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Intermuscular bones. (A) Epineural series of processes and vertebrae in the Early Jurassic teleost {Leptolepis coryphaenoides (BGHan 19562, acid-prepared specimen). Scale 5 1 cm. (B) Series of anteriormost epineural processes in Elops saurus (CAS [SU] 10487). (C) Restoration of {Leptolepis coryphaenoides in lateral view. Note the series of epineural processes associated with the neural arches of the precaudal vertebrae (after Arratia, 1996). (D) Restoration of the Late Jurassic elopomorph {Anaethalion knorri in lateral view (after Arratia, 1996). Note the series of epineural processes associated with the neural arches of the precaudal vertebrae and the short series of small epipleural bones associated to the anteriormost caudal region. Abbreviations: epin.p, epineural processes; na, neural arches; ns, neural spines; sn, supraneurals; ona, accessory neural arch.
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The subclass Teleostei Müller was erected in 1845 to contain all fishes possessing intermuscular bones (e.g., epineurals and epipleurals) and two arterial valves (in the conus arteriosus), and that are characterized also by the absence of muscles at the basal arteria (ventral aorta). Since these characters proved difficult for diagnosing fossils, t...
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... Thrissops, were not included within the teleosts following an incorrect in- terpretation by Agassiz that they possess scales with ganoine (so they were interpreted as holostean ganoids). Other teleostean characters had not yet been discovered in some of the fossil "ganoids", e.g., long epineural processes (in {Leptolepis coryphaenoides; Fig. 4A, C; e.g., Arratia, 1996;Arratia and Hikuroa, 2010) and the presence of two series of intermuscular bones, the epineural and epipleural, in the ichthyodectiforms {Allothrissops and {Thrissops, as in many extant teleosts ( Fig. 4B; Patterson and Johnson, 1995;Arratia, 1997Arratia, , 1999). However, the observation of such delicate ...
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... not yet been discovered in some of the fossil "ganoids", e.g., long epineural processes (in {Leptolepis coryphaenoides; Fig. 4A, C; e.g., Arratia, 1996;Arratia and Hikuroa, 2010) and the presence of two series of intermuscular bones, the epineural and epipleural, in the ichthyodectiforms {Allothrissops and {Thrissops, as in many extant teleosts ( Fig. 4B; Patterson and Johnson, 1995;Arratia, 1997Arratia, , 1999). However, the observation of such delicate structures is only possible when scales are missing or removed and the vertebral column is well articulated, which explains partially why morphological interpretations may be incomplete depending on the preservation or preparation of ...
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... Dingerkus and Uhler, 1977;Taylor and Van Dyke, 1985). Concomitant with staining Recent fishes, the acid procedure to separate fossil bone from the rock was improved by Toombs and Rixon (1959) from a previous method by Toombs in 1948, and more recently by Grande and Bemis (1998). Acid-preparation technique permits the study of fossil bones (e.g., Fig. 4A) in a detailed manner comparable to that of cleared-and-stained specimens, with the difference that the soft structures (and cartilage) are not commonly preserved in fossils, and internal complexes, e.g., endocra- nium and branchial arches, may be obscured by more lateral bones. (2) The availability of special microscopes, including ...
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... processes versus epineural bones.-Long processes of the lateral or posterolateral wall of the neural arch of abdominal vertebrae (Fig. 4A-D) is a synapomorphy of {Eurycormus plus more advanced teleosts (Fig. 9, node D; Arratia, 2013:ch. 102). The processes may become autoge- nous in the last or in all abdominal vertebrae in more advanced teleosts (Patterson and Johnson, 1995). Although both structures are homologous, it is significant to make the distinction between process ...
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... extinct teleosts, such as {Leptolepis coryphaenoides, the epineural processes (Fig. 4A, C) retain an internal core of cartilage, whereas the process is completely ossified in extant teleosts (Fig. 4B). However, the complete ossification represents a further state of transformation of the epineurals among teleosts, as well as its complete loss in some extant lineages, such as in ...
