Content uploaded by Xiaoming Wang
Author content
All content in this area was uploaded by Xiaoming Wang on Oct 22, 2014
Content may be subject to copyright.
A preview of the PDF is not available
Transformation from plantigrady to digitigrady: Functional morphology of locomotion in Hesperocyon (Canidae: Carnivora)
Abstract
The most primitive canid Hesperocyon from the late Eocene to early Oligocene (Duchesnean to Whitneyan) of North America possesses a combination of both cursorial and noncursoiial limb characteristics. Compared to 'the archaic miacoid carnivorans, Hesperocyon has a number of advanced features suggestive of running adaptations, such as absence of a large teres major process on the scapula, a relatively reduced deltoid crest on .the humerus, elongated and adjoined metapodials, and laterally oriented fovea capitis femoris. On the other hand, Hesperocyon retains some primitive , arboreal characteristics such as a short, broad scapula with long acromion, a stout humerus with a deep bicipital groove and a thin-bladed bra-chioradialis crest, an anteriorly bowed ulna, a sharply angled pelvic floor, a relatively large muscle scar for flexor digitorum longus and caudal tibialis on the tibia, and a short, deep, and hooked distal phalanx suggestive of a retractile claw. This combination of cursorial and noncursorial characters shows that Hesperocyon represents a transitional stage from its arboreal plantigrade ancestors to its cursorial digitigrade descendants. Examination of a series of miacoids and primitive canids (Vulpavus, Miacis, Hesperocyon, Cormo-cyon, Leptocyon, and Tomarctus) reveals that the canid metatarsus did not become erect until the Arikareean Cormocyon and Leptocyon. Increased extension angle of the tibioastragalar joint was achieved through realignment of the plantar tendon groove to be continuous with the astragalar trochlea and elimination of the astragalar foramen. By combining anatomical characters with results of a morphometric analysis, I have concluded that Hesperocyon was plantigrade in posture and probably scansorial in life.
... A dorsal foramen present is often taken as an astragalar canal present, with Muizon et al. (2015) being one of the few studies to differentiate between the presence of the two conditions. Both the dorsal foramen and the flexor groove are traditionally considered traits of plantigrade and pentadactyl mammals, and they are often cited as limiting plantar flexion of the foot (Ameghino 1904;Schaeffer 1947;Szalay 1966;Wang 1993;Shockey and Flynn 2007). However, there is little evidence for either case as well as for what is going through the foramen. ...
... However, there is little evidence for either case as well as for what is going through the foramen. Blood vessels, nerves, ligaments and tendons have been proposed to pass through the foramen (Ameghino 1904(Ameghino , 1905Schaeffer 1947;Szalay 1966;Wang 1993;Shockey and Flynn 2007). Ameghino (1904) interpreted the astragalar canal as the passage for the tendon of the flexor hallucis longus and the posterior branch of the tibial artery. ...
... Because the dorsal foramen and the flexor groove are outside the joint capsule, the movement should not go over them (Yakut and Tuncer 2020). The size of the dorsal foramen has been considered an important aspect of its function (Wang 1993) although it has never been measure before. Several authors also suggest that as the dorsal foramen reduces and disappears, the flexor groove is incorporated into the astragalotibial joint, extending its articular surface (Wang 1993;Kynigopoulou et al. 2024). ...
The dorsal foramen and the flexor groove of the astragalus are traditionally considered traits of plantigrade and pentadactyl mammals, and therefore basal unspecialized taxa. These features are often mentioned as limiting plantar flexion of the foot. Blood vessels, nerves, ligaments and tendons have been proposed to pass through the foramen. During the last two years I had the opportunity to dissect three roadkills: a Myocastor coypus, a Felis catus and a Leopardus geoffroyi. I found the distinctive presence of the tissue of the astragalotibial joint capsule more dorsal than what is considered the plantar end of trochlea in the three animals. The boundary of the trochlea was marked by the plantar edges of the lateral and medial malleolar facets. The astragalar foramen was present in both felids with an unidentified blood vessel passing through it. No nerves or ligaments were found. Additionally, the flexor digitorum longus muscle of L. geoffroyi had a sesamoid at the level of the tibioastragalar articulation. Although the flexor groove and the astragalar dorsal foramen are considered traits of plantigrade and pentadactyl mammals, they are common in Carnivora, particularly in felids, being observed at least in the genera Felis, Leopardus, Panthera, Prionailurus, Puma, and Smilodon. Future research on the soft tissues of these animals as well as more quantitative data, may provide new insights into this ongoing discussion.
