Wooster’s Fossil of the Week: An atrypid brachiopod from the Devonian of Spain

April 15th, 2016

1 Atrypid dorsal Lr Couvinian M Dev El Pical Leon SpainOur featured fossil this week is another gift from brachiopod enthusiast Clive Champion of England. This fine specimen of Atrypa sp. was collected from the Middle Devonian (Lower Couvinian) exposed at El Pical, Leon, Spain. Atrypa is the emblematic genus of the atrypid brachiopods, which were common in the Devonian around the world. They were also prominent in the Late Ordovician of the Cincinnati region, as seen here and here. We are looking at the dorsal valve in the above view.

2 Atrypid spiraliaThis particular specimen is not notable for its special beauty (it is, after all, exfoliated and a bit misshapen), but for the view it provides of an internal feature: the spiral brachidium, sometimes called the spiralia. This was a ribbon of calcite that supported the lophophore, a tentacular apparatus used in filter-feeding. We see it here because the dorsal valve eroded away, exposing the inside of the shell. Our friends at The Falls of the Ohio have another specimen showing the spiral lophophore of an atrypid.

3 Atrypid ventralThis is a view of the flat ventral valve of our atrypid brachiopod. Inside during life the spiral lophophore would have looked like two springs perpendicular to the floor of this valve.

Thank you again, Clive, for the beautiful and inspiring brachiopods!

References:

Bose, R. 2013. A geometric morphometric approach in assessing paleontological problems in atrypid taxonomy, phylogeny, evolution and ecology, p. 1-9. In: Biodiversity and Evolutionary Ecology of Extinct Organisms. Springer, Berlin and Heidelberg.
Rudwick, M.J.S. 1960. The feeding mechanisms of spire-bearing fossil brachiopods. Geological Magazine 97: 369-383.

 

Dr. Patrick O’Connor gives the 35th annual Richard G. Osgood, Jr., Memorial lecture at Wooster

April 14th, 2016

1 Patrick GeoClub 041416WOOSTER, OHIO–It was our pleasure to host Dr. Patrick O’Connor of Ohio University, who presented the 35th Annual Richard G. Osgood, Jr., Memorial Lecture. The Osgood Lectureship was endowed in 1981 by the three sons of Dr. Osgood in memory of their father, who was an internationally known paleontologist at Wooster from 1967 to 1981. We have had outstanding speakers through this lectureship, and Dr. O’Connor was one of the best. He gave his public lecture last evening (“Cretaceous Terrestrial Vertebrates from Gondwana: Insights from Eastern Africa and Madagascar”) and then a more detailed presentation to our Geology Club this morning (shown in the image above). We all learned a great deal, and Dr. O’Connor was especially good at asking our students questions.

2 Dinosaur cast 041416In Geology Club today Dr. O’Connor brought casts of fossils (like the above Maastrichtian theropod from Madagascar) and actual fossils (like the Maastrichtian bird bones from Madagascar shown below).

3 Bird bones 041416We very much appreciated Dr. O’Connor’s diverse scientific skills and accomplishments, along with his enthusiasm and good humor. This is exactly what the Osgood Lectureship is about.

 

Wooster’s Fossil of the Week: A crinoid stem internal mold from the Lower Carboniferous of Ohio

April 8th, 2016

crinoid internal mold 1The Biology Department at The College of Wooster is in the midst of a massive move in advance of the construction of the new Ruth Williams Hall of Life Science. The staff has been combing through old specimen collections, giving away items they don’t need for teaching or research. Among the objects are occasional fossils they gave to the Geology Department. The above specimen is one of the most curious: a combination internal and external mold of a crinoid stem from the local Lower Carboniferous rocks.

crinoid internal mold lumen copyThis is a closer view of the fossil. It is a cylindrical cavity with faint rings in a regular distribution. (These are external molds of the individual crinoid columnals.) Suspended down the axis is a segmented pillar with a stellate cross-section. (This is the internal mold of the crinoid stem lumen, a central cavity that runs down the center of the stem.) It appears that an iron-rich cement (probably siderite) filled this lumen after the death of the crinoid. The stem fragment was enveloped in a siderite concretion and the calcite stem columnals dissolved away. This leaves us with both an external mold of the stem and an internal mold of its lumen.

