3D Geometric Morphometrics Research Articles

2D Geometric morphometrics of the first lower molar of the genus Meles Brisson, 1762 including new badger evidence from the Lower Pleistocene Quibas site (Murcia, Spain)

Badgers belong to the genus Meles Brisson, 1762, which comprise four extant species (M. anakuma Temminck, 1844, M. leucurus (Hodgson, 1847), M. canescens Blanford, 1875, and M. meles (Linnaeus, 1758)). The genus is included in the subfamily Melinae Bonaparte, 1838, a polyphyletic group of Eurasian mustelids whose evolutionary relationships need further clarification. The evolutive relationships of the genus are complex and far from being resolved. This work aims to describe a nearly 1 Ma unpublished badger mandible from the Sierra de Quibas (Murcia) and to help clarify the evolutionary patterns of Euroasiatic badgers. To this end, we used 2D geometric morphometric techniques to measure 57 landmarks and semilandmarks in 79 first lower molars (m1) of Meles, ranging from Pleistocene to extant species. Our results show evidence for differentiating between primitive badgers and living species of Meles. The new m1 of Meles from the Quibas site is more gracile (relatively narrower and longer) than the other Eurasian extinct species, and shows that this specimen can be placed in the subspecies M. meles meles (Linnaeus, 1758). Our results also show that the denomination of M. meles atavus Kormos, 1914 as a related subspecies with a primitive morphology is morphologically supported. Therefore, we conclude that the living subspecies of badger M. meles meles was already differentiated in the south of the Iberian Peninsula at around 1 Ma, but some primitive remnant populations persisted in the north of the Iberian Peninsula, for which we recognize the subspecies M. meles atavus.

Morphometric analysis of the hard palate using cone beam computed tomography in a Saudi population

Background and objectivesAnalyzing the anatomical and morphometric information of the hard palate is crucial in prosthodontics, orthodontics, maxillofacial surgery, implant dentistry, and forensic anthropology. No data exist in the literature regarding the morphometric analysis of the hard palate using 3D imaging techniques in Saudi Arabia. Therefore, this study aimed to evaluate the dimensions and types of hard palates using 3D geometric morphometrics and the existence of gender-related differences in a selected Saudi population. Material and methodsThis cross-sectional study was performed by radiological evaluation of arbitrarily collected Cone Beam computed Tomography (CBCT) images includes 130 male and 45 female individuals from our department’s archives, radiology department, Dental Hospital, Qassim University. The Galileos® Comfort Plus System (Sirona 3D, Germany) was used to obtain the CBCT images while standardizing the parameters. Images were linearly measured using Galileos software. Measurements of palatal length, palatal breadth, and palatal height, as well as the calculation of the palatine index and palatal height index, were noted and statistically analyzed. ResultsThe mean palatal length, breadth, height, palatine index, and height index were 48.8 ± 3.9 mm, 36.2 ± 3.8 mm, 11.6 ± 2.4 mm, 74.7 ± 8.9, and 32.4 ± 7.1, respectively. The mean palatal length, breadth, and height were greater in men than in women. The majority of the palatine index values corresponded to leptostaphyline (76.6%), followed by mesostaphylline (12%) and brachystaphylline (11.4%), distribution among males and females were not statistical significance (p > 0.05). Palatal height index analysis revealed that the majority were orthostaphyline (59.4%), followed by chamestaphyline (26.3%), and hypsistaphyline (14.3%) these distributions were not significant statistically among males and females(p > 0.05). ConclusionThe palatine index and palatine height index are useful in prosthodontics, orthodontics, and forensic anthropology for identifying races on the basis of the skull.

Variations in cochlea shape reveal different evolutionary adaptations in primates and rodents

The presence of a coiled cochlea is a unique feature of the therian inner ear. While some aspects of the cochlea are already known to affect hearing capacities, the full extent of the relationships between the morphology and function of this organ are not yet understood—especially when the effect of body size differences between species is minimized. Here, focusing on Euarchontoglires, we explore cochlear morphology of 33 species of therian mammals with a restricted body size range. Using μCT scans, 3D models and 3D geometric morphometrics, we obtained shape information of the cochlea and used it to build phylogenetically corrected least square models with 12 hearing variables obtained from the literature. Our results reveal that different taxonomic groups differ significantly in cochlea shape. We further show that these shape differences are related to differences in hearing capacities between these groups, despite of similar cochlear lengths. Most strikingly, rodents with good low-frequency hearing display “tower-shaped” cochleae, achieved by increasing the degree of coiling of their cochlea. In contrast, primates present relatively wider cochleae and relative better high frequency hearing. These results suggest that primates and rodents increased their cochlea lengths through different morpho-evolutionary trajectories.