... On the canid (cynoid) side, although Hesperocyon gregarius postcrania have been known for more than a hundred years (Scott, 1898;Matthew, 1901;Scott and Jepsen, 1936), due to their abundance from the White River Group (Wang, 1994), including a restoration of a complete skeleton (Matthew, 1901: pl. 37), individual limb bones and vertebrae have not been figured (but see Wang, 1993). Wang et al. (1999) and Tedford et al. (2009), however, did illustrate limb bones of borophagine and canine canids, as well as presenting photographs of a partial (F:AM 63970) and a nearly complete (F:AM 49060) skeleton of an early borophagine, Archaeocyon leptodus, and a partial skeleton of a transitional canine, Eucyon davisi (F:AM 63010). ...
... This would make the clavicle in Eoarctos less reduced than in the more cursorial Hesperocyon but more reduced than in the more arboreal Vulpavus. Wang (1993) mentioned the presence of a clavicle in Hesperocyon (AMNH 8774) that was overlooked in Matthew's (1901) reconstruction. Matthew (1909) similarly overlooked a clavicle in Vulpavus ovatus (AMNH 11498), which has an overhanging acromion process. ...
... The curvature in lateral view shows marked reduction of the deltopectoral crest and is like that of modern Canis. The greater tubercle is poorly developed with its dorsal apex at about the same level as the humeral head, which is probably a plesiomorphic condition for all miacoids and caniforms except canids (Wang, 1993;Heinrich and Houde, 2006). The head of the humerus is rounded, with no apparent limit on inferred mobility. ...
An exquisitely preserved male skeleton of an early arctoid, Eoarctos vorax new genus and species, provides a unique window into the origin and early divergence of Carnivora. Recovered from the Fitterer Ranch locality in the early Oligocene (Orellan to Whitneyan North American Land Mammal ages) Brule Formation of southwestern North Dakota (~32 Ma), the new arctoid offers an opportunity to evaluate the fundamental relationships of the caniform (dog-like) carnivorans. Eoarctos vorax possesses a suite of plesiomorphic characters inherited from its miacid ancestors, making it an ideal model for ancestral arctoids. We present a comprehensive treatment of E. vorax, combining traditional description with photographic documentation, modern microCT, laser scans, and photogrammetry.Showing its plesiomorphic morphology, Eoarctos vorax is scansorial in locomotion, somewhat like a modern raccoon, retaining the ability to climb trees and lacking cursorial adaptations present in the early canid Hesperocyon. However, E. vorax shows clear signs of durophagous cranio-dental adaptations, presumably for an obligatory diet of mollusks, and frequent damage to shell-crushing premolars, plus associated dental infections.We review several other key North American early arctoids and present total-evidence (nuclear DNA and discrete morphological characters) Bayesian and parsimony analyses of Caniformia phylogeny, including extinct stem taxa plus a living member of all modern families. We recognize an endemic North American ursoid clade, family Subparictidae, which includes Eoarctos vorax as its most derived member. We demonstrate the importance of North America as an early cradle of evolution for caniform carnivorans, including early precursors of Canidae, Amphicyonidae, Ursidae, and Pinnipedia.
... The astragalus and tibia are in contact through the crurotarsal joint, which is the main flexion area of the foot. The change of posture therefore noticeably affects this articulation (Wang 1993). The morphology of MHNT. ...
... is similar to that of digitigrade mammals. A deep trochlea is observed for cursorial and saltatorial animals, which have fast parasagittal movements (Ginsburg 1961;Wang 1993). The absence of a astragalar foramen and plantar tendon groove, as found in digitigrade canids, allows the tibia to turn over the entire surface of the trochlea and therefore to have a wider amplitude of flexion-extension (Wang 1993). ...
