scholarly journals Homeotic shift at the dawn of the turtle evolution

2017 ◽  
Vol 4 (4) ◽  
pp. 160933 ◽  
Author(s):  
Tomasz Szczygielski
Keyword(s):  
Vertebral Column ◽  
Phylogenetic Analyses ◽  
Cervical Vertebrae ◽  
Expression Patterns ◽  
Cervical Vertebra ◽  
Late Triassic ◽  
Cervical Region ◽  
Crown Group ◽  
Dorsal Vertebra ◽  
Shift Hypothesis

All derived turtles are characterized by one of the strongest reductions of the dorsal elements among Amniota, and have only 10 dorsal and eight cervical vertebrae. I demonstrate that the Late Triassic turtles, which represent successive stages of the shell evolution, indicate that the shift of the boundary between the cervical and dorsal sections of the vertebral column occurred over the course of several million years after the formation of complete carapace. The more generalized reptilian formula of at most seven cervicals and at least 11 dorsals is thus plesiomorphic for Testudinata. The morphological modifications associated with an anterior homeotic change of the first dorsal vertebra towards the last cervical vertebra in the Triassic turtles are partially recapitulated by the reduction of the first dorsal vertebra in crown-group Testudines, and they resemble the morphologies observed under laboratory conditions resulting from the experimental changes of Hox gene expression patterns. This homeotic shift hypothesis is supported by the, unique to turtles, restriction of Hox-5 expression domains, somitic precursors of scapula, and brachial plexus branches to the cervical region, by the number of the marginal scute-forming placodes, which was larger in the Triassic than in modern turtles, and by phylogenetic analyses.

2. On the Vertebral Column, and some Characters that have been overlooked in the Descriptions both of the Anatomist and Zoologist.

1851 ◽  
Vol 2 ◽  
pp. 166-169
Author(s):  
Macdonald
Keyword(s):  
Vertebral Column ◽  
Lumbar Vertebrae ◽  
Cervical Region ◽  
Normal Position ◽  
Dorsal Vertebra

After noticing that the vertebral skeleton has usually been compared to a column, of which the basis (in man) is formed by the sacrum and coccyx, the shaft or columnar part being the bodies of the true vertebræ, as they are usually styled, and surmounted by the splendid composite capital the cranium, the author proposed restricting the observations to the columnar portion, usually divided into 7 cervical, 12 dorsal, and 5 lumbar vertebræ. This division was denounced, and beginning at the summit, he shewed that the upper or cervical region consisted only of 6 vertebræ, as the 7th, in its normal position in the mammal class, had a rib partly articulated to its body, and therefore acquired the character of a dorsal vertebra.

Mice homozygous for a targeted disruption of Hoxd-3 (Hox-4.1) exhibit anterior transformations of the first and second cervical vertebrae, the atlas and the axis

Development ◽  
1993 ◽  
Vol 119 (3) ◽  
pp. 579-595 ◽  
Author(s):  
B.G. Condie ◽  
M.R. Capecchi
Keyword(s):  
Hox Genes ◽  
Es Cells ◽  
Cervical Vertebrae ◽  
Expression Patterns ◽  
Cervical Vertebra ◽  
Targeted Disruption ◽  
Paralogous Genes ◽  
Variable Extent ◽  
Basioccipital Bone

Gene targeting in embryo-derived stem (ES) cells was used to generate mice with a disruption in the homeobox-containing gene Hoxd-3 (Hox-4.1). Mice homozygous for this mutation show a radically remodeled craniocervical joint. The anterior arch of the atlas is transformed to an extension of the basioccipital bone of the skull. The lateral masses of the atlas also assume a morphology more closely resembling the exoccipitals and, to a variable extent, fuse with the exoccipitals. Formation of the second cervical vertebra, the axis, is also affected. The dens and the superior facets are deleted, and the axis shows ‘atlas-like’ characteristics. An unexpected observation is that different parts of the same vertebra are differentially affected by the loss of Hoxd-3 function. Some parts are deleted, others are homeotically transformed to more anterior structures. These observations suggest that one role of Hox genes may be to differentially control the proliferation rates of the mesenchymal condensations that give rise to the vertebral cartilages. Within the mouse Hox complex, paralogous genes not only encode very similar proteins but also often exhibit very similar expression patterns. Therefore, it has been postulated that paralogous Hox genes would perform similar roles. Surprisingly, however, no tissues or structures are affected in common by mutations in the two paralogous genes, Hoxa-3 and Hoxd-3.

