Tetrapod Zoology

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Everyone interested in animals must, by law, have set eyes on that iconic image of palaeornithologist Kenneth E. Campbell standing next to a life-sized silhouette of the immense Argentinean teratornithid Argentavis magnificens [the image is shown below]. At the International Bird of Prey Centre, Gloucestershire (UK), I quite liked the wooden silhouette of an Andean condor Vultur gryphus and, in the image here, Tone is standing next to it, looking as much like Campbell as she is able. An actual live Andean condor can just about be seen sitting in the enclosure in the background. An Andean condor isn’t quite as big as Argentavis: the latter had a wingspan of over 6 m and probably weighed around 80 kg (Campbell & Tonni 1983, Vizcaíno & Fariña 1999, Palmqvist & Vizcaíno 2003, Chatterjee et al. 2007) whereas the former might have a wingspan of just over 3 m and a heavy male may weigh up to 12 kg (in contrast to most other raptors, male condors are bigger than females).

While they’ve often been imagined or depicted as mega-condors, nobody really seems that sure what Argentavis and its relatives – the teratornithids or teratorns – really are. Most recent papers that express an opinion include them in Ciconiiformes, but never with an adequate explanation: it’s all based on the idea that (1) teratorns are close relatives of New World vultures (aka vulturids or cathartids), and (2) that New World vultures are close kin of storks, and hence part of Ciconiiformes (well, Sibley and Ahlquist complicated things by making Ciconiiformes far more inclusive than it is in its traditional sense). The idea that storks and New World vultures are each other’s closest relatives is no longer popular by the way (see Livezey & Zusi 2007 for a review). And are teratorns close to New World vultures? It looks likely, but someone still needs to examine this question in detail (Emslie (1988a) was able to list multiple derived characters shared by teratorns and New World vultures, most of them present in the tarsometatarsus).

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Vultur is restricted to South America* and probably evolved here from an ancestor that invaded the continent during the American Interchange: fossils indicate that condors are ancestrally North American, and Breagyps clarki from the Pleistocene of California shares several skeletal characters with Vultur that are not present in other condors (Emslie 1988a, b). During the Pliocene, V. gryphus was more widespread in South America: its decline has been blamed on climatic changes and the loss of the megafauna (Tambussi & Noriega 1999).

* In 1988, several individuals were released in California in order to test how successful the possible release of captive-bred Californian condors Gymnogyps californianus might be. These birds were later captured and released back into South America.

So much more to say. But, again, this was meant to be a text-lite ‘picture of the day’ post. D’oh. For previous Tet Zoo articles on raptors see the ver 1 articles When eagles go bad, When eagles go bad, one more time, harrier hawks, and the still incomplete ‘series’ on Haast’s eagle.

Refs – –

Campbell, K. E. & Tonni, E. P. 1983. Size and locomotion in teratorns (Aves: Teratornithidae). The Auk 100, 390-403.

Chatterjee, S., Templin, R. J. & Campbell, K. E. 2007. The aerodynamics of Argentavis, the world’s largest flying bird from the Miocene of Argentina. Proceedings of the National Academy of Sciences 104, 12398-12403.

Emslie, S. D. 1988a. The fossil history and phylogenetic relationships of condors (Ciconiiformes: Vulturidae) in the New World. Journal of Vertebrate Paleontology 8, 212-228.

– . 1988b. An early condor-like vulture from North America. The Auk 105, 529-535.

Livezey, B. C. & Zusi, R. L. 2007. Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion. Zoological Journal of the Linnean Society 149, 1-95.

Palmqvist, P. & Vizcaíno, S. F. 2003. Ecological and reproductive constraints of body size in the gigantic Argentavis magnificens (Aves, Theratornithidae [sic]) from the Miocene of Argentina. Ameghiniana 40, 379-385.

Tambussi, C. P. & Noriega, J. I. 1999. The fossil record of condors (Ciconiiformes: Vulturidae) in Argentina. Smithsonian Contributions to Paleobiology 89, 177-184.

Vizcaíno, S. F. & Fariña, R. A. 1999. On the flight capabilities and distribution of the giant Miocene bird Argentavis magnificens (Teratornithidae). Lethaia 32, 271-278.