... A deep trochlea is observed for cursorial and saltatorial animals, which have fast parasagittal movements (Ginsburg 1961;Wang 1993). The absence of a astragalar foramen and plantar tendon groove, as found in digitigrade canids, allows the tibia to turn over the entire surface of the trochlea and therefore to have a wider amplitude of flexion-extension (Wang 1993). According to Ginsburg (1961), an elongated astragalus -as visible on MHNT.PAL.2019.1.11 ...
New postcranial elements of two mesonychids that lived during the Ypresian (early Eocene) in Europe are here described. The postcranial bones found at La Borie (France; ≈MP8 + 9) can be confidently ascribed to Hyaenodictis raslanloubatieri, while the astragalus found at Palette (France; ≈MP7) probably represents H. rougierae. Our study demonstrates that H. raslanloubatieri and H. rougierae were digitigrade in posture and relatively cursorial in locomotion. A single lumbar vertebra was recovered at La Borie and referred to H. raslanloubatieri; this element suggests this species was a moderately dorsostable predator. In addition, we illustrate the first maxillary fragment referable to H. raslanloubatieri, also discovered at La Borie. In comparison, we describe the postcranial elements of Pachyaena gigantea partially published in the early twentieth century, probably a plantigrade predator species. Morphological data derived from the La Borie specimens were included in phylogenetic analyses and support the reinstatement and monophyly of Hyaenodictis. Hyaenodictis was considered to be a junior synonym of Dissacus, but here we find that the Hyaenodictis clade includes almost all European mesonychids formerly referred to Dissacus along with the North American Wasatchian species H. willwoodensis.
... Both the dorsal foramen and the exor groove are traditionally considered traits of plantigrade and pentadactyl mammals, often cited as limiting plantar exion of the foot There is little evidence for either case as well as for what it is going through the foramen. Blood vessels, nerves, ligaments and tendons have been proposed passing through the foramen and it is cited often as a feature that would have limited plantar exion of the foot (Ameghino, 1904;Schaeffer, 1947;Szalay, 1966;Wang, 1993;Shockey and Flynn;2007). During the last two years I had the opportunity to dissect three roadkills: a coypu (Myocastor coypus), a domestic cat (Felis catus) and a Geoffroy's cat (Leopardus geoffroyi). ...
... This foramen is near the mid trochlea, and not in the trochlear ridges where other foramina may be found. Both features, the dorsal foramen and the exor groove are traditionally considered traits of plantigrade and pentadactyl mammals, and they are often cited as limiting plantar exion of the foot (Ameghino, 1904;Schaeffer, 1947;Szalay, 1966;Wang, 1993 Ameghino (1904) interpreted the astragalar canal as the passage for the tendon of the exor hallucis longus and the posterior branch of the tibial artery. According to this author, the astragalar canal (and with it, the dorsal foramen) was related to the presence of a well-developed functional rst digit and, most importantly, with the transition from plantigrady to digitigrady. ...
The dorsal foramen and the flexor groove are traditionally considered traits of plantigrade and pentadactyl mammals, and therefore basal unspecialized taxa, and they are often cited as a features that would have limited plantar flexion of the foot. Blood vessels, nerves, ligaments and tendons have been proposed passing through the foramen. During the last two years I had the opportunity to dissect three roadkills: a Myocastor coypus , a Felis catus and a Leopardus geoffroyi . I found the distinct presence of the upper joint capsule border before the end of the trochlea in the three animals. The limit of the trochlea being marked by the posterior edges of the lateral and medial malleolar facets. The astragalar foramen was present in both felids. Through the dorsal foramen was a unidentified blood vessel. No nerves or ligaments were found passing through the foramen. The flexor digitorum longus muscle of L. geoffroyi had a sesamoid at the height of the tibioastragalar articulation. Although these are considered traits of plantigrade and pentadactyl mammals, they are common in Carnivora, particularly common in felids, being observed at least in the genera Felis , Leopardus , Panthera , Prionailurus , Puma , and Smilodon .
