Dermal Scales Research Articles

Thrust generation by shark denticles

Direct numerical simulation is performed for flow separation over a bump in a turbulent channel. Comparisons are made between a smooth bump and one where the lee side is covered with replicas of shark denticles – dermal scales that consist of a slender base (the neck) and a wide top (the crown). As flow over the bump is under an adverse pressure gradient (APG), a reverse pore flow is formed in the porous cavity region underneath the crowns of the denticle array. Remarkable thrust is generated by the reverse pore flow as denticle necks accelerate the fluid passing between them in the upstream direction. Several geometrical features of shark denticles, including some that had not previously been considered hydrodynamically functional, are identified to form the two-layer denticle structure that enables and sustains the reverse pore flow and thrust generation. The reverse pore flow is activated by the APG before massive flow detachment. The results indicate a proactive, on-demand drag reduction mechanism that leverages and transforms the APG into a favourable outcome.

Non-dental odontodes in the masticatory apparatus of †pycnodonts (Osteichthyes, Actinopterygii)

ABSTRACT Two specimens of the pycnodont Haquelpycnodus picteti from the Cenomanian (Late Cretaceous) of Lebanon possess small non-dental odontodes flanking the teeth inside the oral cavity. These odontodes are distributed labially with respect to the vomerine and prearticular dentition, corresponding to the internal face of the cheek and in front of the maxilla. They have no relation to any of the bones in the mouth region and were situated in the endo-oral mucosa. This dentition pattern resembles that of the earliest osteichthyans and stem-gnathostomes. SEM-investigation of the non-dental odontodes demonstrates a thick layer of orthodentine covered by two thin outer layers of acrodin. The microchemical composition of these odontodes corresponds to those of the dermal scales (derived from odontodes) that are distributed in the integument of the same examined specimen. Both morphology, ultrastructure, and topographic relationships demonstrate that these structures are dermal and not dental odontodes. The reappearance of dermal odontodes in the dentition of individual specimens of Haquelpycnodus thus reflects the latent capacity of the endo-oral mucosa to form non-dental odontodes. These odontodes probably exerted lateral pressure to the content within the oral cavity, which took place synchronously with the prehensile movements of the incisors.

A new species of the fossil pufferfish genus †Archaeotetraodon (Tetraodontidae) from the Middle Miocene of the North Caucasus, Russia.

The fossil puffer fish genus †Archaeotetraodon Tyler & Bannikov, 1994 is unique among the Tetraodontidae in having the upright central spinule of the dermal scale plates bifid rather than singular and undivided. Six species of this genus have previously been described variously from the Oligocene and Miocene of Russia, Italy, Algeria, and Ukraine. Described herein is a seventh species of this genus, †Archaeotetraodon bemisae sp. nov., based upon two specimens from the Pshekha River, Krasnodar Region, North Caucasus, Russia. These Maikopian specimens are no less than 15 mya, in the basal-most Middle Miocene. The new species is distinguished from the other six species in the genus by the following combination of characters: thick, sturdy, and smooth bifid spinules; frontal width broad over the orbit; 18 vertebrae; slender ventral postcleithrum; a moderately long rayless pterygiophore; height/length ratio of the posteriormost abdominal centrum being 0.78-0.79; 10 dorsal-fin rays; 9 anal-fin rays; and 14 pectoral-fin rays.

New Insights into Geometric Morphometry Applied to Fish Scales for Species Identification.

