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Morphological comparison of saurichthyids with extant needlefish and flying fish. A. Sinosaurichthys longipectoralis. B. Sinosaurichthys longimedialis. C. Sinosaurichthys minuta. D. Saurichthys dawaziensis from Middle Triassic of Dawazi Section, Luoping, Yunnan, China (based on Wu et al. 2009). E. Atlantic needlefish Strongylura marina (Family Belonidae). F. Bluntnose flyingfish Prognichthys gibbifrons (Family Exocoetidae). E and F redrawed from images at http://www.fishbase.org/images/species that were originally from Cervigón et al. (1992).
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A new genus Sinosaurichthys of the Saurichthyidae with three new species, S. longipectoralis, S. longimedialis, and S. minuta, are described and compared with Saurichthys. The new genus is represented by more than a hundred almost complete skeletons, collected from the strata corresponding to the Upper Member of the Guanling Formation (Pelsonian, A...
Citations
... As for fishes, despite numerous neopterygians, basal actinopterygians such as the large saurichthyids and palaeoniscids occupied the highest trophic levels just as in the Zorzino Limestone (Lombardo and Tintori, 2005). Saurichthyiforms were quite abundant and diverse in the Luoping Biota, with two genera and five species (Zhang et al., 2010;Wu et al., 2011Wu et al., , 2017, and Saurichthys could reach a body length of 1 m. It was primarily a pelagic predator, and the relatively small and low-positioned pectoral fins make it an ambush predator rather than a persistent and rapid swimmer (Wu et al., 2011). ...
... Saurichthyiforms were quite abundant and diverse in the Luoping Biota, with two genera and five species (Zhang et al., 2010;Wu et al., 2011Wu et al., , 2017, and Saurichthys could reach a body length of 1 m. It was primarily a pelagic predator, and the relatively small and low-positioned pectoral fins make it an ambush predator rather than a persistent and rapid swimmer (Wu et al., 2011). On the other hand, the body shape and fin arrangement of Sinosaurichthys, especially Sinosaurichthys longipectoralis, suggest it was a rapid swimmer that cruised near the surface (Wu et al., 2011). ...
... It was primarily a pelagic predator, and the relatively small and low-positioned pectoral fins make it an ambush predator rather than a persistent and rapid swimmer (Wu et al., 2011). On the other hand, the body shape and fin arrangement of Sinosaurichthys, especially Sinosaurichthys longipectoralis, suggest it was a rapid swimmer that cruised near the surface (Wu et al., 2011). Besides, the relatively fast swimmer Pteronisculus change, with a maximum total length of 295 mm, occupied the middle to top trophic level, feeding on planktonic invertebrates and smaller fishes (Ren and Xu, 2021). ...
... During the Early and Middle Triassic, the saurichthyiform fishes exhibited global distribution and invaded both marine and freshwater environments (Romano et al., 2012). They also developed diverse swimming and feeding strategies during this period (Wu et al., 2009(Wu et al., , 2011(Wu et al., , 2013(Wu et al., , 2018Kogan et al., 2015). When it came to the Late Triassic, the diversity of these fishes was significantly reduced, and their distribution was basically restricted to the western Paleo-Tethys (Romano et al., 2012). ...
... From those fossil Lagarstätten, increasing evidences suggest that the saurichthyiform fishes, ranking among the top predators in local fossil communities, had successfully evolved during the Middle Triassic of South China. In the past decade, one new family, two new genera, and eight new species of Saurichthyiformes from the Middle Triassic Luoping and Panxian biotas have been established (Wu et al., 2009(Wu et al., , 2011(Wu et al., , 2013(Wu et al., , 2018Zhang et al., 2010). The younger Xingyi biota has yielded many undescribed saurichthyid specimens that show a notable taxonomic diversity (Jin, 2006 and personal observations). ...
... The dermopterotic is of an irregular trapezoid shape and meets its counterpart along a relatively short and straight suture behind the parietal. The anterior and posterior edges of the dermopterotic are slightly concave to accommodate the parietal and (Wu et al., 2009;2011; Scale bars equal 20 mm in A, B and E, 5 mm in C and D, and 2 mm in F and G Anatomical abbreviations: ang. angular; art. ...