... El sistema de referencia utilizado para nominar las estructuras dentarias sigue la propuesta de Smith y Dodson (2003), en cuanto la orientación (e.g., mesial, distal, labial, lingual) y la utilizada por Wang et al. (1999), con respecto al nombre de las cúspides ( Fig. S6 de Información Suplementaria online 1). Para la anatomía osteológica se tomó como base la nomenclatura veterinaria (Barone, 1987(Barone, , 1990Evans, 1993;Evans y deLahunta, 1997), con ciertas modificaciones (e.g., Wang, 1993Wang, , 1994Wang y Tedford, 1994;Wang et al., 1999). Las listas sinonímicas fueron construidas sobre la base de compilaciones previas (Kraglievich, 1928;Berta, 1989;Mones, 1986;Berman, 1994) y la revisión de la bibliografía existente. ...
... En la dentición pueden observarse variaciones, algunas de las cuales fueron ya señaladas por L. Kraglievich (1928, p. 37) y Berta (1989, p. 69 (Wang, 1993;Prevosti, 2006Prevosti, , 2010 muestran que la presencia de la perforación es un estado primitivo, sustentando en parte esta hipótesis, aunque su presencia en los especímenes mencionados es una clara reversión. ...
Durante el Pleistoceno, América del Sur tenía varios géneros y especies de grandes cánidos hipercarnívoros, los cuales se extinguieron completamente al final de esta época. En este trabajo se presenta una revisión sistemática exhaustiva del grupo (cuatro géneros y siete especies), sobre la base de nuevos análisis cladísticos que también contemplan información genómica y un estudio de la variación intraespecífica en cánidos. Se discuten los resultados generados sobre la filogenia, sistemática, bioestratigrafía y biogeografía de los cánidos sudamericanos. Se sinonimizó Protocyon orcesi con Protocyon troglodytes y Canis nehringi con Aenocyon dirus. El género Theriodictis sería parafilético por lo que Theriodictis tarijensis fue transferido a Protocyon. “Canis” gezi claramente no pertenece al género Canis. Las distribuciones de A. dirus y P. troglodytes llegarían hasta la región pampeana y México, respectivamente. Por otro lado, se restringió a la región pampeana la distribución de Theriodictis. El carácter fragmentario de varios taxones de América del Norte y del Sur complican su ubicación filogenética y las interpretaciones biogeográficas y evolutivas, pero se pueden inferir varios eventos inmigratorios desde América del Norte y Central y algunos posteriores en sentido contrario, así como también una diversificación importante dentro de América del Sur. Nuevos ejemplares bien preservados son necesarios para evaluar la presencia de Chrysocyon y Theriodictis fuera de América del Sur y la asignación sistemática de los restos de cánidos de los sitios de Orocual (Venezuela). La evidencia disponible no permite corroborar la presencia de grandes cánidos con anterioridad al Ensenadense (>1,8 Ma).
... cancrivorus, together with the medial epicondyle morphology that it presents (i.e., short and slightly caudal orientation ;Tarquini et al., 2019) are clearly associated with their mainly terrestrial habits, as observed in other cursorial and generalized terrestrial carnivorans (Argot, 2001;Evans & De Lahunta, 2013;Taylor, 1974;Wang, 1993). ...
A comparative analysis of the forelimb myology of two neotropical procyonids (Nasua nasua and Procyon cancrivorus) was performed to assess how observed differences in their myological configuration would be related to their diverse ecological behaviors and phylogeny. Although both species are associated with the arboreal substrate, N. nasua is a more agile climber that usually digs; whereas P. cancrivorus spends most of its time on the ground foraging, climbing on the trees as shelter and is a good swimmer. Here, myological descriptions, muscle maps, phylogenetic optimizations, and muscle mass data of the forelimb of these two procyonids are presented. The main functional muscular groups are discussed in a comparative framework with other carnivorans that present a wide ecological diversity. Also, muscular characters were mapped onto a phylogeny to explore their evolution and to obtain ancestral state reconstructions. Results indicate clear myological differences among the two neotropical procyonids associated with their ecological preferences. One of the most remarkable anatomical differences is the arrangement and relative mass of the extrinsic musculature, mainly the musculus rhomboideus and the delto-pectoral complexes. In Nasua nasua, these suggested a greater stability in their shoulder girdle for climbing and digging and probably would provide stronger neck and head movements when they use them for foraging on the ground. Conversely, P. cancrivorus has a different extrinsic muscular configuration, which would allow an increment on the stride length and faster movements of the forelimb associated with more frequent terrestrial gaits. Also, significant differences are observed in the distal musculature, associated with strong movements of forepaws when climbing and digging in N. nasua; whereas, P. cancrivorus configuration suggested precise forearm and digits movements, related to manipulation of food items when they are catching prey or feeding. Most of the codified features of P. cancrivorus would reflect retention of plesiomorphies acquired in the common ancestor of caniforms or arctoids, whereas N. nasua shows derived traits, particularly in the proximal forelimb region. The present work increases the information available on the myology of these particular taxa and extant generalized arctoid models in general. The analyses presented here will be useful both for other comparative myological studies (morpho-functional and phylogenetic) and for muscular reconstruction in extinct procyonids, as well as other carnivorans.
