From the inside: Pathologies from a histological perspective of two elasmosaurids from the Upper Cretaceous of Antarctica and Argentina

MITIDIERI, MATIAS; TALEVI, MARIANELLA; HERRERA, YANINA; ROTHSCHILD, BRUCE; FERNÁNDEZ, MARTA S.

CRETACEOUS RESEARCH (PRINT)

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Año: 2026 vol. 177

0195-6671

Histopathology plays a fundamental role in the detailed analysis of various pathologies, as it allows fordiagnosing diseases through microscopic examination of the affected tissues. These studies on Mesozoicmarine reptiles are scarce, and almost non-existent in plesiosaurs. Here, two elasmosaurid plesiosaurspecimens were examined: specimen MLP-PV 93-I-5-1, recovered from the lower Maastrichtian Snow HillIsland Formation (Vega Island, Antarctica), and specimen MML-PV 5, retrieved from the upper MaastrichtianJagüel Formation (Salinas de Trapalc�o, Río Negro). To obtain the histological sections, a frag-mented rib was selected from the first specimen; and a transverse process, dorsal rib, and phalanx werechosen from the second. Pathological bone callus was observed on the rib sections of MLP-PV 93-I-5-1.Periosteal growth perpendicular to the long axis of the bone was observed on the transverse process, dorsalrib, and phalanx sections of MML-PV 5. The characteristics observed in specimen MLP-PV 93-I-5-1 areconsistent with the diagnosis of a healing fracture. The characteristics observed in specimen MML-PV 5 areindicative of periostitis. Based on the histopathological study of the two elasmosaurid specimens, it waspossible to identify abnormal internal variations in bone tissue and determine that both pathologiesdeveloped during the life of the elasmosaurids.