Vertebral Elements Research Articles

Para comprender la política digital – Principios y acciones

La irrupción de internet ha obligado a una reformulación de la comunicación en todos los ámbitos y a todos los niveles. Políticos y candidatos se han visto obligados a adaptarse a un medio en constante cambio, donde las reglas de la comunicación unidireccional se pierden, pero las posibilidades técnicas y el alcance de los mensajes se multiplican. Este artículo realiza efectuar una aproximación a las herramientas y prácticas de la tecnopolítica así como el uso táctico y estratégico de las herramientas digitales para la organización, la comunicación y la acción. Para ello, señala las principales plataformas ligadas a internet como web, redes sociales, las plataformas de mensajería instantánea y, más recientemente, las aplicaciones para smartphone de uso exclusivamente político. Asimismo, se analizan las tendencias actuales ligadas a la celebrificación del candidato, el uso de memes, las etiquetas como elemento vertebrador y transversal en la comunicación digital, el análisis de big data como la última frontera y la participación a través de usuarios (semi)automatizados o bots. Desde el punto de vista del ruido comunicativo, se abordan dos de las principales problemáticas de la comunicación política como son el astroturfing - en todas su variantes - y las fake news, ligadas al creciente discurso de odio en plataformas digitales. Finalmente, y tras el análisis realizado, se propone lo que, a juicio de los autores, son las claves para entender la política que está por venir.
 Finalmente, y tras el análisis realizado, se propone lo que, a juicio de los autores, son las claves para entender la política que está por venir.

Analysis and improvement of the three-column spinal theory

BackgroundDenis and Ferguson et al.’s three-column spinal theory has been widely accepted and applied. However, this three-column theory was proposed based solely on observation and experience without thorough documented data and analysis. The aim of this study was to analyze and improve Denis and Ferguson et al.’s three-column spinal theory to propose a novel three-column concept in epidemiology, morphology and biomechanics.MethodsA retrospective analysis of the computed tomography imaging data of patients with a diagnosis of T11-L5 vertebral fractures was conducted between February 2010 and December 2018. Three-dimensional (3D) distribution maps of fracture lines of all subjects were obtained based on 3D mapping techniques. In addition, a 25-year-old health male volunteer was recruited for the vertebral finite element force analysis.ResultsThe present study enrolled 459 patients (age: 48 ± 11.42 years), containing a total of 521 fractured vertebrae. The fracture lines peaked in the upper and the outer third sections of the vertebra, starting from the anterior part of the vertebral pedicles in 3-D maps. Regarding flexion and extension of the spine, the last third of the vertebral body in front of the spinal canal was one main stress center in the finite element analysis. The stress on the vertebral body was greater in front of the pedicles in the lateral bending.ConclusionThe study reveals that the posterior one-third of the vertebral body in front of the spinal canal and the posterior one-third of the vertebral body in front of the pedicle are very different in terms of fracture characteristics and risks to spinal canal (3D maps and stress distributing graphs), therefore, they should be classified as different columns. We provide strong evidence that Su’s three-column theory complies with the characteristics of vertebral physiological structure, vertebral fracture, and vertebral biomechanics.Graphical abstract

Skeletal Anatomy of Acaenasuchus Geoffreyi Long and Murry, 1995 (Archosauria: Pseudosuchia) and its Implications for the Origin of the Aetosaurian Carapace

ABSTRACT Acaenasuchus geoffreyi is a diminutive armored archosaur from the Upper Triassic Chinle Formation of northern Arizona, U.S.A., with uncertain evolutionary relationships and skeletal maturity. Known only from osteoderms, the taxon has been considered a valid taxon of aetosaur, juvenile specimens synonymous with the aetosaur Desmatosuchus spurensis, or a non-aetosaurian pseudosuchian archosaur. Here, we describe new fossils of Acaenasuchus geoffreyi that represent cranial, vertebral, and appendicular elements as well as previously unknown variations in the dorsal carapace and ventral shield. The skull bones are ornamented with the same anastomosing complex of ridges and grooves found on the paramedian and lateral osteoderms, and the appendicular skeleton resembles that of Revueltosaurus callenderi, Euscolosuchus olseni, aetosaurs, and other armored archosaurs such as erpetosuchids. Histology of osteoderms from the hypodigm of Acaenasuchus geoffreyi shows multiple growth lines, laminar tissue, and low vascularity, evidence that the individuals were close to skeletal maturity and not young juveniles. A revised phylogenetic analysis of early archosaurs recovers Acaenasuchus geoffreyi and Euscolosuchus olseni as sister taxa and members of a new clade that is the sister taxon of Aetosauria. This new phylogeny depicts a broader distribution of osteoderm character states previously thought to only occur in aetosaurs, demonstrating the danger of using only armor character states in aetosaur taxonomy and phylogeny. Acaenasuchus geoffreyi is also a good example of how new fossils can stabilize ‘wild card’ taxa in phylogenetic analyses and contributes to our understanding of the evolution of the aetosaur carapace.

