Gemuendina stuertzi
Encyclopedia
Gemuendina stuertzi was an early placoderm species of the order Rhenanida
, of the seas of Early Devonian
Germany. Gemuendina resembled a scaly ray with a pair of staring eyes, a pug-nose, and an upturned mouth. This leads virtually all artists who reconstruct it to give the creature a quizzical, almost shocked expression. It is a good example of convergent evolution
- with its flat body and huge, wing
-like pectoral fins it is highly similar to rays
. Unlike rays, both Gemuendina`s eye
s and nostril
s were placed atop the head.
Unlike most other placoderms, such as the Antiarchs, or the Arthrodires
, Gemuendina and its three other known relatives (six, if the species of Ohioaspis are considered to be rhenanids) had armor made up of a mosaic of unfused bony plates. Because their armor was so fragile, few examples of rhenanids have survived in the fossil record. Because several regions of the Hunsruck
lagerstätte
were anoxic, thus free of scavenging organisms, intact, nearly pristine (albeit flattened) specimens of G. stuertzi have been found as a result. Also unlike other placoderms, it did not have the characteristic tooth plates of placoderms. Instead, it had star-shaped tubercle scales that allowed it to seize, then swallow fish and other animals that swam too close with its mouth.
Rhenanida
Rhenanida was an order of primitive, lightly armored placoderms. Unlike most other placoderms, the rhenanids' armor was made up of a mosaic of unfused scales and tubercles...
, of the seas of Early 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...
Germany. Gemuendina resembled a scaly ray with a pair of staring eyes, a pug-nose, and an upturned mouth. This leads virtually all artists who reconstruct it to give the creature a quizzical, almost shocked expression. It is a good 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...
- with its flat body and huge, wing
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...
-like pectoral fins it is highly similar to rays
Batoidea
Batoidea is a superorder of cartilaginous fish commonly known as rays and skates, containing more than 500 described species in thirteen families...
. Unlike rays, both Gemuendina`s 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 nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s were placed atop the head.
Arthrodira
Arthrodira is an order of extinct armoured jawed fishes of the Placodermi class that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetrating most marine ecological niches....
, Gemuendina and its three other known relatives (six, if the species of Ohioaspis are considered to be rhenanids) had armor made up of a mosaic of unfused bony plates. Because their armor was so fragile, few examples of rhenanids have survived in the fossil record. Because several regions of the Hunsruck
Hunsrück
The Hunsrück is a low mountain range in Rhineland-Palatinate, Germany. It is bounded by the river valleys of the Moselle , the Nahe , and the Rhine . The Hunsrück is continued by the Taunus mountains on the eastern side of the Rhine. In the north behind the Moselle it is continued by the Eifel...
lagerstätte
Lagerstätte
A Lagerstätte is a sedimentary deposit that exhibits extraordinary fossil richness or completeness.Palaeontologists distinguish two kinds....
were anoxic, thus free of scavenging organisms, intact, nearly pristine (albeit flattened) specimens of G. stuertzi have been found as a result. Also unlike other placoderms, it did not have the characteristic tooth plates of placoderms. Instead, it had star-shaped tubercle scales that allowed it to seize, then swallow fish and other animals that swam too close with its mouth.