Pedal Morphology Research Articles

New information on gorgonopsian pedal morphology based on articulated material from Zambia.

Descriptions detailing the postcranial skeleton of gorgonopsians lag far behind those of the group's cranial anatomy. Indeed, most recent phylogenetic recent work has focused exclusively on cranial features, leaving systematic variation in the rest of the skeleton undocumented. Here I describe the articulated pedes of a small gorgonopsian from the upper Permian upper Madumabisa Mudstone Formation of Zambia's Luangwa Basin. Between the two sides, the pedal phalangeal formula can be confidently reconstructed as 2-3-4-5-4, with one disc-like phalanx present in digits three and five, and two discs present in digit four. The lateralmost distal tarsal is confirmed to be a compound element formed by the fusion of distal tarsals four and five, as evidenced by a groove circumscribing the distolateral corner of the element. Nonetheless, a prominent gap was probably present proximal to metatarsal five. A preliminary review of variation in the relative sizes and orientations of the pedal elements shows the possibility that this anatomical unit could contribute phylogenetically useful data. For example, the presence of a disc-like phalanx in digit five likely represents the retention of the primitive phalangeal formula of the pes compared to its absence in a specimen tentatively referred to the derived rubidgeine gorgonopsian Dinogorgon, but this hypothesis requires testing within a broader phylogenetic context.

Exploring the Ecomorphology of Two Cretaceous Enantiornithines With Unique Pedal Morphology

Recently, ∼100 Ma amber from Myanmar has become an important source of information regarding the morphology of Late Cretaceous enantiornithines. Two specimens consisting of partial hindlimbs exhibit unusual morphologies when compared to both extant avian taxa and other Cretaceous enantiornithines. Pedal morphology is extremely ecologically informative in Aves as it represents the interface between body and substrate. These seemingly bizarre pedal morphologies represent adaptations that allowed these birds to utilize certain niches present in their paleoenvironment. Specific ecological niches apply the same general pressures to different species over time, and in doing so, through natural selection, produce morphologies that function much the same, although they may be anatomically dissimilar. As such, extant animals can provide useful information pertaining to the functional morphology of extinct animals, even in the absence of direct analogs, as in the case of these two Hukawng enantiornithines. Comparisons to extant taxa in the same predicted niches of these enantiornithines can be used to either support or contradict previous hypotheses regarding the in vivo function of these unique pedal morphologies. Elektorornis chenguangi exhibits a hypertrophied third pedal digit, originally interpreted as an appendage used for probing. We support this interpretation, which allows informed speculation as to the cranial anatomy of this taxon since extant animals that probe in woody substrates consistently pair elongate probing structures with a second robust structure that functions as a means to penetrate into this hard substrate. This suggests that the rostrum of Elektorornis would have been robust and most likely edentulous. The second specimen YLSNHM01001 exhibits an unusually mediolaterally robust fourth pedal digit, nearly double the width of digit II. Given that no such morphology is present in any other bird in the Mesozoic or Cenozoic we feel the unusual morphology justifies erection of a new taxon, Fortipesavis prehendens gen. et sp. nov. Although distinct, the morphology in F. prehendens resembles the syndactyl condition in some extant avian groups, and we hypothesize the robust digit similarly functioned to increase the surface area of the foot, facilitating grip on perches through increased friction. The necessity for increased grip and the lateral placement of this digit may suggest F. prehendens utilized mobile perches similar to extant kingfishers.

A new basal ornithuromorph bird (Aves: Ornithothoraces) from the Early Cretaceous of China with implication for morphology of early Ornithuromorpha

Ornithuromorpha is the most derived avian group in the Early Cretaceous, advanced members of which encompass all living birds (Neornithes). Here we report on a new basal ornithuromorph bird, Bellulia rectusunguis gen. et sp. nov., represented by a nearly complete skeleton from the Early Cretaceous Jehol Biota in northeastern China. A comprehensive phylogenetic analysis resolved the new taxon in a basal position that is only more derived than Archaeorhynchus and Jianchangornis among ornithuromorphs, increasing the morphological diversity of basal ornithuromorphs. The new specimen has a V-shaped furcula with a short hypocleidium, a feature otherwise known only in Schizooura among Cretaceous ornithuromorphs. We discuss the implications of the new taxon on the evolution of morphology of primitive ornithuromorphs, particularly of pectoral girdle, sternum and limb proportion pertaining to powered flight. The preserved gastroliths and pedal morphology indicate herbivory and lakeshore adaption for this new species. © 2015 The Linnean Society of London

