Canids

Canids

Canids (Canidae) are dog like creatures including wolves, jackals, coyotes, foxes, wild dogs, dingoes and dholes with a total of 13 genera and 36 species extant. They belong to the order Carnivora, placental mammals with a diet almost entirely meat (Macdonald, Zubiri. 2004). Due to their diet, Carnivora is distinguished by the possession of carnassial teeth, used to slice their prey’s flesh (Jensen, 2007). Canidae has two subfamilies being vulpini which includes the foxes and canini which includes wolves, jackals, coyotes, dholes, wild dogs and dingoes.

Figure 1, Dog skull showing predominant Carnassial teeth.
https://en.wikibooks.org/wiki/Anatomy_and_Physiology_of_Animals/The_Skeleton
accessed 9/3/2016 

Canids are from the suborder Caniformia in which there are two superfamilies Cynoidea and Arctoidea (Macdonald, Zubiri. 2004, Jensen, 2007). Canids belong to Cynoidea while Arctoidea includes Ursidae (bears), Pinnipedea (walrus) and Musteloidea (skunks, racoons and otters) (Macdonald, Zubiri. 2004). Today’s canids share a common ancestor from over 40 MYA (Jensen, 2007). Due to this common ancestor, canids share a couple of distinguishing features which have been seen in fossils of even the extinct species (Macdonald, Zubiri. 2004). One of these features is the middle ear structure which can be used to identify between other carnivore families (Jensen, 2007).

The canids inner ear has a large entotympanic bulla (large round bone which holds ear drum) and a septum between the inner ear bones. Canids have also completely lost the stapedial artery, which connects inner ear muscles in fetuses of other mammals (Macdonald, Zubiri. 2004, Jensen, 2007, Fisher, Unknown). The placement of the carotid arteries is also different to other mammals being closer to the brain (Macdonald, Zubiri. 2004, Jensen, 2007). This placement is said to lower the risk of congestion and add protection to the arteries during the hunt (Fisher, Unknown).

Figure 2. Carnivora Family Tree
http://sweetpics.site/f/felidae-family-tree.html
accessed 9/3/16

The original “canids” belonged to the subfamily Hesperocyoninae about 40MYA. This subfamily paved the way for two more subfamilies, Borophaginae and Caninae (Macdonald, Zubiri. 2004). At this stage the dentition began to evolve (Macdonald et al, 2004) which will be mentioned more in weeks to come. The extinction of the Borophaginae subfamily allowed the caninae to populate much of North America (Macdonald, Zubiri. 2004). Leptocyon was the first species of the Caninae (Macdonald et al, 2004). This species was small with an elongated jaw and extremely similar dentition to today’s canids (Macdonald et al, 2004). The Vulpini came about later and began evolving to fit the niches the Canini had left open (Macdonald et al, 2004).  The Canids spread across Europe and Africa, then with the help of humans moved into Australia becoming the world’s largest and most spread group of predators (Macdonald, Zubiri. 2004). 

References:

David W. Macdonald, Claudio Sillero-Zubiri, 2004, The Biology and Conservation of Wild Canids, Oxford

Per Jensen, 2007, The Behavioural Biology of Dogs, CABI

A.G Timbrell Fisher, A Case of Complete Absence of Both Internal Carotid Arteries, With a Preliminary Note on the Developmental History of the Stapedial Artery, Demonstrator of Anatomy and of Surgical Anatomy, P 38-46

David W. Macdonald, Claudio Sillero-Zubiri, Michael Hoffman, Status Survey and Conservation Action Plan, Canids: Foxes, Wolves, Jackals and Dogs, 2004, The World Conservation Union