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Stride lengths and frequencies of arboreal walking in seven species of didelphid marsupials

100%

Delciellos A. C. , Vieira M. V.

tom 52

nr 1

Didelphid marsupials differ in their use of the forest strata, with corresponding differences in morphology and arboreal walking performances. Similar performances may be reached by different combinations of stride length and frequency, but it has been suggested that arboreal walkers increase velocity by longer strides. Our objective was to determine how stride length and frequency contribute to the velocity in the arboreal walking of seven species of didelphid marsupials of the Atlantic Forest of Brazil. Animals were stimulated to cross five 3-m long horizontal supports of different diameters. The cycle of maximum velocity was chosen to measure relative stride length, frequency, and relative velocity. Except forCaluromys philander, the more arboreal species were faster than the terrestrial species, but maximum velocity of arboreal species was reached by two strategies, increasing stride frequency (Gracilinanus microtarsus, Micoureus demerarae, andDidelphis aurita), or reducing frequency and increasing stride length (Marmosops incanus andC. philander). Increasing velocity in arboreal walking by more frequent strides may reduce oscillations of the body, whereas longer strides may reduce branch swaying. Among the terrestrial species,Philander frenatus performed similarly to more arboreal species, suggesting a potential ability to use the canopy, undetected in field observations.

Marsupial larvae of Sinanodonta woodiana (Lea, 1834) (Bivalvia: Unionoida: Unionidae)

84%

Labecka A. M. , Domagala J.

2008

tom 50

nr 1

Marsupials from the Late Cretaceous of Uzbekistan

84%

Averianov A. , Kielan-Jaworowska Z.

nr 1

A fragment of dentary with m4, showing characters of some Late Cretaceous North American marsupials, is assigned to Marsasia sp. Marsasia Nessov, 1997 from the Coniacian of Uzbekistan, represented by M. aenigma known from edentulous dentaries with inflected angular processes, was attributed by Nessov to ?Marsupialia. Marsasia sp., found in the same horizon as the type species, resembles it in size and structure of the masseteric fossa, but dffiers in having a less steep coronoid process. We assign Marsasia to Marsupialia on the basis of the following characters: inflected angular process, shape of the dentary similar to that in Asiatherium, postcanine dental formula, inferred from alveoli for p1-3, ml-4, and sfructure of m4 more similar to Cretaceous marsupials than eutherians. The phylogenetic position of Marsasia may be between the Albian Kokopellia and Campanian Asiatherium. Marsasia is tentatively referred to the orderAsiadelphia, which may represent an endemic Asian marsupial clade.

Mammalian evolution underground. The ecological-genetic-phenetic interfaces

67%

Nevo E.

1995

nr 03

The global adaptive convergence of subterranean mammals currently involves 3 orders: rodents, insectivores and marsupials. These include 11 families, 50 genera, and several hundreds of species. This global evolutionary process followed the stepwise climatic cooling and drought followed by biotic extinction in the transition from the middle Eocene to the early Oligocene, a period of 10 million years (35-45 Ma = million years ago), of profound change in earth geology, climate and biota. The earth changed from the Mesozoic "hot house" to the Neogene (Miocene to Present) "cold house", ie from a warm, equable, mostly subtropical world that persisted from the Mesozoic to the beginning of the present glaciated world. The ecological theater of open country biotas, that opened up progressively in the Cenozoic following the Eocene-Oligocene transition, was associated with increasing aridity, colder climate, and terrestrialism. This climatic change set the stage for a rapid evolutionary play of recurrent adaptive radiations of unrelated mammals on all continents into the subterranean ecotope. The subterranean ecotope is relatively simple, stable, specialised, low or medium in productivity, predictable and discontinuous. Its major evolutionary determinants are specialization, competition and isolation. This ecotope involves the herbivorous (rodents) and insectivorous (insectivores and marsupials) niches. All subterranean mammals share molecular and organismal convergent adaptations to their common unique ecology. By contrast, they display divergent adaptations to their separated niches of herbivory and insectivory and to their different phylogenies. The remarkable adaptive evolution of subterranean mammals involves adaptive structural and functional progression and regression. It is one of the most dramatic examples of global convergent evolution due to underground ecological constraints, at both the molecular and organismal levels of evolutionary theory.