Comments

  1. #1 Scott Belyea
    November 1, 2007

    Life-size one-dimensional condors and teratorns

    Well, I’m no scientist, but I do have 2 degrees in math, and I could swear that those are two-dimensional at the least.

    That’s my opinion, and I’m sticking to it …

  2. #2 Mike Keesey
    November 1, 2007

    I spy at least two dimensions….

  3. #3 Nathan Myers
    November 1, 2007

    Two-dimensional, surely?

  4. #4 Allen Hazen
    November 1, 2007

    Youdid mean TWO dimensional, didn’t you?

    PS: I haven’t had anything to say about your frog posts, so haven’t posted any comments. Doesn’t mean I haven’t been reading, enjoying, learning from, them.

    [from Darren: thanks, appreciate it]

  5. #5 Vasha
    November 2, 2007

    So, if the stork connection is no longer the favored theory for cathartid relationships, what is the best-supported idea currently?

  6. #6 John McKay
    November 2, 2007

    Odd, they look two dimensional to me (height and width). One dimension would be a straight line of zero thickness.

  7. #7 Hai~Ren
    November 2, 2007

    So if cathartids aren’t that close to storks after all, then who might their closest living relatives be?

    I remember how for a period of time, it was in vogue to have owls being closely related to nightjars and frogmouths. Then now they’re apparently close to the diurnal raptors. And I read that falcons might not even be close to accipitrids.

    Bird systematics… UGH. What a mess.

  8. #8 Michael P. Taylor
    November 2, 2007

    As with Mark Witton’s reassessment of super-light pterosaurs, it’s pretty hard to buy that the teratorn outlined next to Campbell weighed only 80 kg — that is, about the same as Campbell himself. BUT it’s about right as an isometric scaling from the Condor mass you gave: twice the wingspan => eight times the mass, which would give 8×12 = 96 kg: near enough. That is just … astounding. Gives me a very visceral sense of how well birds are engineered.

  9. #9 Darren Naish
    November 2, 2007

    Ok ok ok… two dimensions then. Jeee-sus..

    (I cannot stress how thick I am when it comes to stuff that is not directly tetrapod-related).

    So if cathartids aren’t the sister-taxon of ciconiids what are they? They seem instead to be the sister-taxon of other raptors, though I base this mostly on Livezey & Zusi (2007), and what they say is hardly going to be the last word on this subject: see in particular p. 35 of their paper (it’s available, absolutely unconditionally free to everyone, here). There’s always the ‘alternative’ hypothesis that cathartids are part of a clade that also includes hoatzins, seriemas and turacos (go here and here on Tet Zoo ver 1). Funnily enough, Livezey & Zusi weren’t exactly big fans of that proposal…

  10. #10 David Marjanovi?
    November 2, 2007

    Everyone interested in animals must, by law, have set eyes on that iconic image of palaeornithologist Kenneth E. Campbell standing next to a life-sized silhouette of the immense Argentinean teratornithid Argentavis magnificens [the image is shown below].

    If not having seen it is outlawed, only outlaws like me will not have seen it.

    <duck & cover>

    [from Darren: you are scum]

  11. #11 Mike from Ottawa
    November 2, 2007

    “Ok ok ok… two dimensions then. Jeee-sus..”

    If the math whizzes are going to nitpick you over that they should go the whole hog and at least mention that while the condor and Argentavis only show two dimensions of their subjects, the objects themselves are actually three dimensional. And I only have 1 math degree!

    All that’s really an excuse to say I’m following the frog series with great interest.

  12. #12 Cameron
    November 2, 2007

    There have been a couple of recent genetic tests on systematics (Gibb et al 2007 and Slack et al 2007) that support the idea of the Conglomerati group with cathartids floating around somewhere among penguins, loons, storks, albatross, petrel, gulls, and falconiformes. It wasn’t clear if they were a sister group to the latter group or not, but I’m sure somebody is going to iron out this craziness one of these days…

  13. #13 Darren Naish
    November 2, 2007

    The papers Cameron is referring to are..

