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The First Two Days in the Mojave

March 10th, 2015

 

students

Nine students and five faculty and staff are part of Desert Geology 2015, a week-long fieldtrip to the Mojave Desert. Here the nine students, joined by Cam Matesich (Wooster ’14) gathered at an overlook of Death Valley (Dante’s View). Cam joined the group on the second day to guide us through various sites and share his experiences working with Park hydrologists as part of GSA’s GEOCORP Program. We are missing desert expert and usual trip leader Dr. Wilson, and Patrice Reeder this year and greatly thank them for getting the trip organized and sending us off on the right foot.

redrocks

After flying into Las Vegas on the first day the group approaches the red rocks of Red Rock Canyon.

thrust

At Red Rocks the group puzzled over the Keystone Thrust Fault that brought gray Paleozoic Limestones on top of the Mesozoic red sandstones.

notmine

A winter view of the same Keystone Thrust – photo courtesy of the Red Rock Canyon Visitor Center.

zack

The photographer takes a break.

badwater

Day two – The full group at Badwater in Death Valley. Lowest point in the Western Hemisphere.

cam

Cam explains the spring and groundwater flow in Death Valley and how the park monitors and restores the hydrologic landscape in the Park.

devils

The group strikes a pose on the Devils Golf Course – Death Valley.

artist

Along Artists Drive in Death Valley photographers go to work.

nick

Nick strikes a pose on top of a weathered basalt boulder.

caitlin

Caitlin, the staff hydrologist, explains the hydrology of a large diameter well in a gravel wash.

staff

The faculty at Zabriskie Point in Death Valley. 



Wooster’s Fossil of the Week: A lucinid bivalve from the Middle Jurassic of southern Israel

March 6th, 2015

Fimbria CW265 2007 585Above is a specimen of the lucinid bivalve Fimbria sp. from the Matmor Formation (Middle Jurassic) of Makhtesh Gadol in southern Israel. I collected it in 2007 while working with Meredith Sharpe (Wooster ’08) as she pursued the fieldwork for her Independent Study project. It is a nice specimen in part because of its preservation. A closer look (below) shows very fine detail of the shell exterior.
Fimbria closeThe shell is no longer present, though. It was originally composed of the mineral aragonite, which was dissolved away, leaving an external mold that later filled in with very fine crystals of calcite. The sculpture of the shell is exquisitely reproduced; in some places even so well as to show growth lines. Many aragonitic bivalves and gastropods are preserved this way near the top of the Matmor Formation.
F fimbriata Solomon IslandsLucinid bivalves are still common today in the sea. The shell shown above is a modern Fimbria fimbriata from the Solomon Islands. They are infaunal, meaning they live burrowed in the sediment. Since they were not genetically endowed with long siphons, they use the foot to create mucus-lined tubes to the surface for access to seawater. Lucinids have an endosymbiotic relationship with sulfide-oxidizing bacteria in their gill tissues. They have a hemoglobin type that transports hydrogen sulfide to autotrophic bacteria, which in turn provide the bivalves with nutrition and enable them to survive in a variety of environments, from near deep-sea hydrothermal vents to shallow seagrass meadows.

Johann Karl Megerle von Mühlfeld (1765-1842) named Fimbria in 1811. I very much wish I had a portrait to go with that magnificent name. Megerle von Mühlfeld worked at the Naturhistorisches Museum in Vienna through the eventful Napoleonic years. He is best known for his pioneering work with insects, but he also curated the mollusk collections, which led to his description of the new Fimbria.

References:

Anderson, L.C. 2014. Relationships of internal shell features to chemosymbiosis, life position, and geometric constraints within the Lucinidae (Bivalvia), p. 49-72. In: Experimental Approaches to Understanding Fossil Organisms. Springer Netherlands.

Megerle von Mühlfeld, J.K. 1811. Entwurf eines neuen System’s der Schalthiergehäuse. Gesellschaft Naturforschender Freunde zu Berlin, Magazin 5: 38-72.

Monari, S. 2003. A new genus and species of fimbriid bivalve from the Kimmeridgian of the western Pontides, Turkey, and the phylogeny of the Jurassic Fimbriidae. Palaeontology 46: 857-884.

Morton, B. 1979. The biology and functional morphology of the coral-sand bivalve Fimbria fimbriata (Linnaeus, 1758). Records of the Australian Museum 32: 389-420.

