Some Prionitids Lumped

With a few very narrowly defined species, The Prionitidae is a family of very closely related ammonoids.  However most collections, especially from the western US, always contained "Prionitid" or "Prionitid indet.", Prionitids with bullae or ribs, maybe nodes or tubercles, that just didn't fit with any of the other described genera or species.  With new collections from the Smithian (Early Triassic) Sinbad Formation around the Utah/Arizona border, we were able to synonymize all these with ammonoids described in 1929 by Asa Mathews.  By priority, Gurleyites smithi Mathews 1929 replaces Arctoprionites resseri (Mathews 1929).  With a very wide range of intraspecific variation, the new taxon will fit just about anything that doesn't fit in one of the other defined taxa.

See our new paper here.

New middle and late Smithian ammonoid faunas from the Utah/Arizona border: New evidence for calibrating Early Triassic transgressive-regressive trends and paleobiogeographical signals in the western USA basin

 

 

Sexual Dimorphism in Ammonites

Sexual dimorphism as represented by the ammonite Yezoites frontierense (Cobban 1952)

Macroconch (female) 38mm on the left, microconch (male) 18mm on the right

Previously referred to Scaphites frontierense, presumably, the female was much larger to carry eggs.  Many extant cephalopods (the Blanket Octopus for example) show the same relative (?) dimorphism with the males much smaller than the females.

Giant Cephalopod Midden or Mosasaur Feces

Back in 2011, and again in 2013,  Mark and Dianna McMenamin postulated a giant cephalopod created a midden with the bones of Icthyosaurs.  The internet came alive with much fanfare,  comments, news, etc. probably because of the size the cephalopod would have had to been to form such a midden.

Well, back in 1954 two well-known cephalopod paleontologists, John B. Reeside and William A. Cobban (one prominent then, and one then becoming prominent), postulated  that concretions in the Mowry and Aspen Shales were possibly "fecal matter of some large carnivore--reptile, fish or cephalopod", and "The diet of the carnivore would have had to be almost entirely ammonites and fish, and the carnivore would perhaps, like the living octopus, have had to frequent a sort of lair, to which it repaired and in which the mucous-bound fecal matter could accumulate" (Reeside & Cobban 1954, 1960).

Some of these concretions were over 2 meters in diameter, so you have a mosasaur like that in the movie Jurassic World, a very large fish, or another Kraken.  Though nowhere near the size of the Triassic Kraken.

I wonder, had there been the internet in 1954, would there have been the same or similar response?

Plate 28 from Reeside & Cobban 1960

The fossils were found in fossiliferous concretions containing thousands of ammonites, along with a few bivalves and bones of a few fish and a few pterodactyls in some.  These fossiliferous concretions were rare among the many non-fossiliferous concretions.  The authors reported that some concretions contained well over 4200 ammonites, from 10mm to 400mm in diameter, and these probably represented less than half the original content.  Most fossils were preserved in 3D with most of the living chambers crushed or missing, and some had damage to the phragmocone.

It was these fossils that Reeside and Cobban used in their 1960 paper to show the advantages of a population approach in taxonomy to a strictly typological one, especially for ammonoids with a large amount of intraspecific variation.  A significant moment for the lumpers of the world.

References:

McMemamin, M. A. S., and McMenamin, D. L. S., 2011.  Triassic Kraken: The Berlin Icthyosaur Death Assemblage Interpreted as a Giant Cephalopod Midden: Geological Society of America Abstracts with Programs, Vol. 43, No. 5, p. 310

McMemamin, M. A. S., and McMenamin, D. L. S., 2013.  The Kraken's Back: New Evidence Regarding Possible Cephalopod Arrangement of Icthyosaur Skeletons: Geological Society of America Abstracts with Programs, Vol. 45, No. 7, p. 900

Reeside, J. B., Jr., and Cobban, W. A., 1954. Ammonite accumulations in the Cretaceous Mowry and Aspen shales: Science, v. 119, p. 255.

Reeside, J. B., Jr., and Cobban, W. A., 1960. Studies of the Mowry Shale (Cretaceous) and Contemporary formations in the United States and Canada: U.S. Geological Survey Professional Paper 355, 126 p.

