Tetrapod Zoology

Now that the main gekkotan groups have been introduced, it’s time to get down to some of the details. We begin with stuff on lifestyle and behaviour… [gekkotan motley below - mostly assembled from wikipedia - features (top, left to right) Aeluroscalabotes felinus, Pachydactylus bibronii, Rhacodactylus ciliatus and (bottom, left to right) Nephrurus amyae, Phyllodactylus xanti and Phelsuma madagascariensis].

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Gekkotans are mostly insectivorous, but some of the large species prey on other lizards, and even on snails, birds, mammals (including bats) and small snakes. Nectar and pollen is eaten by species of Phelsuma, Hoplodactylus and Naultinus. In general, geckos are predominantly visual predators with large, sensitive eyes. Some species have elaborately shaped, ‘notched’ pupils that close down to form a series of dots connected by zig-zagging lines. All gekkotans except eublepharids have done away with moveable eyelids, and the eyes are covered by immobile, transparent eyelids termed spectacles. They keep these clean by licking them. So it’s not that the eyelids are absent: rather, they’re fused, and the lower one is entirely transparent. Does anyone know how animals with transparent eyelids sleep?

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Gekkotans generally have short, rounded tongues that aren’t used much in detecting or discriminating prey.

The majority of gekkotans are nocturnal, and nocturnal behaviour is so widespread across the clade that it is likely primitive for the gekkotan crown-group. However, diurnality has evolved in many gekkotan clades (most famously in the Phelsuma day geckos of the western Indian Ocean). Some day geckos (like the recently extinct species P. gigas from Rodrigues) are or were nocturnal, meaning that these animals switched from diurnality (primitive condition for Squamata) to nocturnality (primitive condition for crown-Gekkota), then to diurnality (primitive condition for Phelsuma), and then back to nocturnality (derived condition within Phelsuma) within their evolutionary history (Austin et al. 2004). Oh, and some extant diurnal species within Phelsuma may be members of a clade that was ancestrally nocturnal, in which case they went from diurnality to nocturnality to diurnality to nocturnality, and finally back to diurnality [the day gecko Phelsuma inexpectata shown here; from wikipedia].

Lizards with loud voices

About 80 gecko species are highly vocal, and some species make clicks, chirps, quacking noises or loud growls or barks. The word gecko is supposedly a corrupted onomatopoeic reference to the call of the Tokay Gekko gecko, which sounds like ‘Tuck-too’ or ‘Tow-kay’ [Tokay shown below, from wikipedia].

Gecko calls mostly function in social and/or defensive behaviour: geckos in general are territorial reptiles and, in many vocal species, males use their calls to advertise their presence and to keep rivals away. Some species live colonially and have a dominance hierarchy. Among such social species, large choruses with an ‘almost deafening’ volume have been reported.

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How do geckos vocalise? By vibrating vocal cords housed within a cartilaginous larynx. In this respect they differ from other squamates: when non-gekkotan squamates make noises, they (mostly) do so by forcing air past the glottis, or by vibrating the tissues around the glottis. Laryngeal anatomy has proved complicated and diverse within gekkonid geckos: in Ptenopus, for example, the larynx is anteriorly placed in the head, asymmetrical in males, and superficially recalls the vocal apparatus of some frogs (Rittenhouse et al. 1998). Teratoscincus – the wonder geckos or frog-eyed geckos – stridulates by rubbing the armour plates on its tail together. Like many geckos, Teratoscincus species can autotomise (= shed or drop) their tails, and a thrashing autotomised tail also makes a loud hissing noise (Pianka & Vitt 2003).

Most geckos of both sexes possess paired, sac-like structures located posterior to the cloaca – the function of which is unknown – and males also possess bony cloacal rods… the function of which is also unknown (they might be something to do with widening the cloacal aperture during mating). Cloacal sacs and bones are absent in sphaerodactylids (Kluge 1982, Gamble et al. 2007).

Eggs, eggshells and cervical sacs

Most gekkotan species produce just one or two white, round or oval eggs. In contrast to many other lizards, they don’t exhibit parental care of any sort. The eggshell is soft and parchment-like in eublepharids, diplodactylines and pygopodids, but (once dry) hard, highly mineralised and impermeable in most gekkonids (and in the diplodactyline Eurydactyloides). While carphodactyline, diplodactyline and pygopodid eggs are elongate (including those of Eurydactyloides), those of some gekkonids (particularly larger species) are more spherical (Kratochvíl & Frynta 2005).

Gekkonid eggs are adhesive when first laid, and stick hard to the surface they’re laid on. This might be the inside of a hollow branch, under bark, on the underside of a rock or – in species that associate with humans – the side of a window-frame or cavity within a wall or roof. Females will sometimes lay communally, with as many as 186 eggs being recorded from one location.

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Thanks to their mineralised shells, gekkonid eggs can withstand exposure to sea water. This feature – combined with the small size of most geckos and their habit of associating with humans – means that some species have been transported inadvertently on boats and in timber. The Pacific gecko or Common house gecko Hemidactylus frenatus [shown above, from wikipedia] occurs on islands across the Indian and Pacific Ocean, throughout tropical Asia, Australia, on St. Helena in the South Atlantic, in Somalia, and in the USA, Mexico and Panama. It’s also been reported on occasion from Brazil, England and elsewhere. It’s therefore become both a human commensal and an alien invader, and may in fact be responsible for out-competing, and causing the local extinction of, other gecko species (Bauer 2000). Some species (like the Mourning gecko Lepidodactylus lugubris of the Pacific region) are parthenogenetic, and this has also helped them to be good colonisers of new places. Viviparity is present in the diplodactylines Naultinus and Hoplodactylus from New Zealand, and Rhacodactylus from New Caledonia.

