Graptolites of the Cincinnatian

Rich Fuchs (Dry Dredgers, Cincinnati, Ohio, USA)

Dry Dredgers meetings (Cincinnati, Ohio, USA)

28 May 2010 & 21 November 1997

 

Cincinnatian Series Graptolites

Geniculograptus is the most common Cincinnatian Series (type Upper Ordovician of North America) graptolite.

 

The Cincinnatian has biserial and uniserial graptoloid graptolites - uniserial forms are not common, while biserial forms are ~common.

 

James Hall probably was the first to identify Cincinnatian graptolites.  Ruedemann named many Cincinnatian species.  John Taylor's 1974 University of Cincinnati Master's thesis was about Cincinnatian graptolites - it has some omissions.  One problem is tracing original type specimens.  Charles Mitchell & Stig Bergström have revised some Cincinnatian graptolites.

 

Most Cincinnatian forms have had genus reassignments based on modern genus definitions, which are based on sicula structure (the first theca).  Graptolite systematics focuses on the proximal end of the skeleton and how thecae begin to bud off.

The nema is attached to the seafloor or something floating in the water or to a float.

Rich Fuchs hasn’t found nemas attached to floats, probably because they got detached.  Rich did find a possible float once.  Floats are not found because they float away.  Graptolites are worldwide.

 

Dictyonema was a little bush.  It’s now shown upside down (attached to floats & hung down, it’s now thought).

Cincinnatian graptolites are usually simple blades.

Tetragraptus from Australia was pendant with 4 stipes.

Some graptolites were coiled, like the monograptid Spirograptus (Australia; Lower Ordovician of New York).

Many graptolites were floaters - do get distributed very widely.

Graptolites are used for relative dating & correlation.

Ordovician-Silurian rocks are divided into graptolite biozones.

The end-Ordovician experienced an Ice Age - all but 1 or 2 genera of graptolite went extinct.  Every post-Ordovician graptolite is related to these 1 or 2 genera.

All graptolites went extinct in the mid-Mississippian.  They may be alive in the present day, though.

 

There are 7 orders of graptolites.

Dendroidea - sessile, attached; bush-like; have the longest duration of any graptolite group - Middle Cambrian to Middle Mississippian.

Graptoloidea - planktonic (floaters), attached to a float structure; only Ordovician to Silurian.

Dendroids and graptoloids are found in Cincinnatian rocks.

 

Graptolites like deep water - they are found in shales.  They are very fragile.  Shale tends to flake as it ages, so that combination means good graptolites are difficult to find.

Sometimes, graptolites are found on limestone - get better preservation.

 

The Kope Formation has the best Cincinnatian graptolites.  There are 16 genera total in the Cincinnatian, not counting the Utica Shale (Middle Ordovician or Upper Ordovician, depending on who you ask).  Same for the Fulton Shale.

 

There are 31 species of graptolites in the Cincinnatian (Upper Ordovician of the Cincinnati, Ohio area): 9 graptoloid graptolites (Kope Fm. to Waynesville Fm.), 7 dendroid graptolites (including problematic forms) (Kope Fm. to Waynesville Fm.), 5 encrusters (Kope Fm. to Whitewater Fm.), plus other problematic species.

 

Dendroidea

Dictyonema arbusculum - Cincinnatian, Kope Fm.; rare; Rich Fuchs hasn’t found one yet; resembles Dictyonema flabelliforme.

 

Acanthograptus ulrichi - a dendroid like Dictyonema arbusculum, except that it’s in the Fairview Formation.  Rich hasn’t seen it or found one.  Acanthograptus ulrichi is bush-like but with thorns.

 

Graptoloidea

The Cincinnatian Series has scandent, reclined, and reflexed forms - these are prevalent in the Upper Ordovician.  Pendant, declined, and deflexed forms tend to be Lower Ordovician.  So, there’s change through time.

