Footprint evidence of early hominin locomotor diversity at Laetoli, Tanzania.

Bipedal trackways discovered in 1978 at Laetoli site G, Tanzania and dated to 3.66 million years ago are widely accepted as the oldest unequivocal evidence of obligate bipedalism in the human lineage1-3. Another trackway discovered two years earlier at nearby site A was partially excavated and attributed to a hominin, but curious affinities with bears (ursids) marginalized its importance to the paleoanthropological community, and the location of these footprints fell into obscurity3-5. In 2019, we located, excavated and cleaned the site A trackway, producing a digital archive using 3D photogrammetry and laser scanning. Here we compare the footprints at this site with those of American black bears, chimpanzees and humans, and we show that they resemble those of hominins more than ursids. In fact, the narrow step width corroborates the original interpretation of a small, cross-stepping bipedal hominin. However, the inferred foot proportions, gait parameters and 3D morphologies of footprints at site A are readily distinguished from those at site G, indicating that a minimum of two hominin taxa with different feet and gaits coexisted at Laetoli.

A new Miocene ape and locomotion in the ancestor of great apes and humans.

Many ideas have been proposed to explain the origin of bipedalism in hominins and suspension in great apes (hominids); however, fossil evidence has been lacking. It has been suggested that bipedalism in hominins evolved from an ancestor that was a palmigrade quadruped (which would have moved similarly to living monkeys), or from a more suspensory quadruped (most similar to extant chimpanzees)1. Here we describe the fossil ape Danuvius guggenmosi (from the Allgäu region of Bavaria) for which complete limb bones are preserved, which provides evidence of a newly identified form of positional behaviour-extended limb clambering. The 11.62-million-year-old Danuvius is a great ape that is dentally most similar to Dryopithecus and other European late Miocene apes. With a broad thorax, long lumbar spine and extended hips and knees, as in bipeds, and elongated and fully extended forelimbs, as in all apes (hominoids), Danuvius combines the adaptations of bipeds and suspensory apes, and provides a model for the common ancestor of great apes and humans.

The ligamentum teres femoris in orangutans.

OBJECTIVES: It is widely viewed that orangutans lack a ligamentum teres femoris (LTF) inserting on the femoral head because orangutans lack a distinct fovea capitis. Orangutans employ acrobatic quadrumanous clambering that requires a high level of hip joint mobility, and the absence of an LTF is believed to be an adaptation to increase hip mobility. However, there are conflicting reports in the literature about whether there may be a different LTF configuration in orangutans, perhaps with a ligament inserting on the femoral neck instead. Here we perform a dissection-based study of orangutan hip joints, assess the soft tissue and hard tissue correlates of the orangutan LTF, and histologically examination the LTF to evaluate whether it is homologous to that found in other hominoids. MATERIALS AND METHODS: The hip joints from six orangutans were dissected. In the two orangutans with an LTF passing to the femoral head, the LTF was assessed histologically. Skeletonized femora (n=56) in osteological repositories were examined for evidence of a foveal pit. RESULTS: We observed an LTF in two of the three infant orangutans but not in the sub-adult or adult specimens. Histological examination of the infant LTF shows a distinct artery coursing through the LTF to the head of the femur. One percent of orangutan femora present with a foveal scar, but no pit, on the femoral head. DISCUSSION: Despite being absent in adults, the LTF is present in at least some orangutans during infancy. We suggest that the LTF maintains a role in blood supply to the femoral head early in life. Because the LTF can limit hip mobility, this may explain why the LTF may be lost as an orangutan ages and gains locomotor independence. These findings enhance our understanding of orangutan hip morphology and underscore the need for future soft tissue investigations.

Re-evaluating the diets of Morotopithecus bishopi and Afropithecus turkanensis: An anterior dentognathic perspective.

