Bone Histology of the Stegosaur Kentrosaurus aethiopicus (Ornithischia: Thyreophora) from the Upper Jurassic of Tanzania

Abstract

Using bone histology, a slow growth rate, uncommon for most dinosaurs, has been interpreted for the highly derived stegosaur Stegosaurus (Ornithischia: Thyreophora) and the basal thyreophoran Scutellosaurus. In this study, we examine whether this slow growth rate also occurs in the more basal stegosaur Kentrosaurus from the Tendaguru beds of Tanzania. The bone histology of six femora of Kentrosaurus representing an ontogenetic series from subadult to adult was studied, as well as one scapula. The primary bone is mainly highly vascularized fibro-lamellar bone with some reticular organization of the vascular canals. In addition to LAGs and annuli, distinctive shifts in the pattern of vascularization occur, which have been interpreted as potential growth marks. The variation in the development of growth marks may reflect annual climatic fluctuations. The overall bone depositional rate, and hence growth rate in Kentrosaurus appears to be higher than in Stegosaurus and Scutellosaurus. Considering that Stegosaurus is the larger-sized of the two stegosaurs, this would be contrary to an earlier supposition that small-bodied dinosaurs have slower growth rates than larger ones. Our finding of rapid rates of bone deposition in Kentrosaurus suggests that slow growth rates previously reported in Scutellosaurus and Stegosaurus are not a phylogenetic characteristic of the Thyreophora. Thus, slow growth rates are not plesiomorphic for the Thyreophora. We propose that the slow growth rates documented in the highly derived Stegosaurus could have been secondarily derived or alternatively that Kentrosaurus is the exception having increased growth rates. Anat Rec, 296:933-952, 2013

Histologic Examination of an Assemblage of Psittacosaurus (Dinosauria: Ceratopsia) Juveniles From the Yixian Formation (Liaoning, China)

“…Given that all three well preserved Psittacosaurus femora in this study have a single region of radial vascularization combined with a thickened cortex in the caudomedial region of the bone, it would appear that radial organization in juvenile Psittacosaurus specimens is related to the development of the fourth trochanter with a combination of simple reticular and longitudinal organization dominating in other regions. A similar pattern is found in Orodromeus , Maiasaura , Hypacrosaurus , Kentrosaurus , Mussaurus , and Gasparinisaura (Horner et al, ; Cerda and Chinsamy, ; Redelstorff et al, ; Cerda et al, ), but is less evident in Troodon (Horner et al, ), likely related to the smaller fourth trochanter in theropods compared with ornithischians. Mussaurus is somewhat unique in having large resorptive cavities in the fourth trochanter region (Cerda et al, ), but this is not seen in these Psittacosaurus juveniles.…”

“…Other dinosaurs show vascular patterns different from what we found in DMNH D2156. Padian et al () first hypothesized that smaller dinosaurs have slower growth and thus less extensive vascularization than larger dinosaurs (but see Redelstorff et al () for alternate hypotheses in Thyreophora). Padian et al () commented on the relative growth rate of Psittacosaurus based on its size using data from Erickson and Tumanova ().…”

Bone Microstructure of Pareiasaurs (Parareptilia) from the Karoo Basin, South Africa: Implications for Growth Strategies and Lifestyle Habits

“…). This method, inspired from the technique described in Stein and Sander () and already used for paleohistological studies (e.g., Scheyer and Sander, ; Redelstorff and Sander, ; Redelstorff et al, ), leads to the least possible damage to the overall anatomy of skeletal elements. Unlike the standard coring method using a core drill (Stein and Sander, ), we utilized high‐pressure waterjet cutting technology to core our samples (at CHANTEX heavy Mach., Cape Town, South Africa).…”

Dinosaur paleohistology: review, trends and new avenues of investigation

“…EFS have been reported in birds (Ponton et al, 2004) and more recently, in American alligators (Woodward, Horner & Farlow, 2011). EFSs have been described in a few dinosaur specimens (e.g., in some sauropodomorphs, ankylosaurs, stegosaurs, and hadrosaurs; Sander & Klein, 2005; Redelstorff et al, 2013; Stein, Hayashi & Sander, 2013; Woodward et al, 2015). This absence has often been interpreted as a marker of “indeterminate growth” (growth continuous throughout the animal’s life, e.g., Chinsamy, 1993).…”