THEROPOD-BIRD CONVERGENCE

[darren.naish@port.ac.uk]

Forgive me if this has been pointed out before, but I note an 
inconsistency in the Ruben et al. school of phylogeny. 

They are arguing that similarities between birds and theropods are 
convergences. OK, convergences result from similarities in lifestyle: if 
birds and theropods are only similar because of homoplasy, it it 
because they both have similar gaits, are both bipedal etc. Never mind 
the fact that no other documented case of homoplasy - even between 
nimravids and felids, felids and thylacosmilids or thylacinids and 
canids - in biology approaches the degree of similarity seen between 
birds and theropods. Cases of generic-level homoplasy (e.g. some 
salmonid and scincid genera seem near identical but are thought to 
have had separate origins) are erroneous: it's still clear that the taxa 
involved are close relatives. However, at the same time they argue that 
birds and theropods were fundamentally different in lifestyle and 
locomotor modes.... in fact in Florida I think this was the main thrust 
of Ruben's argument (viz, terrestrial theropods vs. arboreal/scansorial 
birds). So, if birds and theropods are so different in lifestyle and 
locomotion, why the convergence if it isn't due to inherited similarity? 
Looking at this impartially, they are flatly contradicting themselves.

DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth, Environmental & Physical Sciences
UNIVERSITY OF PORTSMOUTH
Burnaby Building
Burnaby Road                           email: darren.naish@port.ac.uk
Portsmouth UK                          tel: 01703 446718
P01 3QL