Variation is a naturally occurring phenomenon that is observable at all levels of morphology, from anatomical variations of DNA molecules to gross variations between whole organisms. The structure of the otic region is no exception. The present paper documents the broad morphological diversity exhibited by the inner ear region of placental mammals using digital endocasts constructed from high-resolution X-ray computed tomography (CT). Descriptions cover the major placental clades, and linear, angular, and volumetric dimensions are reported.The size of the labyrinth is correlated to the overall body mass of individuals, such that large bodied mammals have absolutely larger labyrinths. The ratio between the average arc radius of curvature of the three semicircular canals and body mass of aquatic species is substantially lower than the ratios of related terrestrial taxa, and the volume percentage of the vestibular apparatus of aquatic mammals tends to be less than that calculated for terrestrial species. Aspects of the bony labyrinth are phylogenetically informative, including vestibular reduction in Cetacea, a tall cochlear spiral in caviomorph rodents, a low position of the plane of the lateral semicircular canal compared to the posterior canal in Cetacea and Carnivora, and a low cochlear aspect ratio in Primatomorpha.The morphological descriptions that are presented add a broad baseline of anatomy of the inner ear across many placental mammal clades, for many of which the structure of the bony labyrinth is largely unknown. The data included here complement the growing body of literature on the physiological and phylogenetic significance of bony labyrinth structures in mammals, and they serve as a source of data for future studies on the evolution and function of the vertebrate ear. The ear region, which functions in hearing via the cochlea as well as balance and equilibrium via the vestibule and semicircular canals, is one of the most intensively studied sensory systems in vertebrate anatomy and physiology. The external morphology of the petrosal bone, which surrounds the delicate structures of the inner ear in all mammals, is a common source of characters used in phylogenetic analyses A link between body mass and dimensions of the inner ear have been hypothesized for several mammal groups, particularly primates The internal cavities within the petrosal comprise the bony labyrinth of the inner ear, including the cochlea anteroventrally and the vestibular apparatus  posterodorsally . The dimThe labyrinth of the inner ear is difficult to study because the inner ear structures are completely surrounded by bone, and removal of this bone is necessary in order to observe the inner ear cavities . The strMorphology of the inner ear is phylogenetically informative at both more- and less-inclusive taxonomic levels. For example, the cochlea completes at least one complete 360° turn in living therian mammals, but less in monotremes and more basal mammals Given the functional and phylogenetic importance of this region of the skull, it is surprising that broad comparisons of the inner ear of mammals are lacking  is described. The opossum is considered in many respects to retain ancestral morphologies for Theria Didelphis commonly is used as a marsupial outgroup in phylogenetic analyses investigating placental relationships The morphological descriptions of the placental mammal bony labyrinth are arranged in a phylogenetic framework. As a point of departure for comparison, the bony labyrinth of a marsupial  are arranged taxonomically following the relationships recovered for Mesozoic non-placental eutherians From The descriptions of the bony labyrinths of crown placental mammals begin with Afrotheria, and follow in order with Xenarthra, Laurasiatheria, and Euarchontoglires see . The deswww.digimorph.org). No live animals were used for any part of the research reported here. All specimens used in this study are listed in At least one representative of the major clades of placental mammals recovered by the phylogenetic analyses of Bininda-Emonds and others Whenever possible, isolated petrosal bones were CT scanned to maximize the resolution of the images (CT methods described below). The left petrosal was examined for each taxon, with a few exceptions, for consistency. Although cranial asymmetry is known within the ear region Monodelphis domesticaAll specimens were presumed mature, although no rigorous assessment of maturity was ascertained. Although the external surface of the petrosal changes through accretionary growth, there is evidence that the structures of the inner ear do not change significantly once the walls of the bony labyrinth have ossified Trichechus manatus (MSW 03156), which was scanned at Washington University in Saint Louis, MO. Parameters for CT scanning and post-scanning image processing are provided in Digital images obtained through computed tomography (CT) was employed to observe the internal chambers of the petrosal that constitute the bony labyrinth. The majority of the specimens used for this study were scanned at the University of Texas High-resolution X-ray CT facility (UTCT) in Austin, TX. The only specimen not scanned at UTCT was ©©The bony labyrinths were digitally segmented from the CT image data into the various partitions of the inner ear  in order to calculate partial volumes of the osseous cavities, as well as create a 3-dimensional representation of the bony labyrinth for visualization purposes. Segmentation was performed in the computer software packages VGStudio Max 1.2 The endocasts constructed for this study are oriented with the plane of the lateral semicircular canal parallel to the horizon. Such an orientation was selected because the lateral semicircular canal usually is held horizontal when the animal is in a state of alertness Angular, linear, and volumetric measurements were made in the Amira software The total length of the cochlear canal from base to apex was measured using the SplineProbe tool in the Amira software Angles were taken between the planes of all of the semicircular canals, as well as between the basal turn of the cochlea and the plane of the lateral semicircular canal, when the planes were oriented perpendicular to the field of view The total angular deviation of a semicircular canal from its respective plane is calculated trigonometrically using two linear measurements of the canal  of the arcs of the vertical (anterior and posterior) semicircular canals. These ratios have been hypothesized to distinguish aquatic species from their terrestrial ancestors a priori significance level of 5% (P = 0.05) based on the current sample size for which body masses are known (N = 28), any coefficient of correlation 0.38 or above is considered significant using a two-tailed probability model, which is most common in statistical analyses 2) were calculated also to determine the strength of recovered correlations. The coefficient of determination reports the percentage of variation in variable Y that can be explained by X, and coefficients of correlation above 0.70 are considered strong in this study .To ascertain whether the dimensions of the inner ear are correlated to overall body size of the animal, specific measurements were plotted over body mass  and the coefficient of correlation (“r”) was calculated in Microsft Excel 2008 for Macintosh. At an Bathygenys reevesi and Balaenopteridae), and a body mass was not used for Canis familiaris given the broad range of body masses observed in domestic dogs If the body mass of the specimen examined was not known, an average was calculated from various published sources http://morphobank.org/index.php/Projects/ProjectOverview/project_id/833). The matrices include discrete characters only (within the “Matrices” section of the project page), continuous characters only, and a combined discrete and continuous character matrix (the latter two can be downloaded within the “Documents” section of the project page).A phylogenetic analysis was not performed for this study owing to the restricted anatomical region in question and the level at which the taxa were sampled. However, several characters that have been used in phylogenetic analyses, and those are described for the taxa below. Ancestral states, both continuous and discrete, for the hypothetical common ancestors of the clades pictured in aa, anterior ampulla; ac, anterior semicircular canal; am, ampulla; ant, anterior direction; ar, semicircular canal arc radius of curvature; av, bony channel for vestibular aqueduct; cc, canaliculus cochleae for cochlear aqueduct; cf, foramina within cribriform plate; cl, length of cochlear canal; cn, canal for cranial nerve VIII; co, cochlea; cp, plane of semicircular canal; cr, common crus; cv, canal for cochlear vein; dor, dorsal direction; er, elliptical recess of vestibule; fc, fenestra cochleae; fn, canal for cranial nerve VII; fv, fenestra vestibuli; hf, hiatus Fallopii for exit of greater petrosal nerve; ht, height; iam, internal auditory meatus; in, incus; la, lateral ampulla; lat, lateral direction; lc, lateral semicircular canal; ld, linear deviation of semicircular canal from its plane; ma, malleus; med, medial direction; pa, posterior ampulla; pc, posterior semicircular canal; pf, perilymphatic foramen; pl, primary bony lamina; pos, posterior direction; pr, promontorium; ps, outpocketing for perilymphatic sac; rl, reference line for measuring coiling of cochlea; sa, subarcuate fossa; sc, semicircular canal; scr, secondary common crus; sg, canal for spiral ganglion within primary bony lamina; sl, secondary bony lamina; sr, spherical recess of vestibule; st, stapes; vb, vestibule; ven, ventral direction; vn, canal for vestibular branch of cranial nerve VIII; wt, width.Abbreviations used in figures: The inner ear of mammals consists of a set of interconnected spaces within the petrosal bone known as the bony labyrinth , which cThe bony cochlear canal is divided within the promontorium of the petrosal into the scala tympani that communicates with the fenestra cochleae (which is covered with a secondary tympanic membrane to accommodate pressure changes within the membranous labyrinth in life), and the scala vestibuli that terminates at the fenestra vestibuli (which accommodates the footplate of the stapes). The division is formed by a bony primary spiral lamina that curves along the modiolus  on the axial (inner) wall of the cochlea. A secondary bony lamina often mirrors the primary lamina for a short distance on the opposing  wall of the cochlea. The two laminae are connected by the basilar membrane (the laminae do not contact each other directly), upon which the spiral organ of hearing sits. The basilar membrane defines the tympanic wall of the membranous cochlear duct . The vestibular membrane crosses the width of the scala vestibuli to complete the cochlear duct at its vestibular edge. A small opening known as the helicotrema is situated at the apex of the cochlea, and it serves as a connection between the scalae tympani and vestibuli. The cochlear duct is filled with endolymph, and the surrounding space, which includes both the scala tymapni and the scala vestibuli, is filled with perilymph. The perilymphatic duct exits the inner ear near the fenestra cochleae through a bony passage known