Comparative Anatomy - Science topic

I think grays anatomy is nice book for anatomy

Hi Daniel,

Thanks for your answer, and for the references ! They are very interesting, beyond my question. I'll try to contact these authors.

That was a good idea, thank you ! ;)

Cheers

It is a good question that delineates the involvement of Veterinarian in research.

By virtue of his vast knowledge in diverse field, such as microbiology, epidemiology, zoonoses, pathology, anatomy, food safety, environmental health etc, veterinarians have done pioneer, significant, and outstanding research work in the field of zoonotic diseases which pose a serious threat to public health.

I have been working in the field of Veterinary Public Health since 1973 and by the kind blessing of God, we have commendable research work that is recognized globally.I have mentioned the contribution of some veterinarian in zoonoses in my book entitled " Zoonoses" published in 2007 from Satyam Publishers, Jaipur, India.

Hi John,

Thank you very much for taking the time to check! :-)

I managed to get the info without this specific resource.

Kind regards

Hello Mustapha;

The embryology of all of the structures you mention clearly demonstrate that they are homologous to teeth. The adult function of the structure is not part of the developmental characterization. For instance, the food processing structures in the mouths of many turtles are made of keratin, like your fingernails, so they are not homologous to teeth but are analogous to them. That is, their embryological origins are different but their functions are similar.

It's all only a matter of determining how the structure develops and noticing how it functions.

Best regards, Jim des Lauriers

Walter Thiel method, Saturated Salt solution are some of different fixation methods other than formalin.

A common severe abdominal pain can often be associated with a dysfunction of the sacroiliac joint.  This is Baer's SI point.  This can occur on either side.  It is on a line from the ASIS to the umbilicus, two inches from the umbilicus.  Not to be confused with the appendicitis point which is two inches from the ASIS.  I saw a patient with a 4 year history of abdominal pain and LBP.  She had both ovaries removed and still had symptoms.  I did a manual posterior innominate correction and she was free of pain in both the low back and abdomen.  She was a little miffed about the unnecessary loss of her ovaries.

By the way, I forgot an important point/aspect. If you use the Maximum Likelihood approach with the rescaled angles and the Beta Distribution, then beware that it is highly unlikely (no pun intended) that the distribution will be symmetric about the most likely value (which will not be the mean, by the way). You should therefore find the ML value and then calculate an uncertainty range. DO NOT use +/- standard deviation, because ML value + SD has a different probability from ML value - SD. As a peer reviewer, I am chagrined to read submitted papers in which researchers detect (and point out) asymmetric distributions, and then do not shirk from writing ML +/- SD.

Your choice, which probability you choose. +/-25% about the ML value (corresponding to 50% interval) is not only quite useful, but also "easily" (whatever that may mean in statistics) interpretable.

You have the PHd of Isabelle Villemeur (Université Bordeaux 1) for the hand .(Etude morphologique et biomécanique du squelette de la main des Néandertaliens : comparaison avec la main des hommes actuels)

and the PHd of Anne Hambucken for the Member Sup.  HAMBUCKEN, A. (1993). Variabilité morphologique et metrique de l'Humerus, du Radius et de l'Ulna des Néandertaliens. Comparaison avec l'Homme moderne. Thèse de Doctorat, Université Bordeaux I. 

The important question porbably is, what means maturity. Is it sexual maturity (in the sense of fertile germ cells or as age at first reproduction) or is it skeletal maturity (in the sense of all or most epiphyses fusing or even completely fused). Often the second is taken as a proxy for the first. In ungulates this can be quite variable. Like sheep ewes that can be inseminated under favorable consitions as early as with 7 month. We are curating a collection of skulls and parts of the postcranium of Soay sheep with known age-at-death. Some epiphyses show signs of fusion in the course of the second year. In the third year all epiphyses start fusing and show last remnants up to the beginning of the fourth year. Fusion of the basioccipital to the basisphenoid is occuring in the second year of life. So in these creatures this fusion is somewaht inbetween (potential) sexual maturity and skeletal maturity. I would expect it to vary considerably between other genera and even more between orders.