    Gibb, G. C., Kardailsky, O., Kimball, R. T., Braun, E. L. & Penny D. 2007. Mitochondrial genomes and avian phylogeny: complex characters and resolvability without explosive radiations. Molecular Biology Evolution 24, 269–­280.

    Slack, K. E., Delsuc, F., Mclenachan, P. A., Arnason, U. & Penny, D. 2007. Resolving the root of the avian mitogenomic tree by breaking up long branches. Molecular Phylogenetics and Evolution 42, 1-13.

    Both used a pretty small data set… and I’m not sure if I’m amused or appalled by Slack et al.‘s use of the name Cracrafti (aka Conglomerati) for the big raptor-procellariiform-charadriiform assemblage they recognised.

  14. #14 Tommy Tyrberg
    November 2, 2007

    Vultur had a larger distribution in South America much more recently than the Pliocene:

    Alvarenga, H. M. F. 1998. Sobre a ocorrencia do condor (Vultur gryphus) no Holoceno da regiao de Lagoa Santa, Minas Gerais, Brasil. Ararajuba 6:60-63.

    Its disappearance from the lowlands is probably due to the loss of the megafauna, and scavenging opportunities. Where there is a rich coastal fauna with marine mammals condors still occur down to sealevel. I’ve seen it in coastal habitat in Peru and on Tierra del Fuego.

  15. #15 Michael P. Taylor
    November 2, 2007

    If the math whizzes are going to nitpick you over that they should go the whole hog and at least mention that while the condor and Argentavis only show two dimensions of their subjects, the objects themselves are actually three dimensional.

    Well, four if you count their persistence through time.

    Any advance on four?

  16. #16 DDeden
    November 2, 2007

    If tetrapods can have 2 legs or no legs, I have no problem with 1 (or even zero) dimensional cryptic condors.

    Oh, I brought up the principle of sphericity in nature, water isn’t “formless”, it’s spherical, as seen in some ISS youtube videos at my coffee blog. Note the one “drinking tea with chopsticks”, coolness.

  17. #17 Tengu
    November 2, 2007

    You found my fave birdie! thank you!

  18. #18 Nathan Myers
    November 3, 2007

    We can’t expect people who call birds (and even snakes!) “tetrapods” to be especially good at counting … which is a good thing. Imagine paleontologists, with all their other demonstrated skills, *also* able to count! They’d be akin to super-heroes and — in some well-known cases — super-villains.

    So, let us leave them innocent of numeracy, for the safety of ourselves and our kin.

    [from Darren: well, don’t go thinking that I’m representative of my field, as most palaeontologists are pretty good at maths/counting/other functional stuff. I’m highly aberrant]

  19. #19 Sordes
    November 3, 2007

    The popular image of teratorns as oversized condors is really doubtfull, and also boring. I don´t know if Teratorns were really turkey-and hare-hunters, but given the fact that they had legs well adapted for walking on the ground, and much stronger beaks than new world vultures, I would bet that they had also a very own behavior and feeding ecoloy. Something I find really interesting is that it seems that they were the only really giant carnivorous birds (please correct me Darren, I hope there were others!). There were a lot of raptors, especially on islands, which reached very big sizes, but wing-spans of 2,5-3m seems to be the maximum. So if there were monstrous teratorns in the new world, why are there no comparable birds from the open plains of Africa or Europe?
    This is something what drives me sometimes really crazy. Why are some carnivores able to evolve to terrestrial giants, and others not? Why were theropods able to evolve elephant-sized forms, and both warm-blooded mammalian predators and cold-blooded reptilian predators did not really reach weights of much more than 1000kg.
    BTW, it is really strange that the old photo of the argentavis silhouette makes MANY people believe that it is the carcass of a real bird…

  20. #20 Tengu
    November 3, 2007

    My falconry friends would love one of these; think of all the things you could kill with it.

    (but carrying it around might get tiring)

    seriously though, what is the difference between argentavis and a teratorn? are they different but related families?

    [from Darren: Argentavis is a member of the group called Teratornithidae – it is a teratorn. There aren’t many teratorn genera: we only know of Taubatornis from the Oligocene-Miocene of Brazil, Argentavis from the Miocene of Argentina, Aiolornis and Cathartornis from the Pleistocene of North America, and Teratornis from the Pliocene and Pleistocene of North America, and the Pleistocene of Cuba. The Cuban Teratornis is said by some to represent a new genus, but I don’t think a new name has been published yet.]

