Fossil? Bivalves from Milnerton

[Max-fossils]

Hi all,

 

I found those bivalves on Milnerton beach (Cape Town, South Africa). The beach is known to have fossil shark teeth and whale bones, but I don't know if they have fossil seashells. They do have modern ones. Those shells, because of many different features, do make me think that they are fossil. Anyways, I'm interested in 2, if not 3 things:

• Species

• Fossil or modern 

• (if fossil) how old

 

If this species is (locally) extinct, then I think I can quite confidently put them down as fossil, but otherwise I'm not sure. The things that make me think that they are fossil are:

• they are very thick

• they are dull 

• they feel very hard (a lot like stone)

Those features are applicable with shells found on the Zandmotor (NL), to see if they are modern or fossil; whether they are applicable in Cape Town I have no clue.

 

Thanks in advance,

 

Max

[ynot]

Could go either way on this.

The only way to be sure is to find one in situ or, like You said, is it a current species of the area.

Thickness of shell is an environmental adaptation, not a good indication of fossil.

[Max-fossils]

1 minute ago, ynot said:

Could go either way on this.

The only way to be sure is to find one in situ or, like You said, is it a current species of the area.

Thickness of shell is an environmental adaptation, not a good indication of fossil.

Thickness is indeed an environmental factor, but (again in the case of the Zandmotor), the shell will gain some thickness when turning to stone. I know this, as I have (for example) modern Macoma balthica and fossil M. balthica. The fossil ones are thicker than the modern ones. Yet here, as I don't know the area well, I don't know. 

 

Any clue on the species?

[ynot]

2 minutes ago, Max-fossils said:

Any clue on the species?

Sorry but shells are not My strong point. (Can barely tell a bivalve from a gastropod from a clam, all those mollusk things look alike to Me).

[Max-fossils]

22 minutes ago, ynot said:

Sorry but shells are not My strong point. (Can barely tell a bivalve from a gastropod from a clam, all those mollusk things look alike to Me).

Haha ok, no problem. 

 

Btw, a clam is a kind of bivalve 

The 4 kinds of mollusks are: bivalves, gastropods, chitons and cephalopods.

[ynot]

53 minutes ago, Max-fossils said:

The 4 kinds of mollusks are: bivalves, gastropods, chitons and cephalopods.

According to wiki there are 9 mollusks.

[Max-fossils]

1 minute ago, ynot said:

According to wiki there are 9 mollusks.

???

 

Possible. They're a weird group, tbh 

3 minutes ago, ynot said:

According to wiki there are 9 mollusks.

Oh yeah, I forgot about the scaphopods too. I like those. 

 

The 4 I named are the 4 main ones though; others are a lot less "important".

[ynot]

1 minute ago, Max-fossils said:

; others are a lot less "important".

I bet the slugs do not feel that way!

[Max-fossils]

56 minutes ago, ynot said:

I bet the slugs do not feel that way!

Haha, should I be scared? 

[Pilobolus]

2 hours ago, ynot said:

... all those mollusk things look alike to Me).

 

Blasphemer!

[ynot]

1 minute ago, Pilobolus said:

 

Blasphemer!

Oh Me of little faith!

[Coco]

On 11/07/2017 at 7:21 PM, ynot said:

Selon wiki il y a 9 Mollusques.

 

I know 8 of them :

 

- bivalvia

- caudofoveata

- cephalopoda

- monoplacophora

- polyplacophora

- rostrochondia

- scaphopoda

- solenogastres

 

Which one is the 9th ?

 

Coco

 

[ynot]

From wikipedia...

Opinions vary about the number of classes of molluscs; for example, the table below shows eight living classes,[18] and two extinct ones. Although they are unlikely to form a clade, some older works combine the Caudofoveata and solenogasters into one class, the Aplacophora.[9][27] Two of the commonly recognized "classes" are known only from fossils.[16]
Class    Major organisms    Described living species[18]    Distribution
Caudofoveata[9]    worm-like organisms    120    seabed 200–3,000 metres (660–9,840 ft)
Solenogastres[9]    worm-like organisms    200    seabed 200–3,000 metres (660–9,840 ft)
Polyplacophora[10]    chitons    1,000    rocky tidal zone and seabed
Monoplacophora[11]    An ancient lineage of molluscs with cap-like shells    31    seabed 1,800–7,000 metres (5,900–23,000 ft); one species 200 metres (660 ft)
Gastropoda[42]    All the snails and slugs including abalone, limpets, conch, nudibranchs, sea hares, sea butterfly    70,000    marine, freshwater, land
Cephalopoda[43]    squid, octopus, cuttlefish, nautilus, spirula    900    marine
Bivalvia[44]    clams, oysters, scallops, geoducks, mussels    20,000    marine, freshwater
Scaphopoda[15]    tusk shells    500    marine 6–7,000 metres (20–22,966 ft)
Rostroconchia †[45]    fossils; probable ancestors of bivalves    extinct    marine
Helcionelloida †[46]    fossils; snail-like organisms such as Latouchella    extinct    marine
 

[doushantuo]

A phylogram from a low-profile publication:

[doushantuo]

Vermeij with a pretty nice (& recent,too!)piece

 

VermeigastrounivLINNEA2017eScholarship_UC_item_8p93f8z8.pdf