Prehistoric fish are early fish that are known only from fossil records. They are the earliest known vertebrates, and include the first and extinct fish that lived through the Cambrian to the Quaternary. The study of prehistoric fish is called paleoichthyology. A few living forms, such as the coelacanth are also referred to as prehistoric fish, or even living fossils, due to their current rarity and similarity to extinct forms. Fish which have become recently extinct are not usually referred to as prehistoric fish. They were very different from what we have today. They likely were larger and had tougher scales.
The class Osteostraci is an extinct taxon of bony-armored jawless fish, termed "ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian.
Galeaspida is an extinct taxon of jawless marine and freshwater fish. The name is derived from galea, the Latin word for helmet, and refers to their massive bone shield on the head. Galeaspida lived in shallow, fresh water and marine environments during the Silurian and Devonian times in what is now Southern China, Tibet and Vietnam. Superficially, their morphology appears more similar to that of Heterostraci than Osteostraci, there being currently no evidence that the galeaspids had paired fins. A galeaspid Tujiaaspis vividus from the Silurian period of China was described in 2022 as having a precursor condition to the form of paired fins seen in Osteostraci and gnathostomes. Earlier than this, Galeaspida were already in fact regarded as being more closely related to Osteostraci, based on the closer similarity of the morphology of the braincase.
The Pituriaspida are a small group of extinct armored jawless fishes with tremendous nose-like rostrums, which lived in the marine, deltaic environments of Middle Devonian Australia. They are known only by two species, Pituriaspis doylei and Neeyambaspis enigmatica found in a single sandstone location of the Georgina Basin, in Western Queensland, Australia.
Doryaspis is an extinct genus of primitive jawless fish that lived in the Devonian period. Fossils have been discovered in Spitsbergen.
Boreaspis is an extinct genus of osteostracan agnathan vertebrate that lived in the Devonian period.
Jamoytius kerwoodi is an extinct species of primitive, eel-like jawless fish known from the Patrick Burn Formation in Scotland, dating to the Llandovery epoch of the Early Silurian period.
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 armor. They reached a peak in diversity during the Early Devonian and were found throughout the world, particularly in Europe, North America, Asia, South America, and Australia. The petalichthids Lunaspis and Wijdeaspis are among the best known. The earliest and most primitive known petalichthyid is Diandongpetalichthys, which is from earliest Devonian-aged strata of Yunnan. The presence of Diandongpetalichthys, along with other primitive petalichthyids including Neopetalichthys and Quasipetalichthys, and more advanced petalichthyids, suggest that the order may have arisen in China, possibly during the late Silurian.
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.
Gemuendina stuertzi is a placoderm of the order Rhenanida, of the seas of Early Devonian Germany. In life, Gemuendina resembled a scaly ray with an upturned head, or a large-finned stargazer. G. stuertzi is often invoked as an example of convergent evolution- with its flat body and huge, wing-like pectoral fins it has a strong, albeit superficial similarity to rays. Unlike rays, however, both Gemuendina`s eyes and nostrils were placed atop the head, facing upward. Furthermore, G. stuertzi's upturned mouth would have enabled it to suction prey that swam overhead, rather than swallow sediment or suction prey out of the substrate like modern rays.
Antiarchi 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 coined by Edward Drinker Cope, who, when examining some fossils that he thought were armored tunicates related to Chelyosoma, mistakenly thought that the orbital fenestra was the opening for the mouth, or oral siphon, and that the opening for the anal siphon was on the other side of the body, as opposed to having both oral and anal siphons together at one end.
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.
Titanichthys is an extinct genus of giant, aberrant marine placoderm from shallow seas of the Late Devonian of Morocco, Eastern North America, and possibly Europe. Many of the species approached Dunkleosteus in size and build. Unlike its relative, however, the various species of Titanichthys had small, ineffective-looking mouth-plates that lacked a sharp cutting edge. It is assumed that Titanichthys was a filter feeder that used its capacious mouth to swallow or inhale schools of small, anchovy-like fish, or possibly krill-like zooplankton, 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 was estimated to have reached a length of 7–7.6 m (23–25 ft), but Engelman (2023) suggested that Titanichthys was comparable in size to Dunkleosteus, likely measuring about or just over 4.1 metres (13.5 ft) in length.
Acanthothoraci is an extinct group of chimaera-like placoderms closely related to the rhenanid placoderms. Superficially, the acanthoracids resembled scaly chimaeras and (relatively) heavily armored ptyctodonts. They were distinguished from chimaeras by their large scales and plates, a pair of large spines that emanate from their chests, tooth-like beak plates, and the typical bone-enhanced placoderm eyeball. They were distinguished from other placoderms by differences in skull anatomy and by patterns on the skull plates and thoracic plates that are unique to this order.
The ptyctodontids ("folded-teeth") are placoderms of the order Ptyctodontida, containing the family Ptyctodontidae. With their big heads, big eyes, reduced armor and long bodies, the ptyctodontids bore a superficial resemblance to modern day chimaeras (Holocephali). Their armor was reduced to a pattern of small plates around the head and neck. Like the extinct and related acanthothoracids, and the living and unrelated holocephalians, most of the ptyctodontids are thought to have lived near the sea bottom and preyed on shellfish.
Neeyambaspis enigmatica is the lesser known of the two species of pituriaspid agnathans. The species lived in estuaries during the Middle Devonian, in what is now the Georgina Basin of Western Queensland, Australia.
Brindabellaspis stensioi is a placoderm with a flat, platypus-like snout from the Early Devonian of the Taemas-Wee Jasper reef in Australia. When it was first discovered in 1980, it was originally regarded as a Weejasperaspid acanthothoracid due to anatomical similarities with the other species found at the reef.
Jagorina pandora is a rhenanid placoderm of Upper Frasnian Germany. As with other rhenanids, it was a flattened, skate-like fish protected in an armor made up of unfused tubercles, and preyed on other, smaller fish by ambushing them from the sea bottom.
Weejasperaspididae is a family of three extinct acanthothoracid placoderms indigenous to the Early Devonian of Victoria and New South Wales, Australia.
Duboisia hopwoodii is a shrub native to the arid interior region of Australia. Common names include pituri, pitchuri thornapple or pitcheri.