The saurichthyiform fishes, characterized by a pointed rostrum and a streamlined long and slender body plan, ranked among the top predators of the ichthyofauna in the Early Mesozoic oceanic ecosystem. In a cosmopolitan pattern, these fishes rapidly radiated after the end-Permian mass extinction (EPME) and diversified morphologically and ecologically during the Middle Triassic. Thereafter, they seemingly showed a notable shrinkage from a global distribution to an occurrence basically restricted to the western Paleo-Tethys realm since the Late Triassic. Specifically, there is no saurichthyiform fossil record so far from the marine Late Triassic of South China (eastern Paleo-Tethys), where contrastingly they were highly diversified in stratigraphically older Lagerstätten (Middle Triassic Panxian-Luoping and Xingyi biotas). Here we report the discovery of Saurichthys taotie sp. nov. from the Guanling biota of Guizhou and Yunnan provinces, southwestern China. This new species is a medium-sized Saurichthys featured by subtriangular subopercles ornamented with densely arranged vertical striae, faint ornamentation on the posterior part of the skull roof, and strong longitudinal ridges decorating the anterodorsal surface of the rostrum. By marking its own group's first occurrence in the Late Triassic of eastern Paleo-Tethyan province, Saurichthys taotie suggests that the saurichthyiform fishes were actually much more widespread than previously thought during that geological stage when they showed a considerable decline in the diversity. By still possessing some features previously only seen in its Early Triassic congeners elsewhere, Saurichthys taotie sheds new light on the evolutionary and paleobiogeographical history of saurichthyiform fishes.
... Our observations support this assignment. The small vestigial opercle of Saurichthys sui is reminiscent of its analogue in some early Triassic Saurichthys (e.g., S. madagascariensis, S. ornatus and S. hamiltoni) (Stensiö 1925;Lehman 1952;Beltan 1968;Kogan and Romano 2016a) but distinguishes the new species from all Middle and Late Triassic Saurichthys species (Griffith 1959(Griffith , 1962(Griffith , 1977Rieppel 1985Rieppel , 1992Wu et al. 2009;Romano et al. 2012;Wilson et al. 2013;Maxwell et al. 2015Maxwell et al. , 2015Maxwell et al. , 2016Maxwell et al. , 2018Kogan et al. 2020), the Middle Triassic Sinosaurichthys species (Wu et al. 2011) and Yelangichthyidae (Yelangichthys) (Wu et al. 2013) and the Jurassic saurichthyid Saurorhynchus (Hauff 1938;Gardiner 1960;Thies 1985;Maxwell and Martindale 2017;Maxwell and Stumpf 2017). Saurichthys sui's subtriangular subopercle resembles that of S. madagascariensis (Kogan and Romano 2016a), S. orientalis (Kogan et al. 2009), and a new species from the Carnian marine sediments of South China (Fang et al. 2022) but differs from other congeners whose subopercle, when completely preserved, is oval, sub-rectangular or semicircular in shape (Griffith 1959(Griffith , 1962(Griffith , 1977Rieppel 1985Rieppel , 1992Wu et al. 2009;Romano et al. 2012;Wilson et al. 2013;Maxwell et al. 2015Maxwell et al. , 2015Maxwell et al. , 2016Maxwell et al. , 2018Kogan et al. 2020) (Figure 3). ...
... Moreover, even when the scale is similar in size and shape, the ganoine ornamentation is distributed throughout the surface of the anterior mid-lateral scale in the new species, a peculiar state shared by S. madagascariensis (Kogan and Romano 2016a), S. orientalis (Kogan et al. 2009(Kogan et al. , 2020, S. aff. dayi (Kogan 2011) and S. wimani (Kogan and Romano 2016b), and an undescribed specimen from the Middle Triassic Ordos basin in North China (personal observations), whereas in other species, e.g., S. yangjuanensis and Sinosaurichthys species (Wu et al. 2011), the ventral part of scale is smooth. ...
... The pectoral fin is fan-shaped and roundish in the majority of species of Saurichthys (Griffith 1959(Griffith , 1962(Griffith , 1977Rieppel 1985Rieppel , 1992Wu et al. 2009;Romano et al. 2012;Maxwell et al. 2015Maxwell et al. , 2015Maxwell et al. , 2016Maxwell et al. , 2018Kogan et al. 2020) including the basal species S. madagascariensis (Kogan and Romano 2016a) and S. orientalis (Kogan et al. 2009). This fin is triangular and inserted high in the body in Sinosaurichthys species (Wu et al. 2011). Saurichthys sui's pectoral fin is also triangular in shape but inserted rather low. ...
