Comparative study on the forefoot and hindfoot intrinsic muscles of some cavioidea rodents (Mammalia, Rodentia)

The present study compares the forefoot and hindfoot musculature of five representative species of Cavioidea rodents. In all species, the musculature of both forefeet and hindfeet have the same array regardless of the absence of digit I in the manus of Hydrochaeris hydrochaeris and Cavia porcellus. Our results suggest a tendency in these species towards a three-digit system, with a functional loss of digit V and a predominance of digit III in their forefeet. In the same way, the muscular reduction of digit I in the other rodents analyzed indicates a four-digit system with predominance of digit II in Myoprocta acouchy and Dasyprocta leporina and of digit V in Agouti paca. There seems to be an association between the muscular arrangement and functional axis of the foot, raising the general question why this axis runs between the third and forth digit, or along the third digit.     

The Musculature of <Emphasis Type="Italic">Testudinella patina</Emphasis> (Rotifera: Flosculariacea), Revealed with CLSM

The musculature of Testudinella patina was visualized using phalloidin-linked fluorescent dye by confocal laser scanning microscopy. The conspicuous broad retractors appear to be made up of five separate fibers, of which three anchor in the neck region whereas two extend into the corona. Besides the broad retractors, a total of five paired longitudinal retractors are present and all of them extend into the corona. Incomplete circular muscles are found in groups in the neck region and in the medial and posterior parts of the trunk. The foot musculature comprises eight thin ventral foot muscles and six thicker dorsal foot muscles that all extend from the foot basis to the distal part of the foot. At the basis of the foot, each of the dorsal foot muscles anchors on a smaller, S-shaped subterminal foot muscle. The foot musculature furthermore comprises one pair of paraterminal foot muscles that each anchors basally on a subterminal foot muscle, extends into the most proximal part of the foot and attaches on one of the dorsal foot muscles. The visceral musculature is composed of extremely delicate fibers and is restricted to an area around and posterior to the foot opening. The presence of incomplete circular muscles supports that these muscles are a basal trait for Rotifera, whereas the morphology of the broad retractors and foot muscles is much more specialized and may be autapomorphic for Testudinella or alternatively for this genus and its closest relatives. The present results stress that revealing muscles by staining may produce new information from even well-investigated species, and that this information may contribute to a better understanding of functional as well as phylogenetic aspects of rotifer biology.     

Muscle dimensions in the chimpanzee hand

We dissected the forearms and hands of a female chimpanzee and systematically recorded mass, fiber length, and physiological cross-sectional area (PCSA) of all muscles including those of intrinsic muscles that have not been reported previously. The consistency of our measurements was confirmed by comparison with the published data on chimpanzees. Comparisons of the hand musculature of the measured chimpanzee with corresponding published human data indicated that the chimpanzee has relatively larger forearm flexors but smaller thenar eminence muscles, as observed in previous studies. The interosseous muscles were also confirmed to be relatively larger in the chimpanzee. However, a new finding was that relative PCSA, which reflects a muscles capacity to generate force, might have increased slightly in humans as a result of relatively shorter muscle fiber length. This suggests that the human intrinsic muscle architecture is relatively more adapted to dexterous manipulative functions. Shortening of the metacarpals and the intervening interosseous muscles might accordingly be a prerequisite for the evolution of human precision-grip capabilities.     

Analysis of the human and ape foot during bipedal standing with implications for the evolution of the foot

The ratio of the power arm (the distance from the heel to the talocrural joint) to the load arm (that from the talocrural joint to the distal head of the metatarsals), or RPL, differs markedly between the human and ape foot. The arches are relatively higher in the human foot in comparison with those in apes. This study evaluates the effect of these two differences on biomechanical effectiveness during bipedal standing, estimating the forces acting across the talocrural and tarsometatarsal joints, and attempts to identify which type of foot is optimal for bipedal standing. A simple model of the foot musculoskeletal system was built to represent the geometric and force relationships in the foot during bipedal standing, and measurements for a variety of human and ape feet applied. The results show that: (1) an RPL of around 40% (as is the case in the human foot) minimizes required muscle force at the talocrural joint; (2) the presence of an high arch in the human foot reduces forces in the plantar musculature and aponeurosis; and (3) the human foot has a lower total of force in joints and muscles than do the ape feet. These results indicate that the proportions of the human foot, and the height of the medial arch are indeed better optimized for bipedal standing than those of apes, further suggesting that their current state is to some extent the product of positive selection for enhanced bipedal standing during the evolution of the foot.     