Ichthyosaurs from the Upper Triassic (Carnian–Norian) of the New Siberian Islands, Russian Arctic, and their implications for the evolution of the ichthyosaurian basicranium and vertebral column

2021 ◽  
pp. 1-24
Author(s):  
Nikolay G. ZVERKOV ◽  
Dmitry V. GRIGORIEV ◽  
Andrzej S. WOLNIEWICZ ◽  
Alexey G. KONSTANTINOV ◽  
Evgeny S. SOBOLEV
Keyword(s):  
Vertebral Column ◽  
Cervical Vertebrae ◽  
Upper Triassic ◽  
Late Triassic ◽  
Phylogenetic Position ◽  
New Taxon ◽  
Russian Arctic ◽  
Micro Computed Tomography ◽  
New Siberian Islands ◽  
Group Relationships

ABSTRACT The first ichthyosaurian specimens discovered from the Upper Triassic of the Russian Arctic (Kotelny Island, New Siberian Islands) are described herein. They include the remains of large- to small-bodied ichthyosaurians originating from six stratigraphic levels spanning the lower Carnian to middle Norian. The material is mostly represented by isolated vertebrae and ribs, which are not possible to accurately diagnose, but also includes specimens comprising associated vertebrae and a fragmentary skeleton that preserves cranial remains (parabasisphenoid, fragmentary quadrate, partial mandible and hyoids). Based on vertebral and rib morphology, we identify the specimens as representatives of the following taxonomic groups: large-bodied shastasaurids, medium-sized indeterminate ichthyosaurians with a single rib facet in the presacral centra, and small euichthyosaurians with double rib facets present throughout the presacral vertebrae that likely represent toretocnemids and/or basal parvipelvians. In addition, the cranial and mandibular remains preserved in one of the specimens, ZIN PH 5/250, were studied using micro-computed tomography. Its mandible is highly similar to that of toretocnemids, whereas the parabasisphenoid demonstrates a peculiar combination of both plesiomorphic and derived character states, providing the first detailed data on this cranial element in a Late Triassic ichthyosaurian. Furthermore, the specimen also demonstrates a distinctive condition of rib articulation in the anteriormost presacral (cervical) vertebrae, which together with other features allows for the erection of a new taxon – Auroroborealia incognita gen. et sp. nov. Although the phylogenetic position of this taxon is uncertain due to its fragmentary nature, its anatomy, indicating toretocnemid or parvipelvian affinities, further supports the previously hypothesised sister-group relationships between these two clades. The morphology of the parabasisphenoid and vertebral column of the new taxon is discussed in broader contexts of the patterns of evolution of these skeletal regions in ichthyosaurs.

The face and superficial neck

2013 ◽  
Author(s):  
Martin E. Atkinson
Keyword(s):  
Vertebral Column ◽  
Cervical Vertebrae ◽  
Small Body ◽  
Spinous Process ◽  
Odontoid Process ◽  
Cervical Vertebra ◽  
Intervertebral Discs ◽  
The Body ◽  
Thoracic Vertebrae ◽  
The Face

The surface anatomies of the face and neck and their supporting structures that can be palpated have been described in Chapter 20. It is now time to move to the structures that lie under the skin but which cannot be identified by touch starting with the neck and moving up on to the face and scalp. The cervical vertebral column comprises the seven cervical vertebrae and the intervening intervertebral discs. These have the same basic structure as the thoracic vertebrae described in Section 10.1.1. Examine the features of the cervical vertebra shown in Figure 23.1 and compare it with the thoracic vertebra shown in Figure 10.3. You will see that cervical vertebrae have a small body and a large vertebral foramen. They also have two distinguishing features, a bifid spinous process and a transverse foramen, piercing each transverse process; the vertebral vessels travel through these foramina. The first and second vertebrae are modified. The first vertebra, the atlas, has no body. Instead, it has two lateral masses connected by anterior and posterior arches. The lateral masses have concave superior facets which articulate with the occipital condyles where nodding movements of the head take place at the atlanto-occipital joints. The second cervical vertebra, the axis, has a strong odontoid process (or dens because of its supposed resemblance to a tooth) projecting upwards from its body. This process is, in fact, the body of the first vertebra which has fused with the body of the axis instead of being incorporated into the atlas. The front of the dens articulates with the back of the anterior arch of the atlas; rotary (shaking) movements of the head occur at this joint. The seventh cervical vertebra has a very long spinous process which is easily palpable. The primary curvature of the vertebral column is concave forwards and this persists in the thoracic and pelvic regions. In contrast, the cervical and lumbar parts of the vertebral column are convexly curved anteriorly. These anterior curvatures are secondary curvatures which appear in late fetal life. The cervical curvature becomes accentuated in early childhood as the child begins to support its own head and the lumbar curve develops as the child begins to sit up.

