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Natural Science Forum / Biology / Paleontology / April 2006Prolacerta/Prolacertaform Sources
Did a 'clusty' on 'prolacerta' and found a number of sources. I am now looking for more, both online and offline. Yes, I did locate a listing for a book on prolacerta in Antarctica, but it's out of print. If you know where I can find information on the beast it would be most appreciated. From the one picture I found on the web I'd have to say the animal somewhat resembled a monitor lizard superficially. Perhaps the artist was thinking monitor when he did the rendition. > Did a 'clusty' on 'prolacerta' and found a number of sources. I am now > looking for more, both online and offline. Yes, I did locate a listing [quoted text clipped - 5 lines] > somewhat resembled a monitor lizard superficially. Perhaps the artist > was thinking monitor when he did the rendition. A good recent paper is Modesto and Sues (2004) on the skull: http://www.ingentaconnect.com/content/bsc/zoj/2004/00000140/00000003/art00002 will get you the abstract (drop me a line if you can't find it in a library). Prolacerta was an early Triassic archosauromorph, more similar in the basic structure of the skull to a small theropod dinosaur rather than any lizard; postcranially it was more like a crocodile, but with relatively long neck and legs. The most theropod-like lizards living today are certainly the monitors, many of which are similar to Prolacerta in size (head length around 10 cm) and have a long neck, long pointed snout and recurved, blade-like teeth. > > Did a 'clusty' on 'prolacerta' and found a number of sources. I am now > > looking for more, both online and offline. Yes, I did locate a listing [quoted text clipped - 18 lines] > Prolacerta in size (head length around 10 cm) and have a long neck, > long pointed snout and recurved, blade-like teeth. A trip to the UCSD Central Library is in my future. :) Much thanks. From what I've seen so far, it looks like - on a fundamentally different Earth - ol' Prolacerta *sp* would make a great dragon ancestor. (You just knew I was a nefarious soul. :D ) More information is still good, would give my project an even greater air of versimilatude. > Did a 'clusty' on 'prolacerta' and found a number of sources. I am now > looking for more, both online and offline. Yes, I did locate a listing [quoted text clipped - 5 lines] > somewhat resembled a monitor lizard superficially. Perhaps the artist > was thinking monitor when he did the rendition. Wouldn't Tanystropheus work better from your perspective? > > Did a 'clusty' on 'prolacerta' and found a number of sources. I am now > > looking for more, both online and offline. Yes, I did locate a listing [quoted text clipped - 7 lines] > > Wouldn't Tanystropheus work better from your perspective? Not really, Tanystropheus is already too specialized. Prolacerta, while specialized to soom degree, still has a degree of evolutionary wiggle room. Understand that in the world creation business - even when said world is a fantastical one - versimilitude and plausibility count for a lot. You would think that it would be a case of anything goes, but in truth the aim is to be as faithful to reality in the mundane aspects, the better to encourage the acceptance of the fantastic when it appears. Using a real world animal as ancestor to a suite of fantasy creatures (pseudo-mamalliforms for example) adds to the reader's experience. (Think Dinotopia, only without the quasi-utopianism.) Really, when you want to explore alternate evolutionary pathways you need an animal with potential, not one that has become highly specialized. >>>Did a 'clusty' on 'prolacerta' and found a number of sources. I am now >>>looking for more, both online and offline. Yes, I did locate a listing [quoted text clipped - 23 lines] > need an animal with potential, not one that has become highly > specialized. "Highly specialized" is in the eye of the beholder. But no big deal. The real problem to swallow is that duplication of the forelimbs, since nothing of the sort has ever happened in vertebrate evolution. Makes me suspect that you can't get there from here. > >>>Did a 'clusty' on 'prolacerta' and found a number of sources. I am now > >>>looking for more, both online and offline. Yes, I did locate a listing [quoted text clipped - 28 lines] > nothing of the sort has ever happened in vertebrate evolution. Makes me > suspect that you