Academic literature on the topic 'Osteoderms'

Skink lizards have an unusual complex osteoderm, which consists of several bone elements – osteodermitis. We have carried out the first histological and computer microtomographic study of the structure of the original and regenerating complex osteoderms of skink lizards using Eurylepis taeniolata as an object. The topography of osteoderms in the integument of the original region of the tail and its regenerated part was studied. The fundamental similarity of the morphology and microstructure of the original and regenerated osteoderms was showed. A description of the development of the microstructure of a complex osteoderm in the process of regeneration is given. The presence of osteodermin on the surface of osteoderms in the studied species was revealed.

Abstract Cranial exostoses (areas of periosteal ornamentation) are present on the external surfaces of the skull and mandible of Scelidosaurus harrisonii. True osteoderms have also been identified on the skull, forming a ‘brow-ridge’ of three supraorbital bones, dished plates that are attached to the lateral surface of the postorbitals and a pair of larger, horn-shaped structures that project from the posterodorsal surface of the occiput. Postcranial osteoderms form an extensive series of oval-based, ridged osteoderms that extend backward across the dorsal and lateral surfaces of the neck and torso. Smaller, narrow-based ridged osteoderms are also found on the lateral surfaces of the limbs. The tail is surrounded by four longitudinal rows of large, narrow-based, ridged or keeled osteoderms. The neck, unlike the rest of the body, is encased dorsolaterally by a variety of osteoderms. These can be differentiated into two fundamental types: base-plate osteoderms that develop deep within the compact layers of the dermis and, superficial to each base-plate, tall, ridged or cap-like osteoderms. These latter, project outward from the skin surface and were covered by an epidermal scale or a rigid keratinous sheath. The base-plates are true osteodermal components, but to differentiate them from the more familiar superficial osteoderms, they will be called here simply ‘base-plates’. Lying on the dorsal midline between and beneath the occipital horns is a single, ridged, nuchal osteoderm comprising a base-plate and osteoderm cap. The nuchal plate is flanked by a pair of prominent ‘tricorn’ osteoderm arrays mounted on shallowly arched blocks of fused base-plate osteoderms. Behind the tricorn arrays is a succession of four partial collar-like arrays of osteoderms formed (at least in ontogenetically mature specimens) by coalesced base-plates that anchor tall and either carinate or more plate-like osteoderms. The largest of these are always positioned on the ventrolateral margin of each collar. The osteoderms become progressively smaller toward the midline. It is at present unclear whether the base-plate supported collar arrays on either side fuse together along the midline to form cervical half-rings, as is often reported in more derived ankylosaurian thyreophorans. Individual collar arrays do not imbricate with each other, but are likely to have been interconnected by sheets of tough connective tissue. On the ventrolateral flanks of the pectoral region are found the largest, bladed osteoderms. In two partly articulated skeletons an osteoderm is preserved on the posterodistal surface of the scapular blade. Although this position is reminiscent of the parascapular spines found in some stegosaurs, these bones are not regarded as homologues; their placement is a coincidence of positioning an osteoderm row adjacent to the scapular blade. The torso preserves three principal rows of large, ridged osteoderms that show no evidence of accompanying base-plates. The ventrolateral row has the largest osteoderms and these are succeeded in size by the lateral row and dorsolateral row, respectively. There is no evidence to support the existence of a midline dorsal row of osteoderms. The principal rows extend backward across the dorsal and lateral flanks of the body as far as the pelvic area. Smaller cap-shaped osteoderms are scattered between the principal rows, but whether they were organized into subsidiary rows or were more randomly distributed cannot be ascertained. Smaller, narrow-based, ridged osteoderms are found in oblique rows across the anterior chest; they also flank the proximal half of the forelimb (as far as the elbow) and extend to the ankle region in the hind limb. The tail is surrounded by large, narrow-based, high-ridged osteoderms. Unlike the neck and torso, there is a row of dorsal midline osteoderms that are flanked by large, lateral osteoderms, and beneath these there is a midline ventral row. The latter are close-set and particularly deeply keeled in the area nearest to the pelvis. Osteoderms vary considerably both in structure and texture. Base-plates have a rough, porous external texture as a consequence of the abundant vascular canals that penetrate these bones. Internally, their surface is arched and has a woven-textured fabric comprising bundles of mineralized fibres interspersed with large vascular foramina. Accompanying osteoderms are generally a little denser than their base-plates and have a smoother cortex, although abundant small foramina and shallow vascular channels pit and groove this external surface. The pair of occipital osteoderms closely resemble bovid (ungulate mammal) horn-cores and are likely to have been sheathed by keratin (as preserved exceptionally in the ankylosaurians Zuul and Borealopelta). Farther posteriorly, the principal osteoderms in the major rows along the torso and tail are generally thin-walled, cap-shaped and ridged. They have a rough and porous external surface, which suggests that the bone surface was covered by keratinous scales. The generally porous fabric of these osteoderms has been remarked upon and it is probable that these were flushed with blood. Interspersed between the visually dominant parasagittal rows of osteoderms is a scattering of smaller cap-shaped osteoderms and polygonal or rounded, flat ossicles. Scattered populations of these ossicles were probably lost because they were, in effect, ‘invisible’ during excavation and skeletal preparation, being of millimetric dimensions. These smaller osteodermal ossicles formed a mosaic-like pattern on the skin surface and toughened the flexible portions of the skin of the animal. Skin impressions and epidermal peels, probably deriving from the ventral surface of the body, reveal a closely packed mosaic of smaller flat osteoderms that underlie similarly shaped keratinous scales. The discovery of smaller, partly articulated skeletons has revealed aspects of the growth and development of the cervical osteoderm arrays. Individual base-plates begin to form deep in the dermis through mineralization of the woven connective tissue fibres in the stratum compactum and, as these thicken, they also involve the looser and more irregular fibres of the stratum superficiale. Individual base-plates expand peripherally, deepen and form shallowly convex pads externally upon which primordial osteoderms developed. The latter form initially as narrow, elongate, pup-tent-shaped structures with a posteriorly off-set apex and arched, slightly hollow bases. Differential patterns of mineral deposition progressively modify these ‘templates’ into the range of osteoderm morphologies seen in ontogenetically mature skeletons: from subconical curved horns, through tall, carinate blades, to extremely tall, plate-shaped structures, as well as to the simpler oval-based, ridged, pup-tent-shaped osteoderms. As the skeleton approaches full size, in the neck region the base-plates and their osteodermal caps fuse together, and adjacent base-plates interlock before finally fusing together to form partial collars that anchor and support transverse arrays of prominent osteoderms. Osteoderms had the potential to contribute to a number of biological roles in the life of these animals, including protection (defence-retaliation), thermoregulation and more subtle aspects of their behaviour.