Evolution and homologies of primate and modern human hand and forearm muscles, with notes on thumb movements and tool use

In this paper, we explore how the results of a primate-wide higher-level phylogenetic analysis of muscle characters can improve our understanding of the evolution and homologies of the forearm and hand muscles of modern humans. Contrary to what is often suggested in the literature, none of the forearm and hand muscle structures usually present in modern humans are autapomorphic. All are found in one or more extant non-human primate taxa. What is unique is the particular combination of muscles. However, more muscles go to the thumb in modern humans than in almost all other primates, reinforcing the hypothesis that focal thumb movements probably played an important role in human evolution. What makes the modern human thumb myology special within the primate clade is not so much its intrinsic musculature but two extrinsic muscles, extensor pollicis brevis and flexor pollicis longus, that are otherwise only found in hylobatids. It is likely that these two forearm muscles play different functional roles in hylobatids and modern humans. In the former, the thumb is separated from elongated digits by a deep cleft and there is no pulp-to-pulp opposition, whereas modern humans exhibit powerful thumb flexion and greater manipulative abilities, such as those involved in the manufacture and use of tools. The functional and evolutionary significance of a third peculiar structure, the intrinsic hand structure that is often called the ‘interosseous volaris primus of Henle’ (and which we suggest is referred to as the musculus adductor pollicis accessorius) is still obscure. The presence of distinct contrahentes digitorum and intermetacarpales in adult chimpanzees is likely the result of prolonged or delayed development of the hand musculature of these apes. In relation to these structures, extant chimpanzees are more neotenic than modern humans.     

Articular surface defects in the third metatarsal and third cuneiform: Nonosseous tarsal coalition

Frequencies of articular surface defects on the third metatarsal and third cuneiform, seen as pits of varying sizes on the plantar one third of the tarsometatarsal articular face, were investigated in skeletal populations from North America and Japan, as well as in gibbon, orangutan, chimpanzee, and gorilla skeletons. The apes did not exhibit the defects, although the number of observed specimens of each type was small. The newly presented human frequencies corresponded well with those from other published sources. The defects appeared both unilaterally and bilaterally, with no apparent sex or side biases. Statistical tests between the various populations found that, in general, geographically close populations had more similar frequencies of the defect. Possible etiologies for the defect were investigated, including biomechanical influences, degenerative arthritis, infection, trauma, and a developmental condition known as tarsal coalition, which proved to be the best explanation. Tarsal coalition results from the failure of a joint space to form properly during fetal growth. It can occur between any two adjacent bones of the foot. Several clinically important coalitions, whose presence interferes with normal walking, are known. However, coalition between the third metatarsal and third cuneiform has not been reported in the clinical literature, suggesting that the defect causes little or no foot dysfunction. Tarsal coalition is thought to have a strong genetic component, suggesting that the pit defect may be useful as a skeletal nonmetric trait, as others have stated. Am J Phys Anthropol 109:53–65, 1999. © 1999 Wiley-Liss, Inc.     

尾羽龙(Caudipteryx)的新材料及其重要骨骼特征的补充和修订

尾羽龙和原始祖鸟一起被认为是最早发现的带有真正鸟类羽毛的恐龙（Ji et al., 1998）,迄今已发现的尾羽龙包括邹氏尾羽龙（Caudipteryx zoui）和董氏尾羽龙（Caudipteryx dongi）两种（周忠和、汪筱林,2000）,前者包括保存在中国地质博物馆的NGMC 97*4朅和NGMC 97*9朅两件标本,而后者依据的材料仅为保存在中国科学院古脊椎动物与古人类研究所的V 12344。以上标本都不是十分完整。本文依据最近新发现的两件几乎完整的尾羽龙标本,对该属的一些重要形态特征进行补充和修订,以期对其系统关系的讨论及其他相关理论问题的研究提供新的…     

