Cranial modularity drives phenotypic diversification and adaptive radiation of Antarctic icefishes

Modularity among traits is thought to drive morphological evolution and diversification, with more modular species often showing greater disparity and faster evolutionary rates. However, recent studies suggest this pattern is not universal, as higher integration can sometimes be linked to faster rates of evolution. In adaptive radiation, modularity likely facilitates morphological divergence, but its specific role in trait diversification within these events remains uncertain. Antarctic icefishes (Perciformes: Notothenioidei) have undergone adaptive radiation in the frigid Southern Ocean, yet the role of modularity in their craniofacial evolution remains poorly understood. Emerging from a common ancestor 22 million years ago, these fishes developed unique morpho-physiological adaptations, such as antifreeze glycoproteins, that contributed to their evolutionary success, but the contribution of cranial modularity to their diversification is still unexplored. Here, we analyze skull shape a..., Morphological sampling and shape analyses. To investigate skull shape evolution in Notothenioidei, we quantified the skull shapes of 80 Notothenioidei species (representing approximately 51% of total clade diversity, with all seven families included) and 92 species from other Perciformes (encompassing 30 different families). This dataset includes a total of 172 species belonging to 37 families, covering 66% of the Perciformes families (SI Appendix, Table S4 and Fig. S1). We analyzed the three-dimensional skull morphology of each species through micro-computed tomography (μCT) scans. The specimens were scanned at both Rice University and the Natural History Museum of Los Angeles County (LACM) under the oVert and ScanAllFishes initiatives. Additionally, we obtained further scans from Morphosource (http://morphosource.org). These scans were processed in Amira v2.0.0 (Thermo Fisher Scientific, Waltham, MA) to isolate the skull by removing scales and other debris. The resulting skulls were c..., , # Cranial modularity drives phenotypic diversification and adaptive radiation of Antarctic icefishes

[https://doi.org/10.5061/dryad.vq83bk44j](https://doi.org/10.5061/dryad.vq83bk44j)

## Description of the data and file structure

### Files and variables

#### Table S1: Species list used in our study (word format): species, sample number, and origins (Museum or Fieldwork)

* *Species*: Currently valid scientific name
* *Source/Museum*: Fieldwork Belize, museums (BMNH, ANSP, FMNH, KAUM, UF, UWFC, AM, USNM, AMNH, JFBM, UVI), or Uncat (species not deposited in a museum)
* *Catalog number*: voucher number associated with the museum or Uncat (species not deposited in a museum)

- **Shape dataset** (merged_icefishescoords_final.csv): the superimposed landmarks coordinates of 172 perciform species (80 notothenioids and 92 perciform relatives)
* *Species* (categorical variable): Perciform specimens 
* *V1-V435*(numerical variable): landmark coordinates in a 2d array formart
- **Actinopter...,