Burrowing in frogs

More than 95% of burrowing Anura dig hindfeet first into the soil, a pattern unique to frogs among terrestrial vertebrates. The postero-laterally placed hindlimbs and associated musculature of frogs are preadaptations for hindfeet digging. One fossorial, backwards burrower, Glyphoglossus molossus (Microhylidae), has morphological modifications of the hindlimb for positioning the spade-like metatarsal tubercle and for increasing the force of the lower leg during digging. In contrast, in the headfirst burrower Hemisus marmoratus (Ranidae) there is extensive reorganization of the pectoral-cranial morphology compared to that: of a non-burrowing confamilial species. A model links the shifts in the pectoral morphology in Hemisus marmoratus to specific action patterns of headfirst: burrowing. Finally, data on stomach contents, natural history and energy utilization of frog species are presented to demonstrate the interrelationships of distinct loco. motor patterns with specific feeding strategies.     

Metatarsophalangeal joint function and positional behavior in Australopithecus afarensis

Recent discussions of the pedal morphology of Australopithecus afarensis have led to conflicting interpretations of australopithecine locomotor behavior. We report the results of a study using computer aided design (CAD) software that provides a quantitative assessment of the functional morphology of australopithecine metatarsophalangeal joints. The sample includes A. afarensis, Homo sapiens, Pan troglodytes, Gorilla gorilla, and Pongo pygmaeus. Angular measurements of the articular surfaces relative to the long axes of the metatarsals and phalanges were taken to determine whether the articular surfaces are plantarly or dorsally oriented. Humans have the most dorsally oriented articular surfaces of the proximal pedal phalanges. This trait appears to be functionally associated with dorsiflexion during bipedal stride. Pongo has the most plantarly oriented articular surfaces of the proximal pedal phalanges, probably reflecting an emphasis on plantarflexion in arboreal positional behaviors, while the African hominoids are intermediate between Pongo and Homo for this characteristic. A. afarensis falls midway between the African apes and humans. Results from an analysis of metatarsal heads are inconclusive with regard to the functional morphology of A. afarensis. Overall, the results are consistent with other evidence indicating that A. afarensis was a capable climber. © 1994 Wiley-Liss, Inc.     

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.     

Growth and maturation of metatarsals and their taxonomic significance in the jerboas Allactaga and Jaculus (Rodentia: Dipodidae)

The development of metatarsals in Allactaga tetradactyla, Jaculus jaculus jaculus and J. orientalis was studied and their taxonomic significance was elucidated. The five metatarsals, as a rule, are developed and ossified in the three species, but variation in the fate of the first and fifth metatarsals was found. Ossification begins in the median part of the metatarsals; however, it appears in the distal part of the digits’ phalanges, beginning with the third phalanx. The first metatarsal appears just distal to the entocuneiform and develops as a small, separate bone located either in close contact with the distal end of the entocuneiform in A. tetradactyla or completely fused with it, forming a compound bone, in both of J. j. jaculus and J. orientalis. The second, third and fourth metatarsals differentiate distal to the mesocuneiform, ectocuneiform and cuboid, respectively, and fuse with one another into a single long cannon bone in all species. Nevertheless, the fifth metatarsal differentiates ventro‐lateral to the head of the fourth metatarsal and ossifies ventral to the head process of the developing cannon bone. The fifth metatarsal either extends to articulate with the phalanges of the fourth digit in A. tetradactyla or persists as a separate, small bone in both of J. j. jaculus and J. orientalis. On this basis, it is concluded that J. jaculus and J. orientalis are both distinct congeneric species and are somewhat more distant from A. tetradactyla.     

Comparative forefoot trabecular bone architecture in extant hominids

The appearance of a forefoot push-off mechanism in the hominin lineage has been difficult to identify, partially because researchers disagree over the use of the external skeletal morphology to differentiate metatarsophalangeal joint functional differences in extant great apes and humans. In this study, we approach the problem by quantifying properties of internal bone architecture that may reflect different loading patterns in metatarsophalangeal joints in humans and great apes. High-resolution x-ray computed tomography data were collected for first and second metatarsal heads of Homo sapiens (n = 26), Pan paniscus (n = 17), Pan troglodytes (n = 19), Gorilla gorilla (n = 16), and Pongo pygmaeus (n = 20). Trabecular bone fabric structure was analyzed in three regions of each metatarsal head. While bone volume fraction did not significantly differentiate human and great ape trabecular bone structure, human metatarsal heads generally show significantly more anisotropic trabecular bone architectures, especially in the dorsal regions compared to the corresponding areas of the great ape metatarsal heads. The differences in anisotropy between humans and great apes support the hypothesis that trabecular architecture in the dorsal regions of the human metatarsals are indicative of a forefoot habitually used for propulsion during gait. This study provides a potential route for predicting forefoot function and gait in fossil hominins from metatarsal head trabecular bone architecture.     