Comparative forefoot trabecular bone architecture in extant hominids

The appearance of a forefoot push-off mechanism in the hominin lineage has been difficult to identify, partially because researchers disagree over the use of the external skeletal morphology to differentiate metatarsophalangeal joint functional differences in extant great apes and humans. In this study, we approach the problem by quantifying properties of internal bone architecture that may reflect different loading patterns in metatarsophalangeal joints in humans and great apes. High-resolution x-ray computed tomography data were collected for first and second metatarsal heads of Homo sapiens (n = 26), Pan paniscus (n = 17), Pan troglodytes (n = 19), Gorilla gorilla (n = 16), and Pongo pygmaeus (n = 20). Trabecular bone fabric structure was analyzed in three regions of each metatarsal head. While bone volume fraction did not significantly differentiate human and great ape trabecular bone structure, human metatarsal heads generally show significantly more anisotropic trabecular bone architectures, especially in the dorsal regions compared to the corresponding areas of the great ape metatarsal heads. The differences in anisotropy between humans and great apes support the hypothesis that trabecular architecture in the dorsal regions of the human metatarsals are indicative of a forefoot habitually used for propulsion during gait. This study provides a potential route for predicting forefoot function and gait in fossil hominins from metatarsal head trabecular bone architecture.     

Anatomy of a duplicated human foot from a limb with fibular dimelia.

At birth, a patient presented with a right lower limb featuring preaxial polydactyly and fibular dimelia with a complete absence of the tibia. Radiographic studies of the patient's foot revealed a duplicated tarsus with eight metatarsals and toes. The three preaxial toes were surgically removed at 1 year of age. A hallux and four normal-appearing postaxial toes remained. The foot was amputated when the patient was 3 years old. Dissection of the amputated foot revealed that the muscles of the dorsum were normal, except that the tendon of the extensor hallucis brevis muscle inserted into both the hallux and toe 2, rather than only into the hallux. The few abnormalities observed among the muscles on the plantar surface of the foot included absence of the insertions of the tibialis posterior and the abductor hallucis muscles. In addition, the two heads of the adductor hallucis muscle inserted abnormally into the medial (tibial) side of metatarsal 1, rather than into the lateral side. These various muscular anomalies, in addition to the mirror duplication of the foot with the presence of only a single metatarsal 1, leads us to propose that this metatarsal probably represents two lateral (fibular) halves that form a laterally duplicated bone. Although the dorsalis pedis artery was present on the dorsal surface of the foot, most of its derivatives were absent. This artery did give rise to a supernumerary medial branch that ended abruptly in the connective tissue (presumably postsurgical scar) at the medial border of the foot. This branch may have represented a duplicated dorsalis pedis artery associated with the duplicated preaxial portion of the foot. The arteries on the plantar surface of the foot were normal. Even though some anomalies in the pattern of the cutaneous innervation were observed, the nerves of the foot were largely normal. The gross and radiographic anatomy of this specimen and the radiographic anatomy of the leg suggest that some teratogenic event occurred when developmental specification reached the level of the future knee. The teratogenic event, which probably occurred early in the fifth week of development, may have caused damage that led to a lateral duplication of both the leg and the foot with the absence of some of the most medial structures. Teratology 60:272-282, 1999.     

Cortical Structure of Hallucal Metatarsals and Locomotor Adaptations in Hominoids

Diaphyseal morphology of long bones, in part, reflects in vivo loads experienced during the lifetime of an individual. The first metatarsal, as a cornerstone structure of the foot, presumably expresses diaphyseal morphology that reflects loading history of the foot during stance phase of gait. Human feet differ substantially from those of other apes in terms of loading histories when comparing the path of the center of pressure during stance phase, which reflects different weight transfer mechanisms. Here we use a novel approach for quantifying continuous thickness and cross-sectional geometric properties of long bones in order to test explicit hypotheses about loading histories and diaphyseal structure of adult chimpanzee, gorilla, and human first metatarsals. For each hallucal metatarsal, 17 cross sections were extracted at regularly-spaced intervals (2.5% length) between 25% and 65% length. Cortical thickness in cross sections was measured in one degree radially-arranged increments, while second moments of area were measured about neutral axes also in one degree radially-arranged increments. Standardized thicknesses and second moments of area were visualized using false color maps, while penalized discriminant analyses were used to evaluate quantitative species differences. Humans systematically exhibit the thinnest diaphyseal cortices, yet the greatest diaphyseal rigidities, particularly in dorsoplantar regions. Shifts in orientation of maximum second moments of area along the diaphysis also distinguish human hallucal metatarsals from those of chimpanzees and gorillas. Diaphyseal structure reflects different loading regimes, often in predictable ways, with human versus non-human differences probably resulting both from the use of arboreal substrates by non-human apes and by differing spatial relationships between hallux position and orientation of the substrate reaction resultant during stance. The novel morphological approach employed in this study offers the potential for transformative insights into form-function relationships in additional long bones, including those of extinct organisms (e.g., fossils).     

