''Ctenurella'' (from , 'comb' and , 'tail') is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of ptyctodont

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 Late

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 ...

of Germany. The first fossils were found in the Strunde 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 fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

s 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 blunt weapon or implement used in a striking motion to create sound or pain. Whips can be used for flagellation against humans or animals to exert control through pain compliance or fear of pain, or be used as an audible cue thro ...

-like

tail The tail is the elongated section at the rear end of a bilaterian animal's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolution, evolved to los ...

, large

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

s, and robust upper and lower

jaw The jaws are a pair of opposable articulated structures 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 ...

tooth plates. Males also had hook-shaped

sex organ A sex organ, also known as a reproductive organ, is a part of an organism that is involved in sexual reproduction. Sex organs constitute the primary sex characteristics of an organism. Sex organs are responsible for producing and transporting ...

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 Chondrichthyes, cartilaginous fish in the order (biology), order Chimaeriformes (), known informally as ghost sharks, rat fish (not to be confused with rattails), spookfish, or rabbit fish; the last two names are also applied to B ...

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 comm ...

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 east of the Rhine and abo ...

, 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 the ...

'' 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) redescri ...

'', 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 fossi ...

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