DICE microCT and MRI data for Mandibular musculature constrains brain-endocast disparity in sarcopterygians

The scan of the adult <i>Neoceratodus</i> specimen was obtained using the 3T GE Signa Exite HDx human MRI scanner (Signa Excite 750; GE Healthcare; Milwaukee, WI), equipped with an 8-Channel Cardiac Coil, as part of the Digital Fish Library project Berquist et al. (2012). The pulse sequence parameters used were: flip angle of 35 degrees, 12.4 ms repetition time, 3.9 ms echo time, and three averages. Images were collected with slice thickness of 0.7 mm and resulting image resolution of 703 microns. Data were converted to DICOM format for image processing and visualisation. The Magnetic Resonance Imaging (MRI) scan of the adult <i>Neoceratodus</i> specimen was obtained from the Digital Fish Library catalogue, University of California San Diego (http://www.digitalfishlibrary.org). Image segmentation of the brain and braincase was performed using MIMICS v.17 (Materialise MedicalCo Belgium). <br> <i>Protopterus aethiopicus and Protopterus dolloi.</i> Specimens <br> were stained in IKI using the method of Metscher (2009) for three months. Micro-CT (uCT) scans were obtained using a Feinfocus 10-160kV transmission X-ray source and a Perkin Elmer XRD0822 1 MP flat panel X-ray camera. The peak energy used was 120kV, and 2 second exposures were corrected with offset and gain images. The resulting exposures were reconstructed as a tif stack using OctopusV9 resulting in a voxel size of 87.3 and 86.9 microns for <i>P. aethiopicus </i>and <i>P. dolloi</i> respectively. <br> <br> <i>Salamanders. </i>DiceCT contrast staining was completed using a Lugol's Iodine (I2KI) solution. 11.75% Lugol's Iodine was prepared following the protocol of Gignac &amp; Kley (2014) . <i>Ambystoma</i> was stained for 5 days prior to uCT scanning, whereas <i>Cynops</i> was scanned after only 72 hours. Both specimens were imaged using a Skyscan1173 (Bruker) desktop uCT scanner and were reconstructed as a stack of jpegs using NRecon 1.6.6. In both cases, the files were cropped in ImageJ (to reduce file size and sampled images from the stack at an interval of 2 in the Z-plane. The resultant voxel size for <i>Ambystoma</i> is 16.69 x 16.69 x 33.38 microns, and <i>Cynops</i> is 15.868 x 15.868 x 31.727 microns.<br>