Phylogenetic analysis of the Tc1/mariner superfamily reveals the unexplored diversity of pogo-like elements

BackgroundTc1/mariner transposons are widespread DNA transposable elements (TEs) that have made important contributions to the evolution of host genomic complexity in metazoans. However, the evolution and diversity of the Tc1/mariner superfamily remains poorly understood. Following recent developments in genome sequencing and the availability of a wealth of new genomes, Tc1/mariner TEs have been identified in many new taxa across the eukaryotic tree of life. To date, the majority of studies focussing on Tc1/mariner elements have considered only a single host lineage or just a small number of host lineages. Thus, much remains to be learnt about the evolution of Tc1/mariner TEs by performing analyses that consider elements that originate from across host diversity.ResultsWe mined the non-redundant database of NCBI using BLASTp searches, with transposase sequences from a diverse set of reference Tc1/mariner elements as queries. A total of 5158 Tc1/mariner elements were retrieved and used to reconstruct evolutionary relationships within the superfamily. The resulting phylogeny is well resolved and includes several new groups of Tc1/mariner elements. In particular, we identify a new family of plant-genome restricted Tc1/mariner elements, which we call PlantMar. We also show that the pogo family is much larger and more diverse than previously appreciated, and we review evidence for a potential revision of its status to become a separate superfamily.ConclusionsOur study provides an overview of Tc1-mariner phylogeny and summarises the impressive diversity of Tc1-mariner TEs among sequenced eukaryotes. Tc1/mariner TEs are successful in a wide range of eukaryotes, especially unikonts (the taxonomic supergroup containing Amoebozoa, Opisthokonta, Breviatea, and Apusomonadida). In particular, ecdysozoa, and especially arthropods, emerge as important hosts for Tc1/mariner elements (except the PlantMar family). Meanwhile, the pogo family, which is by far the largest Tc1/mariner family, also includes many elements from fungal and chordate genomes. Moreover, there is evidence of the repeated exaptation of pogo elements in vertebrates, including humans, in addition to the well-known example of CENP-B. Collectively, our findings provide a considerable advancement in understanding of Tc1/mariner elements, and more generally they suggest that much work remains to improve understanding of the diversity and evolution of DNA TEs.

Development and evolution of regionalization within the avian axial column

AbstractThe origin of birds from their terrestrial antecedents was accompanied by a wholesale transformation of their skeleton as they transitioned from a terrestrial to aerial realm. Part of this dramatic transformation is the reduction of separate vertebral elements into regional fusions to limit axial flexibility. This is partially mirrored within the development of the axial column, with regions of the axial column experiencing increasing morphological modularity and the loss of skeletal elements through vertebral fusions. Using a detailed description of the morphological development of the axial column in the model domestic chicken, Gallus gallus domesticus, we present a map of axial ossification based on discrete characters. Delays in ossification are found to occur in conjunction with the formation of fusions. Our study shows that the pattern and sequence of fusion and ossification during development may reflect the presence of independent modules as subsets within the typical regions of the avian axial column. Interestingly, few of these fusion modules correspond to the initial axial Hox expression patterns, suggesting another patterning mechanism is driving axial fusion regionalization. Additionally, two regions of fusion are discovered in the synsacrum. The anterior region of seven fused synsacrals may correspond to the non-ornithuran pygostylian synsacrum of the same number of vertebrae.

