Adriana López-Arbarello

Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterygii)

The Ginglymodi is one of the most common, though poorly understood groups of neopterygians, which includes gars, macrosemiiforms, and “semionotiforms.” In particular, the phylogenetic relationships between the widely distributed “semionotiforms,” and between them and other ginglymodians have been enigmatic. Here, the phylogenetic relationships between eight of the 11 “semionotiform” genera, five genera of living and fossil gars and three macrosemiid genera, are analysed through cladistic analysis, based on 90 morphological characters and 37 taxa, including 7 out-group taxa. The results of the analysis show that the Ginglymodi includes two main lineages: Lepisosteiformes and †Semionotiformes. The genera †Pliodetes, †Araripelepidotes, †Lepidotes, †Scheenstia, and †Isanichthys are lepisosteiforms, and not semionotiforms, as previously thought, and these taxa extend the stratigraphic range of the lineage leading to gars back up to the Early Jurassic. A monophyletic †Lepidotes is restricted to the Early Jurassic species, whereas the strongly tritoral species previously referred to †Lepidotes are referred to †Scheenstia. Other species previously referred to †Lepidotes represent other genera or new taxa. The macrosemiids are well nested within semionotiforms, together with †Semionotidae, here restricted to †Semionotus, and a new family including †Callipurbeckia n. gen. minor (previously referred to †Lepidotes), †Macrosemimimus, †Tlayuamichin, †Paralepidotus, and †Semiolepis. Due to the numerous taxonomic changes needed according to the phylogenetic analysis, this article also includes formal taxonomic definitions and diagnoses for all generic and higher taxa, which are new or modified. The study of Mesozoic ginglymodians led to confirm Patterson’s observation that these fishes show morphological affinities with both halecomorphs and teleosts. Therefore, the compilation of large data sets including the Mesozoic ginglymodians and the re-evaluation of several hypotheses of homology are essential to test the hypotheses of the Halecostomi vs. the Holostei, which is one of the major topics in the evolution of Mesozoic vertebrates and the origin of modern fish faunas.

Semionotids (Neopterygii, Semionotiformes) from the Lower Cretaceous Lagarcito Formation, San Luis Province, Argentina

Abstract A revision of the semionotids from the Lower Cretaceous Lagarcito Formation of Argentina leads to the conclusion that only one taxon, Neosemionotus puntanus Bocchino, 1973, is represented, instead of two monospecific genera and one species of Lepidotes as originally thought. Neosemionotus shares with Lepidotes the presence of more than one suborbital arranged in one row and a long posteroventral process of the dentary, features that have previously been thought to be diagnostic of Lepidotes. On the other hand, it shares with Semionotus the presence of conspicuous dorsal ridge scales. However, Neosemionotus is unique in the characteristics of its dorsal and anal fins, which are both flanked only by high and strong paired basal fulcra. These fulcra become gradually higher/deeper posteriorly, reaching approximately the height/depth of the first fin ray. Other probable synapomorphies of Neosemionotus are the presence of a long parietal pit line, a small, approximately triangular interoperculum, the complete absence of fringing fulcra on the dorsal, and anal fins, and the presence of only very few long and slender fringing fulcra on the pelvic and caudal fins. The systematic position of Neosemionotus is still unknown, but the presence of probably primitive features like the high number of extrascapulars, short parietals, the arrangement of suborbitals, and short snout indicate a relatively basal position among semionotids.

New semionotiform (Actinopterygii: Neopterygii) from the Late Jurassic of southern Germany

We report on a new semionotiform taxon, Scheenstia zappi gen. et sp. nov., from Schamhaupten in the Late Jurassic limestones of the Franconian and Swabian Alb, southern Germany. Although the taxon is so far represented by a single specimen, excellent preservation allows a detailed description of its skeletal anatomy. Scheenstia zappi is distinguished by the presence of a sensory canal in the supraorbital bones and a saddle-like articular surface in the quadratojugal, both features so far unknown in other semionotiforms. The new taxon is further diagnosed by a unique combination of characters: more than three pairs of extrascapular bones; frontals less than three times longer than their maximal width; semitritorial dentition; four anterior infraorbitals; middle pit line contained in a groove in the dermopterotic and parietal; concave posterior border of the angular, robust bugle-like process of the posttemporal bone; large basal fulcra; eleven fin rays in the lower lobe of the caudal fin (below the lateral line); and a first, scale-like caudal fin ray reduced. Among semionotiforms it most closely resembles Lepidotes, in particular the large tritorial forms of the Late Jurassic and Early Cretaceous of Europe, such as L. mantelli, L. maximus and L. laevis. The peculiar shape of the quadratojugal in Scheenstia zappi resembles the condition in some basal teleosts in which a ventral articular surface of the quadrate probably served in the rotation of the lower jaw.

