Forelimb Anatomy Research Articles

Body mass estimates from postcranial skeletons and implication for positional behavior in Nacholapithecus kerioi: Evolutionary scenarios of modern apes.

This study reported the body mass (BM) estimates of the Middle Miocene fossil hominoid Nacholapithecus kerioi from Africa. The average BM estimates from all forelimb and hindlimb skeletal elements was 22.7 kg, which is slightly higher than the previously reported estimate of ~22 kg. This study revealed that Nacholapithecus has a unique body proportion with an enlarged forelimb relative to a smaller hindlimb, suggesting an antipronograde posture/locomotion, which may be related to the long clavicle, robust ribs, and some hominoid-like vertebral morphology. Because the BM of Nacholapithecus in this study was estimated to be below 30 kg, Nacholapithecus probably did not have relatively shorter and robust femora, which may result from other mechanical constraints, as seen in extant African hominoids. The BM estimate of Nacholapithecus suggests that full substantial modifications of the trunk and forelimb anatomy for risk avoidance and foraging efficiency, as seen in extant great apes, would not be expected in Nacholapithecus. Because larger monkeys are less arboreal (e.g., Mandrillus sphinx or Papio spp.), and the maximum BM among extant constant arboreal cercopithecoids is ~24 kg (male Nasalis larvatus), Nacholapithecus would be a constant arboreal primate. Although caution should be applied because of targeting only males in this study, arboreal quadrupedalism with upright posture and occasional antipronograde locomotion (e.g., climbing, chambering, descending, arm-swing, and sway) using the powerful grasping capacity of the hand and foot may be assumed for positional behavior of Nacholapithecus.

Reconstruction of the pectoral girdle and forelimb musculature of Megaraptora (Dinosauria: Theropoda).

Megaraptora is a group of enigmatic, carnivorous non-avian theropod dinosaurs from the Cretaceous of Asia, Australia, and especially South America. Perhaps the most striking aspect of megaraptoran morphology is the large, robustly constructed forelimb that, in derived members of the clade, terminates in a greatly enlarged manus with hypertrophied, raptorial unguals on the medialmost two digits and a substantially smaller ungual on digit III. The unique forelimb anatomy of megaraptorans was presumably associated with distinctive functional specializations; nevertheless, its paleobiological significance has not been extensively explored. Here we draw from observations of the pectoral girdle and forelimb skeletons of Megaraptora and myological assessments of other archosaurian taxa to provide a comprehensive reconstruction of the musculature of this anatomical region in these singular theropods. Many muscle attachment sites on megaraptoran forelimb bones are remarkably well developed, which in turn suggests that the muscles themselves were functionally significant and important to the paleobiology of these theropods. Furthermore, many of these attachments became increasingly pronounced through megaraptoran evolutionary history, being substantially better developed in derived taxa such as Australovenator wintonensis and especially Megaraptor namunhuaiquii than in early branching forms such as Fukuiraptor kitadaniensis. When considered alongside previous range of motion hypotheses for Australovenator, our results indicate that megaraptorans possessed a morphologically and functionally specialized forelimb that was capable of complex movements. Notable among these were extensive extension and flexion, particularly in the highly derived manus, as well as enhanced humeral protraction, attributes that very probably aided in prey capture.

Functional Adaptations in the Forelimb of the Snow Leopard (Panthera uncia).