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... extinct teleosts, such as {Leptolepis coryphaenoides, the epineural processes (Fig. 4A, C) retain an internal core of cartilage, whereas the process is completely ossified in extant teleosts (Fig. 4B). However, the complete ossification represents a further state of transformation of the epineurals among teleosts, as well as its complete loss in some extant lineages, such as in ...
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... another series of intermuscular bones, the epipleurals. The presence of epipleurals is a synapomor- phy of {Ascalabos plus more advanced teleosts (Fig. 9, node J; Arratia, 2013:ch. 103; not at node E as it is written in Arratia, 2013). They are few in number and are tiny, thin bones associated with the first haemal arches/spines in basal teleosts (Fig. 4D), whereas they increase in number in some more derived taxa where they can also be associated with the lateral walls of ribs and multiple haemal arches (e.g., in Elops and Megalops; for distribution of epipleurals in living teleosts, see Patterson and Johnson, ...
Citations
... To avoid confusion, the first time that the parietal and postparietal bones are cited in the text, as well as in all figures, the traditional terminology is shown in square brackets, e.g., parietal bone [= frontal]: pa [= fr]. The terminology of the vertebral column follows Arratia et al. (2001) and Arratia (2015), whereas that of the caudal endoskeletal elements follows Schultze and Arratia (1988, 1989, 2013, Arratia and Schultze (1992) and Schultze and Arratia (2013). The method of counting vertebrae follows Tintori et al. (2007), an approach followed by Arratia (2022), to ensure that the results are comparable. ...
... A urohyal has not been observed in any specimen studied here, and it is assumed to be absent as in other marcopoloichthyids (Arratia, 2022), as well as in other stem teleosteomorphs as for instance pachycormiforms, aspidorhynchiforms, pholidophoriforms, and archaeomaenids (e.g., Arratia & Schultze, 1990, 2013Arratia, 1997Arratia, , 1999Arratia, , 2013Arratia, , 2015Arratia, , 2022Bean, 2024). The presence of a urohyal is interpreted as a synapomorphy at the phylogenetic level of Leptolepis coryphaenoides plus more advanced teleosts (e.g., Arratia, 1999Arratia, , 2013. ...
... The tail of marcopoloichthyids (including the new species; Figs. 3, 7A, 11) is homocercal, with both lobes of similar shape and size, and five hypurals somehow producing a fan-shaped figure. This pattern differs from other Triassic teleosteomorphs (e.g., Prohalecites and pholidophorids), which have a hemiheterocercal tail (Arratia, 2013(Arratia, , 2015Arratia & Tintori, 1999;Tintori, 1990). Contrary to other stem teleosteomorphs where the caudal endoskeleton is known, the Swiss marcopoloichthyids do not possess epural bones ( Fig. 11; Arratia, 2022: Figs. 13, 14); however, six dorsal epurals were identified in M. ani, but these elements have an uncommon position above the neural spines of preural centra 3-5 and arcocentral elements in front of hypurals 1-3, which are followed by an unnamed element that is fragmented distally (Tintori et al., 2007: Fig. 5). ...
A new species ( Marcopoloichthys mirigioliensis ) of the stem teleosteomorph genus Marcopoloichthys is described from the lower Besano Formation (late Anisian at Monte San Giorgio, southern Switzerland), making this new species distinct from Marcopoloichthys furreri from the Prosanto Formation (early Ladinian at Ducanfurgga, southeastern Switzerland). Marcopoloichthys mirigioliensis n. sp. is smaller (ca. 32 mm standard length) than M. furreri (ca. 40 mm standard length), and in addition, the two species have some important differences in the caudal endoskeleton and fin, e.g., number of epaxial and hypaxial basal fulcra, uroneural structure, size of hypurals, and presence versus absence of urodermals. Marcopoloichthys mirigioliensis n. sp. is the smallest member of Marcopoloichthyidae which is currently known from at least five species living in the Triassic of China (one species), Italy (two and others that remain undescribed), and Switzerland and according to current information, with its ca. 32 mm standard length is candidate to be considered a miniature fish. Additionally, this size makes it the smallest known stem teleost. As in other marcopoloichthyids, the buccal and suspensorium anatomy of M. mirigiolensis n. sp. corresponds to that of suction-feeder fishes.
