As some of you might know, all of my 'free' time last month was eaten up by a major project (a book chapter) that had a very tight deadline. This meant no time whatsoever for such stuff as blog-writing, hence the (mostly) recycled babirusa stuff. That project is now (mostly!) complete, but I'm still struggling for time due to other projects and jobs. Meanwhile, I thought I'd recycle this...
The illustration was previously used here, back on ver 1 in 2006, and again here in a ver 2 article on ameghinornithids. Eurotamandua joresi, shown at top as a skeleton and in the middle as a life restoration, is a middle Eocene fossil from Messel, Germany.
Its strong similarity to modern anteaters led Storch (1981) and Storch & Habersetzer (1991) to classify Eurotamandua as a true anteater (viz, as a member of the xenarthran clade Vermilingua), and even as a member of the anteater 'subfamily' Myrmecophaginae (within Vermilingua, the 'family' Myrmecophagidae has been split by some authors into Myrmecophaginae [for Protamandua, Tamandua, Neotamandua and Myrmecophaga] and Cyclopinae [for Cyclopes and Palaeomyrmidon]). Given that all other xenarthrans (Xenarthra = armadillos, sloths and anteaters, and their extinct relatives) are almost exclusively South American*, the presence of a member of the group in Eocene Europe - at a time when South America was an island continent - has always posed a major biogeographical enigma [adjacent skeletal reconstruction of Eurotamandua from wikipedia].
* They invaded North America during the Miocene, Pliocene and Pleistocene of course, and an Eocene sloth is known from Seymour Island, Antarctica.
The possibility that anteaters might have swam or rafted across the Atlantic seems somewhat remote, leaving vicariance as the only solution. But South America's terrestrial contact with North America (and hence Europe) and Africa (via Antarctica) became severed in the Cretaceous. Ergo, if Eurotamandua really is an anteater, members of the Eurotamandua lineage would have to go back to the Cretaceous, if vicariance was the explanation for Eurotamandua's presence in Europe. Storch & Habersetzer (1991) embraced this hypothesis, and therefore proposed that cyclopine and myrmecophagine anteaters diverged late in the Cretaceous. The existence of anteaters at this time would also mean that members of the armadillo and sloth lineages were also around in the Cretaceous, and other crown-placentals would have to have existed at the same time as well [life restoration of Eurotamandua below from wikipedia].
But - - is Eurotamandua really a modern-type anteater? Moreover, is it really a member of Vermilingua, and is it really, definitely, a xenarthran? Actually, all of these identifications have been challenged. In a conference abstract (the full results of which were never published so far as I know), Shoshani et al. (1997) proposed that Eurotamandua might not be a xenarthran at all, but that it was instead a close relative of pangolins. A few other authors have noted resemblances to the Messel pangolin Eomanis (this is the animal shown at the bottom of the composite image at the top; the holotype specimen is shown below, from here), and others have suggested that Eurotamandua might be a palaeanodont or palaeanodont relative (Rose & Emry 1993, Rose 1999), and these are regarded as stem-pangolins by some (I really must cover palaeanodonts at some stage... have been meaning to do so for ages). If these suggestions are correct [UPDATE: read the comments for more on Eurotamandua being close to pangolins!], Eurotamandua isn't a xenarthran at all [photo of Eurotamandua holotype below from here].
