Ctenurella
Encyclopedia
Ctenurella is an extinct genus
of ptyctodont placoderm from the Late Devonian
of Germany (Orvig 1960).
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 13 centimetres (5.1 in) in length. It had two dorsal fin
s, with that at the rear of the body being relatively long and low, and large pectoral and pelvic fins. 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 had a long, whip
-like tail
, large eye
s and robust upper and lower jaw
tooth plates. It also had hook-shaped sex organ
s, known as claspers in males. Since all of these features are also found in the unrelated living chimaera
s, they are thought to be an example of convergent evolution
.
Ctenurella gardineri was renamed as the new genus Austroptyctodus by Long (1997) in his review of the Gogo ptyctodontid species, relegating 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 in fact meet each other behind the nuchal plate.
Ptyctodontid placoderms recently have been shown to give birth to live young, with two examples, Materpiscis
and Austroptyctodus
, both from the Gogo Formation
of Western Australia, showing the presence of unborn embryos within the mother fishes (Long et al. 2008)
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of ptyctodont placoderm from the Late Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
of Germany (Orvig 1960).
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 13 centimetres (5.1 in) in length. It had two dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s, with that at the rear of the body being relatively long and low, and large pectoral and pelvic fins. 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 had a long, whip
Whip
A whip is a tool traditionally used by humans to exert control over animals or other people, through pain compliance or fear of pain, although in some activities whips can be used without use of pain, such as an additional pressure aid in dressage...
-like tail
Tail
The tail is the section at the rear end of an animal's body; 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, reptiles, and birds...
, large eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s and robust upper and lower jaw
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 serving to open and close it and is part of the body plan of...
tooth plates. It also had hook-shaped sex organ
Sex organ
A sex organ, or primary sexual characteristic, as narrowly defined, is any of the anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; flowers are the reproductive organs of flowering plants, cones are the reproductive...
s, known as claspers in males. Since all of these features are also found in the unrelated living chimaera
Chimaera
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, ratfish , spookfish , or rabbitfishes...
s, they are thought to be an example of convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
.
Ctenurella gardineri was renamed as the new genus Austroptyctodus by Long (1997) in his review of the Gogo ptyctodontid species, relegating 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 in fact meet each other behind the nuchal plate.
Ptyctodontid placoderms recently have been shown to give birth to live young, with two examples, Materpiscis
Materpiscis
Materpiscis is a genus of ptyctodontid placoderm from the Late Devonian located at the Gogo Formation of Western Australia...
and Austroptyctodus
Austroptyctodus
Austroptyctodus gardineri is a small ptyctodontid placoderm fish from the Upper Devonian Gogo Formation of Western Australia. First described by Miles & Young as anew species of the German genus Ctenurella...
, both from the Gogo Formation
Gogo Formation
The Gogo Formation in the Kimberley region of Western Australia is a Lagerstätte that exhibits exceptional preservation of a Devonian reef community.- Sedimentology :...
of Western Australia, showing the presence of unborn embryos within the mother fishes (Long et al. 2008)