Afropithecus turkanensis (17-17.5 Ma; Kalodirr, Buluk, Locherangan, Moruorot, Nabwal Hills; Kenya) and Morotopithecus bishopi (20.6 Ma; Moroto II; Uganda) are both large-bodied catarrhines from the early Miocene of eastern Africa with relatively primitive cranial and postcanine dental morphology. They are primarily differentiated by a temporal separation of ∼3.6 million years and by postcranial samples suggesting that M. bishopi was capable of orthograde postures and below-branch arboreality, while A. turkanensis was most likely a pronograde quadruped. Several researchers dispute the validity of the postcranial and dating evidence and argue that M. bishopi and A. turkanensis may be congeneric or even conspecific. Although A. turkanensis possesses a derived suite of specialized anterior dentognathic characters that are functionally convergent with extant pitheciins and associated with sclerocarp foraging and maxillary canine dietary function, a similar analysis of M. bishopi anterior dentognathic anatomy is presently lacking. The current study addresses this shortcoming via a detailed morphometric analysis of relevant A. turkanensis and M. bishopi specimens preserving the anterior palate, maxillary canines and incisors. Results indicate that the anterior dentognathic morphologies of A. turkanensis and M. bishopi are distinct and represent significantly dissimilar feeding adaptations. Specifically, M. bishopi lacks the elongated and anteriorly narrow premaxilla, lateral incisors that are more posterior and mesially positioned relative to the central incisors, and pronounced yet evenly distributed mesial curvature of the maxillary canine that are shared by A. turkanensis and extant pitheciins. Given that A. turkanensis anterior dentognathic morphology is functionally convergent with extant pitheciins to the exclusion of M. bishopi, it is likely that M. bishopi and A. turkanensis have dissimilar feeding adaptations. Although a systematic analysis is required to verify these species at the generic and species level, the absence of any substantial morphological similarity in their anterior dentognathic anatomy is most consistent with the interpretation that M. bishopi and A. turkanensis represent, at the least, different species.

Posterior interosseous nerve localization within the proximal forearm - a patient normalized parameter.

AIM: To provide a "patient-normalized" parameter in the proximal forearm. METHODS: Sixty-three cadaveric upper extremities from thirty-five cadavers were studied. A muscle splitting approach was utilized to locate the posterior interosseous nerve (PIN) at the point where it emerges from beneath the supinator. The supinator was carefully incised to expose the midpoint length of the nerve as it passes into the forearm while preserving the associated fascial connections, thereby preserving the relationship of the nerve with the muscle. We measured the transepicondylar distance (TED), PIN distance in the forearm's neutral rotation position, pronation position, supination position, and the nerve width. Two individuals performed measurements using a digital caliper with inter-observer and intra-observer blinding. The results were analyzed with the Wilcoxon-Mann-Whitney test for paired samples. RESULTS: In pronation, the PIN was within two confidence intervals of 1.0 TED in 95% of cases (range 0.7-1.3 TED); in neutral, within two confidence intervals of 0.84 TED in 95% of cases (range 0.5-1.1 TED); in supination, within two confidence intervals of 0.72 TED in 95% of cases (range 0.5-0.9 TED). The mean PIN distance from the lateral epicondyle was 100% of TED in a pronated forearm, 84% in neutral, and 72% in supination. Predictive accuracy was highest in supination; in all cases the majority of specimens (90.47%-95.23%) are within 2 cm of the forearm position-specific percentage of TED. When comparing right to left sides for TEDs with the signed Wilcoxon-Mann-Whitney test for paired samples as well as a significance test (with normal distribution), the P-value was 0.0357 (significance - 0.05) indicating a significant difference between the two sides. CONCLUSION: This "patient normalized" parameter localizes the PIN crossing a line drawn between the lateral epicondyle and the radial styloid. Accurate PIN localization will aid in diagnosis, injections, and surgical approaches.

Dietary correlates associated with the mental foramen in primates: implications for interpreting the fossil record.

