The Madagascan cuckoo-roller or Courol* Leptosomus discolor is a distinctive, large-headed, short-legged predatory bird that inhabits the forests of Madagascar and the Comores [adjacent photo of male Courol taken at Vakona in Madagascar; image courtesy of Mary Blanchard]. It's superficially similar to true rollers (Coraciidae) and ground-rollers (Brachypteraciidae) but, unlike them, has semi-zygodactyl feet (though it has frequently very depicted inaccurately by artists who, in the absence of better information, have assumed that it's anisodactyl, like true rollers). It's often placed in its own 'family', properly termed Leptosomidae but often (incorrectly) referred to as Leptosomatidae (incidentally, there's a nematode 'family' with this latter name).
* I've also seen it spelt Gourol.
The Courol also differs from true rollers and ground-rollers in that it hunts prey high in the forest canopy. It eats insects - including locusts, caterpillars and stick insects - but is particularly well known for preying on chameleons, of which there are an awful lot in Madagascar. It must sometimes eat a lot of caterpillars, as the stomach is often lined with caterpillar hairs (Burton 1984). It has powerful jaws (the temporal fossae are large, housing large jaw muscles, the jugals are stout, and the lacrimals form vertical braces against the jugals) and an extensively ossified palate (Cracraft 1971) [skull diagrams below from Cracraft (1971)]. As is the case in some other birds with extensively ossified palates (like hornbills), prey are grasped firmly between the jaws and beaten against a perch until subdued (Burton 1984). Leptosomus is also unusual in possessing slit-like nostrils that are located further toward the bill's tip than is typical.
Male Courols have an iridescent green back, grey head and whitish underparts while females are mostly brown, with barred head plumage and spotted underparts. This sexual dimorphism is, again, very different from what's seen in true rollers and ground-rollers: like most other birds conventionally grouped in 'Coraciiformes', true rollers and ground-rollers don't exhibit obvious sexual dimorphism [image below of female or juvenile Courol by Frank Wouters, from wikipedia].
It's usually thought that there's just one species of Leptosomus, but three subspecies have been named: L. d. discolor of Madagascar and Mayotte Island, L. d. intermedius of Anjouan, and L. d. gracilis of Grand Comoro. L. d. gracilis is much smaller than the nominate form, has a faster and higher pitched call, and has a distinctly differentiated blue-grey throat and upper breast and pure white belly (in the other forms, the two colours merge into each other). As a result of these differences, some authors (e.g., Sinclair & Langrand 1998) consider the Grand Comoro population to represent a separate species: the Comoro cuckoo-roller L. gracilis.
As should be obvious by now, the Courol has often been considered close to ground-rollers and true rollers and classified with them in the 'coraciiform' group Coracii. However, when first described in 1783, Leptosomus was thought to be a cuckoo: it was originally named Cuculus discolor Herman, 1783 and it didn't get its own genus name until Louis Jean Pierre Vieillot erected Leptosomus in 1816. Indeed, it does resemble a cuckoo, superficially at least. By 1865, Philip Sclater had argued that it wasn't especially similar to cuckoos, and he suggested that it more resembled rollers and ground-rollers. Dissenting opinions were expressed by others (in 1872, Carl Sundevall regarded it as close to toucans, jacamars and honeyguides), but Sclater's idea of roller affinities caught on and became widely regarded as correct.
Cracraft (1971) proposed that Leptosomus represented an early stage in roller evolution that pre-dated the evolution of sexual monomorphism (though he did express some doubt about the Courol's precise affinities). He suggested that it evolved semi-zygodactyl feet from an anisodactyl ancestral roller because its large size and specialisation for arboreal life required improved perching abilities.