Hello Marc,

I agree with Nicole's suggestion of comparing coastal vs. inland populations of Macaca fascicularis.  Another report on long-tailed macaque tool use in a coastal context comes from: Malaivijitnond, S. et al., 2007. "Stone-Tool Usage by Thai Long-Tailed Macaques (Macaca fascicularis)." American Journal of Primatology 69:227–233.

The authors found that long-tailed macaques on Piak Nam Yai Island, southern Thailand, used, "... axe stones to crack not only the oysters attached to the rocks, but also detached gastropods (Thais tissoti, Petit, 1852), bivalves (Gafrarium divaricatum, Gmelin, 1791), and even swimming crabs (Thalamita danae, Stimpson, 1858)." (Malaivijitnond et al., 2007: 231). 

The Brief Report by Malaivijitnond and colleagues (2007) also includes reference to  a paper by A. Carpenter published in 1887 (" Monkeys opening oysters." Nature 36:53) that is likely the earliest report of tool use by nonhuman primates (again, M. fascicularis observed by Carpenter on islands in the Mergui Archipelago, southern Myanmar).  In addition to using extractive foraging as a way of dealing with "protected" food items (i.e., gastropods, bivalves, and crustaceans), which could still introduce hard items (i.e., bits of shell) into the diet of the macaques, in coastal settings they could also potentially end up with some amount of sand mixed in with the gastropods, bivalves, and crustaceans they ingest.  While not exactly hard-object feeding (durophagy), sand/grit in the diet would definitely increase the abrasiveness of the diet and contribute to the possibility of tooth wear -- could be conditions that, over time, would promote selection for increased molar enamel thickness.  As Nicole suggests, "... the answer may be out there."!

First of all with mice that little, I would use a dissection microscope. I use a dissection bath that allows me to pin the pup abdomen down from it is legs, nose and tail, all with an angle to prevent obstruction to vision and access. make a long incision to the skin first along the midline, pull the skin sideways and expose the dorsal part. Then cut the bone from lateral edges, starting from nose region. Then just lift the bone away and you will have a nicely dissected brain. If you have to keep the tissue alive, you have to do this in ice-cold aCSF with 5Mg/1Ca continuously bubbled with carbogen. See my 2013 brain slice preparation chapter for details.

Check out this publication

They are all the Holotype.  Just because part of a specimen is removed does not make it "unpart" of the specimen.  If a museum gives separate catalog numbers to them that is an artifact of the museums catalog system.

It is a relatively common practice to dissect types as part of the description process and the parts are still part of the the holotype.

Now if the parts get mixed up that is also covered by Article 73

"If a subsequent author finds that a holotype which consists of a set of components (e.g. disarticulated body parts) is not derived from an individual animal, the extraneous components may, by appropriate citation, be excluded from the holotype (material may be excluded from a hapantotype if it is found to contain components representing more than one taxon."

The following is a character that more related to the tooth attachment and one has to lucky to find the remains of these attached t the teeth:

The periodontium in mosasaurids differs in arrangement from that of crocodylians. mosarsaur tooth roots are compsed of large quantities of vascularisized, cellular cementum that is anchored to the alveolar bone by  a mineralized periodontal ligament. In crocodylians (just as in mammals or, for that matter diadectids) the tooth root is coated in a thin band of avascular cellular cementum.

See: LeBlanc ARH, Reisz RR. 2013. Periodontal Ligament, Cementum, and Alveolar Bone in the Oldest Herbivorous Tetrapods, and Their Evolutinary Significance. PLoS ONE 8(9): e74697. doi:10.1371/journal.pone.0074697

Their data about mosauroids in turn is based on:

Caldwell MW, Budney LA, Lamoureux DO .2003. Histology of tooth attachment tissues in the Late Cretaceous mosasaurid Platecarpus. J Vertebr Paleontol 23: 622–630.

Caldwell MW .2007. Ontogeny, anatomy and attachment of the dentition in mosasaurs (Mosasauridae: Squamata). Zool J Linn Soc 149: 687–700.

Luan X, Walker C, Dangaria S, Ito Y, Druzinsky R, et al. .2009. The mosasaur tooth attachment apparatus as paradigm for the evolution of the gnathostome periodontium. Evol Dev 11: 247–259.

I hope this can help, at least in some cases.

