''Pseudopetalichthys problematica'' is a lightly armored pseudopetalichthyid

placoderm Placoderms (from Ancient Greek πλάξ 'plax'', ''plakos'''Plate (animal anatomy), plate' and δέρμα 'derma'''skin') are vertebrate animals of the class (biology), class Placodermi, an extinct group of prehistoric fish known from Pal ...

from the Hunsrückschiefer

Lagerstätte A Fossil-Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that preserves an exceptionally high amount of palaeontological information. ''Konzentrat-Lagerstätten'' preserv ...

Early Devonian The Early Devonian is the first of three Epoch (geology), epochs comprising the Devonian period, corresponding to the Lower Devonian Series (stratigraphy), series. It lasted from and began with the Lochkovian Stage , which was followed by the Pr ...

Germany. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

and only known specimen is an articulated, but incomplete individual consisting of a large, mostly intact, plate-covered head, the bases of the pectoral fins, and most of the vertebral column, with a total length of . The specimen superficially resembles ''

Stensioella ''Stensioella heintzi'' is an enigmatic placoderm of arcane affinity. It is only known from the Lower Devonian Hunsrück slate of Germany. The genus is named after Erik Stensiö, the species name honours Anatol Heintz. Anatomy ''Stensioella hei ...

'', though the structures of the mouth, and

orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...

(the orbits being unknown in ''Stensioella''), and placement of the

gill raker Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of th ...

s all differ. Some experts suggest that ''P. problematica'' and the related '' Paraplesiobatis'' are the same species, suggesting that the differences between them are merely due to different circumstances of

taphonomy Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek language, Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientis ...

, but this hypothesis can not be tested until more specimens are found. The holotype was originally held in the Schlosspark Museum in

Bad Kreuznach Bad Kreuznach () is a town in the Bad Kreuznach (district), Bad Kreuznach district in Rhineland-Palatinate, Germany. It is a spa town, known for its medieval bridge dating from around 1300, the Alte Nahebrücke (Bad Kreuznach), Alte Nahebrücke, ...

, but was then lost at an unknown date.

References

External links

''Pseudopetalichthys''
at the

Paleobiology Database The Paleobiology Database (PBDB) is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database originated in the NCEAS-funded Phanerozoic Marine Pale ...

Pseudopetalichthyida Placoderm genera Fossils of Germany Hunsrück Slate fossils {{placoderm-stub