Chondrichthyan phylogeny: a look at the evidence

Maisey, John G.

doi:10.1080/02724634.1984.10012015

Cited by 114 publications

(116 citation statements)

References 38 publications

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“…The earliest undisputed chimaeroids are early Triassic (250 Myr) in age (3), but in addition to iniopterygians a number of Palaeozoic taxa, notably the ''bradyodonts'' and echinochimaerids are also considered as stem chimaeroids because they share with the latter at least some derived characters (e.g., tubular dentine, prepelvic claspers) (3,4,28,29). By contrast, previously described iniopterygian material did not show such characters.…”

Section: Discussionmentioning

confidence: 80%

Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography

Pradel

Langer

Maisey

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Living cartilaginous fishes, or chondrichthyans, include numerous elasmobranch (sharks and rays) species but only few chimaeroid (ratfish) species. The early history of chimaeroids, or holocephalans, and the modalities of their divergence from elasmobranchs are much debated. During Carboniferous times, 358 -300 million years (Myr) ago, they underwent a remarkable evolutionary radiation, with some odd and poorly understood forms, including the enigmatic iniopterygians that were known until now from poorly informative flattened impressions. Here, we report iniopterygian skulls found preserved in 3 dimensions in Ϸ300-Myr-old concretions from Oklahoma and Kansas. The study was performed by using conventional X-ray microtomography ( Carboniferous ͉ chondrichthyans ͉ vertebrate ͉ X-ray phase imaging

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Section: Discussionmentioning

confidence: 80%

Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography

Pradel

Langer

Maisey

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…The morphological disparity exhibited by extant elasmobranchs and holocephalans has fueled much debate about the primitive versus derived nature of fundamental visceral endoskeletal characters in these taxa (2,8,12,(26)(27)(28). Until now, the relative inaccessibility of holocephalan embryos has hindered attempts to address these questions from a molecular developmental perspective.…”

Section: Discussionmentioning

confidence: 99%

“…Dick (10) reconstructed Trystichius arcuatus as possessing elongate hyoid arch rays that supported a functional operculum, as well as relatively short gill arch rays. As Trystichius consistently resolves to the elasmobranch stem (2,4,(6)(7)(8), this likely represents the independent evolution of an operculum supported by elongate hyoid arch rays-and the independent reduction of gill arch branchial rays-in an elasmobranch (Fig. 2).…”

Section: Discussionmentioning

confidence: 99%

“…These appendages extend beyond the limit of the primary gill lamellae, and support the interbranchial septa that sit between adjacent gill slits (1). Holocephalans, on the other hand, have been reported to possess branchial rays only on their hyoid arch (2) (Fig. 1 E and F), where they provide endoskeletal support for an operculum.…”

mentioning

confidence: 99%

“…1 E and F), where they provide endoskeletal support for an operculum. Whether holocephalans have derived the operculate pharyngeal endoskeleton from an elasmobranch-like condition or vice versa has remained an open question for decades, due to strong discordance among hypotheses of stem-group phylogenetic relationships (2)(3)(4)(5)(6)(7)(8) and the absence of unequivocal branchial ray homologs outside of chondrichthyans.…”

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confidence: 99%

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Holocephalan embryos provide evidence for gill arch appendage reduction and opercular evolution in cartilaginous fishes

Gillis

Rawlinson²,

Bell³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Chondrichthyans possess endoskeletal appendages called branchial rays that extend laterally from their hyoid and gill-bearing (branchial) arches. Branchial ray outgrowth, like tetrapod limb outgrowth, is maintained by Sonic hedgehog (Shh) signaling. In limbs, distal endoskeletal elements fail to form in the absence of normal Shh signaling, whereas shortened duration of Shh expression correlates with distal endoskeletal reduction in naturally variable populations. Chondrichthyans also exhibit natural variation with respect to branchial ray distribution-elasmobranchs (sharks and batoids) possess a series of ray-supported septa on their hyoid and gill arches, whereas holocephalans (chimaeras) possess a single hyoid arch raysupported operculum. Here we show that the elongate hyoid rays of the holocephalan Callorhinchus milii grow in association with sustained Shh expression within an opercular epithelial fold, whereas Shh is only transiently expressed in the gill arches. Coincident with this transient Shh expression, branchial ray outgrowth is initiated in C. milii but is not maintained, yielding previously unrecognized vestigial gill arch branchial rays. This is in contrast to the condition seen in sharks, where sustained Shh expression corresponds to the presence of fully formed branchial rays on the hyoid and gill arches. Considered in light of current hypotheses of chondrichthyan phylogeny, our data suggest that the holocephalan operculum evolved in concert with gill arch appendage reduction by attenuation of Shhmediated branchial ray outgrowth, and that chondrichthyan branchial rays and tetrapod limbs exhibit parallel developmental mechanisms of evolutionary reduction.

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Innervation of the medial rectus muscle in the ratfish,Hydrolagus colliei

Puzdrowski

1998

J. Comp. Neurol.

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Oculomotor organization in elasmobranch fish (sharks, skates, and rays) differs from that in other vertebrates in that the medial rectus muscle is innervated by contralateral rather than ipsilateral motoneurons. Distinguishing whether this innervation pattern is unique to the elasmobranchs, or is the ancestral pattern for cartilaginous fishes, requires examination of a representative of the sister group to the elasmobranchs, the holocephalans (ratfish). In the present study, the innervation pattern of the medial rectus was examined in a ratfish, Hydrolagus colliei, by using biotinylated dextran amines (BDA, 3,000 MW). Labeled cells were revealed in the contralateral oculomotor nucleus. Therefore, an innervation pattern in which the medial rectus muscle is innervated by contralateral motoneurons is the primitive condition for cartilaginous fishes.

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Chondrichthyan phylogeny: a look at the evidence

Cited by 114 publications

References 38 publications

Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography

Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography

Holocephalan embryos provide evidence for gill arch appendage reduction and opercular evolution in cartilaginous fishes

Innervation of the medial rectus muscle in the ratfish,Hydrolagus colliei

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