Unknown Fossil

[Elena T.]

Hi, I’ve recently come back from a trip near Benson, Arizona on public land, and found this rock with a fossil. I myself am not a fossil expert or collector, but I’m curious as to what I’ve picked up, thank you.

 

The dimensions are about 1.905 cm x 5.08cm

[Pemphix]

https://en.wikipedia.org/wiki/Orthoceras

 

[Elena T.]

8 minutes ago, Pemphix said:

https://en.wikipedia.org/wiki/Orthoceras

 

Thank you, much appreciated!

[Pemphix]

To get a better analysis, pls. provide size, formation, location.

[BlueFire0044]

It looks like a Orthoceras. You can see alot of fossils from that animal in some older stairways and floors in buildings like these following images.

[Tidgy's Dad]

Orthoceras is confined to the Baltic area, including Sweden, so the specimen posted by Elena is not this genus as hers was found in Arizona. 

It is an orthoconic nautiloid and probably an orthocerid.  

[Elena T.]

10 hours ago, Pemphix said:

To get a better analysis, pls. provide size, formation, location.

I found it 10-30 miles off from a smaller city called Elson, Arizona, in some mountain ranges, in the area of Benson, Arizona and here are some size photos. I’m still looking up rock type but here are some more pictures.

[Elena T.]

I also believe the fossil is on a basalt rock.

 

[Tidgy's Dad]

Looks like limestone to me. 

Fossils don't preserve in basalt. Basalt is an igneous rock formed from fast cooling lava which would destroy animals caught up in it. The shells would melt. 

[Elena T.]

3 minutes ago, Tidgy's Dad said:

Looks like limestone to me. 

Fossils don't preserve in basalt. Basalt is an igneous rock formed from fast cooling lava which would destroy animals caught up in it. The shells would melt. 

Good to hear, limestone is very common in the area so that makes sense.

[FossilDAWG]

For those not familiar with southern Arizona, this is "basin and range" country with numerous small mountain ranges (some smaller and others a bit larger, but all small compared to the Rockies or the Alps for example) separated by broad flat expanses (basins).  The mountains are fault bounded blocks and the basins are down-dropped areas, filled in with material erroded off the mountains.  The geology of the mountains is also complicated by extensive folding and faulting, so in some places the bedrock looks like a classic layer cake of sedimentary formations, and in other places sedimentary and igneous rock of widely different ages are in close proximity.  In most of these small ranges, fossiliferous rocks include Cambrian, Devonian, Lower and Upper Carboniferous (Mississippian and Pennsylvanian), and Permian marine formations, and sometimes Cretaceous (Aptian and Albian) marine limestone and late Cretaceous lake deposits.  Almost all the Devonian, Mississippian, Pennsylvanian, and Permian formations are massive limestones in beds many feet thick, in which fossils are sporadically distributed.  Often the fossils are silicified, so they stand out (to a point) from the rock.  The Aptian/Albian massive limestones (Mural Formation) include rudist reefs in places, but good fossils are difficult to find as they are not silicified and mostly are seen as cross sections.

 

The fossil posted by the OP is a straight-shelled nautiloid.  Such nautiloids are referred to as "orthoconic" (= "straight cone").  100+ years ago these were all called Orthoceras, but today hundreds (maybe thousands) of different genera are recognized based on internal structures.  As has been mentioned, the genus Orthoceras is today restricted to a few species that occur in the Baltic area.  In southeastern Arizona, I have seen orthoconic nautiloids only in the Mississippian formations.  Rayonnoceras has been reported but other genera may be present.  Accurate identification requires close study of internal structures.  The fossil in the OP is silicified, which is why it stands out from the rock, and this supports the idea that is came from one of the upper Paleozoic formations, and most likely the Mississippian.

 

@DPS Ammonite collects in the area and may be able to add to these comments.

 

Don

[Elena T.]

7 minutes ago, FossilDAWG said:

For those not familiar with southern Arizona, this is "basin and range" country with numerous small mountain ranges (some smaller and others a bit larger, but all small compared to the Rockies or the Alps for example) separated by broad flat expanses (basins).  The mountains are fault bounded blocks and the basins are down-dropped areas, filled in with material erroded off the mountains.  The geology of the mountains is also complicated by extensive folding and faulting, so in some places the bedrock looks like a classic layer cake of sedimentary formations, and in other places sedimentary and igneous rock of widely different ages are in close proximity.  In most of these small ranges, fossiliferous rocks include Cambrian, Devonian, Lower and Upper Carboniferous (Mississippian and Pennsylvanian), and Permian marine formations, and sometimes Cretaceous (Aptian and Albian) marine limestone and late Cretaceous lake deposits.  Almost all the Devonian, Mississippian, Pennsylvanian, and Permian formations are massive limestones in beds many feet thick, in which fossils are sporadically distributed.  Often the fossils are silicified, so they stand out (to a point) from the rock.  The Aptian/Albian massive limestones (Mural Formation) include rudist reefs in places, but good fossils are difficult to find as they are not silicified and mostly are seen as cross sections.

