonian Red Hill site in Pennsylvania. Isolated H. lindae scales are among the most common fossils found at Red Hill. The purpose of my project was to describe variation in shape and size of isolated H.lindae scales from Red Hill as a preliminary attempt to assign scales to different body regions of H. lindae. Over 80 isolated scales collected at the Red Hill site as well as those housed at both the Academy of Natural Sciences of Drexel University and the State Museum of Pennsylvania were measured for length and width using digital calipers. Length of each scale was measured from the anterior to the posterior margin while width was measured from the dorsal to the ventral margin. Additionally, each scale was categorized based on overall shape. Shape categories included “elliptical”, “round”, and “reniform” (kidney-shaped). Scales ranged from 5.6mm to 49.4mm in length and 6.5mm to 57.7mm in width. Average length (± 2SE) (27.1mm ± 2.04) and width (± 2SE) (27.8mm ± 2.2) of isolated scales did not differ significantly (p > 0.05). Most scales fell into the reniform category, followed by elliptical and those in the round category. Reniform scales being the most common shape of scales among those I measured could have been located along the main body axis of the animal while round and elliptical scales could have been found on more specialized regions such as the tail and/or fins.