Comment to “Primates in the Eocene” by Gingerich (2012)

In his recent article BPrimates in the Eocene^, Gingerich (2012) presented a broad review of Eocene primate radiations and their place in the primate evolutionary tree, with a particular focus on Adapoidea. While synthetic reviews of early primate evolution are always welcome additions to the literature, within his larger analysis Gingerich (2012) specifically discussed two issues that deserve special comment, the first relating to the evolution of grooming claws within Adapoidea and the second relating to his phylogenetic interpretation of Darwinius and Adapoidea within the order Primates, which was supposedly based on a modification of our own final matrix inMaiolino et al. (2012). Unfortunately, as we will demonstrate below, in both cases the interpretations of Gingerich (2012) are unlikely to be correct. First, Gingerich (2012) characterises the morphology of Notharctus pedal distal phalanges as Bambiguous^. In fact, there is very little ambiguity involved. The analyses provided in Maiolino et al. (2012) demonstrate quite conclusively, both metrically and visually, that pedal distal phalanges bearing grooming claws are readily separated from other unguis forms (ungulae=nails, falculae=non-primate claws, and tegulae= claw-like ungues of callitrichins and aye-ayes) on the basis of facet-shaft angle (FSA), volar feature length (VFL), and other distinctive measures. Univariate and multivariate analyses including FSA and VFL clearly indicate that Notharctus tenebrosus possessed a grooming claw on pedal digit II (Maiolino et al. 2012). To illustrate this point further, a simple bivariate plot of FSA and VFL divided by total phalanx length (TPL) from 512 primate pedal distal phalanges shows the stark distinction between grooming claw and ungula-bearing distal phalanges (Fig. 1). Strepsirrhine and tarsier phalanges that bear grooming claws are well-separated from ungulaand tegula-bearing forms (Fig. 1, dotted line within convex hull surrounding all grooming claws). On the basis of FSA and VFL/TPL, Fig. 1 indicates that Notharctus venticolis (UM 102287), Cantius nuniensis (UM 102193), and Notharctus tenebrosus (AMNH 143612_3 and AMNH 129382) bore grooming claws, confirming the results of Maiolino et al. (2012) for Notharctus tenebrosus and extending them to notharctid pedal morphology, more generally. We note that Gingerich (2012) provides no compelling evidence to the contrary, and the discriminant analyses mentioned by Gingerich (2012) (see also von Koenigswald et al. (2012)) exclude FSA, VFL, VFL/TPL, and other distinctive measures. Until our results are contradicted by a proper study including diagnostic features such as FSA, VFL, and VFL/TPL, the analyses in Maiolino et al. (2012) remain the most comprehensive performed thus far and strongly Electronic supplementary material The online version of this article (doi:10.1007/s12549-015-0184-1) contains supplementary material, which is available to authorized users.

Use of an ungulate‐specific feed structure as a potential tool for controlling feral goats in Australian forest ecosystems

SummaryThe feral Goat (Capra hircus) has successfully exploited a range of landscapes around the world with occurrences of overabundance resulting in significant damage to ecological values. In forested ecosystems in Australia, there are currently limited means to control the species when compared to the range of management techniques available for other pest animals. To redress this deficiency, we designed a feed structure combined with commercially available salt blocks to attract goats to set locations in a forested study area. Structures that exploited differences in the pedal morphology (foot size and shape) of native herbivores (kangaroos and wallabies) and ungulates (feral goats and deer) were found to be highly target‐specific, with feral goats freely able to access salt blocks, whilst nontarget native species were effectively excluded. Other introduced ungulate species, Fallow Deer (Dama dama) and Red Deer (Cervus elaphus), successfully accessed salt blocks in feed structures but at a considerably lower rate than feral goats. The capacity to present a range of bait types within a target‐specific feed structure, once matched with a humane toxicant, could provide land managers with an additional cost‐effective lethal control tool for future management of feral ungulates, particularly goats.