as the canaliculus cochleae.The bony vestibule is divided into the spherical recess inferiorly and the elliptical recess superiorly. The recesses correspond loosely to the saccule  and utricle plus semicircular ducts , but the shapes of the membranous sacs are preserved minimally within the bony vestibule. The saccule, utricle, and semicircular ducts are filled with endolymph (exchange occurs between the cochlea and saccule at their junction), and perilymph fills the remainder of the space. Varying amounts of perilymph surround the semicircular ducts in different species Didelphis virginiana, which is used to represent Marsupialia) and extant placentals (such as Homo sapiens) and all of the descendents of that ancestor. As inferred from ancestral state reconstructions based on the data presented in this paper, the bony labyrinth of the hypothetical therian ancestor possessed a secondary common crus formed between the lateral and posterior semicircular canals . As observed in most mammal species, the arc of the anterior semicircular canal is the largest among the three canals. Ancestral state reconstructions based on the specimens examined for this study indicate that the cochlea completes a 685° coil (nearly two turns). However, as discussed below in the descriptions of the bony labyrinths of Didelphis virginiana and Kulbeckia kulbecke, the cochlea of the therian ancestor likely completed a single 360° turn only The plane of the lateral canal is positioned low with respect to the ampullar entrance of the posterior canal so that the area of the arc of the posterior canal is not divided by the lateral canal in anterior view, as it is in most extant placentals  is higher than that calculated for basal taxa along the eutherian lineage . The ancestor of Theria likely possessed a cochlea with a low aspect ratio given the close similarities between basal metatherian and eutherian labyrinths The cochlea contributes 66% of the total inner ear volume. The aspect ratio of the cochlea of the ancestral therian is reconstructed as low, although the aspect ratio in Didelphis virginiana is described for comparison with the inner ear structures of crown placentals and their Mesozoic eutherian relatives. Dimensions of the bony labyrinth as a whole structure of Didelphis  are provided in The structure of the inner ear of Didelphis is a common animal in North America, despite it being the only North American marsupial. The body mass of the specimen used (TMM M-2517) is 2.8 kg . The cochlear spiral is high in profile .Compared to the reconstructions for the therian ancestor, the bony labyrinth of wo turns . Lastly,Kulbeckia kulbecke is provided here as a representative of non-placental Mesozoic eutherians , Ukhaatherium nessovi, and Zalambdalestes lechei (the latter two taxa from Mongolia). The relationships depicted for these taxa in Kulbeckia are averages across a sample of four petrosal specimens. The bony labyrinth of Kulbeckia is illustrated in Eutheria is defined as the most recent common ancestor of crown Placentalia and all taxa more closely related to Placentalia than to Marsupialia . A brief overview of the labyrinth of Kulbeckia is slightly less than that measured for Didelphis .The plane of the basal turn of the cochlea is rotated from the plane of the lateral semicircular canal by a lesser degree in idelphis , and theidelphis . The sphidelphis . As was s scr in , and thes scr in . The coms scr in . The bonThe planes of the lateral and posterior semicircular canals almost form a right angle, but the angles that each of these canals form with the anterior canal are acute . The antThe anterior semicircular canal deviates the most from its plane, and the lateral canal is the most planar . The antKulbeckia and the other Mesozoic taxa, as well as Didelphis, were used to reconstruct the ancestral states of Eutheria. The bony labyrinth of the ancestor of Eutheria retained the ancestral therian conditions in all respects. The lateral semicircular canal formed a secondary common crus with the posterior canal, the plane of the lateral canal was low compared to the ampullar entrance of the posterior semicircular canal, the arc of the anterior semicircular canal was the largest among the three semicircular canals, and the aspect ratio of the cochlea was low (below 0.55). All ancestors at the nodes leading to crown Placentalia retained the ancestral eutherian states for all discrete characters.The inner ear morphology of Ukhaatherium and Placentalia; 56% for the most recent common ancestor of Zalambdalestidae, which includes Kulbeckia and Zalambdalestes, and Placentalia). The contribution of the cochlea of the ancestral zalambdalestid was 51%.The contribution of the ancestral eutherian cochlea to the total inner ear volume was 64%, which was only slightly less than that reconstructed for Theria (66%), and the percentage decreased through time . As discussed above in the reconstruction of the ancestor of Theria, these values are overestimates, and the ancestral eutherian most likely possessed a cochlea that completed a single turn only  plus all of its descendants. Placentalia is divided into the three major lineages Afrotheria, Xenarthra, and Boreoeutheria, which in turn is divided into Laurasiatheria and Euarchontoglires Placentalia includes the most recent common ancestor of extant placental mammals . The cochlea of the ancestor of placental mammals completes 738° (over two turns), and the volumetric contribution of the cochlea to the entire labyrinth (58%) is less than that of the ancestral eutherian (64%).Entry of the lateral semicircular canal directly into the vestibule in absence of a secondary common crus is the single unambiguous otic synapomorphy for Placentalia, which is a condition not found outside of the crown (at least within Eutheria) The arc of the anterior semicircular canal is the largest among the three canal arcs, which is retained from the ancestor of Theria. The reconstructed states of both the position of the plane of the lateral semicircular canal compared to the ampullar entrance of the posterior canal and the aspect ratio of the cochlea in profile are equivocal owing to variation in the position of the lateral canal within Afrotheria and variation in the shape of the cochlear spiral in both Afrotheria and Boreoeutheria.Afrotheria is a clade of placentals endemic to Africa that includes the groups Afrosoricida (tenrecs and golden moles), Macroscelidea (elephant shrews), Tubulidentata (aardvark), Hyracoidea (hyraxes), Sirenia (dugongs and manatees), and Proboscidea (elephants). Monophyly of Afrotheria is controversial, primarily because it was not recognized in classical morphological studies of placentals, whether based on strict cladistic methodologies or not Macroscelides proboscideus (Macroscelidea), Orycteropus afer (Tubulidentata), a fossil elephantimorph proboscidean (either Mammut or MammuthusTrichechus manatus (Sirenia), Procavia capensis (Hyracoidea), and the two afrosoricids Chrysochloris sp. (Chrysochloridae) and Hemicentetes semispinosum (Tenrecidae). There is a broad range in body mass among these taxa .The bony labyrinth of the ancestor of Afrotheria retained the ancestral morphology of Placentalia in that the lateral semicircular canal entered into the vestibule directly and the arc of the anterior semicircular canal was the greatest among the three canal arcs. The reconstructed ancestral states of the position of the lateral semicircular canal compared with the posterior canal, as well as the aspect ratio of the cochlea, are equivocal based on the afrotherian morphology described here. The states reconstructed and inferred for all of the nodes within Afrotheria are identical to that of the afrotherian ancestor, except the state for the largest semicircular canal arc which is equivocal for the clade consisting of Procavia and Trichechus was the same as that of the afrotherian ancestor (56%), although the contribution of the cochlea of the ancestor of Paenungulata was almost ten percent less (48%), likely on account of the low contribution of the cochlea of the proboscidean (see below). Contributions of 63% and 64% were reconstructed for the ancestors of Afrosoricida and the more inclusive clade that also includes Macroscelidea, respectively. The ancestral afrotherian cochlea coiled 751°, which was greater than the ancestral placental condition, but less than the values reconstructed for the nodes within Afrotheria .The volumetric contribution of the cochlea to the total labyrinthine volume of the ancestral afrotherian was 56%, which was close to that reconstructed for the ancestor of Placentalia (58%). The ancestral cochlear contribution of the paenungulate clade consisting of Erinaceus (hedgehog) and Sorex (shrew), the results of more recent molecular studies Chrysochloris sp. (Chrysochloridae) and Hemicentetes semispinosum (Tenrecidae) represent the afrosoricids.The group Afrosoricida contains Tenrecidae (tenrecs) and Chrysochloridae (golden moles). Although traditional classifications  than in Hemicentetes (50%) as well.The bony labyrinths of ochloris –9 and Hecentetes –11 diffeochloris . The coc coiling . The proHemicentetes  extends from the channel for the vestibular aqueduct to the junction between the elliptical and spherical recesses.No trace of the bony channel for the vestibular aqueduct was observed in the CT slices of centetes . The aquChrysochloris, the largest angle was measured between the posterior and lateral canals, and the smallest was measured between the anterior and lateral canals. The widest angle measured in Hemicentetes is between the anterior and posterior canals, which not only is the largest angle between two semicircular canals in either taxon . The aspect ratio of the posterior canal arc is the lowest among all of the canals between the two species. The ratios between the length of the slender portion of a semicircular canal and the radius of its arc for Chrysochloris are 4.30 for the anterior canal, 3.89 for the lateral canal, and 5.07 for the posterior canal. A similar pattern is observed in Hemicentetes where the posterior semicircular canal has the highest canal length to arc radius ratio (5.41), and the lateral canal has the lowest .The anterior canal is the largest of all semicircular canals in terms of length of the slender portion of the canal and arc radius for both afrosoricid taxa included in the present study . Likewisochloris , indicatChrysochloris are less than that observed for the same canals in Hemicentetes, although the lateral semicircular canal of Chrysochloris is the only planar canal between the taxa . The arc of the posterior canal of Chrysochloris is curved , although the ratio is only 0.47 for the lateral semicircular canal.The angular deviation of the anterior and lateral semicircular canals from their planes in the taxa . The leaed pc in , and thees pc in . Both thChrysochloris and Hemicentetes to an extent that it divides the space enclosed by the arc of the posterior semicircular canal into dorsal and ventral sections when the labyrinth is oriented in anterior view . In fact, the labyrinthine index of Hemicentetes is smaller than that calculated for any other mammal in this study .Lastly, the plane of the lateral semicircular canal is high with respect to the posterior canal in