can't get there from here. That is indeed a problem. One could say that it's a re-expression of the genes in early rhipsidarian fish that produced three or even four pairs of lobed fins, but I thought I'd explain it as a glitch in those Vox Family genes directing forelimb growth allowing for a subsequent expression. After all, just because it didn't happen doesn't mean it couldn't happen. It's just that the right alteration in the genetic code didn't occur to allow for functional vertebrate hexapedy (which is now a word) in our world. The problem is, apparently having three pairs of limbs is not as efficient as having two. The extra expenditure in resources during embryonic development, plus the disadvantages six limbs gives during life compared to four. Then there is the fact that early Dracos was simply not as good as the early primates in their shared niches. They were basically outcompeted. Though the primitive quadrapedal dragons did outlast the early hexapedal dragons. (Note that we're now dealing with the paleontology of an imaginary world. Continuing on in that vein.) The order Dracos is divided into two sub-orders, the Draciform and the Vermiform. The Vermiform having two infraorders, the pseudo-mamalliform and the pseudo-squamate. (So called because of the shen lung's resemblance to a skink. Albeit an eight foot long skink with elongated spinal processes and the ability to fly sans wings.) (In case you're wondering, I am getting my critters from *that* game. My purpose in this series is to put a fantasy game world on a scientific basis. To produce a convincing scientific rationale for my setting. Then there's the fact I like ancient life and I enjoy learing about it.) The first members of the sub-order Draciform rather resembled North American river otters in general conformation. thus the alternate name for the Draciform, the pseudo-theriform. Or, false beast shape. Limbs tucked in, a diaphragm, the classic equine neck. And, unlike other descendents of Prolacerta, Dracos retained the primitive five digit condition. What distinguished them from their pre-Draciform ancestors was the placement of the other two lower jawbones beneath the Dentary, where they play no appreciable role. It was the resulting mammal like jaw hinge which lead one researcher to mistake an early dragon for a mammal, and place it among the triconodonts. It wasn't until a study was done of the specimen's middle ear that the presence of the Stapes alone was noted and the animal correctly assigned. (Which is all more than you were probably asking for, so I'll cut it short here.) >>>>>Did a 'clusty' on 'prolacerta' and found a number of sources. I am now >>>>>looking for more, both online and offline. Yes, I did locate a listing [quoted text clipped - 38 lines] > didn't occur to allow for functional vertebrate hexapedy (which is now a > word) in our world. I hope you fix your spelling problems. The word is rhipidistian, and you should know that it's yet another paraphyletic group like Thecodontia, and not in current use. Also, when you said Vox, did you mean Hox? And which ones were you thinking of with extra fins? Are you perhaps thinking of some acanthodians? Feel free to do anything you like in fiction, but if you want it to be biologically credible, it's not going to, um, fly. > The problem is, apparently having three pairs of limbs is not as > efficient as having two. The extra expenditure in resources during > embryonic development, plus the disadvantages six limbs gives during > life compared to four. Not that I can tell. Hexapedy doesn't even happen as a mutation in vertebrates, as far as I know. It's not selection that forbids it, but the absence of any such mutation. Maybe if it happened selection would dispose of the mutation, but we never get to that point. > Then there is the fact that early Dracos was simply not as good as the > early primates in their shared niches. They were basically outcompeted. [quoted text clipped - 6 lines] > The order Dracos is divided into two sub-orders, the Draciform and the > Vermiform. Note on terminology: Dracos is not a well-formed name for an order. It should be a Latin plural of some kind. Dracones would do, I think. And draciform doesn't work either; it would be draconiform. You also seem to be confusing nouns and adjectives. The suborder would be Draconiformes (capitalized) and the corresponding adjective would be draconiform (not capitalized). More confusing, members