Histology of ankylosaur osteoderms: implications for systematics and function

Scheyer, Torsten M.; Sander, P. Martin

doi:10.1671/0272-4634(2004)024[0874:hoaoif]2.0.co;2

Cited by 136 publications

(238 citation statements)

References 12 publications

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“…The structural organization (compact cortex, cancellous core) and bone histology of the juvenile specimen (UA 9331) are broadly comparable with those of other archosaurs [1][2][3][4]7 . In contrast, the gross anatomical and microscopic structure of the adult-sized specimen (FMNH PR 2342) is unique.…”

Section: Discussionmentioning

confidence: 61%

“…Display, including mate and species recognition, is probably the most commonly cited explanation for dinosaur osteoderms [7][8][9][10] , but Rapetosaurus osteoderms are nondescript in comparison to the elaborate bony display structures of other dinosaurs 7,10 , especially when considered in the context of adult body size 4,6,12 . Moreover, similarly shaped ellipsoid osteoderms have been attributed to five other titanosaurs on as many continents 4 , reducing the likelihood of a widespread role in species individuation 7,9 . Finally, the discovery of several other hollow osteoderms in the Maevarano formation precludes both pathology and individual variation as causes of the internal cavity observed in adult Rapetosaurus.…”

Section: Discussionmentioning

confidence: 99%

“…Among dinosaurs, osteoderms are best known from the ornithischian clades Ankylosauria 7 and Stegosauria 8,9 , where they develop into a variety of plate-and spine-shaped elements and have a characteristic paramedian distribution as multiple rows enveloping the dorsolateral body surface. Among saurischians, osteoderms have been reported for a single carnivorous dinosaur, the ceratosaurian Ceratosaurus 10 , and a number of titanosaurian sauropods [4][5][6] .…”

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confidence: 99%

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Sauropod dinosaur osteoderms from the Late Cretaceous of Madagascar

et al. 2011

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osteoderms are bones embedded within the dermis, and are common to select members of most major tetrapod lineages. The largest known animals that bear osteoderms are members of Titanosauria, a diverse clade of sauropod dinosaurs. Here we report on two titanosaur osteoderms recovered from the upper Cretaceous maevarano Formation of madagascar. Each osteoderm was discovered in association with a partial skeleton representing a distinct ontogenetic stage of the titanosaur Rapetosaurus krausei. Combined, these specimens provide novel insights into the arrangement and function of titanosaur osteoderms. Taphonomic data confirm that Rapetosaurus developed only limited numbers of osteoderms in its integument. The adult-sized osteoderm is the most massive integumentary skeletal element yet discovered, with an estimated volume of 9.63 litres. uniquely, this specimen possesses an internal cavity equivalent to more than half its total volume. Large, hollow osteoderms may have functioned as mineral stores in fecund, rapidly growing titanosaurs inhabiting stressed environments.

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Section: Discussionmentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Sauropod dinosaur osteoderms from the Late Cretaceous of Madagascar

et al. 2011

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“…Ventrally, all osteoderms are straight or slightly concave. The dorsal and ventral surfaces of the osteoderms have a micro-texture interlaced as a mesh, similar to that present in some fossil Eusuchia (Hill & Lucas, 2006) or anchilosaurid dinosaurs (Scheyer & Sander, 2004). The dorsal ornamentation of the osteoderms is also made of many transversally oriented irregular furrows.…”

Section: Dermal Armormentioning

confidence: 60%

A new species of Baurusuchus (Crocodyliformes, Mesoeucrocodylia) from the Upper Cretaceous of Brazil, with the first complete postcranial skeleton described for the family Baurusuchidae

Nascimento¹,

Zaher²

2010

Pap. Avulsos Zool. (São Paulo)