Crouching Theropods in Taxonomic Jungles: Ichnological and Ichnotaxonomic Investigations of Footprints with Metatarsal and Ischial Impressions

Tracks and traces of crouching theropods are rare, known from only three specimens from the Lower Jurassic of New England and the Lower to ?mid Jurassic of China. The New England specimens reveal manus, metatarsal and sub-crescentic ischial callosity impressions associated with Grallator-like tracks. The Chinese traces reveal metatarsal traces and a sub-triangular ischial callosity impression associated with Eubrontes-like tracks. All reveal symmetrical crouching postures. Theropod crouching traces should not be confused with ornithopod crouching traces, often assigned to Anomoepus. The ichnotaxonomy surrounding all these traces and associated footprints is very complex, and over split. Suggestions for simplification allow recognition that the North American and Chinese ichnofaunas have many similarities. The ichnotaxonomy is not as complex and confused as it may at first appear.     

Paleobiological implications of new material of Platybelodon danovi from the Dingjiaergou Fauna,western China

We report on a newly born mandible and an adult pes of Platybelodon danovi from the Dingjiaergou fauna, China. Tooth succession in Platybelodon is very specialised, including a tendency to lose the dp2, an early loss of the di2 perhaps at the foetal stage, a tendency to lose the p3 and a tendency to reduce the P4 and the p4. The pes is also specialised, with metatarsals IV and III nearly equal in length, metatarsal IV less twisted than metatarsal III, metatarsals IV and III more anteroposteriorly compressed and metatarsals aligned nearly at the same level. These findings have important paleobiological significance. First, the relatively derived tooth succession of Platybelodon occurred at a relatively early geological time, thus representing an early evolution of tooth succession independent from other proboscideans. Second, the gravity vector of the hind limb of Platybelodon shifted towards metatarsal IV, and the modified standing posture may imply a lightly built body and rapid locomotion relative to other gomphotheres and elephants. These new paleobiological data add to our knowledge of the life history of Platybelodon and the diverse adaptations of ancient proboscideans.     

New primate hind limb elements from the middle Eocene of China

The continued washing, sorting, and identification of middle Eocene (45 Mya) primates from the Shanghuang fissure-fillings (Jiangsu Province, China) have produced additional hind limb elements. All are isolated elements. The strepsirhine hind limb elements include a first metatarsal and a talus, which are appropriate in size and morphology to pertain to Adapoides troglodytes. Adapoides is interpreted as a quadrupedal-climbing (nonleaping) primate with similarities to living lorises and the fossil primate Adapis. The haplorhine hind limb elements are estimated to span a range of adult body sizes from tiny (17 g) to small (200 g). Included among the new sample of haplorhine hind limb specimens is the smallest primate talus reported thus far. These new postcranial specimens expand our understanding of early haplorhine hind limb anatomy and demonstrate additional similarities between Shanghuang eosimiids and other anthropoids.     

Metatarsal fusion pattern and developmental morphology of the Olduvai Hominid 8 foot: Evidence of adolescence

The morphology of the Olduvai Hominid (OH) 8 foot and the sequence of metatarsal epiphyseal fusion in modern humans and chimpanzees support the hypothesis that OH 8 belonged to an individual of approximately the same relative age as the OH 7 subadult, the holotype of Homo habilis. Modern humans and chimpanzees exhibit a variety of metatarsal epiphyseal fusion patterns, including one identical to that observed in OH 8 in which metatarsal 1 fuses before metatarsals 2-5. More than the metatarsal fusion sequence, however, the principal evidence of the youthful age of OH 8 lies in the morphology of metatarsals 1, 2, and 3. Because both OH 8 and OH 7 come from the same stratum at the FLK NN type site, the most parsimonious explanation of the OH 8 and OH 7 data is that this material belonged to the same individual, as originally proposed by Louis Leakey. The proposition that OH 8 belonged to an adult is unsupported by morphology, including radiographic evidence, and the fusion sequences in human and chimpanzee skeletal material reported here and in the literature.     

