Posts treating: "Haragan formation"
Tuesday, 29 March 2016
I found a few of these tiny, elongated brachiopods while searching the Bois d'Arc formation. I believe it is called Camarotoechia haraganensis. It's a small shell that is longer than it is wide. Both valves are equally convex with strong costellae (or ribs as I sometimes call them). The sides of each valve are fairly flat and nearly at a right angle to the rest of the valve. On the pedicle valve, the beak extends well past the brachial valve with little to no curving with the umbo at the [...]
As I mentioned in the previous post, I found a few specimens of pelecypod in the Bois d'Arc formation that are just casts or molds that I can't really ID. This specimen looks like it may belong to the genus Nucula or Grammysia.This next specimen looks similar to a Modiomorpha sp.This last specimen is a real mystery to me. There is no surface ornamentation preserved but both valves are present. It has very convex valves with what appears to be a flat hinge line.I found the specimens shown on [...]
I found a few pelecypod mold and casts during my hunt among the rocks of the Bois d'Arc formation in Oklahoma. All are without shell material and some have little detail with which to help identify them. One group of specimens does have some detail and appears to belong to the genus Actinopteria and may be A. textilis. The fossils I found are all of single valves but show impressions of the interior or exterior of the left or right valves. The shells have an overall rectangular outline with a [...]
Views of the Mahantango [2016-03-19 08:01:00]
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(669 visits) 
Devonian,Silurian; DE,US
When I'm out collecting I often pick up anything that looks like it might be a fossil and sometimes I know what it is while other times it just looks similar to another shell. Such is the case with Coelospira virginia. This is a very small shell that I probably thought was an Atrypina sp. when I tossed it into my collecting bag. It wasn't until I got home and really looked closely at it that I saw there was a difference. White it does have the same rounded shape as Atrypina sp. with a wide fold [...]
Atrypina hami is an easy brachiopod to ID due to the wavy nature of the shell. It has a generally rounded appearance with flat to slightly concave brachial valve and a convex pedicle valve. The pedicle valve extends beyond the pedicle valve and curves just slightly at the umbo. both valves have widely spaced, concentric growth lines and a handful of very wide ribs that affect the margin of the shell. It's this wavy appearance and the obvious growth lines that make this brachiopod [...]
A highlight of my collecting trip to the Bois d'Arc formation was finding the tiny brachiopod Dicoelosia varica. It is somewhat common in certain horizons of the formation and I probably picked up a dozen or more specimens loose plus a number of specimens on matrix. such as the one below with three specimens.Dicoelosia varica is a member of Order Orthida and is very easy to identify. It is a small shell shaped like the letter "V" with two distinct. rounded lobes. Between the two lobes the shell [...]
I found a number of these round, nut like brachiopods while searching the Bois d'Arc formation in Oklahoma. They are called Sphaerirhynchia lindenensis and seem to have a bit of variability in their features. Overall the shells are rounded to subpentagonal in outline and rectangular to square in cross section. Both valves are convex and have strong, rounded ribs decorating the surface. The margins of both valves are flat except along the anterior margin where the shell develops "teeth" that [...]
The brachiopod genera Atrypa makes an appearance in the Bois d'Arc formation, as one would expect. It's pretty much an index fossil for the Devonian period as far as I'm concerned. In this case we have Atrypa oklahomensis. The shell is rounded with a very convex brachial valve and a slightly convex to flat pedicle valve. The surface of both valves have regularly spaced ribs and fine concentric growth lines. There is a small fold and sulcus present to some degree on every specimen I have found [...]
Views of the Mahantango [2016-03-04 09:01:00]
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(198 visits) Devonian; DE,US,IN
Another flat brachiopod from the class Strophomenata that can be found in the Bois d'Arc formation is Strophonella bransoni. It has a rounded to subrectangular shape with a (notably) convex brachial valve and concave pedicle valve. The surface of the valves have many thin costellae decorating it, which stand out in relief somewhat, and on some specimens very fine concentric growth lines can be seen. Amsden's original description for the species indicates that the pedicle valve has a small beak [...]
Views of the Mahantango [2016-03-01 09:01:00]
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(640 visits) Devonian,Silurian; CA,US
I believe that this next Brachiopod is an Eatonia sp. While Eatonia medialis is listed by Amsden* as being known from the Haragan and Bois d'Arc formations of Oklahoma, the specimen below does not appear to conform to specimens I have found in the Kalkberg formation of New York or Licking Creek formation of Virginia (both formations are correlative to the aforementioned Oklahoma formations).The shell is rounded to sub-pentagonal in shape with coarse plications. The pedicle valve has a sulcus [...]
