''Pterichthyodes'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

antiarch Antiarchi ("opposite anus") is an order of heavily armored placoderms. The antiarchs form the second-most successful group of placoderms after the arthrodires in terms of numbers of species and range of environments. The order's name was coi ...

placoderm fishes from the

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, whe ...

period. Its fossils have been discovered in

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. They were one of the first

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

recognized for what they were, as their

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s are common in the Old Red Sandstone formation studied by

geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althou ...

s in the early 19th century. Due to their extreme divergence from modern-day fish, they were a puzzle unsolved until

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...

brought forward his theories on

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

Description

As with all other antiarchs, ''Pterichthyodes'' had heavily armored heads and forebodies, while their scaly tails were unarmored. Specimen length ranges from to . As placoderms, they were members of the earliest known vertebrates to possess

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 ...

s, though they had grinding plates rather than teeth. The generic name of ''Pterichthyodes'' refers directly to their odd wing-like appendages ("pterichthys" being a compound crassis word from Ancient Greek for "wing-fish"), which correspond to and were derived from the pectoral fins seen in modern fish and other non-antiarch placoderms. Fossils of ''Pterichtyodes'' showing eyes positioned on the direct of the head and a "ventrally flattened

trunk Trunk may refer to: Biology * Trunk (anatomy), synonym for torso * Trunk (botany), a tree's central superstructure * Trunk of corpus callosum, in neuroanatomy * Elephant trunk, the proboscis of an elephant Computing * Trunk (software), in rev ...

shield" suggest that it was a "bottom dweller", living at the bottom of lakes, where it might have crawled using its pectoral appendages. It has also been theorized that ''Pterichthyodes'' and other antiarchs used these appendages to bury itself. ''Pterichthyodes'' would have fed by browsing shallower areas of the lake bed for decaying detritus.

References

{{Taxonbar, from=Q719429 Placoderm genera Placoderms of Europe Antiarchi Fossil taxa described in 1859