A new psittaciform bird from the London Clay (Lower Eocene) of England

A new psittaciform bird from the Lower Eocene (Ypresian) London Clay of England is described. This taxon, Pulchrapollia gracilis gen. et sp. nov., is assigned to the order Psittaciformes (parrots) on the basis of several distinctive structures of the tarsometatarsus, namely the trochlea for metatarsal III (trochlea metatarsi III) bearing a tubercle on its lateral side and the trochlea for metatarsal IV (trochlea metatarsi IV) completely retroverted (fully zygodactyl foot). Comparisons with other fossil and Recent taxa further support this conclusion. Cladistic analysis shows that Pulchrapollia is the sister-taxon of the single extant family within Psittaciformes, the Psittacidae. Palaeopsittacus georgei, a taxon previously described from the London Clay, is most likely based on some unassociated material and is regarded here as incertae sedis.     

Implications of relative robusticity in the Olduvai metatarsus

The relative robusticity of the metatarsals in OH-8 is reviewed in light of the normal variation in metatarsal robusticity in Pan and Homo. The pattern in OH-8 is found to be fully commensurate with a striding gait.     

Locomotor anatomy and biomechanics of the Dmanisi hominins

The Dmanisi hominins inhabited a northern temperate habitat in the southern Caucasus, approximately 1.8 million years ago. This is the oldest population of hominins known outside of Africa. Understanding the set of anatomical and behavioral traits that equipped this population to exploit their seasonal habitat successfully may shed light on the selection pressures shaping early members of the genus Homo and the ecological strategies that permitted the expansion of their range outside of the African subtropics. The abundant stone tools at the site, as well as taphonomic evidence for butchery, suggest that the Dmanisi hominins were active hunters or scavengers. In this study, we examine the locomotor mechanics of the Dmanisi hind limb to test the hypothesis that the inclusion of meat in the diet is associated with an increase in walking and running economy and endurance. Using comparative data from modern humans, chimpanzees, and gorillas, as well as other fossil hominins, we show that the Dmanisi hind limb was functionally similar to modern humans, with a longitudinal plantar arch, increased limb length, and human-like ankle morphology. Other aspects of the foot, specifically metatarsal morphology and tibial torsion, are less derived and similar to earlier hominins. These results are consistent with hypotheses linking hunting and scavenging to improved walking and running performance in early Homo. Primitive retentions in the Dmanisi foot suggest that locomotor evolution continued through the early Pleistocene.     

New pedal remains of Megaladapis and their functional significance

New remains of Megaladapis from the caves within the Ankarana Range of northern Madagascar and the cave site of Ankilitelo near Toliara in southwestern Madagascar add considerably to the present sample of pedal remains for this genus. Here we describe and analyze the new pedal material and discuss the function of the Megaladapis foot in terms of positional behavior and substrate use. The northern specimens belong to the M. madagascariensis/M. grandidieri group in terms of size and morphology, whereas the new southwestern fossils are assigned to M. madagascariensis. The new specimens demonstrate that the small and intermediate sized M. madagascariensis and M. grandidieri were very similar in anatomy and inferred locomotor function, findings that also support the prior suggestion that they belong to a single widespread subgenus (Megaladapis). The new fossils provide the first examples of many pedal elements and present the first opportunity to analyze the whole pedal complex from associated remains. The foot of Megaladapis is distinctive among primates in numerous features. Intrinsic proportions of the hindlimb indicate that the foot is relatively longer than that of any other primate. The first complete calcanei reveal a large and highly modified hindfoot. The calcaneus is reduced distally, indicating an emphasis on climbing over leaping or quadrupedal walking and running. Proximally, a large, medially directed calcaneal tuberosity suggests both a strong inversion component to plantarflexion and a well-developed abductor mechanism and recalls the calcaneal morphology of the larger lorisines in some respects. Talar shape is consistent with considerable tibial rotation during plantarflexion and dorsiflexion. The subtalar joint is designed to emphasize supination/pronation and medial/lateral rotation over proximodistal translation. The distal tarsals are extremely reduced in length, and they form a high transverse arch and a serial tarsus; this configuration promotes inversion/eversion at the transverse tarsal joint. The phalanges are long and moderately curved, and the hallux is very long, robust, and abducted. Pedal morphology suggests that Megaladapis (subgenus Megaladapis) was well adapted to exploit an arboreal environment. The grasping mechanism of Megaladapis is an extreme modification of the prosimian condition, emphasizing a highly inverted set, mobility in rotation, and a powerful abduction/flexion type grasp using large hallux and the lateral abductor musculature. Such a mechanism insures a secure grasp regardless of the position of the hindlimb or the substrate. These pedal design features contrast with the grasping strategy seen in highly arboreal palaeopropithecids (or “sloth lemurs”), a group that reduces and modifies the hindfoot, culminating in Palaeopropithecus, and emphasizes extrinsic digital flexors in a more hook-like mechanism. Much less is known of M. (Peloriadapis) edwardsi. The larger body size, more gorilla-like talar articular morphology, and anatomy of the proximal fifth metatarsal suggest that this species may have been more terrestrial than the smaller forms, but other aspects of pedal morphology suggest it also exploited arboreal habitats.     

