Laramidia was an island continent that existed during the Late Cretaceous period (99.6–66 Ma ), when the Western Interior Seaway split the continent of North America in two. In the Mesozoic era, Laramidia was an island land mass separated from Appalachia to the east by the Western Interior Seaway. The seaway eventually shrank, split across the Dakotas , and retreated toward the Gulf of Mexico and the Hudson Bay . The masses joined, forming the continent of North America.
36-542: Characiformes / ˈ k æ r ə s ɪ f ɔːr m iː z / is an order of ray-finned fish , comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras . The Characiformes form part of a series called the Otophysi within the superorder Ostariophysi . The Otophysi contain three other orders, Cypriniformes , Siluriformes , and Gymnotiformes . The Characiformes form
72-470: A Weberian apparatus , a series of bony parts connecting the swim bladder and inner ear . Superficially, the Characiformes somewhat resemble their relatives of the order Cypriniformes , but have a small, fleshy adipose fin between the dorsal fin and tail . Most species have teeth within the mouth, since they are often carnivorous . The body is almost always covered in well-defined scales. The mouth
108-459: A free-swimming larval stage. However other patterns of ontogeny exist, with one of the commonest being sequential hermaphroditism . In most cases this involves protogyny , fish starting life as females and converting to males at some stage, triggered by some internal or external factor. Protandry , where a fish converts from male to female, is much less common than protogyny. Most families use external rather than internal fertilization . Of
144-587: A group known as the Characiphysi with the Siluriformes and Gymnotiformes. The order Characiformes is the sister group to the orders Siluriformes and Gymnotiformes, though this has been debated in light of recent molecular evidence. Originally, the characins were all grouped within a single family, the Characidae . Since then, 18 different families have been separated out. However, classification varies somewhat, and
180-1610: A number of modern South American characin families have their earliest occurrences in the Maastrichtian of Bolivia, with isolated teeth and skeletal elements identifiable to Acestrorhynchidae , Characidae , and Serrasalmidae . Below is a phylogeny of living Characiformes based on Betancur-Rodriguez et al. 2017 and Nelson, Grande & Wilson 2016. Distichodontidae Günther 1864 [REDACTED] Citharinidae Günther 1864 [REDACTED] Crenuchidae Günther 1864 sensu Froese & Pauly 2001 Hepsetidae Hubbs 1939 [REDACTED] Alestiidae Cockerell 1910 [REDACTED] Tarumaniidae de Pinna et al. 2017 Erythrinidae Valenciennes 1847 [REDACTED] Serrasalmidae Bleeker 1859 [REDACTED] Cynodontidae Eigenmann 1903 [REDACTED] Hemiodontidae Bleeker 1859 [REDACTED] Parodontidae Eigenmann 1910 Prochilodontidae Eigenmann 1909 [REDACTED] Chilodontidae Eigenmann 1903 Curimatidae Gill 1858 [REDACTED] Anostomidae Günther 1864 sensu Nelson 1994 [REDACTED] Ctenoluciidae Schultz 1944 Lebiasinidae Gill 1889 Chalceidae Fowler 1958 Iguanodectidae Eigenmann 1909 Acestrorhynchidae Eigenmann 1912 Triportheidae Fowler 1940 [REDACTED] Bryconidae Eigenmann 1912 [REDACTED] Gasteropelecidae Bleeker 1859 [REDACTED] Characidae Latreille 1825 sensu Buckup 1998 [REDACTED] Characins possess
216-726: A trait still present in Holostei ( bowfins and gars ). In some fish like the arapaima , the swim bladder has been modified for breathing air again, and in other lineages it have been completely lost. The teleosts have urinary and reproductive tracts that are fully separated, while the Chondrostei have common urogenital ducts, and partially connected ducts are found in Cladistia and Holostei. Ray-finned fishes have many different types of scales ; but all teleosts have leptoid scales . The outer part of these scales fan out with bony ridges, while
252-555: A very wide distribution across Laramidia , ranging from Texas to as far north as southern Canada ( Dinosaur Park Formation ). It is likely that the warmer conditions of the Late Cretaceous allowed early characins to range farther north than the present day, with African characins colonizing Europe and South American characins colonizing North America. Early characins may have had some level of salt tolerance, allowing for such colonizations to take place. Within their modern distribution,
