The primate subarcuate fossa and its relationship to the semicircular canals part I: prenatal growth

Studies have reported a functional link between the arc size of the semicircular canals and locomotor agility across adult primates. However, canal size is spatially interlinked with the subarcuate fossa. This fossa can house the petrosal lobule of the paraflocculus, which also plays a role in coordinating head and eye movements. Consequently, it could be that it is the size of the petrosal lobule and fossa that are directly associated with locomotor agility, and not canal arc size. The apparent association of the latter would only follow from the spatial requirement of the canals to accommodate a suitably enlarged subarcuate fossa and petrosal lobule. This study aims to test the ontogenetic basis of this argument by examining high-resolution magnetic resonance images of fetal samples of Homo sapiens, Macaca nemestrina, and Alouatta caraya. Falsifiable null hypotheses examined are (1) that development of the subarcuate fossa is initiated by growth of the petrosal lobule, and (2) that growth of the semicircular canals and of the subarcuate fossa are independent. The findings confirm that the subarcuate fossa forms independently of a petrosal lobule in all three species, thereby falsifying the first hypothesis. Significant correlations were observed between size variables of the semicircular canals and the subarcuate fossa, particularly between the anterior canal and the opening of the fossa. These results falsify the hypothesis that the canals and fossa grow entirely independently. In the human sample, canal growth outpaces fossa growth, possibly because no petrosal lobule is present in humans. In the other two species, the subarcuate fossa simply seems to fill the space made available by canal growth. However, fossa enlargement cannot be excluded as an influence on size increase in the canals. Nevertheless, taken together, the results suggest that canal size is unlikely to be determined primarily by the spatial requirements of the subarcuate fossa and petrosal lobule, rather than by sensory demands reflected in the empirically established link with locomotor agility.     

The subarcuate fossa and cerebellum of extant primates: comparative study of a skull-brain interface

The subarcuate fossa of the petrosal bone houses the petrosal lobule of the cerebellar paraflocculus. Although the subarcuate fossa can be extensive, little is known about its relative size and distribution in primates. Studies indicate parafloccular involvement with cerebellar areas coordinating vestibular, visual, auditory, and locomotor systems. Hypotheses have proposed a role for the paraflocculus in vestibular-oculomotor integration, caudal muscle control, autonomic function, and visual-manual predation. This study examines the morphology and relative extent of the subarcuate fossa/petrosal lobule in a range of living primates. Methods include study of postmortem specimens representing nine mammalian orders, and qualification of the volume of the subarcuate fossa and endocranial cavity in 155 dry primate crania of 36 genera. Results show that, in mammals, the size and morphology of the petrosal lobule is directly related to that of the subarcuate fossa. Craniometric analysis shows that the ratio of subarcuate fossa volume to endocranial volume is largest in lemuriforms. The largest ratio is in Microcebus and Hapalemur. Lorisids show a significant reduction in the size of the subarcuate fossa to almost 50% below the lemuriform mean. Tarsius is near the lemuriform mean. Among platyrrhines, the ratio is high, but significantly reduced compared to lemuiforms. The highest platyrrhine ratio is seen in Ateles, the lowest in Saimiri and Alouatta. Atelids are significantly elevated compared to cebids. In cercopithecids, the fossa is significantly reduced compared to platyrrhines. The trend toward reduction of the cercopithecid fossa is most pronounced in Theropithecus and least evident in Presbytis. In hominoids, the fossa is present only in Hylobates. In great apes and humans, other than Gorilla, the petromastoid canal occupies a similar location to the subarcuate fossa of other primates, but is not homologous to it. Neither the subarcuate fossa nor the petromastoid canal are present in Gorilla. A graded reduction of the subarcuate fossa/petrosal lobule is evident among primates which evolved later in time. The relative size of this cerebellar lobule within primates may reflect size-related factors and/or degree of neocortical evolution as these relate to usage of a specific sensory-mediated locomotor behavior. The subarcuate fossa may serve as an indicator to the differentiation of the petrosal lobule of the paraflocculus in fossil forms.     