both ew lc in . Within Hemicentetes), and the anterior semicircular canal has the greatest radius among the three canals. Although the cochlea of Chrysochloris exhibits a great degree of coiling  was examined in the present study . The plane of the basal turn of the cochlea deviates from that of the lateral semicircular canal by a greater degree in Macroscelides than in Hemicentetes, but not as much as in Chrysochloris  were present during the Neogene of sub-Saharan Africa pus afer  and 15 iOrycteropus afer is significantly greater than any of the other afrotherians described thus far , and the spiral of the cochlea is fairly flat  might be a synapomorphy uniting the remaining afrotheres. However, the absence of the secondary common crus is reconstructed as a synapomorphy for all of Placentalia based on the phylogeny used here . For example, the cochlea completes over one and a half turns , and the posterior semicircular canal has the largest radius, rather than the anterior canal.If sed here . Thus, tA close relationship between Hyracoidea (hyraxes) and ungulates, particularly either Perissodactyla or Tethytheria (Sirenia+Proboscidea), is a classical hypothesis. Although some morphological data support a sistergroup relationship between Hyracoidea and Perissodactyla Procavia capensis was constructed  at several points along its path. The canaliculus is not a straight tube, but rather hooks laterally. The canaliculus cochleae exits the bony labyrinth from a bulge posteromedial to the fenestra cochleae , as well as the longest of the three canals, and the arc radius of curvature of the posterior semicircular canal arc is greater for the posterior canal than for the others . Rather, there is a closer connection between Sirenia and Proboscidea, which is a relationship that has been recognized for several centuries Monophyly of Tethytheria, which is the clade that includes Sirenia, Proboscidea, as well as the extinct groups Desmostylia, “Anthrocobunidae”, and Embrithopoda Trichechus manatus, represents Sirenia. The most notable feature observable on the digital endocast of Trichechus is the absence of the bony canaliculus cochleae for transmission of the cochlear aqueduct  and Macroscelides proboscideus (72%). However, the aspect ratio of the spiral of the cochlea is low in Trichechus . A low degree of coiling may be a synapomorphy for Sirenia, given that a similar degree of coiling is observed in the fossil Hydrodamalis gigasTrichechus than in other afrotherians excepting proboscideans  or paenungulate (48%), the value is not much different from the volumetric percentages calculated for ichechus  relativescelides . The cocscideans . As in pichechus .Trichechus than in other taxa examined, such as Macroscelides and Procavia.The fenestra vestibuli has a low aspect  ratio , which sApertures for the posterior ampulla, common crus, and the posterior limb of the lateral semicircular canal are situated at the posterior end of the vestibule, with the common crus as the medial-most opening cr in . The bonTrichechus, similar to the state observed in Macroscelides. However, the lateral canal enters the vestibule lateral and ventral to the posterior ampulla in Trichechus, which is on the opposite side of the posterior ampulla from Macroscelides and other taxa where the opening for the canal is well separated from the ampulla, such as Procavia. Even in Orycteropus, where the lateral and posterior canals fuse to form a secondary common crus, the lateral canal is situated dorsal and slightly medial to the posterior canal. The morphology observed in Trichechus places the plane of the lateral semicircular canal relatively low on the vestibule, and the lateral canal does not extend posterior to the plane of the posterior canal. However, the lateral canal extends further laterally than the arc of the posterior canal.The vestibular aperture of the lateral semicircular canal opens near the base of the posterior ampulla in Trichechus form acute angles with each other. The angle between the planes of the anterior and lateral semicircular canals is the smallest angle measured between any two canals in any afrotherian specimen  are the largest among the three canals. However, the length of the slender portion of the lateral semicircular canal is noticeably smaller than both the anterior) and posterior semicircular canals , and a low cochlear spiral. The large radius of the lateral semicircular canal is an autapomorphy for Trichechus compared to all other afrotherians. The bony labyrinth of Trichechus retains the ancestral placental condition of the lateral semicircular canal opening directly into the vestibule in the absence of a secondary common crus.Although the results of several recent molecular analyses do not support the monophyly of Tethytheria, the structure of the inner ear supports a sistergroup relationship between Sirenia and Proboscidea among the paenungulates. Notable labyrinthine features that are shared by Sirenia and Proboscidea within Paenungulata are a low position of the lateral semicircular canal compared to the posterior canal  was described elsewhere The bony labyrinth of a specimen of an extinct elephantimorph . The lateral semicircular canal does not extend as far laterally as the posterior canal . The ratios between the length of the slender portion of the canal and arc radius of the anterior canal is 4.93, which is the largest ratio among the three canals, and 4.41 for the posterior canal, which is the smallest value. The ratio for the lateral canal is 4.70. The canals do not deviate from their planes substantially . The ancestral paenungulate state for both of those characters is equivocal.The bony labyrinth of the elephantimorph retains the primitive eutherian morphology observed in There are two major groups of xenarthrans, the armadillos and extinct glyptodonts that belong to Cingulata, and the anteaters and sloths, which make up the clade Pilosa Dasypus novemcinctus, which is the only xenarthran found in the United States, represents Xenarthra in this study. Dasypus as a genus is known from the Pliocene to Recent in North, Central, and South America D. novemcinctus itself has the largest biogeographical distribution of any xenarthran species D. novemcinctus was discussed previously Dasypus are provided in The nine-banded armadillo, Macroscelides), although the successive whorls sit upon the basal turn , and the cochlea contributes a larger percentage of the total inner ear volume than the placental ancestor (66% versus 58%).Although the labyrinth of Dasypus, which might support a sistergroup relationship between Xenarthra and Boreoeutheria, but the ancestral state in Afrotheria could not be reconstructed unequivocally. Owing to variation of the aspect ratio of the cochlear spiral within Laurasiatheria and Euarchontoglires, the condition for the ancestor of Boreoeutheria is equivocal between the high and low conditions.The non-afrotherian and non-xenarthran placentals, or Boreoeutheria, are divided into two sister clades, the Euarchontoglires and Laurasiatheria . The latDasypus (816°), both of which are greater than that reconstructed for Afrotheria (751°). Such a degree of coiling might support a Xenarthra plus Boreoeutheria pairing. However, the volumetric contribution of the cochlea to the entire labyrinth of Boreoeutheria (55%) nearly is identical that reconstructed for Afrotheria (56%), both of which are less than that calculated for Dasypus (66%).The degree of coiling of the ancestor of Boreoeutheria (815°) is almost identical to that of Craseonycteris thonglongyai) – at around 2 g to the largest – the blue whale  – at around 150000 kg Acinonyx jubatus) or Thomson’s gazelle (Eudorcas thomsoni), while others are adapted for fossorial lifestyles, such as the European mole . Furthermore, volant bats and fully aquatic cetaceans are included within Laurasiatheria. As a whole, the clade Laurasiatheria is composed of Cetartiodactyla , Perissodactyla , Carnivora , Pholidota (represented by Manis tricuspis), Chiroptera , and Eulipotyphla . General dimensions of the bony labyrinths of laurasiatheres are provided in Laurasiatheria encompasses a great diversity of placental mammals in terms of body size, ranging from the smallest extant mammal – the hog-nosed bat  was less than that reconstructed for Boreoeutheria (815°), but the contribution of the cochlea to the entire labyrinthine volume of Laurasiatheria (55%) was similar to that of the boreoeutherian ancestor (56%).Within Boreoeutheria, Chiroptera is included in a polytomy with Ferae (Carnivora and Pholidota) and a clade comprising Cetartiodactyla and Perissodactyla . The ancEarly systematic analyses of mammals based on morphology group cetartiodactyls  and perissodactyls in a group called Ungulata along with Sirenia, Hyracoidea, and Proboscidea (and often Tubulidentata) The only state reconstructed for the ungulate ancestor that differs from that of the ancestor of Boreoeutheria was the aspect ratio of the cochlea, which was low in the ancestor of the Perissodactyla+Cetartiodactyla clade. The shape of the boreoeutherian cochlear spiral was reconstructed as equivocal, although the aspect ratio of the cochlea was low in the ancestral therian. The bony labyrinth of the ancestor of the Perissodactyla+Cetartiodactyla clade had a lateral semicircular canal that opened into the vestibule directly , a position of the plane of the lateral canal high compared to the posterior canal (retained from the boreoeutherian ancestor), and an anterior semicircular canal arc as the largest of the three arcs (retained from the therian ancestor). The ancestral coiling of the cochlea of the Perissodactyla+Cetartiodactyla clade was 857°, which was greater than that reconstructed for the ancestor of the ungulate-feran-chiropteran polytomy (815°), and the ancestral ungulate cochlea contributed 55% of the total labyrinthine volume, which was a value retained from the boreoeutherian ancestor.The ancestor of Ferae  are divided into the three major extant groups, which are Suiformes (pigs and hippos), Tylopoda (camels and llamas), and Ruminantia (deer and cows) Bathygenys reevesi . However, this is the only similarity between the cochleae of the two taxa. The cochlear canal is significantly longer  and Sus .Both the radius and diameter of the lumen of the anterior semicircular canal arc is the largest in both thygenys . Howevert in Sus . The ratSus are more planar (fit better onto a single plane) than the canals of Bathygenys. In fact, the anterior semicircular canal is perfectly planar in Sus, whereas the anterior canal deviates from its plane in Bathygenys .The semicircular canals of thygenys . The posys pc in , althougus pc in . Only thThe bony labyrinth of the ancestor of Cetartiodactyla was similar to that reconstructed for the ancestor of the Perissodactyla+Cetartiodactyla clade. The lateral semicircular canal opened into the vestibule directly in absence of a secondary common crus, the arc of the anterior semicircular canal was the largest among the three, the lateral semicircular canal was positioned high compared to the posterior canal, and the aspect ratio of the cochlea was low. The cochlea of Cetartiodactyla coiled to a lesser degree than the Perissodactyla+Cetartiodactyla clade (846° versus 857°), but the cochlear canal