An extinct canid hiding in plain sight in the domestic dog?

Everyone knows that a certain black-and-tan pattern occurs again and again - either on an individual basis or as the colouration typical of the breed - in otherwise diverse breeds of the domestic dog (Canis familiaris).

These range in body size from the chihuahua ( to the rottweiler ( and beyond...

...and in body shape from the daschund ( and and and[pageGallery]/1/) to the afghan hound (

However, what is poorly appreciated is that the black-and-tan (or in some cases 'chocolate-and-cream' or 'chocolate-and-tan') pattern is one of the most significant and unexplained aspects of the domestic dog.

This pattern is bilaterally symmetrical and forms an integral and coherent system of markings connecting the head, chest, legs and hindquarters ( The system includes vestigial/incipient forms of adaptive features typical in wild mammals, such as a frontal flag ( and and an ischial flag ( and

(Please note that the pattern in breeds such as the German shepherd - although often confusingly called black-and-tan - is different, and irrelevant in this context.)

So, what is particularly significant about the black-and-tan pattern in the domestic dog?

Well, could it be that here we have a virtually complete representation of the colouration of an extinct and unnamed wild species of Canis which contributed to the ancestry of this, the oldest of all domestic species?

Many currently believe that the wolf (Canis lupus) is the main or sole ancestor of the domestic dog (e.g. see and And this seems a safe assumption in the case of at least a few breeds such as the saarloos wolfhound (, which lack the black-and-tan pattern in any individual (

However, the trouble is that the black-and-tan colouration is unknown in either the wolf or any other of the living wild species of Canis.

For the black-and-tan pattern to have appeared in descendents of solely the wolf, this entire system of features would have had to arise as a single mutation. Furthermore, the pattern would have had to be strongly preferred by humans during subsequent selective breeding.

These conditions seem implausible for several reasons.

Firstly, the black-and-tan pattern is 'wild-type' in its regular configuration (e.g. see, quite unlike the haphazard mutational features typical of many species of domestic mammals and birds.

Secondly, the black-and-tan pattern is recurrent and persistent among breeds regardless of extreme modification of body size and proportions. This conservatism indicates a deep ancestral feature, not one bred into the dog by domestication.

Thirdly, the black-and-tan pattern shows the same kind of subtle individual variation as do wild-type colourations in mammals in general.

Fourthly, the black-and-tan pattern remains in the populations of 'primitive' or 'retrogressive' relatives of the domestic dog, particularly the dingo.

Fifthly, where any irregular and asymmetrical marking occurs in combination with the black-and-tan pattern, the former is superimposed on the latter, not the other way round (

And sixthly, the black-and-tan pattern has some aesthetic appeal to many persons but not more so than various other, more typically domestic, patterns, such as the patchwork of tones seen in the border collie ( and

What all of this suggests is that the black-and-tan pattern is derived not from the wolf but from a different, extinct ancestor. This was possibly a jackal-like species living in Eurasia in the Pleistocene, which left few recognisable bones.

Let us look with fresh eyes, then, at working breeds such as the kelpie, which have retained/regained medium body size and a generalised body shape ( and and and similar to those of most wild species of Canis.

Is it not plausible that the overall appearance of the kelpie resembles this extinct species?

The likeness I am suggesting is, of course, phenotypic rather than genotypic. Nobody should doubt the complexity of selective breeding, over 15,000 years or more, that separates the kelpie from any extinct ancestor or co-ancestor. And hybridisation with the wolf remains likely as part of this process.

However, what I am suggesting is that - by accident rather than by design - the overall phenotypic trajectory may have circled back to the appearance of an extinct species separate from the wolf.

And - if we dare to hypothesise boldly enough to create a new search-image for this extinct species in the fossil record and in genetic analyses - could we even apply a working name of 'Canis rubronegrus'?

Further illustrations:

Saint Bernard

Tibetan mastiff

Coonhound and and

English toy terrier

Anotado por milewski milewski, 20 de septiembre de 2021 a las 01:43 PM


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