Saturday, May 31, 2014

Baby Dinosaur Found in British Columbia

One of my readers informed me recently about an article on a "new baby dinosaur reveals cause of death." The skeleton of the juvenile (3-year old) specimen is complete. It has been identified as Chasmosaurus bellii, and this genus is a relative of the famous Triceratops. The specimen is of Late Cretaceous age (70 million years old) and from British Columbia. You will need to read more about the specimen to see how this juvenile died.

The link is HERE 

Wednesday, May 28, 2014

Concurrent Range Zone

My previous series of blogs dealt with different species of Turritella in order to demonstrate how paleontologists "tell time" using a temporal (through time) succession of species of the same genus. This new blog shows another technique that is commonly used to "tell time."  It is called the concurrent-range zone = overlap in time of two different fossils (species or genera), or stated in another way, overlap of the first (FAD) and last (LAD) occurrence of two or more fossils.  FAD = first appearance datum; LAD = last appearance datum. Simply stated, if you have, in a layer of sedimentary rock, the co-occurrence of two fossils that overlap in time, then the age of the layer is the age of the overlap interval.

                                fossil 2

D            LAD

         age of layer = S

               fossil 1

A detailed example of a concurrent-range zone using fossil bivalves is shown below (the concept is that if these two genera occur in the same layer of rock, the geologic age of the rock is late Pliocene):

Swiftopecten parmeleei (Dall, 1898)
juvenile, height 33 mm

Swiftopecten parmeleei (Dall, 1898)
early adult, height 71 mm

Cyclocardia occidentalis Conrad, 1855
height 13 mm

Visual summary of the eight Turritella species

This post is a visual summary (see pictures below) of all the previously posted eight species of Turritella. These species are "index fossils" or "guide fossils" of their respective intervals of time. An "index fossil" is one that is not only indicative of a relatively short interval of time, but one that is readily preserved, widespread, and common. 

 Late Cretaceous                                                     early Paleocene                                 middle Eocene
  pescaderoensis                                                      infragranulata                                       lawsoni

late Eocene
early Miocene
middle Miocene
middle Miocene
late Pliocene to Holocene



Sunday, May 25, 2014

Pliocene to Modern Turritella

This is the last Turritella in the series of eight species. This species, which has a fossil record, is extant (still living). 

height 34.5 mm
a fossil specimen
height 29 mm
a modern specimen

                  Turritella cooperi Carpenter, 1864

AGE RANGE: Cenozoic (early Pliocene to Holocene = about 5 million years ago to today)
GEOGRAPHIC RANGE: Central California to Cedros Island off the west coast of central Baja California, Mexico.
REMARKS: Turritella cooperi is characterized by two having two principal spiral ribs on its whorls, but there are variations. This species is very common in storm-related deposits of late upper Pliocene age in southern California. Modern specimens are rarely found as beach drift on some central and southern California beaches. The ocean temperature north of central California is simply too cold today for TurritellaMost modern species of Turritella are found in tropical waters

Friday, May 23, 2014

Middle Miocene Turritella

In this post, I include two Miocene species of Turritella whose geologic ages overlap. This overlap is called a "concurrent-range zone," and I shall illustrate this topic more in a later post. Both species of these turritellas are common in southern California and can occur together in the same deposit. This is result of two separate evolutionary lineages of Turritella co-existing at the same time. 

height 61.5 

Turritella temblorensis Wiedey, 1928          

AGE RANGE: Cenozoic (early to middle Miocene = 23 to about 14 million years ago).
GEOGRAPHIC RANGE: Southern California. 
REMARKS: This species can show much variation.

height 99 mm

Turritella ocoyana topangaensis Merriam, 1941

AGE RANGE: Cenozoic (middle Miocene = about 14 million years ago).
GEOGRAPHIC RANGE: Central and southern California.
REMARKS: This species can also show much


Thursday, May 22, 2014

An early Miocene Turritella

In my on-going series of Turritella species, I did not include an Oligocene example. This is because during the Oligocene, the coast of California began to change its tectonic setting from a subduction-zone, where the ocean floor descended beneath California, to a collision with an ocean-floor spreading center. This collision began about 30 million years ago and initiated the development of the San Andreas Fault system. In response to the collision, nonmarine deposits were the norm during the Oligocene in southern California, and Turritella-bearing shallow-marine deposits became scarce until the Miocene. The following species lived during the early Miocene.

height 43 mm

                Turritella inezana Conrad, 1857

AGE RANGE: Cenozoic (early Miocene = about 22 million years ago).