Domesticating details: 3D geometric morphometrics for the zooarchaeological discrimination of wild, domestic and proto-domestic sheep (Ovis aries) and goat (Capra hircus) populations

The domestication and management of livestock provided a critical source of food and textiles in the ancient world. Investigations into the processes of domestication, improvement, and management of these animals underpin interpretations of the economic structures of ancient societies. Despite this significance, zooarchaeologists continue to face significant problems in determining the state of domestication of key taxa, or even their certain osteological identification. This is particularly a problem during the initial stages of the domestication process. Significant advances in the understanding of certain domestic livestock species (e.g., pigs) have occurred as the result of geometric morphometric analyses but the morphology of other domesticates have caused them to lag behind. This study provides a GMM assessment of astragali from ovicaprines (sheep and goats) to demonstrate its capacity to advance our understanding of the domestication process through its ability to differentiate between wild, proto-domestic, and domestic morphotypes of these animals.

Ontogenetic variability of the intertympanic sinus distinguishes lineages within Crocodylia.

The phylogenetic relationships within crown Crocodylia remain contentious due to conflicts between molecular and morphological hypotheses. However, morphology-based datasets are mostly constructed on external characters, overlooking internal structures. Here, we use 3D geometric morphometrics to study the shape of the intertympanic sinus system in crown crocodylians during ontogeny, in order to assess its significance in a taxonomic context. Intertympanic sinus shape was found to be highly correlated with size and modulated by cranial shape during development. Still, adult sinus morphology distinguishes specimens at the family, genus and species level. We observe a clear distinction between Alligatoridae and Longirostres, a separation of different Crocodylus species and the subfossil Malagasy genus Voay, and a distinction between the Tomistoma and Gavialis lineages. Our approach is independent of molecular methods but concurs with the molecular topologies. Therefore, sinus characters could add significantly to morphological datasets, offering an alternative viewpoint to resolve problems in crocodylian relationships.

Modularity of the wrist in extant hominines.

Wrist shape varies greatly across primates and previous studies indicate that the numerous morphological differences among them are related to a complex mixture of phylogeny and function. However, little is known about whether the variation in these various anatomical differences is linked and to what extent the wrist bones vary independently. Here, we used 3D geometric morphometrics on a sample of extant hominines (Homo sapiens, Pan troglodytes, Gorilla gorilla, and Gorilla beringei), to find the model that best describes the covariation patterns among four of the eight carpals (i.e., capitate, lunate, scaphoid, and trapezium). For this purpose, 15 modular hypotheses were tested using the Covariance Ratio. Results indicate that there is a covariation structure common to all hominines, which corresponds to stronger covariation within each carpal as compared to the covariation between carpals. However, the results also indicate that that there is a degree of codependence in the variation of some carpals, which is unique in humans, chimpanzees, and gorillas, respectively. In humans there is evidence of associated shape changes between the lunate and capitate, and between the scaphoid and trapezium. This covariation between lunate and capitate is also apparent in gorillas, while chimpanzees display the greatest disassociation among carpals, showing low covariation values in all pairwise comparisons. Our analyses indicate that carpals have an important level of variational independence which might suggest a high degree of independent evolvability in the wrists of hominines, and that although weak, the structure of associated changes of these four carpals varies across genera. To our knowledge this is the first report on the patterns of modularity between these four wrist bones in the Homininae and future studies might attempt to investigate whether the anatomical shape associations among carpals are functionally related to locomotion and manipulation.

Palatal surface development from 6 years of age to early adulthood: data modelling using 3D geometric morphometrics.

The study followed the modelling of postnatal growth of a healthy palate of the Central European (Czech) population sample based on transverse data on sex and age from 6 to 19 years. Digitised 3D models of 212 healthy palatal surfaces were evaluated using 3D geometric morphometrics and superimpositions. The individuals were grouped based on age (preschool, younger and older school age, younger and older adolescents, young adults) and sex (♂ n = 101, ♀ n = 111). Female palatal development was non-linear and was interrupted between the 10-12 years and then proceeded intensively until the age of 15 when it ceased. In contrast, male-modelled growth was consistent throughout the follow-up and continued linearly until at least 19 years of age. The palate did not widen further with increasing age, and primarily palatal vaulting and heightening were found. The characteristics and distribution of areas with extensive modelled growth changes were comparable in females and males, as confirmed by the location of principal components (PC1 and PC2) within modal space and growth trajectories. The extent of sexual dimorphism increased from 15 years of age due to pubertal spurt combined with earlier completion of palatal development in females. The study showed modelled healthy palatal development from 6 years of age to early adulthood, which might be utilised as reference standards for the Central European population sample. The comparison of normal reference subjects with patients with cranio-maxillo-facial dysmorphologies represents the first step in diagnosing and establishing effective therapy.

