Palaeozoic fish Research Papers - Academia.edu (original) (raw)

— New fossils of " Gyracanthus " sherwoodi Newberry, 1889 are described primarily from the Late Devonian Red Hill site and Metzger's Quarry (Catskill Formation, late Famennian) of Clinton and Sullivan Counties in central Pennsylvania. The... more

— New fossils of " Gyracanthus " sherwoodi Newberry, 1889 are described primarily from the Late Devonian Red Hill site and Metzger's Quarry (Catskill Formation, late Famennian) of Clinton and Sullivan Counties in central Pennsylvania. The fossils include ornamented prepectoral ventral plates, pectoral, pelvic, and dorsal fin spines, elements of the endoskeletal shoulder girdle (procoracoid and scapulocoracoid), scales, and possible anal fin spines. We distinguish between anterior and posterior dorsal fin spines. A growth series of elements, described for the first time for a gyracanth, show that the adults of this taxon reached about a meter in length, and juveniles already had ossified endoskeletal pectoral elements at body lengths 300-400 mm. The mainly cartilaginous skeleton, paired fin spines, shoulder girdle structure, and scale growth are consistent with gyracanthids being stem chondrichthyans. " Gyracanthus " sherwoodi lived in non-marine conditions in the eastern Laurentian rivers and deltas.

A variety of isolated scales and lepidotrichia from the Early Devonian of New South Wales is referred to the palaeoniscoid Ligulalepis toombsi Schultze 1968, to date known only by isolated scales. Scales of various forms are attributed to... more

A variety of isolated scales and lepidotrichia from the Early Devonian of New South Wales is referred to the palaeoniscoid Ligulalepis toombsi Schultze 1968, to date known only by isolated scales. Scales of various forms are attributed to specific regions of the body, on the basis of comparisons with articulated Palaeozoic palaeoniscoids. Mobility of scales in the forward flank
region appears to have been constrained by a prominent process projecting from the rostrodorsal corner, in addition to the peg, socket and keel of typical palaeoniscoid scales. Such complex interlocking of the scales implies that the body of Ligulalepis toombsi was relatively inflexible. Some suggestions are offered regarding the possible mode of locomotion.

The isolated teeth of a new euselachian shark Artiodus prominens Ivanov and Duffin gen. et sp. nov. have been found in the Artinskian Stage (Early Permian) of Krasnoufimskie Klyuchiki quarry (Sverdlovsk Region, Middle Urals, Russia). The... more

The isolated teeth of a new euselachian shark Artiodus prominens Ivanov and Duffin gen. et sp. nov. have been found in the Artinskian Stage (Early Permian) of Krasnoufimskie Klyuchiki quarry (Sverdlovsk Region, Middle Urals, Russia). The teeth of Artiodus possess a multicuspid orthodont crown with from four to nine triangular cusps; prominent labial projection terminating in a large round tubercle; distinct ornamentation from straight or recurved cristae; oval or semilu-nar, elongate, considerably vascularized base; dense vascular network formed of transverse horizontal, ascending, short secondary and semicircular canals. The teeth of the new taxon otherwise most closely resemble the teeth of some prot-acrodontid and sphenacanthid euselachians possessing a protacrodont-type crown, but differ from the teeth of all other known euselachians in the unique structure of the labial projection. The studied teeth vary in crown and base morphology , and three tooth morphotypes can be distinguished in the collection reflecting a moderate degree of linear gradient monognathic heterodonty. The range of morphologies otherwise displayed by the collection of teeth shows the greatest similarity to that described for the dentitions of relatively high-crowned hybodontids from the Mesozoic. The internal structure of the teeth, including their vascularization system is reconstructed using microtomography. The highest chon-drichthyan taxonomic diversity is found in the Artinskian, especially from the localities of the Middle and South Urals.

The upper Paleozoic strata of Socorro County preserve a series of four distinct environmental phases and their corresponding fish assemblages from the Middle Pennsylvanian to the early Permian. These four phases are: a Middle... more

The upper Paleozoic strata of Socorro County preserve a series of four distinct environmental phases and their corresponding fish assemblages from the Middle Pennsylvanian to the early Permian. These four phases are: a Middle Pennsylvanian marine phase, a Late Pennsylvanian short marine regression/coastal lacustrine phase, a latest Pennsylvanian/earliest Permian short marine transgression, and an early Permian freshwater fluvial phase. Many of the late Paleozoic Socorro fish assemblages are dominated by isolated shark teeth. Rigorous field collection of macro specimens and screen washing programs could greatly expand the taxa and data of the Socorro fish assemblages. The Socorro fish assemblages preserved in these beds could help fill gaps in taxonomic and biogeographic information identified by previous work on global fish evolution and extinction rates.

