Junya Watanabe (2018)
Cladeâspecific evolutionary diversification along ontogenetic major axes in avian limb skeleton.
Evolution (advance online publication)
The evolutionary diversification of birds has been facilitated by specializations for various locomotor modes, with which the proportion of the limb skeleton is closely associated. However, recent studies have identified phylogenetic signals in this system, suggesting the presence of historical factors that have affected its evolutionary variability. In this study, in order to explore potential roles of ontogenetic integration in biasing the evolution in the avian limb skeleton, evolutionary diversification patterns in six avian families (Anatidae, Procellariidae, Ardeidae, Phalacrocoracidae, Laridae, and Alcidae) were examined and compared to the postnatal ontogenetic trajectories in those taxa, based on measurement of 2641 specimens and recently collected ontogenetic series, supplemented by published data. Morphometric analyses of lengths of six limb bones (humerus, ulna, carpometacarpus, femur, tibiotarsus, and tarsometatarsus) demonstrated that: 1) ontogenetic trajectories are diverse among families; 2) evolutionary diversification is significantly anisotropic; and, most importantly, 3) major axes of evolutionary diversification are correlated with cladeâspecific ontogenetic major axes in the shape space. These results imply that the evolutionary variability of the avian limbs has been biased along the cladeâspecific ontogenetic trajectories. It may explain peculiar diversification patterns characteristic to some avian groups, including the longâleggedness in Ardeidae and tendency for flightlessness in Anatidae.
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Oliver A. LÃpez-Conde, Juliana Sterli, MarÃa L. ChavarrÃa-Arellano, Donald B. Brinkman, Marisol Montellano-Ballesteros (2018)
Turtles from the Late Cretaceous (Campanian) of El Gallo Formation, Baja California, Mexico.
Journal of South American Earth Sciences (advance online publication)
Highlights
Assemblages of fossil turtles of the Late Cretaceous of El Gallo Formation.
New occurrences of turtles are reported from El Gallo Formation.
Turtles from El Gallo Formation provide information on the western side of Laramidia.
Mexico has the southern-most Cretaceous localities in North America.
Reported the first record of Basilemys sp. in the Late Cretaceous of Mexico.
Abstract
Turtles are typically important members of Late Cretaceous vertebrate assemblages throughout North America, and are considered a useful tool to define biogeographic patterns. In Mexico, Cretaceous turtles have been recorded in the states of Baja California, Chiapas, Chihuahua, Coahuila, Nuevo LeÃn, Puebla, and Sonora; specifically the state of Coahuila shows so far, the highest diversity of turtles. In this paper, the diversity of Late Cretaceous turtles from the El Gallo Formation (Baja California) is reviewed. Previously, only Naomichelys speciosa was recognized in this Formation. Based on fragments with distinctive sculpture patterns four additional taxa are recognized, Compsemys victa, Basilemys sp., Trionychidae indet., and cf. Chelydridae. With the recognition of these new taxa, the knowledge of Cretaceous turtles diversity of the El Gallo Formation is increased. This assemblage is unusual compared to other North American turtle assemblages because it suggests the presence of previously unrecognized biogeographic patterns. Here we report the first record of Basilemys sp. from the Late Cretaceous of Mexico and the presence of cf. Chelydridae on the western side of Laramidia.
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Pavel P. Skutschas, Veniamin V. Kolchanov, Valeriy V. Bulanov, Andrey G. Sennikov, Elizaveta A. Boitsova, Valeriy K. Golubev ORCID Icon & ÂElena V. Syromyatnikova (2018)
Reconstruction of the life history traits in the giant salamander Aviturus exsecratus (Caudata, Cryptobranchidae) from the Paleocene of Mongolia using zygapophyseal skeletochronology.
Historical Biology (advance online publication)
Here we describe life history traits in the giant cryptobranchid salamander Aviturus exsecratus from the Paleocene of Mongolia using non-destructive approach for skeletochronological analysis based on the counting of cyclical growth rings on articular surfaces of zygapophyseal processes of vertebrae (= zygapophyseal skeletochronology). We found that Aviturus exsecratus had a similar time of the attainment of sexual maturity and decreasing of juvenile growth (5â8 years) and estimated body size at maturity (50â60% of the maximum size) as modern cryptobranchids. Maximum longevity estimated for A. exsecratus is about 25 years. A. exsecratus had a developmental trajectory similar to that of modern cryptobranchids and is not characterized by extended ontogeny.
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