[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: the evolution of disparity in body plans (was Re: synapomorphies)
On Tue, 13 Feb 1996, Chris Nedin wrote:
> Well, one of SJG's theses is almost certainly wrong, but others are
> correct. The 'replaying of events would produce different result' is right,
> as is the fact that it would have been impossible for a Cambrian zoologist
> to predict which groups would survive and which would become extinct.
> However, his claim on maximum disparity is almost certainly wrong. The
> arthropods we know and love/hate today are very derived forms based on
> several distinct body plans. The Cambrian arthropods represent basal or
> stem arthropods - arthropods when such clear divisions had not stablized.
I see the "Ur-arthropod" as a many-segmented, untagmosed animal with
unspecialized, biramous limbs. Does anyone have a problem with this
interpretation? I see the Cambrian arthropods as a carpet of independent
specializations from that primitive state, of which only four survived
the Cambrian: trilobites, chelicerates, crustaceans, and members of the
> "you mean _Anomalocaris_ didn't make it? Get out of here!"
I have a hard time believing that _Anomalocaris_ belongs to a modern
phylum. Or _Obapinia_. Or _Odontogriphus_, _Wiwaxia_ (I am unconvinced
by the sea mouse comparison), _Amiskwia_, or _Nectocaris_ (my personal
fave), for that matter. To what phyla do these supposedly belong?
Pacific Lutheran University
Tacoma, WA 98447
"If you can't convince them, confuse them." -- Harry S Truman