The Experts below are selected from a list of 18 Experts worldwide ranked by ideXlab platform
P. B. Mikheev - One of the best experts on this subject based on the ideXlab platform.
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Variability of Siberian Taimen Hucho taimen (Salmonidae) of The Amur River
Journal of Ichthyology, 2020Co-Authors: N. S. Romanov, P. B. MikheevAbstract:— The morphological variability of nine characters in six samples of Siberian taimen Hucho taimen from the Amur River was studied. The differences in the level of fluctuating asymmetry of fish from different tributaries are small, which indicates the similarity of the conditions of embryonic and early postembryonic development; significant differences between the samples were noted only in six cases. The maximum fluctuations in the coefficient of variation are characteristic for the number of Postorbital Bones and channels of the seismosensory system on the 1^st Postorbital Bone; the minimum, for the number of soft rays in the pectoral fins and channels of the seismosensory system on the preopercular Bones. The largest sum of the variation coefficients values for individual characteristics differs in the sample from the Bikin River; the smallest, the Limuri River. These difference positively correlates with the length and area of the basin of these tributaries. A regular decline in the mean values in the fish sampled at increasing distance from the mouth of the Amur River concerns only the number of Postorbital Bones. Clustering according to the mean values of the features, revealed that the samples form three clusters: (1) the rivers Bol’shaya Ussurka and Tyrma (2^nd order tributaries, the farthest from the Amur mouth), (2) the Limuri River (the least distant from the Amur mouth), 3) the rivers Anyui, Khor and Bikin (geographically close populations). Revealed features may indicate the similarity of the conditions of early development and the likelihood of gene exchange between the last three groups.
N. S. Romanov - One of the best experts on this subject based on the ideXlab platform.
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Variability of Siberian Taimen Hucho taimen (Salmonidae) of The Amur River
Journal of Ichthyology, 2020Co-Authors: N. S. Romanov, P. B. MikheevAbstract:— The morphological variability of nine characters in six samples of Siberian taimen Hucho taimen from the Amur River was studied. The differences in the level of fluctuating asymmetry of fish from different tributaries are small, which indicates the similarity of the conditions of embryonic and early postembryonic development; significant differences between the samples were noted only in six cases. The maximum fluctuations in the coefficient of variation are characteristic for the number of Postorbital Bones and channels of the seismosensory system on the 1^st Postorbital Bone; the minimum, for the number of soft rays in the pectoral fins and channels of the seismosensory system on the preopercular Bones. The largest sum of the variation coefficients values for individual characteristics differs in the sample from the Bikin River; the smallest, the Limuri River. These difference positively correlates with the length and area of the basin of these tributaries. A regular decline in the mean values in the fish sampled at increasing distance from the mouth of the Amur River concerns only the number of Postorbital Bones. Clustering according to the mean values of the features, revealed that the samples form three clusters: (1) the rivers Bol’shaya Ussurka and Tyrma (2^nd order tributaries, the farthest from the Amur mouth), (2) the Limuri River (the least distant from the Amur mouth), 3) the rivers Anyui, Khor and Bikin (geographically close populations). Revealed features may indicate the similarity of the conditions of early development and the likelihood of gene exchange between the last three groups.
Peter L. Forey - One of the best experts on this subject based on the ideXlab platform.
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redescription of chondrosteus acipenseroides egerton 1858 acipenseriformes chondrosteidae from the lower lias of lyme regis dorset england with comments on the early evolution of sturgeons and paddlefishes
Journal of Systematic Palaeontology, 2009Co-Authors: Eric J Hilton, Peter L. ForeyAbstract:Synopsis We present a redescription of †Chondrosteus acipenseroides, a basal member of the order Acipenseriformes (sturgeons, paddlefishes and their fossil relatives) from the Lower Jurassic of England. †Chondrosteus is known from several whole or partial skeletons and many isolated fragmentary elements. Even on many of the articulated skeleton and skull specimens, many aspects of its anatomy are not sufficiently preserved to allow for detailed descriptions. However, we were able to describe it more fully than previous authors and to clarify many points of anatomy, such as the presence of elements we interpret as rostral canal Bones, the absence of a Postorbital Bone, the sclerotic ring being composed of dorsal and ventral elements, a deep lateral groove on the dentary and the presence of an ossified basibranchial. We then comment on the systematic affinities of †Chondrosteidae within Acipenseriformes on the basis of the results of a new phylogenetic analysis. †Chondrosteidae has alternatively been regard...