Taylor, J.D. and Glover, E.A. 2006. Lucinidae (Bivalvia)–the most diverse group of chemosymbiotic molluscs. Zoological Journal of the Linnean Society 148: 421-438.

Wooster’s Fossil of the Week: Star-shaped crinoid columnals from the Middle Jurassic of southern Utah

February 27th, 2015

Isocrinus nicoleti Kane County 585Just a quick Fossil of the Week post. Above we see isolated columnals (stem units) of the crinoid Isocrinus nicoleti (Desor, 1845) found in the Co-Op Creek Member of the Carmel Formation (Middle Jurassic), Kane County, southern Utah. Greg Wiles recently received them as part of a donation to our department collections. They have such perfect star shapes that I had to share them here. For the full analysis, see my previous entry on columnals like these preserved in a limestone from the same location.

References:

Baumiller, T.K., Llewellyn, G., Messing, C.G. and Ausich, W.I. 1995. Taphonomy of isocrinid stalks: influence of decay and autotomy. Palaios 10: 87-95.

Tang, C.M., Bottjer, D.J. and Simms, M.J. 2000. Stalked crinoids from a Jurassic tidal deposit in western North America. Lethaia 33: 46-54.

Wooster’s Fossil of the Week: A molded brachiopod from the Lower Carboniferous of Ohio

February 20th, 2015

Syringothyris bored Wooster CarboniferousWe haven’t had a local fossil featured on this blog for awhile. Above is an external mold of the spiriferid brachiopod Syringothyris typa Winchell, 1863, from the Logan Formation (Lower Carboniferous, Osagean, about 345 million years old) of southeastern Wooster, Ohio. The outcrop is along the onramp from north Route 83 to east Route 30. Older Wooster geologists may remember this area was called “Little Arizona” because of the large roadcuts made for a highway bypass that was never completed. That original outcrop was destroyed several years ago, but the same rocks are exposed in this new section. This is the area where Heather Hunt (’09) did her Senior Independent Study work, and long before her Brad Leach (’83) worked with the same fossils.

The Logan Formation is primarily fine sandstone, with some subordinate conglomerates, silts and shales. It was likely deposited in the proximal portion of a prodelta at or below wavebase. The fossils in the Logan are mostly these large Syringothyris and the bivalve Aviculopecten, along with scattered crinoids, gastropods, bryozoans, nautiloids and ammonoids. This fauna needs more attention. Funny how the fossils in your own backyard are so often ignored.

This brachiopod was first buried in sediment and then the shell dissolved away, leaving an impression behind. Since it is an impression of the exterior of the shell, it is called an external mold. Curiously, all the external molds (and the internal molds as well) in the local Logan Formation have an iron-rich, burnt orange coating much finer than the fine sand matrix. This means that details are preserved that are of higher resolution than the matrix alone would allow. In the case of this fossil, that coating extended down into long, narrow borings in the shell, casting them (see below).
Syringothyris borings 585These borings are odd. Most of them are parallel to the ribs (plicae) of the brachiopod, and appear to have been excavated from the shell periphery towards its apex. This was in the opposite direction of brachiopod shell growth. I suspect they were made by boring annelid worms that started at the growing edge of the shell where the mantle ended. These traces need attention, like most other aspects of this local fossil fauna.

References:

Ausich, W.I., Kammer, T.W. and Lane, N.G. 1979. Fossil communities of the Borden (Mississippian) delta in Indiana and northern Kentucky. Journal of Paleontology 53: 1182-1196.

Bork, K.B. and Malcuit, R.J. 1979. Paleoenvironments of the Cuyahoga and Logan formations (Mississippian) of central Ohio. Geological Society of America Bulletin 90 (12 Part II): 1782-1838.

Leach, B.R. and Wilson, M.A. 1983. Statistical analysis of paleocommunities from the Logan Formation (Lower Mississippian) in Wayne County, Ohio. The Ohio Journal of Science 83: 26.

