Reticulariina sp. ? brachiopod from the Chainman formation of Utah

I believe this next fossil is a Reticulariina sp. brachiopod but am not sure of the species. It comes from the Chainman formation of Utah which is lower Carboniferous in age (Mississippian epoch, Visean stage of the ICS or Mississippian period, Chesterian stage in the US). The shell is small, with a very convex pedicle valve and a flat to slightly convex brachial valve. It sort of resembles a Cyrtia sp. type brachiopod that occurred in the Devonian. Each valve has very coarse plications with 2-3 on each side of the median. There is a sulcus and fold structure present on the valves but it is only noticeable at the anterior margins. It is hard to see but it appears there are some sort of concentric growth lines decorating the shell surface as well. The posterior of the pedicle valve has a large triangular interarea under a beak that recurves back.

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

This specimen came from the Chainman formation at Conger Springs (west of Delta), Utah and is Carboniferous (Mississippian epoch, Visean stage of the ICS or Mississippian period, Chesterian stage in the US) in age.

Anthracospirifer sp. brachiopod from the Chainman formation of Utah

I believe this next brachiopod fossil is Anthracospirifer sp.. It comes from the Chainman formation at Conger Springs in Utah. The shell is missing part of a "wing" but enough is left to help identify it. The pedicle and brachial valves are equally convex, rectangular shaped and have coarse plications. A sulcus on the pedicle valve corresponds with a single fold on the brachial valve. The pedicle valve has a wide interarea with a recurved beak.

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

There are a number of known species of Anthracospirifer but little literature on what specific forms occur in the Chainman formation. One resource, "Mississippian Stratigraphy of the Diamond Peak Area, Eureka County, Nevada", Brew, David, 1971, Indicates that A. occiduus, A. pellaensis, A. increbescens and A. bifurcatus are found in equivalent strata in Nevada but I can find no clear illustrations of those species or those I find do not match what I have here..

The reference "Brachiopoda of the Amsden Formation (Mississippian and Pennsylvanian) of Wyoming.", MacKenzie Gordon, Jr., 1975 lists multiple species of Anthracospirifer, including A. occiduus but none seem to match my specimen.

This specimen came from the Chainman formation at Conger Springs (west of Delta), Utah and is Carboniferous (Mississippian epoch, Visean stage of the ICS or Mississippian period, Chesterian stage in the US) in age.

Cleiothyridina hirsuta brachiopod from the Chainman formation of Utah

Looking very much like an Athyris sp. brachiopod, this fossil is Cleiothyridina hirsuta.  It is a rounded to subovate shell with both the pedicle and brachial valve equally convex. The surface of each valve has concentric growth lines but no obvious costae or sulcus.

Brachial valve

Anterior

Pecidle valve

Posterior

Profile

I used the reference "Brachiopoda of the Amsden Formation (Mississippian and Pennsylvanian) of Wyoming.", MacKenzie Gordon, Jr., 1975 pg. 56, plate 7, fig 31, 38-40, 42-45, 58, 59 to identify this brachiopod. This specimen came from the Chainman formation at Conger Springs (west of Delta), Utah and is Carboniferous (Mississippian epoch, Visean stage of the ICS or Mississippian period, Chesterian stage in the US) in age.

Inflatia sp. brachiopod from the Chainman formation of Utah

I found this specimen of a spiny productid brachiopod at Conger Springs, Utah. I believe it is an example of the genus Inflatia. I am unsure as to the species because the preservation is not the best. It was a spiny brachiopod but not as spiny as a similar genus, Juresania.  The pedicle valve is very convex while the brachial valve is flat to slightly convex and the margins of both meet at a 90 degree angle to the brachial valve.  Both valves are decorated with linear costae but only the pedicle valve has spines. The spines appear somewhat randomly placed although there could be a pattern that I don't recognize.

Pedicle valve

Anterior

Brachial valve

Posterior

Profile

I used the reference "Brachiopoda of the Amsden Formation (Mississippian and Pennsylvanian) of Wyoming.", MacKenzie Gordon, Jr., 1975 pg. 36, plate 3, fig 1-9 to identify this brachiopod.
This specimen came from the Chainman formation at Conger Springs (west of Delta), Utah and is Carboniferous (Mississippian epoch, Visean stage of the ICS or Mississippian period, Chesterian stage in the US) in age.

