Bajaichthys elegans from the Eocene of Bolca (Italy) and the overlooked morphological diversity of Zeiformes (Teleostei, Acanthomorpha)

The Eocene (Ypresian) fauna of Bolca, Italy yields a famous assemblage of marine tropical teleosts. One of the most anatomically distinctive teleosts from Bolca is the enigmatic †Bajaichthys elegans, generally interpreted as a member of Lampridiformes (oarfishes and their allies). Re‐examination of the type and only specimen of †Bajaichthys contradicts this attribution, and we propose that its original description as a member of Zeiformes (dories) was in fact correct. †Bajaichthys bears numerous derived features of zeiforms not found in lampridiforms, including: a pelvic spine, a first vertebra closely associated with the neurocranium, and a reduced metapterygoid not contacting the quadrate. Lampridiform‐like attributes, including a greatly elongated ascending process of the premaxilla, are known to be convergent between this group and Zeiformes. Using a combination of morphological and molecular data, we confirm this revised interpretation and resolve the position of †Bajaichthys within zeiform phylogeny. In terms of overall shape, the very elongate †Bajaichthys contrasts with deep‐bodied Zeiformes and probably had distinctive ecological habits. Our inferred placement of †Bajaichthys and other fossil taxa with extended caudal peduncles (e.g. †Archaeozeus) suggests that the elongate morphotype is ancestral for Zeiformes as a whole, and that the deep‐bodied geometry typical of extant taxa probably appeared several times independently. However, these inferences must be considered preliminary due to low support for patterns of relationships within Zeiformes. The systematic reattribution of †Bajaichthys expands the taxonomic diversity of the Bolca fauna as well as the morphological and ecological diversity of the zeiform clade.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136341/1/pala12280_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136341/2/pala12280.pd

La phylogénie des téléostéens acanthomorphes : approches paléontologique et moléculaire

Acanthomorpha is a group a mainly marine teleosts including more than 15 000 extant species. Acanthomorph interrelationships were almost unknown until the first analyses using cladistic methodology on morphological characters in the beginning of the nineties. The relationships supported by morphology were largely contradicted when molecular phylogenetic studies became available a decade later. The new, "molecular" relationships have never been tested with morphology, which implies that today, several classifications coexist. Moreover, the phylogenetic hypotheses on the first dichotomies of the tree (that is, the first diversification of the group in the early Late Cretaceous) are contradictory from one molecular study to another. For example, some molecular studies based on mitogenomes reject acanthomorph monophyly. My objective during this PhD was to obtain a consensual phylogenetic hypothesis for the base of the acanthomorph tree, allowing reconciling molecular results together and with morphology. In order to obtain this, I constituted morphological datasets with a broad taxonomic sampling covering acanthomorph diversity enough for the molecular hypotheses to be tested by morphology – which previous morphological datasets did not allow. These datasets included fossil taxa for the first time, among which some of the oldest acanthomorphs known on record, that show character state combinations that are extinct today. In parallel, I built molecular dataset using numerous mitochondrial and nuclear markers, in order to better characterize the sources of the incongruence between results. The analysis of my morphological, mitochondrial and nuclear data yielded largely congruent topologies. The clades recovered from one analysis to another have then an increased reliability. For example, Gadiformes (cods) and Zeiformes (dories) are grouped together. Acanthomorph monophyly is supported by all data. The inclusion of fossil taxa is critical to obtain relevant results. In this PhD I obtained a synthetic phylogenetic hypothesis for acanthomorphs, proposing synapomorphies for the "molecular" clades. This phylogeny is replaced in a timeframe thanks to fossil data. The integrative approach I used in my PhD is promising to resolve many other complex phylogenetic questions, especially for deep nodes.Les acanthomorphes sont un groupe de téléostéens principalement marins comprenant plus de 15000 espèces actuelles. Les relations de parenté entre les grands groupes d'acanthomorphes ont longtemps été très mal connues, jusqu'à l'arrivée des premières analyses utilisant la méthode cladistique sur des données morphologiques au début des années 1990. Les relations de parenté proposées par la morphologie ont par la suite été largement remises en question avec l'avènement de la phylogénie moléculaire une décennie plus tard. Ces nouvelles relations de parenté n'ont jamais été testées sur la base de la morphologie, ce qui a comme conséquence qu'à l'heure actuelle, plusieurs classifications existent en parallèle. De plus, les hypothèses sur les premières divergences de l'arbre des acanthomorphes (qui correspondent à la première phase de diversification du groupe, très certainement au début du Crétacé supérieur) sont contradictoires d'une étude moléculaire à l'autre. Notamment, certaines études moléculaires basées sur les génomes mitochondriaux rejettent la monophylie des acanthomorphes. Dans le cadre de cette thèse, mon objectif était d'aboutir à une hypothèse phylogénétique consensuelle pour la base de l'arbre des acanthomorphes, permettant de réconcilier les résultats moléculaires entre eux et avec la morphologie. Pour l'atteindre, j'ai constitué des jeux de données morphologiques dont l'échantillonnage taxonomique couvre suffisamment la diversité des acanthomorphes pour que les hypothèses moléculaires puissent être testées par la morphologie, ce que les précédents jeux de données morphologiques ne permettaient pas. Ces jeux de données incluaient pour la première fois des taxons fossiles, parmi les plus anciens acanthomorphes connus, présentant des combinaisons d'états de caractères inédites dans la nature actuelle. J'ai en parallèle constitué des jeux de données moléculaires, utilisant de multiples marqueurs mitochondriaux et nucléaires, dans l'objectif de mieux caractériser les sources d'incongruence entre les résultats. L'analyse de mes données morphologiques, mitochondriales et nucléaires a livré des topologies très largement congruentes entre elles. La fiabilité des clades ainsi retrouvés d'une analyse à l'autre est renforcée. C'est le cas par exemple du groupement entre les Gadiformes (morues) et les Zeiformes (saint-pierre). La monophylie des acanthomorphes est soutenue par toutes les données. Enfin, il est démontré que l'inclusion des taxons fossiles est cruciale pour obtenir des résultats cohérents. J'ai ainsi obtenu une phylogénie synthétique des acanthomorphes, proposant des synapomorphies pour les clades jusqu'à présent soutenus uniquement par les données moléculaires. Cette phylogénie est replacée dans un contexte temporel grâce aux taxons fossiles. L'approche intégrative adoptée dans cette thèse est prometteuse pour résoudre d'autres questions phylogénétiques complexes, en particulier pour des nœuds profonds