Abstract The functional significance of osteoderms—ossified bony structures in the dermis—has been a topic of discussion for many years in biological sciences. Although a protective function has received significant attention in the past, evidence is accumulating that osteoderms might play an important role during physiological activities, specifically thermoregulation. Previous studies have shown that, in crocodilians, the temperature of the skin overlying the osteoderms differs from that of the non-ossified skin during basking. The direction of these differences, however, appears to vary among studies, warranting the re-evaluation of a potential thermoregulatory function. In this study, we explored the thermal benefits of osteoderm expression in dwarf caimans (Paleosuchus palpebrosus). We compared the difference in dorsal and lateral skin temperatures (ΔT) between individuals with fully developed osteoderms and those devoid of any osteoderms, under three different temperature gradients. Our results show that although significant differences in ΔT are present between individuals and between temperature gradients, they do not relate to the expression of osteoderms. The findings of the present study question the thermoregulatory role that osteoderms play in P. palpebrosus, and vertebrates in general, and we put forward a series of alternative (physiological) hypotheses explaining their enigmatic nature.

Osteoderms are bony structures that develop within the dermal layer of the skin in vertebrates and are very often found in different lizard families. Lizard osteoderms are diverse in topography, morphology, and microstructure. Of particular interest are the compound osteoderms of skinks, which are a complex of several bone elements known as osteodermites. We present new data on the development and regeneration of compound osteoderms based on the results of a histological and Computed Microtomography (micro-CT) study of a scincid lizard: Eurylepis taeniolata. The specimens studied are stored in the herpetological collections of the Saint-Petersburg State University and Zoological Institute of the Russian Academy of Sciences located in St. Petersburg, Russia. The topography of osteoderms in the integuments of the original tail area and its regenerated part was studied. A comparative histological description of the original and regenerated osteoderms of Eurylepis taeniolata is presented for the first time. The first description of the development of compound osteoderm microstructure in the process of caudal regeneration is also presented.