contributed a greater percentage to the overall labyrinthine volume (59% versus 55%).Bathygenys is flattened (low aspect ratio), which is the ancestral condition, although the cochlea of Sus has a high profile. Both labyrinths retain the ancestral cetartiodactyl condition of the high position of the lateral semicircular canal as compared to the posterior canal, and a vestibular entrance of the lateral canal, rather than formation of a secondary common crus.The labyrinths of the two terrestrial cetartiodactyls retain the ancestral cetartiodactyl condition of the anterior canal possessing the largest arc radius. The cochlea of Sus and Cetacea, there are no unambiguous inner ear synapomorphies supporting this relationship. Both Sus and Bathygenys share a high position of the lateral semicircular canal that is absent in Cetaceans (discussed in the following section), but this state was ancestral for crown Placentalia as a whole. Nonetheless, the most recent common ancestor of Sus and Cetacea possessed a bony labyrinth with the lateral semicircular canal opening directly into the vestibule, the anterior semicircular canal arc with the largest radius among the three canals, a high position of the lateral semicircular canal compared to the posterior canal, and a low aspect ratio of the cochlea in profile. The ancestral cochlear coiling of Sus and Cetacea was 1013°, which appears to be a factor of the high degree of coiling in Sus given that the cochleae of the cetaceans do not coil nearly as much (see below). However, the ruminants and tylopods studied by Gray Sus and Cetartiodactyla, which likely is an inflated estimation given the disproportionately large cochlea of the cetaceans.Although the cladogram presented in Balaenoptera musculus), and the toothed whales, Odontoceti, which includes porpoises and dolphins such as Tursiops truncatus. The bony labyrinth of the bottlenose dolphin Tursiops is described, along with the labyrinth of a fossil member of Balaenopteridae (Mysticeti). The balaenopterid fossil used (TMM 42958-35) was collected from Pliocene deposits of the Yorktown Formation at the Lee Creek Mine in Aurora County, North Carolina. Morphologically, the isolated petrosal can be identified as Balaenopteridae following the key and descriptions of extant mysticetes by Ekdale and others With the exception of Sirenia (the bony labyrinth of which was described above in the Afrotheria section), cetaceans are the only fully aquatic extant mammals. Two major cetacean clades recognized are the baleen whales, or Mysticeti, which includes the largest living mammal  The bony labyrinth of the extinct balaenopterid –29 is laTursiops –31 both Tursiops . The greTursiops in all dimensions, including volume, cochlear canal length, degree of coiling, and even aspect ratio, although to a lesser extent (Tursiops (94%) than for the balaenopterid (91%), although the value for the balaenopterid is exceptionally high. The significant contribution of the total volume by the cochlea is higher for the two cetacean taxa than any other mammal investigated here, including the afrotherians Chrysochloris, Macroscelides, and Trichechus (each with a cochlear contribution around 71–72%). The other extreme is the cochlea of the elephantimorph proboscidean, which only contributes 31% of the total volume of the bony labyrinth (see above).The cochlea of the balaenopterid is larger than r extent . The volTursiops  forms a tympanal recess immediately basal to the apical terminus of the secondary bony lamina in the balaenopterid . A similTursiops than in the balaenopterid  extends from the canaliculus cochleae for a short distance on the tympanal surface of the cochlea in the balaenopterid. The angle between the planes of the basal turn of the cochlea and lateral semicircular canal for the balaenopterid and Tursiops are similar to the angles measured for the terrestrial cetartiodactyls Bathygenys and Sus . The vestibule of Tursiops is bowed medially . Although the ratio calculated for the posterior canal of Tursiops was larger than that of the balaenopterid, the ratios for the anterior (4.19) and lateral (4.05) semicircular canals were larger than those calculated for Tursiops (3.47 and 3.38 respectively).The aspect ratio of the posterior semicircular canal is greatest in both nopterid . The aspTursiops fit onto single planes . The only canal of Tursiops that deviates from its plane is the lateral semicircular canal . A second otic synapomorphy that separates Cetacea from the terrestrial cetartiodactyls is a low position of the plane of the lateral semicircular canal compared to the ampullar entrance of the posterior semicircular canal. The state is derived with respect to the ancestral cetartiodactyl condition, and it is a reversal to the ancestral therian state.Tursiops, and a low aspect ratio for the cochlear spiral in profile. The coiling of the cochlea of the ancestral cetacean (853°) was retained from the ungulate ancestor (857°), but the contribution of the ancestral cetacean cochlea to the total labyrinthine volume was greater than that calculated for the Perissodactyla+Cetartiodactyla clade (84% versus 55%). The high contribution of the cochlea to the total volume distinguishes Cetacea from other members of Cetartiodactyla, and likely is greater than that inferred in this study.Additional states reconstructed for the ancestor of Cetacea include the anterior semicircular canal arc as the greatest among the three arcs despite the lateral canal as the largest in Equus caballus, was available for examination. Images of the inner ear and an endocast of the bony labyrinth are presented in The odd-toed ungulates that make up extant Perissodactyla are divided into Equidae (horses), Tapiridae (tapirs), and Rhinocerotidae (rhinoceroses). Monophyly of Perissodactyla is well supported Equus is similar to that of the dolphin Tursiops truncatus , but rather is more in line with the percentage calculated for the terrestrial cetartiodactyl Bathygenys reevesi (54%).The total volume of the inner ear cavities of runcatus . This isody mass . Althoug dolphin . BecauseEquus has a low aspect ratio of . Additionally, the plane of the canal is high relative to other vestibular constituents. The elevated lateral semicircular canal divides the space enclosed by the posterior semicircular canal arc when the endocast of the bony labyrinth is viewed posteriorly  extends from the dorsomedial edge of the spherical recess to the vestibular aperture of the bony channel for the vestibular aqueduct, which is situated ventral and medial to the vestibular aperture of the common crus av in . The chaal av in  and 3.Equus roughly form a right angle with one another, and the angle between the planes of the posterior and anterior canals only is slightly obtuse .The planes of the posterior and lateral semicircular canals of y obtuse . Both the  and Feliformia . Monophyly of Pinnipedia (within Caniformia) has been questioned in the past Canis familiaris and Felis catus), as well as the aquatic Stellar sea lion, Eumetopias jubatus (Pinnipedia). The dog that was used was a particularly small breed (a Chihuahua). Although the cranium varies to extreme degrees among domestic dog breeds, the vast majority of variation is restricted to the craniofacial region rather than the basicranium The carnivorans examined here include two common terrestrial species (Felis (627 slices) and Eumetopias (498 slices) is significantly greater than the number obtained for Canis (92 slices). Because of this, the CT data through the ear region of Canis . Similarly, the length of the inner ear cavity of the dog is not much different than that measured for the cat, and the length of the bony labyrinth of Eumetopias is substantially greater than either of the other species, owing to large body size .The basal whorl of each carnivoran cochlea is separated from the apical turns, where the apical turns fit within the arc created by the basal turn when the cochlea is in vestibular view , and 38DCanis is similar to that measured for the cetaceans and Sus  and also in non-placental mammals.As in the cat and sea lion, the posterior limb of the lateral semicircular canal does not open into the vestibule in Eumetopias was measured between the anterior and posterior semicircular canals , Eumetopias , and Felis .The posterior semicircular canal of the cat is the longest of all of the canals in this species, and the lateral canal is the shortest. Likewise, the lateral semicircular canal of in Felis . Unlike  the dog . Similar species . The aspEumetopias . The anterior canal of Eumetopias does not deviate from its plane substantial , although the lateral and posterior semicircular canals of the sea lion deviate by a substantial amount .The lateral semicircular canal is the least planar of the three canals in metopias . In fact by much . The antEumetopias and Felis. The secondary common crus observed in Canis is an apomorphic reversal to the ancestral therian condition, and it also is observed in Orycteropus among crown placentals. The ancestral coiling of the cochlea of Carnivora is over a quarter of a turn greater than that reconstructed for the ancestor of Ferae (987° versus 888°), and the carnivoran cochlea contributes 5% more to the total labyrinthine volume than that of the feran ancestor (61% versus 56%). The position of the lateral canal is reconstructed as high relative to the vestibule for the ancestral carnivoran, despite the low position in caniforms. In addition, the anterior semicircular canal is the largest in ancestral Carnivora.Two labyrinthine characters are synapomorphies for Carnivora within Ferae. The first is the higher aspect ratio of the carnivoran cochlea in profile that gives the cochlear spiral a “sharp-pointed” profile Felis is positioned high, which is derived from the ancestral eutherian condition, but is plesiomorphic for Carnivora as a whole. The low position of the lateral canal is a reversal for Caniformia. The lateral semicircular canal enters the posterior ampulla in the ancestral caniform (even though a secondary common crus is present in Canis), and the arc of the anterior semicircular canal is the largest of the three canal arcs . The ancestral labyrinth of Caniformia possesses a cochlea with a high aspect ratio that coiled 979° and contributed 60% of the total labyrinthine volume.A single character from the bony labyrinth, reversal to a low position of the lateral semicircular canal in relation to the ampullar entrance of the posterior canal, is optimized as a synapomorphy for Caniformia. The lateral canal of ManisAlthough extant species of pangolins are known only from Africa and Asia, fossils of Pholidota have been recovered from Tertiary deposits of Europe and North America Manis tricuspis (Bathygenys reevesi (29.8 mm3) and Dasypus novemcinctus  and the xenarthran BradypusThe gross volume of the inner ear cavities of the pangolin, ricuspis  and 41, mcinctus . Likewisrd turns . The apird turns  as is obs .The bony labyrinth of There are no unambiguous synapomorphies within the inner ear that support an exclusive Carnivora plus Pholidota clade (Ferae). The ancestor of the clade retained features that were present in the ancestor of Placentalia, including entry of the lateral semicircular canal into the vestibule directly, and an anterior