Effects of lower limb and pelvic pin positions on leg length and offset measurement errors in experimental total hip arthroplasty.

BACKGROUND: Leg length (LL) and offset (OS) are important factors in total hip arthroplasty (THA). Because most LL and OS callipers used in THA depend on fixed points on the pelvis and the femur, limb position could affect measurement error. This study was conducted on a THA simulator to clarify the effects of lower limb position and iliac pin position on LL and OS errors and to determine the permissible range of limb position for accurate LL and OS measurement. METHODS: An LL and OS measurement instrument was used. Two pin positions were tested: the iliac tubercle and the top of the iliac crest intersecting with the extension of the femoral axis. First, the limb was moved in one direction (flexion-extension, abduction-adduction, or internal-external rotation), and LL and OS were measured for each pin position. Next, the limb was moved in combinations of the three directions. Then, the permissible range of combined limb position, which resulted in LL and OS measurement error within ±2 mm, was determined for each pin position. RESULTS: Only 4° of abduction/adduction caused 5-7 mm error in LL and 2-4 mm error in OS, irrespective of pin position. The effects of flexion-extension and internal-external rotation on LL error were smaller for the top of the iliac crest than for the iliac tubercle, though OS error was similar for both pin positions. For LL, the permissible range of the combined limb position was wider for the top of the iliac crest than for the iliac tubercle. CONCLUSION: To minimize LL and OS measurement errors in THA, adduction-abduction must be maintained. The iliac pin position in the top of the iliac crest is preferred because it provides less LL measurement error and a wider permissible range of combined limb position for accurate LL measurement.

The long limb bones of the StW 573 Australopithecus skeleton from Sterkfontein Member 2: Descriptions and proportions.

Due to its completeness, the A.L. 288-1 ('Lucy') skeleton has long served as the archetypal bipedal Australopithecus. However, there remains considerable debate about its limb proportions. There are three competing, but not necessarily mutually exclusive, explanations for the high humerofemoral index of A.L. 288-1: (1) a retention of proportions from an Ardipithecus-like chimp/human last common ancestor (CLCA); (2) indication of some degree of climbing ability; (3) allometry. Recent discoveries of other partial skeletons of Australopithecus, such as those of Australopithecus sediba (MH1 and MH2) and Australopithecus afarensis (KSD-VP-1/1 and DIK-1/1), have provided new opportunities to test hypotheses of early hominin body size and limb proportions. Yet, no early hominin is as complete (>90%), as is the ∼3.67 Ma 'Little Foot' (StW 573) skeleton from Sterkfontein Member 2. Here, we provide the first descriptions of its upper and lower long limb bones, as well as a comparative context of its limb proportions. We found that StW 573 possesses absolutely longer limb lengths than A.L. 288-1, but both skeletons show similar limb proportions. This finding seems to argue against a purely allometric explanation for A.L. 288-1 limb proportions. In fact, our multivariate allometric analysis suggests that limb lengths of Australopithecus, as represented by StW 573 and A.L. 288-1, exhibit a significantly different (p < 0.001) allometric pattern than that which typifies modern humans and African apes. Like some previous analyses, our results also suggest that hominin limb evolution occurred in two stages with: first, a modest increase in lower limb length and a concurrent shortening of the antebrachium between Ardipithecus and Australopithecus, followed by a considerable lengthening of the lower limb along with a decrease of both upper limb elements occurring between Australopithecus and Homo sapiens.

Variations in epiphyseal fusion and persistence of the epiphyseal line in the appendicular skeleton of two identified modern (19th-20th c.) adult Portuguese and Italian samples.

