A ecomorfologia herbívora e padrões de especialização na evolução dos dinossauros terópodas

terça-feira, dezembro 21, 2010

Herbivorous ecomorphology and specialization patterns in theropod dinosaur evolution 

Lindsay E. Zanno1 and Peter J. Makovicky 

- Author Affiliations 

Department of Geology, The Field Museum, Chicago, IL 60605 

Edited by Randall Irmis, Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, and accepted by the Editorial Board November 10, 2010 (received for review August 16, 2010) 


New research by Field Museum scientists finds widespread herbivory in bird-like theropod dinosaurs. Four of the 90-theropod species involved in the study shown with dietary interpretations. All four species derive from the famous feathered dinosaur beds of the Early Cretaceous Yixian Formation, P. R. China, leading the scientists to speculate that dietary diversity may have contributed to the large numbers of contemporaneous theropods in ecosystems like those of the Yixian. (Credit: Dennis Finnin and Roderick Mickens, copyright American Museum of Natural History) Via: Science Daily

Abstract 

Interpreting key ecological parameters, such as diet, of extinct organisms without the benefit of direct observation or explicit fossil evidence poses a formidable challenge for paleobiological studies. To date, dietary categorizations of extinct taxa are largely generated by means of modern analogs; however, for many species the method is subject to considerable ambiguity. Here we present a refined approach for assessing trophic habits in fossil taxa and apply the method to coelurosaurian dinosaurs—a clade for which diet is particularly controversial. Our findings detect 21 morphological features that exhibit statistically significant correlations with extrinsic fossil evidence of coelurosaurian herbivory, such as stomach contents and a gastric mill. These traits represent quantitative, extrinsically founded proxies for identifying herbivorous ecomorphology in fossils and are robust despite uncertainty in phylogenetic relationships among major coelurosaurian subclades. The distribution of these features suggests that herbivory was widespread among coelurosaurians, with six major subclades displaying morphological evidence of the diet, and that contrary to previous thought, hypercarnivory was relatively rare and potentially secondarily derived. Given the potential for repeated, independent evolution of herbivory in Coelurosauria, we also test for repetitive patterns in the appearance of herbivorous traits within sublineages using rank concordance analysis. We find evidence for a common succession of increasing specialization to herbivory in the subclades Ornithomimosauria and Oviraptorosauria, perhaps underlain by intrinsic functional and/or developmental constraints, as well as evidence indicating that the early evolution of a beak in coelurosaurians correlates with an herbivorous diet. 

bird, character correlation, fossil record, vertebrate, paleoecology 

Footnotes 

1To whom correspondence should be addressed. 

E-mail: lzanno@fieldmuseum.org. 

Author contributions: L.E.Z. and P.J.M. designed research, performed research, contributed new reagents/analytic tools, analyzed data, and wrote the paper. 

The authors declare no conflict of interest. 

This article is a PNAS Direct Submission. R.I. is a guest editor invited by the Editorial Board. 

This article contains supporting information online at 

Freely available online through the PNAS open access option.

+++++

FREE PDF GRÁTIS [OPEN ACCESS]

+++++


NOTA DESTE BLOGGER:


Pelo andar da carruagem, daqui a pouco os terrríveis lagartos -- dinossauros, vão se transmutar em dóceis animaizinhos, e precursores há milhões de anos de uma dieta saudável: vegetariana. Ah, vai, esta especulação sua não é científica, antes, é o favorecimento escancarado de certa prática de determinadas subjetividades religiosas! 


Pereça tal pensamento, tenho amigos assim, mas a profecia feita aqui é científica, e traz outras implicações epistêmicas, pois determinado livro oriental antigo há muito já disse que os animais e até os seres humanos, eram vegetarianos!!! Ah, mas lá não tem nada de ciência! Ué, não tem? Mas é um contexto em que a conclusão científica se encaixa! Então por que a conclusão desta pesquisa é científica: os dinos eram vegetarianos, e a outra afirmação é pseudociência? Alguém me belisque, por favor!!!


Fui, nem sei por que, sem entender mais nada da Lógica Darwiniana 101. Aliás, nem os darwinistas xiítas, fundamentalistas, pós-modernos, chiques e perfumados a la Dawkins entendem esta lógica epistêmica do crioulo doido. Como dizia Feyerabend -- vale tudo, quando a questão é Darwin, capice? Até ser parecido nas afirmações e conclusões dos de subjetividades religiosas...