The iconic saurichthyid fishes (‘lizard fish’) are specialised predators in the aquatic realm of Early Mesozoic era. After a rapid diversification in the Middle Triassic, they seemingly shrank their geographical distribution from a global pattern to that mainly confined to Euramerican region and exhibited increasing rarity in the freshwater environment since the Late Triassic. Here, we report a new species of Saurichthys from the Late Triassic freshwater deposits of the Junggar Basin, northwestern China. This new species Saurichthys sui sp. nov. is characterised by a mosaic of primitive and derived features in Saurichthys: large circumorbital bones and spiracular plate, a vestigial opercle and pectoral fins devoid of fringing fulcra. This feature combination supports the hypothesis that the freshwater system might have served as the refugium of some basal saurichthyid species. Saurichthys sui represents the first record of large predatory fishes in the Triassic Junggar Basin and indicates the establishment of a trophically complex lacustrine ecosystem there. Together with the co-occurring fossil insects and plants, Saurichthys sui, showing some affinities to its congeners from central Asia and North China, implies some biogeographical links of the fossil localities of non-marine Saurichthys on the continents north to PalaeoTethys during the Middle-Late Triassic.
... Saurichthyid fishes exploded on the scene in the Middle Triassic ( Figure 3). They originated in the latest Permian (Eosaurichthys from Changxing, Zhejiang, China) and diversified to dozens of species in the Middle Triassic (Wu et al., 2011, Wu et al., 2015, Wu et al., 2018 and continued until the Middle Jurassic (Maxwell, 2016), hence surviving two major biotic crises. In addition, a lineage of saurichthyiform fishes from the Anisian of China had evolved a distinct crushing feeding mechanism, comprising massive jaws but small and blunt teeth . ...
The Triassic has long been recognized as a time during which marine and terrestrial ecosystems modernized dramatically, and it seems to have been a two-step process. First, recovery from the Permian-Triassic mass extinction (PTME) was a time of extraordinary renewal and novelty, and these processes of change were enhanced, it seems, by the effects of the Carnian Pluvial Episode (CPE). After the CPE, in the oceans, not only did the carbonate factory begin to change towards its modern form, but also arguably the Mesozoic Marine Revolution (MMR) speeded up. When the MMR was proposed it was seen as a process that occurred in the Late Jurassic and Cretaceous, as modern crustaceans, gastropods, and fishes enhanced predator-prey arms races. New evidence from China and elsewhere suggests in fact the MMR was already underway in the Middle and Late Triassic, and so was coincident with Sepkoski’s classic idea that Paleozoic faunas were replaced by Modern marine faunas from the beginning of the Triassic. On land, ongoing competition between synapsids and archosauromorphs through the Triassic was marked by a posture shift from sprawling to erect, and a shift in physiology to warm-bloodedness, with insulating skin coverings of hair and feathers. Dinosaurs, for example, originated in the Early or Middle Triassic, but did not diversify until after the CPE. These arms races, the MMR in the sea, and the endothermy shift in tetrapods, were triggered by the PTME, and then enhanced by the CPE.
... In the Pyrenean basin, fossil fishes are poorly known from only two localities ( Fig. 1): (1) Vilanova de la Sal, with reports of an actinopterygian fauna not described in detail , and (2) Odèn, with abundant actinopterygian remains. The Odèn locality was first reported by Lehman (1964), who described postcranial remains assigned to Acidorhynchus, a genus currently considered a subjective junior synonym of Saurichthys (Wu et al., 2011). Later, additional specimens referred to Saurichthys, as well as to Peltopleuridae, Halecomorpha, and the large-bodied Colobodus, were reported from this site (Cartanyà et al., , 2015Fortuny et al., 2011). ...
The Ladinian-Carnian transition in the Tethys domain was accompanied by an important environmental change representing a milestone in the climate evolution of the Triassic.