Eric J Hilton - One of the best experts on this subject based on the ideXlab platform.
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redescription of chondrosteus acipenseroides egerton 1858 acipenseriformes chondrosteidae from the lower lias of lyme regis dorset england with comments on the early evolution of sturgeons and paddlefishes
Journal of Systematic Palaeontology, 2009Co-Authors: Eric J Hilton, Peter L. ForeyAbstract:Synopsis We present a redescription of †Chondrosteus acipenseroides, a basal member of the order Acipenseriformes (sturgeons, paddlefishes and their fossil relatives) from the Lower Jurassic of England. †Chondrosteus is known from several whole or partial skeletons and many isolated fragmentary elements. Even on many of the articulated skeleton and skull specimens, many aspects of its anatomy are not sufficiently preserved to allow for detailed descriptions. However, we were able to describe it more fully than previous authors and to clarify many points of anatomy, such as the presence of elements we interpret as rostral canal Bones, the absence of a Postorbital Bone, the sclerotic ring being composed of dorsal and ventral elements, a deep lateral groove on the dentary and the presence of an ossified basibranchial. We then comment on the systematic affinities of †Chondrosteidae within Acipenseriformes on the basis of the results of a new phylogenetic analysis. †Chondrosteidae has alternatively been regard...
Anjali Goswami - One of the best experts on this subject based on the ideXlab platform.
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Decelerated dinosaur skull evolution with the origin of birds.
'Public Library of Science (PLoS)', 2020Co-Authors: Ryan N Felice, Akinobu Watanabe, Andrew R Cuff, Michael Hanson, Bhart-anjan S Bhullar, Emily R Rayfield, Lawrence M Witmer, Mark A Norell, Anjali GoswamiAbstract:The evolutionary radiation of birds has produced incredible morphological variation, including a huge range of skull form and function. Investigating how this variation arose with respect to non-avian dinosaurs is key to understanding how birds achieved their remarkable success after the Cretaceous-Paleogene extinction event. Using a high-dimensional geometric morphometric approach, we quantified the shape of the skull in unprecedented detail across 354 extant and 37 extinct avian and non-avian dinosaurs. Comparative analyses reveal fundamental differences in how skull shape evolved in birds and non-avian dinosaurs. We find that the overall skull shape evolved faster in non-avian dinosaurs than in birds across all regions of the cranium. In birds, the anterior rostrum is the most rapidly evolving skull region, whereas more posterior regions-such as the parietal, squamosal, and quadrate-exhibited high rates in non-avian dinosaurs. These fast-evolving elements in dinosaurs are strongly associated with feeding biomechanics, forming the jaw joint and supporting the jaw adductor muscles. Rapid pulses of skull evolution coincide with changes to food acquisition strategies and diets, as well as the proliferation of bony skull ornaments. In contrast to the appendicular skeleton, which has been shown to evolve more rapidly in birds, avian cranial morphology is characterised by a striking deceleration in morphological evolution relative to non-avian dinosaurs. These results may be due to the reorganisation of skull structure in birds-including loss of a separate Postorbital Bone in adults and the emergence of new trade-offs with development and neurosensory demands. Taken together, the remarkable cranial shape diversity in birds was not a product of accelerated evolution from their non-avian relatives, despite their frequent portrayal as an icon of adaptive radiations