Ammonoid Family Reunions (revised Feb. 11, 2021)

Two family reunions occurred in the distant past, the Prionitids and the Cardioceratids, this is a short review of those events.  The thing that draws attention to these two reunions is that members of the two families gathered in abundance and almost to the mutual exclusion of other families.  Both are recorded in rocks representing a relatively short time-span, a single biozone, the smallest standard unit used in biostratigraphy, representing a few hundred thousand years more or less.

PRIONITIDAE Hyatt, 1900:

Prionitids

About 251mya the Family Prionitidae met in what is now the western USA.  This event took place all over the world (? Tethys and northern Panthalassa), but for this report I will stick to the event and those attending in the western US.  This Family started with the Genus Meekoceras in the Early Smithian and culminated with the family reunion in the Late Smithian with at least 6 species in 4 genera with a few in open nomenclature.

·         Anasibirites Mojsisovics, 1896                     2 species

·         Hemiprionites Spath, 1929                            2 species

·         Wasatchites Mathews, 1929                          1 species

·         Gurleyites Mathews, 1929                            1 species

With a few Xenoceltitids and Hedenstroemiids.  (See Brayard et al. 2013, Jattiot et al. 2017, Mathews 1929, Smith 1932, for composition of the fauna and Jattiot et al. 2015 for a revision of Anasibirites, Brayard et al. 2020 for a revision of Gurleyites) Recorded in the Thaynes Group, UAZ₅ of Jattiot et al. 2017

Prionitid localities (from Brayard et al 2013)

CARDIOCERATINAE Siemiradzki, 1891:

Cardioceratids

About 162mya the Subfamily Cardioceratinae gathered in the Sundance Sea that covered much of Montana and Wyoming along with parts of Utah, Colorado, Idaho, and South Dakota.  This reunion started with Quenstedtoceras and Pavloviceras coming in from the north in Montana, and closed with 18 species in 4 genera and 3 subgenera. 

·             Cardioceras Neumayr & Uhlig, 1881         

o   Scarburgiceras Buckman, 1924    6 species

o   Cardioceras Buckman, 1923         1 species

o   Goliathiceras Buckman, 1919       2 species

·             Scoticardioceras Buckman, 1925                     2 species

·            Vertebriceras Buckman, 1920                          4 species

·            Cawtoniceras Buckman, 1923                         3 species

With rare Perisphinctids.  (see Imlay 1982, and Reeside 1919 for composition of the fauna, and Howarth 2017 for a revision of the Stephanoceratoidea)  This reunion is recorded in the cordatum Zone of the Swift Formation of Montana, the Sundance Formation of Wyoming, Montana, and South Dakota, and the Stump Formation of Utah, Idaho, and Colorado. 

Cardioceratid localities (from Imlay 1982)

Localities for the reunions in the western US are shown, but the events were probably global.

References:

Brayard, A., Bylund, K. G., Jenks, J., Stephen, D. A., Olivier, N., Escarguel, G., Fara, E. & Vennin, E., 2013, Smithian ammonoid faunas from Utah: implications for Early Triassic biostratigraphy, correlations and basinal paleogeography. Swiss Journal of Paleontology 132:141-219

Brayard, A., Olivier, N., Vennin, E., Jenks, J., Bylund, K., Stephen, D., McShinsky, D., Goudemand, N., Fara, E., Escarguel, G., 2020. New middle and late Smithian ammonoid faunas from the Utah/Arizona border: new evidence for calibrating Early Triassic transgressive-regressive trends and paleobiogeographical signals in the western USA basin. Global and Planetary Change 192

Howarth, Michael K., 2017, Part L, Revised, Volume 3B, Chapter 6: Systematic descriptions of the Stephanoceratoidea and Spiroceratoidea. Treatise Online 84:1–101, 66 fig.

Imlay, R. W., 1982, Jurassic (Oxfordian and Late Callovian) Ammonites from the Western Interior Region of the United States, U.S.G.S. Professional Paper 1232, 44 p., 26 pls.

Jattiot, R., Bucher, H., Brayard, A., Monnet, C., Jenks, J. F. & Hautmann, M., 2015, Revision of the genus Anasibirites Mojsisovics (Ammonoidea): an iconic and cosmopolitan taxon of the late Smithian (Early Triassic) extinction. Papers in Palaeontology 2 (1):155 –188.

