Pharyngula

Materpiscis attenboroughi

Blogging on Peer-Reviewed Research

It’s not often that something as delicate as details of the reproductive tract get preserved, but here’s a phenomenal fossil of a Devonian placoderm containing the fragile bones of an embryo inside, along with the tracery of an umbilical cord and yolk sac.

This is cool: it says that true viviparity, something more than just retention of an egg internally, but also the formation of specialized maternal/embryonic structures, is at least 380 million years old. Hooray for motherhood!

Here’s a reconstruction of what the animal would have looked like in life, as it is giving birth to its young.

i-30bbeb003e04870f189ebaceaad2bd5b-materpiscis_recon.jpg
a, Diagram showing position of embryo and yolk sac within the mother. b, Artist’s reconstruction of Materpiscis gen. nov. giving birth.

Long JA, Trinajstic K, Young GC, Senden T (2008) Live birth in the Devonian period. Nature 453:650-652.

Comments

  1. #1 Lord Zero
    May 29, 2008

    This its so awesome!!! Horaay for paleontologists i say!!
    An umbilical cord… great… i never thought vivipary would
    be so old. You devil evolution, you never cease to impress me… i going to marry it…
    Ah, haaa!… now im going to correct my reproducction class
    in order to reflect this new discovery…

  2. #2 Brownian, OM
    May 29, 2008

    This is cool: it says that true viviparity, something more than just retention of an egg internally, but also the formation of specialized maternal/embryonic structures, is at least 380 million years old. Hooray for motherhood!

    Ah, but how long has Hallmark been trying to guilt us into buying a $5.99 card every May?

  3. #3 SC
    May 29, 2008

    Awesome.

    I like the artist’s reconstruction, too. Nicely done.

  4. #4 GBruno
    May 29, 2008

    P.Z. or anyone -

    Can you explain the relationship between placental development and endogenous retroviruses?

    Thanks.

  5. #5 Serena
    May 29, 2008

    That is very very cool!
    Fossils are bit bitter sweet for me though. I want to know Everything about each one that is found, but what with them being dead and all…..there is some limit. Still awesome.

    “Materpiscis attenboroughi” I assume thats a nod to The David Attenborough. Also very nice.

    Can anybody tell me when it was thought that viviparity had developed? Does this find change what we previously thought?

  6. #6 SteveM
    May 29, 2008

    I don’t mind being the one to ask the stupid question… is this creature named for Sir David? Did he discover it?

  7. #7 Josh
    May 29, 2008

    I just checked and confirmed on the Nature website, they didn’t capitalize Period after Devonian in the title. I’ll have to go check my library, but I never noticed them not doing that before. That’s odd.

  8. #8 Sam B
    May 29, 2008

    Wow, that is an incredible find.

    The embryo in diagram ‘a’ looks really creepy though…

  9. #9 Lord Zero
    May 29, 2008

    Ah, i forgot to mention the ilustration… beautiful…
    I would love to have one of these on my acuarium. Ill check
    the nature magazine right away.

  10. #10 wazza
    May 29, 2008

    GBruno: Basically, ERV3, the virus found whole in the human genome (well, it’s got a couple of introns, but it’s all there) has a gene that tells the immune system to ignore it, which is useful when you’re on the attack against a system that destroys anything foreign. In this case, though, the foreign body isn’t a bacterial or viral infection, but the father’s genes. A baby can essentially be viewed as a sort of parasite on the mother, taking its food and sheltering in its body, and so it needs to be protected from the immune system, which doesn’t recognise it as part of itself. Hence the virus. At some point in our history, we snaffled it up whole (that’s how retroviruses work, they insert themselves into the genome and then get copied out, and one had to get stuck sooner or later) and started using that gene to protect eggs from being attacked by the mother’s immune system. That made it possible for the eggs to stay in the body, which opened up all the various viviparous strategies seen today.

  11. #11 GBruno
    May 29, 2008

    Thanks so much, Wazza. That was very helpful.

    If you don’t mind, can you explain the relationship (if any) between ERV’s and LINES & SINES?

    Thanks.

  12. #12 arachnophilia
    May 29, 2008

    placoderms FTW.

