Shenacanthus
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Shenacanthus vermiformis (Zhu et al., 2022) is a small cartilaginous fish. Fossil materials were found in the early Silurian Landovileian and Trechiian periods in Chongqing, China, about 436 million years ago. The earliest association with well-preserved Chondrichthyes fossils makes fossils from China the decisive evidence for the origin of chondrichthyans.
Classification location: cartilaginous fish
Place of Origin: China - Chongqing - Xiushan
Period: Early Silurian, Landovelles, Trechi, ~436 million years ago
Stratigraphy: Silurian Landovileian Terechian
Origin of name: Shenacanthus vermiformis, whose genus name is Shenacanthus, commemorates the famous writer Shen Congwen. acanthus is from the Greek akantha, meaning spine. The species name vermiformis comes from the English vermiform, which translates as "worm-like", and refers to the middle dorsal piece with worm-like ornamentation.
Morphological characteristics: Shenacanthus vermiformis is only about 3 cm in length. It contains a spindle-shaped body with a small head and 3.5 mm in length from the snout to the shoulder girdle. The snout is relatively blunt; the fish is toothless; the gill area is located at and associated with the back of the cranium; no gill ridges and tongue were found. The dorsal ossicles, the dorsal and ventral sides of the shoulder girdle are wrapped by a large membranous ossicle with two middle dorsal lamellae. It has worm-like decoration; its pectoral fins are paddle-shaped, without spines; anal fins also lack spines. The scales are small diamond-shaped scales. Small linearly decorated scutellum or membranous ossicles along the dorsal and ventral midline.
References[edit]
Zhu, Ya., Li, Q., Lu, J. et al. The oldest complete jawed vertebrates from the early Silurian of China. Nature 609, 954–958 (2022). https://doi.org/10.1038/s41586-022-05136-8
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