[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Turtles and Crocodylians are not Reptiles - no? What are they?

Robert Takata wrote:

> As Pharris and Keesey noted, *closer* in a phylogenetical/hennigian
> context: shared the same evolutionary history for a longer time.

I'm still confused by this, because I would never have equated the term 
"closer" with "shared the same evolutionary history for a longer time."  Even 
in a phylogenetic/Hennigian context.

For example... Say a phylogeny recovers _Eoraptor_ and _Herrerasaurus_ at the 
base of the Theropoda, with _Eoraptor_ and _Herrarasaurus_ as successive 
outgroups to the clade that includes all other theropods (Neotheropoda).  
_Herrerasaurus_ is therefore the sister taxon to Neotheropoda.  _Velociraptor_ 
is a neotheropod.  Thus, _Herrerasaurus_ and _Velociraptor_ form a clade to the 
exclusion of _Eoraptor_.  In other words, _Herrerasaurus_ and _Velociraptor_ 
share the same evolutionary history for a longer time than _Eoraptor_ and 

However, I would *not* say that _Herrerasaurus_ is "closer" to _Velociraptor_ 
than it is to _Eoraptor_.  I would say _Herrerasaurus_ is closer to _Eoraptor_. 
 This is because _Eoraptor_ and _Herrerasaurus_ are relatively closer on the 
phylogenetic tree.  The topology shows only one node separating the two.  Many 
more nodes separate _Herrerasaurus_ from _Velociraptor_ (Ceratosauria, 
Megalosauroidea, Allosauroidea, Ornitholestidae, Tyrannosauroidea, 
Ornithomimosauria, etc).

I'm not trying to be tricky here with semantics - quite the opposite.   I'm 
just trying to get the point across that "closer" in a phylogenetic context 
does *not* necessarily mean "shared ancestry".  Further, "closer" should not 
even imply "shared ancestry".



Use video conversation to talk face-to-face with Windows Live Messenger.