Magnificient Muricid Shells

Marine shells belonging to the gastropod family Muricidae (muricids) are among some of the most exquisite shells known. Species like those shown below are characterized by having three aligned rows (varices) of prominent spines (can be very sharp) and a prominent siphonal canal. Their shells range in length from 6 mm to 305 mm. Most muricids exude a yellow fluid that, when exposed to sun light, becomes a purple dye. This dye was used by ancient human cultures for making the "royal" Tyrian purple color. 

Muricids are voracious predators, and the feed on oysters, other clams, and snails. Muricids bore a hole through the shell of their prey and insert a long proboscis to ingest the prey. Muricids are worldwide in tropical to temperate waters, mostly between 0 to 300 meters depth, although some species occur in deep waters (up to 1900 m depth). They can inhabit rocky or rubble bottoms, but the deeper water forms live on muddy bottoms.

ABOVE: Three views (ventral, side, and dorsal, from top to bottom and left to right) of Siratus alabaster (Reeve, 1845): length 135 mm, width 98 mm. This species is found in deep water off Japan and the Philippines. The shell is white to ivory, and the last whorl (largest one) has three prominent webbed varices, which are the thin, blade-like expansions. 

ABOVE: Three views (ventral, side, and dorsal) of Murex cervicornis Lamarck, 1822: length 68 mm, width 57 mm. This species is found eastern Australia. The shell has very stout spines, arranged in three rows.

Four views (ventral, side, dorsal, and living mode) of Murex pecten Lightfoot, 1786: length 140 mm, width 60 mm. This species, which is known also by its common name "Venus Comb," is found throughout tropical waters in the western Pacific (southeast Japan to Queensland, Australia, as well as in the Solomon Islands. The Latin word "pecten" means either "comb" (which applies to its usage for this gastropod), or it can mean "scallop," in reference to a well-known group of bivalve shells.  

In the living position, the numerous spines of M. pecten totally protect the animal from predators, when it is at rest or moving about, because it carries its own protective "cage." The spines along the dorsal side are very sharp. The spines nearest the ocean floor are long enough to elevate the shell and prevent it from sinking in muddy sediment. These particular spines are also curved inward.

To see an excellent video showing how Murex pecten ploughs through the sand, go to <www.revolvy.com>  Or, you can google: either "Venus comb murex/Revolvy" or "Video matching Venus comb murex/Revolvy." Click on the video indicated in the center of the screen.

The early fossil record of family Muricidae is not well known, but there are a few Late Cretaceous gastropods that might be related.
The first undoubted muricids are of Paleocene age. There a few known Eocene species. By the Miocene, this family became more diverse. Today, there are five known subfamilies and approximately 94 genera.

One of the earliest known muricids on the west coast of North America is shown below. This species is of middle to late middle Eocene age from southern and central California.

Two views (ventral and dorsal) of Laevityphis antiquus (Gabb, 1864) length 9 mm, width 5.5 mm; specimen is from the middle Eocene Ardath Shale, San Diego County, southern California.

Some Interesting Facts About Gold And Its Purity

First some background:

Elements make up minerals. There are 118 natural elements; 94 of these are natural and 24 are synthetic.

Minerals are naturally occurring crystalline substances.

Traditional definitions say that minerals have to be inorganic, but there are also organic minerals (biominerals) [examples: bones and teeth].

Nearly all minerals are combinations of elements.

 

     Examples: halite (ordinary table salt) consists of sodium and chlorine

             Pyrite (“fools gold”) consists of iron and sulfur

            Quartz consists of silicon and oxygen

Minerals consisting of pure (native) elements are rare.

            Metallic examples: gold, silver, copper

            Non-metallic examples: carbon (coal, graphite, or diamonds)

         

Now, let’s talk about gold:

Close-up view of crystals of leaf gold, field of view 1.5 mm width

Gold is measured in karats (K). A karat is defined by its degree of purity. Pure gold is 24K.

