DOCSLIB.ORG

Lung Morphology of Cursorial and Non-Cursorial Mammals: Lagomorphs As a Case Study for a Pneumatic Stabilization Hypothesis

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Lung Morphology of Cursorial and Non-Cursorial Mammals: Lagomorphs As a Case Study for a Pneumatic Stabilization Hypothesis JOURNAL OF MORPHOLOGY 230:299-316 (1996) Lung Morphology of Cursorial and Non-Cursorial Mammals: Lagomorphs As a Case Study for a Pneumatic Stabilization Hypothesis RACHEL S. SIMONS Department of Biology, University of Utah, Salt Lake City, Utah 841 12 ABSTRACT Gross lung morphology is examined in representative species from four genera within the order Lagomorpha (Lepuscalifornicus, Sylvilagus nuttalli, Oryctolagus cuniculus, Ochotona princeps), and compared with a representative rodent out-group (Spermophilus richardonsii ). Examination of pulmonary morphology reveals several correlations between the thoracic mor- phology and locomotor behavior. Lepus, the most cursorial species, exhibits a distinct suite of characteristics: 1) tissue of the right cranial lobe interposed between the heart and sternum; 2) well-defined grooves in the lung tissue for both the aorta and ribs; 3) a fibrous pericardial attachment to the sternum; 4) relatively large heart and lung mass. Sylvilagus, a sprinter, exhibits these features to a lesser degree, whereas Oryctolagus and Ochotona, non-cursorial species, lack most of these features. This same suite of pulmonary features is also observed in a wide range of unrelated cursorial taxa (including selected Artiodactlya, Perissodactyla, Carnivora). Corrosion casts of the internal air- ways demonstrate that the cursorial and non-cursorial taxa examined here have similar branching patterns despite their variable external morphologies. The juxtaposition of pulmonary lobes, heart, and ribs leads to the hypothesis that the lungs themselves provide mechanical support of the heart and visceral mass during locomotion. Analyses of cineradiographic and pneumotacho- graphic data obtained from Oryctolagus tend to support a pneumatic stabiliza- tion hypothesis: the lungs themselves, intimately associated with the chest walls and positively pressurized during landing, may provide some mechanical support to the viscera. This mechanism may be important in stabilizing- the relatively large hearts of the most cursorial species during running. o 1996 Wiley-Liss, Inc. Variation in gross lung structure among tion such as VOZ max (Huey, '82; Lindstedt mammals remains largely unexplored. Al- et al., '91). In addition, other studies address though a few studies document anatomical the integration of mammalian locomotion differences among lungs of mammalian spe- with breathing (Bramble and Carrier, '83; cies (Speransky, '62; Adrian, '64), no studies Bramble, '89a; Young et al., '92a,b; Bramble consider the functional implications of these and Jenluns, '93), and still other reports docu- differences. Moreover, the relationship be- ment cardiopulmonary interaction (although tween the gross pulmonary morphology and primarily in anesthetized or sedentary mam- locomotor behavior remains unexamined. mals; Lloyd, '89; Agostoni and Butler, '91; This paucity is in contrast to the many stud- Hoffman, '93). Yet variation in the gross ies in which micromorphological features of morphology of lungs has not been evaluated the mammalian lung such as alveolar wall within a taxonomic or behavioral framework thickness and diffusing area have been corre- despite its direct relationship to physiological lated with the physiological function of gas function. exchange (Weibel and Taylor, '81; West and Costello, '92), as well as several studies that correlate locomotor performance (speed and Address reprint requests to Rachel Simons, Department of endurance) with indices of pulmonary func- Biology, University of Utah, Salt Lake City, UT 84112. o 1996 WILEY-LISS, INC. 300 R.S. SIMONS The order Lagomorpha is well suited for morphology of representative species from examining the relationship between gross the orders Rodentia, Artiodactyla, Carnivora, lung morphology and locomotion. Within this and Perissodactyla are also included for com- small but behaviorally diverse monophyletic parison. clade, closely related species exhibit a wide range of body size and locomotive ability. MATERIALS AND METHODS Lagomorphs include two families, Ochotoni- Phylogenetic considerations dae (pikas) and Leporidae (rabbits, cotton- tails, and hares). Ochotonidae is considered Gross lung morphology, airway branching to be the more