The fossil record of birds from Antarctica is concentrated in the James Ross Basin,located in north-east of the Antarctic Peninsula.Birds are here represented by an extensive Paleogene record of penguins(Sphenisciform...The fossil record of birds from Antarctica is concentrated in the James Ross Basin,located in north-east of the Antarctic Peninsula.Birds are here represented by an extensive Paleogene record of penguins(Sphenisciformes)and Cretaceous–Paleogene record of Anseriformes,followed by other groups with a minor representation(Procellariiformes,Falconiformes,and Pelagornithidae),and others previously assigned controversially to“Ratites”,Threskiornithidae,Charadriiformes,Gruiformes,Phoenicopteriformes,and Gaviiformes.We provide a complete update of these records,commenting on the importance of some of these remains for the evolution of the major clades.展开更多
The lumbosacral-canal system in birds most likely operates as a sense organ involved in the control of balanced walking and perching,but our knowledge of it is superficial.Penguins constitute interesting objects for th...The lumbosacral-canal system in birds most likely operates as a sense organ involved in the control of balanced walking and perching,but our knowledge of it is superficial.Penguins constitute interesting objects for the study of this system due to their upright walking,but only the Humboldt penguin,Spheniscus humboldti,and some incomplete fossil penguin synsacra have been studied in this respect.Here,we give an integrative comparative in-sight into the synsacral canal of extant Emperor penguin,Aptenodytes forsteri,Adelie penguin,Pygoscelis adeliae,and Eocene giant Anthropornis and/or Palaeeudyptes Antarctic penguins,using computed tomography imaging and associated data-extraction methodologies,complemented by analytical approaches ranging from geometric morphometrics to modularity,curvature,and wavelet analyses.We document that the variability in the number of synsacro-lumbar vertebrae is evolutionarily conserved,and all studied synsacra possess osteological correlates of the lumbosacral-canal system.We also found that Eocene and extant Antarctic penguins were separable on the basis of the main direction of the shape-related(size-independent)variability within said system,and A.forsteri was unique in the entire studied set in terms of the relative cranial shift of this compound structure.Moreover,we suggest that the evolutionary processes,shaping both the terrestrial posture and gait,were responsible,in extant penguins,for the increased simplicity and stability of the synsacral canal cross-sectional periodic patterns,as well as pave the way for the lumbosacral-canal system modularity characterized by reduced atomization/complexity.展开更多
基金CAH was invited to field by the Dirección Nacional del Antártico and the Instituto Antártico ArgentinoFuerza Aérea Argentina provided logistic support,and partial help was provided by the Consejo Nacional de Investigaciones Científicas y Tecnológicas and Universidad Nacional de La Plata(N838)+1 种基金CAH is particularly grateful to Oceanwide Expeditions,Vlissingen(NL)for financial support.JAC gratefully acknowledges U.S National Science Foundation Polar Programs support for field research support as well as descriptive work on Antarctic fossils(Grant nos.NSF OPP-1141820,OPP-0927341,OPP-0408308)the work of many stellar collaborators on these projects.
文摘The fossil record of birds from Antarctica is concentrated in the James Ross Basin,located in north-east of the Antarctic Peninsula.Birds are here represented by an extensive Paleogene record of penguins(Sphenisciformes)and Cretaceous–Paleogene record of Anseriformes,followed by other groups with a minor representation(Procellariiformes,Falconiformes,and Pelagornithidae),and others previously assigned controversially to“Ratites”,Threskiornithidae,Charadriiformes,Gruiformes,Phoenicopteriformes,and Gaviiformes.We provide a complete update of these records,commenting on the importance of some of these remains for the evolution of the major clades.
文摘The lumbosacral-canal system in birds most likely operates as a sense organ involved in the control of balanced walking and perching,but our knowledge of it is superficial.Penguins constitute interesting objects for the study of this system due to their upright walking,but only the Humboldt penguin,Spheniscus humboldti,and some incomplete fossil penguin synsacra have been studied in this respect.Here,we give an integrative comparative in-sight into the synsacral canal of extant Emperor penguin,Aptenodytes forsteri,Adelie penguin,Pygoscelis adeliae,and Eocene giant Anthropornis and/or Palaeeudyptes Antarctic penguins,using computed tomography imaging and associated data-extraction methodologies,complemented by analytical approaches ranging from geometric morphometrics to modularity,curvature,and wavelet analyses.We document that the variability in the number of synsacro-lumbar vertebrae is evolutionarily conserved,and all studied synsacra possess osteological correlates of the lumbosacral-canal system.We also found that Eocene and extant Antarctic penguins were separable on the basis of the main direction of the shape-related(size-independent)variability within said system,and A.forsteri was unique in the entire studied set in terms of the relative cranial shift of this compound structure.Moreover,we suggest that the evolutionary processes,shaping both the terrestrial posture and gait,were responsible,in extant penguins,for the increased simplicity and stability of the synsacral canal cross-sectional periodic patterns,as well as pave the way for the lumbosacral-canal system modularity characterized by reduced atomization/complexity.