The isolated teeth of a new euselachian shark Artiodus prominens Ivanov and Duffin gen. et sp. nov. have been found in the Artinskian Stage (Early Permian) of Krasnoufimskie Klyuchiki quarry (Sverdlovsk Region, Middle Urals, Russia). The... more

The isolated teeth of a new euselachian shark Artiodus prominens Ivanov and Duffin gen. et sp. nov. have been found in the Artinskian Stage (Early Permian) of Krasnoufimskie Klyuchiki quarry (Sverdlovsk Region, Middle Urals, Russia). The teeth of Artiodus possess a multicuspid orthodont crown with from four to nine triangular cusps; prominent labial projection terminating in a large round tubercle; distinct ornamentation from straight or recurved cristae; oval or semilu-nar, elongate, considerably vascularized base; dense vascular network formed of transverse horizontal, ascending, short secondary and semicircular canals. The teeth of the new taxon otherwise most closely resemble the teeth of some prot-acrodontid and sphenacanthid euselachians possessing a protacrodont-type crown, but differ from the teeth of all other known euselachians in the unique structure of the labial projection. The studied teeth vary in crown and base morphology , and three tooth morphotypes can be distingu...

The stratigraphic separation diagram (SSD) is an often neglected tool of fault analysis, which assists with the interpretation of both the fault-surface geometry and the mechanism of faulting. As the SSD needs to evaluate displacement or... more

The stratigraphic separation diagram (SSD) is an often neglected tool of fault analysis, which assists with the interpretation of both the fault-surface geometry and the mechanism of faulting. As the SSD needs to evaluate displacement or separation along the fault, this particular method can be used only in areas with well-documented stratigraphic sequences. This paper presents details of some common patterns obtained when using SSDs and also discusses some real examples of two apparently similar faults found in the Barrandian area in the Czech Republic. Although both the Prague and the Tachlovice faults in the Barrandian area seem to be of the same character (the same strike, remarkable stratigraphic separation, similar localization in the Prague Synform), the SSDs of these two faults demonstrate the difference in fault surface geometries and consequently a very distinct mechanism of origin. The Tachlovice Fault is one of the main thrusts in the Prague Synform. It has ramp-flat geometry and is associated with fault-related folds. The Prague Fault, on the other hand, was formed later, after the initial folding, and belongs to a group of steep translatory faults. It is shown how SSDs are practical, effective tools for the analysis of these types of faults and associated stratigraphies without the need of 3D seismics or boreholes. Copyright © 2010 John Wiley & Sons, Ltd.

The chondrichthyan skeletal structures with the greatest potential for fossilization are teeth, scales, fin and cephalic spines. In the Rio do Rasto Formation, the Chondrichthyes are represented by finspines and teeth attributed to... more

The chondrichthyan skeletal structures with the greatest potential for fossilization are teeth, scales, fin and cephalic spines. In the Rio do Rasto Formation, the Chondrichthyes are represented by finspines and teeth attributed to sphenacanthids, hybodontids and xenacanthids. Herein is presented new finspines collected from an outcrop of the Serrinha Member of the Rio do Rasto Formation, in the Municipality of Jacarezinho, Paraná State. The studied material consists of two finspines that are gradually tapered distally, with convex anterior and lateral faces. The posterior proximal face is strongly concave forming a furrow; absence of pronounced median ridge in the posterior distal face; the lateral faces have non-pectinated ribs separated by intercostal grooves, some of them bifurcated and beaded with rows of rounded closely spaced tubercles are the features that allow the finspines to be ascribed to a new species of Sphenacanthidae.

The vertebrate faunas in limestone samples of earliest Devonian age, which were collected from 10 localities near Trundle, central New South Wales, Australia, include scales of acanthodians Nostolepis lacrima Valiukevicius, 1994,... more

The vertebrate faunas in limestone samples of earliest Devonian age, which were collected from 10 localities near Trundle, central New South Wales, Australia, include scales of acanthodians Nostolepis lacrima Valiukevicius, 1994, Radioporacanthodes porosus (Brotzen, 1934), Gomphonchus sandelensis (Pander, 1856), Trundlelepis sp. and Gomphonchoporus hoppei (Gross, 1947), as well as scales and dermal bone fragments from romundinid, palaeacanthaspid and ?brindabellaspid placoderms, and scales of the palaeoniscoid Terenolepis turnerae Burrow, 1995. Although the vertebrate remains are not plentiful, the assemblages are significant in being dominated by taxa which are found in coeval deposits of the circum-Arctic region.