Carb stem 1For comparison, this is a crinoid stem fragment in its original calcite. It was found in a local Carboniferous limestone.

Carb stem 2Here are cross-sections of the same stems showing sediment-filled stellate lumens in their centers.

Wooster’s Fossils of the Week: An encrusted and bored coral (maybe) from the Upper Ordovician of southeastern Indiana (Part II)

April 1st, 2016

6 Tetradium cavernLast week we looked at a dull gray rock found in a roadcut in southeastern Indiana near the town of Liberty. It is from the Saluda Formation (Upper Ordovician), a thin unit that was likely deposited in very shallow, lagoonal waters along the Cincinnati Arch. We know that it is primarily a platter formed by the mysterious fossil Tetradium, and that it is encrusted with a trepostome bryozoan that was infested by some sort of soft-bodied encruster on its surface, forming the trace fossil Catellocaula vallata. Now we’re examining the wonders revealed by cutting this rock in half. Above we see the surprising and spectacular geode that it is, with calcite crystals surrounding a dark cavity. Let’s see what the fossils look like when polished and magnified.

7 LongitudinalCrossTetraThe orangish, irregular patch in the lower half of the section above is the crystalline calcite near the center of the rock. The sediment-filled tubes in the top half are of the Tetradium specimen. Note that the walls of the tubes are blurry and indistinct, and that they fade and disappear into the calcite crystals below. This is apparently because the skeleton of Tetradium was made of aragonite, an unstable form of calcium carbonate. It is likely that the aragonitc, tubular skeleton of Tetradium dissolved away in the center of this encrusted mass, forming the cavity that later filled with secondary calcite crystals. The remaining tubes were apparently preserved as ghostly molds by infillings of calcitic mud that didn’t dissolve.

8 TetracrossIn this section we are cutting the Tetradium tubes perpendicularly, rather than the longitudinal cuts we saw before. The cross-sections of the tubes show a four-part symmetry, which adds to the mystery of this group. (This is where the name “Tetradium” comes from.) It has been called a chaetetid sponge (as in Termier and Termier, 1980); a “calcareous filamentous florideophyte [red] alga” (Steele-Petrovich 2009a, 2009b, 2011; she renamed it Prismostylus), and most commonly a coral of some sort (as in Wendt, 1989). I now know enough about chaetetids to say that it is not in that group. Chaetetid tubes are not aragonitic, do not show tetrameral symmetry, and have diaphragms (horizontal floors). The corals of the Ordovician are decidedly calcitic, not aragonitic, and they too have internal features in their tubes not seen here. The four-part symmetry, though, is something you see in the coral’s phylum, Cnidaria, so there is that vague resemblance. The red algal affinity strongly urged by Steele-Petrovich may be our best diagnosis for the place of Tetradium.

9 BryoTetra1On top of the tubes of Tetradium is the encrusting trepostome bryozoan. Its tubes (zooecia) are made of stable calcite, so they are well preserved compared to the aragonite tubes of Tetradium below it. Note that the bryozoan is made of two layers. One colony died or went into some sort of remission, and another of the same species grew across it. The second colony could have budded somewhere from the first colony.

10 BrownBodies122915This closer view of the bryozoan section shows details of the zooecia, including the horizontal diaphragms inside. The dark spots at the tops of the zooecia are brown bodies, the remains of polypides preserved here in clear calcite cement. (We’ve seen brown bodies before in this blog.) They likely represent some sort of traumatic event in the life of this bryozoan when this part of the colony essentially shut down and was covered with sediment.

