Functional Morphology

Reconstruction of the cranial musculature and masticatory function of the Pleistocene panamerican ground sloth Eremotherium laurillardi (Mammalia, Xenarthra, Megatheriidae)

by Robert K. McAfee

Published in "Historical Biology" with Virginia L. Naples (Northern Illinois University)

Cranial musculature, dental function and mandibular movement patterns in Eremotherium laurillardi were reconstructed... more Cranial musculature, dental function and mandibular movement patterns in Eremotherium laurillardi were reconstructed from the examination of crania and dentitions. Size, shape and pattern of muscle divisions were reconstructed from the examination of bony rugosities indicating muscle attachments. Details of masticatory muscle structure and function were based on dissections of the tree sloths Bradypus and Choloepus. Among sloths, masticatory muscles in E. laurillardi demonstrate a different synergist–antagonist pattern, reflecting greater emphasis on mediolateral mandibular movements. Eight cranial character complexes (anterior facial, zygomatic arch, superficial masseter, deep masseter–zygomaticomandibularis, pterygoid, temporal, occipital and occlusal) determined by interrelated contributions of each component made to group functions were identified. An elongate anterior face and predental spout in E. laurillardi allowed protrusion of a long narrow tongue at small degrees of gape, reflecting a probably ancestral xenarthran condition. Gape minimisation, in conjunction with the mediolaterally directed masticatory stroke in E. laurillardi, was a unique solution to increase masticatory efficiency by permitting molariform tooth shearing surfaces to remain in or near occlusion for a greater
percentage of each chewing cycle.

Sticky predators: a comparative study of sticky glands in harpactorine assassin bugs (Insecta: Hemiptera: Reduviidae) [Acta Zoologica]

by Guanyang Zhang

Published in 'Acta Zoologica'

For more than 50 years, specialized dermal glands that secrete sticky substances and specialized setae have been known... more For more than 50 years, specialized dermal glands that secrete sticky substances and specialized setae have been known from the legs of New World assassin bugs in the genus Zelus Fabricius (Reduviidae: Harpactorinae). The gland secretions and specialized ‘sundew setae’ are involved in enhancing predation success. We here refer to this predation strategy as ‘sticky trap predation’ and the specialized dermal glands as ‘sticky glands’. To determine how widespread sticky trap predation is among Reduviidae, we investigated taxonomic distribution of sticky glands and sundew setae using compound light microscopical and scanning electron microscopical techniques and sampling 67 species of Reduviidae that represent 50 genera of Harpactorini. We found sticky glands in 12 genera of Harpactorini and thus show that sticky trap predation is much more widespread than previously suspected. The sticky glands vary in shape, size and density, but are always located in a dorsolateral position on the fore tibia. Sundew setae are present in all taxa with sticky glands with the exception of Heza that instead possesses unique lamellate setae. The sticky trap predation taxa are restricted to the New World, suggesting a New World origin of this unique predation strategy.

Resin gathering in Neotropical resin bugs (Insecta: Hemiptera: Reduviidae): Functional and comparative morphology

by Dimitri Forero

Co-authored with: CHOE, D.-H., & WEIRAUCH, C.
Published in: Journal of Morphology 272: 204-229. (2011)

Apiomerini (Reduviidae: Harpactorinae) collect plant resins with their forelegs and use these sticky substances for... more Apiomerini (Reduviidae: Harpactorinae) collect plant resins with their forelegs and use these sticky substances for prey capture or maternal care. These behaviors have not been described in detail and morphological structures involved in resin gathering, transfer, and storage remain virtually undocumented. We here describe these behaviors in Apiomerus flaviventris and document the involved structures. To place them in a comparative context, we describe and document leg and abdominal structures in 14 additional species of Apiomerini that represent all but one of the 12 recent genera in the tribe. Based on these morphological data in combination with the behavioral observations on A. flaviventris, we infer behavioral and functional hypotheses for the remaining genera within the tribe Apiomerini. Setal abdominal patches for resin storage are associated with maternal care so far only documented for species of Apiomerus. Based on the occurrence of these patches in several other genera, we propose that maternal care is widespread within the tribe. Ventral abdominal glands are widespread within female Apiomerini. We propose that their products may prevent hardening of stored resins thus providing long-term supply for egg coating. Judging from the diverse setal types and arrangements on the front legs, we predict six different behavioral patterns of resin gathering within the tribe.

