Halecomorph Fish Research Articles

A new study on the halecomorph fishes from the Triassic of Perledo (Italy) highlights important issues in Palaeoichthyology

A new study on the halecomorph fishes from the Triassic of Perledo (Italy) highlights important issues in Palaeoichthyology

A New Sinamiin Fish (Actinopterygii) from the Early Cretaceous of Thailand: Implications on the Evolutionary History of the Amiid Lineage

The Sinamiidae are a family of halecomorph fishes (Holostei) stratigraphically limited to the Lower Cretaceous and confined to East Asia. The first species of sinamiids were discovered in China, and then new occurrences were recorded in Thailand and Japan. The three recognized genera, Sinamia, Siamamia and Ikechaoamia, are notably characterized by an unpaired parietal. Here, we describe a new genus and species of sinamiid based on material from the Aptian Khok Kruat Formation of Ban Krok Duean Ha, Nakhon Ratchasima, Thailand. The new taxon known from preserved specimens in 3D is characterized by four pairs of extrascapular and tall cylindrical teeth with a conical enamel stalk topped by an arrowhead-shaped acrodine cap, among other characters. A phylogenetic analysis of the halecomorph fishes shows that the new taxon is the sister of the other Thai species, Siamamia naga, and that the two are grouped with two Chinese genera in a strongly supported clade, the Sinamiinae. This subfamily is here grouped with the Amiinae that contained the extant Amia. This new discovery is a clue that Southeast Asia may have been a center of diversification for this fish clade, and the phylogenetic analysis reveals that amiines may have originated somewhere in Asia during the Cretaceous before they spread throughout the northern hemisphere.

Osteology and phylogeny ofRobustichthys luopingensis, the largest holostean fish in the Middle Triassic

The extinct ray-finned fish taxon Robustichthys luopingensis from Luoping, eastern Yunnan, China represents the largest holostean known in the Middle Triassic. Despite its potential significance for investigating the holostean phylogeny and reconstructing the Triassic marine ecosystems, Robustichthys has so far not been described in detail and its phylogenetic position within the Holostei was controversy. This study provides a redescription and revision of Robustichthys based upon a comparative study of eight type specimens and nine new specimens. Newly recognized information includes a toothed parasphenoid, a pair of premaxillae not pierced by the olfactory nerve, a splint-like quadratojugal, a hatchet-shaped hyomandibula, an hourglass-shaped symplectic, anterior and posterior ceratohyals, a complete series of branchiostegal rays, and sclerotic bones. A revised reconstruction of Robustichthys is presented. Results of a cladistic analysis confirmed Robustichthys as an ionoscopiform within the Halecomorphi; the previous placements of Robustichthys as a basal ginglymodian and Ionoscopidae as a basal amiiform clade are not supported. The sister group relationship between Sinamiinae (Sinamia and Ikechaoamia) and Amiinae (Amia and Cyclurus) within the Amiidae is newly recognized. This revised topology provides new insights into the evolution and historical paleoecology of halecomorph fishes.

A new Late Jurassic halecomorph fish from the marine Vaca Muerta Formation, Argentina, southwestern Gondwana

Abstract. The knowledge of Mesozoic fish faunas of the Southern Hemisphere is still inadequate; the diversity and evolution of the Late Jurassic marine ichthyofaunas of Argentina remain unclear. One fish recovered from the Tithonian levels of the Los Catutos Member of the Vaca Muerta Formation, southwestern Argentina was considered a "caturid-like" halecomorph for almost 30 years. Recently, it was proposed that it could belong to the Pachycormiformes. A thorough comparative anatomical study of the material is conducted to test whether it could be included in †Caturidae or †Pachycormidae. The specimen is assigned to †Caturidae as a new genus and species: †Catutoichthys olsacheri (http://zoobank.org/urn:lsid:zoobank.org:act:6884876C-075C-433B-90B7-74187FC04C26, registered on 1 June 2016). The new taxon is based on a unique character combination, three of which are exclusive to †Catutoichthys olsacheri among caturids–diplospondylous vertebral column with triangular basidorsals and well-developed and fan-shaped basiventrals; neural and haemal spines strongly inclined to the body axis at an angle of 14°; a large number of infrahaemals; rounded amioid-type scales with an unornamented free field. The new taxon provides anatomical information useful for further understanding the anatomy and evolution of caturid fishes.

