''Protopsephurus'' is an extinct genus of

paddlefish Paddlefish (family Polyodontidae) are a family of ray-finned fish belonging to order Acipenseriformes, and one of two living groups of the order alongside sturgeons (Acipenseridae). They are distinguished from other fish by their titular elongla ...

containing the single species ''Protopsephurus liui,'' known from the

Yixian Formation The Yixian Formation (; formerly transcribed as Yihsien Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the late Barremian and early Aptian stages of the Early Cretaceous. It is known for its ex ...

Liaoning Liaoning () is a coastal province in Northeast China that is the smallest, southernmost, and most populous province in the region. With its capital at Shenyang, it is located on the northern shore of the Yellow Sea, and is the northernmost ...

, northern

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

from the

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is preceded ...

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

ages of the

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

period around 125-120 million years ago. It is up to be one meter in length. It is currently the oldest and most basal paddlefish known.

Description

The species is known from numerous specimens ranging up to about long. The snout is shorter than that in any other known paddlefish, and is more

sturgeon Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretace ...

-like. The morphology of the skull roof is also more archaic than any other paddlefish. The

axial skeleton The axial skeleton is the part of the skeleton that consists of the bones of the head and trunk (anatomy), trunk of a vertebrate. In the human skeleton, it consists of 80 bones and is composed of six parts; the human skull, skull (22 bones), als ...

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.

Diet

''Protopsephurus'' is thought to have been piscovorous, feeding on smaller fish. One adult specimen of ''Protopsephurus'' was observed with a specimen of ''

Lycoptera ''Lycoptera'' is an extinct genus of fish that lived from the late Jurassic to Cretaceous periods in present-day China, North Korea, Mongolia and Siberia. It is known from abundant fossils representing sixteen species, which serve as important ind ...

'', the most common fish in the formation, preserved in its stomach. Piscivory is likely the ancestral ecology of paddlefish, with only the genus ''

Polyodon The American paddlefish (''Polyodon spathula,'' also known as a Mississippi paddlefish, spoon-billed cat, or spoonbill) is a species of ray-finned fish. It is the only extant taxon, living species of paddlefish (Polyodontidae). This family is m ...

'' making the transition to being

planktivorous A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton. Planktivorous organisms encompass a range of some of the planet's smallest to largest multicellular animals in both the present day and ...

filter feeders.

Etymology

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 Eduard von Martens (18 April 1831 – 14 August 1904) also known as ''Carl'' or ''Karl Eduard von Martens'', was a German zoologist. Born in Stuttgart in 1831, von Martens attended university in University of Tübingen, Tübingen, where he gradua ...

, a German zoologist and the first person to describe its living relative the

Chinese Paddlefish The Chinese paddlefish (''Psephurus gladius''; : literal translation: "white sturgeon"), also known as the Chinese swordfish, is an Extinction, extinct species of fish that was formerly native to the Yangtze and Yellow River basins in China. Wit ...

, did not provide a definition on the meaning of the binomial name.

References

Early Cretaceous fish of Asia Cretaceous bony fish Prehistoric ray-finned fish genera Acipenseriformes Fossil taxa described in 1994 {{Cretaceous-fish-stub

Description

Diet

Etymology

See also

References