semicircular canal arc that was the largest among the three arcs . The plane of the lateral semicircular canal of the ancestor of Ferae was high compared to the ampullar entrance of the posterior canal, which was the state reconstructed for the ancestor of Boreoeutheria. The state of the aspect ratio of the cochlea was equivocal as reconstructed for the feran ancestor.Pteropus lylei is used as a representative; Rhinolophus ferrumequinum was examined here) than between Rhinolophidae and other echolocating bats, which are represented here by the Nycteridae species Nycteris grandis and the Molossidae species Tadardia brasiliensisRhinolophus is included with Nycteris and Tadarida.Chiroptera (bats) is the only group of truly volant mammals, and with over 1,000 species, it forms the second most speciose group of mammals (second only to rodents) Pteropus includes the bats with the largest body sizes Pteropus lylei is an order of magnitude larger than that of the microchiroperan species examined . The aspect ratio of the lateral semicircular canal arc of Pteropus is the highest among the three canals .The ancestor of Chiroptera retained ancestral placental features, including a lateral semicircular canal that was positioned high compared to the posterior canal and that opened into the vestibule directly, as well as the anterior semicircular canal arc as the largest among the three arcs. The ancestral chiropteran cochlea had a high aspect ratio (a condition shared with Carnivora), coiled 764°, and contributed 61% to the overall volume of the inner ear cavities . The labyrinth of Nycteris grandis  and Felis (68%). The cochlea comprises 73% of the labyrinthine volume in Tadarida, which is similar to the percentage calculated in the afrotherians Chrysochloris (71%), Macroscelides (72%), and Trichechus (71%). The largest volumetric contribution among the bats examined was calculated for Rhinolophus (89%). The only other mammals that have a larger contribution than Rhinolophus are the cetaceans .Among the microchiropteran species examined in the present study,  grandis –45, Rhinmequinum –47, and iliensis –49, the abyrinth . LikewisTadarida . The cocRhinolophus  ratio calculated for Nycteris is 1.0, indicating a circular fenestra  than that of Nycteris, yet the channel for the vestibular aqueduct is observed, perhaps because the slices were of a higher resolution (interpixel spacing of 0.043 mm).The common crura of all three bats are tall and especially slender in us cr in  and Nyctis cr in . The bonus av in , but theth av in . The preNycteris , Rhinolophus , and Tadarida .The aspect ratio of the arc of the lateral semicircular canal is the lowest among the three canals for the microchiropterans, particularly for nolophus . Only thTadarida are the most planar among the microchiropterans , but the canal does not deviate substantial in Nycteris .The semicircular canals of opterans , and nonar canal . The degRhinolophus shares a more recent common ancestor with Pteropus than the definitive microchiropterans Nycteris and Tadarida. However, the lateral semicircular canals of both Nycteris and Rhinolophus empty into the posterior ampulla, whereas the lateral canals of Pteropus and Tadarida open into the vestibule directly.There are no unambiguous synapomorphies within the bony labyrinth uniting Chiroptera as a whole, nor is there evidence from the inner ear that Nycteris retains the ancestral condition. Because of this, the state in the ancestor of Microchiroptera is equivocal as reconstructed. Tadarida retains the ancestral therian state of a flattened cochlea, whereas the cochleae of all other bats have a high aspect ratio. Nonetheless, the ancestral microchiropteran condition is a cochlea with a high aspect ratio, which is retained from the ancestor to all of Chiroptera. The largest semicircular canal arc is observed in the anterior canal in all of the bats, although this feature is plesiomorphic and shared with most therian taxa. The cochlea of the microchiropteran ancestor coils 820° and contributes 68% of the total labyrinthine volume, both of which are greater values than those reconstructed for the ancestor of Chiroptera .A secondary common crus is not observed in any of the bats examined. In this regard, the bony labyrinth of Chiroptera is derived from that of the ancestral eutherian, but retains this morphology from the ancestral placental. Most of the bats are derived from the ancestral eutherian condition in the position of the lateral semicircular canal in relation to the ampullar opening of the posterior canal, although Rhinolophus and Tadarida possessed a cochlea with a high aspect ratio, a lateral semicircular canal positioned high compared to the posterior canal, and an anterior semicircular canal arc that was the largest among the three arcs. All of these states also are present in the ancestor of Chiroptera. Because the lateral semicircular canal opened into the vestibule in Tadarida and into the posterior ampulla in Rhinolophus, the state in the most recent common ancestor of these taxa was reconstructed as equivocal. The cochlea of this ancestor coiled 896°, and contributed 76% of the entire labyrinthine volume. Although the cochlea contributed a great amount of the labyrinthine volume, it was not as great as that reconstructed for Cetacea (84%).The most recent common ancestor of Solenodon, and the extinct genus NesophontesThe sister taxon to the Perissodactyla+Cetartiodactyla clade, Ferae, and Chiroptera polytomy is Eulipotyphla. The constituents of Eulipotyphla are Erinaceidae (hedgehogs), Soricidae (shrews), Talpidae (moles), Atelerix albiventris , although the vestibular aperture of the canal of Atelerix is further separated from the base of the posterior ampulla than the canal in Sorex. The lateral canal is positioned high relative to the posterior semicircular canal in both the hedgehog and shrew, particularly in Atelerix , which is a greater value than the lateral canal (0.03 mm3). The volumes of all of the canals in Sorex are identical (0.02 mm3). The cross-sectional diameters of the anterior and posterior semicircular canals are the same in Sorex, which is a smaller value than that measured for the lateral canal  with respective aspect ratios close to 1.0 (Sorex (5.44), and the ratio of the lateral canal is the smallest in the shrew (3.38). The ratio of the lateral canal in Atelerix is the smallest (4.15), and the ratio is identical for the anterior and posterior canals (4.74).The lateral and posterior semicircular canal arcs of e to 1.0  and 52. Sorex deviates the most from its plane , but only the posterior canal of Sorex exhibits substantial deviation .Among the semicircular canals of both eulipotyphlan taxa, the posterior canal ne pc in . The leaar canal , which dChrysochloris and Hemicentetes). Both Sorex and Atelerix are derived from the ancestral eutherian condition in that the lateral semicircular canal enters the vestibule directly rather than forming a secondary common crus with the posterior canal, as well as a high position of the plane of the lateral canal in relation to the ampullar opening of the posterior semicircular canal. Vestibular entry of the lateral canal is inherited from the ancestor of Placentalia. The cochlea of Atelerix is derived from the ancestral eutherian in that the aspect ratio of the spiral is high, whereas the cochlea of Sorex retains the primitive flattened condition reconstructed for the ancestor of Theria.No features of the bony labyrinth support monophyly of Eulipotyphla, nor are there any unambiguous characters that unite the eulipotyphlans with the afrosoricids  and is positioned high compared to the ampullar entrance of the posterior canal (retained from boreoeutherian ancestor), and an anterior semicircular canal arc with the largest radius among the three arcs (retained from therian ancestor). The state of the aspect ratio of the cochlea is reconstructed as equivocal for the ancestor of Eulipotyphla. The cochlea of the most recent common ancestor of Euarchontoglires contains the remaining placental mammal clades. Among these are the highly speciose Rodentia, Lagomorpha, Primates, Dermoptera, and Scandentia. Gross dimensions of the bony labyrinths of Euarchontoglires are provided in The states reconstructed for the bony labyrinth of the most recent common ancestor of Euarchontoglires are the same as those for Boreoeutheria. That is, the lateral semicircular canal opens into the vestibule directly in the absence of a secondary common crus, the lateral semicircular canal is positioned high compared to the posterior semicircular canal, and the anterior canal arc is the largest in terms of radius of curvature among the three arcs. The cochlea of the ancestral euarchontoglire coils 957°, which is over a quarter of a turn greater than that reconstructed for the ancestral boreoeutherian (815°), and the cochlea of Euarchontoglires contributes 53% of the total inner ear volume . An unequivocal state of the aspect ratio of the cochlea could not be reconstructed from the data provided here.Recognition of a close relationship between rodents and lagomorphs can be traced back to the seminal classification of Linnaeus The most recent common ancestor of Rodentia and Lagomorpha (Glires) retained a lateral semicircular canal that opened into the vestibule directly in absence of a secondary common crus from the most recent common ancestor of Placentalia, a position of the lateral canal high compared to the posterior canal from the ancestor of Boreoeutheria, and the highest arc radius of curvature measured for the anterior semicircular canal arc from the ancestor of Theria. Although the euarchontoglire ancestral state of the aspect ratio of the cochlea was equivocal, the ancestral glire possessed a cochlea with a high aspect ratio, which was shared with Scandentia among the members of Euarchontoglires. The cochlea of the ancestral Glires coiled 924°, and the cochlea contributed 55% of the total labyrinthine volume, which was inherited from the ancestral boreoeutherian.Primates, dermopterans, and scandentians together form the clade Euarchonta Rodents make up the most speciose clade of mammals, contributing over 40% of all named extant mammal species Mus musculus . Similarly, the cochlea of Cavia coils to a much greater degree than any other mammal studied here , and the ratio is the smallest in the lateral canal . The canal length to arc radius ratio of the anterior semicircular canal is 4.79 for Cavia and 4.98 for Mus.Both the largest and smallest semicircular canal arc aspect ratios among rodents were measured for the arcs of Cavia . The larCavia are less planar than the canals of Mus (Mus). The lateral semicircular canal of Mus is the most planar canal in either taxon . The linear deviation to cross-sectional diameter ratio is 0.31 for the anterior semicircular canal in Cavia and 3.10 for Mus.The semicircular canals of s of Mus , especiaCavia and Mus retain the ancestral condition reconstructed for Theria in that the largest semicircular arc radius is observed in the anterior canal. Further, the labyrinth of the ancestor of Rodentia retained the ancestral placental entry of the lateral canal (into the vestibule directly), the ancestral boreoeutherian position of the lateral semicircular canal , and the ancestral glire