EVOLUTION OF PLANTS

In the coming posts, I shall present examples of certain specific groups of flowering plants. First, however, I need to "set the stage" and briefly discuss in this current post, the earliest history of the various kinds of flowering plants. In the following text, I mention geologic time periods. To see a quick visual summary of these intervals, please see one of my earliest posts; namely, "GEO TIME SCALE," which was posted in November, 2014. Or, you can look at any historical geology textbook (or go to the online source "Wikipedia") to view the succession of the various periods of geologic times.

Paleozoic Time: Based on fossil spores, the first plants occurred on land about 470-460 mya (million years ago) during middle Ordovician time. By Silurian time, the first vascular land plants occurred, and most of them lived in the Northern Hemisphere. During Devonian time, colonization of the land was well underway. Early Devonian plants, however, had no leaves. By the Late Devonian, forests of large primitive plants (including ferns) appeared.

Mesozoic Time: Lycophytes, cycads, ginkgos appeared; with conifers and many new ferns evolving during Jurassic time. 

FORMATION OF GONDWANALAND (TECTONIC PLATES                IN ACTION=ON THE MOVE!)

During mid early Jurassic time (about 190 m.y.a. [million years ago], most of the continents were in a land mass called Gondwanaland, which lasted until middle Cretaceous time (which was about 100 m.y.a.). During subsequent younger geologic time intervals, Gondwanaland broke apart and eventually Earth’s Southern Hemisphere looked similar to that of today.                 

Figure 1. Jurassic paleogeographic map of the world, when the supercontinent Gondwanaland formed.

During the 19^th century, late Paleozoic coal deposits of India, South Africa, Australia, South America, Antarctica, and New Zealand, as well as the Falkland Islands (in the Atlantic Ocean, east of Argentina), were found to contain fossil plants collectively designated as the “Glossopteris Flora,” a name of the most conspicuous genus, which was a variety of seed fern, called Glossopteris (about 265 million years old = late Permian age.) The presence of this fossil flora, which is found nowadays on widely separated land masses, was one of the major facts that lead to the concept that all of these land masses once were connected in what is now referred to as “Gondwanaland.”  This concept has now been well established as fact via the discovery of other land fossils (including mammal-like reptiles) and paleomagnetism (Stanley, 1999).

The oldest known lineages of flowering plants [= angiosperms] evolved about 140 to 125 m.y.a. [middle Early Cretaceous time]. Flowering plants “bloomed” with the appearance of pollinating insects about 100 m.y.a. [at the beginning of Late Cretaceous time]. In sum, plant evolution was driven by plate tectonics—firstly by continents colliding together and secondly by continents moving apart. When Gondwanaland separated into four continents---[South America, Africa, Australia, and Antarctica]---each of these areas became increasingly isolated, and each took on its own types of genetic diversification caused by these isolations. 

Figure 2. Outline of a Glossopteris late Permian seed-fern leaf (2 inches long = 5 cm].  These leaves were thick, fleshy fibrous, and had a minute-network of parallel lines and groves on their surface. Their presence in the southern continents confirm that these lands were once united into a single supercontinent.

REFERENCE

Stanley, S.M. 1999. Earth System History. W.H. Freeman and Company. New York. 615 pp.

WILDWOOD PARK-GUNSMOKE TV SERIES-GEOLOGY

A notable locale (one of many) that pertains to the popular TV show “Gunsmoke” is Wildwood Regional Park, located just west of California Lutheran University in Thousand Oaks, southern California. This locale, hereafter referred to as “Mount Clef Ridge” is a recognizable landmark used in the filming of numerous western-themed movies and TV shows. In addition to Gunsmoke, some of these are “The Rifleman,” “Bonanza,” “Wagon Train,” “The Big Valley,” “Tales of Wells Fargo,” and many more. Also, many non-western themed movies have used this location (e.g., "Spartacus," "Wuthering Heights," and the list is long!). This park is in the “30-mile zone.” Than is to say, close enough to Hollywood so that studios do not have to pay extra for on-location shooting. 