of the suborder could be referred to as draconiforms (not capitalized). I'm assuming you want to know these picky details. [snippy snip snip] >> The problem is, apparently having three pairs of limbs is not as >> efficient as having two. The extra expenditure in resources during >> embryonic development, plus the disadvantages six limbs gives during >> life compared to four. >Not that I can tell. Hexapedy doesn't even happen as a mutation in >vertebrates, as far as I know. It's not selection that forbids it, but >the absence of any such mutation. Maybe if it happened selection would >dispose of the mutation, but we never get to that point. I could swear I've seen photos of frogs from polluted ponds with an extra set of limbs. Not very well formed or functional limbs, but limbs nevertheless. I assume this is a developmental thing, rather than a mutation, but I don't see why a mutation couldn't have the same effect. Is there any reason to think it really doesn't happen, rather than simply being to rare for us to have noticed it? (And is anyone really looking?)  SignatureJohn Brock jbrock@panix.com >>>The problem is, apparently having three pairs of limbs is not as >>>efficient as having two. The extra expenditure in resources during [quoted text clipped - 13 lines] > doesn't happen, rather than simply being to rare for us to have > noticed it? (And is anyone really looking?) I think we are looking. Developmental anomalies have often been studied as a guide to developmental processes. I don't know of any duplicated limbs, only bifurcated ones, i.e. extra fingers, the occasional extra hand, and perhaps a spare radius and ulna. But never a complete and separate arm. I could be wrong. >>>>The problem is, apparently having three pairs of limbs is not as >>>>efficient as having two. The extra expenditure in resources during >>>>embryonic development, plus the disadvantages six limbs gives during >>>>life compared to four. >>>Not that I can tell. Hexapedy doesn't even happen as a mutation in >>>vertebrates, as far as I know. It's not selection that forbids it, but >>>the absence of any such mutation. Maybe if it happened selection would >>>dispose of the mutation, but we never get to that point. >> I could swear I've seen photos of frogs from polluted ponds with >> an extra set of limbs. Not very well formed or functional limbs, [quoted text clipped - 3 lines] >> doesn't happen, rather than simply being to rare for us to have >> noticed it? (And is anyone really looking?) >I think we are looking. Developmental anomalies have often been studied >as a guide to developmental processes. I don't know of any duplicated >limbs, only bifurcated ones, i.e. extra fingers, the occasional extra >hand, and perhaps a spare radius and ulna. But never a complete and >separate arm. I could be wrong. Well, a quick Google search turned up: http://www.solcomhouse.com/frogs.htm http://news.bbc.co.uk/cbbcnews/hi/sci_tech/newsid_2117000/2117263.stm http://www.sciam.com/article.cfm?articleID=0004B992-1F95-1C75-9B81809EC588EF21 http://www.news.wisc.edu/9233.html ...and..., um..., http://www.orehole.com/nffrogs.htm SignatureJohn Brock jbrock@panix.com >>>>>The problem is, apparently having three pairs of limbs is not as >>>>>efficient as having two. The extra expenditure in resources during [quoted text clipped - 29 lines] > > http://www.news.wisc.edu/9233.html OK, so we get as far as duplicating the femur. But what's required here is an entire extra pelvic girdle. (Or, in the case the author wants here, the pectoral girdle. > ...and..., um..., > > http://www.orehole.com/nffrogs.htm That actually appears to be some kind of frog/human hybrid. on Fri, 07 Apr 2006 02:42:42 GMT, John Harshman <jharshman.diespamdie@pacbell.net> sez: ` John Brock wrote: ` > In article <OqgZf.55890$F_3.2747@newssvr29.news.prodigy.net>, ` > ` >>John Brock wrote: ` > ` > ` >>>In article <IqaZf.55805$F_3.37105@newssvr29.news.prodigy.net>, ` > ` > ` >>>>Alan Kellogg wrote: ` > ` > ` >>>>>The problem is, apparently having three pairs of limbs is not as ` >>>>>efficient as having two. The extra expenditure in resources during ` >>>>>embryonic development, plus the disadvantages six limbs gives during ` >>>>>life compared to four. ` > ` > ` >>>>Not that I can tell. Hexapedy doesn't even happen as a mutation in ` >>>>vertebrates, as far as I know. It's not selection that forbids it, but ` >>>>the absence of any such mutation. Maybe if it happened