FOSSILS THAT LOOK LIKE GRAINS OF RICE

Fusulinids are much larger than most foraminifera, which are extinct single-cell protists that consisted of an amoeba-like organism surrounded by a cylindrical/tubular calcareous shell (test = exoskeleton). Most fusulinids, which are between 5 and 20 mm in length and shaped like grains of rice, are of Late Paleozoic (Carboniferous (Late Mississippian) and Permian) age. They show rapid evolutionary development during the Permian. They were bottom-dwelling (benthic) organisms that chiefly lived in warm-water, shallow-marine offshore environments. Their calcareous remains (tests) are commonly major components of limestone. They did not inhabit brackish water nearshore or high-saline embayment environments. Fusulinids have been used extensively by oil companies for determining geologic ages of strata cored during oil-well drilling.

A hand specimen (19 cm wide and 80 cm high) of calcareous (limy) siltstone containing many specimens of fusulinids of Permian age from the Guadalupe Mountains in southeastern New Mexico. The largest specimen (20 mm length) is on the upper middle right side of the rock.

Numerous specimens (about 100) of Fusulina sp. tests weathered out of their enclosing rock matrix. The largest ones are 10 mm in length. These specimens are of Middle Pennsylvanian in age and from shale rock in the Hueco Mountains, near El Paso, Texas.

Because the tests of the approximately 50 known genera of fusulinids can be externally very similar looking, it is necessary to cut thin sections of their tests in order to microscopically examine their distinctive internal structures and thus determine their genus and species. A longitudinal section (axial) and a cross section (sagittal) are illustrated in the following sketch shown below. 

Axial and sagittal cross-section views.

The center of this photomicrograph (taken via a microscope) shows an axial view of a fusulinid test in a thin-section of rock. In the background are some sagittal views of nearby specimens. 

EQUISETUM: A LIVING FOSSIL

Equisetum (Latin, meaning horsetail) is a distinctive plant whose geologic time range is Eocene to Recent. It is native to North America, but it has spread to other continents (e.g., South America and is considered an invasive plant in New Zealand). There are about 15 species today, and they inhabit salt flats, banks of streams, and moist low parts of forests. They cannot live in water.

The higher classification of Equisetum is in a state of flux. It is closely allied to ferns based on how they both reproduce via spores and not by seeds. But Equisetum differs: Equisetum is stiff not soft, it does not have true leaves, it bears its spores in a capsule at the top of the plant rather than underneath leaves.

Above is a close-up of Equisetum showing the structures that contain the spores at the top of the plant. 

Equisetum is the only living genus of joint-stem trees, which range back to Late Paleozoic time (Devonian Period), and had slender, unbranching, and longitudinally ribbed stems with a thick core of pith and rings of small leaves at each transverse joint. These trees were most abundant in sands and muds that accumulated along levees and floodplains of rivers but were uncommon in permanently wet swamps. During the Carboniferous interval, joint-stem trees were especially common.

Equisetum, also called “horsetail rush” or “water rush bamboo,” grows rapidly and can reach heights of up to 8 feet (2.5 m). Except for its relatively small size, modern-day Equisetum is very similar to the Late Paleozoic forms. Once a Equisetum plant gets established, it spreads via its rhizomes and can quickly colonize a substantial area if left unchecked. It is best to contain the plant with barriers.

Most species of Equisetum are referred to as “scouring rushes.” They have stems that are rough and abrasive due to the presence of silica deposits in the outer layer of the stem. They were used for cleaning (scouring) pots and pans in colonial days and are still used by many modern-day campers.

Another name for Equisetum is “snake grass.” The main reason is probably because it resembles a snake, with its tube-like body. In my experience, another reason is because when you walk through a stand of it, there is a harsh grating sound (because of the silica in the stems) that can sound like the rattle sound made by a rattlesnake!

Nurseries sell Equisetum for modest prices. It is a hardy plant that has a distinctive decorative look to it. The images below are of a stand of cultivated Equisetum hyemale that I found growing in small plot of land adjacent to a pool of water in a patio of a commercial building. These plants which have leafless stems standing erect 2 to 5 feet tall, with rigid dark-evergreen hollow jointed nodes with a blackish rim around them. 

Equisetum (about 3.5 feet tall) growing in a small plot of land surrounded by walls. The locale is Los Angeles, Southern California.

A more close-up view of the same plot of Equitsetum.

An even more close-up view of the same plot of Equisetum.