In Storch's 1981 description of Eurotamandua, rugose areas on the posterior thoracic and anterior lumbar vertebrae were interpreted as accessory xenarthrous articular surfaces (aka xenarthrales), and adjacent concavities on the sides of the centra were regarded as articular facets for these structures. The presence of these bits and pieces would show that Eurotamandua was xenarthrous, and hence a member of Xenarthra. The detailed photos published by Szalay & Shrenk (1998) showed, however, that the anapophyses of Eurotamandua (these are the projecting structures that support the xenarthrales) are not dorsoventrally deep, nor do they have dorsal and ventral articular processes as they do in xenarthrans; furthermore, the supposed articular areas on the sides of the centra (for reception of the xenarthrales) are artifacts and unlike the two distinct facets present in xenarthrans. Gaudin (1999) also argued that xenarthrales are absent in Eurotamandua and that an affinity with xenarthrans was unlikely. Szalay & Shrenk (1998) looked at a lot of other characters in Eurotamandua, and also concluded that it wasn't a xenarthran; instead, they proposed that it represented an entirely different, anteater-like lineage that they termed Afedentata (they first used that term in a 1994 abstract: I don't know what it means). They suggested that 'afredentatans' might share an ancestor with xenarthrans and palaeanodonts. All of these groups share a tubular muzzle and a few other features.
Gaudin & Branham (1998) found, however, that when all the morphological character data available was included in a data set with xenarthrans and other xenarthran-like placentals (such as pangolins and palaeanodonts), Eurotamandua still came out as a xenarthran, albeit not as a member of Vermilingua. Instead, they recovered it as a sister-taxon to the Pilosa + Vermilingua clade (the sloth + anteater clade) within Xenarthra. And what does all this mean for the biogeographical problem alluded to above?
Such a phylogenetic position leaves open the mystery of how a group which originated in and purportedly was restricted to the island continent of South America until the emergence of the Panamanian isthmus 2 million years ago managed to land an early member in Western Europe in the middle Eocene some 40-50 million ago (Gaudin & Branham 1998, p. 260).
In other words, we're still none the wiser, and the 'out of place anteater' problem becomes an 'out of place xenarthan' one if Gaudin & Branham (1998) are right. Are they right? As mentioned above, Tim Gaudin concluded in a more recent paper (Gaudin 1999) that Eurotamandua is not a xenarthran at all, meaning that this might represent the 'consensus view' among specialists [Eomanis holotype shown here].
The identification of Eurotamandua as an anteater hasn't just been challenged by morphological data: molecular studies also indicate that it's unlikely to be correct. Delsuc et al. (2001) used molecular dating to show that the earliest divergence in Xenarthra (between armadillos and the members of the sloth + anteater clade) must have occurred round about the time of the Cretaceous-Paleogene boundary, and that sloths and anteaters must have diverged in the Early Eocene. Eurotamandua really doesn't fit with this, as there is really no obvious way for Vermilingua to have originated in South America in the Early Eocene and to have then gotten to Europe within about 10 million years (unless anteaters are actually expert mariners, or able to teleport). Delsuc et al. (2001) therefore noted that their results better agreed with a non-xenarthran position (a la Szalay & Shrenk (1998) and Rose (1999)) or basal xenarthran position (a la Gaudin & Branham (1998)) for Eurotamandua.
Incidentally, Delsuc et al. (2001) dated the cyclopine-myrmecophagine split to the Late Eocene. While we're talking about anteater phylogeny, let's use this opportunity to remind ourselves that the Giant anteater Myrmecophaga tridactyla is, according to the phylogeny, a secondarily terrestrial descendant of arboreal ancestors, given that other myrmecophagines, and cyclopines, are arboreal. Arboreal ancestry might explain some of the peculiar morphological details of the Giant anteater, but that's a subject for another time.
In conclusion... while we remain uncertain just what Eurotamandua really is, the idea that it's a member of Vermilingua is pretty much dead, and the idea that it's a xenarthran is now widely doubted. I personally think that Rose (1999) made a good argument for palaeanodont affinities. If this is right, that 'out of place xenarthan' problem disappears.
So, must get round to palaeanodonts some time. And ernanodontids.
For other Tet Zoo articles on xenarthrans see...
- Ten things you didn't know about sloths
- Five things you didn't know about armadillos
- What was that skull? (on glyptodonts)
- I, Priodontes, the tatuasu
- The Panamanian Blue Hill Monster (or Cerro Azul Monster)
Refs - -
Delsuc, F., Catzeflis, F. M., Stanhope, M. J. & Douzery, E. J. P. 2001. The evolution of armadillos, anteaters and sloths depicted by nuclear and mitochondrial phylogenies: implications for the status of the enigmatic fossil Eurotamandua. Proceedings of the Royal Society of London B 268, 1605-1615.