OBJECTIVES: The aim of this work is to study age, sex, and population variations in epiphyseal fusion and persistence of the epiphyseal line in the appendicular skeleton of two identified modern (19th-20th c.) adult skeletal samples, using a specifically designed macroscopic scoring method. The use of epiphyseal closure and persistence of the epiphyseal line as an adult-age marker is also discussed. MATERIALS AND METHODS: This study examined 981 adult skeletons of both sexes from two identified modern (20th c.) skeletal samples from the Sassari Collection (Museum of Anthropology, University of Bologna, Italy) and the Colecção de Esqueletos Identificados (Museum of Anthropology, University of Coimbra, Portugal). Our scoring method considers a five-degree scale, from nonfusion (Degree 0) to complete fusion (Degree 4). In addition, the persistence of the epiphyseal line, a feature that is not commonly collected during routine anthropological analyses, is taken into account here as Degree 3. RESULTS: Intra- and interobserver errors of 1.2% and 5.2%, respectively, were found, suggesting a good reproducibility of this scoring method. Some sites show variable degrees of epiphyseal fusion still in adult skeletons (e.g., secondary center of ossification of the clavicle, iliac crest, ischial tuberosity, distal epiphysis of the radius and ulna). CONCLUSIONS: Population differences have been observed, showing a delay in the complete epiphyseal closure for the Sassari sample compared to the Coimbra sample. Degree 3 seems to be a good adult-age indicator for individuals less than 35-year-old.

Ontogeny and variability of trabecular bone in the chimpanzee humerus, femur and tibia.

OBJECTIVES: Trabecular bone structure is known to be influenced by joint loading during life. However, many additional variables have the potential to contribute to trabecular bone structure of an adult individual, including age, sex, body size, genetics, and overall activity level. There is little research into intraspecific variability in trabecular bone and ontogeny of trabecular bone structure, especially in nonhuman primates. MATERIALS AND METHODS: This study investigates trabecular structure in adult and immature chimpanzees from a single population using high-resolution microcomputed tomographic scans of the proximal humerus, proximal femur, and distal tibia. Trabecular bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular spacing (Tb.Sp), and degree of anisotropy (DA) were quantified in specific regions of adult and immature chimpanzees, and color maps were generated to visualize the distribution of BV/TV throughout the joint in the metaphysis of immature specimens. RESULTS: The results demonstrate that variability in adult trabecular structure cannot be explained by sex or body size. During ontogeny, there is a general increase in trabecular BV/TV and Tb.Th with age, and ratios of trabecular parameters between the fore- and hindlimb may be consistent with locomotor transitions during ontogeny. DISCUSSION: Variation in trabecular morphology among adult individuals is not related to sex or body size, and the factors contributing to intraspecific variability, such as overall activity levels and genetic differences, require further investigation. Trabecular ontogeny in chimpanzees differs from humans in some respects, most notably the absence of a high BV/TV at birth.

Anterolateral Ligament of the Knee: What we Know About its Anatomy, Histology, Biomechanical Properties and Function.

To better control anterolateral rotational instability (ALRI) after anterior cruciate ligament reconstruction (ACLR), many recent studies have examined the anterolateral ligament (ALL). Although some inconsistencies have been reported, anatomic studies demonstrated that the ALL runs on the lateral side of the knee from the femoral lateral epicondyle area to the proximal tibia, between Gerdy's tubercle and the fibula head. Histologic research has characterized the ALL structure, which is more than a simple capsular thickening; it shows a dense collagen core, typical bony insertions and mechanoreceptor function. An analysis of biomechanical properties suggests that the ALL is weaker than other knee ligaments. While its contributions to tibial anterior translation control and to a high grade on the Pivot-Shift test are still unclear, there is a consensus that the ALL controls tibial internal rotation. Further research will be needed to clarify the significance of ALL injuries and to gauge the value of combined ACL and ALL reconstructions.

The Creation and Validation of a Knee Bone Age Atlas Utilizing MRI.