The mandibular nerve is a sensory and motor nerve that innervates the muscles of mastication, the lower dentition, and the lower lip and surrounding structures. Although this nerve contains both efferent and afferent fibers, the mental nerve, a terminal branch of the mandibular nerve, is a strictly sensory nerve that exits the mental foramen and innervates the lower lip, the skin overlaying the mandible, and the oral mucosa around the mandible. Osteological foramina are often used as proxies for nerve cross section area and they often correlate well with some aspect of a primate's ecology (e.g., optic foramen and visual acuity). The primary objective of this study is to explore the correlation between the mental foramen and dietary preference among primates. The mental foramen of 40 primate species (n = 180) was measured from 3-D surface models of the mandible. Both conventional and phylogenetic tests indicate that although frugivores have larger mental foramina than folivores, the differences were not significant. These results show that while structures like the infraorbital foramen correlate well with diet and touch sensitivity, the mental foramen does not. Based on these findings, the mental foramen is not a suggested morphological character for interpreting of the fossil record. J. Morphol. 277:978-985, 2016. © 2016 Wiley Periodicals, Inc.

The hand of Homo naledi.

A nearly complete right hand of an adult hominin was recovered from the Rising Star cave system, South Africa. Based on associated hominin material, the bones of this hand are attributed to Homo naledi. This hand reveals a long, robust thumb and derived wrist morphology that is shared with Neandertals and modern humans, and considered adaptive for intensified manual manipulation. However, the finger bones are longer and more curved than in most australopiths, indicating frequent use of the hand during life for strong grasping during locomotor climbing and suspension. These markedly curved digits in combination with an otherwise human-like wrist and palm indicate a significant degree of climbing, despite the derived nature of many aspects of the hand and other regions of the postcranial skeleton in H. naledi.

Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa.

Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.

Neuron-based heredity and human evolution.

It is widely recognized that human evolution has been driven by two systems of heredity: one DNA-based and the other based on the transmission of behaviorally acquired information via nervous system functions. The genetic system is ancient, going back to the appearance of life on Earth. It is responsible for the evolutionary processes described by Darwin. By comparison, the nervous system is relatively newly minted and in its highest form, responsible for ideation and mind-to-mind transmission of information. Here the informational capabilities and functions of the two systems are compared. While employing quite different mechanisms for encoding, storing and transmission of information, both systems perform these generic hereditary functions. Three additional features of neuron-based heredity in humans are identified: the ability to transfer hereditary information to other members of their population, not just progeny; a selection process for the information being transferred; and a profoundly shorter time span for creation and dissemination of survival-enhancing information in a population. The mechanisms underlying neuron-based heredity involve hippocampal neurogenesis and memory and learning processes modifying and creating new neural assemblages changing brain structure and functions. A fundamental process in rewiring brain circuitry is through increased neural activity (use) strengthening and increasing the number of synaptic connections. Decreased activity in circuitry (disuse) leads to loss of synapses. Use and disuse modifying an organ to bring about new modes of living, habits and functions are processes in line with Neolamarckian concepts of evolution (Packard, 1901). Evidence is presented of bipartite evolutionary processes-Darwinian and Neolamarckian-driving human descent from a common ancestor shared with the great apes.

Incisor crown bending strength correlates with diet and incisor curvature in anthropoid primates.

Anthropoid incisors are large relative to the postcanine dentition and function in the preprocessing of food items. Previous analyses of anthropoid incisor allometry and shape demonstrate that incisor morphology is correlated with preferred foods and that more frugivorous anthropoids have larger and more curved incisors. Although the relationship between incisal crown curvature and preferred foods has been well documented in extant and fossil anthropoids, the functional significance of curvature variation has yet to be conclusively established. Given that an increase in crown curvature will increase maximum linear crown dimensions, and bending resistance is a function of linear crown dimensions, it is hypothesized that incisor crown curvature functons to increase incisor crown resistance to bending forces. This study uses beam theory to calculate the mesiodistal and labiolingual bending strengths of the maxillary and mandibular incisors of hominoid and platyrrhine taxa with differing diets and variable degrees of incisal curvature. Results indicate that bending strength correlates with incisal curvature and that frugivores have elevated incisor bending resistance relative to folivores. Maxillary central incisor bending strengths further discriminate platyrrhine and hominoid hard- and soft-object frugivores suggesting this crown is subjected to elevated occlusal loading relative to other incisors. These results are consistent with the hypothesis that incisor crown curvature functions to increase incisor crown resistance to bending forces but does not preclude the possibility that incisor bending strength is a composite function of multiple dentognathic variables including, but not limited to, incisor crown curvature.