Autopodial skeleton evolution in side-necked turtles (Pleurodira)

Carpal and tarsal anatomy was documented based on the observation of dry skeletons of adult specimens representing 25 species in 15 genera and on data taken from the literature. In addition, histological sections and cleared and double‐stained autopodia of recently hatched and juvenile specimens representing seven chelid and pelomedusoid species were studied. There is much more morphological diversity in the manus than in the pes. Variation in autopodial skeletons includes: the astragalus and calcaneum are either separated or fused; fusion of distal carpals 3–4−5 or just 4–5; number of centralia in the carpus; and presence/absence of a pisiform and of an accessory radial element. The widespread and probably basal phalangeal formula for Pleurodira is 2.3.3.3.3. Deviations are Pelomedusa subrufa, exhibiting a reduction to 2.2.2.2.2, Pelusios spp. with one phalanx less in digit I and for one species in digit V as well, and Acanthochelys pallidipectoris with an additional phalanx in the fourth finger. Six discrete characters itemizing some of the morphological variation observed were plotted on a composite pleurodire phylogeny, revealing not only homoplastic patterns but also the utility of some characters in supporting the monophyly of several clades. The pisiform is the last carpal element to ossify in Chelus fimbriatus. We hypothesize that the so‐called fifth hooked metatarsal represents the fusion of distal tarsal 5 with metatarsal V. The accessory radial element that was occasionally present in the turtles examined may represent an atavism of the otherwise lost radiale of turtles.     

Postcranial Morphology of the Extinct Rodent Neoepiblema (Rodentia: Chinchilloidea): Insights Into the Paleobiology of Neoepiblemids

In this paper, we study the postcranial morphology (humerus, ulna, innominate, femur, tibia, astragalus, navicular, and metatarsal III) of Neoepiblema, a giant Late Miocene South American rodent, searching for evidence about its paleobiology based on unpublished specimens from Solimões Formation (Upper Miocene, Brazil). The study includes a morphofunctional analysis of the postcranial bones and a comparison with extant and extinct rodents, especially Phoberomys. The morphofunctional analysis of the postcranial bones suggests that Neoepiblema (as well as Phoberomys) would have a crouched forelimb that was not fully extended, with powerful pectoral and triceps musculature, and able to produce movements of pronation/supination and possibly with a hand able to grasp. The combination of characters of the innominate bone, femur, and tibia indicates a predominance of parasagittal movements and a thigh with powerful musculature used during propulsion. In sum, the analyzed postcranial features are consistent with the limb morphology of ambulatory rodents, but with faculty to dig or swim. The sedimentary evidence of the localities in which fossils of neoepiblemids have been found suggests that these rodents lived in wet and water-related environments (near swamps, lakes, and/or rivers).

Graphical abstract

     

Articular to diaphyseal proportions of human and great ape metatarsals

This study proposes a new way to use metatarsals to identify locomotor behavior of fossil hominins. Metatarsal head articular dimensions and diaphyseal strength in a sample of chimpanzees, gorillas, orangutans, and humans (n = 76) are used to explore the relationships of these parameters with different locomotor modes. Results show that ratios between metatarsal head articular proportions and diaphyseal strength of the hallucal and fifth metatarsal discriminate among extant great apes and humans based on their different locomotor modes. In particular, the hallucal and fifth metatarsal characteristics of humans are functionally related to the different ranges of motion and load patterns during stance phase in the forefoot of humans in bipedal locomotion. This method may be applicable to isolated fossil hominin metatarsals to provide new information relevant to debates regarding the evolution of human bipedal locomotion. The second to fourth metatarsals are not useful in distinguishing among hominoids. Further studies should concentrate on measuring other important qualitative and quantitative differences in the shape of the metatarsal head of hominoids that are not reflected in simple geometric reconstructions of the articulation, and gathering more forefoot kinematic data on great apes to better understand differences in range of motion and loading patterns of the metatarsals. Am J Phys Anthropol 143:198–207, 2010. © 2010 Wiley‐Liss, Inc.     