11 Gypsumflower122915Finally, there is a mineralogy story here too! Attached to the dog-tooth calcite spar in the center of this geode is this tiny gypsum flower. The gypsum crystals are white and very delicate. The dark needles among them are mysterious. Dr. Meagen Pollock and her students will subject them to x-ray diffraction in her lab later this semester. I’ll report the results here.

It is a simple tool, the rock saw. For geologists and paleontologists, it is one of our essential instruments for discovery.

References:

Hatfield, C.B. 1968. Stratigraphy and paleoecology of the Saluda Formation (Cincinnatian) in Indiana, Ohio, and Kentucky. Geological Society of America Special Papers 95: 1-30.

Li, Q., Li, Y. and Kiessling, W. 2015. The first sphinctozoan-bearing reef from an Ordovician back-arc basin. Facies 61: 1-9.

Palmer, T.J. and Wilson, M.A. 1988. Parasitism of Ordovician bryozoans and the origin of pseudoborings. Palaeontology 31: 939-949.

Steele‐Petrovich, H M. 2009a. The biological reconstruction of Tetradium Dana, 1846. Lethaia 42: 297-311.

Steele‐Petrovich, H M. 2009b. Biological affinity, phenotypic variation and palaeoecology of Tetradium Dana, 1846. Lethaia 42: 383-392.

Steele-Petrovich, H.M. 2011. Replacement name for Tetradium DANA, 1846. Journal of Paleontology 85: 802–803.

Termier, G. and Termier, H. 1980. Functional morphology and systematic position of tabulatomorphs. Acta Palaeontologica Polonica 25: 419-428.

Wendt, J. 1989. Tetradiidae — first evidence of aragonitic mineralogy in tabulate corals. Paläontologische Zeitschrift 63: 177–181.

 

Wooster’s Fossils of the Week: An encrusted and bored coral (maybe) from the Upper Ordovician of southeastern Indiana (Part I)

March 25th, 2016

1 TopEncrustedTetradiumI found this lump of a gray rock in southeastern Indiana along a highway near the town of Liberty. It is from the Saluda Formation (Upper Ordovician), a thin unit that was likely deposited in very shallow, lagoonal waters along the Cincinnati Arch. It is not especially notable in this view. I intend to show you the wonders that can be revealed in such dull rocks by simply sawing them in half. First, though, let’s have a look at the outside. Inn the view above you can see on the left side a large trepostome bryozoan with some irregular holes in it. We’ll come back to that.

2 BaseEncrustedTetradiumFlipping the rock over we find that most of it is a fibrous fossil shaped like a dinner plate with limestone matrix and encrusting bryozoans covering most of the center.

3 CloserTubesTetraA closer view of the fibrous part shows thousands of thin tubes radiating out from the center of the plate. This is the Ordovician fossil known as Tetradium. It is strange and mysterious enough that we will use the next Fossil of the Week blog post to describe it. It has been called a chaetetid sponge (as in Termier and Termier, 1980); a “calcareous filamentous florideophyte alga” (Steele-Petrovich 2009a, 2009b, 2011; she renamed it Prismostylus), and most commonly a coral of some sort (Wendt, 1989). Interesting range of options! We’ll explore later.

4 Catellocaula122915Now, back to the trepostome bryozoan visible on the top surface. There are three kinds of holes on this specimen. The smallest are the zooecia of the bryozoan itself, each of which would have hosted a zooid (a bryozoan individual). They are the background texture of the fossil. The large holes above are a bioclaustration structure that Time Palmer and I named in 1988 as Catellocaula vallata (little chain of walled  pits). It is explained thoroughly in one of the early Fossil of the Week posts. Basically they are pits formed when the bryozoan grew up and around some sort of soft-bodied colonial organism sitting on top of the surface, forming these embedment structures connected together by tunnels at their bases.

5 Trypanites122915A third kind of hole in this bryozoan is a boring cut down into its skeleton. These are the trace fossil Trypanites, formed when some kind of filter-feeding worm bored straight into the calcite zoarium (colonial skeleton) to make a protective home, as many polychaete worms do today.