Dear Francisco, I have already done my work so please don't bother. Thank you anyway! 

Hi Justin and Syed,

This can, of course, only be purely speculative. We can predict something about dinosaur hearing (Gleich, O., Dooling, R.J., Manley, G.A. (2005) Audiogram, body mass, and basilar papilla length: correlations in birds and predictions for extinct archosaurs. Natur-wissenschaften 92, 595-598.  and Walsh, S.A., Barrett, P.M., Milner, A.C., Manley, G.A., Witmer, L.M. (2009) Inner ear anatomy is a proxy for deducing auditory capability and behaviour in reptiles and birds. Proc. Roy. Soc. B. 276, 1355-1360.), but putting reliable limits on frequency ranges and, especially, sensitivity, is not possible. We recently showed that although it is known that male Caparcaillie produce very-low-frequency sounds with their wings (Lieser, M., Berthold, P., Manley, G.A. (2005) Infrasound in the capercaillie (Tetrao urogallus).. J. Ornithol. 146, 395-398), the females do not respond to such sounds (Lieser, M., Berthold, P., Manley, G.A. (2006) Infrasound in the flutter jumps of the capercaillie (Tetrao urogallus): apparently a physical by-product. J. Ornithol. 147, 507-509.). The frequencies produced by such fluttering wings would, of course, by of higher frequency if the feathered dinosaurs were smaller than Capercaillie.

Detection is a product of hearing sensitivity and distance, making it even harder to speculate whether feathered dinosaurs used such sounds to communicate, as we have no idea how sensitive or how loud they were. If we knew more about their environment, we might understand better the selection pressures on communication. For example: Did they live in dense vegetation and be - generally - unable to see each other?

Hi Andrey,

This is a fascinating topic - The pattern of absences and presences strongly suggests that convergent evolutions of a gallbladder are at least possible. And certainly it is often lost (as in many bird groups). This is a secondary source, but Kardong's textbook (Vertebrates) states that the gallbladder is lacking in "cyclostomes" (518). This might also be loss; people tend to forget that hagfish and lampreys are highly specialized animals. 

If you intend to pursue this further, the next step might be to rework a Gorham and Ivy -style diagram, but with modern relationships. Since their paper, taxonomic opinions and cladistics in particular have changed much of this phylogeny. I see you have added Afrotheria, which brings out the pattern of loss in Elephants. Contra the figure sharks certainly have a gall bladder, by the median lobe of the liver in dogfish for example.

I can't agree more that there are some fascinating lacunae left behind in modern science - ample work for us to pursue. 

Robert Barton has published several comparative works that looked at specific (usually sensory) brain structures:

1 Barton R, Purvis A, Harvey PH. 1995. Evolutionary radiation of visual and olfactory brain systems in primates, bats and insectivores. Philos Trans R Soc Lond B Biol Sci 348:381–392. 

2 Barton R. 2006. Olfactory evolution and behavioral ecology in primates. Am J Primatol 68:545–558.

3 Barton R, Harvey PH. 2000. Mosaic evolution of brain structure in mammals. Nature 405:1055–1058.

Your question is much too broad to have a simple answer, and to some extent you've already provided a partial answer.

Although we often distinguish between "humans and animals", in biological terms, humans are just another animal species, a mammal.

Many fundamental physiological mechanisms are common to all animals - the pioneering studies explaining the basics of nerve and muscle function were carried out on invertebrates.

It's because of these similarities that every pharmaceutical for human use has first undergone extensive animal testing. It is also due to subtle species differences that some pharmaceuticals which appear promising in animal trials may still fail to deliver benefits when tested on humans.

However, over-all, since the start of experimental physiology in the 1840's, animal studies have proven to be invaluable for the understanding of human physiology, and basically every fact you read in your human physiology textbook is derived from animal studies. 

It's important to choose a correct model animal for each study. For some studies, pigs are ideal, for other studies scientists have to use primates as models, and in other areas, the octopus might just do fine! 

