Barstow Formation Fossils In The Public Domain

Middle Miocene--17 million years old

Fossil Insect Canyon, Mojave Desert, Calfornia

Please Note: I have taken all but three of the following black and white images of Barstow Formation fossil arthropods from a specific Public Domain source. Unless otherwise noted, the specimens were dissolved out of calcium carbonate concretions with a diluted solution of formic acid.

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Left to right: (1) This is a mature larva of a predacious diving water beetle, Shistomerus californense--a co-dominant in the Barstow fossil arthropod fauna--8 millimeters long (about a third of an inch); (2) A second mature larva from the predacious diving water beetle Shistomerus californense; it is 6 millimeters in length (roughly a quarter inch).

This particular species of predacious water beetle most closely resembles the living Deronectes striatellus, which is widely distributed throughout the southwestern United States.

 

 

Left to right--(1) A nearly complete adult male midge, Dasyhelea australis antiqua--2.5 millimeters long (a tenth of an inch); (2) A female midge, Dasyhelea australis antiqua; it is 3 millimeters in length (one-eighth of an inch). The pupal stage of this particular midge is one of the three dominants in the Barstow Fauna--along with water beetle larvae and fairy shrimp remains. Adult midge specimens remain elusive for many ardent "Barstow bug" enthusiasts, but can certainly be found with dedicated effort.

The Barstow variety of midge most clostely resembles Dasyhelea australis australis, now living on the islands of Islas Juan Fernandez, roughly 400 miles west of Santiago, Chile. Dasyhelea-type mides, by the way, while commonly referred to as "biting midges," do not actually consume animal blood. They thrive on the nectar from flowers.

 

 
Left to right: (1) A complete adult jumping spider, Argenna fossilis--1.42 millimeters long (less than twelveth of an inch). Its closest living relatives can now be found soley in Europe; (2) A pupa from a biting midge, Culicoides megacanthus; 2.4 millimeters long (almost a tenth of an inch); modern, living members of this particular genus are what lots of folks call a "no see-'em"--they suck animal blood and often cause severe allergic reactions.

 

 

Left to right: (1) A dragonfly larva, Orthemis sp., 15 millimeters long (three-fifths of an inch); this is actually an incredibly historic specimen, indeed. It was the very first fossil insect discovered in the middle Miocene Barstow Formation, collected by a United States Geological Survey geologist in January, 1954; (2) A nearly mature dragonfly larva, Orthemis sp., 20 millimeters long (four-fifths of an inch).

The Barstow specimen closely resembles the living Caribbean dragonfly, Orthemis furruginea.

 

 

 
Left to right: (1) Both sides of the same female leafhopper specimen, of the Subfamily Deltocephalani (genus-species undetermined)--about 3.2 millimeters long (slightly over an eighth of an inch). Modern members of the Deltocephalani range throughout the United States and Canada, but can only be found year-round in three states--Alabama, California and Florida; (2) A milkweed bug, Procymophyes lithax--2.32 millimeters in length (almost a tenth of an inch). The living genus Cymophamus, now native to North Africa, Asia Minor and an area ranging from Greece to Turkestan, appears in many important characteristics most like the fossil Barstow species of milkweed bug.

 

 

Left to right: (1) An unhatched female midge, Dasyhelea australia antiqua preserved in its pupa--about 1 to 2 millimeters in length (less than a twelveth of an inch). The Barstow variety of midge most clostely resembles Dasyhelea australis australis, now living on the islands of Islas Juan Fernandez, roughly 400 miles west of Santiago, Chile. Dasyhelea-type mides, by the way, while commonly referred to as "biting midges," do not actually consume animal blood. They thrive on the nectar from flowers.

(2) This particular specimen might not look like much, but it really is a significant find; it's one of only two or three fairly complete fairy shrimp ever found in the fossil record, world-wide--and, it's the best-preserved fossil fairy shrimp ever found. The scientific name is Archaebranchinecta barstowensis and it's almost 3 millimeters long (slightly less than an eighth of an inch). Fragmentary fairy shrimp remains are among the most abundant specimens recovered from the Barstow Formation calcareous concretions; often, fairy shrimp fossil fecal pellets (poop), preserved as minute (less than a millimeter, or twenty-fourth of an inch long) rod-like structures, form distinct layers throughout many of the calcium carbonate concretions.

Interestingly, this specific species of fossil fairy shrimp from the middle Miocene Barstow Formation is most similar to the living Archaebranchinecta pollicifera, now native to the mountains of Bolivia and Peru, around Lake Titicaca.

This is a photomicrograph of a fossil springtail called paleoentomologically Entomobrya kirkyae, an image taken from a specific scientific paper; dissolved by a professional paleoentomologist from a calcareous concretion collected from the middle Miocene Barstow Formation, Fossil Insect Canyon, Mojave Desert, California. The specimen is 1.5 millimeters in actual length (roughly one-sixteenth inch). Such springtails of the genus Entomobrya are commonly called "slender springtails". Its closest living modern representative is Entomobrya atrocincta, a springtail known to inhabit stagnant water pools in California.

Here is a termite wing, preserved as an extraordinarily rare (very uncommon for the "Barstow Bug" fauna, anyhow) cast impression on the surface of a calcareous concretion from the middle Miocene Barstow Formation, Fossil Insect Canyon, Mojave Desert California--an image taken from a specific scientific paper. The specimen measures 6.7 millimeters in actual length, slightly over a quarter inch. Scientific name is Reticulitermes laurae. Closest living relative is probably Reticulitermes tibialis, also called the The Arid-Land subterranean termite--which is commonly found from the Pacific Coast to Indiana, and southwards from Montana to lower California, Texas, and Mississippi--although the Barstow fossil termite's wings were substantially longer.

This is a photomicrograph of an adult thrip, dissolved by a professional paleoentomologist from a calcareous concretion collected from the middle Miocene Barstow Formation, Fossil Insect Canyon, Mojave Desert, California--an image taken from a specific magazine that went belly-up, defunct, several years ago. Its formal scientific, entomological name is Anaphothrips (Proscirtothrips) vitreus; actual length of specimen is .8 millimeter, or slightly less than one twenty-fifth of an inch. Resembles the living thrip Proscirtothrips zeae that presently lives in California, Oregon, Arizona, Nevada, Utah, Idaho, and South Dakota.

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