Like all large extant mammals,
kangaroos had smaller ancestors (Fig 1). These are the pre-kangaroos and their relatives in the large reptile tree (LRT, 2319 taxa) to scale.
Figure 1. A phylogenetic series of kangaroo skulls, but see figure 2 for a derived split.
Hypsiprymnodon moschatus
(Ramsey 1876, snout-vent up to 27cm) isthe extant musky rat-kangaroo, restricted to NE Australia. This omnivore is traditionally allied with kangaroos, but in the LRT nests with potoroos, like Potorous, also kangaroo kin. The last premolars (cyan) converge with those of multituberculates.
Potorous tridactylus
(Kerr 1792; body length: 36cm, taili: 15-24cm) is the extant long-nosed potoroo, a member of the rat-kangaroo family. Nocturnal Potorous hops about while it digs for roots and fungi.
Tarsipes rostratus
(Gervais & Verreaux 1842; Beck, Voss and Jansa 2022, up to 8.5cm snout-vent length + up to 10cm) is the extant and nocturnal honey possum, a tiny nectar eater related to Potorous. The tiny teeth are reduced to cones and widely spaced. Gestation lasts for 28 days, with two to four young being produced. At birth, they are the smallest of any mammal, weighing 0.005 g. Pouch development takes 60 days. When the babies emerge they are left in a sheltered area, but within days start to cling to the mother during her travels.
Nambaroo gillespieae
(N. tarrinyeri Flannery & Rich, 1986; Kear et al. 2007; Late Oligocene, 25 mya) was reported to be the “granddaddy of kangaroos” and to have had fangs, ‘probably for display,’ and mostly ate soft food such as fruit and fungi (Kear 2007). It was found in Australia. The short rostrum suggests a long soft trunk or nose. The very long tibia ends in a very kangaroo-like pes.
Bettongia setosa
(Gray 1837) is the extant bettong, a kangaroo ancestor derived from Potorous.
Figure 2. At left, the extant kangaroo, Macropus, and its ancestor, Lagostropheus. At right, the extinct short-faced kangaroo, Procoptodon, and its relative in the LRT, Dendrolagus. Skulls scaled to a common lenglth, making the short-faced kangaroo actually a deep-faced kangaroo. Subtle differences lump and separate these taxa in the LRT.
Lagostrophus fasciatus
(originally Lagorchestes fasciatus Thomas 1887) is the extant banded hare-wallaby. Note the descending process of the maxilla below the jugal.
Dendrolagus ursinus
(Müller 1840; up to 82 cm snout-vent length+ up to 94 cm tail) is the extant black tree kangaroo.
Figure 3. Bettongia is a kangaroo ancestor in the LRT and it’s still extant.
Macropus giganteus
(Shaw 1790, extant) is the eastern gray kangaroo. The forelimbs were elongated. The hind limbs even more so. The pedal digits were reduced, all but the second digit, which was robust. Kangaroos hop bipedally and rest tripodally with the tail. Note the pelvis is essentially vertical here and the proximal femur was lower than the distal femur. The canines were absent and a diastema separated the incisors from the molars, convergent with rodents and multituberculates. The lower incisors were elongated and procumbent.
Figure 4. Procoptodon is a derived kangaroo.
Procoptodon goliah
(Owen 1873, extant, 2m tall; Pleistocene) is the extinct short-face kangaroo. The skull was very much like that of another marsupial, Interatherium, which has sheep-like propotions. This caused problems earlier, resolved now.
These are the sort of convergence problems getting resolved in the latest round of housekeeping in the LRT. If you want to learn taxonomy, build your own LRT and stumble through until it all comes together.
References
Cuvier G 1822. Recherches sur les Ossemens Fossiles (Nourvelle Edition) Voume 2 paert 1. Chez G. Dufour et E. D’Ocagne, Paris, France.
Gray 1837. Mag. Nat. Hist. [Charlesworth’s] 1:584.
Holbrook LT 2009. Osteology of Lophiodon Cuvier, 1822 (Mammalia, Perissodactyla) and Its Phylogenetic Implications. Journal of Vertebrate Paleontology 29(1): 212-230.
Flannery TF and Rich TH 1986. Macropodoids from the middle Miocene Namba Formatiion, South Australia, and the homology of some dental structures in kangaroos. Journal of Paleontology 60:418-447.
Kear BP, Cooke BN, Archer M and Flannery TF 2007. Implications of a new species of the Oligo-Miocene kangaroo (Marsupialia: Macropodoidea) Nambaroo, from the Riversleigh World Heritage Area, Queensland, Australia, in Journal of Paleontology 81:1147-1167.
Müller S 1840. Over de Zoogdieren van den Indischen Archipel. Pp. 1-8 [1839], Pp. 9-57+6 unnumbered pp. [1840], in Verhandelingen over de Natuurlijke Geschiedenis der Nederlandsche overzeesche bezittingen, door de Leden der Natuurkundige Commissie in Indiö en andere Schrijvers (C. J. Temminck, ed.). [V. 3] Zoology [1839-1845]. J. Luchtmans en C. C. van der Hoek.
Owen R 1873. Procoptodon goliah, Owen. Proceedings of the Royal Society of London 21, 387.
Shaw G 1790. Macropus giganteus. Nat. Miscell. plate 33 and text. kangaroo online pdf
Thomas O 1887. On the wallaby commonly known as Lagorchestes fasciatus. Proceedings of the Zoological Society of London. 1886: 544–547.
wiki/Macropus
wiki/Dendrolagus
wiki/Banded_hare-wallaby – Lagosttopheus
wiki/Bettong
wiki/Procoptodon
wiki/Nambaroo
The Pterosaur Heresies 