Morphology of the limbs in the semi-fossorial desert rodent species of Tympanoctomys (Octodontidae, Rodentia) (original) (raw)
Related papers
Evolutionary convergence of the highly adapted desert rodent Tympanoctomys barrerae (Octodontidae)
Journal of Arid …, 1999
Octodontid rodents have a long evolutionary history in arid landscapes of South America. The red vizcacha rat, Tympanoctomys barrerae, is a monotypic, micro-endemic species that inhabits salt pan-sand dune habitats in west-central Argentina. Its natural history is almost unknown. We present an analysis of the ecology, morphology, behavior, and physiology of the red vizcacha rat and assess the overall degree of convergence of this species with rodents that inhabit similar habitats in different deserts. Our results show that Tympanoctomys barrerae is highly adapted to salt flat basin habitats. Its diet of halophytic vegetation with a high salt content, and physiological and anatomical traits related to salt consumption, are similar to those found in some members of the families Heteromyidae (Dipodomys microps) of North America, and Muridae (Psammomys obesus and Rhombomys opimus) of Africa and Asia. Similarities include feeding behavior, diet composition, kidney morphology, and urine concentration, among other traits. Tympanoctomys barrerae is more similar to these desert rodents than it is to confamilials that do not feed on halophytes.
Journal of Arid …, 1999
Octodontid rodents have a long evolutionary history in arid landscapes of South America. The red vizcacha rat, Tympanoctomys barrerae, is a monotypic, micro-endemic species that inhabits salt pan-sand dune habitats in west-central Argentina. Its natural history is almost unknown. We present an analysis of the ecology, morphology, behavior, and physiology of the red vizcacha rat and assess the overall degree of convergence of this species with rodents that inhabit similar habitats in different deserts. Our results show that Tympanoctomys barrerae is highly adapted to salt flat basin habitats. Its diet of halophytic vegetation with a high salt content, and physiological and anatomical traits related to salt consumption, are similar to those found in some members of the families Heteromyidae (Dipodomys microps) of North America, and Muridae (Psammomys obesus and Rhombomys opimus) of Africa and Asia. Similarities include feeding behavior, diet composition, kidney morphology, and urine concentration, among other traits. Tympanoctomys barrerae is more similar to these desert rodents than it is to confamilials that do not feed on halophytes.
Zoology
Rodents of the family Octodontidae, endemic to South America, represent a group with low taxonomic richness group (six genera and 14 species) but have great ecomorphological diversity with epigean, semi-fossorial, fossorial, and subterranean forms. We analyzed morphometric variation in humerus and ulna, the possible relationship with substrate preference use, and the presence of a phylogenetic signal in the forelimbs traits (five biomechanical indices). Our results show that, in octodontids, the forelimb variation was not primarily associated with their phylogeny and some attributes are highly explanatory in terms of function, with a clear differentiation between the substrate use gradient extremes (i.e. epigean and subterranean forms). The two forelimb traits, the development of humeral epicondyles and the olecranon process of the ulna, indicative of adaptive trends found in Octodontidae are consistent with most of those described for other mammals and corroborate the relevance of forelimb characters to differentiate modes of locomotion or substrate preferences.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2002
New mandibular remains of one specimen of the desert-adapted South American rodent Tympanoctomys from the Pleistocene of central Argentina are described. These materials, together with a hemimandible previously analyzed by Ameghino, represent the limited paleontological record of the genus, and the first undoubted record of a living genus of the Octodontinae subfamily. The taxonomic, paleoenvironmental and biogeographic significance of these materials is discussed. The sediments yielding the new remains, at the coastal region of Mar del Plata, represent one of the glacial events that deposited the Pichileufu Drift in the Cordillera region of Argentina (between isotopic stages 23 and 25). We propose that, as a consequence of the glaciation, favorable habitats for populations of Tympanoctomys would have extended eastwards. Consequently, the present distributional pattern of the genus may be considered a relict. ß
Morphological structure and function in the desert heteromyid rodents
Great Basin Naturalist Memoirs, 1983
(1932) comparative study of vertebral architecture in saltatorial rodents, and Wood's (1935) important survey of the fossil and Recent Heteromyidae. Herman's (1979) recent multivariate statistical analysis of hind limb bone and muscle morphology in bipedal rodents constitutes a very significant extension beyond the older comparative anatomical works. Recent functional morphologic studies have been more analytical and experimental, but also of more limited scope. Thus, Pink
Portal orientation and architecture of burrows in Tympanoctomys barrerae (Rodentia, Octodontidae)
2003
Abstract The red viscacha rat, Tympanoctomys barrerae, is an octodontid rodent endemic to the Monte and Patagonian deserts of Argentina. It lives in burrows with numerous portals facing different directions. We studied climatic factors as possible determinants of burrow architecture and portal orientation, in 2 populations. Climatic factors examined were sunlight, direction of sun's rays, and wind frequency and intensity. Variables analyzed for burrow architecture were portal orientation, slope, and depth at the 1st turn.