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As just mentioned, those hard-shelled gekkonid eggs have highly mineralised shells. Animals that produce calcareous eggshells have to somehow store and mobilise the calcium they need. Female birds produce a special kind of bone (medullary bone) that acts as a calcium reservoir: it forms on the inside surfaces of their bone walls, and when the time is right, they’re able to mobilise huge amounts of calcium for eggshell generation. How do geckos produce all the extra calcium they need for eggshell production? The answer seems to be that they possess special, calcium-storing sacs or pouches – called endolymphatic glands – on either side of the neck (the sacs of Phyllodactylus shown here, from Kluge (1987)). Prior to egg-laying, these sacs enlarge and fill up with a sort of ‘calcium milk’. Because some geckos have semi-translucent skin, the sacs are visible in some individuals at some times. I’m sure there must be some funky x-ray images of reproductively active female geckos out there, but I can’t find any right now.

I should point out that endolymphatic glands are not unique to gekkotans – they’re actually widespead within squamates – and enlarged neck sacs are not unique either, as they’re also present in such iguanians as chameleons and agamids.

Comments

#1 John Scanlon, FCD
April 23, 2010

Does anyone know how animals with transparent eyelids sleep?

If they’re sleeping in the dark, disturbance by light is presumably not going to be a problem. Observation with infrared cameras is the way to look at this properly, but failing that I’ve got some naked-eye anecdotes.

On a few occasions I’ve uncovered a captive snake that then apparently remained asleep until touched, when they go straight from fully relaxed to a startle response (‘Oh sorry, I thought you were already awake’). And once or twice I’ve seen a sudden change in pupil diameter not related to change of lighting, which I would also identify as the moment of waking.

Snakes have relatively poorly developed ocular muscles but the eye can move a bit in the socket, and I’ve sometimes noticed what appeared to be saccades. From what I understand of neural optics, if saccades were turned off in us, for example, we’d pretty soon stop registering much of an image. Being able to switch them off might be just as effective as having eyelids, really.
#2 Bruce J. Mohn
April 23, 2010

My captive tokays would close down their pupils entirely during the day, which I would assume would be very similar to closing one’s eyelids, allowing sleep to take place.

On the tokay call, I had several males that produced a distinct TOW-KAY and a female who called GEK-KO.
#3 Alan
April 23, 2010

At one time we had Tokays living in the Reptile House here at Bristol – they bred several times. One summer evening one of them was seen to exit the skylight on the roof and catch a starling – they are serious predators!
#4 Neil
April 23, 2010

Sadly nothin interesting on constructive to contribute but Im liking the gecko posts
#5 Anthony Docimo
April 23, 2010

>Does anyone know how animals with transparent eyelids sleep?
is this a bad time to say “Very carefully”?

as to the parthenogenic Pacific colonizers, wouldn’t they be better able to colonize new niches if they alternated parthenogenisis and sexual reproduction? or is their niche such that they don’t need to adapt – their niche is de facto on every island?
#6 rajita
April 23, 2010

Great article. Is there a correlation between bright coloration and diurnality in gekkos? All nocturnal gekkos I have seen are either dull grey or pale brown somewhat like human skin color. I wonder if someone has done studies on the genetic relatedness in colonial gekkos ?
#7 Jura
April 23, 2010

Anthony Docimo wrote:

as to the parthenogenic Pacific colonizers, wouldn’t they be better able to colonize new niches if they alternated parthenogenisis and sexual reproduction? or is their niche such that they don’t need to adapt – their niche is de facto on every island?

They do alternate. The parthenogens that Darren was talking about, normally employ sexual reproduction. It is just that in the long term absence of males, females can asexually reproduce.

The benefit for island colonization comes in the fact that male reptiles from species that use genetic sex determination are homozygous. Theoretically one need only have one instance of parthenogenesis before switching back to sexual reproduction (admittedly a weak bloodline, but probably better than a clonal one).
#8 Jura
April 23, 2010

Another neat thing about geckos that wasn’t mentioned is that – unlike mammals – they have nocturnal colour vision.

Roth,L.S.V. and Kelber, A. 2004. Nocturnal Colour Vision in Geckos. Proc.R.Soc.Lond.B. Vol.271:S485-S487.
#9 Dr. Nick
April 24, 2010

Off-topic, but I was wondering whether you’d seen the new Genome Research paper advocating the recognition of multiple Orcinus species–

Morin PA, Archer FI, Foote AD, Vilstrup J, Allen EE, Wade P, Durban J, Parsons K, Pitman R, Li L, Bouffard P, Abel Nielsen SC, Rasmussen M, Willerslev E, Gilbert MTP, Harkins T. Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome Res, DOI: 10.1101/gr.102954.109 (Apr. 22, 2010)

–and if you happen to have access to a copy, whether I could get one.

Story at Science Daily: http://www.sciencedaily.com/releases/2010/04/100422121704.htm
#10 CS Shelton
April 24, 2010

OMGz, Jura… How do they have nocturnal color vision?
The most startling thing I took away from this post was the vocalization. I looked it up on youtube, and various gecko species make crazy weird noises. I had never seen a reptile do more than hiss. A world of freaky sounds has opened to me.
#11 Hai~Ren
April 25, 2010

Geckos are so common here in urban Singapore; we’ve got at least 3 commensal species, and a larger variety found in our forests. The tokay gecko itself seems to be extremely rare though, maybe because its not as adept as hiding in modern apartment blocks, and more prone to being killed when spotted by paranoid humans.
#12 Nathan Myers
April 25, 2010

I grew up with Hemidactylus frenatus, in Hawaii. (Thank you for identifying it.) I never noticed a detached tail hissing, but I didn’t know to listen for it.