The adaptive significance of mandibular symphyseal fusion in mammals

by Jeremiah Scott

Published in Journal of Evolutionary Biology in 2012
Coauthored with Aaron Hogue and Matthew Ravosa

The mandibular symphyseal joint is remarkably variable across major mammalian clades, ranging in adults from unfused... more The mandibular symphyseal joint is remarkably variable across major mammalian clades, ranging in adults from unfused (amphiarthrosis) to partially fused (synarthrosis) to completely ossified (synostosis). Experimental work conducted on primates suggests that greater ossification of the symphysis is a response to increased recruitment of the balancing-side (i.e. nonchewing side) jaw-adductor muscles during forceful unilateral biting and chewing, with increased fusion strengthening the symphysis against correspondingly elevated joint stresses. It is thus expected that species with diets composed primarily of foods that require high-magnitude bite forces and ⁄ or repetitive loading to process will be characterized by greater degrees of symphyseal ossification than species with relatively easy-to-process diets (i.e. food items typified by low toughness and ⁄ or low stiffness). However, comparative support for this idea is limited. We tested this hypothesis in four dietarily diverse mammalian clades characterized by variation in symphyseal fusion – the Strepsirrhini, Marsupialia, Feliformia, and Caniformia. We scored fusion in adult specimens of 292 species, assigned each to a dietary category based on literature accounts, and tested for an association between these two variables using Pagel’s test for the correlated evolution of binary characters. Results indicate that greater fusion is associated with diets composed of resistant items in strepsirrhines, marsupials, and feliforms, providing some support for the hypothesis. However, no such relationship was detected in caniforms, suggesting that factors other than dietary mechanical properties influence symphyseal ossification. Future work should focus on such factors, as well as those that favour an unfused mandibular symphysis.

Modeling the human mandible under masticatory loads: which input variables are important?

by Flora Gröning

2012, Anatomical Record, DOI: 10.1002/ar.22455

Finite element analyses (FEA) that have simulated masticatory loadings of the human mandible differ significantly with... more Finite element analyses (FEA) that have simulated masticatory loadings of the human mandible differ significantly with regard to their basic input variables such as material properties, constraints, and applied forces. With sensitivity analyses it is possible to assess how the choice of different input values and the degree of model simplification affect FEA results. However, published FEA studies are rarely accompanied by sensitivity analyses so that the robusticity of their results is impossible to assess. Here, we conduct a sensitivity analysis with an FE model of a human mandible to quantify the relative importance of several modeling decisions: (1) the material properties assigned to the cancellous bone tissue; (2) the inclusion or not of the periodontal ligament; (3) the constraints at the joints and bite point; and (4) the orientation of applied muscle forces. We study the effects of varying these properties by analysing the strain magnitudes and directions across the model surface. In addition, we perform a geometric morphometric analysis of the deformation resulting from the loading of each model. The results show that the effects of altering the different model properties can be significant and that most effects are potentially large enough to cause problems for the biological interpretation of FEA results. We therefore recommend that researchers conduct more sensitivity analyses than at present to assess the robusticity of their FEA results and their biological conclusions.

Virtual functional morphology: novel approaches to the study of craniofacial form and function

by Flora Gröning

2012, Evolutionary Biology, DOI: 10.1007/s11692-012-9173-8

Recent developments in simulating musculoskeletal functioning in the craniofacial complex using multibody dynamic... more Recent developments in simulating musculoskeletal functioning in the craniofacial complex using multibody dynamic analysis and finite elements analysis enable comprehensive virtual investigations into musculoskeletal form and function. Because the growth of the craniofacial skeleton is strongly influenced by mechanical functioning, these methods have potential in investigating the normal and abnormal development of the skull: loading history during development can be predicted and bony adaptations to these loads simulated. Thus these methods can be used to predict the impact of altered loading or modifications of skull form early in ontogeny on the subsequent development of structures. Combining functional models with geometric morphometric methods (GMM), which are principally concerned with the study of variations of form, offers the opportunity to examine variations in form during development and the covariations between form and factors such as functional performance. Such a combination of functional models and GMM can potentially be applied in many useful ways, for example: to build and modify functional models, to assess the outcomes of remodelling studies by comparing the results with morphological changes during ontogeny, and to compare the outcomes of finite element analyses within a multivariate framework. Studies using these tools can not only investigate the development of the skull but also the mechanical processes and thus to some degree, behaviours underlying the development of variation among extant and fossil skeletal elements. By bringing together these tools from quite different comparative traditions, a novel and potentially powerful framework for simulation and statistical biomechanical analyses of form and function emerges. This paper reviews these recent developments in the context of the evolutionary and functional influences on skull development.

