THE GASTROPOD CASMARIA: ITS SPECIES CAN BE “SHAPE SHIFTERS”

The tropical shallow-marine gastropod genus Casmaria (family Cassidae = the "helmet shells") is widely distributed on sandy bottoms in the Indo-Pacific region: from Madagasgar to Hawaii and some Caribbean Sea localities. The word Casmaria is Latin for “a helmet shape from the sea.”

Only a few living species of Casmaria species have been identified. The two most commonly occurring ones are C. erinaceus (Linnaeus, 1758) and C. ponderosa (Gmelin, 1791). Both are very widespread. They show morphologic variation, thus they have been commonly referred to as polymorphic species. A molecular/gene study by Fedosov et al. (2014) showed that C. erinaceus, characterized by relatively thin shells with considerable ornamentation and coloration, is the same species as C. ponderosa, characterized by thick sturdy shells with reduced ornamentation and coloration.

I recently came across a small-sized specimen (shown below) of Casmaria with solid/heavy, robust shells having sparse but prominent ornamentation of ribs and nodes, as well as having limited coloration. I tried unsuccessfully to identify this specimens as to species, based only on shell morphology. Although it resembles C. ponderosa it is not a perfect match. After reading the paper by Fedosov et al., I would identify this specimen as part of the C. erinaceus “species complex

Three views (ventral, right side, and dorsal) of Casmaria ponderosa? with an almost monochromic (white), heavy, thick shell: length 3.5 cm, width 2.1 cm. Australia.

Reference Cited:

Fedosov, A. et al., 2014. A new species of Casmaria H. Adams & A. Adams, 1853 (Gastropoda, Cassidae) from the Philippines identified by molecular data. European Journal 78:1–13.   [a pdf is available and free]. 

ITACOLUMITE, THE WORLD’S MOST BENDABLE ROCK

This naturally occurring, rare, and unusual rock is named for a mountain range in the southern part of Minas Geras, Brazil, which is a region famously known for being very rich in quartz and other minerals (Wikipedia, 2023).

Itacolumite (pronounced “ita-col-um-nite”) is only found in a few places in the world; for example, Brazil, Charkhi Dadri District, Harynana, northern-central India, North Carolina, and Georgia. At the Indian locality, itacolumite is exposed in small quarries and occurs in a nearly 3 m-thick that is non-flexible bed, traceable over several tens of meters in length. The bendable sandstones, however, occur only in thin slabs extracted from this bed (Kumar and others, 2019). 

Thin short slabs (hand-specimen size) of this so-called “magical rock” will bend due to their own weight. If turned over, each slab will bend in the opposite direction. If a slabs bend too much, it will break.

                          A

                          B

                                    C

Three views of a slab of itacolumite [8.5 inches (24 cm) long, 1.5 inches (3.75 cm) wide, and just over 1.2 inches (1.5 cm) in thickness].   

A. Side view of slab bent downward. B. Top view. C. Close-up view of the slab. This rock, which is pinkish red with gray-colored zones (boundaries diffuse), consists of medium-grained feldspathic quartz sandstone. Locality unknown.

Small pieces of this rock are pricey! For example, the slab shown above, goes for $200! 

                          D

                          E

                                 F

Three views of a second slab of itacolumite [6 inches (15 cm) long, 1.5 inches (nearly 4 cm) wide, and about ¼ inches (7 mm) in thickness]. D. Side view This slab, which is grayish yellow in color [typical for itacolumite], consists of fine-grained muscovite-rich quartz sandstone. Locality unknown.

Itacolumitre is porous and consists of quartz-rich sandstone. The porosity (void spaces), which enables the bending process, is apparently caused by chemical corrosion (leaching) of feldspar grains in the rock (Kumar and others, 2019). Fine-grained muscovite mica can also present, but its presence has been determined not to be a factor in the bending process.

Note: Several short, interesting videos are available on Youtube.com that show the bending of slabs of this rock. 

 Sources of Information: 

Kumar, P. and others. 2019. Itacolumite (flexible sandstone) from Kalinana, Charki Dadri Districth, Haryana, India. Journal of Geological Society of India 93:278-284. Pdf is free.

Youtube.com/watch?v=ALHkg-11Lkk

Wikipedia. 2023

AN UNUSUAL VENERID CLAM WITH LONG SPINES

The official name of this clam is now Hysteroconcha lupanaria (Lesson, 1831). Until recently, it used to be identified as Pitar lupanaria, but like many names of seashells, new information results in name changes. This clam belongs to the family Veneridae (the “Venus clams”). 