Revision ofSemionotus bergeri Agassiz, 1833 (Upper Triassic, Germany), with comments on the taxonomic status ofSemionotus (Actinopterygii, Semionotiformes).

Semionotus bergeri Agassiz, 1833, from the Upper Triassic (Carnian) of southern Germany, the type species ofSemionotus, is here described in detail for the first time, including so far unstudied material in the Naturkunde-Museum Coburg, which allows a fairly complete reconstruction of this fish. The species is diagnosed by the presence of long frontals, about 4 times longer than wide, with antorbital lateral processes, 6–7 posterior infraorbitals, infraorbital at the posteroventral corner of the orbit notably larger than adjacent ones, infraorbitals at the posterior border of the orbit being as deep as long, and the middle element anteroventrally expanded, dorsal fin base about two times the anal fin base.S. elegans from the Late Triassic-Early Jurassic of the Newark Supergroup in North America, is so far the best know species ofSemionotus and is the only species of this genus that has been included in phylogentic analyses. However, the comparison ofS. bergeri with other proposed speciesof Semionotus, such asS. elegans, and other semionotids casts doubt on the monophyly of this genus as currently understood, since these species exhibit a mosaic distribution of characters.Semionotus bergeriAgassiz, 1833, from the Upper Triassic (Carnian) of southern Germany, the type species ofSemionotus, is here described in detail for the first time, including so far unstudied material in the Naturkunde-Museum Coburg, which allows a fairly complète reconstruction of this fish. The species is diagnosed by the présence of long frontals, about 4 times longer than wide, with antorbital lateral processes, 6–7 posterior infraorbitals, infraorbital at the posteroventral corner of the orbit notably larger than adjacent ones, infraorbitals at the posterior border of the orbit being as deep as long, and the middle élément anteroventrally expanded, dorsal fin base about two times the anal fin base.S. elegans from the Late Triassic-Early Jurassic of the Newark Supergroup in North America, is so far the best know species ofSemionotus and is the only species of this genus that has been included in phylogentic analyses. However, the comparison ofS. bergeri with other proposed speciesof Semionotus, such asS. elegans, and other semionotids casts doubt on the monophyly of this genus as currently understood, since these species exhibit a mosaic distribution of characters.ZusammenfassungDie Typusart der GattungSemionotus, Semionotus bergeriAgassiz, 1833, aus der oberen Trias (Karnium) Süddeutschlands, wird hier zum ersten Mal im Detail beschrieben, unter anderem anhand von bisher unbeschriebenem Material aus dem Naturkunde-Museum Coburg, was eine fast vollständige Rekonstruktion dieses Fisches erlaubt. Die Art lässt sich anhand der folgenden Merkmale diagnostizieren: verlängerte Frontalia, die circa 4 mal so lang wie breit sind und laterale Fortsätze vor der Orbita aufweisen, 6–7 posteriore Infraorbitalia, Infraorbitale am posteroventralen Rand der Orbita deutlich größer als die angrenzenden Infraorbitalia, Infraorbitalia am Hinterrand der Orbita so hoch wie lang und das mittlere Element nach anteroventral expandiert, Ansatz der Rückenflosse in etwas zweimal so lang wie der Ansatz der Analflosse.S. elegans aus der oberen Trias / unterem Jura der Newark Supergruppe Nordamerikas war bisher die bestbekannte Art vonSemionotus und der einzige Vertreter dieser Gattung, der in phylogenetischen Analysen berücksichtigt wurde. Der Vergleich vonS. bergeri mit anderen zu der GattungSemionotus gestellten Arten, darunterS. elegans, und mit anderen Gattungen der Semionotiden lässt allerdings Zweifel an der Monophylie dieser Gattung, wie sie derzeit verstanden wird, aufkommen, da diese Arten eine mosaikartige Verteilung von Merkmalen aufweisen.

