Friday, December 8, 2023


Recently, while working up my post on the state fossil of California (see my Dec. 3, 2023 post on the saber-tooth Smilodon fatalis), I became curious as to what are the other state fossils of the United States.

I used the following excellent website (which lists the fossil names and also provides an illustration of each fossil: 

I discovered that most states have an official state fossil, but only four do not: Arkansas, Hawaii, New Jersey, and Rhode Island.

Three other states: Iowa, Minnesota, and New Hampshire were formerly holdouts, but recently they tentatively proposed state fossils.

Most of the state fossils were designated as such in the 1980’s, and most of these state fossils are vertebrates (dinosaurs or mammoths).

A few states designated fossil mollusks as their state fossils; these are:

Maryland: shallow-marine gastropod Ecphora garderae of Miocene age.

Tennessee: shallow-marine bivalve Pterotrigonia thoracic of Cretaceous age.

Virginia: shallow-marine bivalve (pectinid = scallop) Chesapecten jeffersonius of Cenozoic age.

Furthermore I discovered that elsewhere in North America, only Nova Scotia in Canada has an official fossil: Hylonomus lyelli, a lizard-like reptile of Carboniferous age .

Sunday, December 3, 2023


Smilodon fatalis is well know to most people interested in late Pleistocene Ice-Age fossils, especially if they have visited the Rancho La Brea Tar Pits and Page Museum in Los Angeles. The word “Smilodon” means “scalpel” and is derived from: “two edged knife” combined with tooth.

Smilodon fatalis is the second most common (dire wolves are the first most common) large fossil found in the La Brea Tar (asphalt) pits in Los Angeles, California. Over 100,000 bones of S. fatalis have been recovered from these pits.

Figure 1. Plastic model of S. fatalis.

Figure 2.  Smilodon fatalis skeleton, Page Museum, Los Angeles, Los Angeles County, California. 

Smilodon fatalis was a true sabretooth cat, as opposed to the sabre-tooth marpusial carnivore, known as Thylacosmilus, which lived only in South America during the late Miocene and Pliocene. 

Sabertooth cats belong to the cat family Felidae. There are two subfamilies in this family: the extinct Machairodontinae (sabertoothed cats) and the extant Felinae (true cats).

In size and weight, S. fatalis was as large as a modern-day African lion, but unlike modern-day large predatory cats, S. fatalis was a stealth, ambush predator with strong front legs and relatively light hind legs. Thus, it was not a swift runner. Smilodon fatalis has only 26 teeth, fewer teeth than in other cats. Additionally, the sharp saber teeth (upper canines) of S. fatalis were most likely used stab into skin/flesh and/or bite open the soft underbelly of its prey, rather than biting into bones in order to subdue its prey (as in large cats living today). Also, the enlarged, but relatively narrow upper canines of S. fatalis have a distinct backward curve in order to minimize resistance and they have tiny serrations on the inside of the curve.

Figure 3. Smilodon fatalis skull.


Figure 4. Another Smilodon fatalis skull.

Figure 5. Smilodon fatalis canine tooth; 9 inches (23 cm) long from “tip to bottom of tooth.” Widest part of tooth is 1.5 inches (4 cm).

Figure 6. Closeup of previous image of S. fatalis canine tooth. Notice the presence of tiny serrations on the inside edge of this canine. 

Figure 7. Smilodon fatalis jaw muscles (exhibit at Page Museum).

Figure 8. Smilodon fatalis skulls showing progressive replacement of canine teeth (exhibit at Page Museum).

Smilodon is known only from Cenozoic deposits in North and South America. There are three known species. They are from oldest to youngest:  S. gracilis [2.5 mya to 500,000 years ago] and known only with certainty from North America; S. fatalis [1.6 mya to 10,000 years ago] and known only with certainty from North America (California, Texas, Mexico, Nebraska, and Florida]; and S. populator [1 mya to 10,000 years ago] and known only from South America (Wikipedia, 2023). The occurrence of the land bridge (GABI = Great American Land Bridge, which enabled exchange of species between North and South America during the late Pliocene [see one of my earlier posts on GABI], was responsible for the dispersal of Smilodon from North America to South America. Smilodon populator  Berta (1985) did detailed research on the South American species Smilodon populator.

Figure 9. Smilodon gracilis. This skull, which is/was on display at the San Diego Museum of Natural History, is most likely from Southern California (Anza Borrego Desert region). According to Shaw and Cox (1986), fossils of this sabertooth cat have also been found in Florida
and Pennsylvania. 

References Used:

Berta, A. 1985. The status of Smilodon in North and South America. Contributions in Science, no. 370, 14 pp. [free pdf]

Lindsey, E.L. (ed.). 2018. Rancho La Brea: Treasures of the tar pits. A Natural History Museum of Los Angeles County publication. Third edition. 72 pp.

Savage, R.J.G. and M.R. Long. 1986. Mammal evolution, an illustrated guide. British Museum (Natural History). 258 pp.

Shaw, C.A. 2001. The sabertoothed cats. In, Rancho La Brea: Death Trap and Treasure Trove, pp. 26–27. Terra. Natural History Museum Special Edition, v. 38, no. 2.

Shaw, C.A. and S. Cox. 2006. The large carnivorans: Wolves, Bears, and Big Cats. In Fossil Treasures of the Anza-Borrego Desert. The last seven million years. Sunbelt Publications, San Diego, California. 394 pp.

Stock, C, (revised by J.H. Harris). 1992. Rancho La Brea, a record of Pleistocene life in California. Seventh edition. Natural History Museum of Los Angeles County, Science Series 37, 113 pp.

en. Wikipedia. 2023. Smilodon.

Thursday, November 30, 2023


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]. 

Sunday, November 26, 2023


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.




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! 




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 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.

Wikipedia. 2023

Saturday, November 25, 2023


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. 


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.

Sunday, November 19, 2023


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.

Tuesday, November 14, 2023


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