West Texas Echinoid Trip

[Uncle Siphuncle]

I made my first trip to a certain part of West Texas yesterday and dragged a buddy along. I found some old documentation on several areas but really didn't know what to expect. After hours of driving we showed up around daylight and the first site appeared to be fenced. We followed our gut instinct and went to a nearby roadcut in the Boquillas formation, an Eaqle Ford equivalent (90 MYA).

In short the first echinoids, Hemiaster jacksoni, were found within minutes, and we felt drawn to explore other sites after 2 or 2 1/2 hours, but not before hauling off 800-1000 echinoids from this site which appeared to have never been collected. In addition to the well preserved H. jacksoni which were presented loose and in clusters from juvie through adult, I noticed micro Coenholectypus echinoids hiding in the matrix and ultimately bulk sampled the layer they came from. I also took 3 unidentified Holasterids. The latter 2 types of echie are not nearly as well known in this formation; in fact I've seen no reference to them in this age.

From there a cut in the Buda limestone gave up an ammonite, crab claw, and a few rough echies. The Del Rio fm gave up lots of micro pyritized gastropod slabs, something possibly of interest to JKFoam. I've included an image. Also, our final stop in an Edwards fm equivalent rudist reef coughed up a couple nice albeit small Goniopygus echies.

This was my first trip this area, and in many cases my first visit to these formations, and we had a blast. Not every day of prospecting works out this well. In fact last weekend didn't produce much paydirt. In all the excitement I lost my chisel and misplaced my wallet - OUCH! I get pretty stupid sometimes when the collecting is good.

[Uncle Siphuncle]

More pics.

The chunks of matrix shown all have multiple echinoids in them like the close up shown. It will take me a while to prep all this stuff but should be pretty cool when done, especially the multiple specimen nodules.

[ebrocklds]

as always, great stuff dan. keep up the good work saving all those fossil from the elements. someones got to do it!!

i really like the tiny ones. just something about small fossils?

brock

[Mike Murphy]

Hey Dan:

It appears that this was a very productive collecting trip for you in West Texas. The abundance of exposures and the prolific fauna are the things that I missed about West Texas after I moved to Okahoma. I have collected the same Boquillas Formation (actually the Rock Pen member of the Boquillas Formation) and collected the same types of echinoids, only about 20 years ago. Actually, it is likely that my specimens were collected from the same roadcut as you collected yours since the accessible exposures of the Rock Pen member are limited. The 5 holasterids I have identified as Isomicraster rossi Cooke. The 8 near-micro holectypoids I have (with some reservation) identified as Coenholectypus cf bullardi Ikins. You might research these descriptions for your unidentified echinoids. Let me know what you determine on the identification your Boquilas holasterids and holectypoids. In addition to hundreds of Hemiaster jacksoni Maury, I also collected a specimen that was virtually identical to Smiser's 1936 description of Leiostomaster bosei. I have labelled it as such, but it may just be that this specimen is a large, aberrant Hemiaster jacksoni Maury.

It was amazing comparing the sheer numbers of echinoids found in the Rock Pen member of the Boquillas as compared to the relative absence of echinoids in the Boquillas further west and to the Eagle Ford group of North Texas.

Most of my multiples of my Hemiaster jacksoni collection are still firmly imbedded in matrix after 20 years. I did limited cleaning on these, but was only been able to partially expose them in the surprisingly hard and adherent sandy limestone and marl found in the Rock Pen member. It will be interesting to see how you pursue the exposure of these echinoids. Please keep us apprised as to your progress and procedures.

By the way, examine the "gastropods" on the slab in the photograph closely, especially the aperture ends. I think that these gastropods are actually macroscopic foraminiferans. Haplostiche texana (Conrad) is an index foram for the upper Washitan and are abundant in certain Washitan beds (Weno, Pawpaw and Del Rio equivalents especially) in West Texas.

