This article is inspired, although specific studies (mentioned at the end), but rather deals with recent progress on the issue in general. This problem is the ability to smell and theropods in particular, how it changed during avian evolution. It is clear that the sense of smell can tell us much about the food habits and ecology, and several authors therefore tried to determine how well has been developed in theropods.
Smell theropods, as to the size of the olfactory lobes (apparently down from CT scans) zkvantifikovali Zelenitsky et al. (2011, see end of article). Values \u200b\u200bfor individual nodes are calculated at peak efficiency. During the evolution of olfactory ability maniraptoriformní theropods grew up with some of the common ancestor eumaniraptorů (birds and deinonychosaurů) "stop". In this respect, survived up to a common ancestor pygostylianů (birds and konfuciusornitidů) from which increasingly began to grow again. Colors of branches (complete with a legend at the bottom left) shows the position of the regression line to the Taxon: theropods in black and purple branches have a worse sense of smell than we expected, the branches green and red contrast await better "sniffer". Red branches are apparently unique to modern birds, not even their closest relatives Ichthyornis thus did not have the developed sense of smell. For further legend see caption in the picture. (Source: palaeoblog.blogspot.com)
names of the authors of the article will be repeated quite often. Among those who deal with the issue long and nejsystematičtěji, includes Zelenitsky and Therrien, who participated in the study, which sought to ascertain the evolutionary origin of the so-called "etmoidního complex, originally described from the tyrannosaur and subsequently discovered in many other theropods (Ali et al. 2008). This consists of an element with a kind of groove shape on the front which is connected to some kind of median barrier, which is above and attached to the edge prefrontálům (předčelním bones), and frontal bones, and then back to orbitosfenoidům (small wings cuneiform bones). Screens the kind of perched on top of the dorsal plate. Ali et al. (2008) tried to determine which elements of living archosaurs (crocodiles and birds), these structures are responsible. They found that žlábkovitý department is homologous to the front of the so-called planum supraseptale is well known from crocodiles and partly from embryonic birds (which sometimes osifikuje and becomes part of the small orbitosfenoidů), while the baffle plate and deposited it corresponds mezetmoidu bird. Authors devised a new anatomical terminology to describe this complex (combining tradition paleontological and newly identified homology), but above all think about what the new discovery tells the olfactory abilities theropods. Judging from the living archosaurs, olfactory lobes of the brain had to be established in the "groove" (now called sfenetmoid) just behind the counter (mezetmoidem). This significantly restricts their size - some previous estimates, placing the bones of the frontal lobes, předčelní and tear, while reckoned that the tyrannosaur would lobes can grow into his brain hemispheres (Brochu 2000).
Zelenitsky and Therrien to olfaction teropodímu back very quickly, and at work, which I wrote of my time an old version of the blog (Zelenitsky et al. 2008). They used pretty well proven fact, and specifically the link between the size of the olfactory lobes and the resolving power of smell. (The word "resolution" here has a meaning. Olfactory lobes are unrelated to olfactory sensitivity, that is how weak the smell is still able to capture the animal - it has more impact area, and thus the number of cells, the olfactory mucosa. On the other hand, the size of the olfactory lobe directly correlates with how smells like the animal is able to distinguish.) The authors then compared the average diameter of the olfactory lobe of the cerebral hemispheres (the value of maniraptoriformů both "hard" set of mozkoven preserved, while the rest had theropod reckon with the fact that the brain omit a skull). Then they built the resulting graph values \u200b\u200bon the weight of theropods and proložili by the regression line. Above it is placed and tyrannosauridi dromeosauridi, indicating that their nose was above average and theropods, along with the previously demonstrated stereoscopic vision was a clear adaptation to the predatory way of life. Smell oviraptorosaurů ornitomimosaurů and vice versa was below average, which could be related to their omnivorousness. Large eye cup and optic lobes suggest that these dinosaurs relied more on vision than on smell. Olfactory ceratosaurů distinctive skills, karnosaurů, basal tyrannosauroidů, and troodontidů archeopteryga (avialanů sole representative in the analysis) were average. Interestingly, the stereoscopic vision troodontidů suggests that this group began to increasingly rely on vision, but without losing ancestral good sense of smell.
