[Taxacom] Australian turtles

[Michael Heads]

Hi Scott,
You can identify a fragmentary group as, e.g. chelids or pan-chelids,
without being able to place the group precisely in a phylogeny because of
the poor fossilisation. My point was simply that turtles don't always
fossilize 'really well'.
   Your suggestion that Chelidae are with Araripemydidae is v different
from the phylogeny in Ferreira et al 2018 in which the American
Araripemydidae are sister to the African Auraxemydidae (interesting!). Is
this a situation in which there is fundamental disagreement about the
phylogenetic placement of the fossils?

On Fri, Dec 3, 2021 at 1:13 PM Scott Thomson <scott.thomson321 at gmail.com>
wrote:

> Well. Over the years as a paleo I have learnt that wishing for what could
> have been preserved is fruitless. So you learn to work with what you have.
>
> As for fragmentary remains, if they cannot be identified how do you know
> they are chelids. I have examined Cretaceous chelids in Lightning Ridge and
> QM. They can be identified to genus and are clearly new species. The oldest
> chelid I am aware of in Australia is a jawbone, clearly chelid and a new
> genus and species. Though it is a long neck. I dont use Pan-Chelidae
> because that grouping is poorly defined and missrepresents the
> relationships of the family. What I have learnt is you cannot work on the
> deep relationship's of this family without looking at Australian and South
> American evolution together.
>
> Cheers Scott
>
> I
>
> On Thu, Dec 2, 2021, 7:44 PM Michael Heads <m.j.heads at gmail.com> wrote:
>
>> Hi Scott,
>>
>> You wrote: 'With turtles we have a major advantage over a lot of groups,
>> they fossilise really well. The shell is very hard, so if it is a
>> depositional environment
>> and turtles were there there will always be turtle fossils'. But not if
>> the fossiliferous rocks have been removed by erosion or metamorphosed. Or
>> the fossils may just be too fragmentary to identify properly, as with the
>> Australian fossil 'pan-chelids' from Early Cretaceous.
>>
>> Also, just because a group has it's sister in area X doesn't mean that
>> that is the centre of origin.
>>
>>
>> On Fri, Dec 3, 2021 at 11:11 AM Scott Thomson via Taxacom <
>> taxacom at mailman.nhm.ku.edu> wrote:
>>
>>> The Chelids are related to the Araripemyidae as I said. That family is
>>> only
>>> found in South America and the oldest chelids are also from those beds.
>>>
>>> With turtles we have a major advantage over alot of groups, they
>>> fossilise
>>> really well. The shell is very hard, so if it is a depositional
>>> environment
>>> and turtles were there there will always be turtle fossils. There are
>>> 1200
>>> odd species of fossil turtles compared to 357 living ones.
>>>
>>> So yes in turtles the known stratigraphic setting has bearing. Could they
>>> have been elsewhere sure, but generally if they were we would have found
>>> them. So what I am saying is based on physical existing evidence.
>>>
>>> Cheers Scott
>>>
>>> On Thu, Dec 2, 2021, 5:56 PM John Grehan <calabar.john at gmail.com> wrote:
>>>
>>> > Thanks for that update Scott.  You say that "When looking at
>>> relationships
>>> > of the Chelidae they clearly arose in South America" - how do
>>> relationships
>>> > determine that?
>>> >
>>> > You also note that "the oldest Chelid fossils being from Argentina."
>>> Are
>>> > you saying that the location of the oldest fossil has something to do
>>> with
>>> > a taxon being there longest?
>>> >
>>> > Cheers, John
>>> >
>>> > On Thu, Dec 2, 2021 at 4:48 PM Scott Thomson <
>>> scott.thomson321 at gmail.com>
>>> > wrote:
>>> >
>>> >> The Georges and Thomson 2010 paper is now 11 years old and significant
>>> >> work has been done since. The 2021 TTWG checklist will give a better
>>> >> appreciation of species.
>>> >>
>>> >> When looking at relationships of the Chelidae they clearly arose in
>>> South
>>> >> America, the oldest Chelid fossils being from Argentina. My own view
>>> is the
>>> >> evolved from the Araripemidae an extinct group of Pelomedusoides
>>> turtle. So
>>> >> although their modern sister group is the living Pelomedusoides,
>>> >> Podocnemidae and Pelomedusidae that arrangemt is honestly
>>> paraphyletic and
>>> >> Chelids should be considered Pelomedusoides along with the other
>>> families.
>>> >> Most people think of Chelids backwards by the way, short necks
>>> evolved from
>>> >> long necks not the other way around. Araripemys was a long neck. The
>>> split
>>> >> occurred Cretaceous at the latest, Aptian.
>>> >>
>>> >> Geographically they evolved in South America and spread through
>>> >> Antarctica to Australia. The are fossils of turtles from Antarctica
>>> >> believed to be Pleurodiran. I have not examined but I would hazard
>>> they are
>>> >> Chelids. So Gondwannan yes but southern Gondwannan. There movement
>>> into the
>>> >> tropics of South America and Australia is only recent, last 40 million
>>> >> years. They remain the most cold resilient freshwater turtle
>>> families. So
>>> >> when I show the distribution of the Chelidae you need to centre the
>>> earth
>>> >> on Antarctica to understand their distribution. Chelids are salt
>>> >> intolerant, sea water is a barrier for them. No fossils of Chelids
>>> have
>>> >> been found outside of southern Gondwanna.
>>> >>
>>> >> Trionychididae are sister to the Carettochelyidae and both groups are
>>> >> ancient going back to early Cretaceous with world eide distributions.