288-587: Is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of skin supported by radially extended thin bony spines called lepidotrichia , as opposed to the bulkier, fleshy lobed fins of the sister class Sarcopterygii (lobe-finned fish). Resembling folding fans , the actinopterygian fins can easily change shape and wetted area , providing superior thrust-to-weight ratios per movement compared to sarcopterygian and chondrichthyian fins. The fin rays attach directly to
324-450: Is also usually not truly protractile. The largest characins are Hydrocynus goliath and Salminus franciscanus and Hoplias aimara , both of which are up to 1.2 m (3.9 ft). The smallest in size is about 1.7 cm (0.67 in) in the Bolivian pygmy blue characin, Xenurobrycon polyancistrus . Many members are under 3 cm (1.2 in). Characins are most diverse in
360-540: Is divided into the infraclasses Holostei and Teleostei . During the Mesozoic ( Triassic , Jurassic , Cretaceous ) and Cenozoic the teleosts in particular diversified widely. As a result, 96% of living fish species are teleosts (40% of all fish species belong to the teleost subgroup Acanthomorpha ), while all other groups of actinopterygians represent depauperate lineages. The classification of ray-finned fishes can be summarized as follows: The cladogram below shows
396-531: Is named after the Laramide orogeny . The name was coined by J. David Archibald in 1996. Laramidia stretched from modern-day Alaska to Mexico . The area is rich in dinosaur fossils. Tyrannosaurs , dromaeosaurids , troodontids , hadrosaurs , ceratopsians (including Kosmoceratops and Utahceratops ), pachycephalosaurs , and titanosaur sauropods are some of the dinosaur groups that lived on this landmass. A strong latitudinal climatic gradient existed on
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#1732848690186432-564: Is no paleontological support for characiforms having marine origins. Uniquely, Late Cretaceous characiform fossils are found significantly north of their modern distribution. Indeterminate characiform teeth are known from the Santonian of Hungary and Maastrichtian of France, which have a large, multi-cusped appearance reminiscent of African alestids . Similarly, two Campanian freshwater characiform genera, Primuluchara and Eotexachara , are known from North America, with Primuluchara having
468-432: Is relatively rare and is found in about 6% of living teleost species; male care is far more common than female care. Male territoriality "preadapts" a species for evolving male parental care. There are a few examples of fish that self-fertilise. The mangrove rivulus is an amphibious, simultaneous hermaphrodite, producing both eggs and spawn and having internal fertilisation. This mode of reproduction may be related to
504-641: The Americas . A few characins become quite large, and are important as food or game. Most, however, are small shoaling fish. Many species commonly called tetras are popular in aquaria because of their bright colors, general hardiness, and tolerance towards other fish in community tanks. Actinopterygii Actinopterygii ( / ˌ æ k t ɪ n ɒ p t ə ˈ r ɪ dʒ i aɪ / ; from actino- 'having rays' and Ancient Greek πτέρυξ (ptérux) 'wing, fins'), members of which are known as ray-finned fish or actinopterygians ,
540-500: The Cyprinidae (in goldfish and common carp as recently as 14 million years ago). Ray-finned fish vary in size and shape, in their feeding specializations, and in the number and arrangement of their ray-fins. In nearly all ray-finned fish, the sexes are separate, and in most species the females spawn eggs that are fertilized externally, typically with the male inseminating the eggs after they are laid. Development then proceeds with
576-565: The Neotropics , where they are found in lakes and rivers throughout most of South and Central America . The red-bellied piranha , a member of the family Serrasalmidae within the Characiformes, is endemic to the Neotropical realm. At least 209 species of characins are found in Africa, including the distichodontids , citharinids , alestids , and hepsetids . The rest of the characins originate from
612-587: The deep sea to subterranean waters to the highest mountain streams . Extant species can range in size from Paedocypris , at 8 mm (0.3 in); to the massive ocean sunfish , at 2,300 kg (5,070 lb); and to the giant oarfish , at 11 m (36 ft). The largest ever known ray-finned fish, the extinct Leedsichthys from the Jurassic , has been estimated to have grown to 16.5 m (54 ft). Ray-finned fishes occur in many variant forms. The main features of typical ray-finned fish are shown in