However, molecular and morphological evidence have shown pretty convincingly that the Courol's affinities lie elsewhere, and that it isn't a roller at all. Herremanns & Louette (1992) suggested a position close to cuckoos. Given the strong sexual dimorphism and barred, brown female plumage of the Courol, its semi-zygodactyl feet, strong, reinforced jaws, and habit of eating caterpillars, this proposed link - which, ironically, puts the Coural back where it started in 1783 - is intriguing (cuckoos have really interesting jaws, as do the possibly related turacos and hoatzins) [sexual dimorphism in the cuckoo Cuculus canorus shown here, pic from wikipedia]. Mayr (1998) included Leptosomus in a phylogenetic analysis with other 'coraciiforms', and found it to be outside of a clade that included all other putative members of this group. Furthermore, he suggested that it might group together with podargids (frogmouths), which seems odd but is at least consistent with some characters that are shared by the two (such as two powder down patches on the back). More recently, Mayr et al. (2003) found Leptosomus to group with frogmouths in the 'nightbird' + apodiform clade, Ericson et al. (2006) found Leptosomus to be outside of a land bird clade that includes owls, mousebirds, 'core coraciiforms', trogons and piciforms (woodpeckers and kin), and Hackett et al. (2008) found Leptosomus to be close to (but outside of) a clade that includes trogons, piciforms and 'core coraciiforms'. Livezey & Zusi (2007) did find the Courol to be a roller, and to be the sister-taxon to ground-rollers. However, Mayr (2008a) argued that this was the result of incorrect character scoring whereby the Courol had wrongly been given the same characters states as ground-rollers [some possible positions for Leptosomus - depicted on a sort of very rough 'consensus' cladogram - are shown below].
The implication from these results is that Leptosomus is definitely not a 'core coraciiform' (and definitely not a roller) and that, while its precise affinities remain rather unclear, it represents some sort of ancient lineage that might lie within the region of the tree that includes 'nightbirds' and swifts, or piciforms and/or 'core coraciiforms'. The problem with this statement is that some of these affinities are sometimes mutually incompatible: Hackett et al. (2008), for example, found frogmouths to be about as far removed as possible from piciforms and 'core coraciiforms'*. On the other hand, if frogmouths, trogons, piciforms, 'core coraciiforms' and so on are all in the same region of the neoavian tree, then the results of the above-mentioned studies could all be more or less compatible. Do fossils provide any perspective on this subject?
* Hackett et al. (2008) recovered a neoavian clade that included flamingos and grebes (mirandornithines, if you like), tropicbirds, sandgrouse, mesites, pigeons, swifts and hummingbirds, and nightjars, frogmouths and so on. This clade formed the sister-group to all other neoavians in their analysis. This clade is extremely similar in content and position to the clade that Fain & Houde (2004) and Ericson et al. (2006) had earlier termed Metaves. Whether Metaves is real or not has become a really interesting question (Morgan-Richards et al. 2008)
Plesiocathartes from the Eocene and Oligocene of Europe and Eocene of North America - originally described as a New World vulture - seems to be a stem-leptosomid [P. kelleri Mayr, 2002 from Messel shown here; image from here]. In fact, it's so similar overall to Leptosomus that Mayr (2008b) regarded the latter as a possible 'living fossil' (though Plesiocathartes does differ from Leptosomus in being anisodactyl).
The modern restriction of leptosomids to Madagascar may, therefore, be relictual following their extinction elsewhere, as the fossils show that these birds were once widespread across the Northern Hemisphere. If this is correct, why have leptosomids become so restricted? Were they out-competed by other roller-like birds? Were they unable to cope with the climatic changes of the Neogene? Once more, a poorly known and understudied bird is clearly deserving of a lot more attention.
For previous Tet Zoo articles on assorted land birds from this region of the cladogram (perhaps!) see...
- Sibley and Ahlquist's 'Tapestry'
- Ground hornbills: savannah-dwelling, avian pseudo-hominids
- The other ground hornbill
- A case of dead kingfishers
- Perhaps the weirdest chicks of all
Refs - -
Burton, P. J. K. 1984. Anatomy and evolution of the feeding apparatus in the avian orders Coraciiformes and Piciformes. Bulletin of the British Museum of Natural History (Zoology) 47, 331-443.
