Palæos:		Unit 90: Teleostomi
The Vertebrates		100: Teleostomi

Teleostomi

Acanthodians

Thelodonti
|--PLACODERMI
`--+--CHONDRICHTHYES
   `--Teleostomi 
      |--Acanthodii
      |  |--Climatiiformes
      |  `--+--Ischnacanthiformes
      |     `--Acanthodiformes
      `--Osteichthyes
         |--Actinopterygii
         |  |--Cladistia
         |  `--Actinopteri
         |     |--Chondrostei
         |     `--NEOPTERYGII
         `--SARCOPTERYGII

Taxa on This Page

1. Acanthodiformes X

2. Acanthodii X

3. Climatiiformes X

4. Ischnacanthiformes X

5. Teleostomi

Teleostomi: Tuna > sharks.

Range: From the Late Ordovician or Early Silurian.

Phylogeny: Eugnathostomata: Chondrichthyes + *: Acanthodii + Osteichthyes. 

Characters: Mouth terminal; braincase deep and narrow; braincase shows ventral fissure, otic-occipital fissure; separate ant and post nostrils; large bone operculum and/or branchiostegal rays. 

APW 040806.

Acanthodii: Acanthodus. 

Range: Ordovician to Early Permian. 

Phylogeny: Teleostomi: Osteichthyes + *: Climatiiformes + (Ischnacanthiformes + Acanthodiformes). 

Update: Hanke & Wilson (2006) have redescribed Brochoadmones, an acanthodian of uncertain affinities, on the basis of superlative material from the MOTH locality in Northerrn Canada.  As originally reported, it looked a great deal like our image of Acanthodes. Among many new and interesting features, two points stand out.  First, in addition to the ventral spine pairs, Brochoadmones has a thin, very osteichthyan pectoral fin, located about midway up the body wall. The fin has a short pectoral fin spine (much shorter than the fin) "resembling a bivalve shell" but no ossified endoskeleton.  The implication seems to be that the osteichthyan pectoral fin is only indirectly related to the usual ventral fin spines of the acanthodians.  Second, the head turns out to be very small, the fish being deep-bodied and almost trapezoidal overall.  ATW061003.  

Characters: Crania based on 4 large plates bridged by cartilage; subterminal mouth; branchiostegal rays present; no enamel on teeth, teeth not regularly replaced; jaws of dermal bone; orbits large and far anterior, with circumorbital plates; bony operculum; branchiostegal rays present; otoliths in inner ear; narrow-based braincase with a transverse ventral fissure; braincase & otic capsule well-ossified; primitively, several opercular scales; vertebral centra not ossified; no ribs; heterocercal tail; fin spines on all except caudal fins; generally membranous fins without rays except for spines; various articulations of pectoral spine with shoulder girdle; up to 6 paired intermediate spines between pectoral and pelvic fins; scales like Chondrichthyes, but no pulp cavity: base bulges & new odontodes of dentine or mesodentine surround and overgrow old with layered effect; fins covered with similar scales, like lepidotrichia of Osteichthyes; cranial large scales not homologous to Osteichthyes. 

Links: acanthodii.htm; Replicas of Paleozoic Fishes; Biology 356; Acanthodii; Class:Incertae Sedis Acanthodii; Acanthodii; Paleontology and Geology Glossary; Acanthodii -families; acanthodii.htm; Dictionary of Animals - Acanthodii; Systematics of major fish groups IV; Replicas of Paleozoic Fishes; V The four other mass extinctions; Acanthodii; Zajic_1988_jaws.pdf; Primative Fish & the Evolution of Jaws & Lungs; Devonian Times - More about Acanthodians; Lecture 8; Acanthodii - Biognomen (definition); Class-Incertae Sedis Acanthodii (bibliography); ACANTHODII PLACODERMI (Slovenian: apparantly a nice summary); Genomgång Osteichthyes (Swedish: another apparantly good discussion in another language to which we have no access); Comparative Anatomy Topic 3 - Fishes (some characters); OTHER FISH (the usual amazing images from this site); Acanthodian (Acanthodii) jaws from the borehole Sa-2a (don't be out off by title & format -- interesting paper.  Various other relevant short papers & abstracts by Zaijicat Publications). APW 040806.

Climatiiformes: Climatius. 

Range: Late Silurian to Early Carboniferous. 

Phylogeny: Acanthodii: (Ischnacanthiformes + Acanthodiformes) + *. 

Characters: May be paraphyletic basal group. Generally small-bodied (<15 cm); teeth minute & petalliform, not shed; extramandibular absent; palatoquadrate elongate & without otic articulation; 1 large and several small gill covers; broad-based spines with ridges; 2 dorsal fins; 2+ intermediate spines between pectoral and pelvic fins; well-developed dermal pectoral plates. 

Links: acanthodii.htm; Devoniano (Italian); Devonian Times: Gyracanthus sp.; fish.htm; p1; ??????? (Japanese); p3d.htm (original in Japanese).

Note: The orbit shown in the image may be a bit small and there may be one too many sets of intermediate spines. APW 040806.

Ischnacanthiformes: Ischnacanthus. 

Range: Devonian. 

Phylogeny: Acanthodii:: Acanthodiformes + *. 

Characters: Large toothed bones on palatoquadrate (looks like a shark); dermal pectoral covering reduced; 1 large gill cover; fin spines slender, with orthodentine superficial layer; some large (2m) species. APW 040806.

Acanthodiformes: Acanthodus; Howattacanthus. 

Range: Late Silurian to Early Permian.

Phylogeny: Acanthodii:: Ischnacanthiformes + *. 

Characters: Extramandibular bone present; large orbits; well-developed gill rakers; 1 dorsal fin; 1 very large gill cover; no teeth; no intermediate spines between pectoral and pelvic fins; some elongated forms. 

Links: Abstract; Correction; acanthodii.htm (Best on the Web); Acanthodiformes; superordo Acanthoda; CHAP4E.HTM. APW 040806.

checked APW 040806.