A new species of the basal "kangaroo" Balbaroo and a re-evaluation of stem macropodiform interrelationships

PLoS One. 2014 Nov 19;9(11):e112705. doi: 10.1371/journal.pone.0112705. eCollection 2014.

Abstract

Exceptionally well-preserved skulls and postcranial elements of a new species of the plesiomorphic stem macropodiform Balbaroo have been recovered from middle Miocene freshwater limestone deposits in the Riversleigh World Heritage Area of northwestern Queensland, Australia. This constitutes the richest intraspecific sample for any currently known basal "kangaroo", and, along with additional material referred to Balbaroo fangaroo, provides new insights into structural variability within the most prolific archaic macropodiform clade--Balbaridae. Qualitative and metric evaluations of taxonomic boundaries demonstrate that the previously distinct species Nambaroo bullockensis is a junior synonym of B. camfieldensis. Furthermore, coupled Maximum Parsimony and Bayesian phylogenetic analyses reveal that our new Balbaroo remains represent the most derived member of the Balbaroo lineage, and are closely related to the middle Miocene B. camfieldensis, which like most named balbarid species is identifiable only from isolated jaws. The postcranial elements of Balbaroo concur with earlier finds of the stratigraphically oldest balbarid skeleton, Nambaroo gillespieae, and suggest that quadrupedal progression was a primary gait mode as opposed to bipedal saltation. All Balbaroo spp. have low-crowned bilophodont molars, which are typical for browsing herbivores inhabiting the densely forested environments envisaged for middle Miocene northeastern Australia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Animals
  • Australia
  • Conservation of Natural Resources
  • Macropodidae / anatomy & histology
  • Macropodidae / classification*
  • Macropodidae / genetics
  • Phylogeny*
  • Skull / anatomy & histology

Grant support

Support for Riversleigh research has been provided by the Australian Research Council grants to MA, Suzanne J. Hand and KHB (DE130100467, DP043262, DP1094569, LP0453664, LP0989969, LP100200486), Xstrata Community Partnership Program North Queensland, Queensland Parks and Wildlife Service, Environment Australia, the Queensland and Australian Museums, University of New South Wales, P. Creaser and the CREATE Fund at UNSW, Outback at Isa, Mount Isa City Council and the Waanyi people of northwestern Queensland. R. Day provided funding to the University of Queensland to create a postdoctoral position for KJT. BPK acknowledges funding from the Swedish Research Council. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.