DOI: 10.5061/dryad.n8pk0p38p
title: CT Data for: Synchrotron data reveal nautiloid-characters in <em>Pohlsepia mazonensis</em>, refuting a Palaeozoic origin for octobrachians

description: Pohlsepia mazonensis, from the late Carboniferous Mazon Creek Lagerstätte
 (311 - 306 Ma), has been suggested to be the oldest fossil octopus. This
 single specimen provides a key calibration point for molecular clock
 studies which estimated a Palaeozoic origin for octobrachians, pushing the
 fossil record of crown octopuses back 150 million years. Despite being a
 textbook ‘phylogenetic fuse’ example, the systematic position of Pohlsepia
 is controversial and, consequently, our understanding of cephalopod
 evolution remains in flux. We present the first comprehensive reassessment
 of this enigmatic fossil, alongside multiple new specimens, using a suite
 of advanced analytical techniques. Synchrotron micro-X-ray fluorescence
 elemental mapping reveals a radula obscured by the matrix, definitively
 confirming a molluscan affinity. Crucially, radular tooth count and
 morphology indicate that Pohlsepia is not an early octobrachian but rather
 a decomposed nautiloid. This reinterpretation refutes a Palaeozoic origin
 for octobrachians and provides the only unequivocal evidence of nautiloid
 soft tissue in the Palaeozoic fossil record. Our findings demonstrate how
 analytical methods can be used to resolve the interpretive challenges
 posed by the exceptional but often ambiguous soft tissue preservation in
 the Mazon Creek Lagerstätte, offering great potential for the
 re-evaluation of other fossil specimens from this iconic site.
description: # CT Data for: Synchrotron data reveal nautiloid-characters in *Pohlsepia
 mazonensis*, refuting a Palaeozoic origin for octobrachians Dataset DOI:
 [10.5061/dryad.n8pk0p38p](https://doi.org/10.5061/dryad.n8pk0p38p) ##
 Description of the data and file structure 6 supplementary data files
 pertaining to the raw CT slice images and the associated metadata of the
 *Pohlsepia mazonensis* (PE51727) fossil part (A) and counterpart (B). ##
 ### Files and variables #### File: Pohlsepia_A.ctprofile.xml
 **Description:** XCT settings and metadata for Pohlsepia A 
 
 #### File: PohlA_ctdata.txt **Description:**  metadata for Pohlsepia A
 scan  ##### Variables * Projections * Frames * Exposure(ms) 
 
 #### File: Pohlsepia_B.ctprofile.xml **Description:** XCT settings and
 metadata for Pohlsepia B 
 
 #### File: PohlB_ctdata.txt **Description:** metadata for Pohlsepia B
 scan ##### Variables * Projections * Frames * Exposure(ms) 
 
 #### File: SLICES_Pohlsepia_A.zip **Description:** Raw slices .bmp files
 of Pohlsepia A (cropped and resliced) Folders: * Cropped: slices from
 microCT scans after they had been cropped in Fiji to the
 region-of-interest. * Resliced: slices that were resliced in different
 axes in Fiji * PohlA: SPIERS edit working files for Pohlsepia fossil A
 #### File: SLICES_Pohlsepia_B.zip **Description:** Raw slices .bmp files
 of Pohlsepia B (cropped and resliced) Folders: * Cropped: slices from
 microCT scans after they had been cropped in Fiji to the
 region-of-interest. * Resliced: slices that were resliced in different
 axes in Fiji * PohlB: SPIERS edit working files for Pohlsepia fossil B|
 #### File: Pohlsepia_concretion_clements.mkv **Description:** Video of
 PE51727 part and counterpart.