In Bali, when a gecko in the ceiling begins chirping, conversation stalls as the chirps are counted. If it reaches seven, that’s taken as good luck for the household. Probably moreso for the gecko, I imagine, if the females can count that high.
#13 Darren Naish
April 25, 2010

WRT parthenogenesis (comment 7), I mentioned the Mourning gecko in the article, and isn’t this an obligate parthenogen? There are no males in the species at all.

Nathan (comment 12): detached tails only make a noise in the highly weird Teratoscincus.
#14 DD
April 25, 2010

The geckos’ endolymphatic glands contain calcium for eggshells, do they have facial NaCl salt glands?… do penguins which produce ‘milk’ for their chicks simply vomit the stomach contents or is there a supplemental gland in the neck similar to squamates that excretes some special nutrients into the ‘milk’ (Ca, hormone, oil)?

Female birds have pneumatic bones and medullary bone and air sacs but not calcium endolymphatic sacs. Almost makes me think that early birds were “squamate pufferfish” (or “inflatable frogs”) with small barbed skin spines that eventually became feathers. Might have feathers derived from poisonous skin spines? I recall that at least one tropical bird has poisonous feathers.
#15 Random Walker
April 25, 2010

L. lugubris is an obligate parthenogen. It’s a hybrid between two related gecko species, that has arisen multiple times. Some gecko species (Heteronotia binoei and Nactus pelagicus) are comprised of both sexual and asexual populations, so that might be where Jura was getting that from, though I don’t think they can’t switch back and forth. There are also some non-gecko lizards that can show parthenogenesis when there aren’t males around (Komodo Dragons come to mind, though I’m not sure if that’s been seen in the wild or not).

For more information, I recommend Clonality by John Avise. For all your asexual vertebrate needs. It also includes a lot of cool stuff about fish. Like the all female species that steal sperm from males of other species. Or the fish that are selfing hermaphrodites…

Also, I’m rather a fan of geckoes (I collect them! Except I’m poor and a student, so by ‘collect them’ I mean I have two species and would buy more if I could), so these posts have gotten me very excited
#16 Lela Criswell
April 25, 2010

Just purchased one of your newer books & am enjoying it very much. Unfortunately, there’s an error in the map on page 19 of the U.S. edition of The Great Dinosaur Discoveries. Morrison, Colorado, is north of Canyon City, so the names of these sites were somehow exchanged.
#17 John Scanlon, FCD
April 26, 2010

re. commensal geckos: where I live, we have four species around the house: Gehyra ?australis and occasionally Oedura rhombifer on the walls inside and outside, Hemidactylus frenatus in/on the sheds and front fence, and Strophurus ?ciliaris in the adjacent bushes. I don’t really keep up with species revisions in lizards these days, but the Gehyra is one of several species that occur around here on slightly different microhabitats (e.g. distinct species on rockfaces, fenceposts, and artificially lit walls within metres of each other). Hemidactylus is the only one that makes much noise (usually about ten notes to a call); the house dtella Gehyra has a similar call that is whispered rather than shouted, and ‘squelch’ noises when fighting each other. Juveniles emerge earlier in the evening to avoid competing with aggressive adults, and when two dtellas are close to each other the submissive one keeps its pigment on the surface (irregularly banded pattern in this species), while a dominant (or lone) gecko is ghostly grey while active at night.

There are also at least three skink species around the yard, a dragon, a goanna (seen once), a python and an elapid (Pseudonaja mengdeni), with many more species within a few hundred metres. Last week my wife saw a white-plumed honeyeater (sparrow-sized insectivore/nectivore) bashing a small snake-like squamate against its perch in the manner of a kookaburra, then swallowing it; from the size that was most likely a pygopodid (Delma, one of two species seen nearby). Anybody wonder why I like the tropics?
#18 David Marjanović
April 26, 2010

Almost makes me think that early birds were “squamate pufferfish” (or “inflatable frogs”)

Bird air sacs generally lack valves; they’re only in- and deflatable by ribcage action.

Besides, feathers are much older than birds. Surely you haven’t forgotten Sinosauropteryx already?

with small barbed skin spines that eventually became feathers. Might have feathers derived from poisonous skin spines? I recall that at least one tropical bird has poisonous feathers.

Feathers may well have originated as defensive spines, but the poisonous passerines from New Guinea (various species of Pitohui and Ifrita; the poison is pretty much in the whole body) don’t make their own poison, they get it from their food — poisonous beetles closely related to those that some South American poison-dart frogs get their poison from. It’s the same poison, hemibatrachotoxin.
#19 Chris Clark
April 26, 2010

Ok, now when do we get the really good stuff about geckos, like climbing up walls and nocturnal colour vision? There’s a couple of super-powers I would like to have…
#20 DD
April 26, 2010

DM, sorry, my error, I meant really early dino-birds, definitely including sinosauropteryx types and earlier. (Long wings just increased efficiency of arboreal ambushing.) I was actually thinking more along the lines of bristle-like porcupine barbed quills causing internal throat inflammation. (They also would provide support for perching.) Self-inflation, protruding barbed spines and possible emission of skin irritant onto sensitive throat tissue during predator swallowing could be very detrimental to a predator, and might be a behavioral precursor to todays’ animals expanding their perceived size with fur/feathers during attacks. This matches with many of todays’ snakes being either poisonous/fanged (airsacs deflate) or constrictor (airsacs explode), or fast chasers which simply swallow (since most fast prey species lack poison, spines and self-inflation).
#21 David Marjanović
April 27, 2010

Long wings just increased efficiency of arboreal ambushing.

Arboreal? Sinosauropteryx?

I was actually thinking more along the lines of bristle-like porcupine barbed quills causing internal throat inflammation. [...]

