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Functional adaptations of primate forearm and leg muscle fiber architecture
No full texthas been correlated with locomotion, posture
and substrate use in primates, but less attention
has been paid to myological adaptations.
Previously we presented data on the functional
correlates of primate forearm muscle fiber
architecture variables: fascicle length (FL), physiological
cross-sectional area (PCSA) and reduced
PCSA (RPCSA). Here, we greatly expand thesample to include 9 strepsirrhine, 15 platyrrhine,
and 20 catarrhine taxa spanning the entire size
range of the order (Microcebus to Gorilla), and we
also include fiber data from the leg.
Forearm muscle mass scales with positive
allometry across all primates. Catarrhines exhibit
positive allometry in their PCSA and RPCSA
indicating that larger catarrhines have relatively
stronger forearm muscles. While PCSA and
RPCSA scale with isometry for terrestrial species,
they scale with positive allometry for arboreal
ones – thus larger arboreal primates have relatively
stronger forearms. Surprisingly, there are
no differences in the forearm architecture of
quadrupeds (QUAD) when compared to vertical
clinging and leaping/suspensory species (VCL).
All leg strength variables (mass, PCSA, RPCSA)
scale with positive allometry, and speed/stretch
measure (FL) scales with isometry across the
sample. Thus, larger primates are relatively
stronger though not more flexible/faster. There is
no other phylogenetic signal in the leg muscles.
Arboreal primates have greater leg RPCSA and
QUAD have statistically heavier leg muscles than
VCL, though they are not greater in cross-sectional
area or reduced in FL
Leg Muscle Architecture in Primates and Its Correlation with Locomotion Pattern
Get PDFBone biomechanical studies indicate that leg bone structure can be
related to different locomotor patterns. The osteological correlates of
extant primates’ locomotion patterns and substrate use are important to
consider when estimating corresponding behaviors of extinct primates.
Here, we test if these same patterns are seen in the differences in leg
muscular architecture. Muscle mass, fascicle lengths (FL), physiological
cross-sectional area (PCSA), reduced PCSA (RPCSA) and tendon-tomuscle
belly ratio were studied in 33 primate species (6 strepsirrhines, 14
platyrrhines and 13 catarrhines). Muscles were grouped into toe and
ankle flexors and extensors and studied for phylogenetic and functional
signals. All variables strongly correlate with body mass: strength variables
(mass, PCSA and RPCSA) scale with positive allometry, whereas the
speed/stretch measure (FL) trend toward negative allometry. Thus, larger
primates are relatively stronger than smaller species, but they have relatively
shorter leg muscle fibers than smaller primates. The strongest
functional signal emerged when comparing belly-muscle tendon unit
(MTU) length ratio in leaping and non-leaping primates. Leapers show
significantly smaller plantarflexor belly-MTU ratio. Surprisingly, no significant
results reflect a correlation between muscle architecture and substrate
and locomotor groups. However, several trends suggest that a
larger sample and more fine-grained defined categories could produce significant
results. These results show the complex relation between leg
bone biomechanics and muscle architecture and demand for further studies
on this topic
Evaluating the Hominin Scavenging Niche through Analysis of the Carcass-Processing Abilities of the Carnivore Guild
No full textHumans are more carnivorous than other hominoids. It has been hypothesized that, during the evolution of this increased carnivory, hominins transitioned through a scavenging niche made viable by certain carnivoran taxa (especially sabertooths) that may have lacked the morphology necessary to fully utilize all parts of carcasses (e.g., marrow), therefore leaving an open niche in the form of high-quality scavengable remains available for hominins. In this dissertation, I examine the postcanine dentition of modern carnivorans, using quantifications of occlusal radii of curvature and intercuspid notches, and study the correlation of this morphology with carcass-processing behavior. I use these correlations to deduce the carcass-processing capabilities of the Plio-Pleistocene carnivores of South Africa (a guild for which we have a good appreciation of taxonomic diversity, and that existed at an important time during the evolution of our lineage - possibly the time that we transitioned into that guild), and compare these results with those of previous studies that relied on more conventional morphological measures.Both radius of curvature and intercuspid notch data do a good job of separating taxa by dietary category, revealing subtle patterns including possible differences in the carcass-processing abilities of fossil and modern members of some extant species. Other strong trends confirm that the "hunting-hyena," Chasmaporthetes, was probably a hypercarnivore, and not a durophage like its modern confamilial taxa. Somewhat surprisingly, results do not support the hypothesis that sabertooth felids were more hypercarnivorous than modern felids. Furthermore, though the sympatric hypercarnivorous taxa were more numerous, so to were the durophageous taxa, with one taxon, Pachycrocuta, probably exceeding the durophageous capabilities of modern durophages.As such, this dissertation shows no evidence that members of the paleo-carnivore guild were capable of producing higher quality scavengable carcasses than are modern carnivorans, and thus, based on these analyses of fossil carnivorans, it does not appear that high-quality scavengable remains were more available in the Plio-Pleistocene than there are today. Therefore, though there is clear evidence from other sources that hominins did scavenge at least occasionally, this dissertation does not support the hypothesis that there was an open niche consisting of high-quality scavengable remains.</p
Scaling of primate forearm muscle architecture as it relates to locomotion and posture
Get PDFIt has been previously proposed that distal humerus morphology may
reflect the locomotor pattern and substrate preferred by different primates.