The Extent of Metaplastic Hard Tissue Within the Appendicular Skeleton of the Nine‐Banded Armadillo (Dasypus novemcinctus)

The developmental and functional advantages of vertebrate metaplastic hard tissue is still relatively unclear. Metaplastic tissue forms from the direct transformation of one cell type to another. Specifically, mineralization of preformed dense connective tissue results in intratendinous metaplastic tissue, and has been described in a variety of taxa and elements including turtle shell, reptilian osteoderms, sturgeon scutes, dinosaur cranial and vertebral elements, ossified tendons, portions of bird skeletons, and tendinous entheses in mammalian bone. However, histological analysis of the extent of metaplastic hard tissues, both across Mammalia and within individual mammalian bones, is lacking. Here we serially sectioned both tibiae of a nine‐banded armadillo, Dasypus novemcinctus [Xenarthra: Cingulata], transversely and longitudinally to identify the existence and possible patterns of metaplastic hard tissue. All skeletal elements were processed using standard procedure for the preparation of undecalcified bone. We found evidence of metaplastic hard tissue in the tibial crest, as well as the medial side of the diaphysis and the proximal lateral side of the tibia. The metaplastic tissue in the tibial crest appears interstitially within a primary woven bone matrix. Along the lateral side, metaplastic tissue forms a thin patch in the mid‐cortex superficial to compact coarse cancellous bone. The presence of metaplastic hard tissue seems consistent with tendinous insertions through fibrous entheses along the length of the tibia and tibial crest. The entrapment of metaplastic tissue within the tibia is likely due to appositional bone growth at the enthesis. However, the presence of metaplastic hard tissue on the medial side of the mid‐diaphyseal and proximal portion of the tibia does not appear to be associated with any tendinous insertions. Previously, unassociated metaplastic tissue was found extensively in osteoderms, ankylosaur tail clubs, and dinosaur cranial ornamentation such as the parietal frill of Triceratops. Study of metaplastic hard tissue in modern bone, independent of tendinous insertions, can improve our understanding of its potential biomechanical advantages and thereby possibly provide clues to its use in ornamentation and within the appendicular skeleton. Metaplastic hard tissues have likely been misidentified and understudied in previous investigations of modern hard tissue microstructure. Additionally, because Xenarthra is proposed to be one of the four original clades of placental mammals, analysis of metaplastic tissue in the skeleton of D. novemcinctus could have implications for early mammalian bone development patterns.Support or Funding InformationPartial funding was provided by Montana State University Undergraduate Scholar’s ProgramFigure 1

Horizontal transfer and evolution of transposable elements in vertebrates

Horizontal transfer of transposable elements (HTT) is an important process shaping eukaryote genomes, yet very few studies have quantified this phenomenon on a large scale or have evaluated the selective constraints acting on transposable elements (TEs) during vertical and horizontal transmission. Here we screen 307 vertebrate genomes and infer a minimum of 975 independent HTT events between lineages that diverged more than 120 million years ago. HTT distribution greatly differs from null expectations, with 93.7% of these transfers involving ray-finned fishes and less than 3% involving mammals and birds. HTT incurs purifying selection (conserved protein evolution) on all TEs, confirming that producing functional transposition proteins is required for a TE to invade new genomes. In the absence of HTT, DNA transposons appear to evolve neutrally within genomes, unlike most retrotransposons, which evolve under purifying selection. This selection regime indicates that proteins of most retrotransposon families tend to process their own encoding RNA (cis-preference), which helps retrotransposons to persist within host lineages over long time periods.

Association between osteoporotic femoral neck fractures and DXA-derived 3D measurements at lumbar spine: a case-control study.

The aim of the present study was to evaluate the association between DXA-derived 3D measurements at lumbar spine and osteoporotic hip fractures. We analyzed a case-control database composed by 61 women with transcervical hip fractures and 61 age-matched women without any type of fracture. DXA scans at lumbar spine were acquired, and areal bone mineral density (aBMD) was measured. Integral, trabecular and cortical volumetric BMD (vBMD), cortical thickness, and cortical surface BMD (sBMD) at different regions of interest were assessed using a DXA-based 3D modeling software. Descriptive statistics, tests of difference, odds ratio (OR), and area under the receiver operating curve (AUC) were used to compare hip fracture and control groups. Integral vBMD, cortical vBMD, cortical sBMD, and cortical thickness were the DXA-derived 3D measurements at lumbar spine that showed the stronger association with transcervical hip fractures, with AUCs in the range of 0.685-0.726, against 0.670 for aBMD. The highest AUC (0.726) and OR (2.610) at the lumbar spine were found for integral vBMD at the posterior vertebral elements. Significantly, lower AUC (0.617) and OR (1.607) were found for trabecular vBMD at the vertebral body. Overall, total femur aBMD remains the DXA-derived measurement showing the highest AUC (0.838) and OR (6.240). This study showed the association of DXA-derived measurements at lumbar spine with transcervical hip fractures. A strong association between vBMD at the posterior vertebral elements and transcervical hip fractures was observed, probably because of global deterioration of the cortical bone. Further studies should be carried out to investigate on the relative risk of transcervical fracture in patients with long-term cortical structural deterioration.