Hysteroconcha lupanaria, which often reaches lengths to 7 cm or more, lives buried in sand on sand beaches and sand flats at depths of about 10 m in warm, shallow-marine waters from the Gulf of California in Baja California Sur, Mexico to northern Peru (Olsson, 1961; Parker, 1964). After storms, specimens of this clam are commonly found washed up along beaches. Unlike most venerid clams, H. lupanaria have two rows of long, slender, curved, spines along the posterior slopes of its two valves.

Hysteroconcha lupanaria is one of only a few venerids having long spines. They point upward and are very sharp. They surround the soft tissue of the siphons of the clam. These siphons are used for the intake of clear water and also for the expulsion of waste water. Apparently, the long and sharp spines protect the siphons from being nibbled on by fish.

The shell of H. lupanaria is white, tinted with violet and with violet spots at the bases of the spines. 

Hysteroconcha lupanaria: exterior and interior views of the same left valve), 55 mm length (including longest spine). 

Hysteroconcha lupanaria: right-valve exterior, 47.5 mm length (including longest spine). The color of this specimen is faded because of exposure to sunlight. 

References:

Olsson, A.A. 1961. Mollusks of the tropical eastern Pacific. Paleontological Research Institution, Ithaca, New York, 574 pp., 86 pls.

Parker, R.H. 1964. Zoogeography and ecology of macro-invertebrates, Gulf of California and continental slope off Mexico. Vidensk. Medd. Fra Dansk Naturh. Foren, 178 pp.

SOME INTERESTING TRACE FOSSILS

The following information and images concern some trace fossils (= tracks and trails left behind by the activities of various ancient animals) that my students and I found during the many decades that I taught my undergraduate and graduate paleontology classes, as well as  my field-mapping classes.

An unnamed feeding-trail? trace fossil in a slab of rock (10 inches length) consisting of metamorphosed muddy silstone. Early Cambrian age, Inyo Mountains, eastern California. 

Side view of Gyrolithes sp., a spiral trace fossil that reminds me of an "automobile spring" about 4.5 inches tall, in mudstone of the Eocene Cozy Dell Shale, Ventura County, Sespe Creek, southern California. Gyrolites burrows, like this one, are  probably the result of  activity of a decapod crustacean. This trace fossil is typically found in ocean waters largely unaffected by storms.

The next two views are of meniscate burrows from Miocene lacustrine-fluvial deposits in the Miocene non-marine Diligencia Formation, Orocopia Mountains, Riverside Coutny, southern California (see Squires and Advocate, 1984, for more information).

Side view of meniscate burrows. A U.S.A. quarter coin is used for scale.

Top view of another slab with meniscate burrows from the Miocene lacustrine-fluvial deposits in the Miocene non-marine Diligencia Formation, Orocopia Mountains, Riverside County, southern California. 

Top view of a large (about 10 inches diameter) circular-trace fossil in  fine-grained sandstone. Locally unknown. This specimen was displayed in my paleontology-classroom for decades (hopefully the specimen is still there). Many geologists have seen it, but, so far, no has been able to assign an ichnogenus name to it. 

Note: If you are interested in seeing some additional trace fossils that I have shown earlier, check out my blog post on Rusophycus, August 29, 2014. Especially interesting in that post are my images of a plaster cast of a Cambrian trilobite nestled inside of its resting/feeding? “burrow.”

Reference Cited:

Squires, R.L. & D.M. Advocate. 1984. Meniscate burrows from Miocene lacustrine-fluvial deposits, Diligencia Formation, Orocopia Mountains, southern California. Journal of Paleontology 58(2):593-597, figs. 1-2.

STROMATOLITES: OUR SOLAR SYSTEM’S OLDEST FOSSILS

Stromatolites are layered colonial structures formed by cyanobacteria (also referred to as “blue-green bacteria.” They are found in warm, waters, mainly in marginal-marine environments, namely, the supratidal, intertidal, and, shallow subtidal zones. They form squishy, sticky mounds of communal-living microbs that need sunlight. In the process, these microbes produce free oxygen via photosynthesis, and they were extremely important in producing the free oxygen in Earth’s early atmosphere. Today, stromatolites are rare because they fell victim to crazing animals.

They are the oldest fossils known on Earth, where their geologic range is 3.5 billion years ago (Early Archean) to today. Fossil stromatolites about the same age (3.7 billion) have also been found recently in outcrops on the planet Mars, in the Meridiani Planum, by means of explorations associated with the NASA rovers "Opportunity", "Spirt", and "Curiosity" (Rhawn et al. 2020). 

1  Precambrian stromatolite, Asburn Formation, Saint John, New Brunswick, Canada. This rock is about 12 inches in length.