primitive family and is com- patterns, and locomotor behaviors were exam- posed of non-cursorial species (Gambaryan, ined in representative lagomorph species from '74; Dawson, '81; Corbet, '83). The leporids four genera: Lepus californicus (n = 15),Syl- include numerous species whose cursorial vilagus nuttalli (n = 8), Oryctolagus cunicu- specializations have been well documented lus (n = 25),and Ochotonaprinceps (n = 10) (Camp and Borell, '37; Howell, '65; Gam- (Fig. 1).Observations from Lepus townsendii baryan, '74; Schnurr and Thomas, '84; (n = 4) are also included as the pulmonary Bramble, '89b). Hares (Lepus) are the most morphology of L. townsendii is indistinguish- specialized runners, combining speed, endur- able from that of L. californicus. Rodentia is ance, and agility (Howell, '65; Gambaryan, widely considered to be the sister group to '74; Bramble, '89b). Lagomorpha (Novacek and Wyss, '86). Anon- This study examines gross pulmonary mor- cursorial rodent species, Spermophilus rich- phology primarily within the order Lagomor- ardsonii (n = 71, representing the most primi- pha. The objectives are three-fold: 1) to tive rodent suborder Sciurognathi (Nowak, describe the lung morphology and the rela- '91), was included for out-group comparison tionships of the lung to adjacent thoracic and character polarization. Unfortunately, elements (ribs and heart) of selected cursors the phylogenetic relationships among the and non-cursors, 2) to experimentally evalu- leporids remain largely unresolved (Dawson, ate the functional implications of pulmonary '81; Corbet, '83). For the purposes of this design using data from high speed cineradiog- study, the phylogenetic hypothesis from Hib- raphy and pneumotachography from domes- bard ('63; Fig. 1) is used, but other phyloge- tic rabbits, and 3) to introduce an hypothesis netic hypotheses (Corbet, '83; Biju-Duval et of a non-respiratory function for mammalian al., '91) would not substantially change the lungs. Based on morphological and behav- conclusions of this study. In addition to lago- ioral differences, particular attention is given morphs and rodents, cursorial and non- to contrasts between the functional lung cursorial species from the orders Artiodact- morphology of the endurance runner Lepus lya ke., pronghorn antelope and domestic californicus and the similarly sized but pigs) and Carnivora (i.e., dogs, cats, and rac- less cursorial Oryctolagus cuniculus. Lung coons) are considered in this study. Species Body mass g '32 Behavior 2 (ground squirrel) (non-cursorial) - Ochotona princeps 113-202 Sprinter (pika) (non-cu rsorial) - Lepus californicus 1300 - 3100 Endurance runner - (black tail jack rabbit) (highly cursorial) LAGOMORPH LUNG MORPHOLOGY 30 1 Morphology To further characterize gross lung mor- All but one lagomorph species examined phology, the primary branching patterns of were collected from their natural habitats the pulmonary airways were examined using (collection permits obtained from Utah Divi- corrosion casting techniques. Dow Corning sion of Wildlife Resources and Nevada Depart- silicone rubber (base #3112 and catalyst 1; ment of Wildlife); Oryctolagus, the domestic ratio 20:l) was injected into the airways of rabbit, was obtained from a laboratory colony lungs that were retained within the isolated at the University of Utah. Morphological ob- (i.e., decapitated, limbs removed) but un- servations and measurements were made on opened thorax. The thorax was maintained freshly dead specimens. Dried lungs were in a “standing” posture. The lungs were prepared by washing excised lungs with wa- removed from the thorax following a twenty- ter to remove blood, then inflating the lungs four hour curing period and lung tissue was (pressures of 40-60 cm HaO) to greater than dissolved using a concentrated NaOH solu- 100% total lung capacity (to compensate for tion. The corrosion casts confirmed the accu- shrinkage; see below) with an air source at racy of the gross morphology of the in vitro the trachea and allowed to dry (Hildebrand, dried lung preparations. ’68). As an estimate of the contact area be- For comparative purposes, dried lungs from other representative mammalian species (e.g., tween lungs and chest wall, projected surface pronghorn antelope, raccoon, pig, and dog) area measurements were obtained from video were prepared in the same manner described images of the dry lungs using NIH-Image above. Additional information on the pulmo- software. Images were acquired with a Pana- nary anatomy of various domestic species sonic camera (AG-450) and VCR (AG-7390) (e.g., dogs, cats, and pigs) was obtained from interfaced with a Power Macintosh com- Evans, ’93). puter. No lateral measurements were made the literature (Getty, ’75; of Ochotona’s left lung; some distortion of Kinematic and pneumotachographic data the specimens precluded reliable measures. Oryctolagus (n = 3) were trained over a However, in life, (and before air-drying) the four-month period to run on a variable speed right and left lungs of Ochotona are sym- treadmill. Clear, plexiglass walls prevent indi- metrical. Therefore, the surface area mea- viduals from dodging laterally or leaping off sures from the right lung are sufficient to the treadmill. At all but the fastest running describe both the right and left
Load more

Recommended publications
  • Longest Terrestrial Migrations and Movements Around the World Kyle Joly 1*, Eliezer Gurarie2, Mathew S
    www.nature.com/scientificreports OPEN Longest terrestrial migrations and movements around the world Kyle Joly 1*, Eliezer Gurarie2, Mathew S. Sorum3, Petra Kaczensky 4,5, Matthew D. Cameron 1, Andrew F. Jakes6, Bridget L. Borg7, Dejid Nandintsetseg8,9, J. Grant C. Hopcraft10, Bayarbaatar Buuveibaatar11, Paul F. Jones12, Thomas Mueller8,9, Chris Walzer 5,13, Kirk A. Olson11, John C. Payne5,11,13, Adiya Yadamsuren14,15 & Mark Hebblewhite16 Long-distance terrestrial migrations are imperiled globally. We determined both round-trip migration distances (straight-line measurements between migratory end points) and total annual movement (sum of the distances between successive relocations over a year) for a suite of large mammals that had potential for long-distance movements to test which species displayed the longest of both. We found that caribou likely do exhibit the longest terrestrial migrations on the planet, but, over the course of a year, gray wolves move the most. Our results were consistent with the trophic-level based hypothesis that predators would move more than their prey. Herbivores in low productivity environments moved more than herbivores in more productive habitats. We also found that larger members of the same guild moved less than smaller members, supporting the ‘gastro-centric’ hypothesis. A better understanding of migration and movements of large mammals should aid in their conservation by helping delineate conservation area boundaries and determine priority corridors for protection to preserve connectivity. The magnitude of the migrations and movements we documented should also provide guidance on the scale of conservation eforts required and assist conservation planning across agency and even national boundaries.
    [Show full text]
  • The Evolution of Micro-Cursoriality in Mammals
    © 2014. Published by The Company of Biologists Ltd | The Journal of Experimental Biology (2014) 217, 1316-1325 doi:10.1242/jeb.095737 RESEARCH ARTICLE The evolution of micro-cursoriality in mammals Barry G. Lovegrove* and Metobor O. Mowoe* ABSTRACT Perissodactyla) in response to the emergence of open landscapes and In this study we report on the evolution of micro-cursoriality, a unique grasslands following the Eocene Thermal Maximum (Janis, 1993; case of cursoriality in mammals smaller than 1 kg. We obtained new Janis and Wilhelm, 1993; Yuanqing et al., 2007; Jardine et al., 2012; running speed and limb morphology data for two species of elephant- Lovegrove, 2012b; Lovegrove and Mowoe, 2013). shrews (Elephantulus spp., Macroscelidae) from Namaqualand, Loosely defined, cursorial mammals are those that run fast. South Africa, which we compared with published data for other However, more explicit definitions of cursoriality remain obscure mammals. Elephantulus maximum running speeds were higher than because locomotor performance is influenced by multiple variables, those of most mammals smaller than 1 kg. Elephantulus also including behaviour, biomechanics, physiology and morphology possess exceptionally high metatarsal:femur ratios (1.07) that are (Taylor et al., 1970; Garland, 1983a; Garland, 1983b; Garland and typically associated with fast unguligrade cursors. Cursoriality evolved Janis, 1993; Stein and Casinos, 1997; Carrano, 1999). In an in the Artiodactyla, Perissodactyla and Carnivora coincident with evaluation of these definition problems, Carrano (Carrano, 1999) global cooling and the replacement of forests with open landscapes argued that ‘…morphology should remain the fundamental basis for in the Oligocene and Miocene. The majority of mammal species, making distinctions between locomotor performance…’.