The possibility of quick and cheap recognition of a fish species from a single dermal scale would be interesting in a wide range of contexts. The methods of geometric morphometry appear to be quite promising, although wide studies comparing different approaches are lacking. We aimed to apply two methods of geometric morphometry, landmark-based and outline-based, on a dataset of scales from five different teleost species: Danio rerio, Dicentrarchus labrax, Mullus surmuletus, Sardina pilchardus, and Sparus aurata. For the landmark-based method the R library "geomorph" was used. Some issues about landmark selection and positioning were addressed and, for the first time on fish scales, an approach with both landmarks and semilandmarks was set up. For the outline-based method the R library "Momocs" was used. Despite the relatively low number of scales analyzed (from 11 to 81 for each species), both methods achieved quite good clustering of all the species. In particular, the landmark-based method used here gave generally higher R2 values in testing species clustering than the outline-based method, but it failed to distinguish between a few couples of species; on the other hand, the outline-based method seemed to catch the differences among all the couples except one. Larger datasets have the potential to achieve better results with outline-based geometric morphometry. This latter method, being free from the problem of recognizing and positioning landmarks, is also the most suitable for being automatized in future applications.

A new method for extracting conodonts and radiolarians from chert with NaOH solution

AbstractMicrofossils are important components of sedimentary rocks used for palaeontological, biostratigraphic, palaeoenvironmental and palaeoclimatic investigations. They are usually extracted from rocks using an acid solution, which might vary depending on the embedding rock lithology. Here we propose a new method using common NaOH (sodium hydroxide; soda) to digest cherts (micro‐ and cryptocrystalline quartz) instead of the standard technique based on HF (hydrofluoric acid). This new method allows the collection of undamaged specimens of different kinds of microfossils, such as conodonts, radiolarians, teeth and dermal scales, the minerology of which is still preserved (e.g. biogenic apatite in conodonts). The use of soda is thus recommended, as it is less dangerous, less expensive, and it better preserves the extracted microfossils both in shape and mineralogy.

Evo Devo of the Vertebrates Integument

All living jawed vertebrates possess teeth or did so ancestrally. Integumental surface also includes the cornea. Conversely, no other anatomical feature differentiates the clades so readily as skin appendages do, multicellular glands in amphibians, hair follicle/gland complexes in mammals, feathers in birds, and the different types of scales. Tooth-like scales are characteristic of chondrichthyans, while mineralized dermal scales are characteristic of bony fishes. Corneous epidermal scales might have appeared twice, in squamates, and on feet in avian lineages, but posteriorly to feathers. In contrast to the other skin appendages, the origin of multicellular glands of amphibians has never been addressed. In the seventies, pioneering dermal–epidermal recombination between chick, mouse and lizard embryos showed that: (1) the clade type of the appendage is determined by the epidermis; (2) their morphogenesis requires two groups of dermal messages, first for primordia formation, second for appendage final architecture; (3) the early messages were conserved during amniotes evolution. Molecular biology studies that have identified the involved pathways, extending those data to teeth and dermal scales, suggest that the different vertebrate skin appendages evolved in parallel from a shared placode/dermal cells unit, present in a common toothed ancestor, c.a. 420 mya.

On the identities of Caecilia degenerata Dunn, 1942 and of C. corpulenta Taylor, 1968 (Amphibia: Gymnophiona: Caeciliidae) with descriptions of three new species of Caecilia Linnaeus, 1758 from the Cordillera Oriental of Colombia

The Central portion of the Cordillera Oriental of Colombia is currently reported to harbor two species of Caecilia distributed at comparable elevations on opposite versants of these Mountains. These are C. corpulenta, known from Virolín, Santander, at 1700-2000 m on the western slopes of the Cordillera Oriental and C. degenerata, known from Garagoa, Boyacá, and Choachí and Fomequé, Cundinamarca, at 1800-2100 m on the eastern slopes of the Cordillera Oriental. Both species have dermal scales and lack secondary grooves, and have been subjected to misidentifications by herpetologists studying the Gymnophiona of the Eastern Andes of Colombia. Our results indicate that only the latter species is found in Colombia and the former is restricted to Peru, leaving those populations previously referred to C. corpulenta and those distinct from C. degenerata pending names. We here present an account for C. degenerata based on material from Choachí and Fómeque, Cundinamarca, as well as descriptions of three new species from the Cordillera Oriental and adjacent Venezuela: C. atelolepis sp. nov., C. epicrionopsoides sp. nov., and C. macrodonta sp. nov. We also provide additional morphological information for the recently described C. pulchraserrana.

