dziwne-zwierzęta-oceaniczne: Timeline of fish evolution

Evidence: 100 • authority: 72

The evolution of fishes took place over a timeline which spans the Cambrian to the Cenozoic, including during that time in particular the Devonian, which has been dubbed the "age of fishes" for the many changes during that period. The Late Devonian extinctions played a crucial role in shaping the evolution of fish, or vertebrates in general. Fishes evolved during the Early Paleozoic; by the Devonian, all modern groups (Agnatha, Chondrichthyes, and Osteichthyes) were already present. Devonian aquatic environments were also marked by placoderms and acanthodians, which are only known from fossils, however. After suffering large losses during the Late Devonian extinctions, cartilaginous fishes…

Evidence: 50 • authority: 72

Sarcopterygii (; from Ancient Greek σάρξ (sárx) 'flesh' and πτέρυξ (ptérux) 'wing, fin') is a clade (traditionally a class or subclass) of vertebrate animals which includes a group of bony fishes and all four legged land animals, including humans. The common name for this clade is lobe-finned fish. Lobe-finned fish have muscular limb buds (lobes) within their fins, which are supported by appendicular skeletons. This is in contrast to the other clade of bony fishes, the Actinopterygii, which have only skin-covered bony spines supporting the fins. Sarcopterygii emerged in the Silurian and early Devonian periods consisting entirely of aquatic species, but today the vast majority of its species…

Evidence: 50 • authority: 72

A fish is an aquatic, anamniotic, gill-bearing vertebrate animal with a tough cranium to protect the brain, but lacking limbs with digits. Fish can be grouped into the more basal jawless fish and the more common jawed fish, the latter including all living cartilaginous and bony fish, as well as the extinct placoderms and acanthodians. Tetrapods are descended from fish, so in a break from the long tradition of grouping all fish into a single class (Pisces), modern phylogenetics views fish as a paraphyletic group that includes all vertebrates except tetrapods. To treat fish as a monophyletic group, one would have to classify tetrapods as a clade/subgroup of specialized fish, which would make…

Evidence: 42 • authority: 88

Pathologies in the fish fossils from the Upper Devonian, Famennian deposits of Latvia. The Upper Devonian deposits of Latvia are rich in fossil vertebrate remains that have been studied for several decades. Attention to pathologies in these remains has been given only recently.The paleontological record of parasitic behaviour is quite incomplete, particularly regarding the parasites of vertebrates. Although fossil remains of parasitic organisms are very rare, traces of their action and parasite-induced pathologies can be found more often even though these are hard to identify and it is even more complicated to determine what was the organism that left the traces. Various skeletal pathologie…

Evidence: 42 • authority: 80

On some new or little known fossils from the Silurian and Devonian rocks of Ontario

Evidence: — • 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: — • 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: — • 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: — • 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: — • 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: — • 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 (†)