Pedal Proportions of Poposaurus gracilis: Convergence and Divergence in the Feet of Archosaurs

The crocodile-line basal suchian Poposaurus gracilis had body proportions suggesting that it was an erect, bipedal form like many dinosaurs, prompting questions of whether its pedal proportions, and the shape of its footprint, would likewise "mimic" those of bipedal dinosaurs. We addressed these questions through a comparison of phalangeal, digital, and metatarsal proportions of Poposaurus with those of extinct and extant crocodile-line archosaurs, obligate or facultatively bipedal non-avian dinosaurs, and ground birds of several clades, as well as a comparison of the footprint reconstructed from the foot skeleton of Poposaurus with known early Mesozoic archosaurian ichnotaxa. Bivariate and multivariate analyses of phalangeal and digital dimensions showed numerous instances of convergence in pedal morphology among disparate archosaurian clades. Overall, the foot of Poposaurus is indeed more like that of bipedal dinosaurs than other archosaur groups, but is not exactly like the foot of any particular bipedal dinosaur clade. Poposaurus likely had a digitigrade stance, and its footprint shape could have resembled grallatorid ichnotaxa, unless digit I of the foot of Poposaurus commonly left an impression.

Manus Track Preservation Bias as a Key Factor for Assessing Trackmaker Identity and Quadrupedalism in Basal Ornithopods

BackgroundThe Las Cerradicas site (Tithonian–Berriasian), Teruel, Spain, preserves at least seventeen dinosaur trackways, some of them formerly attributed to quadrupedal ornithopods, sauropods and theropods. The exposure of new track evidence allows a more detailed interpretation of the controversial tridactyl trackways as well as the modes of locomotion and taxonomic affinities of the trackmakers.Methodology/Principal FindingsDetailed stratigraphic analysis reveals four different levels where footprints have been preserved in different modes. Within the tridactyl trackways, manus tracks are mainly present in a specific horizon relative to surface tracks. The presence of manus tracks is interpreted as evidence of an ornithopod trackmaker. Cross-sections produced from photogrammetric digital models show different depths of the pes and manus, suggesting covariance in loading between the forelimbs and the hindlimbs.Conclusions/SignificanceSeveral features (digital pads, length/width ratio, claw marks) of some ornithopod pes tracks from Las Cerradicas are reminiscent of theropod pedal morphology. This morphological convergence, combined with the shallow nature of the manus tracks, which reduces preservation potential, opens a new window into the interpretation of these tridactyl tracks. Thus, trackmaker assignations during the Jurassic–Cretaceous interval of purported theropod trackways may potentially represent ornithopods. Moreover, the Las Cerradicas trackways are further evidence for quadrupedalism among some basal small- to medium-sized ornithopods from this time interval.

Martharaptor greenriverensis, a New Theropod Dinosaur from the Lower Cretaceous of Utah

BackgroundThe Yellow Cat Member of the Cedar Mountain Formation (Early Cretaceous, Barremian?) of Utah has yielded a rich dinosaur fauna, including the basal therizinosauroid theropod Falcarius utahensis at its base. Recent excavation uncovered a new possible therizinosauroid taxon from a higher stratigraphic level in the Cedar Mountain Formation than F. utahensis.Methodology/Principal FindingsHere we describe a fragmentary skeleton of the new theropod and perform a phylogenetic analysis to determine its phylogenetic position. The skeleton includes fragments of vertebrae, a scapula, forelimb and hindlimb bones, and an ischium. It also includes several well-preserved manual unguals. Manual and pedal morphology show that the specimen is distinct from other theropods from the Cedar Mountain Formation and from previously described therizinosauroids. It is here named as the holotype of a new genus and species, Martharaptor greenriverensis. Phylogenetic analysis places M. greenriverensis within Therizinosauroidea as the sister taxon to Alxasaurus + Therizinosauridae, although support for this placement is weak.Conclusions/SignificanceThe new specimen adds to the known dinosaurian fauna of the Yellow Cat Member of the Cedar Mountain Formation. If the phylogenetic placement is correct, it also adds to the known diversity of Therizinosauroidea.

