Cellular, bone-like tissue in the bucklers of the thornback ray Raja clavata (Batoidea, Chondrichthyes)

Chondrichthyans have lost the cellular bone characteristic of other jawed vertebrate skeletons. However, we identify cellular bone-like tissue in the ‘bucklers’ of one group of extant batoids (rays). Bucklers are modified scales, distinctive for some rays, with enlarged bases. As placoid scales, they possess crowns of orthodentine and osteodentine, but a unique basal tissue. This consists of a cell-rich material, previously misidentified as an acellular tissue. The newly formed basal tissue grows appositionally and episodically from a cell-rich periosteum-like layer. This closely resembles cellular bone, with entombed cells situated between bundles of attachment fibres anchoring the buckler to the underlying dermal tissue and the ‘periosteum’ to the buckler surface. In histologically more mature buckler tissue, the cell spaces and attachment fibres are remodelled, forming enlarged fluid-filled spaces. The result is a unique mineralized tissue in these rays, initially sharing similaritie..., CT-scanning
A single buckler specimen was CT-scanned in Science Innovation Platforms, Natural History Museum (NHM), on a Zeiss Radia Versa equipped with a 10W sealed transmission source at 100kV, 10µA and an HE1 source filter. 3001 projections were generated at 7.1µm voxel size.  Scans were rendered using Avizo 3D 2021.2 (https://www.thermofisher.com/uk/), including virtual slices and rotatable models., , # Cellular, bone-like tissue in the bucklers of the thornback ray Raja clavata (Batoidea, Chondrichthyes)

[https://doi.org/10.5061/dryad.6t1g1jx96](https://doi.org/10.5061/dryad.6t1g1jx96)

## Description of the data and file structure

*CT-scanning*

A single buckler specimen was CT-scanned in Science Innovation Platforms, Natural History Museum (NHM), on a Zeiss Radia Versa equipped with a 10W sealed transmission source at 100kV, 10µA and an HE1 source filter. 2034 projections were generated, with 10 projections lost due to processing errors. We confirm that these do not affect the overall scan reconstruction (internal and external morphology), nor our interpretations and conclusions.  Scans were rendered using Avizo 3D 2021.2 (https://www.thermofisher.com/uk/), including virtual slices and rotatable models 

### Files and variables

#### File: Buckler_CT_scan_data.zip

**Description:** CT scan data of a dermal denticle (buckler) of the chondrichthyan Raja clavata.
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