Perhaps the most common fossil brachiopod to be found in the Bois d'Arc formation is Rhipidomelloides oblata. Most are small but some can get about an inch in width. The shell is rounded to subrectangular with both valves generally convex. A gentle curve is sometimes present in the anterior margin. The pedicle valve has a beak that recurves over the brachial valve. Both valves have fine striae and concentric lines decorating their surface.Pedicle valveAnteriorBrachial valvePosteriorProfileWhile [...]
The Bois d'Arc formation has some inarticulate brachiopods that can be found but they are often fragile and weather away quickly. I was fortunate enough to find two examples of varying preservation. I can't locate any literature that describes species that could be found and it appears that the inarticulate brachiopods were ignored by Amsden when he initially described the brachiopod fauna from the Lower Devonian of Oklahoma.The first is a Lingula type specimen. I am not sure if the shell is [...]
Orthostrophia strophomenoides is a species that I have not found anywhere else from the lower Devonian but is fairly prolific in the Bois d'Arc formation of Oklahoma. I have posted about specimens from the Haragan formation in the past but other than that I have not seen any specimens of the genus from elsewhere in the world. The shell of Orthostrophia strophomenoides is subrectangular in outline with both valves being slightly convex. The surface of the valves are decorated with coarse striae [...]
I've written about the brachiopod Meristella atoka from the Haragan formation of Oklahoma a few years back, but these next examples come from the Bois d'Arc formation. Both have the typical subtriangular to subpentagonal shape (this means they are roughly shaped like a triangle or pentagon when looking at a valve from the dorsal or ventral side), smooth shell with just a few concentric growth lines and a simple fold and sulcus. The latter feature is highly variable as can be seen in the two [...]
As may be expected, one of the more common brachiopod fossils from the Bois d'Arc formation is Leptanea rhomboidalis. The shell of the specimens I found are typical for the species with a rectangular outline when viewed from the dorsal or ventral side. Both valves are relatively flat with wide, concentric growth rings and decorated with fine striae The margins of both valves (except along the hinge) are turned 90 degrees from the rest of the shell and this is most noticeable at the [...]
Views of the Mahantango [2016-02-09 09:01:00]
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(176 visits) Devonian,Silurian; DE,US
The genus Anastrophia first becomes widely seen in the Silurian and it extends into the lower Devonian before disappearing from the fossil record. The specimens below are Anastrophia grossa from the Bois d'Arc formation of Oklahoma. The shell is subpentagonal in outline with coarse costae present on both valves. There is a shallow sulcus on the pedicle valve that becomes much more expressed at the anterior margin forming a "u" shape. The corresponding fold is also shallow. Both valves are [...]
While the majority of my vacation last fall was to Utah and Wyoming, I did a quick couple of days in Texas and Oklahoma. Texas was kind of a bonus for the visit as my primary goal was to collect in the prolifically fossiliferous exposures of lower Devonian aged rocks found around Clarita, Oklahoma. There are two main formations that are extremely productive, the Haragan formation and the Bois d'Arc formation. They are sequential formations, with the latter [...]
Today's fossil is Delthyris sculptilis which is an appropriate name due to the high relief and heavy decoration on the shell. D. sculptilis has a long hinge line connecting the pedicle and brachial valves. Each valve is deeply incised by plications to the point that there does not appear to be a lot of room for the body. The shell has very obvious growth lines that help decorate the shell and perhaps prevented predators or parasites from gaining a foothold.Brachial valveAnteriorPedicle [...]
Contrasting with the small brachiopod in yesterday's post, today I have Meristella obtusa from the Silurian aged (Wenlock epoch, Sheinwoodian to Homerian stage) Wenlock formation, near Dudley, England. The shell is smooth and round, about the same ratio wide as it is long. There is a wide but shallow sulcus and a heavily recurved umbo on the pedicle valve. Brachial valveAnteriorPedicle valvePosteriorProfileI have featured several species of Meristella on my blog before like Meristella atoka [...]
An ubiquitous member of many faunal assemblages of the early Paleozoic is Leptaena. It must have been quite the generalist because I've found it in rocks from the Ordovician through the Devonian. The specimen below is Leptaena depressa from the Silurian aged (Wenlock epoch, Sheinwoodian to Homerian stage), Wenlock formation near Dudley, England. The shell is rectangular in shape with wavy growth lines and very fine radial ribs. Most specimens also have a feature where the pedicle and brachial [...]