However, estimations on paleodiversity composition and paleoenvironmental conditions across this interval are scarce in marine settings due to the lack of fossil-bearing successions. In this work, a refined paleontological and sedimentological study has allowed us to better characterize a well-preserved marine ?Ladinian-Carnian carbonate succession in the South Central Pyrenees (Odèn site, Catalonia, NE Spain). Vertebrate faunas include numerous actinopterygian specimens, forming an assemblage composed of at least four taxa: Peltopleurus cf. P. nuptialis Lombardo, 1999, Saurichthys sp., Colobodus giganteus (Beltan, 1972), and an indeterminate halecomorph. Specimens belonging to the genus Peltopleurus are dominant; the long-snouted Saurichthys, the halecomorph, and the large-bodied Colobodus giganteus are less abundant. Tetrapod remains are scarcely present and are assigned to sauropterygians. Invertebrate faunas include bivalves (Pseudocorbula gregaria [Münster in Goldfuss, 1838]) and brachiopods (Lingula sp.). The fossil assemblage was recovered from organic-rich laminated silty mudstone layers. Sedimentological and textural analyses suggest that fossil biotas were deposited below the fair-weather wave base in shallow subtidal coastal settings. These environments were sporadically sourced by silt/clay. The age of the Odèn site, on the basis of the recovered fauna, is assigned to the ?late Ladinian-middle Carnian (Middle-Late Triassic), which is in agreement with previously published ages based on palynomorph data. The refined integration of paleontological, sedimentological, and biostratigraphic data from the Odèn site and other vertebrate-bearing localities in the Tethys domain can help better constrain the paleoenvironmental conditions and paleo geographical configuration impacting ecosystem diversity during the late Ladinian-Carnian interval.
... In addition to the new species of Pteronisculus reported here, other macrofossils have been reported from the same fossiliferous horizons at the Luoping localities, including plants, invertebrates, diverse marine reptiles and other taxa of ray-finned fishes (Tintori et al., 2007(Tintori et al., , 2010Sun et al., 2009Sun et al., , 2015Sun et al., , 2016López-Arbarello et al., 2011;Wu et al., 2011;Xu and Wu, 2012;Feldmann et al., 2012;Wen et al., 2012Wen et al., , 2013Wen et al., , 2019Xu and Ma, 2016;Xu and Zhao, Fig. Xu et al., 2014a, b;Ma and Xu, 2017;Xu, 2020a). The whole of the fossil assemblage, known as the Luoping Biota, was suggested to have inhabited a semi-enclosed intraplatform basin (Hu et al., 2011;Benton et al., 2013). ...
Actinopterygii, the largest group of extant vertebrates, includes Cladistia, Actinopteri (Chondrostei plus Neopterygii) and closely related fossil taxa. The extinct genus Pteronisculus belongs to a stem lineage of actinopterygian fishes represented by 11 species from the Early Triassic of Madagascar, Europe and North America, and a single species from the early Middle Triassic of China. Here, we report the discovery of a new species of this genus, Pteronisculus changae, on the basis of five well-preserved specimens from the Middle Triassic (Anisian) marine deposits exposed in Luoping, eastern Yunnan, China. The discovery documents the second convincing species of Pteronisculus in the Middle Triassic and the largest stem actinopterygian fish in the Luoping Biota, having a maximum total length of up to 295 mm. The new species possesses a toothed lacrimal, which is characteristic of Pteronisculus, but it is easily distinguished from other species of the genus by some autapomorphies, e.g., a medial process at the middle portion of the intertemporal, 21 supraneurals, and 83 lateral line scales. The results of our cladistic analysis provide new insights into the relationships of early actinopterygians and recover Pteronisculus as a sister taxon of the Carboniferous rhadinichthyid Cyranorhis at the actinopterygian stem. Based on the body form, teeth and other features, it can be deduced that Pteronisculus changae is likely a relatively fast-swimming predator, feeding on planktonic invertebrates and smaller or younger fishes known to occur in the same biota. As one of the youngest species of the genus, the new species provides additional evidence to suggest that the diversity of Pteronisculus is higher than previously thought and that the eastern Paleotethys Ocean likely constituted a refuge for species of this genus during the early Middle Triassic.
... In addition to the new species of Pteronisculus reported here, other macrofossils have been reported from the same fossiliferous horizons at the Luoping localities, including plants, invertebrates, diverse marine reptiles and other taxa of ray-finned fishes (Tintori et al., 2007(Tintori et al., , 2010Sun et al., 2009Sun et al., , 2015Sun et al., , 2016López-Arbarello et al., 2011;Wu et al., 2011;Xu and Wu, 2012;Feldmann et al., 2012;Wen et al., 2012Wen et al., , 2013Wen et al., , 2019Xu and Ma, 2016;Xu and Zhao, Fig. Xu et al., 2014a, b;Ma and Xu, 2017;Xu, 2020a). The whole of the fossil assemblage, known as the Luoping Biota, was suggested to have inhabited a semi-enclosed intraplatform basin (Hu et al., 2011;Benton et al., 2013). ...
