Protopsephurus is an extinct genus of paddlefish containing the single species Protopsephurus liui, known from the Yixian Formation in Liaoning, northern China from the Barremian to Aptian ages of the Early Cretaceous period around 125-120 million years ago.^[1][2] It is currently the oldest and most basal paddlefish known.

Quick Facts Scientific classification, Binomial name ...

Protopsephurus Temporal range: Early Cretaceous PreꞒ Ꞓ O S D C P T J K Pg N
Fossil of P. liui, Tianjin Natural History Museum
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Acipenseriformes
Family:	Polyodontidae
Subfamily:	†Protopsephurinae
Genus:	†Protopsephurus Lu, 1994
Species:	†P. liui
Binomial name
†Protopsephurus liui Lu, 1994

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The species is known from numerous specimens ranging up to about 80 cm (31 in) long. The snout is shorter than that in any other known paddlefish, and is more sturgeon-like. The morphology of the skull roof is also more archaic than any other paddlefish. The axial skeleton is poorly ossified. Like other extinct polyodontids, it also has tiny non-interlocking scales approximately 1 mm in diameter called denticles that cover the trunk, which bear a fringe of spikes.^[3]

Protopsephurus is thought to have been piscivorous, feeding on smaller fish. One adult specimen of Protopsephurus has been observed with a specimen of Lycoptera, the most common fish in the formation, preserved in its stomach. Piscivory is likely the ancestral ecology of paddlefish, with only the genus Polyodon making the transition to being planktivorous filter feeders.^[3]

The name comes from Ancient Greek words "protos" (first) and "psepharos" (cloudy/gloomy one). However the name also translates to "first pebble bearer" from the words "psephus" (pebble) and "phorus" (holder), commonly spelled as "psephurus". Eduard von Martens, a German zoologist and the first person to describe its living relative the Chinese Paddlefish, did not provide a definition on the meaning of the binomial name.

• Jiufotang Formation
• Paleobiota of the Yixian Formation