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Chimaeroids (Ratfishes) A new taxon of cartilaginous fish from the Smoky Hill Chalk
Copyright © 2006-2010by Mike Everhart
Page created 08/26/2006Last updated 02/24/2010
LEFT: Hydrolagis trolli painting by Ray Troll, a newly named species of modern ratfish from New Caledonia. © Ray Troll, used with permission. Read more about this new species on TrollArt.com |
PUBLICATION (March, 2008):
Cicimurri, D. J., D. C. Parris and M. J. Everhart. 2008. Partial dentition of a chimaeroid fish (Chondrichthyes, Holocephali) from the Upper Cretaceous Niobrara Chalk of Kansas, USA. Journal of Vertebrate Paleontology 28(1):34–40.
Although there have been many species of chimaeroids around since the Triassic, their remains are relatively rare in the fossil record. Chimaeroids are cartilaginous fish, closely related to sharks, and thus most chimaeroid remains are limited to teeth (tritors), dorsal fin spines and paired jaw plates. Ratfish have three pairs of jaw plates (vomerines, palatines and mandibulars). Although the jaw plates (see below) appear to be bone, they are actually composed of well-calcified cartilage. The "teeth" (tritors) on these jaw plates are composed of even tougher hypermineralized cartilage. Modern ratfishes use their crushing dentition to feed on hard shelled prey. Example of a modern ratfish: Chimaera monstrosa – Linnaeus 1758 (Rabbit fish). Go here for more information about modern chimaeroids: Dr. Dominique Dagit
Systematics Phylum: Chordata Class: Chondrichthyes Huxley, 1880 Superorder: Holocephali Bonaparte, 1832 Order: Chimaeriformes Obruchev, 1953 Family Callorhynchidae Garman, 1901 Subfamily: Edaphodontinae Stahl 1999 Edaphodon laqueatus |
THE SMOKY HILL CHALK CHIMAEROID The remains of FHSM VP-16685 were recently collected from the Smoky Hill Chalk and were identified first by Ken Carpenter (Denver Museum of Nature and Science) in August, 2006. They were also independently identified a couple of days later by David Parris (New Jersey Museum of Natural History) and David Cicimurri (Bob Campbell Geology Museum, Clemson University). Based on a comparison with the type specimen of Edaphodon laqueatus (Leidy 1873 - see below) in the Academy of Natural Sciences of Philadelphia, we now believe the two individuals are closely related.
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LEFT: FHSM VP-16685 is only the second known remains of a ratfish
(chimaeroid) from the Smoky Hill Chalk. The first, a large, dorsal fin spine (BMNH P 10343), was collected by English
immigrant H.T. Martin along Hackberry Creek in Gove County about 1900, and was acquired by
the British Museum of Natural History (see also
Stahl, 1999, fig. 143). The fin spine is approximately 45 cm (18 in) long. This
specimen was collected within ten miles of the FHSM VP-16685 material and at approximately
the same horizon. (Photo credit: British Museum of Natural History, London). Note that Handel Tong (H.T.) Martin worked for many years as a collector for the University of Kansas Museum of Natural History and was the preparator of the type specimen of Dolichorhynchops osborni (KUVP 1300). |
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LEFT: KUVP 1136 - Ichthypriapis hubbsi; A chimaeroid clasper described by Hibbard in 1942 (Figs. 1-4). The specimen was collected by G.F. Sternberg in Logan County about 1912. It had been associated with a specimen of Protosphyraena gladius (KUVP 465), but remained unidentified until Hibbard decided it was probably part of a chimaeroid. Adapted from a photo by Matt Friedman. |
| RIGHT: Figure 21 and 22 of Plate XIX modified from Leidy 1873
showing a medial view (21) and an occlusal view (22) of the right volmerine of the
type specimen of Edaphodon laqueatus (ANSP 5324). The specimen was discovered by
Dr. William Spillman of Columbus, Mississippi. See Manning (1994) for a biography of
Dr. Spillman. Leidy's original name for the specimen was Eumylodus laqueatus
but it was later "lumped" into Edaphodon. A more recent photo is HERE Leidy's caption for these figures reads: Fig. 21, 22. Eumylodus laqueatus: Mandible [vomerine] two-thirds natural size. From the Cretaceous formation of Mississippi, discovered by William Spillman. |
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LEFT: The paired vomerines of the new specimen (FHSM
VP-16685), in lateral view. The vomerines fit together along the curved edge and
the blunt ends form the upper "beak" of the fish. The right palatine was also
collected, but the left palatine and both mandibulars are missing. (Scale = cm) RIGHT: The paired vomerines of the new specimen, in mesial view (another view here) and the right palatine. It is difficult to estimate the size of the fish on the basis of these mouth parts but I am guessing that this individual would have been more than 4 feet in length, somewhat larger than most modern species. (Scale = cm) |
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LEFT: A close up of the right palatine in oral view. Note the
widely spaced, oblong areas where the cartilage is roughened. These are where the tritors
("teeth") are formed. The tritors are used for crushing and grinding prey.
