Falcatus falcatus (St. John & Worthen 1883)

Taxonomy

Shark

Kingdom: Animalia
Phylum: Chordata Haeckel 1874
Class: Chondrichthyes Huxley 1880
Order: Symmoriiformes Zangerl 1981
Family: Falcatidae Zangerl 1990
Genus: Falcatus
Species: Falcatus falcatus
Author Citation (St. John & Worthen 1883)

Geological Time Scale

Eon: Phanerozoic
Era: Paleozoic
Period: Carboniferous
Sub Period: Mississippian
Epoch: Late
International Age: Serpukhovian

Stratigraphy

Big Snowy Group
Heath Formation

Provenance

Acquired by: Purchase/Trade

Dimensions

Length: 13 cm

Location

Bear Gulch
Fergus County
Montana
United States

• bear gulch
• carboniferous
• falcatus
• fergus county
• heath formation
• montana
• tff-oilshale-ch2523

Comments

Female, head disarticulated and displaced. The fish is embedded in a mass of filamentous algae.
Alternative combination: Physonemus falcatus.
"The genus Physonemus was originally erected for P. arcuatus by McCoy (1848) to receive elegant forwardly-curved, well omamented Paleozoic fin spines of unknown affìnities ... The Paleozoic fin spine Physonemus falcatus St. John and Worthen 1883, from the Valmeyeran St. Louis Limestone of St. Louis, Missouri, has been found on sexually mature males of a small, highly sexually dimorphic chondrichthyan from the Chesterian Bear Gulch Limestone of Montana" (Lund 1985, p.1).

Diagnosis from Lund 1985, p.3: “Small sharks, maximum known size 145 mm fork length, with forwardly-curved spines, inclined at mean angle of 14.5 degrees to the horizontal. Neither spine nor first dorsal fin present on juveniles below 124 mm length, nor on females. Males with elongate rostrum, denticles covering dorsum of rostrum, cranium and dista] portion of dorsal rod, females with short rostrum and devoid of denticles. Teeth delicate, cladodont, tooth whorls of larger, non-cladodont teeth external to jaws. Pectoral fin with five prearticular basals, a metapterygium bearing six radials, and an axis of seven elements with only one radial. Pelvic girdle supports 8—10 radials; clasper of male consisting of 6—8 axials and a three-part mixopterygium. Second dorsal fin of 12—14 well spaced radials followed by a triangular basal plate, l9—21 distal radials. Axial skeleton of 44 precaudal segments, 18 preural caudals and 16—18 ural caudals. Caudal fin deeply forked, equilobate, with no radials between dorsal and ventral lobes.”
Line drawing from Lund 1985, p. 13:

References:
St. John, O. H. and Worthen, A. H. (1875). Descriptions of fossil fishes. Geological Survey of Illinois 6:245—488.
St. John, O. H. and Worthen, A. H. (1883). Descriptions of fossil fishes; a partial revision of the Cochliodonts and Psammodonts. Geological Survey of Illinois 7:55—264.
Lund, Richard (1985). The morphology of Falcatus falcatus (St. John and Worthen), a Mississippian stethacanthid chondrichthyan from the Bear Gulch Limestone of Montana, Journal of Vertebrate Paleontology, 5:1-19, 
DOI: 10.1080/02724634.1985.10011842.