REMARKS: This species has a very prominent spiral rib, called a carina, on the posterior part of each whorl. The function of this carina is unknown, but it probably helped the snail stabilize its shell in silty deposits on the ocean floor. 


Saturday, May 17, 2014

A late Eocene Turritella

This fourth species in the series of selected species of Turritella to show how the morphology (shape) of this genus changes over time. This is how field geologists can readily decipher the geologic age of a bed containing a particular species of Turritella. The detailed reasons for the change in morphology are rarely understood, but they are undoubtedly related to changes in micro-environments, as well as to the possibility of genetic mutations. 

height 46 mm
Turritella uvasana sargeanti Anderson and Hanna, 1925

AGE RANGE: Cenozoic (late Eocene = about 38 million years ago).

GEOGRAPHIC RANGE: Southern California.

REMARKS: This species can be variable in its morphology.


Thursday, May 15, 2014

An early middle Eocene Turritella

This is the third post in the continuing series of using fossil Turritella shells to "tell time." 

height 87 mm                                                                                                           

Turritella andersoni lawsoni Dickerson, 1916

AGE RANGE: Cenozoic (early middle Eocene = 45 million years ago).

GEOGRAPHIC RANGE: Central California to northern Baja California, Mexico.

REMARKS: In order to correctly identify this species, it is necessary to have a nearly complete individual specimen that shows both the immature and mature growth stages. Note that the posterior part (immature stage) of the shell of T. andersoni lawsoni looks different that the anterior part (mature stage). A complete specimen of this subspecies reminds me of a "Tootsie Roll."

This turritellid is a subspecies, which is a group very similar to a species (in this particular case, very similar to the slightly geologically older T. andersoni Dickerson, 1916) but slightly different.


Tuesday, May 13, 2014

A late Paleocene Turritella

This is my second blog in a series of eight that deal with the same subject (plus a ninth one that summarizes the eight). It shows a late Paleocene Turritella species, which is morphologically different from the Late Cretaceous species that I previously showed.

height 65 mm
height 43.5 mm

Turritella infragranulata Gabb, 1864

AGE RANGE: Cenozoic (late Paleocene = about 58 million years ago).

GEOGRAPHIC RANGE: Northern to southern California.

REMARKS: This large species is very distinctive because of the nodes on some of its spiral ribs.

William More Gabb, who was the first paleontologist of the Geological Survey of California, described and named this species in 1864. If you wish to read an interesting article that I wrote a few years ago about his profound contributions to the paleontology of California, visit the California Geology website (see below)--

In their search box, for Title of Article, type %William More Gabb% and be sure to put a % symbol before and after the name. In the second line, type 1999; and in the third line, type paleontology.

for the link, click HERE and then click "Go to link"

The link should take you to vol. 52, issue 04, and p. 11. Also, while you visit this website, you will see many other useful articles on California Geology. Although you can read their articles online, it seems that you cannot download a pdf for your own use.


Sunday, May 4, 2014

A Late Cretaceous Turritella


The reason for creating this first series of posts is to demonstrate one of the major uses of fossils: "to tell time." The following pictures show common fossil gastropods (snail seashells) belonging to genus Turritella that you might find on hikes in the mountains or to beach cliffs in the southern California area. Turritella is a group of species that look similar. Although there are many fossil species of Turritella in southern California, I selected eight common ones. The youngest species is still living but also has a fossil record.

The time interval in which each species lived will be shown on its accompanying time diagram. These eight species collectively span an interval of about 75 million years (from Late Cretaceous to Holocene). The Holocene includes recent time.

Fossil species are called "morpho-species" because they are determined solely by differences in morphology (size, shape, sculptural details). By studying the pictures, you will see that they are different from each other in the following possible ways (see labeled picture below): shell narrowness, number of spiral ribs (cords) on each whorl (one 360° turn), how strong the ribs are relative to each other, and whether or not nodes are present on any of the ribs. It is amazing to me how many variations of differences occur in just these few morphologic characteristics.

height 53.5 m
 Turritella chicoensis pescaderoensis Arnold, 1908

AGE RANGE: Late Cretaceous (late Campanian = about 75 million years ago).

GEOGRAPHIC RANGE: Northern California to northern Baja California, Mexico.

REMARKS: This species is abundant in the Santa Ana Mountains, Orange County, and in the Simi Hills, Ventura County.

In this and my subsequent posts, you will see that the genus and species names are always italicized (follows international protocol); also, the first letter of the genus name is always capitalized, but the
first letter of the species name is always lowercase.

The author who named the species and the year in which is was named should be included in the name of a species. The genus name can be abbreviated to just one letter (as in T. chicoensis pescaderoensis), if it is clear as to what the "T." means to the reader.