Monday, March 26, 2007

Triassic Paleoenvironment, Paleogeography and Shell Beds

A list of some references for the anasibirites beds

Roger L. Batten and Wm. Lee Stokes, 1986, Early Triassic gastropods from the Sinbad member of the Moenkopi Formation,San Rafael Swell, Utah. American Museum Novitates no.2864, .33 p.

Ron Blakeys web site.

DIANA L. BOYER, DAVID J. BOTTJER and MARY L. DROSER, 2004, Ecological Signature of Lower Triassic Shell Beds of the Western United States, PALAIOS, v. 19; no. 4; p. 372-380

Carr, T. R. and Paull, R. K., 1983, Early Triassic stratigraphy and paleogeography of the Cordilleran Miogeocline, in Reynolds and Dolly, eds., Mesozoic paleogeography of the west-central United States: Denver, Rocky Mountain Section of the Society of Economic Paleontologists and Mineralogists, Rocky Mountain Paleogeography Symposium 2, p. 39-55

Margaret L. Fraiser, Richard J. Twitchett, David J. Bottjer, 2005, aUnique microgastropod biofacies in the Early Triassic: Indicator of long-term biotic stress and the pattern of biotic
recovery after the end-Permian mass extinction, C. R. Palevol 4, 475–484


Nützel, A. 2005. A new Early Triassic gastropod genus and the recovery of gastropods from the Permian/Triassic extinc−
tion. Acta Palaeontologica Polonica 50 (1): 19–24.

Woods A. D. and Bottjer, D. J., 2000, Distribution of Ammonoids in the Lower Triassic Union Wash Formation (Eastern California): Evidence for Paleoceanographic Conditions During Recovery from the End-Permian Mass Extinction: PALAIOS, V 15, p.535-545

Anasibirites-Wasatchites a polymorphic species?

Placenticeras syrtale dimorphs (top) and Anasibirites and Wasatchites (bottom)

With the amount of intermediate forms between Anasibirites kingianus (Waagen) 1895, and Wasatchites perrini Mathews 1929, is it reasonable to consider them as a dimorphic/polymorphic species?

From the website: "Because of the variable morphology in some populations all specimens are a seperate species, or all are one species with variable morphology. Mathews (1929) described (a) 32 species of Anasibirites, 5 species of Gurlyeites, 9 of Hemiprionites "Goniodiscus" and 1 of Kashmirites, and (b) 4 species of Wasatchites, 3 of Kashmirites and 1 of Keyserlingites, from Cephalopod Gulch near Salt Lake City, Utah. Later workers placed alot of them (a) in synonomy with Anasibirites kingianus (Waagen) and (b) in Wasatchites. In the Anasibirites Beds (about 300mm thick) of the Confusion Range of western Utah. there are representatives of all these genera, they grade from Hemiprionites to Anasibirites to Gurleyites to Wasatchites with intermediates between each."
Silberling (in Hose and Repenning, 1959) idententified these as Anasibirites kingianus and Wasatchites meeki without reference to any intermediate forms. See the two papers by E.T. Tozer (1971 and 1994) to see how he deals with these genera.

For reference, the Santonian (Late Cretaceous) ammonite Placenticeras syrtale is a polymorphic species which has been referred to many names of many ages (Kennedy and Cobban 1991, Kennedy Landman & Cobban 2001, Kennedy, Hancock, Cobban & Landman 2004, Wolleben 1967), to find one by itself you would be unable to place it in time or one of a number of subspecies described by Wolleben. There are 2 basic morphotypes of P. syrtale, a smooth shelled form (P. planum) and an ornamented form (P. syrtale, P. guadalupae, P. pseudocostatum, P. sancarlosensis etc.) much like the forms of Anasibirites and Wasatchites. The species or subspecies of P. syrtale exist in time for about 8 my with known ancestors and descendants and those of Anasibirites and Wasatchites for maybe 1 my, and I know of no ancestors or descendants.