 

The fossil posted by the OP is a straight-shelled nautiloid.  Such nautiloids are referred to as "orthoconic" (= "straight cone").  100+ years ago these were all called Orthoceras, but today hundreds (maybe thousands) of different genera are recognized based on internal structures.  As has been mentioned, the genus Orthoceras is today restricted to a few species that occur in the Baltic area.  In southeastern Arizona, I have seen orthoconic nautiloids only in the Mississippian formations.  Rayonnoceras has been reported but other genera may be present.  Accurate identification requires close study of internal structures.  The fossil in the OP is silicified, which is why it stands out from the rock, and this supports the idea that is came from one of the upper Paleozoic formations, and most likely the Mississippian.

 

@DPS Ammonite collects in the area and may be able to add to these comments.

 

Don

Thank you so much for the help! It’s my first time finding a fossil in Arizona, and there’s always something new to learn about the history of the earth and life.

[DPS Ammonite]

4 hours ago, Elena T. said:

I found it 10-30 miles off from a smaller city called Elson, Arizona, in some mountain ranges, in the area of Benson, Arizona and here are some size photos. I’m still looking up rock type but here are some more pictures.

Welcome to the Forum.
 

I agree that it is an orthoconic nautiloid. If we know the formation that it came from then we may be able to determine species. I have collected orthoconic nautiloids from the early Permian Fort Apache Limestone in north central Arizona. I have heard that they also occur in the Mississippian: look up Nautiloid Canyon in the Grand Canyon.

 

Did you mean to say that it was found near Elgin instead of Elson?

 

Check out my Arizona Paleontology Guide: http://www.thefossilforum.com/index.php?/topic/86597-arizona-paleontology-guide/

 

[minnbuckeye]

10 hours ago, Tidgy's Dad said:

Orthoceras is confined to the Baltic area, including Sweden

@Tidgy's Dad, I hate to point out your mistake, BUT, Orthoceras IS found in Minnesota!!!!! 

 

 

  

Barbarea orthoceras (American Yellow Rocket)

Plant Info

Also known as:	American Winter Cress, Northern Winter-cress
Genus:	Barbarea
Family:	Brassicaceae (Mustard)
Life cycle:	biennial, short-lived perennial
Origin:	native
Habitat:	part shade, sun; moist sandy or rocky soil; meadows, shores, open woods, rocky slopes, cliffs, gravel pits, sandbars
MN county distribution (click map to enlarge):

[Tidgy's Dad]

2 minutes ago, minnbuckeye said:

@Tidgy's Dad, I hate to point out your mistake, BUT, Orthoceras IS found in Minnesota!!!!! 

 

I stand corrected. 

Actually, I'll sit corrected if you don't mind, much more relaxing on the spine.

One learns something new every day. 

[Elena T.]

6 hours ago, DPS Ammonite said:

Welcome to the Forum.
 

I agree that it is an orthoconic nautiloid. If we know the formation that it came from then we may be able to determine species. I have collected orthoconic nautiloids from the early Permian Fort Apache Limestone in north central Arizona. I have heard that they also occur in the Mississippian: look up Nautiloid Canyon in the Grand Canyon.

 

Did you mean to say that it was found near Elgin instead of Elson?

 

Check out my Arizona Paleontology Guide: http://www.thefossilforum.com/index.php?/topic/86597-arizona-paleontology-guide/

6 hours ago, DPS Ammonite said:

Welcome to the Forum.
 

I agree that it is an orthoconic nautiloid. If we know the formation that it came from then we may be able to determine species. I have collected orthoconic nautiloids from the early Permian Fort Apache Limestone in north central Arizona. I have heard that they also occur in the Mississippian: look up Nautiloid Canyon in the Grand Canyon.

 

Did you mean to say that it was found near Elgin instead of Elson?

 

Check out my Arizona Paleontology Guide: http://www.thefossilforum.com/index.php?/topic/86597-arizona-paleontology-guide/

 

It was Elgin, my bad.

Edited April 21, 2020 by Elena T.

[ClearLake]

Not to get too picky (or get in the middle of @Tidgy's Dad and @minnbuckeye  ) but generally when someone refers to Orthoceras as not being found in the Baltic (or any such comment), they are referencing the genus (or some higher taxonomic level) name, not the species name.  The forum is for a pretty general audience so we play fast and loose with nomenclature which is fine, but I would say a species name should never be given without the genus, as it is somewhat meaningless.  Genus without species is fine as it denotes a somewhat larger, less specific group. 

 

And yes, I realize Mike was just having a little fun, I'm more commenting on the general topic of binomial nomenclature which is fundamental to modern biology (long dead and living) so that folks don't get confused since many may not be all that familiar with it.  One step off my soapbox!

[Randyw]

5 hours ago, minnbuckeye said:

I hate to point out your mistake, BUT, Orthoceras IS found in Minnesota!!!!! 

[Coco]

4 hours ago, ClearLake said:

The forum is for a pretty general audience so we play fast and loose with nomenclature which is fine, but I would say a species name should never be given without the genus, as it is somewhat meaningless. 

I agree ! I fight for that too !

 

Coco