cochlear aspect ratio (high). The cochlea of the rodent ancestor coiled 1003° (close to 1013° reconstructed for the most recent common ancestor of Cetacea plus Sus) and contributed 56% of the total labyrinthine volume (close to 55% contribution of the cochlea of Boreoeutheria).The labyrinths of Lagomorphs  are classically allied with rodents  is a larger species overall than the eastern cottontail (Sylvilagus) Lepus is over twice that measured for Sylvilagus .Two lagomorph species examined here were fornicus –59 and Soridanus –61. The  longest , and thelvilagus , althougLepus is slightly larger than that of Sylvilagus .The fenestrae vestibuli are less elliptical in the lagomorphs than for the rodents . The channel is a delicate passage in Sylvilagus, and it does not end as a flattened fissure as in most other mammals, including Lepus. The channel is longer in Lepus than it is in Sylvilagus, both in terms of absolute length .The bony channel for the vestibular aqueduct exits the inner ear cavities medial to the vestibular aperture of the common crus  is greater than either the lateral (0.25 mm3) or posterior canals (0.24 mm3), although the most voluminous canal within the labyrinth of Sylvilagus is the lateral semicircular canal . The cross-sectional diameter of the posterior semicircular canal of Lepus is greater than either the anterior or lateral semicircular canal  is greater than that computed for the anterior (4.84) and lateral semicircular canals (4.38). However, the greatest ratio among the canals of Lepus was calculated for the anterior semicircular canal .The aspect ratios of the anterior and posterior canals are greater in in Lepus , but theSylvilagus deviates from its plane to a greater degree than that of Lepus. The posterior canal of Sylvilagus deviates to a substantial degree , as does the posterior canal of Lepus (ratio is 1.09). The lateral semicircular canal of Lepus is the most planar among all of the canals between the two species, but the linear deviation is not substantial for either species . The anterior semicircular canal deviates from its average plane by a lesser degree in Lepus, and only the anterior canal of Sylvilagus deviates to a substantial degree .The posterior semicircular canal is the least planar canal in both taxa , where tThere are no unambiguous synapomorphies that support monophyly of Lagomorpha within Glires or Euarchontoglires. The states reconstructed for the ancestor of Lagomorpha are the same as those for both Rodentia and Glires, as the lagomorphs retain the ancestral therian condition of the largest radius of curvature measured for the anterior semicircular canal arc, the placental condition of the direct vestibular entrance of the lateral semicircular canal, the ancestral boreoeutherian condition of the high position of the lateral semicircular canal compared to the ampullar opening of the posterior canal, and the glire condition of the high aspect ratio of the cochlea. The cochlea of the most recent common ancestor of lagomorphs coils 751° and contributes 53% to the total volume of the inner ear cavities.Primates consists of two major lineages, Strepsirhini which includes the lemurs and lorises, and Haplorhini which includes monkeys and apes. The haplorhines are divided further into three groups, which are Tarsiidae (tarsiers), Platyrhini (New World monkeys), and Catarhini (Old World monkeys and apes). Monophyly of all of these clades is supported by numerous phylogenetic analyses Macaca mulatta . Only the cochlea of the elephantimorph proboscidean contributes less (31%) to the bony labyrinth among the mammal species discussed so far.The two primate species examined here are the rhesus monkey,  mulatta –63, and  sapiens –65. The  sapiens . The huml length , but theMacaca completes a greater degree of coiling than the cochlea of Homo , and the apical turns sit on top of one another  and 64D.n Macaca . The angr mammal .Cavia porcellus. The vestibule is constricted internal to the fenestra vestibuli, thereby defining the border between the spherical and elliptical recesses. The bony channel for the vestibular aqueduct leaves the inner ear dorsal to the medial edge of the common crus and terminates as a fissure in both species  and Homo .The aspect ratios of the arcs of the semicircular canals are similar between the two primate taxa . The higMacaca is less than that measured for the posterior canal, and the posterior semicircular canal is the most planar within the labyrinth of Homo. The deviation of the anterior canal is substantial for both primates , but only the posterior canal of Macaca deviates substantially . The degree of deviation of the lateral semicircular canal is not substantial in either species .The anterior semicircular canal is the least planar canal in each primate . The totHomo was measured for the posterior canal arc. The arc of the posterior semicircular canal of no other euarchontoglire is the largest in terms of radius of curvature, and the only mammals for which the posterior canal arc is the greatest are Manis , Dasypus (the distribution within Xenarthra beyond this taxon is unknown), and Orycteropus and Procavia among afrotherians.There are no unambiguous synapomorphies in the bony labyrinth to support monophyly of Primates, and the clade retains the ancestral primatomorphan morphology of the cochlear spiral in that the cochlea has a low aspect ratio in profile. The anterior semicircular canal arc has the largest radius of curvature, which is retained from the ancestor to Theria, although the greatest radius in The ancestral primate retained the ancestral placental condition of the direct vestibular entrance of lateral semicircular canals in the absence of a secondary common crus, and the plane of the lateral canal was high relative to the ampullar entrance of the posterior canal, which was retained from the ancestor of Boreoeutheria, if not earlier . The cochlea of the ancestor of Primates coiled 980°, and the cochlea contributed 48% of the total labyrinthine volume, which is the same value as that reconstructed for Paenungulata, but slightly less than that for Primatomorpha (50%).Cynocephalus volans and Galeopterus variegatusCynocephalus is used as a representative of Dermoptera. Phylogenetic analyses based on molecular data reconstruct a close relationship between Primates and Dermoptera The colugos are gliding mammals divided into two extant species, Cynocephalus is less than the rabbit Sylvilagus floridanusCynocephalus contributes 48% of the total labyrinthine volume, which is similar to the contribution calculated for Homo sapiens (50%). The cochlear spiral completes nearly two and two thirds whorls  is greatest among the canals , which is different than the condition in most of the mammals examined here, where the greatest ratio is observed in the posterior semicircular canal. The anterior canal is the least planar of the three semicircular canals . The aspect ratio of the cochlea is low (retained from Primatomorpha), the lateral semicircular canal is high compared to the ampullar opening of the posterior semicircular canal (retained from Boreoeutheria), the lateral canal opens into the vestibule directly in the absence of a secondary common crus , and the greatest arc radius of curvature was measured for the anterior semicircular canal (retained from Theria). The contribution of the cochlea calculated for Cynocephalus (48%) is retained from the ancestor of Primatomorpha (50%), and the coiling of the cochlea (954°) is similar to that reconstructed for the ancestor of Euarchontoglires (957°).The bony labyrinth of Tupaia glis  ratio of similar to the rhesus monkey, Macaca mulatta , a condition that is unique to Tupaia among euarchontoglires, but shared by Hemicentetes, Cetacea, Equus, Carnivora (except Canis), and the bats Nycteris and Rhinolophus. The greatest arc radius of curvature was measured for the anterior semicircular canal in Tupaia, which is consistent for most of the therian mammals considered here.The bony labyrinth of Tupaia is derived from the ancestral eutherian condition, which the taxon shares with Glires within Euarchontoglires. The shape of the cochlear spiral may be a synapomorphy supporting a Tupaia plus Glires clade, although the ancestral state of Euarchontoglires is equivocal with respect to this character. The cochlea coils to a greater degree (1125°) than that reconstructed for the ancestor of Euarchontoglires (957°), but less than one half turn. The cochlea of Scandentia contributes 55% of the total labyrinthine volume, which is he same percentage calculated for the cochlea of Boreoeutheria.The high aspect ratio of the cochlea of Trichechus manatus and Equus caballus are among the most voluminous, while the inner ears of Mus musculus and Sorex monticolus are the smallest. In order to test if there is a correlation between body size and inner ear dimensions, the coefficient of correlation was calculated between specific measurements and body mass , although weak positive correlations are found between degree of coiling and both canal length  and aspect ratio of cochlear spiral , as summarized in The degree of coiling exhibited by the cochlea is not correlated with body mass . That is, large animals, such as th Century Observation of variation across the sample of bony labyrinths of placental mammals is a long-recognized phenomenon predating the seminal works of Gustaf Retzius in the late 19Dasypus novemcinctus, where the posterior canal is the most sensitive, or Eumetopias jubatus where the lateral canal is the most sensitive. In the case of Eumetopias, the size of the lateral semicircular canal as the largest might be related to an aquatic lifestyle as discussed previously Trichechus manatus and Tursiops truncatus.General patterns in the bony labyrinth anatomy include the arc radius of curvature of the anterior semicircular canal being the largest among the three canals in the majority of the mammals examined here (24 out of 32 species). This pattern has been observed in most mammal species Monodelphis domestica) The posterior semicircular canal is the least planar of the three canals in more bony labyrinths (15 out of 32 species) than either the anterior (9 out of 32 species) or lateral canals (8 out of 32species), and the lateral canal is the most planar for the majority of taxa (18 out of 32 species). The ratio of the total linear deviation to the cross-sectional diameter of the semicircular canal is used in the present study to describe the degree of planar deviation of a semicircular canal, where a ratio above 1 (linear deviation greater than diameter) is considered substantial. Any physiological importance of planar deviation has yet to be explored in a rigorous sense, and such substantial deviation may not have any basis in function. The ratio is used for descriptive and comparative purposes only. Although the ratio is arbitrary, evidence suggests that, even in species with broad ranges of planarities  are less than that observed in terrestrial mammals (range of 28% for Macroscelides to 69% for the elephantimorph). The vestibular contribution of Trichechus (29%) is on the low end of the entire mammal range, but it is still greater than the vestibular apparati of both Macroscelides (28%) and Chrysochloris (29%), which are strictly