Caudal vertebral body articular surface morphology correlates with functional tail use in anthropoid primates.

Prehensile tails, capable of suspending the entire body weight of an animal, have evolved in parallel in New World monkeys (Platyrrhini): once in the Atelinae (Alouatta, Ateles, Brachyteles, Lagothrix), and once in the Cebinae (Cebus, Sapajus). Structurally, the prehensile tails of atelines and cebines share morphological features that distinguish them from nonprehensile tails, including longer proximal tail regions, well-developed hemal processes, robust caudal vertebrae resistant to higher torsional and bending stresses, and caudal musculature capable of producing higher contractile forces. The functional significance of shape variation in the articular surfaces of caudal vertebral bodies, however, is relatively less well understood. Given that tail use differs considerably among prehensile and nonprehensile anthropoids, it is reasonable to predict that caudal vertebral body articular surface area and shape will respond to use-specific patterns of mechanical loading. We examine the potential for intervertebral articular surface contour curvature and relative surface area to discriminate between prehensile-tailed and nonprehensile-tailed platyrrhines and cercopithecoids. The proximal and distal intervertebral articular surfaces of the first (Ca1), transitional and longest caudal vertebrae were examined for individuals representing 10 anthropoid taxa with differential patterns of tail-use. Study results reveal significant morphological differences consistent with the functional demands of unique patterns of tail use for all vertebral elements sampled. Prehensile-tailed platyrrhines that more frequently use their tails in suspension (atelines) had significantly larger and more convex intervertebral articular surfaces than all nonprehensile-tailed anthropoids examined here, although the intervertebral articular surface contour curvatures of large, terrestrial cercopithecoids (i.e., Papio sp.) converge on the ateline condition. Prehensile-tailed platyrrhines that more often use their tails in tripodal bracing postures (cebines) are morphologically intermediate between atelines and nonprehensile tailed anthropoids.

The interpretive power of infraorbital foramen area in making dietary inferences in extant apes.

The infraorbital foramen (IOF) is located below the orbit and transmits the sensory infraorbital nerve (ION) to mechanoreceptors located throughout the maxillary region. The size of the IOF correlates with the size of the ION; thus, the IOF appears to indicate relative touch sensitivity of maxillary region. In primates, IOF size correlates well with diet. Frugivores have relatively larger IOFs than folivores or insectivores because fruit handling/processing requires increased touch sensitivity. However, it is unknown if the IOF can be used to detect subtle dietary differences among closely related hominoid species. Hominoids are traditionally grouped into broad dietary categories, despite the fact that hominoid diets are remarkably diverse. This study examines whether relative IOF size is capable of differentiating among the dietary preferences of closely related species with overlapping, yet divergent diets. We measured IOF area in Hylobates lar, Symphalangus syndactulus, Pongo pygmaeus spp., Pan troglodytes, Gorilla gorilla, Gorilla beringei graueri, and Gorilla beringei beringei. We classified each species as a dedicated folivore, mixed folivore/frugivore, soft object frugivore, or hard object frugivore. The IOF is documented to be larger in more frugivorous species and smaller in more folivorous taxa. Interestingly, G.b. beringei, had the largest relative IOF of any gorilla, despite being a dedicated folivore. G.b. beringei does have unique food processing behavior that relies heavily on maxillary mechanoreception, thus this finding is not entirely unsupported behaviorally. The results of this study provide evidence that the IOF is an informative feature in interpretations of fossil apes.

New evidence for diet and niche partitioning in Rudapithecus and Anapithecus from Rudabánya, Hungary.