Now let’s cut this stone in half —

6 Tetradium cavernInside we find a wonderful cavern of crystals — a geode! The crystals are mostly calcite, with dog-tooth spar lining the cavity and blocky spar replacing large parts of the Tetradium skeleton. There’s a story here, and it will be told in the next Fossil of the Week post!

References:

Hatfield, C.B. 1968. Stratigraphy and paleoecology of the Saluda Formation (Cincinnatian) in Indiana, Ohio, and Kentucky. Geological Society of America Special Papers 95: 1-30.

Li, Q., Li, Y. and Kiessling, W. 2015. The first sphinctozoan-bearing reef from an Ordovician back-arc basin. Facies 61: 1-9.

Palmer, T.J. and Wilson, M.A. 1988. Parasitism of Ordovician bryozoans and the origin of pseudoborings. Palaeontology 31: 939-949.

Steele‐Petrovich, H M. 2009a. The biological reconstruction of Tetradium Dana, 1846. Lethaia 42: 297-311.

Steele‐Petrovich, H M. 2009b. Biological affinity, phenotypic variation and palaeoecology of Tetradium Dana, 1846. Lethaia 42: 383-392.

Steele-Petrovich, H.M. 2011. Replacement name for Tetradium DANA, 1846. Journal of Paleontology 85: 802–803.

Termier, G. and Termier, H. 1980. Functional morphology and systematic position of tabulatomorphs. Acta Palaeontologica Polonica 25: 419-428.

Wendt, J. 1989. Tetradiidae — first evidence of aragonitic mineralogy in tabulate corals. Paläontologische Zeitschrift 63: 177–181.

Last day of fieldwork in Israel: More Jurassic enjoyment

March 20th, 2016

1 SU66 at Meredith 032016MITZPE RAMON, ISRAEL — For my last day of fieldwork during this short Spring Break trip to Israel, I returned to Makhtesh Gadol to collect a bit more data from subunits 65 and 66 of the Matmor Formation (Middle Jurassic, Callovian). The above image shows part of my field site in the Meredith section north of the “British Road” across the top of the makhtesh. The yellowish marls are subunit 66, with the white limestone of subunit 65 peeking out at their base. The Matmor Formation is distinguished by this alternation of carbonates and marls, and the faunas in each sediment type are very different.

2 SU65 bivalve at Meredith 032016I did not do any collecting today. Most of my work was tracing rock units, photographing fossils, and taking lots of notes. Above is a nice bivalve in the limestone of subunit 65.

3 SU65 bivalve and bullet 032016Here’s another bivalve with a spent bullet for scale. (Dramatic effect. There is far less ordnance in Makhtesh Gadol than other places I’ve worked in the Negev.) Note that the bivalve is articulated (both valves are locked together), meaning it likely was buried alive. Almost all the bivalves in subunit 65 are articulated.

4 SU65 branching coral 032016There is one horizon in subunit 65 with a surprising number of branching corals. These look very much like the modern Acropora, but they’re not.

5 SU65 SU66 boundary at Meredith 032016This is again the boundary between the white and resistant subunit 65 and the yellowish and nonresistant subunit 66. I have no images of fossils to show you from subunit 66 because they weren’t very photogenic. They are relatively rare and consist mostly of small solitary and colonial corals and occasional oysters.

Thus ends my 2016 fieldwork in Israel! I learned a lot in these eight days of exploration and study, and I worked with excellent colleagues. I have some ideas now for a project that will place these Middle Jurassic rocks and fossils in a global paleobiogeographic and evolutionary context. Many future Independent Study projects are possible!