Gaudin, T. J. 1999. The morphology of xenarthrous vertebrae (Mammalia: Xenarthra). Fieldiana: Geology 41, 1-38.
- . & Branham, D. G. 1998. The phylogeny of the Myrmecophagidae (Mammalia, Xenarthra, Vermilingua) and the relationship of Eurotamandua to the Vermilingua. Journal of Mammalian Evolution 5, 237-265.
Rose, K. D. 1999. Eurotamandua and Palaeanodonta: convergent or related? Paläontologische Zeitschrift 73, 395-401.
- . & Emry, R. J. 1993. Relationships of Xenarthra, Pholidota, and fossil "edentates": the morphological evidence. In Szalay, F. S., Novacek, M. J. & McKenna, M. C. (eds) Mammal Phylogeny (placentals). Springer (New York), pp. 81-102.
Shoshani, J., McKenna, M. C., Rose, K. D. & Emry, R. J. 1997. Eurotamandua is a pholidotan not a xenarthran. Journal of Vertebrate Paleontology 17 (supp. 3), 76A.
Storch, G. 1981. Eurotamandua joresi, ein Myrmecophagidae aus dem Eozän der "Grube Messel" bei Darmstadt (Mammalia, Xenarthra). Senckenbergiana lethaea 61, 247-289.
- . & Habersetzer, J. 1991. Rückverlagerte Choanen und akzessorische Bulla tympanica bei rezenten Vermilingua und Eurotamandua aus dem Eozän von Messel (Mammalia: Xenarthra). Zeitschrift für Säugetierkunde 56, 257-271.
Szalay, F. S. & Schrenk, F. 1998. The Middle Eocene Eurotamandua and a Darwinian phylogenetic analysis of "edentates". Kaupia 7, 97-186.
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Ah, that explains everything! And the ones that screw up end up underground and become fossilized!
;-þ
Supposing two swallows carried it together?
and become fossilized...
... in the wrong stratum! Fortunately, all the carboniferous anteaters are being oxidized and vented to the atmosphere, thereby avoiding embarrassments.
I don't know enough about mammal osteology to critically examine the characters in the Gaudin & Branham set, has this been done by someone competent? How many traits place Eurotamandua within the Xenarthra, and are they subject to selection?
If the characters indeed are good, the implications are stunning. I find an Eocene divergence to fit reasonably well the Platyrrhini/Cercopithecoidea split - and after all, the Platyrrhini managed to disperse to South America quite successfully. A hypothetical, arboreal sloth+anteater stemgroup could probably disperse the same way. The arboreal nature of this group would explain a poor fossil record, hence the lack of old world Xenarthrans.
This of course postulates an old-world origin and subsequent extinction of the Pilosa; which is highly unlikely given that armadillos only are found in the Americas. However, it could be worth considering _if_ Xenarthra-like fossils are found in African rocks.
"pangolins are unique
among living placental mammals in possessing an osseous
tentorium that separates the cerebral and cerebellar
compartments of the cranium" ... from Shoshani, J. and McKenna, M.C. (1998)...
if Eurotamandua were to be a stem pangolin it should be that mentioned tentorium ...isn't it ?
CARNIVORES and pangolins are unique
among living placental mammals in possessing an osseous
tentorium that separates the cerebral and cerebellar
compartments of the cranium .. from Shoshani, J. and McKenna, M.C. (1998)...
if Eurotamandua were to be a stem pangolin it should be that mentioned tentorium ...isn't it ?
SORRY, I COPY-PASTED WRONG ...
Africa broke off Antarctica much earlier (early Early Cretaceous) than it broke off South America (end of the Early Cretaceous).
