Erythrinolepis was a prehistoric freshwater fish which lived in western North America during the middle to late Cretaceous Period approximately 100-66 million years ago.
The name Erythrinolepis was coined by the paleontologist Theodore D. A. Cockerell in 1919. The name means “Erythrinus scale”, in reference to the similar appearance of the preserved fossil scales to those belonging to the living genus Erythrinus, known as the Red Wolf Fish. However, Cockerell noted that the scales were also comparable to those within the family Cyprinidae (carp) and to the genera Phractolaemus (the African Hinge-Mouth) and Pantodon (the African Freshwater Butterfly Fish) (Cockerell 1919, page 182).
The extant genus Erythrinus, which T. D. A. Cockerell noted possessed scales which were most similar in shape to those of Erythrinolepis, currently belongs to the family Erythrinidae (Cockerell 1919, page 182). However, Erythrinus was formerly placed within the family Characidae. Characidae is a large family of tropical freshwater fishes native to Central and South America, and are commonly referred to as “tetras” within the aquarium trade. The prehistoric genus Erythrinolepis has been referred to within scientific reports as a “characin” (Schaeffer 1947, page 27) and as a “characoid” (Novacek and Marshall 1976, pages 1-12). This would make Erythrinolepis a member of the family Characidae or the sub-family Characinae, both of which are exclusively freshwater.
However, despite its freshwater affinities, all known fossils of Erythrinolepis have been found in saltwater deposits (Cockerell 1919, pages 182-183; Mindat. “Erythrinolepidae”). One explanation for this is that Erythrinolepis was a marine genus in contrast to its exclusively freshwater brethren, but a more likely explanation is that these are fossils of individuals who inhabited freshwater environments, died, and were then swept out to sea. If this explanation is correct, then this would suggest that Erythrinolepis inhabited rivers instead of ponds and lakes.
There are two species within this genus: E. mowriensis and E. chicoensis. Both are known exclusively from fossilized fish scales. No skeletal fossils are known (Cockerell 1919, pages 182-183).
- Erythrinolepis mowriensis was found in Wyoming within the rocks of the Mowry Shale, which was deposited within the Mowry Sea. The Mowry Shale is the uppermost depositional layer which was laid down within the Mowry Sea, and dates to the uppermost part of the Albian Stage of the Cretaceous Period, approximately 100 MYA. Its scales measured 5-7 mm in diameter (Cockerell 1919, page 182; Ludvigson et al 2010, page 10).
- Erythrinolepis chicoensis was found in California within the Moreno Formation, which is part of the Chico Group. The Moreno Formation dates to the Maastrichtian Stage of the late Cretaceous, 70-66 MYA. Its scales measure 10-11 mm in diameter (Cockerell 1919, pages 182-183; Bartow 1996).
The fact that there is a substantial gap in geologic time between these two species is concerning. It suggests that there may be other species of Erythrinolepis which inhabited western North America during the intervening time.
When it comes to reconstructing what Erythrinolepis looked like in life, we need to delve into speculation. It has been claimed that this genus belonged to the sub-family Characinae, but there is numerous morphological variation within this group. Just for the sake of argument, let’s assume (and I cannot stress enough that this is an assumption) that Erythrinolepis lay within the archetypal tribe Characini, and would likely have been similar in appearance to the archetypal extant genus Charax. How may we determine its size based upon only a handful of preserved fish scales? A paratype specimen of the species Charax awa had a recorded total length of 2.45 inches (62.2 mm), but other examined specimens reached almost twice this size at 4.72 inches (120 mm) (Guimarães et al 2018). The largest scales on the paratype measured approximately 0.04 inches (1 mm) in diameter. Using a ratio of 1:62.2, and scaling it up to a total length of 120 mm, this produces a scale diameter size of 1.93 mm. If Erythrinolepis followed a Charax-type bodyplan, and if the proportions between the two were identical, then this would mean that Erythrinolepis mowriensis was 3.62 times larger than Charax awa, and would have measured at 17.12 inches (435 mm), and likewise Erythrinolepis chicoensis would have measured 5.7 times larger than Charax awa, and would have measured at 26.9 inches (684 mm). Those are some BIG tetras! However, as I mentioned earlier, these measurements are based upon the assumption that the genus Erythrinolepis looked similar in appearance to the extant genus Charax. Until complete or reasonably complete skeletal fossils are found, these measurements will need to be taken with a large dose of caution.