selection would ` >>>>dispose of the mutation, but we never get to that point. ` > ` > ` >>>I could swear I've seen photos of frogs from polluted ponds with ` >>>an extra set of limbs. Not very well formed or functional limbs, ` >>>but limbs nevertheless. I assume this is a developmental thing, ` >>>rather than a mutation, but I don't see why a mutation couldn't ` >>>have the same effect. Is there any reason to think it really ` >>>doesn't happen, rather than simply being to rare for us to have ` >>>noticed it? (And is anyone really looking?) ` > ` > ` >>I think we are looking. Developmental anomalies have often been studied ` >>as a guide to developmental processes. I don't know of any duplicated ` >>limbs, only bifurcated ones, i.e. extra fingers, the occasional extra ` >>hand, and perhaps a spare radius and ulna. But never a complete and ` >>separate arm. I could be wrong. ` > ` > ` > Well, a quick Google search turned up: ` > ` > http://www.solcomhouse.com/frogs.htm ` > ` > http://news.bbc.co.uk/cbbcnews/hi/sci_tech/newsid_2117000/2117263.stm ` > ` > http://www.sciam.com/article.cfm?articleID=0004B992-1F95-1C75-9B81809EC588EF21 ` > ` > http://www.news.wisc.edu/9233.html ` OK, so we get as far as duplicating the femur. But what's required here ` is an entire extra pelvic girdle. (Or, in the case the author wants ` here, the pectoral girdle. ` > ...and..., um..., ` > ` > http://www.orehole.com/nffrogs.htm ` That actually appears to be some kind of frog/human hybrid. I have a vague memory of seeing a pic of a deformed calf with an extra leg sticking out at some odd angle... yeah, here's a link - it even has the orientation in the right ballpark... http://www.tellmewhereonearth.com/Web%20Pages/Weirdest/Weirdest_Page_4.htm Signature========================================================================== vincent@triumf[munge].ca Pete Vincent Disclaimer: all I know I learned from reading Usenet. > on Fri, 07 Apr 2006 02:42:42 GMT, John Harshman > <jharshman.diespamdie@pacbell.net> sez: [quoted text clipped - 64 lines] > > http://www.tellmewhereonearth.com/Web%20Pages/Weirdest/Weirdest_Page_4.htm Looks like he has extra toes on the left hind foot, too. It would be nice to see how much of a leg he actually has. We need an x-ray or a skeleton. It doesn't look as if there's anything proximal to the carpals/tarsals. > >>>>>The problem is, apparently having three pairs of limbs is not as > >>>>>efficient as having two. The extra expenditure in resources during [quoted text clipped - 35 lines] > is an entire extra pelvic girdle. (Or, in the case the author wants > here, the pectoral girdle. A radical proposition to solve a radical problem, how did dragons get their wings? As in science the fantastist had better have a damn good argument in hand when he goes to upset tradition. :) > Developmental anomalies have often been studied > as a guide to developmental processes. I don't know of any duplicated > limbs, only bifurcated ones, i.e. extra fingers, the occasional extra > hand, and perhaps a spare radius and ulna. But never a complete and > separate arm. I could be wrong. With Siamese-twinning you can get a complete and nearly separate whole body (although these are often somewhat reduced), so why not a complete and separate limb? Is the question then whether Siamese-twinning could ever be a heritable mutation? Why not? (I could be not even wrong.) Cliff >>Developmental anomalies have often been studied >>as a guide to developmental processes. I don't know of any duplicated [quoted text clipped - 6 lines] > not a complete and separate limb? Is the question then whether > Siamese-twinning could ever be a heritable mutation? Why not? Because it's not a mutation at all. Anyway, the reason this is difficult is that to be functional, a front limb has to be attached to a pectoral girdle, and has to have a particular relationship to other bones: the rib cage, sternum, clavicles, vertebrae, and to the muscles that attach to them. If you put the limb in a different spot, none of these relationships are there any more. Do you duplicate the whole upper torso? That causes developmental problems too, because the internal organs are using the same locational cues. It's not a simple matter. Consider the difficulty Philip Jose Farmer had in designing a centaur, for example (in The Maker of Universes). > (I could be not even wrong.) > > Cliff > >>Developmental anomalies have often been studied > >>as a guide