Restoration of the superficial facial musculature in nimravids

The size, shape and position of the mouth and sensory features such as the nose, eyes and ears in the nimravid barbourofelins are reconstructed. The earliest barbourofelin studied, Sansanosmilus , is the most similar to both pantherine and nonpantherine felids in sensory structure morphology. Through time, the species of the barbourofelin lineage diverge from felids with regard to facial features. Evolutionary trends include expansion of the nasal region, a more lateral orientation of the eyes and lowered position for the ears. Increased width and shortening of the muzzle accommodates the large oral opening required by the large gape of Barboumfelis , culminating in B. fricki with eyes oriented laterally enough to reduce stereoscopic vision. The ear position in this species is also significantly lower than in the earlier barbourofelins or felids. This may reflect an anatomic compromise between sensory structure position and changes in relative size, shape and position of other skull features. These changes correlate with increased canine tooth length and increased gape, exemplified by Barboumfelis fricki. Cranial soft tissue structures are restored through scars of attachment on the fossil bones, and the proportions of these features to one another determined. New observations provide criteria for reconstructing soft tissue anatomy in extinct animals.     

Variations in cruropedal musculature

The comparative anatomy of primate musculature has been established frequently from single specimens or small samples which are assumed to be typical for their species. However, a series of dissections of platyrrhine monkeys reported here reveals considerable variation within species and genera. Selected muscles of the leg and foot were examined and compared for discrete variations in attachments. The results were supplemented by observations in the anatomical literature for these and other primates. The range of variation reported across the order also presents itself as widespread polymorphism within most taxonomic groups, down to the species level. Since correlations with phylogeny and positional behavior are expressed only weakly, adaptationist explanations can account for only a part of the variation. Functional redundancy among the muscles supports the conclusion that the behavioral significance of the variations is slight. It is apparent that both genetic and nongenetic factors influence muscle form, and it is likely that observed polymorphisms have been characteristic of populations throughout primate evolution. Therefore, traits involving muscular form, especially as observed on small samples, within species, should be used cautiously in phyletic and adaptationist analyses.     

Linkage mechanisms in the vertebrate skull: Structure and function of three‐dimensional,parallel transmission systems

Many musculoskeletal systems, including the skulls of birds, fishes, and some lizards consist of interconnected chains of mobile skeletal elements, analogous to linkage mechanisms used in engineering. Biomechanical studies have applied linkage models to a diversity of musculoskeletal systems, with previous applications primarily focusing on two‐dimensional linkage geometries, bilaterally symmetrical pairs of planar linkages, or single four‐bar linkages. Here, we present new, three‐dimensional (3D), parallel linkage models of the skulls of birds and fishes and use these models (available as free kinematic simulation software), to investigate structure–function relationships in these systems. This new computational framework provides an accessible and integrated workflow for exploring the evolution of structure and function in complex musculoskeletal systems. Linkage simulations show that kinematic transmission, although a suitable functional metric for linkages with single rotating input and output links, can give misleading results when applied to linkages with substantial translational components or multiple output links. To take into account both linear and rotational displacement we define force mechanical advantage for a linkage (analogous to lever mechanical advantage) and apply this metric to measure transmission efficiency in the bird cranial mechanism. For linkages with multiple, expanding output points we propose a new functional metric, expansion advantage, to measure expansion amplification and apply this metric to the buccal expansion mechanism in fishes. Using the bird cranial linkage model, we quantify the inaccuracies that result from simplifying a 3D geometry into two dimensions. We also show that by combining single‐chain linkages into parallel linkages, more links can be simulated while decreasing or maintaining the same number of input parameters. This generalized framework for linkage simulation and analysis can accommodate linkages of differing geometries and configurations, enabling novel interpretations of the mechanics of force transmission across a diversity of vertebrate feeding mechanisms and enhancing our understanding of musculoskeletal function and evolution. J. Morphol. 277:1570–1583, 2016. © 2016 Wiley Periodicals, Inc.     

Functional anatomy of the trunk musculature in the slow loris (Nycticebus coucang)

Lorisid locomotor and postural behaviour exhibits a number of features that distinguish it clearly from other primates. The comparative myological study of the trunk in the slow loris (Nycticebus coucang) and the squirrel monkey (Saimiri sp.) presented here reveals differences that are related to unique aspects of lorisid positional behaviour. While quadrupedal running and leaping requires flexion and extension of the spine, slow climbing quadrupedalism in lorisids depends on spinal lateral flexion and rotation. The contrasting development of the epaxial musculature in the two species dissected reflects these different requirements. Bipedal suspension is a common posture in the lorisids during which rotation and dorsiflexion of the head is made possible by the robustly developed deep, dorsal, cervical musculature. The long lower lever arm in the M. rectus abdominis may play a significant role in the ventroflexion required to regain a quadrupedal stance. © 1995 Wiley-Liss, Inc.     