A new non-parasemionotiform order of the Halecomorphi (Neopterygii, Actinopterygii) from the Middle Triassic of Tethys

The halecomorph fish Panxianichthys imparilis, from the Pelsonian (Anisian, Middle Triassic) of Panxian County, Guizhou Province, South China, was recently described in brief. Here we present a thorough revision of this taxon based on 22 specimens, which allows a much better understanding of its anatomy and, consequently, its phylogenetic relationships. Newly recognized anatomical features include a flat quadratojugal, a symplectic articulating with the lower jaw ventral to the quadrate articulation, five infraorbitals, up to three suborbitals, and a large tail body lobe. Panxianichthys represents the oldest known non-parasemionotiform halecomorph and has a crescent-shaped preopercle and a maxillary branch of infraorbital sensory canal, but it is excluded from the ‘Ionoscopiformes–Amiiformes’ clade mainly by the presence of a quadratojugal, a dermosphenotic hinged to the side of the skull roof with a smooth innerorbital flange bearing no sensory canal, and a symplectic articulation much more ventral than that of the quadrate. A comparison with other Triassic non-parasemionotiform halecomorphs, together with the phylogenetic analysis, supports the erection of a new halecomorph order, Panxianichthyiformes, which is the sister group to the post-Triassic ‘Ionoscopiformes–Amiiformes’ clade. In addition, Robustichthys, also from the Anisian and previously ascribed to Ionoscopiformes, is recognized here as a new stem-group Ginglymodi.http://zoobank.org/urn:lsid:zoobank.org:pub:5594E962-985F-466D-AC52-2E9A5AC07787

An Early Cretaceous (late Albian) halecomorph (? Ionoscopiformes) fish from the Toolebuc Formation of the Eromanga Basin, Queensland

The partial neurocranium of a relatively small, halecomorph fish is described as Canaryichthys rozefeldsi gen. et sp. nov. and represents the first possible ionoscopiform from the Cretaceous of Australia. The specimen was collected from the marine Toolebuc Formation of the Eromanga Basin, near Boulia, in the central west of Queensland, deposited during the Early Cretaceous (late Albian) when an epeiric sea covered much of the centre of the State. It is undistorted and preserved in 3-dimensions but lacks all but the cranial vault. Canaryichthys has many features in common with the enigmatic English Jurassic ‘caturid’ neurocranium redescribed and figured by Patterson (1975) as ‘Aspidorhynchus’ sp., (originally described by Rayner, 1948) and also appears to have affinity with the Early Cretaceous (Aptian), Oshunia, from South America.

Prey content in a Saurichthys reveals the presence of advanced halecomorph fishes in the Middle Triassic of Monte San Giorgio

Prey content in a Saurichthys reveals the presence of advanced halecomorph fishes in the Middle Triassic of Monte San Giorgio

Late Jurassic jaw bones of Halecomorph fish (Actinopterygii: Halecomorphi) studied with X-ray microcomputed tomography

Late Jurassic jaw bones of Halecomorph fish (Actinopterygii: Halecomorphi) studied with X-ray microcomputed tomography

The oldest ionoscopiform from China sheds new light on the early evolution of halecomorph fishes

The Halecomorphi are a major subdivision of the ray-finned fishes. Although living halecomorphs are represented solely by the freshwater bowfin, Amia calva, this clade has a rich fossil history, and the resolution of interrelationships among extinct members is central to the problem of understanding the origin of the Teleostei, the largest clade of extant vertebrates. The Ionoscopiformes are extinct marine halecomorphs that were inferred to have originated in the Late Jurassic of Europe, and subsequently dispersed to the Early Cretaceous of the New World. Here, we report the discovery of a new ionoscopiform, Robustichthys luopingensis gen. et sp. nov., based on eight well-preserved specimens from the Anisian (242-247 Ma), Middle Triassic marine deposits of Luoping, eastern Yunnan Province, China. The new species documents the oldest known ionoscopiform, extending the stratigraphic range of this group by approximately 90 Ma, and the geographical distribution of this group into the Middle Triassic of South China, a part of eastern Palaeotethys Ocean. These new data provide a minimum estimate for the split of Ionoscopiformes from its sister clade Amiiformes and shed new light on the origin of ionoscopiform fishes.