I know. It’s a neat idea, but there’s no evidence for it.

poisonous/fanged (airsacs deflate) or constrictor (airsacs explode)

Inflatable airsacs are much too rare to be a selection pressure on snakes.
#22 strangetruther
April 27, 2010

Don’t forget the two gliding gekkos – there was a nice prog on SE Asian gliders at the W/E on the Japanese channel NHK (Sky 516). (30 gliding species in SE Asia, a handful in Africa and none in S America).
#23 strangetruther
April 27, 2010

DD – Feathers could have evolved from defensive spines initially, and early use in arboreal ambushing looks like a good idea to me – though in both cases think Permian! – and there are a number of important stages subsequent to that for us to understand first! And bird feathers didn’t go via the Sinosauropteryx stage
#24 Sebastian Marquez
April 27, 2010

…a thrashing autotomised tail also makes a loud hissing noise

What?! That’s fascinating. How fast exactly can a shed tail thrash anyways? Are the scales loosely connected to the tail itself? I only ask because its difficult for me to see how an autotomised tail rubs against itself to stridulate.
#25 DD
April 27, 2010

DM: “Sinosauropteryx?” Yes, Sino. as post-arboreal. “Inflatable airsacs are much too rare..” Yes, today, partly due to snakes having been selected for constriction & poison fangs. (Air sacs can also provide buoyancy to non-diving waterside fauna, so doubly advantageous.)
#26 David Marjanović
April 28, 2010

And bird feathers didn’t go via the Sinosauropteryx stage

What makes you think so?

How fast exactly can a shed tail thrash anyways?

Till it dies from thirst or hunger. (Oxygen isn’t much of an issue for muscles.)

What did you think death means in a multicellular organism? Every cell dies for itself.

Yes, Sino. as post-arboreal.

Then please provide some evidence for an arboreal ancestry.

Yes, today, partly due to snakes having been selected for constriction & poison fangs.

Frankly, I haven’t seen such obvious special pleading in a long time.

(Air sacs can also provide buoyancy to non-diving waterside fauna, so doubly advantageous.)

Completely unnecessary, lungs already do that.
#27 Jaime A. Headden
April 28, 2010

I’d just like to insert a comment into this conversation and note that Sinosauropteryx lacks elongated forelimbs and under only the most derivative definition could it be said to have had “wings.”

Also, there is at least a subset of apparently respected followers of paleontology [palaeontology fot you guys across the pond] that argue that the structures in Sinosauropteryx‘ non-degraded-collagen “halo”, with their bundled and hollow nature, are derived from structures that can only come from arboreal theropods, i.e., that arboreality is one of the raisons d’être for the existence of any such structure.

It should be noted as well that Sinosauropteryx in this case has some of the most robust, and shortest, forelimbs for its bodyplan, leading one to think its particular appendicular morphology is derived. It only makes sense that larger limbs and “fluff” were present in an ancestor of Sinosauropteryx.

[please forgive the length of this post, the lack of citations, and a postscript I am using to lampshade this postscript.]
#28 Sebastian Marquez
April 28, 2010

David, I think there is a slight misunderstanding. I should have asked more clearly. The original question probably should have been if the noise made by the tails of wonder geckos are made in the same manner, shed or not.

No big deal, I was just surprised reading that an autotomised tail generates a loud hissing noise. Perhaps I read too much into that.
#29 DD
April 28, 2010

DM: “arboreal ancestry”~ DD: Arboreal opossums have 35 caudal vertebrae (most of any mammal), sino. had 64 (most of any theropod). DM: “special pleading”~ DD: What special pleading?
DM: “lungs”~ DD: Amongst non-divers, as lungs exhale they sink, air sacs allow sustained respiring while at surface. Divers develop alternatives (backfloating, partial/instantaneous exhale, non-alveolar lung areas).
#30 Jaime A. Headden
April 29, 2010

DD:

How precisely then would a longer tail then indicate aboreality?

Number of caudal vertebrae are not seemingly relevant to the issue of arboreality unless you can constrain them to other features. Unlike opossum, the dinosaurs in question lack any sort of opposable digits on any limb, were parasagittal in their limb design and could not effectively “hug” the branch, and their limbs seem ill-suited to quadrupedal motion anywhere (forelimbs being so much shorter than the hind).
#31 David Marjanović
April 29, 2010

DD: Arboreal opossums have 35 caudal vertebrae (most of any mammal), sino. had 64 (most of any theropod).

It’s not like as if climbing were the only reason to have a long tail. Running is another (attachment surface for the leg-retracting caudifemoralis muscle, balance). Please do keep in mind that the mobility of a tail depends on the shape of the vertebrae in very well understood ways, and that we can therefore tell that no known theropod had an anywhere-near-prehensile tail, Sinosauropteryx explicitly included. They were all stiff.

DM: “special pleading”~ DD: What special pleading?

You say snake fangs evolved as an adaptation to inflatable airsacs of prey. I point out that there’s no evidence for inflatable airsacs anywhere in bird ancestry. You say that this lack of evidence is caused by the evolution of snake fangs — congratulations, you’ve just made your own hypothesis untestable!

Like in the joke: “So, you want to work for us as a woodcutter. Where did you learn to fell trees?” — “In the Sahara.” — “What? There aren’t any trees in the Sahara!” — “Not anymore.”

Snake fangs only date from the Eocene, BTW.

DM: “lungs”~ DD: Amongst non-divers, as lungs exhale they sink, air sacs allow sustained respiring while at surface.