Figure 1. The "Mount Clef" location, as it looked in June of 2025.

This location was used in the filming of some episodes of "Gunsmoke." This mountain, also known as, “Mount Clef Ridge,” is 1,076 feet (or 994 feet) in elevation, [the elevation depending on the map you use]. It is a ridge of volcanic deposits of middle Miocene age (16 to 13 million years old). It is a basalt-flow breccia, and Dibblee (1993) mapped the deposit as unit “Tccbb,” in the upper part of the Conjeo Volcanic rocks.

Figure 2. Another view of the “Mount Clef Ridge” location.

There is no longer any evidence on the ground that suggests this site was used by filming crews. Homes now occupy the areas immediately east, south, and west of the locale. For more details of how this movie site once looked, please see the informative website: https:www.youtube.com/watch

Reference:

Dibble Foundation [year 1993] Geologic Map #DF-49).

SOME MAMMALS SEEN RECENTLY IN SOUTHERN CALIFORNIA

I have been slowly adding the following few species to my blog because seeing them is rapidly become rare due to the constantly increasing populated/overbuilt areas occupying former "wild lands" in northern Los Angeles County, Southern California.

WESTERN BRUSH? RABBIT

I was unable to see the tail of this rabbit, thus I was unable to positively identify it. I think it is it the Western Brush Rabbit (Sylvilagus bachman), a species of cottontail rabbit that is gray, black, or brown with small ears and a small dark tail (unable to see in my photo). Just as soon as I took this picture, this very shy specimen “took off running” into the dense foliage. I did not even think to look at the color of its tail! Next time, I shall be more observant.

This species is found from Oregon to the southern tip of Baja California, Mexico. Its range is also the east side of the Sierra Nevada in California.

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WESTERN FOX SQUIRREL

This post concerns a genus of squirrel native to North America. Today, there is the “Eastern” Fox Squirrel and and “Western” Fox Squirrel. The latter, which was introduced to the western United States near the turn of the century, evolved from the Eastern Fox Squirrel. That particular squirrel lives today in the eastern and central United States and ranges from Canada to Mexico. That particular variant has gray color and is smaller than the new variant that now lives in California. The new variant is characterized by gold-colored fur on its belly and a bushy tail. It is also the largest species (up to 29 inches long and weighs up to 3 pounds) of tree squirrels native to the United States. 

Classification:

Kingdom Animalia

Phylum Chordata

Class Mammalia

Genus Sciurus

Species S. niger Linnaeus, 1758

This squirrel is most active in late morning and mid-day. It is aboreal (i.e., spends most of its time in trees). They do not live in groups.

The geologic range of “fox” squirrels sensu lato [= in the broad sense] is Middle Holocene (7,000 years ago) to present day.

Remains have been found at Rancho La Brea (tar pits) = Pleistocene age. 

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COYOTE

Coyotes can be found throughout the United States, including Alaska. They are omnivores and eat practically anything. They can weight up to about 40 pounds (collie-dog size). I have seen many of them in my years of hiking and field work in southern California. Unlike a few human land owners I have come across, they have never been aggressive toward me. They are most common around where humans dump their garbage in an irresponsible manner.

Classification:

Kingdom Animalia

Phylum Chordata

Class Mammalia

Genus Canis

Species C. latrans

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BLACK BEAR

 Bear image taken by a security video camera in the evening, just north 

of Santa Clarita, Los Angeles County, southern California. 

This elusive species comes in many different colors: from solid black to shades of brown and tan. They eat grass, berries, flowers, nuts, grub, insects, honey, fish, and small mammals. They are usually not aggressive but their behavior, like all wild animals, can be unpredictable.

