Scottish Journal of Geology A sauropod-dominated tracksite from Rubha nam Brathairean (Brothers’ Point), Isle of Skye, Scotland by Paige E. dePolo, Stephen L. Brusatte, Thomas J. Challands, Davide Foffa, Dugald A. Ross, Mark Wilkinson, and Hong-yu Yi Scottish Journal of Geology Volume 54(1):1-12 May 18, 2018 © 2018 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved

(a, b) The geographical context of the tracksite with (c) a sedimentary log of the bedding-level stratigraphy of the tracksite. (a, b) The geographical context of the tracksite with (c) a sedimentary log of the bedding-level stratigraphy of the tracksite. Maps adapted from BGS 1:50 000 [Shapefile geospatial data], scale 1:50 000, tile: SC0803, version 2016, British Geological Survey, UK, using: EDINA Geology Digimap Service http:/.digimap.edina.ac.uk, downloaded October 2017, © Geological Map Data BGS © NERC 2017. Paige E. dePolo et al. Scottish Journal of Geology 2018;54:1-12 © 2018 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved

Photograph of the sediment deformation observed at the BP2 site. Photograph of the sediment deformation observed at the BP2 site. The range in bedding deflection can be seen with low-angle deformation directly below the yellow fieldbook and with medium- to high-angle deformation associated with the track immediately to the right. The photograph was taken facing SW along the portion of the bedding place with the highest track density containing Trackways 1 and 2. The long edge of the fieldbook is 18.5 cm. Paige E. dePolo et al. Scottish Journal of Geology 2018;54:1-12 © 2018 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved

The length (L) and width (W) measurements taken for sauropod manus and pes tracks at the BP2 site. The length (L) and width (W) measurements taken for sauropod manus and pes tracks at the BP2 site. The measurement scheme was adapted from Marty (2008) and adjusted to the less than ideal preservation conditions of the tracksite (where displacement rims and inner track outlines were poorly defined or non-existent). Paige E. dePolo et al. Scottish Journal of Geology 2018;54:1-12 © 2018 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved

Measurements for tridactyl tracks at the BP2 site. Measurements for tridactyl tracks at the BP2 site. Total footprint length (L) is measured from the back edge of the heel to the most distal portion of digit III and total footprint width (W) is measured between the outermost edges of the lateral digits (II and IV). The total digital lengths (LII and LIV) are measured from the back of the heel to the most distal portion of the digit. K and M represent the heel-interdigital curve (hypex) distances. Basal digital lines are defined by connecting the terminations of the hypex lines. The basal digital lengths (BL2, BL3, BL4) are measured from the basal digital lines to the distal ends of the digit. The basal digital widths (WBII, WBIII, WBIV) are measured along the basal digital lines of each digit. The middle digit width (WMII, WMIII, WMIV) is measured perpendicular to the middle point of the BL line. The interdigital angles between digit II and digit III and digit III and digit IV are measured between lines traced from the back edge of the heel and the distal ends of the digits in question. Tridactyl track measurement parameters were based on Leonardi (1987), Moratalla et al. (1988) and Thulborn (1990). Paige E. dePolo et al. Scottish Journal of Geology 2018;54:1-12 © 2018 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved

An orthophotograph and site map of the BP2 tracksite showing the distribution of the tracks across the site and the location of crossing trackways. An orthophotograph and site map of the BP2 tracksite showing the distribution of the tracks across the site and the location of crossing trackways. The locations and rough shapes of individual tracks at the site are shown with black outlines while details of the platform (steps in the stratigraphy and distinctive fractures) are shown with lighter grey outlines. The track numbers detailed in this figure are combined with the site name to create the identification numbers referenced in the text (i.e. 40 on the site map has a field identification number of BP2_40). Paige E. dePolo et al. Scottish Journal of Geology 2018;54:1-12 © 2018 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved

A composite figure of the different presentations of sauropod tracks at site BP2 to demonstrate both the variety of the tracks and the difficulty of determining ichnological characteristics. A composite figure of the different presentations of sauropod tracks at site BP2 to demonstrate both the variety of the tracks and the difficulty of determining ichnological characteristics. (a) BP2_08 represents the elongate track formed when manus and pes impressions overprint one another with a correspondingly elongate cast filling; (b) BP2_09 shows a sauropod pes track preserved as a shallow impression filled with a heavily-weathered cast that retains hints of at least one anteriorly directed digit; (c) impressions of a manus–pes set belonging to Trackway 1; and (d) a pes impression with a pronounced lateral deformation rim and a flattened anterior margin with a single, slightly deflected digit preserved (left side of image). Paige E. dePolo et al. Scottish Journal of Geology 2018;54:1-12 © 2018 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved

An orthophotograph and line drawing of the distribution of the tracks between Trackway 1 and 2. An orthophotograph and line drawing of the distribution of the tracks between Trackway 1 and 2. Purple outlines are used to denote tracks belonging to Trackway 1 whereas bright green is used to denote tracks from Trackway 2. The black ‘x’ shows the position of the rock hammer. The crossing lines are intended to show the general extent and orientation of the trackways and not to denote the trackway midlines. Paige E. dePolo et al. Scottish Journal of Geology 2018;54:1-12 © 2018 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved

Photograph and line drawing of track BP2_40. Photograph and line drawing of track BP2_40. This footprint is one of the most striking at the site and preserves evidence of a possible fleshy heel pad in addition to four distinct toes. Paige E. dePolo et al. Scottish Journal of Geology 2018;54:1-12 © 2018 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved

A sampling of the types of large tridactyl track morphologies observed at site BP2 with (a) BP2_48 presenting as a bulbous-toed tridactyl track with a clear claw mark on digit III; (b) BP2_23 constituting a skinny-toed faint track with a broken right lateral digit and a hint of a proximal hallux impression; and (c) BP2_26 representing a large track with sharply tapering, narrow toes and elongated hypices. A sampling of the types of large tridactyl track morphologies observed at site BP2 with (a) BP2_48 presenting as a bulbous-toed tridactyl track with a clear claw mark on digit III; (b) BP2_23 constituting a skinny-toed faint track with a broken right lateral digit and a hint of a proximal hallux impression; and (c) BP2_26 representing a large track with sharply tapering, narrow toes and elongated hypices. Paige E. dePolo et al. Scottish Journal of Geology 2018;54:1-12 © 2018 The Author(s). Published by The Geological Society of London for EGS and GSG. All rights reserved