Rudabánya is rare among Eurasian Miocene fossil primate localities in preserving both a hominid and pliopithecoid, and as such provides the unique opportunity to reconstruct the nature of sympatry and niche partitioning in these taxa. Rudapithecus and Anapithecus have similar locomotor and positional behavior and overlapping body mass ranges. While prior analyses of molar occlusal anatomy and microwear identify Rudapithecus as a soft-object frugivore, reconstructing the dietary behavior of Anapithecus has been more problematic. This taxon has been interpreted to be more folivorous by some, and more frugivorous by others. Here, we use high-resolution polynomial curve fitting (HR-PCF) to quantify and evaluate the mesiodistal and cervico-incisal curvatures of the incisor crowns of Rudapithecus and Anapithecus to identify diet-specific morphological variation in these taxa. Results are consistent with the interpretation that Anapithecus and Rudapithecus were primarily frugivorous and had diets that included similar resource types. However, Anapithecus may have consumed greater amounts of foliage, similar to extant mixed folivore-frugivores (i.e., Gorilla gorilla gorilla, Symphalangus syndactylus), while Rudapithecus generated elevated compressive loads in the incisor region consistent with a specialized role for the anterior dentition in food processing (i.e., removal of tough protective fruit pericarps). We interpret these findings in light of the paleoecology at Rudabánya and conclude that, if these taxa were indeed sympatric, Anapithecus may have used additional leaf consumption as a seasonal fallback resource to avoid direct competition with Rudapithecus. Conversely, Rudapithecus may have relied on less preferred and harder fruiting resources as a seasonal fallback resource during periods of fruit scarcity.

Clavicle morphometry revisited: a 3-dimensional study with relevance to operative fixation.

BACKGROUND: The advocacy for operative fixation of midshaft clavicle fractures has prompted a reemergence of interest in clavicle anatomy. Three-dimensional (3D) anatomical studies provide more information than 2-dimensional studies, but are currently rare. MATERIAL AND METHODS: Twenty-five skeletonized clavicles were digitized using a laser scanner. Three-dimensional computer software was used to analyze the data. Clavicles were divided into medial, middle, and lateral segments based on the medial and lateral apices of curvature and their lengths and midpoint cortical diameter measured. The angles of medial and lateral curvatures were measured in standardized axial and coronal planes. The medial and lateral curvatures were fitted with circles and the radii of curvature measured. Correlations between the intrinsic dimensions of the clavicle were assessed. RESULTS: The mean length was 136.7 mm. The medial, middle, and lateral segments had mean lengths of 48, 56, and 32.7 mm, respectively. In the axial plane, the mean medial and lateral angles were 149.5° and 145.8°, respectively. In the coronal plane, the mean medial and lateral angles were 178.2° and 174.2°, respectively. The mean midpoint cortical diameter was 10.9 mm. The mean medial and lateral radii of curvature were 66.4 and 33.5 mm, respectively. The length and cortical diameter and length and medial radius of curvature were found to positively correlate, R(2) = .355 and .184, respectively. CONCLUSION: Using standardized measurements, we were able to accurately characterize the dimensions of the clavicle. We found that the length of the clavicle correlates with the midpoint cortical diameter and with the radius of medial curvature.

New evidence for canine dietary function in Afropithecus turkanensis.

Despite considerable post-cranial and cranial morphological overlap with Proconsul, Afropithecus turkanensis is distinguished from that taxon by a suite of anterior dental and gnathic characters shared in common with extant pitheciin monkeys (i.e. low crowned, robust and laterally splayed canines, procumbent incisors, prognathic premaxilla, powerful temporalis muscles, reduced or absent maxillary sinuses, and deep mandibular corpora). Pitheciins are unique among living anthropoids because their canines serve a habitual dietary function and are not strictly influenced by inter-male competition. Given the functional association between pitheciin canine morphological specializations and sclerocarp foraging, a feeding strategy where the hard pericarps of unripe fruit are mechanically deformed by the canines, it has been suggested that Afropithecus may also have used its canines in a dietary context. This is confirmed by quantitative morphometric analyses of Afropithecus canine curvature and basal dimensions demonstrating that Afropithecus and extant pitheciins (Chiropotes, Cacajao) are distinguished from all other anthropoids by pronounced and evenly distributed mesial canine crown contours as well as greater resistance to canine bending in both the mesiodistal and labiolingual axes. In addition, Afropithecus, Chiropotes and Cacajao are also shown to have significantly longer and more curved premaxillae with greater incisor procumbency that effectively isolates the incisor and canine functional complexes. These morphological similarities are a result of convergence and not a shared derived ancestry. Despite their considerable morphological overlap, it is unlikely that Afropithecus and extant pitheciin diets are identical given significant dissimilarities in their post-canine morphology, maximum angular gape and body size. Nevertheless, Afropithecus canine dietary function is unique among hominoids and may have been a key component for the expansion of hominoids into Eurasia at the end of the early Miocene.