 

Geniculograptus typicalis typicalis - the first identified Cincinnatian graptolite, the most common, and most well studied Cincinnatian graptolite is the graptoloid Geniculograptus typicalis typicalis (there are other subspecies) - it’s common in the Southgate Member of the Kope Formation; it's uper range is not really known, but it goes down into the Middle Ordovician.  James Hall’s 1800s list of New York graptolites listed Climacograptus typicalis but no description accompanied the name.  Hall named it and figured it.  This was the first reference to that graptolite.  Ruedemann’s description gave species credit to Hall, though he never originally described Climacograptus typicalis.  Ruedemann claims he described it in 1908.  James apparently described it in 1892.  This species is biserial.  Riva recognized that typicalis isn't a Climacograptus.  Mitchell, using sicular morphology, put typicalis in Geniculograptus - no longer in Climacograptus.  Riva also proposed a new genus name (Uticagraptus), but that name was published one month after Mitchell's new genus name.  In northern Kentucky, troughs/trough fillings of Geniculograptus have been found with the graptolites all lined up (Ron Fine found these).  G. typicalis typicalis is 2-5 cm long (3/4" to 2").  Its thecae have a slightly tapering square appearance.  These alternate on either side of the virgula.

 

Geniculograptus typicalis magnificus is a big biserial form in the Maysville Stage.  typicalis typicalis has lengths up to 3.5 cm (1 3/8"), but typicalis magnificus can get to 7 cm long (almost 3").  It looks like it has smaller thecae, but they are just spread out more, because the rhabdosome is wider between thecae.

 

Geniculograptus typicalis posterus is a smaller-than-magnificus form in the Fairview Formation.

 

Geniculograptus pygmaeus is also a now-well studied form.  It has been tossed around from time to time as typicalis.  It can be confused with typicalis, but it’s a lot smaller than typicalispygmaeus is younger - it occurs in the upper Kope Fm. and lower Fairview Fm.  pygmaeus and typicalis do overlap, but pygmaeus is younger & typicalis is older.  Geniculograptus pygmaeus is usually <1 cm long and ~1 mm or so wide (small & narrow).  Geniculograptus typicalis is ~1.25” (2 to 3 cm long).  G. pygmaeus has square thecae that taper more than in G. typicalis.

 

An intermediate form between G. typicalis typicalis and G. pygmaeus is known - found from in the top of the Southgate Member of the Kope Formation in Kentucky - it’s not named yet, apparently - Geniculograptus sp. - longer and skinnier than pygmaeus, but still smaller than typicalis.

 

Orthograptus quadrimucronatus - short spines come out of the sides; found in the Kope Fm. to Arnheim Fm. (the Richmondian Stage form is a subspecies - O. quadrimucronatus richmondensis).  Biserial; thecae are more triangular and have thecal spines; the thecae are chevron-shaped (V-shaped), while Geniculograptus, in contrast, has squarish thecae.  This is a larger species than Arnheimograptus anacanthus.

 

Arnheimograptus anacanthus - found at Mt. Orab (look for graptolites there, not trilobites!); a relatively new genus (Mitchell); only ~1 cm long; has chevron-shaped thecae; biserial.

 

Dicranograptus nicholsoni - Rich Fuchs has never seen it; a reclined graptolite - has a scandent portion, then it splits; it has a two-stipe rhabdosome with a biserial extension (Y-shaped rhabdosome - the root is biserial; the two upper branches are uniserial).  Occurs in the bottom of the Kope Formation (Fulton Shale Member), which is mostly flooded now.

 

Dicellograptus forchammeri - a uniserial grapolite supposedly in the Fairveiw Formation; formerly Leptograptus annectens (a Ruedemann name).  Mitchell and Bergström reassigned it to Dicellograptus, because Leptograptus has a two-stipe rhabdosome.  The Cincinnatian form is actually Dicellograptus sp. aff. Dicellograptus forchammeri.  It has a V-shaped or U-shaped rhabdosome.

 

Amplexograptus maxwelli - bottom of the Kope Fm., in the Fulton Shale; similar to Geniculograptus typicalis posterus, but don't worry - it occurs in beds below water level along the Ohio River in Cincinnati; biserial; square thecae - slightly rounded lip of thecae; tip is different from Geniculograptus.

 

Climacograptus - there’s still one of these in the Fairview Fm.

 

Uncertain placement graptolites

Most of what's been assigned to the Cincinnatian dendroid graptolites is Mastigograptus, but there's lots of conjecture about what it is.  Five or so species of Mastigograptus in the Cincinnatian Series.  They appear as plain, black lines (flattened tubes) in rock - "pepper rock".  The five species range from the Kope Formation to the Waynesville Formation.  The best way to figure out the species is to use the stratigraphic horizon.

 

Mastigograptus tenuiramosus - delicate; occurs in the bottom half of the Kope Fm.; usually fragile - forms pepper rock.  Pepper rock usually has scolecodonts.  Branch angles are at 45°.

