All posts for the month December, 2012

Frechiella or A nautilus with an ammonite suture…

Frechiella subcarinata (YOUNG & BIRD, 1822), 8.5 cm diameter, Port Mulgrave, with a Dactylioceras fragment and a belemnite phragmocone in the aperture

Frechiella is one of the rarest Yorkshire lias ammonites and in some respects also one of the oddest.

It comes from a so-called “aberrant” line of ammonites, previously thought to come from one subfamily Bouleiceratinae of the family Hildoceratidae,

but nowadays after some more analysis (Rouleau et al 2003) is being split up into the 3 subfamilies Bouleiceratinae (lower Toarcian),

Leukadiellinae (middle Toarcian) and Paroniceratinae (upper Toarcian, including Frechiella) but all still under Hildoceratidae.

All are much more common in the tethyan realm, and are rare “strays” into the north-west european faunal province.

All members show a characteristically reduced, sometimes “ceratitic” suture (named after the triassic ammonite genus Ceratites, which showed a similar suture).

Oxyparoniceras telemachi (RENZ), 2 cm
This is a member of the same subfamily, but not found in Britain, but somewhat further south from Barjac in the south of France (and purchased by me).

This is also the main diagnostic feature, otherwise one could easily confuse these very involute ammonites with a nautilus , especially when they are wave-rolled –

In fact, Frechiella subcarinata was originally called Nautilus subcarinatus YOUNG & BIRD, 1822 –

you can just believe that, if it weren’t for the very characteristic suture, and I guess some of you might now go checking the nautilus in their collections …

(and of course : Frechiella is an ammonite, not a nautilus !)

Well preserved specimen show a faint keel on a rounded, sometimes slightly rectangular venter, faint radial ribs, sometimes flat waves can be seen close to the umbilicus.

With almost all specimen I’ve seen (and that’s not many…) the body chamber is more or less crushed or imploded.

Frechiella subcarinata (YOUNG & BIRD, 1822), 10 cm, Hawsker Bottoms

Frechiella subcarinata (YOUNG & BIRD, 1822) , the only Yorkshire species in the genus Frechiella found so far,

occurs only in the main alum shales, commune subzone, bed 54 (HOWARTH 1992).

It is one of the rarest Yorkshire coast lias ammonites, and many regard it as the “holy grail” of upper lias ammonites.

I had for a time almost given up on trying to find one myself, and bought an unprepared specimen, found at Port Mulgrave (the one pictured below the title),

from Mike Marshall in September 2003.

But as it happened – and doesn´t it always happen like this ?! – a year later in September 2004 one twinkled up at me from the cliff debris on one of my favourite

spots around Hawsker Bottoms – this is the one pictured above – I have not found one since, not even a fragment.

AndyS

by andysfossils on December 31, 2012 • Permalink

Posted in Ammonites, Uncategorized

Posted by andysfossils on December 31, 2012

https://andysfossils.com/2012/12/31/frechiella-or-a-nautilus-with-an-ammonite-suture/

I´m learning something new every time or A year review

Christmas trees in the snow – Eleganticeras sutures

As the year 2012 draws to a close, it`s time for a yet another year review…

I´ve started this blog in May 2012, and 36 blog posts later I can still say : It works for me !
It works for me because it drives me to write a post every couple of weeks, and that requires research into the ammonites I want to write about, photographs of the ammonites and maybe even a re-prep to make them presentable (allthough that sometime pushes back the publication date, because when you see those fossils through the lense, it´s so much easier to notice all the imperfections in the prep-work…).

It´s sometimes hard to stick to the schedule, because I do have a (non-fossil-related) , sometimes stressful day job and sometimes require a time-out from working at the keyboard, but I think it´s the right sort of methodology to keep work on the ultimate goal – the book – going.

And, the great thing is : I´m learning something new every time I research a new genus of ammonites for posting…

I´ve made some wonderful new contacts through people who have come forward and commented on posts and revived some old contacts who allowed me to photograph
some of their beautiful fossils. Thanks to all of you and I´d hopefully meet you next year to photograph some more !

But does it work for you ?

Countries with 6 or more visits to this blog , there are 30 more countries below this list !

Looking at the map, it does seem so… Of course, most of the readers are in Great Britain, that´s where the fossils come from, those are the readers this english language blog is made for. You know what they say about a prophet in his own country, I guess it´s the language issue why there is only a comparatively small participation from my fellow countrymen in Germany. But what makes me particularly proud is the worldwide readership…isn´t the internet a wonderful thing sometimes ?

But I have a request, too: Compared to the amount of visits (close to 10,000, I know this is not all that much, but then this is not a fashion blog…)
there are just a bit more than 60 comments (and some are from me as well…)

So, I´d really love to hear from you more ! What are your questions, what are your finds, don´t be shy !
And remember : If you comment, you have to leave a valid e-mail address, but nobody else other than me can read it and I do not pass on e-mail adresses !

And a few little steps can make it so much easier to follow this blog, as you get an e-mail whenever I write something new.

The folks from WordPress have a handy little explanation on how to follow a blog :

http://en.support.wordpress.com/following/

If you don´t like to post a comment here, you can reach me in the UKFOSSILS forum (www.discussfossils.com) as AndyS and
on the german Steinkern forum (www.steinkern.de/forum) as AndyS (for both forums : You still need an account there to post messages).

