''Titanichthys'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of giant, aberrant marine placoderm from shallow seas of the Late

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, w ...

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria ...

, Eastern North America, and possibly Europe. Many of the species approached '' Dunkleosteus'' in size and build. Unlike its relative, however, the various species of ''Titanichys'' had small, ineffective-looking mouth-plates that lacked a sharp cutting edge. It is assumed that ''Titanichthys'' was a

filter feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

that used its capacious mouth to swallow or inhale schools of small,

anchovy An anchovy is a small, common forage fish of the family Engraulidae. Most species are found in marine waters, but several will enter brackish water, and some in South America are restricted to fresh water. More than 140 species are placed in 1 ...

-like fish, or possibly

krill Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word ', meaning "small fry of fish", which is also often attributed to species of fish. Krill are consid ...

-like

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

, and that the mouth-plates retained the prey while allowing the water to escape as it closed its mouth. A study has since confirmed this assumption as its jaws are functionally closer to that of filter feeders like baleen whales and basking sharks, and it appears to have developed from benthic durophagists that became pelagic suspension feeders. This would make it the first (known) large-sized vertebrate filter feeder. ''Titanichthys'' reached a length of though in older paper it was estimated at .

Species

The genus shows a great diversity in the

Famennian The Famennian is the latter of two faunal stages in the Late Devonian Epoch. The most recent estimate for its duration estimates that it lasted from around 371.1 million years ago to 359.3 million years ago. An earlier 2012 estimate, still used ...

-aged Cleveland Shale, though species are also found in similarly aged strata in Morocco and possibly the Holy Cross Mountains in Poland.

''T. agassizi''

This is the type species, from the Cleveland Shale. Its infrognathals are strongly recurved medially, and is elongated with a spatula-like process at the anterior end. The headshield averages about in length.

''T. attenuatus''

This Cleveland Shale species is based on an infragnathal bone more than in length. May possibly be a synonym of ''T. agassizi''.

''T. clarkii''

This Cleveland Shale species has infragnathals that are not as recurved as ''T. agassizis. The cranial roof is comparatively narrower and more rounded. It is the largest known species in the genus, and possibly one of the largest Devonian vertebrates known. The head is about in length.

''T. hussakofi''

This Cleveland Shale species is known from a badly preserved, incomplete infragnathal. It was originally described by Claypole as "Brontichthys clarki" in 1894. As "Brontichthys" is a junior synonym of ''Titanichthys'', it should not be confused with another, similarly-named arthrodire, '' Bruntonichthys'' of Dunkleosteidae.

''T. rectus''

This Cleveland Shale species has an infragnathal as large as that of ''T. clarkii'', though ''T. rectus''' infragnathal is much straighter, and does not have a spatula-like process on its anterior end.

''T. kozlowskii''

This species placement within the genus is in doubt. It is based on incomplete nuchal and central plates found in Upper Famennian-aged marine strata of the Holy Cross Mountains in Poland.

''T. termieri''

This species is found in Lower Famennian-aged marine strata of Tafilalet, Southern Morocco. The fossil material of this species strongly suggests it is as large as the Cleveland Shale' ''T. clarkii''. The average combined length of the head and trunk shields for ''T. termieri'' is estimated to be When the first fossils of ''T. termieri'' were found by geologist Henri Termier, the specimens were originally placed within the genus '' Gorgonichthys'' - that is, after Termier was able to convince his colleagues that the bone scraps were of a placoderm, and not a

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

.See Janvier (1998) p.323 for details.

References

Bibliography

* (1998): ''Early Vertebrates''. Oxford University Press, Oxford, New York.