''Ctenurella'' (from el, κτείς , 'comb' and el, ουρά , 'tail') is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

ptyctodont The ptyctodontids ("folded-teeth") are placoderms of the order Ptyctodontida, containing the family Ptyctodontidae. With their big heads, big eyes, reduced armor and long bodies, the ptyctodontids bore a superficial resemblance to modern day chi ...

placoderm from the Late

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, w ...

of Germany. The first fossils were found in the

Strunde Strunde is a river of North Rhine-Westphalia, Germany. It flows through Bergisch Gladbach, and joins the Flehbach or Faulbach near Cologne-Buchheim. See also *List of rivers of North Rhine-Westphalia A list of rivers of North Rhine-Westphalia, ...

valley in the Paffrather Kalkmulde.

Description

As with other ptyctodonts, the armor of ''Ctenurella'' was reduced to a few thin plates on the head and shoulder region. It was also relatively small for a placoderm, at just in length. ''Ctenurella'' had two

dorsal fins A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

and the rear of the body was relatively long and low. Most ptyctodonts are presumed to have fed on the ocean floor, but the well-developed fins of this genus indicate that it probably also swam in open waters. Ctenurella gladbachensis

''Ctenurella'' had a long,

whip A whip is a tool or weapon designed to strike humans or other animals to exert control through pain compliance or fear of pain. They can also be used without inflicting pain, for audiovisual cues, such as in equestrianism. They are generally ...

-like

tail The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals ...

, large

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

s, and robust upper and lower

jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...

tooth plates. Males also had hook-shaped

sex organ A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, ...

s, known as

clasper In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's ...

s. Since analogous features are also found in the unrelated living

chimaera Chimaeras are cartilaginous fish in the order Chimaeriformes , known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with rattails, Opisthoproctidae, or Siganidae, respectively. A ...

s, chimaeras and ptyctodonts are thought to be an example of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

Etymology

The specific name of the type species, ''C. gladbachensis'', is a reference of the place

Bergisch Gladbach Bergisch Gladbach () is a List of cities and towns in Germany, city in the Cologne/Bonn Region of North Rhine-Westphalia, Germany, and capital of the Rheinisch-Bergischer Kreis (district). Geography Bergisch Gladbach is located east of the river ...

, where it was founded.Hans Martin Weber: ''Weltberühmte Fische und Krebse aus dem Devon des Strundetals in

'', in: Schriften der Bodendenkmalpflege in NRW, Band 9, Hrsg. Thomas Otten, Römisch-Germanisches Museum der Stadt Köln und Verlag von Philipp Zabern, Mainz 2010, S. 24 ff.

Taxonomy and evolution

The species ''Ctenurella gardineri'' was split off into the new genus ''Austroptyctodus'' by Long (1997) in his review of the Gogo ptyctodontid species, stipulating that the genus ''Ctenurella'' as only coming from the German sites. A new description of ''Ctenurella gladbachensis'' by Long (1997) showed that the original restoration had wrongly restored the skull-roof as the central bones do not in fact meet each other behind the nuchal plate. Ptyctodontid placoderms recently have been shown to give birth to live young, with specimens of pregnant females from two genera, ''

Materpiscis ''Materpiscis'' (Latin for ''mother fish'') is a genus of ptyctodontid placoderm from the Late Devonian located at the Gogo Formation of Western Australia. Known from only one specimen, it is unique in having an unborn embryo present inside th ...

'' and ''

Austroptyctodus ''Austroptyctodus gardineri'' is a small ptyctodontid placoderm fish from the Upper Devonian Gogo Formation of Western Australia. First described by Miles & Young (1977) as a new species of the German genus '' Ctenurella''. Long (1997) redescr ...

'', both from the

Gogo Formation The Gogo Formation in the Kimberley region of Western Australia is a Lagerstätte that exhibits exceptional preservation of a Devonian reef community. The formation is named after Gogo Station, a cattle station where outcrops appear and foss ...

of Western Australia, showing the presence of unborn embryos within the mother fishes (Long et al. 2008)

References

* Long, J.A. 1997. Ptyctodontid fishes (Vertebrata, Placodermi) from the Late Devonian Gogo Formation, Western Australia, with a revision of the genus ''Ctenurella'' Orvig, 1960. ''Geodiversitas'' 19 (3): 515-555. * Long, J.A., Trinajstic, KJ., Younbg, G.C. & Senden, T. 2008. Live birth in the Devonian period. ''Nature'' 453: 650-652. {{Taxonbar, from=Q4806854 Ptyctodontids Placoderms of Europe Placoderm genera