The giraffe (Giraffa camelopardalis) cervical vertebral column: a heuristic example in understanding evolutionary processes?

The current study considers the osteological morphology of the giraffe (Giraffa camelopardalis) vertebral column, with emphasis on evaluating both the adaptive and constraining features compared with other ungulates as a heuristic example in understanding evolutionary processes. Vertebral columns of giraffes varying in age from calf to adult were studied in order to understand the potential evolutionary scenarios that might have led to the modern phenotype. Data from the giraffe sample were then compared with the results from several other ungulate species, including the okapi and two species of camelids that also have visibly elongated necks. Our results show that the elongated neck of the modern giraffe appears to specifically result from evolutionary changes affecting the seven cervical vertebrae, independent of the remainder of the vertebral column. The cervical vertebrae comprise over half of the length of the total vertebral column in the giraffe. The increases in cervical vertebrae lengths also appear to be allometrically constrained, with alterations in the overall length of the neck resulting from the elongation of the entire cervical series, rather than from a single vertebra or subset of vertebrae. We place our results in the context of hypotheses concerning the origin and evolution of the giraffe neck, and the evolution of long necks in a broader sense. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 736–757.     

A new long-necked ‘sauropod-mimic’ stegosaur and the evolution of the plated dinosaurs

Stegosaurian dinosaurs have a quadrupedal stance, short forelimbs, short necks, and are generally considered to be low browsers. A new stegosaur, Miragaia longicollum gen. et sp. nov., from the Late Jurassic of Portugal, has a neck comprising at least 17 cervical vertebrae. This is eight additional cervical vertebrae when compared with the ancestral condition seen in basal ornithischians such as Scutellosaurus. Miragaia has a higher cervical count than most of the iconically long-necked sauropod dinosaurs. Long neck length has been achieved by ‘cervicalization’ of anterior dorsal vertebrae and probable lengthening of centra. All these anatomical features are evolutionarily convergent with those exhibited in the necks of sauropod dinosaurs. Miragaia longicollum is based upon a partial articulated skeleton, and includes the only known cranial remains from any European stegosaur. A well-resolved phylogeny supports a new clade that unites Miragaia and Dacentrurus as the sister group to Stegosaurus; this new topology challenges the common view of Dacentrurus as a basal stegosaur.     

The scent of the reticulated giraffe (Giraffa camelopardalis reticulata)

The giraffe (Giraffa camelopardalis) emits a scent that can be detected by humans over considerable distances. Dichloromethane extracts of hair samples from adult male and female reticulated giraffes (G. c. reticulata) were analysed by gas chromatography–mass spectrometry. Two highly odoriferous compounds, indole and 3-methylindole, identified in these extracts appear to be primarily responsible for the giraffe’s strong scent. Other major compounds identified were octane, benzaldehyde, heptanal, octanal, nonanal, p-cresol, tetradecanoic acid, hexadecanoic acid, and 3,5-androstadien-17-one; the last compound has not previously been identified from a natural source. These compounds may deter microorganisms or ectoparasitic arthropods. Most of these compounds are known to possess bacteriostatic or fungistatic properties against mammalian skin pathogens or other microorganisms. The levels of p-cresol in giraffe hair are sufficient to repel some ticks.     

Functional morphology and anatomy of cervical vertebrae in Nacholapithecus kerioi, a middle Miocene hominoid from Kenya

This paper describes the morphology of cervical vertebrae in Nacholapithecus kerioi, a middle Miocene primate species excavated from Nachola, Kenya in 1999-2002. The cervical vertebrae in Nacholapithecus are larger than those of Papio cynocephalus. They are more robust relative to more caudal vertebral bones. Since Nacholapithecus had large forelimbs, it is assumed that strong cervical vertebrae would have been required to resist muscle reaction forces during locomotion. On the other hand, the vertebral foramen of the lower cervical vertebrae in Nacholapithecus is almost the same size as or smaller than that of P. cynocephalus. Atlas specimens of Nacholapithecus resemble those of extant great apes with regard to the superior articular facet, and they have an anterior tubercle trait intermediate between that of extant apes and other primate species. Nacholapithecus has a relatively short and thick dens on the axis, similar to those of extant great apes and the axis body shape is intermediate between that of extant apes and other primates. Moreover, an intermediate trait between extant great apes and other primate species has been indicated with regard to the angle between the prezygapophyseal articular facets of the axis in Nacholapithecus. Although the atlas of Nacholapithecus is inferred as having a primitive morphology (i.e., possessing a lateral bridge), the shape of the atlas and axis leads to speculation that locomotion or posture in Nacholapithecus involved more orthograde behavior similar to that of extant apes, and, in so far as cervical vertebral morphology is concerned, it is thought that Nacholapithecus was incipiently specialized toward the characteristics of extant hominoids.     

