Role of development in the evolution of the scapula of the giant sthenurine kangaroos (Macropodidae: Sthenurinae)

Sears, Karen E.

doi:10.1002/jmor.10353

Cited by 7 publications

(4 citation statements)

References 28 publications

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“…We consider that another important difference between sthenurines and other macropodids, again relating to their probable locomotor habits, is the relative size of the supraspinatus muscle. The scapula of sthenurines is unusual in having a highly reduced supraspinous fossa, the area of origin of the supraspinatus muscle (Wells and Tedford 1995; see also Sears 2005). Wells and Tedford (1995:84) described the sthenurine scapula as "curiously human-like," and proposed that this morphology enabled sthenurines to raise their forelimb above their head.…”

Section: Discussionmentioning

confidence: 99%

Proximal Humerus Morphology Indicates Divergent Patterns of Locomotion in Extinct Giant Kangaroos

et al. 2020

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Sthenurine kangaroos, extinct "giant kangaroos" known predominantly from the Plio-Pleistocene, have been proposed to have used bipedal striding as a mode of locomotion, based on the morphology of their hind limbs. However, sthenurine forelimb morphology has not been considered in this context, and has important bearing as to whether these kangaroos employed quadrupedal or pentapedal locomotion as a slow gait, as in extant kangaroos. Study of the correlation of morphology of the proximal humerus in a broad range of therian mammals shows that humeral morphology is indicative of the degree of weightbearing on the forelimbs during locomotion, with terrestrial species being distinctly different from arboreal ones. Extant kangaroos have a proximal humeral morphology similar to extant scansorial (semi-arboreal) mammals, but sthenurine humeri resemble those of suspensory arboreal taxa, which rarely bear weight on their forelimbs, supporting the hypothesis that they used bipedal striding rather than quadrupedal locomotion at slow gaits. The humeral morphology of the enigmatic extinct "giant wallaby," Protemnodon, may be indicative of a greater extent of quadrupedal locomotion than in extant kangaroos.

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Section: Discussionmentioning

confidence: 99%

Proximal Humerus Morphology Indicates Divergent Patterns of Locomotion in Extinct Giant Kangaroos

et al. 2020

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“…As part of this hypothesis, the marsupial mode of reproduction is argued to constrain the ability of marsupial development to generate phenotypic variation in newborns and adults. However, it is only within the last decade that this hypothesis has begun to be rigorously tested, by my lab and others (Sears, ; Sears, ; Sears, ; Cooper and Steppan, ; Doroba and Sears, ; Kelly and Sears, ; Kelly and Sears, ; Sears et al, ; Sears et al, ; Hübler et al, ).…”

Section: Case Study: Constraints On Marsupial Limb Developmentmentioning

confidence: 94%

Quantifying the impact of development on phenotypic variation and evolution

Sears

2014

J Exp Zool Pt B

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A primary goal of evolutionary biology is to identify the factors that shape phenotypic evolution. According to the theory of natural selection, phenotypic evolution occurs through the differential survival and reproduction of individuals whose traits are selectively advantageous relative to other individuals in the population. This implies that evolution by natural selection is contingent upon the distribution and magnitude of phenotypic variation among individuals, which are in turn the products of developmental processes. Development therefore has the potential to affect the trajectory and rate of phenotypic evolution. Recent research in diverse systems (e.g., mammalian teeth, cichlid skulls, butterfly wings, and marsupial limbs) supports the hypothesis that development biases phenotypic variation and evolution, but suggests that these biases might be system-specific.

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“…Sthenurines, possess similarly curved, flattened distal manual phalanges with small flexor tubercles. These phalanges were hypothesised to be adapted for grasping foliage during browsing (Wells & Tedford 1995;Sears 2004), though sthenurine phalanges II-IV were far more elongate than those of P. mamkurra sp. nov.…”

Section: Protemnodon Anakmentioning

confidence: 99%

Systematics and palaeobiology of kangaroos of the late Cenozoic genus Protemnodon (Marsupialia, Macropodidae)

KERR,

CAMENS,

VAN ZOELEN

et al. 2024

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Species of the kangaroo genus Protemnodon were common members of late Cenozoic communities across Australia and New Guinea until their extinction in the late Pleistocene. However, since the genus was first raised 150 years ago, it has proven difficult to diagnose, as have the species allocated to it. This is due primarily to the incompleteness of the type material and a heavy reliance on cheek tooth size and slight variations in premolar form. Along with the rare association between cranial and postcranial material, this has hampered understanding of the palaeobiology of these large-bodied kangaroos. Here we review and re-diagnose Protemnodon, recognising a total of seven species and providing a hypothesis of species interrelationships. The following new synonymies are made: Protemnodon chinchillaensis is synonymised with P. otibandus and P. hopei with P. tumbuna. The following are considered nomina dubia: Protemnodon brehus, P. roechus, P. mimas, P. antaeus, and P. devisi. We reveal that the morphology of the cheek dentition is not as consistently useful for differentiating species of Protemnodon as features of the cranium and postcranial skeleton. As a whole, the species share anatomical features that reflect stability and power in the limb joints, yet they differ in body proportions, and axial and limb morphology. This we interpret as showing locomotory adaptations to different habitats. Of the three Pliocene species, Protemnodon snewini is interpreted as a medium- to high-geared hopper, suggesting proficiency in more open environments, whereas P. dawsonae sp. nov. we infer to have been a medium-geared inhabitant of eastern Australian forests and woodlands. Protemnodon otibandus, with a range extending through the woodlands and forests of eastern Australia into the rainforests of eastern New Guinea, displays adaptations to slower hopping. Its Pleistocene descendant, P. tumbuna, is convergent on the morphology of modern New Guinea forest wallabies, and was likely facultatively quadrupedal. Of the three Australian Pleistocene species, the long-necked P. anak is hypothesised to have been a large, medium-geared, eastern Australian species, and P. mamkurra sp. nov. a robust, low-geared resident of well-wooded southern Australia habitats. By contrast, P. viator sp. nov. was larger but more gracile, suggested to be a medium- to high-geared species convergent in some traits on large extant kangaroos. This and a wide inland distribution point to adeptness in open, arid environments. Protemnodon mamkurra sp. nov. and P. viator sp. nov. occupy the morphospace previously occupied by P. roechus and P. brehus. Overall, the species of Protemnodon exhibit a degree of ecomorphological variation suggestive of a broader array of ecological adaptations than hitherto envisioned.

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Role of development in the evolution of the scapula of the giant sthenurine kangaroos (Macropodidae: Sthenurinae)

Cited by 7 publications

References 28 publications

Proximal Humerus Morphology Indicates Divergent Patterns of Locomotion in Extinct Giant Kangaroos

Proximal Humerus Morphology Indicates Divergent Patterns of Locomotion in Extinct Giant Kangaroos

Quantifying the impact of development on phenotypic variation and evolution

Systematics and palaeobiology of kangaroos of the late Cenozoic genus Protemnodon (Marsupialia, Macropodidae)

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