Monday, July 17, 2023

Devonian Orthocones

Devonian Actinoceratids in the Fitchville Formation on Wanlass Hill.  Found by David Johnson earlier this year and reported to me :)  I went out with him and a few other students to check them out earlier this year.


Also, some nice coral (Syringopora)


Monday, May 8, 2023

Early Triassic Stomatopod

Smith CPA, Aubier P, Charbonnier S, Laville T, Olivier N, Escarguel G, Jenks JF, Bylund KG, Fara E, Brayard A., 2023, Closing a major gap in mantis shrimp evolution - first fossils of Stomatopoda from the Triassic, Bulletin of Geosciences, volume 98, issue 1; pages: 95 - 110 

Mantis shrimps (Stomatopoda) are marine benthic predators well known for their raptorial claws that have, through time, evolved into unique structures with exceptional stunning, piercing or even dismembering functions. Known since the Carboniferous, Stomatopoda fossils have started providing insights into the rise of these predators, however, major gaps in the fossil record remain. In particular, neither Permian, nor Triassic specimens have ever been uncovered. Such a long hiatus strongly hinders our understanding of their evolutionary history, especially regarding the transition between Palaeozoic and Mesozoic forms. We here report two mantis shrimp specimens from the Early Triassic Paris Biota of Idaho, USA, formally described as Triassosculda ahyongi gen. et sp. nov., partially closing an over 100 myr gap in the fossil record. Despite being incomplete, these specimens present distinct and well-preserved diagnostic characters on the posterior trunk and the tail fan. The telson shows a triangular shape closely resembling that of Palaeozoic mantis shrimps. The broadness of both the pleon and anterior rim of the telson, however, differs from that of most Palaeozoic forms, which have an overall narrow telson, and is more similar to that of modern representatives of Stomatopoda. Additionally, the uropodal exopods of Triassosculda ahyongi gen. et sp. nov. presents a considerable number of movable spines that are common among Jurassic and more recent taxa, but that have never been reported among Palaeozoic Stomatopoda. These features further support and above all, allow temporal refinement of previously suggested evolutionary scenarios. In the latter, and as for other major clades of crustaceans, Stomatopoda are assumed to have evolved from a shrimp-like morphology with a narrow triangular telson to a more lobster-like one with a broad and rather square-shaped telson. Triassosculda ahyongi gen. et sp. nov. indicates this transition was underway by the Early Triassic.

Saturday, September 10, 2022

More Taxonomy

A new paper just out trying to update the nomenclature and authorship of ammonoids:

The higher taxonomic nomenclature of Devonian to Cretaceous ammonoids and Jurassic to Cretaceous ammonites including their authorship and publication

Hoffmann, René; Howarth, Michael K.; Fuchs, Dirk; Klug, Christian; Korn, Dieter

It may be the latest but it won't be the last.  I'm sure that just like those back in the fifties they're getting close to something natural. This should last 70 years just like the old scheme, with plenty of differing options in the interim.  

Thursday, July 21, 2022

Paris Biota Decapods

The Paris Biota decapod (Arthropoda) fauna and the diversity of Triassic decapods

We describe here the early Spathian (Early Triassic) Paris Biota decapod fauna from the western USA basin. This fauna contains two taxa of Aegeridae (Dendobranchiata), namely Anisaeger longirostrus n. sp. and Aeger sp. that are the oldest known representatives of their family, thus extending its temporal range by 5 Myr back into the Early Triassic. This fauna also includes two representatives of Glypheida (Pleocyemata) with Litogaster turnbullensis and Pemphix krumenackeri n. sp., confirming for the former and extending for the latter the temporal ranges of their respective superfamilies back to the Early Triassic. Overall, the Paris Biota decapods are some of the oldest known representatives of Decapoda, filling in an important gap in the evolutionary history of this group, especially during the Triassic that marks the early diversification of this clade. Additionally, we compile and provide overviews for all known Triassic decapods, which leads to the revision of four species of Middle and Late Triassic Aegeridae, and to a revised family assignment of a Middle Triassic Glypheida. Based on this refined dataset, we also investigate decapod diversity throughout the Triassic. We show that the apparent increase in decapod taxonomic richness is probably driven by the heterogeneity of the fossil record and/or sampling effort, and that the decapod alpha diversity is actually relatively high as soon as the Early Triassic and remains rather stable throughout the Triassic.

