Phyllolepida ("leaf scales") is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually 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 ...

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

of flattened

placoderms Placodermi (from Greek πλάξ 'plate' and δέρμα 'skin', literally 'Plate (animal anatomy), plate-skinned') is a Class (biology), class of armoured prehistoric fish, known from fossils, which lived from the Silurian to the end of the Devoni ...

found throughout the world, with fossils being found in

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 ...

strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

. Like other flattened placoderms, the phyllolepids were bottom-dwelling

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

s that ambushed prey. Unlike other flattened placoderms, the phyllolepids were inhabitants of freshwater environments. Unlike the

Rhenanida Rhenanida ("Rhine (fish)") is an Order (biology), order of scaly placoderms. Unlike most other placoderms, the rhenanids' armor was made up of a mosaic of unfused scales and tubercles. The patterns and components of this "mosaic" correspond to t ...

, the armor of the phyllolepids were made of whole plates, rather than numerous tubercles and scales, and unlike the

Petalichthyida Petalichthyida is an extinct order of small, flattened placoderm fish. They are typified by their splayed pectoral fins, exaggerated lateral spines, flattened bodies, and numerous tubercles that decorated all of the plates and scales of their ...

, the components of the comparatively wide mouth are known. The phyllolepids are considered to have been blind, as the orbits for the eyes are extremely small, so much so as to suggest that the eyes were vestigial, and that they were placed on the sides of the head, as opposed to visually-oriented bottom-dwelling predators, like, say

stargazer Stargazer may refer to: * an observational astronomer, particularly an amateur Aerospace * Stargazer (aircraft), a Lockheed L-1011 airliner used to launch the Pegasus rocket * Orbiting Astronomical Observatory 2, nicknamed Stargazer, the first s ...

s or

flatfish A flatfish is a member of the Ray-finned fish, ray-finned demersal fish order (biology), order Pleuronectiformes, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the ...

, which have the eyes placed high on top of the head. Phyllolepis12DB

Despite having a relatively clear idea of the phyllolepids' lifestyle and anatomy, most fossils consist of fragments of their

thoracic The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the crea ...

armor, and only two

genera 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 nomenclat ...

, '' Phyllolepis'' and ''

Austrophyllolepis ''Austrophyllolepis ''is an extinct genus of phyllolepid arthrodire placoderm from Middle to Late Devonian freshwater strata of Australia. The type species, ''A. ritchiei'' is found in Givetian to early Frasnian-aged freshwater strata near what ...

'' have been thoroughly studied. From the articulation of the thoracic and head plates, it has been suggested that they are either the sister group of order

Arthrodira Arthrodira (Greek for "jointed neck") is an order of extinct armored, jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetrating most marine eco ...

, or are in fact, a group of highly derived arthrodires.

Taxonomy

The Phyllolepids are divided into two

families Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideall ...

, the more primitive Gavinaspididae, represented only by '' Gavinaspis'' of Early Devonian

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

, and

Phyllolepididae Phyllolepididae is one of two families of phyllolepid placoderms. The family, as a whole, is believed to be descended from the Chinese placoderm, '' Gavinaspis ''(which forms the other, monotypic family, "Gavinaspididae"). All but two genera ar ...

, which contains all other genera. Barring the Chinese ''Gavinaspis'', the cosmopolitan '' Placolepis'' (fossils of which have been found in Australia,

Turkey Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a list of transcontinental countries, transcontinental country located mainly on the Anatolia, Anatolian Peninsula in Western Asia, with ...

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

, and

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...

), and the Euro-North American '' Phyllolepis'', the majority of genera are found in Early to Middle Devonian

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. By the Famennian, only ''Phyllolepis'' survived, and became extinct at the close of the Devonian.

References

Long, John A. The Rise of Fishes: 500 Million Years of Evolution Baltimore: The Johns Hopkins University Press, 1996. Prehistoric fish orders {{Placoderm-stub