    [Show full text]
  • Wildlife Ecology Provincial Resources
    MANITOBA ENVIROTHON WILDLIFE ECOLOGY PROVINCIAL RESOURCES !1 ACKNOWLEDGEMENTS We would like to thank: Olwyn Friesen (PhD Ecology) for compiling, writing, and editing this document. Subject Experts and Editors: Barbara Fuller (Project Editor, Chair of Test Writing and Education Committee) Lindsey Andronak (Soils, Research Technician, Agriculture and Agri-Food Canada) Jennifer Corvino (Wildlife Ecology, Senior Park Interpreter, Spruce Woods Provincial Park) Cary Hamel (Plant Ecology, Director of Conservation, Nature Conservancy Canada) Lee Hrenchuk (Aquatic Ecology, Biologist, IISD Experimental Lakes Area) Justin Reid (Integrated Watershed Management, Manager, La Salle Redboine Conservation District) Jacqueline Monteith (Climate Change in the North, Science Consultant, Frontier School Division) SPONSORS !2 Introduction to wildlife ...................................................................................7 Ecology ....................................................................................................................7 Habitat ...................................................................................................................................8 Carrying capacity.................................................................................................................... 9 Population dynamics ..............................................................................................................10 Basic groups of wildlife ................................................................................11
    [Show full text]
  • The Origin of Birds
    The Origin of Birds Birds have many unusual synapomorphies among modern animals: [ Synapomorphies (shared derived characters), representing new specializations evolved in the most recent common ancestor of the ingroup] • Feathers • Warm-blooded (also in mammals) • Specialized lungs & air-sacs • Hollow bones • Toothless beaks • Large brain Technical name for birds is Aves, and “avian” means “of or concerning birds”. • Cervicals very different from dorsals, allowing neck to fold into “S”-shape • Backwards-pointing pubis • Synsacrum (sacrum fused to pelves; pelvic bones • Fibula reduced to proximal splint fused together) • Astragalus & calcaneum fused to tibia • Proximal caudals very mobile • Hinge-like ankle joint • Pygostyle (distal caudals all fused together) • Furcula - (the wishbone) • Tarsometatarsus (distal tarsals fused to • Forelimb very long, has become wing metatarsals; all metatarsals fused together) • Carpometacarpus (semilunate carpal block fused • Main pedal digits II-IV to metacarpals; all metacarpals fused together) • Pedal digit I reversed, placed at bottom of • Three fingers, but digits all reduced so no unguals tarsometatarsus 1 Compare modern birds to their closest relatives, crocodilians • Difficult to find relatives using only modern animals (turtles have modified necks and toothless beaks, but otherwise very • different; bats fly and are warm-blooded, but are clearly mammals; etc.) • With discovery of fossils, other potential relations: pterosaurs had big brains, “S”- shaped neck, hinge-like foot, but wings are VERY different. • In 1859, Darwin published the Origin; some used birds as a counter-example against evolution, as there were apparently known transitional forms between birds and other vertebrates. In 1860, a feather (identical to modern birds' feathers) was found in the Solnhofen Lithographic Limestone of Bavaria, Germany: a Late Jurassic formation.