BACKGROUND: In managing many pediatric knee conditions, an accurate bone age assessment may be critical for diagnostic, prognostic, and treatment purposes. The aim of this study was to create an atlas of magnetic resonance imaging (MRI) studies of the knee spanning the pediatric and adolescent years that would enable accurate skeletal age to be assessed, potentially forgoing the need for a left-hand radiograph. METHODS: We performed a retrospective assessment of 11 to 31 MRIs from male and female patients of each age from 2 to 19 years. Radiographic features specific to the patella, tibia, fibula, and femur were documented with respect to their presence or absence. From these data, age and sex "standards" were established, allowing the creation on an atlas. A separate cohort of MRIs with 2 to 13 patients per age and sex was then used to validate the reliability and reproducibility of the atlas. RESULTS: In the creation of the atlas, a total of 859 MRIs were reviewed. The patella, tibia, fibula, and femur were noted to undergo a reproducible sequence of skeletal ossification. The patella provided the best age assessment in early childhood. Features specific to the tibia, particularly ossification of the tibial spine and the tibial tubercle, were of particular importance in children between the ages of 6 and 12 years. MRI features of the fibula and femur served a more important role in age assessment later in skeletal maturity. From a separate cohort of 323 MRIs utilized to validate the atlas, a strong correlation between chronologic age and bone age was shown, as was excellent interobserver and intraobserver reliability. CONCLUSIONS: The predictable ossification pattern of the patella, tibia, fibula, and femur enables accurate bone age calculations to be made from knee MRIs. When treating conditions about the knee that require MRI, obtaining an additional left-hand radiograph for bone age may be unnecessary. This information can be used to potentially avoid additional radiation exposure, impart cost savings, and lead to greater clinic efficiency.

Macro-anatomical and morphometric studies of the hindlimb of grasscutter (Thryonomys swinderianus, Temminck-1827).

The hindlimb of the grasscutter (Thryonomys swinderianus, Temminck-1827) was studied using 12 adult (≥6 months) rats of either sex with the mean weights of 1.42 ± 0.20 kg and 0.82 ± 0.13 kg for buck (n = 6) and doe (n = 6), respectively (p < .05). Characteristics of the bones were studied by gross observation after their preparation. Measurements of different segments of the hindlimb were also taken, giving a total average length of 31.80 cm. Correlation coefficients between length of bone and weight of rats were positive (p < .05) in bucks for all bone segments, except the pes (p > .05), whereas those in does were all non-significant (p > .05), with significant sexual dimorphism in the relationships. The average total number of bones in the hindlimb was 92, with no apparent sexual dimorphism. The bones of the hindlimb revealed important differences and similarities in morphology with those of other rodents. The Os coxae presented a relatively large obturator foramen, formed by the ramus of the ischium and shaft of the pubis. The femur had a body and two extremities with a prominent head, well-defined neck and trochanter. The fibula, a slender bone with triangular-shaped proximal extremity, ran down the length of tibia with proximal attachment (via cartilage) and distal fusion, leaving an extensive interosseus space. The pes revealed eight tarsals and four metatarsals; each of the metatarsals showed three phalanges.

The Osteometry of Equine Third Phalanx by the Use of Three-Dimensional Scanning: New Measurement Possibilities.

This study consisted in analyzing the asymmetry between bilateral third phalanges (coffin bones) in cold-blood horses based on the angle range of the plantar margin of the bone. The study employed a scanner projecting a hybrid set of images, consisting of sinusoidal stripes preceded by a Gray code sequence. As it turned out, three-dimensional scanning can be used to effectively determine the angle range for a selected portion of the studied bone. This provides broad possibilities for osteometric studies, as it enables the determination of angle distribution in a given fragment. The results obtained indicate a weak correlation between age and bilateral third-phalanx asymmetry in terms of the angle range of the plantar margins and no correlation between body weight and the asymmetry described.

Comparison of 3D bone models of the knee joint derived from CT and 3T MR imaging.

PURPOSE: To examine whether magnetic resonance (MR) imaging can offer a viable alternative to computed tomography (CT) based 3D bone modeling. METHODS: CT and MR (SPACE, TrueFISP, VIBE) images were acquired from the left knee joint of a fresh-frozen cadaver. The distal femur, proximal tibia, proximal fibula and patella were manually segmented from the MR and CT examinations. The MR bone models obtained from manual segmentations of all three sequences were compared to CT models using a similarity measure based on absolute mesh differences. RESULTS: The average absolute distance between the CT and the various MR-based bone models were all below 1mm across all bones. The VIBE sequence provided the best agreement with the CT model, followed by the SPACE, then the TrueFISP data. The most notable difference was for the proximal tibia (VIBE 0.45mm, SPACE 0.82mm, TrueFISP 0.83mm). CONCLUSIONS: The study indicates that 3D MR bone models may offer a feasible alternative to traditional CT-based modeling. A single radiological examination using the MR imaging would allow simultaneous assessment of both bones and soft-tissues, providing anatomically comprehensive joint models for clinical evaluation, without the ionizing radiation of CT imaging.