Histology and structural integration of the major morphologies of the Cypriniform Weberian apparatus.

The Weberian apparatus, a diagnostic feature of otophysan fishes, is a novel hearing adaptation integrating several developmental and morphological systems (ear-vertebral column-swim bladder). Otophysan fishes are one of the largest and most successful freshwater clades, with over 10,000 species across most continents. The largest otophysan order, Cypriniformes, dominates the freshwaters of Asia, Europe, North America, and Africa. Spanning such a wide variety of environments, the Weberian apparatus undergoes morphological modifications to maintain functionality. Within Cypriniformes, we propose three distinct morphological classes of the Weberian apparatus based on the level of skeletal expansion around the swim bladder: simple (typical of most Cyprinidae), anterior plate (found in families such as Gyrinocheilidae, Catostomidae, and Botiidae), and encapsulated (either single-capsule as found, e.g., in Gobionidae and Cobitidae, or double-capsule as found, e.g., in Nemacheilidae and Balitoridae). Little ontological or comparative data exists regarding the construction or integration of these different morphologies, and less is known about the tissue level integration and variation within these morphologies. We used paraffin histology to document the hard and soft tissue anatomy of the Weberian apparatus in six species representing all morphological classes. We found sites of similarity across the morphologies including size and structure of the saccule, aspects of ossicle ossification, and swim bladder tunica composition, indicating potential sites of developmental and functional constraint. In contrast, we found differences across both auditory and nonauditory features in otic chamber size, ossification within ossicles and other vertebral elements, and composition of ligaments, indicating likely sites of adaptability. Some of these changes are likely evolutionary (taxonomic), but may be influenced by the environmental niche occupied by the clade. These results show a clear need for increased ontological and comparative study of the complete cypriniform Weberian apparatus, particularly histologically, as well as increased auditory studies across morphological types.

Stent screw-assisted internal fixation (SAIF): clinical report of a novel approach to stabilizing and internally fixating vertebrae destroyed by malignancy.

Severe lytic cancerous lesions of the spine are associated with significant morbidity and treatment challenges. Stabilization and restoration of the axial load capability of the vertebral body (VB) are important to prevent or arrest vertebral collapse. Percutaneous stent screw-assisted internal fixation (SAIF), which anchors a VB stent/cement complex with pedicular screws to the posterior vertebral elements, is a minimally invasive, image-guided, 360° internal fixation technique that can be utilized in this patient cohort. The purpose of this study was to assess the feasibility, safety, and stabilization efficacy of VB reconstruction via the SAIF technique in a cohort of patients with extensive lytic vertebral lesions, who were considered to have an unstable or potentially unstable spine according to the Spinal Instability Neoplastic Score (SINS). This study was a retrospective assessment of a prospectively maintained database of a consecutive series of patients with neoplastic extensive extracompartmental osteolysis (Tomita type 4-6) of the VB treated with the SAIF technique. VB reconstruction was assessed on postprocedure plain radiographs and CT by two independent raters. Technical and clinical complications were recorded. Clinical and imaging follow-ups were assessed. Thirty-five patients with extensive osteolytic metastatic lesions of the VB underwent 36 SAIF procedures. SAIF was performed as a stand-alone procedure in 31/36 cases and was associated with posterior surgical fixation in 5/36 (4/5 with decompressive laminectomy). In 1 case an epidural cement leak required surgical decompression. VB reconstruction was categorized as satisfactory (excellent or good rating) by the two raters in 34/36 cases (94.5%) with an interrater reliability of 94.4% (Cohen's kappa of 0.8). Follow-up, ranging from 1 to 30 months, was available for 30/36 levels. Long-term follow-up (6-30 months, mean 11.5 months) was available for 16/36 levels. Stability during follow-up was noted in 29/30 cases. SAIF provides 360° nonfusion internal fixation that stabilizes the VB in patients with extensive lytic lesions that would otherwise be challenging to treat.