A NEW SPECIES OF THE GENUS Caecilia LINNAEUS, 1758 (AMPHIBIA: GYMNOPHIONA: CAECILIIDAE) FROM CAQUETÁ, COLOMBIA

We here describe a new species of the genus Caecilia from Caquetá, Colombia, whose most salient characters are its large size, its very high counts of primary and secondary grooves, the presence of dermal scales throughout its body length, the size and arrangement of its mandibular teeth, and its lack of an unsegmented terminal shield. Groove counts are close to those of C. disossea, known from the Ecuadorian and Peruvian Amazon but these differ on the previously mentioned characters (among others).

Deep-scaled fish (Osteichthyes: Actinopterygii) from the lower Permian (Cisuralian) lacustrine deposits of the Parnaíba Basin, NE Brazil

The richly fossiliferous deposits of the Brazilian Pedra de Fogo Formation originated in an extensive aquatic system in tropical Pangaea, and grade from marginal lacustrine into marine deposits at the depocenter in the western part of the Parnaíba Basin. In addition to the well-known tetrapod and macrofloral records from these deposits, the Pedra de Fogo Formation yields extensive fish fossils indicating a diverse and abundant ichthyofauna. Among the actinopterygians, deep-bodied morphotypes are represented by whole fish as well as disarticulated dermal scales found at various localities in the states of Maranhão and Piauí. The gross morphology, ornamentation, and histology of some of these scales is highly distinctive, indicating the presence of a novel taxon (Piratata rogersmithii gen. et sp. nov.). The external surface of a Piratata scale is covered in multiple round-to-slightly elongated tubercles. The scale lacks a ganoin cover and is made up of cellular bone and odontocomplexes of orthodentine composing the tuberculated scale surface. The scale morphology and ornamentation most closely resemble that of Cleithrolepis granulatus from the Triassic of Australia and Cleithrolepis extoni from the Triassic Stormberg Beds of South Africa, but the new taxon differs from previously described species in several diagnostic morphological features. The use of scale characters in the taxonomy of ray-finned fishes and the palaeogeographic, palaeoenvironmental, and geochronological implications of the new taxon are discussed.

Squamation and scale morphology at the root of jawed vertebrates.

Placoderms, as the earliest branching jawed vertebrates, are crucial to understanding how the characters of crown gnathostomes comprising Chondrichthyes and Osteichthyes evolved from their stem relatives. Despite the growing knowledge of the anatomy and diversity of placoderms over the past decade, the dermal scales of placoderms are predominantly known from isolated material, either morphologically or histologically, resulting in their squamation being poorly understood. Here we provide a comprehensive description of the squamation and scale morphology of a primitive taxon of Antiarcha (a clade at the root of jawed vertebrates), Parayunnanolepis xitunensis, based on the virtual restoration of an articulated specimen by using X-ray computed tomography. Thirteen morphotypes of scales are classified to exhibit how the morphology changes with their position on the body in primitive antiarchs, based on which nine areas of the post-thoracic body are distinguished to show their scale variations in the dorsal, flank, ventral, and caudal lobe regions. In this study, the histological structure of yunnanolepidoid scales is described for the first time based on disarticulated scales from the type locality and horizon of P. xitunensis. The results demonstrate that yunnanolepidoid scales are remarkably different from their dermal plates as well as euantiarch scales in lack of a well-developed middle layer. Together, our study reveals that the high regionalization of squamation and the bipartite histological structure of scales might be plesiomorphic for antiarchs, and jawed vertebrates in general.

Complex enameloid microstructure of †Ischyrhiza mira rostral denticles.

