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Trilobite of the week #217 is Stapeleyella inconstans of Early Ordovician age from the Hope Shales, Shelve Inlier at Minsterley, West Shropshire, England.  This is another member of the Trinucleidae.

 

 

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Trilobite of the week #218 is Aulacopleura konincki of Early Silurian age from the Motol Formation at Lodenice, Czech Republic.  This proetid is in the family Aulacopleuridae so is what I call an eponymous trilobite -- a bug whose genus gives the family it's in its name.   I figure eponymous trilobites probably represent the family they're in better than most.

 

The preservation is flat and ghost like.  I'm sure it was a lot more 3D in real life.

 

 

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Trilobite of the week #219 is Proetus cf. granulatus, a Silurian proetid found in the Hemse bed from Gotland, Sweden.  This trilobite is is in the family Proetidae within the order Proetida, so it's another eponymous trilobite.  And, indeed, it is a quite typical member of the Proetidae, with genal spines but no radical spines, and no fancy rostrum or other bizarre features, but quite 3 dimensional.  The hypostome is exposed.

 

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Mark Kmiecik

Is this nicknamed the "Jimmy Durante bug"? If not, it should be. :)

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Posted (edited)

Trilobite of the week #220 is Tomagnostus fissus, of Middle Cambrian age and from Nine Wells, Wales.  This species may be unfamiliar to most American collectors, but its family, Ptychagnostidae, should be known to most collectors of American Cambrian agnostid trilobites.  It's 13 mm long, respectable size for an agnostid.

 

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KathyGrant
On 5/19/2019 at 2:43 PM, piranha said:

AMNH has the correct name as Ditomopyge productaPaladin does not have a median preoccipital lobe (termed 'praeoccipital' by Weber) which is a key feature for Ditomopyge.  Additionally, the genal spines of Paladin transilis only extend to the 7th thoracic segment and for Ditomopyge producta the genal spines extend to the pygidium along with coarse granulation of the occipital ring. 

@piranha , so this one is also Ditomopyge producta? Thanks!

 

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I have three species of Modocia, three species of Amecephalus and here you see that I have two species of Cernuolimbus.  Trilobite #221 is Cernuolimbus pegakanthodes of Late Cambrian age, from the McKay Group of British Columbia, Canada.  As with Cernuolimbus ludvigseni, there is a line of tiny pits at the front of its head.  These are not as well preserved on the current specimen, but are still readily visible on the front left and are a bit pushed into the head on the front right.  So this is apparently a general feature of the genus.

 

Although it is not clear from these closeups, this has the same sort of preparation as my Modocia typicalis -- it was found as a ventral when they split the rock, so they glued the two halves back together and prepared it from the other side to get a dorsal trilobite.  As a result the trilobite is in a bit of a well on the rock.

 

 

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Trilobite of the week #222 is Monodechenella macrocephala of Middle Devonian age from the Kashong Shale, Moscow Formation at Livingston County, New York.  This specimen is crunched in on the left side, so it's not my best bug.  OTOH, a dinosaur paleontologist would be thrilled to find a specimen as complete and non-distorted as this; we trilobite collectors are spoiled.

 

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Trilobite of the week #223 is Bumastoides milleri of Late Ordovician age from the Platteville Formation at Grant County, Wisconsin.  I have two specimens of this bug.  The large one (3.1 cm long) has some of the thorax pushed under the head.  The small one is near perfect but is only 2 cm long.  That's a common case -- the big but imperfect bug vs. the small but perfect bug.  This species is in the Illaenidae and has the classic face of an Illaenid.

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Trilobite of the week #224 is Ptychoparia striata of Middle Cambrian age from the Jince Formation at Jince, Czech Republic.  There are two good specimens on this rock and one broken up specimen.  The piebald coloration is natural and common in this formation.  This is genus Ptychoparia in family Ptychopariidae in superfamily Ptychoparioidea in suborder Ptychopariina in order Ptychopariida, so it's as eponymous as a trilobite can get.

 

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  • 2 weeks later...

Trilobite #225 is Dechenella sp.  of Middle Devonian age from Tabamakhlouft Mountain at Issoumour, Morocco.  This isn't my best bug, there is some erosion of the thoracic segments.

 

 

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piranha
2 hours ago, rew said:

Trilobite #225 is Dechenella sp.  of Middle Devonian age from Tabamakhlouft Mountain at Issoumour, Morocco. 

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This one is Cyberella lemkei.  A few of the key identifying features are a preglabellar area approximately equal or longer than the glabella, triangular contour of the frontal glabellar lobe and genal spines that extend to the 7th thoracic segment. Martin Basse in Basse & Müller 2004 erected this new Moroccan species.

 

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Basse, M., Müller, P. 2004

Eifel-Trilobiten III: Corynexochida, Proetida (2), Harpetida, Phacopida (2), Lichida.