terrestrial. Furthermore, the vestibular apparatus of Eumetopias contributes 47% of total labyrinthine volume, which is only slightly larger than the mean for terrestrial mammals (44%). This suggests that aquatic behavior alone cannot explain a reduced vestibular system in all aquatic taxa.The low contribution of the vestibule  might be related to an aquatic lifestyle nonetheless. As an initial investigation of this hypothesis, the relative contributions of the cochlea and vestibule are compared between terrestrial and aquatic taxa examined in this study. Because bats are the only true volant mammals and their ears likely are specialized for aerial locomotion, Chiroptera was not incorporated into this comparison. The vestibular contribution of t-test assuming unequal variances (determined through an F-test). An a priori significance level of 0.05 was selected Although the ranges of vestibular contribution overlap between the terrestrial and aquatic samples, the means of each group may differ significantly. The small number of aquatic species used here limits the effectiveness of statistical analysis. The hypothesis that the mean contribution of the vestibule differs significantly between terrestrial and aquatic mammals was tested, with a two-tailed Trichechus manatus and Eumetopias jubatus appear as though they have been compressed  and Phocaena communis, the sirenian Dugong dugon, and the pinniped carnivorans Phoca vitulina, Halichoerus grypus, and Otaria pulsillaAdditional features that may have an importance in determining evolutionary relationships that can be observed within the bony labyrinth include the size of otoliths within the vestibular apparatus, coiling of the cochlea, and shape of the cochlear spiral. The otoliths are tiny in most mammal species, but sizeable otoliths have been observed within the labyrinths of the marsupial Chrysochloris and Atelerix, thereby preserving the membranous labyrinths with the otoliths supposedly intact.There are several reasons for the absence of otoliths on the CT scans. The composition and density of otoliths makes it virtually impossible that they would have been missed in CT data if present. Indeed, CT scans of many non-mammalian vertebrates reveal otoliths Eumetopias, which has a cochlear aspect ratio of 0.68 similar to other carnivorans, and Sus, which has an aspect ratio of 0.71. However, Gray Sus as intermediate between “flattened” and “sharp-pointed”, but he described the cochleae of pinnipeds as “flattened”.Two cochlear shapes termed “sharp-pointed”  and “flattened”  are thought to be phylogenetically informative Cavia porcellus has the highest aspect ratio (1.29), and it is the only species in this study in which the height of the cochlear spiral is greater than the width across the basal turn of the cochlea. Similar high-spired cochleae are observed within other caviomorph rodents, including Hydrochoerus capybaraMyocastor coypuDolichotis patagonum , and Chinchilla laniger . A high-spired cochlea is likely a synapomorphy for caviomorph rodents , but other members of their clades possess high degrees of coiling . Phylogenetic patterns extend beyond Mammalia, and additional systematic information can be found in the inner ear labyrinths of squamate reptiles The coiling of the cochlea is phylogenetically informative and can be used to distinguish therian and non-therian mammals Didelphis virginiana) does, in fact, possess a fenestra vestibuli that falls below the 1.8 cut-off (ratio of 1.6). However half of the placentals examined here  exhibit the ‘marsupial condition’ (below 1.8) of Segall Nycteris is 1.0, which is the observed condition among monotremes The stapedial ratio is an index commonly used in phylogenetic analyses to explore the relationships between Mesozoic therians Rhinolophus is similar to that observed in cetaceans, but the vestibular  contribution calculated for other bats fall within the range of other mammals. Because a large cochlea is phylogenetically informative for Cetacea, the phenomenon may also be informative within Chiroptera, upon which a denser sampling of taxa might shed light. Furthermore, a low contribution of the cochlea independently unites zalambdalestids, primatomorphs, and eulipotyphlans , and absence of a secondary common crus is a synapomorphy for crown Placentalia . Even so, entry of the lateral canal into the posterior ampulla is reconstructed as a synapomorphy of Cetacea, as well as Carnivora . Although the entry of the posterior limb of the lateral semicircular canal does not express any major pattern with the taxonomic sampling employed by the current study, potential for informativeness at lower levels is apparent. For example, the lateral canal opens into the posterior ampulla in the cetaceans, but it opens into the vestibule in terrestrial artiodactyls , but potentially phylogenetic patterns are observed . In order to fully understand the functional and evolutionary implications within the structure of the bony labyrinth, both physiology and phylogeny must be considered, as these two phenomena are not mutually exclusive. Future detailed studies of the inner ear among closely related species will increase our knowledge of the phylogenetic and functional implications of the inner ear, and foster the application of bony labyrinth morphology to the biological interpretation of fossil vertebrates.Table S1Taxa examined and scanning parameters.a Definitions of parameters are as follows: FR, field of reconstruction refers to the dimensions of an individual CT slice, expressed in millimeters; Pixel, interpixel spacing, or vertical and horizontal dimensions of an individual pixel, expressed in millimeters, and calculated as FR/Size; Size, number of pixels in a CT slice, either 512×512 or 1024×1024 pixels; Slices, number of CT slices through the ear collected in the coronal  slice plane; Space, interslice spacing, or distance between consecutive slices, expressed in millimeters. b Taxonomy and systematic arrangement follows published phylogenies c This specimen was the 156th Mortality South West in 2003, collected by S. Rommel at University of North Carolina Wilmington.(PDF)Click here for additional data file.Table S2Additional information, imagery, and sources of data selected specimens. Further imagery is available at http://morphobank.org/index.php/Projects/ProjectOverview/project_id/833. Institutional abrreviations listed in (PDF)Click here for additional data file.Table S3Ancestral character state reconstructions for ancestral nodes in text . Letters in the first column refer to node labels in text (PDF)Click here for additional data file.


Healthcare associated infections exact a heavy toll in terms of preventable death and disability in patients and are responsible for additional costs of hospitalization in health care facilities in resource-limited countries. The baseline mean attack rates for surgical site infections ranged from 27.3% to 54.2% in the surgical wards of four district hospitals in northern Benin. To this end, a program of prevention and reduction of surgical site infections is implemented to ensure the safety of patient care.Halve the surgical site infections in hospitals targeted by the program.The clinical audit methodology is based on the use of standard criteria for prevention of surgical site infections in order to identify gaps and propose a plan for improvement. In addition samples of pus were analyzed in the lab to confirm the surgical site infection by identifying the causative organisms. A study protocol sheet with data collection monitoring has been developed for the calculation of incidence of suppuration with confidence intervals.The observance of protocol implementation of preventive measures  at all operating system has improved the following indicators:- The rate of handwashing compliance improved from 25% to 45% in one year,- The reduction of surgical site infections in hospitals by 25% in 2005 to 3% in 2012,- The decrease in the average length of stay in health care for 22 days to 7 days.The introduction of the prevention of healthcare associated infections in the management of hospital management has reduced the risk of infection and improves the quality of patient care.The change introduced in improving patient safety in these institutions remained a source of motivation for the generalization of the program in other services.None declared


The definition of Purkinje cell zones by their white matter comprtments, their physiological properties, and their molecular identity and the birthdate of their Purkinje cells will be reviewed. The cerebellar Purkinje cell layer generally is described as a homogeneous structure. Its subdivision into discrete longitudinal zones with abrupt changes in their connectivity at their borders was based on the observation of the subdivision of the cerebellar white matter of the cerebellum of the cat and the ferret into compartments. In transverse sections a regular pattern of mediolaterally disposed bundles of medium-sized myelinated Purkinje cell axons was observed, separated by darker staining slits consisting of smaller fibers Fig.  that wasIn the same period, Olav Oscarsson and his collaborators from the Department of Physiology in Lund, Norway recorded positive surface-climbing fiber potentials and Purkinje cell complex spikes from the anterior lobe of the cat in preparations where they had transected the spinal cord, except for one of the funiculi. Oscarsson found that climbing fiber potentials on stimulation of peripheral nerves always were located in parasagittal zones . OscarssMore recently Voogd et al.  and SugiPukinje cell zones develop early from a series of superficial, mediolaterally disposed Purkinje cell clusters . Recentl


The presentation illustrates the process for the development of the recent NICE Headache Guidelines and the importance of careful topic selection. The methodology, timescale, and the role of the Expert Group including patient representatives are described. The Guidelines are intended for the non-specialist in Primary Care where most patients present and can be safely diagnosed and managed.The Guidelines provide support with the diagnosis of primary headache including the value of neuroimaging which evidence suggests should not be used only for reassurance. The importance of excluding secondary causes, in particular medication overuse which is found among migraine sufferers is emphasised. Specific advice is given for management of the three most common types of primary headache; migraine, tension headache and cluster headache. Changes are recommended to current practice including prescribing combination therapy in acute migraine and indications for prophylactic topiramate. The management of female migraine sufferers of child baring potential also receives attention and caution is advised in the use of combined hormonal contraception for patients with aura due to increased risk of stroke. There are also recommendations for perimenstrual prophylaxis with frovatriptan or zolmitriptan.Improved recognition of common headache disorders and better targeting of treatments should reduce the burden of headache without requiring substantial extra resource. Where more specialised advice is required the Guideline recommends referral to a neurologist or GP with special interest in headache.