This is complete nonsense. You don’t understand what you’re talking about.
#32 DD
May 9, 2010

JH: arboreal tails? DD: arboreals (except very small ones) typically tend to favor upright posture resulting in changed limb proportions and have either very long tails (curled or straight) or extremely shortened tails in association with perching hooks (curved claws/phallanges) or sticky fingertips. In birds and pterosaurs and some dinos, long stiff tail feathers replaced long stiff tails (with bristled scales/feathers) of elongated multiple vertebrae, typically in association with jaw changes (heavy teeth to keratin beak). I view Sino. as a sort of leopard-toucan dino.
DM: “running” tail~ DD: runners generally have medium tails but long tail hair or feathers. (insect swatting is a factor) DM: “prehensile” DD: apparently you define that only as curling around branches. I use it to define anchoring to tree, both curling and straight with bristle scales/feathers. DM: “caudifemoralis” DD: Don’t arboreals retract their legs? (tailless indris & siamangs)
DM: “snake fangs, air sacs”: I said “partly” a factor, with flotation and communication (vocal, size) being factors in air sac evolution. Eocene snake fangs sounds right, after titanaboa, fangs allowed smaller snakes. Birds have air-filled (inflated) sacs which cause the whole bird to be buoyant (and harder to swallow whole), they do not have completely deflatable air sacs, unlike frogs and most apes. There are trees in the Sahara, two grow at the salt springs of Teguidda-n-Tessoumt, Niger. DM: “nonsense” DD: What precisely is nonsense? Air (gas) in water (liquid) rises, water (liquid) in air (gas) drops. I’ve watched frogs floating with inflated air sacs at surface.
http://www.californiaherps.com/movies/pregillacall708.mov
#33 David Marjanović
May 9, 2010

In birds and pterosaurs and some dinos, long stiff tail feathers replaced long stiff tails (with bristled scales/feathers) of elongated multiple vertebrae,

Not in pterosaurs, obviously.

Not in all that many birds either.

typically in association with jaw changes (heavy teeth to keratin beak).

Plenty of short-tailed birds have a full dentition, from Sinornis to Yanornis. Then there are those with an almost complete dentition, like Boluochia, the hesperornithiforms, and Ichthyornis.

Almost all short-tailed pterosaurs retain a full dentition with, usually, very large teeth that must have weighed something! Pteranodon, Nyctosaurus, and the azhdarchoids are exceptions.

I know many textbooks say the lack of teeth in modern birds is a weight-saving adaptation. I think they’re all wrong, and lack of teeth is an adaptation to whichever specific diet(s).

I view Sino. as a sort of leopard-toucan dino.

Why? It was a running terrestrial predator — we have its stomach contents to show it.

DM: “running” tail~ DD: runners generally have medium tails but long tail hair or feathers. (insect swatting is a factor)

You’re thinking of mammals. I’m thinking of tails that contain most of the leg-retracting musculature and are used for balance in a biped.

DM: “prehensile” DD: apparently you define that only as curling around branches. I use it to define anchoring to tree, both curling and straight with bristle scales/feathers.

You don’t get to redefine technical terms. “Prehensile” means “grasping”, so, yes, a prehensile tail by definition curls around stuff. Latin prehendere = take ~ grasp. A tail used as a prop, like a woodpecker’s tail feathers, isn’t prehensile.

DM: “caudifemoralis” DD: Don’t arboreals retract their legs? (tailless indris & siamangs)

Your examples are mammals and, like all mammals, use a different muscle for leg retraction. That muscle does not attach to the tail, which is why tail reduction is so easy and so common in mammals.

Birds have air-filled (inflated) sacs

They’re not inflated — they don’t increase the volume of the animal. They occupy space that would otherwise be filled with fat or belong to the lung.

which cause the whole bird to be buoyant

A bit more than otherwise. You’re buoyant, too, unless you exhale completely (and have very little body fat).

There are trees in the Sahara

That’s an impressive way to completely miss my point.

I’ve watched frogs floating with inflated air sacs at surface.

They’d still float even without those air sacs. So do you — you should try it. They just stick out of the water a little more than otherwise.

My point is that air sacs are not necessary for floating. (And those of birds would be unsuitable for that anyway.)
#34 DD
May 9, 2010

DM: “Pterosaurs” DD: oops, I meant long bony tails were lost, arb. birds & dinos replaced them with long tail feathers, while pterosaurs retained had flexible necks/heads (unlike evolution of most arboreal birds) and perching claws while shrinking the inflexible tails. I think all modern birds derived from long-feathered-tailed ancestors, so contra your “not in all that many birds”. Birds that lift-off from water usually shrink/curl the tail feathers, (even arboreal wood ducks), so that’s a factor. DM: Short tailed/Sinornis DD: yes, short snouted opposing a short tail. Dental changes were slower evolving than claw changes in birds and pterosaurs, because claw gripping replaced teeth gripping. Teeth loss due to flight, can’t have heavy bone/teeth at front/rear except in long gliders which launched from solid substrates (ground, thick branches). Toothy short-tailed pterosaurs probably lifted-off from water surface or from springy twigs. DM: “sino” runner DD: yes but derived from more arboreal ancestor, and only partly runner. So prehensile means hook, a curved tail, claw or finger, tensile + precessional (90 degrees to axis), not compressional. But the scale/feather barbs did act as hooks, just at a smaller scale, and they were semi-controllable, as feathers are today. Only a long straight tail without barbs would be non-prehensile (eg. used as a pendulum for balance, not traction). DM: “doesn’t attach to tail” DD: OK, early short tailed birds hopped when climbing but walked while on ground, frogs & kangaroos the opposite. Birds have permanently inflated air sacs, bats don’t, both float on water but birds float higher partly due to selection for ancestral float foraging. Tidal breathers have inflatable air sacs to float forage (eating, breathing, vocalizing while not on solid surface). Rainforest canopy dwellers (tree frogs, gibbons) lose the air sacs and reduce size, subcanopy dwellers retain both (frogs, apes) because they spend more time near open water. Accordingly dinobirds were subcanopy (ambush gliders on low branches), then became canopy dwellers with reduced size (but retained large air sacs) and weight (teeth/tail/organ reduction). DM: “They just stick out of the water a little more than otherwise.” DD: Precisely my point, just enough to keep the nostrils always above the surface while breathing, eating, vocalizing while resting. (Humans and sea otters can’t do that except backfloating, where nostrils are above surface during rest) Freshwater floating – large air sacs (frogs, apes); marine floating – small air sacs (or air-trap fur) and/or non-alveolar lung areas. I’d expect that pterosaurs could not dive deep being too buoyant, so I referred to skimming but that would include shallow submerging.