Reverse flow instep island flap.

The retrogradely perfused medial plantar artery flap was used in a leprosy patient with a plantar ulcer over the heads of the second and third metatarsals. The flap is based on the anastomosis of the medial plantar artery with the branch of the first plantar metatarsal artery, which supplies the medial side of the great toe. This design provides reconstruction with like local tissues while not distorting the weight-bearing pattern of the foot.     

Pennation angles of the intrinsic muscles of the foot

As mathematical models of the musculoskeletal system become increasingly detailed and precise, they require more accurate information about the architectural parameters of the individual muscles. These muscles are typically represented as Hill-type models, which require data on fiber length, physiological cross-sectional area (PCSA) and pennation angle. Most of this information for lower limb muscles has been published, except for data on the pennation angle of the intrinsic muscles of the foot. Each (n=20) intrinsic muscle of three human feet was dissected free. The dorsal and plantar surfaces were photographed and a digitized color image was imported into Abobe Photoshop. The muscles were divided into "anatomical units". For each anatomical unit (n=26), a line was drawn along the tendon axis and a number of other lines were drawn along individual muscle fibers. The angle between the tendon line and each fiber line was defined as the pennation angle of that fiber. By visual inspection, an effort was made to take measurements such that they represented the distribution of fibers in various parts of the muscle. Although some individual muscles had higher or lower pennation angles, when averaged for all specimens, the second dorsal interosseous had the smallest pennation angle (6.7+/-6.81 degrees) while the abductor digiti minimi had the largest (19.1+/-11.19 degrees). Since the cosines of the angles range from 0.9932 to 0.9449, the effect of the pennation angle on the force generated by the muscle was not great.     

The Treatment of Pes Cavus: (Section of Orthopædics)

(A) REVIEW OF EARLIER METHODS: Manipulations; fasciotomy; Phelps' operation; Steindler's operation; anterior arch-plates.(B) Reasons for their relative failure.-(1) Correction of the deformity is imperfect, and (2) as they deal with the existing deformity only, and not with its cause, the result is not permanent; relapse occurs.(C) Evolution of the modern operation.-Two facts in connexion with the ordinary "idiopathic" type of pes cavus are constant, and therefore noteworthy, viz.: (a) the deformity is entirely a fore-foot deformity, consisting of dropping-down of the fore-foot, and (b) paralysis of the lumbrical or of the interosseous muscles is never found at operation.This suggests that a cause for the fore-foot drop should be sought. Pes cavus never occurs in flail foot, but may develop in mild cases of paralysis of the anterior tibial (extensor) group of muscles; this suggests that in less marked cases of paresis of these muscles, pes cavus may result; in fact, this has been observed.Finally, a case in which the legs were known to have been normal, and one was damaged, anteriorly (thereby weakening the long extensor action) resulted in the development of typical unilateral pes cavus.The part played by the interossei and lumbrical muscles is purely passive, and results from the dropping-down of the metatarsal heads beyond their line of action. This can be demonstrated on any case in which contracture of the soft parts of the toes has not occurred; pushing-up the anterior arch brings down the toes, and vice versa.The problem, then, seems to consist of finding a means to strengthen the relatively weak long extensors, and of giving them a stronger and more direct lifting action upon the metatarsal heads.(D) The modern operation.-This consists of two distinct parts: (a) the correction of existing deformity, and (b) the adoption of measures to prevent recurrence of the deformity. (a) Mere non-selective elongation of the structures of the sole is inadequate; those on the inner side must be lengthened and flattened more than those on the outer side; therefore, the joint-capsules, fasci?, tendon-sheaths, etc., are divided as freely as possible, by open operation, on the inner side of the foot. Steindler's section of all structures attached to the os calcis then allows the whole foot to elongate; this is followed by vigorous manipulation, and this completes stage (a).(b) The extensor tendons are then transplanted into holes bored through the necks of the metatarsal bones (Murk Jansen's operation, modified), and are sutured, the foot being held over-corrected meanwhile.If the toes are contracted, and the above method does not correct the deformity, arthrodesis of the proximal interphalangeal joints is performed; the fifth toe may perhaps be amputated.(E) After-treatment and results.-Other Points: The results seen to be permanent. At what age should this operation be performed? Treatment, at earlier ages, The type and degree of disability caused by pes cavus. Relief of advanced cases.     

