Possible notochordal chordoma in a fossil fish from the Late Cretaceous of Lebanon

Abstract

ObjectiveTo describe a case of an expansive endocavitary lesion at the level of the caudal tract of the vertebral column of a juvenile fish (Pycnodont) from the Late Cretaceous (Cenomanian) of Lebanon (Hjoula). MaterialsThe specimen is part of the Paleontological Collection of the University Museum of Chieti, Italy, Inventory Number P #23752. MethodsThe specimen was observed macroscopically, as well as under the stereo-microscope (Leica Wild M 8); aspersion with ethanol and razing light were used to improve the observations and to take micro-photos. ResultsThe fossil juvenile fish has a visibly altered macroscopic anatomical morphology at the level of the caudal part of the vertebral column, which is pathological in comparison with the normal anatomy of the Pycnodonts. ConclusionsAlthough diagnosis cannot be certain, comparative analysis notes morphological and topographic affinity between the paleopathological case described here and notochordal chordoma, which affects some living fish. SignificanceThis lesion represents the first case of a nonosseous tumor in a fossil fish, and suggests that this type of neoplasm was among the first of the neoplastic diseases to appear on Earth. LimitationsDiagnosis rendered from fossil remains is complex and is further limited by the rarity of the condition in the past. Suggestions for further researchContinued comparative analysis of bony changes noted in this specimen with other fossil and living fish will contribute to our understanding of disease in the Earth’s earliest inhabitants.