A new fossil from the mid-Paleocene of New Zealand reveals an unexpected diversity of world's oldest penguins.

We describe leg bones of a giant penguin from the mid-Paleocene Waipara Greensand of New Zealand. The specimens were found at the type locality of Waimanu manneringi and together with this species they constitute the oldest penguin fossils known to date. Tarsometatarsus dimensions indicate a species that reached the size of Anthropornis nordenskjoeldi, one of the largest known penguin species. Stem group penguins therefore attained a giant size very early in their evolution, with this gigantism existing for more than 30 million years. The new fossils are from a species that is phylogenetically more derived than Waimanu, and the unexpected coexistence of Waimanu with more derived stem group Sphenisciformes documents a previously unknown diversity amongst the world's oldest penguins. The characteristic tarsometatarsus shape of penguins evolved early on, and the significant morphological disparity between Waimanu and the new fossil conflicts with recent Paleocene divergence estimates for penguins, suggesting an older, Late Cretaceous, origin.

The thigh and leg of Homo naledi.

This paper describes the 108 femoral, patellar, tibial, and fibular elements of a new species of Homo (Homo naledi) discovered in the Dinaledi chamber of the Rising Star cave system in South Africa. Homo naledi possesses a mosaic of primitive, derived, and unique traits functionally indicative of a bipedal hominin adapted for long distance walking and possibly running. Traits shared with australopiths include an anteroposteriorly compressed femoral neck, a mediolaterally compressed tibia, and a relatively circular fibular neck. Traits shared with Homo include a well-marked linea aspera, anteroposteriorly thick patellae, relatively long tibiae, and gracile fibulae with laterally oriented lateral malleoli. Unique features include the presence of two pillars on the superior aspect of the femoral neck and a tubercular distal insertion of the pes anserinus on the tibia. The mosaic morphology of the H. naledi thigh and leg appears most consistent with a species intermediate between Australopithecus spp. and Homo erectus and, accordingly, may offer insight into the nature of the earliest members of genus Homo. These fossils also expand the morphological diversity of the Homo lower limb, perhaps indicative of locomotor diversity in our genus.

Skeletal assessment and secular changes in knee development: a radiographic approach.

OBJECTIVES: The purpose of this study is to conduct an analysis of ossification patterns in the distal femoral, proximal tibial, and proximal fibular epiphyses, and the patella. The results generated from this analysis will be compared with previous standards published by Elgenmark () and Garn et al. () to determine if clinical and skeletal age assessment standards should be updated for contemporary Americans. MATERIALS AND METHODS: Using the Pediatric Radiology Interactive Atlas (Patricia), a total of 1,317 epiphyses were scored for presence or absence from radiographs of 1,056 white individuals born in or after 1990. Statistical modeling of epiphyseal appearance was conducted for all major percentiles, including the 5th and 95th percentiles through logistic regression. RESULTS: Compared with Elgenmark () and Garn et al. (), our data suggest that the distal femoral and proximal tibial epiphyses show overall earlier ossification, while the proximal fibular epiphysis shows later ossification. When examining the pooled sex 50th percentile for our data, we found that ossification timing differences are 1.2 weeks earlier in the distal femoral epiphysis, 2.1 weeks earlier in the proximal tibial epiphysis, and 1.4 years later in the proximal fibular epiphysis. DISCUSSION: The epiphyses that appear early in life, for example the distal femoral epiphysis, require gestational age information to accurately estimate appearance times. There are considerable differences between the ossification timing patterns presented in this study and those of previous standards, which did not include gestational ages. Several factors may explain the observed differences in the epiphyses of the knee including: the availability of gestational age information, the analysis of longitudinal versus cross-sectional data, differences in socioeconomic status and prenatal care, and secular change. KEYWORDS age estimation, growth standards, ossification, skeletal maturation, subadult/juvenile growth.