Several articulated, but incomplete, acanthodians from the Bunga Beds (late Givetian/early Frasnian) of the southern coast of New South Wales are tentatively identified as ischnacanthids. Heads are missing from all three prepared... more

Several articulated, but incomplete, acanthodians from the Bunga Beds (late Givetian/early Frasnian) of the southern coast of New South Wales are tentatively identified as ischnacanthids. Heads are missing from all three prepared specimens. They exhibit the following characters: two dorsal fin spines; long, slender scapulocoracoids; slender, relatively deeply inserted, unpaired fin
spines; minute scales with a fairly smooth, flat, crown; and an increase in size of normal body scales towards the tip of the tail. The fish are preserved in black, finely laminated shales, which
were probably deposited as deep water, lacustrine sediments. The rarity, burial conditions, and headless state of the Bunga Beds acanthodians indicate that they might have died in shallow water, sunk to the bottom, refloated by gas-induced buoyancy, with the heads lost while drifting out to deeper waters, where the bodies finally sank to a scavenger-free, anaerobic substrate.

Lepidotrichia are dermal elements located at the distal margin of osteichthyan fins. In sarcopterygians and actinopterygians, the term has been used to denote the most distal bony hemisegments and also the more proximal, scale-covered... more

Lepidotrichia are dermal elements located at the distal margin of osteichthyan fins. In sarcopterygians and actinopterygians, the term has been used to denote the most distal bony hemisegments and also the more proximal, scale-covered segments which overlie endochondral bones of the fin. In certain sarcopterygian fishes, including the Rhizodontida, these more proximal, basal segments are very long, extending at least half the length of the fin. The basal segments have a subcircular cross section, rather than the crescentic cross section of the distal lepidotrichial hemisegments, which lack a scale cover and comprise short, generally regular, elements. In rhizodonts and other sarcopterygians, e.g. Eusthenopteron, the basal elements are the first to appear during fin development, followed by the endochondral bones and then the distal lepidotrichia. This sequence ontradicts the ‘clock-face model’ of fin development proposed by Thorogood in which the formation of endochondral bones is followed by development of lepidotrichia. However, if elongate basal ‘lepidotrichia’ are not homologous with more distal, jointed lepidotrichia and if the latter form within a distal fin-fold and the former outside this fold, then Thorogood’s ‘clock-face’ model remains valid. This interpretation might indicate that the fin-fold has been lost in early digited stem-tetrapods such as Acanthostega and Ichthyostega and elongate basal elements, but not true lepidotrichia, occur in the caudal fins of these taxa.

ABSTRACT Disarticulated elements in a large, uncompressed regurgitate from Tillywhandland Quarry (Lochkovian), as well as serial sections of an articulated specimen, reveal the three-dimensional shape and structure of fin spines,... more

ABSTRACT Disarticulated elements in a large, uncompressed regurgitate from Tillywhandland Quarry (Lochkovian), as well as serial sections of an articulated specimen, reveal the three-dimensional shape and structure of fin spines, scapulocoracoid and dermal plates, and the histological structure of dermal and endoskeletal hard tissues of the climatiid acanthodian Climatius reticulatus. Globular calcified cartilage is the only form of mineralization of the head endoskeleton, with the jaws preserved as double-layered globular calcified cartilage. Tooth whorls are borne on both the upper and lower jaws and comprise a vascularized bone base and tooth cusps composed of a vascular network and mesodentine, without a central pulp cavity. The short admedian spine is the only strongly laterally compressed spine; the anterior dorsal fin spine has a wide, splayed base. No evidence was found of large dermal plates between the pectoral fin spine and the median lorical plates, with the prepectoral pinnal plates with spines being the only large paired dermal components of the shoulder girdle. The anterior lorical plate, pinnal plates, and tesserae on the scapulocoracoid bear ornament comparable to the postbranchial apronic ornament in acanthothoracid placoderms. Branchiostegal plates have a thin, dense inner bone layer and an outer dentinous ornament layer but lack a middle osteodentine layer; other postcranial plates and fin spines have a smoothsurfaced inner layer of bone and a thick middle osteodentine layer. Body scales have a crown with areal growth zones formed of Stranggewebe and syncitial mesodentine on a cellular bone base.