The cerebellar paraflocculus and the subarcuate fossa in<Emphasis Type="Italic">Monodelphis domestica</Emphasis> and other marsupial mammals — ontogeny and phylogeny of a brain-skull interaction

The development of the subarcuate fossa and the cerebellar paraflocculus was studied in an ontogenetic series ofMonodelphis domestica Wagner, 1842 The spatial relation between these structures was examined qualitatively in adult specimens of several marsupial taxa. The fossa is first formed without participation of the cerebellar paraflocculus, which fills the fossa first fully and then partially later in development. The correlation between the size of the petrosal lobule of the paraflocculus and the subarcuate fossa in adults is weak. The volume of the subarcuate fossa was measured in 68 specimens representing 19 species of recent marsupials. Its size is negatively allometric with respect to skull size. The didelphids examined (‘large opossums’) have relatively smaller subarcuate fossae than the other marsupials examined, andSarcophilus laniarius is the major outlier, with a very small fossa. Loss of the subarcuate fossa has occurred at least twice in metatherian evolution (some sparassodonts and wombats). All marsupials examined to date, with the exception of wombats, have a differentiated petrosal lobule of the paraflocculus.     

The primate subarcuate fossa and its relationship to the semicircular canals part II: adult interspecific variation

Studies have reported an empirical link between the size of the semicircular canals and locomotor agility across adult primates. In this paper, we investigate the possibility that this relationship does not follow from the function of the semicircular canals to sense head rotations, but rather reflects spatial constraints imposed by the subarcuate fossa. The latter sits among the three canals and contains the petrosal lobule of the cerebellar paraflocculus, a structure involved in neural processing of locomotion-related eye movements. Hence, it is feasible that agility-related variations of lobule and fossa size affect the arc size of the surrounding semicircular canals. The present study tests such hypothetical correlations by evaluating canal size, fossa size, and agility among extant adult primates. Phylogenetically informed multivariate regression analyses show that, after controlling for body mass, the size of the subarcuate fossa has a significant positive effect on the overall size of the anterior canal and the width of the posterior canal. Multivariate regressions involving the height of the posterior canal and overall size of the lateral canal are not significant. Further bivariate analyses confirm that fossa size is unlikely to play a role in the previously reported link between agility and the size of the posterior and lateral canals. However, fossa size, especially its opening though the arc of the anterior canal, cannot be excluded as a factor that influences the size of the anterior canal more than agility. The findings show that the most reliable functional signals pertaining to locomotion in species that possess a patent subarcuate fossa are likely to come from the lateral canal and are least likely to come from the anterior canal.     

Reexamination of the morphological evidence for the cohort Epitheria (Mammalia,Eutheria)

Novacek and co-workers recognized a monophyletic clade Epitheria, comprising all eutherians except edentates and the extinct palaeoryctoids, on the basis of two synapomorphies: a stirrupshaped stapes and a foramen ovale enclosed within the alisphenoid. To evaluate this phylogenetic hypothesis, we reexamined the distributions of stapedial morphologies and positions of the foramen ovale across Recent and extinct mammals and nonmammalian cynodonts. The states and distributions of the stapes and forament ovale characters used by Novacek and coworkers were modified by recognizing two stapedial characters (one relating to shape of the crura, the other to the nature of the foramen) and a single, multistate foramen ovale character (within, behind, and lateral to the alisphenoid). The taxon-character matrix used by Novacek (1989, 1992b), substituting our amended stapedial and foramen ovale characters and adding several previously unscored extinct taxa and three new characters, was subjected to a series of PAUP manipulations. Identified among the most parsimonious trees were three major topologies for the base of Eutheria: (1) a polytomy including an Edentata/Ungulata clade, (2) a polytomy with Edentata and Ungulata as separate clades, and (3) Edentata and (when included) Palaeoryctoidea as the successive outgroups to a monophyletic Epitheria. We conclude that topology 2 best reflects the current state of knowledge. An edentate/ungulate clade is supported by three characters (from the mastoid region and subarcuate fossa); however, other morphological studies require modification of the distributions of these characters in xenarthrans and bassal ungulates, thereby eliminating support for this clade. In nearly all manipulations, obtaining a monophyletic Epitheria required that one or two steps be added to the most parsimonious trees. When a monophyletic Epitheria was obtained, it was supported by a triangular stapes and, in some trees, the reappearance of a stapedial artery (lost earlier at the level of Recent therians) and a transpromontorial internal carotid artery. In the most parsimonious trees, a foramen ovale within the alisphenoid was an equivocal synapomorphy of Recent therians or cutherians, and a stapes with strongly convex crura (our state closest to the stirrup-shaped state of Novacek and co-workers) appeared independently within various eutherian lineages. The reduction or loss of the stapedial foramen was identified as an independent event in monotremes and within marsupials and various eutherian lineages.To whom correspondence should be addressed.     