Hi

Here are some articles regarding morphometry of human ear pinna

Hope, might be helpful

Hi Scott,

You're in for a lot of reading! Here you have a recent review paper on morphometrics:

And that whole issue of Hystrix is dedicated to morphometrics; you can see there all the big names working in the field:

I suggest you browse also the Stony Brook Mophometrics site:

And the Morphometrics Library, which has lots of up-to-date literature (although not in mammals, I'm afraid):

You can also join the MORPHMET mailing list if you are joining the field:

If it is specifically mouse papers you're after, I'm not a specialist, but you can perhaps start with this one and work your way through its references:

I hope this helps. All the best,

Miguel

Dear Colleague,

Thank you for this interesting question. It shows us that there is still a lot to discover and to describe in anatomy, and that comparative anatomy e.g., primatology, can be of great value in this. In the recent past, e.g., with respect to functional anatomy of primates and their predecessors (like the marsupials that we studied), the Journal of Anatomy papers by the late Professor F.G. Parsons (1863-1943) did help us a lot ! I therefore attach this 1898 paper by Prof. Parsons, with his description of the levator claviculae muscle from p. 449 on, plus some sketches. Remarkably, he calls this muscle also "omo-trachelian". 

I  think that his explanations make sense, be they quite short. Unfortunately, I could not figure out right now, where his second lecture on head & neck anatomy was published.

Anyway, I still hope that this paper will give you some of the wanted information.

Wishing you success, with kind regards,

Koos Jaap van Zwieten

Be aware: Apoptosis is a late process in limb development. It is not responsible for bone patterning itself or for early digit formation. When digit separation occurs, digit bones are already perfectly built. Mammals also show apoptosis, but in mouse embryo this occurs  after  E12.0. 

It's is actually from a box of old victorian skeleton displays.

So I'm afraid there's not a lot more to go on the the morphology.

Having searched a bit further a Pole Cat seems to be a pretty good fit,

But any other suggestions would be greatly appreciated !

Hello everyone, to start with the question - pygal vertebrae are a specialized form of caudal vertebrae that lack an articulating/or fused haemal arch or chevron bone, but possess a transverse process that does not have an articulating rib.  Typical caudal vertebrae have chevron bones (fused or articulating depending on the kind of mosasaur), and transverse processes without articulating ribs.  Presacral or dorsal vertebrae (the term lumbar is really a mammalian term reflecting specializations of the axial skeleton in derived synapsids) have shorter transverse processes with articulating ribs, and no chevron bones or haemapophyses.  The pygal region in mosasaurs is unique in that there are usually a rather large number of such vertebrae in the caudal series, potentially due to the loss of a sacroiliac joint - the 2 sacrals must go somewhere and so it is possible that in mosasaurs they have become part of the "pygal series" thus upping the count.  In more primitive sistergroups to mosasaurs there is a good sacrum (2 vertebrae) and 2 pygals prior to the typical caudal anatomy; this is why in derived mosasaurs the pygals are considered to be a specialized form of caudal vertebra.  Many modern lizards have 0 (Heloderma) to 1 (Varanus) or 3-4 (Iguanians, etc.) vertebrae at the base of the tail that display a pygal-like anatomy.  However, those same vertebrae in modern lizards usually possess grooves or forks that support lymph node networks - these are not apparent in mosasaur pygals.  It a reasonable supposition that the loss of the sacroiliac joint modified numerous soft tissues systems including the lymph tissues and their placement on the tips of the transverse processes of anterior caudals such as the pygal series.  Interestingly, the reverse is true for snakes, where despite the loss of the sacroiliac joint, the postcloacal vertebrae in proximity to the pelvic elements still possess lymphapophyses. Just to keep it confusing, snakes also present small hemapophyses on the first lympapophysis bearing postcloacal vertebra.

Hi, which species do you need, and what stages? We have a comparative embryo collection, so could try to do something for you. We, in turn, would like to see your Alligator paper.

Hi Williem,

Ask your friendly anatomy lab technicians if you can get access prior to embalming. We do this regularly in my lab. We could probably provide additional data from our cadavers if you are interested. The landmarks are also bone so should be ok to find on our cadavers. Let me know if you need help.