Pott's Disease: An Emerging Source of Potentially Inappropriate Treatment.

Spinal Tuberculosis in children is uncommon, even more so in cases of involvement of posterior vertebral elements, and its diagnosis is often delayed. Here we report the case of a young female presenting neuroradiological features and clinical symptoms suspicious for malignant tumor. Histological examination of biopsy specimen evidenced a Pott's disease. We highlight the importance of suspecting this disorder in children with both aspecific systemic and neurological symptoms, in order to reach a timely diagnosis for appropriate and targeted intervention, avoiding the risk of overtreatment and malpractice claims.

Knockdown of aristaless-like homeobox1 inhibits epithelial-mesenchymal transition through Wnt/β-catenin signaling pathway in melanoma cells

Aristaless-like homeobox1 (ALX1), a member of the ALX family, is capable of mediating survival and development of mesenchyme-derived elements in vertebrates and its mutation will prevent the fusion of frontonasal and maxillary elements. Recently, ALX1 has been reported to be associated with cancer progression. However, the specific roles of ALX1 in melanoma remain unclear. In this study, we investigated the expression pattern and biological functions of ALX1 in melanoma. We found that ALX1 was highly expressed in melanoma tissues and cell lines. Knockdown of ALX1 suppressed the proliferation and invasion of melanoma cells. Furthermore, we showed that ALX1 knockdown reversed the epithelial-mesenchymal transition (EMT) process in melanoma cells, which might be attributed to inactivation of the Wnt/β-catenin pathway. Taken together, this study provided a new insight into the role of ALX1 as a therapeutic target for melanoma treatment.

The Synarcual of the Little Skate, Leucoraja erinacea: Novel Development Among the Vertebrates

Evolutionary variation in anteroposterior patterning of the axial skeleton is a major contributor to the evolution of the vertebrate body plan, with five canonical vertebral types in tetrapods (cervical, thoracic, lumbar, sacral, caudal). However, less is known about the evolutionary origin and variation in vertebral regionalization patterns outside of tetrapods where described vertebral types range from as few as two in some chondrichthyans to eight or more in some teleost fishes. The synarcual is a specialized adaptation of the anterior axial skeleton comprising a putatively fused array of vertebral elements characteristic of jawed vertebrate (gnathostome) clades such as batoid and chimaeroid chondrichthyans where they support enlarged pectoral fins and dorsal fin spines respectively, as well as a fossil group known as the placoderms. Placoderms represent the phylogenetically most basal jawed vertebrates and the presence of a synarcual in these and chondrichthyans may suggest a conserved vertebral type for jawed vertebrates, predating the divergence of stem and crown gnathostomes. Alternatively, synarcuals may have evolved independently in these lineages, exhibiting a remarkable case of morphological convergence. In order to address this question, we investigated the early development of the cervicothoracic synarcual of an emerging model chondrichthyan: the Little skate Leucoraja erinacea. By combining x-ray computed tomography, and classical histology, we show that the skate synarcual is a complex composite element which develops from a hollow, continuous cartilaginous element devoid of any vertebral centra anterior to the pectoral girdle, and fusion/remodeling of initially distinct vertebrae posteriorly. A de novo transcriptome assembly for two developmental stages of the skate synarcual and post-synarcual axial skeletal elements supported this two-phase development, with differences in expression levels of several developmental genes, including Hox family transcription factors, which suggest anterior-posterior regionalization along the vertebral column, potentially linked to the synarcual. In addition, multiple genes related to skeletal remodeling were found to be more highly expressed at stage 33, including genes related to osteoclast activity, normally associated with removal of bone, a tissue absent in chondrichthyans. These genes are potentially related to loss of mineralization as vertebral elements are incorporated into the synarcual.