As regards birds, Zelenitsky et al. rearranged the hypothesis that the olfactory abilities in bird evolution progressively worse with how the increased dependence on vision (Rogers 1999; Franzos 2004). This type of shift had to be sure, but much later than the authors cited considered: early olfactory avialanů and their closest relatives among deinonychosaurů was still very good, so to change the "brain architecture" could occur sometime in the creation orniturinních birds. This indirectly supports the conclusion that the early-type avialani archeopteryga konfuciusornise or could not fly well - does not need to modify the "think-plan" of their flightless ancestors.
Zelenitsky and Therrien, but not the only ones devoted to the topic. Dealt with it as well, Larry Witmer, a paleontologist and anatomist known for his participation in the discussion of the origin of birds (Witmer 1991, 1999, 2002), but especially his studies of dinosaur mozkoven (Holliday & Witmer 2008) and the pneumatization (Witmer 1990 ; Witmer & Ridgely 2008). Theropod smell analyzed along with Ryan Ridgelym in the study of tyrannosaur, published the year before last (Witmer & Ridgely, 2009). CT scans were able to reconstruct much of the olfactory tyrannosaurova system: for example, showed that the cavity marrying his olfactory tract (bundle of axons based on the so-called mitral cells of olfactory lobes, the lobe connects with other brain regions) was compared to other theropods unusually short and broad, broader than necessary to accommodate two paired tracts and cerebral blood vessels. Witmer and Ridgely also confirmed the findings of Ali et al. on small olfactory lobes, but showed that the areas that Brochu (2000) considered completed olfactory lobes were completed the olfactory mucosa. They agreed also that sfenetmoid mezetmoid and surrounded by bundles of olfactory nerves and blood vessels leading from the olfactory lobe, which intervened in the sfenetmoidního ring. Overall, Witmer & Ridgely (2009) agreed that with new, more accurate reconstruction of the olfactory lobes true original conclusion that these bodies were larger than in other theropods celurosaurů or velkotělých (Franzos & Rowe 2005; Zelenitsky et al. 2008). He also indicated that if the olfactory mucosa filled tyrannosaur in the same part of the nasal cavity, as is the case in living archosaurs had to go to the emergency area. Such a conclusion would be quite fit to what turns out neontologických many studies either focused on genomics (Steiger et al. 2008) and ethology (Nevitt 2008, Roth et al. 2008) - that even wild birds rely on smell more than previously thought.
Zelenitsky Now, Therrien, Witmer and Ridgely (along with one more author, A. McGee) joined forces on bird evolution have focused a little more closely. It is known that the olfactory ability of living birds are highly variable, while the smell of basal birds (Neornithes thinking outside , or Crown group) know almost nothing. Generally it is assumed (as is evident from the above) that the smell is worse along with it, as - due to flight - perfecting vision and spatial orientation. To test this hypothesis, focusing Zelenitsky et al. (2011) on the relative size of the olfactory lobes, defined as a practical measure for the softness of smell. The authors analyzed the parameters of 157 terminal taxa of living and fossil birds and theropods neptačích. The results? In the early stages of evolution maniraptoriformů the sense of smell improved. ( Maniraptoriformes smallest asset, which includes as an "ostrich imitators" of the group Ornithomimosauria and wild birds. Furthermore, here comes the rest avialanů, deinonychosauři, oviraptorosauři, alvarezsaur [a] and Idi terizinosauři) During what Zelenitsky et al. (2011) called "a shift from neptačích theropods to birds' (which in their submission was apparently at the base vided Avialae , ie the creation of the first animals more closely related to living birds than deinonychosaurům), this trend bent and major changes to avoid olfactory abilities. After this transition, however, the size of lobes started to increase again, which is clearly seen in early avialanů and even the first modern birds. In later stages of evolution neornitů size remained stable and the olfactory lobes to the groups derived neoavianů (= of all living birds sparrows closer than ducks) there has been some reduction.