IN HUMAN HEART

the atrial branches of the right coronary artery are sometimes described as anterior, lateral (right or marginal) and posterior groups, they are usually small single vessels 1mm in diameter. The right anterior and lateral branches are occasionally double, very rarely triple, and mainly supply the right atrium. The posterior branch is usually single and supplies the right and left atria. The artery of the sinoatrial node is an atrial branch, distributed largely to the myocardium of both atria, mainly the right. Its origin is variable: it comes from the circumflex branch of the left coronary in 35%. However, more commonly it arises from the anterior atrial branch of the right coronary artery, less often from its right lateral part, least often from its posterior atrioventricular part. This ‘nodal' artery thus usually passes back in the groove between the right auricular appendage and aorta. Whatever its origin, it usually branches around the base of the superior vena cava, typically as an arterial loop from which small branches supply the right atrium. A large ‘ramus cristae terminalis' traverses the sinu-atrial node .it would seem more appropriate to name this branch the ‘nodal artery', as most of the currently named vessel actually supplies the atria and serves as the ‘main atrial branch'

nodal artery usually identified by its course -- described above

REFER : GRAY'S ANATOMY 40 th edition vascular supply and lymphatic drainage of heart (Fig. 56.18A–C);

I would not be that excited; nervous tissue is composed of many cell types each of which is equally important; definitions such as "managers" and "workers" are greatly counterproductive; nervous system evolved through cellular specialisation; and each cell does its own function, which all are fundamental fro the function of the tissue as the whole.  I personally believe hat the matter of "gliotransmision" has been rather hyped recently; astrocytes are not neurones and they are unlikely to be direct elements for cognition for example; at the same time neuropathology is mot likely gliopathology, because when homeostatic element does not work disease develops. When studying teh brain therefore I would advocate for a much more integrated approach which will reveal internal intercellular links that underlie the function without dividing these cells into bad or good, superior or inferior.

Thank you Gordon W Schuett for your answer. I will check David Cundall work. Im already reading about intramaxillary joint in O. Reippel works but I will also check Cundall & Irish (1989) work.

Im the most interested in for example leght of quadrate and supratemporale (and other bones) on maximum size of prey consumed by snake. Which bones are usefull in what environment. More precisly what propotions of snake bones have influence on snake fittnes in particulary environment. I'm also looking for work about sexual dimorphism in Boidae and Pythonidae.

Some interesting works are already done for Natricinae between sexual dimorphism and prey catching environment.

Hibbitts, T.J., Fitzgerald, L.A., 2005. Morphological and ecological convergence in two natricine snakes. Biological Journal of the Linnean Society. 85, 363–371. doi:10.1111/j.1095-8312.2005.00493.x

Vincent, S.E., Moon, B.R., Shine, R., Herrel, A., 2006b. The functional meaning of “prey size” in water snakes (Nerodia fasciata, Colubridae). Oecologia 147, 204–211. doi:10.1007/s00442-005-0258-2,

Shine, R., 1986. Sexual differences in morphology and niche utilization in an aquatic snake, Acrochordus arafurae. Oecologia 69, 260–267.

Borczyk, B., 2014. Allometry of head size and shape dimorphism In Grass Snake (Natrix natrix). Turk. J. Zool. (In press).

Hampton, P.M., 2011. Comparison of cranial form and function in association with diet in natricine snakes. J. Morphol. 272, 1435–1443. doi:10.1002/jmor.10995 - And I'm looking for something similiar for other snakes.

I already read thoose works:

Arnold, S., 1993. Foraging theory and prey-size-predator-size relations in snakes. Ecological Behaviour, New York: McGraw Hill Seigel RA, Collins JT, 87–115.

Aubret, F., Bonnet, X., Harris, M., Maumelat, S., 2005. Sex Differences in Body Size and Ectoparasite Load in the Ball Python, (Python regius). J. Herpetol. 39, 315–320. doi:10.1670/111-02N

Bertona, M., Chiaraviglio, M., 2003. Reproductive biology, mating aggregations, and sexual dimorphism of the Argentine Boa Constrictor (Boa constrictor occidentalis). J. Herpetol. 37, 510–516.

Camilleri, C., Shine, R., 1990. Sexual Dimorphism and Dietary Divergence: Differences in trophic Morphology between Male and Female Snakes. Copeia 3, 649 – 658.

Chiaraviglio, M., Bertona, M., Sironi, M., Lucino, S., 2003. Intrapopulation variation in life history traits of Boa constrictor occidentalis in Argentina. Amphib. Reptil. 24, 65–74.