Regards,

Mike

[Uncle Siphuncle]

Mike

You answered many of the questions I failed to articulate in my post. Thanks! Being new to the Boquillas, I'm not sure what member I was in. It was a lot more marly than the other flaggy exposures I saw. There were 2 lithologies present: soft marl I could split with bare fingers and pluck out individual echinoids, and harder nodules. I don't think they were terribly hard as I dropped one and it broke into many pieces. It looked like it would yield easily to my scribe. Some of the loose echies cleaned up with a toothbrush and water. I'm hoping that a brass brush scrub and blast of baking soda will do the trick in short order. As for the nodules, I hope to be able to scribe around them a little to expose them better then cut the base flat and finish blast them for free standing displays.

I looked at Akers to compare periproct position with my specimens. Although it is not noted as an Eagle Ford form, Coenholectypus nanus seems to closely resemble what I found as the periproct cuts deeply into the margin. In fact it is almost centered on the margin in all my specimens, while that of C. bullardi is said to cut slightly into the margin. Are your specimens handy for comparison? Do you think its possible that we have 2 different species? I was intrigued by everything we found.

Can you describe the lithology of the Rock Pen? The Atlas of TX map doesn't call the members by name, but mentions the presence of 4 members. Also, where is this member stratigraphically in comparison to the base of the formation? If I found a rarely exposed member I'll write it off to serendipity as a didn't exactly know where I was going. Research got me in a high percentage area but with no knowledge of lithology or stratigraphic level I had to fly seat of the pants, picking what looked "echinoidy" to me in the first rays of dawn.

My only other experience with the Kbo was a couple years ago on CTPS trip to Study Butte. While everyone else combed the valley, I billy goated up the mountain side for some solitude only to find the brownish limestone caprock loaded with calcitic ammonites equivalent to the Upper Britton forms of Dallas Co (Allocrioceras, Worthocers, Metoicoceras). The rest of the club thought I had inside information, but it was really dumb luck. Any idea with this member may be?

Hey Dan:

It appears that this was a very productive collecting trip for you in West Texas. The abundance of exposures and the prolific fauna are the things that I missed about West Texas after I moved to Okahoma. I have collected the same Boquillas Formation (actually the Rock Pen member of the Boquillas Formation) and collected the same types of echinoids, only about 20 years ago. Actually, it is likely that my specimens were collected from the same roadcut as you collected yours since the accessible exposures of the Rock Pen member are limited. The 5 holasterids I have identified as Isomicraster rossi Cooke. The 8 near-micro holectypoids I have (with some reservation) identified as Coenholectypus cf bullardi Ikins. You might research these descriptions for your unidentified echinoids. Let me know what you determine on the identification your Boquilas holasterids and holectypoids. In addition to hundreds of Hemiaster jacksoni Maury, I also collected a specimen that was virtually identical to Smiser's 1936 description of Leiostomaster bosei. I have labelled it as such, but it may just be that this specimen is a large, aberrant Hemiaster jacksoni Maury.

It was amazing comparing the sheer numbers of echinoids found in the Rock Pen member of the Boquillas as compared to the relative absence of echinoids in the Boquillas further west and to the Eagle Ford group of North Texas.

Most of my multiples of my Hemiaster jacksoni collection are still firmly imbedded in matrix after 20 years. I did limited cleaning on these, but was only been able to partially expose them in the surprisingly hard and adherent sandy limestone and marl found in the Rock Pen member. It will be interesting to see how you pursue the exposure of these echinoids. Please keep us apprised as to your progress and procedures.

By the way, examine the "gastropods" on the slab in the photograph closely, especially the aperture ends. I think that these gastropods are actually macroscopic foraminiferans. Haplostiche texana (Conrad) is an index foram for the upper Washitan and are abundant in certain Washitan beds (Weno, Pawpaw and Del Rio equivalents especially) in West Texas.