The snow leopard (Panthera uncia) is anatomically and physiologically adapted for life in the rocky terrain of alpine zones in Central and South Asia. Panthera uncia is scansorial, and typically hunts solitarily by using overhead ambush of prey, rather than the typical stalking pattern of other large pantherines. In this study, we conducted dissections, detailed documentation, and illustrated the forelimb anatomy of two adult P. uncia specimens (1M/1F). Qualitative and quantitative data revealed an intriguing combination of functional adaptations illustrating a balance between the diverse demands of head-first descent, pouncing, climbing across rocky terrain, restraint of large prey, rapid pursuit, and navigating deep snow. In many forelimb proportions, P. uncia is intermediate between the cursorial Acinonyx jubatus (cheetah) and the scansorial forest dwelling Panthera onca (jaguar). Enlarged scapular and pectoral musculature provide stability to the shoulder girdle during grappling with large prey, as well as support during jumping and climbing. A small, unarticulated bony clavicle may provide greater stability to the forelimb, while still allowing flexibility. In the brachium and antebrachium of P. uncia, there is a functional compromise between the powerful grip needed for grasping large prey and the stability necessary for rapid pursuit of prey over uneven, rocky terrain. A unique bifurcation in the tendon of m. biceps brachii may provide additional functional stability at the radiohumeral joint. Intrinsic muscles of the palmar manus are broad and fleshy, acting as an enlarged surface area to evenly distribute body weight while walking on soft snow. However, muscles that act to provide fine manual manipulation are reduced, as in other large prey specialists. Overall, P. uncia displays morphological adaptive parallels with scansorial, large prey specializing pantherines, such as P. onca, while also showing adaptations for running.

4D formation of human embryonic forelimb musculature.

ABSTRACTThe size, shape and insertion sites of muscles enable them to carry out their precise functions in moving and supporting the skeleton. Although forelimb anatomy is well described, much less is known about the embryonic events that ensure individual muscles reach their mature form. A description of human forelimb muscle development is needed to understand the events that control normal muscle formation and to identify what events are disrupted in congenital abnormalities in which muscles fail to form normally. We provide a new, 4D anatomical characterisation of the developing human upper limb muscles between Carnegie stages 18 and 22 using optical projection tomography. We show that muscles develop in a progressive wave, from proximal to distal and from superficial to deep. We show that some muscle bundles undergo splitting events to form individual muscles, whereas others translocate to reach their correct position within the forelimb. Finally, we show that palmaris longus fails to form from early in development. Our study reveals the timings of, and suggests mechanisms for, crucial events that enable nascent muscle bundles to reach their mature form and position within the human forelimb.

How moles walk; it's all thumbs.

A recurring theme in the evolution of tetrapods is the shift from sprawling posture with laterally orientated limbs to erect posture with the limbs extending below the body. However, in order to invade particular locomotor niches, some tetrapods secondarily evolved a sprawled posture. This includes moles, some of the most specialized digging tetrapods. Although their forelimb anatomy and posture facilitates burrowing, moles also walk long distances to forage for and transport food. Here, we use X-ray Reconstruction Of Moving Morphology (XROMM) to determine if the mole humerus rotates around its long axis during walking, as it does when moles burrow and echidnas walk, or alternatively protracts and retracts at the shoulder in the horizontal plane as seen in sprawling reptiles. Our results reject both hypotheses and demonstrate that forelimb kinematics during mole walking are unusual among those described for tetrapods. The humerus is retracted and protracted in the parasagittal plane above, rather than below the shoulder joint and the 'false thumb', a sesamoid bone (os falciforme), supports body weight during the stance phase, which is relatively short. Our findings broaden our understanding of the diversity of tetrapod limb posture and locomotor evolution, demonstrate the importance of X-ray-based techniques for revealing hidden kinematics and highlight the importance of examining locomotor function at the level of individual joint mobility.

Evolution of Hindlimb Muscle Anatomy Across the Tetrapod Water-to-Land Transition, Including Comparisons With Forelimb Anatomy.

Tetrapod limbs are a key innovation implicated in the evolutionary success of the clade. Although musculoskeletal evolution of the pectoral appendage across the fins-to-limbs transition is fairly well documented, that of the pelvic appendage is much less so. The skeletal elements of the pelvic appendage in some tetrapodomorph fish and the earliest tetrapods are relatively smaller and/or qualitatively less similar to those of crown tetrapods than those of the pectoral appendage. However, comparative and developmental works have suggested that the musculature of the tetrapod forelimb and hindlimb was initially very similar, constituting a "similarity bottleneck" at the fins-to-limbs transition. Here, we used extant phylogenetic bracketing and phylogenetic character optimization to reconstruct pelvic appendicular muscle anatomy in several key taxa spanning the fins-to-limbs and water-to-land transitions. Our results support the hypothesis that transformation of the pelvic appendages from fin-like to limb-like lagged behind that of the pectoral appendages. Compared to similar reconstructions of the pectoral appendages, the pelvic appendages of the earliest tetrapods had fewer muscles, particularly in the distal limb (shank). In addition, our results suggest that the first tetrapods had a greater number of muscle-muscle topological correspondences between the pectoral and pelvic appendages than tetrapodomorph fish had. However, ancestral crown-group tetrapods appear to have had an even greater number of similar muscles (both in terms of number and as a percentage of the total number of muscles), indicating that the main topological similarity bottleneck between the paired appendages may have occurred at the origin of the tetrapod crown group. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 303:218-234, 2020. © 2018 American Association for Anatomy.