Feldman, A., Meiri, S., 2013. Length–mass allometry in snakes. Biol. J. Linn. Soc. 108, 161–172. doi:10.1111/j.1095-8312.2012.02001.x

Forsman, A., Shine, R., 1997. Rejection of non-adaptive hypotheses for intraspecific variation in trophic morphology in gape-limited predators. Biology Journal of the Linnean Society 62, 209–223.

Frazzetta, T.H., 1959. Studies on the morphology and function of the skull in the Boidae (Serpentes). Part 1. Cranial differences between Python sebae and Epicrates cenchris. Bulletin of the Museum of Comparative Zoology. 119, 453–472.

Frazzetta, T.H., 1975. Pattern and Instability in the Evolving Premaxilla of Boine Snakes. American Zoologist 15, 469–481. doi:10.1093/icb/15.2.469

Gans, C., 1961. The Feeding Mechanism of Snakes and Its Possible Evolution. American Zoologist 1, 217–227.

Greene, H.W., 1983. Dietary Correlates of the Origin and Radiation of Snakes. American Zoologist doi:http://dx.doi.org/10.1093/icb/23.2.431

Greene, H.W., Burghardt, G.M., 1978. Behavior and phylogeny: constriction in ancient and modern snakes. Science 200, 74–77. doi:10.1126/science.635575

Lee, M.S.Y., Bell Jr., G.L., Caldwell, M.W., 1999. The origin of snake feeding. Lett. Nat. 400.

Luiselli, L., Angelici, F.M., 1998. Sexual size dimorphism and natural history traits are correlated with intersexual dietary divergence in royal pythons (python regius) from the rainforests of southeastern Nigeria. Ital. J. Zool. 65, 183–185. doi:10.1080/11250009809386744

Monteiro, L.R., 1998. Ontogcnetic changes in the skull of Corallus caninus L., 1758 and Corallus enydris L., 1758 (Serpentes: Boidae), an allometric study. SNAKE-NITTAGUN- 28, 51–58.

Pearson, D., Shine, R., Williams, A., 2002. Geographic variation in sexual size dimorphism within a single snake species ( Morelia spilota , Pythonidae). Oecologia 131, 418–426. doi:10.1007/s00442-002-0917-5

Pough, F.H., Groves, J.D., 1983. Specializations of the Body Form and Food Habits of Snakes. American Zoologist 23, 443–454. doi:10.1093/icb/23.2.443

Rodríguez-Robles, J.A., Bell, C.J., Greene, H.W., 1999. Gape size and evolution of diet in snakes: feeding ecology of erycine boas. J. Zool. 248, 49–58. doi:10.1111/j.1469-7998.1999.tb01021.x

Shine, R., 1994. Sexual Size Dimorphism in Snakes Revisited. Copeia 1994, 326. doi:10.2307/1446982

Shine, R., Harlow, P.S., Keogh, J.S., Boeadi, 1998. The influence of sex and body size on food habits of a giant tropical snake, Python reticulatus. Funct. Ecol. 12, 248–258. doi:10.1046/j.1365-2435.1998.00179.x

That is what I have found but I'm still searching. If anyone have some suggestions or doing research about it, I will be very gratefull to hear about it. I'm looking for those informations for my Master degree paper.

thank you very much,

this can have consequences for species lists in the fossil record of the Netherlands. Do you know this from your own observations?

Is there an example given in the literature other than Gromov & Polyakov?

Lex parsimoniae!

Thanks a lot for your response!

If the subolfactory process is the same thing as ventrolateral process (see the attached image 1), than I think that parolfactory bulb recess is not the subolfactory process. I guess that paired parolfactory bulb recesses should be the depressions on the medial sides of ventrolateral processes that indicates olfactory bulb.

But than there should be the space between the olfactory bulb and frontal? (image 3) What for?

My drawings of frontal sections are correct?

In mosasaurs olfactory canal not embraced ventrally by ventrolateral processes (0); or canal almost or completely enclosed below (1) (Image 2)

I hope that I have correctly stated my point!

Thanks for the Gauthier et al. paper!

