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

Black KH, Travouillon KJ, Den Boer W, Kear BP, Cooke BN, Archer M - PLoS ONE (2014)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, Australia.

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.

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Ordered Bayesian analysis of our modified version of the Kear and Pledge [13] phylogenetic data set.Numbers at nodes represent Posterior Probabilities (PP). Fossil taxa are indicated by †. Balbaroo nalima sp. nov. is highlighted in bold.
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pone-0112705-g018: Ordered Bayesian analysis of our modified version of the Kear and Pledge [13] phylogenetic data set.Numbers at nodes represent Posterior Probabilities (PP). Fossil taxa are indicated by †. Balbaroo nalima sp. nov. is highlighted in bold.

Mentions: Parsimony analyses using “Trichosurus vulpecula” as the user-specified outgroup, with uninformative characters excluded, and state ordering enforced, yielded 96 MPTs of length {L}  = 288 (Consistency Index {CI}  = 0.4375, Rescaled Consistency Index {RCI}  = 0.3168: see strict consensus in Figure 16), and returned Hypsiprymnodon moschatus + Propleopus oscillans + Ekaltadeta ima + Balbaridae as a monophyletic sister clade to all other Macropodoidea (sensu Meredith et al. [14]). Unfortunately, support for this grouping was weak (bootstrap/Bremer <50/1), as previously acknowledged by Kear et al. [12] and Kear and Pledge [13]. Indeed, bootstrap/Bremer support values (<50/1) were negligible for almost all higher-level clades (Figure 16) except Dorcopsoides fossilis + Macropodidae sensu stricto (57/3), and Sthenurinae (75/3). Irrespectively, balbarid taxa maintained coherence following imposition of unordered states (140 MPTs of L = 284, CI = 0.4437, RCI = 0.3207: Figure 17), as well as within our Bayesian topologies (PP = 0.91 averaged from ordered (Figure 18) and unordered (Figure 19) runs), which unanimously excluded Balbaridae from Potoroidae + Macropodidae sensu lato (PP = 0.95) thus advocating placement along the macropodiform stem (sensu Cooke and Kear [2], Kear and Cooke [7]). Inspection of the individual parsimony character transformations found that the balbarid constituent taxa Nambaroo gillespieae + Ganawamaya acris + Wururoo dayamayi + Balbaroo spp. were united by homoplastic (ch.24.2, ch.26.1) or symplesiomorphic (ch.32.0) dental states. Moreover, potential postcranial apomorphies (ch.104.1, sensu Kear et al. [12]) could only be scored for Balbaroo nalima and N. gillespieae, thus their significance is unclear without data from other fossils. The genus Balbaroo incorporated W. dayamayi to form a basal polytomy with Balbaroo gregoriensis (Figures 16–17), a result consistent with our proposed synonymy. These taxa specifically shared a narrow trigonid basin on the m1 (ch.30.1; secondarily expanded in B. nalima, ch.30.2), but otherwise manifested traits widely expressed in other clades (ch.43.1). Placement of additional species within Balbaroo likewise relied upon convergent dental features (ch.29.1 to unite Balbaroo fangaroo + B. nalima + Balbaroo camfieldensis; ch.28.1 for B. nalima + B. camfieldensis), which prompts our conclusion that existing character sets reliant upon fragmentary dental remains and limited postcranial material are inadequate for robustly delimiting balbarid interrelationships.


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

Black KH, Travouillon KJ, Den Boer W, Kear BP, Cooke BN, Archer M - PLoS ONE (2014)

Ordered Bayesian analysis of our modified version of the Kear and Pledge [13] phylogenetic data set.Numbers at nodes represent Posterior Probabilities (PP). Fossil taxa are indicated by †. Balbaroo nalima sp. nov. is highlighted in bold.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4237356&req=5

pone-0112705-g018: Ordered Bayesian analysis of our modified version of the Kear and Pledge [13] phylogenetic data set.Numbers at nodes represent Posterior Probabilities (PP). Fossil taxa are indicated by †. Balbaroo nalima sp. nov. is highlighted in bold.
Mentions: Parsimony analyses using “Trichosurus vulpecula” as the user-specified outgroup, with uninformative characters excluded, and state ordering enforced, yielded 96 MPTs of length {L}  = 288 (Consistency Index {CI}  = 0.4375, Rescaled Consistency Index {RCI}  = 0.3168: see strict consensus in Figure 16), and returned Hypsiprymnodon moschatus + Propleopus oscillans + Ekaltadeta ima + Balbaridae as a monophyletic sister clade to all other Macropodoidea (sensu Meredith et al. [14]). Unfortunately, support for this grouping was weak (bootstrap/Bremer <50/1), as previously acknowledged by Kear et al. [12] and Kear and Pledge [13]. Indeed, bootstrap/Bremer support values (<50/1) were negligible for almost all higher-level clades (Figure 16) except Dorcopsoides fossilis + Macropodidae sensu stricto (57/3), and Sthenurinae (75/3). Irrespectively, balbarid taxa maintained coherence following imposition of unordered states (140 MPTs of L = 284, CI = 0.4437, RCI = 0.3207: Figure 17), as well as within our Bayesian topologies (PP = 0.91 averaged from ordered (Figure 18) and unordered (Figure 19) runs), which unanimously excluded Balbaridae from Potoroidae + Macropodidae sensu lato (PP = 0.95) thus advocating placement along the macropodiform stem (sensu Cooke and Kear [2], Kear and Cooke [7]). Inspection of the individual parsimony character transformations found that the balbarid constituent taxa Nambaroo gillespieae + Ganawamaya acris + Wururoo dayamayi + Balbaroo spp. were united by homoplastic (ch.24.2, ch.26.1) or symplesiomorphic (ch.32.0) dental states. Moreover, potential postcranial apomorphies (ch.104.1, sensu Kear et al. [12]) could only be scored for Balbaroo nalima and N. gillespieae, thus their significance is unclear without data from other fossils. The genus Balbaroo incorporated W. dayamayi to form a basal polytomy with Balbaroo gregoriensis (Figures 16–17), a result consistent with our proposed synonymy. These taxa specifically shared a narrow trigonid basin on the m1 (ch.30.1; secondarily expanded in B. nalima, ch.30.2), but otherwise manifested traits widely expressed in other clades (ch.43.1). Placement of additional species within Balbaroo likewise relied upon convergent dental features (ch.29.1 to unite Balbaroo fangaroo + B. nalima + Balbaroo camfieldensis; ch.28.1 for B. nalima + B. camfieldensis), which prompts our conclusion that existing character sets reliant upon fragmentary dental remains and limited postcranial material are inadequate for robustly delimiting balbarid interrelationships.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, Australia.

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.

Show MeSH
Related in: MedlinePlus