Phylogenetic Relationships of the Triassic Archaeosemionotus Deecke (Halecomorphi, Ionoscopiformes) from the 'Perledo Fauna'

The lagerstatten 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

A new species of the deep-bodied actinopterygian Dapedium from the Middle Jurassic (Aalenian) o f southwestern Germany

Dapedium is one of the most abundant and diverse genera of ganoid fishes from the Early Jurassic fossil lagerstatte of Europe. In spite of its abundance, however, its timing of extinction is poorly constrained, with the youngest described material being Early Jurassic in age. We describe new diagnostic and relatively complete material of a large species of Dapedium (standard length estimated at 50 cm) from the Middle Jurassic (earliest Aalenian) Opalinuston Formation of Baden-Wurttemberg, Germany. The Aalenian material represents a distinct species, D. ballei sp. nov., differing from Early Jurassic species in a unique combination of characters pertaining to the shape of the dermal skull elements, pectoral fin position, and scale shape and ornamentation. However, although D. ballei sp. nov. exhibits a unique combination of characters, there are no autapomorphies with which to distinguish it from the Toarcian species of Dapedium. Dapedium ballei represents the geologically youngest species of Dapedium, extending the range of this genus into the Middle Jurassic. The Opalinuston Formation fills an important gap in the marine vertebrate fossil record, and finds from this horizon have the potential to greatly improve our understanding of evolutionary dynamics over this period of faunal transition

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

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. 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. 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

Estudio taxonómico de los percíctidos (Osteichthyes : Perciformes) actuales de Argentina

La presente tesis contiene el estudio taxonómico de las especies argentinas de Percichthys (Perciformes, Percichthyidae). Partiendo dela hipótesis sistemática más reciente para el grupo, en la que se aceptaba la existencia de cuatro especies nombradas y una Percichthys sp., se realizó en primer lugar un análisis morfométrico muitivariado. Como resultado de este análisis fue posible reconocer tres formas geométricas claramente diferenciables, fundamentalmente por la morfología de la boca y la longitud de las aletas pares. Luego se llevó a cabo un análisis osteológico detallado que permitió delimitar tres grupos perfectamente correlacionables con las formas geométricas identificadas en el análisis anterior. Reuniendo los resultados de ambos análisis se establece que son dos las especies válidas de Percichthys en Argentina: P. colhuapiensis y P. trucha. Ambas especies están bien definidas por una serie de caracteres osteológicos relativos al esplacnocráneo y que tienen un significado morfofuncional ya que están directamente relacionados con la mecánica del aparato bucal. Asimismo, se establece la sinonimia de P. altispinis y P. vinciguerrae con P. trucha. P. altispinis no es más que la forma juvenil de P. trucha y P. vinciguerrae no pudo ser diferenciada ni morfométrica ni osteológicamente, y los caracteres que la diagnosticaban resultaron comprendidos dentro del rango de varibilidad de P. trucha. Finalmente, se plantea la hipótesis acerca de la validez de P. laevis, especie que habia sido sinonimizada con P. trucha. Esta hipótesis se basa en la diferenciación, tanto morfométrica como osteológica, de un lote de percíctidos colectados en el rio Chico (provincia de Santa Cruz).Fil:López Arbarello, Adriana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Sexual dimorphism in Patagonotothen sima (Richardson, 1844)

In Argentina, the Nototheniidae is represented by about 20 species, which mostly live in coastal waters of the continental shelf and slope. A few species inhabit inshore waters along the coasts of Patagonia and the Fueguian and Falkland (Malvinas) archipelagos and even reach rocky intertidal zones (Norman 1937, Hart 1946). Patagonotothen sima (Richardson 1844) is distributed in the Atlantic from the San Matías Gulf (around 42°S) to the Beagle Channel (54°50'S), inhabiting shallow waters including the intertidal zones. During faunal surveys in the rocky intertidal zone in Puerto Deseado, Santa Cruz (by A. Gosztonyi), it was noted that males of P. sima, one of the most common fish species in that habitat, appeared to have a higher second dorsal fin than the females.Peer Reviewe

Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterygii)

<div><p>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 †<em>Pliodetes</em>, †<em>Araripelepidotes</em>, †<em>Lepidotes</em>, †<em>Scheenstia,</em> and †<em>Isanichthys</em> 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 †<em>Lepidotes</em> is restricted to the Early Jurassic species, whereas the strongly tritoral species previously referred to †<em>Lepidotes</em> are referred to †<em>Scheenstia</em>. Other species previously referred to †<em>Lepidotes</em> represent other genera or new taxa. The macrosemiids are well nested within semionotiforms, together with †Semionotidae, here restricted to †<em>Semionotus</em>, and a new family including †<em>Callipurbeckia</em> n. gen. <em>minor</em> (previously referred to †<em>Lepidotes</em>), †<em>Macrosemimimus</em>, †<em>Tlayuamichin</em>, †<em>Paralepidotus</em>, and †<em>Semiolepis</em>. 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.</p> </div

Strict consensus of 69 most parsimonious trees (92 characters, 39 taxa).

<p>Tree length  = 327; consistency index (CI)  = 0.3547; homoplasy index (HI)  = 0.6453; retention index (RI)  = 0.6608; rescaled consistency index (RC)  = 0.2344. Bootstrap and Bremer values are given above and below the branches leading to each node, respectively.</p

Callibrated phylogenetic hypothesis of ginglymodians interrelationships based on a simplyfied version of the strict consensus tree shown in <b>Figure 17</b>.

<p>Callibrated phylogenetic hypothesis of ginglymodians interrelationships based on a simplyfied version of the strict consensus tree shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039370#pone-0039370-g017" target="_blank"><b>Figure 17</b></a>.</p