Cracraft, J. 1971. The relationships and evolution of the rollers: families Coraciidae, Brachypteraciidae, and Leptosomatidae. The Auk 88, 723-752.
Ericson, P. G. P., Anderson, C. L., Britton, T., Elzanowski, A., Johansson, U. S., Källersjö, M., Ohlson, J. I., Parsons, T. J., Zuccon, D., and Mayr, G. 2006. Diversification of Neoaves: integration of molecular sequence data and fossils. Biology Letters 22, 543-547.
Hackett, S. J., Kimball, R. T., Reddy, S., Bowie, R. C. K., Braun, E. L., Braun, M. J., Cjojnowski, J. L., Cox, W. A., Han, K.-L., Harshman, J., Huddleston, C. J., Marks, B., Miglia, K. J., Moore, W. S., Sheldon, F. H., Steadman, D. W., Witt, C. C. & Yuri, T. 2008. A phylogenomic study of birds reveals their evolutionary history. Science 320, 1763-1768.
Herremanns, M. & Louette, M. 1992. Sexual dimorphism in the juvenile plumage of the Coural Leptosomus discolor and considerations on its affinities. Bulletin of the British Ornithologists' Club 112, 182-185.
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.
Mayr, G. 1998. "Coraciiforme" und "piciforme" Kleinvögel aus dem Mittel-Eozän der Grube Messel (Hessen, Deutsch-land). Courier Forschungsinstitut Senckenberg 205, 1-101.
- . 2008a. Avian higher- level phylogeny: well-supported clades and what we can learn from a phylogenetic analysis of 2954 morphological characters. Journal of Zoological Systematics and Evolutionary Research 46, 63-72.
- . 2008b. The Madagascan "Cuckoo-roller" (Aves: Leptosomidae) is not a roller -- notes on the phylogenetic affinities and evolutionary history of a "living fossil". Acta Ornithologica 43, 226-230.
- ., Manegold, A. & Johansson, U. S. 2003. Monophyletic groups within 'higher land birds' - comparison of morphological and molecular data. Journal of Zoological and Systematic Evolutionary Research 41, 233-248.
Morgan-Richards, M., Trewick, S. A., Bartosch-Härlid, A., Kardailsky, O., Phillips, M. J., McLenachan, P. A. & Penny, D. 2008. Bird evolution: testing the Metaves clade with six new mitochondrial genomes. BMC Evolutionary Biology 2008, 8:20 doi:10.1186/1471-2148-8-20
Sinclair, I. & Langrand, O. 1998. Birds of the Indian Ocean Islands: Madagascar, Mauritius, Réunion, Rodrigues, Seychelles and the Comoros. Struik, Cape Town.
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That would be another way in which Leptosomus resembles true cuckoos, or at least the European cuckoo Cuculus canorus; the latter eats plenty of hairy caterpillars that most other birds won't touch.
That I didn't know; how interesting! I also seem to have been under a false impression regarding the size of Plesiocathartes - I thought that it was, well, 'vulture-sized'.
What makes a bird a roller?
Dartian: some cuckoos (Cuculus in particular) can be regarded as caterpillar specialists. What isn't well known is that they possess weird platform-like structures on their jaws that allow them to do a lot of oral processing of these prey. In fact, cuckoos, turacos and hoatzins all do what can be described as chewing - this was bought to attention by Korzun et al. (2003) and isn't yet widely known (Gary Kaiser did his bit to big it up in The Inner Bird)...
Korzun, L. P., Erard, C., Gasc, J.-P., and Dzerzhinsky, F. J. 2003. Biomechanical features of the bill and jaw apparatus of cuckoos, turacos and the hoatzin in relation to food acquisition and processing. Ostrich 74: 48-57.
I should blog about this some time. The structures seen on turaco and hoatzin bills are awesome.