  13. #13 windy
    May 29, 2008

    That made it possible for the eggs to stay in the body, which opened up all the various viviparous strategies seen today.

    Just a clarification: in placental mammals. We don’t know how the other animal groups including Materpiscis got theirs.

  14. #14 Ichthyic
    May 29, 2008

    Have you embraced your inner fish today?

  15. #15 Dave Godfrey
    May 29, 2008

    The species is indeed named for Sir David Attenborough, who helped publicise the Gogo fossils when they were first found.

    Anyway, Placoderms are deeply cool, and its very interesting that they’ve also evolved viviparity like sharks (which may or may not be their closest living relatives depending on who you believe).

  16. #16 SeeMoreGlass
    May 29, 2008

    GBruno:
    Maybe you have your answer already, but Frank Ryan has a good review of human endogenous retroviruses and talks a good deal about their role in mammalian placental development. He writes:

    “Certain viruses have the capacity to fuse mammalian cells into confluent multinucleated sheets of tissue. Multinucleated giant cells are a pathological feature of AIDS. Fusion of cells is also a characteristic feature of the mammalian placenta, where a microscopically thin and confluent tissue layer known as the syncytium forms the physiological barrier between maternal and fetal circulations. All nutrients from the mother and waste from the fetus must pass through this syncytial layer. The syncytium also serves to prevent maternal immune rejection of the fetus, which inherits half of its antigens from the father. There is growing evidence that endogenous retroviruses contribute importantly to the structure and function of the syncytium.”

    So as well as telling the immune system to bugger off, genes from ERVs seem to play a central role in actually forming part of the physical structure of the placenta to begin with.

    ____

    Separately, about the diagram: is the fish being born tail-first? Is there a reason for that? Seems strange.

  17. #17 Glen Davidson
    May 29, 2008

    OT, but very interesting:

    Where do you get your genes? If you are an animal, you inherit them from your parents at the moment of conception, and that’s about it. No later incorporation of environmental DNA for you, unless you become host to a parasite or an endosymbiont that somehow transfers bits of its genome into yours (which is a rarely documented event). Unless you are a bdelloid rotifer, that is.

    This odd, microscopic, freshwater animal is making news once again, this time for the startling discovery of numerous chunks of foreign DNA in its genome. In a paper published this week in Science, evidence for massive horizontal gene transfer–from bacteria, fungi, even from plants–into the bdelloid rotifer genome is presented by Irina Arkhipova and Matthew Meselson, scientists at the MBL’s Josephine Bay Paul Center and at Harvard University, and Harvard graduate student Eugene Gladyshev.

    While horizontal gene transfer is common in bacterial species, it was unheard of in the animal kingdom on such a massive scale – until this study.

    “It is quite amazing that bdelloids are able to recruit foreign genes, which were acquired from remarkably diverse sources, to function in the new host,” says Arkhipova. “Bdelloids may have the capacity for tapping into the entire environmental gene pool, which may be of (evolutionarily) adaptive significance during expansion into new ecological niches, and may even contribute to bdelloid speciation,” she says.

    This finding may help to explain why bdelloids, which are exclusively asexual, have managed to diversify into more than 360 species over 40 million years of evolution. Sometimes called an “evolutionary scandal,” bdelloids contradict the notion that sex- which recombines the DNA from the parents in their offspring-confers diversity and greater adaptability on a population, thereby boosting its evolutionary success. Arkhipova’s study suggests that if bdelloids can incorporate foreign DNA from their environment, they could also pick up DNA from other bdelloids which, from an evolutionary standpoint, is almost as good as having sex.

    How bdelloids have been able to gobble up such a variety of genes from their environment and incorporate it into their genome is a good question. Typically in animals, the germ line-the heritable egg and sperm cells-are protected from environmental assaults, such as intrusion of foreign DNA, by the rest of the body cells, which are not heritable and serve to “sequester” the germ line. Ideas on why the bdelloids’ germ line is so exposed to environmental exchange, Arkhipova says, “are all speculative. But we talk about this a lot!”

