Many earlier authorities such as Le Souef and  Burrell (1926), and Troughton (1967) usually categorized the thylacine with the Dasyuridae partly because the dasyurids are the only carnivorous, polyprotodont, didactylous group in Australia.
 

. A thylacine "kangaroo standing" at the Hobart Zoo (Domain site).  In the wild, thylacines use this upright posture to gain a better view of their surroundings.  Because the thylacine's heel has a long and narrow tract of bare, roughened skin along its length, it is evident that the animal frequently rests it on the ground in a kangaroo-like stance.  This image is from a film taken in 1928.

The majority of the distinctive features of the thylacine are specializations of characteristics present in all marsupicarnivore stocks, as well as placental carnivores.  The thylacine's limb proportions are similar to those of the dasyurids, despite its larger size.  Its reproductive system is also quite dasyurine in form.  By most counts, Thylacinus is no further removed from the Dasyuridae than is Myrmecobius (numbat). The thylacine was considered by Tate (1947) to be related to the Short-haired marsupial "mice" (Murexia spp.) of New Guinea on the basis of the progressive increase in size of the posterior molars, and the tubular braincase with post-orbital constriction which is seen in some mature male examples of Murexia.  However, since these characteristics are virtually the only similarities between the genera (Archer 1976c), this theory gained little support.

    On a dental basis, the relationship becomes tenuous.  The morphology of the shearing crest differs from that of all dasyurids, and the loss of the stylar cusps in a form with enlarged third premolars also contrasts with the overall dasyurid trend.  This suggests that the dasyurid and thylacinid lines diverged quite early.  A closer relationship to the now extinct borhyaenids of South America was proposed by Bensley (1903).  Formerly, this view was partly upheld by Archer (1976c).  However, Archer (1976b) stated that basicranial evidence tends to point to a didelphid rather than borhyaenid relationship.
 

By 1982, a comparative study of blood proteins called albumins had demonstrated that the thylacine is in fact very closely related to the dasyurids, and suggested that it had branched off from the main dasyurid line approximately 12 million years ago.  A decade later, analysis of DNA recovered from a preserved thylacine pelt provided an even stronger confirmation of this evolutionary affinity.  The borhyaenid link was simply another deceptive case of evolutionary convergence: similar lifestyles create similar physical forms.  However, the albumin study also misled evolutionary biologists by underestimating how long ago the thylacinids and dasyurids had diverged from an early proto-dasyurid predecessor.

. A thylacine photo taken by Harry Burrell at the Hobart Zoo (Beaumaris site) in 1912.  As was the case with the other thylacine photos from Burrell's series (all of which were probably taken on the same day), this one was greatly cropped before being published.  Compare it with the original version.

    The recent discoveries of a number of fossil thylacinid species and at least one ancestral dasyurid at Riversleigh (north-western Queensland) from approximately 22 million years ago suggest a minimum divergence time of 25 million years, and possibly even as far back as 30 to 40 million years ago.  Although fossils of primitive marsupicarnivores have been found in the rocks of central Australia (Archer 1976a), our understanding of the precise history of this group remains as of yet rather incomplete.
 

. Another one of Burrell's thylacine photos (1912).  This particular image is considered by some to have played an important role in promoting the unsubstantiated belief that the thylacine was a significant predator of poultry.  While it is true that thylacines may have occasionally been fed chickens in zoos, there is no strong evidence that the species ever posed any serious threat to domestic fowl, sheep or other livestock.  The structure of the thylacine's jaws and teeth appears to be much more suited to dealing with species of wild prey such as small to medium-sized mammals.  The photo shown above is the cropped version which appeared in a 1921 issue of Australian Museum Magazine, as well as various other publications.  Compare it with the original.

The thylacine's preferred habitat and hunting technique remain under debate.  The widespread distribution of fossil T. cynocephalus material proves that, even allowing for climatic change, the species' range of habitats was once wide, a fact which is demonstrated by the fossils that have been found in  association with it.  Similarly, the thylacine's alleged preference for dense forest may have possibly come about as a result of persecution by man.