Reidentification of Avian Embryonic Remains from the Cretaceous of Mongolia

Embryonic remains within a small (4.75 by 2.23 cm) egg from the Late Cretaceous, Mongolia are here re-described. High-resolution X-ray computed tomography (HRCT) was used to digitally prepare and describe the enclosed embryonic bones. The egg, IGM (Mongolian Institute for Geology, Ulaanbaatar) 100/2010, with a three-part shell microstructure, was originally assigned to Neoceratopsia implying extensive homoplasy among eggshell characters across Dinosauria. Re-examination finds the forelimb significantly longer than the hindlimbs, proportions suggesting an avian identification. Additional, postcranial apomorphies (strut-like coracoid, cranially located humeral condyles, olecranon fossa, slender radius relative to the ulna, trochanteric crest on the femur, and ulna longer than the humerus) identify the embryo as avian. Presence of a dorsal coracoid fossa and a craniocaudally compressed distal humerus with a strongly angled distal margin support a diagnosis of IGM 100/2010 as an enantiornithine. Re-identification eliminates the implied homoplasy of this tri-laminate eggshell structure, and instead associates enantiornithine birds with eggshell microstructure composed of a mammillary, squamatic, and external zones. Posture of the embryo follows that of other theropods with fore- and hindlimbs folded parallel to the vertebral column and the elbow pointing caudally just dorsal to the knees. The size of the egg and embryo of IGM 100/2010 is similar to the two other Mongolian enantiornithine eggs. Well-ossified skeletons, as in this specimen, characterize all known enantiornithine embryos suggesting precocial hatchlings, comparing closely to late stage embryos of modern precocial birds that are both flight- and run-capable upon hatching. Extensive ossification in enantiornithine embryos may contribute to their relatively abundant representation in the fossil record. Neoceratopsian eggs remain unrecognized in the fossil record.     

四川自贡大山铺西蜀鳄一新种

记述了西蜀鳄一新种──大山铺西蜀鳄（Ｈｓｉｓｏｓｕｃｈｕｓ ｄａｓｈａｎｐｕｅｎｓｉｓ）,新种保存了完好的吻端,填补了西蜀鳄在这方面的缺失。新种的内鼻孔位置靠前,上颌骨和腭骨构成其边缘;眶下孔存在但较小;产于自贡市大山铺下沙溪庙组。     

The petrosal of Omomys carteri and the evolution of the primate basicranium

The first omomyine petrosals, those of Omomys carteri, are described. Omomys probably had a tympanic bulla and canals for the intratympanic carotid circulation derived from the petrosal bone. The stapedial and promontory canals were complete, large and subequal. The posterior carotid foramen entered the bulla posteromedially. The intratympanic portion of the facial nerve was fully enclosed in bone, the stapedius fossa is extrabullar and the parotic fissure is patent. The mastoid was pneumatized from the epitympanic recess and a supracochlear cavity may have been present. The Omomys petrosals exhibit a generic omomyiform morphology, exhibiting no features that can be interpreted as autapomorphies and only one feature shared with adapiforms. The monophyly of Omomyiformes is based on other cranial characters, dental and postcranial characters assessed elsewhere. The similarity of the Shanghuang petrosal to the petrosals of omomyiforms, as well as the ambiguous evidence of its association, suggest that an omomyiform affinity for that petrosal cannot be ruled out.     

