Description and etiology of paleopathological lesions in the type specimen of Parasaurolophus walkeri (Dinosauria: Hadrosauridae), with proposed reconstructions of the nuchal ligament

Abstract

Paleopathology, or the study of ancient injuries and diseases, can enable the ecology and life history of extinct taxa to be deciphered. Large-bodied ornithopods are the dinosaurs with the highest frequencies of paleopathology reported to-date. Among these, the crested hadrosaurid Parasaurolophus walkeri is one of the most famous, largely due to its dramatic elongated and tubular nasal crest. The holotype of Parasaurolophus walkeri at the Royal Ontario Museum, Canada, displays several paleopathologies that have not been discussed in detail previously: a dental lesion in the left maxilla, perhaps related to periodontal disease; callus formation associated with fractures in three dorsal ribs; a discoidal overgrowth above dorsal neural spines six and seven; a cranially oriented spine in dorsal seven, that merges distally with spine six; a V-shaped gap between dorsal spines seven and eight; and a ventral projection of the pubic process of the ilium which covers, and is fused with, the lateral side of the iliac process of the pubis. These lesions suggest that the animal suffered from one or more traumatic events, with the main one causing a suite of injuries to the anterior aspect of the thorax. The presence of several lesions in a single individual is a rare observation and, in comparison with a substantial database of hadrosaur paleopathological lesions, has the potential to reveal new information about the biology and behavior of these ornithopods. The precise etiology of the iliac abnormality is still unclear, although it is thought to have been an indirect consequence of the anterior trauma. The discoidal overgrowth above the two neural spines also seems to be secondary to the severe trauma inflicted on the ribs and dorsal spines, and probably represents post-traumatic ossification of the base of the nuchal ligament. The existence of this structure has previously been considered in hadrosaurs and dinosaurs more generally through comparison of origin and insertion sites in modern diapsids (Rhea americana, Alligator mississippiensis, Iguana iguana), but its presence, structure, and origin-attachment sites are still debated. The V-shaped gap is hypothesized asThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Osteohistology of the hyperelongate hemispinous processes of Amargasaurus cazaui (Dinosauria: Sauropoda): Implications for soft tissue reconstruction and functional significance

“…The continuity of this system of interspinous ligaments, which was covered by the integumentary system, resulted in the formation of a prominent cervical sail in this taxon (and other dicraeosaurids with the same feature, Figure 7). Morphological and histological evidence for interspinous ligaments has been previously reported for some groups of non‐avian dinosaurs (Bertozzo et al, 2021; Cerda et al, 2015a; Woodruff et al, 2016), including theropods (Wilson et al, 2016). The absence of distinct morphological evidence of interspinous ligaments in Amargasaurus can be explained in the function of the hyperelongate condition of the hemispinous processes in this taxon.…”

Description of the first definitive Corythosaurus (Dinosauria, Hadrosauridae) specimens from the Judith River Formation in Montana, USA and their paleobiogeographical significance

“…It should be noted that the alveolar margin of the left maxilla is slightly swollen at around the midpoint of the maxilla. The swollen area has a rugose surface that resembles the lesion identified on a Parasaurolophus maxilla (Bertozzo et al, 2020). Medially, the gently arched row of alveolar foramina is located dorsal to the midline of the maxilla.…”

New information on paleopathologies in non-avian theropod dinosaurs: a case study on South American abelisaurids

“…Studies on pathological fossil bones has allowed to know about physiology and ecology of extinct organism [ 1 ], providing a better knowledge about life history (e.g., [ 2 – 4 ]), inter- and intraspecific relationships [ 5 – 18 ], and behaviour (e.g., [ 19 , 20 ]). Among extinct vertebrates, non-avian dinosaurs have drawn attention also in terms of pathological evidences, since different current diseases are noticed in these successful animals.…”