Adult size in Scaphites

Three adult specimens of Scaphites showing the size range.  The two on the left are probably progenetic dwarfs of contemporary full size species.  Pteroscaphites pisinnus (far left) from the Scaphites whifieldi Zone, undetermined example (center) from the Prionocyclus hyatti Zone, and Scaphites carlilensis (right) from the Prinocyclus macombi Zone.  Only adults grow a hook for a body chamber.  Sexual dimorphs have been reported for most Scaphites, with microconchs being about the same size as Macroconchs but a lot less inflated.  The genus Yezoites may show dimorphic size differences comparable to that shown above, but that is for another post.

Ugly Map Colors

Too bad modern geology is taking a step backward with their geologic mapping colors.  I have yet to see an official standard calling out the new colors. You used to get a choice at stratigraphy.org, but no more.  Are they using a traditional system for the sake of tradition under the guise of priority.  This is almost as bad as illustrating ammonoids upside down of their assumed life position (again, mainly tradition).  It is like moving away from Metric Units back to Imperial feet and inches.  Why random colors?  The divisions are called Systems or in the case of rock units, Series.  Why wouldn't the colors look better in order or series?

CGMW		USGS
	Quarternary
	Neogene
	Paleogene
	Cretaceous
	Jurassic
	Triassic
	Permian
	Pennsylvanian
	Mississippian
	Devonian
	Silurian
	Ordovician
	Cambrian
	“preCambrian”

I tried to match the colors from the latest time scale from www.stratigraphy.org for the CGMW colors, and from the pdf linked below for the USGS colors

Hopefully no rocks on your map from the Cretaceous, Mississippian, or Cambrian come in contact with each other, they would be difficult to separate.

CGMW		USGS
	Cretaceous
	Mississippian
	Cambrian

How about Jurassic, Pennsylvanian, and Silurian?

CGMW		USGS
	Jurassic
	Pennsylvanian
	Silurian

Why even use colors to distinguish different Formations or Series if they are so similar to others?

Are the old Standards to be changed?
The USGS published some suggestions back in 2005.

USGS Colors (pdf)

And the Geologic Data Subcommittee (GDS) of the Federal Geographic Data Committee (FGDC)

published standards for GIS in 2008.
Are these going to change?  Will they use the random color system of the CGMW?

Some pages (just a few I've run across so far) already using the CGMW colors:
This map (from SVP) was modified from an existing map and strat column with the new colors.
Macrostrat using the new colors.

I think it is unfortunate that these new colors are being adopted, and it seems to me a step backwards.

Whine over :(

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. 

Website back!

The website

www.ammonoid.com

Fossil Cephalopods in Utah

is back up and running

Fish near the Early Triassic Equator!

Romano, C., Jenks, J., Jattiot, R., Scheyer, T., Bylund, K., & Bucher, H. 2017. Marine Early Triassic Actinopterygii from Elko County (Nevada, USA): Implications for the Smithian equatorial vertebrate eclipse. Journal of Paleontology, 1-22. doi:10.1017/jpa.2017.36

Abstract

The Early Triassic vertebrate record from low paleolatitudes is spotty, which led to the notion of an ‘equatorial vertebrate eclipse’ during the Smithian. Here we present articulated ray-finned fishes (Actinopterygii), collected from the marine Lower Triassic Thaynes Group at three new localities in Elko County (Nevada, USA), which were deposited within the equatorial zone. From the Smithian of the Winecup Ranch, we describe two partial skulls of the predatory actinopterygian Birgeria (Birgeriidae), attributed to B. americana new species and Birgeria sp. Birgeria americana n. sp. is distinguished from other species by a less reduced operculogular series. With an estimated total length of 1.72–1.85m, it is among the largest birgeriids. We confirm that Birgeria encompasses species with either two or three rows of teeth on the maxilla and dentary, and suggest that species with three well-developed rows are restricted to the Early Triassic. From the latest Smithian of Palomino Ridge, we present a three-dimensional, partial skull of the longirostrine predator Saurichthys (Saurichthyidae). This and other occurrences indicate that saurichthyids were common in the western USA basin. From the early late Spathian of Crittenden Springs, we describe a posterior body portion (Actinopterygii indet.). This find is important given the paucity of Spathian osteichthyan sites. We provide a summary of Early Triassic vertebrate occurrences in the United States, concluding that vertebrate fossils remain largely unstudied. The presence of predatory vertebrates in subequatorial latitudes during the Smithian confirms that Early Triassic trophic chains were not shortened and contradicts the ‘equatorial vertebrate eclipse’.

An Early Triassic Starfish from Utah

The Starfish shortly after mechanical decomposition of a limestone slab in the field near Torrey, Utah.

Superstesaster promissor gen. et sp. nov., a new starfish (Echinodermata, Asteroidea) from the Early Triassic of Utah, USA, filling a major gap in the phylogeny of asteroids

Loïc Villier, Arnaud Brayard, Kevin G. Bylund, James F. Jenks, Gilles Escarguel, Nicolas Olivier, Daniel A. Stephen, Emmanuelle Vennin, and Emmanuel Fara

Journal Of Systematic Palaeontology

Unexpected Early Triassic marine ecosystem

Our latest work.

Artistic reconstruction of the Paris Biota. Artistic view of the early Spathian diversified and complex marine ecosystem of southeastern Idaho as revealed by the Paris Biota (with permission of Jorge Gonzalez).

A. Brayard, L. J. Krumenacker, J. P. Botting, J. F. Jenks, K. G. Bylund, E. Fara, E. Vennin,
N. Olivier, N. Goudemand, T. Saucède, S. Charbonnier, C. Romano, L. Doguzhaeva, B. Thuy,
M. Hautmann, D. A. Stephen, C. Thomazo, G. Escarguel, Unexpected Early Triassic marine
ecosystem and the rise of the Modern evolutionary fauna. Sci. Adv. 3, e1602159 (2017).

In the wake of the end-Permian mass extinction, the Early Triassic (~251.9 to 247 million years ago) is portrayed as an environmentally unstable interval characterized by several biotic crises and heavily depauperate marine benthic ecosystems. We describe a new fossil assemblage—the Paris Biota—from the earliest Spathian (middle Olenekian, ~250.6 million years ago) of the Bear Lake area, southeastern Idaho, USA. This highly diversified assemblage documents a remarkably complex marine ecosystem including at least seven phyla and 20 distinct metazoan orders, alongwith algae.Most unexpectedly, it combines early Paleozoic and middle Mesozoic taxa previously unknown from the Triassic strata, among which are primitive Cambrian-Ordovician leptomitid sponges (a 200–million year Lazarus taxon) and    gladius-bearing coleoid cephalopods, a poorly documented group before the Jurassic (~50 million years after the Early Triassic). Additionally, the crinoid and ophiuroid specimens show derived anatomical characters that were thought to have evolved much later. Unlike previous works that suggested a sluggish postcrisis recovery and a low diversity for the Early Triassic benthic organisms, the unexpected composition of this exceptional assemblage points toward an early and rapid post-Permian diversification for these clades. Overall, it illustrates a phylogenetically diverse, functionally complex, and trophically multileveled marine ecosystem, from primary producers up to top predators and potential scavengers. Hence, the Paris Biota highlights the key evolutionary position of Early Triassic fossil ecosystems in the transition from the Paleozoic to the Modern marine evolutionary fauna at the dawn of the Mesozoic era.