Predicting the buoyancy, equilibrium and potential swimming ability of giraffes by computational analysis

Giraffes (Giraffa camelopardalis) are often stated to be unable to swim, and while few observations supporting this have ever been offered, we sought to test the hypothesis that giraffes exhibited a body shape or density unsuited for locomotion in water. We assessed the floating capability of giraffes by simulating their buoyancy with a three-dimensional mathematical/computational model. A similar model of a horse (Equus caballus) was used as a control, and its floating behaviour replicates the observed orientations of immersed horses. The floating giraffe model has its neck sub-horizontal, and the animal would struggle to keep its head clear of the water surface. Using an isometrically scaled-down giraffe model with a total mass equal to that of the horse, the giraffe's proportionally larger limbs have much higher rotational inertias than do those of horses, and their wetted surface areas are 13.5% greater relative to that of the horse, thus making rapid swimming motions more strenuous. The mean density of the giraffe model (960 gm/l) is also higher than that of the horse (930 gm/l), and closer to that causing negative buoyancy (1000 gm/l). A swimming giraffe - forced into a posture where the neck is sub-horizontal and with a thorax that is pulled downwards by the large fore limbs - would not be able to move the neck and limbs synchronously as giraffes do when moving on land, possibly further hampering the animal's ability to move its limbs effectively underwater. We found that a full-sized, adult giraffe will become buoyant in water deeper than 2.8 m. While it is not impossible for giraffes to swim, we speculate that they would perform poorly compared to other mammals and are hence likely to avoid swimming if possible.     

Genetic structure of two populations of the Namibian giraffe,Giraffa camelopardalis angolensis

Two geographically distinct populations of giraffe (Giraffa camelopardalis) were sampled for this study, the northern Namib Desert and Etosha National Park. Population genetic parameters and relationships within subpopulations were estimated to better understand the genetic architecture of this isolated subspecies. Gene flow between the geographically separated populations can be attributed to recent translocation of giraffe between the two populations. Inbreeding estimates in the six subpopulations studied were low though we found evidence that genetic drift may be affecting the genetic diversity of the isolated populations in northern Namibia. Population dynamics of the sampling locations was inferred with relationship coefficient analyses. Recent molecular systematics of the Namibian giraffe populations indicates that they are distinct from the subspecies Giraffa camelopardalis giraffa and classified as G. c. angolensis. Based on genetic analyses, these giraffe populations of northern Namibia, the desert‐dwelling giraffe and those protected in Etosha National Park, are a distinct subspecies from that previously assumed; thus we add data on G. c. angolensis to our scientific knowledge of this giraffe of southern Africa.     

Updated geographic range maps for giraffe,Giraffa spp., throughout sub‐Saharan Africa,and implications of changing distributions for conservation

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Implications of the placental structure compatibility for interspecies embryo transfer

Comparative histological features of the chorionic villi in placental cotyledons of the common eland (Taurotragus oryx ) and bongo (Boocercus euryceros ) antelopes and okapi (Okapia johnstoni ) and giraffe (Giraffa camelopardalis ) were examined. The chorionic villi in both antelope species showed only moderate branching and/or surface corrugation and their cross-sections were polygonal to oval. The close similarity in the structure of cotyledons has been apparently a contributing factor for success in mutual interspecies embryo transfer. The chorionic villi in okapi and giraffe had very different structures. In okapi the villi on cross-section were round and filled with thin connective tissue. They showed minimal branching and surface corrugation. In giraffe the villi showed extensive surface corrugation, had multiple fine branches, and were filled with a more dense connective tissue. Prospect for materno-fetal compatibility in mutual embryo transfer between these species is guarded.     

Characterization of 16 microsatellite marker loci in the Maasai giraffe (Giraffa camelopardalis tippelskirchi)

Sixteen polymorphic microsatellite markers with an average allele size of k = 4.3 are identified from a genomic plasmid library constructed for giraffe (Giraffa camelopardalis ssp.). Primer sequences and marker data are reported in tabular form. The markers were screened in a population of 25 Maasai giraffe (G. c. tippelskirchi) collected near the Athi River, Kenya. The average observed heterozygosity for each marker was 0.36 with an average expected heterozygosity of 0.535. Hardy–Weinberg deviations are reported from this population, which is suspected to be inbred. The markers will be used to screen the captive giraffe population for subspecific or hybrid classification.     