Wooster’s Fossil of the Week: Sponge and bivalve borings from the Miocene of Spain

February 13th, 2015

Miocene Bored Cobble OutsideThis week we have a rather unimposing limestone cobble, at least from the outside. It was collected way back in 1989 by my student Genga Thavi (“Devi”) Nadaraju (’90) as part of a Keck Geology Consortium field project in southeastern Spain. It comes from the Los Banós Formation (Upper Miocene) exposed near the town of Abanilla. The holes are borings excavated into the carbonate matrix by marine animals. This cobble was tossed about in a coral reef complex that was part of the ancient Fortuna Basin.
Miocene Bored Cobble CutSeeing the cobble in cross-section makes it much more interesting. (Geologists love their rock saws!) We now see two categories of borings: one is large and flask-shaped, and the other a small network of spherical cavities. The large borings were produced by bivalves that tunneled into the limestone to make living chambers (domichnia) from which they could filter-feed. As the bivalve grew, the hole became deeper and wider. There was no escape — making and living in a boring like this is a lifetime occupation. These bivalve borings are classified as the trace fossil Gastrochaenolites lapidicus Kelly and Bromley, 1984. The smaller borings were made by clionaid demosponges that used acid to create a series of connected chambers, also for filter-feeding. These sponges could only penetrate about ten mm or so before their filtering became ineffective, so they are confined to the outer periphery of the cobble. The sponge borings are given the trace fossil ichnogenus Entobia Bronn, 1837.

On the inside surface of the largest boring (right side), encrusting tubes of a serpulid worm are just visible. This serpulid was also a filter-feeder. It took advantage of the cozy hole after the bivalve borer died and decayed. It is called a coelobite, or cavity-dweller. Serpulids would have had a rough time cementing to the outside of the cobble as it rolled around in this high-energy environment.

References:

Bronn, H.G. 1834-1838. Lethaea Geognostica (2 vols., Stuttgart).

Kelly, S.R.A. and Bromley, R.G. 1984. Ichnological nomenclature of clavate borings. Palaeontology 27: 793-807.

Mankiewicz, C. 1995. Response of reef growth to sea-level changes (late Miocene, Fortuna Basin, southeastern Spain). Palaios 10: 322-336.

Mankiewicz, C. 1996. The middle to upper Miocene carbonate complex of Níjar, Almería Province, southeastern Spain, in Franseen, E.K., Esteban, M., Ward, W.C., and Rouchy, J.-M., eds., Models for carbonate stratigraphy from Miocene reef complexes of the Mediterranean regions: Tulsa, SEPM (Society for Sedimentary Geology), p. 141-157.

Nadaraju, G.T. 1990. Borings associated with a Miocene coral reef complex, Fortuna basin, southeastern Spain. Third Keck Research Symposium in Geology (Smith College), p. 165-168.

Taylor, P.D. and Wilson, M.A. 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62: 1-103.

Wooster’s Fossil of the Week: A Pleistocene octocoral holdfast from Sicily

February 6th, 2015

OctocoralHoldfastPleistoceneSicilyMy Italian colleague Agostina Vertino collected this beautiful specimen from the Pleistocene of Sicily and brought it to Wooster when she visited five years ago. It is the attaching base (holdfast) of the octocoral Keratoisis peloritana (Sequenza 1864). Octocorals (Subclass Octocorallia of the Class Anthozoa) are sometimes called “soft corals” because of their organic-rich, flexible skeletons. They are distinguished by polyps with eight tentacles, each of which is pinnate (feathery). Octocorals include beautiful sea fans and sea whips that require a hard substrate for stability. This particular holdfast is on a small slab of limestone.

The genus Keratoisis is known as the “bamboo coral” because it looks jointed like stalks of the plant. I collected fragments of Pleistocene Keratoisis branches during my visit to Sicily last year.
Giuseppe SeguenzaGiuseppe Seguenza (1833-1889) named the species Keratoisis peloritana. He was a Sicilian natural historian with broad interests, especially in geology. Although educated as a pharmacist, he found geology much more exciting on the volcanically active islands of the Mediterranean. He eventually became a professor of geology at the University of Messina (where the bust of him shown above resides). Italian sources say Seguenza received the famous Wollaston Medal from the Geological Society of London, but that does not appear to be true. Instead it appears that he was given “the balance of the proceeds of the Wollaston Fund” as a donation at the time the medal was awarded to Thomas Huxley (in 1876). The records of the society say that “the stipend of an Italian professor was too small to enable him to prosecute his palaeontological researches as fully as he could desire” (Woodward, 1876). Giuseppe Seguenza died in Messina at 56 years old.

References:

Di Geronimo, I., Messina, C., Rosso, A., Sanfilippo, R., Sciuto, F., and Vertino, A. 2005. Enhanced biodiversity in the deep: Early Pleistocene coral communities from southern Italy. In: Cold-Water Corals and Ecosystems, p. 61-86. Springer: Berlin, Heidelberg.