new study conclusions are surprising, if not revolutionary: the importance of smell in the evolution of birds increased, not decreased. Note that this conclusion is in good agreement with the above-cited studies of living birds, which also show that their sense of smell is kind of a relic from the days when dinosaurs still fly. Zelenitsky et al. (2011), however, are still on and trying to track down what was a powerful smell good birds. Conclude that a better sense of smell first neornitům allow compared with basal birds to forage more efficiently or improve navigation. So perhaps Zelenitsky et al. encountered another factor contributing to the enormous evolutionary success of modern birds. Perhaps he was just a better sense of smell is why we Neornithes survived extinction at the end of the Cretaceous and Paleogene, while hesperorniti, or flying protiptáci dromeosauridi Sun
Zelenitsky and Therrien to olfaction teropodímu back very quickly, and at work, which I wrote of my time an old version of the blog (Zelenitsky et al. 2008). They used pretty well proven fact, and specifically the link between the size of the olfactory lobes and the resolving power of smell. (The word "resolution" here has a meaning. Olfactory lobes are unrelated to olfactory sensitivity, that is how weak the smell is still able to capture the animal - it has more impact area, and thus the number of cells, the olfactory mucosa. On the other hand, the size of the olfactory lobe directly correlates with how smells like the animal is able to distinguish.) The authors then compared the average diameter of the olfactory lobe of the cerebral hemispheres (the value of maniraptoriformů both "hard" set of mozkoven preserved, while the rest had theropod reckon with the fact that the brain omit a skull). Then they built the resulting graph values \u200b\u200bon the weight of theropods and proložili by the regression line. Above it is placed and tyrannosauridi dromeosauridi, indicating that their nose was above average and theropods, along with the previously demonstrated stereoscopic vision was a clear adaptation to the predatory way of life. Smell oviraptorosaurů ornitomimosaurů and vice versa was below average, which could be related to their omnivorousness. Large eye cup and optic lobes suggest that these dinosaurs relied more on vision than on smell. Olfactory ceratosaurů distinctive skills, karnosaurů, basal tyrannosauroidů, and troodontidů archeopteryga (avialanů sole representative in the analysis) were average. Interestingly, the stereoscopic vision troodontidů suggests that this group began to increasingly rely on vision, but without losing ancestral good sense of smell.
As regards birds, Zelenitsky et al. rearranged the hypothesis that the olfactory abilities in bird evolution progressively worse with how the increased dependence on vision (Rogers 1999; Franzos 2004). This type of shift had to be sure, but much later than the authors cited considered: early olfactory avialanů and their closest relatives among deinonychosaurů was still very good, so to change the "brain architecture" could occur sometime in the creation orniturinních birds. This indirectly supports the conclusion that the early-type avialani archeopteryga konfuciusornise or could not fly well - does not need to modify the "think-plan" of their flightless ancestors.
Zelenitsky and Therrien, but not the only ones devoted to the topic. Dealt with it as well, Larry Witmer, a paleontologist and anatomist known for his participation in the discussion of the origin of birds (Witmer 1991, 1999, 2002), but especially his studies of dinosaur mozkoven (Holliday & Witmer 2008) and the pneumatization (Witmer 1990 ; Witmer & Ridgely 2008). Theropod smell analyzed along with Ryan Ridgelym in the study of tyrannosaur, published the year before last (Witmer & Ridgely, 2009). CT scans were able to reconstruct much of the olfactory tyrannosaurova system: for example, showed that the cavity marrying his olfactory tract (bundle of axons based on the so-called mitral cells of olfactory lobes, the lobe connects with other brain regions) was compared to other theropods unusually short and broad, broader than necessary to accommodate two paired tracts and cerebral blood vessels. Witmer and Ridgely also confirmed the findings of Ali et al. on small olfactory lobes, but showed that the areas that Brochu (2000) considered completed olfactory lobes were completed the olfactory mucosa. They agreed also that sfenetmoid mezetmoid and surrounded by bundles of olfactory nerves and blood vessels leading from the olfactory lobe, which intervened in the sfenetmoidního ring. Overall, Witmer & Ridgely (2009) agreed that with new, more accurate reconstruction of the olfactory lobes true original conclusion that these bodies were larger than in other theropods celurosaurů or velkotělých (Franzos & Rowe 2005; Zelenitsky et al. 2008). He also indicated that if the olfactory mucosa filled tyrannosaur in the same part of the nasal cavity, as is the case in living archosaurs had to go to the emergency area. Such a conclusion would be quite fit to what turns out neontologických many studies either focused on genomics (Steiger et al. 2008) and ethology (Nevitt 2008, Roth et al. 2008) - that even wild birds rely on smell more than previously thought.
