Brian Dalrymple and colleagues from The International Sheep Genomics Sequencing Consortium report a high-quality reference genome for the sheep, Ovis aries (Science 344, 1168–1173, 2014). They sequenced the genomes of two Texel breed sheep: a 6-month-old ewe and an inbred ram. They used high-density radiation hybrid and linkage maps to aid in assembly, with a total assembled length of ∼2.61 Gb. They constructed a phylogenetic tree on the basis of single-copy orthologous genes across livestock and humans and dated the separation of sheep from goats at 4.3 million years ago (confidence interval of 3.2–5.7 million years ago), overlapping with the expansion of C4 grasses. They also performed RNA sequencing analysis of 94 samples from 40 tissues. Protein clustering analysis across mammalian species identified 73 subfamilies specific to and 321 expanded in the ruminant lineage. They also characterized expression of genes within the mammalian epidermal development complex (EDC) region, involved in the development of the rumen, skin and wool. They identified keratin genes highly expressed in the rumen, including TCHHL2, encoding a putative keratin cross-linking protein. LCE7A was highly expressed in skin and was suggested to be involved in wool development, along with components of fatty acid metabolism and lipid enzymes.