Ontogeny and homology of the basipterygoid articulation in Pantodon buchholzi (Teleostei: Osteoglossomorpha)

The basipterygoid articulation, an articular connection between the base of the braincase and the palatoquadrate, is widespread among gnathostome vertebrates. However, among living teleosts it is present only in the osteoglossomorphs Arapaima , Heterotis , Scleropages , Osteoglossum and Pantodon . Study of the development of the hyopalatine arch and the basipterygoid articulation in Pantodon buchholzi based on an ontogenetic series of cleared and double stained specimens yielded the following results: the symplectic process of the hyosymplectic cartilage never develops and the symplectic is absent; the pars hyomandibularis fuses with the palatoquadrate; the dermopalatine and ectopterygoid originate as separate bones, but fuse subsequently; the basal process is first visible on the pars metapterygoidea of the palatoquadrate at 7.0 mm standard length (SL); at 11.5 mm SL the basipterygoid process appears on the parasphenoid and contacts the basal process, establishing the basipterygoid articulation; the endopterygoid is initially not involved in the articulation, but during subsequent development enlarges and eventually forms an articular groove for the reception of the basipterygoid process of the parasphenoid; the distal tip of the basal process of the metapterygoid, however, still forms the caudolateral part of the articular groove in the adult. We discuss previous hypotheses about the homology of the basipterygoid articulation of osteoglossoids in light of these findings. Based on the numerous shared similarities and its occurrence in all major actinopterygian lineages, we argue that the basipterygoid articulation in osteoglossoids is homologous to that in non teleostean actinopterygians and represents a plesiomorphic character state at the level of Osteoglossomorpha.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 144 , 1−13.     

可口革囊星虫肾管肌组织的结构特征

采用显微及亚显微技术观察了可1：7革囊星虫肾管肌组织的结构特征。肾管肌组织位于柱状上皮层下,由纵肌及环肌组成。肌细胞（肌纤维）呈长梭形,核位于细胞边缘并明显突向细胞外基质中,核周围有较多线粒体及少量内质网。肌纤维表面有许多囊状或指状突起的肌质囊,内含肌浆、光面内质网、线粒体及糖原颗粒。肌质囊之间的肌膜内面具膜相关电子致密斑。肌纤维内含粗、细两种肌丝,细肌丝围绕在粗肌丝周围,在肌丝之间分布有糖原颗粒、线粒体及胞质致密体。线粒体及糖原为肌纤维的代谢提供能量,肌组织的收缩对促进肾管的过滤排泄及繁殖时配子进入肾管可能起重要作用。     

Cytology and localization of chromatophores in the skin of the Tuatara (Sphenodon punctaus)

Alibardi, L. 2012. Cytology and localization of chromatophores in the skin of the Tuatara (Sphenodon punctaus). —Acta Zoologica (Stockholm) 93 : 330–337. The study deals with skin pigmentation in the reptile Sphenodon punctatus where neither strong colors nor rapid color changes are present. Dark areas of the skin derive from an intense pigmentation of beta‐keratinocytes of the epidermis. Only epidermal melanocytes are involved in the process of melanosome transfer into keratinocytes. The basement membrane is a structural boundary separating melanocytes from melanophores that are sparse or concentrated in some dermal areas where they contribute to the dark coloration of the skin. In these regions, dermal melanophores give rise to the dark dots or to the irregular spots or to the dark stripes present in the skin. Ultrastructurally only eu‐melanosomes are present, although only molecular studies can detect whether also pheomelanins are synthesized in these organelles. Chromatophores are not organized in functional dermal melanophore units. Xantophores are distributed under the epidermis and store lipid‐containing droplets or lamellated pterinosomes. Their specific yellow‐orange hues become evident on the skin surface. Iridophores are generally localized among the melanosomes and form reflecting platelets that are derived form the endoplasmic reticulum and probably are also elaborated in the Golgi apparatus. The role in color production of the latter cells in the skin remains to be identified.     

An ultrastructural and histochemical study of the axial musculature in the African lungfish

Summary Red, intermediate, and white axial muscle fibres of African lungfish were studied using histochemical techniques and electron microscopy. Gross dissection revealed the presence of a small wedge of red coloured muscle along the lateral line. This wedge was shown by histochemical demonstrations of lactate and succinate dehydrogenases, of adenosine triphosphatases, and of lipid to be composed of a mosaic of red and intermediate fibres measuring 23.63 and 34.30 m in average diameter, respectively. The bulk of the myotome was composed of white fibres having an average diameter of 67.35 m. Mitochondrial density, capillarity and lipid content were very low for all fibres. These data suggest that the axial musculature is geared primarily for anaerobic function. The mosaic arrangement of fibres, and the lack of a subsarcolemmal band of mitochondria suggests that the lungfish have a muscle organisation that is transitional between lower vertebrates and amphibians.     