24K gold = theoretically 100%, but some sources describe the purity as only 99.9%

22K = 91.6 (i.e., divide 22 by 24 = 91.6%)

18K = 75%

14K = 60%

12K gold = 50%

10K = 41.6%

1K= 4.1%

24K gold is very soft; it tends to bend or scratch easily. In order to make gold harder for making jewelry, gold is alloyed with copper, silver, or other elements. When alloys are added, the purity of gold decreases correspondingly.

Enrolled Trilobites

Trilobites are common fossils of the Paleozoic Era. They are easily recognized and treasured among collectors. Trilobites are an extinct group of marine arthropods in which the tri-lobed body is divided into a distinct head (cephalon, with compound eyes), segmented body (thorax), and, in some cases, a distinct "tail" (pygidium). The exoskeleton is divided also length-wise into three parts. See my previous post ["Amazing eyes of the trilobite Phacops dana from Ohio; July 2, 2015] for more information.

Three views (top, bottom, and side) of a plastic model of a Cambrian trilobite (12 cm length). The mineralized "shell" is  green, the numerous legs and antennae are red, and the gills (located on top of the legs) are white.

An actual specimen of a representative trilobite (28 mm length) is shown above. The left eye is better preserved that the right eye, which was "smoothed over" by weathering. This specimen, which is slightly curved, appears to show the initial stage of enrollment (curling up).

Some trilobites are found enrolled. That is to  say, their mineralized exoskeletons rolled up (partially or completely), much like modern pill bugs do. Enrollment was the way for
trilobites to protect their legs, soft undersides, and antennae from predators. 


The ability to enroll developed during early, as a few Cambrian forms have been found preserved this way. It became common in the Ordovician, Silurian, and Devonian but was not acquired by all genera.

Calymene meeki (enrolled state), Ordovician, Ohio. 15 mm width.

Some trilobites could "tuck" the end of their pygidium under the edge of the cephalon, thereby allowing more resistance to being pried apart by a predator. On the image on the right, you can see how the edge of the cephalon is indented to accommodate the projected end of the pygidium.

Eohippus: One of the earliest "horses" in North America

Hundreds of published articles have depicted the classic treatment of horse evolution as shown in the image below: a gradual linear evolution showing the earliest horses changing, over time, into larger size, fewer toes, and larger teeth.

                   from en.wikipedia.org (2019), under the title of "Horse evolution"

Modern studies show that the earliest horses should be referred to, however, as "horses" (in quote marks). Some researchers maintain, furthermore, that only the very modern horse, Equus, is a true horse. Most modern researchers maintain that the evolution of the horse was contrary to the diagram shown above, and definitely not linear nor gradual. 

The name Hyracotherium Owen, 1841, which has been long been traditionally regarded as the earliest horse, is now known to be a too all-encompassing name, because the earliest "horses" were comprised of several genera, not just one genus (Froehlich, 2002--see reference at the end of this post). Hyracotherium is still a valid genus name, but it applies today only to rare specimens of early Eocene "horses" (evolutionarily speaking, very primitive and, thus, the basal group of subsequent horse-like animals) found near London and Paris. The early Eocene "horses" known from western North America [Wyoming, northwestern New Mexico, and to a lesser degree in Colorado] belong to at least five genera (some of which are morphologically very similar to each other), and one is Eohippus Marsh, 1876.

What is somewhat confusing is that, originally, the western North American earliest "horse" remains were identified as belonging in genus Eohippus, later changed to Hyracotherium, and are now reassigned to Eohippus.

Eohippus was small-dog size. It had four toes on its front legs and three toes on the rear legs. Eohippus lived during the early and middle Eocene epochs (55 to 40 million years ago). 

An entire skeleton (about 12 inches high at the shoulder) of Eohippus angustidens (Cope, 1875) of Eocene age from Wyoming. This specimen is still on display at the Natural History Museum of Los Angeles County (LACM). By permission of LACM, it was photographed R. Squires and used in a published article by Squires and Squires (1981).

Eohippus angustidens is found in lower Eocene (Ypresian Stage) strata in Wyoming, northwestern New Mexico, Colorado, and tentatively from Baja California, Mexico. 

