Many species of plants and animals have become extinct throughout the geologic past. Ammonites, trilobites, and dinosaurs are among the more familiar types whose vanished representative lineages now famously reside within the rocks of the earth's crust. Still, despite the fact that such sensational, long-lived species died out, the larger grouping or classification of animals to which they belonged continues to survive to this date. The ammonite, for example, was a cephalopod mollusk--rather distantly related to our modern day chambered nautilus; the trilobite, in turn, belonged to a scientific phylum called Arthropoda, a phylum that includes such successful relatives as insects, crabs, crustaceans, and spiders; and the dinosaurs of course were vertebrate animals, whose backboned kinds are very much alive and well.

While each of the above-listed creatures became extinct for varying paleobiological reasons, the broader category, or phylum to which they belonged has survived. And, as far as paleontologists can determine, virtually all the major groups of animals present during the dawn-age Cambrian Explosion of approximately 535 to 510 million years ago, when there occurred a phenomenal, unprecedented radiation of biological diversification, are still alive today--despite the fact that capricious culling periodically eliminates innumerable species throughout geologic time.

A notable exception to this pattern of persisting phylum survival is the paleontological occurrence of curious critters paleontologists call salterella and Volborthella. They're invertebrate animals exclusive to the early Cambrian that secreted conical to ice cream cone-shaped shells roughly a quarter inch-long long; and they're now placed into their own unique phylum called Agmata, a phylum that went belly-up, extinct, approximately 510 million years ago--among only a select few of the major taxonomic categories of animals ever to vanish completely, leaving no discernible descendants or relatives.

To put this in perspective, the extinction of an entire phylum such as Agmata is analogous to having all the corals, for example, disappear from our oceans--or, every animal with a backbone suddenly gone forever. By all speculative accounts, this was a terribly traumatic event in the history of our planet. Prime hunting grounds for Agmata small shelly fossils include the Great Basin wilds of western to central Esmeralda County, Nevada.

Yet another fascinating animal preserved in rocks exclusively of early Cambrian geologic age is the enigmatic archaeocythid, an invertebrate type that along with Agmata salterella-Volborthella and Olenellid trilobites thrived in earth's warm shallow seas roughly 528 to 510 million years ago. Although those creatures never survived the early Cambrian age, only the Agmata represent a complete, unique phylum that went extinct. Olenellid trilobites and archaeocythids belong to the living phyla Arthropoda and Porifera (the sponges), respectively.

Still and all, not too many years ago a consensus of invertebrate paleontologists considered archaeocyathids members of their own unique Phylum called Archaeocyatha, preferring to count them among the select few phyla ever to go belly-up, to vanish forever with no known modern biological affinity.

The archaeocyathid was an exclusively marine invertebrate animal that never survived beyond the early Cambrian of the Cambrian Period; it goes absent from the geologic record around 510 million years ago. Yet, during a life span of perhaps "only" 18 million years (roughly 528 to 510 million years) it was able to attain worldwide distribution while developing into scores of different species. In morphological aspect, an archaeocyathid has been variously described as a peculiar cross between a coral and a sponge. White it admittedly reveals obvious similarities to both, it is in fact decidedly different in many key delineating comparisons.

Pioneering early Cambrian investigators separated almost immediately into two warring camps over the exact zoological classification of the archaeocyathid. That is to say: just where exactly should one place the animal--is it a coral or sponge? Some paleontologists argued in favor of the coral category (see the classic 1868 publication "On a remarkable new genus of corals" in American Journal of Science, 2nd service, volume 46, pages 62-64), while others--the majority opinion, actually--vociferously proclaimed that it most closely resembled a sponge; hence the ubiquitous, "endearing" term "pleosponge" came about to describe the archaeocyathid, a designation still found in many older textbooks on invertebrate paleontology.

Although it's true that both battling camps could adduce compelling evidence to support their views, all the controversy occurred before any serious analysis of the archaeocyathid was undertaken. When some especially well preserved specimens were finally examined with that proverbial fine-toothed comb, paleontologists came to the conclusion that, yes, while the archaeocyathid did show apparent similarities to both corals and sponges, it was indeed sufficiently different from coral coelenterates and typical Porifera to warrant placement in a new, separate phylum--then known as Archaeocyatha.

That zoological classification of archaeocyathids as a distinct, unique phylum lasted for several decades. When somebody named a new species of archaeocyathid, the official peer-reviewed scientific paper in which the formal description appeared always placed an archaeocyathid type specimen within the phylum Archaeocyatha. In recent years, though, rigorous cladistic phylogenetic analysis nests archaeocyathids pretty convincingly among the Porifera--the sponges; more specifically, it is now usually considered an extinct calcareous sponge--the first shell-secreting member of the phylum Porifera to appear during the Cambrian Explosion, and the very first known sponge to go extinct, disappear completely from the geologic record.