to developmental processes. I don't know of any duplicated [quoted text clipped - 22 lines] > > > > Cliff And then have an animal that can fare well enough to have descendents. I don't know enough about the problems to speculate, which is why I'm not even going to handle the problem in the setting. The scientists there have their ideas about how it all began, but they don't know. Even the dragons have no idea, because it might have happened in the Early Jurassic at the latest, and even as far back as the Late Triassic. (You try keeping a family journal for over 100 million years.) >> >>Developmental anomalies have often been studied >> >>as a guide to developmental processes. I don't know of any duplicated [quoted text clipped - 30 lines] > Jurassic at the latest, and even as far back as the Late Triassic. (You > try keeping a family journal for over 100 million years.) If you went back to the age of fish you might have a fish with three fin pairs end up making the grade rather than tetripods. > >> >>Developmental anomalies have often been studied > >> >>as a guide to developmental processes. I don't know of any duplicated [quoted text clipped - 33 lines] > If you went back to the age of fish you might have a fish with three fin > pairs end up making the grade rather than tetripods. Or hexapedal vertebrates along with quadrapedal. However I wanted something more closely related to crocodylia than what that would give me. And something that was not as optimally adapted as its competition, since it would give me a good excuse to render the terrestrial form extinct in a short period of time, even in the paradise that was the Jurassic. :) BTW, the first blog post on the subject is up at Mythusmage Opines. http://www.mythusmageopines.com/wp/archives/45 And a question for you all. Who in this newsgroup would like to have a Mesozoic dragon named after him? > >> The problem is, apparently having three pairs of limbs is not as > >> efficient as having two. The extra expenditure in resources during [quoted text clipped - 13 lines] > doesn't happen, rather than simply being to rare for us to have > noticed it? (And is anyone really looking?) I think things are developmental and not due to genetic alterations. Another thing to note is that such limbs are not functional. At least not by any reasonable definition of functional. About the only functional duplication of a body part I know of are the extra heads found in turtles, snakes, and humans. > >>>>>Did a 'clusty' on 'prolacerta' and found a number of sources. I am now > >>>>>looking for more, both online and offline. Yes, I did locate a listing [quoted text clipped - 44 lines] > which ones were you thinking of with extra fins? Are you perhaps > thinking of some acanthodians? I knew I was getting things wrong. My thanks for the corrections. I was indeed thinking of hox instead of vox, and a better example of surplus limb pairs is indead the acanthodians. In the matter of forelimb duplication being rather unlikey. I agree. At the same time, considering the type of created world I'm working, it's a dang sight more likely than some supernatural being decreeing their existence. > Feel free to do anything you like in fiction, but if you want it to be > biologically credible, it's not going to, um, fly. Not realistically. But what I'm going for is the appearance of realism. A trick, as strategem aimed at promoting the acceptance of the setting as real on its own terms. > > The problem is, apparently having three pairs of limbs is not as > > efficient as having two. The extra expenditure in resources during [quoted text clipped - 5 lines] > the absence of any such mutation. Maybe if it happened selection would > dispose of the mutation, but we never get to that point. Just because a mutation hasn't happened doesn't mean it can't. Some mutations may be bloody unlikely, but all that means is some mutations are bloody unlikely. > > Then there is the fact that early Dracos was simply not as good as the > > early primates in their shared niches. They were basically outcompeted. [quoted text clipped - 15 lines] > to as draconiforms (not capitalized). I'm assuming you want to know > these picky details. Nit-picky details are what science is all about. :) Dracones is henchforth the order's name. Draconiformes the name of the sub-order. Hence the other sub-order would be the Vermiformes. You have been a help. |
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