From head to hind: Elucidating function through contrasting morphometrics of ancient and modern pedigree dogs.

Used together, caliper- and geometric-based morphometric analyses provide complimentary approaches to classifying form and function of archaeozoological remains. Here we apply these analytical tools to the skeletal remains of an ancient male dog unearthed from a rural farm settlement of Roman date near present day Warmington, United Kingdom. Our comparisons of the Warmington Roman dog against the morphological characteristics of modern dog breeds enabled us to establish the former's size and shape. It was of medium stature. Analysis of viscerocrania and neurocrania indicate it falls within the meso- to dolichocephalic rankings of modern dogs. The neurocranium shape and the dimensions of its long bones strongly suggest that the Warmington dog shares similarities to modern sight hounds. Historically sight hounds were bred for speed, as necessitated of a hunter that runs down small prey. Our analysis suggests that the Warmington dog was likely bred for, or derived from, Roman hunting stock. By revealing the Warmington Roman dog's form from cranial and postcranial analyses, we shed light on Roman life in one of the furthest outposts of the Roman Empire.

Canine Brachycephaly Is Associated with a Retrotransposon-Mediated Missplicing of SMOC2.

In morphological terms, "form" is used to describe an object's shape and size. In dogs, facial form is stunningly diverse. Facial retrusion, the proximodistal shortening of the snout and widening of the hard palate is common to brachycephalic dogs and is a welfare concern, as the incidence of respiratory distress and ocular trauma observed in this class of dogs is highly correlated with their skull form. Progress to identify the molecular underpinnings of facial retrusion is limited to association of a missense mutation in BMP3 among small brachycephalic dogs. Here, we used morphometrics of skull isosurfaces derived from 374 pedigree and mixed-breed dogs to dissect the genetics of skull form. Through deconvolution of facial forms, we identified quantitative trait loci that are responsible for canine facial shapes and sizes. Our novel insights include recognition that the FGF4 retrogene insertion, previously associated with appendicular chondrodysplasia, also reduces neurocranium size. Focusing on facial shape, we resolved a quantitative trait locus on canine chromosome 1 to a 188-kb critical interval that encompasses SMOC2. An intronic, transposable element within SMOC2 promotes the utilization of cryptic splice sites, causing its incorporation into transcripts, and drastically reduces SMOC2 gene expression in brachycephalic dogs. SMOC2 disruption affects the facial skeleton in a dose-dependent manner. The size effects of the associated SMOC2 haplotype are profound, accounting for 36% of facial length variation in the dogs we tested. Our data bring new focus to SMOC2 by highlighting its clinical implications in both human and veterinary medicine.

Do large dogs die young?

In most animal taxa, longevity increases with body size across species, as predicted by the oxidative stress theory of aging. In contrast, in within-species comparisons of mammals and especially domestic dogs (e.g. Patronek et al., '97; Michell, '99; Egenvall et al., 2000; Speakman et al., 2003), longevity decreases with body size. We explore two datasets for dogs and find support for a negative relationship between size and longevity if we consider variation across breeds. Within breeds, however, the relationship is not negative and is slightly, but significantly, positive in the larger of the two datasets. The negative across-breed relationship is probably the consequence of short life spans in large breeds. Artificial selection for extremely high growth rates in large breeds appears to have led to developmental diseases that seriously diminish longevity.