The phylogenetic intrarelationships of spiny-rayed fishes (Acanthomorpha, Teleostei, Actinopterygii): fossil taxa increase the congruence of morphology with molecular data

Acanthomorpha (spiny-rayed fishes) is a clade of teleosts that includes more than 15 000 extant species. Their deep phylogenetic intrarelationships, first reconstructed using morphological characters, have been extensively revised with molecular data. Moreover, the deep branches of the acanthomorph tree are still largely unresolved, with strong disagreement between studies. Here, we review the historical propositions for acanthomorph deep intrarelationships and attempt to resolve their earliest branching patterns using a new morphological data matrix compiling and revising characters from previous studies. The taxon sampling we use constitutes a first attempt to test all previous hypotheses (molecular and morphological alike) with morphological data only. Our sampling also includes Late Cretaceous fossil taxa, which yield new character state combinations that are absent in extant taxa. Analysis of the complete morphological data matrix yields a new topology that shows remarkable congruence with the well-supported molecular results. Lampridiformes (oarfishes and allies) are the sister to all other acanthomorphs. Gadiformes (cods and allies) and Zeiformes (dories) form a clade with Percopsiformes (trout-perches) and the enigmatic Polymixia (beardfish) and Stylephorus (tube-eye). Ophidiiformes (cusk-eels and allies) and Batrachoidiformes (toadfishes) are nested within Percomorpha, the clade that includes most of modern acanthomorph diversity. These results provide morphological synapomorphies and independent corroboration of clades previously only recovered from molecular data, thereby suggesting the emergence of a congruent picture of acanthomorph deep intrarelationships. Fossil taxa play a critical role in achieving this congruence, since a very different topology is found when they are excluded from the analysis

First record of non-mineralized cephalopod jaws and arm hooks from the latest Cretaceous of Eurytania, Greece