Size And Locomotor Ecology Have Differing Effects on the External and Internal Morphologies of Squirrel (Rodentia: Sciuridae) Limb Bones.

Mammals exhibit a diverse range of limb morphologies that are associated with different locomotor ecologies and structural mechanics. Much remains to be investigated, however, about the combined effects of locomotor modes and scaling on the external shape and structural properties of limb bones. Here, we used squirrels (Sciuridae) as a model clade to examine the effects of locomotor mode and scaling on the external shape and structure of the two major limb bones, the humerus and femur. We quantified humeral and femoral morphologies using 3D geometric morphometrics and bone structure analyses on a sample of 76 squirrel species across their four major ecotypes. We then used phylogenetic generalized linear models to test how locomotor ecology, size, and their interaction influenced morphological traits. We found that size and locomotor mode exhibit different relationships with the external shape and structure of the limb bones, and that these relationships differ between the humerus and femur. External shapes of the humerus and, to a lesser extent, the femur are best explained by locomotor ecology rather than by size, whereas structures of both bones are best explained by interactions between locomotor ecology and scaling. Interestingly, the statistical relationships between limb morphologies and ecotype were lost when accounting for phylogenetic relationships among species under Brownian motion. That assuming Brownian motion confounded these relationships is not surprising considering squirrel ecotypes are phylogenetically clustered; our results suggest that humeral and femoral variation partitioned early between clades and their ecomorphologies were maintained to the present. Overall, our results show how mechanical constraints, locomotor ecology, and evolutionary history may enact different pressures on the shape and structure of limb bones in mammals.

Early Archaic landscape use, cultural transmission, and aggregation in the lower Ohio River valley

ABSTRACT In this paper, we use GIS and 2D geometric morphometrics to explore landscape use and social interaction among Kirk Cluster populations in the lower Ohio River valley. Using cultural transmission as a theoretical foundation, we develop models for identifying assemblages produced by macroband aggregations. We show that two distinct populations occupied northern Indiana and southwestern Kentucky. Intensively occupied sites in these areas are situated in near-upland settings in close proximity to a variety of resources including chert, higher order rivers, and sinkholes. In contrast, the Butterfield site in central Kentucky lies in the lowlands with the Green River as the only obvious resource. Analyses reveal that Butterfield was a macroband aggregation site visited by populations from Indiana, but groups from southwestern Kentucky only minimally participated in aggregations at Butterfield. Results further show that the Ohio River was not a barrier to social interaction in the Early Holocene.

Allometry then locomotor diversification shaped the evolution of lumbar morphology in early placental mammals

Abstract After the end-Cretaceous mass extinction, placental mammals rapidly diversified in size and locomotor mode, setting the stage for mammals to move into almost every habitat on Earth. Locomotion in extant mammals includes unique sagittal flexion of the trunk primarily driven by lumbar vertebrae, a ribless region of the spine. Consequently, variation in lumbar morphology is associated with a wide variety of locomotor styles. While the origin of this region in early therian mammals in the Mesozoic has been studied, along the therian stem, the later functional diversification of lumbar morphology in placental mammals, the dominant extant group, has been essentially unstudied. We measured the shape of lumbar vertebrae from early placental mammals to test how body size, locomotor specialization, and phylogeny interacted in the diversification of lumbar function after the end-Cretaceous mass extinction. We used 3D geometric morphometrics to quantify shape and compare variation between these Palaeogene mammals and modern mammals. We found that Palaeogene mammals had high disparity in lumbar morphology and that this variation correlated with size and locomotor style. Surprisingly, several ‘archaic’ placentals, like hyaenodontids, showed highly mobile lumbar morphology. These findings show that lumbar vertebrae formed an important and evolvable functional unit at the beginning of the Cenozoic.

Intravertebral vs. intervertebral integration and modularity in the vertebral column of mammalian carnivorans.