scholarly journals A comprehensive anatomical and phylogenetic evaluation of Dilophosaurus wetherilli (Dinosauria, Theropoda) with descriptions of new specimens from the Kayenta Formation of northern Arizona

2020 ◽  
Vol 94 (S78) ◽  
pp. 1-103 ◽  
Author(s):  
Adam D. Marsh ◽  
Timothy B. Rowe
Keyword(s):  
Phylogenetic Analyses ◽  
Cervical Vertebrae ◽  
Pop Culture ◽  
Single Species ◽  
Axial Skeleton ◽  
Late Triassic ◽  
Monophyletic Clade ◽  
Navajo Nation ◽  
Northern Arizona ◽  
Nasal Process

AbstractDilophosaurus wetherilli was the largest animal known to have lived on land in North America during the Early Jurassic. Despite its charismatic presence in pop culture and dinosaurian phylogenetic analyses, major aspects of the skeletal anatomy, taxonomy, ontogeny, and evolutionary relationships of this dinosaur remain unknown. Skeletons of this species were collected from the middle and lower part of the Kayenta Formation in the Navajo Nation in northern Arizona. Redescription of the holotype, referred, and previously undescribed specimens of Dilophosaurus wetherilli supports the existence of a single species of crested, large-bodied theropod in the Kayenta Formation. The parasagittal nasolacrimal crests are uniquely constructed by a small ridge on the nasal process of the premaxilla, dorsoventrally expanded nasal, and tall lacrimal that includes a posterior process behind the eye. The cervical vertebrae exhibit serial variation within the posterior centrodiapophyseal lamina, which bifurcates and reunites down the neck. Iterative specimen-based phylogenetic analyses result in each of the additional specimens recovered as the sister taxon to the holotype. When all five specimens are included in an analysis, they form a monophyletic clade that supports the monotypy of the genus. Dilophosaurus wetherilli is not recovered as a ceratosaur or coelophysoid, but is instead a non-averostran neotheropod in a grade with other stem-averostrans such as Cryolophosaurus ellioti and Zupaysaurus rougieri. We did not recover a monophyletic ‘Dilophosauridae.’ Instead of being apomorphic for a small clade of early theropods, it is more likely that elaboration of the nasals and lacrimals of stem-averostrans is plesiomorphically present in early ceratosaurs and tetanurans that share those features. Many characters of the axial skeleton of Dilophosaurus wetherilli are derived compared to Late Triassic theropods and may be associated with macropredation and an increase in body size in Theropoda across the Triassic-Jurassic boundary.

scholarly journals Atlantoaxial Instability in Down Syndrome

PEDIATRICS ◽  
1984 ◽  
Vol 74 (1) ◽  
pp. 152-154
Author(s):  
Keyword(s):  
Down Syndrome ◽  
Head And Neck ◽  
Cervical Vertebrae ◽  
Clinical Manifestations ◽  
Odontoid Process ◽  
Cervical Vertebra ◽  
Cervical Region ◽  
Atlantoaxial Instability ◽  
Atlantoaxial Joint ◽  
Special Olympics