Due to the lower fossilization potential of chitin, non-mineralized cephalopod jaws and arm hooks are much more rarely preserved as fossils than the calcitic lower jaws of ammonites or the calcitized jaw apparatuses of nautilids. Here, we report such non-mineralized fossil jaws and arm hooks from pelagic marly limestones of continental Greece. Two of the specimens lie on the same slab and are assigned to the Ammonitina; they represent upper jaws of the aptychus type, which is corroborated by finds of aptychi. Additionally, one intermediate type and one anaptychus type are documented here. The morphology of all ammonite jaws suggest a desmoceratoid affinity. The other jaws are identified as coleoid jaws. They share the overall U-shape and proportions of the outer and inner lamellae with Jurassic lower jaws of Trachyteuthis (Teudopseina). We also document the first belemnoid arm hooks from the Tethyan Maastrichtian. The fossils described here document the presence of a typical Mesozoic cephalopod assemblage until the end of the Cretaceous in the eastern Tethys

Character matrix for Analysis 1

This matrix is used for Analysis 1: morphological matrix of extant and fossil Zeiformes. It is adapted from the matrix of: Tyler, J.C. & Santini, F. (2005) A phylogeny of the fossil and extant zeiform-like fishes, Upper Cretaceous to Recent, with comments on the putative zeomorph clade (Acanthomorpha). Zoologica Scripta 34, 157–175

Data from: Bajaichthys elegans from the Eocene of Bolca (Italy) and the overlooked morphological diversity of Zeiformes (Teleostei, Acanthomorpha)

The Eocene (Ypresian) fauna of Bolca, Italy yields a famous assemblage of marine tropical teleosts. One of the most anatomically distinctive teleosts from Bolca is the enigmatic †Bajaichthys elegans, generally interpreted as a member of Lampridiformes (oarfishes and their allies). Re-examination of the type and only specimen of †Bajaichthys contradicts this attribution, and we propose that its original description as a member of Zeiformes (dories) was in fact correct. †Bajaichthys bears numerous derived features of zeiforms not found in lampridiforms, including: a pelvic spine, a first vertebra closely associated with the neurocranium, and a reduced metapterygoid not contacting the quadrate. Lampridiform-like attributes, including a greatly elongated ascending process of the premaxilla, are known to be convergent between this group and Zeiformes. Using a combination of morphological and molecular data, we confirm this revised interpretation and resolve the position of †Bajaichthys within zeiform phylogeny. In terms of overall shape, the very elongate †Bajaichthys contrasts with deep-bodied Zeiformes and probably had distinctive ecological habits. Our inferred placement of †Bajaichthys and other fossil taxa with extended caudal peduncles (e.g. †Archaeozeus) suggests that the elongate morphotype is ancestral for Zeiformes as a whole, and that the deep-bodied geometry typical of extant taxa probably appeared several times independently. However, these inferences must be considered preliminary due to low support for patterns of relationships within Zeiformes. The systematic reattribution of †Bajaichthys expands the taxonomic diversity of the Bolca fauna as well as the morphological and ecological diversity of the zeiform clade

First record of non-mineralized cephalopod jaws and arm hooks from the latest Cretaceous of Eurytania, Greece

International audienceDue to the lower fossilization potential of chitin, non-mineralized cephalopod jaws and arm hooks are much more rarely preserved as fossils than the calcitic lower jaws of ammonites or the calcitized jaw apparatuses of nautilids. Here, we report such non-mineralized fossil jaws and arm hooks from pelagic marly limestones of continental Greece. Two of the specimens lie on the same slab and are assigned to the Ammonitina; they represent upper jaws of the aptychus type, which is corroborated by finds of aptychi. Additionally, one intermediate type and one anaptychus type are documented here. The morphology of all ammonite jaws suggest a desmoceratoid affinity. The other jaws are identified as coleoid jaws. They share the overall U-shape and proportions of the outer and inner lamellae with Jurassic lower jaws of Trachyteuthis (Teudopseina). We also document the first belemnoid arm hooks from the Tethyan Maastrichtian. The fossils described here document the presence of a typical Mesozoic cephalopod assemblage until the end of the Cretaceous in the eastern Tethys

Exceptional preservation of a Cretaceous intestine provides a glimpse of the early ecological diversity of spiny-rayed fishes (Acanthomorpha, Teleostei)