Actinopterygii, the largest group of extant vertebrates, includes Cladistia, Actinopteri (Chondrostei plus Neopterygii) and closely related fossil taxa. The extinct genus Pteronisculus belongs to a stem lineage of actinopterygian fishes represented by 11 species from the Early Triassic of Madagascar, Europe and North America, and a single species from the early Middle Triassic of China. Here, we report the discovery of a new species of this genus, Pteronisculus changae, on the basis of five well-preserved specimens from the Middle Triassic (Anisian) marine deposits exposed in Luoping, eastern Yunnan, China. The discovery documents the second convincing species of Pteronisculus in the Middle Triassic and the largest stem actinopterygian fish in the Luoping Biota, having a maximum total length of up to 295 mm. The new species possesses a toothed lacrimal, which is characteristic of Pteronisculus, but it is easily distinguished from other species of the genus by some autapomorphies, e.g., a medial process at the middle portion of the intertemporal, 21 supraneurals, and 83 lateral line scales. The results of our cladistic analysis provide new insights into the relationships of early actinopterygians and recover Pteronisculus as a sister taxon of the Carboniferous rhadinichthyid Cyranorhis at the actinopterygian stem. Based on the body form, teeth and other features, it can be deduced that Pteronisculus changae is likely a relatively fast-swimming predator, feeding on planktonic invertebrates and smaller or younger fishes known to occur in the same biota. As one of the youngest species of the genus, the new species provides additional evidence to suggest that the diversity of Pteronisculus is higher than previously thought and that the eastern Paleotethys Ocean likely constituted a refuge for species of this genus during the early Middle Triassic.
... Along with the new species of Feroxichthys, other taxa from the same fossiliferous level in Panxian localities include invertebrates, marine reptiles, the colobodontid Colobodus baii , saurichthyiforms (Wu et al., 2011(Wu et al., , 2013(Wu et al., , 2015, holosteans (Chen et al., 2014; and birgeriiforms . The whole fossil assemblage has been referred to the Panxian Fauna or Biota (Motani et al., 2008;Benton et al., 2013). ...
Neopterygii is a taxonomically diverse clade of ray-finned fishes, including Teleostei, Holostei and closely related fossil taxa. The Colobodontidae is a stem group of large-sized neopterygians with a durophagous feeding adaption from the Middle to Late Triassic marine ecosystems in Europe and South China. Here, we report the discovery of a new colobodontid, Feroxichthys panzhouensis sp. nov., based on a well-preserved specimen from the early Middle Triassic (Anisian) of Panzhou (formerly known as Panxian), Guizhou, China. The discovery extends the geographical distribution of Feroxichthys from eastern Yunnan into western Guizhou, and demonstrates a more rapid diversification of early colobodontids than previously thought. The new species possesses diagnostic features of Feroxichthys (e.g., a fused lacrimal-maxilla), but it is easily distinguished from the type species Feroxichthys yunnanensis and other colobodontids by some derived features on the skull and, especially, the relatively short and deep body with a prominent postcranial hump. This body form, previously unknown in colobodontids, implicates a morphological adaptation to structurally complex habitats in light of ecological studies of modern ray-finned fishes with a similar body form. In addition, the feeding apparatus suggests a more obligate durophagous diet for F. panzhouensis sp. nov. than other colobodontids. Results of a cladistic analysis recover the new species as a sister taxon of F. yunnanensis within the Colobodontidae, and suggest that a hump-backed body form has independently evolved multiple times in Triassic neopterygians. As such, the new finding provides an important addition for our understanding of the morphological and ecological diversity of neopterygian fishes from the Triassic marine ecosystems in South China.
... Region IV is divided into a short anterior region, characterized by very short haemal processes (IVa) interspersed with ossified interventrals, and a longer posterior region (IVb), characterized by alternating haemal processes and interventrals. Region V is differentiated by the loss of haemal processes and neural spines (T-shaped neural arches; Wu et al., 2011). In Region VI, haemal processes reappear, but differentiation of Regions V and VI is relatively weak in this clade. ...