>>> Their
>>> >> group the Trionychoidea are sister to all other Cryptodirous turtles
>>> the
>>> >> split probably goes back to the Jurassic. The Trionychoidea are salt
>>> >> tolerant and even now can be found in open ocean. There are fossil
>>> >> Trionychids in Australia. Carettochelyidae may only have one modern
>>> species
>>> >> but it has 20 described species in 4 genera.
>>> >>
>>> >> The genus Natator like a lot of sea turtles is just another species of
>>> >> Chelonia. Sea turtles suffer both taxonomic inflation and taxonomic
>>> >> inertia. Sinking sea turtle taxa is almost impossible due to their
>>> high
>>> >> profile. Only one species of sea turtle has been sunk in 100 years
>>> Chelonia
>>> >> agassizi, even that is still argued about. So Natator is of course
>>> syster
>>> >> to C. mydas and should be in the same genus. Modern Sea turtles are
>>> only 70
>>> >> million years old, not that old for turtles.
>>> >>
>>> >> Hard thing with turtles is they disobey many assumptions, basically
>>> >> because they had time. The Triassic and KT extinction knocked off a
>>> lot of
>>> >> species but they got through both fine. The oldest turtles are now
>>> back to
>>> >> 240mya so lets call that 1/4 of a billion cause that is a soft
>>> maximum, its
>>> >> from China, specimens of similar age are found in Europe and Africa.
>>> So in
>>> >> all likely hood turtles have had a world wide existance since just
>>> after
>>> >> the first amniotes appeard. I consider them the most successful
>>> amniote,
>>> >> they were there at the beginning or shortly after, still here now.
>>> >>
>>> >> Cheers Scott
>>> >>
>>> >>
>>> >> On Thu, Dec 2, 2021, 4:35 PM John Grehan via Taxacom <
>>> >> taxacom at mailman.nhm.ku.edu> wrote:
>>> >>
>>> >>> Scott - turtles are not a group I have studied, but in a quick
>>> glancing
>>> >>> look at Georges & Thomson (2010) I note:
>>> >>>
>>> >>> "Trionychidae  30 living species in North America, Africa, Asia, and
>>> >>> New Guinea." Interesting range. Does that include Madagascar? What
>>> is the
>>> >>> sister group?
>>> >>>
>>> >>> "Chelidae.Australia, New Guinea, Timor and Roti ...South America.
>>> This is
>>> >>> said to be of " of undisputed Gondwanan origin", but is it? What we
>>> have
>>> >>> seems to be a circum-Pacific range rather than one including core
>>> >>> Gondwana
>>> >>> (e.g. Africa, India, Madagascar. What is the sister group?
>>> >>>
>>> >>> Heads (2014) notes that the sea turtles Natator that breeds along the
>>> >>> coast
>>> >>> of northern Australia has a sister group, Chelonia, that has a
>>> worldwide
>>> >>> distribution. Heads suggests that as with Arhemia (plant genus) and
>>> its
>>> >>> relatives, the distribution is consistent with early vicariance of
>>> >>> widespread ancestors at breaks around the Arafura and Coral Seas.
>>> >>>
>>> >>> By the way, (2010) is a very nice overview, but I would selfishly
>>> have
>>> >>> liked to have seen distribution maps for each taxon. That would have
>>> made
>>> >>> the paper much easier to assimilate for the biogeographer where
>>> locations
>>> >>> are recognized as informative. Perhaps something to keep in mind in
>>> the
>>> >>> future please? (if RepFocus has the ranges illustrated then not such
>>> a
>>> >>> problem, but it is nice when one can cite a publication source
>>> directly).
>>> >>>
>>> >>> Cheers, John
>>> >>> _______________________________________________
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>>> >>>
>>> >>> Nurturing nuance while assailing ambiguity for about 34 years,
>>> 1987-2021.
>>> >>>
>>> >>
>>> _______________________________________________
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>>>
>>> Nurturing nuance while assailing ambiguity for about 34 years, 1987-2021.
>>>
>>
>>
>> --
>> Dunedin, New Zealand.
>>
>> My books:
>>
>> *Biogeography and evolution in New Zealand. *Taylor and Francis/CRC,
>> Boca Raton FL. 2017.
>> https://www.routledge.com/Biogeography-and-Evolution-in-New-Zealand/Heads/p/book/9781498751872
>>
>>
>> *Biogeography of Australasia:  A molecular analysis*. Cambridge
>> University Press, Cambridge. 2014. www.cambridge.org/9781107041028
>>
>>
>> *Molecular panbiogeography of the tropics. *University of California
>> Press, Berkeley. 2012. www.ucpress.edu/book.php?isbn=9780520271968
>>
>>
>> *Panbiogeography: Tracking the history of life*. Oxford University
>> Press, New York. 1999. (With R. Craw and J. Grehan).
>> http://books.google.co.nz/books?id=Bm0_QQ3Z6GUC
>> <http://books.google.co.nz/books?id=Bm0_QQ3Z6GUC&dq=panbiogeography&source=gbs_navlinks_s>
>>
>>
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>>

-- 
Dunedin, New Zealand.

My books:

*Biogeography and evolution in New Zealand. *Taylor and Francis/CRC, Boca
Raton FL. 2017.
https://www.routledge.com/Biogeography-and-Evolution-in-New-Zealand/Heads/p/book/9781498751872


*Biogeography of Australasia:  A molecular analysis*. Cambridge University
Press, Cambridge. 2014. www.cambridge.org/9781107041028


*Molecular panbiogeography of the tropics. *University of California Press,
Berkeley. 2012. www.ucpress.edu/book.php?isbn=9780520271968


*Panbiogeography: Tracking the history of life*. Oxford University Press,
New York. 1999. (With R. Craw and J. Grehan).
http://books.google.co.nz/books?id=Bm0_QQ3Z6GUC
<http://books.google.co.nz/books?id=Bm0_QQ3Z6GUC&dq=panbiogeography&source=gbs_navlinks_s>