1758 [domestic dog]" and "dingo Meyer, 1793 [domestic dog]", with the comment "Includes the domestic dog as a subspecies, with the dingo provisionally separate – artificial variants created by domestication and selective breeding. Although this may stretch the subspecies concept, it retains the correct allocation of synonyms." Wozencraft included hallstromi – the New Guinea singing dog – as a taxonomic synonym for the dingo. Wozencraft referred to the mtDNA study as one of the guides in forming his decision. Mammalogists have noted the inclusion of familiaris and dingo together under the "domestic dog" clade, and they debate this classification. Taxonomic debate This classification by Wozencraft is debated among zoologists. Mathew Crowther, Stephen Jackson, and Colin Groves disagree with Wozencraft and argue that based on ICZN Opinion 2027, a domestic animal cannot be a subspecies. Crowther, Juliet Clutton-Brock and others argue that because the dingo differs from wolves by behaviour, morphology, and because the dingo and dog do not fall genetically within the extant wolf clade, that the dingo should be considered the distinct taxon Canis dingo Meyer 1793. Janice Koler-Matznick and others believe that the New Guinea singing dog Canis hallstromi Troughton 1957 should not be classified under Canis lupus dingo on the grounds that it has behavioural, morphological and molecular characteristics that are distinct from the wolf. Jackson and Groves do not regard the dog Canis familiaris as a taxonomic synonym for (or subspecies of) the wolf Canis lupus, but instead rank them both equally, as distinct species. They also disagree with Crowther, based on the overlap between dogs and dingoes in their morphology, in their ability to easily hybridise with each other, and that they show the signs of domestication by both having a cranium of smaller capacity than their progenitor, the wolf. Given that Canis familiaris Linnaeus 1758 has date priority over Canis dingo Meyer 1793, they regard the dingo as a junior taxonomic synonym for the dog Canis familiaris (i.e. being included within the circumscription of the latter species). Further, the dingo is regarded as a feral dog because it descended from domesticated ancestors. Gheorghe Benga and others support the dingo as a subspecies of the dog. as Canis familiaris dingo Meyer 1793, with the domestic dog being the subspecies Canis familiaris familiaris. In 2008, the palaeontologists Xiaoming Wang and Richard H. Tedford propose that the dog could be taxonomically classified as Canis lupus familiaris under