Pterichthyodes
Encyclopedia
Pterichthyodes is a genus
of placoderm fishes from the Devonian
period, now all extinct
. They were one of the first species
recognized for what they were, as their fossil
s are common in the Old Red Sandstone
formation studied by geologist
s in the early 19th century. Due to their extreme divergence from modern-day fish, they were a puzzle unsolved until Charles Darwin
brought forward his theories on evolution
.
Pterichthyodes had heavily armored heads and front bodies, while their tail ends were uncovered. As placoderms, they were members of one of the first group of animals to possess jaw
s, though they had grinding plates rather than teeth. The Pterichthyodes are distinguished easily from other placoderms by their odd wing-like appendage where fins would be found on a modern fish ("pterichthys" is Ancient Greek
for "wing-fish") -- strictly speaking, these are not fins as we normally think of them, which evolved in another group of fish, the Actinopterygii
.
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 placoderm fishes from the 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...
period, now all extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
. They were one of the first species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
recognized for what they were, as their fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s are common in the Old Red Sandstone
Old Red Sandstone
The Old Red Sandstone is a British rock formation of considerable importance to early paleontology. For convenience the short version of the term, 'ORS' is often used in literature on the subject.-Sedimentology:...
formation studied by geologist
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...
s in the early 19th century. Due to their extreme divergence from modern-day fish, they were a puzzle unsolved until Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
brought forward his theories on evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
.
Pterichthyodes had heavily armored heads and front bodies, while their tail ends were uncovered. As placoderms, they were members of one of the first group of animals to possess 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...
s, though they had grinding plates rather than teeth. The Pterichthyodes are distinguished easily from other placoderms by their odd wing-like appendage where fins would be found on a modern fish ("pterichthys" is Ancient Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
for "wing-fish") -- strictly speaking, these are not fins as we normally think of them, which evolved in another group of fish, the Actinopterygii
Actinopterygii
The Actinopterygii or ray-finned fishes constitute a class or sub-class of the bony fishes.The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines , as opposed to the fleshy, lobed fins that characterize...
.