A diverse assemblage of fossil fishes was found in the Sly Gap Formation of Alamo and Deadman canyons in the Sacramento Mountains of Otero County, New Mexico, USA. This assemblage includes the remains of placoderms, chondrichthyans,... more

A diverse assemblage of fossil fishes was found in the Sly Gap Formation of Alamo and Deadman canyons in the Sacramento Mountains of Otero County, New Mexico, USA. This assemblage includes the remains of placoderms, chondrichthyans, acanthodians, and actinopterygians. The chondrichthyans dominate over other fishes and are represented by phoebodontiforms, symmoriiforms, ctenacanthiform, protacrodontids, hybodontiforms, an orodontid, helodontids, and a petalodontid. The assemblage mostly contains taxa with long stratigraphic ranges. According to the analysis of taxa ranges, the Sly Gap vertebrate assemblage is a mixture of different stratigraphic intervals of the Late Devonian and Early Carboniferous.

Acanthodian scales with Nostolepis-type histological structure are separated into five groups based on the presence/absence and extent of stranggewebe, odontocytic and syncitial mesodentine networks, cellular unipolar mesodentine,... more

Acanthodian scales with Nostolepis-type histological structure are separated into five groups based on the presence/absence and extent of stranggewebe, odontocytic and syncitial mesodentine networks, cellular unipolar mesodentine, bone-like mesodentine and durodentine in scale crowns. Two new families of acanthodians are erected, based primarily on histological structure of scales: the Vesperaliidae (stranggewebe extending throughout the scale crown) and the Acritolepidae (bone-like mesodentine in the scale crown). The latter family includes species erected for articulated fish. The families Tchunacanthidae and Lenacanthidae are united in the single family Tchunacanthidae, characterized by having scale crowns with mesodentine formed mainly by unipolar cells. A sixth group, which we exclude from the Nostolepis-type, has scale crowns composed of dentine without lacunae, plus durodentine, and bases with only rare osteocyte cavities. The new groups promote the revision and reassignment of many “nostolepid” taxa, in particular removing many species from the genus Nostolepis. Four new genera are erected: Pechoralepis (including part of Nostolepis), assigned to Acritolepidae nov.; and three genera assigned to an indeterminate family, which scales are composed of only odontocytic mesodentine without stranggewebe: Nostovicina (including part of Nostolepis), Nobilesquama (including part of Nostolepis), and Peregrinosquama (including part of Watsonacanthus). Histological structures are considered the primary characters of taxonomical value when based on isolated scales. Unfortunately, scale histology is unknown for most articulated acanthodians.

Abstract: Circumorbital dermal bones are found in most groups of early vertebrates that have dermal bony plates on the head. Taxonomic distribution of dermal sclerotic plates on the eye itself is less clear, partly because the eyeball is... more

Abstract: Circumorbital dermal bones are found in most groups of early vertebrates that have dermal bony plates on the head. Taxonomic distribution of dermal sclerotic plates on the eye itself is less clear, partly because the eyeball is rarely preserved and sometimes because sclerotic bones have been misinterpreted as circumorbital bones. Based on the examination of climatiid Climatius plus mesacanthid, cheiracanthid and acanthodid acanthodiform acanthodians, we conclude that most, if not all, acanthodiforms and climatiids had sclerotic rings. Presence and number of these elements should be included as a character in phylogenetic analyses of early jawed vertebrates.

The Placodermi are extinct basal gnathostomes which had extensive dermal and perichondral bone, but which lacked the endochondral bone which characterizes the more derived bony fishes. Thin sections of bone from a specimen of the antiarch... more

The Placodermi are extinct basal gnathostomes which had extensive dermal and perichondral bone, but which lacked the endochondral bone which characterizes the more derived bony fishes. Thin sections of bone from a specimen of the antiarch placoderm Bothriolepis canadensis, from the Escuminac Formation (Frasnian, Upper Devonian), Quebec, Canada, reveal that part of the cancellous layer in its dermal and endoskeletal
bone formed from perichondral bone trabeculae growing around cartilage spheres. The resultant structure mimics that of osteichthyan endochondral bone. The layout and dimensions of this polygonal mosaic patterning of the bone trabeculae and flattened cartilage spheres resemble those of the prismatic layers of calcified cartilage in chondrichthyans. If the lack of endoskeletal bone in chondrichthyans is a derived character, then
the structure identified in B. canadensis could represent a ‘template’ for the formation of prismatic calcified cartilage in the absence of bone.

Palaeozoic microvertebrate remains are documented from the Point Hibbs Formation, Point Hibbs, western Tasmania. They comprise scales, teeth and omamented dermal bone from: acanthodians "Nostolepis" guangxiensis, Nostolepis spp.,... more

Palaeozoic microvertebrate remains are documented from the Point Hibbs Formation, Point Hibbs, western Tasmania. They comprise scales, teeth and omamented dermal bone from:
acanthodians "Nostolepis" guangxiensis, Nostolepis spp., Gomphonchus? bogongensis, Trundlelepis cervicostulata and Watsonacanthus? sp., onychodontiform sarcopterygians, and four types of placoderms. The microvertebrate fauna supports a Lower Devonian (Pragian) age for the deposIt, when compared with other eastern Australian occurrences of these taxa.