Serving in a foraging or self-defense capacity, pristiophorids, pristids, and the extinct sclerorhynchoids independently evolved an elongated rostrum lined with modified dermal denticles called rostral denticles. Isolated rostral denticles of the sclerorhynchoid Ischyrhiza mira are commonly recovered from Late Cretaceous North American marine deposits. Although the external morphology has been thoroughly presented in the literature, very little is known about the histological composition and organization of these curious structures. Using acid-etching techniques and scanning electron microscopy, we show that the microstructure of I. mira rostral denticles are considerably more complex than that of previously described dermal denticles situated elsewhere on the body. The apical cap consists of outer single crystallite enameloid (SCE) and inner bundled crystallite enameloid (BCE) overlying a region of orthodentine. The BCE has distinct parallel bundled enameloid (PBE), tangled bundled enameloid (TBE), and radial bundled enameloid (RBE) components. Additionally, the cutting edge of the rostral denticle is produced by a superficial layer of SCE and a deeper ridges/cutting edge layer (RCEL) of the BCE. The highly organized enameloid observed in the rostral denticles of this batomorph resembles that of the multifaceted tissue architecture observed in the oral teeth of selachimorphs and demonstrates that dermal scales have the capacity to evolve histologically similar complex tooth-like structures both inside and outside the oropharyngeal cavity.

Regenerating zebrafish scales express a subset of evolutionary conserved genes involved in human skeletal disease

BackgroundScales are mineralised exoskeletal structures that are part of the dermal skeleton. Scales have been mostly lost during evolution of terrestrial vertebrates whilst bony fish have retained a mineralised dermal skeleton in the form of fin rays and scales. Each scale is a mineralised collagen plate that is decorated with both matrix-building and resorbing cells. When removed, an ontogenetic scale is quickly replaced following differentiation of the scale pocket-lining cells that regenerate a scale. Processes promoting de novo matrix formation and mineralisation initiated during scale regeneration are poorly understood. Therefore, we performed transcriptomic analysis to determine gene networks and their pathways involved in dermal scale regeneration.ResultsWe defined the transcriptomic profiles of ontogenetic and regenerating scales of zebrafish and identified 604 differentially expressed genes (DEGs). These were enriched for extracellular matrix, ossification, and cell adhesion pathways, but not in enamel or dentin formation processes indicating that scales are reminiscent to bone. Hypergeometric tests involving monogenetic skeletal disorders showed that DEGs were strongly enriched for human orthologues that are mutated in low bone mass and abnormal bone mineralisation diseases (P< 2× 10−3). The DEGs were also enriched for human orthologues associated with polygenetic skeletal traits, including height (P< 6× 10−4), and estimated bone mineral density (eBMD, P< 2× 10−5). Zebrafish mutants of two human orthologues that were robustly associated with height (COL11A2, P=6× 10−24) or eBMD (SPP1, P=6× 10−20) showed both exo- and endo- skeletal abnormalities as predicted by our genetic association analyses; col11a2Y228X/Y228X mutants showed exoskeletal and endoskeletal features consistent with abnormal growth, whereas spp1P160X/P160X mutants predominantly showed mineralisation defects.ConclusionWe show that scales have a strong osteogenic expression profile comparable to other elements of the dermal skeleton, enriched in genes that favour collagen matrix growth. Despite the many differences between scale and endoskeletal developmental processes, we also show that zebrafish scales express an evolutionarily conserved sub-population of genes that are relevant to human skeletal disease.

Joermungandr bolti, an exceptionally preserved 'microsaur' from the Mazon Creek Lagerstätte reveals patterns of integumentary evolution in Recumbirostra.