Since the actual archaeocyathid soft-bodied animal has never been found preserved, researchers base their conclusions concerning the creature on study of the available fossil shell material. The archaeocyathid secreted a conical to cup-shaped calcium carbonate structure typically half an inch to three inches longs, and one-eighth to one inch in diameter. A few aberrant species can reach a foot or more in length, however. Some varieties in the class Irregularia began to sport wildly radiating, branching shell designs, a feature which distinguishes them from all other kinds of archaeocyathids. Most, though, retained their conical, elongated configuration right up to the end of their reign. Apparently the creature led a sessile life attached to the sea floor; some types sometimes formed minor reef-like communities. As a matter of fact, it seems to have been the very first Cambrian Explosion shell-bearing animal to develop a quasi-reef, or biohermal structure on the sea floor, a life-style greatly impoved upon by the corals, which succeeded the archaeocyathid in the geologic record during Ordovician Period times.

Typically, archaeocyathids formed "gardens" in the shallow early Cambrian seas, parallel to the ancient coastlines, where they probably fed by filtering for microscopic plants and animals, similar to the habits of present day sponges, corals, bryozoans, brachiopods, and barnacles. Their shell was extremely fragile--it is indeed miraculous that we have as many complete specimens to study as we do--and they disdained with a passion any degree of muddy water. It is conjectured that they reproduced by giving rise to free-floating larvae that swan about for a time before settling to the sea floor. Additionally noteworthy is that sometimes seen preserved with archaeocyathids are the remains of cyanobacterial blue-green algae, suggesting some degree of symbiotic relationship.

All archaeocyathids became extinct by the close of the early Cambrian, approximately 510 million years ago. They left no discernible descendants. They remain the only major group of sponges to leave no living representatives. In North America and Australia, extinction of the archaeocyathids coincides with the disappearance of Olenellid trilobites, and this leads to the interesting idea that perhaps the two shared some kind of symbiotic, mutually beneficial relationship, perishing in tandem when their required conditions for life vanished. Exactly why the archeocyathid died out is a major paleontological mystery, much like the more notorious debate over the demise of the dinosaur. At present, the most logical hypothesis is that the archaeocyathid, possessing a very primitive silt filtering system, was unable to adapt to increasingly muddy waters, that corals and siliceous sponges were much more efficient, successful adapters in general, and therefore were primed and ready to claim each available paleo-ecological niche the archaeocyathid was forced to surrender. This idea finds support in the lithology of the rocks in which fossil archaeocyathids are today preserved: They occur almost exclusively in pure limestones that are uncontaminated by silts or muds.

Because archaeocyathids gained worldwide distribution within such a finite, "short" life span--around 18 million years--they are an excellent guide fossil to the early Cambrian geologic age. Find an archaeocyathid anywhere on the planet and you know immediately that you are dealing with rocks dating from the early Cambrian. Their remains have been identified from several geographic localities, including Morocco, Sardinia, Mexico, Yukon Territory, British Columbia, Labrador, China, Ural Mountains of the former Soviet Union, Siberia, East Antarctica, West Antarctica, Australia, and the United States.

In the United States, archaeocyathids occur in Alaska, Washington state, Alabama, Georgia, Virginia, New Jersey, Pennsylvania, New York, Nevada, and California. As a matter of fact, some of the best archaeocyathid localities in the world occur in western to central Nevada and eastern California. Here, sprawling across an area encompassing hundreds of square miles in Inyo County, California, and neighboring Esmeralda County, Nevada, lies the land of the archaeocyathid. Most occur in a geologic rock unit called the Poleta Formation, lower Cambrian in age of course, a formation named for its extensive and typical exposures in Poleta Canyon a few miles east of Bishop, California. This is a remarkably widespread and distinctive series of strata consisting of alternating limestones, quartzites (heat and pressure-altered sandstone), and shales. And, in keeping with their invariable characteristic distribution in other parts of the world, archaeocyathids occur only in the silt-free limestones. Within the Poleta Formation, these fossil-bearing calcium carbonate accumulations can be found in the lowest, or oldest stratigraphic sections of exposures, below thick deposits of Poleta greenish shales and brownish quartzites which, while barren of archaeocyathids, are noted for locally common Olenellid trilobites, annelid trails, and echinoderms.

These preserved archaeocyathids represent, in fact, some of the oldest recognizable remains of animals with hard parts from the Cambrian Explosion period, which began 535 million years ago--a moment in geologic time some 965 million years after the appearance of what scientific investigators now consider the first undisputed eukaryote (a cell with a nucleus; all complex, modern plant and animal life is eukaryotic) and only about 65 million years following the first multicellular eukaryotic animals at roughly 600 million years ago (the earth is approximately 4.55 billion years old).

Prime hunting grounds for the fossil include western to central Nevada and the northernmost quarter to third of Inyo County, California. And one of the very best regions in which to paleo-prospect for archaeocyathids lies a few miles east of Big Pine, California, in the White-Inyo Mountains, along Westgard Pass. The drive over State Route 168 toward Westgard Pass slices through several thick outcroppings of the fossiliferous limestones lowest in the Poleta Formation, within which occur locally common to abundant remains of archaeocyathids, some in primitive reef form.