Wherever you are, and whatever tradition you follow during the days at the end of the year:

Have a good time with your family and the ones you love, a healthy new year, and, if you´re collecting fossils, a fossiliferous year 2013 !

All the best,

AndyS

by andysfossils on December 24, 2012 • Permalink

Posted in Ammonites, Introductory

Posted by andysfossils on December 24, 2012

https://andysfossils.com/2012/12/24/im-learning-something-new-every-time-or-a-year-review/

Ovaticeras or End of the line

Section of septarian nodule with Dacytlioceras sp (fron) and Ovaticeras ovatum (back)

Section of septarian nodule with Dactylioceras sp (front) and Ovaticeras ovatum (back)

If you read the title of this blog and start to worry that I might stop working on the book and on the blog – well, don’t. This is just referring to the subject of this post, the ammonite genus Ovaticeras…
The title specimen by the way (you might have guessed by the quality of the prepwork) is a specimen purchased from Mike Marshall. Maximum size of the Ovaticeras on this piece is 8 cm.

Ovaticeras is a somewhat rarer ammonite which seems to be very restricted, both in terms of local distribution (it’s apparently only really documented from Britain, with its main occurrence in Yorkshire) and in terms of its relative short-livedness (it has only been found in the approx. 35 cm of the so called ovatum bed at the top of the falciferum subzone of the lower toarcian (of course named after the species O. ovatum) and shortly below it. It is thought to have descended from Harpocas falciferum (HOWARTH 1992) and apparently left no descendants itself – end of the line.

I have found Ovaticeras ovatum at Saltwick Bay, at Hawsker and at Ravenscar, but you should be able to find it everywhere on the Yorkshire coast,
where there’s an outcrop of the aforementioned bed.

View of Ovaticeras keel and typical oval whorl section

The oval whorl shape of Ovaticeras is quite characteristic, as are the sloping umbilical walls without an edge,
which differentiates it from large Eleganticeras body chambers.

Comparison of umbilical edges of Eleganticeras (top) and Ovaticeras (bottom), both approx. 12 cm

Adult specimen have a bit of a “hood” at the end of the body chamber, where the keel slightly overarches the whorl.
The ribs are those of a typical Harpoceratid, of weak falcoid form, receding to mere sinuous growth stripes on adult specimens’ body chambers.
It does have a simple keel with smooth areas to the side of it that also grows weaker on large body chambers.

Large 17 cm Ovaticeras ovatum

This large, 17 cm, complete specimen was found on Oct 7, 1991 at Saltwick Bay in a large nodule with a strong pyrite crust and was
extracted from the nodule using hammer and small chisels alone (on the kitchen table of our holiday flat, if you need to know…)
It is not my prettiest specimen, but my largest and the first of the species I’ve found.

Suture of Ovaticeras

This partial specimen shows the nice characteristical sutures of Ovaticeras.
Must be getting close to Christmas, I see Christmas trees everywhere…

AndyS

by andysfossils on December 15, 2012 • Permalink

Posted in Ammonites

Posted by andysfossils on December 15, 2012

https://andysfossils.com/2012/12/15/ovaticeras-or-end-of-the-line/

Hildoceras or A plague of snakes

Whitby Abbey (2003)

Legend has it that St. Hilda, founding abbess of Whitby abbey, turned a plague of snakes to stone and threw them off the cliff, thus creating the ammonites we can find there today.
This legend was immortalized by Alpheus Hyatt in 1876 by naming the ammonite genus I´d like to present to you next after her: Hildoceras.

In Victorian times, snake heads were often carved on ammonites to capitalize on this legend – today there seems to be a renaissance of this art going on, and the quality
you´ll find on places like ebay is usually quite good, although these are mostly Dactylioceras ammonites.

But back to palaeontological reality :

In Yorkshire, there are 3 species of Hildoceras (I´m following HOWARTH´s “The Ammonite Family Hildoceratidae in the Lower Jurassic of Britain” here) :

Hildoceras bifrons (BRUGUIÈRE, 1789)

Hildoceras bifrons, 13.5 cm

Hildoceras bifrons is the lead ammonite for the bifrons zone of the lower Toarcian. It has a strong spiral groove, strong ribbing on the external half of the side,

and a keel with strong side furrows.

Hildoceras semipolitum BUCKMAN, 1902

Hildoceras bifrons (left), Hildoceras semipolitum (right), both 10 cm

Hildoceras semipolitum has a higher whorl section than H. bifrons, both spiral groove and ribbing are finer. The outer whorls overlap the inner whorls to a degree that

the ribs on the inner whorls are no longer or just about visible. As H. semipolitum is considered a descendant of H. bifrons, there are many intermediates.

Hildoceras lusitanicum MEISTER, 1913

Hildoceras lusitanicum, 15 cm

Hildoceras lusitanicum (also known under the synonym Hildoceras sublevisoni) is very similar in ribbing to H. bifrons,
the main difference is the missing spiral groove on the side of the whorl.

Yorkshire Ammonites (and other fossils ) revisited

All posts for the month December, 2012

Frechiella or A nautilus with an ammonite suture…

I´m learning something new every time or A year review

Ovaticeras or End of the line

Hildoceras or A plague of snakes

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