Enlargement of sternum traits facilitated the evolution of powered flight in birds

An enlarged sternum with a prominent keel is a central feature of the flight apparatus of modern birds. However, sterna of near-bird dinosaurs (Pennaraptora) and early avialans are either significantly different from those of living birds or absent altogether, raising questions on how specialized sternal structures evolved in birds and how they are related to function. This remains poorly understood due to the fragmentary nature of the fossil record, and the challenges in inferring form and function from crushed fossils. We employ ancestral character estimations to trace sternal trait acquisition through the bird stem group, and multivariate phylogenetic regressions to analyze relationships between sternum morphology, body mass, and flight capabilities. We find that sternum evolution was episodic: basal members of Pennaraptora had proportionally small sterna, which became larger and more craniocaudally elongated in Avialae. This enlargement precedes the appearance of a midline ridge, a ..., , # Data from: Enlargement of sternum traits facilitated the evolution of powered flight in birds

Associated publication: Lowi-Merri, T.M., Benson, R., Hu, H., et al. Enlargement of sternum traits facilitated the evolution of powered flight in birds. Nat. Ecol. Evol.

## Dryad dataset

Dataset DOI: [10.5061/dryad.jsxksn0ng](10.5061/dryad.jsxksn0ng)

## Description of the data and file structure

Comparative analysis of fossil stem avian sternum size and dimensions to determine the evolutionary trajectory of the sternum across the dinosaur-bird transition and during the evolution of flight.

### Files and variables

Most variables are self-explanatory and are defined when deemed necessary. All units of measurement are in millimetres (mm) unless specified otherwise.

#### File: Fossils25.csv

**Description:** Morphological data on fossil specimens for which sternum size and metrics were collected.

##### Variables

* Taxon
* Specimen number
* Higher Classification: larger clade that the ta...,