Fois, E. 1990. Stratigraphy and palaeogeography of the Capo Milazzo area (NE Sicily, Italy): clues to the evolution of the southern margin of the Tyrrhenian Basin during the Neogene. Palaeogeography, Palaeoclimatology, Palaeoecology 78: 87-108.

Langer M. 1989. The holdfast internodes and sclerites of Keratoisis melitensis Goldfuss 1826 Octocorallia in the Pliocene foraminifera marl Trubi of Milazzo Sicily Italy. Palaeontologische Zeitschrift 63: 15-24.

Woodward, H. 1876. Reports and proceedings, Geological Society of London. Geological Magazine 13: 181-182.

Wooster’s Fossil of the Week: A stromatoporoid from the Silurian of Estonia

January 30th, 2015

Densastroma pexisumStromatoporoids are extinct sponges that formed thick, laminated skeletons of calcite. They can be very common in Silurian and Devonian carbonate units, sometimes forming extensive reefs. The stromatoporoid above is Densastroma pexisum (Yavorsky, 1929) collected from the Mustjala Member of the Jaani Formation (Silurian, Wenlock) exposed on Saaremaa Island, Estonia. It was part of Rob McConnell’s excellent Senior Independent Study he completed in 2010.
Densastroma pexisum sectionStromatoporoids are rather featureless lumps until you cut a section through them. Then you see their characteristic laminae of calcite. Looking very close you might also glimpse the tiny vertical pillars between the laminae. Identifying the species of stromatoporoid always involves a thin-section or acetate peel to discern the forms of the pillars and laminae.

In the upper left of the sectioned D. pexisum is an oval boring cut through the fabric of the stromatoporoid. This is likely the trace fossil Osprioneides kampto Beuck and Wisshak, 2008. This is the largest known Palaeozoic boring. It is relatively common in Silurian stromatoporoids of the Baltic region. Last year Olev Vinn, Mari-Ann Mõtus and I published a paper describing the same ichnospecies in large trepostome bryozoans from the Estonian Ordovician.
8 schematic drawing of Osprioneides kampto
This diagram of O. kampto is from Figure 8 of the Beuck et al. (2008) paper. The organism that made the boring was almost certainly a filter-feeding worm of some kind that gained a feeding advantage by placing itself high on a hard substrate.
Flügel in 7000 ts by Chris SchulbertDensastroma was originally named in 1958 by Erik Flügel (1934-2004). He combined the Latin densus with the Greek stroma, meaning “dense-layered”. (Yes, taxonomic purists will object to the mix of Latin and Greek in one name.) Flügel was a highly accomplished and diverse scientist who founded the Institute of Paleontology at the University of Erlangen-Nuremberg as well as the journal Facies. He is best known for his advocacy of detailed study of carbonate facies through petrography (“microfacies analysis“), developing a series of techniques and principles that I found very useful in my dissertation work. The above image is a fitting tribute to Erik Flügel made by Chris Schulbert. It is a portrait made of 7000 carbonate thin-sections!

References:

Beuck, L., Wisshak, M., Munnecke, A. and Freiwald, A. 2008. A giant boring in a Silurian stromatoporoid analysed by computer tomography. Acta Palaeontologica Polonica 53: 149-160.

Flügel, E. 1959. Die Gattung Actinostroma Nicholson und ihre Arten (Stromatoporoidea). Annalen des Naturhistorischen Museums in Wien 63: 90-273.

Freiwald, A. 2004. Erik Flügel: 1934–2004. Facies 50: 149-159.

Vinn, O., Wilson, M.A. and Mõtus, M.-A. 2014. The earliest giant Osprioneides borings from the Sandbian (Late Ordovician) of Estonia. PLoS ONE 9(6): e99455. doi:10.1371/journal.pone.0099455.

Three Days on Ice

January 25th, 2015

group

Dr. Lowell and a crew from the University of Cincinnati spent thee days with us on the ice at Browns Lake Bog. The objectives were to take a series of long cores from the ice platform at the bog and, in the big lake,  to take a short surface core that the Wooster Geomorphology class will study. In addition we installed a series of four nested monitoring wells in the sediments around the lake.coring_theoryThe coring crew taking the deep core – about 24 meters in two meters of water depth.

coring_sed_water

The sediment-water interface on TV – note the screen on the ice that helped guide the coring process to be sure the actual sediment-water interface was captured.

sed_water

Subsampling the upper core to be sure the modern sediments at the interface were in the bag.

coring_1

The ongoing coring.

probe1

Measuring dissolved oxygen, pH, TDS, ORP and Temperature along a depth profile.

