Introduction
Melvius was a prehistoric freshwater fish which lived in North America during the late Cretaceous Period 74-66 million years ago.
Melvius belonged to a family called Amiidae. Today, the only surviving amiid is the Bowfin (Amia calva), which is native to southeastern Canada and the eastern United States, and typically grows to 2 feet long, although some unusually large specimens reaching 3.5 feet have been caught. The oldest-known fossils belonging to Amiidae date to the late Triassic Period, 213 MYA. Bowfins are a missing link between very archaic fish like gars (bowfins are actually related to gars) and more advanced bony fish; their skeletons are comprised of a mixture of both bone and cartilage. They were originally a very widespread and diverse group, with species inhabiting both freshwater and saltwater environments. The modern-day Bowfin is, therefore, considered by many to be a “living fossil” (Gilbert and Williams 2002, page 89).
The family Amiidae is divided into four sub-families: Amiinae, Amiopsinae, Solnhofenamiinae, and Vidalamiinae; Melvius is classified as a member of Vidalamiinae. This sub-family is further split into two sub-divisions called “tribes”, which are Calamopleurini (found in South America and Africa) and Vidalamiini (found in North America, Europe, and Asia); Melvius is currently classified as a member of the tribe Vidalamiini. Closely-related species include the eponymous Vidalamia (130-125 MYA) and Pachyamia (100-95 MYA) (Grande and Bemis 1998, pages 1-2).
Melvius thomasi
The genus Melvius is divided into two species: M. chauliodous, which has been found in New Mexico, and M. thomasi, which has been found within the Hell Creek Formation.
Melvius thomasi was officially named and described in 1987 by Laurie Jean Bryant of the University of California Museum of Paleontology (UCMP). It was named in honor of Mr. Melvin Thomas of Garfield County, Montana “in gratitude for his generous assistance to UCMP field crews” (Bryant 1987, page 349). The holotype specimen is currently housed within the University of California Museum of Paleontology (collection ID code: UCMP 129600) (Bryant 1987, page 349; Bryant 1989, page 22).
Based upon the size of its remains, Melvius was an unusually large bowfin, measuring 5.25 feet (160 cm) long, making it one of the largest-known amiids (Bryant 1987, page 360).
Reconstruction of the skull of Melvius thomasi based upon the holotype specimen “UCMP 129600” and other pieces. No measurement for the scale bar was given within the article. Bryant, Laurie Jean (1987). “A new genus and species of Amiidae (Holostei; Osteichthyes) from the Late Cretaceous of North America, with comments on the phylogeny of the Amiidae”. Journal of Vertebrate Paleontology, volume 7, issue 4 (December 1987). Page 360.
Fossils belonging to fifty or so specimens of Melvius thomasi have been uncovered from Montana and Wyoming, and more specimens which have been provisionally ascribed to this species have also been uncovered from North Dakota, South Dakota, Utah, Texas, and New Mexico. This would make it one of the most widespread large-sized freshwater fish from North America during the end of the Cretaceous Period. Its distribution suggests that this species lived in large rivers all along the coast of the Western Interior Sea. All fossils have been recovered from rocks which date to the Maastrichtian Stage of the late Cretaceous Period, 70-66 MYA (Bryant 1987, pages 349-351; Bryant 1989, page 22). Stratigraphically, fossils of M. thomasi have been found at all levels of the Hell Creek Formation. A survey was conducted in the early 2000s concerning the variety and quantity of fossils which were found at various sites within the Hell Creek Formation within southwestern North Dakota and northwestern South Dakota. This study found that specimens of M. thomasi were found in 17% of the sites examined, which demonstrated that it was somewhat widespread. However, the total number of these specimens formed only 0.66% of the overall fossil count, indicating that, while covering a wide geographic range, its population numbers were low (Pearson et al 2002, page 156).
Melvius chauliodous
A second species of Melvius called M. chauliodous was named eleven years afterwards in 1998 by Lance Grande and William E. Bemis. The species name chauliodous is ancient Greek for “prominent teeth”. Fossils are known from the Campanian Stage of the Hunter Wash Member of the Kirtland Formation of east-central New Mexico, and date to approximately 74 million years ago. It is almost identical to M. thomasi except for a slight difference in the shape of the postinfraorbital bone. This has led some to claim that this minor anatomical difference is not sufficient enough to warrant M. chaulidous’ status as a separate species. The holotype specimen is currently housed within the collections of the University of Kansas Museum of Natural History (collection ID code: KUVP 88378) (Grande and Bemis 1998, pages 401-405; Sullivan et al 2011, page 475).