Crikey! Hoatzin chewing I've actually heard of but that cuckoos do it too... Wow!
Dartian - Plesiocathartes has been described as crow-sized. There were several species*, so I guess there was probably some variation. Certainly some sources that still treated them as cathartids referred to them as the smallest of the cathartids.
* Mayr in Paleogene Fossil Birds states there are "Five species of Plesiocathartes have been named: Plesiocathartes europaeus Gaillard, 1908 from an unknown horizon of the Quercy fissure fillings, P . geiselensis Mayr, 2002 from the Geisel Valley, P. kelleri Mayr, 2002 from Messel, as well as P. wyomingensis Weidig, 2006 and P . major Weidig, 2006 from the Green River Formation (Mayr 2002a, g; Mourer- Chauviré 2002; Weidig 2006). As yet unnamed species occur in the London Clay (Mayr 2002g)."
Mayr also states that they are "remarkably similar to the Courol in their osteological features". He adds "As in extant Leptosomidae, the coracoid exhibits a foramen for the supracoracoideus nerve and a cup-like scapular articulation facet. These presumably plesiomorphic traits are absent in other âcoraciiformâ birds. Plesiocathartes further shares with the extant Courol a derived morphology of the tibiotarsus (condyles very low and widely separated) and tarsometatarsus (hypotarsus with two furrows which are closed to canals in Leptosomus , trochlea for the second toe reaching farther distally than that for the fourth toe... As in extant Leptosomidae, the postorbital processes of the skull are greatly elongated."
As for differences he notes: "These Eocene stem group Leptosomidae differ from Leptosomus in the morphology of the furcula, which has a smaller omal extremity, is more widely U-shaped, and whose shafts are not strap-like as in the Courol. They are further distinguished from Leptosomus by their proportionally longer legs, details of the pelvis morphology (the pubis is not reduced in its midsection and the obturator foramen is caudally open ), and by the absence of an accessory tarsometatarsal trochlea for the fourth toe, which indicates that the feet were anisodactyl and not semizygodactyl as in the extant Courol."
"What makes a bird a roller?" - possibly something to do with not being a rocker? :)
Interesting, werd bill.
BTW, where the name 'courol' comes from? Shorthand of cuckoo-roller?
Okay, I've gotta ask - why are nematode (typo in the text there) families suspect, deserving of quotes? Whatdya got against roundworms, which are (sorry, vertebrate folk) the coolest animals around?
Darby: I got nothing in particular against nematodes, but I do have a problem with rank-based classifications. The quotes are there to remind you that a 'family' is a totally subjective concept.
Ah, I see. I tend to see the other approaches using their own subjectivities - I guess we're happiest with our familiar definitions and parameters. That, and it's not so easy with millions of very similar species to sort through.
I think you meant to type "menadotes" there, or maybe "denamotes" or "nedatomes". Excellent names, all.
Chewing by cuckoos, turacos and hoatzins is spectacular. An article about it would be awesome.
I did notice that you'd put family in quotes and I almost bit then. I tend to agree with so much of what you say Darren, but on this one we disagree fundamentally. I guess whenever I refer to any of the phylocode nonsense I should put it in quotes then.
Mark:
My first and main impression of Plesiocathartes came from a very New World vulture-ish reconstruction of it in James Fisher's and Roger Tory Peterson's classic The World of Birds. (A lovely book IMO, even though it's nowadays outdated beyond hope.)
Jerzy:
Not likely; courol is the French name of this bird.
Mark again:
You'll delibrately risk going loggerheads with David MarjanoviÄ over nomenclatural issues? You, sir, are a braver man than I am.