Regards,

Mike

[Mike Murphy]

Dan:

I will have to do some serious digging back through my texts and papers (many of which have been in storage since a house fire in 2000) to find the references on the "Rock Pen" member of the Boquillas Formation. There was no specific mention of the marly member in the "Geology of Terrell County" nor in the "Geology of Valverde County". The information might be in the UT publications, "The Geology of Texas, Volume I" or in "The Geology of Texas, Volume II". The information that I had handy were the notes that I kept in my echinoid collecting journal from when I lived in West Texas. As best as I remember, the Rock Pen member was a local facies change, possibly a lentil, from the normal limestone flags encountered in the Boquillas from the Pecos River area westward through the Big Bend. The lithology was a yellow to tan sandy to marly limestone that occurred as marl beds with thin interbedded nodular limestone. The facies was reportedly of shallower water origin than the deep water flag facies normally encountered in the Boquillas. It seems that the Rock Pen member was the uppermost identified Eagle Ford group strata below the Austin Chalk. In fact, if memory serves me right, the Rock Pen member was exposed in a road cut on the west side of a large canyon and the next roadcut on the east side of the large canyon, which was slightly higher topographically, was Austin Chalk. I collected several small ophiuroids (Ophiura texana) in a slab from the Austin Chalk at that locality.

I have not collected from the brown limestone caprock that you referred to in the Study Butte area, nor do I have any specific knowledge as to the stratigraphy of that zone. I will try to determine what I can concerning that caprock exposure where you found the ammonites. Most of my collecting in the Study Butte and Terlingua area was from the Boquillas flag facies, the marine Pen Formation, the lower marine Aguja Formation and from the terrrestrial upper Aguja Formation.

As I stated, my identification of the 8 holectypoids that I collected as Coenholectypus bullardi was made with reservation. I used Akers also in trying to identify the holectypoids. Their very small size (largest specimen was only 3 millimeters in diameter) made more detailed identification difficult. As you noted, the appearance is similar to Coenholectypus nanus Cooke from the Pawpaw Formation, including the marginal incision by the periproct. The size was similar also to the smaller Coneholectypus nanus that occurred en masse in slabs much like the juvenile Goniophorus sp in the middle Del Rio. The larger specimens (5mm+) of Coenholectypus nanus that I collected from the Pawpaw in Fort Worth had periprocts that only slightly incised the margins. It may be that the deep marginal incision may be a temporary property of the juvenile forms and that subsequent plate growth might force the periproct lower on the margin. The very small holectypoids from the Boquillas might represent juvenile forms.

Many of the Hemiaster jacksoni that were found loose readily cleaned with a brass brush, but the brass brush provided only limited benefit in exposing and cleaning the clsutered specimens in the harder limestone nodules. The limestone did not want to release from the shell of the echinoids. Air abrasion may help. Let me know how the scribe works with the echinoids. If i can come up with a better way to expose the echinoids, I may dig mine back out of storage.

Let me know how the echinoid preparation works out and also let me know if you find anything else on the holasterids and the holectypoids.

Regards,

Mike

[Uncle Siphuncle]

Mike

I may be confusing my formations a little. Not having much experience in west TX, I have to first ask if the Boquillas and Boquillas flags are different formations as I may have collected the ammonites in the latter if they are indeed different. I'd infer from the ammonites that they were coincident with whatever was going on in Dallas in Upper Britton times, but then again I've not spoken with anyone well versed about it until now.

I had concluded also yesterday that the echies came from a shallower facies based on lithology. Have you heard of ammonites or shark teeth coming from the flags? Just curious.

The biggest Coenholectypus I've found so far is about 6 mm the smallest is about 2 mm. I expect to find many more when splitting my bulk sample.

I'll experiment first with baking soda then with dolomite on the echies. I've only brushed a few so far. The small size makes them hard to deal with, i.e. I'm brushing my skin more than the test. Maybe I'll set up some sort of soft jaws in a set of pliers and go from there. Clearly I have lots of experimenting to conduct. If mechanical means fail I'll attempt a KOH treatment and see if the tests hold up. Echies from certain formations (Glen Rose, Walnut, Corsicana) tend to be attacked by this chemical while others (Goodland, Duck Creek, Fort Worth, Boracho) seem to respond to it much better with no deleterious effects.

