The Long Bone Histology of the Sauropodomorph, Antetonitrus ingenipes

Abstract

This analysis of the long bone microstructure of Antetonitrus ingenipes fills a crucial gap in our understanding of the growth dynamics of sauropodomorph dinosaurs. The bone histology of basal Sauropodomorpha are often characterized by zonal tissue, and contrasts with that of more derived sauropod taxa which show a shift toward the deposition of uninterrupted fibrolamellar bone (with lines of growth being either absent or only present in the outer circumferential layer). In Antetonitrus, growth patterns in the youngest individuals exhibit uninterrupted fibrolamellar bone without any growth marks. Subadult individuals, also exhibit highly vascularized fibrolamellar bone throughout the cortex, as in more derived Sauropods and Mussaurus, but growth lines occur intermittently (although not regularly) throughout the cortex as in Lessemsaurus. This indicates that Antetonitrus does not exhibit the growth dynamics previously considered characteristic of Sauropoda. Despite this, the largest (and possibly the oldest femur, NMQR 1705/163) does show an incipient external fundamental system (EFS). Our findings further suggest that growth marks are decoupled from bone size, which indicates a level of developmental plasticity in this taxon. Modulations or textural shifts in the pattern of vascular channel arrangements throughout the fibrolamellar bone in the cortex may be related to periods of resource limitations, although the lack of consistency of these modulations suggest that it is unlikely due to seasonal fluctuations. Localized bands of radial fibrolamellar bone, followed by resumption of normal growth in two samples are interpreted as evidence of a disease infliction, and subsequent recovery thereof. Anat Rec, 301:1506Rec, 301: -1518Rec, 301: , 2018 Bone microstructure (osteohistology) provides a direct record of ontogenetic growth and provides a wealth of data on various aspects of dinosaur paleobiology, such as, growth rates, ontogenetic stages, and termination of growth (e.g., Chinsamy-Turan, 2005;Cerda et al., 2013). Studies of the bone histology of sauropodomorph bones have been

Extreme growth plasticity in the early branching sauropodomorph Massospondylus carinatus

“…The presence of extreme growth plasticity in the Late Triassic basal sauropodomorph P. trossingensis and the Early Jurassic basal sauropodomorph M. carinatus suggests that at least EBSMs retained the ability to respond (via changing skeletal growth) to climatic and resource fluctuations throughout the Triassic–Jurassic transition, and that environments at higher latitudes were also relatively unstable during that time period. More generally, developmental plasticity (morphological or growth) appears to have been common in early dinosaurs [18,19]. It provides a potential preadaptive feature of dinosaurs that allowed them to thrive in unstable post-extinction environments.…”

“…This hypothesis was contradicted by the first explicit studies of growth plasticity in early dinosaurs in 2005 by Sander & Klein [9], and later expanded upon by Klein & Sander [8] in 2007, who studied the EBSM Plateosaurus trossingensis . Since then, only a handful of studies have investigated any form of developmental plasticity in dinosaurs [18], and these have largely focused on external markers of plasticity such as muscle insertion scars [19].…”

A Giant Dinosaur from the Earliest Jurassic of South Africa and the Transition to Quadrupedality in Early Sauropodomorphs

“…Ledumahadi exhibited high growth rates during early ontogeny, annual temporary decreases in growth from midontogeny, and a gradual transition to parallel-fibered bone and closely spaced growth marks near the periphery representing an external fundamental system ( Figure S2; STAR Methods). The closely related sauropodiforms Lessemsaurus [13] and Antetonitrus [14] also exhibit rapid, but cyclical, growth throughout ontogeny. Given that Ledumahadi presents growth marks from at least mid-ontogeny (early growth destroyed by secondary remodeling), it is likely that it grew similarly to these other sauropodiforms.…”

Long bone histology of Chersina angulata : Interelement variation and life history data

“…Bone histology and skeletochronology of extinct animals provides valuable biological information (e.g., age, lifestyle and sexual maturity) since its structural integrity is generally preserved even after fossilization (e.g., Chinsamy, ; Chinsamy, Chiappe, Marugán‐Lobón, Chunling, & Fengjiao, ; Chinsamy‐Turan, ; de Ricqlès, , ; Francillon‐Vieillot et al, ). Such techniques have been applied to study various vertebrate groups including dinosaurs (Angst, Chinsamy, Steel, & Hume, ; Cerda et al, ; Chinsamy, ; Chinsamy & Dodson, ; Chinsamy‐Turan, ; Handley, Chinsamy, Yates, & Worthy, ; Krupandan, Chinsamy‐Turan, & Pol, ; Zhang, Chiappe, Han, & Chinsamy, ), basal turtles (Scheyer & Sander, ), mammals, and their ancestors (Botha & Chinsamy, ; Botha‐Brink, Soares, & Martinelli, ; Chinsamy & Abdala, ; Chinsamy & Hurum, ; Ray, Botha, & Chinsamy, ). To date, the most important studies on the genus Chersina have focused on quantifying their gross morphology, diet, ecology, abundance over geological time and taphonomic signatures associated with archaeological deposits (Avery et al, ; Branch, ; Meylan & Auffenberg, ; Thompson & Henshilwood, ; van den Berg & Baard, ).…”