Iyuku raathi, a new iguanodontian dinosaur from the Early Cretaceous Kirkwood Formation, South Africa.

We name and describe a new iguanodontian dinosaur from the Early Creteceous Kirkwood Formation, Eastern Cape Province, South Africa. This dinosaur is one of only two ornithopod dinosaurs known from the Cretaceous of southern Africa, and is unique in being represented primarily by hatchling to young juvenile individuals as demonstrated by bone histological analysis. All of the juvenile material of this new taxon comes from a single, laterally-restricted bonebed and specimens were primarily recovered as partial to complete single elements, although rare articulated materials and one partial skeleton were found. Sedimentology of the bonebed suggests that this horizon heralds a change in environment upsection to a drier and more seasonal climate. This accumulation of bones is interpreted as seasonal mortality from a nesting site or nesting grounds and may be linked to this environmental shift.

The Long Bone Histology of the Sauropodomorph, Antetonitrus ingenipes.

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. Sub-adult 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, 301:1506-1518, 2018. © 2018 Wiley Periodicals, Inc.