Assessment of the role of sutures in a lizard skull: a computer modelling study

Sutures form an integral part of the functioning skull, but their role has long been debated among vertebrate morphologists and palaeontologists. Furthermore, the relationship between typical skull sutures, and those involved in cranial kinesis, is poorly understood. In a series of computational modelling studies, complex loading conditions obtained through multibody dynamics analysis were imposed on a finite element model of the skull of Uromastyx hardwickii, an akinetic herbivorous lizard. A finite element analysis (FEA) of a skull with no sutures revealed higher patterns of strain in regions where cranial sutures are located in the skull. From these findings, FEAs were performed on skulls with sutures (individual and groups of sutures) to investigate their role and function more thoroughly. Our results showed that individual sutures relieved strain locally, but only at the expense of elevated strain in other regions of the skull. These findings provide an insight into the behaviour of sutures and show how they are adapted to work together to distribute strain around the skull. Premature fusion of one suture could therefore lead to increased abnormal loading on other regions of the skull causing irregular bone growth and deformities. This detailed investigation also revealed that the frontal-parietal suture of the Uromastyx skull played a substantial role in relieving strain compared with the other sutures. This raises questions about the original role of mesokinesis in squamate evolution.     

Osteology and cranial musculature of Caiman latirostris (crocodylia: Alligatoridae)

Caiman latirostris Daudin is one of the extant species of Caimaninae alligatorids characterized taxonomically only by external morphological features. In the present contribution, we describe the cranial osteology and myology of this species and its morphological variation. Several skull dissections and comparisons with other caimans were made. Although jaw muscles of living crocodiles show the same general “Bauplan” and alligatorids seem to have a similar cranial musculature pattern, we describe some morphological variations (e.g., in C. latirostris the superficial portion of the M. adductor mandibulae externus did not reach the postorbital; the M. adductor mandibulae internus pars pterygoideus dorsalis did not reach the pterygoid and lacrimal and contrary to the case of C. crocodilus the M. adductor mandibulae internus pars pterygoideus ventralis attaches to the posterodorsal surface of the pterygoid and the pterygoid aponeurosis, without contacting the dorsal and ventral surface of the pterygoid margin; the M. intermandibularis is attached to the anterior half of the splenial and posteriorly inserts medially by a medial raphe that serves as attachment zone for M. constrictor colli, and the M. constrictor colli profundus presents a medial notch in its anterior margin). In addition, the skull of C. latirostris differs from that of other caimans and possesses several characters that are potential diagnostic features of this species (e.g., outline of glenoid cavity in dorsal view, extension of the rostral ridges, and occlusion of the first dentary tooth). Nevertheless, these characters should be analyzed within the phylogenetic context of the Caimaninae to evaluate its evolutionary implications for the history of the group. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

The submandibular musculature of phyllomedusinae (Anura: Hylidae): A reappraisal

The submandibular musculature of 37 species of the five currently recognized genera of the subfamily Phyllomedusinae (Anura: Hylidae) is described; observations are made on the variation and ontogeny of these muscles. Supplementary apical elements of the m. intermandibularis occur in all phyllomedusines studied, in addition to the supplementary posterolateral elements previously reported. Our observations are discussed in the context of 1) the proposed homology between supplementary apical and posterolateral elements; 2) the homology with the apical elements reported for Pelodryadinae (sister taxon of Phyllomedusinae); and 3) the implications for our understanding of the relationships between Phyllomedusinae and Pelodryadinae. Anatomical differences between the apical and posterolateral elements and their co‐occurrence in phyllomedusines indicate that these supplementary elements are not homologous. Despite differences between phyllomedusines and pelodryadines in the adhesion of supplementary fibers to the principal element of the m. intermandibularis and the occurrence of a broad aponeurosis or a medial raphe, the extensive morphological and developmental resemblances of the apical elements indicate that these structures are homologous, and that the presence of apical elements is a synapomorphy of Phyllomedusinae + Pelodryadinae. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

Cranial muscles of the anurans leiopelma hochstetteri and ascaphus truei and the homologies of the mandibular adductors in lissamphibia and other gnathostomes