Some issues related to participation in certain sports by persons with Down syndrome require clarification. Since 1965 there have been occasional reports about a condition described at various times as instability, subluxation, or dislocation of the articulation of the first and second cervical vertebrae (atlantoaxial joint) among persons with Down syndrome.1-15 This condition has also been found in patients with rheumatoid arthritis,16,17 abnormalities of the odontoid process of the second cervical vertebra,4,5,12,13,15 and various forms of dwarfism.18 Atlantoaxial (C-1, C-2) instability has not attracted general attention because clinical manifestations are rare and the condition is limited to a small portion of the population. The incidence of atlantoaxial instability among persons with Down syndrome has been reported by various observers to be 10% to 20%.2,9,15 When atlantoaxial instability results in subluxation or dislocation of C-1 and C-2, the spinal cord also may be injured. This is a rare but serious complication. In March 1983, the Special Olympics, Inc, sponsors of a nationwide competitive athletic program for developmentally disabled persons, without prior announcement, mandated for participants with Down syndrome special precautions to prevent serious neurologic consequences from stress on the head and neck in sports competition.19 Although thousands of persons with Down syndrome have taken part in sports events during the 15-year history of the Special Olympics without a known occurrence of neurologic complications due to participation, the new directive requires all persons with Down syndrome who wish to participate in certain sports that might involve stress on the head and neck (gymnastics, diving, pentathlon, butterfly stroke in swimming, diving start in swimming, high jump, soccer, and warm-up exercises that place undue stress on the head and neck muscles) to have a medical examination, lateral-view roentgenograms of the upper cervical region in full flexion and extension, and certification by a physician that the examination did not reveal atlantoaxial instability or neurologic disorder.

Gross Morphological Studies on the Vertebral Column of Indian Eagle Owl (Bubo bengalensis)

2020 ◽  
Author(s):  
P. Sridevi ◽  
K. Rajalakshmi ◽  
M. Sivakumar ◽  
A. Karthikeyan
Keyword(s):  
Vertebral Column ◽  
Cervical Vertebrae ◽  
Lumbar Vertebrae ◽  
Cervical Vertebra ◽  
Neural Spine ◽  
Thoracic Vertebrae ◽  
Post Mortem ◽  
Post Mortem Examination ◽  
Morphological Studies ◽  
Eagle Owl

Background: Indian eagle owl known to rotate their necks up to 270 degrees in either direction without injuring their vessels running below the head thereby without cutting off blood supply to their brains. The vertebral column in birds carry peculiar features like higher number of cervical vertebrae due to long mobile neck, lumbar and sacral vertebrae fused together giving rigidity which aid in flight. The extensive fusion of vertebral column posterior to the neck provides the required rigidity in the trunk region, this inflexibility feature might reduce weight, as it avoids the need for extensive musculature to maintain a streamlined and rigid body posture during flight. The current study aimed to study the vertebral column of Indian eagle owl in order to understand the anatomical adaptations related to this species. Methods: The specimens were procured from three Indian eagle owl brought for post mortem examination during the year 2019 to the Department of Veterinary Pathology, Rajiv Gandhi Institute of Veterinary Education and Research, Puducherry. After completion of the post-mortem examination the carcass was collected and macerated as per the standard technique and various measurements on vertebral column bones were measured using vernier calliper. Result: The study revealed that vertebral column of Indian eagle owl consisted of 14 cervical vertebrae, 7 thoracic vertebrae, 13 to 14 lumbar vertebrae fused with sacral vertebrae forming synsacrum and 7 coccygeal vertebrae. The hypapophyses of the 14th cervical vertebra and first two thoracic vertebrae were trifid in nature specific feature seen in Indian eagle owl. The vertebral column had characteristics features of hypapophyses, transverse process, pneumatic foramen and neural spine which enable the owl to adapt for head rotation and various task involving vertebrae.

scholarly journals Atlanto-occipital Approach for Cervical Myelography in Horse with Spinal Cord Compression

2018 ◽  
Vol 75 (2) ◽  
pp. 182
Author(s):  
Cosmin PEŞTEAN ◽  
Liviu OANA ◽  
Cristian CRECAN ◽  
Alexandra MUREŞAN ◽  
Robert PURDOIU ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Compression ◽  
Vertebral Column ◽  
Neurological Diseases ◽  
Cervical Vertebrae ◽  
Cord Compression ◽  
Cervical Region ◽  
Radiographic Images ◽  
Head Positions ◽  
Lateral Recumbency

The aim of this study was to establish a specific interdisciplinary protocol for evaluation of horses with spinal cord compression. A filly was presented with signs of ataxia at the Faculty of Veterinary Medicine Cluj-Napoca. After neurological examination the presumptive diagnostic was spinal cord compression. Under general anesthesia, the patient was placed for radiological examination in lateral recumbency with head elevated. After antisepsia of cervical region, a Tuohy needle was inserted in atlanto-occipital space and contrast substance was administrated. Radiographic images of the cervical vertebral column were obtained in the neutral, flexed, and extended head positions. The anesthesia protocol was effective, the needle was placed safely in the subarachnoid space and the contrast substance flowed caudally. The obtained radiographic images confirmed spinal cord compressions at the level of cervical vertebrae C3, C4, C5. This working protocol was effective to obtain radiographical images with contrast substance in horses with neurological diseases.