Clavicle anatomy and the applicability of intramedullary midshaft fracture fixation.

BACKGROUND: This study investigated the morphologic safety and applicability of intramedullary fixation of midshaft clavicle fractures by analyzing the pertinent clavicle anatomy using 3-dimensional computer simulation. MATERIALS AND METHODS: Computed tomography was used to scan 22 skeletonized clavicles. Computer software was used to simulate middle-segment fracture fixation by fitting a cylindrical corridor within the clavicle in the area that intramedullary devices normally cross during surgery. The cylindrical corridor crossed the fracture line on both sides, and the number of cortical diameters that were bypassed was recorded. We assumed that 1 to 2 cortical diameters had to be bypassed to achieve adequate fixation. The medial and lateral exit points of the cylindrical corridor were measured and described in relation to the sternoclavicular and acromioclavicular ends respectively. RESULTS: Simulation revealed that 15 of 22 clavicles could be bypassed by 2 cortical diameters on either side of the midline fracture, 6 clavicles could be bypassed by 1 cortical diameter medial to the fracture line, and 1 clavicle could not be bypassed by any cortical diameters medial to the fracture line. The medial exit point of the cylindrical corridor was anterior in 20 of 22 cases and an average of 44.2 mm lateral to the sternoclavicular end. The lateral exit point of the cylindrical corridor was posterosuperior in 16 of 22 cases and an average of 26.5 mm medial to the acromioclavicular end. CONCLUSION: In most clavicles, straight intramedullary fixation appears to be a morphologically safe and effective method of fixation.

Mechanoreceptivity of prehensile tail skin varies between ateline and cebine primates.

Prehensile tails evolved independently twice in primates: once in the ateline subfamily of platyrrhine primates and once in the genus Cebus. Structurally, the prehensile tails of atelines and Cebus share morphological features distinguishing them from nonprehensile tails (e.g., robust and strong caudal vertebrae, well developed lateral tail musculature, etc.). However, because of their independent evolutionary histories, the prehensile tails of atelines exhibit some differences from the Cebus prehensile tail. Ateline tails are relatively longer than those of Cebus, and they have less well-developed extensor compartment musculature. However, perhaps the most obvious difference is the distinctive hairless friction pad on the ventrodistal surface of the ateline tail; the tail of Cebus is completely covered in hair. This study documents the presence of four epicritic histologic mechanoreceptors in the friction pad of atelines: Meissner's corpuscles, Pacinian corpuscles, Ruffini corpuscles, and Merkel discs. Ruffini corpuscles and Merkel cells were also identified in the ventrodistal skin of the Cebus tail. However, Meissner's and Pacinian corpuscles (not typically associated with hairy skin) were not found in Cebus. Cebus was also compared to its closest living sister taxon, nonprehensile-tailed Saimiri, in which genus only Ruffini corpuscles are observed (no Merkel discs). The differences in mechanoreceptor type and morphology are attributed to the contrasting behavioral and tactile demands of the tail as it is used in posture and locomotion, which also distinguishes atelines from Cebus.

Early Miocene catarrhine dietary behaviour: the influence of the Red Queen Effect on incisor shape and curvature.