... PGMS summarises which specimens can be used in a geometric morphometrics analysis to study the shape of the cranium, the post-cranium, and the relative position of the fins following the criteria used in previous studies (Cavalcanti et al. 1999;Cawley et al. 2018;Liyandja et al. 2022). PMS indicates the specimens in which it is possible to count the number of vertebrae; the dorsal, pelvic, anal and caudal fin rays; and hypurals, because of their extended use as diagnostic characters in taxonomy of fishes (Guerrero et al. 2016), and particularly in basal teleostean lineages (Arratia 2015). ...
Postmortem body curvature introduces error in fish morphometric data. Compared to living fish, the causes of such body curvature in fossils may be due to additive taphonomic processes that have been widely studied. However, a protocol that helps to correct its effect upon morphometric data remains unexplored. Here, we test two different mathematical approaches (multivariate regression and the so-called ‘unbending functions’) available to tackle fish geometric morphometric data in two exceptionally preserved gonorynchiformes fossil fishes, Rubiesichthys gregalis and Gordichthys conquensis , from the Las Hoyas deposits (Early Cretaceous, Spain). Although both methods successfully correct body curvature ( i.e ., removing misleading geometric variation), our results show that traditional approaches applied in living fishes might not be appropriate to fossil ones, because of the additional anatomical alterations. Namely, the best result for 2D fossil fishes is achieved by correcting the arching of the specimens (mathematically “unbending” them). Ultimately, the effect of body curvature on morphometric data is largely taxon independent and morphological diversity mitigates its effect, but size is an important factor to take into account (because larger individuals tend to be less curved).
... scales as elasmoid scales. Elasmoid scale have been identified in certain basal Sarcopterygians and the majority of Actinopterygians [26,27]. Schultz [12,28] posits that elasmoid scales have their origins in ganoid or cosmoid scales, differentiating them into two primary types: amioid scale with radial ridges on the surface of the scale, and round scale with concentric rings running parallel to the edge (including ctenoid and cycloid scales). ...
The study of morphological characteristics and growth information in fish scales is a crucial component of modern fishery biological research, while it has been less studied in fossil materials. This paper presents a detailed morphological description and growth analysis of a fossil ctenoid scale obtained from the Upper Cretaceous Campanian lacustrine deposits in northeastern China. The morphological features of this fossil scale are well-preserved and consistent with the structures found in ctenoid scales of extant fish species and display prominent ring ornamentation radiating outward from the central focus, with grooves intersecting the rings. A comparative analysis of the morphological characteristics between the fossil ctenoid scale and those well-studied extant fish Mugilidae allows us to explore the applicability of modern fishery biological research methods to the field of fossil scales. The scale length, scale width, the vertical distance from the focus to the apex of the scale, and the total number of radii have been measured. The age of the fish that possessed this ctenoid scale has been estimated by carefully counting the annuli, suggesting an age equal to or more than seven years. The distribution of growth rings on the scale potentially reflects the warm paleoclimatic condition and fish-friendly paleoenvironment prevalent during that period. This paper, moreover, serves as a notable application of fishery biological methods in the examination of fossil materials.
... Since many years Gloria Arratia studies basal Teleostomorpha (e.g. Arratia, 1997aArratia, , 1997bArratia, , 2000aArratia, , 2000bArratia, , 2001Arratia, , 2004Arratia, , 2013Arratia, , 2015Arratia & Schultze, 2024). In 2022, she published a paper on the outstanding small suctionfeeder Marcopoloichthys furreri from the Middle Triassic Prosanto Formation of Graubünden (Arratia, 2022). ...