Classification:

Kingdom Animalia

Phylum Chordata

Class Mammalia

Genus Ursus

Species U. americanus

Black bears were introduced to Southern California in the 1930’s after over hunting by humans caused the extinction of the California grizzly bear.

In all my field work over many years in Southern California, I only saw one black bear (a mature one!), and it was about a quarter-of-a-mile away and never detected me.

RHINO FOSSILS IN CALIFORNIA

The scientific analysis of any fossil records is always a “process.” Initially, it is based on 1) previous observations; then it proceeds to 2) any new data. Then, as step 3), it is then usually possible to make new interpretations. That is certainly the history of rhino fossils in California.

Previous observations. Chester Stock wrote several papers about the “earliest rhino fossils” found in California. These were conveniently summarized, in the form of sketches, of supposedly the earliest California rhinos, by Savage and Downs (1954, fig. 2).

New data. In the past few years, there have been exciting discoveries (e.g.,  through out the world, namely China and Elsmere Island (in the Arctic region of Canada). 

New interpretations. Prothero and Schoch (2002) did a detailed analysis of the fossil record of rhinos and made some very useful observations. Rhinoceros likely originated from tapir-like animals during the middle Eocene, but this transition remains controversial.  Bai et al (2020) made a significant step in our understanding of fossil rhinos. From these two papers, it is now possible to state that the first true rhino is the horse-like Hydrachyus, known from Inner Mongolia (China), Europe, and Arctic Canada (Elsmere Island). 

On the west of North America, the hippo-like, short-legged rhinoceros (no horn) Teleoceras is known from middle to late Miocene [13.5 to 7.3 mya, in the Dove Spring Formation (part of the Ricardo Group) in the El Paso Mountains of Kern County, California. About 100 intact specimens belonging to this genus are famously known from a Miocene volcanic ash-fall event in Nebraska (see Wikipedia). 

Also living on the west coast of North America was the rhino (no horn) Aphelops from the middle upper Miocene Mint Canyon Formation in the Soledad Basin of southern California. This was the last native occurrence of fossil rhinos in California.

Note: Ancestral forms of Teleoceras and Aphelops “arrived” in California via a land bridge called “Beringia 2”, [see my earlier posts on Nov. 1, 2022]. Beringia 2 occurred between 25 and 5 mya, when northeast Asia and northern Alaska were “linked” together.

Figure 1. Teleoceras fossiger Cope, 1878, from a public domain sketch by Horsfall in (1912) 1913, a renowned American wildlife illustrator. This genus was endemic to North America and is found in rocks ranging in geologic age from Miocene to Pliocene. [Note: The Los Angeles County Museum of Natural History has a skeleton of Teleoceras on display].  

Figure 2. Aphelops was also endemic to North America, and the representative fossil used here is from the upper Miocene Mint Canyon Formation in Soledad Canyon, northern Los Angeles County. Fossils of Aphelops are found in rocks ranging in geologic age from Miocene to Pliocene. My drawing is modified from an image by Jay Matternei (www.facebook.com/photo). 

Figure 3. Modern “Black Rhino” living (many years ago) at the Los Angeles County Zoo. Image via R. Squires. Today, of course, these rhinos are from Africa and elsewhere and have been imported to zoos throughout the world. 

References

Bai et al. 2020. The origin of Rhinocerotoidea and phylogeny of Ceratomorpha (Mammalia, Perissodactyla). Communications Biology. https://doi.org/10.1038/s42003-020-01205-8 pdf available online for free.

Horsfall, R. B. 1913. A public domain document available online (e.g., Wikipedia). 

Prothero, D.R. and R.M. Schoch. 2002. Horns, tusks, and flippers: The evolution of hoofed mammals. The John Hoplins University Press. Baltimore.

Savage, D.E. and T. Downs. 1954. Cenozoic land life of southern California. Chapter 6, pp. 43-58. In Geology of Southern California, Bullein 170, Chpater 3, Historical Geology. Division of Mines, San Francisco.