Community hub
Recent from talks
Knowledge base stats:
Talk channels stats:
Members stats:
Orthacanthus
Orthacanthus is an extinct genus of fresh-water xenacanthiform cartilaginous fish, named by Louis Agassiz in 1843, ranging from the Upper Carboniferous into the Lower Permian. Orthacanthus had a nektobenthic life habitat, with a carnivorous diet. Multiple authors have also discovered evidence of cannibalism in the diet of Orthacanthus and of "filial cannibalism" where adult Orthacanthus preyed upon juvenile Orthacanthus. Synonyms of the genus Orthacanthus are Dittodus Owen, 1867, Didymodus Cope, 1883, Diplodus Agassiz, 1843, Chilodus Giebel, 1848 (preoccupied by Chilodus Müller & Troschel, 1844).
During the Late Carboniferous-Early Permian, Orthacanthus was an apex predator of freshwater swamps and bayous in Europe and North America. Mature Orthacanthus reached nearly 3 meters (10 feet) in length. Orthacanthus teeth have a minimum of three cusps, two principal cusps, and an intermediate cusp, where the principal cusps are variously serrated, with complex base morphology. Additionally, Orthacanthus can be diagnosed by major transverse axes of proximal ends at a 45-degree angle to and often almost parallel to the labial margin of the base between the cusps. Deformed teeth are characteristic of the xenacanthiform sharks and of Orthacanthus.
The two genera Orthacanthus and Pleuracanthus were erected by Louis Agassiz based on isolated "ichthyodorulites" from the British Carboniferous System, and at the time were mistakenly thought of as the first indicators of skates. They were initially found in the United Kingdom in Dudley, Leeds, North Wales, Carluke, and Edinburgh. Three additional species from the Carboniferous formation of Ohio were described by John Strong Newberry, but two of them were junior homonyms of another species, Orthacanthus gracilis (Giebel, 1848). Accordingly, these two species received replacement names, O. adamas Babcock 2024 and O. lintonensis Babcock, 2024. Teeth associated with Diplodus, a genus of sharks, was found in the Carboniferous slates of England in Stafford, Carluke, and Burdiehouse, and in Nova Scotia. A well preserved impression from Ruppelsdorf, Bohemia, was described by Goldfuss, and in a separate paper, the same specimen was described under the name Xenacanthus dechenii. One year later, in 1849, Dr. Jordan mistakenly identified this specimen as the remains of a fossil shark, Triodus sessilis. This mistake was corrected and the specimen was identified as Xenacanthus by Mr. Schnur.
The larger teeth of Orthacanthus compressus and Orthacanthus texensis are differentiated by a more pronounced basal tubercle in O. compressus. The basal tubercle of a typical tooth file is on the apical button of the underlying tooth. The larger adult teeth of O. compressus have a wider rather than longer base, similar to O. texensis, and tend to have serrations on both carinae of each cusp, while the medial carinae of smaller adult teeth are not serrated. The juvenile teeth of O. compressus are longer than wide, have a thinner base, and lack serrations, similar to O. platypternus teeth.
Orthacanthus platypternus from the Craddock Bonebed shark layer in Texas, USA, shows evidence of resorption, and the equivalent of an "enamel pearl." Some of the teeth specimens found at this location show evidence of resorption, which has not been previously observed in other faunal members at the same location. Where the superjacent basal tubercle is expected to be resorbed if the teeth were to undergo resorption, the apical button is resorbed instead.
The difference in characteristics between the large and small O. compressus adult teeth might indicate sexual dimorphism.
The spines of O. platypternus showing 3 to 4 dentine layers are interpreted to be subadults or young adults, and are separated into two size classes where females have the largest spines in comparison to males, indicating sexual dimorphism.
The dorsal spines of Orthacanthus platypternus from the Craddock Bone Bed in Texas, USA, preserve a highly vascularized wall mainly composed of centrifugally growing dentine (the outer layer of the wall of the spine) in a succession of inwardly growing dentine layers that line the pulp cavity. These dentine layers are likely deposited periodically in accordance with seasonal variations in water temperature and food availability. More specifically, the periodic nature of the dentine layer deposits could be due to variation in calcium phosphate deposition following the changes in water temperature. Spines of individuals with 1-2 dentine layers are likely juveniles and result in the smallest sizes, whereas individuals showing at least 3-4 dentine layers result in two separate size classes. The cross section is oval near the opening of the pulp cavity and circular/subtriangular in the distal part of the non-denticulated region and circular in the denticulated region. The pulp cavity of the spine is filled with calcite, quartz, and opaque minerals.