Functional morphology of the primate head and neck

The vertebral column plays a key role in maintaining posture, locomotion, and transmitting loads between body components. Cervical vertebrae act as a bridge between the torso and head and play a crucial role in the maintenance of head position and the visual field. Despite its importance in positional behaviors, the functional morphology of the cervical region remains poorly understood, particularly in comparison to the thoracic and lumbar sections of the spinal column. This study tests whether morphological variation in the primate cervical vertebrae correlates with differences in postural behavior. Phylogenetic generalized least-squares analyses were performed on a taxonomically broad sample of 26 extant primate taxa to test the link between vertebral morphology and posture. Kinematic data on primate head and neck postures were used instead of behavioral categories in an effort to provide a more direct analysis of our functional hypothesis. Results provide evidence for a function-form link between cervical vertebral shape and postural behaviors. Specifically, taxa with more pronograde heads and necks and less kyphotic orbits exhibit cervical vertebrae with longer spinous processes, indicating increased mechanical advantage for deep nuchal musculature, and craniocaudally longer vertebral bodies and more coronally oriented zygapophyseal articular facets, suggesting an emphasis on curve formation and maintenance within the cervical lordosis, coupled with a greater resistance to translation and ventral displacement. These results not only document support for functional relationships in cervical vertebrae features across a wide range of primate taxa, but highlight the utility of quantitative behavioral data in functional investigations. Am J Phys Anthropol 156:531–542, 2015. © 2015 Wiley Periodicals, Inc.     

A New Titanosaurian Sauropod from the Hekou Group (Lower Cretaceous) of the Lanzhou-Minhe Basin,Gansu Province,China

Increased excavation of dinosaurs from China over the last two decades has enriched the record of Asian titanosauriform sauropods. However, the relationships of these sauropods remain contentious, and hinges on a few well-preserved taxa, such as Euhelopus zdanskyi. Here we describe a new sauropod, Yongjinglong datangi gen. nov. et sp. nov., from the Lower Cretaceous Hekou Group in the Lanzhou Basin of Gansu Province, northwestern China. Yongjinglong datangi is characterized by the following unique combination of characters, including seven autapomorphies: long-crowned, spoon-shaped premaxillary tooth; axially elongate parapophyses on the cervical vertebra; very deep lateral pneumatic foramina on the lateral surfaces of the cervical and cranial dorsal vertebral centra; low, unbifurcated neural spine fused with the postzygapophyses to form a cranially-pointing, triangular plate in a middle dorsal vertebra; an “XI”-shaped configuration of the laminae on the arches of the middle dorsal vertebrae; a very long scapular blade with straight cranial and caudal edges; and a tall, deep groove on the lateral surface of the distal shaft of the radius. The new specimen shares several features with other sauropods: a pronounced M. triceps longus tubercle on the scapula and ventrolaterally elongated parapophyses in its cervical vertebra as in Euhelopodidae. Based on phylogenetic analyses Yongjinglong datangi is highly derived within Titanosauria, which suggests either a remarkable convergence with more basal titanosauriform sauropods in the Early Cretaceous or a retention of plesiomorphic features that were lost in other titanosaurians. The morphology and remarkable length of the scapulocoracoid reveal an unusual relationship between the shoulder and the middle trunk: the scapulocoracoid spans over half of the length of the trunk. The medial, notch-shaped coracoid foramen and the partially fused scapulocoracoid synostosis suggest that the specimen is a subadult individual. This specimen sheds new light on the diversity of Early Cretaceous Titanosauriformes in China.     

Evolution of the axial skeleton in armadillos (Mammalia,Dasypodidae)

Intraspecific and interspecific variation in cervical, thoracic, and lumbar region of the vertebral column of Dasypodidae were examined in a phylogenetic framework. The number of vertebrae for each region were recorded for 86 specimens and metric data for each vertebra (centrum length, high, and width) were recorded for 72 specimens, including eight of the nine living genera. The number of vertebrae and degree of fusion between them were used to define four characters which were plotted on two alternative phylogenies of Dasypodidae. The ratio between centrum height and width is similar across all taxa analyzed except for Chlamyphorus, which exhibits a deviation in the last two lumbars. Tolypeutes matacus is unique among the taxa examined in having a second co-osified bone called postcervical bone, which is a fusion of the seventh cervical and first thoracic vertebrae. The thoraco-lumbar numbers of dasypodids are reduced when compared with other xenarthrans and are more diverse than those of some other mammalian clades of similar geological age and higher ecomorphological diversity. Changes in size are somewhat coupled with changes in the number of body segments. Independent of the phylogenetic framework taken, changes in size are accompanied with small changes in numbers of thoracolumbar vertebrae within each genus. There are functional and phylogenetic correlates for changes in number of thoraco-lumbar vertebrae in dasypodids.     