Afro-Edentata. Probably they thought it was the sister-group of Xenarthra, with the split between them being caused by the break-up between South America and Africa, then followed by dispersal from Africa to Europe... it would be rather stupid to enshrine such speculations in nomenclature, but there's precedent.
I thought 3 million?
Hmmmm.
Are you sure Eldeceeon isn't a chimaera made of an anthracosaur-thingy-whatever and an anteater? It does have ribless lumbar vertebrae, you know. And while a detailed description was promised in or soon after the preliminary one in 1994, it still hasn't come out... Are they hiding something?
And if there are enough of them. And if there are enough taxa.
Hint: I haven't read the paper, but there can't possibly be enough taxa in that analysis. That would require a great big eutherian analysis; while such a thing is slowly forthcoming according to the 2008 SVP meeting, it hasn't come out yet, and Gaudin and Branham are AFAIK not involved.
The Phylogeny of Living and Extinct Pangolins (Mammalia, Pholidota) and Associated Taxa: A Morphology Based Analysis)
Journal of Mammalian Evolution (2009)
Abstract:
ract The present study was undertaken in order to effect a comprehensive phylogenetic analysis of the order Pholidota, examining seven of the eight currently recognized extant species (absent is Manis culionensis, formerly recognized as a subspecies of Manis javanica) and nearly all the well-known fossil taxa, and employing a wide range of osteological characters from the entire skeleton. In addition, the relationship of pangolins to several putative early Tertiary relatives, including palaeanodonts and the enigmatic âedentateâ Eurotamandua joresi, were investigated. The goal of the study was to improve understanding of the systematics and the biogeographic and evolutionary history of the pangolins. A computer-based cladistic analysis of phylogenetic relationships among seven extant species of pangolins, five extinct pangolin species (including all but one of the well-preserved taxa), as well as Eurotamandua and two genera of metacheiromyid palaeanodonts, Palaeanodon and Metacheiromys, was performed based upon 395 osteological characteristics of the skull and postcranial skeleton. Characters were polarized via comparison to the following successive outgroups: the basal feliform carnivoran Nandinia binotata and the hedgehog Erinaceus sp., a eulipotyphlan laursiatherian placental. A revised classification is presented based on the results of the analysis. The results support the monophyly of Pholidota and Palaeanodonta by providing new anatomical characters that can serve to diagnose a pangolin/palaeanodont clade, termed here Pholidotamorpha. Pholidota is defined so as to include all living and fossil pangolins, including all three taxa of middle Eocene âedentatesâ from the Messel fauna of Germany, among them Eurotamandua joresi. The results do not support the monophyly of the remaining two Messel âedentatesâ originally placed in the same genus Eomanis, which is restricted to the type species Eomanis waldi. Euromanis, new genus, is named with Eomanis krebsi Storch and Martin, 1994, as the type species, to form a new combination Euromanis krebsi (Storch and Martin, 1994). The analysis strongly supports the monophyly of a crown clade of pangolins diagnosed by many anatomical synapomorphies, the family Manidae. This crown clade is sister to the family Patriomanidae, which includes two Tertiary taxa, Patriomanis americana and Cryptomanis gobiensis, within the superfamily Manoidea. The relationship of the Tertiary European pangolin Necromanis to these two families is unresolved. Within Manidae, the extant species are divided into three well-supported, monophyletic genera, Manis for the Asian pangolins, Smutsia for the African ground pangolins, and Phataginus for the African tree pangolins. The latter two form a monophyletic African assemblage, the subfamily Smutsiinae. The biogeographic implications of this phylogeny are examined. A European origin for Pholidota is strongly indicated. The fossil record of pangolins would seem to support a European origin for the modern forms, with subsequent dispersal into sub-Saharan African and then to southern Asia, and the phylogeny produced in this analysis is consistent with such a scenario.
Wow, thanks: I had, obviously, completely missed this paper. Does anyone have a pdf they can send?
Quoted article by Timothy J. Gaudin, Robert J. Emry and John R. Wible.