 

instrument_wellMeasuring the same parameters in four sets of nested monitoring wells  – one deep, one shallow.

on_iceDrilling holes in the ice along  grid and measuring depth profiles in the big lake.

ice_holesOne of the ice hole teams.

probingThe mud probing team – not a glamorous job but necessary.

water_levelMeasuring the water levels in the well after bailing.

weather_stationThe weather station installed at the bog. 

well_prepDrilling a series of holes to act as a screen in the monitoring wells.

pumpingPumping the wells for isotope samples and installing a transducer to keep track of water levels.

shootingErika takes aim at the upper branches of a white oak – she will extract the water from these twigs and buds and measure their isotopic composition.

shavingPealing the twigs and bagging them up for transport.

our_coreTom recovering the surface core from the middle of Browns Lake – the big lake. Now the ball is in our court to do some analysis. Great thanks go out to the Core Boss and his crew.



Wooster’s Fossil of the Week: A predatory gastropod from the Pliocene of Cyprus

January 23rd, 2015

Naticarius millepunctatus Pliocene CyprusThis week we have another fossil from the Nicosia Formation (Pliocene) of the Mesaoria Plain in central Cyprus. It is again from a Keck Geology Consortium project in 1996 with Steve Dornbos (’97). This time, though, instead of our Coral Reef locality, our featured creature is from a sandy marl outcrop we called “Exploration”. We have above an aperture view of Naticarius millepunctatus Risso, 1826, a species still alive today and known as the “many-spotted moon shell”. It is a naticid gastropod, heir to a predatory tradition that strikes fear in the tiny hearts of bivalves.
Naticarius millepunctatus Pliocene Cyprus View 2Naticid gastropods, like our Naticarius, have a well-muscled foot that they use to essentially swim through loose sand to capture infaunal bivalves and other shelled prey. They then use their specialized radula to drill into the shell, kill the unfortunate animal, and then consume the soft goodies. Naticids leave distinct drill holes in the shells of their victims, as shown in a previous Fossil of the Week post. We found a few drilled bivalve shells with our Naticarius millepunctatus at the Exploration site.
André_Marie_Constant_DumérilNaticarius was named as a genus in 1806 by André Marie Constant Duméril (1774-1860). Duméril was another member of that marvelous group of French zoologists that lived through the French Revolution. He was a professor of anatomy, herpetology and ichthyology at the Muséum National d’Histoire Naturelle in Paris, corresponding and collaborating with such eminents as Georges Cuvier and Alexandre Brongniart. His most prominent work was Zoologie analytique, published in 1806. In this massive treatise he compiled descriptions of all the known genera of animals in an effort to sort them out in a repeatable way.
Dumeril KeyThis is a page from Duméril’s Zoologie analytique. We immediately recognize this as a binary taxonomic key, even if we can’t read the French. Starting from the left we make yes or no decisions about the anatomy of the animal we’re trying to identify, eventually ending on the right with a genus. (Naticarius is at number 10.)

André Marie Constant Duméril did prodigious work with reptiles as well, describing in detail 1393 “species” over nine volumes. (Oddly, in defiance of his fellow zoologists, he insisted that amphibians should be counted among the reptiles, thus the quotes around his number of “reptiles”.) Duméril also had major works on insects. His son, Auguste Duméril, was also a zoologist. As the elder Duméril retired, Auguste gradually took over his scientific projects.

References:

Cowper Reed, F.R. 1935. LII.—Notes on the Neogene Faunas of Cyprus.—III. The Pliocene Faunas. Journal of Natural History 16: 489-524.

Dornbos, S.Q. and Wilson, M.A. 1999. Paleoecology of a Pliocene coral reef in Cyprus: Recovery of a marine community from the Messinian Salinity Crisis. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 213: 103-118.

Duméril, C. 1806. Zoologie analytique, ou Méthode naturelle de classification des animaux, rendue plus facile à l’aide de tableaux synoptiques. Allais, Paris. 344 pp.

Tyler, C.L. and Schiffbauer, J.D. 2012. The fidelity of microstructural drilling predation traces to gastropod radula morphology: paleoecological applications. Palaios 27: 658–666.

