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 paraphyletic, and consist 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, their characteristic traits and literal extinction. 380-million-year-old fossils of three other genera, Incisoscutum, Materpiscis and Austroptyctodus, represent the oldest known examples of live birth.
Ctenurella is an extinct genus of ptyctodont placoderm from the Late Devonian of Germany. The first fossils were found in the Strundevalley in the Paffrather Kalkmulde.
Rolfosteus canningensis is an extinct arthrodire placoderm from the Late Devonian of the Gogo Formation of Western Australia.
Materpiscis is a genus of ptyctodontid placoderm from the Late Devonian located at the Gogo Formation of Western Australia. Known from only one specimen, it is unique in having an unborn embryo present inside the mother, with remarkable preservation of a mineralised placental feeding structure. This makes Materpiscis the oldest known vertebrate to show viviparity, or giving birth to live young.
John Albert Long is an Australian paleontologist who is currently Strategic Professor in Palaeontology at Flinders University in Adelaide, South Australia. He was previously the Vice President of Research and Collections at the Natural History Museum of Los Angeles County. He is also an author of popular science books. His main area of research is on the fossil fish of the Late Devonian Gogo Formation from northern Western Australia. It has yielded many important insights into fish evolution, such as Gogonasus and Materpiscis, the later specimen being crucial to our understanding of the origins of vertebrate reproduction.
Carolowilhelmina geognostica is an extinct arthrodire placoderm fish that lived in the Late Eifelian epoch of Spain. In life, C. geognostica was a long-snouted pelagic fish, superficially similar to the Australian Rolfosteus, from Gogo Formation and the European Oxyosteus of the Kellwasser facies of Bad Wildungen, Germany. As with Rolfosteus, Carolowilhelmina possessed a long tubular rostral plate, with small postnasal plates and low inferognathal plates. According to Mark-Kurik & Carls (2002), this placoderm may have lived in a pelagic environment with lush, floating algae and epiplankton. It is currently known only from an incomplete cranium that is about 40 cm (16 in) long. The fossil material is housed in the Natural Sciences museum of the University of Zaragoza, Spain.
Eastmanosteus is a fossil genus of dunkleosteid placoderms. It was closely related to the giant Dunkleosteus, but differed from that genus in size, in possessing a distinctive tuberculated bone ornament, a differently shaped nuchal plate and a more zig-zagging course of the sutures of the skull roof.
Bruntonichthys is an arthrodire placoderm from the Gogo Reef Formation. The skull is about 139 millimetres long, and had proportionally large eye sockets. Researchers suggest it may have preyed on small mollusks.
Incisoscutum is a genus of arthrodire placoderm from the Late Frasnian Gogo Reef, from Late Devonian Australia. The genus contains two species I. ritchiei, named after Dr. Alex Ritchie, a palaeoichthyologist and senior fellow of the Australian Museum, and I. sarahae, named after Sarah Long, daughter of its discoverer and describer, Dr. John A. Long.
Mcnamaraspis kaprios is an arthrodiran placoderm of the Family Plourdosteidae that inhabited the ancient reef system of north Western Australia during the Frasnian epoch of the Late Devonian period. The type specimen was found and described by John A. Long from the Gogo Formation near Fitzroy Crossing. This fossil fish showed new anatomical features in arthrodires, like the well-preserved annular cartilages of the snout, previously inferred to be present by Erik Stensiö of Sweden.
Pinguosteus thulborni is a species of arthrodire placoderm from the Gogo Reef Formation, of Late Devonian Australia. The proportions of its armor, coupled with the relative lack of otherwise diagnostic ornamentation on the armor make its classification difficult, and so it was placed as incertae sedis within the placoderm group Coccosteina. It is the only known species of the genus Pinguosteus.
Camuropiscidae is a family of mostly small, bullet or spindle-shaped arthrodire placoderms from the Late Devonian. With the exception of the snub-nosed Simosteus, camuropiscid placoderms are characterized by an elongated, tubular snout. The entire family is restricted to the Frasnian Gogo Reef Formation of Australia.
Fallacosteus turneri is an extinct species of arthrodire placoderm from the late Devonian of the Gogo Formation of Western Australia. As with almost all other camuropiscids, F. turnerae had an elongated snout that may have enhanced its hydrodynamic streamlining.
Camuropiscis is an extinct genus of arthrodire placoderm from the late Devonian of the Gogo Formation of Western Australia. The species of Camuropiscis had a flattened, elongated snout that may have aided in enhancing its hydrodynamic streamlining.
Tubonasus lennardensis meaning “tube nose” is a long-snouted arthrodire placoderm from the Gogo Formation of Late Devonian Western Australia.
Latocamurus coulthardi is a flat-nosed arthrodire placoderm from the Gogo Formation of Late Devonian Western Australia.
Rhinosteus is a genus of small to medium selenosteid arthrodire placoderms known from the Upper Frasnian Kellwasserkalk facies of Late Devonian Germany and Morocco.
Xiangshuiosteus wui is a brachythoracid arthrodire placoderm from the Late Emsian epoch of Wuding, Yunnan. It has recently been reassessed as a dunkleosteid.
Synauchenia coalescens is a trout-sized, highly compressed arthrodire placoderm restricted to the Late Frasnian-aged Kellwasserkalk Fauna of Bad Wildungen.
Brian George Gardiner PPLS is a British palaeontologist and zoologist, specialising in the study of fossil fish (palaeoichthyology).
