Tetrapod Zoology

More on babirusas! Go here for part I.

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While babirusas look pig-like and are classified as part of Suidae, they’re distinctive and unusual [image above from wikipedia]. Combining rather slender legs with a barrel-shaped body, they can exceed 1 m in length and have a shoulder height of 65-80 cm. Some individuals weigh as much as 100 kg. Babirusas are odd in having particularly remarkable canines (more about those soon), but less well known is that they differ from other pigs in several details of their anatomy, and in fact resemble peccaries and other artiodactyls in a few features. The tendons of their feet and some of their throat muscles are strikingly peccary-like, and they resemble ruminants (though only superficially) in a few details of their pectoral musculature, and in having a complex, multi-chambered stomach. Furthermore, the babirusa snout is not as specialised as that of other pigs.

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In a curious parallel to this combination of anatomical features, the word babirusa combines babi, meaning pig, with rusa, meaning deer. It is supposed that Sulawesi people chose this name as the large canines of babirusas recall antlers, but it is also possible that the name reflects the amalgamation of deer-like slender legs and a multi-chambered stomach with the pig-like traits of the animal. Sulawesi people have always known of pigs other than babirusas, as Sulawesi is also home to the Sulawesi warty pig Sus celebensis*. Incidentally, you may recognise Rusa as the old generic name for the Sambar Cervus unicolor and other deer of Indonesia, the Philippines and adjacent islands [Sambar shown here, from wikipedia]. The Sunda sambar or Timor deer C. timorensis occurs on Sulawesi, but was probably introduced there from Java or Bali.

* A large extinct Pleistocene suid, Celebochoerus heekereni, was also endemic to Sulawesi, but (so far as we know) was not related to either babirusas or Sus celebensis.

In view of the divergent anatomy of babirusas, most artiodactyl specialists agree that they represent an ancient lineage, Babyrousinae, which branched off from the rest of Suidae early in its evolution (Thenius 1970). This is supported by chromosome data, as several autosomes present in babirusas have no equivalent in other suids. Unfortunately babirusa fossils only go back as far as the Pleistocene, but in theory we should expect to find babyrousines going back to the Oligocene [UPDATE: molecular data suggests Miocene - see comments below]. Is it possible that babirusas aren’t part of Suidae? Such a view was favoured by Deninger (1909) who argued that babirusas descended from anthracotheres like Merycopotamus. Anthracotheres, a widespread extinct group that appeared in the Eocene and survived into the Pleistocene in eastern Asia, are probably ancestral to hippos (and thus perhaps not close to suids at all), and while Deninger’s idea has been mostly dismissed it was viewed favourably by Groves (1981). He thought it at least possible that babirusas might really be extant anthracotheres, which is a pretty radical thought. For the record, no, this has not been accepted and babirusas are universally regarded as suids.

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Despite the ancient divergence of babyrousines from other suids, a male babirusa hybridised with a female domestic pig at Copenhagen Zoo in 2006. Of the five resulting piglets, one died but the others survived. As you can see from the photo here, they look surprisingly normal. While the successful mating has surprised some biologists, we should remember that successful hybridisation can occur between species that are only distantly related, so it actually doesn’t mean much.

More next…

For previous articles on babirusas see…

For other Tet Zoo articles on artiodactyls see…

Refs – –

Deninger, K. 1909. Über Babirusa. Ber. Naturf. Ges. Freiburg 17, 179-200.

Groves, C. P. 1981. Ancestors for the Pigs: Taxonomy and Phylogeny of the Genus Sus. Technical Bulletin 3, Department of Prehistory, Research School Pacific Studies, Australian National University.

Thenius, E. 1970. Zur Evolution und Verbreitungsgeschicht der Suidae (Artiodactyla, Mammalia). Zeitschrift für Säugetierkunde 35, 321-342.

Comments

  1. #1 David Marjanović
    February 15, 2010

    Verbreitungsgeschicht

    -e.

  2. #2 Mu
    February 15, 2010

    Interesting critter, is that inner set of tusks actually anchored in the lower jar and grown through the upper jaw?

  3. #3 John Harshman
    February 15, 2010

    I hate to seem like a molecule snob, but what about the DNA sequence data for babirusas? I see plenty in GenBank, but I don’t have any of the publications on hand.