The vertebral column is a multicomponent structure whose organization results from developmental and functional demands. According to their distinct somitic origins, individual vertebrae exhibit intravertebral modularity between the centrum and neural spine. However, vertebrae are also organized into larger units called intervertebral modules that result from integration between adjacent vertebrae due to locomotory demands or from common developmental origins due to resegmentation. A previous hypothesis suggested that the boundaries of intervertebral modules coincide with changes in the patterns of intravertebral integration. Here, we explicitly test whether the patterns of modularity and integration between the centrum and neural spine (i.e., intravertebral) in the boundary vertebrae among previously defined intervertebral modules change with respect to those in the vertebrae within intervertebral modules. We quantified intravertebral modularity patterns and quantified the strength of intravertebral integration for each vertebra of the presacral region in 41 species of carnivoran mammals using 3D geometric morphometrics. Our results demonstrate a significant intravertebral modular signal between the centrum and neural spine in all post-cervical vertebrae, including the boundary vertebrae among intervertebral modules. However, the strength of intravertebral integration decreases at the boundary vertebrae. We also found a significant correlation between the degree of intravertebral integration and intervertebral integration. Following our results, we hypothesize that natural selection does not override the integration between the centrum and neural spine at the boundary vertebrae, a pattern that should be influenced by their distinct somitic origins and separate ossification centers during early development. However, natural selection has probably influenced (albeit indirectly) the integration between the centrum and neural spine in the vertebrae that compose the intervertebral modules.

Geometric morphometrics of 4D motion data: a proof of concept for applications in palaeoanthropology

This paper presents a proof of concept in the study of human respiratory motion from a palaeoanthropological approach. The hybrid methodology proposed merges Motion Capture techniques (optoelectronic plethysmography) with 3D geometric morphometrics of the superior torso surface during incremental running exercise. Results reveal the importance of the expiratory phase during high-intensity exercise breathing and arouse a discussion about the structure and function of the respiratory system in human evolution.

Deciphering carnivoran competition for animal resources at the 1.46 Ma early Pleistocene site of Barranco León (Orce, Granada, Spain)

Barranco León (Orce, Guadix Baza, Spain) is one of the sites with the oldest evidence of human activity in south-western Europe. This site has yielded human remains in association with both fauna and lithic artefacts, linked through the presence of anthropogenic cut and percussion marks. Nevertheless, while this site is a clear example of early hominin access to carcasses, the accumulations have been identified as a palimpsest, where multiple agents including carnivorans played a role in modifying and interacting in site formation processes. From this perspective, the interpretation and study of the Barranco León site is of great difficulty. Traditionally, interpretations have presented Barranco León as an area where hominins as well as the giant hyena, Pachycrocuta brevirostris, competed for access to carcasses left by machairodontine felids, such as the saber-toothed Homotherium latidens. Nevertheless, as will be presented in this study, the complexity and trophic pressure of Barranco León is much more complicated than originally hypothesized. This study presents a detailed taphonomic analysis of carnivoran activities in the level D1 of the Barranco León assemblage. 3D modelling, geometric morphometrics, and computational learning are used to provide new insights into the tooth pits observed on faunal materials. Here we show that Canis mosbachensis plays a pivotal role in the formation of the site, followed by Pachycrocuta, Homotherium, Ursus etruscus, and Xenocyon (Lycaon) lycaonoides. From this perspective, it can be seen that while Pachycrocuta and Homotherium were active agents in the formation of the site, other carnivorans are also important agents to consider when investigating the Guadix Baza region.

Reevaluation of the status of the Central American brocket deerMazama temama(Artiodactyla: Cervidae) subspecies based on morphological and environmental evidence

AbstractThe Central American brocket deer (Mazama temama) is widespread across the Mesoamerican forests, yet it remains largely unknown. Three subspecies are recognized currently within M. temama using pelage coloration as the primary diagnostic character. However, it remains unclear if there is any pattern of morphological variation throughout its distribution. We compared two models of morphological subdivision, namely the traditional subspecies and another based on biogeographic provinces via 2D geometric morphometrics and ecological niche modeling. The second model presented a better fit to the observed variation in cranial shape and size. We found divergence in skull size between individuals from Mexico and Guatemala (northern group) relative to specimens from Honduras, Nicaragua, Costa Rica, and Panama (southern group), the latter being 8% larger than the northern group. Centroid size showed a significant correlation with geographic distance suggesting an isolation-by-distance pattern. Low geographical overlap between the two clusters suggests niche conservatism. Late Pleistocene dispersal from South to Central America and differences in available resources with subsequent isolation due to climatic barriers therefore may have promoted differentiation in size albeit without extensive changes in shape. In this context, the Motagua-Polochic-Jolotán fault system probably plays a key role in promoting morphological differentiation by climatic isolation. Finally, we suggest that M. t. temama (Kerr, 1792) and M. t. reperticiaGoldman, 1913 should remain as valid names for the two morphological and ecologically differentiated groups detected here.