Around the middle of the nineteenth century, Italian palaeontologists began to investigate fossils of fishes and reptiles from the Middle Triassic outcrops in the vicinity of Monte San Giorgio (Canton Ticino, Switzerland). In 1924, researchers from the University of Zurich started their scientific excavations on the Swiss side. The many fish fossils found since then have often stood in the shadow of the more spectacular and mostly larger fossils of various aquatic reptiles. Beginning around 1980 the fish fossils in the collection of the Palaeontological Institute and Museum of Zurich University have subsequently been brought out of this shadow. The picture presently emerging is that of a species rich fish fauna located in six different fossiliferous beds of Anisian and Ladinian age with a few chondrichthyan, some coelacanth and a wealth of different actinopterygian taxa, many of them well preserved. The ongoing work not only results in taxonomic and systematic novelties, but gives also new insights into their palaeobiology, palaeoecology and palaeobiogeography.
... Cranial bone terminology follows Schultze (2008) and Teng et al. (2019); alternative nomenclature is indicated in square brackets, e.g., parietal [¼ frontal]: pa [¼ fr]. Terminology for the vertebral column follows Arratia et al. (2001) and Arratia (2015), whereas caudal endoskeletal terms follow Schultze & Arratia (1988, 1989, and Arratia & Schultze (1992. Descriptions of fin rays, scutes, fulcra, procurrent rays, epaxial rudimentary rays, and principal rays follows definitions provided by Arratia (2008Arratia ( , 2009. ...
The discovery of an exceptionally preserved specimen of the Mesozoic teleost fish Aphnelepis australis from the upper Kimmeridgian (Upper Jurassic) Talbragar Fossil Fish Bed in New South Wales, together with historic confusion over its phylogenetic affinities, has prompted a detailed reassessment of the taxon. The new specimen of A. australis is skeletally complete and exhibits the dorsal fin with long principal dorsal fin rays and characteristic squamation comprising heavy rhombic scales anterior to insertions of the dorsal fin and anal fin, and much lighter and thinner weakly crenulate scales on the posterior half of the body. A cladistic analysis resolves A. australis as a member of Archaeomenidae, along with Archaeomene tenuis, Wadeichthys oxyops, Oreochima ellioti, Gurvanichthys mongoliensis, Zaxilepis quinglongensis, and Aphnelepis australis.
... Heterocercal tails, like those of modern sturgeons, have a larger upper lobe containing the vertebral column and a continuous set of bony fin rays. Homocercal tails have, instead, a short upward-bent column that ends at the base of the fin and two sets of caudal rays separated into discrete upper and lower lobes of roughly equal size (Fig. 1, A to D) (3,4,(6)(7)(8). Early naturalists identified a similar morphological transformation during the ontogeny of modern teleosts, which initially develop a heterocercal-like tail (Fig. 1C) that then acquires the homocercal shape of adult tails (1-3, 6, 9). Thus, the main difference between heterocercal and homocercal tails in development and evolution lies in the organization and extension of the posterior end of the body axis ( Fig. 1, A to C). ...
... A homeotic transformation underlies the heterocercal-to-homocercal transition Intriguingly, zebrafish b13a −/− and c13a −/− single mutants exhibit similarities to the heterocercal tails of primitive teleosteomorphs, including the absence of uroneurals, additional preural and ural centra, a reduced number of principal rays, and the lack of the hypural diastema (6,8,42,43). Thus, to critically compare b13a −/− and c13a −/− phenotypes to ancestral caudal fin morphologies, we extracted a subset of caudal fin characters that were significantly modified in our mutants from morphological matrices of stem teleost phylogenies (Supplementary Text and table S2) (44)(45)(46) and coded mutant phenotypes as character states (Fig. 7B). ...
... 6 [3]), while †Aspidorhynchiformes acquired characters attributed to b13a (Chars. 1 to 4, [1]), including the convergent modification of ural neural arches into uroneurals (4,7). In the lineage leading to modern teleosts ( †Prohalecites plus Teleostei), all seven characters were gradually acquired until the establishment of the homocercal tail in the early Jurassic †Leptolepis coryphaenoides (Fig. 7B) (8). Subsequently, the teleost caudal skeleton stabilized with fewer than six preurals (Char. 1 [1]), two ural vertebrae (Char. 2 [1]), uroneurals (Char. ...