The Carboniferous Pennsylvanian-aged (309–307 Ma) Mazon Creek Lagerstätte produces some of the earliest fossils of major Palaeozoic tetrapod lineages. Recently, several new tetrapod specimens collected from Mazon Creek have come to light, including the earliest fossorially adapted recumbirostrans. Here, we describe a new long-bodied recumbirostran, Joermungandr bolti gen. et sp. nov., known from a single part and counterpart concretion bearing a virtually complete skeleton. Uniquely, Joermungandr preserves a full suite of dorsal, flank and ventral dermal scales, together with a series of thinned and reduced gastralia. Investigation of these scales using scanning electron microscopy reveals ultrastructural ridge and pit morphologies, revealing complexities comparable to the scale ultrastructure of extant snakes and fossorial reptiles, which have scales modified for body-based propulsion and shedding substrate. Our new taxon also represents an important early record of an elongate recumbirostran bauplan, wherein several features linked to fossoriality, including a characteristic recumbent snout, are present. We used parsimony phylogenetic methods to conduct phylogenetic analysis using the most recent recumbirostran-focused matrix. The analysis recovers Joermungandr within Recumbirostra with likely affinities to the sister clades Molgophidae and Brachystelechidae. Finally, we review integumentary patterns in Recumbirostra, noting reductions and losses of gastralia and osteoderms associated with body elongation and, thus, probably also associated with increased fossoriality.

Dermal denticle shedding rates vary between two captive shark species

Shark dermal scale (denticle) accumulation in the fossil record can provide information about the abundance and composition of past shark communities. Denticles are shed continuously, such that a single shark leaves a scattered composite of many isolated denticles in sediments. However, the rate of denticle shedding as well as how these rates vary among shark species with different life modes and their consistency over time are unknown, limiting the interpretation of denticle assemblages. To better understand the process of denticle shedding and calibrate the relationship between absolute shark abundance in the environment and denticle deposition in sediments, we captured denticles shed by 2 shark species in a large aquarium over 9 mo. We then simulated how these aquarium-derived shedding rates shape the relationship between shark abundance and denticle accumulation. Bonnethead sharks Sphyrna tiburo, a more active, benthopelagic species with small, thin denticles, shed 3.6 times faster on average than zebra sharks Stegostoma fasciatum, a more sedentary, demersal species with large, robust denticles. This pattern persisted when shedding rates were corrected by estimated denticle quantities, shark space use, and methodological factors (2.2- to 3.8-fold difference). Over the study, bonnethead shark shedding rates declined while zebra shark shedding rates increased slightly. Finally, denticle assemblage composition corresponded with the relative abundance of denticles on the body of each species, consistent with natural shedding rather than selective loss. Overall, we show that shark taxa contribute unevenly to the denticle record, indicating that shedding rate measurements can help inform and constrain ecological interpretations of denticle assemblages.

An insight into the skin glands, dermal scales and secretions of the caecilian amphibian Ichthyophis beddomei.

The caecilian amphibians are richly endowed with cutaneous glands, which produce secretory materials that facilitate survival in the hostile subterranean environment. Although India has a fairly abundant distribution of caecilians, there are only very few studies on their skin and secretion. In this background, the skin of Ichthyophis beddomei from the Western Ghats of Kerala, India, was subjected to light and electron microscopic analyses. There are two types of dermal glands, mucous and granular. The mucous gland has a lumen, which is packed with a mucous. The mucous-producing cells are located around the lumen. In the granular gland, a lumen is absent; the bloated secretory cells, filling the gland, are densely packed with granules of different sizes which are elegantly revealed in TEM. There is a lining of myo-epithelial cells in the peripheral regions of the glands. Small flat disk-like dermal scales, dense with squamulae, are embedded in pockets in the dermis, distributed among the cutaneous glands. 1-4 scales of various sizes are present in each scale pocket. Scanning electron microscopic observation of the skin surface revealed numerous glandular openings. The skin gland secretions, exuded through the pores, contain fatty acids, alcohols, steroid, hydrocarbons, terpene, aldehyde and a few unknown compounds.