The Field Museum has a couple in their collection, one from Malaysia and one from Pakistan. The American Museum of Natural History has a few as well. The Smithsonian has several in their collection of birds from several different places in Asia. I would suspect that others, such as the Philadelphia Academy of Sciences, have them as well. That is if you are only focusing on collections in the US. I would suspect other countries have them as well, such as the museum in Paris, especially the closer you get to the collection location.

Glad to be of help!

For further information I suggest you take a look at "Mammal Teeth, origin, evolution and diversity" by Peter Ungar (2010).

Kind regards,

Matt

One idea: Perhaps evolution of tracheae cannot be explained through a physical advantage but by constraints of body morphology, e.g. tracheae evolved in a tracheatan ancestor with many similar segments (metamerism) whereas evolution of lungs occurred in arachnids with a comparatively derived (spider-like) morphology.

(Perhaps insects would actually be better off with lungs but lung evolution was inhibited by the presence of tracheae, so insects were stuck with the latter.)

I do not think that you find a significant anatomical differences in a smaller vessels but you can definitely find the differences in hormone responses which regulate the tone due to distinct nitric oxide and superoxide production. This is a primary reason we use males in our experiments since we cannot properly compare male to female mice.

Look also at publication below:

Sex differences in intracranial arterial bifurcations.

Gend Med. 2010 Apr;7(2):149-55. doi: 10.1016/j.genm.2010.03.003.

Lindekleiv HM, Valen-Sendstad K, Morgan MK, Mardal KA, Faulder K, Magnus JH, Waterloo K, Romner B, Ingebrigtsen T.

Department of Clinical Medicine, University of Tromsø, Norway.

now thát is an extensive answer! thanks a lot! I'll retrieve these suggested pdf's.

Concurring with some of the previous answers, I would say that there are very few species for which there is a definite lineage tree, with C. elegans and similar nematodes being extreme examples of fixed lineage. For a number of the major developmental model organisms there are fate maps that give (statistical) predictions of cell fate from cell positions at earlier stages of development. The prime examples of these are from amphibian (Xenopus) but there are others (zebrafish, chick, Drosophila). These fate maps are almost never represented as fate decision trees. This is partly because intermediate internal specification states of cells are usually unknown, but it is also because developmental biologists tend not to think this way and it is something you could probably extract from existing data (although there's a lot of work to be done to do it). Also, it is important to know that fate map starts at a given stage and this isn't necessarily the zygote - it is usually much later and sometimes very much later. Mouse is rather poorly fate mapped because it is relatively inaccessible at developmental stages but there are some parts that are better mapped, such as parts of the central nervous system (e.g. Cepko lab for retina) and the lungs (see the very nice work from the Krasnow lab). There is a good review of fate mapping technology by Margaret Buckingham (Buckingham ME, Meilhac SM., Dev Cell. 2011 Sep 13;21(3):394-409) that might be a good lead into other work in this area.

If anything, a Bauplan is by definition a full set of plesiomorphies, that is, of widely conserved structural characteristics of animal bodies, plus their mutual spatial relationships in the body (important not to forget this, Bruno). Synapomorphies are the variations (additions) that may render homology analysis difficult. Georges Cuvier liked to add functional aspects to Bauplans, and was famously opposed in this by his colleague Ètienne Geoffroy de Saint-Hilaire (to concede partially the point made by F.Solano; look up this controversy in the Wikipedia; in retrospect, it was Saint-Hilaire wo was closer to what we now know). Bruno should be aware of this, since he works at the very place where Saint-Hilaire and Cuvier worked out the Bauplan concept ('les embranchements'; they would not use a German word), before the publication of the theory of evolution (Lamarck also worked there). If Bauplans are now obsolete, as Bruno thinks, how do you recognize that your cat is not a monkey? We recognize synapomorphies -specific characters of the cat- because we first notice the plesiomorphies, that is, because the special items contrast significantly within the generally conserved Bauplan (even subconsciously, you compare ear to ear and nose to nose). Maybe we are now into molecular taxonomy, but we cannot do without parallel morphological taxonomy to put order into all those gene sequences found across the exuberance of life forms. Bodies taken as 'mere aggregates of synapomorphies' can be conceived also as mere aggregates of energy quanta. Both visions are perhaps true in a sense, but do not help us with our biological problems.