scholarly journals Tip dating supports novel resolutions of controversial relationships among early mammals

2020 ◽  
Vol 287 (1928) ◽  
pp. 20200943
Author(s):  
Benedict King ◽  
Robin M. D. Beck
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Morphological Evolution ◽  
Phylogenetic Analyses ◽  
Late Triassic ◽  
Crown Group ◽  
Jehol Biota ◽  
Rates Of Evolution ◽  
Mammal Evolution ◽  
Minimum Divergence

The estimation of the timing of major divergences in early mammal evolution is challenging owing to conflicting interpretations of key fossil taxa. One contentious group is Haramiyida, the earliest members of which are from the Late Triassic. Many phylogenetic analyses have placed haramiyidans in a clade with multituberculates within crown Mammalia, thus extending the minimum divergence date for the crown group deep into the Triassic. A second taxon of interest is the eutherian Juramaia from the Middle–Late Jurassic Yanliao Biota, which is morphologically very similar to eutherians from the Early Cretaceous Jehol Biota and implies a very early origin for therian mammals. Here, we apply Bayesian tip-dated phylogenetic methods to investigate these issues. Tip dating firmly rejects a monophyletic Allotheria (multituberculates and haramiyidans), which are split into three separate clades, a result not found in any previous analysis. Most notably, the Late Triassic Haramiyavia and Thomasia are separate from the Middle Jurassic euharamiyidans. We also test whether the Middle–Late Jurassic age of Juramaia is ‘expected’ given its known morphology by assigning an age prior without hard bounds. Strikingly, this analysis supports an Early Cretaceous age for Juramaia , but similar analyses on 12 other mammaliaforms from the Yanliao Biota return the correct, Jurassic age. Our results show that analyses incorporating stratigraphic data can produce results very different from other methods. Early mammal evolution may have involved multiple instances of convergent morphological evolution (e.g. in the dentition), and tip dating may be a method uniquely suitable to recognizing this owing to the incorporation of stratigraphic data. Our results also confirm that Juramaia is anomalous in exhibiting a much more derived morphology than expected given its age, which in turn implies very high rates of evolution at the base of therian mammals.

scholarly journals The role of B-mode ultrasonography in the musculoskeletal anatomical evaluation of the cervical region of the dog spine

2014 ◽  
Vol 34 (1) ◽  
pp. 91-97 ◽  
Author(s):  
Cibely G. Sarto ◽  
Maria Cristina F. N. S. Hage ◽  
Luciana D. Guimarães ◽  
Robson F. Giglio ◽  
Andréa P. B. Borges ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Computed Tomography ◽  
Magnetic Resonance ◽  
Ultrasound Examination ◽  
Cervical Vertebrae ◽  
Cervical Vertebra ◽  
Cervical Region ◽  
Resonance Imaging ◽  
Musculoskeletal Anatomy

This study characterized the normal musculoskeletal anatomy of the cervical segment of the spine of dogs by means of B-mode ultrasonography. The objective was to establish the role of B-mode ultrasonography for the anatomical evaluation of the cervical spine segment in dogs, by comparing the ultrasonographic findings with images by computed tomography and magnetic resonance imaging. The ultrasound examination, in transverse and median sagittal sections, allowed to identify a part of the epaxial cervical musculature, the bone surface of the cervical vertebrae and parts of the spinal cord through restricted areas with natural acoustic windows, such as between the atlanto-occipital joint, axis and atlas, and axis and the third cervical vertebra. The images, on transverse and sagittal planes, by low-field magnetic resonance imaging, were superior for the anatomical identification of the structures, due to higher contrast between the different tissues in this modality. Computed tomography showed superiority for bone detailing when compared with ultrasonography. As for magnetic resonance imaging, in addition to the muscles and cervical vertebrae, it is possible to identify the cerebrospinal fluid and differentiate between the nucleus pulposus and annulus fibrosus of the intervertebral discs. Although not the scope of this study, with knowledge of the ultrasonographic anatomy of this region, it is believed that some lesions can be identified, yet in a limited manner, when compared with the information obtained mainly with magnetic resonance imaging. The ultrasound examination presented lower morphology diagnostic value compared with the other modalities.

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