    [Show full text]
  • Muscle Function During Swimming and Running in Aquatic, Semi-Aquatic and Cursorial Birds
    Muscle Function During Swimming and Running in Aquatic, Semi-Aquatic and Cursorial Birds A dissertation presented by Jennifer A. Carr To The Department of Biology In partial fulfillment of the requirements for the degree of Doctor of Philosophy in the field of Biology Northeastern University Boston, Massachusetts January 2008 ii Muscle Function During Swimming and Running in Aquatic, Semi-Aquatic and Cursorial Birds A dissertation presented by Jennifer A. Carr ABSTRACT OF DISSERTATION Submitted n partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biology in the Graduate School of Arts and Sciences of Northeastern University, January 2008 iii Abstract The function of large hindlimb muscles with long fascicles and complicated architecture has been studied in many organisms specialized for terrestrial locomotion. Studies of muscle function, energetics and blood flow have allowed a to more accurate determination of which muscles play an important roles during running. One muscle that has been hypothesized to play such a role in birds is the Iliotibialis Lateralis pars Post Acetabularis (ILPO). The ILPO is a large muscle in the hindlimb of cursorial birds, receives a large proportion of the blood flow during running at high speeds, and tends to be reduced or lost in birds that do not employ walking or running as their primary form of locomotion. One of the goals of this study was to comprehensively characterize the function of the ILPO, taking into account the ILPO’s long fascicles that vary in length, the muscle’s complex origin and insertion, and its anatomical variations seen across different bird orders.
    [Show full text]
  • The Biodynamics of Arboreal Locomotion: the Effects of Substrate Diameter on Locomotor Kinetics in the Gray Short-Tailed Opossum (Monodelphis Domestica) Andrew R
    The Journal of Experimental Biology 207, 4325-4336 4325 Published by The Company of Biologists 2004 doi:10.1242/jeb.01231 The biodynamics of arboreal locomotion: the effects of substrate diameter on locomotor kinetics in the gray short-tailed opossum (Monodelphis domestica) Andrew R. Lammers1,* and Audrone R. Biknevicius2 1Department of Biological Sciences, Ohio University, Athens, OH 45701, USA and 2Department of Biomedical Sciences, Ohio University College of Osteopathic Medicine, Athens, OH 45701, USA *Author for correspondence at present address: Department of Health Sciences, Cleveland State University, Cleveland, OH 44115, USA (e-mail: [email protected]) Accepted 9 August 2004 Summary Effects of substrate diameter on locomotor biodynamics segregated between limbs on the terrestrial trackway, fore were studied in the gray short-tailed opossum limbs were dominant both in braking and in propulsion on (Monodelphis domestica). Two horizontal substrates were the arboreal trackway. Both fore and hind limbs exerted used: a flat ‘terrestrial’ trackway with a force platform equivalently strong, medially directed limb forces on the integrated into the surface and a cylindrical ‘arboreal’ arboreal trackway and laterally directed limb forces on the trackway (20.3·mm diameter) with a force-transducer terrestrial trackway. We propose that the modifications in instrumented region. On both terrestrial and arboreal substrate reaction force on the arboreal trackway are due substrates, fore limbs exhibited higher vertical impulse and to the differential placement of the limbs about the peak vertical force than hind limbs. Although vertical limb dorsolateral aspect of the branch. Specifically, the pes impulses were lower on the terrestrial substrate than on typically made contact with the branch lower and more the arboreal support, this was probably due to speed laterally than the manus, which may explain the effects because the opossums refused to move as quickly on significantly lower required coefficient of friction in the the arboreal trackway.
    [Show full text]
  • Population Dynamics and Disease in Endangered African Wild Dogs Elizabeth Claire Arredondo University of Arkansas, Fayetteville
    University of Arkansas, Fayetteville ScholarWorks@UARK Theses and Dissertations 5-2018 Defending Wild Dogs: Population Dynamics and Disease in Endangered African Wild Dogs Elizabeth Claire Arredondo University of Arkansas, Fayetteville Follow this and additional works at: http://scholarworks.uark.edu/etd Part of the Animal Diseases Commons, Terrestrial and Aquatic Ecology Commons, and the Zoology Commons Recommended Citation Arredondo, Elizabeth Claire, "Defending Wild Dogs: Population Dynamics and Disease in Endangered African Wild Dogs" (2018). Theses and Dissertations. 2823. http://scholarworks.uark.edu/etd/2823 This Thesis is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of ScholarWorks@UARK. For more information, please contact [email protected], [email protected]. Defending Wild Dogs: Population Dynamics and Disease in Endangered African Wild Dogs A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Biology by Elizabeth Arredondo University of Arkansas Bachelor of Science in Biology, 2011 May 2018 University of Arkansas This thesis is approved for recommendation by the Graduate Council ____________________________________ Steven Beaupre, PhD Thesis Director ___________________________________ ___________________________________ J.D. Willson PhD Adam Siepielski, PhD Committee Member Committee Member ABSTRACT African wild dogs (Lycaon pictus) are endangered carnivores whose population is decreasing from habitat loss and fragmentation, interspecific competition, and disease. Survival rates are especially low in Kruger National Park (KNP), though it is unclear why. I estimated the abundance in KNP and survival rates over different time spans, six years and nine months, using public photographic survey data.
