Mesacanthus

Extinct genus of cartilaginous fishes

Mesacanthus
Temporal range: Devonian
Life reconstrucion of M. pusillus
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Acanthodii
Genus:
Mesacanthus

Traquair, 1888

Mesacanthus ('middle spine') is an extinct genus of acanthodian fish from Devonian Scotland.[1] It is among the more primitive of the Devonian acanthodians.

Description

Mesacanthus peachi fossil from the Sandwick Fish Beds of Quoyloo, Scotland.

Mesacanthus body fossils have pectoral, pelvic, anal and dorsal fin spines, as well as a pair of prepelvic spines, which are intermediate between the pectoral and pelvic fin spines.[1] They also have small, unornamented, diamond shaped scales. According to Agassiz, the genus also has a distinct tail in which the upper lobe extends to a sharp point and the lower lobe forms a small triangle.[1] Overall the genus is small (average length = 30mm) and fairly conservative, anatomically speaking, for acanthodians.[1][2]

Taxonomy

The genus was erected by Ramsay Traquair in 1888 to accommodate certain species that had been previously assigned to Acanthodes by Louis Agassiz.[3] These species included Mesacanthus mitchelli, Mesacanthus pusillus, Mesacanthus peachi and Mesacanthus coriaceus. [3] The genus is found in both Lower Old Red Sandstone and Middle Old Red Sandstone assemblages, with M. pusillus, M. peachi and M. coriaceus known from the Middle Devonian and M. mitchelli being the only known species from the Lower Devonian.[1] [3] Arthur Smith Woodward formally synonymized M. peachi and M. coriaceus in 1891.[4] In 2015 a study published in PeerJ reassessed the two remaining Middle Devonian species (M. pusillus and M. peachi) and found that they also could not be distinguished from one another. Hence, only two species from the Orcadian Basin and Midland Valley areas of Scotland are currently considered to be valid: M. mitchelli from the Lower Devonian and M. pusillus from the Middle Devonian.[1]

See also

  • List of acanthodians

References

  1. ^ a b c d e f Baron, MG (2015). "An investigation of the genus Mesacanthus (Chordata: Acanthodii) from the Orcadian Basin and Midland Valley areas of Northern and Central Scotland using traditional morphometrics". PeerJ. 3: e1331. doi:10.7717/peerj.1331. PMC 4631467. PMID 26539330.
  2. ^ Agassiz, L. (1833). Recherches sur les poissons fossiles.. (Vol. 1). chez l'auteur.
  3. ^ a b c Traquair, R. H. (1888). Old Red Sandstone fishes.
  4. ^ Woodward, A. S. (1901). Catalogue of the fossil fishes in the British Museum (Natural History). Printed by order of the Trustees.
  • v
  • t
  • e
Total group Chondrichthyes (including "acanthodians")
Gnathostomata
    • see Gnathostomata
Chondrichthyes
    • see below↓
  • Cassidiceps
  • Euthacanthus
  • Latviacanthus
  • Ramirosuarezia?
Sinacanthidae
  • Hunanacanthus
  • Neosinacanthus
  • Sinacanthus
  • Tarimacanthus
"Ischnacanthiformes"
  • Acanthospina
  • Campylodus
  • Granulacanthus
  • Machaeracanthus?
  • Onchus
  • Serradentus
Acritolepidae
Ischnacanthidae
  • Arcticacanthus
  • Arenaceacanthus
  • Atopacanthus
  • Bracteatacanthus
  • Cacheacanthus
  • Erymnacanthus
  • Euryacanthus
  • Gomphonchus
  • Grenfellacanthus
  • Ischnacanthus
  • Marsdenius?
  • Persacanthus
  • Plectrodus
  • Rockycampacanthus
  • Rohonilepis
  • Taemasacanthus
  • Tricuspicanthus
  • Xylacanthus
Podoliacanthidae
Poracanthodidae
  • Gomphonchoporus
  • Machaeraporus
  • Obruchevacanthus?
  • Poracanthodes
  • Radioporacanthodes
  • Taimyrolepis
  • Trundlelepis
  • Zemlyacanthus
Diplacanthiformes
  • Bryantonchus
  • Culmacanthus?
  • Devononchus
  • Striacanthus
  • Tetanopsyrus
  • Uraniacanthus
Diplacanthidae
Acanthodiformes
  • Halimacanthodes
  • Howittacanthus
Acanthodidae
Cheiracanthidae
Mesacanthidae
  • Lodeacanthus
  • Melanoacanthus
  • Mesacanthus
  • Orcadacanthus
  • Promesacanthus
  • Teneracanthus?
  • Triazeugacanthus
"Climatiiformes"
and related taxa
Climatiidae
Gyracanthidae
"Conventionally defined
chondrichthyans"
    • see below↓
Ischnacanthus gracilis

Diplacanthus sp. Acanthodes lopatini

Brochoadmones milesi
"Conventionally defined chondrichthyans"
"Conventionally defined chondrichthyans"
Antarctilamnidae
Mcmurdodontidae
Pucapampellidae
  • Gydoselache
  • Pucapampella
Omalodontiformes
  • Siberiodus
Aztecodontidae
Omalodontidae
  • Doliodus?
  • Omalodus
  • Portalodus
"Ctenacanthiformes"
  • Neosaivodus
  • Saivodus
  • Sculptospina
  • Tamiobatis
Ctenacanthidae
Heslerodidae
Jalodontidae
  • Adamantina
  • Isacrodus
  • Jalodus
  • Keuperodus
  • Texasodus
Phoebodontidae
Symmoriiformes
Cladoselachidae?
Falcatidae
Symmoriidae
Bransonelliformes
Xenacanthiformes
Diplodoselachidae
  • Decentrodus
  • Diplodoselache
  • Hagenoselache
  • Hokomata
  • Lebachacanthus
  • Taquaralodus
Xenacanthidae
Crown-Chondrichthyes
Doliodus problematicus

Ctenacanthus concinnus Cobelodus sp.

Xenacanthus decheni
Incertae sedis scale-based taxa
Altholepidiformes?
Elegestolepidida?
  • Kannathalepis
Elegestolepididae
Mongolepidida?
  • Solinalepis
Mongolepididae
  • Mongolepis
  • Rongolepis
  • Sodolepis
  • Taklamakanolepis
  • Teslepis
Shiqianolepidae
  • Chenolepis
  • Shiqianolepis
  • Tielikewatielepis
  • Xiaohaizilepis
  • Xinjiangichthys
Tchunacanthidae
  • Fecundosquama
  • Lenacanthus
  • Tchunacanthus
Vesperaliidae
  • Acanthacanthus
  • Vesperalia
Others
  • Canyonlepis?
  • Frigorilepis?
  • Funicristata
  • Gualepis
  • Ivanelepis
  • Jolepis
  • Karksilepis
  • Lunalepis
  • Nobilesquama
  • Nostolepis
  • Nostovicina
  • Ohiolepis
  • Seretolepis
  • Tuvalepis
  • Wellingtonella?
  • Yuanolepis
  • Category
Taxon identifiers
Mesacanthus