    What about O’Leary & Gatesey 2008, Cladistics 24:397-442?

  4. #4 Nick Gardner
    February 15, 2010

    http://www.boneclones.com/images/bc-251-lg.jpg

    A quick search for images of ‘babirusa skull’ on Google confirms what should be obvious. The upper tusks are not from the lower jaw.

  5. #5 DDeden
    February 15, 2010

    To me the babirusa is the closest extant match to the cetiartiodactyle last common ancestor, as much as Indohyus or hippos anyway. Dolphins have multi-chamber stomachs. Have any of the zoo hybrids reproduced?

  6. #6 Steve P
    February 15, 2010

    So babirusas can hybridise with domestic pigs: doesn’t this mean that they should be classified as a species of Sus?

  7. #7 AnJaCo
    February 15, 2010

    …we should remember that successful hybridisation can occur between species that are only distantly related, so it actually doesn’t mean much.

    Well I give it some meaning. But I am unsettled on just how much. If babirusas were anthracotheres I would be shocked at their successful mating with pigs. In fact, given the lack of a babirusa fossil record, those little piglets are the best evidence that they are suids and not anthracotheres. For me anyways. Has anyone tried to mate a pygmy hippo with a large pig, and how did that work out?

    Among tetrapods, which are the most “distantly related” species that have successfully reproduced? And are they known to be fertile or not? I have heard of many hybrids but none that really seem to be from truly “distantly related” species.

  8. #8 John Harshman
    February 15, 2010

    Distant hybrids: There are quite a few known, apparently fertile hybrids between various species of ducks (Anatinae) and geese (Anserinae), which diverged at least 30 million years ago. How’s that?

  9. #9 Cameron
    February 15, 2010

    Steve P:

    So babirusas can hybridise with domestic pigs: doesn’t this mean that they should be classified as a species of Sus?

    There is no definition for what a ‘genus’ constitutes. Ideally the concept should be used to express diversity, and all hybridization tells us is that through some evolutionary quirk no reproductive barriers evolved. A cursory glance through phylogenetic data suggests Babyrousa is nowhere near Sus.

    AnJaCo:

    Among tetrapods, which are the most “distantly related” species that have successfully reproduced?

    Discussed several times on these forums. Here are a few (and there are a lot more):
    Puma x Leopard
    Camel x Llama
    False Killer Whale x Bottlenose Dolphin
    Turkey x Chicken

    This page has a lot more, mostly feline.

  10. #10 David Marjanović
    February 15, 2010

    is that inner set of tusks actually anchored in the lower jar and grown through the upper jaw?

    No, it’s the upper canines that grow upwards instead of downwards. Fascinating and unique, but actually not much more bizarre than wisdom teeth growing in all manner of transverse directions in humans.

    The outer set consists of the lower canines which grow upward as usual.

  11. #11 Christopher Taylor
    February 15, 2010

    all hybridization tells us is that through some evolutionary quirk no reproductive barriers evolved

    Or, alternatively, reproductive barriers were lost. I’m not aware of any cases where this has been demonstrated for post-mating isolation methods but it has been for pre-mating methods. For instance, lacewing species in North America have different courtship songs from other closely related species in North America, but may have identical songs to more distantly related species in Asia. Presumably, when the chance of individuals of two separate populations to encounter each other is pretty much nil, there’s no reason for selective pressure to stop them converging on the same characters through drift.

    One of the best examples of the non-linear nature of reproductive isolation is probably Aix sponsa (the Carolina wood duck) versus Aix galericulata (the mandarin duck). Despite their being (as far as I know) undoubted sister taxa, wood ducks seem to have the usual duck ability to hybridise with almost any other duck (a Google search brings up hybrids with mallard, shoveler and hooded merganser) while mandarin ducks seem to be incapable of producing hybrids (with possible contentious exceptions of hybrids with wood ducks).

    I found this page with a few neat pictures of hybrids between domestic birds, including peacock X guinea fowl. In fact, Galloanserae as a whole seem to think that reproductive isolation is something other people do.

