Data: I found these fossils in Thousand Oaks, California about 6 years ago in the hills between TO and Simi Valley high up on the top of the hill.

The large rock (1) is about 15 pounds and is 10" x 8", and is 7" tall. The smaller one (2) is about 3 pounds, is 5" x 3 & a half inches, and is 2" tall.

They were sticking out of a trail wall (obviously someone had a tractor up there to make a fire break, and they left a 'wall' on the side where they plowed) and it didn't take much to get them out.

Much more than that I do not know. I found them and brought them home, and now I am going to show them in the fair.

I plan on showing them in the fair this year, as they go in 3 weeks from now, and it is mandatory that the exhibitor put the genus name down along with the common name (neither of which I know!).

I really appreciate any help that is given to me!

Send Ideas to: Diane

Question #1: What is the difference between Turritella ocoyana & Turritella andersoni? Both are spiral shells...Diane

Answer:

• First and foremost the three species are different ages: Turritella peninsularis [Paleocene, ca 60 mybp], T. andersoni [Eocene, ca. 50 mybp], and T. ocoyana [Miocene, ca. 15-16 mybp] and since the formation is Paleocene in age your specimens are T. peninsularis. Obviously, there is an advantage to knowing the proverbial territory (ie., the geology of southern California).
  
  Regarding comparisons, see the following web site for what several living species of turritellas look like www.seashellcity.com/seashells/turritellashells.html (I have absolutely no affiliations to this business site … it just happened to show several different species for comparison sake).
  
  Both T. peninsularis and T. ocoyana are larger and heavier species than T. andersoni and both have a greater ‘plural angle’ than in T. andersoni. This is the angle formed if you laid the specimen on a piece of paper and drew lines along each shell margin from the apex (the spiral tip) towards the apertural end. Turritella andersoni and its related species and subspecies are all much slimmer so to speak that the other two species.
  
  Aside from the age difference, T. peninsularis and T. ocoyana look very similar but T. ocoyana has much more bold spiral sculpture (ie., the lines that spiral around the shell from the apex to the aperture) than does T. peninsularis.
  
  If specimens are poorly preserved such as yours, we must rely on our knowledge of what species are found in what formations and make comparisons and yes … sometimes simply guess....Lindsey

 

Discussions:

• May be -Turritella andersoni ? See: Gastropods from California ...Avril B.

• Top photo is Turretella. Have fun... Jack D.

• The shells in the larger rock are Turritella sp. For some reason, Turritella shells are often fossilized in huge masses, and the hard rock containing such masses are often referred to as "turritella agate"... Paul M.

  • Actually, standard "Turritella agate" contains Eocene Juga spp., freshwater pleurocerids from the Green River Formation in Colorado and Wyoming. "Turritella" is a misnomer in that case.
    However, the present specimens come from not far from the modern California coast and probably represent actual turritellids. There's a fair amount of research that has been done on the fossils of the general region. The California Geological Survey website would probably be a good source of information, or a geology department at a nearby college...Dr. David C.

• These specimens are all from the Paleocene (ca. 60 mybp) Santa Susana Formation of the Simi Hills, Ventura County, California. Image 1 is almost exclusively Turritella peninsularis Anderson & Hanna, 1935. Image 2 contains Gyrodes robustus Waring, 1917 (the large naticid or moon snail), some small T. peninsularis, an oyster fragment, and a fragment of the large bivalve Venericardia sp.
  FYI, in certain outcrops the fine-grained mudstone/ siltstone nature of the matrix of this formation is like concrete, hence the fossils contained are usually very worn and virtually impossible to extract whole. Hope this information help...
  Aloha,...Lindsey

2.

• Gyrodes robustus Waring, 1917 (the large naticid or moon snail), some small T. peninsularis, an oyster fragment, and a fragment of the large bivalve Venericardia sp. See NOTE

Answer: Regarding the differences between Gyrodes robustus and Polinices recluzianus and Polinices sp. cf. lewisii once again it is imperative that someone knows the territory.
First, Polinices reclusiana had yet to appear in the fossil record in California in the Paleocene so obviously it couldn’t be that species. FYI it ranges from late Eocene (ca. 40 mybp) to Recent. The same goes for P. lewisii as it ranges from late Miocene (ca. 6 mybp) to Recent. Not to confuse the issue further but those two species have been reassigned to different genera … Polinices recluzianus now is Glossaulax reclusiana and Polinices sp. cf. lewisii now is Euspira lewisii. (when collectors or researchers use ‘sp.’ and/or ‘cf.’ it means that they are uncertain as to the species identification hence the use of ‘sp.’ and ‘cf.’ when they think it may be that species but cannot be sure.)
As far as physical differences between the genera Gyrodes is usually has a much lower spire than Polinices and has channeled suture area whereas Polinices does not. The suture is the line where each spiral of the shell joins itself when completing each revolution. With most moon snails this is a smooth feature whereas in Gyrodes this line is like a shallow furrow around each revolution....Lindsey

• any possibility of this being an ammonite?
  See: http://www.sdnhm.org/fieldguide/fossils/ammonite.html
  OR - Polinices sp. cf. P. lewisii (Lewis' moon snail)
  See: http://www.sdnhm.org/fieldguide/fossils/lmoonsnail.html
  OR - Bellerophon hilli ? See: Gastropods from California
  Avril B.

• moon snail. Have fun. Jack D.

• The main shell in the smaller rock appears to be a naticid (moon snail), but I can't rule out a trochid (top shell)... Paul M.

• These specimens are all from the Paleocene (ca. 60 mybp) Santa Susana Formation of the Simi Hills, Ventura County, California. Image 1 is almost exclusively Turritella peninsularis Anderson & Hanna, 1935. Image 2 contains Gyrodes robustus Waring, 1917 (the large naticid or moon snail), some small T. peninsularis, an oyster fragment, and a fragment of the large bivalve Venericardia sp.
  FYI, in certain outcrops the fine-grained mudstone/ siltstone nature of the matrix of this formation is like concrete, hence the fossils contained are usually very worn and virtually impossible to extract whole. Hope this information help
  Aloha,...Lindsey