The significance of cephalopod beaks as a research tool: An update.

The use of cephalopod beaks in ecological and population dynamics studies has allowed major advances of our knowledge on the role of cephalopods in marine ecosystems in the last 60years. Since the 1960's, with the pioneering research by Malcolm Clarke and colleagues, cephalopod beaks (also named jaws or mandibles) have been described to species level and their measurements have been shown to be related to cephalopod body size and mass, which permitted important information to be obtained on numerous biological and ecological aspects of cephalopods in marine ecosystems. In the last decade, a range of new techniques has been applied to cephalopod beaks, permitting new kinds of insight into cephalopod biology and ecology. The workshop on cephalopod beaks of the Cephalopod International Advisory Council Conference (Sesimbra, Portugal) in 2022 aimed to review the most recent scientific developments in this field and to identify future challenges, particularly in relation to taxonomy, age, growth, chemical composition (i.e., DNA, proteomics, stable isotopes, trace elements) and physical (i.e., structural) analyses. In terms of taxonomy, new techniques (e.g., 3D geometric morphometrics) for identifying cephalopods from their beaks are being developed with promising results, although the need for experts and reference collections of cephalopod beaks will continue. The use of beak microstructure for age and growth studies has been validated. Stable isotope analyses on beaks have proven to be an excellent technique to get valuable information on the ecology of cephalopods (namely habitat and trophic position). Trace element analyses is also possible using beaks, where concentrations are significantly lower than in other tissues (e.g., muscle, digestive gland, gills). Extracting DNA from beaks was only possible in one study so far. Protein analyses can also be made using cephalopod beaks. Future challenges in research using cephalopod beaks are also discussed.

Combining quantitative approaches to differentiate between backed products from discoidal and Levallois reduction sequences

Backed flakes (core edge flakes and pseudo-Levallois points) represent special products of Middle Paleolithic centripetal flaking strategies. Their peculiarities are due to their roles as both a technological objective and in the management of core convexities to retain its geometric properties during reduction. In Middle Paleolithic contexts, these backed implements are commonly produced during Levallois and discoidal reduction sequences. Backed products from Levallois and discoidal reduction sequences often show common geometric and morphological features that complicate their attribution to one of these methods. This study examines the identification of experimentally produced discoidal and recurrent centripetal Levallois backed products (including all stages of reduction) based on their morphological features. 3D geometric morphometrics are employed to quantify morphological variability among the experimental sample. Dimensionality reduction though principal component analysis is combined with 11 machine learning models for the identification of knapping methods. A supported vector machine with polynomial kernel has been identified as the best model (with a general accuracy of 0.76 and an area under the curve [AUC] of 0.8). This indicates that combining geometric morphometrics, principal component analysis, and machine learning models succeeds in capturing the morphological differences of backed products according to the knapping method.

Dental morphological variation in Chalcolithic and Bronze Age human populations from North-Eastern Romania

BackgroundThis study aims to evaluate the dental variability and the phenetic relationships among archaeological human populations of the Chalcolithic and Bronze Age in North-Eastern Romania. MethodsThe evaluation of phenotypic variability was performed using the 2D Geometric Morphometrics on the second molars (upper – M2, and lower – M2) belonging to adult skeletons discovered in archaeological sites of the Chalcolithic and Bronze Age in North-Eastern Romania. ResultsThe size (Centroid Size, CS) and shape analysis of the second molar highlighted specific characteristics for each prehistoric period. The CS doesn’t achieve any statistical significance for two of the comparison criterium used (i.e., period, archaeological site). Instead, statistically significant differences were recorded between males and females. The greater variability in the shape of M2 compared to M2 was noticed. The M2 model of the Bronze Age is flattened mesiodistal compared to the Chalcolithic one, while differences in M2 morphotypes are associated with the hypocone shape, particularly. ConclusionThis study of dental morphology provides new data that could contribute as evidence of interactions between biological human groups in different regional prehistoric contexts.