A large halecomorph fish (Actinopterygii: Holostei) from the Valanginian (Early Cretaceous) of southeast France

A new species of the halecomorph fish †Tomognathus, †T. gigeri, is described on the basis of an isolated piece of a snout found in the Valanginian in the vicinity of Toulon, southeast France. Although very fragmentary, the specimen shows several of the very specialized characters of †Tomognathus, such as fused premaxillae with a posterior ventral process that sutures with an unpaired vomer, a blunt stout, a compound ethmoid ossification with no distinct lateral ethmoid and pre-ethmoid, as well as large, hollow teeth with a thin wall. Several characters, however, clearly indicate that the specimen represents a new species, which is 40 million years older than the type species (Valanginian and Cenomanian respectively). †Tomognathus had a debated systematic status for more than a century, and its placement within the halecomorphs is recent. Characters of the new species confirm this assignment, in particular the carinate shape of the acrodine tips of its teeth, which differs from those of the type species, but is similar to the teeth of the halecomorph superfamily Caturoidea.

Paleopathology of a fossil fish from the Solnhofen Lagerstätte (Upper Jurassic, southern Germany)

The collection of fossil fishes from Solnhofen (Upper Jurassic, southern Germany), deposited at the Bavarian State Collection for Paleontology and Geology was examined for the detection of integument or skeletalpathologies. Among 50 studied specimens, only one halecomorph fish exhibited lesions: these are diagnosed as skin tumors. In extant taxa the causes of this disease are varied (toxins, infectious agents, physical or immunological causes, nutritional and metabolic perturbations). The morphology of these skin lesions is identical to those previously observed in fossil fishes from Monte Bolca (Eocene, northern Italy). This case study represents one of the oldest paleopathology in fossil fishes.

A new species of Placidichthys (Halecomorphi: Ionoscopiformes) from the Lower Cretaceous Marizal Formation, northeastern Brazil, with a review of the biogeographical distribution of the Ophiopsidae

Abstract A new halecomorph fish is described from the Early Cretaceous Marizal Formation of Tucano Basin. This new material is identified as a new species of Placidichthys, P. tucanensis sp. nov. based on the absence of an anal fin, the lower number of flank scales in the caudal region, the slender shape of the body, and body proportions. Placidichthys tucanensis sp. nov. increases the distribution and diversity of ophiopsids in the western part of the Tethys Sea, being distributed along the epicontinental seas of Gondwana. Placidichthys is considered the sister-taxon of the exclusively Cretaceous taxa Teoichthys + Macrepistius from the western Tethys. These groups show a discernible geographical distribution pattern with Placidichthys known only from the Southern margin of the Tethys region (South America), whilst Teoichthys and Macrepistius are known only from North America and possibly Europe.

A new halecomorph fish from the Middle Triassic of Switzerland and its Systematic implications

ABSTRACT The described actinopterygian—from the Middle Triassic of Canton Graubünden, Switzerland—is a small fish with bones and scales covered with a thick layer of ganoine and with a cranium characterized by large nasal bones sutured medially, an orbital region with an uncommon, large postero-dorsal infraorbital 4+5, possibly one small accessory suborbital bone, and an enlarged preopercle with an expanded antero-ventral region that almost contacts the lateral margin of the skull roof throughout the dorsal limb. The new fish shares with halecomorphs the presence of a supra-maxillary bone, and a new halecomorph synapomorphy—the presence of a well-developed dorsal supramaxillary process of the maxilla bearing a posterior notch or articulatory surface for contact with the supramaxilla. The interopercle is small and far away from the posterior part of the lower jaw unlike the condition in halecomorphs and teleosts. †Prosantichthys buergini new genus and new species is proposed as a Halecomorphi incertae sedis, probably close to parasemionotids, but not yet assignable to any of the known halecomorph subgroups.

