Friday mystery object #82 answer

Apologies for the late posting of this answer – I was travelling back from Ireland yesterday and didn’t manage to get this post anywhere near as complete as I was hoping.

On Friday I gave you this mystery object to identify:

Pretty much everyone recognised it as being the skull of a dog or dog-like animal, but the large size of this skull (27cm long) caused some confusion. Quite a variety of breeds were suggested, but Rachel, Jamie Revell and Jake all ended up going for it being a  Newfoundland Canis lupus familiaris Linnaeus, 1758 – which is what I also concluded it is. [N.B. but it is in fact a Boarhound, as came to light later in an old catalogue.]

Domestic dogs show a remarkably diverse range of sizes – consider that a Chihuahua’s entire bodylength can be shorter than the length of the skull of the Newfoundland. Just comparing this specimen with a ‘normal’ sized Collie-type skull shows a remarkable difference in scale:

Dog skull shape is also hugely variable, depending on what the dog breed has been selected for. For example, Bulldogs have bizarre skulls, with a very shortened rostrum (muzzle), with a mandible (lower jaw) that doesn’t seem to fit:

Because of this variability and the care taken to protect pedigree lines, domestic dogs can provide a valuable insight into the genetic mechanisms involved in the development of morphological traits. One study in particular (Fondon & Garner, 2004) shows the remarkable rate at which mutations can occur within dog breeds, neatly summed up in this diagram:

Fig. 3 from Fondon & Garner, 2004 DOI:10.1073/pnas.0408118101

Rapid and sustained evolution of breeds. (A) Purebred St. Bernard skulls from ≈1850 (Top), 1921 (Middle), and 1967 (Bottom). (B) Purebred bull terrier skulls from 1931 (Top), 1950 (Middle), and 1976 (Bottom) (24). (C) Purebred Newfoundland skulls from 1926 (Top), 1964 (Middle), and 1971 (Bottom). Despite the lack of genetic diversity caused by population structure and history, these breeds are able to continually create new and more extreme morphological variations at a rapid and sustained pace.

This diagram also provides a useful reference for comparing St. Bernard and Newfoundland skulls – they are of a similar size and shape, but the St. Bernard has the upper second molar (the very last tooth in the back of the jaw) in a more elevated position above the upper first molar (the next tooth along) than the Newfoundland. The nuchal crest (the bony ridge at the back of the skull) is also straighter and lower in the St. Bernard. [Unfortunately there is little information available about the skulls of Boarhounds for comparison.]

This piece of research is interesting at several levels and I particularly like the fact that it is a good example of the value of museum collections for providing a snippet of the past to compare with the present. Without historical specimens there would be no way to get the base-line information needed to unpick the type and rate of change that has given us what we see today. This ability to look into the past informs us about the future.

To finish I want to offer a hearty thanks to everyone for their suggestions – they pointed me in the direction of more information on a variety of dog breeds and related species, which was fascinating and has helped me improve my confidence in the identification [even though I was wrong!]. For me, the comments I receive on the FMO are the most valuable part of running a blog, because they make me look at objects in a different light.

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