Ecological associations of autopodial osteology in Neotropical geckos

Coevolution of form and function inspires investigation of associations between morphological variation and the exploitation of specific ecological settings. Such relationships, based mostly on traits of external morphology, have been extensively described for vertebrates, and especially so for squamates. External features are, however, composed by both soft tissues and bones, and these likely play different biomechanical roles during locomotion, such as in the autopodia. Therefore, ecological trends identified on the basis of external morphological measurements may not be directly correlated with equivalent variation in osteology. Here, we investigate how refined parameters of autopodial osteology relate to ecology, by contrasting climbing and nonclimbing geckos. Our first step consisted of inferring how external and osteological morphometric traits coevolved in the group. Our results corroborate the hypothesis of coevolution between external and osteological elements in the autopodia of geckos, and provides evidence for associations between specific osteological traits and preferred locomotor habit. Specifically, nonclimbers exhibit longer ultimate and penultimate phalanges of Digit V in the manus and pes and also a longer fifth metatarsal in comparison with climbers, a pattern discussed here in the context of the differential demands made upon locomotion in specific ecological contexts. Our study highlights the relevance of osteological information for discussing the evolution of ecological associations of the tetrapod autopodium. J. Morphol. 278:290–299, 2017. © 2017 Wiley Periodicals, Inc.     

CAENOGENESIS,DEVELOPMENTAL VARIABILITY,AND EVOLUTION IN THE CARPUS AND TARSUS OF THE MARBLED NEWT TRITURUS MARMORATUS

In this paper, after a comparative analysis of the development of Triturus marmoratus, we explore the existence of caenogenetic events and their ontogenetic and phylogenetic consequences. The adult morphology of the Triturus marmoratus limb, in terms of number and spatial arrangement of skeletal elements, agrees with the general pattern of urodeles. The congruence in the typical pattern of adult morphology does not hint at the striking differences in embryonic development. These differences can be summarized as follows: 1) Presence of a “central axis” that develops in a distal-to-proximal direction. It originates in the basale commune giving rise to the centrale and the intermedium. Thus, there is no postaxial branching as found in Ambystoma mexicanum. 2) Again, unlike in Ambystoma mexicanum, we find a postaxial structure composed of the ulnare (fibulare)-distal carpal (tarsal) 4-metacarpal (metatarsal) 4 which is independent of the “digital arch.” 3) The (forelimb) digits, in particular, digits 1, 2, and 3, undergo disproportionate elongation. For example, the second digit, composed of a thin continuous, cartilaginous rod, becomes longer than the rest of the limb. Our study of the patterns of embryonic connectivity suggests the coexistence of three directions of growth and morphogenesis in the development of the Triturus marmoratus limb. 1) A proximo-distal one that gives rise to the preaxial axis, “primary axis,” and individual digits. 2) An anterio-posterior axis of development that gives rise to the “digital arch” and determines the number of digits. 3) A disto-proximal central axis that originates in the basale commune and sequentially generates the centrale and the intermedium. We speculate that heterochronic interspecific variation in the time of onset of limb bud formation is related to the degree of precocious digital elongation. Selection for long extremities in early larval stages, associated with functional demands for locomotion and balancing, may be the cause for the above listed changes in developmental pattern. Thus, the reported system is an example of how selection during ontogeny can result in the evolution of the developmental process.     

A putative upupiform bird from the Early Oligocene of the Central Western Carpathians and a review of fossil birds unearthed in Slovakia

An isolated hind limb of a miniature bird from an Early Oligocene locality (30–34 Ma) near Bystré (Slovakia) is described and analyzed. The tarsometatarsus (TMT) of the specimen is remarkably short relative to the tibiotarsus. When relative length ratios of the bones are compared with a sample of 29 extant and extinct birds with short metatarsi, the specimen variably clusters with some alcedinids, coraciids and trochilids. Log‐clusters give less ambiguous results and indicate significant proximity of the Bystré specimen to the extinct messelirrisorids (Upupiformes) and the recent acledinids (Coraciiformes). With regard to morphological details, such as those of the first metatarsal, II‐IV metatarsal trochleae, intertrochlear incisurae and phalanges, the Slovak specimen shows a combination of features, which are distributed among recent upupiforms and coraciiforms as well as extinct upupiforms (Messelirrisor) and apodiforms (Eocypselus, Parargornis). Taken together, the metric and morphological data sets suggest that the specimen from Bystré is a coraciiform sensu lato rather than an apodiform bird. Within the Coraciiformes, the robust trochlea of MT‐I with expanded dorsal shelf, the large medial and slit‐like lateral intertrochlear incisura, and the long hindtoe suggest upupiform rather than alcedinid relationships.