A Lower Cretaceous chondrichthyan dermal denticle assemblage and its bearing on placoid scale diversity and histology

Dermal denticles of Mesozoic chondrichthyans are rarely documented, which tremendously limits the knowledge of different morphotypes during this time and for the whole clade. Here we describe an extraordinarily diverse assemblage of dermal denticles from deposits of Austria, comprising 17 different morphotypes. Based on the functional types of the denticles and their morphological similarities with both extinct and extant representatives, we attempt an order-level taxonomic attribution of the morphotypes recovered. The herein recorded occurrences of Hexanchiformes, Squaliformes, Squatiniformes, Heterodontiformes, the family Protospinacidae (Squalomorphii incertae sedis), and probably Rajiformes or Chimaeriformes increase previous tooth-based taxic diversity estimates of Valanginian cartilaginous fishes from Austria from four to at least nine orders. Additionally, we discuss the absence of denticles of cladodontomorph chondrichthyans, whose teeth were previously reported from the same deposits. Etched sections and light microscope analysis were carried out using the most abundant morphotypes with the aim of exploring the histology of chondrichthyan dermal denticles. Our results confirm previous studies in reporting a single crystallite enameloid, but we also report for the first time the presence of bundled enameloid in dermal scales, a condition so far restricted to the tooth enameloid of some chondrichthyans. Additionally, a putative new dentine type is observed, leading to the introduction of the descriptive term ‘nepedentine’ for the internal, dense, and poorly supplied dentine core by vascular channels.

Evolutionary developmental genetics of teeth and odontodes in jawed vertebrates: a perspective from the study of elasmobranchs.

Most extant vertebrates display a high variety of tooth and tooth-like organs (odontodes) that vary in shape, position over the body and nature of composing tissues. The development of these structures is known to involve similar genetic cascades and teeth and odontodes are believed to share a common evolutionary history. Gene expression patterns have previously been compared between mammalian and teleost tooth development but we highlight how the comparative framework was not always properly defined to deal with different tooth types or tooth developmental stages. Larger-scale comparative analyses also included cartilaginous fishes: sharks display oral teeth and dermal scales for which the gene expression during development started to be investigated in the small-spotted catshark Scyliorhinus canicula during the past decade. We report several descriptive approaches to analyse the embryonic tooth and caudal scale gene expressions in S. canicula. We compare these expressions wih the ones reported in mouse molars and teleost oral and pharyngeal teeth and highlight contributions and biases that arise from these interspecific comparisons. We finally discuss the evolutionary processes that can explain the observed intra and interspecific similarities and divergences in the genetic cascades involved in tooth and odontode development in jawed vertebrates.

Light and transmission electron microscopic structure of skin glands and dermal scales of a caecilian amphibian Gegeneophis ramaswamii, with a note on antimicrobial property of skin gland secretion.

Amphibian skin secretions contain a variety of bioactive compounds that are involved in diverse roles such as communication, homeostasis, defence against predators, pathogens, and so on. Especially, the caecilian amphibians possess numerous cutaneous glands that produce the secretory material, which facilitate survival in their harsh subterranean environment. Inspite of the fact that India has a fairly abundant distribution of caecilian amphibians, there has hardly been any study on their skin and its secretion. Herein, we describe, using light microscopy and electron microscopy, two types of dermal glands, mucous and granular, in Gegeneophis ramaswamii. The mucous glands are filled with mucous materials. The mucous-producing cells are located near the periphery. The granular glands are surrounded by myoepithelial cells. A large number of granules of different sizes are present in the lumen of the granular gland. The granule-producing cells are present near the myoepithelial lining of the gland. There are small flat disk-like dermal scales in pockets in the transverse ridges of the posterior region of the body. Each pocket contains 1-4 scales of various sizes. Scanning electron microscopic (SEM) study of the skin surface showed numerous funnel-shaped glandular openings. The antibacterial activity of the skin secretions was revealed in the test against Escherichia coli, Klebsiella pneumoniae, and Aeromonas hydrophila, all gram-negative bacteria. SEM analyses confirm the membrane damage in bacterial cells on exposure to skin secretions of G. ramaswamii.