Hub AI
Orthacanthus AI simulator
(@Orthacanthus_simulator)
Orthacanthus
Orthacanthus is an extinct genus of fresh-water xenacanthiform cartilaginous fish, named by Louis Agassiz in 1843, ranging from the Upper Carboniferous into the Lower Permian. Orthacanthus had a nektobenthic life habitat, with a carnivorous diet. Multiple authors have also discovered evidence of cannibalism in the diet of Orthacanthus and of "filial cannibalism" where adult Orthacanthus preyed upon juvenile Orthacanthus. Synonyms of the genus Orthacanthus are Dittodus Owen, 1867, Didymodus Cope, 1883, Diplodus Agassiz, 1843, Chilodus Giebel, 1848 (preoccupied by Chilodus Müller & Troschel, 1844).
During the Late Carboniferous-Early Permian, Orthacanthus was an apex predator of freshwater swamps and bayous in Europe and North America. Mature Orthacanthus reached nearly 3 meters (10 feet) in length. Orthacanthus teeth have a minimum of three cusps, two principal cusps, and an intermediate cusp, where the principal cusps are variously serrated, with complex base morphology. Additionally, Orthacanthus can be diagnosed by major transverse axes of proximal ends at a 45-degree angle to and often almost parallel to the labial margin of the base between the cusps. Deformed teeth are characteristic of the xenacanthiform sharks and of Orthacanthus.
The two genera Orthacanthus and Pleuracanthus were erected by Louis Agassiz based on isolated "ichthyodorulites" from the British Carboniferous System, and at the time were mistakenly thought of as the first indicators of skates. They were initially found in the United Kingdom in Dudley, Leeds, North Wales, Carluke, and Edinburgh. Three additional species from the Carboniferous formation of Ohio were described by John Strong Newberry, but two of them were junior homonyms of another species, Orthacanthus gracilis (Giebel, 1848). Accordingly, these two species received replacement names, O. adamas Babcock 2024 and O. lintonensis Babcock, 2024. Teeth associated with Diplodus, a genus of sharks, was found in the Carboniferous slates of England in Stafford, Carluke, and Burdiehouse, and in Nova Scotia. A well preserved impression from Ruppelsdorf, Bohemia, was described by Goldfuss, and in a separate paper, the same specimen was described under the name Xenacanthus dechenii. One year later, in 1849, Dr. Jordan mistakenly identified this specimen as the remains of a fossil shark, Triodus sessilis. This mistake was corrected and the specimen was identified as Xenacanthus by Mr. Schnur.
The larger teeth of Orthacanthus compressus and Orthacanthus texensis are differentiated by a more pronounced basal tubercle in O. compressus. The basal tubercle of a typical tooth file is on the apical button of the underlying tooth. The larger adult teeth of O. compressus have a wider rather than longer base, similar to O. texensis, and tend to have serrations on both carinae of each cusp, while the medial carinae of smaller adult teeth are not serrated. The juvenile teeth of O. compressus are longer than wide, have a thinner base, and lack serrations, similar to O. platypternus teeth.
Orthacanthus platypternus from the Craddock Bonebed shark layer in Texas, USA, shows evidence of resorption, and the equivalent of an "enamel pearl." Some of the teeth specimens found at this location show evidence of resorption, which has not been previously observed in other faunal members at the same location. Where the superjacent basal tubercle is expected to be resorbed if the teeth were to undergo resorption, the apical button is resorbed instead.
The difference in characteristics between the large and small O. compressus adult teeth might indicate sexual dimorphism.
The spines of O. platypternus showing 3 to 4 dentine layers are interpreted to be subadults or young adults, and are separated into two size classes where females have the largest spines in comparison to males, indicating sexual dimorphism.
The dorsal spines of Orthacanthus platypternus from the Craddock Bone Bed in Texas, USA, preserve a highly vascularized wall mainly composed of centrifugally growing dentine (the outer layer of the wall of the spine) in a succession of inwardly growing dentine layers that line the pulp cavity. These dentine layers are likely deposited periodically in accordance with seasonal variations in water temperature and food availability. More specifically, the periodic nature of the dentine layer deposits could be due to variation in calcium phosphate deposition following the changes in water temperature. Spines of individuals with 1-2 dentine layers are likely juveniles and result in the smallest sizes, whereas individuals showing at least 3-4 dentine layers result in two separate size classes. The cross section is oval near the opening of the pulp cavity and circular/subtriangular in the distal part of the non-denticulated region and circular in the denticulated region. The pulp cavity of the spine is filled with calcite, quartz, and opaque minerals.