Biological Journal of the Linnean Society, 2008
To examine the evolution of burrowing specializations in the sister families Octodontidae and Ctenomyidae (Rodentia: Caviomorpha), we produced a synthetic phylogeny (supertree), combining both molecular and morphological phylogenies, and including both fossil and extant genera. We mapped morphological specializations of the digging apparatus onto our phylogenetic hypothesis and attempted to match morphological diversity with information on the ecology and behaviour of octodontoid taxa. Burrowing for sheltering and rearing is the rule among octodontids and ctenomyids, and adaptations for digging have been known from the Early Pliocene onward. However, only a few taxa have evolved fully subterranean habits. Scratch-digging is widespread among both semifossorial and fully subterranean lineages, and morphological changes associated with scratch-digging are not restricted to subterranean lineages. By contrast, various adaptations for chisel-tooth digging are restricted to some subterranean lineages and are combined differently in the octodontid Spalacopus, the fossil ctenomyid Eucelophorus, and some living Ctenomys. Some octodontid taxa are able to dig complex burrows in spite of having no substantial changes in musculoskeletal attributes. Hence, we suggest that, during the early evolution of those branches giving rise to fully subterranean ctenomyids and octodontids, a change in behaviour probably preceded the origin of structural adaptations.
Forelimb proportions and fossorial adaptations in the scratch-digging rodent Ctenomys (Caviomorpha)
Members of the genus Ctenomys (tuco-tuco; Rodentia: Caviomorpha: Octodontidae) are considered scratch diggers. We compared the forelimbs of adult C. azarae with those of 13 species within other genera of caviomorph rodents to identify morphofunctional variation in osseous elements related to fossorial habits. Eight measurements of the humerus and ulna were used to construct five functional indices that were subjected to principal components analysis and simple comparisons among means. Ctenomys has a general morphology similar to that of terrestrial caviomorph rodents but exhibits some features that reflect its specialized fossorial condition, such as its comparatively large epicondyles. These features indicate greater muscular development and capacity for force production in the pronators and supinators of the forelimb and manus and flexors of the manus. The deltoid complex is well developed, indicating a large moment arm for the deltoid and latissimus dorsi muscles, which increases the capacity for force production on humeral flexion. Humeral indices are the best for differentiating fossorial forms from diggers, occasional diggers, generalized, and cursorial forms. Limb bone segments are used differently by highly fossorial and scratch-digging forms. w w w . m a m m a l o g y . o r g Journal of Mammalogy, 92(3):683-689, 2011 683 * Highlights variables with loadings .0.7.
Allometry and adaptation in the long bones of a digging group of rodents (Ctenomyinae)
Zoological Journal of the Linnean Society, 1993
Previous studies of rodent appendicular morphology suggest that digging activity induces changes in long bones, producing shorter and thicker structures. Subsequent hypotheses have been tested in Ctenomyinae, a group of octodontid rodents globally adapted to subterranean life. Slopes of the equations calrulated for extant animals and their corresponding confidence intervals agree with expectations in almost all cases. Results on fossil taxa are less clear, but suggest a morphocline from a plesiomorphic condition of the appendicular skeleton, present in the fossil genera, departing little from that of the current epigeous rodents, to a more derived long bone design in the species of the living genus Ctenomys, in accordance with their digging activity.