Development of an Open-Source, Discrete Element Knee Model.

OBJECTIVE: Biomechanical modeling is an important tool in that it can provide estimates of forces that cannot easily be measured (e.g., soft tissue loads). The goal of this study was to develop a discrete element model of the knee that is open source to allow for utilization of modeling by a wider audience of researchers. METHODS: A six degree-of-freedom tibiofemoral and one degree-of-freedom patellofemoral joint were created in OpenSim. Eighteen ligament bundles and tibiofemoral contact were included in the model. RESULTS: During a passive flexion movement, maximum deviation of the model from the literature occurred at the most flexed angle with deviations of 2° adduction, 7° internal rotation, 1-mm posterior translation, 12-mm inferior translation, and 4-mm lateral translation. Similarly, the overall elongation of the ligaments agreed with literature values with strains of less than 13%. CONCLUSION: These results provide validation of the physiological relevance of the model. SIGNIFICANCE: This model is one of the few open source, discrete element knee models to date, and has many potential applications, one being for use in an open-source cosimulation framework.

Flapping before Flight: High Resolution, Three-Dimensional Skeletal Kinematics of Wings and Legs during Avian Development.

Some of the greatest transformations in vertebrate history involve developmental and evolutionary origins of avian flight. Flight is the most power-demanding mode of locomotion, and volant adult birds have many anatomical features that presumably help meet these demands. However, juvenile birds, like the first winged dinosaurs, lack many hallmarks of advanced flight capacity. Instead of large wings they have small "protowings", and instead of robust, interlocking forelimb skeletons their limbs are more gracile and their joints less constrained. Such traits are often thought to preclude extinct theropods from powered flight, yet young birds with similarly rudimentary anatomies flap-run up slopes and even briefly fly, thereby challenging longstanding ideas on skeletal and feather function in the theropod-avian lineage. Though skeletons and feathers are the common link between extinct and extant theropods and figure prominently in discussions on flight performance (extant birds) and flight origins (extinct theropods), skeletal inter-workings are hidden from view and their functional relationship with aerodynamically active wings is not known. For the first time, we use X-ray Reconstruction of Moving Morphology to visualize skeletal movement in developing birds, and explore how development of the avian flight apparatus corresponds with ontogenetic trajectories in skeletal kinematics, aerodynamic performance, and the locomotor transition from pre-flight flapping behaviors to full flight capacity. Our findings reveal that developing chukars (Alectoris chukar) with rudimentary flight apparatuses acquire an "avian" flight stroke early in ontogeny, initially by using their wings and legs cooperatively and, as they acquire flight capacity, counteracting ontogenetic increases in aerodynamic output with greater skeletal channelization. In conjunction with previous work, juvenile birds thereby demonstrate that the initial function of developing wings is to enhance leg performance, and that aerodynamically active, flapping wings might better be viewed as adaptations or exaptations for enhancing leg performance.

An alternative approach for estimating stature from long bones that is not population- or group-specific.

An accurate and precise estimate of stature can be very useful in the analysis of human remains in forensic cases. A problem with many stature estimation methods is that an unknown individual must first be assigned to a specific group before a method can be applied. Group membership has been defined by sex, age, year of birth, race, ancestry, continental origin, nationality or a combination of these criteria. Univariate and multivariate sex-specific and generic equations are presented here that do not require an unknown individual to be assigned to a group before stature is estimated. The equations were developed using linear regression with a sample (n=244) from the Terry Collection and tested using independent samples from the Forensic Anthropology Databank (n=136) and the Lisbon Collection (n=85). Tests with these independent samples show that (1) the femur provides the best univariate results; (2) the best multivariate equation includes the humerus, femur and tibia lengths; (3) a generic equation that does not require an unknown to first be assigned to a given category provides the best results most often; (4) a population-specific equation does not provide better results for estimating stature; (5) sex-specific equations can provide slightly better results in some cases; however, estimating the wrong sex can have a negative impact on precision and accuracy. With these equations, stature can be estimated independently of age at death, sex or group membership.

