Taxacom: supposed evidence of Pacific ignuana dispersal

[Geoff Read]

Hello Lynn,

We are discussing the Scarpetta et al article. It includes a world map of potential movement scenarios (fig. 3) clearly labelled as being a representation of landmasses "34 Ma on a Robinson projection" (plus other tech details).  This explains why some countries look somewhat odd in shape.
As I said yesterday this figure is also freely shown in the press release (with a less technical caption but beginning "A map of the world 34 million years ago").  It doesn't show all the features you would like to know about (such as climate) but does show the essential one in this case - the relative ocean distances (at the time) to be traversed where rafting is required. Clearly at the time there would also be considerable rafting required to arrive in Fiji from the West or from the Southeast, as well as direct from the Northeast (California).  This would apply whether or not their node age for divergence of the Fijian genus is correct. The authors say it is "late Paleogene (median age ~34 to 31 Ma) near or after the origin time of the Fijian islands".

Again here is the link: https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fnews.berkeley.edu%2F2025%2F03%2F17%2Figuanas-floated-one-fifth-of-the-way-around-the-world-to-colonize-fiji%2F&data%7C02%7Ctaxacom%40lists.ku.edu%7Cd9097e12913c4b6afe4a08dd6b414f5d%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638784650463911884%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=UmesSdeRnxCzk05fClhwbxjgoaqlIrf%2BeKS7AqHZxzU%3D&reserved=0

Geoff
--
Geoffrey B. Read, Ph.D.
Wellington, NEW ZEALAND
gread at actrix.gen.nz



>---- Original Message ----
>From: Lynn Raw via Taxacom <taxacom at lists.ku.edu>
>To: "Taxacom" <taxacom at mailman.nhm.ku.edu>
>Sent: Tue, Mar 25, 2025, 7:16 AM
>Subject: Re: Taxacom: supposed evidence of Pacific ignuana dispersal
>
>As John Grehan has pointed out, the age of fossils only indicates existence rather than origin.
>
>It seems that most of the rafting hypotheses seem to be based on the Earth as it is now rather than how it may have been in the past. 
>
>The Earth?s surface is constantly changing, even in our own lifetime. On the macro level sea levels change, continents move, collide and divide, there is uplift and erosion along with subsidence and deposition.
>
>The climate gets colder or hotter, drier or wetter with all the consequent ecological changes that result in populations changing, expanding and contracting with some going extinct while others split.
>
>It seems therefore that any biogeographical study should be based on an in-depth knowledge of the Earth history of the areas concerned. In those few papers that I have read, this does not seem to be the case. Maybe there are others that do?
>
>Just my thoughts. Let me know if I am mistaken.
>
>Lynn Raw