This is Mazon Monday post #177. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Elonichthys hypsilepus was described in 1900 by Oliver Perry Hay (1846 - 1930) in the paper "Descriptions of some vertebrates of the Carboniferous age, Proceedings American Philosophical Society, Philadelphia". Hay was an American herpetologist, ichthyologist, and paleontologist. He worked at the Field Columbian Museum, which became the Field Museum of Natural History. He served as Assistant Curator of Zoology and wrote "On Some Collections of Fishes" in 1896 and "Bibliography and Catalogue of the Fossil Vertebrata of North America" in 1902.
Photo from the Hay family collection showing Oliver Perry Hay at his desk at the Carnegie Institution circa 1920. Permission to share openly granted by great-granddaughter Donna Hay.
E. hypsilepus appears on page 140 in Jack Wittry's "The Fossil Fauna of Mazon Creek".
Elonichthys hypsilepus, Hay 1990
'Elonichthys' hypsilepus is a small, deep-bodied fish. The length and height of the head are approximately equal. The long, forked caudal fin has an extremely elongated upper lobe. The triangular dorsal fin has 25 fin rays (range 20-28) and arises at about the midlength of the body from a raised base. The anal fin extends from opposite the back of the dorsal fin to the caudal fin. It has a long base with an average of 43 fin rays. The pelvic fins have long bases as well; the fin rays are jointed and forked or bifurcated at the end away from the body. The pectoral fins have fin rays graded from very long in front to short in back. Fulcra or spine-like scales are located in front of all the fins. Scales develop from a line roughly following the lateral line. Those growing along the bottom of this line are decorated with striae while those toward the posterior of the fish are completely covered with denticles. Specimens have been found at Pits 6 and 11 and collecting sites along the Mazon River. E. perpennatus is a juvenile form now included with E. hypsilepus.
E. peltigerus and E. hypsilepus are the most common paleoniscoid fish in the Mazon Creek Biota and occur in both the marine and freshwater faunas. Scale ornamentation and number of fin rays are useful characteristics for specimen identification, as are the position and shape of the fins. Only large scales are found as evidence of adult fish. Intact specimens are deemed juveniles based on incomplete scale formation. E. peltigerus also occurs at sites in Ohio, Pennsylvania, and England.
E. hypsilepus is included in chapter 17 "Fishes" written by David Bardack in the "Richardson's Guide to the Fossil Fauna of Mazon Creek" on pages 232-233.
"Elonichthys" hypsilepus, Hay
This fish shows a deep abdomen and very elongated upper lobe of the caudal fin. The long based anal fin with 32 to 50 rays is barely separated from the caudal fin. The anal fin starts opposite the middle or posterior part of the triangular dorsal fin which has 20 to 28 rays and arises from an elevated base opposite the posterior part of pelvic fin. The pectoral fin base is lobed. The first ray of this fin is elongated, closely jointed, and covered anteriorly by small, thickly packed fringing fulcra. Small ridges are seen on the ventral parts of the scales. The front end of the head is rounded, and the posterior part of maxilla is 8 times deeper than the anterior part. There are about 25 specimens from Braidwood and Essex faunas. "E." perpennatus Eastman is a juvenile form and is included in "E." hypsilepus. Amblypterus macropterus? (Newberry and Worthen) also belongs in "E." hypsilepus (Schultze and Bardack, 1987). Holotype. USNM 4848, Mazon Creek, Grundy County.
Specimens
From Wittry's "The Fossil Fauna of Mazon Creek".
Page 121 from georgesbasement.com.
ESCONI member Jake Fill, Fossil Friday #173