Below is an illustration of what Erythrinolepis might have looked like, based upon the living genus Charax. The illustration was made with No.2 pencil and colored pencils on printer paper.
Erythrinolepis. © Jason R. Abdale (November 20, 2023).
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Bibliography
Bartow, J. A. (1996). “Geologic map of the west border of the San Joaquin Valley in the Panoche Creek-Cantua Creek area, Fresno and San Benito Counties, California”. U.S. Geological Survey Miscellaneous Investigations Series Map, I-2430.
https://ngmdb.usgs.gov/Prodesc/proddesc_13036.htm.
Cockerell, T. D. A. (1919). “Some American Cretaceous fish scales, with notes on the classification and distribution of Cretaceous fishes”. U. S. Geological Survey. Shorter Contributions to General Geology, professional paper 120. Pages 165-206.
https://www.google.com/books/edition/Professional_Paper/43fdNoV0ybIC?hl=en&gbpv=0.
Guimarães, Erick Cristofore; De Brito, Pâmella Silva; Ferreira, Beldo Rywllon Abreu; Ottoni, Felipe Polivanov (2018). “A new species of Charax (Ostariophysi, Characiformes, Characidae) from northeastern Brazil”. Zoosystematics and Evolution, volume 94, issue 1 (February 1, 2018). Pages 83-93.
https://zse.pensoft.net/article/22106/.
Ludvigson, Greg A.; Witzke, Brian J.; Joeckel, R. M.; Ravn, Robert L.; Phillips, Preston Lee; González, Luis A.; Brenner, Robert L. (2010). “New Insights on the Sequence Stratigraphic Architecture of the Dakota Formation in Kansas–Nebraska–Iowa from a Decade of Sponsored Research Activity”. Current Research in Earth Sciences, Bulletin 258, part 2. Pages 1-35.
https://www.kgs.ku.edu/Current/2010/Ludvigson/Bull258part2.pdf.
Novacek, Michael J.; Marshall, Larry G. (1976). “Early Biogeographic History of Ostariophysan Fishes”. Copeia, volume 1976, issue 1 (March 12, 1976). Pages 1-12.
https://www.jstor.org/stable/1443767.
Schaeffer, Bobb (1947). “Cretaceous and Tertiary Actinopterygian Fishes from Brazil”. Bulletin of the American Museum of Natural History, volume 89, article 1 (April 30, 1947). Pages 1-40.
https://core.ac.uk/download/pdf/18222965.pdf.
Mindat. “Erythrinolepidae”. https://www.mindat.org/taxon-P355209.html.
Categories: Paleontology, Uncategorized
DINOSAURS AND BARBARIANS 
So lovely! I love all your illustrations, but I especially love your fish reconstructions. They have a certain lifelike quality to them that is every bit as lovely as some of the illustrations I’ve seen in “field guides”. I am curious, have you ever had a museum approach you for reconstructions? Your illustrations have that quality I could easily imagine seeing on a museum plaque. 🙂
Thank you for your kind words. I’m glad that you enjoy my prehistoric fish illustrations. Yes, I have been contacted by museums. Once every three or four years, someone will reach out to me and ask if they can use one of my drawings in an exhibit. Recently, paleontologists have started contacting me (twice this year), and have asked if they can use my artwork in their publications. I’m hopeful that I’ll get noticed more by the academic community and get more art commissions. Who knows – maybe one day I’ll even be asked to pitch in as a research assistant.