International audienceAcanthomorph teleosts (spiny-rayed fishes) account for approximately a third of extant vertebrate species. They appeared during the Late Cretaceous and have been a major component of aquatic biodiversity since the early Cenozoic. They occupy today most trophic levels and ecological niches in aquatic environments, however very little is known about those that were adopted by the earliest representatives of the group. Here, we report on an exceptional glimpse into the ecological diversity of early spiny-rayed fishes provided by the unusual preservation of a newly discovered specimen of the freshwater acanthomorph Spinocaudichthys from the Upper Cretaceous of Morocco. A combination of major-to-trace elemental mapping methods reveals that the gross morphology of the specimen's intestine has been remarkably preserved owing to the rapid mineralization of iron hydroxides around it. Differing with the typically short and straight intestinal tract of carnivorous teleosts, the intestine in Spinocaudichthys is long and highly convoluted, indicating a probable herbivorous diet. Acanthomorphs would therefore have conquered various ecological niches in their early evolutionary history, prior to their subsequent phylogenetic diversification in both marine and freshwater environments that followed the K-Pg extinction event

Histology of the endothermic opah (Lampris sp.) suggests a new structure–function relationship in teleost fish bone

International audienceEndothermy, production and retention of heat by the body, appeared convergently in mammals, birds and four spiny-rayed teleost fish lineages. Of these, red-muscle endothermy over most or all of the body has only appeared in two groups: tunas and the opah (Lampris). Hitherto, tunas have been the only spiny-rayed fishes known to have bones containing embedded osteocyte cells; others have acellular bone. We examined bone histology in Lampris for the first time, demonstrating the presence of cellular bone very similar to that of tunas. This contrasts with the acellular condition of its ectothermic close relatives. The distribution of this character suggests that it co-evolved with red-muscle endothermy, hinting at a common physiological mechanism that would link bone histology to endothermy in these distantly related teleost lineages

Anatomy and relationships of †<i>Aipichthys pretiosus</i> and †‘<i>Aipichthys</i>’ <i>nuchalis</i> (Acanthomorpha: Lampridomorpha), with a review of Late Cretaceous relatives of oarfishes and their allies

<div><p>The Cenomanian acanthomorph teleost †<i>Aipichthys</i> is best known from two species: †<i>Aipichthys minor</i> and †<i>Aipichthys velifer</i>. Two poorly studied species of †<i>Aipichthys</i>, †<i>Aipichthys pretiosus</i> from Slovenia and †<i>Aipichthys nuchalis</i> from the English Chalk, have been excluded from all recent studies of the genus. Previous accounts of †<i>A. pretiosus</i> – the type species of †<i>Aipichthys</i> – are inadequate, while †<i>A. nuchalis</i> has been described as too incomplete to interpret. Here we completely redescribe †<i>A. pretiosus</i> and utilize computed tomography to reveal previously hidden skeletal anatomy of †<i>A. nuchalis</i>. †<i>Aipichthys pretiosus</i> has a long sagittal crest, with the supraoccipital, frontal and mesethmoid bones contributing to this structure. Based on this and other features, we find that †<i>A. pretiosus</i> belongs to a clade that is more closely related to extant Lampridiformes than all other nominal species of †<i>Aipichthys</i>. As †<i>A. pretiosus</i> is the type species for the genus, we recommend all other species of the genus should be temporarily referred to as †‘<i>Aipichthys</i>’. †‘<i>Aipichthys</i>’ <i>nuchalis</i> possesses a concave posterior margin and a thickened anterior margin to the supraoccipital crest, and is placed in a polytomy alongside †‘<i>A.</i>’ <i>minor</i>, †‘<i>A.</i>’ <i>velifer</i>, †‘<i>Aipichthys</i>’ <i>oblongus</i> and †<i>Freigichthys</i>. Further investigation is needed to determine whether †‘<i>Aipichthys</i>’ is congeneric with and can be reassigned to †<i>Freigichthys</i>, or whether a new generic name is needed for these taxa. We also include two additional taxa in our analysis: †<i>Nardovelifer altipinnis</i>, the oldest fossil previously attributed to the lampridiform crown, and †<i>Gigapteryx tethyestris</i>, an <i>incertae sedis</i> acanthopterygian. We find that †<i>Nardovelifer</i> has a number of primitive characters not found in crown Lampridiformes, and resolve it as a stem lampridiform. We find that †<i>Gigapteryx</i> is closely related to †<i>Pycnosteroides</i>, together forming the sister clade to all other lampridomorphs. Finally, we examine the diversity of Cretaceous lampridomorphs and discuss their palaeobiogeography and palaeoecology.</p></div