    One clue is the unusual ability of bdelloids to survive total desiccation (drying out), which is fatal for most organisms. When water disappears from their environment, bdelloids enter a kind of suspended, dehydrated state, and can stay there for months or even years. But once water returns, they spring back to action, move around, eat things, and start reproducing again.

    During the desiccation phase, Arkhipova says, “you would imagine there is potential for membrane damage and DNA damage in the rotifer. And not only the rotifer desiccates, but also everything it just consumed.” If the DNA of both the rotifer and its food are broken up during desiccation, “this would provide an opportunity for the (foreign) DNA to enter the rotifer’s germ line. During rehydration, the DNA breakage is somehow repaired, and the foreign DNA may get incorporated,” she says.

    This idea was inspired by recent work by Gladyshev and Meselson (2008) that showed bdelloids are exceptionally good at recovering from ionizing radiation, which shatters their DNA. The rotifers’ talent for repairing DNA breaks may have evolved due to their desiccation-prone lifestyle. “The effects of radiation and desiccation may be quite similar and involve damage to chromosomal DNA as well as membranes,” Arkhipova says.

    Most of the foreign genes that Arkhipova’s team found in the bdelloid genomes were clustered near the tips of chromosomes, called the telomeres. If the bdelloids are picking up foreign DNA during desiccation, “it may be occasionally added to deprotected telomeres, as we previously demonstrated for mobile elements (Gladyshev and Arkhipova, 2007),” Arkhipova says. “Or it may simply not be selected against as efficiently as the more deleterious DNA insertions into the central, gene-rich regions of the chromosome.”

    http://www.physorg.com/news131296402.html

    Glen D
    http://tinyurl.com/2kxyc7

  18. #18 GBRuno
    May 29, 2008

    Thanks, SMG, that it helpful. I’m still wondering if ERV’s are a component of LINES & SINES or something completely non-related. Any thoughts?

  19. #19 Sili
    May 29, 2008

    “Motherfish” – how sweet.

  20. #20 Stanton
    May 29, 2008

    Separately, about the diagram: is the fish being born tail-first? Is there a reason for that? Seems strange.

    It’s how (viviparous) sharks are born.

  21. #21 windy
    May 29, 2008

    I’m still wondering if ERV’s are a component of LINES & SINES or something completely non-related.

    There is a type of transposable element, “LTR (long terminal repeat) retrotransposon”, which is very closely related to retroviruses but lacks the envelope protein. SINEs and LINEs are “non-LTR retrotransposons” and are less like viruses – I don’t know if they are completely non-related or not.

  22. #22 amplexus
    May 29, 2008

    “Materpicis” Translates as “Motherfish”. If I ever manage to break into the field of science i’m going to name some things after rockstars. Like the protien “Jimorrisin” Or the flower:”hendrixcies purpea hazea”

  23. #23 amplexus
    May 29, 2008

    “Materpicis” Translates as “Motherfish”. If I ever manage to break into the field of science i’m going to name some things after rockstars. Like the protien “Jimorrisin” Or the flower:”hendrixhazea purpea” And name parasites after Bill O’ Reilly and bunch. Preferably one of those symbiotic fish that eats shark feces.

  24. #24 Becca
    May 29, 2008

    That’s just the most beautiful thing I’ve seen all day.

  25. #25 Lancelot Gobbo
    May 29, 2008

    It reminds me of the ‘Nightmares’ in Pathways Into Darkness!

  26. #26 Ichthyic
    May 29, 2008

    Separately, about the diagram: is the fish being born tail-first? Is there a reason for that? Seems strange.

    actually, IIRC, many viviparous sea-bound vertebrates, mammals included, give birth tail first.

    In the case of mammals, the advantage is obvious: you want the blowhole to be the last thing that exits, when the umbilical cord is broken.

    as to why organisms that breathe water are born tail-first?

    well, hard to say, given that some of them do both head and tail first (like surfperches).

    In some cases, it appears that tail-first birth is the least harmful to the mother (rays), so there might have been some precedent with a common ancestor that just carried over as drift.

    strangely enough, with all the years I’ve spent working with fish, I don’t recall ever discussing this particular pattern before.