Jordi says that 'Homology strictly means "that one structure in 2 organisms is inherited from a common ancestor"'. This is a banal truism, since all parts of any two vertebrates are inherited from a common ancestor (and some ancestor inherited his own characters from an invertebrate ancestor -odd this, isn't it?-, etc, etc, back to the origin of life). The conclusion is that everything within a monophyletic radiation is homologous to something, which in a sense was my original point. New animal parts simply do not fall from the sky, they come from your ancestors. The tendency to think that only some chosen body parts are homologous, and others are not, possibly correlates with the old error of confusing homology with similarity. What we often do not know, given some problematic body parts, is to what specific body parts of other animals they may be homologous. But we can investigate such things.

Jordi further says: 'so if a structure is only found in one group, it can't have a homologue outside the group'. This agrees with what I said previously about looking for cortical layer 4 homologs in birds, which don't have any layers. However, if we would like to have credible causal explanations, we need to see how the novel mammalian structure emerged out of preexisting structure (and how a given genome got more or less sophisticated than other genomes). My position is that developmental topologic homology within a detailed Bauplan allows looking for such explanations. We forget about the cortical layers, and look instead at the primordia topologically comparable to those in mammals out of which the cortical novelty apparently arose. Both sets of primordia and their respective adult derivatives would be field homologous, as wholes. Comparable distinct sets of neurons may be observed, or not, possibly in a different arrangement. Any definable primordia to compare must occupy a specific neighborhood within the local Bauplan (that is, within the spatial map of conserved features among all compared species). Experimental fate maps allow converting embryonic maps into adult maps. There is differential molecular coding of these neighborhoods, which can be mapped and shown to be widely shared, with invariant mutual relationships.

As regards the common ancestor that justifies at the bottom our homologies, it is a credible hypothesis, but we usually do not know which animal it was precisely, and experts tend to discrepate strongly among any particular choices. So, what is its practical use when dealing with complex brain parts or any soft body parts? Moreover, any evidence that a given extinct animal really was our ancestor will be strongly based on our preconceived homology-fundamented notions of taxonomy, and on the idea of a vertebrate Bauplan with variations. There is circular reasoning lurking here.

When you want to form an opinion on the homology of noses among elephants, whales and humans, you do not think of looking up the common ancestor in a museum, and see what it had as a nose. What you do is examine the heads of these living animals and check out where is the mouth, the eyes,and the ears relative to any nose candidate. Usually there is one obvious result. In difficult cases you will check more animals (see about cladistics). Children do such topologic checking without visible effort, though maybe they would miss the nose of the whale. This tells you that we use Bauplans dayly, without realizing it, and that these include a texture of mutual spatial relationships between the recognized body items; scientists will attend to finer details (a Bauplan is not a simple list of characters, as was already emphasized by Saint-Hilaire, who insisted on 'les relations'). You would never accept a nose placed under the mouth, irrespective of its aspect (by the way, having come to this point, it may be interesting for you to ponder about why in the cyclopic malformation the fused single eye appears under the fused nose, above the mouth).

Once you have a nice homolog candidate, then you can proceed to study relevant developmental patterns and mechanisms, which may allow you to understand the topologic invariants, as well as what causes both conserved and varied aspects of the structure. Invariants are morphostatic phenomena in a particular arrangement (like mouths, noses and eyes), which nowadays we tend to explain as the result of 'attractor' mechanisms in the complex interactive dynamics of multi-level molecular phenomena guiding what cells do during development. A synapomorphy implies the emergence of a new attractor, usually by modification of preexistent ones ('les catastrophes'). Finally, if the molecular control of face formation is minimally known, you will proceed to check crucial gene patterns across embryos of the different species, with rather well defined predictions about what you will find. If the data are adverse, you will have to start again with a fresh approach.

Michael, why do you think the artery is superficial?? It is between fibula and m. flexor hallucis longus.

According to it beginning and end, it seems to be the tibialis posterior a., It supplies m. soleus and (partially) m. gastrocnemius, and behind the malleolus medialis has two terminal branches: plantar arteries.

The anterior tibial a. is normal here.