Heteropelta boboi is a new archosauriform reptile from the upper Anisian of northeastern Italy represented by a fragment of dorsal armor with a row of neural arches of the dorsal vertebrae. The dorsal armor of the new taxon is composed of two columns of paramedian osteoderms and at least six columns of lateral osteoderms. Unlike other armored archosaurs, the osteoderms are imbricated with the posterior osteoderm overlapping the anterior one. The low neural arches bear small neural spines and long postzygapophyses. The osteoderms of the lateral columns increase in size and change in shape from the most medial to the most lateral columns. Among the Archosauriformes, only the non-archosaur proterochampsians Vancleavea campi, Litorosuchus somnii, and the doswelliids have dorsal armor comprised of more than two columns of osteoderms per side, but the morphology and arrangement of their osteoderms is unlike those of the new Italian taxon. A cladistic analysis of Archosauromorpha positions Heteropelta boboi as either a basal phytosaur or a basal suchian. However, a second cladistic analysis focused on armored archosaurs alternatively positions the new taxon as a basal archosauriform, basal suchian, basal loricatan or crocodylomorph. Better resolution of the phylogenetic relationships of Heteropelta boboi will likely be obtained only with the discovery of cranial and postcranial remains associated with its diagnostic armor elements.

Abstract. It has been hypothesized that the pronounced differences of stegosaur humeral shapes, with large forms having more slender and small forms having more robust humeri, may be explained by a difference in relative centre of mass (COM) placement caused by differing distributions of osteoderms. To test this hypothesis, digital 3-D models of the bones and osteoderms of the Tanzanian stegosaur Kentrosaurus aethiopicus and of the North American stegosaur Stegosaurus armatus were used to create a 3-D computer-aided design life reconstruction. On these models osteoderm placement was varied drastically, recreating both existing and hypothetical forms. These models show that COM position varies somewhat with realistic osteoderm distributions, but insufficiently to explain major differences in humeral shape. The uniform weight distribution between forelimbs and hindlimbs found between the two taxa also casts doubt on the hypothesis that differences in relative COM position caused by other factors than osteoderm distribution can explain differences in humeral robustness.

Although the evolution and function of “exaggerated” bony projections in ornithischian dinosaurs has been subject to significant debate recently, our understanding of the structure and morphology of their epidermal keratinized coverings is greatly limited. The holotype ofBorealopelta, a new nodosaurid ankylosaur, preserves osteoderms and extensive epidermal structures (dark organic residues), in anatomic position across the entire precaudal length. Contrasting previous specimens, organic epiosteodermal scales, often in the form of horn-like (keratinous) sheaths, cap and exaggerate nearly all osteoderms, allowing for morphometric and allometric analyses of both the bony osteoderms and their horny sheaths. A total of 172 osteoderms were quantified, with osteoderm spine length and height being positively allometric with respect to basal length and width. Despite tight correlations between the different measures amongst all other osteoderms, the large parascapular spines represent consistent outliers. Thickness and relative contribution of the keratinized epiosteodermal scales/sheaths varies greatly by region, ranging from 2% to 6% for posterior thoracics, to ∼25% (1.3×) for the parascapular spines—similar to horn sheaths in some bovid analogues. Relative to the bony cores, the horny portions of the spines are strongly positively allometric (slope = 2.3, CI = 1.8–2.8). Strong allometric scaling, species-specific morphology, and significant keratinous extension of the cervicoscapular spines is consistent with elaboration under socio-sexual selection. This marks the first allometric analysis of ornithischian soft tissues.