To reach an excellent fossil-bearing area where nice specimens of archaeocyathids can be found, first travel to Big Pine, California, a wonderful community in the Owens Valley at the base of the great Sierra Nevada, 15 miles south of Bishop, or 44 miles north of Lone Pine along Highway 395. From the northern outskirts of Big Pine along Highway 395, take State Route 168 east. But be sure to take time to observe the striking specimen of giant sequoia (Big Tree-Sierra Redwood) at the intersection of 395 and State Route 168--it's The Roosevelt Tree, planted July 23, 1913 in honor of US president Teddy Roosevelt, to commemorate the opening of SR 168 to automobile traffic over Westgard Pass. Proceed two and four-tenths miles to the intersection with the Death Valley-Saline Valley Road. Recheck your mileage here, then continue onward along SR 168.

From the junction with Death Valley-Saline Valley Road, travel another nine and nine-tenths miles. At this point route 168 begins to cut through a "narrows" in the limestones of the lower Cambrian Poleta Formation; the limestones here are massive (showing indistinct layering characteristics), blue-gray to orange-mottled, and fossiliferous with the remains of archaeocyathids. For the next six-tenths of a mile the Poleta limestones are prominent and easily accessible on both sides of SR 168. Find a convenient--and safe--pullout on which to park (the road does indeed narrow considerably here; extreme caution must be exercised), then hike to the slopes above the road to the locally fossiliferous calcium carbonate accumulations.

You will need to hike with assiduous attention in order to observe the best-preserved specimens. Remember, obviously, that lots of folks have been here before you, including innumerable geology classes from all over the United States, Canada, and Mexico--in addition to any number of interested amateur paleontology enthusiasts and visiting professional paleontologists from all over the world, as well. And so it is inevitable, then, that everybody must indeed have their own turn at exploring these remarkable Poleta archaeocyathid-bearing exposures, and multitudes who've previously secured a special use permit from the US National Forest Service invariably collect "a few" sample specimens to take home. Nevertheless, with attentive, dedicated searchings, one should be able to spot here many nicely preserved archaeocyathids, some preserved in their original growth positions for roughly 520 million years in isolated reefy communities. Watch for their distinctive cross-sections approximately a quarter to one-half inch in diameter, an oval to circular section revealing a double outer wall separated by many partitions. In longitudinal, or lengthwise section, most specimens measure around one-half to two inches long. Among the more commonly observed genera in the rocks are Ethmophylum, Ajacicyathus, Archaeocyathus, Protophaetra, Annulofungia, and Robustocyathus.

Lying in stratigraphic position above the archaeocyathid-bearing limestones are exposures of greenish to olive-gray shales and quartzites representing progressively younger deposits of the Poleta Formation. In these mostly detrital strata occur scattered and localized concentrations of Olenellid trilobites, including such genera as Esmeraldina, Fremontia, Laudonia, Nevadella, Nevadia, and Holmia. Also identified from the interstratified shales and quartzites have been brachiopods, hyolithids (an extinct variety of mollusk), and two rare, early forms of echinoderms, Helicoplacus and an edrioasteroid--the oldest remains of echinoderms ever discovered. As a matter of fact, both Helioplacus and the Olenellids represent the very first shell-bearing members of their respective phyla (Echinodermata and Arthropoda) to appear in rocks deposited during the Cambrian Explosion, and became the first types from their major zoological groups to go extinct. But the most commonly seen paleontologic specimens in the Poleta Formation shales and quartzites are very conspicuous ichnofossils--undescribed annelid and arthropod trails preserved as sinewy ridges several inches in length, winding their way across the bedding planes. Over in neighboring Esmeralda County, Nevada, by the way, the Poleta Formation Cambrian Explosion sedimentary rocks also yield quality specimens of Anomalocaris, an extinct, presumably predatory arthropod that probably terrorized trilobites during the early Cambrian.

While this general area provides excellent opportunities to find archaeocyathids, other sites along SR 168 between "the narrows" and Westgard Pass up ahead (farther north) also often disclose locally common examples of additional early Cambrian invertebrate fossils preserved in the Poleta Formation and the stratigraphically older underlying Montenegro Member of the Campito Formation--a predominantly detrital unit of greenish to tan shales and brownish quartzites that yield sporadic occurrences of Olenellid trilobites, primarily. Outcropping below the Montenegro Member is the Andrews Mountain Member of the Campito Formation; and near the top (youngest horizons) of the Andrews Mountain Member, in strata close to 522 million years ancient, the oldest trilobites in North America--and possibly the world--have been discovered, an Olenellid form resembling the Siberian trilobite Repinaella.

For those planning a visit to the Westgard Pass area in search of paleontologic specimens, several fine reference publications are available for study. Among the more informative works are: Guidebook for Field Trip to Pre-Cambrian-Cambrian Succession White-Inyo Mountains, California by C.A. Nelson and J. Wyatt Durham; "Stratigraphic Distribution of Archaeocyathids in the Silver Peak Range and White and Inyo Mountains, Western Nevada and Eastern California" by Edwin H. McKee and Roland A. Gangloff, Journal of Paleontology, volume 43, number 3, May, 1969; and Geologic Map of the Blanco Mountain Quadrangle, Inyo and Mono Counties, California, U.S. Geological Survey Quadrangle Map 529. This last one shows the geographic distribution of outcrops of rock formations in the Westgard Pass area, drawn over a topographic base map--an invaluable reference to consult when exploring here.