If Eurotamandua was a true anteater, transatlantic dispersion would be analogous to platyrrhines and caviomorphans. It seems that its pholidotan status is becoming more consistent. The article postulated Pholidotans (Eupholidotans + Eurotamandua) as an European group. Palaenodonts were an Euramerican usual group since Middle Paleocene, but its absence (until now) in Earliest North American strata points to an Early Paleocene European source. Stem Pholidotans may have split from Paleanodonts, becoming isolated in some European "island".
Forgive my amateurishness, but don't Xenarthran skulls all have that little downward-projecting doohickey on their zygomatic arches? I've noticed it on sloth skulls, glyptodonts, anteaters, armadillos, but it doesn't seem to be present on this little critter.
Also, I notice you have two reconstructions, one furred, one scaly. Is there any way to tell by the fossil which is more likely?
That's not enough by an order of magnitude. It assumes that Pholidota, Palaeanodonta, and Eurotamandua are more closely related to each other than to Nandinia or Erinaceus.
Reporting the existence of new characters is always good, and a matrix with 395 characters is already a great achievement in itself -- but, see above, Pholidot"a"morpha (should be -o-) is a basic assumption of the analysis, not a result.
For crying out loud, there isn't even a xenarthran in the matrix!
I'd appreciate a pdf. :-)
The scaly one is Eomanis.
David: *facepalm* Aahhh, I shoulda known. That's what I get for commenting before having my morning shower to wake me up.
One more question: What is the term for that little projection that comes down from the zygomatic arches on Xenarthran skulls?
(i) Re: comments 9,12: I ***think*** I can forward pdfs from "Journal of Mammalian Evolution," and will try to send one to eotyrannus: D.M., can you send me your e-mail address so I can try to send one to you? I'm aphazen(atsign)ualberta(dot)ca
(ii) As for the date of divergence of Xenarthra... There seems to be some disagreement about the branching order of Xenarthra and Afrotheria, but the molecular stuff I've seen all agrees that Boreutheria (have I remembered the name? the clade containing carnivorans, perissodactyls, artiodactyls, chiropterans and "rump-eulipotyphlans,": what's left of "insectivora" after everything else gets reallocated) and Euarchontoglires form a natural group. So Xenarthra would have to have diverged from them before the split between Boreu and Euarcho. And-- on the not absolutely certain but I'm happy to bet (small sums of money) on it assumption that Purgatorius is a Plesiadapiform hence Primate hence Euarchontoglire-- THAT split had to have happened in the Cretaceous.
(iii) There are weird and wonderful things in the late Cretaceous and early Tertiary mammalian record of South America (Gondwanatheres! Monotrematum! whatever Reigitherium was!), but as far as I know the origins and early diversification of Xenarthra are unknown.
Well, it's being stated recently that Maastrichtian Indian Deccanolestes is a basal Adapisoriculid, and that these are stem Euarchontans.
South American Xenarthrans came from another place, since placentals only reached S.America during Campanian or Maastrichtian.
1) Hypothesis One, most plausible, they came from Western North America, following the same way that marsupials, ungulates and hadrosaurs.
2) Hypothesis Two: they were much older, predating separation between Africa and S.America.
3) Hypothesis Three (speculative): they came from Africa in Late Cretaceous, by island-hopping. If Atlantic crossing was somehow possible in Late Eocene (monkeys and rodents), it would be easier in Cretaceous. Maybe some island ridge became crossing possible (Proto-Canaries? South Atlantic Ridge?)
Hey Darren,
Nice and concise as ever. I will be throwing in more stuff on the Eurotamandua debate the next time I give a presentation on the group.
Just to make sure though... Xenarthrans aren't exclusive to South America except after the great faunal interchange. They are found in Antartica too. And of course in the Carribean islands and possibly pre GFI in North America, so it's another arguement considering their migration power and possibly pushing their distribusion back and wider afield. Not a great arguement though.