The predatory ecology of Deinonychus and the origin of flapping in birds

by Denver Fowler

FOWLER, D.W., FREEDMAN, E.A., SCANNELLA, J.B., & KAMBIC, R.E. (2011) PLoS One 6(12): e28964. doi:10.1371/journal.pone.0028964

Additional notes/images:
http://www.denverfowler.com/index.php?module=htmlpages&func=display&pid=48

Most non-avian theropod dinosaurs are characterized by fearsome serrated teeth and sharp recurved claws.... more Most non-avian theropod dinosaurs are characterized by fearsome serrated teeth and sharp recurved claws. Interpretation of theropod predatory ecology is typically based on functional morphological analysis of these and other physical features. The notorious hypertrophied ‘killing claw’ on pedal digit (D) II of the maniraptoran theropod Deinonychus (Paraves: Dromaeosauridae) is hypothesized to have been a predatory adaptation for slashing or climbing, leading to the suggestion that Deinonychus and other dromaeosaurids were cursorial predators specialized for actively attacking and killing prey several times larger than themselves. However, this hypothesis is problematic as extant animals that possess similarly hypertrophied claws do not use them to slash or climb up prey. Here we offer an alternative interpretation: that the hypertrophied D-II claw of dromaeosaurids was functionally analogous to the enlarged talon also found on D-II of extant Accipitridae (hawks and eagles; one family of the birds commonly known as “raptors”). Here, the talon is used to maintain grip on prey of subequal body size to the predator, while the victim is pinned down by the body weight of the raptor and dismembered by the beak. The foot of Deinonychus exhibits morphology consistent with a grasping function, supportive of the prey immobilisation behavior model. Opposite morphological trends within Deinonychosauria (Dromaeosauridae + Troodontidae) are indicative of ecological separation. Placed in context of avian evolution, the grasping foot of Deinonychus and other terrestrial predatory paravians is hypothesized to have been an exaptation for the grasping foot of arboreal perching birds. Here we also describe “stability flapping”, a novel behaviour executed for positioning and stability during the initial stages of prey immobilisation, which may have been pivotal to the evolution of the flapping stroke. These findings overhaul our perception of predatory dinosaurs and highlight the role of exaptation in the evolution of novel structures and behaviours.

Predatory functional morphology in raptors: Interdigital variation in talon size is related to prey restraint and immobilisation technique

by Denver Fowler

FOWLER, D.W., FREEDMAN, E.A., & SCANNELLA, J.B. (2009) PLoS One 4(11)

Despite the ubiquity of raptors in terrestrial ecosystems, many aspects of their predatory behaviour remain poorly... more Despite the ubiquity of raptors in terrestrial ecosystems, many aspects of their predatory behaviour remain poorly understood. Surprisingly little is known about the morphology of raptor talons and how they are employed during feeding behaviour.

Talon size variation among digits can be used to distinguish families of raptors and is related to different techniques of prey restraint and immobilisation. The hypertrophied talons on digits (D) I and II in Accipitridae have evolved primarily to restrain large struggling prey while they are immobilised by dismemberment. Falconidae have only modest talons on each digit and only slightly enlarged D-I and II. For immobilisation, Falconini rely more strongly on strike impact and breaking the necks of their prey, having evolved a ‘tooth’ on the beak to aid in doing so. Pandionidae have enlarged, highly recurved talons on each digit, an adaptation for piscivory, convergently seen to a lesser extent in fishing eagles. Strigiformes bear enlarged talons with comparatively low curvature on each digit, part of a suite of adaptations to increase constriction efficiency by maximising grip strength, indicative of specialisation on small prey. Restraint and immobilisation strategy change as prey increase in size. Small prey are restrained by containment within the foot and immobilised by constriction and beak attacks. Large prey are restrained by pinning under the bodyweight of the raptor, maintaining grip with the talons, and immobilised by dismemberment (Accipitridae), or severing the spinal cord (Falconini).

Within all raptors, physical attributes of the feet trade off against each other to attain great strength, but it is the variable means by which this is achieved that distinguishes them ecologically. Our findings show that interdigital talon morphology varies consistently among raptor families, and that this is directly correlative with variation in their typical prey capture and restraint strategy.