<i>Vitakrisaurus saraiki</i> Theropod from South Asia

Vitakrisaurus saraiki abelisauroid theropod dinosaurs reported from Pakistan and extended distribution into India. Vitakrisaurus saraiki is medium to large sized theropod which is represented by associated vertebral and limb elements and especially hand elements. Out of 14 small to large bodied theropods from Indo-Pakistan subcontinent, only less than half of these are restricted to some common elements. Vitakrisaurus saraiki theropod of Pakistan is based on associated vertebral and limb elements especially hand including articulated carpals, metacarpals, phalanges and claws which are significant for Gondwanan paleobiogeographic link, comparisons and systematic.

Medium Sized Stocky Titanosaur from South Asia

Recently, four coexisted titanosaurs from latest Maastrichtian Vitakri Lameta Formation of Indo-Pakistan are recognized as Isisaurus and Pakisaurus of large-sized slender pakisaurids, Saraikimasoom and Gspsaurus of the smallest and medium sized transversely stocky gspsaurids. Gspsaurus pakistani based on associated skull (with conical teeth tapering gradually from base to tip), vertebral and appendicular elements found from Alam 19 locality of Vitakri area, Barkhan district, Balochistan, Pakistan, South Asia. Gspsaurus bears sufficient skeletal elements and can be used for evolutionary studies.

Shape does matter: A geometric morphometric approach to shape variation in Indo-Pacific fish vertebrae for habitat identification

Traditional fish vertebrae identification relies on the availability of comprehensive reference collections that include every element from the neural spine for each taxon. In regions with great taxonomic diversity, such as the Indo-Pacific, the identification of fish vertebrae to species is difficult. This results in taxonomic lists with many skeletal elements identified only to family. However family level identifications often tell us little about the environmental preferences of the fish and thus, by inference, human fishing practices. Here we apply geometric morphometrics (GM) to examine shape variations within vertebrae in modern specimens of a variety of pelagic and reef species to determine if this method can be used to reliably inform on habitat preferences. Digitized vertebral elements of reef (Acanthuridae, Balistidae, Labridae, Lethrinidae, Lutjanidae and Serranidae) and pelagic/open water (Scombridae and Carangidae) families were scored using 2D landmarks. These were subjected to Generalized Procrustes Analysis and discriminatory multivariate analyses (Linear Discriminant Analysis and Discriminant Function Analysis) in order to assess whether shape can be used to differentiate habitats. Our results suggest that geometric morphometrics do allow the differentiation of habitat in vertebrae and provide an alternative method for the classification of archaeological fish assemblages. These analyses were applied to a sample of archaeological fish remains from a site in Alor Island (Nusa Tenggara Timur, Indonesia) and compared with the results of an earlier traditional comparative icthyoarchaeological analysis. We found that the main component of the Pleistocene marine human diet comprised reef species, with the sporadic addition of open water species, supporting the pattern recorded with traditional analyses. This methodology could be widely applied to archaeological fish material from across the Indo-Pacific allowing a greater number of bones in assemblages to contribute to insights into human exploitation of coastal habitats and fishing techniques over time.

Osteological development and deformities in hatchery-reared longtooth grouper (Epinephelus bruneus ): Vertebral column, dorsal-fin supports and caudal-fin skeleton

Skeletal deformities are one of the serious problems in hatchery-reared longtooth grouper (Epinephelus bruneus). In this study, seed production of longtooth grouper was carried out in four large hatchery-grade tanks. Osteological development of the vertebral column, caudal-fin skeleton and dorsal-fin supports in larvae and juveniles was described. The vertebral ontogeny started at 4.8 mm total length (TL) with the formation of neural spines 2 and 3, and the vertebral centra began forming at 5.3 mm TL. By 16 mm TL, all vertebral bony elements were formed except for the dorsal ribs. The onsets of the ontogeny of the caudal-fin skeleton and dorsal-fin supports occurred at approximately 5.1 mm and 3.9 mm TL, respectively, and the completion of these bony elements occurred at approximately 20 mm TL. The incidence of deformity was examined; some type of deformity was observed in 57%–68% of the specimens. These deformities mainly occurred as three types: lordosis, around vertebrae 1–5; saddleback-like syndrome, around vertebrae 7–11; and vertebrae fusion, around vertebrae 22–24. The incidence of prehaemal lordosis was significantly higher among individuals with an uninflated swim bladder than among those with an inflated swim bladder.

