The dentition of the narrownose smooth-hound shark, mustelus schmitti

Abstract

The present study provides a quantitative and qualitative analysis on the dentition of Mustelus schmitti, and estimates the tooth-replacement rate. In total, 47 males and 56 females of M. schmitti were collected on scientific trawl surveys conducted by the National Institute of Fisheries Research and Development (INIDEP) in Argentina during the months of November 2007, November 2008 and December 2008. The dental laminas were extracted from the jaw cartilage and attached to onionskin paper for dehydration treatment, maintaining the original jaw position. Tooth replacement rate was estimated following established methods used for fossil sharks, instead of the established technique of clipping teeth, based on the premise that tooth length within each row decreases from the lingual to the labial side of the jaw as a consequence of wear. The length difference between consecutive teeth in four representative rows should be proportional to the tooth-replacement rate. Mustelus schmitti exhibited homodont dentition, where teeth were similar in shape or design, and are arranged in a semi-pavement-like dentition. The dental formula was 47-63/50-63 for juveniles and 50-77/50-69 for adult specimens. The estimated mean replacement rate was 4 days series-1.