Peter M. Galton (2017)
Purported earliest bones of a plated dinosaur (Ornithischia: Stegosauria): a "dermal tail spine" and a centrum from the Aalenian-Bajocian (Middle Jurassic) of England, with comments on other early thyreophorans.
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 285(1): 1-10
The supposed base of a slender dermal tail spine from the Inferior Oolite Group (shallow marine deposit, early Middle Jurassic, Aalenian-Bajocian) of Dorset, England, previously reported as "Stegosaurus " and Thyreophora indet., is a half centrum of a caudal vertebra, Archosauria indet. A dorsally and ventrally incomplete vertebra from the same locality has a low centrum that is slightly wider transversely than it is long and, as there is a parapophysis anteriorly, it is part of a cervical vertebra. However, it does not match those of marine reptiles from the Middle Jurassic (Callovian) of England in which the cervical centra are elongate in crocodylomorphs, plate-like in ichthyosaurs, and short and wide in some sauropterygians (plesiosaurs and pliosaurs) but the parapophysis is mid-ventrally situated. The Dorset centrum does not correspond to those of most contemporaneous dinosaurs, viz. theropods, basal sauropodomorphs, basal sauropods and ornithopods. However, its proportions correspond to posterior neck vertebrae of the basal thyreophoran Scelidosaurus (Lower Jurassic, England) and those of eurypod thyreophorans, the dacentrurine stegosaur Dacentrurus (described as Miragaia, Upper Jurassic, Portugal) and the nodosaurid ankylosaur Mymoorapelta (Upper Jurassic, USA), so the Dorset centrum is tentatively identified as Thyreophora indet. The earliest skeletal records for armored dinosaurs are from the Middle Jurassic: for Eurypoda a proximal ulna from the early Bajocian of Scotland, for Stegosauria two large sub-vertical plates from the earliest Bathonian of England, and for Ankylosauria the ?Bathonian-Callovian of China or the early middle Callovian of England. However, the stegosaurian footprint taxon Deltapodus brodricki (Aalenian) of England pushes the origin of Stegosauria (and sister group Ankylosauria) down into the Early Jurassic.
Peter M. Galton & Krishnan Ayyasami (2017)
Purported latest bone of a plated dinosaur (Ornithischia: Stegosauria), a "dermal plate" from the Maastrichtian (Upper Cretaceous) of southern India.
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 285(1): 91-96
A stegosaurian "dermal plate" was reported from the Kallamedu Formation (Upper Cretaceous, Maastrichtian) of southern India. However, histologically the dermal plates of stegosaurs, typified by Stegosaurus (Upper Jurassic, USA), have a thin outer cortex enclosing very cancellous bone having large vascular spaces. The Kallamedu fragment of eroded compact bone has no cortex and is probably from a sauropod dinosaur. Bones found in situin this formation typically disintegrate very quickly pon exposure to the air, but this bone is well preserved, although worn. It was found as float in a stream bed, indicating that there is a stratum upstream with well-preserved bones, that is still to be discovered in the Maastrichtian of southern India. Stegosaur remains from the underlying Coniacian (Upper Cretaceous) of southern India represents the most recent osteological record of a stegosaur. However, stegosaurs may have continued into the Maastrichtian (Lameta Formation) of western India as indicated by a pes print of Deltapodus sp., a stegosaurian ichnotaxon.