Developmental patterns of bilateral asymmetry in ancestral puebloans.

OBJECTIVES: Producing and maintaining a bilaterally symmetric phenotype throughout the lifespan is energetically demanding. Over the course of an individual's life, various intrinsic and external stressors impact the growth trajectory. These perturbations can compromise the allocation of energetic resources to processes that maintain developmental precision, potentially resulting in bilateral asymmetry (BA). Because different stressors are present during the lifespan, BA is a valuable tool for examining the unique factors impacting symmetrical growth and development. This study examines BA in paired long bones across a developmental skeletal series. METHODS: The humeri, radii, femora, and tibiae of 198 individuals from Ancestral Puebloan New Mexico (919-1670 CE) are analyzed to explore BA across development. Individuals are separated into five age categories, and by sex when possible, to explore patterns of BA. RESULTS: Significant BA is found in the bones of the upper limb when the interaction between bone and age is examined. Results suggest that BA in the humerus and radius becomes more right-biased with age. These directional trends are not observed in the lower limbs. Division into age categories illuminates patterns of asymmetry associated with age-related activities and physiological maturity, indicating that BA is differentially affected by varying environmental stressors across development. CONCLUSIONS: Our findings support the hypothesis that BA in long bones is influenced by environmental stressors that impact an individual's ability to produce symmetric morphological traits over the lifespan. Right-biased BA in the upper limb bones indicates that this variation from a symmetric ideal is strongly influenced by handedness resulting from habitual manual activities. Am. J. Hum. Biol. 28:421-430, 2016. © 2015 Wiley Periodicals, Inc.

Degree of terrestrial activity of the elusive sun-tailed monkey (Cercopithecus solatus) in Gabon: Comparative study of behavior and postcranial morphometric data.

We carried out a multidisciplinary study linking behavioral and morphological data from a little-known guenon species, Cercopithecus solatus, endemic to Gabon. Over a period of 9 months, we documented the pattern of stratum use associated with postural and locomotor behavior by direct observation (650 hrs) of a semi-free-ranging breeding colony. We also conducted a morphometric analysis of the humerus and limb proportions of 90 adult specimens from 16 guenon species, including C. solatus. Field observations indicated that C. solatus monkeys spent a third of their time on the ground, similar to semi-terrestrial guenon species. We detected two patterns of stratum use: at ground level, and in trees, at a height of 3-10 m. The monkeys spent more time on the ground during the dry season than the wet season, feeding mainly at ground level, while resting, and social behaviors occurred more frequently in the tree strata. Our study of humerus size and shape, together with the analysis of limb proportions, indicated morphofunctional adaptation of C. solatus to greater terrestriality than previously thought. We therefore characterize C. solatus as a semi-terrestrial guenon, and propose a new hypothesis for the ancestral condition. By combining behavioral and morphological results, we provide new information about the adaptive strategies of the species, and the evolutionary history of guenons, thus contributing to the conservation of the sun-tailed monkey in the wild.

Limb bone morphology, bone strength, and cursoriality in lagomorphs.

The primary aim of this study is to broadly evaluate the relationship between cursoriality (i.e. anatomical and physiological specialization for running) and limb bone morphology in lagomorphs. Relative to most previous studies of cursoriality, our focus on a size-restricted, taxonomically narrow group of mammals permits us to evaluate the degree to which 'cursorial specialization' affects locomotor anatomy independently of broader allometric and phylogenetic trends that might obscure such a relationship. We collected linear morphometrics and µCT data on 737 limb bones covering three lagomorph species that differ in degree of cursoriality: pikas (Ochotona princeps, non-cursorial), jackrabbits (Lepus californicus, highly cursorial), and rabbits (Sylvilagus bachmani, level of cursoriality intermediate between pikas and jackrabbits). We evaluated two hypotheses: cursoriality should be associated with (i) lower limb joint mechanical advantage (i.e. high 'displacement advantage', permitting more cursorial species to cycle their limbs more quickly) and (ii) longer, more gracile limb bones, particularly at the distal segments (as a means of decreasing rotational inertia). As predicted, highly cursorial jackrabbits are typically marked by the lowest mechanical advantage and the longest distal segments, non-cursorial pikas display the highest mechanical advantage and the shortest distal segments, and rabbits generally display intermediate values for these variables. Variation in long bone robusticity followed a proximodistal gradient. Whereas proximal limb bone robusticity declined with cursoriality, distal limb bone robusticity generally remained constant across the three species. The association between long, structurally gracile limb bones and decreased maximal bending strength suggests that the more cursorial lagomorphs compromise proximal limb bone integrity to improve locomotor economy. In contrast, the integrity of distal limb bones is maintained with increasing cursoriality, suggesting that the safety factor takes priority over locomotor economy in those regions of the postcranial skeleton that experience higher loading during locomotion. Overall, these findings support the hypothesis that cursoriality is associated with a common suite of morphological adaptations across a range of body sizes and radiations.