Possible Additional Species
Fossils which had been ascribed to the sub-family Vidalamiinae have also been uncovered within the Cloverly Formation, which dates to the middle of the Cretaceous Period about 115-105 MYA. These fossils may or may not belong to another species of Melvius, but at the moment, these specimens are not distinctive enough to be positively identified as belonging to this or that particular species. The famous paleontologist John Ostrom, who named Deinonychus and Tenontosaurus, discovered the remains of a partial left dentary measuring 37.5 mm (collection ID code: YPM 5519). In 1970, he tentatively identified this jawbone as belonging to a fish in the super-family Amioidea (Ostrom 1970, pages 56-57). Additionally, seventeen teeth were uncovered from two localities (USNM Localities 42183 and 42222). In 2013, Oreska et al stated that these teeth belonged to the sub-family Vidalamiinae – the same family that Melvius belongs to – but it was not given a more specific identification than this (Oreska et al 2013, pages 267, 270). “These teeth possess labial and lingual carinae that expand downward from the apex (Fig. 3E), have transparent tips, and could derive from the dentary, premaxilla, maxilla, vomer, or dermopalatine. They are referred to Vidalamiinae based on the combined presence of an arrowhead-shaped tip and well-developed carinae” (Oreska et al 2013, page 270). A study conducted by Matt Carrano and his colleagues in 2016 determined that this as-yet-unidentified amiid bowfin was the most common fish species found within the Cloverly Formation based upon the abundant number of teeth which were found there (Carrano et al 2016, page 4).
Conclusion
Below is an illustration which I made of what Melvius would have looked like. The head shape is based upon the illustration seen in Bryant (1987), page 360. The body shape is based upon the related species Pachyamia mexicana. The illustration was made with No.2 pencil and colored pencils on printer paper.
Melvius. © Jason R. Abdale (April 9, 2023).
Bibliography
Bryant, Laurie Jean (1987). “A new genus and species of Amiidae (Holostei; Osteichthyes) from the Late Cretaceous of North America, with comments on the phylogeny of the Amiidae”. Journal of Vertebrate Paleontology, volume 7, issue 4 (December 1987). Pages 349-361.
Bryant, Laurie Jean (1989). “Non-dinosaurian lower vertebrates across the Cretaceous-Tertiary boundary in northeastern Montana”. University of California Publications in Geological Sciences, volume 134 (October 1989). Pages 1-107.
Carrano, Matthew T.; Oreska, Matthew P. J.; Lockwood, Rowan (2016). “Vertebrate Paleontology of the Cloverly Formation (Lower Cretaceous), II: Paleoecology”. Journal of Vertebrate Paleontology, volume 36, issue 2 (March 2016). Pages 1-12.
https://www.wm.edu/as/geology/documents/facultypubs/rowan/Carrano%20et%20al%202016.pdf.
Gilbert; Carter R; Williams, James D. National Audubon Society Field Guide to Fishes. New York: Alfred A. Knopf, 2002.
Grande, Lance; Bemis, William E. (1998). “A comprehensive phylogenetic study of amiid fishes (Amiidae) based on comparative skeletal anatomy: An empirical search for interconnected patterns of natural history”. Journal of Vertebrate Paleontology, volume 18, supplement 1 (1998). Pages 1-696.
Oreska, Matthew P. J.; Carrano, Matthew T.; Dzikiewicz, Katherine M. (2013). “Vertebrate Paleontology of the Cloverly Formation (Lower Cretaceous), I: Faunal Composition, Biogeographic Relationships, and Sampling”. Journal of Vertebrate Paleontology, volume 33, issue 2 (March 2013). Pages 264-292.
https://www.researchgate.net/publication/236886285_Vertebrate_Paleontology_of_the_Cloverly_Formation_Lower_Cretaceous_I_Faunal_Composition_Biogeographic_Relationships_and_Sampling.
Ostrom, John H. (1970). “Stratigraphy and Paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin Area, Wyoming and Montana”. Bulletin of the Peabody Museum of Natural History, Yale University, bulletin 35 (August 1970). Pages 1-234.
https://images.peabody.yale.edu/publications/bulletin/Bulletin35_1970.pdf.
Pearson, Dean A.; Schaefer, Terry; Johnson, Kirk R.; Nichols, Douglas J.; Hunter, John P. (2002). “Vertebrate biostratigraphy of the Hell Creek Formation in southwestern North Dakota and northwestern South Dakota”. In J. H. Hartman, J. R. Johnson, and D. J. Nichols (eds.), The Hell Creek Formation and the Cretaceous-Tertiary Boundary in the Northern Great Plains: An Integrated Continental Record of the End of the Cretaceous, Geological Society of America Special Paper 361 (2002). Pages 145-167.
https://www.researchgate.net/publication/236153389_Vertebrate_biostratigraphy_of_the_Hell_Creek_Formation_in_southwestern_North_Dakota.
Sullivan, Robert M.; Lucas, Spencer G.; Jasinski Steven E. (2011). “Preliminary observations on a skull of the amiid fish Melvius, from the Upper Cretaceous Kirtland Formation, San Juan Basin, New Mexico”. In R. M. Sullivan, S. G. Lucas & J. A. Spielmann (eds.), Fossil Record 3. New Mexico Museum of Natural History and Science Bulletin 53 (2011). Pages 475-483.
https://www.researchgate.net/publication/266885902_Preliminary_observations_on_a_skull_of_the_amiid_fish_Melvius_from_the_Upper_Cretaceous_Kirtland_Formation_San_Juan_Basin_New_Mexico.
Categories: Paleontology, Uncategorized
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