The aetosaur Stagonolepis robertsoni was the first reptile to be named from the Late Triassic Lossiemouth Sandstone Formation of Morayshire. Its characteristic rectangular armour plates have been reported in isolation and in association with skeletal remains. Here we present for the first time a three-dimensional reconstruction of the armour plates around the tail in association with caudal vertebrae and a chevron, to give direct evidence of the body outline. The caudal vertebral column was surrounded by eight bony osteoderms, paired paramedian dorsal and ventral plates, and a pair of lateral osteoderms on right and left. The tail shape was subcircular, broader than high. The osteoderms overlap like roofing tiles, the posterior margin of each overlapping the osteoderm following behind. The success of these scans suggests that computed tomography scanning could reveal excellent detail of all the Elgin reptiles in the future.Supplementary material: Three-dimensional models of the two fossil specimens are available at: https://doi.org/10.6084/m9.figshare.c.4824183

AbstractWe describe a new species of the aetosaurCoahomasuchus,C.chathamensis, based on an incomplete, but largely articulated, anterior portion of a skeleton recovered from a quarry in the Upper Triassic Pekin Formation of Chatham County, North Carolina. This is only the second documented occurrence ofCoahomasuchus, with the other being the holotype ofC.kahleorumHeckert and Lucas, 1999 from the Upper Triassic Colorado City Formation of Texas. Although much of the specimen is the same size as the holotype ofC.kahleorum, the dorsal paramedian osteoderms of the North Carolina taxon are considerably (~1.3×) wider than homologous counterparts inC.kahleorum, and the ventral thoracic osteoderms are also rectangular (~1.5× wider than long), rather than square, presumably to accommodate the wider body. This is a rare instance where two articulated specimens of closely related aetosaur species are available for direct comparison of homologous osteoderms. Isolated osteoderms with similar ornamentation from the same locality indicate thatC.chathamensismay have been one of the earliest aetosaurs to attain the broad osteoderm proportions (width:length >3.5:1) otherwise known solely from later branching, spinose taxa such asTypothorax. The co-occurrence ofLucasuchusandCoahomasuchusin both North Carolina and Texas supports past correlations indicating an Otischalkian (Carnian) age for these strata and demonstrates that plesiomorphic, non-spinose aetosaur genera were not necessarily endemic to a single basin in North America.

The article shows morphometry of large and small lateral osteoderms on the Nile crocodile body, which forms into arc-like lines. Length of large lateral osteoderms is 2.52 times greater than small lateral osteoderms, width of large lateral osteoderms is 2.20 times greater than small lateral osteoderms, and area of large lateral osteoderms is 5.59 times greater than small lateral osteoderms. Configuration index (length to width ratio) is similar in large (2.03 ± 0.06) and small (1.92 ± 0.17) lateral osteoderms, but scale range of this factor is less significant in large lateral osteoderms (1.67–2.50), than in small lateral osteoderms (1.00–3.00).