  21. #21 shiva
    November 4, 2007

    I’m not quite sure that that Argentavis silhouette is an accurate representation. Assuming Tone is roughly 1.6m tall, then the beak-to-tail length of Vultur is about 1.1-1.2m (which fits well with my observations of Old World raptors, such as Gyps spp, which are slightly smaller than V. gryphus).

    Theorising Argentavis as a scaled-up Vultur, its beak-to-tail length would be about 2.2-2.4m, which sounds reasonable for an 80kg bird. However, assuming Kenneth Campbell to be about 1.7-1.8m tall, the beak-to-tail length of the silhouette seems to be well over 3m. Those proportions look completely wrong for such a huge bird – in fact, it’s got about the same body proportions as a medium-sized corvid (eg. C. corone or C. brachyrhynchus). Something as huge as Argentavis would in all probability actually have an even greater wing size to body size ratio than Vultur.

    As to the infamous “Thunderbird Photo”, i believe it’s a conflation of several pictures, including the Argentavis silhouette, another photo that i’ve seen of two men posing with a dead large Leptoptilus stork, and a line drawing of a pterosaur…

    BTW, it’s interesting that some V. gryphus were released in the US. Many “Thunderbird” reports describe a bird extremely similar to V. gryphus, even down to the white ring around its neck (which Gymnogyps lacks). Are Vultur and Gymnogyps each other’s closest living relatives, or are any smaller New World vultures placed “between” them?

  22. #22 Darren Naish
    November 4, 2007

    Those people who suffer from ‘thunderbird syndrome’ have in fact based their erroneous recollections on this image 🙂

    As for condors – yes, the two living taxa are each other’s closest relatives. Of the other extant NW vultures, mid-sized Sarcorhamphus is supposedly closest to the condors, with the other taxa being more distant.

  23. #23 Raymond
    November 4, 2007

    Darren, I’ve seen the thunderbird photo and no, it is not a pterosaur, a dead marabou stork or anything else.It is positioned along a barn like the posted parody, rightside up, not inverted.

    Whatever it is, hoax, mass shared delusion of some sort, or a genuine article it is simple _weird_.It certainly made the hairs on the back of my neck stand up when I saw it 15 years ago.

  24. #24 johannes
    November 5, 2007

    > Something I find really interesting is
    > that it seems that they were the only really
    > giant carnivorous birds

    What about phorurhacids? Or did you mean flying birds?

    > Why were theropods able to evolve elephant-sized forms,

    Because they were stiff-legged? Because they were lightly built and could grow large without becoming too massive to hunt? And/or because their prey was also gigantic?

    > and both warm-blooded mammalian predators and
    > cold-blooded reptilian predators did not really reach
    > weights of much more than 1000kg.

    The Miocene alligatorid *Purussaurus* reached 20 metric tons (20.000 kg). It was probably semi-aquatic, like modern alligatorids, but it was able to move on land.

  25. #25 DCN
    November 7, 2007

    I’ve always seen the body length at Argentavis estimated at 10-12 feet, a foot of which was beak.

  26. #26 Raymond
    November 8, 2007

    >> Why were theropods able to evolve elephant-sized forms,

    >Because they were stiff-legged? Because they were lightly >built and could grow large without becoming too massive >to hunt? And/or because their prey was also gigantic?

    Well….*Andrewsarchus* was not a pipsqueak and *Daeodon*
    certainly wasn’t chump change either, (for their times).
    Giant mammal herbivores are actually a dime a dozen, what with titanotheres, indricotheres, proboscideans and others routinely reaching 8 to 12 tons with an outlier of, say 20-25 tons.This size range fed tyrannosaurs.

    I think it isn’t just stiff leggedness that enabled the theropods to get so big, or the phorusrachids would’ved been far more pants-soiling than they were.

    The real secret is likely the fact that every dinosaur herbivore seems to have bred like rats.

  27. #27 David Marjanovi?
    November 8, 2007

    The Miocene alligatorid *Purussaurus* reached 20 metric tons (20.000 kg).