  12. #12 John Harshman
    February 15, 2010

    You’re overstating slightly. While mandarin hybrids are rare, they aren’t unknown. There are known hybrids between mandarin and gadwall, long-tailed duck, Laysan teal, and redhead. Probably more, but that’s all I found in a quick search.

  13. #13 Christopher Taylor
    February 15, 2010

    Damn, I’m gonna have to find another example.

  14. #14 John Scanlon FCD
    February 16, 2010

    T-shirt slogan: Interfertility is symplesiomorphy.

  15. #15 Squiddhartha
    February 16, 2010

    Was the babirusa/pig hybridization intentional or, y’know, opportunistic?

  16. #16 Mike from Ottawa
    February 16, 2010

    Poster #15: I hope the “q” in your name is a typo!

  17. #17 AnJaCo
    February 16, 2010

    Thanks to Cameron and Chris Taylor for the observations and links. I remembered the messybeast.com page from an earlier post on big cats, and I hadn’t followed the non-cats links. Just did. Neat stuff.

    Both links provide info informing the observation that “successful” hybridisation (which I define here as producing a living ‘healthy’ adult) is a graded phenomenon: from being a high probability event (e.g. mules) to a very-low-to-zero probability event (e.g. ~1% turkey-chicken [from Chris' link]).

    OK, so can one say which species ‘wins’ in answer to my original question of “which are the most ‘distantly related’ species that have successfully reproduced?”.

    Can one objectively rank a chicken-pheasant hybrid as a more or less distant pairing than say, a camel-llama cross? Would the time of divergence be the sole factor? Would the degree of morphological divergence – regardless of when – play a part in the ranking?

    Just askin’…

  18. #18 Christopher Taylor
    February 16, 2010

    The problem, I think, would be coming up with a meaningful way of measuring ‘morphological divergence’ that would allow for comparisons. Even overall genetic divergence may not be directly informative because it has been shown that in at least some cases reproductive isolation may be dependent on a single gene.

    I also can’t resist mentioning the case of Wolbachia infection in insects where two individuals may be “cured” of reproductive isolation.

  19. #19 David Marjanović
    February 16, 2010

    Poster #15: I hope the “q” in your name is a typo!

    No, and neither is the u behind it. The second h is.

    OK, so can one say which species ‘wins’ in answer to my original question of “which are the most ‘distantly related’ species that have successfully reproduced?”.

    You need to define “distantly related” first.

  20. #20 Dartian
    February 16, 2010

    Darren:

    in theory we should expect to find babyrousines going back to the Oligocene

    Molecular data do not support such a contention. Randi et al. (1996)* estimated that the Babyrousa lineage diverged from other suids as recently as 10-19 MYA, i.e., in the Miocene.

    * 1996 was a while ago but I’m not aware of any more recent molecular studies of babyrousine origins; if anyone is, please tell.

    Reference:

    Randi, E., Lucchini, V. & Diong, C.H. 1996. Evolutionary genetics of the Suiformes as reconstructed using mtDNA sequencing. Journal of Mammalian Evolution 3, 163-194.

  21. #21 Andreas Johansson
    February 16, 2010

    Is it known how babirusas ended up with their aberrant upper canines? Did they somehow rotate upwards (passing through a stage of pointing out horizontally), or are we looking at a hopeful-monster type mutation?

  22. #22 Jerzy
    February 16, 2010

    Thanks for another pic of hybrids! I find it very strange that two look like white piglets, but the third is brown… can any zootechnology guru explain why?

    BTW – there are hybrids of chicken and several cracid genera – which old Sibley classified in different orders!

  23. #23 AnJaCo
    February 16, 2010

    You need to define “distantly related” first.

    My follow-on question (above) was a [perhaps weak] attempt to elicit a way to quantify how distantly related 2 taxa are, and a way to compare that to the distance between 2 other taxa.

    Is time of divergence any more or less important than morphological divergence? And how about DNA base-pair divergence?

    The World of Cladograms (a place I am obliged to visit but not reside) is loaded with language such as ‘taxon A consists of organisms closer to X than to Y’. I take the word “closer” to be the opposite of “more distantly related”. And since phylogenetic analyses are presumably time-free, then would not a cladist quantify the distance of a relationship solely on morphological distance/divergence regardless of when it happened?