2 Precambrian? stromatolite, eastern California. The orange arrow points to a USA nickel (diameter 2.1 cm) used for scale.

3A-C: Three successive views (oblique top, and side) of the same  2.5-inch “cube” of rock, cut out (and subsequently polished) of a Precambrian stromatolite (locality unknown),

4 : Diagram showing stromatolite environments at Shark Bay, West Australia.

5: A vertical-cross section of a modern-day intertidal stromatolite from Shark Bay, West Australia showing a “cabbage-head”-like, porous internally layered structure. The base of this stromatolite encrusts a rock. Based on studies from this locale, stromatolites grow at a maximum of only 0.3 mm per year.

6: This image shows how the Shark Bay stromatolites and associated boardwalk were severely damaged by strong surge waves generated by the severe tropical cyclone Seoja in April, 2021. (The site is still currently closed to the public until ?). The four domal-shaped structures (located between the two pilings) are the tops of stromatolites (exposed at low tide). It will take thousands and thousands, etc. of years for the stromatolites to redbuild to their previous sizes. Image kindly provided by Matt Ventimiglia, 2023.  

7: Tidepool stromatolites, northern Gulf of Baja California, Mexico, 1974.

Reference Consulted:

Rhawn, J.G. et al. 2020. Oceans, lakes, and stromatolites on Mars. Advances in Astronomy. DOI:10:1155/2020/695932. Open access. 

AN EARLY “BIG” BIRD: GASTORNIS GIGANTEA

In 1876, Cope wrote a brief paper about a single large tarso-metataursus bone that he found in the southwestern United States, in the state of New Mexico. That kind of bone occurs only in the lower leg of birds, as well as in some non-avian dinosaurs. He named his discovery: Diatryma gigantea. In 1916, the first skull of this same large fossil bird was found in the Willwood Formation in the Bighorn Basin of Wyoming. Then, in 1917, the first nearly complete skeleton of this bird was found. Cope realized that all of these fossils represent the same species of flightless bird: namely one that had wings reduced to small stumps, a head as large as that of a modern horse, a large beak with a sizable hook on its end (similar to that found on eagles), and feet with small talons. Most vertebrate paleontologists currently believe that D. gigantea was a fierce predator, but a there are some who believe it was a grazing herbivore that used its sharp beak as a scythe (uwyo.edu/geomuseum/exhibits/diatryma-giganteus.html).

Gastornis gigantea (Cope, 1876) (modified from a figure on p. 498 of Fenton and Fenton, 1958). The adult of this flightless bird was 7 feet tall (2.14 m) and weighed 385 pounds.

In 1884, genus Diatryma was recognized by vertebrate paleontologists as being the junior synonym of genus Gastornis, which up until then had only been found in France (Paris Basin region). It has now been found also in England, Belgium, and Germany (Wikipedia, 2023). According to the international bylaws of taxonomic classification, the name Gastornis is the senior synonym of this animal, thus it has official priority because it was named first. It was not long until paleontologists realized that Gastornis gigantea indeed roamed both the American West (Wyoming, New Mexico, and New Jersey), as well as western Europe during the late Paleocene through middle Eocene times. This interval of time coincided with a worldwide, warm (greenhouse) climate. 

According to the very informative account of Gastornis in Wikipedia (2023), there are five to seven species of this extinct genus, including one in the Henan Province of central China. According to Buffetaut (2013), who did a taxonomic update/revision of this sole Chinese species, which is based on a single leg bone of early Eocene age, this particular species should be identified as Gastronis xichuanensis (Hou, 1980). 

In 1975, fossil remains of Gastronis were discovered by the paleontologists Mary R. Dawson and Robert M. West doing field work on Ellsemere Island, Canada’s High Arctic area. This fossil occurs in the Margaret Formation of early Eocene age (equivalent to the North American Land Mammal Wasatchian Age). This formation was deposited in a high-latitude area during the worldwide “greenhouse”-time environment, with mild and ice-free temperatures in this particular area. During the winter months, however, it was dark at this locale. The sedimentary rocks containing the fossils were deposited in a coastal-deltaic-plain sediments that grade upsection into a lush lowland-swamp-forest environment. The area is presently at approximately a latitude of 78.4°N in Eureka Sound. Most of the fossils, especially the vertebrate-animal remains are fragmentary and weather worn (Eberle, 2007).

Google-Earth image showing location of the Elsmere Island Eocene fossils and surrounding geographic features. 