The Jinniushan hominin pedal skeleton from the late Middle Pleistocene of China

Bipedalism has long been recognized as the seminal adaptation of the hominin radiation and thus used to distinguish hominins from great ape fossils. Notwithstanding preconceptions and varied interpretations, the distinctive features of the modern human foot and accompanying striding gait, appear to be recent innovations that are largely absent in the earliest facultative bipeds. These distinctive features are mainly components of fixed longitudinal and transverse pedal arches, and of a uniquely derived hallucal metatarsophalangeal joint. They enhance ankle joint plantar flexor function and accommodate localized peak plantar pressures at the medial ball during terminal stance. To date, the paleontological record has yielded very little of the hominin foot, especially of the Middle Pleistocene hominins. New specimens from this time interval should help provide insights into the timing and pattern of what appears to be a mosaic pattern of evolution of the modern human foot features. Here we describe the fossil hominin foot skeleton recovered from the Jinniushan site, Liaoning Province, People's Republic of China. It affords a singular glimpse of the pedal morphology of a late Middle Pleistocene hominin (c.f. Homo heidlebergensis). Dated to 200 ka or older, this foot offers the earliest evidence for increased stability of the medial longitudinal arch, while retaining a number of primitive features apparently characteristic of robust premodern hominins, including lower arches and a less stable hallucal metatarsophalangeal joint (medial ball) than in modern humans. These features reflect different foot capabilities and suggest the bipedal stride of the Jinniushan hominin differed subtlety from that of modern humans.

The ‘Goldilocks’ effect: preservation bias in vertebrate track assemblages

Finite-element analysis was used to investigate the extent of bias in the ichnological fossil record attributable to body mass. Virtual tracks were simulated for four dinosaur taxa of different sizes (Struthiomimus, Tyrannosaurus, Brachiosaurus and Edmontosaurus), in a range of substrate conditions. Outlines of autopodia were generated based upon osteology and published soft-tissue reconstructions. Loads were applied vertically to the feet equivalent to the weight of the animal, and distributed accordingly to fore- and hindlimbs where relevant. Ideal, semi-infinite elastic-plastic substrates displayed a 'Goldilocks' quality where only a narrow range of loads could produce tracks, given that small animals failed to indent the substrate, and larger animals would be unable to traverse the area without becoming mired. If a firm subsurface layer is assumed, a more complete assemblage is possible, though there is a strong bias towards larger, heavier animals. The depths of fossil tracks within an assemblage may indicate thicknesses of mechanically distinct substrate layers at the time of track formation, even when the lithified strata appear compositionally homogeneous. This work increases the effectiveness of using vertebrate tracks as palaeoenvironmental indicators in terms of inferring substrate conditions at the time of track formation. Additionally, simulated undertracks are examined, and it is shown that complex deformation beneath the foot may not be indicative of limb kinematics as has been previously interpreted, but instead ridges and undulations at the base of a track may be a function of sediment displacement vectors and pedal morphology.

The Olduvai Hominid 8 foot: Adult or subadult?

Olduvai Hominid 8 (OH 8), an articulating set of fossil hominin tarsal and metatarsal bones, is critical to interpretations of the evolution of hominin pedal morphology and bipedal locomotion. It has been suggested that OH 8 may represent the foot of a subadult and may be associated with the OH 7 mandible, the type specimen of Homo habilis. This assertion is based on the presence of what may be unfused distal metatarsal epiphyses. Accurately assessing the skeletal maturity of the OH 8 foot is important for interpretations of the functional morphology and locomotor behavior of Plio-Pleistocene hominins. In this study, we compare metatarsal fusion patterns and internal bone morphology of the lateral metatarsals among subadult hominines (85 modern humans, 48 Pan, and 25 Gorilla) to assess the likelihood that OH 8 belonged to either an adult or subadult hominin. Our results suggest that if OH 8 is indeed from a subadult, then it displays a metatarsal developmental pattern that is unobserved in our comparative sample. In OH 8, the fully fused base of the first metatarsal and the presence of trabecular bone at the distal ends of the second and third metatarsal shafts make it highly improbable that it belonged to a subadult, let alone a subadult that matches the developmental age of the OH 7 mandible. In total, the results of this study suggest that the OH 8 foot most likely belonged to an adult hominin.

