Brachiopod labelled as Rhynchonellid species?

[DE&i]

Brachiopod labelled as.

Rhynchonellid species?

Lower Lias

Black Ven Marls

Lyme Regis (West Dorset)

 

 

[DE&i]

Continued :

 

I was wondering if this fossil brachiopod might be Rhynchonelloidella wattonesis but I’m not sure if this has been revised since.

 

 

[TqB]

I think it's Calcirhynchia calcarea Buckman. (ID from the Palaeontological Association guide, "Fossils from the Lower Lias of the Dorset Coast).

[DenBoy]

Seems to have too few ridges to be Rhynchonelloidella wattonesis, it does look like Calcirhynchia calcarea as Tarquin has suggested but looks a bit worn to make a positive ID and to be honest I have many Rhychonellids I can't 100% name because there are so many so similar & some have different names even though they appear identical but just a few miles apart, I find it a nightmare

[FossilDAWG]

21 minutes ago, DenBoy said:

Seems to have too few ridges to be Rhynchonelloidella wattonesis, it does look like Calcirhynchia calcarea as Tarquin has suggested but looks a bit worn to make a positive ID and to be honest I have many Rhychonellids I can't 100% name because there are so many so similar & some have different names even though they appear identical but just a few miles apart, I find it a nightmare

Homeomorphy is a big issue with these brachiopods: quite distinct genera and species, based on internal features of the shell, can have very similar exterior appearances.  Very good locality/stratigraphy data can help avoid the need to grind serial sections to reveal the internal structure.

 

Don

[DenBoy]

@FossilDAWG Thanks for the advise, Some of my Rhynchonellides when exposed cross section are geode inside making internal ID difficult if not impossible , but they do look amazing, hope to post some pics soon when have sun & better camera.R

[Ridgehiker]

22 hours ago, FossilDAWG said:

Homeomorphy is a big issue with these brachiopods: quite distinct genera and species, based on internal features of the shell, can have very similar exterior appearances.  Very good locality/stratigraphy data can help avoid the need to grind serial sections to reveal the internal structure.

 

Don

 

I have about 240 species of Rhynchonellid brachiopods.  The outward morphology can be more similar on distinct genera than on two specimens of the same species. 

 

As Don mentions, identification is done through a serial grind and, even then, you often need the type specimen to confirm the ID.

 

There is something that many collectors dont quite understand when identifying certain phyla of invertebrares...such as Corals and Brachs. Identification is nearly always for 'practical' purposes only.  The attempt isnt to identify 'biological' species as much as to name index fossils that can be used in biostratigraphy to date strata, etc.  This doesnt mean that a species cant also be a 'biological' species but that there is no means of confirming if it is or not.  Taxa are more 'tools'.

 

One can take a sample of similar brachiopods from a location, lump them together or divide them up according to some critera.  Call them one species or create 5 species. At the end of the day, nobody can really say if here is 5 biological species. However, one can can comment on whether such a division has any purpose other than to just over complicate the taxonomy.

[DE&i]

Thank you @TqB @DenBoy @FossilDAWG @Canadawest for all your valuable input. If I had to pick a single fossil on the TFF to come to a conclusive species i.d. it would most certainly be the Brachiopod. The knowledge that is available here is second to none and is my first port of call.

 

All noted and now scribbled in my journal.