    Another way to illustrate the dilemma:
    2 genera diverged in the Cretaceous, but their morphology remains very similar.
    2 other genera diverged in the Miocene, and their morphology differs radically.
    Which of these pairs is more distantly related? I presume that the cladist would say the latter without blinking. Am I wrong on that? And I would suggest that the time of divergence has to play some role in assessing distance of relationships.

    I suppose that all this is just my way of noting that when I find phrases in the literature such as “closer to” or “more distantly related” it is not always clear whether time of divergence or morphological divergence is what is being discussed. Unless its a cladogram. :-)

  24. #24 Allen Hazen
    February 16, 2010

    AnJaCo–
    I think I understand what you are saying, and that you are right in your understanding of what “cladists” say.
    My impression is that the phrase “more closely related to… than” is typically used in making three-way comparisons than in four-way. That is, usually in saying things like
    “X is more closely related to Y than to Z,”
    and only very infrequently (I can’t off hand recall seeing it in ANY technical literature in recent years) in saying things like
    “X is more closely related to Y than Z is to W.”
    The three-place comparison is the central concept of cladistics, and is defined as meaning that X and Y have a more recent common ancestor than X and Z or than Y and Z. Morphological similarities are taken as at best EVIDENCE for this, and sometimes misleading evidence: witness the standard trout/coelacanth/cow example, meant to show that fins and scales versus legs and hair ISN’T conclusive on the which is nearer to which question.

    My sense is that many cladists (and probably non-cladists) would say the four-place comparison is useless if not meaningless. Four-place comparisons of similarity can, I suppose, be useful in practice sometimes, but the useful ones are likely to be just matters of similarity, NOT of relatedness in the phylogenetic sense. Compare linguistic comparisons: it may be useful to say that English is more like German than Estonian is like Hungarian (or vice versa– I don’t know), but any practical interest in this (from the point of view of, say, predicting how easy it is for someone who speaks one language to learn another) is INDEPENDENT of the “phylogenetic” question of whether the diverrgence of the Gerrmanic languages is more or less recent than the divergence of the Finno-Ugrian languages.

  25. #25 Andreas Johansson
    February 16, 2010

    Estonian and Hungarian diverged long before English and German.

    (The English-German divergence, BTW, isn’t the basal one within the Germanic languages – exactly which is is disputed, but English and German both belong to the West Germanic sub-branch.)

  26. #26 DDeden
    February 16, 2010

    While humans and seals have BAT brown fat, 20ma domestic pig and wild boar ancestors (like penguins and marine iguanas) lost the ability to produce thermal brown fat due to mutation (so piglets must shudder or snuggle to get warm), does anyone know if babirusa also lack brown fat? http://www.physorg.com/news75117516.html

  27. #27 AnJaCo
    February 16, 2010

    Allen Hazen-

    You are right about the three-way vs. four-way comparisons. The former are de rigueur in the taxonomic literature while the latter are, well, I can’t recall any off hand.

    Going back to my original question:

    “Among tetrapods, which are the most “distantly related” species that have successfully reproduced?”

    This may be impossible to answer objectively.

    This pairing of the male babirusa with pigs was apparently the result of zoo keepers responding to perceived “depression” in the babirusa that was being housed alone. Now if only there was a zoo with a lonely pygmy hippo …

    I’d pay cash moneys to see those babies.

  28. #28 Christopher Taylor
    February 16, 2010

    My sense is that many cladists (and probably non-cladists) would say the four-place comparison is useless if not meaningless.

    Not necessarily meaningless, I would say, but probably too difficult to calculate in a meaningful manner in most cases. I think the big problem is that such comparisons almost always represent a major over-simplification. For instance, if we were comparing two pairs of languages as in your example above, the members of one pair might be more different in their verb formation, but the members of the other pair might be more different in their use of pronouns.

  29. #29 John Harshman
    February 16, 2010

    “More closely related” has a simple, even somewhat operational four-taxon meaning: time. If A and B diverged from each other more recently than C and D diverged from each other, then A and B are more closely related than C and D. This of course says nothing about the degree of morphological difference, though it’s at least somewhat related to overall genetic difference. The only other problem is in estimating divergence dates.