What does modern human variation in MT1 abduction angle and arch height reveal about hominid pedal morphology?

Although modern humans exhibit many different morphologies, anthropological wisdom dictates that an effective bipedal foot is one with an adducted first metatarsal (MT) and medial longitudinal arch (MLA). The recently announced pedal morphology of Ardipithecus calls into question this assumption, prompting the question of what variation among modern human feet might reveal about the function of extinct hominid feet.Using anterior‐posterior and lateral radiographs of 50 osteological adults (aged 15–78 years, 25 women), arch height and the angle between MTs (MT12, MT23, MT34, MT45, MT15) were measured. MT12 of STW 575 and MT angles of OH 8 were measured on photographs/drawings of reconstructions.In the modern sample, MT12 ranged from 3–15° (mean = 9°, σ = 3°) and feet with more abducted 1st MT tended to have more abducted 5th MT (p = 0.051) and higher arches (p=0.018). MT12 measured 20° on STW 575 and 10° on OH 8.For MT12, STW 575 is > 3σ from the human mean, while OH 8 exhibits the human mean value. If the fossil reconstructions are accurate representations of weight‐bearing position, then the 1st MT of STW 575 was more abducted than is typically seen in modern humans, but what, if any, functional consequences accrue from this difference are less clear. As with other morphological features, effective bipedal feet can come in many forms.

The position of the claws in Noasauridae (Dinosauria: Abelisauroidea) and its implications for abelisauroid manus evolution

In this note we reassess the position of putative pedal phalanges of some South American noasaurid theropods (Abelisauroidea). Noasaurids were considered as to be distinctive abelisauroids with a peculiar “sickle claw” on the second toe of the foot, convergently developed with that of deinonychosaurians. Among noasaurids, the Argentinean species Noasaurus leali (latest Cretaceous) and Ligabueino andesi (Early Cretaceous) are known from incomplete specimens, including dissarticulated non-ungueal phalanges, and, in N. leali, a claw. A detailed overview of these elements indicates that the supposed raptorial claw of the second pedal digit of N. leali actually belongs to the first or second finger of the manus, and the putative pedal non-ungual phalanges of both genera also pertain to the manus. Thus, the new interpretations of noasaurid pedal morphology blur the distinctions between Noasauridae and Velocisauridae proposed by previous authors. Finally, we suggest, on the basis of phalangeal and metacarpal morphology, that abelisaurids probably lost their manual claws by means of the loss of function of the HOXA11 and HOXD11 genes. Thus Noasauridae differs from Abelisauridae in retaining plesiomorphic long forelimbs with well developed claws, as occurs plesiomorphically in most basal theropods (e.g., Coelophysis).

An articulated titanosaur from Patagonia (Argentina): New evidence of neosauropod pedal evolution

Most titanosaur dinosaurs are represented by incomplete skeletal elements lacking articulated pes. An exceptionally preserved specimen from the Late Campanian–Early Maastrichtian strata of Patagonia (Argentina) provides new data on pedal morphology and the evolutionary trends of these huge dinosaurs. This finding is one of the few articulated titanosaur pes known in the world, and shows a phalangeal formula of 2-2-2-2-0. The first three digits possess sickle-shaped claws and the articular facets of ungual phalanges, suggesting mobility in horizontal and vertical planes. A comparative analysis of available record suggests that titanosaurs had a progressive reduction of size and number of pedal phalanges in digits III and IV during the Late Cretaceous.