Wooster’s Fossil of the Week: Another vermetid gastropod from the Pliocene of Cyprus

January 16th, 2015

Petaloconchus intortus (Lamarck, 1818)Why another one of those strange twisty gastropods from the Pliocene of Cyprus for our Fossil of the Week? Because this one fooled me for years. Above is a pair of images of a specimen of the vermetid gastropod Petaloconchus intortus (Lamarck, 1818) from the Nicosia Formation (Pliocene) of central Cyprus. It is encrusting a branch of the coral Cladocora. Ever since 1996 I’ve cataloged this and other such Cypriot specimens as serpulids, a type of polychaete worm that constructs adherent calcareous tubes like these. In fact, I placed on Wikipedia an image of the specimen below as a serpulid example.
Petaloconchus Cyprus Pliocene 585Last week an anonymous editor on Wikipedia changed the caption on my image from “serpulid worm tube” to “Petaloconchus“. I did some research and yes, he or she was correct. I’ve since remade the image and updated all the Wikipedia pages where it appeared. This is not the first time I’ve posted a fossil image online and been corrected, and I hope it’s not the last. Such feedback and criticism is a major advantage of online science, and I learn a great deal.

In my research on Petaloconchus, I found a delightful Journal of Paleontology paper by Stephen Jay Gould in which he defines a new subspecies of Petaloconchus sculpturatus and discusses the genus and its evolution in classic Gouldian ways (Gould, 1994). He, for example, found this quote by Myra Keen (1961, p. 183):

The Vermetidae (worm gastropods) probably hold a record among molluscs for the degree of confusion they have promoted, both in collections, and in the literature; for they have been misconstrued at every level from subspecies to phylum.

I’m happy to see I’m not the only one who has had trouble with vermetid gastropods. Even in Gould’s (1994, p. 1035) taxonomy of his new subspecies we see some of the issues with Petaloconchus:

Etymology.–alaminatus to recognize key feature of the absent internal laminae. The Linnean name is a paradox, as Petaloconchus means laminate shell (the supposed, but inadequate, definition of the genus), while the subspecific name alaminatus negates this characteristic feature. But who ever denied either nature’s complexity or evolution’s capacity to eliminate structures?

HCLeaPetaloconchus was named in 1843 by Henry Charles Lea (1825-1909), an American historian and political activist — an unexpected description of someone who named a snail. Lea came from a family deeply embedded in early American politics, and his father, Isaac Lea (1792-1886) was a prominent naturalist. Henry was clearly a prodigy in many endeavors. Note that his paper describing Petaloconchus and other fossils was completed when he was just 18 years old. In 1847, as a young man of 22, he suffered a mysterious nervous breakdown. During his long convalescence he read French medieval history, which turned his interests to the humanities. He eventually became a renowned historian of the Spanish Inquisition. (No one expects the Spanish Inquisition.)
LeaPetaloconchusOriginal image of Petaloconchus sculpturatus by Lea (1843).

Serpulids Cyprus PlioceneAbove are some real serpulid worm tubes from the Pliocene of Cyprus, although I’m open to corrections!

References:

Aguirre, J., Belaústegui, Z., Domènech, R., de Gibert, J.M., and Martinell, J. 2014. Snapshot of a lower Pliocene Dendropoma reef from Sant Onofre (Baix Ebre Basin, Tarragona, NE Spain). Palaeogeography, Palaeoclimatology, Palaeoecology 395: 9-20.

Bradley, E.S. 1931. Henry Charles Lea. A Biography. Philadelphia, University of Pennsylvania Press, 418 pages.

Carpenter P. 1857. First steps toward a monograph of the recent species of Petaloconchus, a genus of Vermetidae. Proceedings of the Zoological Society of London 24: 313-317.

Gould, S.J. 1994. Petaloconchus sculpturatus alaminatus, a new Pliocene subspecies of vermetid gastropods lacking its defining generic character, with comments on vermetid systematics in general. Journal of Paleontology 68: 1025-1036.

Keen, A.M. 1961. A proposed reclassification of the gastropod family Vermetidae. Bulletin of the British Museum (Natural History), Zoology, 7:183-213.

Lea, H.C. 1843. Descriptions of some new fossil shells, from the Tertiary of Petersburg, Virginia. Transactions of the American Philosophical Society 9: 229-274. [The volume was actually published in 1846.]

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