    But I suggest that by this definition, my duck/goose hybrids must be at least close to the vertebrate maximum. Good estimates are hard to come by, but I estimate a minimum of 30 million years divergence. Got anything better?

  30. #30 John Scanlon FCD
    February 16, 2010

    Not sure if it beats the duck-goose split, but pythons don’t seem to care much about miscegenation. A number of viable Morelia x Liasis crosses have been reported, as well as ones between the M. spilota and M. amethistina groups. Putting dates on these splits depends on the exact phylogenetic position of fossils I refer to Morelia from the early Miocene and late Oligocene; Rawlings et al. (2008) would make it about 35 my, but used a dodgy-looking tree and calibration procedure. I strongly suspect it will shorten a bit when the fossils are included explicitly and external calibrations are used as well, but may still be over 20.
    There’s also folks on the interwebs advertising things like Python m. bivittatus x Python reticulatus, which (because Broghammerus reticulatus is actually closer to the Australian lineage than to Python sensu stricto) is necessarily a deeper split than Morelia-Liasis (more than 45 my according to Rawlings et al.), and could well beat your goose-duck.

    Rawlings, LH, DL Rabosky, SC Donnellan and MN Hutchinson. 2008. Python phylogenetics: inference from morphology and mitochondrial DNA. Biol J Linn Soc 93: 603-619.

  31. #31 John Scanlon FCD
    February 16, 2010

    The hybrid python business is bigger than I realised, with some very decorative products out there (for example, gallery here). They certainly cross the deepest splits in the phylogeny, whichever tree you prefer (e.g. Python regius x Aspidites ramsayi!!!) without looking grossly deformed at all, and I gather that many of the crosses are fertile to some extent. I’ve long wondered whether some of the problems with phylogeny in the group are caused by hybrid origin of some species (I’m looking at you, Apodora papuana), but I don’t think the molecular evidence to test that is out there yet.

  32. #32 Dartian
    February 17, 2010

    John H. and John S.: I see your anatids and your pythons, and raise you sea turtles. Several chelonid species are known to hybridise in the wild (and there are even suggestions that the hybrids themselves may be fertile), and some such hybridisations have occurred between lineages that separated for more than 50 MYA (Karl et al. 1995; James et al. 2004).

    Also, Wilson et al. (1974) list a large number of anuran species that supposedly have hybridised under laboratory conditions; some of these hybridisations might conceivably be between members of even more anciently diverged lineages than in the case of the sea turtles (though I haven’t yet looked up what the most recent frog and toad phylogenies say).

    References:

    James, M.C., Martin, K. & Dutton, P.H. 2004. Hybridization between a green turtle, Chelonia mydas, and loggerhead turtle, Caretta caretta, and the first record of a green turtle in Atlantic Canada. The Canadian Field-Naturalist 118, 579-582.

    Karl, S.A., Bowen, B.W. & Avise, J.C. 1995. Hybridization among the ancient mariners: characterization of marine turtle hybrids with molecular genetic assays. Journal of Heredity 86, 262-268.

    Wilson, A.C., Maxson, L.R. & Sarich, V.M. 1974. Two types of molecular evolution. Evidence from studies of interspecific hybridization. PNAS 71, 2843-2847.

  33. #33 Dartian
    February 17, 2010

    AnJaCo:

    This pairing of the male babirusa with pigs was apparently the result of zoo keepers responding to perceived “depression” in the babirusa that was being housed alone.

    Desmond Morris wrote in one of his books (can’t remember which) of a case where an Old World porcupine and a New World porcupine were housed together in a zoo cage. The animals were of different genders (can’t remember which one was which, but that doesn’t really matter) and the male tried to mate with the female. That, however, turned out to be a very painful experience for the male, due to a different arrangement of the quills on the other, very distantly related species’ back…

  34. #34 AnJaCo
    February 17, 2010

    Dartian:

    1. Youch!
    2. Males. Heh heh. Gotta love ‘em.

    I’d wager that most/all of these fascinating hybridisations were instigated by the males.