Measurements on the grade of the human skull base and angle determinations]

1. The angle between the Os sphenoidale and the Clivus has been determined on 106 skulls. The mean was 117.68 degrees. 2. The altitude of the Foramen magnum with respect to the Frankfort plane was determined at -1.96 cm on the average. 3. The angle of inclination of the Foramen magnum to the Frankfort plane was determined from the altitude of the Basion and Opisthion and from the length of the Foramen magnum. The mean was -13.71 degrees. 4. In the inner base of the skull the altitudes of following structures have been determined: Planum sphenoidale (mean 2.34 cm), ground of the Fossa hypophysialis (1.32 cm), ground of the middle cranial fossa (-0.03 cm), ground of the posterior cranial fossa (-2.30 cm), upper edge of the Os petrosum (1.12 cm), Tuberculum jugulare (-0.21 cm), ground of the Meatus acusticus internus (0.45 cm). 5. In order to provide numerical data for the step-like building of the inner base of the skull, the differences between the altitudes of important structures from the inner base have been determined: Margo superior partis petrosae - Tuberculum jugulare (mean 1.35 cm). Opisthion - ground of the posterior cranial fossa (0.11 cm), Planum sphenoidale - ground of the middle cranial fossa (2.38 cm), ground of the middle cranial fossa - ground of the posterior cranial fossa (2.27 cm), Margo superior partis petrosae - ground of the posterior cranial fossa (3.35 cm), Margo superior partis petrosae - ground of the middle cranial fossa (1.15 cm).     

菱臼齿兽((犭亚)目、哺乳纲)耳区的骨骼结构

本文详细描述了菱臼齿兽耳区各个部分的基本结构;并指出了耳区结构与某些啮齿类的相似性,以及中耳鼓泡组成成份与戈壁(犭亚)兽(Anagale gobiensis)的区别。     

不同重金属污染水平下生物结皮及下层土壤细菌群落的差异性分析

为了探究生物结皮及下层土壤细菌群落多样性及结构在不同重金属污染水平下的差异及其影响因素,以宁夏东部工矿区和封育草地内广泛分布的两类生物结皮为研究对象,采用高通量测序技术,分析结皮层(A层)和结皮下层(B层)土壤细菌群落结构和多样性差异。采用相关分析、冗余分析探讨两个生境生物结皮各层次细菌群落与土壤环境因子的关系。结果表明：(1)相较于封育区,工矿区2类生物结皮对源自大气降尘的重金属元素具有更显著的表层富集作用,并表现出显著的种间差异：苔藓结皮>藻结皮。污染负荷指数评价结果显示：工矿区生物结皮各层次重金属污染程度更高,且均表现为A层污染程度高于B层。(2)两个生境的优势细菌门组成基本一致,均为放线菌门、变形菌门、酸杆菌门。受生物结皮类型、重金属污染程度的影响,细菌群落结构差异显著,主要表现为：工矿区藻结皮A、B层的α多样性指数均大于封育区,而苔藓结皮A、B层的细菌多样性指数高于封育区,丰富度指数低于封育区。主坐标分析结果显示,不同生境的生物结皮细菌群落结构差异明显,而同一生境的生物结皮细菌群落结构相似。重金属As、Pb、土壤黏粒含量和pH是影响生物结皮细菌群落结构的主要土壤环境因子...     

Fine structural studies of the bipolarization of the mitotic apparatus in the fertilized sea urchin egg. I. The structure and behavior of centrosomes before fusion of the pronuclei

During fertilization the sperm brings two centrosomes into the egg. One centrosome contains a centriole of normal length originally seen as the basal body of the sperm flagellum. Characteristically, the proximal half is enwrapped in osmiophilic material. This centrosome is attached to the centrosomal fossa, a bowl-shaped depression of the nuclear envelope of the male pronucleus. Microtubules radiate out from the osmiophilic half characterizing this structure as a centrosome and microtubule organizing center (MTOC). The second centrosome which also acts as an MTOC is attached to the mitochondrion of the sperm. At the beginning it appears as an unstructured accumulation of osmiophilic material out of which later on centriolar microtubules grow. Though this centrosome is marked by an immature centriole it is capable of organizing microtubules and of reproducing itself. This centrosome becomes loosely associated with the female pronucleus by means of microtubules. Then it separates from the mitochondrion which finally is lost. When the two pronuclei fuse, the centrosome derived from the basal body remains firmly attached to the centrosomal fossa, which has persisted in the envelope of the zygote nucleus after pronuclear fusion. Using the fossa as a marker of the position of this centrosome on the nuclear surface, we conclude that it is a stationary centrosome in the process of bipolarization for the first mitosis.     