O registro de gliptodontes no sul do Brasil se trata principalmente de osteodermos, muitas vezes isolados e que por uma questão tafonômica, de preservação (estrutura mineralizada) e proporção (presença de centenas de osteodermos em uma carapaça) são os mais abundantes. Panochthus é o segundo gênero de maior representação de Glyptodontidae nos depósitos do Rio Grande do Sul, ficando atrás apenas de Glyptodon. Os depósitos fossilíferos onde foram encontrados registros de Panochthus são: Rosário do Sul (Rincão dos Fialho), Santa Vitória do Palmar (Arroio Chuí e Balneário Hermenegildo), Touro Passo (Uruguaiana) e Sanga dos Borba (Pantano Grande). Na presente dissertação, foram estudados novos espécimes coletados nas localidades pleistocênicas nos municípios de Rosário do Sul, Santa Vitória do Palmar e Uruguaiana, bem como uma revisão dos materiais previamente descritos e referidos pertencentes ao gênero Panochthus para o Pleistoceno do Rio Grande do Sul. O material corresponde basicamente em uma grande quantidade de osteodermos isolados e alguns fragmentos de tubos caudais, depositados no Museu de Ciências Naturais do Rio Grande do Sul, Museu Nacional do Rio de Janeiro, Museu de Ciências Tancredo Filho Melo e Laboratório de Geologia e Paleontologia da Universidade Federal de Rio Grande. Com este estudo corroborou-se que a principal característica apresentada pelos osteodermos e superfície dos tubos caudais é o similar padrão de figuras tuberculares distribuídas de maneira aleatória sem qualquer formação de figuras em forma de roseta, com exceção de regiões específicas da carapaça; e que para identificação das espécies de Panochthus é necessário observar os caracteres do tubo caudal. Panochthus tuberculatus tem seu registro historicamente feito para o Rio Grande do Sul principalmente por meio de osteodermos isolados. Na análise feita nos novos materiais, pode-se confirmar a presença dessa espécie apenas para o Balneário Hermenegildo e também registrar a presença de P. cf. P. greslebini para a mesma localidade. Por se tratarem somente de osteodermos isolados, nas demais localidades os materiais estudados foram atribuídos a Panochthus sp.<br>The record of glyptodonts in southern Brazil is constitute mainly of osteoderms, oftently isolated, and by bias taphonomic of preservation (mineralized structure) and proportion (presence of hundreds of osteoderms on carapace) are the most abundant. Panochthus is the second genus with greater of representation in deposits of Rio Grande do Sul, behind only Glyptodon. The fossiliferous deposits where are found Panochthus: Rosário do Sul (Rincão dos Fialho), Santa Vitória do Palmar (Arroio Chuí and Balneário Hermenegildo), Touro Passo (Uruguaiana) and Sanga of Borba (Pantano Grande). In this dissertation, new speciemen collected in Pleistocene localities in the municipalities of Rosario do Sul, Santa Vitória do Palmar and Uruguaiana were studied, and a revision made of the materials previously described and those belonging to Panochthus. The material is basically a lot of isolates osteoderms and fragments of caudal tubes, deposited in the Museu de Ciências Naturais do Rio Grande do Sul, Museu Nacional do Rio de Janeiro and Museu Tancredo Melo Filho e Laboratory of Geology and Paleontology da Universidade Federal do Rio Grande. In this study, we corroborated that the main feature presented by osteoderms and tube caudal surface is the similar pattern of tubercular figures randomly distributed without any formation of rosetteshaped figures, except for specific regions of the carapace and to Panochthus species identification is necessary to observe the characters of the caudal tube. Panochthus tuberculatus has registry historically done to Rio Grande do Sul, mainly through isolated osteoderms. The analysis made in the new material, one can confirm the presence of that species only to Balnário Hermenegildo and also register the presence of P. cf. P. greslebini to the same location. In other localities studied is attributed to Panochthus sp, because there are only isolated osteoderms.