The early Miocene catarrhine fossil record of East Africa represents a diverse and extensive adaptive radiation. It is well accepted that these taxa encompass a dietary range similar to extant hominoids, in addition to some potentially novel dietary behaviour. There have been numerous attempts to infer diet for these taxa from patterns of dental allometry and incisor and molar microwear, however, morphometric analyses until now have been restricted to the post-canine dentition. It has already been demonstrated that given the key functional role of the incisors in pre-processing food items prior to mastication, there is a positive correlation between diet and incisal curvature (Deane, A.S., Kremer, E.P., Begun, D.R., 2005. A new approach to quantifying anatomical curvatures using High Resolution Polynomial Curve Fitting (HR-PCF). Am. J. Phys. Anthropol. 128(3), 630-638.; Deane, A.S., 2007. Inferring dietary behaviour for Miocene hominoids: A high-resolution morphometric approach to incisal crown curvature. Ph.D. Dissertation. The University of Toronto.). This study seeks to re-examine existing dietary hypotheses for large-bodied early Miocene fossil catarrhines by contrasting the incisal curvature for these taxa with comparative models derived from prior studies of the correlation between extant hominoid incisor curvature and feeding behaviour. Incisor curvature was quantified for 78 fossil incisors representing seven genera, and the results confirm that early Miocene fossil catarrhines represent a dietary continuum ranging from more folivorous (i.e., Rangwapithecus) to more frugivorous (i.e., Proconsul) diets, as well as novel dietary behaviours that are potentially similar to extant ceboids (i.e., Afropithecus). Additionally, early Miocene fossil catarrhine incisors are less curved than extant hominoid incisors, indicating a general pattern of increasing mesio-distal and labial curvature through time. This pattern of morphological shifting is consistent with the Red Queen Effect (Van Valen, L., 1973. A new evolutionary law. Evol. Theory 1, 1-30), which predicts that taxa that are removed from one another by geological time, although potentially having similar diets, may exhibit differing degrees of a similar dietary adaptation (i.e., differing degrees of incisal curvature).

Broken fingers: retesting locomotor hypotheses for fossil hominoids using fragmentary proximal phalanges and high-resolution polynomial curve fitting (HR-PCF).

Phalangeal curvature has frequently been used as a proxy indicator of fossil hominoid and hominin positional behavior and locomotor adaptations, both independently and within the context of broader discussions of the postcranium as a whole. This study used high-resolution polynomial curve fitting (HR-PCF) to measure the shaft curvature of fragmentary proximal phalanges that have previously been excluded from analyses of phalangeal curvature owing to design limitations of existing methods. In doing so, the available sample of fossil specimens was increased substantially, making it possible to test prevailing locomotor hypotheses for many taxa with new specimens. The results generated from the HR-PCF analysis of extant primate manual and pedal phalangeal samples suggest that, although capable of identifying suspensory hominoids with some degree of accuracy, phalangeal curvature values reported for extant terrestrial and arboreal quadrupeds overlap considerably. Consequently, it is difficult to reliably predict the locomotor adaptations for fossil taxa with phalangeal curvatures similar to these groups, although the curvature values reported for most taxa were broadly consistent with existing locomotor hypotheses. Only the curvature values reported for Pierolapithecus, which are most similar to those of suspensory hominoids, are inconsistent with previously published locomotor hypotheses. Likewise, although not inconsistent with bipedality, curvature values reported for Australopithecus confirm earlier conclusions that, despite a general reduction in phalangeal length relative to Pan, these taxa have similar and overlapping ranges of phalangeal curvature.

Temporal squama shape in fossil hominins: relationships to cranial shape and a determination of character polarity.

In 1943, Weidenreich described the squamosal suture of Homo erectus as long, low, and simian in character and suggested that this morphology was dependent upon the correlation between the size of the calvarium and the face. Many researchers now consider this character to be diagnostic of H. erectus. The relationship between cranial size and shape and temporal squama morphology, however, is unclear, and several authors have called for detailed measurements of squamosal variation to be collected before any conclusions are drawn regarding the nature of the morphology observed in H. erectus. Thirteen fossil and extant taxa were examined to address two questions: 1) Are size and shape of the temporal squama correlated with cranial vault morphology? and 2) Is the H. erectus condition plesiomorphic? To answer these questions, measurements were collected and indices were calculated for squamosal suture height, length, and area in relation to metric variables describing cranial size and shape. A two-dimensional morphometric study was also completed using High Resolution-Polynomial Curve Fitting (HR-PCF) to investigate correlations between curvature of the squamosal suture and curvature of the cranial vault. Results of both analyses indicate that squamosal suture form is related to cranial size and shape. Furthermore, the plesiomorphic condition of the squamosal suture for hominins was identified as high and moderately arched; this condition is retained in H. erectus and is distinct from the great ape condition. It is suggested that this similarity is the result of increased cranial length without a corresponding increase in cranial height.