Pakistani Titanosauria: are Armoured Dinosaurs?

Abstract

Four types of dermal amour bones of Titanosauria are discovered for the first time from the Late Cretaceous Pab Formation of Vitakri and Basti Ghulam Rasul (Zubra), Barkhan district, Balochistan Pakistan. These dermal armour bones/osteoderms and scutes are different in morphology and are present in the red, maroon and greenish grey shale/clays zone of upper Pab Formation, just below or on the boundary of Mesozoic (Cretaceous) and Cenozoic (Tertiary/Pa;eocene). The upper Pab Formation seems to be a fresh water deposition in the Sulaiman range deduced from sedimentary structure and it has yielded a large number of archosaurian such as dinosaur and crocodilian fossils discovered during this study.

The variation of size and shape of dermal armour bones may depend on different positions. However, their positions are not clear because these are found fragmentary and are not articulated. The first and second types can be positioned such as above the ribs, on back/tail/limbs etc., due to their light weight. The positions of third and fourth types of armour plate can be positioned on axial column, especially from neck to sacral region like ornithishian. These may occur as single median or double row. In general view these seem to belong to omithischian, but materials found nearby belong to both Titanosaurids (Pakisaurids) and Saltasaurids. Recently five new genus and species of Titanosauria (Titanosaurids/Pakisaurids, and Saltasaurids) are erected on the basis of morphology of caudal vertebrae, but the assignment of dermal armour bones at species/ genus/ family level is difficult. However, their assignment to Pakistani Titanosauria is confirmed at this level.