  27. #27 OrchidGrowinMan
    May 29, 2008

    OK,

    Latin: I has it.
    Some new Slime-Mold Beetles are named
    Agathidium bushi Miller and Wheeler
    A. cheneyi Miller and Wheeler
    A. rumsfeldi Miller and Wheeler
    http://www.news.cornell.edu/stories/april05/slime-mold.bush.cheney.ssl.html

    http://home.earthlink.net/~misaak/taxonomy/taxPuns.html

    Chemical names too: http://www.chm.bris.ac.uk/sillymolecules/sillymols.htm
    (Hmm. “Moronic acid”! “Spamol” “Constipatic acid”: What would you call their ester? “Spamyl Constipate”?)

  28. #28 Jaycubed
    May 29, 2008

    Oh Dear,

    I got so excited I Spilt my Milt.

    .

  29. #29 Hematite
    May 29, 2008

    Wow! Thanks wazza for a great answer, GBruno for asking a question I didn’t know enough to ask myself, Glen Davidson for the great link on bdelloid rotifers, and most of all PZ for making this all possible!

    I am filled with the great feeling of knowing much more than I did 10 minutes ago!

  30. #30 David Marjanovi?, OM
    May 29, 2008

    I just checked and confirmed on the Nature website, they didn’t capitalize Period after Devonian in the title. I’ll have to go check my library, but I never noticed them not doing that before. That’s odd.

    I can’t remember having ever seen a geologist or paleontologist capitalizing “period”.

    During rehydration, the DNA breakage is somehow repaired

    Not “somehow”. A recent paper said it has to do with their being tetraploid — they can use the fragments as templates for each other, because no chromosome breaks in the same places when it breaks apart at random.

    In the case of mammals, the advantage is obvious: you want the blowhole to be the last thing that exits, when the umbilical cord is broken.

    Same for ichthyosaurs.

  31. #31 Spinoza
    May 29, 2008

    Materpiscis is a great name for that fish!

  32. #32 Scott
    May 29, 2008

    I know nothing about how fossils are interpreted, but can they really tell the difference here between developing embryonic bones, and a small fish that the larger one might have eaten whole? How can they tell the difference between a recrystalized yolk sack, and some other internal organ? Can they actually get some kind of residual chemical signature from the remains, or might it be microscopic analysis? It’s just that the placement of the smaller creature seems kind of problematic for either interpretation, and to these untrained eyes one small lump of stone-link stuff looks like a lot of other lumps. :-)

    Did they give any estimates on the uncertainties in their interpretation? Does that even make sense in this kind of analysis?

  33. #33 Ichthyic
    May 29, 2008

    but can they really tell the difference here between developing embryonic bones, and a small fish that the larger one might have eaten whole?

    yes. It’s not that hard, actually.

    How can they tell the difference between a recrystalized yolk sack, and some other internal organ?

    placement, structure.

    Can they actually get some kind of residual chemical signature from the remains

    not in this case. typically fossilization replaces tissue/bone with mineral. rarely (thinking certain dino bones that shall go nameless) some “tissue” gets preserved, but that’s very much the exception.

    or might it be microscopic analysis?

    yup. in many cases, very fine detail is preserved as imprint or via the mineralization process, and can indeed shed light on exactly what the original structure was.

    Did they give any estimates on the uncertainties in their interpretation? Does that even make sense in this kind of analysis?

    not really, though there are several lurking paleos that would have more to say on the subject.

  34. #34 Ichthyic
    May 29, 2008

    btw, I don’t recall seeing it mentioned yet, but that critter looks remarkably like modern Chimaeridae (ratfishes).

    http://en.wikipedia.org/wiki/Chimaera

    I think, like most chondrichthyans, they show a range of reproductive strategies from viviparity to oviparity, with oviparity being most common.

    I do recall reading a paper on the evolution of reproductive strategies in chondrichthyans a while back, but am now wondering if this new find will modify their conclusions somewhat:

    http://www.sfu.ca/biology/faculty/reynolds/documents/Dulvy_Reynolds_PRS_97.pdf

  35. #35 Vince
    May 29, 2008

    Thanks for sharing fossil on the placoderm as well as the cool scientific name. Here’s two I used these when I was teaching middle school science. There are many more that kids find amusing.

