A symmoriiform chondrichthyan braincase and the origin of chimaeroid fishes

  title={A symmoriiform chondrichthyan braincase and the origin of chimaeroid fishes},
  author={Michael I. Coates and Robert W. Gess and John A. Finarelli and Katharine E. Criswell and Kristen Tietjen},
Chimaeroid fishes (Holocephali) are one of the four principal divisions of modern gnathostomes (jawed vertebrates). Despite only 47 described living species, chimaeroids are the focus of resurgent interest as potential archives of genomic data and for the unique perspective they provide on chondrichthyan and gnathostome ancestral conditions. Chimaeroids are also noteworthy for their highly derived body plan. However, like other living groups with distinctive anatomies, fossils have been of… 

An early chondrichthyan and the evolutionary assembly of a shark body plan

Preliminary phylogenetic results highlight the likely convergent evolution of conventional chondrichthyan conditions among earliest members of this primary gnathostome division, while skeletal morphology points towards the likely suspension feeding habits of Gladbachus, suggesting a functional origin of the gill slit condition characteristic of the vast majority of living and fossil chondRichthyans.

The earliest chimaeriform fish from the Carboniferous of Central Russia

The ancestry of chimaeriform chondrichthyan fishes can be traced back to the Late Triassic (∼220 Ma). To date, only one chimaeriform suborder, the Echinochimaeroidei, has been recognized from the

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The early elasmobranch Phoebodus: phylogenetic relationships, ecomorphology and a new time-scale for shark evolution

The first skeletal remains of Phoebodus from the Famennian (Late Devonian) of the Maïder region of Morocco are reported, revealing an anguilliform body, specialized braincase, hyoid arch, elongate jaws and rostrum, complementing its characteristic dentition and ctenacanth fin spines preceding both dorsal fins.

The morphology and evolution of chondrichthyan cranial muscles: a digital dissection of the elephantfish Callorhinchus milii and the catshark Scyliorhinus canicula

3D data acquired is used to carry out a digital dissection of a holocephalan and an elasmobranch widely used as model species: the elephantfish, Callorhinchus milii, and the small-spotted catshark, Scyliorhinus canicula, with great potential as a resource for researchers using these model species for zoological research and functional morphologists requiring models of musculature and skeletons.

The Evolution of the Spiracular Region From Jawless Fishes to Tetrapods

The first confirmed example of a complete spiracular gill in any vertebrate is presented, in the galeaspid (jawless stem gnathostome) Shuyu, and comparisons with two other groups of jawless stem Gnathostomes indicate that they also probably possessed full-sized Spiracular gills and that this condition may thus be primitive for the gnathOSTome stem group.

The neurocranium of the Lower Carboniferous shark Tristychius arcuatus (Agassiz, 1837)

ABSTRACT Tristychius arcuatus, from the late Viséan of Scotland, is known from numerous ironstone nodule-encased specimens. These are reinvestigated using computerised tomography (CT) scanning and

Hagfish from the Cretaceous Tethys Sea and a reconciliation of the morphological–molecular conflict in early vertebrate phylogeny

By addressing nonindependence of characters, phylogenetic analyses recovered hagfish and lampreys in a clade of cyclostomes (congruent with the cyclostome hypothesis) using only morphological data, which potentially resolve the morphological–molecular conflict at the base of the Vertebrata.



Skull and brain anatomy of Late Carboniferous Sibyrhynchidae (Chondrichthyes, Iniopterygia) from Kansas and Oklahoma (USA)

The data presented here show the three-dimensionally preserved braincase of a possible stem-holocephalan as these new specimens share with extant chimaeroids some key neurocranial characters, which may provide means for a comparative study of skull anatomy in Paleozoic representatives of the main two chondrichthyan clades.

Acanthodes and shark-like conditions in the last common ancestor of modern gnathostomes

A new description of the Acanthodes braincase is presented, yielding new details of external and internal morphology, notably the regions surrounding and within the ear capsule and neurocranial roof that contribute to a new reconstruction that, unexpectedly, resembles early chondrichthyan crania.

Chondrenchelys problematica (Traquair, 1888) redescribed: a Lower Carboniferous, eel-like holocephalan from Scotland

  • J. FinarelliM. Coates
  • Biology
    Earth and Environmental Science Transactions of the Royal Society of Edinburgh
  • 2014
Chondrenchelys problematica, from the Viséan (Holkerian) of Scotland, is the earliest holocephalan known from extensive cranial and postcranial material and is recommended as a hard minimum age for the last common ancestor of elasmobranchs and chimaeroids, because of its secure association with other holocephalans, and current uncertainties concerning elasmOBranch stem lineage membership.

Relationships of the Chimaeriformes and the basal radiation of the Chondrichthyes

  • R. LundE. Grogan
  • Environmental Science
    Reviews in Fish Biology and Fisheries
  • 2004
Morphological examination of fossil chondrichthyans indicates that the plesiomorphous state of the gnathostome suspensorium is autodiastylic and that complex labial cartilages are primitive and likely to have been critical to the mechanical architecture of the first jaws.

The braincase of the chondrichthyan Doliodus from the Lower Devonian Campbellton Formation of New Brunswick, Canada

Doliodus has curious bar-like, paired subcranial ridges ending posteriorly at the hyomandibular articulation, adding circumstantial palaeontological support to the old proposal that parts of visceral arches may be incorporated into the gnathostome braincase, although it seems more plausible that they formed in the lateral margins of the embryonic parachordal or hypotic lamina.

A Palaeozoic shark with osteichthyan-like branchial arches

A 325 million year (Myr)-old Palaeozoic shark-like fossil is described that represents the earliest identified chondrichthyan in which the complete gill skeleton is three-dimensionally preserved in its natural position, and its visceral arch arrangement is remarkably osteichthyan-like, suggesting that this may represent the common ancestral condition for crown gnathostomes.

Osteichthyan-like cranial conditions in an Early Devonian stem gnathostome

A conjunction of well-developed cranial processes in Janusiscus helps unify the comparative anatomy of early jawed vertebrate neurocrania, clarifying primary homologies in ‘placoderms’, osteichthyans and chondrichthyans.

A review of the sensory biology of chimaeroid fishes (Chondrichthyes; Holocephali)

  • T. J. Lisney
  • Environmental Science
    Reviews in Fish Biology and Fisheries
  • 2010
A survey of the existing literature on the major senses in chimaeroids is provided in order to stimulate and identify areas for future research to help protect and management of these fascinating fishes.

The braincase of a primitive shark

Plesiomorphic conditions for chondrichthyan braincases are found to include the presence of a persistent otico-occipital fissure, projection of the median dorsal aorta anterior to the occipital level, and absence of suborbital shelves.

Elephant shark genome provides unique insights into gnathostome evolution

The whole-genome analysis of a cartilaginous fish, the elephant shark (Callorhinchus milii), finds that the C. milii genome is the slowest evolving of all known vertebrates, and features extensive synteny conservation with tetrapod genomes, making it a good model for comparative analyses of gnathostome genomes.