A new rhynchocephalian from the late jurassic of Germany with a dentition that is unique amongst tetrapods.

Background Rhynchocephalians, the sister group of squamates (lizards and snakes), are only represented by the single genus Sphenodon today. This taxon is often considered to represent a very conservative lineage. However, rhynchocephalians were common during the late Triassic to latest Jurassic periods, but rapidly declined afterwards, which is generally attributed to their supposedly adaptive inferiority to squamates and/or Mesozoic mammals, which radiated at that time. New finds of Mesozoic rhynchocephalians can thus provide important new information on the evolutionary history of the group. Principle Findings A new fossil relative of Sphenodon from the latest Jurassic of southern Germany, Oenosaurus muehlheimensis gen. et sp. nov., presents a dentition that is unique amongst tetrapods. The dentition of this taxon consists of massive, continuously growing tooth plates, probably indicating a crushing dentition, thus representing a previously unknown trophic adaptation in rhynchocephalians. Conclusions/Significance The evolution of the extraordinary dentition of Oenosaurus from the already highly specialized Zahnanlage generally present in derived rhynchocephalians demonstrates an unexpected evolutionary plasticity of these animals. Together with other lines of evidence, this seriously casts doubts on the assumption that rhynchocephalians are a conservative and adaptively inferior lineage. Furthermore, the new taxon underlines the high morphological and ecological diversity of rhynchocephalians in the latest Jurassic of Europe, just before the decline of this lineage on this continent. Thus, selection pressure by radiating squamates or Mesozoic mammals alone might not be sufficient to explain the demise of the clade in the Late Mesozoic, and climate change in the course of the fragmentation of the supercontinent of Pangaea might have played a major role.

Macrosemimimus, gen. nov. (Actinopterygii, Semionotiformes), from the Late Jurassic of Germany, England, and France

ABSTRACT We describe a new semionotiform genus, which was recognized while studying Macrosemimimus fegerti, gen. et sp. nov., from the Late Jurassic Solnhofen Archipelago, Germany. Macrosemimimus (Lepidotes) lennieri from the early Kimmeridgian of Cap de la Hève, France, including Lepidotes toombsi from the Lower Kimmeridge Clay in Cambridgeshire, England, as a junior synonym, also belong to the new genus. Though different species, the presence of the same fish genus in different biodiversity zones suggests that semionotiforms might have been less sensible to the ecological and physical factors that caused the endemisms recognized in the invertebrate faunas. Macrosemimimus is mainly distinguished by the peculiar shape of the antorbital portion of the frontal bones, a single pair of extrascapular bones that do not reach the dorsal midline, anteriorly open circumborbital ring, only two suborbital bones, edentulous maxilla, a large quadratojugal involved in the jaw articulation, four postcleithra, and the pectoral fins placed very low and joining ventrally. The two included species differ in the ornamentation of the skull bones, the morphology of the scales, the relative size and position of the extrascapular bones, the dorsal extension of the preoperculum, and the kind of dentition. Although the phylogenetic relationships of Macrosemimimus are not yet established, the particular shape of the antorbital portion of the frontals and the patterns of the extrascapular and suborbital bones indicate possible systematic affinity with the macrosemiids, “Lepidotes” gloriae from the Oxfordian of Cuba, and “Lepidotes” microrhis and “Lepidotes” tanyrhis from the Barremian of Las Hoyas, Spain.

A new genus of coccolepidid fishes (Actinopterygii, Chondrostei) from the continental Jurassic of Patagonia