Fossils found associated with Gastornis include many land plants (e.g., Metasequoia, ginkgo trees, walnut trees) and numerous vertebrates e.g., fish, amphibians, turtles, crocodiles, boa snake, rodents, tapir, brontochere, hyaena, and a few primate-like mammals (Dawson et al. 1976; Eberle and Greenwood, 2012). For a more complete list, see (en.Wikipedia.org/wiki/Strathonca Fiord).

All of the known European fossils of Gastronis are of Paleocene age. All the known North American (USA and Canada) fossils are early Eocene age, as is the China occurrence. Most workers are in agreement that Gastronis originated in Europe. Most workers believe also that the most plausible migratory route that Gastornis underwent is the following: it originated during the Paleocene in western Europe; migrated during the early Eocene to both central China and western North America: all of this about 55 to 50 million years ago. This interval coincided with the greenhouse “Paleocene-Eocene Thermal Maximum” (PETM) event, which was warmest time interval of the entire Cenozoic (see Groves and Squires, 2023).

The exact route of the paleogeographic distribution of Gastornis out of Europe, however, needs more fossil finds (with precise geologic age dating) in order to resolve exactly how this non-flying bird moved from Europe to North America and China. A very plausible scenario [and shortest route] is the following: Gastrornis migrated during the early Eocene from western Europe into Greenland, then to Ellsmere Island (northern Canda), and then to Wyoming, all via the North Atlantic Land Bridge [NatLB]–De Geer–Thulean land-bridge complex (see map below). Then to complete its migration, Gastornis could have travelled from Wyoming to China during the Eocene, via the Beringia #1 Land Bridge. As a possible alternative to Beringia #1, Gastornis might have migrated from Europe to Asia by an intermittent land connection during the early Eocene. 

Paleogeographic map of the northern land masses of the world during the early to middle Eocene (adapted from Brikiatis, 2014—see one of my previous posts about “TERTIARY LAND BRIDGES”, published in November, 2022).

Beard (2002) reported that mammals from the Old World (Europe and Asia) invaded North America at least three times near the Paleocene/Eocene boundary. This boundary is documented best in the Bighorn Basin of Wyoming (this happens to be where most of the North American fossils of Gastornis are found). 

Note: Fossil birds similar to Gastornis are the South America phorusrhacids of early late Paleocene through early Pleistocene age, and especially the Miocene (see one of my earlier posts concerning “TERROR BIRDS,” published on November 28, 2021). As mentioned in that blog, only a few of these birds entered southern North America, and not until the late Pliocene via the Panama Canal isthmus (i.e., The GABI event---see one of my previous posts concerning “TERTIARY LAND BRIDGES,” which also includes the GREAT AMERCIAN BIOTIC INTERCHANGE [GABI],” published in November, 2022).

REFERENCES CITED:

Beard, C. 2002. East of Eden at the Paleocene/Eocene boundary. Science v. 295, pp. 47(11):1302–1307. (pdf not free)

Brikiatis, L. 2014. Late Mesozoic North Atlantic land bridges. Earth-Science Reviews 159:47–57. (pdf not free).

Buffetaut, E. 2013. The giant bird Gastornis in Asia: a revision of Zhongyuanus xichuanensis Hon, 1980, from the early Eocene of China. Paleontological Journal

Cope, E.D. 1876. On a gigantic bird from the Eocene of New Mexico. Proceedings of the Academy of Natural Sciences of Philadelpia 28(2):10-11. (free pdf)

Dawson, M.R., R.M. West, W. Langston, Jr., and J.H. Hutchison. 1976. Paleogene terrestrial vertebrates: northernmost occurrence, Ellsemere Island, Canada. Science, v. 192, pp. 781–782.

Eberle, J.J. 2007. Ellesmere Island Eocene fossils. The canadianencyclopedia.ca/en/article/ellesmere-island-eocene-fossils

Eberle, J.J. and D.R. Greenwood. 2012. Life at the top of the greenhouse Eocene world—a review of the Eocene flora and vertebrate fauna from Canada’s High Arctic. Geological Society of America Bulletin 124:3–23.

Fenton, C.L. and M.A. Fenton. 1958. The fossil book. Doubleday, New York, 740 pp.

Groves, L.T. and R.L. Squires. 2023. Revision of northeast Pacific Paleogene cypraeoidean gastropods including recognition of three new species: implications for paleobiogeographic distribution and faunal turnover. PaleoBios 40(10):1–52. (free pdf).

Hou, L. 1980. New form of the Gastrornithidae from the lower Eocene of the Xichuan, Honan. Vertebrata PalAsiatea 18:111–115.

en.Wikipedia.org  Gastornis. 

uwyo.edu/geomuseum/exhibits/diatryma-giganteus.html. 2023. Diatryma.