648-481: The oviparous teleosts, most (79%) do not provide parental care. Viviparity , ovoviviparity , or some form of parental care for eggs, whether by the male, the female, or both parents is seen in a significant fraction (21%) of the 422 teleost families; no care is likely the ancestral condition. The oldest case of viviparity in ray-finned fish is found in Middle Triassic species of † Saurichthys . Viviparity
684-651: The sister lineage of all other actinopterygians, the Acipenseriformes (sturgeons and paddlefishes) are the sister lineage of Neopterygii, and Holostei (bowfin and gars) are the sister lineage of teleosts. The Elopomorpha ( eels and tarpons ) appear to be the most basal teleosts. The earliest known fossil actinopterygian is Andreolepis hedei , dating back 420 million years ( Late Silurian ), remains of which have been found in Russia , Sweden , and Estonia . Crown group actinopterygians most likely originated near
720-917: The Devonian-Carboniferous boundary. The earliest fossil relatives of modern teleosts are from the Triassic period ( Prohalecites , Pholidophorus ), although it is suspected that teleosts originated already during the Paleozoic Era . The listing below is a summary of all extinct (indicated by a dagger , †) and living groups of Actinopterygii with their respective taxonomic rank . The taxonomy follows Phylogenetic Classification of Bony Fishes with notes when this differs from Nelson, ITIS and FishBase and extinct groups from Van der Laan 2016 and Xu 2021. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Laramidia Laramidia
756-569: The Early Cretaceous ( Albian Age) of Brazil . This presumably marine taxon was used as evidence of characiformes potentially having marine origins. However, more recent studies indicate that Santanaichthys is likely a basal otophysan rather than a characiform. Similarly, Salminops from Spain and Sorbinicharax from Italy, previously also considered potential marine characiforms, are now thought to have no characiform affinities and are considered indeterminate teleosts . Given this, there
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#1732848690186792-402: The adjacent diagram. The swim bladder is a more derived structure and used for buoyancy . Except from the bichirs , which just like the lungs of lobe-finned fish have retained the ancestral condition of ventral budding from the foregut , the swim bladder in ray-finned fishes derives from a dorsal bud above the foregut. In early forms the swim bladder could still be used for breathing,
828-463: The bichirs and holosteans (bowfin and gars) in having gone through a whole-genome duplication ( paleopolyploidy ). The WGD is estimated to have happened about 320 million years ago in the teleosts, which on average has retained about 17% of the gene duplicates, and around 180 (124–225) million years ago in the chondrosteans. It has since happened again in some teleost lineages, like Salmonidae (80–100 million years ago) and several times independently within
864-706: The different actinopterygian clades (in millions of years , mya) are from Near et al., 2012. Jaw-less fishes ( hagfish , lampreys ) [REDACTED] Cartilaginous fishes ( sharks , rays , ratfish ) [REDACTED] Coelacanths [REDACTED] Lungfish [REDACTED] Amphibians [REDACTED] Mammals [REDACTED] Sauropsids ( reptiles , birds ) [REDACTED] Polypteriformes ( bichirs , reedfishes ) [REDACTED] Acipenseriformes ( sturgeons , paddlefishes ) [REDACTED] Teleostei [REDACTED] Amiiformes ( bowfins ) [REDACTED] Lepisosteiformes ( gars ) [REDACTED] The polypterids (bichirs and reedfish) are
900-432: The fish's habit of spending long periods out of water in the mangrove forests it inhabits. Males are occasionally produced at temperatures below 19 °C (66 °F) and can fertilise eggs that are then spawned by the female. This maintains genetic variability in a species that is otherwise highly inbred. Actinopterygii is divided into the subclasses Cladistia , Chondrostei and Neopterygii . The Neopterygii , in turn,
936-548: The former Appalachian continent. In western North America, during the Cretaceous, the dominant theropods were the tyrannosaurs , huge predatory dinosaurs with proportionately large heads built for tearing flesh from their prey. In Laramidia, there were the theropods of Tyrannosaurinae such as Tyrannosaurus rex , Nanuqsaurus hoglundi , Daspletosaurus , Teratophoneus , and theropods of Albertosaurinae such as Albertosaurus and Gorgosaurus , all being included under
