STUNNING Squatinactis Paleozoic Shark Fossil

"Spectacular soft tissue preservation from Bear Gulch"

Part and Counterpart Specimen

Squatinactis caudispinatus (AKA Squatinactis montanus)

Class Chondrichthyes, Order Squatinactida, Family Squatinactidae

Geological Time: Mississippian (~320 m.y.a.)

Size (25.4 mm = 1 inch): Fossil is 185 mm long (tip of nose to tip of tail along backbone) by 85 mm wide at pectoral fins on a 220 mm by 210 mm and 170 mm by 140 mm matrix pair

Fossil Site: Heath Shale Formation, Bear Gulch Limestone, Fergus County, Montana

Fossil Code: BGF571

Price: Sold

Squatinactis Paleozoic Shark FossilThe Bear Gulch Limestone is a deposit of some 70 square km in extent and 30 m in depth that has been a source of one of the most diverse assemblages of fossil fish with some 110 species having been described over the past 30 years. Most were new to science, and provided a unique view of the marine environment of Mississippian times. Fine preservation of both fish and invertebrates is a hallmark of these deposits, presumably due to an anoxic depositional environment.

This specimen is a most unusual shark with a batoid morphology. This is the first example found by my field Squatinactis from Bear Gulchcollector in a 30 year career, and joins only THREE OTHERS I know about in the literature. To date no evidence of pelvic fins has been found. While the other specimens were in part less complete, the degree of preservation seen here seems indicative that it did not have them. It presumably sculled along the bottom seeking prey. Note the incredible details to the fin rays and coloration, as well as the skeletal structure, amazing for a specimen composed of cartilage. The Gill structure, eyes, vertebral column, dermal denticles, and jaws are all readily seen. Note too the robust shoulder girdle that supported the flambouyant pectorals. The teeth are most likely contained within the jaw cartilage, and are indicated by the nodules contained therein. Note also the spine in the tail which is exposed at the side of the matrix that is the source of the species name and the lateral line canal which extends along the posterior third of the tail. Restoration has been minimal: both sides have had repairs to the matrix. The A side (above left) has a restoration to the tip of the complete pectoral and tail and a small portion of the tail where a natural crack resulted in loss of material, while the B side (above right) has had the tail restored. I will be glad to supply photos from the preparator that detail the restoration as outlined.

Annals of the Carnegie Museum, Volume 45, pp 43-55, Dec 27,1974
Journal of Vertebrate Paleontology, Volume 8, pp 340-343, Sept 1988.

Fish Fossil Sales

click to enlarge fossil pictures

Part - Side A
Counterpart - Side B

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