DOI: 10.6071/m3rt05
title: Data from: Decoding the dynamics of dental distributions: insights from shark demography and dispersal

description: Shark teeth are the most abundant vertebrate fossil, and because tooth
 size generally correlates with body size, their accumulations document the
 size structure of populations. Understanding how ecological and
 environmental processes influence size structure, and how this extends to
 influence these dental distributions, may offer a window into the
 ecological and environmental dynamics of past and present shark
 populations. Here we examine the dental distributions of sand tigers,
 including extant Carcharias taurus and extinct Striatolamia macrota, to
 reconstruct the size structure for a contemporary locality and four Eocene
 localities. We compare empirical distributions against expectations from a
 population simulation to gain insight into potential governing ecological
 processes. Specifically, we investigate the influence of dispersal
 flexibility to and from protected nurseries. We show that changing the
 flexibility of initial dispersal of juveniles from the nursery and annual
 migration of adults to the nursery explains a large amount of dental
 distribution variability. Our framework predicts dispersal strategies of
 an extant sand tiger population, and supports nurseries as important
 components of sand tiger life history in both extant and Eocene
 populations. These results suggest nursery protection may be vital for
 shark conservation with increasing anthropogenic impacts and climate
 change.
description: Shark species in the fossil record are largely identified by
 their tooth morphology due to the poor preservation of cartilaginous
 skeletons. Striatolamia macrota teeth are identified by emphasized
 striations on the lingual side relative to the smooth labial side.
 Anterior teeth (A1-2 and a1-2) are recognized by their long and narrow
 shape, compared to the lateral and posterior teeth that have a short,
 blade-like appearance. The anterior teeth have an acute angle between the
 two roots and have two small lateral cusplets. This tooth position was
 chosen as a proxy for body size because its large size and distinct
 morphology compared to other tooth positions within the jaw. Limiting the
 positions measured from fossil teeth prevents potential for over
 representation of a single individual within the assemblage. Because the
 shark body length and tooth crown height relationship established by
 Shimada (2002) for C. taurus may not be representative and accurate for
 the Eocene species S. macrota, we reconstruct body length using anterior
 crown height. We measured anterior tooth height from the enameloid base to
 the blade tip with digital calipers to an accuracy of 0.1 mm. The labial
 and lingual sides of the tooth, and the maximum width was also measured
 and recorded. The labial side of the tooth is adjacent to the cheek of the
 shark, and the lingual is that side adjacent to the tongue. Every seventh
 tooth was re-measured for 0.3 mm accuracy. The modern analogue for the
 Eocene S. macrota is the extant sand tiger C. taurus based on the
 similarities in tooth shape throughout the entire dentition. We
 transformed total length measurements from the 2012 tagging season in
 Delaware Bay to anterior tooth crown height based on the allometric
 relationships from Shimada 2002 and previously applied to fossil
 <em>S. macrota</em> in Kim et al. 2020. For each assemblage,
 we tested the sample size needed to estimate the mean and standard
 deviation of the tooth distribution. We then calculated the means and
 standard deviations of each tooth distribution and performed a power test
 to calculate the sample size required to estimate the mean and standard
 deviation within a 95% confidence level and 10% margin of error.
 Striatolamia macrota teeth from Banks Island are curated at the Canadian
 Museum of Nature (Ottawa, ON Canada); Seymour Island are curated at the
 University of California Museum of Paleontology (UCMP; Berkeley, CA USA),
 Paleontological Research Institute (PRI; Ithaca, NY USA), and Swedish
 Natural History Museum (NRM; Stockholm, Sweden); Red Hot Truck Stop
 locality are curated at the Carnegie Museum of Natural History (CM;
 Pittsburgh, PA); and Whiskey Bridge locality are curated at the Whiteside
 Museum of Natural History (WMNH; Seymour, TX). Locality descriptions are
 included in the Supplementary Materials. Details
 regarding the population simulation are detailed in the method
 section.
description: The anterior tooth length data from Eocene fossil sharks are
 labeled as the following columns: "Red_Hot" is the Red Hot Truck
 Stop locality of the Bashi/Tuscahoma Formations (Fm); Whiskey_Bridge is
 the Whiskey Bridge locality in the Stone City Member of the Crockett Fm.;
 Banks is Banks Island in the Cyclic Member of the Eureka Sound Fm. in the
 Arctic; Seymour is Seymour Island in the La Meseta Fm. of Antartica. The
 modern data from Delaware Bay takes total length data from the 2012
 Delaware State and University of Delaware shark tagging program and
 transforms it to labial measurements of anterior tooth crown height (shown
 as column "modern_DE").