The frogs Ascaphus truei and Leiopelma hochstetteri are members of the most basal lineages of extant anurans. Their cranial muscles have not been previously described in full and are investigated here by dissection. Comparison of these taxa is used to review a controversy regarding the homologies of the jaw adductor muscles in Lissamphibia, to place these homologies in a wider gnathostome context, and to define features that may be useful for cladistic analysis of Anura. A new muscle is defined in Ascaphus and is designated m. levator anguli oris. The differences noted between Ascaphus and Leiopelma are in the penetration of the jaw adductor muscles by the mandibular nerve (V³). In the traditional view of this anatomy, the paths of the trigeminal nerve branches define homologous muscles. This scheme results in major differences among frogs, salamanders, and caecilians. The alternative view is that the topology of origins, insertions, and fiber directions are defining features, and the nerves penetrate the muscle mass in a variable way. The results given here support the latter view. A new model is proposed for Lissamphibia, whereby the adductor posterior (levator articularis) is a separate entity, and the rest of the adductor mass is configured around it as a folded sheet. This hypothesis is examined in other gnathostomes, including coelacanth and lungfish, and a possible sequence for the evolution of the jaw muscles is demonstrated. In this system, the main jaw adductor in teleost fish is not considered homologous with that of tetrapods. This hypothesis is consistent with available data on the domain of expression of the homeobox gene engrailed 2, which has previously not been considered indicative of homology. Terminology is discussed, and “adductor mandibulae” is preferred to “levator mandibulae” to align with usage in other gnathostomes. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

The influence of caudofemoral musculature on the titanosaurian (Saurischia: Sauropoda) tail skeleton: morphological and phylogenetic implications

Due to their abundance, taxonomic and morphological diversity, wide range of body sizes and broad geographical distribution, titanosaurian sauropods were one of the most important Cretaceous herbivorous dinosaur groups. Consequently, titanosaurs constitute one of the best samples in which to evaluate the relationship between bony structures and unpreserved soft-tissues within Sauropoda. We reconstruct the morphology and interpret the implications of selected soft-tissues associated with the titanosaurian caudal skeleton. These tissues, especially the M. caudofemoralis longus (CFL), exerted a considerable influence on the anatomy of the caudal vertebrae and haemal arches. In all studied titanosaurian taxa, the reconstructed caudofemoral musculature corresponds to one of three principal morphotypes that accord with previously recognised phylogenetic patterns within the clade. Basal titanosaurians had an elongate M. CFL that extended for much of the proximal half of the tail; in saltasaurines, this muscle was much shorter. Non-saltasaurine lithostrotians exhibited an intermediate condition. Furthermore, the differing position of the fourth trochanter, and therefore, the insertion of the caudofemoral muscles, among various titanosaurian taxa suggests distinctions in the locomotor function of these animals.     

Morphology of the cranial skeleton and musculature in the obligate carnivorous tadpole of Lepidobatrachus laevis (Anura: Ceratophryidae)

Ziermann, J.M., Infante, C., Hanken, J. and Olsson, L. 2011. Morphology of the cranial skeleton and musculature in the obligate carnivorous tadpole of Lepidobatrachus laevis (Anura: Ceratophryidae). —Acta Zoologica (Stockholm) 00 :1–12. Lepidobatrachus laevis (Ceratophryidae: Ceratophryinae) is a bizarre frog endemic to the Chacoan desert of central South America. Its tadpole is an obligate carnivore that can catch and consume live prey nearly its own size. Morphological adaptations associated with this unique feeding mode, including the larval skull anatomy and associated cranial musculature, have only been partly described. We studied the head of Stages 26–27 larvae using gross dissection, immunohistochemistry, and standard histology. Derived features of this tadpole compared to the microphagous, herbivorous larvae of most other anurans include simplified chondrocranial cartilages and very robust jaw muscles. The mm. suspensorio‐ et quadratoangularis do not take their origin from the processus muscularis of the palatoquadrate, as in most other tadpoles, but instead originate from the corpus of the palatoquadrate caudal to this process. The jaw levators are unusually large. The tadpole of Ceratophrys, another member of the ceratophryine clade, also consumes large animal prey, but its morphology is very different. It probably has evolved independently from a generalized, mainly herbivorous tadpole similar to the larva of Chacophrys, the third ceratophryine genus. Most specialized features of the larval head of Lepidobatrachus laevis are adaptations for ‘megalophagy’—ingestion of whole, very large animal prey.     

Design and application of a flexible and implantable sensor for detecting uterine musculature contraction

It is very important to obtain the parameters of deformation size and contraction frequency of women's uterine musculature in medical research. This paper proposes a type of sensor for measuring these parameters and analyzes its force situation. The flexibility of the sensor makes it easy for doctors to let the sensor pass through woman's narrow cervix and get to her uterine cavity. The experiment shows that the sensitivity of three coils in the sample sensor achieves 22.38 nH/mm² both for left and right coils, 22.84 nH/mm² for top coil, which can meet the requirements of sensitivity for testing the contraction situation of uterine musculature. Furthermore, an interface designed in the back end system can display the parameters of deformation size and vivid contraction situation of women's uterine musculature in real-time. The sensor has been applied in some medical fields.