[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Cretaceous, yes -- Netherlands, yes -- marsupial, unlikely

Thank you for using "Archive", take the trees persented with a grain of
salt... :)

So, based on David's analysis, I should place this critter as a
"Ameridelphia incertae sedis"?

Question: Who is Nortedelphys??

--Mikko Haaramo


Mikko K. Haaramo, M.Sc.

Paleontologist & IT-Manager

Department of Geology
P.O.Box 64 (Gustaf Hällströminkatu 2)
FIN-00014  University of Helsinki

sposti: mailto:mikko.haaramo@helsinki.fi
www: Mikko's Phylogeny Archive [http://www.fmnh.helsinki.fi/users/haaramo/]


> -----Original Message-----
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu] 
> On Behalf Of David Marjanovic
> Sent: 2. tammikuuta 2006 0:55
> To: DML
> Subject: Cretaceous, yes -- Netherlands, yes -- marsupial, unlikely
> The most spectacular news first. Mammal hair is mentioned in 
> passing to occur in amber from the Campanian of Siberia!!!
> -----------------------------------
> I've now read the paper:
> James E. Martin, Judd A. Case, John W. M. Jagt, Anne S. 
> Schulp & Eric W. A. 
> Mulder: A New European Marsupial Indicates a Late Cretaceous 
> High-Latitude Transatlantic Dispersal Route, Journal of 
> Mammalian Evolution 12(3/4),
> 495 -- 511 (December 2005)
> The authors don't even try to find out whether 
> *Maastrichtidelphys*, called a "pouched mammal" once, is a 
> crown-group marsupial or not. Before the paleobiogeography 
> section the word Metatheria is never mentioned; even in it, 
> *Didelphodon*, peradectids and pediomyids are "marsupials". Only
> *Marsasia* and *Asiatherium* are not "marsupials". It seems 
> to follow that "Marsupialia" is used for something like the 
> "Neometatheria" of 
> http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma
> /Chordata/Synapsida/Metatheria/Metatheria.htm
> or the "Archimetatheria" of
> http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma
> /Chordata/Synapsida/Metatheria/Metatheria_2.htm,
> which may or may not be the crown-group depending on the 
> phylogeny, and is much bigger than the crown-group on the 
> currently accepted phylogenies. 
> Which phylogenies Martin et al. consider likely (let alone 
> why!) is never explained, and neither do they even just 
> mention that some (most??) people use a different definition 
> of Marsupialia. IMHO this counts as a significant failure of 
> peer-review.
> Martin et al. say *Maastrichtidelphys* is a herpetotheriid, 
> say that Herpetotheriidae is known from the early 
> Maastrichtian (of North America) onwards, and say that this 
> group is "seemingly related to the North American opossum". 
> In the "Systematic Paleontology" section, they accordingly 
> put Family Herpetotheriidae into Superfamily Didelphoidea and 
> Order Didelphimorphia, which they put into Cohort 
> Ameridelphia -- I'm certain they know that this latter taxon 
> is paraphyletic. (Marsupialia is a supercohort, in case 
> you're wondering...) In other words, they clearly don't think 
> that only clades (and species) should be named.
> *Maastrichtidelphys* "shares the greatest number of character 
> states with species (albeit not all) of" the early Eocene 
> herpetotheriids
> *Amphiperaterium* (Europe) and *Garatherium* (Africa). I 
> wonder what this exercise in phenetics is for.
> Despite the phenetics, a phylogenetic analysis is done. 
> *Nortedelphys* (described a year earlier by the same authors) 
> comes out as a herpetotheriid.
> First analysis -- only North American taxa and 
> *Maastrichtidelphys*, to find out which of the former is 
> closest to the latter:
> --+--+--*Maastrichtidelphys*
>   |  `--*Nortedelphys*
>   `--+--*Didelphodon*
>      `--+--*Alphadon*
>         `--+--*Albertatherium*
>            `--+--*Protalphadon*
>               `--+--*Pediomys*
>                  `--*Turgidodon*
> The authors do not explain how this tree was rooted.
> Second analysis -- to find out where *Maastrichtidelphys* 
> lies among "other latest Cretaceous and Paleocene didelphoid 
> marsupial taxa":
> --+--*Didelphodon*
>   `--+--*Alphadon*
>      `--+--*Jashkadelphys*
>         `--+--*Mizquedelphys*
>            `--+--*Pucadelphys*
>               `--+--*Itaboraidelphys*
>                  `--+--*Maastrichtidelphys*
>                     `--*Nortedelphys*
> This tree is rooted with *Didelphodon* and *Alphadon* as 
> outgroups. Note that the topology contradicts the first tree. 
> *Pucadelphys* and
> *Itaboraidelphys* come from the Paleocene of South America, 
> making the idea that Herpetotheriidae belongs to the 
> crown-group more plausible
> (*Pucadelphys* is close to the crown, but apparently 
> outside). But note that the monophyly of "Didelphoidea" is 
> not tested; not one non-"didelphoid" is included, if we 
> assume that the authors still include everything in 
> "Didelphoidea" that was included _fifty_ years ago.
> I could obviously be wrong, but I conclude that the authors 
> have likely a priori assumed that their "Didelphimorphia" and 
> "Didelphoidea" are clades and built their conclusions (like a 
> South American origin for
> *Nortedelphys*) on this assumption that they have not tested. 
> Both of their poorly supported cladograms can probably be 
> safely ignored (in spite of the rather high number of 
> characters -- 41 in total).
> On the other hand, the biogeography looks quite robust, 
> despite the disgusting mixture of Cretaceous and recent 
> coastlines in fig. 4.
> BTW, the specific epithet should end in -orum instead of -i. 
> Mr Meuris and Mr Smet are two people. <blood pressure rising>