Submitted by Isaac Francisco de Souza Dias (isaac.souzadias@ufpe.br) on 2016-01-19T18:49:08Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) PALEOHISTOLOGIA COMPARADA EM OSTEODERMOS_YumiOliveira.pdf: 4564618 bytes, checksum: 11a11b43fc46b44343376f6534be1232 (MD5)<br>Made available in DSpace on 2016-01-19T18:49:08Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) PALEOHISTOLOGIA COMPARADA EM OSTEODERMOS_YumiOliveira.pdf: 4564618 bytes, checksum: 11a11b43fc46b44343376f6534be1232 (MD5) Previous issue date: 2015-05-22<br>CAPES<br>Osteodermos constituem um osso tegumentar com alto potencial de fossilização que proporciona inúmeras informações sobre a morfologia do tegumento de animais existentes e fósseis, apresentando um alto grau de diversidade morfológica e histológica. Entre os mamíferos, osteodermos ocorrem principalmente em membros do clado Xenarthra. A escassez de informações sobre a microestrutura de osteodermos de xenartros indica a necessidade de estudos semelhantes para mamíferos encouraçados, como aqueles da Ordem Cingulata (tatus, pampatérios e gliptodontes). Aqui são apresentados novos dados sobre a histologia de osteodermos de dois gliptodontes Panochthus sp. e Neuryurus sp., no intuito de diferenciar as duas espécies através da histologia dos seus osteodermos. O material utilizado é proveniente dos Estados de Pernambuco, Paraíba, Alagoas e Rio Grande do Sul. Os osteodermos de Neuryurus sp. apresentam uma pobre organização espacial das fibras e uma grande área trabecular na região central, indicando um padrão ósseo diferente do encontrado em Panochthus, que se caracteriza por uma região central menos esponjosa que Neuryurus. Através do programa Bone Profiler foi obtido o grau de compactação dos espécimes, sendo Neuryurus sp. em torno de 70%, enquanto que para Panochthus sp. este valor ficou em aproximadamente 90%, demonstrando a diferença no padrão ósseo do osteodermo. O presente trabalho evidencia a variação microestrutural nos osteodermos estudados e mostra a importância da paleohistologia como ponto de partida para um melhor conhecimento de táxons extintos.<br>Osteoderms are integumentary bones with high fossilization potential that hold information about the anatomy of the skin in many extant and fossil animals, presenting a high degree of morphological and histological diversity. Among mammals, osteoderms occur mainly in members of the Xenarthra clade. The scarcity of information on the xenarthran osteoderms microstructure indicates the need for similar studies for armored mammals of the Order Cingulata (armadillos, pampatheres and glyptodonts). Here is presented new data on the osteoderms histology from two glyptodoonts, Panochthus sp. and Neuryurus sp., in order to differentiate the two species through the histology of their osteoderms. The material used in this study is from the states of Pernambuco, Paraíba, Alagoas and Rio Grande do Sul. The osteoderms of Neuryurus sp. have a poor spatial organization of the mineralized fibers and a large trabecular area in the central region, indicating a different bone pattern found in Panochthus, which is characterized by a central region less spongiosa than Neuryurus. Through the Bone Profiler program was obtained the degree of compactness of the specimens, with about 70% for Neuryurus sp. and approximately 90% for Panochthus sp. showing the difference in bone pattern osteoderm. This work demonstrates the microestrutural variation studied in osteoderms, and shows the importance of paleohistology as a starting point for a better understanding of extinct taxa.

Here I assess the use of osteoderms in systematics with comparative material from fossil and extant tetrapod taxa. Putative differences among three groups (ankylosaurid, nodosaurid, and polacanthid) were evaluated. Archosaur osteoderms have cortices surrounding a cancellous core. Ankylosaurs are united by a superficial cortex distinguishable from the core, lack of Sharpeys fibers, and mineralized structural fibers. Nododsaurids lack a deep cortex and have dense superficial cortical fibres. Ankylosaurid osteoderms are thinner than those of other ankylosaurs. Polacanthids (and some nodosaurids and ankylosaurids) have a cancellous core. Cortical thickness overlaps among groups, so a thick cortex is not diagnostic for polacanthids. Modified elements diverge histologically from the primitive condition for specific functions. Haversian bone in the core is not indicative of any group. Some shapes and superficial textures are diagnostic for specific taxa. Parsimony analyses show support for the Ankylosauridae and Nodosauridae, but not a monophyletic polacanthid clade.<br>Systematics and Evolution

碩士<br>國立清華大學<br>材料科學工程學系<br>101<br>Alligator is a well-adapted living fossil covered with a dorsal armor. This dermal shield consists of bony plates, called osteoderms, interconnected by sutures and non-mineralized collagen fibers, providing a dual function of protection and flexibility. Osteoderm features a sandwich structure, combining an inner porous core and an outer dense cortex, to offer enhancements for bending stiffness and energy absorbance. In this study, hierarchical structure and mechanical behaviors of the American alligator (Alligator mississippiensis) osteoderm were investigated. Micro-computed tomography was applied to reveal the complex 3-dimesional neurovascular network. Through the observation under optical and scanning electron microscopes, the osteoderm was found to consist of woven bone in the dorsal region and lamellar-zonal bone in ventral region. Nanoindentation and compressive tests were performed to evaluate the mechanical properties of osteoderms. The varying mineral contents and porosity resulted in a graded mechanical property: from a hard and stiff dorsal cortex gradually transform to a more compliant ventral base. Three protective mechanisms were proposed and observed for alligator osteoderms: (1) flexibility provided by sutures and non-mineralized collagen fibers; (2) energy absorption under compression contributed from the interior cellular foams; (3) non-uniform microstructure and graded mechanical properties offer load re-distribution and impact resistance. The inspirations from alligator osteoderms may lead to the optimized design of novel synthetic armors and advanced composites.