Musculature of an illoricate predatory rotifer Asplanchnopus multiceps as revealed by phalloidin fluorescence and confocal microscopy

The pattern of muscles in the actively swimming predatory rotifer Asplanchnopus multiceps is revealed by staining with tetramethyl-rhodamine isothiocyanate (TRITC)-labelled phalloidin and confocal scanning laser microscopy (CSLM). The major components of the musculature are: prominent semicircular muscles of the corona; paired lateral, dorsal and ventral retractors in the trunk; a network of six seemingly complete circular muscles and anastomosing longitudinal muscles in the trunk; two short foot retractors, originating from a transverse muscle in the lower third of the trunk. The sphincter of the corona marks the boundary between the head and the trunk. The muscular patterns in rotifers with different lifestyles differ clearly, therefore, the muscular patterns seem to be determined by the mode of locomotion and feeding behaviour.     

Arteriographic study of the arterial supply of the foot in one hundred cadaver feet

The arterial supply of 100 human cadaver feet (87 cadavers) was investigated by stereoscopic arteriography and was compared phylogenetically to that of the macaque foot. The deep plantar arch was always well developed and complete, whereas the superficial plantar arch was usually slender and incomplete. The first proximal perforating artery arising from the dorsalis pedis artery formed the main component of the deep plantar arch in 82% of the feet. The second proximal perforating artery arising from the dorsal rete contributed to the deep plantar arch in 43% of the feet, and formed most of the arch in one foot. The dorsal rete was classified into four groups of variants based on the arterial source of the second dorsal metatarsal artery. These were the arcuate artery (25%), distal lateral tarsal artery (12%), proximal lateral tarsal artery (6%), and nondorsal rete (57%) variants. In the first intermetatarsal space, the dorsal and plantar metatarsal arteries shared a common trunk in 54% of the feet, but this did not occur in the other intermetatarsal spaces. The second dorsal metatarsal artery arose from the dorsal rete in 43% of the feet, and this artery was quite large, sometimes being the largest of all the dorsal and plantar metatarsal arteries. Variations of the arterial supply found in humans sometimes resembled the typical pattern found in the macaque.     

Partial skeleton of Proconsul nyanzae from Mfangano Island,Kenya

A partial skeleton attributed to Proconsul nyanzae (KNM-MW 13142) is described. The fossils were found at a site on Mfangano Island, Kenya, which dates to 17.9 ± .1 million years ago. KNM-MW 13142 consists of six partial vertebrae (T12-S1), a nearly complete hipbone, most of the right femur and left femoral shaft, a fragmentary tibia and fibula, and a nearly complete talus and calcaneus. This skeleton provides the first pelvic fossil known for any East African Miocene hominoid. The new Proconsul specimen is compared to a large sample of extant anthropoids to determine its functional and phylogenetic affinities. In most aspects of its anatomy, KNM-MW 13142 closely resembles nonhominoid anthropoids. This individual had a long, flexible spine, narrow torso, and habitually pronograde posture, features characteristic of most extant monkeys. Evidence of spinal musculature suggests a generalized condition intermediate between that of cercopithecoids and hylobatids. The hindlimb of KNM-MW 13142 exhibits relatively mobile hip and ankle joints, with structural properties of the femur like those of hominoids. This mix of features implies a pattern of posture and locomotion that is unlike that of any extant primate. Many aspects of the Proconsul nyanzae locomotor skeleton may represent the primitive catarrhine condition. © 1993 Wiley-Liss, Inc.     