Clawed forelimbs allow northern seals to eat like their ancient ancestors.

Streamlined flippers are often considered the defining feature of seals and sea lions, whose very name ‘pinniped’ comes from the Latin pinna and pedis, meaning ‘fin-footed’. Yet not all pinniped limbs are alike. Whereas otariids (fur seals and sea lions) possess stiff streamlined forelimb flippers, phocine seals (northern true seals) have retained a webbed yet mobile paw bearing sharp claws. Here, we show that captive and wild phocines routinely use these claws to secure prey during processing, enabling seals to tear large fish by stretching them between their teeth and forelimbs. ‘Hold and tear’ processing relies on the primitive forelimb anatomy displayed by phocines, which is also found in the early fossil pinniped Enaliarctos. Phocine forelimb anatomy and behaviour therefore provide a glimpse into how the earliest seals likely fed, and indicate what behaviours may have assisted pinnipeds along their journey from terrestrial to aquatic feeding.

Cryptoprocta spelea (Carnivora: Eupleridae): What Did It Eat and How Do We Know?

The extent to which Madagascar’s Holocene extinct lemurs fell victim to nonhuman predators is poorly understood. Madagascar’s Holocene predator guild included several now-extinct species, i.e., crocodiles, carnivorans, and raptors. Here we focus on mammalian carnivory, specifically the roles of Cryptoprocta spelea and its still-extant but smaller-bodied sister taxon, C. ferox, the fosa. Cryptoprocta spelea was the largest carnivoran on Madagascar during the Quaternary. We ask whether some extinct lemurs exceeded the upper prey-size limits of C. spelea. We use univariate and multivariate phylogenetic generalized least squares regression models to re-evaluate the likely body mass of C. spelea. Next, we compare characteristics of the forelimb bones of C. ferox and C. spelea to those of other stealth predators specializing on small, mixed, and large-bodied prey. Finally, we examine humeri, femora, crania, and mandibles of extinct lemurs from six sites in four ecoregions of Madagascar to identify damage likely made by predators. We test the relative prevalence of carnivory by mammals, raptors, and crocodiles at different sites and ecoregions. Our data reveal that crocodiles, raptors, and the largest of Madagascar’s mammalian predators, C. spelea, all preyed on large lemurs. Cryptoprocta opportunistically consumed lemurs weighing up to ~85 kg. Its forelimb anatomy would have facilitated predation on large-bodied prey. Social hunting may have also enhanced the ability of C. spelea to capture large, arboreal primates. Cryptoprocta carnivory is well represented at cave and riverine sites and less prevalent at lake and marsh sites, where crocodylian predation dominates.

Macroscopic description of thoracic member musculature in Cuniculus paca (Linnaeus, 1766) (Rodentia, Cuniculidae)

http://dx.doi.org/10.5007/2175-7925.2017v30n2p43A paca (Cuniculus paca) é um animal que pertence ao Filo Chordata, Classe Mammalia e Família Cuniculidae. A grande demanda pela carne desse animal levou à sua domesticação e ao desenvolvimento de criatórios na região Amazônica e em outros estados do país. Apesar do crescente consumo da carne de paca, o conhecimento sobre a musculatura ainda é escasso. A descrição anatômica dos membros torácicos da paca dará subsidio para futuros estudos zootécnicos e veterinários, possibilitando o desenvolvimento amazônico concomitante à preservação da espécie. Para o presente estudo, foram utilizadas quatro pacas adultas, provenientes do Projeto Caboclinho da Fazenda Experimental Catuaba/UFAC, sob a autorização IBAMA n°509309, fixadas em solução de formol a 10%. Após dissecação do membro torácico dos animais, foi realizada a descrição anatômica com o subsequente registro fotográfico. Os músculos descritos do membro torácico são semelhantes a outros grupos de animais domésticos, quanto à origem e à inserção muscular.

