Phareodus testis e Knightia alta

Phareodus testis and Knightia alta Slab footprint with numerous fish affected by mass mortality event (MME), about 45 million years ago, United States Fossil 87x50x3 cm Provenance: market (Italy) Conservation status. Surface: 70% (original pectoral fin, color additions on other fins; in predator dentition mostly original) Conservation status. Support: 70% (gaps, additions, consolidation) Looking at this fossil plate, one has the strange feeling of observing a 45-million-year-old aquarium: so natural and alive are the positions and movements of the fish, among which one can easily recognize a phareodus testis close to preying on the school of tall knightie (or eocena) moving around it. Phareodus is a genus of freshwater fish widespread, from the Paleocene to the Eocene, in Australia, Europe and the Americas. It includes at least four species: testis (identified by Leidy in 1873), encaustus in North America, muelleri in Europe, and queenslandicus in Australia. Some of the best specimens date from the middle Eocene and, like the present one, were excavated in the Green River Formation in Wyoming. In particular, the testis species-at auction-had an oval outline, small head and slightly pointed snout. The dorsal and anal fins were located posteriorly, with the anal fin being larger. The caudal fin was slightly forked. It also had small pelvic fins but long and narrow pectoral fins. Knightie-which have their main range in Montana and Wyoming, for which they are the symbolic fossil-are in the same taxonomic family as herring and sardines, and resemble the former to the extent that originally both genera-Knightia alta and Knightia eocaena-were described as herring of the genus clupea. In knightie, rows of dorsal and ventral shields run from the back of the head to the medial fins. The scales were heavy and the teeth conical. Knightia eocaena was the longest, up to 25 cm (although most specimens did not exceed 15 cm), while tall knightia was shorter and relatively wider, with specimens averaging between 6 and 10 cm. Both fed on algae and diatoms, as well as insects and occasionally smaller fish. In turn, as a small schooling fish, knightia provided an abundant food source for Eocene predators. Just as in our "picture," many fossil plates from the Green River Formation show knightie and larger fish together, such as diplomystus, lepisosteus, amphiplaga, myoplosus, amia, asstephus and precisely phareodus, all found with knightie in their jaws or stomachs. In 2022, biological residues were detected in knightie fossils from the Green River Formation, which opens up the staggering possibility of examining DNA from 50 million years ago (Misra, Anupam K.; Rowley, Sonia J.; Zhou, Jie; Acosta-Maeda, Tayro E.; Dasilveira, Luis; Ravizza, Gregory; Ohtaki, Kenta; Weatherby, Tina M.; Trimble, A. Zachary; Boll, Patrick; Porter, John N.; McKay, Christopher P. (2022-06-17). "Biofinder detects biological remains in Green River fish fossils from Eocene epoch at video speed". Scientific Reports. 12 (1): 10164. doi:10.1038/s41598-022-14410-8).