Mark: I've been putting ranked taxa ('genera', 'families', 'orders' etc.) in quotes for ages, am surprised you've only just noticed if it bothers you that much! Are you seriously saying that ranks are in some way useful, or good? They're not: they're totally arbitrary, and misleading as goes their influence on people's perceptions of diversity. The sooner we give up on them the better. This is all sounding very, very familiar :)
To echo Darren on the topic of ranks:
It should be noted that their least useful quality is the perceived existence of a rank without a taxon to actually support it supposes that the rank is somehow real without the taxon.
This includes "Family," "Subfamily," and "Superfamily;" but it is not limited to just those pre-presumed existing taxa. Essentially, naming one causes the others to come into existence, and be their names (which is about nomenclators' egos, for the most part, and not science).
A second issue with ranks, but sort of a sub-point of this issue, is that it is simply too resolved to reflect the diversity of organisms, and that retaining it ill-reflects Life's real diversity, and the best example of this is birds themselves.
In classical arguments, birds are a Class, Aves; but so are reptiles, Reptilia. Traditionally, ranks support hierarchies of organisms, but not ancestor-descendants, unless they are then just shifted out of a rank it's own relatives are in. As in the above example, Aves when assumed to derive from within reptiles, are rendered outside of them, as if they were sister taxa. You therefore lose resolution, not to mention accuracy, in keeping with this system. Lately, the practice has been to invent rank upon rank to represent the intervening branchings in the tree of life, with various infra-, super- and sub- modifiers. Very creative, and very uselessly unscientific.
"Not likely; courol is the French name of this bird."
It could come from French "coucou-rollier" though. My French isn't very good, but wouldn't this mean "roller-cuckoo" instead of "cuckoo-roller"? It doesn't seem to be the Malagasy name, which is "Vorondreo" according to this stamp: http://www.birdtheme.org/showimages/malagasy/i/mlg198202l.jpg
The German name is "Kurol", which is pronounced just like courol. Probably someone thought this was the native name.
Darren:
But why do you even keep mentioning the traditional ranks at all anymore? Why don't you just switch to calling everything and anything a clade, if you think that traditional nomenclature is so misleading?
'Totally' arbitrary? That's a bit unfair, isn't it? Most rank-using taxonomists at least attempt to only recognise monophyletic groups nowadays, do they not?
You make it sound as if the triumph of the rank-free system is all but inevitable. But what happens if the majority of biologists refuses to give up on ranks, even after the long-awaited companion volume has been published? Will supporters of rank-free nomenclature ever concede defeat, or may we look forward to a future of interminable biological nomenclature wars? What does the PN supporters' worst-case scenario look like?
Jaime:
Unscientific, yes, but let's not make the mistake of thinking that rank-free nomenclature is any more, or any less, scientific than rank-using nomenclature. Nomenclature is convention, not science.
Because I'm talking about history! (e.g., Leptosomus has traditionally been given its own 'family'). And ranks are, indeed, arbitrarily defined by nothing more than historical inertia: e.g., 5000 amphibian species get (say) 100 'families', simply because that's what everyone has always done, whereas 5000 bird species get (say) 1500 families for the same reason. So - the birds are 'more diverse', or somehow represent 'more phylogeny' than the amphibians? No. It's actually damaging, because people take views on 'families' and such and apply them to real diversity (and hence to such things as conservation priority).
And the PhyloCode is irrelevant here; I don't understand why it's been mentioned.
Ouch. Isn't there a single big data matrix that doesn't contain sloppy mistakes like that.
:-D :-D :-D Almost total phylogenetic grass! But of course it's true, that's what the consensus looks like at the moment.
Thirded! I barely knew about the "triturating surfaces" on various turtle beaks and had no idea of analogs in birds!
:-D
<rolling up sleeves>
<spitting into both cupped palms at once>
<rubbing to distribute spit across palms>
<beating right fist into left palm>
<beating left fist into right palm>
<rubbing>
<right fist>
<left first>
<snarl>
"PhyloCode" or "nonsense"? Which is it? :-)
What information do ranks contain that isn't positively misleading (by implying that taxa of the same rank are somehow comparable, which they never are)?