Xenarthran Synsacrum Morphology and Evolution

Xenarthra is unique in having striking features in the axial skeleton, usually very different from the rest of the eutherian clades. Some of these features are widely spread among the members of the group (e.g., the presence of xenarthrales in most cingulates and all pilosans, and the synsacrum with sacroischial union to the pelvis in almost all xenarthrans) and others are restricted to some taxa (e.g., deviated number of cervical vertebrae in Bradypus and Choloepus). In this study, we aim to explore the great diversity of vertebral elements composing the xenarthran synsacrum within a phylogenetic framework. Vertebral counts of the adult synsacrum was obtained from almost all extant genera, with the exception of Calyptophractus, and several fossils. The modal number of vertebrae from the adult synsacrum was mapped onto a composite phylogeny of Xenarthra. The ancestral number of synsacrals for Xenarthra was recovered as ambiguous, although one of the optimizations recorded a number of six synsacrals, probably three iliac and three post-iliac vertebrae. The clade Cingulata is characterized by a high number of vertebrae forming the synsacrum (eight synsacrals), which is fused to the ischium through the tip of the transverse processes of the most posterior vertebrae. In pilosans, the ancestral number of synsacral vertebrae seems to be lower, probably formed by five or six vertebrae, and the union with the ischium is achieved through the base of the transverse processes of the most posterior vertebrae. Two exceptions stand out, one involving the extant suspensory sloths and Megalocnus, and the other involving a family of ground sloths, the Mylodontidae. A probable relationship of the synsacral number in the different taxa to the lifestyles is discussed.

Morphology of the core fibrous layer of the cetacean tail fluke.

The cetacean tail fluke blades are not supported by any vertebral elements. Instead, the majority of the blades are composed of a densely packed collagenous fiber matrix known as the core layer. Fluke blades from six species of odontocete cetaceans were examined to compare the morphology and orientation of fibers at different locations along the spanwise and chordwise fluke blade axes. The general fiber morphology was consistent with a three-dimensional structure comprised of two-dimensional sheets of fibers aligned tightly in a laminated configuration along the spanwise axis. The laminated configuration of the fluke blades helps to maintain spanwise rigidity while allowing partial flexibility during swimming. When viewing the chordwise sectional face at the leading edge and mid-chord regions, fibers displayed a crossing pattern. This configuration relates to bending and structural support of the fluke blade. The trailing edge core was found to have parallel fibers arranged more dorso-ventrally. The fiber morphology of the fluke blades was dorso-ventrally symmetrical and similar in all species except the pygmy sperm whale (Kogia breviceps), which was found to have additional core layer fiber bundles running along the span of the fluke blade. These additional fibers may increase stiffness of the structure by resisting tension along their long spanwise axis.

Pathology in a Permian parareptile: congenital malformation of sacral vertebrae

AbstractPareiasaurs were a group of herbivorous reptiles that lived during the middle to late Permian (265–252 Ma). About 20 species are currently recognized from a fossil record spanning Europe, Asia, South America, and Africa. All pareiasaurs have a peculiar vertebral anatomy characterized by ‘swollen’ neural arches. Some species grew to large body size (e.g., 600 kg) and evolved up to five sacral vertebrae, but the detailed anatomy of the sacral region is poorly documented. Vertebral elements referable to the derived pareiasaur subclade Velosauria were recently recovered from the upper Madumabisa Mudstone Formation (Luangwa Basin) of Zambia and are described here. The specimen exhibits an abnormal morphology: the neural arches of the second, third, and fourth sacral vertebrae share a single, elongate centrum that is fused anteriorly with a ‘normal’ first sacral vertebra, and articulates posteriorly with a slightly disarticulated first caudal vertebra. We suggest two distinct pathologies are responsible for this morphology: (1) spondyloarthropathy (re‐ossified intervertebral joint) and (2) congenital block vertebra. The processes of development of neural arches and centra, while evolutionarily independent in origin, have been found to be conserved in all amniotes. While paleopathological morphologies can provide insight into environmental and disease‐based etiologies, pathological congenital malformations are particularly rare in fossil record and have the potential to be informative for understanding the evolution of vertebral development. The anatomy described here sheds light on pareiasaurian sacral morphology and provides insight into the pathology in one of the earliest clades of large‐bodied reptiles near the base of the amniote tree.