A New Approach to the Quantitative Analysis of Bone Surface Modifications: the Bowser Road Mastodon and Implications for the Data to Understand Human-Megafauna Interactions in North America

Toward the end of the Pleistocene, the world experienced a mass extinction of megafauna. In North America these included its proboscideans—the mammoths and mastodons. Researchers in conservation biology, paleontology, and archaeology have debated the role played by human predation in these extinctions. They point to traces of human butchery, such as cut marks and other bone surface modifications (BSM), as evidence of human-animal interactions—including predation and scavenging, between early Americans and proboscideans. However, others have challenged the validity of the butchery evidence observed on several proboscidean assemblages, largely due to questions of qualitative determination of the agent responsible for creating BSM. This study employs a statistical technique that relies on three-dimensional (3D) imaging data and 3D geometric morphometrics to determine the origin of the BSM observed on the skeletal remains of the Bowser Road mastodon (BR mastodon), excavated in Middletown, New York. These techniques have been shown to have high accuracy in identifying and distinguishing among different types of BSM. To better characterize the BSM on the BR mastodon, we compared them quantitatively to experimental BSM resulting from a stone tool chopping experiment using “Arnold,” the force-calibrated chopper. This study suggests that BSM on the BR mastodon are not consistent with the BSM generated by the experimental chopper. Future controlled experiments will compare other types of BSM to those on BR. This research contributes to continued efforts to decrease the uncertainty surrounding human-megafauna associations at the level of the archaeological site and faunal assemblage—specifically that of the BR mastodon assemblage. Consequently, we also contribute to the dialogue surrounding the character of the human-animal interactions between early Americans and Late Pleistocene megafauna, and the role of human foraging behavior in the latter’s extinction.

Sexually mediated phenotypic variation within and between sexes as a continuum structured by ecology: The mosaic nature of skeletal variation across body regions in Threespine stickleback (Gasterosteus aculeatus L.).

Ecological character displacement between the sexes, and sexual selection, integrate into a convergent set of factors that produce sexual variation. Ecologically modulated, sexually mediated variation within and between sexes may be a major contributor to the amount of total variation that selection can act on in species. Threespine stickleback (Gasterosteus aculeatus) display rapid adaptive responses and sexual variation in many phenotypic traits. We examined phenotypic variation in the skull, pectoral and pelvic girdles of threespine stickleback from two freshwater and two coastal marine sites on the Sunshine Coast of British Columbia, Canada, using an approach that avoids a priori assumptions about bimodal patterns of variation. We quantified shape and size of the cranial, pectoral and pelvic regions of sticklebacks in marine and freshwater habitats using 3D geometric morphometrics and an index of sexually mediated variation. We show that the expression of phenotypic variation is structured in part by the effects of both habitat marine vs freshwater and the effects of individual sites within each habitat. Relative size exerts variable influence, and patterns of phenotypic variation associated with sex vary among body regions. This fine‐grained quantification of sexually mediated variation in the context of habitat difference and different anatomical structures indicates a complex relationship between genetically inferred sex and environmental factors, demonstrating that the interplay between shared genetic background and sexually mediated, ecologically based selective pressures structures the phenotypic expression of complex traits.

Mosaic Evolution of the Skull in Labrid Fishes Involves Differences in Both Tempo and Mode of Morphological Change.

Modularity is a ubiquitous feature of organismal design that plays an important role in structuring patterns of morphological diversification. Modularity can facilitate evolutionary changes by allowing subsets of traits to coevolve as integrated units and follow quasi-independent evolutionary trajectories, a pattern that may be particularly consequential in the case of highly complex morphological structures. Here we examine modularity in a complex and highly kinetic structure, the teleost skull, and ask if a modular organization of the skull has influenced the diversification dynamics of the shapes of its osteological components across the labrid phylogeny. We compiled one of the largest 3D morphological data sets of fishes to date and used geometric morphometrics to quantify patterns of cranial shape evolution across 184 species of wrasses (Labridae). We then tested several hypotheses of modularity inspired by functional and developmental relationships between cranial bones and compared phenotypic rates among modules. We also compared the fit of models of trait evolution for the entire skull and the various articulated bones that it comprises. Our analyses indicated strong support for a 2-module hypothesis, one that encompasses the oral and pharyngeal jaws and another module comprised of the neurocranium, hyoid apparatus, and operculum. This functional hypothesis yielded one of the highest significant rate differentials across modules, yet we also found that the best-fitting models of trait evolution differed among skull bones. These results suggest that modularity can influence morphological diversification in complex biological structures via differences in both the tempo and mode of evolutionary change. [3D geometric morphometrics, cranial morphology, evolutionary modularity, Labridae, phenotypic rates, structural complexity.].