    – – –

    Gratuitous comment for these Flag Waving-Olympic Days:
    If you haven’t looked at John Scanlon FCD’s link to the gallery of hybrid pythons/boas, check out the red, white, and blue hybrid Emerald Tree Boa (Corallus caninus) x Amazon Tree Boa (Corallus hortulanus). (If you are French: check out the bleu, blanche, et rouge hybrid…). (BTW, how do Brits list their colours?). Not your usual color combo in a snake.

  35. #35 David Marjanović
    February 17, 2010

    Those python and sea turtle hybrids are mind-blowing…

    Is time of divergence any more or less important than morphological divergence? And how about DNA base-pair divergence?

    You choose.

    The World of Cladograms (a place I am obliged to visit but not reside) is loaded with language such as ‘taxon A consists of organisms closer to X than to Y’.

    Well, definitions of taxon names like this are phylogenetic nomenclature, not cladistics…

    I take the word “closer” to be the opposite of “more distantly related”. And since phylogenetic analyses are presumably time-free, then would not a cladist quantify the distance of a relationship solely on morphological distance/divergence regardless of when it happened?

    Neither nor. If A and B share a common ancestor with each other but not with C, they’re more closely related to each other than to C. That’s the cladistic definition of “more closely related”.

    My sense is that many cladists (and probably non-cladists) would say the four-place comparison is useless if not meaningless.

    Pretty much.

    Choosing absolute time as a criterion only leads back to the question if rates of morphological-or-whatever evolution should be considered…

  36. #36 John Conway
    February 17, 2010

    I think a big part of what makes hybridisation interesting is morphological divergence. So even if we could settle on a different metric for relatedness, we’d come up with a boring winner.

  37. #37 Darren Naish
    February 17, 2010

    Wow, awesome, very interesting discussion – thanks to all. A few select responses.

    Remember that the article at top was written in 2007, and I haven’t had time to update it. The whole ‘babyrousines may have diverged in the Oligocene’ thing (see comments 3 and 20) comes from statements in Thenius (1970) and Groves (1980). However, I should have changed this in view of Randi et al. (1996) and other publications. Will alter article.

    Regarding ‘long distance’ hybrids, the python and sea turtle examples given above are pretty incredible (I was aware of the turtles, but not the more obscure pythons). The example I usually give is also Riversleigh-inspired: it involves hybridisation between the Australian lizards Egernia cunninghami (Cunningham’s skink) and the bluetongue Tiliqua scincoides. Both are relatively common species in captivity (Cunningham’s is, I’m sorry to say, the only Egernia species I’ve ever seen). Fossils often said to be of Egernia are known from the Miocene, so are perhaps 15-20 million years old… though whether they’re Egernia in the strict sense is now questionable I think (Gardner et al. (2008) showed that Egernia sensu lato represents four clades, and they restricted the name Egernia to the lineage that includes Cunningham’s skink). Anyway… a 15-20 Ma divergence that still ‘permits’ hybridisation is no longer so impressive given some of the other examples discussed here.

    Anurans: Wilson et al. (1974) do list a load of anuran hybrids (comment 32), but most are between species in traditional ‘genera’ like the over-bloated monster that is Bufo sensu lato. Using the new taxonomy (toads have been featured once or twice on Tet Zoo, in case you didn’t know), some of these hybrids are between such genera as Anaxyrus and Epidalea, and therefore occur betweeen taxa that have been separated since some time in the Oligocene at least. In other words, a separation of about 30 million years.

    Refs – –

    Gardner, M. G., Hugall, A. F., Donnellan, S. C., Hutchinson, M. N. & Foster, R. 2008. Molecular systematics of social skinks: phylogeny and taxonomy of the Egernia group (Reptilia: Scincidae). Zoological Journal of the Linnean Society 154, 781-794.

    Groves, C. P. 1980. Notes on the systematics of Babyrousa (Artiodactyla, Suidae). Zoologische Mededelingen 55, 29-46.

    Randi, E., Lucchini, V. & Diong, C.H. 1996. Evolutionary genetics of the Suiformes as reconstructed using mtDNA sequencing. Journal of Mammalian Evolution 3, 163-194.

    Thenius, E. 1970. Zur Evolution und Verbreitungsgeschichte der Suidae (Artiodactyla, Mammalia). Zeitschrift für Säugetierkunde 35, 321-342.