    Zappa confluentus – a fish, for Frank Zappa

    Strigiphilus garylarsoni – a louse, for Gary Larson

    I had a long list. It’s buried in my notes somewhere.

  36. #36 Crudely Wrott
    May 29, 2008

    I noticed an article about this new fossil find on a newswire earlier. As is expected, the article put no flesh on the bare bones of the find. For that I come here and the information content indicator is pegged. Much obliged to all of you who ask the next question and to those of you who answer with such obvious enjoyment. Just one more reason why I really like this place. Thank you, PZ, for the ahh, ambiance.

    Think of it. The remains of a fish 380 million years old. A female, we know, because she still carries her tiny offspring. They are the oldest pair of their kind known. We call them Mother Fish. They are placoderms and I can’t shake the notion that the sight of the remains has a placid appearance, the arrangement of mother and child looks familiar, correct, as it should be. And just a moment ago, according to a clock that runs deeper than mine, this small bit of rock was a mother about to give birth. There is deep connection here and palpable continuity.

    All from a handful of stone. Yeah. How ’bout them fossils, anyway? And how the ground just keeps spittin’ ‘em out, one after another. Most useful teaching aids.

  37. #37 Cory Albrecht
    May 29, 2008

    It that actually true viviparity? Given that it has what is called a “yolk sack” rather than a placenta, wouldn’t that make placoderms ovoviviparous like guppies and platies rather than viviparous like mammals and splitfins?

  38. #38 Patricia C.
    May 29, 2008

    I am confused by this picture. In chickens the baby chick draws in the yolk sac just before hatching and can survive 2 to 3 days without food or water. Hence the shipping of day old chicks by mail all over the USA.
    So is this what this baby fish will do? The picture shows it hooked to it’s yolk sac. Or do we know what happens just before birth?

  39. #39 genesgalore
    May 30, 2008

    380 million years is a long time. it really is amazing what one species has destroyed in the last 70,000.

  40. #40 Malcolm
    May 30, 2008

    GBruno,
    Do a search for Peg10
    I think it is the retrovirus derived gene you were looking for.

  41. #41 David Marjanovi?, OM
    May 30, 2008

    can they really tell the difference here between developing embryonic bones, and a small fish that the larger one might have eaten whole?

    Isn’t it too big for that?

    I do recall reading a paper on the evolution of reproductive strategies in chondrichthyans a while back, but am now wondering if this new find will modify their conclusions somewhat:

    Er, no, because it’s not a chondrichthyan. The placoderms appear to be the sister-group of all other gnathostomes combined — in other words, the chondrichthyans are more closely related to us than to the placoderms.

    Or do we know what happens just before birth?

    No, because we have this one specimen.

    ———————————–

    I’ll try to read the paper today.

  42. #42 David Marjanovi?, OM
    May 30, 2008

    Only this one specimen, I mean.

  43. #43 DaveH
    May 30, 2008

    Vince and Serena. Sir David A also got Zaglossus attenboroughi , a long-nosed echidna! I am utterly jealous, he gets all the cool species

  44. #44 Josh
    May 30, 2008

    I can’t remember having ever seen a geologist or paleontologist capitalizing “period”

    David, see (just random stuff I had and could lay my hands on quickly):

    Nichols, 2003. Journal of Asian Earth Sciences 21, no.8, p. 823-833.
    Mancinelli et al. 2003. Cretaceous Research 24, no.6, p. 729-741.
    Boland et al. 2003. Economic Geology 98, no.4, p. 787-795.
    McBride et al. 2003. Tectonophysics 368, no.1-4, p. 171-191.
    Grimaldi et al. 2003. Journal of Paleontology 77, no.2, p. 368-381.
    Zheng et al. 2002. Geophysical Journal International 151, no.2, p. 654-662.
    Sheehan et al. 2000. Geology 28, no.6, p. 523-526.

    I also found many papers where period wasn’t capitalized (and Nature seems consistent in not doing it). Seems there is a rather large amount of disagreement among the various journals. I just found it odd, since Period is a formal designation. I didn’t ever really notice the lack of agreement.