Coordination of flipflopping neural signals and head turning during pheromone-mediated walking in a male silkworm moth Bombyx mori

Male silkworm moths, Bombyx mori, move their heads side-to-side during zigzag walking toward a source of sex pheromone. High-speed video analysis revealed that changes in walking direction were synchronized with this head turning. Thus the direction of the walking is indicated by the direction of the head turning. Head turning was regulated by neck motor neurons which innervate the cervical ventral muscles and the ventral muscles through the second cervical nerve. To determine the role of the `flipflop' state transition in spike activity carried by descending interneurons from the brain to the thoracic ganglion, we recorded pheromonal responses simultaneously from flipflop descending interneurons and a single cervical ventral 1 neck motor neuron. The activity of the cervical ventral 1 neck motor neuron was synchronized to that of the flipflop descending interneurons. The cervical ventral 1 neck motor neuron was morphologically identified using confocal imaging. Our results demonstrate that the flipflop signals play an important role in instructing turning signals during the pheromone-mediated behavior in a male B. mori. Accepted: 11 June 1998     

Androgen changes and flexible rutting behaviour in male giraffes

The social organization of giraffes (Giraffa camelopardalis) imposes a high-cost reproductive strategy on bulls, which adopt a ‘roving male’ tactic. Our observations on wild giraffes confirm that bulls indeed have unsynchronized rut-like periods, not unlike another tropical megaherbivore, the elephant, but on a much shorter timescale. We found profound changes in male sexual and social activities at the scale of about two weeks. This so far undescribed rutting behaviour is closely correlated with changes in androgen concentrations and appears to be driven by them. The short time scale of the changes in sexual and social activity may explain why dominance and reproductive status in male giraffe in the field seem to be unstable.     

Reconstruction of the neck of Azhdarcho lancicollis and lifestyle of azhdarchids (Pterosauria, Azhdarchidae)

A computer reconstruction of isolated cervical vertebrae of Azhdarcho lancicollis from the Turonian of Uzbekistan allows three-dimensional model of the cervical region of the vertebral column of this animal. The relative length of cervical vertebrae (I + II < III < IV < V > VI > VII > VIII > IX) is the same as in pterodactyloids with short cervical vertebrae. An increase in neck length is provided mostly by the middle cervical vertebrae (IV–VI). In a neutral posture, the neck of azhdarchids was not straight, as often reconstructed, but S-shaped, with the maximum angles between the V–VI (20°), VI–VII (20°), and VIII–IX (17°) vertebrae. The feeding strategy of azhdarchids was probably similar to that of pelicans. In a search for prey, azhdarchids were soaring above the water surface of large inland or nearshore marine water bodies. Their prey (predominantly fish) was captured by the widely open mouth and fell into the throat sac, the presence of which is suggested by the spiral jaw joint. Prey was swallowed during the abrupt neck flexion in the posterior segment, which brought the head in an almost horizontal position. A storklike wading ecology for azhdarchids is less probable, because these clumsy on land animals were vulnerable to terrestrial predators.     

Giraffe (Giraffa camelopardalis) social networks in areas of contrasting human activity and lion density

The adaptive value of close social bonds and social networks has been demonstrated in a variety of vertebrate taxa. While the effect of predators on populations is well established, disturbance by humans is increasingly being identified as affecting the behaviour and reproductive success of animals and can have significant impacts on their survival. We used a concurrent analysis of two adjacent giraffe Giraffa camelopardalis populations in Kenya to determine whether human activities and high predation affected their social networks. One study site was a premier tourist destination with a high volume of human activity in the form of tourist traffic and lodge infrastructure, alongside a high density of lions which preferentially prey on giraffe calves; the other was a private wildlife conservancy with minimal human activity and no lion population. Giraffes in both networks showed preferred associations and avoidances of other individuals, which were independent of space use. Bond strength was lower in the population exposed to high levels of human activity and lions, and the network had lower density and clustering, and shorter path lengths, suggesting that it was more fragmented. We suggest that human activity and predator density may influence the patterns of social interactions in giraffes and highlight the importance of understanding the impact of tourism and management on the survival and success of wild animal populations.     