    [Show full text]
  • Study on the Pelvic System of Birds and on the Origin of Flight Pauline Provini
    Study on the pelvic system of birds and on the origin of flight Pauline Provini To cite this version: Pauline Provini. Study on the pelvic system of birds and on the origin of flight. Revue de Paléobiologie, Museum d’Histoire Naturelle de la Ville de Geneve, 2013. hal-02341363 HAL Id: hal-02341363 https://hal.archives-ouvertes.fr/hal-02341363 Submitted on 31 Oct 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. 1661-5468 VOL. 32, N° 2, 2013 Revue de Paléobiologie, Genève (décembre 2013) 32 (2): 405-411 ISSN 0253-6730 Study on the pelvic system of birds and on the origin of flight Pauline PROVINI1, 2 Abstract Among the main hypotheses proposed to explain the acquisition of flight, two theories have been the subject of an animated debate for several decades, the terrestrial theory and the arboreal theory. According to the first hypothesis, small cursorial feathered theropods would have used their hindlimbs and their proto-wings to jump higher, leading to the apparition of flapping flight. This idea is supported by the discovery of Sinosauropteryx, a small cursorial dinosaur with feathers. The second hypothesis – the arboreal theory – supposes that theropod dinosaurs started flying after an arboreal stage.
    [Show full text]
  • The Mechanics of Terrestrial Locomotion and the Function and Evolutionary History Of
    The Mechanics of Terrestrial Locomotion and the Function and Evolutionary History of Head-bobbing in Birds A dissertation presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Doctor of Philosophy Jennifer Ann Hancock August 2010 © 2010 Jennifer Ann Hancock. All Rights Reserved. 2 This dissertation titled The Mechanics of Terrestrial Locomotion and the Function and Evolutionary History of Head-bobbing in Birds by JENNIFER ANN HANCOCK has been approved for the Department of Biological Sciences and the College of Arts and Sciences by ___________________________________________ Audrone R. Biknevicius Associate Professor of Biomedical Sciences ___________________________________________ Benjamin M. Ogles Dean, College of Arts and Sciences 3 ABSTRACT Hancock, Jennifer Ann, Ph.D., August 2010, Biological Sciences The Mechanics of Terrestrial Locomotion and the Function and Evolutionary History of Head-bobbing in Birds (194 pp.) Director of Dissertation: Audrone R. Biknevicius Head-bobbing is the fore-aft movement of the head exhibited by some birds during terrestrial locomotion. It is primarily considered to be a response to enhance vision. This has led some researchers to hypothesize that head-bobbing should be found in birds that are visual foragers and may be correlated with the morphology of the retina. In contrast, other researchers suggest that head-bobbing is mechanically linked to the locomotor system and that its visual functions are secondarily adapted. This dissertation explored the mechanics of terrestrial locomotion and head- bobbing of birds in both the lab and field. In the lab, the kinetics and kinematics of terrestrial locomotion in the Elegant Crested Tinamous (Eudromia elegans) were analyzed using high-speed videography and ground reaction forces.
