rekiny-i-płaszczki: Timeline of fish evolution

Evidence: 58 • authority: 92

Re-make, re-model: evolution and development of vertebrate cranial lateral lines.. Lateral lines are placodally derived mechanosensory systems on the heads and trunks of many aquatic vertebrates. There is evidence of lateral lines in the earliest known vertebrate fossils, and they exist in organisms with widely different craniofacial morphologies - including the presence or absence of jaws, external or internal nostrils, and variable positions of the cranial cartilages with respect to eyes and braincase. Consequently, the lateral lines make an ideal study system to understand how morphological variation in a deeply conserved sensory system responds to overall evolution of the head. However,…

Evidence: 50 • authority: 72

Fish began evolving about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fish lineages were jawless. Early examples include Haikouichthys. During the late Cambrian, eel-like jawless fish called the conodonts, and small mostly armoured fish known as "ostracoderms", first appeared. Most jawless fish are now extinct; but the extant lampreys may approximate ancient pre-jawed fish. Lampreys belong to the Cyclostomata, which includes the extant hagfish, and this group may have split early on from other agnathans. The earliest jawed vertebra…

Evidence: 42 • authority: 92

A new 'acanthothoracid' placoderm from the Arctic Canada (Early Devonian) and its bearing on the evolution of jaws and teeth.. The origin of jaws and teeth represents one of the most formative episodes in our own evolutionary history. However, this event is poorly understood because of a lack of detailed knowledge of key lineages, including the 'acanthothoracid' placoderms, which were among the earliest jawed vertebrates. Here, we describe Romundina gagnieri sp. nov., a new species of 'acanthothoracid' from the Early Devonian of Arctic Canada. The new species displays anterior supragnathal plates with teeth that we have characterized using synchrotron tomography. Our study shows that teeth…

Evidence: 42 • authority: 72

Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes). They are currently considered to represent a paraphyletic grade of various fish lineages basal to extant Chondrichthyes, which includes living sharks, rays, and chimaeras. Acanthodians possess a mosaic of features shared with both osteichthyans (bony fish) and chondrichthyans (cartilaginous fish). In general body shape, they were similar to modern sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteians (gars, bowfins). The popular name "spiny sharks" is because they were superficially shark-shaped, with a streamlined body, paired fins, a strongly upturned tail, and stou…

Evidence: 42 • authority: 72

Gnathostomata (; from Ancient Greek: γνάθος (gnathos) 'jaw' + στόμα (stoma) 'mouth') are jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all extant vertebrates, including all living bony fishes (both ray-finned and lobe-finned, including the terrestrial tetrapods) and cartilaginous fishes, as well as extinct prehistoric fish such as placoderms and acanthodians. Most gnathostomes have retained ancestral traits like true teeth, a stomach, and paired appendages (pectoral and pelvic fins, limbs, wings, etc.). Other traits are elastin, horizontal semicircular canal of the inner ear, myelinated neurons, and an adaptive immune system which has d…

Evidence: 42 • authority: 72

This list of acanthodian genera is an attempt to create a comprehensive listing of all genera that have ever been included in the subclass Acanthodii, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomina dubia), or were not formally published (nomina nuda), as well as junior synonyms of more established names, and genera that are no longer considered acanthodians. Not counting their descendants, the modern chondricthyans, all acanthodians are extinct. Extinct genera are marked with a dagger (†)

Evidence: — • authority: 65