Correction (to my comment 14): bats+cats+horses+cows is Laurasiatheria. (Boreoeutheria is Laurasiatheria+Euarchontoglires. So, if I had remembered the nomenclature, I could have put the claim in my (ii) more simply: the split between Boreoeutheria and Xenarthra was "certainly" in the Cretaceous.)
--
Re: JS Lopes (15): taxonomic placement of Deccanolestes is, I think, at least as uncertain as that of Purgatorius! But thanks for reminding me about it. New version of my argument: if EITHER Purgatorius or Deccanolestes is a Euarchontoglire, then...
Re: Steve Vidovic (16): when you do give your next presentation, can you put an added comment on this string? Please?
Oh. Forgot to add:
I've started reading the Gaudin etc article. And the "osseous tentorium" mentioned by daniel (comment 5) is trait 361 in their matrix. Three states: none, small, large. Erinaceus, as an outgroup to the supposedly osseously tentoriate clade Carnivora+pangolins has the "primitive" state: no osseous tentorium. Nandinia (chosen, I suppose, because its basicranial features made the authors think it a fairly plesiomorphic Carnivoran) and all the living pangolins have the derived (large) state. One of the tertiary pangolins-- maybe it was Necromanis, but I don't remember-- has the intermediate (small) stqate. And the Palaeanodonts and the Messel species (Eurotamandua, Eomanis, Euromanis) have... data missing.
Chris Taylor (of "Catalogue of Organisms") told me (when I raised the issue in response to one of his posts about early-tertiary Eutherians) that horses have a (convergent?) osseous tentorium. I was curious about Creodonts (Chris didn't think the currently available evidence supported their traditional placement as close relatives of Carnivores), but I have seen only one, not very specific, reference to tentoriousness in relation to them. I'm still curious.
Regarding the Gaudin et al. (2009) paper; I have had a pdf version of it saved on my hard drive for some time now, but I still haven't found the time to read it (it's 71 pages long). Now it seems that it isn't quite as good as I had hoped.
David:
Damn right; choosing the outgroups that they did totally defeats the authors' purpose of resolving the phylogenetic affinities of the 'pholidotamorphans'. And for the same reason, there is no excuse for not including any xenarthrans in the analysis.
What a disappointment. I had looked forward to reading the paper. (I will, of course, still read it eventually, mammalogy geek that I am.)
~34ma The Great African Rift Valley formed, large cosmic impacts, Argentina-Antarctica Archipelago ruptured, Antarctic Circumpolar Current formed and Antarctica Froze. Cavies and new world monkeys had occupied a mild coastal forest that connected (previously Africa to) Antarctica to Argentina. The then-coastal areas are today under thick ice masses or eroded away except for a few uplifted areas. (more at my URL)
ot: Female rhinos and horses have a hymen, do tapirs? I would say yes, as a conserved trait, but am unable to confirm.
Got the paper now (thanks!), will read it tomorrow.
Except that only one tooth of Purgatorius, out of a very large number, has been found in a sieve that had been used to screenwash K sediments, and that the latest greatest analysis -- the Maelestes paper, Wible et al. 2007, Nature -- has found Purgatorius, Protungulatum, and Oxyprimus to form a clade that lies just outside Placentalia. I'm not quite happy with that analysis (all characters were unordered, some are correlated...), but several people are working on that; we'll see.
To me, the question is where the vertical gene transfer the taeniodonts lie in eutherian phylogeny. There is a Cretaceous taeniodont (Schowalteria).
Gondwanatheres: do seem to be multituberculates now, but I've had the thesis that tries to show this lying around on my harddisk for years and still haven't read it.
Monotrematum: what it says on the tin.
Reigitherium: yet another dryolestidan.
Will be interesting to see how that develops. Biogeographically it's hard to imagine.
Or indeed the early Paleocene. There's only one "eutherian" tooth from the Cretaceous of South America (late Maastrichtian of Peru)... and the Cretaceous mammalian record of SA is rich, chock full of dryolestidans for instance.