At some point you must start collecting data

March 18th, 2016

1 Acacia at Meredith SectionMITZPE RAMON, ISRAEL — Today my friend Yoav Avni (Geological Survey of Israel) and I returned to Makhtesh Gadol to pursue a project with Subunit 65 of the Matmor Formation (Callovian, Middle Jurassic). You may recall this limestone contains an extraordinary bedding plane of fossils preserved in near-life positions (as seen in a recent Fossil of the Week entry). Yoav’s job was to find additional exposures of this subunit in the area; mine was to map the distribution of fossils on the bedding plane. This area of the makhtesh, by the way, is called “Meredith’s Section” after IS student Meredith Sharpe, who did splendid work here. The acacia tree above is our traditional lunch spot (when the camels aren’t using it).

2 SU65 bedding plane 031816This is the bedding plane of Subunit 65. I went over every square centimeter of it photographically mapping and detailing it with a square-meter quadrat. It was hot work, and a bit of drudgery compared to the previous days of exploring new exposures.

3 SU65 quadrat 031816This is a typical quadrat, complete with my boot toes. I took 41 quadrat photos like this, and then detailed the fossils within and their positions. In the meantime, Yoav wandered the hills and found many excellent exposures of the same unit, although none with a bedding plane like this. We will be able to compare the fossils in the “traditional” exposures with what we see here.

That’s pretty much it for my day in the desert!

Wooster’s Fossils of the Week: A Jurassic seafloor assemblage

March 18th, 2016

1 DSC_0184 copyImages from fieldwork this week. These are all fossils exposed on a single bedding plane in the Matmor Formation (Middle Jurassic, Callovian) exposed in Makhtesh Gadol. I found them many years ago while working through the stratigraphy near the top of the formation. They present a vignette of life in a shallow carbonate Jurassic sea. They are so well preserved you can almost feel the gentle waves and hear the squawks of the pterosaurs wheeling above. In the top image we have my favorite of the set: A gastropod shell in the middle surrounded by mytilid bivalves. The bivalves were no doubt attached to the gastropod by their thin byssal threads, holding them in place in the choppy waters. The preservation is remarkable. All these shells are calcitized, but retain their ornamentation. They are exposed on a bank of a wadi, and so they have been lightly etched from the matrix by sandy water during floods.

2 DSC_0180 copyJust to show the gastropod-bivalve association is not a fluke of preservation, here’s another set. On this bedding plane are four such assemblages.

3 DSC_0178 copyHere’s another gastropod, this one with heavy spines.

4 DSC_0179 copyA high-spired gastropod is on the left, with a mytilid in side-view on the right.

5 DSC_0181 copyAnother gastropod to end the set. These are just a few of the many such fossils exposed on this bedding plane of the Matmor Formation.

Paleontological heaven in the northern part of Makhtesh Gadol

March 17th, 2016

0 Makhtesh Gadol satellite viewMITZPE RAMON, ISRAEL — Today I spent quality time with two Israeli students and some of the most interesting fossils in the world. Yael Leshno and Or Eliasson, students at Hebrew University, joined me for a walking journey through the Zohar and Matmor Formations (Middle Jurassic) in the northeastern part of Makhtesh Gadol. I’ve included a Google map above showing the makhtesh (an erosional crater in a breached anticline, to make it simple). The structure is about 10 km long, walled by Cretaceous sandstones with a soft, delightful core of Jurassic sediments. We worked today in a portion south of the main road through the makhtesh.

1 SU51 view 031716Or is standing here on the top of the basal unit of the Matmor Formation. We used this surface as a walkway to the brown hills in the background. Our first goal was to visit several outcrops of “Subunit 51”.

2 SU51 at 004This unremarkable scene is actually the location of important and very well preserved Jurassic invertebrate fossils. The brown marls are the easternmost exposure of Subunit 51 of the Matmor Formation. They are loaded with corals, echinoids, crinoids, brachiopods, bryozoans (yes!), and other treasures. The soft marl helped preserve the fossils from most of the ravages of diagenesis, and makes them easy to free from the matrix. Some of the fossils we found here will be future Fossils of the Week on this blog. I particularly enjoyed our work in this interval today because Yael and Or are such excellent field paleontologists. They put their young eyes to good use.

