''Palanasaspis chekhivensis'' is an extinct species of pteraspidid heterostracan

agnatha Agnatha (; ) or jawless fish is a paraphyletic infraphylum of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws. The group consists of both extant taxon, living (Cyclostomi, cyclostomes such as hagfish ...

n which existed during the

Pragian The Pragian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.8 ± 2.8 million years ago to 407.6 ± 2.8 million years ago. It was preceded by the Lochkovian Stage and followed by the Emsian Stage. The most important ...

epoch of the early

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

period in what is now

Podolia Podolia or Podillia is a historic region in Eastern Europe located in the west-central and southwestern parts of Ukraine and northeastern Moldova (i.e. northern Transnistria). Podolia is bordered by the Dniester River and Boh River. It features ...

Ukraine Ukraine is a country in Eastern Europe. It is the List of European countries by area, second-largest country in Europe after Russia, which Russia–Ukraine border, borders it to the east and northeast. Ukraine also borders Belarus to the nor ...

. It is known primarily from a wide

rostral Rostral may refer to: Anatomy * Rostral (anatomical term), situated toward the oral or nasal region * Rostral bone, in ceratopsian dinosaurs * Rostral organ, of certain fish * Rostral scale The rostral scale, or rostral, in snakes and other sca ...

plate, which is referenced in the generic name, a compound word combining the Latin words ''pala'', "shovel," and ''nasus'', "nose," with the Greek suffix ''aspis,'' "a small shield." Although the rostral plate clearly marks the creature as a pteraspidoid heterostracan, that literally nothing else of its anatomy is known forces researchers to leave it as ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

''.

References

Pteraspidiformes genera Devonian jawless fish Early Devonian fish Early Devonian fish of Europe Enigmatic Heterostraci taxa Early Devonian first appearances Early Devonian genus extinctions Pragian life {{Devonian-jawless-fish-stub