The postcranial axial skeleton of actinopterygian fishes is typically divided into three regions: (1) an anterior abdominal region, (2) a posterior caudal region and (3) those vertebrae supporting the caudal fin. However, in some actinopterygians, the axial skeleton is more finely subdivided, with up to six morphologically distinct sub‐regions recognized. Phylogenetic continuity and homology of structures across these sub‐regions have not been investigated in detail, either between or among groups. We examine variation in axial regionalization in saurichthyid fishes, a clade of extinct non‐teleostean actinopterygians with highly variable axial skeletal morphology but an otherwise conservative body plan, and compare these findings to other non‐teleostean actinopterygians to assess conservation of a regionalized axial skeleton within bony fishes. We document up to eight distinct regions in the vertebral column of Triassic Saurichthys: (1) a postoccipital region, (2) an anterior and (3) a posterior abdominal region, (4) a transitional region spanning the abdominal–caudal boundary, (5) an anterior and (6) a posterior caudal region and (7) preural and (8) ural regions. Based on taphonomical and morphological evidence, the transitional region appears to function in axial stiffening in the area of the median fins, whereas the abdominal region is highly flexible. The degree to which these axial regions are osteologically differentiated is highly variable across Saurichthyidae, implying iterative evolution of differentiation and de‐differentiation over relatively short geological timescales. Such variably expressed regionalization was also identified in the outgroup non‐teleostean actinopterygians Birgeria and Australosomus. Despite variation in morphological disparity, the regions identified in saurichthyids correlate well with those documented in some teleosts and Paleozoic actinopterygians, suggesting potential deep patterning homology but independent evolution of specific regionalized axial morphologies in response to changing functional demands.
... In Italy, a new locality in the Dolomites (Prà della Vacca/ Kühwiesenkopf) has produced specimens of Bobasatrania, Dipteronotus, Habroichthys, Placopleurus. Peltoperleidus, Ptycholepis, and Saurichthys (Tintori et al., 2016 Wu et al., 2011, Geng et al., 2012Sun et al., 2012, Wen et al., 2012, Benton et al., 2013Wen et al., 2013, Wu et al., 2013Xu et al., 2014a, Xu et al., 2014bShen 2015;Sun et al., 2016b;Xu and Zhao, 2016;Wu et al., 2018;Xu et al., 2018;Wen et al., 2019;Xu 2020a, Xu 2020c). These are mostly endemic taxa, suggesting incipient regionally contrasted ichthyofaunas in the eastern Tethys in the Pelsonian (as opposed to the cosmopolitan faunas of the Griesbachian-Smithian interval). ...
About half of all vertebrate species today are ray-finned fishes (Actinopterygii), and nearly all of them belong to the Neopterygii (modern ray-fins). The oldest unequivocal neopterygian fossils are known from the Early Triassic. They appear during a time when global fish faunas consisted of mostly cosmopolitan taxa, and contemporary bony fishes belonged mainly to non-neopterygian (“paleopterygian”) lineages. In the Middle Triassic (Pelsonian substage and later), less than 10 myrs (million years) after the Permian-Triassic boundary mass extinction event (PTBME), neopterygians were already species-rich and trophically diverse, and bony fish faunas were more regionally differentiated compared to the Early Triassic. Still little is known about the early evolution of neopterygians leading up to this first diversity peak. A major factor limiting our understanding of this “Triassic revolution” is an interval marked by a very poor fossil record, overlapping with the Spathian (late Olenekian, Early Triassic), Aegean (Early Anisian, Middle Triassic), and Bithynian (early Middle Anisian) substages. Here, I review the fossil record of Early and Middle Triassic marine bony fishes (Actinistia and Actinopterygii) at the substage-level in order to evaluate the impact of this hiatus–named herein the Spathian–Bithynian gap (SBG)–on our understanding of their diversification after the largest mass extinction event of the past. I propose three hypotheses: 1) the SSBE hypothesis, suggesting that most of the Middle Triassic diversity appeared in the aftermath of the Smithian-Spathian boundary extinction (SSBE; ∼2 myrs after the PTBME), 2) the Pelsonian explosion hypothesis, which states that most of the Middle Triassic ichthyodiversity is the result of a radiation event in the Pelsonian, and 3) the gradual replacement hypothesis, i.e. that the faunal turnover during the SBG was steady and bony fishes were not affected by extinction events subsequent to the PTBME. Based on current knowledge, hypothesis three is favored herein, but further studies are necessary to test alternative hypotheses. In light of the SBG, claims of a protracted diversification of bony fishes after the PTBME should be treated with caution.