In this specimen, much of the tritor material appears to have been lost during
preservation. (Scale = cm) RIGHT: Close-up of the right vomerine showing serrated bite marks attributable to a scavenging by a Squalicorax sp. shark. Both of the vomerines show shark bite marks. (Scale = mm) |
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LEFT: Top - Close up of the left vomerine in lateral view. Note
that only 4 small, circular tritors were found on the left vomerine (five on the right). Bottom: A close-up of the right vomerine of FHSM VP-16685 showing five circular patches where the tritors were originally attached to this tooth plate. The oval outline indicates the larger and anteriormost tritor on the beak of the vomerine. (Scale = mm) |
Credits: Copy of figures from Leidy 1873 provided by Earl Manning.
Other Oceans of Kansas webpages on Late Cretaceous fish:
Field Guide to Sharks and Bony Fish of the Smoky Hill Chalk
Sharks:
Bony Fish
Plethodids:
SUGGESTED REFERENCES:
Cicimurri, D. J., D. C. Parris and M. J. Everhart. 2008. Partial dentition of a chimaeroid fish (Chondrichthyes, Holocephali) from the Upper Cretaceous Niobrara Chalk of Kansas, USA. Journal of Vertebrate Paleontology 28(1):34–40.
Cope, E.D. 1875. The vertebrata of the Cretaceous formations of the West. Report, U. S. Geological Survey Territory (Hayden). 2:302 p, 57 pls. (see pages 281-293 for descriptions of several chimaeroids, mostly from the east coast)
Duffin, C.J. 1996. Holocephalans in the Staatliches Museum für Naturkunde in Stuttgart: 4. The earliest German chimeroid. Stuttgarter Beitr. Naturk. Ser. B., Nr. 240, 10 pp., 4 fig.
Duffin, C.J.
2001. A chimaerid (Holocephali, Chimaeriformes) vomerine toothplate from the Upper Cretaceous of Belgium. Palaeontology, 44(6)1179-1188.Hibbard, C.W. 1942 A new chimaeroid fish from the Niobrara Cretaceous of Logan County, Kansas. University Kansas Science Bulletin 28-2(11):237-240, 4 fig.
Hoganson, J.W. and Erickson, J.M. 2005. A new species of Ischyodus (Chondrichthyes: Holocephali: Callorhynchidae) from Upper Maastrichtian shallow marine facies of the Fox Hills and Hell Creek formations, Williston Basin, North Dakota, USA. Palaeontology 48(4), 709-721.
Hussakof, L. 1912. The Cretaceous chimaeroids of North America. Bulletin of the American Museum of Natural History 31: 195-228.
Leidy, J. 1873. Contributions to the extinct vertebrate fauna of the western interior territories. Rept., U.S. Geological Survey Territories (Hayden) 1:358 pp., 37 pls.
Manning, E. M. 1994. Dr. William Spillman (1806-1886), pioneer paleontologist of Mississippi. Mississippi Geology. 15(4):64-69.
Parmley, D. and Cicimurri, D.J. 2005. First record of a chimaeroid fish from the Eocene of the southeastern United States. Journal of Paleontology 79(6): 1219-1221.
Stahl, B.J. 1999. Chondrichthyes III. Holocephali. Handbook of Paleoichthyology 4. Verlag Dr. Friedrich Pfeil, Munich. 164 p.
Stahl, B.J. and Parris, D.C. 2004. The complete dentition of Edaphodon mirificus (Chondrichthyes: Holocephali) from a single individual. Journal of Paleontology 78(2), 388-392.
