Re "considering ectothermy"

["Larry Febo" <larryf@capital.net>]

{Hello again Christian.}

Please, Please read the literature on the Protothyrididae and their
relationship to synapsids (well, there is no relationship other than that
they
are amniotes).

{haven`t read all the "details" yet, but Carroll`s book "Vertebrate
Paleontology and Evolution" shows diagram pg.201, with lines leading FROM
the Protorothyridae TOWARDS Sinapsids in the early Pennsylvanian and
Diapsids in the later Pennsylvanian, although all these lines are "dashed"
in their initial sections. Do you think maybe Carroll was just "speculating?

 Now, the Eothyrididae (don't confuse the two, very different
animals despite both being small [with some exceptions] and lizardy) are the
most primitive synapsids, and form a sister group to the highly specialized
herbivorous caseids.

{The Eothyridae (as spelled per Carroll`s index), the author shows as
existing in the Permian (as per diagram pg 362), as well he states : "We do
not recognize any members of these families before the Lower Permian." (this
refering to the families Eothyrids and Varanopseids). This, and his diagram
would indicate that the  Eothyridae are NOT the most primative Synapsids.The
family Ophiacodontidae contains the "..oldest-known and most primative
pelycosaurs..." (pg. 365) Further, Archaeothyris, from mid-Pennsylvanian
provides the earliest evidence of pelycosaur skeletal configurations.
(pg362) He also states :( on pg 361), " The ancestors of mammals are
identified from the same horizon and locality as the earliest conventional
reptile, Hylonomus, in the early Pennsylvanian of Joggins, Nova Scotia
(Carroll 1964)."}

 The protothyridids are nested pretty deep within
Sauropsida, past captorhinomorphs and all those guys and are possibly the
direct ancestors of the diapsids, but based on nearly every pertinent facet
of
their anatomy are vastly different from the eothyridids and varanopseids
(the
earliest synapsids) and are not a possible ancestor of these.

{You`re probably right here Christian, maybe that`s why all the dotted, and
not exactly connected lines in diagram pg 201, . Perhaps the better "basal
group" to search for a possible (if any) common origen of "brooding
endothermy" would more probably be the Order Captorhinida.}

Sincerely,
Christian Kammerer
P.S.-I still strongly suggest getting a copy of the Hopson chapter of
_Origins
of the Higher Groups of Tetrapods_ as it deals very well with all of this.

{will check it out. Larry}