Ancient bony fishes had heterocercal tails, like modern sharks and sturgeons, with asymmetric caudal fins and a vertebral column extending into an elongated upper lobe. Teleost fishes, in contrast, developed a homocercal tail characterized by two separate equal-sized fin lobes and the body axis not extending into the caudal fin. A similar heterocercal-to-homocercal transition occurs during teleost ontogeny, although the underlying genetic and developmental mechanisms for either transition remain unresolved. Here, we investigated the role of hox13 genes in caudal fin formation as these genes control posterior identity in animals. Analysis of expression profiles of zebrafish hox13 paralogs and phenotypes of CRISPR/Cas9-induced mutants showed that double hoxb13a and hoxc13a mutants fail to form a caudal fin. Furthermore, single mutants display heterocercal-like morphologies not seen since Mesozoic fossil teleosteomorphs. Relaxation of functional constraints after the teleost genome duplication may have allowed hox13 duplicates to neo-or subfunctionalize, ultimately contributing to the evolution of a homocercal tail in teleost fishes.
... For instance, Prohalecites porroi from the Middle Triassic (late Ladinian, ca. 240-237 Ma) of Italy was interpreted as the oldest teleosteomorph by Arratia (2015). However, at the same time two new pholidophorids (Malingichthys nimaiguensis and M. wanfenglinensis from the Late Ladinian of China were proposed as the oldest teleosts by Tintori et al. (2015). ...
As the fossil record reveals, neopterygians had a major diversification after the great mass extinction at the Permian-Triassic boundary , including the appearance of the major clade Teleosteomorpha. Detailed studies of new taxa (Pseudopholidoctenus germanicus, Barschichthys ruedersdorfensis, and Ruedersdorfia berlinensis) from the lower Anisian (middle Muschelkalk) of Germany and their comparisons with other Triassic relatives are presented, including new information concerning size, shape, and diet. Two families, Pholidophoridae and Marcopoloichthyidae, made a modest appearance during the Anisian of Europe and Asia almost simultaneously , with Pseudopholidoctenus (and the teleosteomorphs Barschichthys and Ruedersdorfia) from the Germanic Basin, being the oldest stem teleosts (244 Ma), followed shortly by Marcopoloichthys ani from Italy. The early teleostean diversification was fast-already in the late Ladinian three lineages were present: Prohalecitiidae (Europe), Pholidophoridae (Asia, Europe), and Marcopoloichthyidae (Asia, Europe), with ca. 20 species inhabiting the Tethys Ocean during the Middle-Late Triassic. Most Triassic teleosteomorphs were small, ca. 50 mm standard length, and a few as possibly miniature, with torpedo or oblong shapes, and suction feeders-probably a plankton based-diet. These first Triassic radiations were replaced during the early Sinemurian of marine ecosystems of Europe with two major groups: (a) non-monophyletic 'pholidophoriforms' and (b) proleptolepids and leptolepids, having an average size (ca. 100 mm SL) longer than Triassic forms, with oblong and fusiform shapes. A fast dispersion from the Tethys to the Paleo-Pacific followed, as demonstrated by the presence of small (ca. 50 mm SL) suction feeder proleptolepids in the early Sinemurian of Chile.
... Within the Teleostei, schooling species are found among different orders and families, ranging from basal (Elopidae, Albulidae and others) and more advanced (Cyprinidae, Clupeidae, Salmonidae, Osmeridae) and ending with the youngest (Gasterosteidae, Centriscidae, Mugilidae, Percidae and many others). They occupy different positions on the phylogenetic tree of Teleostei (Arratia, 2000(Arratia, , 2015Origin and phylogenetic …, 2010), which gives the right to speak about the multiple and independent emergence of schooling behavior in the evolution of Teleostei. ...