The image on the left is the side view of a single molar tooth (a cheek tooth), 6.5 mm height and 10 mm length, of Eohippus angustidens (Cope, 1875) from Eocene rock in Wyoming. The image on the right is the top view of the same molar tooth. The fact that the molar teeth (cheek teeth) of Eohippus has low crowns indicates that the animal was a browser that fed on fruit, leaves, and twigs, rather than grasses.

Compared to geologically younger horses, including the modern horse Equus caballus, Eohippus was much smaller with shorter legs, more toes per foot, and had a much smaller skull with smaller teeth. Shown above  is the comparative size of a molar tooth of Eohippus versus that of a corresponding molar tooth (partial specimen [52 mm height] because the lower part is missing) of the modern-day horse Equus caballus. 

This image is the top view of the same molar tooth (24.3 mm width) of the modern-day horse shown above. There has been, however, some differential weathering of the top surface. The molar teeth of Equus caballus are broad and relatively flat for the purposes of crushing and grinding grass. The teeth of E. caballus are called hyposodont teeth because they possess thick tough layers folded down into the main structure of the tooth. These kind of teeth allowed horses more modern than Eohippus to graze on silica-rich grasses. 

Treating the geologic history of "horses," including their migrations among the continents is beyond the scope of this post. For an excellent and succinct animation depicting this history, Google:
                                netnebraska.org                 

Froehlich, D.J. 2002. Quo vadis eohippus? The systematics and taxonomy of the early Eocene equids (Perissodactyla). Zoological Journal of the Linnean Society 134:141-256. [available online as a free PDF].

Squires, J. and R. Squires. 1981. Can you name the first horse? Equus 40:52-53, 58.

Southern California’s Highest Mountain

Google Earth Pro Oct., 2019 image showing location of San Gorgonio Mountain.

 San Gorgonio Mountain is the highest peak [11,503 feet (3506 m)] in southern California. The peak is 27 mi (43 km) east of the city of San Bernardino, San Bernardino County and is a easy drive from most of Los Angeles and Orange counties. It is the peak with the greatest vertical gain (5,840 feet) in California. The mountain hosts the longest recorded line of sight in the contiguous United States; it is plainly visible from the summit of Mt. Whitney, 190 miles away.

View north-northeast from a commercial airliner. Image taken in mid July, 2010.

Closer view north from the same airliner. San Gorgonio Mountain has a few patches of snow near its summit. Under the wing, Big Bear Lake is visible. The mountain has a somewhat pyramid shape with a steep north face and a slightly shallower south face. 

An even closer view of summit of San Gorgonio Mountain. The summit plateau is large and broad (1 square mile). The summit has an Alpine climate, and snow can be present, even as late as mid-July. 

Northwest view of San Gorgonio Mountain (its summit has a few patches of snow left on it). Three major southern California rivers have their source on the mountain: the Whitewater River (shown here just right of the center of image), the San Gorgonio River, and the Santa Ana River.

San Gorgonio Mountain is part of the Transverse Ranges, an east-to-west mountain chain formed by tectonic forces between the Pacific and North American plates along the San Andreas fault, which lies just south of San Gorgonio Mountain.

The mountain is a massive block of quartz monzonite igneous rock (please see my earlier post--March 3, 2017, San Andreas Fault Displacement of a Distintive Granite), which sits on an ancient platform of Precambrian gneissic metamorphic rocks. Glacial and fluvial deposits dominate the surface of the lowest part of the mountain. During the Pleistocene “Ice Age,” there were two separate episodes of glaciation (both Wisconsin age, which was 75,000 to 11,000 years ago) on San Gorgonio Mountain, as evidenced by cirques and huge terminal embankments of coarse angular debris, up to 700 feet thick.

An ancient "sundial"

The common name of the gastropod genus Architectonica Röding, 1798 is the "sundial" snail. There are140 extant (recent) species, and they have distinctive discoidal shells with a high "spiral staircase" in the center of the underneath side of the shell. Architectonica is widespread today, and most of the species live between 40°N and S, in subtropical to tropical marine waters (e.g., Indo-Pacific, East Africa, Japan, Hawaii). Although they range in depths between intertidal and abyssal, they are most commonly found in 10-65 m depths. They are carnivorous gastropods and prey mainly on sea anemones, sea pens, and corals.

