Journal article
The Extraordinary Occipito-Vertebral Skeleton and Swim Bladder of South American Hypophthalmus Catfishes (Siluriformes: Pimelodidae): Improved Illustration, Description, and Interpretation
Copeia, v 103(4), pp 806-820
01 Dec 2015
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
The pimelodid catfish genus Hypophthalmus has an unusually modified Weberian apparatus, reduced swim bladder, and associated bones of the occiput and pectoral girdle. Using high resolution X-ray tomography and traditional skeletal preparations of adult and juvenile specimens, we reexamined and illustrated this occipito-vertebral complex. Comparisons were made to the plesiomorphic architecture of the complex exhibited by phylogenetically deep pimelodid genera. Hypophthalmus has the swim bladder reduced to a pair of separate bilobed sacs, each doubly encapsulated by outer and inner layers of bone. The anterior vertebrae and occipital bones are shortened and contorted with apparent loss or fusion of the first centrum and development of novel joints between the basioccipital and complex vertebra. Two pairs of the Weberian ossicles are lost: claustra and intercalaria. The posttemporal-supracleithrum is reshaped and solidly united to a recurved arm of the 4th parapophysis with both extended far posteriorly to brace the outer swim bladder capsule and articulate with the cleithrum. The extrascapula is found in juveniles and apparently fuses with the adjacent pterotic. The third supraneural is present between the supraoccipital and complex vertebra. We point out conflicting results and interpretations among four previous studies and our treatment of the occipito-vertebral complex and swim bladder of Hypophthalmus. Based on unambiguous morphological and molecular evidence, Hypophthalmus belongs to the sorubimine clade of the family Pimelodidae. In this evolutionary context the morphology of the occipito-vertebral complex and swim bladder of Hypophthalmus is distinctly divergent from that of other sorubimines. The complex of Hypophthalmus is also distinct from the partially encapsulated swim bladders of the Calophysus and Megalonema clades. The morphology of the occipito-vertebral complex and swim bladder of Hypophthalmus is uniquely autapomorphic.
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Details
- Title
- The Extraordinary Occipito-Vertebral Skeleton and Swim Bladder of South American Hypophthalmus Catfishes (Siluriformes: Pimelodidae): Improved Illustration, Description, and Interpretation
- Creators
- John G. Lundberg - Academy of Natural Sciences of Drexel UniversityKyle R. Luckenbill - Academy of Natural Sciences of Drexel University
- Publication Details
- Copeia, v 103(4), pp 806-820
- Publisher
- Amer Soc Ichthyologists & Herpetologists
- Number of pages
- 15
- Grant note
- DEB-0089612 / US National Science Foundation; National Science Foundation (NSF) 1258878 / Division Of Earth Sciences; National Science Foundation (NSF); NSF - Directorate for Geosciences (GEO)
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Academy of Natural Sciences of Drexel University
- Web of Science ID
- WOS:000366679700007
- Scopus ID
- 2-s2.0-84947066349
- Other Identifier
- 991019335232104721
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- Web of Science research areas
- Zoology