| Debeeriidae Temporal range: Mississippian
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| Life reconstruction of Debeerius, the type genus | |
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| Life reconstruction of Heteropetalus | |
Scientific classification 
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Holocephali |
| Order: | †Debeeriiformes |
| Family: | †Debeeriidae Grogan & Lund, 2000 |
| Type genus | |
| Debeerius Grogan & Lund, 2000
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| Genera | |
| Synonyms | |
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Debeeriidae is an extinct family of cartilaginous fish from the Mississippian subperiod of the Carboniferous period. It is the only family of the order Debeeriiformes. It is named after the type genus, Debeerius, which itself is named in honor of biologist Gavin de Beer. Members of this family and order possess a spine on the first dorsal fin, an opercular cover over the gills, and a form of jaw suspension termed autodiastyly. Two genera are placed in the family, Debeerius and Heteropetalus, and both are known from exceptionally well-preserved specimens found in the Bear Gulch Limestone member of the Heath Formation.
History of research
The first member of the family to be named and described was Heteropetalus from the Bear Gulch Limestone unit of the Heath Formation in Montana, USA, which was named in 1977 by paleontologist Richard Lund.1 When first described, details of the animal's anatomy such as the structure of the jaws and teeth were misinterpreted, and the genus was variously considered a relative of various different groups of extinct cartilaginous fish. Works by Lund and fellow researcher Eileen Grogan in the 1990s better clarified the anatomy and relations of Heteropetalus.2
In 2000 Lund and Grogan described another fish from the Bear Gulch Limestone, which they named Debeerius after embryologist Gavin de Beer. This genus shares key distinguishing features in common with Heteropetalus, and the two were classified together within the newly-coined family Debeeriidae based on cladistic analyses.3
Both genera are known from multiple complete skeletons with soft tissues preserved.1 Skin pigments are known in Debeerius,3 while blood pigments are known in Heteropetalus.2
Description
Members of Debeeriidae had a first dorsal fin with a spine, paired pectoral and pelvic fins, and heterocercal caudal fins.3 The bodies of debeeriids were completely scaleless,2 and Debeerius had a striped pattern along the length of its body.3 The gills of debeeriids were covered by a soft flap termed an operculum, which was supported by the fish's hyomandibular arch.23 The jaws of debeeriids were supported in a manner termed autodyastyly, where the upper jaw (palatoquadrates) is separated from the skull but is immobile, and the lower jaw (Meckel's cartilages) is not supported by the hyomandibular.3 The internal skeletons of debeeriids were composed of cartilage.13
Classification
The Debeeriidae is a member of the monotypic order Debeeriiformes.45 They are cartilaginous fish in the Class Chondrichthyes, and the subclass Holocephali.4
References
References
- Lund, Richard (1977-09-30). "A new petalodont (Chondrichthyes, Bradyodonti) from the Upper Mississippian of Montana". Annals of the Carnegie Museum. 46: 129––155. Bibcode:1977AnCM...46..129L. doi:10.5962/p.330526.
- Grogan, Eileen D.; Lund, Richard (1995-01-01). "Pigment patterns; soft anatomy and relationships of Bear Gulch Chondrichthyes (Namurian E2b; Lower Carboniferous; Montana; USA)". Geobios. Premiers Vertandébrandés et Vertandébrandés Infandérieurs. 28: 145–146. Bibcode:1995Geobi..28..145G. doi:10.1016/S0016-6995(95)80102-2. ISSN 0016-6995.
- Grogan, Eileen D.; Lund, Richard (2000). "Debeerius ellefseni (Fam. Nov., Gen. Nov., Spec. Nov.), an autodiastylic chondrichthyan from the Mississippian Bear Gulch Limestone of Montana (USA), the relationships of the chondrichthyes, and comments on gnathostome evolution". Journal of Morphology. 243 (3): 219–245. doi:10.1002/(SICI)1097-4687(200003)243:3<219::AID-JMOR1>3.0.CO;2-1. ISSN 0362-2525. PMID 10681469.
- Nelson, Joseph S.; Grande, Terry C.; Wilson, Mark V. H. (2016). Fishes of the World (5th ed.). Wiley. pp. 48–51. doi:10.1002/9781119174844. ISBN 978-1-118-34233-6.
- Laan, Richard van der (2018-10-11). "Family-group names of fossil fishes". European Journal of Taxonomy (466): 38. doi:10.5852/ejt.2018.466. ISSN 2118-9773.