A new halecomorph with two dorsal fins, Placidichthys bidorsalis n. g., n. sp. (Actinopterygii: Halecomorphi) from the Lower Cretaceous of the Araripe Basin, northeast Brazil

A halecomorph fish is described for the first time from the Lower Cretaceous of the Araripe Basin, northeast Brazil. This new material is identified as a new genus and a new species, Placidichthys bidorsalis. This taxon shares a number of synapomorphies with the Ionoscopiformes, but its position within this clade is still uncertain.

A Comprehensive Phylogenetic Study of Amiid Fishes (Amiidae) Based on Comparative Skeletal Anatomy. an Empirical Search for Interconnected Patterns of Natural History

ABSTRACT The comparative osteology, phylogenetic relationships, and historical biogeography of all known taxa of fossil and living amiid fishes (Halecomorphi: Amiidae) are investigated in detail. Previously, the detailed osteology of nearly all fossil amiids was unknown. We present the first well-supported comprehensive phylogeny for fossil and living amiid fishes. We synthesize clearly documented phylogenetic data on amiids and other halecomorph fishes with other historical phenomena such as ontogeny, historical biogeography, stratigraphic paleontology, and paleoecology (both “stationary” and “historical”). We also use our study of halecomorph fishes as a platform to explore several fundamental methodological and theoretical concepts important to phylogenetic/evolutionary investigations. These concepts pertain mainly to (1) the use of comparative empirical data to interpret various historical patterns and (2) the practice of integrating fossil and living species together in original (i.e., non-literature...

The halecomorph fishes Caturus and Amblysemius in the lithographic limestone of Solnhofen (Tithonian), Bavaria

The halecomorph genus Caturus is represented in Solnhofen by the species C. furcatus and the robust form C. giganteus.The anatomy of the skull of C. pachyurus is different form C. furcatus and C. giganteus, but similar to C. bellicianus a species known from Cerin and Solnhofen, originally described as Amblysemius bellicianus. The genus Amblysemius is revived, represented in Solnhofen by the species A. pachyurus and A. bellicianus.

The Effects of Altered Aquatic and Aerial Respiratory Gas Concentrations on Air-Breathing Patterns in a Primitive Fish (Amia Calva)

ABSTRACT The mechanisms and physiological control of air-breathing were investigated in an extant halecomorph fish, the bowfin (Amia calva). Air flow during aerial ventilation was recorded by pneumotachography in undisturbed Amia calva at 20–24°C while aquatic and aerial gas concentrations were independently varied. Separation of aquatic and aerial gases was used in an attempt to determine whether Amia calva monitor and respond to changes in the external medium per se or to changes in dissolved gases within the body. Air flow measurements revealed two different types of ventilatory patterns: type I air-breaths were characterized by exhalation followed by inhalation; type II air-breaths, which have not been described previously in Amia calva, consisted of single inhalations with no expiratory phase. Expired volume (Vexp) for type I breaths ranged from 11.6±1.1 to 26.7±2.9mlkg−1 (95% confidence interval; N=6) under normoxic conditions and was unaffected by changes in aquatic or aerial gases. Gas bladder volume (VB), determined in vitro, was 80mlkg−1; the percentage of gas exchanged for type I breaths ranged from 14 to 33% of VB in normoxia. Fish exposed to aquatic and aerial normoxia , or aerial hypercapnia in normoxic water, used both breath types with equal frequency. Aquatic or aerial hypoxia significantly increased air-breathing frequency in four of eight fish and the ventilatory pattern changed to predominantly type I air-breaths (75–92% of total breaths). When fish were exposed to 100% O2 in the aerial phase while aquatic normoxia or hypoxia was maintained, air-breathing frequency either increased or did not change. Compared with normoxic controls, however, type II breaths were used almost exclusively (more than 98% of total breaths). Type I breaths appear to be under feedback control from O2-sensitive chemoreceptors since they were stimulated by aquatic or aerial hypoxia and were nearly abolished by aerial hyperoxia. These results also indicate that Amia calva respond to changes in intravascular ; however, externally facing chemoreceptors that stimulate air-breathing in aquatic hypoxia cannot be discounted. Type II air-breaths, which occurred in aerial hyperoxia, despite aquatic hypoxia, appear to be stimulated by reductions of VB, suggesting that type II breaths are controlled by volume-sensitive gas bladder stretch receptors. Type II breaths are likely to have a buoyancy-regulating function.