And did you know that ranks won't be forbidden under the PhyloCode? Article 3, the only article to mention them, merely restricts their application: they are not part of nomenclature and have no influence on things like the spelling of names, instead they can only be tacked on afterwards, after nomenclature has been done.
Yes.
That's how it has worked for Mesozoic dinosaurs, Mesozoic mammals, stem- and possible stem-tetrapods, extant "protists" at least at the higher levels...
Easy -- that's the status quo :-)
Look at this from the point of view of a PN agnostic (e.g., yours truly). I would like to see with my own eyes how well the proposed new system can stand on its own legs, free from the shackles (or baggage, if you prefer) of rank-based nomenclature.
Or consider this analogy: Imagine that you were a male stripper*, and people were expecting you to do the full monty. But, instead, at the end of the show you'd just keep your smurf underpants on. Could you then blame the audience for feeling a bit disappointed?
* Which, if I've understood it correctly, is a perfectly normal career choice for blokes in post-industrial English towns. Someone should make a movie about it.
In other words, we (or I, anyway) want you to lead by example on this issue.
If the PhyloCode is, or will be, the very foundation and starting point of the official rank-free system, I'd say that it's highly relevant to each and every discussion about phylogenetic nomenclature, no?
By the way and for the record: I'll admit that for the sake of argument, I was assuming in my previous comment that 'supporters of rank-free nomenclature' form a monolithic, goose-stepping, hive-minded mass. That was inappropriate of me; my only defence is that I like to keep my strawmen simple.
To give you the simplest response possible: I don't get your 'show us the full monty' thing... we already use rank-free nomenclature all the time!
Dartian - you have a point - while I don't fear Darren (much), the Mighty MarjanoviÄ is a whole different story.
I did put together a rather long reply with some of my reasons for preferring rank-based approaches (and why I deplore the Phylocode), but ended up deleting it all because I decided that I am in danger of making myself about as welcome here as a pork pie in a synagogue, or may be as a creationist on Pharyngula :)
I'm sure we have all heard the arguments for both sides many times, so I guess this is one we are just going to have to agree to disagree on
Dartian, I must admit you somewhat lost me with the Full Monty references - but you should note that in some cases the audience may be relived not disappointed if the underpants are kept on.
Maybe we should head back to something less controversial - Plesiocathartes was a good start, or maybe some other paleogene birds.
Not to digress too much from long-palated oral-crushing birds, but the phrase "the full monty"'s allocation to removal of clothing is a recent, but not he original, meaning of the phrase (otherwise being a cards term for going all out): http://en.wikipedia.org/wiki/The_Full_Monty_%28phrase%29
Mark:
'Lay your hand on him; Remember the battle; You will not do it again!'
From what I've seen, it's admittedly not completely impossible to "defeat" David on teh internet, but it's certainly very, very hard. If you decide to try, you better know damn well what you're doing and be packing some serious intellectual heat.
Not your fault, it was a joke that fell flat. There kinda sorta was a serious point to it too (believe it or not), but I did not make that point very well. And I'm not sure if I should even attempt to explain it differently anymore either; I would probably just get myself mired deeper still in the morass of nomenclature discussions. (But at least I unexpectedly learned something new about the origin of that phrase - thanks, Jaime!)
Agreed. Back to Leptosomidae and chewing cuckoos.
We're actually suffering from the lack of chew toys and collateral wisdom that results from the now mandatory registration over there.
I'm not. For instance, other than Phil Cantino, Dick Olmstead, and the like, there are no botanists in my ivory tower. It's entirely possible that phylogenetic nomenclature isn't as easy to apply to everything as it is to Mesozoic dinosaurs -- and if so, I don't know about it.
Chewing in Hoatzins, Cuckoos and Turacos is neat. If the Hoatzins have co-opted their crops as a sort of fermenting foregut, are the oral processing cuckoos and turacos doing anything interesting with theirs?