Could be synapomorphic -- Zooamata!
There's no evidence that Hyaenodontidae and Oxyaenidae are closely related.
Well, no. Antarctica and Africa broke apart very early in the Cretaceous, and South America and Africa completed their breakup at the end of the Early Cretaceous, just over 100 Ma ago. The New World rodents and the New World monkeys must have rafted in across the sea -- there is no alternative.
| Well, it's being stated recently that Maastrichtian Indian Deccanolestes is a basal Adapisoriculid, and that these are stem Euarchontans. ||Will be interesting to see how that develops. Biogeographically it's hard to imagine.|
Not so hard, if we consider that Greater India (India+Seychelles+other microplates) had some Late Cretaceous connexion to Northern Africa, and Afro-European crossing was possible a few times during Cretaceous (for example, abelisaurids, madtsoiid snakes and ziphodont crocs reached Europe). It's a bit hard, since the whole scenario of North Africa/Southeast Europe/Southwest Europe/ West Asia/Greater India is not fully understood, but we may assume that stem Euarchontans in India came from North Africa, and these African hypothetical ancestors came from Europe or Asia. So, Asian placentals could have reached: North America via Beringia; Europe via one or more isthmuses in Western Asia; Africa via Europe (or via Near East);South America via North America. The presence of Neornithes in Antarctica (Vegavis, Polarornis) would also need a similar pattern.
"Creodont" position is one of the most intringuing issues in Mammalian paleontology. Oxyaenids suddenly appeared in Late Middle Paleocene, in North America, with no clear previous American ancestry. Maybe they came from Europe (whose Early Paleocene record is still poor), from some unexploited region of Central America, or some proto-Caribbean island. Perhaps the sustained existence of a few proto-islands in Caribbean area in Late Cretaceous and Paleocene would explain the origin of so many mammal clades in North and South America with no clear ancestry.
Hyenodont ancestry is being recovered in African Late Paleocene. What is their ancestry? Weasel-like Afrotheres? Odd Euachontans? Stem Ferae that became nested in Africa, while miacids arose in Asia and "pholidotamorphans" in Europe? This is a bunch of speculative guessings. Forgive me if it sounds too weird.
DM: "Well, no. Antarctica and Africa broke apart very early in the Cretaceous, and South America and Africa completed their breakup at the end of the Early Cretaceous, just over 100 Ma ago. The New World rodents and the New World monkeys must have rafted in across the sea -- there is no alternative."
What you wrote is ~true until "must have rafted" which is fiction. They merely moved along the Antarctic coasts northward to Brazil. (South African coastal chacma baboons eat shark egg cases, South America coastal capuchins eat oysters, both climb/wade rather than swim, indicating warm land - cold (oceanic) water.)
All you're changing is the target: from Oligocene South America to Eocene Antarctica. You still fail to take the ocean away, which has been there between Africa and Antarctica since the beginning of the Cretaceous.
"Fiction"? The Dunning-Kruger effect is talking.
Incidentally, primates have not been found in the Eocene of Seymour Island, or of anywhere else. The NW monkeys seem to have arrived in SA after SA and Antarctica broke apart.
... except riding their trusty steeds: teleporting anteaters... !!
Kerguelen plateau: "was emergent or under shallow water for up to 40 million years of its history. Wood fragments and coal found in Late Cretaceous sediments indicate that the plateau may have been covered with forests." gov/au/oceans
'New fossil platyrrhines from the Pinturas Formation, southern Argentina' by John G. Fleagle
Early Miocene NWM fossils at Patagonia coasts from "Miocene Climatic Optimum at >51° South"
(refs @ my URL)
And when the molecular clock data suggest a younger date than the fossils purportedly do that should sound an alarm.
Yes, it was in the Cretaceous, and it still was in the Eocene. But it never had a contact with Africa. It's between India and Antarctica, and the contact with India ended in the Late Cretaceous.
