Silispondylus

Silispondylus is a genus of extinct ray-finned fish that lived during the Late Triassic period. The only known species, Silispondylus mutabilis, was described in 2004 based on fossil remains found in the Chinle Formation of Arizona, United States. The genus name "Silispondylus" is derived from Latin words meaning "hollow vertebra," referring to a characteristic feature of its vertebral centra.

The fossil evidence indicates that Silispondylus was a relatively small fish, with preserved specimens measuring up to approximately 15 centimeters in length. Its body was elongated and covered in scales. Key anatomical features that distinguish Silispondylus include its fin ray counts, the structure of its skull, and the aforementioned hollow vertebral centra. These features suggest it was adapted for life in freshwater environments, possibly rivers or lakes.

The discovery of Silispondylus adds to our understanding of the diversity of freshwater fish faunas present during the Triassic, a critical period for the evolution of ray-finned fishes. Its presence in the Chinle Formation provides further insights into the ecological communities that inhabited North America before the widespread diversification of dinosaurs. The specific ecological role and behavior of Silispondylus remain subjects of ongoing research, inferred from its morphology and the broader context of its fossil assemblage.