Forelimb anatomy and the discrimination of the predatory behavior of carnivorous mammals: the thylacine as a case study.

Carnivorous mammals use their forelimbs in different ways to capture their prey. Most terrestrial carnivores have some cursorial (running) adaptations, but ambush predators retain considerable flexibility in their forelimb movement, important for grappling with their prey. In contrast, predators that rely on pursuit to run down their prey have sacrificed some of this flexibility for locomotor efficiency, in the greater restriction of the forelimb motion to the parasagittal plane. In this article, we measured aspects of the forelimb anatomy (44 linear measurements) in 36 species of carnivorous mammals of known predatory behavior, and used multivariate analyses to investigate how well the forelimb anatomy reflects the predatory mode (ambush, pursuit, or pounce-pursuit). A prime intention of this study was to establish morphological correlates of behavior that could then be applied to fossil mammals: for this purpose, five individuals of the recently extinct thylacine (Thylacinus cynocephalus) were also included as unknowns. We show that the three different types of predators can be distinguished by their morphology, both in analyses where all the forelimb bones are included together, and in the separate analyses of each bone individually. Of particular interest is the ability to distinguish between the two types of more cursorial predators, pursuit and pounce-pursuit, which have previously been considered as primarily size-based categories. Despite a prior consideration of the thylacine as a "pounce-pursuit" or an "ambush" type of predator, the thylacines did not consistently cluster with any type of predatory carnivores in our analyses. Rather, the thylacines appeared to be more generalized in their morphology than any of the extant carnivores. The absence of a large diversity of large carnivorous mammals in Australia, past and present, may explain the thylacine's generalized morphology.

Analyis of the forelimb of Felis catus in comparison to Smilodon fatalis

Much is known about the anatomy of the domestic cat, and this species is studied extensively as a model of structure and function in anatomy laboratories. Nevertheless, knowledge of the smaller muscles remains unpublished. Musculoskeletal studies of living species permit identification of the corresponding features of extinct animals. This comparative anatomical method was used to expand what is presently known about the forelimb muscles of the saber‐tooth cat Smilodon fatalis. Comparing the forelimb anatomy of the domestic cat to the saber‐tooth was necessary to understand the habits, movement patterns, and hunting strategies of the extinct species. S. fatalis, a dirk‐toothed cat that lived during the Pleistocene, was a deadly ambush predator. This sabercat had a heavy muscular build, making it more powerful when compared with many other cats. Complete, accurate muscle maps have not been published for domestic cats or other felids. The muscle maps of Felis catus that were drawn in this study have proven beneficial for comparison with the extinct saber‐tooth. Using information from the muscle maps created for the domestic cat as a means of comparing relative sizes of muscle scars to the same regions of the corresponding bones of S. fatalis allowed creation of muscle maps for this saber tooth. These maps show that the musculature of F. catus and S. fatalis differ in relative proportions and movement patterns.Grant Funding Source : Undergraduate

Functional Anatomy of the Forelimb Muscles of the Ocelot (Leopardus pardalis)

The myology of most members of the cat family (Felidae) is poorly documented. This study describes the forelimb myology of the ocelot (Leopardus pardalis) and compares the forelimb anatomy of the ocelot to that of other well-documented felids (Felis catus, Panthera leo). A substantial number of myological features vary among the three species and are distributed in a manner consistent with major ecomorphological variables (prey size preference and locomotor repertoire). The origin of m. triceps brachii caput longum is most extensive in Panthera leo, consistent with the fact that this species pursues prey over greater distances compared to F. catus or L. pardalis. In addition, the origins and insertions of the pronator and supinator musculature are reduced in Felis catus, which has little need to supinate during locomotion or prey capture. Furthermore, muscles serving the digits are best developed in the lion and ocelot, both of which make greater use of the forelimb for grasping and manipulation than does the domestic cat. However, while the lion probably retains the primitive morphology for the family, the ocelot shows evidence of secondary adaptation to increased mobility of the digits. Overall, results indicate that additional studies of felid forelimb myology are warranted, as they are likely to provide valuable functional insights.