972-438: The inner part is crossed with fibrous connective tissue. Leptoid scales are thinner and more transparent than other types of scales, and lack the hardened enamel - or dentine -like layers found in the scales of many other fish. Unlike ganoid scales , which are found in non-teleost actinopterygians, new scales are added in concentric layers as the fish grows. Teleosts and chondrosteans (sturgeons and paddlefish) also differ from
1008-534: The land connection between Africa and Asia. The earliest they could have spread into Central America was the late Miocene . The earliest characiform fossils date back to the Late Cretaceous, around the Santonian . Other fossil teeth date back to the Cenomanian of Morocco , but it has been suggested that these teeth may be of early ginglymodians . Previously, the oldest characiform was assumed to be Santanichthys of
1044-574: The landmass in the final 15 million years of the Cretaceous, helping drive regional provincialism of dinosaur faunas. Vertebrate fossils have been found in the region from Alaska to Coahuila . From the Turonian age of the Late Cretaceous to the very beginning of the Paleocene , Laramidia was separated from Appalachia to the east. As a result, the fauna evolved differently on each land mass over that time. Geological conditions were generally favorable for
1080-461: The main clades of living actinopterygians and their evolutionary relationships to other extant groups of fishes and the four-limbed vertebrates ( tetrapods ). The latter include mostly terrestrial species but also groups that became secondarily aquatic (e.g. whales and dolphins ). Tetrapods evolved from a group of bony fish during the Devonian period . Approximate divergence dates for
1116-402: The most recent (2011) study confirms the circumscribed Characidae as monophyletic . Currently, 18 families , about 270 genera , and at least 1674 species are known. The suborder Citharinoidei , which contains the families Distichodontidae and Citharinidae , is considered the sister group to the rest of the characins, suborder Characoidei . This group has a very ancient divergence from
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1152-579: The preservation of fossils in Laramidia, making the western United States one of the most productive fossil regions in the world. Less is known about Appalachian biodiversity in the Cretaceous as few fossiliferous deposits exist in the region today and half of the fossil beds in Appalachia were destroyed during the Pleistocene ice age . However, fossil beds which haven't been discovered yet could exist in areas of
1188-494: The proximal or basal skeletal elements, the radials, which represent the articulation between these fins and the internal skeleton (e.g., pelvic and pectoral girdles). The vast majority of actinopterygians are teleosts . By species count, they dominate the subphylum Vertebrata , and constitute nearly 99% of the over 30,000 extant species of fish . They are the most abundant nektonic aquatic animals and are ubiquitous throughout freshwater and marine environments from
1224-588: The rest of the Characiformes, dating back to the Early Cretaceous or earlier, and it has been suggested that it be better treated as its own order, the Cithariniformes . The Characiformes likely first originated and diversified on the supercontinent of West Gondwana (composed of modern Africa and South America) during the Cretaceous period, though fossils are poorly known. During the Cretaceous Period,
1260-516: The rift between South America and Africa would be forming; this may explain the contrast in diversity between the two continents. Their low diversity in Africa may explain why some primitive fish families and the Cypriniformes coexist with them whereas they are absent in South America, where these fish may have been driven extinct. The characiforms had not spread into Africa soon enough to also reach
1296-563: The same family of Tyrannosauridae , although not all are contemporary. Another common group of North American dinosaurs were the hadrosaurs , the so-called "duck-billed" dinosaurs. The fossil record shows a staggering variety of hadrosaur forms in Laramidia. Other differences in genera appear between the island land masses. Sauropods roamed Laramidia during the Cretaceous after apparently dying out in Appalachia. Nodosaurs , though, appear to have been more plentiful in Appalachia. Nodosaurs were large, herbivorous armored dinosaurs which lacked
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