reconstruction of the olfactory system tyrannosaur, which I give because it is a nice color. Are marked in green the nasal cavities were filled with the olfactory mucosa (while Brochu [2000] would put them into the olfactory lobes). The true extent of the olfactory lobe is marked in blue. The arrow shows how the air went the airways - from the nasal cavity (w) over choanu, internal nostril, through the pharynx. Odor signal contrast wandered through the olfactory region nasal cavity (OLF) to the olfactory lobe of the brain (OB). Other abbreviations: (CER) cerebral hemisphere (oevc) channel for connecting vein (v emissariae), opening into orbit (OTC) cavity olfactory tract (ovc) orbital venous channel running out of the olfactory area of \u200b\u200bthe nasal cavity into the orbit. (Source: Witmer & Ridgely, 2009: Figure 6)
Zelenitsky Now, Therrien, Witmer and Ridgely (along with one more author, A. McGee) joined forces on bird evolution have focused a little more closely. It is known that the olfactory ability of living birds are highly variable, while the smell of basal birds (Neornithes thinking outside , or Crown group) know almost nothing. Generally it is assumed (as is evident from the above) that the smell is worse along with it, as - due to flight - perfecting vision and spatial orientation. To test this hypothesis, focusing Zelenitsky et al. (2011) on the relative size of the olfactory lobes, defined as a practical measure for the softness of smell. The authors analyzed the parameters of 157 terminal taxa of living and fossil birds and theropods neptačích. The results? In the early stages of evolution maniraptoriformů the sense of smell improved. ( Maniraptoriformes smallest asset, which includes as an "ostrich imitators" of the group Ornithomimosauria and wild birds. Furthermore, here comes the rest avialanů, deinonychosauři, oviraptorosauři, alvarezsaur [a] and Idi terizinosauři) During what Zelenitsky et al. (2011) called "a shift from neptačích theropods to birds' (which in their submission was apparently at the base vided Avialae , ie the creation of the first animals more closely related to living birds than deinonychosaurům), this trend bent and major changes to avoid olfactory abilities. After this transition, however, the size of lobes started to increase again, which is clearly seen in early avialanů and even the first modern birds. In later stages of evolution neornitů size remained stable and the olfactory lobes to the groups derived neoavianů (= of all living birds sparrows closer than ducks) there has been some reduction.
new study conclusions are surprising, if not revolutionary: the importance of smell in the evolution of birds increased, not decreased. Note that this conclusion is in good agreement with the above-cited studies of living birds, which also show that their sense of smell is kind of a relic from the days when dinosaurs still fly. Zelenitsky et al. (2011), however, are still on and trying to track down what was a powerful smell good birds. Conclude that a better sense of smell first neornitům allow compared with basal birds to forage more efficiently or improve navigation. So perhaps Zelenitsky et al. encountered another factor contributing to the enormous evolutionary success of modern birds. Perhaps he was just a better sense of smell is why we Neornithes survived extinction at the end of the Cretaceous and Paleogene, while hesperorniti, or flying protiptáci dromeosauridi Sun
Sources:
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