In addition to the significant fossils, there are other wonders to explore in the Westgard Pass lands. To the immediate west and north, for example, lie the famous Bristlecone Pine groves in the White Mountains at elevations over 10,000 feet. Here, the oldest continuously living, non-cloning thing on earth--the Bristlecone Pine, a few have been accurately calculated at over 4,000 years old--survives atop a geologic rock formation, the Reed Dolomite, that dates from earth's oldest geological division, the Precambrian of over 550 million years ago. This is certainly a unique and appropriate coincidence.

When hunting for fossils in the Westgard Pass region, be sure to abide by the rules and regulations--don't keep anything found within the Inyo National Forest unless you've obtained a special use permit from the US Forest Service ranger station in Bishop, California. Also, by way of caution, elevations here range from around 7,000 feet to way over 10,000 feet, so try to keep your physical activities moderate until you are well-acclimated. There is a vast area of potential fossil-bearing material to explore and it would be inadvisable--not to mention downright risky--to try to cover it all in a single day. With so much recreation so accessible, this would be an ideal place for a stay of a week or two, preferably during summer when the roads at higher elevations are open.

During the early Cambrian, the Westgard Pass area was a warm, shallow sea situated near the equator in which numerous species of now long-extinct animals flourished--among them, the very first shell-bearing examples of three great zoological categories to appear in sedimentary strata deposited during the crucial Cambrian Explosion period of 535 to 510 million years ago--Olenellid trilobites, Helicoplacus echinoderms, and archaeocyathids who, individually, belong to the living phyla Arthropoda, Echinodermata, and Porifera, respectively.

Perhaps we may never fully understand the exact reasons for their complete disappearance, yet because Olenellid trilobites, Helicoplacus echinoderms, and archaeocyathids were the first of their respective phyla to contribute no more to the geologic record beyond the early Cambrian 510 million years ago, their paleontological presence together at Westgard Pass demonstrates that they never really went away; they're still alive, on their way to a kind of immortality--a vanished invertebrate association of Cambrian Explosion creatures who now survive not only in the rocks, preserved in place for over a half billion years, but also in the lives of prehistory explorers, so that we may learn of a time and remember for all time a distant age when multicellular animal life on earth was relatively new, and of perilous existence.

Click on the images for a larger pictures. Left--An ancient Bristlecone Pine grows atop the late Precambrian Reed Dolomite (some 550 million years old, from Earth's oldest geologic time subdivision, the Precambrian) in California's White Mountains, north of the Westgard Pass archaeocyathid-trilobite-echinoderm paleontologic localities. The Bristlecone Pine is the oldest continuously living, non-cloning thing on earth--a few have been accurately calculated at over 4,000 years old. Image processed through photoshop from a photograph taken and originally uploaded to Google Earth by an individual named Sonny Thornborrow.

Right--A view westward to the Sierra Nevada along California State Route 168, several miles east of Big Pine. Here, SR 168 cuts through a narrows in the metamorphosed mudstones, shales, sandstones, and quartzites of the early Cambrian Andrews Mountain Member of the Campito Formation (roughly 526 to 522 million years old); quartzitic shales in the youngest phases of deposition yield the oldest trilobites recognized from the White-Inyo Mountains Precambrian-Cambrian geologic complex. Note bicycle rider along pavement for scale. Image processed through photoshop from a photograph taken and originally uploaded to Google Earth by an individual who goes by the cyber-moniker "Delphigrup."

Click on the pictures for larger images. Left to right: A chunk of limestone from the lower Cambrian Poleta Formation that reveals several natural cross-sections of archaeocyathids--an extinct calcareous sponge (phylum Porifera)--in their classic preservational aspect--a hollow interior surrounded by a double-wall exterior separated by many partitions. The specimens are approximately 520 million years old.

At right is an Olenellid trilobite cephalon (head shield) from the lower Cambrian Poleta Formation. It is certainly of the genus Nevadia, and most likely can be assigned with a fair degree of accuracy to Nevadia parvoconica. The specimen is roughly 518 million years old.

Click on the pictures for larger images. Left to right: A slab of quartzite (heat and pressure-altered sandstone) from the lower Cambrian Poleta Formation bearing numerous annelid (worm) trails--the sinewy ridges that crisscross the rock surface. Such ichnofossils are typical of Poleta Formation exposures that lie directly above (hence, they are younger) the archaeocyathid-rich limestone accumulations at the base of the Poleta stratigraphic section. The specimens are roughly 518 million years old.

At right is an Olenellid trilobite cephalon (head shield) from the lower Cambrian Montenegro Member of the Campito Formation. Angle and length of genal spines, in combination with thickened area at top of cephalon and general shape of glabella all help to place this specimen in the genus Nevadella sp., which is about 521 million years old.

Click on the pictures for larger images. Left to right: An Olenellid trilobite cephalon (head shield) from the lower Cambrian Montenegro Member of the Campito Formation. As far I can determine, it matches no known previously described Campito Formation trilobite. I found this specimen in virtually the same spot that I located the Campito Formation Nevadella specimen, directly above, so presumably it came from an identical early Cambrian biozone--usually referred to by paleontologists as the Fallotaspis Zone, in honor of the most characteristic trilobite present at that specific stratigraphic horizon. The extinct arthropod is around 521 million years old.