... La familia Canidae presenta una radiación sucesiva de tres subfamilias: Hesperocyoninae, Borophaginae y Caninae, a esta última pertenecen todos las especies de cánidos actuales (Tedford et al. 1995, Wang 1993, 1994, Wang et al. 1999. Los cánidos vivientes (tabla 1) varían en muchos aspectos, entre ellos el tamaño, las preferencias de hábitat, la dieta y el comportamiento social. ...
Las relaciones de parentesco entre los cánidos recientes han sido conflictivas. Entre los problemas más notables se tienen la monofilia del clado de los lobos por un lado y la de los cánidos suramericanos por el otro, así como las posiciones filogenéticas de Nyctereutes, Urocyon, Otocyon, Chrysocyon, Speothos y Lycaon. En este trabajo analizamos las relaciones filogenéticas de las 35 especies de cánidos recientes mediante análisis de congruencia de caracteres bajo máxima parsimonia utilizando datos morfológicos, moleculares, citogenéticos, de historia de vida, ecológicos y comportamentales. Con el objeto de reconocer el aporte de cada matriz y evaluar su combinabilidad, realizamos análisis de congruencia taxonómica entre particiones. No se detectaron incongruencias duras entre las particiones, lo que nos permitió realizar un análisis combinado sin alteraciones sobre la matriz. La topología resultante sugiere que Nyctereutes radia temprano en la historia de la subfamilia Caninae, mientras que el resto de taxones se agrupan en tres clados: zorros rojos, lobos y cánidos suramericanos. Se corrobora la monofilia de los géneros Urocyon, Lycalopex y Vulpes, pero no la de Canis. Los taxones Urocyon y Otocyon son grupos hermanos y quedan ubicados en la base del clado de los zorros rojos (Vulpini). Las especies de Vulpes quedan organizadas en términos biogeográficos con dos clados hermanos, uno conformado por las especies holárticas y el otro por las especies afrotropicales e indomalayas. La evolución de los cánidos suramericanos presenta una estructura de radiación jerárquica con el género Lycalopex en la parte terminal. El taxón Speothos forma un clado con los otros dos géneros monotípicos que poseen talón cortante (Lycaon y Cuon), lo que indica que esta adaptación a la hipercarnivoría evolucionó una sola vez en la historia de los Caninae.
... The mid Miocene mammal communities included an extraordinary number of browsing herbivore species, more than found even in tropical forest today, which may have been supported by especially high primary productivity in the warm environments around the MMCO (Janis et al., 2004). Turnover in mammalian carnivores saw a proportional increase in the number of digitigrade cursorial taxa through the Miocene, especially among the canids, with pursuit hunting strategies dominating ecosystems of the late Miocene (Wang, 1993), a transformation that occurred later than the origins of cursoriality in herbivores (Janis and Wilhelm, 1993). ...
Ecometrics is the quantitative study of functional traits at the community level, and the environmental sorting of those traits at regional and continental scales. Functional traits are properties of organisms that have a direct physical or physiological relationship to an underlying quality of the environment, which in turn has indirect links to broader environmental factors such as temperature, precipitation, elevation, atmospheric composition, or sea level. When the same environmental factor affects the performance of many taxa, ecometric sorting is the result. Ecometric patterns in trait distributions across space and through time are therefore a product of biogeographic sorting, evolution, and extinction driven by changes in Earth systems. We review concepts associated with ecometrics, with examples that illustrate how trait-based approaches differ from taxon-based methods, how ecometrics can be used to study Earth-life transitions in the fossil record, and how ecometrics can be used to compare Earth-life transitions that differ in temporal or geographic scale. This paper focuses on the climatic and biome changes of the Great Plains of North America during the Miocene, when grasslands came to be the dominant vegetation type, and of the Anthropocene of the American Midwest, which saw extensive landscape changes in the nineteenth century.