166

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“…Tenocytes of avian tendons can transform into osteoblasts (Adams and Organ, 2005;Agabalyan et al, 2013) and most importantly, secondary cartilage can transform into CB in paralyzed embryonic chicks (Hall, 1972). Moreover, even though it is not possible to know the exact mode of formation of fossilized tissues, due to the unusual histology of some dinosaur mineralized tissues, metaplastic transformations have been hypothesized to play a role in the formation of dinosaur skulls (Goodwin and Horner, 2004;Hieronymus and Witmer, 2008;Horner and Lamm, 2011;Horner et al, 2015) and osteoderms (Main et al, 2005, Scheyer andSander, 2004). It appears also that this unusual histology was much more abundant in the skulls of dinosaur than in those of extant mammals and birds (J. Horner personal observations).…”

Section: Dinosaurian Chondroid Bone and Secondary Cartilagementioning

confidence: 99%

Chondroid bone in dinosaur embryos and nestlings (Ornithischia: Hadrosauridae): Insights into the growth of the skull and the evolution of skeletal tissues

Bailleul

Behets

Lengelé

et al. 2016

Comptes Rendus Palevol

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In histology textbooks, the vertebrate skeleton is represented as almost entirely made of bone and cartilage. This is a false dichotomy and in fact, a continuum of intermediate tissues between bone and cartilage exists. Chondroid bone ([CB] or chondroid tissue), one of the most well-known intermediate tissues, has been reported in mammals, birds and crocodilians. It accommodates (1) rapid growth of the skull and (2) the development of craniofacial sutures. Since CB is present in the extant phylogenetic bracket of the Dinosauria, we hypothesized that it was also present in non-avian dinosaurs. By means of paleohistological examination and microradiography, we report for the first time the presence of CB in nonavian dinosaur embryos and nestlings (Ornithischia: Hadrosauridae). It was found in five locations: (1) scattered within the bone trabeculae of an embryonic surangular; (2) and (3) in the coronoid process and in the alveolar processes of an embryonic dentary; (4) in the mandibul... In histology textbooks, the vertebrate skeleton is represented as almost entirely made of bone and cartilage. This is a false dichotomy and in fact, a continuum of intermediate tissues between bone and cartilage exists. Chondroid bone ([CB] or chondroid tissue), one of the most well-known intermediate tissues, has been reported in mammals, birds and crocodilians. It accommodates (1) rapid growth of the skull and (2) the development of craniofacial sutures. Since CB is present in the extant phylogenetic bracket of the Dinosauria, we hypothesized that it was also present in non-avian dinosaurs. By means of paleohistological examination and microradiography, we report for the first time the presence of CB in non-avian dinosaur embryos and nestlings (Ornithischia: Hadrosauridae). It was found in five locations: (1) scattered within the bone trabeculae of an embryonic surangular; (2) and (3) in the coronoid process and in the alveolar processes of an embryonic dentary; (4) in the mandibular symphyses of an embryonic and a post-hatching dentary; (5) at the fronto-postorbital suture of an embryo. In these areas, CB was present in large amounts, suggesting that it played an important role in the rapid growth of the hadrosaurian skull during embryonic development. Moreover, the CB present in the sutural borders of a Hypacrosaurus frontal suggests that it was also involved in sutural growth, as it has been reported to be in mammalian and avian sutures. This is the first step taken to document and understand dinosaurian sutures from a histological perspective and it sheds light on an old problem by reporting the presence of CB in an additional clade within the Vertebrata. It is parsimonious to propose that CB in the chick embryo, Gallus gallus, the American alligator, Alligator mississippiensis and the hadrosaurs of the present study are homologous and that CB arose once and was inherited from their common ancestor.©

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Histology of ankylosaur osteoderms: implications for systematics and function

Cited by 136 publications

References 12 publications

Sauropod dinosaur osteoderms from the Late Cretaceous of Madagascar

Sauropod dinosaur osteoderms from the Late Cretaceous of Madagascar

A new species of Baurusuchus (Crocodyliformes, Mesoeucrocodylia) from the Upper Cretaceous of Brazil, with the first complete postcranial skeleton described for the family Baurusuchidae

Chondroid bone in dinosaur embryos and nestlings (Ornithischia: Hadrosauridae): Insights into the growth of the skull and the evolution of skeletal tissues

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