At right is the best trilobite I found in the Lower Cambrian Montenegro Member of the Campito Formation during a visit to Esmeralda County, Nevada. Must have been beginner's luck. I wasn't at the main trilobite quarry more than five minutes, splitting chunks of shale others had neglected to split thoroughly, when a nondescript piece of shale literally cleaved in my hands to reveal a mostly complete specimen of Fallotaspis cf. bondoni. This is just about the oldest articulated trilobite one can be expected to find in the geologic record. A species of Eofallotaspis occurs in a rather narrow 30 centimeter bed directly below where I found my Fallotaspis, but they're all fragmentary, disarticulated remains of head shields--except, that is, for a few very rare, poorly preserved complete specimens; and quite rare, stray occurrences of trilobites have been spotted a few tens of feet below the Eofallotaspis bed in the Andrews Mountain Member of the Campito Formation. The Eofallotaspis bed exposed throughout Esmeralda County, Nevada, marks the base of the proposed Montezuman Stage of the Early Cambrian Waucoban Series, which is that point in the geologic record where the first common trilobites begin to appear. Estimated geologic age of the specimen is approximately 521 million years old.

• The Acoustic Guitar Solitaire Of Inyo: A Cyber-CD: I play 30 covers of some of my favorite songs on an acoustic 6-string guitar; it's all free music.
• Beyond The Timberline--A Cyber-CD: I play 32 selections comprised of covers and original tunes on acoustic 6 and 12-string guitars; it's all free music.
• The Distant Path--A Cyber-CD: I play 32 acoustic guitar covers and original compositions; it's all free music.
• Inyo And Folks--A Musical History--A Quintuple Cyber-CD: My parents and I play 203 selections; it's all free music.
• Acoustic Stratigraphy--A Cyber-CD: I play 34 covers of some of my favorite songs on 6 and 12-string guitars; it's all free music.
• Back To Badwater--A Cyber-CD: I play 32 covers and original compositions on 6 and 12-string guitars; it's all free music.
• All Inyo All The Time: All six of my cyber-cds in one place (includes a quintuple cyber-cd box set); links to all of my solo acoustic guitar playing, in addition to selections my parents and I recorded during the Golden Age of our spontaneous, impromptu recording sessions. Includes an option to stream all 364 selectons; thirteen hours, seventeen minues and forty seconds of music (it's all free music).
• It's A Happening Thing--Music From The Year 1967: All songs that charted US Billboard Hot 100 (#1 to #100) and Bubbling Under (records that charted in positions #101 to #135) in 1967.