  45. #45 SteveM
    May 30, 2008

    I just found it odd, since Period is a formal designation. I didn’t ever really notice the lack of agreement.

    Regardless of the science, doesn’t grammar demand that it be capitalized when it is in the title?

  46. #46 Josh
    May 30, 2008

    Regardless of the science, doesn’t grammar demand that it be capitalized when it is in the title?

    Apparently not…
    They didn’t capitalize “birth” in the the title either (that’s in the spirit of your question, right?). The journals follow whatever internally consistent style guide that they set up for themselves. The guides are very different between journals.

  47. #47 thalarctos
    May 30, 2008

    Regardless of the science, doesn’t grammar demand that it be capitalized when it is in the title?

    There are (at least) two different styles for titles.

    This Is An Example of the First Style

    and

    This is an example of the second style.

    So only Devonian is capitalized in that style, and that’s only because it’s a proper noun.

  48. #48 Josh
    May 30, 2008

    So only Devonian is capitalized in that style, and that’s only because it’s a proper noun.

    Indeed, although Nature seems to not capitalize Period as a rule, which struck me as odd with respect to what I know regarding rules of stratigraphy and such. But, as I indicated above, I had somehow missed that numerous journals do not use a capitalized Period when writing out the formal unit (e.g., Permian period).

  49. #49 raven
    May 30, 2008

    Apparently it isn’t that hard to evolve a placenta. There are placental sharks, placental lizards, and placental mammals.

    And now a placental placoderm from a long time ago. There may as well have been placental marine reptiles, ichthyosaurs, pleisiosaurs, mosasaurs. The gave birth to live young but whether they were ovoviparious or placental might be known but not by me.

    The old biology textbook, mammals give birth to live young was way too simple. Some mammals don’t and many other groups of vertebrates do.

  50. #50 John Scanlon, FCD
    May 30, 2008

    Everyone I know, most of the time both in ordinary discourse and in technical writing, uses terms like Devonian, Mesozoic, Maastrichtian etc. as proper nouns (referring to specific time intervals) and adjectives (referring to the life, rocks, climate etc. of the time). They are quite capable of standing by themselves, without appending ‘Period’ or ‘Era’ or ‘Epoch’. This has a lot in common with rankless taxonomy of organisms: Primates, or Archosauria, or Hominini can be given precise definitions that make them real things, not abstract categories, so they don’t need to be propped up with ‘Order’, ‘Subclass’, ‘Tribe’ etc.
    When I used ‘Oligo-Miocene’ as a noun (meaning an informal, fuzzily defined time interval spanning the Oligocene-Miocene boundary) in the title of a paper and had it accepted in Nature, it created a problem for their subeditors which, I suspect, delayed the publication by at least several weeks. They read their style guide as demanding that Oligocene or Miocene (when referring to the time intervals, i.e. as nouns) needed to be followed by the word ‘Epoch’ even though that wouldn’t add anything to the meaning. And in this case, as I told them, it would have been quite wrong, because there just isn’t an Oligo-Miocene Epoch by anyone’s definition. Eventually it ended up back on Henry Gee’s desk and the paper came out with my original wording.
    It was very like another paper, in a slightly less prominent journal, where I’d specifically stated that I wouldn’t use categorical ranks for taxa above that of genus, and a bloody editor (after I’d checked the proofs, and without asking) went and stuck ‘Family’ in front of a perfectly good clade name that just happened to end in ‘-idae’.
    Materpiscis is a viviparous Devonian placoderm, it lived in the Devonian. Period.

  51. #51 johannes
    May 30, 2008

    > btw, I don’t recall seeing it mentioned yet, but that critter looks
    > remarkably like modern Chimaeridae (ratfishes).

    Many scientists considered placoderms to be the ancestors of ratfishes.
    This might actually have been the ruling opinion until, lets say, 1965.
    For some reason, the idea of a ratfish-placoderm connection was especially popular among scandinavian paleontologists.