However, relationships between these behaviors and the morphological capabilities
of muscles originating on these osteological structures have not been
fully explored. Here, we present data about forearm muscle architecture in a
sample of 44 primate species (N555 specimens): 9 strepsirrhines, 15 platyrrhines,
and 20 catarrhines. The sample includes all major locomotor and substrate
use groups. We isolated each antebrachial muscle and categorized them
into functional groups: wrist and digital extensors and flexors, antebrachial
mm. that do not cross the wrist, and functional combinations thereof. Muscle
mass, physiological cross-sectional area (PCSA), reduced PCSA (RPCSA), and
fiber length (FL) are examined in the context of higher taxonomic group, as
well as locomotor/postural and substrate preferences. Results showthatmuscle
masses, PCSA, and RPCSA scale with positive allometry while FL scales with
isometry indicating that larger primates have relatively stronger, but neither
faster normore flexible, forearms across the sample. When accounting for variation
in body size, we found no statistically significant difference in architecture
among higher taxonomic groups or locomotor/postural groups. However,
we found that arboreal primates have significantly greater FL than terrestrial
ones, suggesting that these species are adapted for greater speed and/or flexibility
in the trees. These data may affect our interpretation of the mechanisms
for variation in humeral morphology and provide information for refining biomechanical
models of joint stress and movement in extant and fossil primates
Functional Morphology and Behavioral Correlates to Postcranial Musculature
Get PDFIn this the second issue of a two-volume set of the Anatomical Record
on the relationship between muscle functional morphology and behavior,
the focus is on the postcranial musculature. Traditionally, when talking
of the postcranium we think of the skeletal parts that primarily provide
the lever system necessary for body movements. However, without the
force produced by muscle, the postcranial skeleton could not perform
these or most other tasks. In this special issue, our colleagues present ten
papers that focus on postcranial muscle morphology and function from
different perspectives. They include papers on forelimb and hindlimb
muscle functional morphology of vertebrates, including lizards, bats, primates,
a carnivoran and a rodent, and involved in different substrate use
(arboreal, terrestrial, and flying) and locomotion behavior (quadrupedal,
leaper, and suspensory) along with a historical overview to help bookend
the contextualization of the issues. The picture that these papers provide
is one of great liveliness in the field of muscle functional morphology
where both young students and affirmed professors continue to contribute
with both traditional approaches and new techniques to further our
knowledge of muscle morphology and its relationship with animal behavior
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Quantitative assessment of grasping strength in platyrrhine monkeys
No full textObjectives: Despite the longstanding importance of grasping adaptations in theories
of primate evolution, quantitative data on primate grasping strength remain rare. We
present the results of two studies testing the prediction that callitrichines—given
their comparative retreat from a small-branch environment and specialization for
movement and foraging on tree trunks and large boughs—should be characterized by
weaker grasping forces and underdeveloped digital flexor muscles relative to other
platyrrhines.
Methods: First, we directly measured manual grasping strength in marmosets (Callithrix
jacchus) and squirrel monkeys (Saimiri boliviensis), using a custom-constructed
force transducer. Second, we reanalyzed existing datasets on the fiber architecture
of forearm and leg muscles in 12 platyrrhine species, quantifying digital flexor muscle
physiological cross-sectional area (i.e., PCSA, a morphometric proxy of muscle
strength) relative to the summed PCSA across all forearm or leg muscles.
Results: Callithrix was characterized by lower mean and maximum grasping forces
than Saimiri, and callitrichines as a clade were found to have relatively underdeveloped
manual digital flexor muscle PCSA. However, relative pedal digital flexor PCSA
did not significantly differ between callitrichines and other platyrrhines.
Conclusions: We found partial support for the hypothesis that variation in predominant
substrate usage explains variation in empirical measurements of and morphological
correlates of grasping strength in platyrrhines. Future research should extend the
work presented here by (1) collecting morphological and empirical metrics of grasping
strength in additional primate taxa and (2) extending performance testing to include
empirical measures of primate pedal grasping forces as well
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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