Jurassic freshwater fish faunas are still poorly known, with the only assemblage of that age known from southern South America being the “Almada fauna” of the Cañadón Calcáreo Formation (Oxfordian-Tithonian) of Chubut, Argentina. This fauna is composed mainly by abundant teleosts and a much rarer basal actinopterygian, originally described as †Oligopleurus groeberi and currently usually placed in the genus †Coccolepis. This taxon is here redescribed on the basis of the original specimens and more numerous and better preserved new material from several localities within the Cañadón Calcáreo Formation. The species shows several differences to other coccolepidid taxa, including the apomorphic presence of a sensory canal in the gular plate, and cannot be referred to a known genus. Thus, a new genus name, †Condorlepis gen. nov., is proposed. The detailed anatomical description of †Condorlepis gen. nov. groeberi provides further evidence for the chondrostean affinities of the Coccolepididae and their close relationships with the Acipenseriformes, since this species shows six characters that were hitherto considered to be autapomorphies of the latter clade. A comparison of the Almada fauna with other Gondwanan Jurassic freshwater fish faunas shows close similarities with the roughly contemporaneous fauna of Talbragar, Australia, which also includes an abundant basal teleost and coccolepidids. In contrast, there are marked differences with the faunas of the Early to Middle Jurassic Kota Formation of India, the Late Jurassic to Early Cretaceous Stanleyville beds of the Democratic Republic of the Congo, and the probably Late Jurassic Tacuarembó Formation of Uruguay, in which basal, non-teleostean neopterygians and sarcopterygians are abundant. Adriana López-Arbarello. Bayerische Staatssammlung für Paläontologie und Geologie, Richard-WagnerStrasse 10, D-80333 München, Germany. E-mail: a.Lopez-Arbarello@lrz.uni-muenchen.de and Museo Paleontológico Egidio Feruglio, Av. Fontana 140, 9100 Trelew, Argentina Emilia Sferco. Laboratorio de Paleontología Evolutiva de Vertebrados, Departamento de Geología, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina emiliasferco@gmail.com and Museo Paleontológico Egidio Feruglio, Av. Fontana 140, 9100 Trelew, Argentina Oliver W.M. Rauhut. Bayerische Staatssammlung für Paläontologie und Geologie, Richard-WagnerStrasse 10, D-80333 München, Germany o.rauhut@lrz.uni-muenchen.de PE Article Number: 16.1.7A Copyright: Palaeontological Association February 2013 Submission: 3 September 2012. Acceptance: 30 January 2013 López-Arbarello, Adriana, Sferco, Emilia, and Rauhut, Oliver W.M. 2013. A new genus of coccolepidid fishes (Actinopterygii, Chondrostei) from the continental Jurassic of Patagonia, Palaeontologia Electronica Vol. 16, Issue 1; 7A 23p; palaeo-electronica.org/content/2013/397-new-coccolepidid-from-patagonia LÓPEZ-ARBARELLO ET AL: NEW COCCOLEPIDID FROM PATAGONIA and Museo Paleontológico Egidio Feruglio, Av. Fontana 140, 9100 Trelew, Argentina and Department of Earth and Environmental Sciences and GeoBioCenter, Ludwig-Maximilians-University, Richard-Wagner-Strasse 10, 80333 Munich, Germany

New holostean fishes (Actinopterygii: Neopterygii) from the Middle Triassic of the Monte San Giorgio (Canton Ticino, Switzerland)

The new neopterygian genus Ticinolepis, including two new species T. longaeva and T. crassidens is described from Middle Triassic carbonate platform deposits of the Monte San Giorgio. The anatomy of this fish shows a mosaic of halecomorph and ginglymodian characters and, thus, the new taxon probably represents a basal holostean. During the latest Anisian to earliest Ladinian the two new species coexisted in the intraplatform basin represented by the uppermost Besano Formation, but only T. longaeva sp. nov. inhabited the more restricted basin represented by the Ladinian Meride Limestone (except for the Kalkschieferzone). The more widely distributed type species shows interesting patterns of intraspecific variation including ontogenetic changes and morphological variation over time. The second species presents anatomical features that strongly indicate a strictly durophagous diet. The different distribution of the species is interpreted as a result of habitat partitioning and different adaptability to palaeoenvironmental changes.

Phylogenetic relationships of the triassic archaeosemionotus deecke (halecomorphi, ionoscopiformes) from the 'perledo fauna'.

The lagerstätten in the Monte San Giorgio have provided excellent fossils representing one of the most important windows to the marine life during the Triassic. Among these fossils, fishes are abundant and extraordinarily well preserved. Most of these fishes represent extinct lineages and were difficult to understand and classify during the early years after discovery. These difficulties usually led to a mixture of species under the same taxonomic name. This is the case of fishes referred to the genus Archaeosemionotus. The name bearing type of A. connectens, the type species of this genus, represents a basal halecomorph, but most other fishes referred to this genus represent basal ginglymodians. Therefore, we conducted this study to clarify the taxonomic status and phylogenetic relationships of A. connectens, which is a member of the family Furidae (Halecomorphi, Ionoscopiformes) representing the second cladistically supported evidence of ionoscopiforms in the Triassic and it is thus one of the two oldest reliable records of this group. Ionoscopiforms have a long stratigraphic range, though their fossil record is rather patchy. In our analysis, the sister taxon of Archaeosemionotus is Robustichthys from the Anisian of China, and they together form a clade with Furo, which is known from several localities ranging from the Early to the Late Jurassic. Other ionoscopiforms are so far known from the Kimmeridgian to the Albian and it is thus evident that recent efforts have concentrated on the later history of the group (Late Jurassic to Cretaceous). The phylogenetic relationships obtained for the Ionoscopiformes do not show a clear palaeobiogeographic pattern, but give important new insights into the origin, divergence date and early history of this clade.