    Come on. Ten meters long (at most) and twenty tonnes? Two tonnes per meter of body length? Never. Two tonnes maybe.

  28. #28 johannes
    November 8, 2007

    >> The Miocene alligatorid *Purussaurus* reached 20
    >> metric tons (20.000 kg).

    > Come on. Ten meters long (at most) and twenty tonnes?
    > Two tonnes per meter of body length? Never. Two tonnes maybe.

    Ten meters seem to be rather conservative. The sources available by googling *Purussaurus* give size estimates from 15 to 18 meters for large animals, 12 meters for average ones.
    A ten meter alligatorid with a 1,5 meter head must have been an animal of strange proportions (*Purussaurus* had a broad, compact head, not a long-snouted one like, let’s say, *Sarcosuchus*), looking more like a giant dissorophid temnospondyl than a crocodylian, leave alone an alligatorid. Such an animal would be, of course, possible (and in fact more interisting than one that was just very, very large), but the idea looks counterintuitive to me.

  29. #29 Sordes
    November 9, 2007

    Johannes, I meant only flying birds, not flightless ones. And again, isn´t it interesting that for example phorusrhacids did not come close to the size of the bigger theropods, although they had a comparable anatomy?
    I know that Purussaurus and other crocodylians became really gigantic, but they were semi-aquatic and preyed only in the water, so I don´t count them as terrestrial.
    About the weight of Purussaurus: It is very dependent how big they actually were. I read several probably lengths between 12 and 17m, and also some very ridiculous ones about more than 20m. A typical crocodile would weigh about 8000 kg at 12m, probably a bit more, because they become more stockier with increasing size. I calculated theoretical weights of about 10.000kg for a 13m crocodile, 12.700kg for a 14m crocodile, 15.600kg for a 15m crocodile, 19.000 kg for 16m, 22.700kg for 17m and 27.000kg for 18m. This are huge differences, because weight increases with the cube. One metre more or less can cause a massive difference in weight. So it is really important to actually know as exact lengths as possible. The imagination that there were once crocodiles the size of a smaller grey whale is really shocking.
    I would still love to know how accurate the length estimations for Ramphosuchus are.

  30. #30 shiva
    November 9, 2007

    “I’ve always seen the body length at Argentavis estimated at 10-12 feet, a foot of which was beak.”

    I can see that if it had the proportions of a stork, rather than those of something between a crow and a vulture…

  31. #31 Raymond
    November 10, 2007

    -Sordes

    IIRC, there was a theory advanced within “Magnificent Mihirungs” by Peter F. Murray and Patricia Vickers-Rich
    that phorusrhacids preyed mostly on hystericomorph rodents.
    I wonder what would’ve happened if all the SA ungulate taxon had gone extinct by the miocene, leaving the much more prolific rodents to dominate all large bodied herbivorous niches?Even capybaras breed more like pigs than like the sympatric deer and peccaries they live next to.There’s no real reason to suppose the buffalo sized extinct taxon reduced their litters either.

  32. #32 Graham King
    October 13, 2009

    If the math whizzes are going to nitpick you over that they should go the whole hog and at least mention that while the condor and Argentavis only show two dimensions of their subjects, the objects themselves are actually three dimensional.

    Well, four if you count their persistence through time.

    Any advance on four?

    yes, plenty; maybe as many as twenty-six! but they are mostly folded up real small.

  33. #33 Jorge W. MorenoBernal
    June 29, 2010

    “The Miocene alligatorid *Purussaurus* reached 20 metric tons (20.000 kg). It was probably semi-aquatic, like modern alligatorids, but it was able to move on land.”

    “The sources available by googling *Purussaurus* give size estimates from 15 to 18 meters for large animals, 12 meters for average ones.”

    This is a clear overestimation. Largest Purussaurus specimens know must have been about 10 meters in length and weighted some ~3.5 tones.

    Purussaurus is not so short snouted! it has a snout/skull length proportion similar to that of big Crocodilus or Alligator.

  34. #34 Darren Naish
    June 30, 2010

    A Tet Zoo article dedicated to Purussaurus can be found here.

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