About the Cover

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCoverThe images on the cover depict two morphotypes of the scaly-foot gastropod Chrysomallon squamiferum from deep-sea hydrothermal vents in the Indian Ocean, over 2300 meters in depth. This is the only gastropod mollusc known to exhibit dermal scales. The color is linked to vent fluid chemistry: a higher iron sulfide content leads to a darker coloration.The extraordinary feature of the scaly-foot, however, is hidden underneath its scale armor, in its anatomy. This snail has a specialized internal organ to house chemoautotrophic symbionts, as well as an unusually hypertrophied circulatory system to supply nutrients to these endosymbionts. This strategy is distinct from other vent holobiont molluscs, which host bacteria in the gill epidermis that comes in direct contact with vent fluid and which have less extensive circulatory systems, exemplified by the provannid Alviniconcha marisindica that co-occurs with the scaly-foot.On pages 102–112 of this issue, J. D. Sigwart and C. Chen report on the physiology of Indian Ocean vent animals, using closed-chamber respirometry to investigate whether the scaly-foot’s strategy of having an internal symbiont-housing organ increases its routine metabolism. By comparing the oxygen consumption of both Chrysomallon and Alviniconcha at different temperatures, they show that housing symbionts in an internal organ does not fundamentally increase the oxygen requirement. The scaly-foot, however, was able to maintain a steady metabolic demand across experiment temperatures, while Alviniconcha showed stress responses at low temperature. Vent habitats have steep temperature gradients between the superheated vent fluid and the cold surrounding seawater, and such physiological constraints likely play important roles in defining niches in these environments.Credits: Top photo (white), Suguru Nemoto, Enoshima Aquarium; bottom photo (dark), David Shale. Cover design, Jeannie Harrell, University of Chicago Press. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 235, Number 2October 2018 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/701310 © 2018 by The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.

A rare, articulated sturgeon (Chondrostei: Acipenseriformes) from the Upper Cretaceous of Dinosaur Provincial Park, Alberta, Canada

Although fragmentary remains of sturgeon, such as scutes and pectoral spines, are relatively common in fossil deposits, articulated fossilized skeletons are rare in Upper Cretaceous sediments of North America. Currently, there are four extinct species referred to Acipenseridae reported from the Upper Cretaceous of North America; two of them (†Acipenser eruciferus and †A. albertensis) are of doubtful validity because they are based on isolated elements that are probably not diagnostic. Only two species, †Priscosturion longipinnis and †Protoscaphirhynchus squamosus, have been described based on articulated skeletons. In June 2016, an articulated sturgeon specimen was discovered in the Campanian Dinosaur Park Formation of Dinosaur Provincial Park, Alberta, Canada. This specimen preserves the skull and anterior half to two-thirds of the body but is missing the pelvic, dorsal, anal, and caudal fins. This new specimen cannot be included in any of the previously named taxa, so we describe it here as a new genus and species, †Anchiacipenser acanthaspis. A combination of several characters allows us to diagnose the new sturgeon from Dinosaur Provincial Park as a new taxon, including the dermal cranial bones being strongly ornamented with straight and anastomosing ridges, the dorsal scutes being large and laterally expanded and bearing median spines, and the presence of an extensive cover of smaller dermal scales on the flanks. A phylogenetic analysis indicates that this new taxon belongs in Acipenseridae, although its precise relationships within this clade are not clear.http://zoobank.org/urn:lsid:zoobank.org:pub:854CE883-AB0A-4A21-93F2-54E308F95AB4Citation for this article: Sato, H., A. M. Murray, O. Vernygora, and P. J. Currie. 2018. A rare, articulated sturgeon (Chondrostei: Acipenseriformes) from the Upper Cretaceous of Dinosaur Provincial Park, Alberta, Canada. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1488137.