Reply to Axsmith et al. (2007) paper published in Ameghiniana 44 : 223-230: 'The wew approach to corystospermales' and the Antarctic fossil record: A critique'

摘要

This contribution replies to the critique of Axsmith, Taylor and Taylor published in the previous number of Ameghiniana. In first place, it is insisted on not admitting 'as unequivocal evidence' the supposed attachment of Dicroidium odontopteroides leaf to the axis with short shoots reported by Axsmith et al. (2000) at Alfie locality, Antarctica. Furthermore, the present analysis of cupulate organs, described at same locality by Axsmith et al. (2000), suggests that Umkomasia uniramia belongs to another morphotaxon with peltasperm affinities. It is remarked that in Artabe and Brea's contribution published in Alcheringa all the characters present in Argentinean corystosperm stems were analyzed and not one record from Antarctica was ignored nor the evidence that the material provides to the understanding of the corystosperms. In addition, above mentioned Axsmith et al. 's paper, has opened the discussion regarding to the Corystospermales concept, the reconstructions used in phylogenetic approaches and the vegetative characters selected in cladistic analysis. The study of Argentinean corystosperm stems allows visualizing the biased use -in cladistics- of discriminative vegetative characters in Medullosales, Cycadales and Corystospermales. As it happens with Medullosales and Cycadales, Corystospermales should include two end members corresponding to the reconstructions proposed for Antarctica and Argentina.