[Eifel-Trilobites III: Corynexochida, Proetida (2), Harpetida, Phacopida (2), Lichida.]

Goldschneck im Quelle & Meyer Verlag GmbH & Co., Wiebelsheim, 261 pp.

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Thanks.  One more bug in my collection now correctly identified.

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Trilobite #226 is Hesslerides arcentensis of Mississippian age from the Lake Valley Formation of Luna County, New Mexico.  This is the only trilobite I have from New Mexico.  This is as good a specimen as you'll ever see -- it is as well preserved as the one on the AMNH trilobite gallery and at 3 cm in length it is slightly bigger.  Like most members of the Phillipsiidae it is a plain Jane bug.  I don't know why it was the small and plain trilobites that survived the Devonian mass extinctions, but that's how it turned out.

 

 

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Trilobite of the week #226 is an Asaphid usually called Homotelus bromidensis but I see that on Sam Gon's trilobite site he has Homotelus as a junior synonym of Isotelus, so this bug might properly be called Isotelus bromidensis.  I'll let piranha have the last word on this issue.  It is of Middle Ordovician age from the Pooleville Member, Bromide Formation at Criner Hills, Carter County, Oklahoma.  This is the same location that Frencrinuroides capitonis (trilobite #71) comes from.  This is a fairly typical multiple specimen plate, with two fully articulated specimens and two disarticulated specimens.

 

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piranha

Jell & Adrain 2003 and Whittington 1950 regard Homotelus as a synonym of Isotelus. Amati 2014 suggested that some species of Homotelus including H. bromidensis might be synonymous with Vogdesia, but unfortunately did not recognize the previous synonymy of Shaw 1974.

 

A colleague commented recently:

 

"The holotype of Vogdesia bearsi has been lost. A neotype has been designated, and there are topotypes. It has very high eyes, nothing like Isotelus simplex, or Homotelus bromidensis. In my opinion, Vogdesia should be restricted to the type species. Given the controversy I still carry mine as Homotelus."
 
 
 

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Shaw, F.C. 1974
Simpson Group (Middle Ordovician) Trilobites of Oklahoma.
Journal of Paleontology 48(5) Supplement: Memoir 6:1-54

 

 

"Homotelus was erected by Raymond (1920) for isotelines lacking genal spines but with wide cranidia, weak axial furrows, elevated palpebral lobes and a lateral border. Jaanusson (in Moore, 1959) added that a frontal area is lacking and the palpebral lobes are positioned slightly in front of the transverse mid-line of the cranidium. Whittington (1950) noted that the differences between Homotelus and Isotelus are small and recommended restricting the genus to the type. I agree that the genus should be restricted but feel that the lack of a frontal area on the cranidium allies Homotelus more closely with Vogdesia than Isotelus. Some species previously assigned to Homotelus (e.g., H. bromidensis, Esker, 1964) may belong in Vogdesia."

 

Amati, L. 2014

Isoteline Trilobites of the Viola Group (Ordovician: Oklahoma): Systematics and Stratigraphic Occurrence.

Oklahoma Geological Survey, Bulletin 151:1-125  PDF LINK

 

Jell, P.A., Adrain, J.M. 2003
Available Generic Names for Trilobites.
Memoirs of the Queensland Museum, 48(2):331-553  PDF LINK

 

 

"Homotelus differs from Isotelus in that it is a proportionately broader form, has the eyes placed farther forward, and has an ornament of fine pustules, not the characteristic small, closely-spaced pits of l. gigas. The hypostomes of the two genera are closely comparable. The differences between the two forms are thus small, and it is doubtful if they should be ranked as separate genera. I consider that if the name Homotelus is retained it should be used at present only for the genotype, and that it is probable that many of the species referred to this genus by Raymond (1920, pp. 288-292; 1925, pp. 88-95) do not belong here."

 

Whittington, H.B. 1950

Sixteen Ordovician Genotype Trilobites.

Journal of Paleontology, 24(5):531-565

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Okay, Homotelus it is, at least for the time being.

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Trilobite of the week #227 is Bristolia harringtoni of Early Cambrian age from the Latham Shale at San Bernardino County, California.  This species is lower in the formation than Bristolia bristolensis and has a different genal angle.  B. harringtoni is considered to be an intermediary between B. mojavensis and B. bristolensis.

 

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1 hour ago, rew said:

Trilobite of the week #227 is Bristolia harringtoni of Early Cambrian age from the Latham Shale at San Bernardino County, California.  This species is lower in the formation than Bristolia bristolensis and has a different genal angle.  B. harringtoni is considered to be an intermediary between B. mojavensis and B. bristolensis.

 

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Beautiful Bristolia. I have a couple cephalons but nothing close to complete from the site.

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18 hours ago, Sjfriend said:

Beautiful Bristolia. I have a couple cephalons but nothing close to complete from the site.

 

I was fortunate to snag this one.

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