Functional Anatomy and Adaptation of Male Gorillas (Gorilla gorilla gorilla) With Comparison to Male Orangutans (Pongo pygmaeus)

Great apes diversified during the Miocene in Old World forests. Two lineages, gorillas in Africa and orangutans in Asia, have sexual dimorphisms of super-sized males, though they presumably diverged from a smaller common ancestor. We test the hypothesis that they increased in body mass independently and convergently, and that their many postcranial differences reflect locomotor differences. Whole body dissections of five adult male gorillas and four adult male orangutans allowed quantification of body mass distribution to limb segments, of body composition (muscle, bone, skin, and fat relative to total body mass), and of muscle distribution and proportions. Results demonstrate that gorilla forelimb anatomy accommodates shoulder joint mobility for vertical climbing and reaching while maintaining joint stability during quadrupedal locomotion. The heavily muscled hind limbs are equipped for propulsion and weight-bearing over relatively stable substrates on the forest floor. In contrast, orangutan forelimb length, muscle mass, and joint construction are modified for strength and mobility in climbing, bridging, and traveling over flexible supports through the forest canopy. Muscles of hip, knee, and ankle joints provide rotational and prehensile strength essential for moving on unstable and discontinuous branches. We conclude that anatomical similarities are due to common ancestry and that differences in postcranial anatomy reflect powerful selection for divergent locomotor adaptations. These data further support the evolutionary conclusion that gorillas fall with chimpanzees and humans as part of the African hominoid radiation; orangutans are a specialized outlier.

A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora)

Therizinosaurians are among the most poorly understood dinosaurs. Their unusual morphology and fragmentary fossil record has precluded a synthetic understanding of the group since their remains were first discovered over 60 years ago. Although the clade was recently substantiated as a monophyletic group of maniraptoran theropods, little foundational work has been conducted at the species level. A recent plethora of therizinosaurian discoveries – including the most complete primitive and derived members recovered to date – permits an alpha taxonomic and phylogenetic re-evaluation of the clade. The phylogenetic analysis presented is the most comprehensive yet conducted for Therizinosauria, and provides a foundation for scrutinizing previous definitions of Therizinosauria, Therizinosauroidea and Therizinosauridae. Here, support is provided for the maintenance of all three taxa; however, Therizinosauria is redefined and Falcarius is excluded from Therizinosauroidea. In addition, the previously described therizinosauroids, Beipiaosaurus, Enigmosaurus, Suzhousaurus, Segnosaurus and Therizinosaurus, are rediagnosed and photodocumented. In contrast to other analyses, the ingroup topology recovered in this study suggests intermediate (therizinosauroid) status for Neimongosaurus, Erliansaurus and Enigmosaurus (based on relatively primitive pelvic morphology), despite the derived forelimb anatomy evident in the former two taxa. Here, the large-bodied taxa Nothronychus and Nanshiungosaurus brevispinus are recovered as therizinosaurids. This discrepancy indicates a relatively complex pattern of mosaic evolution, which may ultimately be found to correlate with body-size trends in the clade. This work also reviews the chronostratigraphic and biogeographic distribution of therizinosaurian taxa and putatively referred elements and finds no compelling evidence of the clade outside of Asia and North America, nor for the referral of therizinosaurian materials from Kazakhstan to cf. Neimongosaurus. Time calibration of ingroup relationships indicates a pre-Turonian dispersal event is needed to account for the presence of therizinosaurids in the Late Cretaceous of North America and Asia; this conclusion supports previous hypotheses of a Laurasian faunal interchange event during the Albian.