3 Yael ZoharAfter lunch on the Matmor Formation, we walked south to find the lowest exposures of the Zohar Formation, which underlies the Matmor and “Kidod”. Here is the first outcrop we found, located in a wadi. Yael is doing here lithological and paleontological descriptions so that she can plan her next expedition to these rocks for her dissertation work.

4 Zohar long viewThe lowest Zohar Formation in the makhtesh is exposed along a central wadi. Yael is on the skyline scouting it out. The upper beds where she is walking are very rich in mollusks, brachiopods, and echinoderms.

5 Zohar view 031716The Zohar Formation contains alternating limestones and marls, much like the Matmor.

6 Zohar ThalassinoidesThis is the underside of a thick layer of Zohar Formation limestone. It has convex hyporeliefs of Thalassinoides burrows about 5-10 cm in diameter. These were produced by burrowing crustaceans in shallow waters. The early geologists in this area did not recognize these features as trace fossils, referring to them as “negative mudcracks”.

7 Zohar and ballonIn this perspective on the Zohar limestones, you can just make out a white balloon in the far distant sky. This tethered balloon is operated by the Israel Defense Forces to watch over the border with Jordan with all kinds of fancy detection equipment (I imagine).

8 Gecko 031716This little gecko watched us work at the Zohar outcrop.

9 Mousterian workshop floorOn our walk back to the car, sharp-eyed Or pointed out numerous flint flakes in a patch of desert pavement several meters square. These are the remains of a tool-making workshop. These are Mousterian and, astonishingly, about 150,000 years old. They were worked by Neanderthals!

10 Lithic Core Negev 585This is a lithic core, from which flakes were chipped by our busy cousins. I’ve seen this flint material all over the Negev, but hadn’t realized how old it is and who was responsible. I am very much in the Old World here.

 

A day in the Zohar and Matmor Formations of the Negev

March 15th, 2016

1 Zohar outcrop 031516MITZPE RAMON, ISRAEL — It was another very windy day in southern Israel, but still just fine for fieldwork. Yael Edelman-Furstenburg, Yael Leshno and I returned to Makhtesh Gadol to work on Yael Leshno’s data collection procedures for her PhD project in the Middle Jurassic sequence here. Our first task was figuring out the detailed stratigraphy, which is not especially easy considering all the faulting and somewhat dated lithological descriptions for orientation. The above image is of the Zohar Formation just below its contact with the Kidod Formation (depending on what stratigraphic scheme you follow!).

2 Zohar disconformityThe top few meters of the Zohar Formation are a series of argillaceous limestones with numerous trace fossils (Planolites and Thalassinoides, mainly) and this gorgeous erosion surface (disconformity). The white limestone beneath was lithified when it was exposed and downcut by sand-bearing currents. On the left you can see pieces of the limestone incorporated into the overlying calcareous sandstone. Classic.

3 Goldberg trench 031516We then moved up section into the Kidod Formation (or upper Zohar!) to the site of the first stratigraphic column constructed through these rocks. Right of center you can see a trench dug into the marls by Moshe Goldberg in 1962. This was part of his project to describe the entire Jurassic section in Makhtesh Gadol. We still use his iconic work today as “Goldberg, 1963”.

4 Quadrat start 031516Here are the Yaels starting the very first quadrat measurements within the Matmor Formation. Within a half-meter square they are counting and identifying all the fossils — every little bit over a few millimeters. Student Yael has many of these quadrats in her future!

5 Makhtesh view 031516Here is a view of the Makhtesh with the Yaels at work. You can see our white field vehicle from the Geological Survey in the middle distance.

6 Matmor bedding plane 031516We ended the day at this bedding plane in the upper Matmor Formation I remembered finding many years ago. It has spectacular clam and gastropod fossils across its surface, many in apparent life positions. I’d show you images of the critters, but I’m saving them for a Fossil of the Week post!

 

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