[Taxacom] Podocnemididae turtles in northern S America and Madagascar

[John Grehan]

HiScott,

Thanks for that information. I'll check that citation.  It would seem that
the fossil record in this case will tie in nicely with vicariance of the S
Americana and Madagascan genera, and yes it is very possible that the
former connection was across Africa (there are plenty of modern disjuncts
across Africa in living taxa, some for example between the Canaries and SE
Africa/Madagascar). Not sure what you mean by " this group may be too old ".
Point is that it would be old enough, by age of fossilization, for
vicariance between the New and Old Worlds. Iguanas - biogeographically they
are at least as old. The separation of the Fiji group from its New World
sister group, for example, ties in nicely with the formation of the Pacific
plate. I appreciate your offer to help with the fossil data when you get
back. Fossils have always been an integral part of panbiogeographic
analysis (sometimes there are absurd assertions made that we
ignore fossils, but I guess that comes from people who have not bothered to
read the literature properly).

Cheers, John

On Sat, Dec 4, 2021 at 11:30 AM Scott Thomson <scott.thomson321 at gmail.com>
wrote:

> Hi John,
>
> Podocnemidae are complex. At a guess I would say Thomson et al 2021 may
> help from a molecular perspective. Thats Robert Thomson by the way not me.
> However your looking at a family that is a remnant of past diversity with
> dozens of genera in the fossil record with an almost global distribution.
>
> To discuss this one in detail I will need to access the fossil record and
> in this case its not a group I worked directly on. I would need my computer
> to answer that and I am in field till next Monday.
>
> I would hazard this group may be too old also they go back to the Jurassic
> and hence the distribution was a very different world. I gather the
> Iguanidae are not this old.
>
> From memory the Podocnemidae were found in the region of Africa / Brazil
> that wre connected. There are fossils in Morroco and Egypt, also Europe and
> North America. As I recall they were likely found throughout Aftica and
> died out on the mainland leaving remnants on Madagascar. They have remained
> succsesful in South America in absence of Emydids etc. However I am saying
> that from memory I can give you papers that discuss their paleozoogeography
> next week.
>
> Cheers Scott
>
> On Sat, Dec 4, 2021, 3:58 AM John Grehan via Taxacom <
> taxacom at mailman.nhm.ku.edu> wrote:
>
>> Scott, I would be interested in your take on the current status of
>> the Podocnemididae, if you have any opinion about that. At this moment the
>> most recent molecular account I have seen is Vargas-Ramírez et al 2008.
>> With two genera in northern South America and one in Madagascar, this
>> group
>> would seem to provide a nice biogeographic parallel to that of the
>> iguanas.
>>
>> John Grehan
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