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• A Visit To Fossil Valley, Great Basin Desert, Nevada: Take a virtual field trip to a Nevada locality that yields the most complete, diverse, fossil assemblage of terrestrial Miocene plants and animals known from North America--and perhaps the world, as well. Yields insects, leaves, seeds, conifer needles and twigs, flowering structures, pollens, petrified wood, diatoms, algal bodies, mammals, amphibians, reptiles, bird feathers, fish, gastropods, pelecypods (bivalves), and ostracods.
• Fossils At Red Rock Canyon State Park, California: Visit wildly colorful Red Rock Canyon State Park on California's northern Mojave Desert, approximately 130 miles north of Los Angeles--scene of innumerable Hollywood film productions and commercials over the years--where the Middle to Late Miocene (13 to 7 million years old) Dove Spring Formation, along with a classic deposit of petrified woods, yields one of the great terrestrial, land-deposited Miocene vertebrate fossil faunas in all the western United States.
• Cambrian And Ordovician Fossils At Extinction Canyon, Nevada: Visit a site in Nevada's Great Basin Desert that yields locally common whole and mostly complete early Cambrian trilobites, in addition to other extinct organisms such as graptolites (early hemichordate), salterella (small conical critter placed in the phylum Agmata), Lidaconus (diminutive tusk-shaped shell of unestablished zoological affinity), Girvanella (photosynthesizing cyanobacterial algae), and Caryocaris (a bivalved crustacean).
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• Fossil Plants Of The Ione Basin, California: Head to Amador County in the western foothills of California's Sierra Nevada to explore the fossil leaf-bearing Middle Eocene Ione Formation of the Ione Basin. This is a completely undescribed fossil flora from a geologically fascinating district that produces not only paleobotanically invaluable suites of fossil leaves, but also world-renowned commercial deposits of silica sand, high-grade kaolinite clay and the extraordinarily rare Montan Wax-rich lignites (a type of low grade coal).
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• Fossil Plants In The Neighborhood Of Reno, Nevada: Visit two famous fossil plant localities in the Great Basin Desert near Reno, Nevada--a place to find leaves, seeds, needles, foilage, and cones in the middle Miocene Pyramid and Chloropagus Formations, 15.6 and 14.8 to 13.3 million years old, respectively.
• Dinosaur-Age Fossil Leaves At Del Puerto Creek, California: Journey to the western edge of California's Great Central Valley to explore a classic fossil leaf locality in an upper Cretaceous section of the upper Cretaceous to Paleocene Moreno Formation; the plants you find there lived during the day of the dinosaur.
• A Visit To Ammonite Canyon, Nevada: Explore one of the best-exposed, most complete fossiliferous marine late Triassic through early Jurassic geologic sections in the world--a place where the important end-time Triassic mass extinction has been preserved in the paleontological record. Lots of key species of ammonites, brachiopods, corals, gastropods and pelecypods.
• Fossil Plants At The Chalk Bluff Hydraulic Gold Mine, California: Take a field trip to the Chalk Bluff hydraulic gold mine, western foothills of California's Sierra Nevada, for leaves, seeds, flowering structures, and petrified wood from some 70 species of middle Eocene plants.
• Field Trip To The Alexander Hills Fossil District, Mojave Desert, California: Visit a locality outside the southern sector of Death Valley National Park to explore a paleontological wonderland that produces: Precambrian stromatolites over a billion years old; early skeletonized eukaryotic cells of testate amoebae over three-quarters of billion years old; early Cambrian trilobites, archaeocyathids, annelid trails, arthropod tracks, and echinoderm material; Pliocene-Pleistocene vertebrate and invertebrate faunas; and late middle Miocene camel tracks, petrified palm wood, petrified dicotlyedon wood, and permineralized grasses.
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• Plant Fossils At The La Porte Hydraulic Gold Mine, California: Journey to a long-abandoned hydraulic gold mine in the neighborhood of La Porte, northern Sierra Nevada, California, to explore the upper Eocene La Porte Tuff, which yields some 43 species of Cenozoic plants, mainly a bounty of beautifully preserved leaves 34.2 million years old.
• Late Triassic Ichthyosaur And Invertebrate Fossils In Nevada: Journey to two classic, world-famous fossil localities in the Upper Triassic Luning Formation of Nevada--Berlin-Ichthyosaur State Park and Coral Reef Canyon. At Berlin-Ichthyosaur, observe in-situ the remains of several gigantic ichthyosaur skeletons preserved in a fossil quarry; then head out into the hills, outside the state park, to find plentiful pelecypods, gastropods, brachiopods and ammonoids. At Coral Reef Canyon, find an amazing abundance of corals, sponges, brachiopods, echinoids (sea urchins), pelecypods, gastropods, belemnites and ammonoids.
• Fossils From The Kettleman Hills, California: Visit one of California's premiere Pliocene-age (approximately 4.5 to 2.0 million years old) fossil localities--the Kettleman Hills, which lie along the western edge of California's Great Central Valley northwest of Bakersfield. This is where innumerable sand dollars, pectens, oysters, gastropods, "bulbous fish growths" and pelecypods occur in the Etchegoin, San Joaquin and Tulare Formations.
• Field Trip To The Kettleman Hills Fossil District, California: Take a virtual field trip to a classic site on the western side of California's Great Central Valley, roughly 80 miles northwest of Bakersfield, where several Pliocene-age (roughly 4.5 to 2 million years old) geologic rock formations yield a wealth of diverse, abundant fossil material--sand dollars, scallop shells, oysters, gastropods and "bulbous fish growths" (fossil bony tumors--found nowhere else, save the Kettleman Hills), among many other paleontological remains.
• A Visit To The Sharktooth Hill Bone Bed, Southern California: Travel to the dusty hills near Bakersfield, California, along the eastern side of the Great Central Valley in the western foothills of the Sierra Nevada, to explore the world-famous Sharktooth Hill Bone Bed, a Middle Miocene marine deposit some 16 to 15 million years old that yields over a hundred species of sharks, rays, bony fishes, and sea mammals from a geologic rock formation called the Round Mountain Silt Member of the Temblor Formation; this is the most prolific marine, vertebrate fossil-bearing Middle Miocene deposit in the world.