... This difference is becoming even more pronounced (Marsicano et al., 2016;Martinelli et al., 2017;Ottone et al., 2014;Wynd et al., 2017). These developments result in a significant stratigraphic gap in a fossil record of numerous continental vertebrate groups, in particular stem mammals, lissamphibians, archosaurs, stem turtles, lepidosauromorphs, and freshwater neopterygians, which developed crucial anatomical adaptations in the Triassic (Arratia, 2015;Dalla Vecchia, 2013;Evans & Borsuk-Białynicka, 1998;Li et al., 2008;Pardo et al., 2017;Piechowski & Tałanda, 2020;Schoch et al., 2020;Sobral et al., 2020;Soul & Benson, 2017;Sterli et al., 2021;Sulej et al., 2020;Szczygielski & Słowiak, 2022;Szczygielski & Sulej, 2019;Whiteside, 1986). Later in the Mesozoic and Cenozoic, these groups dominated the terrestrial and aquatic ecosystems, but in the Triassic they coexisted with numerous other vertebrates (e.g., dicynodonts, rhynchosaurs, tanystropheids, chroniosuchians, doswellids, procolophonians, placodonts, capitosaurian temnospondyls, perleidiforms) that probably did not survive into the Jurassic (Dunhill & Wills, 2015). ...
The Middle Triassic remains a poorly understood time in the evolution of land vertebrates. Here, we report a new Ladinian-age vertebrate assemblage from Miedary (southern Poland). It consists of more than 20 taxa including fish (four
species of Hybodontiformes, cf. Gyrolepis, Redfieldiiformes, ‘Thelodus’, Saurichthys, Serrolepis, Prohalecites, Ptychoceratodus), amphibians (Mastodonsaurus, Gerrothorax, Plagiosternum, chroniosuchian Bystrowiella), and reptiles (Owenettidae, Blezingeria, Nothosaurus, Tanystropheus, an additional, yet unidentified tanystropheid, the doswelliid Jaxtasuchus, and another archosauromorph, as well as eight archosauriform tooth morphotypes). Preliminary comparisons suggest biogeographic and environmental similarities with roughly contemporaneous localities known from the southwestern part of the Germanic Basin. Among differences in these two areas are the presence of a new armored archosauromorph and a surprising abundance of Tanystropheus remains in the new Polish site. Miedary is currently the richest source of three-dimensionally preserved Tanystropheus material in the world, which will be crucial for a better understanding of the preferred environment and lifestyle of this highly specialized reptile.
... Anatomical studies of various extant and extinct fishes have revealed that the main part of the caudal fin derives from the tissue below the notochord/vertebral column (Goodrich, 1930;Metscher and Ahlberg, 2001;Hadzhiev et al., 2007;Schultze and Arratia, 2013;Arratia, 2015;Desvignes et al., 2018). Evolutionary analysis has suggested that "the teleost caudal fin is actually the ventral lobe of the ancestral fin" (Sallan, 2016). ...
... The platyfish caudal fin has a rounded shape supported by approximately 18 principal rays ( Figures 1A, B). Among them, 16 rays are branched plus one unbranched at the dorsal and the ventral side, as defined by anatomical conventions (Schultze and Arratia, 1989;Arratia, 2008;Schultze and Arratia, 2013;Arratia, 2015). Ray branches, also called bifurcations, are formed through dichotomous splitting of the source ray during their distal growth, which occurs at the tip of the fin. ...
Fin regeneration has been extensively studied in zebrafish, a genetic model organism. Little is known about regulators of this process in distant fish taxa, such as the Poeciliidae family, represented by the platyfish. Here, we used this species to investigate the plasticity of ray branching morphogenesis following either straight amputation or excision of ray triplets. This approach revealed that ray branching can be conditionally shifted to a more distal position, suggesting non-autonomous regulation of bone patterning. To gain molecular insights into regeneration of fin-specific dermal skeleton elements, actinotrichia and lepidotrichia, we localized expression of the actinodin genes and bmp2 in the regenerative outgrowth. Blocking of the BMP type-I receptor suppressed phospho-Smad1/5 immunoreactivity, and impaired fin regeneration after blastema formation. The resulting phenotype was characterized by the absence of bone and actinotrichia restoration. In addition, the wound epidermis displayed extensive thickening. This malformation was associated with expanded Tp63 expression from the basal epithelium towards more superficial layers, suggesting abnormal tissue differentiation. Our data add to the increasing evidence for the integrative role of BMP signaling in epidermal and skeletal tissue formation during fin regeneration. This expands our understanding of common mechanisms guiding appendage restoration in diverse clades of teleosts.