    Wilson, A. C., Maxson, L. R. & Sarich, V. M. 1974. Two types of molecular evolution. Evidence from studies of interspecific hybridization. Proceedings of the National Academy of Sciences 71, 2843-2847.

  38. #38 Adam Yates
    February 17, 2010

    The Egernia cunninghami X Tiliqua scincoides hybrid that Darren mentions actually spans a slightly older divide than the Miocene. Tiliqua fossils are known from late Oligocene / earliest Miocene of Riversleigh. These are much more apomorphic than plain old Egernia so the id is more secure. Note that this fossil is already diagnostic for Tiliqua , meaning that Cyclodomorphus and the Egernia luctuosa groups (which split from the Tiliqua lineage after Egernia s.s.) must have already diverged by the beginning of the Miocene.

  39. #39 Darren Naish
    February 17, 2010

    Cool, thanks for that Adam. It was thanks to you that I learnt of this stuff in the first place. Hey, I can’t remember my phone number, my wife’s birthday or which mobile network I’m on, but I can remember a conversation about fossil skinks that happened more than 10 years ago :)

  40. #40 Darren Naish
    February 17, 2010

    Incidentally, the Egernia luctuosa group is now Lissolepis Peters, 1872… again.

  41. #41 Adam Yates
    February 17, 2010

    Thats cool Darren, I’m glad I make an impression on someone. However I have to add that what I wrote just minutes ago is actually inaccurate. I said that The Egernia luctuosa group had diverged after Egernia s.s. had diverged from Tiliqua. According to Gardner et al. the luctuosa group (for which they coin a new name) is actually basal to the whole lot. My statement was based on my recollection of a conversation I had with Mark Hutchinson years ago on what was then unpublished work. Whether my memory is simply faulty or whether new data caused the position of the luctuosa group to change dramatically I do not know.

  42. #42 Adam Yates
    February 17, 2010

    OOPs again! damn, I must read carefully before typing. OK Lissolepis is NOT a new genus, but a ressurection of an old one

  43. #43 Darren Naish
    February 17, 2010

    If anyone’s interested, the Riversleigh Egernia/Lissolepis (originally named Proegernia) were described in…

    Martin, J. E., Hutchinson, M. N., Meredith, R., Case, J. A. & Pledge, N. S. 2004. The oldest genus of scincid lizard (Squamata) from the Tertiary Etadunna Formation of South Australia. Journal of Herpetology 38, 180-187.

    … and it states therein that the fossils are Late Oligocene, so I was being dumb in mentioning Miocene. Anyway, the divergence is pegged at something like 30 million years ago. John Scanlon’s gonna be peeved that he missed all this :)

  44. #44 Squiddhartha
    February 17, 2010

    For the record, neither the q (with its u) nor the h are typos. They’re there on purpose.

    Thanks to AnJaCo for answering my question!

  45. #45 Blackbird
    February 17, 2010

    Sorry to be a party spoiler, but has anybody considered that the female pig was already pregnant when housed with the male babyrusa? Those little piglets look just like little piglets to me! I want proof -some genetic analysis should be easy enough. Things would have been easier to believe if it had been a female babyrusa in the zoo.

  46. #46 John Scanlon FCD
    February 17, 2010

    Darren, for someone supposed to be too busy to blog…

    (I was aware of the turtles, but not the more obscure pythons)

    …you seem to be overcompensating for that ‘snake guilt’ you mentioned a while back. What did I miss to be peeved about? – Of course I knew that Egernia-group skinks hybridise like mad and have some sort of fossil record (not only at Riversleigh; the Etadunna Fm is in South Australia) and calibrated phylogeny, but it slipped my mind because they’re only good for snake food.
    Actually most are too big and bony-scaled for that, but, well, skinks. I get lots of ‘em in the late Oligocene stuff I’m working on, but not Proegernia or Tiliqua, just Eulamprus-like water skinks and a couple of smaller things. Lollies for Nanowana.