Scratch-digging sauropods, revisited

by Denver Fowler

FOWLER, D.W., & HALL, L.E. (2011) Historical Biology 23(1): 27-40 doi:10.1080/08912963.2010.504852

The unguals of sauropod dinosaurs are notable for their unusual shape and orientation, and quite different from the... more The unguals of sauropod dinosaurs are notable for their unusual shape and orientation, and quite different from the graviportal mammals to which they are often compared. Early in their evolution, sauropod manual unguals underwent severe reduction, being lost on all digits except digit (D)-I. In stark contrast, the pedal unguals become hypertrophied and laterally compressed with an unusual angled orientation. Recent workers dismissed an early suggestion of a scratch-digging function, supporting instead substrate-gripping during locomotion, although neither hypothesis has been adequately tested, and rejection of the scratch-digging hypothesis was based on inadequate comparison. Here we show that sauropod nesting traces are morphologically consistent with being excavated by scratch-digging, and that this behaviour is also observed in extant tortoises, which possess flattened unguals with a functionally analogous orientation. In this initial qualitative study, we surveyed claw morphology and use in a range of tortoises, based on previously published accounts and observation of specimens and video footage. Our findings suggest that there is a good case for re-examining the scratch-digging hypothesis for sauropods, although further work is required. The influence of reproductive behaviours on morphology is discussed, including the suggestion that the single manus claw of sauropods may have functioned for mate-gripping during copulation.

Jaw shape diversity in platyrrhine 'sclerocarpic foragers' [abst]

by Zachary Klukkert

This abstract is for the poster session "functional skeletal anatomy" at the 2012 annual meetings of the AAPA

Finite element analysis in functional morphology

by Callum Ross

Richmond, B.G., Wright, B., Grosse, I., Dechow, P.C., Ross, C.F., Spencer, M., Strait, D.S. (2005). Finite Element Analysis in functional morphology. Anatomical Record 283A: 259-274.

How to carry out functional morphology

by Callum Ross

Ross, C.F. (1999) How to carry out functional morphology? Evolutionary Anthropology 7: 217-222

Comment on "The effects of modelling simplifications on craniofacial finite element models: The alveoli (tooth sockets) and periodontal ligaments" (volume 44, issue 10, pages 1831-1838)

by Flora Gröning

2012, Journal of Biomechanics, DOI: 10.1016/j.jbiomech.2011.10.042

Dear Editor,
We read with interest the recent article “The effects of modelling simplifications on craniofacial... more Dear Editor,
We read with interest the recent article “The effects of modelling simplifications on craniofacial finite element models: The alveoli (tooth sockets) and periodontal ligaments” by Wood et al. (2011). Using a finite element (FE) model of a primate cranium the authors investigated the effects of filling empty tooth sockets with bone material and changing the mechanical properties of the periodontal ligament (PDL). At the end of their paper the authors discuss previous findings from similar studies with mandibles. Unfortunately, we identified some errors and misunderstandings in this discussion. Two of these refer to one of our recent papers (Gröning et al., 2011) and we therefore see the need for a correction. ...

URL of the response: http://www.sciencedirect.com/science/article/pii/S0021929012000929

On the Article-like Use of the Px2Sg in Dolgan, Nganasan and Some Other Languages in an Areal Siberian Context

by Marek Stachowski

Px2Sg = Possessive suffix of the second person singular.

This is a (polemic) continuation of the article "An example of Nganasan-Dolgan linguistic contact."

Alcune osservazioni sul l- di accusativo in aramaico

by Francesco Aspesi

Loprieno, A., (a cura di), Atti della Quinta Giornata Comparatistica, Perugia 1991, pp. 1-18 Loprieno, A., (a cura di), Atti della Quinta Giornata Comparatistica, Perugia 1991, pp. 1-18

SECONDARY SEXUAL CHARACTERS OF PTEROMALID WASPS (HYMENOPTERA: CHALCIDOIDEA, PTEROMALIDAE)

by Mircea-Dan Mitroiu

Scratch-digging sauropods, revisited.