Evidence for a grooming claw in a North American adapiform primate: implications for anthropoid origins

Among fossil primates, the Eocene adapiforms have been suggested as the closest relatives of living anthropoids (monkeys, apes, and humans). Central to this argument is the form of the second pedal digit. Extant strepsirrhines and tarsiers possess a grooming claw on this digit, while most anthropoids have a nail. While controversial, the possible presence of a nail in certain European adapiforms has been considered evidence for anthropoid affinities. Skeletons preserved well enough to test this idea have been lacking for North American adapiforms. Here, we document and quantitatively analyze, for the first time, a dentally associated skeleton of Notharctus tenebrosus from the early Eocene of Wyoming that preserves the complete bones of digit II in semi-articulation. Utilizing twelve shape variables, we compare the distal phalanges of Notharctus tenebrosus to those of extant primates that bear nails (n = 21), tegulae (n = 4), and grooming claws (n = 10), and those of non-primates that bear claws (n = 7). Quantitative analyses demonstrate that Notharctus tenebrosus possessed a grooming claw with a surprisingly well-developed apical tuft on its second pedal digit. The presence of a wide apical tuft on the pedal digit II of Notharctus tenebrosus may reflect intermediate morphology between a typical grooming claw and a nail, which is consistent with the recent hypothesis that loss of a grooming claw occurred in a clade containing adapiforms (e.g. Darwinius masillae) and anthropoids. However, a cladistic analysis including newly documented morphologies and thorough representation of characters acknowledged to have states constituting strepsirrhine, haplorhine, and anthropoid synapomorphies groups Notharctus tenebrosus and Darwinius masillae with extant strepsirrhines rather than haplorhines suggesting that the form of pedal digit II reflects substantial homoplasy during the course of early primate evolution.     

CLSM analysis of the phalloidin-stained muscle system in Nerilla antennata, Nerillidium sp. and Trochonerilla mobilis (Polychaeta; Nerillidae)

The entire muscle system of Nerilla antennata, Nerillidium sp. and Trochonerilla mobilis was three-dimensionally reconstructed from whole mounts. In juvenile and adult specimens the F-actin musculature subset was stained with FITC-conjugated phalloidin and visualized with a confocal laser scanning microscope (cLSM). The muscle system shows the following major organization: 1) circular muscles are totally absent in the body wall; 2) the longitudinal muscles are confined in two ventral and two dorsal thick bundles; 3) additional longitudinal muscles are located in the ventro- and dorsomedian axis; 4) three segmental pairs of ventral oblique muscles elongate into the periphery: the main dorsoventral muscles that run along the body side posterior and dorsally and the anterior and posterior oblique parapodial muscles, which contribute to the ventral chaetal sacs; 5) one segmental pair of dorsal oblique parapodial muscles, contributing to the dorsal chaetal sacs; 6) five to seven small dorsoventral muscles per segment; and 7) complex head and pharyngeal musculature. These results support the belief that absence of circular muscles in the polychaete body wall is much more widely distributed than is currently presumed.     

Computer keyswitch force–displacement characteristics affect muscle activity patterns during index finger tapping

This study examined the effect of computer keyboard keyswitch design on muscle activity patterns during finger tapping. In a repeated-measures laboratory experiment, six participants tapped with their index fingers on five isolated keyswitch designs with varying force–displacement characteristics that provided pairwise comparisons for the design factors of (1) activation force (0.31 N vs. 0.59 N; 0.55 N vs. 0.93 N), (2) key travel (2.5 mm vs. 3.5 mm), and (3) shape of the force–displacement curve as realized through buckling-spring vs. rubber-dome switch designs. A load cell underneath the keyswitch measured vertical fingertip forces, and intramuscular fine wire EMG electrodes measured muscle activity patterns of two intrinsic (first lumbricalis, first dorsal interossei) and three extrinsic (flexor digitorum superficialis, flexor digitorum profundus, and extensor digitorum communis) index finger muscles. The amplitude of muscle activity for the first dorsal interossei increased 25.9% with larger activation forces, but not for the extrinsic muscles. The amplitude of muscle activity for the first lumbricalis and the duration of muscle activities for the first dorsal interossei and both extrinsic flexor muscles decreased up to 40.4% with longer key travel. The amplitude of muscle activity in the first dorsal interossei increased 36.6% and the duration of muscle activity for all muscles, except flexor digitorum profundus, decreased up to 49.1% with the buckling-spring design relative to the rubber-dome design. These findings suggest that simply changing the force–displacement characteristics of a keyswitch changes the dynamic loading of the muscles, especially in the intrinsic muscles, during keyboard work.