Architectonica is classified as belonging to the family Architectonicidae Gray, 1850, which, in turn, belongs to a poorly resolved group of snails known as the "lower heterobranchs," whose larval shells are diagnostic in their morphology.

The following three images are of a recent shell of Architectonica perspective (Linnaeus, 1758), from Oman. The views are dorsal, apertural, and ventral, in the order they are shown. The specimen is 48 mm in diameter and 25 mm in height.

The next two images are of the fossil Architectonica cognata Gabb, 1864, of middle Eocene age (approximately 48 million years old), from southern California. The views are dorsal and ventral, in the order they are shown. 

The central region of this specimen is "plugged up" with hard siltstone. Careful cleaning is needed in order to expose the delicate shell underneath. Cleaning of fossil specimens demands expertise, otherwise, critical features can be damaged.

The geologic range of Architectonica is Paleocene to Recent. Architectonicids do not occur in older rocks (Mesozoic and Paleozoic).

For those who seek more detailed information (i.e., I used this reference for many of the above facts), see:

Bieler, R., and R.E. Petit. 2005. Catalogue of Recent and fossil taxa of family Architectonicidae Gray, 1850 (Mollusca: Gastropoda). Zootaxa 1101:119 pp.

MASTODON VS. MAMMOTH TEETH

Mastodons and mammoths are extinct proboscideans, a group animals that includes the present-day elephants. 

This excellent image, which is from Wikipedia.org, shows how the general body of a mastodon (on the right) differed from that of a wooly mammoth (on the left, which could be up to 13 feet tall and weigh up to 8 tons). Mastodons were somewhat smaller had shorter legs, more muscular bodies, and a sloping (rather than a bulbous) head. 

Mastodon species inhabited North and Central America in the Pliocene, up to their extinction at the end of the Pleistocene, 10,000 to 11,000 years ago.

Mastodons ate coarse vegetation (twigs, leaves, roots, etc.) than did the mammoths. The evidence is provided by the shape of their molar teeth. As shown in the following image, they are cusp-shaped and were designed to crush coarse vegetation.

     A plaster replica of mastodon teeth (about 5 inches height). 



Mammoth teeth, in striking comparison, consist of a series of enamel plates, designed for chewing leaves and other "soft" vegetation (e.g., sunflowers, milkweed), or possibly even grasses. The latter contains silica, which would wear down teeth unless they are constructed in these parallel enamel plates, as shown in the following image.

    A plaster replica of a mammoth tooth (about 6.5 inches height).

Mammoth species were more widespread than mastodons and went extinct later, about 4,000 years ago.

An unusual Turritella gastropod about 50 million years old from the west coast of the United States

Turritella gastropods are very common shallow-marine fossils. Their geologic time range is from the Cretaceous to modern-day. Their shells are long and narrow, with spiral sculpture (ribs), although some species can have small nodes on the spirals.

During my years as a paleontologist, I have collected many Turritella. One of my favorite subspecies is Turritella meganosensis protumescens (approximately 51 million years old = early Eocene), because it is very unusual in having, at least on the adult part of the shell, only one very thick, spiral rib.

Turritella meganosensis protumescens Merriam and Turner, 1937,

Ventura Co., southern California;

 height of largest specimen 2 1/4 in. (57 mm)

This subspecies of turritellid gastropod has been found in only a few places, and most are in California (two areas in Ventura County and one in Riverside County). It has also been found, however, in southwestern Oregon.

Specimens of this gastropod are associated commonly with coarse-grained sediments (including pebbles), which were deposited in nearshore, high-energy ancient environments. Apparently, the thick shell of T. m. protumescens with its wide spiral rib on the upper part of each whorl was well adapted for these turbulent waters.

Turritella meganosensis protumescens Merriam and Turner, 1937,

Ventura County, southern California;

 height of specimen 2.5 in. (62 mm).

The specimen shown immediately above is the largest specimen I have collected of this turritellid. The early part of its shell is weathered, and, therefore, does not show the spiral ribs that are normally present there.