  52. #52 Darby
    May 30, 2008

    Raven, I’m pretty sure that a placenta is a more specific structure than what’s at work here, it’s a set-up for direct transfer between the mother and offspring’s circulation. Here, there’s a yolk sac but (presumably) no egg casing; I may be wrong on this but I’ve always assumed that the line between ovovipariwhatever and vivipariwhatever was whether something that could be called an egg (that is, a casing of some type) was produced and retained.

  53. #53 Josh
    May 30, 2008

    I was never arguing that Devonian must be followed by period. I wasn’t arguing anything, point of fact. I was merely noting that I found it odd that Nature didn’t follow stratigraphic convention on capitalizing the word when using it because I hadn’t noticed the practice before (largely because, as you said, most of the time we do not follow the name with the “rank” because system and period (etc.) names tend to work just fine on their own and quite often read better).

    I don’t think, however, that we can equate stratigraphic “ranks” tightly with taxonomic “ranks” with respect to their plasticity. Whereas there are very sound reasons not to refer to Abelisauridae as a “family” in the Linnaean sense, there isn’t really anything geologically wrong with writing Cretaceous Period. I don’t think that the lack of rigorous consistency in defining some stratigraphic units doesn’t really present the issues that families or orders or whatever not all being equivalent can present.

  54. #54 John
    May 30, 2008

    Oh that is just twice as neat as anything else I’m gonna read today.

    Oh wait check it out I found something neater:
    http://en.wikipedia.org/wiki/Placoderm#History_of_study
    The first guy to pin down the anatomy of ‘em did so with this primitive, 1920s equivalent of a CAT scan. That’s just as neat as it gets.

    So I’m trying to figure out where the Placodermii fit in the scheme of things, and it looks like they’re the split right before Chondrichthyes. Agnathans reproduce externally…

    So Placodermi is viviparous, Chondrichthyes is ovoviviparous, Teleostomii and Agnatha are external fertilization…
    So what was the ancestral condition? This stuff is all over the place.
    I suppose the ancestral condition would be that requiring the least specialized anatomy, which would be external fertilization. And I suppose that’d mean that, disappointingly, there’s no chance of like a straight line of vivipary from the Chondrichthyes/Placodermii ancestor to us today.
    O well. Still the neatest thing I’ll read today.

  55. #55 Discgrace
    May 30, 2008

    We just talked about viviparity in my biology classes earlier this week, so I was happy to be able to put this up on the overhead this morning. Lots of oohs and ahhs from the kids – many of them even sincere-sounding! =b

  56. #56 raven
    May 30, 2008

    Raven, I’m pretty sure that a placenta is a more specific structure than what’s at work here, it’s a set-up for direct transfer between the mother and offspring’s circulation.

    Yeah probably. I didn’t look at the diagram too closely and just saw the umbilical cord. Humans have a yolk sac too but it doesn’t contain yolk proteins anymore.

    Still there are what are called placental sharks and placental lizards.

  57. #57 David Marjanovi?, OM
    May 30, 2008

    Regardless of the science, doesn’t grammar demand that it be capitalized when it is in the title?

    First, that’s not grammar, it’s orthography. Grammar is about the language, not about how you put the language to clay paper computer screen.

    </Hulk mode>

    English is pretty unique in Allowing Almost Anything To Be Capitalized In Titles. (French allows something similar, but that isn’t often done.) Whether this is actually done is up to everyone’s choice; thus, some journals (like Science) do it, others (like Nature) don’t. Yet others (like the Journal of Vertebrate Paleontology) avoid the issue by having titles in all-caps.

  58. #58 David Marjanovi?, OM
    May 30, 2008

    Should rather have written “that isn’t done often”.

    So Placodermi is viviparous, Chondrichthyes is ovoviviparous, Teleostomii and Agnatha are external fertilization…

    Most chondrichthyans do lay their eggs.

  59. #59 David Marjanovi?, OM
    May 30, 2008

    And (sorry for the third post in a row…) you can’t draw conclusions about all placoderms from a single member! We have no idea what the rest of this large, diverse clade did, and no way to find out unless we find more such spectacular fossils.