• High Sierra Nevada Fossil Plants, Alpine County, California: Visit a remote fossil leaf and petrified wood locality in the Sierra Nevada, at an altitude over 8,600 feet, slightly above the local timberline, to find 7 million year-old specimens of cypress, Douglas-fir, White fir, evergreen live oak, and giant sequoia, among others.
• In Search Of Fossils In The Tin Mountain Limestone, California: Journey to the Death Valley area of Inyo County, California, to explore the highly fossiliferous Lower Mississippian Tin Mountain Limestone; visit three localities that provide easy access to a roughly 358 million year-old calcium carbate accumulation that contains well preserved corals, brachiopods, bryozoans, crinoids, and ostracods--among other major groups of invertebrate animals.
• Middle Triassic Ammonoids From Nevada: Travel to a world-famous fossil locality in the Great Basin Desert of Nevada, a specific place that yields some 41 species of ammonoids, in addition to five species of pelecypods and four varieties of belemnites from the Middle Triassic Prida Formation, which is roughly 235 million years old; many paleontologists consider this specific site the single best Middle Triassic, late Anisian Stage ammonoid locality in the world. All told, the Prida Formation yields 68 species of ammonoids spanning the entire Middle Triassic age, or roughly 241 to 227 million years ago.
• Late Miocene Fossil Leaves At Verdi, Washoe County, Nevada: Explore a fascinating fossil leaf locality not far from Reno, Nevada; find 18 species of plants that prove that 5.8 million years ago this part of the western Great Basin Desert would have resembled, floristically, California's lush green Gold Country, from Placerville south to Jackson.
• Fossils Along The Loneliest Road In America: Investigate the extraordinary fossil wealth along some 230 miles of The Loneliest Road In America--US Highway 50 from the vicinity of Eureka, Nevada, to Delta in Millard County, Utah. Includes on-site images and photographs of representative fossils (with detailed explanatory text captions) from every geologic rock deposit I have personally explored in the neighborhood of that stretch of Great Basin asphalt. The paleontologic material ranges in geologic age from the middle Eocene (about 48 million years ago) to middle Cambrian (approximately 505 million years old).
• Fossil Bones In The Coso Range, Inyo County, California: Visit the Coso Range Wilderness, west of Death Valley National Park at the southern end of California's Owens Valley, where vertebrate fossils some 4.8 to 3.0 million years old can be observed in the Pliocene-age Coso Formation: It's a paleontologically significant place that yields many species of mammals, including the remains of Equus simplicidens, the Hagerman Horse, named for its spectacular occurrences at Hagerman Fossil Beds National Monument in Idaho; Equus simplicidens is considered the earliest known member of the genus Equus, which includes the modern horse and all other equids.
• Field Trip To A Vertebrate Fossil Locality In The Coso Range, California: Take a cyber-visit to the famous bone-bearing Pliocene Coso Formation, Coso Mountains, Inyo County, California; includes detailed text for the field trip, plus on-site images and photographs of vertebrate fossils.
• Fossil Plants At Aldrich Hill, Western Nevada: Take a field trip to western Nevada, in the vicinity of Yerington, to famous Aldrich Hill, where one can collect some 35 species of ancient plants--leaves, seeds and twigs--from the Middle Miocene Aldirch Station Formation, roughly 12 to 13 million years old. Find the leaves of evergreen live oak, willow, and Catalina Ironwood (which today is restricted in its natural habitat solely to the Channel Islands off the coast of Southern California), among others, plus the seeds of many kinds of conifers, including spruce; expect to find the twigs of Giant Sequoias, too.
• Fossils From Pleistocene Lake Manix, California: Explore the badlands of the Manix Lake Beds on California's Mojave Desert, an Upper Pleistocene deposit that produces abundant fossil remains from the silts and sands left behind by a great fresh water lake, roughly 350,000 to 19,000 years old--the Manix Beds yield many species of fresh water mollusks (gastropods and pelecypods), skeletal elements from fish (the Tui Mojave Chub and Three-Spine Stickleback), plus roughly 50 species of mammals and birds, many of which can also be found in the incredible, world-famous La Brea Tar Pits of Los Angeles.
• Field Trip To Pleistocene Lake Manix, California: Go on a virtual field trip to the classic, fossiliferous badlands carved in the Upper Pleistocene Manix Formation, Mojave Desert, California. It's a special place that yields beaucoup fossil remains, including fresh water mollusks, fish (the Mojave Tui Chub), birds and mammals.
• Trilobites In The Nopah Range, Inyo County, California: Travel to a locality well outside the boundaries of Death Valley National Park to collect trilobites in the Lower Cambrian Pyramid Shale Member of the Carrara Formation.
• Ammonoids At Union Wash, California: Explore ammonoid-rich Union Wash near Lone Pine, California, in the shadows of Mount Whitney, the highest point in the contiguous United States. Union Wash is a ne plus ultra place to find Early Triassic ammonoids in California. The extinct cephalopods occur in abundance in the Lower Triassic Union Wash Formation, with the dramatic back-drop of the glacier-gouged Sierra Nevada skyline in view to the immediate west.
• A Visit To The Fossil Beds At Union Wash, Inyo County California: A virtual field trip to the fabulous ammonoid accumulations in the Lower Triassic Union Wash Formation, Inyo County, California--situated in the shadows of Mount Whitney, the highest point in the contiguous United States.
• Ordovician Fossils At The Great Beatty Mudmound, Nevada: Visit a classic 475-million-year-old fossil locality in the vicinity of Beatty, Nevada, only a few miles east of Death Valley National Park; here, the fossils occur in the Middle Ordovician Antelope Valley Limestone at a prominent Mudmound/Biohern. Lots of fossils can be found there, including silicified brachiopods, trilobites, nautiloids, echinoderms, bryozoans, ostracodes and conodonts.
