The shoulder girdle of early chondrichthyans grew by skeletal remodelling

A distinct shoulder region, defined by endoskeletal and dermal girdles and associated pectoral musculature, is a major evolutionary adaptation of jawed vertebrates. In teleost model species the large (macromeric) pectoral dermal bones can be derived from multiple embryonic tissues, identifying the shoulder of osteichthyans as a developmentally complex area at the head-trunk boundary. The absence of bone in living chondrichthyans makes Palaeozoic stem groups capable of dermal ossification key to understanding the underpinnings of skeletal growth in the shoulder of crown gnathostomes (osteichthyans and chondrichthyans). Here, using synchrotron X-ray tomography we demonstrate that individual pectoral plates in the oldest unequivocal jawed vertebrate, the Silurian (c. 439 Mya) chondrichthyan Fanjingshania renovata, develop from five separate growth centres. These centres correspond to pectoral bony spines that fuse neighbouring dermal scales into a pinnal plate and their expansion is accomp..., (a) Material
The studied skeletal elements of Fanjingshania renovata are part of a larger fossil collection (more than 1000 fin spines, spines, tesserae, scales and dermal plates belonging to the species) recovered from the lower Silurian (Aeronian) beds of the Rongxi Formation, exposed near the village of Leijiatun, Shiqian county, Guizhou province, China. They are represented by a pinnal plate fragment (IVPP V27433.8) and other incomplete pinnal plates fused to prepectoral (IVPP V27433.9) and admedian (IVPP V27434.2) spines and pectoral fin spine fragments (IVPP V27433.10, IVPP V27433.11, IVPP V27433.12, IVPP V27433.4). All specimens were deposited at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences.
(b) Synchrotron radiation X-ray tomographic microscopy
The fossil material was analysed with synchrotron radiation X-ray tomographic microscopy at the TOMCAT-X02DA beamline of the Swiss Light Source, Paul Scherrer Institute, Villigen, Swit..., # Data from: The shoulder girdle of early chondrichthyans grew by skeletal remodelling

Dataset DOI: [10.5061/dryad.5mkkwh7j8](10.5061/dryad.5mkkwh7j8)

## Description of the data and file structure

**Description of the data files:**

File: 3D_model_of_IVPP_V27433.11.stl
Description: 3D surface geometry file of a pinnal plate fragment fused to an incomplete pectoral fin spine (IVPP V27433.11) belonging to *Fanjingshania renovata*. File generated from a synchrotron tomography dataset acquired at the TOMCAT beamline at the Swiss Light Source.

File: 3D_model_of_IVPP_V27433.8.stl
Description: 3D surface geometry file of a pinnal plate fragment (IVPP V27433.8) belonging to *Fanjingshania renovata*. File generated from a synchrotron tomography dataset acquired at the TOMCAT beamline at the Swiss Light Source.

File: 3D_model_of_IVPP_V27434.2.stl
Description: Description: 3D surface geometry file of a pinnal plate fragment fused to admedian spines (IVPP V27434.2) belonging to *Fanjingshania ..., ,