The use of talcum powder is incorrectly part of the traditional care of infants. Its acute aspiration is a very dangerous condition in childhood. Although the use of baby powder has been discouraged from many authors and the reports of its accidental inhalation have been ever more rare, sometimes new cases with several fatalities have been reported. We report on a patient in which accidental inhalation of baby powder induced severe respiratory difficulties. We also point out the benefits of surfactant administration. Surfactant contributed to the rapid improvement of the medical and radiological condition, preventing severe early and late complications and avoiding invasive approaches. The use of talcum powder is incorrectly part of the traditional care of infants. Acute aspiration of baby powder is a very dangerous condition in childhood and several fatalities have been reported . Talcum A18 month female child was admitted for appearance of cough and respiratory distress after one hour from the inhalation of talc powder, accidentally happened during a nappy change. She was apyrectic and presented with cough and only a mild respiratory distress, tachypnea (40/minute), 98% oxygen saturation, heart frequency of 145/minute. On examination there was no evidence of cyanosis, the respiratory sounds were normal on both sides and other systems were normal. Chest x-ray revealed a consolidation in central and middle lung zones and basal emphysema on both sides Figure . An empiBaby powders are usually insoluble in water and may drie up the surface of the mucous membranes of the tracheobronchial tree, thus impairing the function of cilia and the mechanism of pulmonary clearance. Bronchoalveolar lavage is ineffective in washing away the talc powder from the airways, due to its water insolubility . FurtherWritten informed consent was obtained from the parents of the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.The authors declare that they have no competing interests.FM drafted the manuscript and participated in management of the case. MC and PV managed the case and participated in design of the study. MCM participated in management of the case and in drafting the manuscript. CLP performed the respiratory physiotherapy and participated in drafting the manuscript. GC coordinated the study and participated in its design. All authors read and approved the final manuscript.


In the Results section of the article, the first paragraph under the heading "Monitoring of infection status postmortem." had an error in its last sentence as a result of issues in the typesetting process. The correct sentence is available below."With regard to culture of spirochetes, none of the treated animals yielded a positive culture and only one of the untreated animals was culture-positive (lung tissue)."


In this issue of the journal we present the locally agreed management guidelines of the four most common urologic cancers: renal cell cancer, bladder cancer, prostate cancer and testicular cancer.Medical practitioners in Saudi Arabia are either multicultural or trained in different parts of the world. This usually results in different treatment approaches and management plans for patients of similar problems. Under the direction of the Saudi Oncology Society, a committee of experts from the medical oncology, urology and radiation oncology was established.The mission of the genitourinary guidelines committee was to oversee the development of guidelines for the common genitourinary cancers that will improve the practice of medicine for urologic cancers in Saudi Arabia and to establish minimum recommendations that can be used by health authorities in their decision making when coming across cancer management. This committee is one of the different committees that was established for the development of management guidelines in all cancer sites, of which the first to be published was the lung cancer guidelines. Ongoing Members of the genitourinary guidelines committee represented major institutions from all different parts of the kingdom and are listed in The committee agreed to use the established bulleted format used by the lung cancer committee. The committee nominated different members to present a draft of the guidelines on each cancer site that takes into account available evidence for each item. The draft is finalized during one or two sessions. Each recommendation is either referenced and level of evidence is indicated. Final draft was circulated for approval by all members.The committee also agreed to use the evidence level (EL) categories used by the lung cancer committee which are summarized as follow:EL-1 (high level): well-conducted phase III randomized studies or meta-analysisEL-2 (intermediate level): good phase II data or phase III trials with limitationsEL-3 (low level): observational/retrospective studies/expert opinionFinally, committee members agreed that clinical research is integral part of patients care and is the only way to advance and improve patient care, increase cure rate and decrease the presence of adverse effects from medical and surgical therapies.


This study provides an experimental confirmation of the proportionality hypothesis predicted by the theoretical model of emotion ,2 based The proportionality relationship between emotional intensity and perceived disparity in sharing in a social interaction has been confirmed by using the ultimatum game paradigm (UG)  based onThe results confirmed similar finding of proportionality relationship between the amplitude of the evoked EEG signals and the disparity in offer-ratio. This provided independent confirmation of the emotional model using electrophysiological measurements to detect the neural response to the disparity signal in social sharing. This provides further evidence supporting the proportionality hypothesis using electrophysiological measures of neural responses, in addition to the previous psychological study using self-report rating as a measure.


With full genome sequencing of bacterial genomes becoming more affordable, the number of publications, which deploy this elegant and modern technique is rapidly increasing. Full genome sequences of hundreds of bacterial strains have been determined and described. However, on reading some of the literature, sometimes one wonders if the use of this method with enormous resolving power is really ‘balanced’ or justified by the specific questions that are being addressed. Or – to put it differently – what exactly were the specific questions for which sequencing was supposed to provide the answer is sometimes unclear.Staphylococcus aureus (MRSA) clone in two farms located in Denmark  to resolve an epidemiological puzzle that involves zoonotic transmission of a methicillin-resistant mecC gene  which shared identical ST, Application of WGS and determination of SNPs in the core genome of the isolates clearly show that this was not the case. Phylogenetic analysis showed that the MRSA isolates could be clearly differentiated into two clusters each specific for the particular farm and isolates recovered from the farmer and livestock from the same farm were virtually identical, differing only by 3–5 SNPs at most.Was the infection in the farmers preceded by colonization at nasal carriage sites frequently inhabited by MRSA? And did the infection start in the farm animals and passed on to the farmers or the other way around?In Farm A, nasal swabs and blood isolates showed no SNP differences. This is a potentially important observation since genetic difference between colonizing and invading forms of the same clone has been considered in the literature. The data suggest that colonization of the farmer preceded the blood infection. Isolates from the cows and the farmer only differed by five SNPs indicating clearly a transmission; however, the direction of transmission was not immediately obvious.In Farm B, the MRSA isolates from sheep 1 and 2 and the farmer only differed by 3–5 SNPs, while the rest of the sheep had multiple (30–40) SNPs. The presence of multiple SNPs suggests either a prolonged circulation of the clone among the animals or multiple introductions of the same MRSA clone into the flock. Together the data suggest that the most likely direction of the zoonotic infection on this farm was from sheep to the human.In view of the virtually identical MRSA shared by human and animal hosts, the authors also took a close look at the status of virulence genes and the accessory genome in general in the two kinds of isolates, none of which carries the Panton Valentine toxin PVL. This part of the paper also abounds in extremely interesting observations.This study provides a clear illustration of exactly how and at what point of an epidemiological investigation WGS could increase the resolving power of the study. The authors make the important point that WGS cannot replace other more traditional forms of epidemiological inquiry, but it can greatly and in highly specific ways increase the resolving power of such studies. WGS of isolates from each farm proved beyond doubt the identity and unique nature of the particular MRSA clone recovered from animals and the farmer of the same farm. However, determining the direction of transmission still required a combination of conventional as well as WGS techniques.


Allergic asthma as a complex outcome of pathogenic immunological, cellular and functional modifications of the airways is initiated by allergic reactions as a response mostly to inhalant allergens. Dysregulation of innate and adaptive immune functions contribute to the pathogenesis of the disease. A hallmark is the development of a Th2-driven inflammatory response in the airways. The underlying Th2-skewed balance is the result of a multi-functional process in which genetic predisposition and environmental exposures interact as major players. Maturation of the immune system already starts in utero, the most critical phase in the ontogenetic programming of the offspring. Endogenous as well as exogenous exposures may influence the maturation and differentiation of immune cells of the fetus and may thereby contribute to disorders such as allergies and asthma later on in life. Epigenetic mechanisms are proposed to mediate these effects. A comprehensive overview on the interaction of fetal exposures and the developing immune system will be provided that may contribute to or protect the progeny against the development of asthma. The new and exciting field of epigenetics will be highlighted with respect to T-cell differentiation and early allergic disease development. Furthermore, we emphasize new investigations that aimed to analyze fetal host innate immune responses to environmental microbial microorganisms and their possible future application in asthma protection.


Although there are treatments that can impede progress of the disease, there are no cures or vaccines. The most common route for transmission of the virus is via heterosexual intercourse. The animal models that are currently available do not accurately replicate the physiological environment of vaginal intercourse, so the effects of factors such as seminal fluid composition on HIV infectivity have not been thoroughly examined. Here, Mary Jane Potash and colleagues describe a system for reproducible and efficient sexual transmission of HIV in mice. Using this model, the group show that the rate of viral transmission dramatically declines during estrus in mice, demonstrating that the local environment in the female reproductive tract can influence viral infectivity. The study provides an effective