Crurithyris sp.? brachiopod from the Chainman formation of Utah

This next brachiopod looks very similar to a genera called Crurithyris that is present in the Pennsylvanian. I can't locate any literature or examples from the Chainman formation at Conger Springs, Utah that indicate this could be any other genera. So I am tentatively labeling this as Crurithyris sp. The shell is small, wider than long with a very convex pedicle valve and a slightly convex brachial valve. The valves are smooth with no obvious ornamentation. The pedicle valve recurves back over the interarea and the margins of the valves are flat with no evidence of a fold or sulcus.

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

This specimen came from the Chainman formation at Conger Springs (west of Delta), Utah and is Carboniferous (Mississippian epoch, Visean stage of the ICS or Mississippian period, Chesterian stage in the US) in age.

Eumetria costata brachiopod from the Chainman formation of Utah

While search for fossils at Conger Springs, Utah I found lots of examples of these little brachiopods called Eumetria costata. They are small shells that are longer than wide with the widest point about midway between the umbo and the anterior margins. Each valve is roughly equally convex and has around 20 radiating costae on the surface. The umbo extends beyond the brachial valve and curves slightly to the point where the circular formen opening is located.

Specimen #1 - Brachial valve

Anterior

Pedicle valve

Posterior

Profile

Specimen #2 -Brachial valve

 Anterior

 Pedicle valve

 Posterior

 Profile

I used the reference "Geology of Millard County, Utah", Lehi F. Hintze & Fitzhugh D. Davis, 2003 pg. 106, fig.142 to identify these brachiopods. These specimens came from the Chainman formation at Conger Springs (west of Delta), Utah and are Carboniferous (Mississippian epoch, Visean stage of the ICS or Mississippian period, Chesterian stage in the US) in age.

Composita elongata brachiopod from the Chainman formation of Utah

Another Composita species that I found in the Chainman formation of Utah is Composita elongata. This species is narrower than some but this particular specimen has a very strong fold and sulcus that is well developed. According to MacKenzie (see below for reference), C. elongata may intergrade with C. subtilita (see previous post). This means that the two species sometimes share the same form but remain distinct.

I used the reference "Brachiopoda of the Amsden Formation (Mississippian and Pennsylvanian) of Wyoming.", MacKenzie Gordon, Jr., 1975 pg. 64, plate 10, fig 16-25 to identify this brachiopod.This specimen came from Conger Springs west of Delta, Utah and is Carboniferous (Mississippian epoch, Visean stage of the ICS or Mississippian period, Chesterian stage in the US) in age.

Pedicle valve

Anterior

Brachial valve

Posterior

Profile (with pedicle valve on top)

Profile (with brachial valve on top)

I used the reference "Brachiopoda of the Amsden Formation (Mississippian and Pennsylvanian) of Wyoming.", MacKenzie Gordon, Jr., 1975 pg. 64, plate 10, fig 16-25 to identify this brachiopod.

Composita subtilita brachiopod from the Chainman formation of Utah

Today I have a specimen of what I believe is Composita subtilita from the Carboniferous (Mississippian epoch, Visean stage of the ICS or Mississippian period, Chesterian stage in the US) rocks of Utah. It was found near Conger Springs which is about 63 miles (as the crow flies) west of the town of Delta in Millard County. The rocks exposed at Conger springs are the Chainman formation and are the youngest Mississippian layers before changing to the Pennsylvanian. The shell of Composita subtilita is round to ovate with a fold in the pedicle valve that corresponds to a sulcus in the brachial valve. The fold is shallow at the beak and gets gradually wider and deeper as it progresses to the anterior margins. Both valves are equally convex and are widest about mid way between the anterior and posterior.

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

I used the reference "Brachiopoda of the Amsden Formation (Mississippian and Pennsylvanian) of Wyoming.", MacKenzie Gordon, Jr., 1975 pg. 64, plate 10, fig 33-37 to identify this brachiopod.

Rhipidomella nevadensis brachiopod from the Chainman formation of Utah

So it has been a few months since I posted anything new. It's been a busy time for me at work and this has been stressing me out so I tend not to write much. But things seem to be improving and I've been able to get a decent queue of posts lined up so you'll be seeing regular updates for the next couple of months (hopefully!). Thanks for reading and I hope you enjoy my posts.

      While on vacation in Millard County, Utah this past September I had the option to collect at numerous well exposed sites all through the Confusion Range. These are a range of mountains that are just west of the more often visited House Range and the Wheeler Amphitheater (known for it's Cambrian Trilobite fauna). As my time was limited I could only visit one site and I choose Conger Springs as the geologic map showed rocks that ranged from the Devonian to Pennsylvanian periods could be exposed.

