Trichosurus, 1828

Beck, Robin M. D., Voss, Robert S. & Jansa, Sharon A., 2022, Craniodental Morphology And Phylogeny Of Marsupials, Bulletin of the American Museum of Natural History 2022 (457), pp. 1-353 : 333-334

“ Trichosurus ”

SPECIES SCORED: “ Trichosurus ” † dicksoni .

GEOLOGICAL PROVENANCE OF SCORED SPECIMENS: Riversleigh Faunal Zone C, Riversleigh World Heritage Area, Queensland, Australia.

AGE OF SCORED SPECIMENS: Riversleigh Faunal Zone C is interpreted to be middle Miocene based on biostratigraphy (see above). In the absence of radiometric dates, we have assumed the entire span of the middle Miocene (Langhian to Serravallian; Cohen et al., 2013 [updated]) for this terminal.

ASSIGNED AGE RANGE: 15.970 –11.630 Mya.

REMARKS: “ Trichosurus ” † dicksoni was described by Flannery and Archer (1987c) as the oldest fossil member of the Recent phalangerid genus Trichosurus , based on specimens from Riversleigh Faunal Zone C (?middle Miocene) sites. If correct, this implies that Trichosurus had diverged from its extant sister taxon, Wyulda , prior to the?middle Miocene. However, in her unpublished Ph.D. thesis, Crosby (2002b) concluded that “ T. ” † dicksoni is not, in fact, referable to Trichosurus , but warrants referral to a separate, entirely extinct, genus. Crosby (2007: fig. 7) presented an informal phylogeny that placed “ T.” † dicksoni closer to † Onirocuscus (see above) than to Recent trichosurins, but this was not based on a formal, algorithmic analysis of character data. Crosby (2002b), however, did present formal phylogenetic analyses of phalangerid relationships that failed to support a close relationship between “ T.” † dicksoni and extant Trichosurus species.

It is also noteworthy that some recent molecular studies (Meredith et al., 2009b; Mitchell et al., 2014) estimated that Trichosurus and Wyulda did not diverge from each other until the late Miocene, i.e., after the inferred age of “ Trichosurus ” † dicksoni , although others suggested that the Trichosurus - Wyulda split may have occurred prior to this (Ruedas and Morales, 2005; Kealy et al., 2019). Regardless, all recent molecular-clock analyses indicated that the Wyulda + Trichosurus lineage (= Trichosurini ) had diverged from the rest of Phalangeridae by the middle Miocene or earlier (Ruedas and Morales, 2005; Raterman et al., 2006; Meredith et al., 2009b; Mitchell et al., 2014; Kealy et al., 2019).