This chewing thing is interesting... and as always, there are comparable situations in snakes, another group well known for (supposedly) not chewing their food.
Depending on the type of teeth or other triturating structures, there are various things that can be done to a food item by cycles of jaw abduction and adduction (and whatever other kinds of kinesis go along with that), and we can use the word 'chewing' for any one that is not better described as 'biting' (prehension and/or cutting) or 'transport' (towards and into the oesophagus, leading to swallowing proper).
Few non-venomous snakes chew, apparently; I think that things like Xenopeltis are exceptions - not that feeding has actually been described in this taxon, but it has been in the pygopodid gekkotan 'lizard' Lialis, which has similar long jaws with small, hinged teeth, and uses the jaws to compress the prey item causing death by asphyxiation, similar to constriction. As well as Xenopeltis there are several colubroid groups with similar teeth and a hypertrophied muscle at the corner of the mouh, and all have been interpreted as specialists on skinks or other hard-scaled (osteoderm-bearing) lizards. Repeatedly squashing the prey item by mandibular adduction, after biting and before getting it lined up with the throat and ratcheting it down (hooking the spatulate tooth tips under the scale margins), sounds like 'chewing' to me.
Then there are venomous snakes. Those with anterior fangs use them to stab the prey and inject venom by 'biting', whether or not there is a strike (action of the anterior trunk and 'neck') and with or without releasing immediately after biting. Many elapids hold onto the prey after biting with fangs and other anterior teeth, and go through many cycles of 'chewing', not only compressing with the mandible (relatively ineffective as a killing mechanism) but using modified jaw-adductor muscles to compress the venom glands on each cycle, and also using the various muscles attaching to the pterygoid to drive the palatopterygoid bar forward and backward, causing the front of the maxilla (with fangs) to go up and down, plunging the fangs in and out of the prey. The snake-bite literature reports 'chewing' bites as common in Australian Tiger snakes and Brown snakes, but it hasn't been described in detail. The two upper jaw arches may alternate (as typical in prey transport) or move in synchrony (as typical of strike-biting). Usually the protraction of the pterygoid erects the maxilla and fang, lifting it out of the prey before retraction pulls it back in, but in at least one 'genus' of elapids (Demansia) the maxilla does not seem to erect at all, but is depressed well below resting position during retraction (the fang goes in and out like a sewing-machine needle). Chewing tends to go on intermittently as long as the prey struggles, and may resume again after beginning orientation and transport.
Then there's chewing with rear rather than front teeth; reported for rear-fanged colubroids, though again I don't think it's been adequately described and I have almost no personal experience with them. One group of elapids, the shovel-snouted Brachyurophis, does this (after getting the prey item well back in the mouth with typical biting, orientation and transport moves) to saw open parchment-shelled lizard eggs with enlarged, blade-like posterior pterygoid teeth. Unlike the bird-egg-eating Dasypeltis, they swallow the shell as well as the contents.
Sorry to butt in on this bird-fest, but if Darren won't get around to posting more on snakes...
:-D
As for the chewing, don't parrots chew too? After all, their bill joint allows them great rostral dexterity. Parrots do make a chewing motion when handling some foodstuffs.
>>It's entirely possible that phylogenetic nomenclature isn't >>as easy to apply to everything as it is to Mesozoic dinosaurs >>-- and if so, I don't know about it.
When one starts dealing with groups that do horizontal gene transfer freely, problems arise. (Also, species produced by hybridization like some Brassica or the "Lonicera fly" (see URL to paper in my name, to avoid spamfilter, etc.) I know the PhyloCode allows for this by clades that overlap, but I'm not convinced it's a particularly good answer.
Bowler = Bowerbird x Roller hybrid?
I think this is a problem of phylogenetics, not of nomenclature; once a phylogenetic hypothesis exists, nomenclature can be applied to it. The PhyloCode will also allow for good old hybrid formulae, and clades that originated by hybridization can be named just like all others.