reverse-dissection-dicect-reveal-otherwise-hidden-data-evolution

Reverse Dissection and DiceCT Reveal Otherwise Hidden Data in the Evolution of the Primate Face

Facial expressions, or facial displays, of social or emotional intent are produced by many mammalian taxa as a means of visually communicating with ...

North Carolina State University

Bone 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-to-muscle 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. Anat Rec, 301:515-527, 2018. © 2018 Wiley Periodicals, Inc.

Leg Muscle Architecture in Primates and Its Correlation with Locomotion Patterns.

It is widely viewed that orangutans lack a ligamentum teres femoris (LTF) inserting on the femoral head because orangutans lack a distinct fovea capitis. Orangutans employ acrobatic quadrumanous clambering that requires a high level of hip joint mobility, and the absence of an LTF is believed to be an adaptation to increase hip mobility. However, there are conflicting reports in the literature about whether there may be a different LTF configuration in orangutans, perhaps with a ligament inserting on the femoral neck instead. Here we perform a dissection-based study of orangutan hip joints, assess the soft tissue and hard tissue correlates of the orangutan LTF, and histologically examination the LTF to evaluate whether it is homologous to that found in other hominoids.

The ligamentum teres femoris in orangutans.

Exudativory, the consumption of gums, is an obligate or a facultative dietary niche for some primates and marsupials. Exudativory has been cited as a dietary niche that may have been present in early primates, so finding a dental signature for exudativory is highly desirable. The present study combines exudativorous lorisoids (galagos and lorises) into one sample to compare to closely related, non-exudativorous lorisoids to search for a consistent dental signature of exudativory. Linear measurements were taken from the toothcomb, P , M , upper canine, and P from skulls of 295 adult galagids and lorisids. Also, differential distribution of enamel on the anterior teeth was qualitatively investigated as a dental signature for gouging (a behavior that facilitates some exudativory) by micro-CT scanning one specimen each from two gougers, Nycticebus coucang and Callithrix jacchus, and two non-gougers, Perodicticus potto, and Saguinus fuscicollis. Non-primate gouging mammals, the vampire bat Desmodus rotundus and the sugar glider Petaurus breviceps, were compared to non-gouging relatives. Statistical analysis revealed that exudativorous galagos and lorises had significantly (p<0.05) reduced M relative to non- exudativorous galagos and lorises. While the sample sizes for assessing enamel thickness were small, preliminary results show that gouging primates and non-primate mammals have reduced lingual enamel thickness on the anterior dentition compared to non-gouging relatives. We suggest that reduction of mastication, and, therefore, M dimensions are a likely dental signature for exudativory in Primates. While broader samples are needed to statistically confirm, differential distribution of enamel in the anterior dentition may also be a signature of exudativory This article is protected by copyright. All rights reserved.

Article	Year
Leg Muscle Architecture in Primates and Its Correlation with Locomotion Patterns. Anatomical record (Hoboken, N.J. : 2007)\| PubMed ID: 29418119	2018
The ligamentum teres femoris in orangutans. American journal of physical anthropology\| PubMed ID: 30132799	2018
DENTAL SIGNATURES FOR EXUDATIVORY IN LIVING PRIMATES, WITH COMPARISONS TO OTHER GOUGING MAMMALS. Anatomical record (Hoboken, N.J. : 2007)\| PubMed ID: 30548805	2018

Adam Hartstone-Rose

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