The yolk nucleus in the freshwater teleost Garra gotyla gotyla (Gray)

The structure and functional significance of the yolk nucleus in Garra are described. The study shows that the yolk nucleus appears in the cytoplasm of the early perinucleolus stage of the oocyte. It is present as a deeply stained structure enclosed in a vesicle. It disappears in the yolk vesicle stage and vitellogenesis begins soon afterwards. This probably indicates that it plays a role in the initiation of vitellogenesis. When yolk formation starts, the yolk nucleus disappears; this also suggests that it is of functional significance in yolk synthesis.     

Genetic structure of the Danish red deer (Cervus elaphus)

The red deer (Cervus elaphus) population in Denmark became almost extinct in recent historical times due to over‐hunting. The species has subsequently recovered within remote areas, but non‐Danish individuals have been introduced at several localities. To assess genetic structure, past demographic history, and the possibility of a still existing original stock, we analysed 349 specimens from 11 geographically separate areas and from three enclosed areas, genotyping 11 microsatellite loci. Moreover, an 826‐bp fragment of the control region of the mitochondrial DNA was sequenced for 116 recent specimens and seven museum specimens. There was a significant difference in mean expected heterozygosity (H_E) between the three enclosed areas and the 11 unenclosed areas. Significant departures from Hardy–Weinberg equilibrium were observed in the three enclosed areas and in nine of the unenclosed areas. The overall degree of genetic differentiation among all 14 areas was significant (F_ST = 0.09, P < 0.01), primarily because the mean pairwise F_ST for the three enclosed areas was significantly higher than that for the 11 unenclosed areas. A Bayesian clustering procedure detected three genetically distinct populations and indicated reduced gene flow between the enclosed and unenclosed areas. The individuals in the unenclosed areas show genotypic mixture, presumably as a result of gene flow among them. Markov Chain Monte Carlo simulations, based on the genealogical history of the microsatellite alleles, suggest a drastic decline in the effective population size of the enclosed areas some 188–474 years ago. Mitochondrial DNA analysis of the recent specimens showed seven haplotypes. Individuals from the enclosed Jægersborg Dyrehave contain haplotypes that occur all over Denmark and also are found in Western Europe. A close relationship between Scandinavian and Western European red deer is most likely. Only individuals from the unenclosed Lindenborg Estate and the enclosed Tofte Skov did not group with any other Danish individuals. As six of seven museum specimens had haplotypes also found in modern Danish samples, the current population of red deer in Denmark is genetically close to the original Danish red deer. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 688–701.     

Intracranial venous outflows associated with myofascial syndrome according to the data of computer tomography and magnetic resonance imaging

To have a pictorial view of the extent of large paired sinuses of the posterior cranial fossa, jugular foramens, temporomandibular joints, magnetic resonance imaging and computed tomography were used to examine 1600 patients. The findings specified that the cross sizes of sinuses and jugular veins rather widely varied, their relative increase being observed with age. Furthermore, in most cases the paired sinuses of the posterior cranial fossa, internal jugular veins and jugular foramens are asymmetrically developed, the asymmetry being clearly defined only in infants aged more than 1 year. Thereafter, a group of patients with the asymmetrical structure ofjugular foramens was observed to have the signs characterizing the atypical structure or position of the heads of the mandible.     

Long-term vegetation change in the Juncus squarrosus grassland at Moor House,northern England

Data from the long-term experiment on sheep grazing versus zero sheep grazing (i.e. in an enclosure) on the composition of the Juncus squarrosus grassland at the Moor House NNR are presented. The data have been analysed to assess change in (1) the abundance of individual species, (2) higher plant and bryophyte communities, and (3) vegetation structure. The higher plant data suggested that both the enclosed-and grazed plots were changing in the same direction, but the enclosed plot was moving much faster. The general tendency was towards a blanket bog vegetation dominated by Eriophorum vaginatum and Calluna vulgaris. Juncus squarrosus has declined very quickly in the enclosed plot, but there has also been a slower decline in the grazed one. A significant increase in Calluna vulgaris has occurred only in the enclosed plot. In contrast, the bryophyte data showed completely different successional trajectories in the two treatment plots.The vegetation structure changed markedly after release from grazing, with a decrease in phytomass, but increase in necromass in the lowest height strata. There was no noticeable change in structure over the 18 year period in the grazed plot.Particular problems found in this study were that some species either fluctuated widely in response, or changed in a curvilinear manner.     

