Ontogeny of the Early Carboniferous acanthodian Acanthodes lopatini Rohon

Beznosov, P. A.

doi:10.1134/s0031030117070024

Cited by 6 publications

(11 citation statements)

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“…Our characterisation of the mandibular splint in Acanthodopsis and Acanthodes as a dermal bone with a distinctive shape allows reassessment of these mandibular bones in other taxa. The morphology in other acanthodids appears likely to match that in the two taxa we describe in that they have a slightly sinusoidal shape, for example in other species of Acanthodes (20,29,37), Halimacanthodes (30), and Howittacanthus (38). In Ischnacanthus (figure S3), the ventral margin of Meckel's cartilage is reinforced and laterally flattened; we suggest this is also likely to be the case in other ischnacanthids with "mandibular splints" (33).…”

Section: Discussionsupporting

confidence: 53%

Diverse stem-chondrichthyan oral structures and evidence for an independently acquired acanthodid dentition

Dearden

Giles

2020

Preprint

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The teeth of sharks famously form a series of parallel, continuously replacing files borne directly on the mandibular cartilages. In contrast, bony fishes possess site-specific shedding dentition borne on dermal plates. Understanding how these disparate systems evolved is challenging, not least because of poorly understood relationships and the profusion of morphologically and terminologically diverse bones, splints and whorls seen in the earliest chondrichthyans. Here we use tomographic methods to investigate the nature of mandibular structures in several early branching 'acanthodian'-grade stem-chondrichthyans. We characterise the gnathal plates of ischnacanthids as growing bones, and draw similarities between early chondrichthyan and stem gnathostome teeth and jaws. We further build the case for Acanthodopsis, a Carboniferous taxon, as an acanthodid, and show that, unexpectedly, its teeth are borne directly on the mandibular cartilage. Mandibular splints are formed from dermal bone and appear to be an acanthodid synapomorphy. The development of a unidirectionally growing dentition may be a feature of the chondrichthyan total-group. More generally, ischnacanthid and stem gnathostome gnathal plates share a common construction and are likely homologous, and shedding teeth evolved twice in gnathostomes.

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Section: Discussionsupporting

confidence: 53%

Diverse stem-chondrichthyan oral structures and evidence for an independently acquired acanthodid dentition

Dearden

Giles

2020

Preprint

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“…). This is also the case for Acanthodes , which been reported from a variety of lacustrine, fluvial, estuarine/deltaic, and fully marine settings (Zidek ; Beznosov ; Burrow et al . ; Sallan & Coates ).…”

Section: Discussionmentioning

confidence: 52%

“…; Sallan & Coates ). First appearing in the Middle Devonian, this was the only acanthodiform family to persist into the Carboniferous and Permian (Beznosov ; Sallan & Coates ). The best known acanthodidid genus, Acanthodes , was widely distributed, occurring in Australia, South Africa, Europe, North America, Greenland and Siberia from the Middle Devonian to the late Permian (Denison ; Sallan & Coates ).…”

Section: Systematic Palaeontologymentioning

confidence: 99%

“…The best known acanthodidid genus, Acanthodes , was widely distributed, occurring in Australia, South Africa, Europe, North America, Greenland and Siberia from the Middle Devonian to the late Permian (Denison ; Sallan & Coates ). However, the earliest known articulated specimens ( Acanthodes lopatini Rohon, ) are from the Tournaisian of south‐central Siberia (Beznosov ) and many earlier isolated scales and ichthyoliths assigned to Acanthodes sp. are considered doubtful (Burrow et al .…”

Section: Systematic Palaeontologymentioning

confidence: 99%

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Fish and tetrapod communities across a marine to brackish salinity gradient in the Pennsylvanian (early Moscovian) Minto Formation of New Brunswick, Canada, and their palaeoecological and palaeogeographical implications