  47. #47 Dartian
    February 18, 2010

    Slightly off-topic, but regarding mammalian hybrids, I can’t resist mentioning that in Maracay Zoological Park, Venezuela, several hybrid offspring between a male spectacled bear Tremarctos ornatus and a female Asian black bear Ursus thibetanus have been born over the years. That is mentioned here; unfortunately, that site has no pictures of the hybrid bears*. (There is a photo of the spectacled bear and the black bear shagging, though.) What makes this noteworthy is the fact that the spectacled bear and the Asian black bear are quite distantly related; the clade Tremarctini and the clade Ursini diverged from each other in the mid-Miocene, about 12.4-15.6 MYA, according to a recent molecular estimate (Krause et al. 2008). By mammalian standards (if not by reptilian), hybridisation between members of so anciently diverged lineages is pretty remarkable.

    * There appears to be a technical paper describing the first of these hybrids (Mondolfi & Boede 1981), but, alas, I’ve not seen it.

    Back to pig phylogeny; Funk et al. (2007), while not primarily investigating the phylogenetic position of Babyrousa, incidentally noted that it is far from certain that it really is the most basal extant suid. In their words, ‘[u]nderstanding evolutionary relationships between the genera of Suidae will require further sampling and sequencing, especially for Babyrousa and Potamochoerus‘ (p. 433). (Funk et al. also reported that according to molecular data, inclusion of the pygmy hog in Sus would make this genus paraphyletic, and they thus recommended placing the pygmy hog in a separate genus, Porcula.)

    References:

    Funk, S.M., Verma, S.K., Larson, G., Prasad, K., Singh, L., Narayan, G. & Fa, J.E. 2007. The pygmy hog is a unique genus: 19th century taxonomists got it right first time round. Molecular Phylogenetics and Evolution 45, 427-436.

    Krause, J., Unger, T., Noçon, A., Malaspinas, A.-S., Kolokotrinis, S.-O., Stiller, M., Soibelzon, L., Spriggs, H., Dear, P.H., Briggs, A.W., Bray, S.C.E., O’Brien, S.J., Rabeder, G., Matheus, P., Cooper, A., Slatkin, M., Pääbo, S. & Hofreiter, M. 2008. Mitochondrial genomes reveal an explosive radiation of extinct and extant bears near the Miocene–Pliocene boundary. BMC Evolutionary Biology 8(220), doi:10.1186/1471-2148-8-220

    Mondolfi, E. & Boede, E.O. 1981. A hybrid of a spectacled bear (Tremarctos ornatus) and an Asiatic black bear (Selenarctos thibetanus) born at the Maracay Zoological Park, Venezuela (Mammalia; Ursidae). Memoria de la Sociedad de Ciencias Naturales La Salle 41, 143–148.

  48. #48 Darren Naish
    February 18, 2010

    Blackbird (comment 45): the domestic pig was definitely not already pregnant.

    John (comment 46): in terms of ‘what you missed’, I was referring to the whole fossil skink discussion. I wrote my comments as if all of the fossils were from Riversleigh, and forgot that the Etadunna Formation had been important in the story too (however, Egernia sensu lato is still present at Riversleigh).

    Dartian (comment 47): thanks for the refs. Interesting, then, that all of the claims made pre-2006 about ancient divergence of babirusas may well be erroneous. And, a reminder to anyone who didn’t know: my babirusa articles are recycled from Tet Zoo ver 1, were written in 2006, and have not been updated.

  49. #49 Graham King
    February 18, 2010

    yay, Babirusas!
    (Why are the genus and species parts of name Babyrousa babirussa spelt (pronounced?) differently?)
    Looking at the skull photo, I wonder whether, developmentally, the upper tusks (or their toothbuds) start out oriented like normal teeth and then rotate out and up.. If so, at what embryonic stage?.. or whether they form directed upward like that from the start.

    My sister had to have a tooth removed in her early teens that was growing horizontally in the roof of her mouth, rather than in a tooth-row at all. How rare is that?

  50. #50 Graham King
    February 18, 2010

    Oh, now I see the answer to my second question given in Darren’s Part III.

  51. #51 David Marjanović
    February 18, 2010

    (Why are the genus and species parts of name Babyrousa babirussa spelt [...] differently?)

    Because in the 19th century people found it funny to do this to names from “exotic languages”. There are a few more such names.

    My sister had to have a tooth removed in her early teens that was growing horizontally in the roof of her mouth, rather than in a tooth-row at all. How rare is that?

    Happens to wisdom teeth fairly often.

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