The fossils of the India Muerta Formation (Neogene, Tucumán Province, Northwestern Argentina) include several vertebrate groups,mainly metatherian, xenarthran, and notoungulate mammals. Nevertheless, these remains have been scarcely mentioned in the literature, being mostly noted in faunistic lists, without a focus on taxonomic or morphological aspects. Additionally, most of the biostratigraphic or paleobiogeographic considerations, which are based merely on lithostratigraphic inferences, have suggested a correlation mainly with theAndalhuala (Late Miocene–Pliocene) and the Corral Quemado (Pliocene) formations, both units corresponding to the Santa María sedimentarybasin of the Calchaquí valleys of Northwestern Argentina. Here, we present a study of a notoungulate assemblage recently recovered from levels of the India Muerta Formation, clarifying the geological context and correlating fossil levels with western outcrops. Our study identifies remains grouped systematically as two toxodontids, one mesotheriid, and four hegetotheriids, some of which represent the first records for the unit and/or the region. The sedimentological analysis suggests that this fauna developed in a paleoenvironment corresponding to a complex of braided to meandering fluvial systems. Based on these new data, the fossiliferous levels of the India Muerta Formation reinforce a Late Miocene (Tortonian) age. Consequently, our chronological proposal leads to a closer correlation between the India Muerta Formation and the Las Arcas and Chiquimil formations, which immediately underlie the Andalhuala Formation in western valleys. These inferences agree with previous radioisotopic analyses and, hence, the evidence yielded by the presence of these newly documented notoungulates stands as our most reliable basis for stratigraphic correlation.
Vertebrate limb morphology often reflects the environment due to variation in locomotor requirements. However, proximal and distal limb segments may evolve differently from one another, reflecting an anatomical gradient of functional specialization that has been suggested to be impacted by the timing of development. Here we explore whether the temporal sequence of bone condensation predicts variation in the capacity of evolution to generate morphological diversity in proximal and distal forelimb segments across more than 600 species of mammals. Distal elements not only exhibit greater shape diversity, but also show stronger within-element integration and, on average, faster evolutionary responses than intermediate and upper limb segments. Results are consistent with the hypothesis that late developing distal bones display greater morphological variation than more proximal limb elements. However, the higher integration observed within the autopod deviates from such developmental predictions, suggesting that functional specialization plays an important role in driving within-element covariation. Proximal and distal limb segments also show different macroevolutionary patterns, albeit not showing a perfect proximo-distal gradient. The high disparity of the mammalian autopod, reported here, is consistent with the higher potential of development to generate variation in more distal limb structures, as well as functional specialization of the distal elements.
The impact of environment, interspecific competition, and, to a lesser extent history, on the structure of the guild of large predatory mammals is explored in one fossil and four Recent communities. Two aspects are emphasized: (1) the number of species within each guild and (2) the extent of locomotor convergence as inferred from morphology among the constituent species. Locomotor behavior reflects habitat choice, hunting mode, and escape strategy, all of which appear to be important avenues of adaptive divergence among coexisting predators.
Locomotor behavior in extinct and extant predators is determined from body weight and five measured characteristics of the postcranial skeleton, including ungual shape, elbow shape, and limb proportions. Results indicate that levels of morphologic and inferred ecologic similarity between large predators are higher in the tropical grassland guild of East Africa than in the equivalent guilds of either tropical or temperate forest. This may be due to the great density and diversity of terrestrial herbivores in the productive grasslands. The fossil guild, from the Late Chadron–Orellan (Oligocene) of North America, appears most similar to the tropical forest guilds, but the predators seem to have been slower and more robust than their modern counterparts. Since the Orellan represents an early stage in the evolution of large, fissiped carnivores, both ancestry and time could have influenced Orellan guild structure.