OT – Do parthenogenic species have faster mutating gut bacteria and mtDNA than sexual reproducing species? I’d guess so.
#35 DD
May 9, 2010

Sorry, typo, “while pterosaurs had long flexible necks/heads…” (birds varied, owls have short, storks have long necks).
#36 David Marjanović
May 10, 2010

DD, please start using the Enter key. A wall of text can be a bit confusing.

while pterosaurs retained had [long] flexible necks/heads

What? Pterosaur necks were remarkably inflexible — the longer, the more inflexible.

I think all modern birds derived from long-feathered-tailed ancestors

Why do you think so?

Birds that lift-off from water usually shrink/curl the tail feathers, (even arboreal wood ducks), so that’s a factor.

Well, no, because lifting off from water is an advanced ability that must have evolved late.

claw gripping replaced teeth gripping.

What?

Teeth loss due to flight, can’t have heavy bone/teeth at front/rear except in long gliders which launched from solid substrates (ground, thick branches).

Gliders can’t launch from the ground, by definition, unless you mean off a cliff. Many pterosaurs were too big to climb into a tree, and many lived in environments known to lack cliffs.

Toothy short-tailed pterosaurs probably lifted-off from water surface or from springy twigs.

Then why did they ever land on beaches, as their footprints demonstrate? No, they lifted off the same way as azhdarchids. That’s the only option that makes sense.

DM: “sino” runner DD: yes but derived from more arboreal ancestor, and only partly runner.

Evidence for both of these remarkable assertions, please.

the scale/feather barbs did act as hooks

How? I’m not sure I understand what you mean.

early short tailed birds hopped when climbing but walked while on ground

Evidence, please.

birds float higher partly due to selection for ancestral float foraging

Birds are ancestrally aquatic? I didn’t get the memo. Evidence, please.

Tidal breathers have inflatable air sacs

…but the air sacs of birds are not separately inflatable. The only way to in- or deflate them is to breathe!

subcanopy dwellers retain both (frogs, apes) because they spend more time near open water

You seriously compare frogs and apes?

How many apes other than us ever swim? The closest I’ve seen is rare footage of orang-utans walking into water a bit.

Accordingly dinobirds were subcanopy (ambush gliders on low branches), then became canopy dwellers with reduced size (but retained large air sacs)

Then where are their adaptations to climbing? Or to gliding, in fact.

DM: “They just stick out of the water a little more than otherwise.” DD: Precisely my point, just enough to keep the nostrils always above the surface while breathing, eating, vocalizing while resting.

Please. We’re talking about animals with long necks that are held in an S-shape. The nostrils of such animals are always high above the surface unless the animal is comatose or dead.

This, incidentally, is also why we don’t need to backfloat while swimming. In fact, I hate backfloating, because water gets into my ears that way.

Freshwater floating – large air sacs (frogs, apes)

Why do you keep fantasizing about floating apes?

Do parthenogenic species have faster mutating gut bacteria and mtDNA than sexual reproducing species? I’d guess so.

Mutation rates absolutely don’t care about such things, they’re limited by basic chemistry, so I suppose you mean rates of evolution (mutations that persist into the following generations).

And for those, my answer is no. Gut bacteria aren’t inherited in different ways in sexual and parthenogenetic species, and neither are mitochondria (inheritance of paternal mitochondria is rare); importantly, mitochondria themselves don’t do sexual reproduction.
#37 Dartian
May 10, 2010

David:

many textbooks say the lack of teeth in modern birds is a weight-saving adaptation. I think they’re all wrong, and lack of teeth is an adaptation to whichever specific diet(s)

Interesting. Can you elaborate on this idea? (Or is this a case of ‘Wait for the paper’?)
#38 DD
May 10, 2010

DM: pterosaur necks ~ DD: I was thinking of arboreal pterosaurs, not albatross-like ones which would indeed be expected to have inflexible necks.
DM: bird tail length~ DD: long tails allowed tree anchorage, as perching claws evolved shorter tail feathers gave an advantage to water birds and springy-twig nesters but not as much to ground birds (eg. swimming rheas).
DM: water lifting birds late~ DD: http://www.sciencedaily.com/releases/2006/06/060615234900.htm and later Dasornis emuinsus
DM: What? DD: upright branch perching improved predatorial grasping. Toothy cats and dogs will swat, but birds will grasp and constrict with the claws.
DM: long glider launching~ DD: dunes, hillocks, riverbanks during daylight would have differential sunny/shade breezes giving lift. High cliffs not necessarily required.
DM: Why’d they land on beaches? DD: Why wouldn’t they? Wood ducks & herons do too, sometimes high tide brings food. Short tail feathers = launch, not landing, advantage.
DM: sino-evidence~ DD: given (most caudal vertebrae)
DM: barb hooks? DD: velour crochet, velcro on trees

DM: evidence for hop-climbing & ground walking DD: logical inference, running dinobirds couldn’t climb upright, hop-climbing birds never lost walking ability (cf upright siamangs, sifakas and qpal goats climb trees but running ostriches can’t). DM: birds aquatic? DD: bird ancestors selected for waterside foraging gave flotation an advantage, food mostly near water during drought, (but unaccessible during freeze).
DM: bird air sacs~ DD: always inflated, always buoyant.
DM: frogs and apes DD: precise parallel, those in canopy or underwater lack air sacs, those in-between retain them.
AFAICT The primary protein source of the vegetarian lowland gorilla at Ndoki swamp is hydrocharis, a floating plant which they wade to and rake with fingers; face-up air sac inflation/flotation provide a significant foraging survival advantage, while horizontal swimming (too weedy) and vertical diving do not. Early humans got protein from both the surface and benthos, so diving & backfloating was selected for. Swimming is action, burns energy, floating is inaction and doesn’t (in calm warm water). An orphan orangutan surface-swam one meter.