Friday, April 15, 2022

Cephalopod Phylogenetics

The more things are found to be the same the more they are found to be different. It may never end
Pohle et al. BMC Biology (2022) 20:88

Wednesday, March 9, 2022

Ammonite Chamber Internal Mold

An internal mold of an ammonite chamber. Left, lateral view, right, apertural view

Two views of an internal mold of one of the chambers from the phragmocone of an ammonite (Prionocyclus macombi Meek 1876).  The chamber was hollow and probably filled with gas and a little liquid while the animal was alive, and was probably empty of any solids after it died.  How long it sat empty on the seafloor, and while it was being buried under sediment is unknown. Eventually, it was filled with what we have here, dark sparry calcite crystals. I imagine the crystals grew from the inner walls of the chamber towards the center until it was completely filled. You can see the siphuncle at the top of the chamber (the keel here is missing), and on the bottom, in the apertural view, you can see a notch where the keel of the preceding whorl would have fit.

Ammonites preserved in limestone or concretions are more often found this way because the surrounding shell was preserved uncrushed as the matrix around the shell hardened. Those found in sandstone or shale many times have the phragmocone and most of the chambers crushed unless the chambers were filled with sediment.

Sunday, December 5, 2021

The Canadian System (Period) as proposed by Flower (1957)

Because the Cephalopods were so different, Rousseau H. Flower wrote proposing the Canadian System with four divisions of unspecified rank (Flower 1957 p. 17).  Quoting from Flower:

"Faunally, the Canadian is relatively isolated from the Ordovician above and is characterized by stocks of its own. In the cephalopods..., the Canadian-Ordovician boundary involves changes never lower than of generic rank, and generally of the rank of families and orders."

Someone looking at only, or mostly Cephalopod fossils could see the column this way. The four divisions are areas where Flower collected cephalopods. The Cassinian from the Ft. Cassin area in Vermont, the Jeffersonian from the Adirondacks in NY, the Demingian from the Florida Mts. in New Mexico, and the Gasconadian from the Ozark Mt. area of Missouri. I don't think his later collections in Utah and Nevada changed anything.  His boundary is just above Zone K, which is basically the Hesperonomiella minor bed (e.g. Li and Droser 1999) or the base of the Whiterockian Stage of the Ordovician.

Chart modified from Flower 1964 (p. 23, fig. 3) Ross-Hintze Zones on the right.

These days, the Canadian System of Flower (later referred to as the Canadian Series) has been replaced with the Ibexian Series (Ross et al., 1997) and the Lower Ordovician Series of the ICS.


Flower, R.H., 1957, Studies of the Actinoceratida, Memoir 2, New Mexico Bureau of Mines and Mineral Resources, Socorro, NM.

Flower, R.H., 1964, The Nautiloid Order Ellesmeroceratida (Cephalopoda), Memoir 12, New Mexico Bureau of Mines and Mineral Resources, Socorro, NM.

Li, X., and Droser, M.L., 1999, Lower and Middle Ordovician Shell Beds from the Basin and Range Province of the Western United States (California, Nevada, and Utah) PALAIOS, V. 14.

Ross, R.J., Jr, Hintze, L.F., Ethington, R.L., Miller, J.F., Taylor, M.E. & Repetski, J.E., 1997, The Ibexian, lowermost series in the North American Ordovician. United States Geological Survey Professional Paper, 1579-A.

Monday, November 8, 2021

Wiping the smile off the face of the horizontal Nautiloid

The cover of New Mexico Bureau of Mines & Mineral Resources Memoir 32 (1977), and the description from inside the front cover (below) (both used with permission from the New Mexico Bureau of Geology and Mineral Resources).  Showing the contented and smiling face of an orthoconic cephalopod with cameral (or siphonal) deposits counterweighting the gas-filled phragmocone letting it float horizontally and getting its face "out of the mud".  The non-counterweighted forms with disgusted frowns floating vertically (or about to).  I've had a smile on my face ever since first seeing this paper over 30 years ago just thinking of how happy the nautiloids on the cover were. 

Needless to say, I now have to re-arrange the thoughts of horizontal nautiloids having smiles and put the smile on the vertical nautiloid.

This might be just as hard as giving up the Geosynclinal Theory I was taught back in 1972.