• Paleobotanical Field Trip To The Sailor Flat Hydraulic Gold Mine, California: Journey on a day of paleobotanical discovery with the FarWest Science Foundation to the western foothills of the Sierra Nevada--to famous Sailor Flat, an abandoned hydraulic gold mine of the mid to late 1800s, where members of the foundation collect fossil leaves from the "chocolate" shales of the Middle Eocene auriferous gravels; all significant specimens go to the archival paleobotanical collections at the University California Museum Of Paleontology in Berkeley.
• Early Cambrian Fossils In Western Nevada: Explore a 518-million-year-old fossil locality several miles north of Death Valley National Park, in Esmeralda County, Nevada, where the Lower Cambrian Harkless Formation yields the largest single assemblage of Early Cambrian trilobites yet described from a specific fossil locality in North America; the locality also yields archeocyathids (an extinct sponge), plus salterella (the "ice-cream cone fossil"--an extinct conical animal placed into its own unique phylum, called Agmata), brachiopods and invertebrate tracks and trails.
• Fossil Leaves And Seeds In West-Central Nevada: Take a field trip to the Middlegate Hills area in west-central Nevada. It's a place where the Middle Miocene Middlegate Formation provides paleobotany enthusiasts with some 64 species of fossil plant remains, including the leaves of evergreen live oak, tanbark oak, bigleaf maple, and paper birch--plus the twigs of giant sequoias and the winged seeds from a spruce.
• Ordovician Fossils In The Toquima Range, Nevada: Explore the Toquima Range in central Nevada--a locality that yields abundant graptolites in the Lower to Middle Ordovician Vinini Formation, plus a diverse fauna of brachiopods, sponges, bryozoans, echinoderms and ostracodes from the Middle Ordovician Antelope Valley Limestone.
• Fossil Plants In The Dead Camel Range, Nevada: Visit a remote site in the vicinity of Fallon, Nevada, where the Middle Miocene Desert Peak Formation provides paleobotany enthusiasts with 22 species of nicely preserved leaves from a variety of deciduous trees and evergreen live oaks, in addition to samaras (winged seeds), needles and twigs from several types of conifers.
• Early Triassic Ammonoid Fossils In Nevada: Visit the two remote localities in Nevada that yield abundant, well-preserved ammonoids in the Lower Triassic Thaynes Formation, some 240 million years old--one of the sites just happens to be the single finest Early Triassic ammonoid locality in North America.
• Fossil Plants At Buffalo Canyon, Nevada: Explore the wilds of west-central Nevada, a number of miles from Fallon, where the Middle Miocene Buffalo Canyon Formation yields to seekers of paleontology some 54 species of deciduous and coniferous varieties of 15-million-year-old leaves, seeds and twigs from such varieties as spruce, fir, pine, ash, maple, zelkova, willow and evergreen live oak
• High Inyo Mountains Fossils, California: Take a ride to the crest of the High Inyo Mountains to find abundant ammonoids and pelecypods--plus, some shark teeth and terrestrial plants in the Upper Mississippian Chainman Shale, roughly 325 million years old.
• Field Trip To The Copper Basin Fossil Flora, Nevada: Visit a remote region in Nevada, where the Late Eocene Dead Horse Tuff provides seekers of paleobotany with some 42 species of ancient plants, roughly 39 to 40 million years old, including the leaves of alder, tanbark oak, Oregon grape and sassafras.
• Fossil Plants And Insects At Bull Run, Nevada: Head into the deep backcountry of Nevada to collect fossils from the famous Late Eocene Chicken Creek Formation, which yields, in addition to abundant fossil fly larvae, a paleobotanically wonderful association of winged seeds and fascicles (bundles of needles) from many species of conifers, including fir, pine, spruce, larch, hemlock and cypress. The plants are some 37 million old and represent an essentially pure montane conifer forest, one of the very few such fossil occurrences in the Tertiary Period of the United States.
• A Visit To The Early Cambrian Waucoba Spring Geologic Section, California: Journey to the northwestern sector of Death Valley National Park to explore the classic, world-famous Waucoba Spring Early Cambrian geologic section, first described by the pioneering paleontologist C.D. Walcott in the late 1800s; surprisingly well preserved 540-510 million-year-old remains of trilobites, invertebrate tracks and trails, Girvanella algal oncolites and archeocyathids (an extinct variety of sponge) can be observed in situ.
• Petrified Wood From The Shinarump Conglomerate: An image of a chunk of petrified wood I collected from the Upper Triassic Shinarump Conglomerate, outside of Dinosaur National Monument, Colorado.
• Fossil Giant Sequoia Foliage From Nevada: Images of the youngest fossil foliage from a giant sequoia ever discovered in the geologic record--the specimen is Lower Pliocene in geologic age, around 5 million years old.
• Some Favorite Fossil Brachiopods Of Mine: Images of several fossil brachiopods I have collected over the years from Paleozoic, Mesozoic and Cenozoic-age rocks.
• For information on what can and cannot be collected legally from America's Public Lands, take a look at Fossils On America's Public Lands and Collecting On Public Lands--brochures that the Bureau Of Land Management has allowed me to transcribe.
• In Search Of Vanished Ages--Field Trips To Fossil Localities In California, Nevada, And Utah--My fossils-related field trips in full print book form (pdf). 98,703 words (equivalent to a medium-size hard cover work of non-fiction); 250 printed pages (equivalent to about 380 pages in hard cover book form); 27 chapters; 30 individual field trips to places of paleontological interest; 60 photographs--representative on-site images and pictures of fossils from each locality visited.

• United States Geological Survey Professional Paper 264-J: Fossils Birds From Manix Lake California, by Hildegarde Howard.
• United States Geological Survey Bulletin 1928: Stratigraphy of the Lower And Middle(?) Triassic Union Wash Formation, East-Central California by Paul Stone, Calvin H. Stevens, and Michael J. Orchard.
• United States Geological Survey Professional Paper 483-F: An Unusual Lower Cambrian Trilobite Fauna From Nevada by Allison R. Palmer.
• United States Geological Survey Bulletin 1527: Age Of The Coso Formation, Inyo County, California by C. R. Bacon, D. M. Giovannetti, W. A. Duffield, W. A. Dalrymple and R. E. Drake.