Functional morphology of cercopithecoid primate metacarpals

The primate fossil record suggests that terrestriality was more common in the past than it is today, particularly among cercopithecoid primates. Whether or not a fossil primate habitually preferred terrestrial substrates has typically been inferred from its forelimb anatomy. Because extant large-bodied terrestrial cercopithecine monkeys utilize digitigrade hand postures during locomotion, being able to identify if a fossil primate habitually adopted digitigrade postures would be particularly revealing of terrestriality in this group. This paper examines the functional morphology of metacarpals in order to identify osteological correlates of digitigrade versus palmigrade hand postures. Linear measurements were obtained from 324 individuals belonging to digitigrade and palmigrade cercopithecoid species and comparisons were made between hand posture groups. Digitigrade taxa have shorter metacarpals, relative to both body mass and humerus length, than palmigrade taxa. Also, digitigrade taxa tend to have metacarpals with smaller dorsoventral diameters, relative to the product of body mass and metacarpal length, compared to palmigrade taxa. The size and shape of the metacarpal heads do not significantly differ between hand posture groups. Multivariate analyses suggest that metacarpal shape can only weakly discriminate between hand posture groups. In general, while there are some morphological differences in the metacarpals between hand posture groups, similarities also exist that are likely related to the fact that even digitigrade cercopithecoids can adopt palmigrade hand postures in different situations (e.g., terrestrial running, arboreal locomotion), and/or that the functional demands of different hand postures are not reflected in all aspects of metacarpal morphology. Therefore, the lack of identifiable adaptations for specific hand postures in extant cercopithecoids makes it difficult to determine a preference for specific habitats from fossil primate hand bones.

A reevaluation of the manus structure in Triceratops (Ceratopsia: Ceratopsidae)

ABSTRACT A Triceratops, NSM PV 20379, excavated from the Upper Cretaceous Hell Creek Formation, Bowman County, North Dakota, USA, confirms the articulation of the right forearm. Detailed study of the forelimb anatomy presented here indicates the manus is in a semi-supinated orientation. This reconstruction is based upon the following morphology: the row of the metacarpals was arranged in an ‘L’-shape in proximal view, as is the distal articular surface of the forearm is in articulation; the second digit is directed parallel to the rotational plane of the elbow joint, reinforced by neighboring digits I and III, and these three inner digits are articulated with the broad articular surface of the radius. Arrangement and directions of robust inner digits seem to be suitably arranged for a powerful stroke exerted by the elbow joint extension. Cerapods, including ceratopsians and ornithopods, share following morphology of the manus: long and robust metacarpals II and III, ungual phalanges on digits I to III, reduced digits IV and V, and a divergent metacarpal V. A laterally oriented manus with reduced outer digits is present in the basal bipedal group of the Cerapoda. Although reversal to a quadrupedal stance and a evolution to a large, heavy body occurred independently in many lineages of Cerapoda, the basic features of the manus were retained throughout Neoceratopsia.

Functional anatomy of the gibbon forelimb: adaptations to a brachiating lifestyle

It has been shown that gibbons are able to brachiate with very low mechanical costs. The conversion of muscle activity into smooth, purposeful movement of the limb depends on the morphometry of muscles and their mechanical action on the skeleton. Despite the gibbon's reputation for excellence in brachiation, little information is available regarding either its gross musculoskeletal anatomy or its more detailed muscle-tendon architecture. We provide quantitative anatomical data on the muscle-tendon architecture (muscle mass, physiological cross-sectional area, fascicle length and tendon length) of the forelimb of four gibbon species, collected by detailed dissections of unfixed cadavers. Data are compared between different gibbon species and with similar published data of non-brachiating primates such as macaques, chimpanzees and humans. No quantitative differences are found between the studied gibbon species. Both their forelimb anatomy and muscle dimensions are comparable when normalized to the same body mass. Gibbons have shoulder flexors, extensors, rotator muscles and elbow flexors with a high power or work-generating capacity and their wrist flexors have a high force-generating capacity. Compared with other primates, the elbow flexors of gibbons are particularly powerful, suggesting that these muscles are particularly important for a brachiating lifestyle. Based on this anatomical study, the shoulder flexors, extensors, rotator muscles, elbow flexors and wrist flexors are expected to contribute the most to brachiation.