Ontogenetic changes in intralimb proportions in a Romano-Christian period sample from the Dakhleh Oasis, Egypt.

OBJECTIVES: The purpose of this study is to document the appearance of adult patterns in intralimb indices during ontogeny in a skeletal sample from the Kellis 2 cemetery, Dakhleh Oasis, Egypt. In addition, this study explores evolvability in intralimb indices to understand relative differences in sensitivity to ecogeographic variables. METHODS: Brachial and crural indices were compared across age cohorts with Welch's ANOVA tests and post-hoc Dunnett-Tukey-Kramer (DTK) pairwise multiple comparison tests. Spearman's rank correlation coefficients were used to examine developmental conservation and evolvability in intralimb proportions. RESULTS: Brachial and crural indices are greatest in the fetus/perinate cohort as compared to all other cohorts, decrease during infancy and early childhood, and increase during middle/late childhood. The adult pattern in the brachial index is first evident in infancy, but is not maintained throughout development. Conversely, the adult pattern in the crural index appears during early childhood and is maintained throughout development. The brachial index shows a higher degree of evolvability than the crural index in utero. CONCLUSIONS: The shifting pattern in intralimb proportions during development in the Kellis 2 sample is similar to that previously reported from globally diverse samples, which likely reflects the differential growth acceleration of proximal and distal intralimb skeletal elements during ontogeny. The brachial index may be more responsive to climatic conditions while the crural index may be more conserved due to functional demands. The data indicate that Kellis 2 juveniles were under strong selective pressures from climatic factors.

The osteology of the basal archosauromorph Tasmaniosaurus triassicus from the Lower Triassic of Tasmania, Australia.

Proterosuchidae are the most taxonomically diverse archosauromorph reptiles sampled in the immediate aftermath of the Permo-Triassic mass extinction and represent the earliest radiation of Archosauriformes (archosaurs and closely related species). Proterosuchids are potentially represented by approximately 15 nominal species collected from South Africa, China, Russia, Australia and India, but the taxonomic content of the group is currently in a state of flux because of the poor anatomic and systematic information available for several of its putative members. Here, the putative proterosuchid Tasmaniosaurus triassicus from the Lower Triassic of Hobart, Tasmania (Australia), is redescribed. The holotype and currently only known specimen includes cranial and postcranial remains and the revision of this material sheds new light on the anatomy of the animal, including new data on the cranial endocast. Several bones are re-identified or reinterpreted, contrasting with the descriptions of previous authors. The new information provided here shows that Tasmaniosaurus closely resembles the South African proterosuchid Proterosuchus, but it differed in the presence of, for example, a slightly downturned premaxilla, a shorter anterior process of maxilla, and a diamond-shaped anterior end of interclavicle. Previous claims for the presence of gut contents in the holotype of Tasmaniosaurus are considered ambiguous. The description of the cranial endocast of Tasmaniosaurus provides for the first time information about the anatomy of this region in proterosuchids. The cranial endocast preserves possibly part of the vomero-nasal ( = Jacobson's) system laterally to the olfactory bulbs. Previous claims of the absence of the vomero-nasal organs in archosaurs, which is suggested by the extant phylogenetic bracket, are questioned because its absence in both clades of extant archosaurs seems to be directly related with the independent acquisition of a non-ground living mode of life.