    [Show full text]
  • Caudipteryx As a Non-Avialan Theropod Rather Than a Flightless Bird
    Caudipteryx as a non−avialan theropod rather than a flightless bird GARETH J. DYKE and MARK A. NORELL Dyke, G.J. and Norell, M.A. 2005. Caudipteryx as a non−avialan theropod rather than a flightless bird. Acta Palaeontolo− gica Polonica 50 (1): 101–116. Caudipteryx zoui is a small enigmatic theropod known from the Early Cretaceous Yixian Formation of the People’s Re− public of China. From the time of its initial description, this taxon has stimulated a great deal of ongoing debate regarding the phylogenetic relationship between non−avialan theropods and birds (Avialae) because it preserves structures that have been uncontroversially accepted as feathers (albeit aerodynamically unsuitable for flight). However, it has also been pro− posed that both the relative proportions of the hind limb bones (when compared with overall leg length), and the position of the center of mass in Caudipteryx are more similar to those seen in extant cusorial birds than they are to other non−avialan theropod dinosaurs. This conclusion has been used to imply that Caudipteryx may not have been correctly in− terpreted as a feathered non−avialan theropod, but instead that this taxon represents some kind of flightless bird. We re− view the evidence for this claim at the level of both the included fossil specimen data, and in terms of the validity of the re− sults presented. There is no reason—phylogenetic, morphometric or otherwise—to conclude that Caudipteryx is anything other than a small non−avialan theropod dinosaur. Key words: Dinosauria, Theropoda, Avialae, birds, feathers, Yixian Formation, Cretaceous, China. Gareth J.
    [Show full text]
  • Canids of the World Wolves, Wild Dogs, Foxes
    INTRODUCTION © Copyright, Princeton University Press. No part of this book may be distributed, posted, or reproduced in any form by digital or mechanical means without prior written permission of the publisher. RECOGNITION The Canid family is a lineage of terrestrial carnivorans, adapted for swift running, which includes Wolves, Coyotes, Jackals, Foxes, Dogs, Dingoes, Dholes and other Dog-like mammals, with a total of 13 genera and at least 37 extant species. They are mostly social animals, living together in family units or small groups and behaving cooperatively. Most are seasonal breeders producing a single litter each year. They exhibit many reproductive and behavioral traits uncommon in other mammals, such as monogamy with paternal care, long-term incorporation of young adults into the social group, alloparenting, inhibition of reproduction in subordinate individuals, monoestrus, and a copulatory tie. They inhabit temperate and tropical forests, savanna, tundra and deserts throughout the world, with the exception of some oceanic islands and Antarctica. Most Canids feed on mammalian prey, but vegetable matter, carrion, and invertebrates are also an important source of food in many species. Size and body shape (fig. 1): Canids vary widely in size, from the Gray Wolf, which may be up to 160 cm long, and can weigh up to 80 kg, to the diminutive Fennec Fox, which may be as little as 24 cm in length, and weighs less than 1 kg. Most Fox species weigh 1.5 to 9.0 kg, while most other species are 5 to 27 kg. Body lengths (without tail) range between 35 and 160 cm, and tail lengths are approximately 12 to 56 cm.
    [Show full text]
  • African Wild Dogs Have Vestigial First Digit and Muscular Adaptations for Life on the Run 7 September 2020
    African wild dogs have vestigial first digit and muscular adaptations for life on the run 7 September 2020 communicate their vote via "sneezing". They also have a nomadic lifestyle with packs traveling up to 50 km per day and geographically extensive home ranges of 560 to 3000 km2. African wild dogs also differ from other canid (dog) species in the absence of a fully formed first digit (tetradactyly), which may allow for increased speed and stride length, facilitating long-distance pursuit of prey. In a recent study published in PeerJ, a team of anatomists discovered a small, vestigial first metacarpal deep to the skin of the African wild dog. Surprisingly, this species is not fully tetradactyl as previously thought, but instead has a rudimentary digit 1. Prior to this study, the vestigial first digit of African Wild Dog, Lycaon pictus at Savuti Chobe the African wild dog had never been described. The National Park, Botswana. Credit: Derek Keats/ unexpected reduced digit results in a Wikimedia, Creative Commons Attribution Generic 2.0 reconfiguration of some of the associated forelimb license muscles to assist with proprioceptive functions (the body's perception of its own position and movement). According to Heather F. Smith, the study's lead author, "We now not only know that Anatomists identify a vestigial first digit in the this vestigial digit exists, but how its presence forelimb of the African wild dog and document completely reorganizes and repurposes the anatomical adaptations to its unique lifestyle of muscles typically associated with the first digit." long-distance running and exhaustive predation African wild dogs (Lycaon pictus) are known for their unique hunting style, often referred to as "exhaustive predation", in which they chase their prey to exhaustion, rather than hunting using speed, strength, or stealth.
    [Show full text]