The Miocene comes after the Eocene. Long after.
Absolutely. It means either that the molecular dating is miscalibrated or that the oldest fossils don't actually belong to the group.
Meant to write Oligocene. I don't know if Eocene terrestrial fossils are known from the Kerguelen plateau.
The Kerguelen ref. was simply to point out that emergent forested isles existed at that latitude, not that NWM & cavies necessarily transited through there.
DM: "The Miocene comes after the Eocene"
Yes, but similar climate warming induces similar taxa to expand polewards, so potentially both before (34ma) and after (Miocene "optimum") Oligocene glaciation of Patagonian coasts there may have been the same forest fauna.
Based on Fig. 5 and text from Ali-Aitchison 2009
http://147.8.184.46/Ali-Aitchison-JoB-2009.pdf
83.5ma parts of We. Africa & So. America were closer than much of Australia-Antarctica of that period, and might allow for vegetative rafting distance-wise (note their hypothesis of giant frogs moving the opposite direction along the same route, earlier). If the straits remained relatively narrow there until 30ma, inter-island rafting isn't unreasonable. I was objecting to the idea of vegetative rafting across a full size ocean, which I view as untenable.
Ok, what about this fossil sloth from Antarctic island - shouldn't sloths appear much later than Antarctica split?
It doesn't do anything except point out that specifically the Kerguelen plateau was emergent & forested.
Islands are islands; getting there requires swimming, rafting, or flying.
This doesn't help. In the Eocene, SA was connected to Antarctica (though not to Africa, however indirectly!); in the Miocene, SA wasn't connected to anything.
Why do you act as if we didn't know precisely how narrow the Atlantic was at any given time? We know all that. The age of every square km of the floor of the Atlantic is known.
No, why? What's wrong with a late Eocene sloth?
There is another South American mammal that may have got there pre-Panama land bridge: the pygmy squirrel _Sciurillus pusillus_. According to a few molecular studies (Mercer and Roth, 2003, Science 299:1568â1572; Steppan et al., 2004, Mol. Phyl. Evol. 30:703â719), it is a basal sciurid, and divergence within _Sciurillus_ goes back about 10 Ma according to Mercer and Roth's molecular clock, but there is no fossil record of the genus. The oldest sciurids are from 40â35 Ma or so in North America.
forested "at that latitude" re. map
That "tropical" mammals were at Patagonia/Antarctic Isles both in Eocene and Miocene, and that Africa had been linked earlier, means that African "tropicals" could have expanded to Eocene Antarctic coastal forests (poor fossil preservation) and gone north to SA previous to the disconnect 34ma, then returned south during a similar Miocene warm period. I don't think we know precisely when cavies and monkeys entered the new world.
David, in your opinion, what would have been an appropriate outgroup (or outgroups) for Gaudin et al. to use in this analysis? A metatherian?
How was the dating calibrated?
But this would require both monkeys and rodents to have been present in South America one hundred fucking five million years ago!!!
You can't go from Africa to Antarctica, except by sea, or by walking through South America before 105 Ma ago.
If they had been there in the Eocene, we'd have found them. Instead, we find polydolopoids and the like. The earliest cavy & monkey fossils are Oligocene.
Interestingly, the oldest known NW monkey had terrestrial adaptations and lived in a rather open woodland or something. Worldwide, the forests were small in the Oligocene.
Except I didn't. I procrastinated from procrastination. :-(
<grunt mode="pessimism">Metatheria as a whole should have been the outgroup, and Eutheria should have been the ingroup, so we can finally figure out if all those weird Paleogene eutherians -- palaeanodonts included! -- were placentals or not.</grunt>
That would, of course, have amounted to a PhD thesis or three. Using a smaller taxon sample runs the risk of long-branch attraction because there's so much morphological diversity even within Placentalia. I'll read the paper, though.
David:
Holy shit, I've missed that! Do you have a reference?
I think it's an SVP meeting abstract from 2008. I'll try to search the pdfâ¦