Thanks for your input and I'll keep you posted on things. In the meantime I've enlisted the help of George Phillips from the Mississippi Museum of Natural Science to weigh in with his expertise and opinions.

[Mike Murphy]

Dan:

The following i some of the data that I have been able to access and summarize from my library. This data is derived directly from the literature as I am no expert on the Boquillas Formation. The Boquillas in far west Texas changes laterally from the deeper water flaggy facies to more typical Eagle Ford facies and Austin facies as one travels from west to east. From my understanding, the facies change occurs in Val Verde County but begins the transition in southeastern Terrell County. To the west is the Boquillas Formation, which is comprised primarily of deep water flaggy limestones with thin zones of marl. To the east in Kinney County are the shales and limestones of the Eagle Ford Formation and the typical Austin Chalk lithology. There are 2 primary members of the Boquillas Formation, the older Ernst member, which is Cenomanian to Turonian, and the younger San Vicente member, which is Coniacian to Santonian and correlates to the lower Austin Formation. The San Vicente member Gray is composed of chalk and flaggy limestone; yellowish-brown limestone interbedded with gray marl. The San Vicente member contains more chalk and marl than the underlying Ernst member according to R.A. Maxwell in "Geology of Big Bend National Park, Brewster County, Texas". Also, according to Maxwell, the San Vicente member correlates with upper part of Sawmill Mountain, and all of Fizzle Flat Members of Boquillas Formation in Agua Fria area. According to Maxwell. "fossil ammonites, pelecypods, echinoids, foraminifers identified". The Ernst member is composed of yellowish-brown flaggy limestone interbedded with marl. Apparently there is an erosional contact between the members, but the contact is generally determined by faunal analysis. The Ernst is the member that is referred to as the "Boquillas Flags" although both members contain considerable flagstone. The Ernst correlates with lower part of Sawmill Mountain Member of Boquillas Formation in Agua Fria area, northwest of [big Bend] Park.

Ammonites are found in certain beds of the Boquillas Formation, and there are 23 ammonite species listed for the Boquillas Formation in "Texas Cretaceous Ammonites and nautiloids" by Emerson, Emerson, Akers and Akers, HGMS Publication 5. The genera you list would be found in the Ernst member, which is Cenomanian and Turonian. They are listed as such in the HGMS Publication 5 on page 38. The Rock Pen member and its echinoids are found in the lower Austin equivalence.

Hopefully, Mr. Phillips will be able to assist you and I both in the identification of these echinoids and allow me to correct any of mine that might be misidentified.

Regards,

Mike

[Mike Murphy]

Dan:

I wanted to let you know that the 5 holasterids I had actually identified as Cardiaster sp., not as Isomicraster rossi Cooke. They are definitely not Isomicraster. They may not be Cardiaster either. Isomicraster rossi is also found in the Boquillas Formation near Terlingua. They may not be Cardiaster either due to the differences in the anterior sinus and the posterior truncation. The largest holasterid that I collected was 5 mm in length with the smallest at 3 mm in length. It will be interesting to see what George Phillips can determine on both the holasterids and the holectypoids. Maybe they are both new species. Keep me posted.

Regards,

Mike

[Uncle Siphuncle]

Mike

George Phillips and some other experts rejected I. rossi as the holasterid I found, and once I looked it up in Cooke I agreed with them. I too saw some characteristics that made them appear similar to the Cardiaster leonensis I've found in the Maastrichtian. I have a bad habit of trying to pigeon hole species into taxa reported from the state collected, in this case Texas, at times referring only to Akers and Akers out of personal laziness, and as you know the line drawings and science behind this reference are sub par. At any rate, also in Cooke, I noticed strat level and plates for Holaster feralis, a Turonian form from the Greenhorn limestone of CO. I threw this possibility George Phillips' direction and currently await feedback. The 6 examples I've found so far in my sample range from about 15 to 25 mm, some showing good amb detail. These will certainly be well photographed in my upcoming April report. It is possible that occurrence of a known form such as this simply hasn't been documented in TX yet. Maybe I'll try to coauthor something at some point with George if it hasn't been done; who knows.