Revised Vertebral Count in the “Longest-Necked Vertebrate” Elasmosaurus platyurus Cope 1868, and Clarification of the Cervical-Dorsal Transition in Plesiosauria

Elasmosaurid plesiosaurians are renowned for their immensely long necks, and indeed, possessed the highest number of cervical vertebrae for any known vertebrate. Historically, the largest count has been attributed to the iconic Elasmosaurus platyurus from the Late Cretaceous of Kansas, but estimates for the total neck series in this taxon have varied between published reports. Accurately determining the number of vertebral centra vis-à-vis the maximum length of the neck in plesiosaurians has significant implications for phylogenetic character designations, as well as the inconsistent terminology applied to some osteological structures. With these issues in mind, we reassessed the holotype of E. platyurus as a model for standardizing the debated cervical-dorsal transition in plesiosaurians, and during this procedure, documented a “lost” cervical centrum. Our revision also advocates retention of the term “pectorals” to describe the usually three or more distinctive vertebrae close to the cranial margin of the forelimb girdle that bear a functional rib facet transected by the neurocentral suture, and thus conjointly formed by both the parapophysis on the centrum body and diapophysis from the neural arch (irrespective of rib length). This morphology is unambiguously distinguishable from standard cervicals, in which the functional rib facet is borne exclusively on the centrum, and dorsals in which the rib articulation is situated above the neurocentral suture and functionally borne only by the transverse process of the neural arch. Given these easily distinguishable definitions, the maximum number of neck vertebrae preserved in E. platyurus is 72; this is only three vertebrae shorter than the recently described Albertonectes, which together with E. platyurus constitute the “longest necked” animals ever to have lived.     

Macrauchenia patachonica Owen, 1838: Limb bones morphology,locomotory biomechanics,and paleobiological inferences

Macrauchenia patachonica Owen, 1838 was among the last and largest litopterns, an extinct order of South American native ungulates. Macrauchenia patachonica had anatomical peculiarities as extremely retracted nasals, enlarged cervical vertebrae, and limb bones proportions without good living analogs that lead to asking about its paleobiology. To quantitatively assess the strange combination of limb bone features in M. patachonica, we constructed an indicator of differences in anatomical adaptations for efficient running between forelimb and hind limb (IDFH). We also made a multivariate analysis using data on osteological ratios of living mammals and two other litopterns. We discuss several biomechanical and paleobiological implications of the striking differences between hind limb and forelimb design in M. patachonica. Our main suggestion is that M. patachonica, during fast locomotion, probably used a posture with the neck in a horizontal position.     

A review of the social behaviour of the giraffe Giraffa camelopardalis: a misunderstood but socially complex species

1. Until around 2000, giraffe Giraffa camelopardalis were believed to have no social structure. Despite a resurgence of interest in giraffe behaviour in around 2010, most studies are of isolated populations, making it difficult to draw general conclusions. Although it is now well established that giraffe social organisation is non-random, there is little consensus as to what influences preferred and avoided associations or the underpinning mechanisms.
2. We test two hypotheses: first, giraffe have a complex cooperative social system, exhibited by 1) stable groups of females, 2) offspring that stay in their natal group for part or all of their lives, 3) support by non-mothers in rearing young, and 4) non-reproductive females in the group; and second, giraffe form matrilineal societies, evidenced by 1) male dispersal, 2) female philopatry, 3) assistance in raising or protecting offspring, and 4) individual benefits gained from social foraging.
3. We reviewed 404 papers on giraffe behaviour and social organisation; captive studies were included where they supplemented information from free-living populations.
4. We show that giraffe exhibit many of the features typical of mammals with complex cooperative social systems and matrilineal societies. However, the social complexity hypothesis posits that such species also require complex communication systems to regulate interactions and relations among group members; giraffe communication systems are poorly understood.
5. Quantifying the fitness and survival benefits of the giraffe’s social organisation is necessary to ensure its long-term survival. Giraffe numbers have declined by 40% since 1985, they have been declared extinct in seven (possibly nine) countries and are listed as Vulnerable by the International Union for Conservation of Nature. We identify research areas that will advance our understanding of giraffe behaviour and conservation requirements.