Gilliodus

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Gilliodus
Temporal range: Carboniferous 315.2–303.7  Ma
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order:† Eugeneodontiformes
Family:† Eugeneodontidae
Genus:† Gilliodus
Zangerl, 1981
Type species
* †Gilliodus orvellei
Zangerl, 1981
Other species
  • †G. peyeriZangerl, 1981

Gilliodus is an extinct genus of eugeneodontid cartilaginous fish from the Carboniferous of North America. Two species, G. orvellei and G. peyeri, are known. The postcranial skeleton of the genus is indistinguishable in appearance to the distantly related caseodontid Caseodus , and the genus is differentiated by the anatomy of its teeth. An isolated tooth from the Late Devonian of Poland has been suggested to belong to Gilliodus, but later authors have concluded that this tooth more likely belonged to a different order of fishes.

Contents

Discovery and naming

Gilliodus is known from fossils of Late Carboniferous (Moscovian to Kasimovian) age, found in shales in the Midwestern United States. G. orvellei is known from Indiana, while G. peyeri is known from both Indiana and Nebraska. [1] [2] [3] The genus and both species were described in 1981 by paleontologist Rainer Zangerl. The genus name and the name of the type species honor Orville "Gillie" Gilpin, who was a fossil curator at the Field Museum of Natural History. [2]

Additional teeth from the Late Carboniferous of Colorado may have belonged to G. peyeri, [4] and a tooth from the Late Devonian of the Świętokrzyskie Mountains, Poland has been suggested to belong to the genus as well. [5] The Devonian tooth has since been reclassified as that of an unrelated fish in a different taxonomic order by Michal Ginter and coauthors. [1]

Description

The teeth of Gilliodus consisted of both rows of rectangular teeth along the lateral edges of the jaws, and a set of teeth along the midline of the lower jaw termed a tooth-whorl, which was similar to that of Caseodus . The lateral teeth differed between the two species: in G. peyeri they were blade-like while in G. orvellei they were not. Both species are united by possessing well-developed ridges on their lateral teeth. The teeth of Gilliodus were covered in an outer layer of enameloid. The lower jaws (Meckel's cartilages) of both species were not fused at their anterior end. The postcranial skeleton of Gilliodus was identical in appearance to that of the caseodontid Caseodus. [1] [2]

Classification

Gilliodus is a member of the order Eugeneodontiformes (also spelled Eugeneodontida), [2] and more specifically the family Eugeneodontidae. [1] [6] Rainer Zangerl considered the genus to be the sister taxon of Eugeneodus , based on morphological analysis, in his 1981 description of the family and order. [2]

Paleobiology

In life, Gilliodus were nektonic carnivores. [7] Based on the enameloid coatings on its teeth, Zangerl suggested that Gilliodus had a rapid rate of tooth-replacement. [2]

References

  1. 1 2 3 4 Ginter, Michał; Hampe, Oliver; Duffin, Christopher J. (2010). Handbook of paleoichthyology: teeth. München: F. Pfeil. pp. 122–123. ISBN   978-3-89937-116-1.
  2. 1 2 3 4 5 6 Zangerl, Rainer (1981). Chondrichthyes I: paleozoic Elasmobranchii. Handbook of paleoichthyology. Fischer. pp. 2, 74–91. ISBN   978-3-437-30337-1.
  3. ↑ Bruner, John Clay; Bruner, John Clay; History, Field Museum of Natural (1992). A catalogue of type specimens of fossil fishes in the Field Museum of Natural History. Chicago, Ill: Field Museum of Natural History. p. 28. doi:10.5962/bhl.title.3361.
  4. ↑ Itano, Wayne M.; Houck, Karen J.; Lockley, Martin G. (2012-08-01). "Systematics and occurrences of Edestus (Chondrichthyes) worldwide and new occurrences from Colorado and Texas" . Historical Biology. 24 (4): 397–410. doi:10.1080/08912963.2012.658569. ISSN   0891-2963.
  5. ↑ Liszkowski, Jerzy; Racki, Grzegorz (1993). "Ichthyoliths and deepening events in the Devonian carbonate platform of the Holy Cross Mountains" (PDF). Acta Palaeontologica Polonica. 37 (2–4): 407–426.
  6. ↑ Nelson, Joseph S.; Grande, Terry; Wilson, Mark V. H. (2016). Fishes of the world (5th ed.). Hoboken, New Jersey: John Wiley & Sons. ISBN   978-1-119-22081-7.
  7. ↑ "PBDB Taxon". paleobiodb.org. Retrieved 2025-06-07.
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