DM: dinobird signs of climbing & gliding? DD: dinobirds were generalists, not specialists, their short ambush-leap-gliding was associated with upright hop-climbing (using forelimbs for assistance). Later, birds were more flight-specialised due to perching/constricting claws, still hop-climbed but also flew to the canopy.
DM: S shaped long necked~ DD: Yes, most evolved around water but don’t backfloat, to rest they tuck their bills around back, just above the inflated abdominal air sac in a P shape rather than an S shape. Pterosaurs with stiff long necks maybe couldn’t do that, so maybe they slept between beach dunes ashore or unihemispherically like terns/sharks/dolphins do.
DM: backfloating and ears~ DD: ear plugs for coldwater. I think earwax is specifically anti-salt crystal, similar to how sea otter fur oil prevents salt & ice crystal formation during sleep.
#39 David Marjanović
May 11, 2010

DM: pterosaur necks ~ DD: I was thinking of arboreal pterosaurs

There are no known arboreal pterosaurs! Except probably “Nemicolopterus“, which is most likely a baby Sinopterus, and adult Sinopterus were clearly not arboreal.

You don’t even seem to notice when you’re making stuff up.

long tails allowed tree anchorage

How does the tail of Archaeopteryx allow any such thing?

DM: water lifting birds late~ DD: http://www.sciencedaily.com/releases/2006/06/060615234900.htm and later Dasornis emuin[...]us

Sorry for being unclear — that’s what I mean by “late”. Gansus is a 115-million-year-old derived euornithine; the split between Enantiornithes and Euornithes happened at least 25 million years earlier than that, and the splits between these two together ( = Ornithothoraces) and other short-tailed flying birds like Confuciusornis and Sapeornis must have happened earlier still.

upright branch perching improved predatorial grasping. Toothy cats and dogs will swat, but birds will grasp and constrict with the claws.

You completely overlook the fact that the ability to grasp with the foot (which means that the 1st toe is positioned opposite the others) came after the birds shortened their tails. It’s basically limited to Ornithothoraces and Scansoriopterygiae; the confuciusornithids had about half of it, Archie lacked it entirely…

The feet of other dinosaurs like Deinonychus have occasionally been illustrated with an opposed 1st toe. All that has turned out to be wrong, starting with the work of Kevin Middleton in 1999.

This, together with the lack of other adaptations to climbing, is good evidence that bird flight did not start in the trees.

DM: long glider launching~

I think you refer to my statement that “gliders can’t launch from the ground”. Right?

DM: Why’d they land on beaches? DD: Why wouldn’t they? Wood ducks & herons do too, sometimes high tide brings food.

Herons can’t even land on water. But the important part is that both ducks and herons can take off from the ground! A glider just can’t take off from a beach!

Short tail feathers = launch, not landing, advantage.

Details, please.

DM: sino-evidence~ DD: given (most caudal vertebrae)

No. Fuck no. I already told you the tail wasn’t mobile enough for climbing. Why do you simply ignore that?

It’s a counterweight and provides attachment surface for the musculus caudifemoralis longus.

DM: barb hooks? DD: velour crochet, velcro on trees

Please. You don’t believe that yourself. Take a feather, hold it to a tree trunk, and tell me what happens.

That’s embarrassing.

DM: evidence for hop-climbing & ground walking DD: logical inference, running dinobirds couldn’t climb upright, hop-climbing birds never lost walking ability (cf upright siamangs, sifakas and qpal goats climb trees but running ostriches can’t).

From what do you infer hopping?

DM: birds aquatic? DD: bird ancestors selected for waterside foraging

What makes you think there was any selection for waterside foraging?

That’s the part I don’t get. As far as I can tell, you simply assume it.

DM: frogs and apes DD: precise parallel, those in canopy or underwater lack air sacs, those in-between retain them.

Are gibbons not in the canopy?

Why do you extrapolate from one single parallel to everything else?

AFAICT The primary protein source of the vegetarian lowland gorilla at Ndoki swamp is hydrocharis, a floating plant which they wade to and rake with fingers; face-up air sac inflation/flotation provide a significant foraging survival advantage, while horizontal swimming (too weedy) and vertical diving do not.

But horizontal swimming is where flotation is an advantage. For wading it’s completely unnecessary.

And why do you simply assume that the lifestyle of the Ndoki gorillas is ancestral for African apes as a whole? Just because it fits your concept?

An orphan orangutan surface-swam one meter.

Good. Does that happen often enough for natural selection to kick in? And isn’t 1 m just its own body length?

DM: dinobird signs of climbing & gliding? DD: dinobirds were generalists, not specialists

Those that we’ve found so far were pretty highly specialized for a terrestrial existence, the scansoriopterygids excepted.

Also, there’s no evidence for gliding.

Later, birds were more flight-specialised due to perching/constricting claws

See above: perching came long after flight.

DM: S shaped long necked~ DD: Yes, most evolved around water

Coelophysis?

