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

Objective: To 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). Materials: The specimen is part of the Paleontological Collection of the University Museum of Chieti, Italy, Inventory Number P #23752. Methods: The 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. Results: The 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. Conclusions: Although diagnosis cannot be certain, comparative analysis notes morphological and topographic affinity between the paleopathological case described here and notochordal chondroma, which affects some living fish. Significance: This 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. Limitations: Diagnosis rendered from fossil remains is complex and is further limited by the rarity of the condition in the past. Suggestions for further research: Continued 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.