On my personal blog I provide an object for identification from the collections of the Horniman Museum every Friday (my imaginatively titled 'Friday mystery object'). Often the object is something I've had to identify (or reidentify) myself as part of my work as a natural history curator. Last Friday I used this specimen:
Pretty much all of my regulars 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 possible species and dog breeds were suggested, but Rachel, Jamie Revell and Jake converged on my identification of Newfoundland dog Canis lupus familiaris Linnaeus, 1758.
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:
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.
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 helps inform us about the future.
To finish I want to offer a hearty thanks to everyone who made suggestions - they sent me in the direction of more information on a variety of canid species and dog breeds, which was fascinating and has helped me improve my confidence in the identification. For me, the comments I receive are the most valuable part of running a blog, because they make me look at museum objects in a different light. I will be posting a Friday mystery object on the Scientopia guest blogge this week, so I hope you'll join in and have a go at working out what it is.