Toxodon platensis

Toxodon Temporal range: Late Miocene-Holocene (Mayoan-Atlantic) PreЄ Є O S D C P T J K Pg N
Skeleton of Toxodon in Buenos Aires
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	†Notoungulata
Family:	†Toxodontidae
Subfamily:	†Toxodontinae
Genus:	†Toxodon Owen, 1837
Type species
†Toxodon platensis Owen, 1837
Other species
†T. burmeisteri Giebel, 1866 †T. chapalmalensis Ameghino, 1908 †T. darwini Burmeister, 1866 †T. ensenadensis Ameghino, 1887 †T. expansidens Cope, 1886 †T. gracilis Gervais and Ameghino, 1880
Synonyms
Genus-level Dilobodon Ameghino, 1886 Chapalmalodon Pascual, 1957 Chapadmalodon Tonni et al., 1992 (lapsus calami) T. platensis T. angustidens Owen, 1846 T. owenii Burmeister, 1866 T. gervaisii Gervais & Ameghino, 1880 T. aguirrei Ameghino, 1917 T. gezi Ameghino, 1917 T. burmeisteri T. paradoxus Ameghino, 1882 T. protoburmeisteri Ameghino, 1887 T. bilobidens Ameghino, 1887 T. chapalmalensis Chapalmalodon chapalmalensis Pascual, 1957 T. chapadmalensis Cione & Tonni, 1995 (lapsus calami) T. chapalmalalensis Oliva & Cerdeno, 2007 (lapsus calami) T. ensenadensis T. giganteus Moreno, 1888 T. elongatus Roth, 1898 T. gracilis T. voghti Moreno, 1888

Genus-level

T. platensis

T. burmeisteri

T. chapalmalensis

T. ensenadensis

T. gracilis

Toxodon (meaning "bow tooth") is an extinct genus of South American mammals from the Late Miocene to Middle Holocene epochs (Mayoan to post-Lujanian in the SALMA classification) (about 11.6 million to 5000 years ago). It is a member of Notoungulata, one of several now extinct orders of hoofed mammals indigenous to South America. It was among the largest and last members of its order, and was probably the most common large-hoofed South American mammal of its time.

Charles Darwin was one of the first to collect Toxodon fossils, after paying 18 pence for a T. platensis skull from a farmer in Uruguay. In The Voyage of the Beagle Darwin wrote, "November 26th - I set out on my return in a direct line for Monte Video. Having heard of some giant's bones at a neighbouring farm-house on the Sarandis, a small stream entering the Rio Negro, I rode there accompanied by my host, and purchased for the value of eighteen pence the head of the Toxodon." Since Darwin discovered that the fossils of similar mammals of South America were different from those in Europe, he invoked many debates about the evolution and natural selection of animals.

Analysis of collagen sequences obtained from Toxodon as well as from Macrauchenia found that South America's native notoungulates and litopterns form a sister group to perissodactyls, making them true ungulates. This finding has been corroborated by an analysis of mitochondrial DNA extracted from a Macrauchenia fossil, which yielded a date of 66 Ma for the time of the split with perissodactyls.

In 2014, a study identifying a new species of toxodontid resolved the phylogenetic relations of the toxodontids, including to Toxodon. The below cladogram was found by the study:

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Wikipedia