  60. #60 lithopithecus
    May 30, 2008

    i may be getting on this late, but for #4/ gbruno
    try this one, it might be interesting for you:
    http://www.pnas.org/cgi/content/abstract/103/39/14390
    Endogenous retroviruses regulate periimplantation placental growth and differentiation

    -cheers!

  61. #61 John
    May 30, 2008

    David #58: oh yeah, “mermaid’s purses”.

    Is that “most” or “some”?

  62. #62 Jason J Brunet
    May 30, 2008

    It’s just a bunch of rocks…

  63. #63 Peter Ashby
    May 30, 2008

    There is a LINE element upstream of the mouse myogenin gene. It is present in the 1kb upstream region, when you cut it down to 333bp it is gone. The pattern of linked transgenes is not altered, but the strength of expression is much reduced. We do not know if it is down to the LINE, but there is precious little else there.

    So it may be that such elements are retained as they are functional in gene regulation and if they position themselves serendipitously then that is just part of the wonderful variation that selection can work on.

  64. #64 Ichthyic
    May 30, 2008

    Er, no, because it’s not a chondrichthyan.

    Well, the issue is that typically chondies are proposed to be the first to evolve viviparity. This find would tend to modify that thinking.

    I thought about clarifying what I meant right after I typed it, but figured nobody would really care anyway.

  65. #65 Ichthyic
    May 30, 2008

    …that viviparity first appeared in the chondies is also raised in the last big book on chondie reproduction:

    The Reproduction and Development of Sharks, Skates, Rays and Ratfishes.

    http://www.amazon.com/Reproduction-Development-Ratfishes-Developments-Environmental/dp/0792325095

    Like I said, this new find will tend to change things.

  66. #66 Ichthyic
    May 30, 2008

    Is that “most” or “some”?

    it’s “some”

    most are ovoviviparous, with oviparity coming a close second, and viviparity coming a distant third.

    teleosts range over the spectrum as well, but oviparity is much more common than other modes.

  67. #67 DDeden
    May 30, 2008

    “Yet others (like the Journal of Vertebrate Paleontology) avoid the issue by having titles in all-caps.” @ #57

    Then they employ super-caps for emphasis, right? Same problem, just elevated to the next level.

  68. #68 Ichthyic
    May 30, 2008

    I may be wrong on this but I’ve always assumed that the line between ovovipariwhatever and vivipariwhatever was whether something that could be called an egg (that is, a casing of some type) was produced and retained.

    The line is whether the mother provides direct nutrition to developing embryos via a connection with her own blood supply, or some other mechanism (there are other, less developed forms). There are “gray areas”, for example, some sharks will provide nourishment for developing young by continuing to produce unfertilized eggs internally.

    oviparity: external egg laying

    ovoviparity: egg retained internally until hatched, and sometimes for some period of development afterwards (no nourishment outside of the egg yolk provided).

    viviparity: egg retained internally, mother directly provides nourishment for developing young.

    note that viviparity does not exclude the young also obtaining nourishment from egg yolk.

  69. #69 David Marjanovi?, OM
    May 30, 2008

    Then they employ super-caps for emphasis, right?

    No, they don’t emphasize anything in titles in the first place. Duh. :-|

  70. #70 Darby
    May 30, 2008

    Y’know, I started to write “oviparity,” saw the “parity” in it, and started to doubt that it was the right term. Figured the folks here would know what I meant without the proper endings.

  71. #71 Drhoz!
    May 31, 2008

    You know, that looks VERY like a Brian Choo painting – which would make sense, since he works with John Long, and told me about this discovery months ago :D WE just had to keep our mouths shut until the paper came out.

    Also cool that John’s gone back over fossils he collected earlier and found one with THREE babies inside.

  72. #72 Ichthyic
    May 31, 2008

    Also cool that John’s gone back over fossils he collected earlier and found one with THREE babies inside.

    indeed.

    will there be pics, or not until the “next” paper?

  73. #73 Jack
    May 31, 2008

    Here’s a jellyfish named after Zappa as well. Phialella zappai
    In general I dislike things named after famous people, especially if they have no interest or involvement in the science. Attenborough did publicize the Gogo site though in this case.

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