The Devonian is a geologic period and system of the Paleozoic, spanning 60.3 million years from the end of the Silurian, 419.2 million years ago (Mya), to the beginning of the Carboniferous, 358.9 Mya. It is named after Devon, England, where rocks from this period were first studied.
Placodermi is a class of armoured prehistoric fish, known from fossils, which lived from the Silurian to the end of the Devonian period. Their head and thorax were covered by articulated armoured plates and the rest of the body was scaled or naked, depending on the species. Placoderms were among the first jawed fish; their jaws likely evolved from the first of their gill arches. Placoderms are thought to be paraphyletic, consisting of several distinct outgroups or sister taxa to all living jawed vertebrates, which originated among their ranks. This is illustrated by a 419-million-year-old fossil, Entelognathus, from China, which is the only known placoderm with a type of bony jaw like that found in modern bony fishes. This includes a dentary bone, which is found in humans and other tetrapods. The jaws in other placoderms were simplified and consisted of a single bone. Placoderms were also the first fish to develop pelvic fins, the precursor to hindlimbs in tetrapods, as well as true teeth. Paraphyletic groupings are problematic, as one can not talk precisely about their phylogenic relationships, characteristic traits, and complete extinction. 380-million-year-old fossils of three other genera, Incisoscutum, Materpiscis and Austroptyctodus, represent the oldest known examples of live birth. In contrast, one 2016 analysis concluded that placodermi are likely monophyletic.
Xiphosura is an order of arthropods related to arachnids. They are sometimes called horseshoe crabs. They first appeared in the Hirnantian. Currently, there are only four living species. Xiphosura contains one suborder, Xiphosurida, and several stem-genera.
The Givetian is one of two faunal stages in the Middle Devonian period. It lasted from 387.7 million years ago to 382.7 million years ago. It was preceded by the Eifelian stage and followed by the Frasnian stage. It is named after the town of Givet in France. The oldest forests occurred during the late Givetian. The lower GSSP is located at Jebel Mech Irdane, Tafilalt, Morocco.
Psammosteidae is an extinct family of flattened, benthic heterostracan vertebrates that lived in marine and estuary environments in Europe, Russia & North America. They arose during the Early Devonian, with the first known genus, Drepanaspis from the Hunsrück lagerstätte. The Psammosteids were the only heterostracans that survived the Upper Frasnian extinction event during the Late Devonian, dying out in the extinction event at the very end of the Devonian.
The zosterophylls are a group of extinct land plants that first appeared in the Silurian period. The taxon was first established by Banks in 1968 as the subdivision Zosterophyllophytina; they have since also been treated as the division Zosterophyllophyta or Zosterophyta and the class or plesion Zosterophyllopsida or Zosteropsida. They were among the first vascular plants in the fossil record, and had a world-wide distribution. They were probably stem-group lycophytes, forming a sister group to the ancestors of the living lycophytes. By the late Silurian a diverse assemblage of species existed, examples of which have been found fossilised in what is now Bathurst Island in Arctic Canada.
The Frasnian is one of two faunal stages in the Late Devonian period. It lasted from 382.7 million years ago to 372.2 million years ago. It was preceded by the Givetian stage and followed by the Famennian stage.
Rhenanida is an 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 the plates of armor in other, more advanced placoderms, suggesting that the ancestral placoderm had armor made of unfused components, as well.
Phyllolepida is an extinct taxon of flattened placoderms found throughout the world, with fossils being found in Devonian strata. Like other flattened placoderms, the phyllolepids were bottom-dwelling predators that ambushed prey. Unlike other flattened placoderms, the phyllolepids were inhabitants of freshwater environments.
Tornoceratidae is a family of goniatitid ammonoids from the middle and upper Devonian. The family is included in the suborder Tornoceratina and the superfamily Tornoceratoidea.
Eusthenodon is an extinct genus of prehistoric tristichopterids from the Late Devonian period, ranging between 383 and 359 million years ago. They are well known for being a cosmopolitan genus with remains being recovered from East Greenland, Australia, Central Russia, South Africa, and Belgium. Compared to the other closely related genera of the Tristichopteridae clade, Eusthenodon was one of the largest lobe-finned fishes and among the most derived tristichopterids alongside its close relatives Cabonnichthys and Mandageria.
The Clydonautiloidea are a superfamily within the nautiloid order Nautilida characterized by smooth, generally globular, shells with nearly straight sutures, in early forms, but developing highly differentiated sutures in some later forms. Where known, the siphuncle tends to be central to subcentral.
Macroloxoceras is a large pseuorthocerid from the upper Devonian of Central Colorado and Southern New Mexico with features resembling those found in actinocerids. Pseudorthocerids and actinocerids are extinct nautiloid cephalopods, generally with long straight shells and expanded siphuncle segments filled with organic deposits.
Taeniocrada is a genus of extinct plants of Devonian age. It is used as a form genus for fossil plants with leafless flattened stems which divided dichotomously and had prominent midribs regarded as containing vascular tissues. It has been suggested that some species assigned to this genus were aquatic.
Laccognathus embryi is an extinct species of porolepiform lobe-finned fish recovered from Ellesmere Island, Canada. It existed during the Frasnian age of the Late Devonian epoch.
Tinirau is an extinct genus of sarcopterygian fish from the Middle Devonian of Nevada. Although it spent its entire life in the ocean, Tinirau is a stem tetrapod close to the ancestry of land-living vertebrates in the crown group Tetrapoda. Relative to more well-known stem tetrapods, Tinirau is more closely related to Tetrapoda than is Eusthenopteron, but farther from Tetrapoda than is Panderichthys. The type and only species of Tinirau is T. clackae, named in 2012.
Polonoceras is a genus included in the goniatitid subfamily Aulatornoceratinae named by Dybczynski, 1913. The type species is Polonoceras planum Dybczynski. According to Miller, et al. in the American Treatise on Invertebrate Paleontology, 1957, Polonoceras is a subgenus of Tornoceras.
Homostiidae is a family of flattened arthrodire placoderms from the Early to Middle Devonian. Fossils appear in various strata in Europe, Russia, Morocco, Australia, Canada and Greenland.
Archipolypoda is an extinct group of millipedes known from fossils in Europe and North America and containing the earliest known land animals. The Archipolypoda was erected by Scudder (1882) but redefined in 2005 with the description of several new species from Scotland. Distinguishing characteristics include relatively large eyes with densely packed ocelli, and modified leg pairs on the 8th body ring. Some species had prominent spines while others had a flattened appearance.
The Waterloo Farm lagerstätte in South Africa is a unique fossil site which preserves a wide range of 360 million-year-old plant, invertebrate and vertebrate fossils from a high-latitudinal Gondwanan setting. Collectively they provide a holistic record of a Famennian estuarine ecosystem. The fossils are preserved as flattened silvery-white impressions in black shale.