As for the Coenholectypus, I've looked through descriptions of many holectypoids this week and the closest physical match in my limited opinion seems to be C. nanus. This however presents somewhat of a problem though, since C. nanus is a Pawpaw form. If that is indeed its ID, then where are they in the fossil record during Mainstreet, Grayson, and Woodbine times? This represents roughly a 10 million year hiatus unless this is a much more common form than my limited field and armchair academic experience would suggest.

BTW, the C. c.f. nanus I picked up range from roughly 1.5 to 6 mm and I think I'll have a statistically significant sample once I prep everything out, perhaps as many as 100 specimens. One theory is that this could represent the full size range for the species. In the same exposure I found a full size spectrum for H. jacksoni, from roughly 5 to 30 mm. I'm not sure how mobile these nanus were, but my layman's opinion is that maybe they weren't very mobile, and instead we are looking at a full size spectrum of a small form. Otherwise I don't know where larger adults would be hiding as you'd think collecting bias would favor their discovery. Deeper water sediments are present at the same site as evidenced by nodular limestone, and I did see a few nanus there, fewer of them in number but still in the same size range as the others, possibly suggesting that bigger specimens, if they indeed existed, didn't simply migrate to deeper water. Still, specimens found are quite a bit smaller than adult size recorded in Pawpaw sediments (10 mm), so I'm open to the idea of these being a different species than C. nanus, perhaps even a new one.

Back to Akers and Akers being a mess. Not only are the line drawings a poor guide in comparison to the original plates, but the science and editing are flawed. By this I mean that every description ever published for Texas specimens is thrown in, with no consideration for later superseding descriptions which may have lumped genera, etc. Specifically I noticed the mention of Hemiaster jacksoni and Leiotomaster bosei in Akers' Eagle Ford faunal list. The descriptions and figures made it hard to see diagnostic differences between the 2. A well studied collecting buddy told me this week that Cooke 1953 lumps L. bosei in with H. jacksoni, superseding Smiser's 1936 description of L. bosei.

There is a movement in place to supersede Akers with a better written tome employing pro digital shots in lieu of the hand illustrations. At first Neil Immega instigated this effort and for whatever reason things stalled. Now the project sits with my personal friend and current VP of the Dallas Paleo Society, Frank Holterhoff. When Frank finally gets around to this he'll contact individual collectors with are and high grade specimens in their collections so that photos of them can be included. I'll certainly grant him access to my collection for that purpose. As for published locality info, I think formation and county are all that will be included.

I can tell that you are much more experienced and better studied than myself on this subject, and I'm open to rejection or correction of any arguments I've presented above. I'm pretty inquisitive and look forward to learning more from you and others about echinoids specifically and paleo in general. Don't be afraid to hurt my feelings if my logic and assertions are flawed.

[jkfoam]

Dan,

Don't be too hard on Akers and Akers and their publication. I don't believe it was ever meant to be a scholarly work and it probably never under went academic peer review. It was published by the Paleontology Section of the Houston Gem and Mineral Society primarily as an identification aid for the amateur fossil collectors. For the Akers, it was a labor of love. The Paleontology Section generally has a very limited budget for these projects which probably explains why it was done with line drawings instead of photography, That and the fact it predates popular digital photography.

I think that the Akers publication and the HGMS Paleontology Sections publication series, Texas Paleontology Series serves as an excellent project model for other amateur paleontology organizations.

JKFoam

[Uncle Siphuncle]

JK

Point taken. There is a certain phase in collecting when many folks aren't quite ready to run down original references. For me this phase lasted years. Folks just need to understand that the info contained therein may not in some cases be as complete or accurate as the original descriptions, although it is still useful to a point. A handful of basic references for each state of interest form a solid core for building a personal library and a collection there. The general references often point you to the original refs if you need further detail.