Forelimb anatomy of the aardvark, Orycteropus afer (Mammalia, Tubulidentata)

Soft tissue anatomy, especially myology, has been largely neglected by systematic biologists reconstructing the phylogeny of Mammalia. This is due to inadequate description and illustration of structures in many mammalian orders, and conflicting or inaccurate terminology in the existing descriptions. While anatomical terminology has been standardized for the domestic animals and their myology is well known, many rare mammals have not been dissected in decades and the available descriptions lack standardization and often compare taxa now known to be genetically unrelated. This leaves systematic biologists unable to verify muscle character states in the exotic mammals whose evolutionary relationships are most controversial. For example, little morphological evidence has been found to support the clade Afrotheria, which unites several mammalian orders thought to be unrelated until the advent of genetic sequencing.Here I present the forelimb anatomy of the aardvark, Orycteropus afer, the one living member of the order Tubulidentata and a member of the clade Afrotheria, based on my dissections of two alcohol‐preserved museum specimens. These dissections are part of a dissertation project to document the limb anatomy of several mammalian orders, particularly the little known smaller afrotheres, for use in systematics research. This research was supported by the Field Museum of Natural History Visiting Scholar Fund.Grant Funding SourceNational Science Foundation

The trouble with flippers: a report on the prevalence of digital anomalies in Cetacea

The forelimbs of cetaceans (whales, dolphins, and porpoises) are unique among mammals as the digits exhibit hyperphalangy, and the entire limb is encased in a soft tissue flipper that functions to generate lift. The typical morphology of cetacean digits has been well documented by detailed anatomical studies. This study however furthers our understanding of cetacean forelimb anatomy by conducting a taxonomically broad survey of cetacean digital anomalies. Forelimb radiographs from museum collections provided the basis upon which we calculated the prevalence and documented the morphology of cetacean digital abnormalities. Results indicated that 11% (n = 255) of toothed whales displayed some type of aberrant ossification: the majority of these cases displayed a fusion of elements within a single digital ray, whereas cases exhibiting branched digits were rare. A small sample of baleen whale radiographs (n = 6) contained the only documented case of baleen whale polydactyly in a specimen of the gray whale (Eschrichtius). Furthermore, some Balaenoptera specimens displayed ossified elements within the interdigital spaces that lacked attachment to the adjacent digits and carpus. In addition, we speculated on the role that several genes may have played in creating cetacean digital anomalies. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155, 722‐735.

Primitive Early Eocene bat from Wyoming and the evolution of flight and echolocation

Bats (Chiroptera) represent one of the largest and most diverse radiations of mammals, accounting for one-fifth of extant species. Although recent studies unambiguously support bat monophyly and consensus is rapidly emerging about evolutionary relationships among extant lineages, the fossil record of bats extends over 50 million years, and early evolution of the group remains poorly understood. Here we describe a new bat from the Early Eocene Green River Formation of Wyoming, USA, with features that are more primitive than seen in any previously known bat. The evolutionary pathways that led to flapping flight and echolocation in bats have been in dispute, and until now fossils have been of limited use in documenting transitions involved in this marked change in lifestyle. Phylogenetically informed comparisons of the new taxon with other bats and non-flying mammals reveal that critical morphological and functional changes evolved incrementally. Forelimb anatomy indicates that the new bat was capable of powered flight like other Eocene bats, but ear morphology suggests that it lacked their echolocation abilities, supporting a 'flight first' hypothesis for chiropteran evolution. The shape of the wings suggests that an undulating gliding-fluttering flight style may be primitive for bats, and the presence of a long calcar indicates that a broad tail membrane evolved early in Chiroptera, probably functioning as an additional airfoil rather than as a prey-capture device. Limb proportions and retention of claws on all digits indicate that the new bat may have been an agile climber that employed quadrupedal locomotion and under-branch hanging behaviour.