Kennedy, Hancock, Cobban and Landman, 2004, A revision of the ammonite types described in F. ROEMER’S ‘Die Kreidebildungen von Texas und ihre organischen Einschlüsse’ (1852), Acta Geologica Polonica, No. 4, pp. 433-445
Kennedy, W. J., and W. A. Cobban, 1991. Upper Cretaceous (upper Santonian) Boehmoceras fauna from the Gulf Coast region of the United States. Geol. Mag. 128: 167–189.

Kennedy, W. J., Landman, N. H., and Cobban W. A., 2001, Santonian Ammonites from the Blossom Sand in Northeast Texas, American Museum Novitates, No. 3332, 9 p.

Wolleben, J. A., 1967. Senonian (Cretaceous) Mollusca from Trans-Pecos Texas and northeastern Chihuahua, Mexico. J. Paleontol. 41:1150–1165.

Mathews, Asa A. L., 1929, The Lower Triassic Cephalopod Fauna of the Fort Douglas Area, Utah, Walker Museum Memoirs Vol.1 No.1 University of Chicago Press

Hose, R. K., and Repenning, C. A., 1959, Stratigraphy of Pennsylvanian, Permian, and Lower Triassic Rocks of the Confusion Range, West-Central Utah, A.A.P.G. Bulletin vol. 43, no. 9

Tozer, E. T., 1971, Triassic Time and Ammonoids: Problems and Proposals, Canadian Journal of Earth Science, 8

Tozer, E. T., 1994, Canadian Triassic Ammonoid Faunas, GSC Bulletin 467

Tuesday, March 20, 2007


In the Anasibirites beds of the Confusion Range is a serpenticone ammonoid I refer to Wyomingites. I cannot see any constrictions on the early whorls (maybe just an artifact of preservation) so I am hesitant to refer it to Xenoceltites. Boreoceras, as figured by Dagys 1999, and the fossils in the Confusion Range look to be congeneric if not conspecific. However, the name Boreoceras is preoccupied by an Ordovician endocerid. So I guess I will keep it referred to Wyomingites until I get the whole thing clarified.

Reference: Dagys, A., 1999, Evolution of the Family Sibiritidae and Detailed Biostratigraphy of the Siberian Upper Olenekian (Triassic), in Advancing Research on Living and Fossil Cephalopods, ed. F. Olóriz and F. Rodriguez-Tovar, 109-123. New York: Kluwer Academic/Plenum Press.

See Here for an update

Monday, March 19, 2007

Scaphites renamed

I just got a copy of this paper:

Cooper, M. R., 1994, Towards a phylogenetic classification of the Cretaceous ammonites III, Scaphitaceae: Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 193 (2), 165-193.

referenced from Cobban, W.A., Walaszczyk, Ireneusz, Obradovich, J.D., and McKinney, K.C., 2006, A USGS zonal table for the Upper Cretaceous middle Cenomanian−Maastrichtian of the Western Interior of the United States based on ammonites, inoceramids, and radiometric ages: U.S. Geological Survey Open-File Report 2006-1250, 45 p.

I cant figure out why Cobban et. al. only noted the new genera Cooper proposed. It seems to me to note them is to accept them.

I think I will change them on the website when I get some time. The changes would be as follows:

The species carlislensis, warreni, ferronensis and whitfieldi will be referred to Coloradoscaphites.

Pteroscaphites is unchanged

The species preventricosus and impendicostatus will be referred to Anascaphites

The species depressus will be referred to Clioscaphites

The species vermiformis will be referred to Billcobbanoceras

The species uintensis, frontierensis and hippocrepis will stay in Scaphites

And the species praespiniger will stay in Trachyscaphites.

The species binneyi and tetonensis really dont fit in Anascaphites or Billcobbanoceras, Cooper placed them both in Anascaphites tentatively, they seem to be more like the later except the hook dont touch the phragmocone.

The Beginning

The start of the ammonoidea blog. More to come.