Jattiot, R., Bucher, H., Brayard, A., Brosse, M., Jenks, J.F., Bylund, K.G., 2017, Smithian ammonoid faunas from northeastern Nevada: implications for Early Triassic biostratigraphy and correlation within the western USA basin. Palaeontographica A (Paleozoology, Stratigraphy), doi: 10.1127/pala/2017/0070.

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, 46 p., 11 pls.

Reeside, J. B., Jr., 1919, Some American Jurassic Ammonites of the Genera Quenstedticeras, Cardioceras and Amoeboceras, Family Cardioceratidae, U.S.G.S. Professional Paper 118, 64 p., 24 pls.

Smith, J. P., 1932, Lower Triassic Ammonoids of North America, U.S.G.S. Professional Paper 167,199 p., 81 pls. 

PRIONITE-MARE

The Family PRIONITIDAE is a nightmare of taxonomy.  The amount of intraspecific variation, or even intrageneric variation is overwhelming.  Most generic assignments are based on the shape, size, amount, and/or lack of ribs, bullae, nodes, whether they cross the venter or stop short, whether the nodes are mid flank or start near the umbilicus, whether the inner whorls or the outer whorls are smooth.  A lot of specific and generic assignments are arbitrary, a slightly arched venter instead of a flat venter is cause for different generic assignment of forms that basically look exactly alike. 

Tozer, 1994, in his monograph of Canadian Triassic Ammonoids, discussed the differences between Population Taxonomy and Typological Taxonomy and admitted that his classification, especially of the Prionitidae, was arbitrary, and to use a strictly typological taxonomy would mean almost every specimen was a seperate species.  He also talked about using the typological method just to show what the taxon looked like.

To see a Prionitid, it is easily assigned to the Prionitidae, and the beds containing it are easily assigned to the Late Smithian, and usually to the biozone and/or beds known for the Prionitidae.  Is it really necessary to split them into a bunch of different species or genera?  I suppose I could live with a few nominal species divided amongst a few genera for the time being, at least until the family is revised and a more natural classification determined.  Still, what a Prionite-mare.

For references see THIS old post, along with an old rant of the same topic. ;)

Intraspecific variation in Forresteria

Forresteria alluaudi (Boule, Lemoine & Thevenin) 1907, from depressed, evolute, spinose to compressed, involute, almost smooth, a nice range of intraspecific variation. Is it any wonder why these, and some like these, were placed in 4 separate species in 3 separate subgenera (Reeside, 1932), Barroisiceras (Forresteria) forresteri, B. (F.) stantoni, B. (Alstadenites) sevierense, and B. (Harleites) castellense. Kennedy, Wright and Klinger (1983) put them all in synonymy with F. alluaudi.

Many ammonoids show intraspecific variation, including, for example, Placenticeras from the Cretaceous and, at least in my mind and experience, Anasibirites and Wasatchites from the Early Triassic. Found in the same bed or group of beds worldwide, to see one would tell you precisely what age the rock they were in is. Unlike the Triassic example, where there are differences in ornamentation and shape from one part of the world to another (maybe some kind of latitudinal or provincial thing), F. alluaudi is basically the same, that is different, wherever found.

Forresteria was named after the late Robert Forrester of Salt Lake City, Utah, who found the type material in southern Castle Valley, eastern Sevier County, Utah.

Polymorphism, Intraspecific Variation, Dimorphism, Covariation

A few terms that at first seem to be self explanatory. The first two seem to be interchangeable as do the last two. Reading a paper the other day, the title used one term but the body of the paper was filled with the other term. Could someone fill me in on the correct usage of these four terms, are they really all about the same. For years an ammonite was an ammonite until I found out that some were ammonoids, actually all are ammonoids and I was just using the wrong term for the whole group. It just took an explanation... like the one I am looking for now.
There are a few posts in this blog labeled with the term "Polymorphism", this term seems to have a deeper meaning than I was intending, so from now on this term will be replaced with "Intrapsecific variation", though not as snazzy sounding it probably is more in line with my intended meaning.