2020 Ontario Trilobite Hunting

[piranha]

It seems self evident ... the marginal brim is a key feature on Eobronteus.

[Kane]

Mostly been rummaging through materials close to home as I'm in between big trips. I've been finding most of the same stuff lately, so won't post photos of all the bits and non-trilobitic items for now.

 

The only interesting find for today was this pygidium -- I only partially prepared this to discern the diagnostic traits enough to identify it with certainty -- of Trypaulites calypso. I've found a few of these already this year. Ludvigsen (1979) tells us they are not reported in Ontario, but are found in correlative rocks in both Michigan and New York, spanning the equivalent Ontario strata of Bois Blanc, Amherstburg, and Dundee Fms.

 

T. calypso's main distinguishing pygidial features would be the relatively large number of pygidial ribs (10-14), but also the saggital ridge on the axis that looks triangular in cross-section.

 

What is more significant about this particular specimen is that the ornamentation of scattered granules appears here, although Lesperance (1975) tells us those are rarely ever preserved. Specimen measures approximately 10 mm long. 

[Malcolmt]

Most Excellent Discovery.........

[piranha]

The older photos are difficult to judge--do the previous Trypaulites specimens have smooth axial rings? 

This one certainly fits well with the diagnosis of sagittally elongated pygidial axial nodes for T. calypso:

 

"Sagittal part of axis generally broken so that large rounded nodes are seen; when preservation is better, these nodes are sagittally elongated (PI. 2, fig. 10) and elevated up to 0.6 mm above level of axial rings and their rounded bases."

 

Lespérance, P.J. 1975

Stratigraphy and Paleontology of the Synphoriidae (Lower and Middle Devonian Dalmanitacean Trilobites). Journal of Paleontology, 49(1)91-137

[Tidgy's Dad]

Very tasty.

[Kane]

Thanks, Malcolm & Adam.  If only to find a complete one! One day...

 

@piranha From what I initially read in Lesperance, most of the specimens collected did not preserve the ornamentation very well (not to say it was entirely effaced!):

 

"Ornamentation seldom preserved and as seen three specimens (one of which is MPUM 15132) consists of scattered granules, 0.1-0.15 mm in diameter, on anterior and posterior parts of pleurae, the steeply dipping parts of the pygidial axis and on the ?border. On a specimen from the Grand Tower Limestone, the ornamentation appears to be restricted to the border and the terminus is only slightly upturned; a few other pygidia from the same limestone also have slightly upturned pygidia." (Ibid, p. 117). 

 

Anecdotally, of the about twelve or so examples I've collected between two formations, the lithology does not favour a finer preservation. The Amherstburg Fm examples are usually entirely silicified, while the Dundee Fm examples come out as steinkerns (with one exception that retains shell, but does seem entirely effaced, most likely due to erosional forces as it was exposed). The example collected here was far more favourable, but also appearing in a slightly different matrix, which might account for its granular detail.

[piranha]

I was referring to the nodes on the axial rings.

[Kane]

2 minutes ago, piranha said:

I was referring to the nodes on the axial rings.

Ah, and I was pointing to the little granules! But, the axial nodes are absolutely how I generally discern this species from its nearby cousin (T. erinus) that lacks the triangular ridge... or at least the nodes give it that ridged appearance!

[piranha]

Is it possible to discern any axial nodes on the previous specimens?

[Kane]

10 minutes ago, piranha said:

Is it possible to discern any axial nodes on the previous specimens?

On mine? Let me double check...

 

This one from the Dundee Fm. The nodes are present, but  very abraded...

[Kane]

They show up better in the impression:

[Monica]

I love those granules on the T. calypso 

[Kane]

An interesting day of "it was meant to be."

I had to make a run to the hardware store to replace the brick hammer I misplaced, and it happened to be the last one in stock. Deb told me that there were some river rocks near her sister's house, which is just a few minute drive from our place, so I figured I'd christen the new hammer. The material was all Dundee Fm, but most of it at the wrong horizon (mostly littered in tiny brachs). I came upon a different matrix type that I knew contained sometimes fairly plump fragments of Eldredgeops rana.

 

Within a few minutes of poking around, this nearly 2 inch monster appears. I've kept the impression so as to be able to replace missing skin when I get to prepping it. The spot is small and can be exhausted in a few hours, but I'll give it another go later on this month. 

 

There may actually be more complete ones in this same rock, albeit much smaller. Even if not, I think this was a great way to break in a new hammer.  

[FossilDAWG]

Nice one!

Don

[Fossildude19]

Serendipity!  

[digit]

4 hours ago, Kane said:

I think this was a great way to break in a new hammer.  

Well done--you'll have to christen this new hammer 'Bug Sniffer'.

 

 

Cheers.

 

-Ken

[Ludwigia]

Well, how 'bout that! Nice catch!

[Kane]

Thanks, gents -- it was quite the surprise! Finding them full here is a rare and delightful event, and not like at Penn Dixie!

 

@digit -- Heh, I don't know if "sniffer" makes for a fitting name for a hammer.  

[FossilDAWG]

Perhaps "bug magnet"?

 

Don

[Kane]

2 minutes ago, FossilDAWG said:

Perhaps "bug magnet"?

 

Don

"And suddenly, without warning, an enormous swarm of mosquitoes engulf Kane and he is never seen again."  

[FossilDAWG]

Hmmm.  I thought there was something familiar about "bug magnet".  Actually, that was "mosquito magnet".  Personally, calling trilobites "bugs" always seemed wrong to me, but then again I am an entomologist (well sort of).

 

Don

[Kane]

Two trips in the last week. Nothing new to the list, but more samples.

 

Amherstburg Fm material.

Acanthopyge contusa (poorly preserved fragments)

[Kane]

Amherstburg Fm

Obligatory Crassiproetus crassimarginatus pygidia. I cheekily nickname the pair Fat Man and Little Boy.  

[Kane]

Amherstburg Fm

An Echinolichas sp. pygidium that is partially buried and will be put in the prep queue.

A Mystrocephala stummi pygidium.

 

All of these Amherstburg bugs were from a single bloc. There were numerous Pseudodechenella sp. parts that I don't pick up.

[Kane]

From my Dundee Fm location.

Slightly better diagnostic samples of Odontocephalus pygidia with the caudal "fork"