Morphological changes in pedal phalanges through ornithopod dinosaur evolution: A biomechanical approach

The evolution of ornithopod dinosaurs provides a well-documented example of the transition from digitigrady to subunguligrady. During this transition, the ornithopod pes was drastically altered from the plesiomorphic dinosaurian morphology (four digits, claw-shaped unguals, strongly concavo-convex joints, phalanges longer than wide, excavated collateral ligament fossae, presence of sagittal ridge, and prominent processes for the attachment of tendons) to a more derived condition (tridactyly, modification of the unguals into hooves, phalanges wider and thinner than long, lack of collateral ligament fossae, loss of sagittal ridge and tendon attachment processes, relatively flattened articular surfaces). These changes are particularly noteworthy given the overall conservatism in pedal morphology seen across Dinosauria. But what are the functional consequences of these specific morphological transitions? To study them, we examine a wide range of pedal morphologies in four non-avian dinosaurs and two birds. Our analyses of the external morphology, two-dimensional models (using Finite Element Analysis), and internal bone structure demonstrate that this evolutionary shift was accompanied by a loss of digit mobility and flexibility. In addition, pedal posture was modified to better align the pes with the main direction of the ground reaction force, thus becoming well suited to support high loads. These conclusions can be applied to other, parallel evolutionary changes (in both dinosaurs and mammals) that involved similar transitions to a subunguligrade posture.

New skeletal remains of Omomys(Primates, Omomyidae): functional morphology of the hindlimb and locomotor behavior of a Middle Eocene primate

New associated craniodental and postcranial remains of Omomys carteri from Bridger C beds in Uinta County, Wyoming represent the largest and most nearly complete single taxon sample of omomyid postcranial fossils presently known. They allow, for the first time, a description and detailed analysis of the functional morphology of the hindlimb of this middle Eocene omomyine primate. Comparisons of pelvic, femoral, tibial, and pedal morphology and metrics with a large sample of prosimian primates of known locomotor behavior suggest that Omomys possessed a highly distinctive mosaic of functional adaptations related to active quadrupedalism and leaping. Traits suggestive of quadrupedalism include the lengths of the ischium and ilium, position of the femoral trochanters, and lengths and features of the tarsal bones. Morphological traits that suggest leaping include a semi-cylindrical femoral head with moderate posterior expansion of the articular surface, greater trochanter projecting anterior to the femoral shaft, deeper than wide femoral condyles, narrow and deep patellar groove with prominent lateral border, elongated calcaneus, and close aposition of distal tibia and fibula. While Omomys most closely resembles active quadrupedal cheirogaleids like Cheirogaleus and Mirza, leaping must have been an important component of its locomotor repertoire. In this respect, Omomys closely resembles other North American omomyines (notablyHemiacodon ), and is significantly more generalized postcranially than European microchoerines (e.g.,Microchoerus , Nannopithex, and Necrolemur).

The contribution of anaerobic energy to gastropod crawling and a re-estimation of minimum cost of transport in the abalone, Haliotis kamtschatkana (Jonas)

The contribution of anaerobic metabolism to the minimum cost of transport (COT min; energy required to transport a unit mass over a unit distance, excluding maintenance and postural costs) was determined for the abalone Haliotis kamtschatkana. Abalone were induced to crawl in water for 6 m at speeds up to 9.9 shell lengths·min −1. Changes in the concentrations of the anaerobic metabolites tauropine, d-lactate, arginine phosphate, and arginine occurred in foot muscle, but only at speeds at or above five shell lengths·min −1. These metabolites did not change significantly in the shell adductor muscle. The amount of anaerobically derived ATP used during crawling was calculated and the values were compared with data for aerobic ATP production. Anaerobic metabolism accounted for 54% of COT min, and the aerobic COT min estimated by Donovan and Carefoot (1997) [Donovan, D.A., Carefoot, T.H., 1997. Locomotion in the abalone Haliotis kamtschatkana: pedal morphology and cost of transport. J. Exp. Biol. 200, 1145–1153] was thus adjusted from 20.3 J·kg −1 m −1 to 44.1 J·kg −1 m −1. This new value places abalone above the regression line of log 10COT min on log 10mass for running vertebrates, indicating that transport costs for abalone are more expensive than for the average similar-sized runner. The contribution of anaerobic metabolism was also determined for prolonged air exposure and whole animal righting behavior to allow comparisons to be made with other abalone species for which these data, but not data on anaerobic metabolism during crawling, were available in the literature. On this basis, we suggest that in comparison to H. kamtschatkana, Haliotis lamellosa and Haliotis iris may have lower aerobic scopes during crawling, while that of Haliotis asinina may be considerably higher.

