title: Unusual endosteally formed bone tissue in a patagonian basal sauropodomorph dinosaur.
abstract: Mussaurus patagonicus (Dinosauria: Sauropodomorpha) is a basal sauropodomorph from the Late Triassic of southern Argentina that is known from a large number of individuals, including juveniles, subadults, and adults. Here, we report on the occurrence of an unusual bone tissue in an individual of M. patagonicus. The rather atypical bone tissue is located within the femoral medullary cavity and also occurs within several erosion cavities of the midinner part of the cortex. This tissue is well vascularized and is composed of a matrix that consists of abundant and densely packed osteocyte lacunae. Although some features of this tissue resembles avian medullary bone, the histological features are distinctive and share more features with the pathological, reactive bone produced in extant birds in response to a retrovirus-induced disease (avian osteopetrosis). Here, we also discuss and provide histological features to effectively differentiate endosteally formed medullary bone from pathological avian osteopetrosis.
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917 (C1033AAJ), Ciudad Autónoma de Buenos Aires, República Argentina; Instituto de Investigación en Paleobiología y Geología, Universidad Nacional de Río Negro, Museo Carlos Ameghino, Belgrano 1700, Paraje Pichi Ruca (predio Marabunta), Cipolletti, Río Negro, Argentina.
authors.forename: Ignacio A
authors.initials: IA
authors.lastname: Cerda
authors.forename: Anusuya
authors.initials: A
authors.lastname: Chinsamy
authors.forename: Diego
authors.initials: D
authors.lastname: Pol
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001842:Bone and Bones / Q000033:anatomy & histology / Q000473:pathology*; D025061:Dinosaurs / Q000033:anatomy & histology* / Q000502:physiology; D005269:Femur / Q000033:anatomy & histology* / Q000502:physiology
keywords: Dinosauria; Sauropodomorpha; avian osteopetrosis; bone histology; bone pathology; medullary bone