 

Mastigograptus gracillimus - decent-sized fossils cf. to Cincinnatian graptoloids; Kope Fm. to Fairview Fm.

 

Mastigograptus perixilis - Waynesville Formation.

 

Mastigograptus strictus - has shallow branching angles.  Occurs in the Arnheim Fm. - can be found at Mt. Orab.  But, it could be the same species as Mastigograptus tenuiramosus.

 

Mastigograptus multifasciatus - upper Fairview Formation.

 

Are there visible thecae in Mastigograptus?  Ruedemann said thecae in Mastigograptus are known from other areas.  Taylor found only one thecae-bearing specimen.  Rich has never seen thecae in Cincinnatian Mastigograptus.  The Treatise has thecae drawn in on the Mastigograptus illustration.

 

Mastigograptus is sometimes listed as a dendroid, sometimes listed as uncertain.

 

Bulman didn’t know where to place Mastigograptus within the graptolites.

 

Ultrastructure studies show Mastigograptus is a graptolite.  But some say they look like seawhips.

 

Rich Fuchs thinks that Mastigograptus is similar to seawhips.  He thinks it is almost definitely not a graptolite.  Seawhips are a form of coral (horny coral).  After seawhips die, the outer organic material comes off, resulting in a Mastigograptus-like thing.

 

Dave Meyer: seawhips now are much larger than Mastigograptus, but the point is well taken.  There’s nothing saying Ordovician seawhips couldn’t have been small enough to be Mastigograptus.

 

Urbanek did an SEM study of Mastigograptus - it’s structure is consistent with graptolites; the chemistry is the same as graptolites; therefore, it could be a graptolite; but, it still could be something else.  There’s still no evidence of thecae.

 

There are 5 or 6 species of Cincinnatian Chaunograptus named.  Most are Liberty Formation forms.  Most are based on one specimen.  Most of the holotypes are now missing (museum-wise).  The Smithsonian renumbered their collections a while ago and lost the Chaunograptus.  One was lost in a Dayton flood.  Few holotypes are left.  Chaunograptus are extremely fragile - not often found.

 

Chaunograptus is an encruster that may not be a graptolite.  It is fairly rare and easily overlooked.  It is more like to be found in the Richmondian Stage, especially encrusting brachiopod shells.  Chaunograptus is classified as a dendroid or uncertain.  There are several species, but some don't look like the rest.  Ruedemann listed 11 species - 7 were Upper Ordovician - 6 were Cincinnatian.  Now we're down to five species.  John Taylor said two of them were synonymous.  Taylor's thesis says that Chaunograptus shideleri is the same as Chaunograptus delicatus.  Most of the species are Richmondian.  Chaunograptus fossils have been found at Newport Shopping Center.  Rich Fuchs has found what he calls Chaunograptus contortus and Chaunograptus delicatus in the Kope Formation.  This is probably a form whose ranges are not well known.

 

Chaunograptus contortus - encrusting black spots on nodules.  Twisted thecae with extremely thin lines (nemas).  Rich Fuchs has found Chaunograptus contortus in the Kope Fm., but it was described from the Liberty Fm.  The type is missing - couldn't be found by Taylor.

 

Chaunograptus delicatus - the type specimen is encrusting a nodule; thicker lines than C. contortus; the lines trail around; occasional thecae structures; the lines move out from a central point.  Also first described from the Liberty Fm.  Occurs in the Liberty Fm. and Whitewater Fm.  The type specimen is known.

 

Chaunograptus vermiformis - Liberty Fm.  The type specimen is in the Smithsonian - it's been renumbered, but it has been found.

 

Chaunograptus macrothecae - Grant Lake Fm.  Type specimen can't be found.

 

Chaunograptus gemmatus - Kope Fm.  The type specimen (one specimen) is known.

 

Inocaulis - a worse genus than Mastigograptus in terms of identifying structure and determining affinities.  This is a rare fossil that's supposedly a graptolite.  Inocaulis is a non-descript collection of tubes, forming a stem - looks like a series of tubes (= the thecae) bundled together.  Two Cincinnatian species - Inocaulis simplex (Kope Fm.) and Inocaulis grandis (Maysville Stage); doesn’t look like a graptolite, but it’s listed as a dendroid.  Grammaria is a modern hydrozoan - it has a similar arrangement of tubes put together.  Inocaulis may be another graptolite that really isn’t.

 


 

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