New callipurbeckiid genus (Ginglymodi: Semionotiformes) from the Tithonian (Late Jurassic) of Canjuers, France

Ginglymodian fishes are abundant and diverse in Upper Jurassic limestones of Germany, but rarer in coeval sequences in France. Only a single ginglymodian is so far known from the Tithonian at Canjuers. Our study of this excellently preserved specimen revealed that it represents a new taxon †Occitanichthys canjuersensis gen. et sp. nov., which is retrieved in a cladistic analysis as a member of the semionotiform family †Callipurbeckiidae. Additionally, two specimens among fishes from the Middle Purbeck Beds at Swanage referred to †Callipurbeckia minor were found to represent the new callipurbeckiid taxon. The new taxon inhabited the epicontinental seas that covered most of Europe connecting the Tethys with the North Atlantic during Jurassic and Cretaceous, and its minimum biochron ranges from the Early Tithonian to the Early Cretaceous. After incorporation of the new and recently described taxa and the re-evaluation and addition of morphological characters, our cladistic analysis recovered a somewhat different pattern of relationships compared with previous phylogenetic hypotheses for Ginglymodi. Mainly, in the new topology, a monophyletic †Lepidotidae includes the Jurassic genera †Lepidotes and †Scheenstia, and the Tithonian–Berriasian †Camerichthys from Spain, which has been classified in †Semionotiformes. Among semionotiforms, our results retrieved the family †Macrosemiidae as the sister group of †Semionotidae occupying a more distal position within the clade †Semionotiformes than previously thought.KurzfassungDie Fische der Ginglymodi sind im Oberjura von Deutschland weit verbreitet, in gleichaltrigen Schichten Frankreichs hingegen eher selten vorkommend. Nur ein Exemplar der Ginglymodi ist bisher aus dem Tithon von Canjuers in Frankreich bekannt. Unsere Untersuchungen ergaben für dieses gut erhaltenen Stück ein neues Taxon: †Occitanichthys canjuersensis gen. et sp. nov., welches nach kladistischer Analyse innerhalb der †Semionotiformes der Familie der †Callipurbeckiidae zugeordnet werden kann. Zusätzlich zeigte sich, dass zwei Exemplare aus dem Mittleren Purbeck in Swanage, welche als †Callipurbeckia minor beschrieben wurden, weitere Vertreter dieses neuen callipurbeckiid Taxons darstellen. Das neue Taxon bewohnte das Epikontinentalmeer, welches während Jura und Kreide einen Großteil Europas bedeckte und die Tethys mit dem Nordatlantik verband. Die stratigraphische Reichweite des neuen Taxons erstreckt sich mindestens vom Frühen Tithon bis zur Frühkreide. Nach der Einordnung des neu beschriebenen Taxons, der Re-Evaluierung und dem Hinzufügen neuer morphologischer Merkmale, ergaben unsere kladistischen Analysen ein neues Verwandschaftsmuster, verglichen mit früheren phylogenetischen Hypothesen für die Teilklasse der Ginglymodi. In erster Line konnte eine neue Topologie festgestellt werden, bei welcher sich †Lepidotidae als monophyletische Gruppe darstellte, welche die Genera †Lepidotes und †Scheenstia und aus dem Tithonium-Berriasium Spaniens †Camerichthys umfasst. Zuvor wurde †Camerichthys den Semionotiformes zugeordnet. Laut unseren Untersuchungen ist unter den †Semionotiformes die Familie der †Macrosemiidae die Schwestergruppe der †Semionotidae und erhält somit eine distalere Stellung innerhalb der †Semionotiformes als vorher gedacht.