From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to... more

From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to infer a wealth of palaeobiological and palaeoecological information. As in extant species, aspects of gross morphology such as streamlining, fin position and tail type are optimized even in the earliest fishes, indicating similar life strategies have been present throughout their evolutionary history. As hydrodynamical studies become more sophisticated, increasingly complex fluid movement can be modelled, including vortex formation and boundary layer control. Drag-reducing riblets ornamenting the scales of fast-moving sharks have been subjected to particularly intense research, but this has not been extended to extinct forms. Riblets are a convergent adaptation seen in many Palaeozoic fishes, and probably served a similar hydrodynamic purpose. Conversely, structures which appear to increase skin friction may act as turbulisors, reducing overall drag while serving a protective function. Here, we examine the diverse adaptions that contribute to drag reduction in modern fishes and review the few attempts to elucidate the hydrodynamics of extinct forms.

Gnathostome vertebrate remains from fine-grained sandstones of the Silverband Formation in the Grampians, Victoria include dissociated fin spines, scales and teeth. These elements are assigned herein to the acanthodians Sinacanthus?... more

Gnathostome vertebrate remains from fine-grained sandstones of the Silverband Formation in the Grampians, Victoria include dissociated fin spines, scales and teeth. These elements
are assigned herein to the acanthodians Sinacanthus? micracanthus (fin spines) and Radioporacanthodes sp. cf. R. qujingensis (scales and tooth whorls). This fauna indicates
a Late Silurian (?Iate Ludlow) age for the vertebrate-bearing stratum. Under current systematic groupings, the two gnathostome taxa from the Silverband Formation belong to two different families, the Sinacanthidae and the Poracanthodidae.
However, the preserved association could indicate that the three element types derived from the same biological species. The possibility that the Sinacanthidae is a sister group to the Climatiidae and the Poracanthodidae is raised by this scenario. The Sinacanthidae is tentatively reassigned to the Acanthodii, as it is considered to lack diagnostic chondrichthyan characters.

The articulated acanthodian Gyracanthides murrayi Woodward from the Lower Carboniferous of Mansfield, Victoria, Australia, is redescribed from original and newly aquired material. It includes the only known head region from a member of... more

The articulated acanthodian Gyracanthides murrayi Woodward from the Lower Carboniferous of Mansfield, Victoria, Australia, is redescribed from original and newly aquired material. It includes the only known head region from a member of the Gyracanthidae. A new reconstruction and interpretation of the pectoral area are proposed, incorporating the elements from the original description as well as a new bone interpreted as a procoracoid attached
to a prepectoral spine. The posterior free pectoral spine described by Woodward is reinterpreted as a scapulocoracoid. A subsequent reconstruction of the pectoral girdle which synonymised the anterior and posterior prepectoral spines is
rejected. A clear difference in size and shape of the pectoral and pelvic fin spines is established. The morphology of the tubercular ornament of the paired fin spines is used to distinguish species of Gyracanthides. Gyracanthides murrayi had a covering of dermal polyodontodia with spinose crowns and a concave base with a central vascular canal opening. The systematic position of the Gyracanthidae remains unclear, with the family retained within the Climatiiformes only on the basis of the broad-based, fin spines with nodose ornament.

A new species of Gyracanthides from the mid-Visean Ducabrook Formation of Middle Paddock site, near Springsure in the Drummond Basin, central Queensland, is based on isolated three-dimensionally preserved elements. The specimens comprise... more

A new species of Gyracanthides from the mid-Visean Ducabrook Formation of Middle Paddock site, near Springsure in the Drummond Basin, central Queensland, is based on isolated three-dimensionally preserved elements. The specimens comprise paired and unpaired spines and pectoral girdle elements, procoracoids and scapulocoracoids, and include growth series. The morphology, especially of the shoulder girdle bones and the form and tubercular ornamentation of the paired fin spines, is used to distinguish the new taxon. These characters also help differentiate the numerous described gyracanthid species. Aspects of palaeobiology including possible sexual dimorphism are explored. A hypothetical reconstruction of the fish is based on our interpretation of the articulation of isolated elements combined with examination of wear patterns on fin spines. Gyracanthides hawkinsi sp. nov. is compared with other Australian taxa as well as with gyracanthids from North America, Europe, Russia, Iran, Africa and Antarctica, some of which are tentatively reassigned here to the Gondwanan genus Gyracanthides.