Massospondylus?

Hello?

An S-shaped neck is normal for saurischians.

DM: backfloating and ears~ DD: ear plugs for coldwater. I think earwax is specifically anti-salt crystal, similar to how sea otter fur oil prevents salt & ice crystal formation during sleep.

Then why don’t I produce enough earwax for that?

Why can’t earwax simply have the same functions as snot? Keep in mind that the outer ear, which is limited to mammals, is lined with normal skin rather than mucosa.
#40 David Marjanović
May 11, 2010

Besides, please learn to use the <blockquote> tag. This:

<blockquote>text</blockquote>

appears this way:

text

Your summaries of what I said are so extremely brief that I often have trouble recognizing what you’re referring to, and trouble figuring out if you remembered it correctly when you wrote the summary.
#41 Andreas Johansson
May 11, 2010

David Marjanović wrote:

This, together with the lack of other adaptations to climbing, is good evidence that bird flight did not start in the trees.

Perhaps it got started because protobirds, not being well adapted to perching or climbing, kept falling out of trees?
#42 DD
May 13, 2010

(busy now, a comment I sent to Laelaps on amph. elephants)
Mammoths, dugongs, rock hyraxes and kin derive from antarctic-temperate Gondwana swamp hyraxes which fed on annual plant rhyzomes and perennial plant cambium tissues (parallel to arctic-temperate Laurasian giant beavers) with functional cutting incisors, then due to change to tropical African climate specialized on other foods with resulting change in dentition and niche specializations.

A similar parallel occurred in primate-anthropoid-hominoid LCA, eg. the lowland gorilla, Oreopithecus and Gigantopithicus foraged in wetlands eating plants but combined prehensile hands and teeth (not prehensile lips and tusks due to inflated laryngeal air sac) to rake, dig and peel herbaceous vegetation, (this induced greater upright posture part-time). Human ancestors added benthic foods, while small gibbons stopped waterside foraging, both lost their lar. air sacs.

AJ: falling~ DD: controlled descent = pounce! Early ones were not that high up, I figure leaping-leopard-like.
#43 DD
May 13, 2010

DM, notice the frond tail in the illustration
http://en.wikipedia.org/wiki/Archaeopteryx
The tail muscles loosened and tightened the frond, giving a zipper-velcro effect of prehensile anchorage to treebark, NOT by curling the tail; possibly the partial-reversed toe muscle was linked to this tail muscle in some way, (caudifemoralis?) to constrict it forwardly, as part of improved perching on smaller branches; then the long tail shrank and become fan-like feathers. Leap-pouncing did not require strong reversed-toe constriction, just directed mass with jaws and claws, but post-attack carrying-flight to evade competition from other pouncers did. (Where do leopards take their prey? Tree branches, easier to defend.)
#44 David Marjanović
May 13, 2010

DD, will you please stop describing your dreams as facts!?!

Mammoths, dugongs, rock hyraxes and kin derive from antarctic-temperate Gondwana swamp hyraxes

This is just ridiculous. Hyraxes have never occurred outside Africa and (since the Miocene) adjacent parts of Eurasia. South Africa’s south coast was tropical already in the Paleocene…

Why do you always build your ideas on so few facts? You always overlook tons of facts that don’t fit your ideas.

which fed on annual plant rh[i]zomes and perennial plant cambium tissues (parallel to arctic-temperate Laurasian giant beavers)

Hooray! Speculative zoology! You invent animals that could possibly have existed, granted, but for which there is zero evidence!

with functional cutting incisors,

Hyraxes? Cutting incisors? The second incisors are lengthened and pointed; same in elephants.

then due to change to tropical African climate specialized on other foods with resulting change in dentition and niche specializations.

What changes to tropical African climate? From tropical to tropical?

A similar parallel occurred in primate-anthropoid-hominoid LCA, eg. the lowland gorilla, Oreopithecus and Gigantopithicus foraged in wetlands eating plants but combined prehensile hands and teeth (not prehensile lips and tusks due to inflated laryngeal air sac) to rake, dig and peel herbaceous vegetation, (this induced greater upright posture part-time).

Wetlands?

You’re making shit up, as, sadly, usual. Gigantopithecus lived in bamboo forests… and we don’t fucking know if it walked upright, let alone if it had a laryngeal air sac! The damn beast is only known from isolated teeth and jaw fragments!!!

Besides, neither Oreopithecus nor Gigantopithecus are among our ancestors.

Human ancestors added benthic foods, while small gibbons stopped waterside foraging, both lost their lar. air sacs.

Nice scenario, but unparsimonious. No evidence for it.

The tail muscles loosened and tightened the frond

Possibly. Neither the bones nor the feathers tell us. To state it as a fact is… irresponsible.

giving a zipper-velcro effect

Really, where do you get that idea from? ~:-|

the partial-reversed toe

No. For a long time it was thought the 1st toe was wholly or partially reversed, but new studies, and the 10th (Thermopolis) specimen, show unambiguously that that toe was not reversed at all. If you want me to send you the PDFs of two papers on this issue, find me in Google Scholar and drop me an e-mail.

possibly the partial-reversed toe muscle was linked to this tail muscle in some way, (caudifemoralis?)

Just… no. That’s not what vertebrate anatomy is like. Forget about it.

Where do leopards take their prey? Tree branches, easier to defend.

Yes, but they’re better climbers than any Mesozoic dinosaur (and almost all extant ones), and descended from even more scansorial or arboreal animals. They’re not like dinosaurs.
#45 DD
May 13, 2010

blockquote? This is tetrapod zoology. How about tetrahedronquote? Minimum volume, maximum surface area, prime structure, per Bucky (Buckyball) Fuller. Children play with blocks!