by Lee Hall

Co-authored with Denver Fowler

Unguals of sauropod dinosaurs are notable for their unusual shape and orientation, and differ from those of... more Unguals of sauropod dinosaurs are notable for their unusual shape and orientation, and differ from those of graviportal mammals to which they are often compared. Early in their evolution, sauropod manual unguals underwent severe reduction, being lost on all digits except digit (D)-I. In contrast, the pedal unguals become hypertrophied and laterally compressed with an unusual angled orientation. Recent workers dismissed an early suggestion of a scratch-digging function, supporting instead substrate-gripping during locomotion, although neither hypothesis has been adequately tested, and rejection of the scratch-digging hypothesis was based on inadequate comparison. Here, we show that sauropod nesting traces are morphologically consistent with being excavated by scratch-digging, and that this behaviour is also observed in extant tortoises, which possess flattened unguals with a functionally analogous orientation. In this initial qualitative study, we surveyed claw morphology and use in a range of tortoises, based on previously published accounts and observation of specimens and video footage. Our findings suggest that there is a good case for re-examining the scratch-digging hypothesis for sauropods, although further work is required. The influence of reproductive behaviours on morphology is discussed, including the suggestion that the single manus claw of sauropods may have functioned for mate-gripping during copulation.

Interpreting sabretooth cat (Carnivora; Felidae; Machairodontinae) postcranial morphology in light of scaling patterns in felids

by Margaret Lewis

Lewis ME, Lague MR (2010) Interpreting sabretooth cat (Carnivora; Felidae; Machairodontinae) postcranial morphology in light of scaling patterns in felids. In: Goswami A, Friscia A (eds) Carnivoran Evolution: New Views on Phylogeny, Form and Function. Cambridge University Press, Cambridge, pp 411-465

Reconstructing the behaviour and ecology of extinct felids, especially that of machairodontine felids, has been of... more Reconstructing the behaviour and ecology of extinct felids, especially that of machairodontine felids, has been of great interest within the field of vertebrate paleontology. The anatomical design of these animals has been investigated with respect to dental function and prey acquisition behaviour, and, to a lesser degree, locomotion.

Few large felids exist today, and machairodontine felids were sometimes even larger than the largest extant felids, lions and tigers. This leads to the question of how much of the morphology observed in large machairodontines is simply an extension of size-related shape trends observed in modern felids. That is, to what extent are the morphological differences between machairodontines and smaller extant felids due to differences in size? Which extinct forms appear to be scaled-up versions of smaller felids, and which ones exhibit morphology indicative of functional differences?

This preliminary study investigates machairodontine postcranial morphology in light of scaling patterns in extant felids and examines how well trends in smaller extant felids predict the morphology of larger felids.We also look for any overall trends in machairodontine postcranial morphology that unite them
as a group, much like the possession of machairodont dentition does.

Plio-Pleistocene carnivoran guilds: Implications for hominid paleoecology

by Margaret Lewis

Lewis ME (1995) Plio-Pleistocene Carnivoran Guilds: Implications for Hominid Paleoecology. Ph.D. thesis. Department of Anthropology. State University of New York, Stony Brook, p 524

ity of extrinsic limb muscles in dogs at walk, trot and gallop.

by Stephen Deban

The extrinsic limb muscles perform locomotor work and must adapt their activity to changes in gait and locomotor... more The extrinsic limb muscles perform locomotor work and must adapt their activity to changes in gait and locomotor speed, which can alter the work performed by, and forces transmitted across, the proximal fulcra of the limbs where these muscles operate. We recorded electromyographic activity of 23 extrinsic forelimb and hindlimb muscles and one trunk muscle in dogs while they walked, trotted and galloped on a level treadmill. Muscle activity indicates that the basic functions of the extrinsic limb muscles – protraction, retraction and trunk support – are conserved among gaits. The forelimb retains its strut-like behavior in all gaits, as indicated by both the relative inactivity of the retractor muscles (e.g. the pectoralis profundus and the latissimus dorsi) during stance and the protractor muscles (e.g. the pectoralis superficialis and the omotransversarius) in the first half of stance. The hindlimb functions as a propulsive lever in all gaits, as revealed by the similar timing of activity of retractors (e.g. the biceps femoris and the gluteus medius) during stance. Excitation increased in many hindlimb muscles in the order walk–trot–gallop, consistent with greater propulsive impulses in faster gaits. Many forelimb muscles, in contrast, showed the greatest excitation at trot, in accord with a shorter limb oscillation period, greater locomotor work performed by the forelimb and presumably greater absorption of collisional energy