et al. 2016

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42The cosmopolitan biogeography of many fish genera strongly indicates marine-based 43 dispersal, while strontium isotopic data suggest these same fish were exposed, at times, to ). An intriguing characteristic of this episode was the apparent widespread adoption of 68 a euryhaline habit amongst organisms as diverse as microconchids, ostracodes, xiphosurans 69 and fish (Anderson and Shuster 2003; Carpenter et al. 2011; Bennett et al. 2012; Gierlowski-70 Kordesch and Cassle 2015). Euryhaline animals are relatively rare in modern ecosystems 71 (Edwards and Marshall 2013; McCormick et al. 2013), and their dominance in Carboniferous 72 times suggests marine communities converged on similar osmoregulatory strategies in order 73 to utilise empty non-marine coastal ecospace for feeding and breeding (Williams et al. 2006; 74 Carpenter et al. 2014), prior to the widespread colonisation of freshwater tracts further inland. 75The mid-Carboniferous diversification event coincided with a sharp growth of 76Gondwanan ice sheets and the onset of significant Milankovitch-driven glacio-eustatic 86Much recent attention has been given to the apparent dominance of a euryhaline mode 87 of life amongst mid-Carboniferous fish communities (Schultze 2009; Carpenter et al. 2011 Carpenter et al. , 88 2014Carpenter et al. , 2015. However, consensus regarding ecology is currently lacking, with some 89 researchers arguing on palaeogeographic, sedimentological and geochemical grounds that fish 90 taxa, especially xenacanthid sharks (Masson and Rust 1984), may have been obligate 91 freshwater organisms (Śtamberg and Zajíc 2008;Fischer et al. 2011 Fischer et al. , 2013 Montañez and 92 Cecil 2013). In this paper, we describe a new fish fauna from the Carboniferous 93 (Pennsylvanian) of New Brunswick, Canada (Fig. 1A), and demonstrate -based on 94 independent indicators of palaeo-salinity -that fish taxa existed across a brackish to marine 95 gradient, and that communities must therefore have been euryhaline. We discuss how these 96 new findings improve understanding of Carboniferous fish ecology and the mid- 97Carboniferous diversification of non-marine ecosystems in particular. The fish fossils reported here were obtained from opencast mine sites (now reclaimed) within 102 the Minto Coalfield, Queens County, New Brunswick, Canada (Fig. 1A-C 98 +REVISE FOR TETRAPOD STORY 123Extensive borehole arrays indicate that this basal unconformity is marked by a major silcrete 124 paleosol, up to 9 m thick in places (Sullivan 1981; St Peter 2000), which mantles the 125 basement complex and indicates seasonally-dry climate weathering over the preceding (Fig. 3A), implying that the basin deepened towards the 137 southwest, and sediment progressively onlapped towards the northeast; and (2) NE-SW- Coal, fine towards the southwest (Fig. 3B) and suggest sediment transport in that direction. 140We note, however, that this inferred palaeoflow direction opposes regional patterns of Geological Surveys Branch, Fredericton (Fig. 4A). 154The low...

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“…The only other cheiracanthid known from articulated fish is Homalacanthus Russell, 1951, with the type and only valid species being H. concinnus (Whiteaves, 1887) from the Frasnian of Quebec. Miles (1966) also assigned Protogonacanthus and Carycinacanthus to the Cheiracanthidae, but we consider them to be acanthodids, based on their unornamented scale crowns; also, Carycinacanthus is now considered to be a junior synonym of Acanthodes (Beznosov, 2009). Miles (1966) and Denison (1979) considered the cheiracanthids to be a grade within the Family Acanthodidae, but we maintain Berg's (1940) classification, with the Cheiracanthidae being a Family within the order Acanthodiformes based on their endoskeletal structure and scale ornament (Burrow and den Blaauwen in press).…”

Section: Introductionmentioning

confidence: 97%

A redescription of the three longest-known species of the acanthodian Cheiracanthus from the Middle Devonian of Scotland

Burrow

Blaauwen

Newman³

2020

Palaeontol Electron

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The cheiracanthid acanthodiforms were widespread during the Middle Devonian, often being the most abundant acanthodians in northern European vertebrate macroand microfaunal assemblages. Three species of cheiracanthids, Cheiracanthus murchisoni, C. grandispinus, and C. latus, have been known from the Middle Devonian (Eifelian-Givetian) of northern Scotland since the nineteeth century. Here we review the anatomy of these species and show that the main distinguishing features for the three species are the scale ornamentation, general body shape, and relative robustness of their scapulocoracoids and fin spines. They also show different stratigraphic and geographic distributions in the Orcadian Basin. All three species appear at the base of the Coccosteus cuspidatus + Pterichthyodes milleri placoderm biostratigraphic zone; C. latus disappears towards the upper limit of this zone, C. murchisoni extends into the base of the overlying Dickosteus threiplandi zone, and C. grandispinus reaches up to the middle of this zone. Some cheiracanthid taxa based on isolated scales from the Baltic countries, Belarus, and Russia are considered junior synonyms of the Scottish species. The new data we provide should prove helpful in further elucidating the taxonomic position of cheiracanthids.

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Ontogeny of the Early Carboniferous acanthodian Acanthodes lopatini Rohon

Cited by 6 publications

References 10 publications

Diverse stem-chondrichthyan oral structures and evidence for an independently acquired acanthodid dentition

Diverse stem-chondrichthyan oral structures and evidence for an independently acquired acanthodid dentition

Fish and tetrapod communities across a marine to brackish salinity gradient in the Pennsylvanian (early Moscovian) Minto Formation of New Brunswick, Canada, and their palaeoecological and palaeogeographical implications

A redescription of the three longest-known species of the acanthodian Cheiracanthus from the Middle Devonian of Scotland

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