Three‐dimensional ultrastructure of chloroplast pockets formed under salinity stress

We investigated the invagination structure of a chloroplast that surrounds organelles such as mitochondria and peroxisomes within a thin layer of chloroplast stroma, which is called a chloroplast pocket. In this study, chloroplast pockets were observed in rice plants subjected to salinity stress but not under moderate growth condition. They included cytosol, transparent structure, lipid bodies, mitochondria, and peroxisomes. We constructed the three‐dimensional architecture of chloroplast pockets by using serial images obtained by transmission electron microscopy and focused ion beam‐scanning electron microscopy. Three types of chloroplast pockets were observed by transmission electron microscopy: Organelles were completely enclosed in a chloroplast pocket (enclosed type), a chloroplast pocket with a small gap in the middle part (gap type), and a chloroplast pocket with one side open (open type). Of the 70 pockets observed by serial imaging, 35 were enclosed type, and 21 and 14 were gap and open types, respectively. Mitochondria and peroxisomes were often in contact with the chloroplast pockets. Focused ion beam‐scanning electron microscopy revealed chloroplasts with a sheet structure partially surrounding peroxisomes. This fact suggests that chloroplasts might construct large sheet structures that would be related to the formation of chloroplast pockets.     

Morphogenesis of the cranium of Cavia porcellus L. II: Comparative part and literature

The development of the chondrocranium of Cavia porcellus is compared to those of other rodents. The tectum posterius of the investigated rodents is orientated vertically. This position is functionally caused by the attachment of the muscles of the neck and shoulder girdle. The paracondylar process is a typical feature of rodents although absent in Mesocricetus. Only in Cavia and Tatera, the connection between the lamina supraoccipitalis and the auditory capsule-the supraoccipitocapsular commissure-is missing. Youssef's (1966) generalization that the course of the notochord in rodents is of transbasal type cannot be confirmed. In Cavia, the auditory capsule is connected with the occipital region only by the exoccipitocapsular commissure. The connection between auditory capsule and basal plate is established by the alicochlear and the anterior basicapsular commissures. In comparison to other rodents, the number of commissures in Cavia is reduced. In rodents, there is always a subarcuate fossa which in later stages of development is filled out by the flocculus cerebelli. In contrary to Rajtova's (1972a) statement, Cavia shows a suprafacial commissure as all mammals do (Reinbach 1952). As the tegmen tympani is absent in Otomys and Erethizon, it is not a typical rodent feature. The carotid foramen is well developed in Cavia but the internal carotid artery obliterates until the 25 mm CRL-stage. In embryonic rodents, the ala temporalis may have a foramen ovale but not a foramen rotundum. During ontogeny rodents show the ala hypochiasmatica for the attachment of the straight muscles of the eyeball. In Cavia the ala hypochiasmatica develops independently and fuses with the postoptic root of the ala orbitalis in later stages. In myomorphs and sciumorphs, the orbitoparietal and orbitonasal commissures are present. Only in caviomorphs this part of the primary sidewall of the skull is uncomplete. Erethizon, however, shows an orbitonasal commissure whereas in Cavia both commissures are missing. In this respect the guinea-pig resembles the condition of primates. There is no interorbital septum in rodents. The nasal capsule of rodents contains 1 atrioturbinal, 1 maxilloturbinal, 1 nasoturbinal, and at least 3 ethmoturbinals. Due to the strong development of the alveoli of the incisors, the maxilloturbinale is flected in the caviomorphs. The epiphanial foramina are present. The lamina transversalis anterior is continuous with the nasal septum so that there is a complete zona anularis in rodents. The paraseptal cartilages are continuous with the lamina transversalis anterior but not with the lamina transversalis posterior.(ABSTRACT TRUNCATED AT 400 WORDS)