INOCERAMUS: A WIDESPREAD EXTINCT BIVALVE (CLAM) GENUS

The name Inoceramus is Greek, meaning “strong pot.” This genus, which ranges from the Permian? Period (about 255 million years ago) to very near the end of the Cretaceous Period (about 68 million years ago), is very useful for geologic time correlation.  Species of this genus were lived epifaunally on the ocean floor in depths ranging from nearshore sands to deep-sea muds. Their larvae were readily dispersed by currents, and some species became widely distributed. They preferred temperate waters. 

Inoceramus is characterized by having a thin shell with relatively few morphologic characters to distinguish it from similar looking genera; also, the species of Inoceramus can be morphologically similar. In general, both the valves of Inoceramus are somewhat lowly inflated, and they are longer than they are wide. Concentric ribs are common, but radial ribs are rare. The prismatic microstructure of their shells, as well as minute details of their hinges, are useful in helping to differentiate Inocermamus from some other similar looking Mesozoic (Jurassic and Cretaceous) bivalves (e.g., Buchia). Some species of Inoceramus have a small posterior winglike extension, which makes them superficially resemble “winged pearly oysters” of the extant bivalve genus Pteria. 

Overall Inoceramus valves resemble “Ruffle Potato Chips.” Some workers have lumped species, whereas others have overnamed them. Specimens can range up to giant size (3 meters in length!). While alive, these giant valves could serve as a shelter for schools of small fish, which have been found preserved as impressions inside of the bivalves.

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Inoceramus subundatus Meek, complete specimen, (a) left valve and (b) right valve, Late Cretaceous (Campanian Stage), h 6 cm, w 5 cm. Southern California, California.

Inocermaus subundatus Meek RLS collection, incomplete right-valve specimen, h 4.5 cm, w 3.7 cm. Late Cretaceous (Campanian Stage), Chatsworth Formation, Simi Hills, southern California.

Inoceramus subundatus Meek, partial valve, h 3 cm, w 2.6 cm, Late Cretaceous, Santa Monica Mountains, southern California.  

Inoceramus orientalis ambiguous Nagao and Matsumoto, 1939, plaster

cast, h 6.5 cm, w 4 cm, Late Cretaceous (upper Santonian Stage), Clover Creek, Millville quadrangle, Shasta County, northern California.

Inoceramus sp. Partial valve, h 8 cm, w 5 cm, Late Cretaceous (upper Santonian Stage), Wheeler Springs area, southern California. Specimen is in situ in the outcrop.

THE RED-BELLIED PIRANHA FISH

This fish is well known to the public because movies and television shows have usually made piranha fish to be  senseless “killers” of any unfortunate animal that happens to be wounded and falls into an Amazon River. Some of these rumors surrounding the ferocity of this fish stem from “staged” incidents where the fish were captured, starved, and then fed meat.

Yes, this fish, and its many relatives can feed on flesh, but, piranha are classified scientifically as omnivores, which means it can eat plants and meat. Piranhas are known to be attracted by blood and activity in the water. Thus, it would not be a good idea to be thrashing about in a wild Amazon River if you have an open (bleeding) injury.

The derivation of the word “piranha” is not exactly known, but it probably stems from the words pirá [meaning fish] and ánha, meaning [cut], or sainha [meaning tooth]. In summary, piranha most likely means “biting fish.”

There are four genera and anywhere between 30 to 60 species. All of these are indigenous to the Amazon Basin in South America and its main tributaries; especially in the Venezuela and Colombia river systems, as well as in some other river systems (e.g., in Paraguay, and the coastal rivers of northeast Brazil). Most of the species are restricted to a single river system (for example, the Orinoco River System).

Adult piranhas are mostly between 5 and 14 inches long. The largest living species is the red-bellied piranha, Piranaha Pygocentrius natteri, which is illustrated below. They are the least aggressive of piranhas. Some adults of the extinct Megapiranha are up to 28 inches long.

All piranhas have a single row of extremely sharp teeth in both jaws. Their triangular-shaped teeth are bladelike, tightly spaced, finely serrated, and are interlocking (via small cusps). They are very effective for rapid puncture and shearing. Piranhas have one of the strongest bites found in bony fishes. They occur in "schools"  when hunting their prey.

Right-side view of fish. Length of fish is 8.5 inches. Its eyes are large, almost 0.5 inches wide. This allows them to see well in murky waters.

Top view of fish.

View looking directly downward into its mouth, which is 1.5 inches wide.

Oblique side view of the jaws. The opening is slightly over 1.25 inches high. The largest teeth are 1/4 inches tall. All of the teeth are pointed and, as mentioned before, extremely sharp!