Onychites ?

[belemniten]

I recently post this fossil in anther topic. This was found by me in Holzmaden, but never find something like this before...

It could be a belemnit arm ?? or a fish fin ray or spine.....

Ḿaybe somebody can help me ? Or have a similar fossil ?

Detailed:

[GeschWhat]

I can't help you but it is definitely interesting!

[belemniten]

I can't help you but it is definitely interesting!

Thanks !

Nobody any ideas for id ?

[Archie]

Whats the size belemniten? First two things that popped into my head were belemnite hook or something fishy but just complete guesses there!

[belemniten]

Thanks. Good question ! The fossil is about 3 cm long.

[mohsenamini]

It should be 1 shell of a bivalve. and the color maybe because of the Chert :/

[abyssunder]

Cephalopods are known to develop arm hooks. Cephalopod arm hooks from the Mesozoic (Onychites) are usually attributed to belemnoids. Rare, articulated belemnoid animal fossils with soft−part preservation show rows of hooks along the arms. The studied Jurassic belemnite specimens have double rows of small hooks on each arm (0.3 - 5.0mm in length), grouped as micro-Onychites, also larger ones are present (5.0 - 40.0mm in length), grouped as mega-Onychites which were probably positioned either within the arm crown or on the tips of two modified arms (hectocotyli). These are much rarer than the small hooks and the individuals posessed two of this, present only in males, considered (like in modern squids) to be developed as a function of maturity with the principal role in reproduction rather than in predation. (These very large pair of hooks enabled the male to keep a firm hold of the female during copulation, but at the same time keep clear of the numerous and very sharp small hooks covering the arms.)
The small hooks functioned to catch prey, to hold it and to bring it within reach of the jaws. They were independent of sucker rings. Engeser (1987a, p. 5; 1987b, p. 4) has estimated that belemnites had between 5 and 40 paired arm hooks on each of their ten arms, so that the total number of hooks on one belemnite animal may vary from 100 to 800. Because of their soft-tissue composition, arms are normally very rarely preserved.

As Engeser (1987a, p. 12) has shown, a single cephalopod may have a number of types of hook that, when dissociated in the fossil environment, may each warrant a separate taxonomic name for descriptive purposes. This is a convenient, readily applicable and useful means of classification. Such taxonomic groups are referred to as form taxa. A consensus has evolved that form taxa (i.e. parataxonomy) should be used in the classification and description of belemnite arm hooks. The use of form taxa to differentiate belemnite hooks is comparable to the use of ichnotaxa for trace fossils.
Although somewhat artificial, form taxa are useful in palaeontology as a means of reference to isolated animal parts which, for practical reasons, need to be provided with binary names.

In fossil cephalopods, arm hooks commonly range in length from 0.5 to 10.0mm but occasionally the range may extend from 0.32mm up to 40.0 mm. Several authors have divided cephalopod arm hooks into two informal categories: mega-Onychites and micro-Onychites. A length of 5.0mm has been taken by authors (e.g. Kulicki & Szaniawski 1972) as an informal boundary between them. A system of terminology similar to that proposed by Kulicki & Szaniawski (1972, fig. 4) for micro-Onychites has been proposed by Engeser (1987b, fig. 1, 2) for mega-Onychites.

Outlines of a selection of the mega-Onychites that have been described in the literature are illustrated in Fig. 4. As may be seen from the outlines, there is very little variation in the basic hook shape. The variation consists of differences in the degree of curvature.

[abyssunder]

continue.......

Ornamentation also varies. As may be seen from the outlines in Fig. 4, in many instances the base of the hook has been broken off along with the spurs.

Seems that the dimensions and the morphology of the mega-Onychites resembles the specimen in question, so I conclude that it could be.

[TqB]

Thanks to abyssunder for putting the plates up!

I agree, it could be a mega-onychite, the shape is right and the ornamentation is feasible though I've not seen it in onychites from the Posidonienschiefer. The ones in published illustrations from there are more or less smooth.

Can anyone say that it's definitely not a fish bone?

[Guguita2104]

It should be 1 shell of a bivalve. and the color maybe because of the Chert :/

I agree with mohsenamini. IMO, it's a valve of a bivalve.

However it's also a nice find.

Regards,

Guguita

[belemniten]

First thanks all (excpecially you abyssunder ! )

Are you sure with valve of a bivalve ? Do you have a picture ?

[TqB]

It looks as if it's a discreet element lying flat on the bedding surface and isn't a cross section through anything.

[abyssunder]

I agree. Maybe little bits of external and internal sides of the shaft and the proximal end of the specimen are a little embedded in the matrix, hiding the inner/outer spur at the base. I'm not sure about the presence of the orbicular scar (looks to be there), maybe is not well-preserved, but the ornamentation looks to be right, compared to the Onychites macnaughti specimen (Fig. 6) which is described consisting of small knob-like elongated tubercles arranged in approximately converging diagonal lines on either side of the medial line of the hook. " The overall chevron effect has the appearance of a herring-bone pattern (a term used to describe a pattern of stitching used in the weaving of cloth for clothing; the pattern resembles that made by the individual bones of the thoracic skeleton of a herring)."

I wish I had the specimen in hand...

Edited March 24, 2016 by abyssunder

[belemniten]

I am sry, that i cannt post that much because of holiday. And i am also sorry, that i dont understand every word in english, so i cant describe the specimen enough

I agree with abyssunder...the structure looks like Onychites.

Thanks all ! I will sort it as Onychites macnaughti.

Regards Sebastian

[TqB]

Onychites macnaughti is actually Kimmeridgian/Tithonian so yours will have to be another species of Onychites.

[belemniten]

Oh embarrasing Thats what I wrote but i should also read carefully

Thanks tarquin, so only Onychites

[Ludwigia]

It is extremely complicated to give Onchyites a species name. Some have been coupled to belemnite species due to coherent finds, but many have only been found isolated, so they have separate species names just according to their form (as with ichnofossils) and stratigraphic location, although 2 or more "species" may very well derive from the same belemnite since along the arms of one animal the forms themselves vary. I'm assuming that yours comes from the Posidonienschiefer. I had a look at the few pages in Schlegelmilch's "Die Belemniten des Süddeutschen Juras" about them and found a picture of one which may fit yours which comes from the middle of an arm of a Passaloteuthis sp., although he doesn't give either the belemnite or the Onychites a species name.

Edited March 25, 2016 by Ludwigia

[abyssunder]

I agree with Tarquin and Roger. Here are two examples of Passaloteuthis laevigata (female and male) from Urwelt Museum Hauff, Holzmaden, showing the micro/mega-Onychites. As you can see the little hooks are arranged in two rows along the arms and in male are present the pair of big hooks.

https://dinosaurpalaeo.wordpress.com/2013/01/30/palaeontology-of-sw-germany-3-1-14-spineless-hauff/

[mohsenamini]

Thanks to Abyssunder for great information

But still i think it is one plate of Bivalve. those Cephalopoda hooks, should not remain like this in rock i think :/

[TqB]

Hooks are often found in this rock (Posidonienschiefer) - both of the specimens in abyssunder's last post are from it.

Edited March 26, 2016 by TqB