Does archosaur phylogeny hinge on the ankle joint?

ABSTRACT Cladistic phylogenies of the archosaur ingroup are reviewed in light of recent concerns regarding an over-dependence on characters relating to tarsal and pedal morphology. The use of simple statistical techniques shows that the exclusion of ankle characters from recent cladistic phylogenies has no significant effect on the relative support of relationships proposed. Contrary to current opinion, ankle characters should be considered unimportant when attempting to reconstruct the broad shape of archosaur phylogeny.

Swift and sure-footed on the Savanna: A study of Hadzabe gaits and feet in Northern Tanzania.

Data on footprints and gait of 54 Hadzabe, 6-70 years of age expand understanding of pedal morphology of unshod people and assist the development of ideas about the evolution of hominid bipedality and upright posture. Contrary to published data on gaits and pedal morphology of unshod populations, Hadzabe (also known as Hadza) from northern Tanzania exhibit values of stride length, relative stride length, and walking speeds that exceed those of rural and small-town populations. In all observable plantar features, including foot indices, an interdigital space between the hallux and second toe, fanning of the foot anteriorly, and foot angles (in-toeing and out-toeing), Hadzabe feet are comparable with those of never-shod Machiguengas in Perú. On average, Hadzabe hallucal gaps and ball widths are narrower than those of Machiguengas and other unshod short people. Hadzabe feet are also characterized by valgus halluces versus the varus halluces of never-shod Machiguengas and certain West Africans. Although characterized by a valgus toe, Hadzabe hallucal angles, which do not exceed 20°, are lower than those of Northern Hemispheric urbanites and shod rural populations of the Southern and Northern Hemispheres. Hadzabe also exhibit less medial and lateral rotation of the hip joint than Machiguengas do. The heel and the longitudinal arch impressions of the Hadzabe footprints closely resemble those of the Laetoli bipeds in the manner of weight distribution during locomotion. The striking similarity of footprint impressions, especially the heel and the longitudinal arch, between Hadzabe and Laetoli hominid footprints clearly imply that the pedal features of the Laetoli printmakers are remarkably humanoid. Am. J. Hum. Biol. 9:303-321, 1997. © 1997 Wiley-Liss, Inc.

Four-toed theropod footprints and a paleomagnetic age from the Whetstone Falls Member of the Harebell Formation (Upper Cretaceous: Maastrichtian), northwestern Wyoming

The Harebell Formation is a syntectonic sequence of conglomeratic sediments deposited in a narrow, rapidly subsiding trough that formed in the latest Cretaceous along the eastern margin of the ancestral uplift of what are today the Teton and Gros Ventre Mountains of northwestern Wyoming. On at least two occasions subsidence temporarily exceeded the rate of sediment supply and the area was flooded by a brackish or marine incursion from the Western Interior Seaway that lay to the east. The age of the Harebell Formation is Maastrichtian, corroborated by 4 0K/ 4 0Ar isotopic ages, vertebrate and palynomorph biostratigraphy, and a preliminary magnetostratigraphic analysis which correlates it to the geomagnetic reversal time scale from the upper part of C31R to the base of C30N. Sandstone slabs collected from the lower Whetstone Falls Member contain nine partial and complete footprints attributable to a theropod (Dinosauria: Saurischia). The footprints were formed as surface tracks in the tabular-bedded sandstone by dinosaurs that roamed the burrowed and leaf-littered sand flats and shallow waters along the margins of a low-energy, brackish-water embayment. Eight of the nine footprints represent a hitherto unknown ichnogenus, representing a four-toed pedal morphology for a theropod dinosaur which is unprecedented in the Late Cretaceous. The theropod nature of the tracks is implied by the length and narrowness of the digits and the sharp claw impressions. The tracks have clearly defined impressions of four toes, none of which appears to be a hallux in the traditional theropod sense of a small, retroverted hallux. The metapodial impression is also unlike that of other known theropod tracks: greater in relief than the digits but quite small in area. The tracks represent at least two individuals, although no clear trackways are available. Exallopus lovei, gen. et sp. nov., represents a type of theropod not currently recognized from body fossils.