      The trip to get to the site took a couple of hours with the last 10 miles on gravel roads. The gravel roads were graded well enough but, once at the springs, I heard a hissing noise as I got out of my vehicle. The noise was constant so I knew it wasn't a snake and immediately turned my ear to listen at each tire on the rental SUV I was driving. Sure enough, one of the tires had been punctured by a sharp rock. I am not ashamed to say that I briefly panicked because I was traveling alone, it was ten miles to the nearest highway, seventy miles to the nearest garage and I was in a high desert environment. My initial thought was to immediately drive back to the highway in the hopes that the punctured tire, which was not flat in any sense yet, would hold out at least until I got there and could flag someone down. This is not as good a prospect as you might think. The road I had come out on was US 6/50 which is often described as "the loneliest stretch of road in America". Driving out to the turn off to Conger Springs I had seen or passed only one other vehicle in the hour long journey. Tamping down the anxiety I felt, I then wondered if the rental vehicle had a spare. Lucky for me it did and it was a full size spare to boot! So I set about changing the tire and made sure none of the other tires had any problems. Task completed, I could now turn my attention to the main reason I had come out to this remote location, to look for fossils. Here are a couple of pictures of the area around the springs.

Looking south past an old fence.

Looking north at Conger Mountain which is capped by the Pennsylvanian/Permian aged Ely formation.

      I was really hoping to find some Devonian fossils so I set out to hike to some nearby hills, that my geologic maps showed had the right age of rock. I spent a few hours wandering around the scrubby terrain looking for ANY signs of fossils but with no luck. This is often the case when trying to prospect for a new location or find an old, obscure site. I returned to my vehicle and decided, in a last attempt, to look around the immediate area as Mississippian aged fossils were supposed to be present nearby. I lucked out and found a small hillside that had a number of fairly well preserved fossils eroding out. The day was getting long and the sun starting to set in the sky so I only spent a hour or so collecting. I did not want to have to drive unfamiliar gravel roads in the dark. I managed to fill a small lunch baggie with miscellaneous brachiopod fossils and crinoid stems which was enough to call the trip a success.

      Once back home in Pennsylvania, I set about to try and identify the fossils I found. The book "Geology of Millard County, Utah" by Hintze, Lehi F. and Fitzhugh, Davis D., Bulletin 133, Utah Geological Survey, 2003. and the geologic maps produced by the Utah Geological Survey indicated I had collected in the uppermost Chainman shale (actually a formation) which was lower Carboniferous in age. With that information I did some Google searches to see if anyone had written a paper that listed fossils that could be found in that rock unit. I found in the United States Geological Survey Professional Paper 1368, "Late Mississippian Gastropods of the Chainman Shale, West-Central Utah", Gordon, MacKenzie, Jr. and Yochelson, Ellis L.,  1987, this paragraph which was extremely helpful:

The upper beds of the Chainman Shale are exposed in the vicinity of Conger Spring in the NE V4 NW lk sec. 2, T. 19 S., R. 17 W. Brachiopods of these beds are those of the Rhipidomella nevadensis Zone, the uppermost brachiopod zone in the Chainman, particularly that part of the zone in which the productoid Carlinia phillipsi (Norwood and Pratten) also occurs. A small area of hillslope about 1,000 feet (305 m) south by east from the spring has provided a large collection of brachiopods (USGS colln. 17021-PC). A partial section measured by Gordon in June 1959, shows that a fauna is weathering from 14 feet (4.3 m) of greenish-gray shale, the top of which is 22 feet (6.7 m) below the base of the Ely Limestone.

Armed with this info I did more searches for the "Rhipidomella nevadensis" zone in the hopes I could find a list of the fauna typical of that zone. Unfortunately I found nothing specific but several other publications did give me clues. The reports "Brachiopoda of the Amsden Formation (Mississippian and Pennsylvanian) of Wyoming.", MacKenzie Gordon, Jr., 1975 and "Mississippian Stratigraphy of the Diamond Peak Area, Eureka County, Nevada",  MacKenzie Gordon, Jr., 1971 were helpful as they either provided lists of fauna found in equivalent strata or had detailed descriptions and plates to which I could compare my finds.

In fact, I did find an articulated fossil brachiopod which does indeed look like a Rhipidomella species that I think may be Rhipidomella nevadensis.

Brachial valve

 Anterior

 Pedicle valve

 Posterior (sadly much of the posterior shell is missing from this specimen, lost to weathering)

 Profile

Over the next few weeks I'll be posting more of the fauna I found in the Chainman formation. Should anyone have more experience and knowledge about this locality or the fossils please contact me.