Coral Identification

[digit]

 

4 minutes ago, FranzBernhard said:

Last Thursday, I visited the Langhian Weißenegg-formation about 30 km south of Graz. I have only checked out areas north of Heimschuh in the Sausal hills this day, that I have prospected already four years ago for coral specimens. The Weißenegg-formation is mostly limestone, containing in some parts coral carpets and patch reefs, witness of the subtropical to tropical climate in this area about 15 Million years ago.

Fossils in the "wild" (aka forests) are not super-abundant in this formation, with corals being the most common, but there is a very large, active quarry for portland cement fabrication in Retznei nearby, that is famous for all kind of marine stuff, incl. Meg teeth and other large vertebrates. But as some of you may know, I am not interested in active quarries . (Note: The quarry operators are very cooperative and supportive saving fossils encountered during mining, and fossil collectors are welcome!)

 

Quite a distance below a small limestone cliff in a forest north of Heimschuh, this coral specimen was presenting itself on the soil below an overturned tree. Its shape is essentially that of a half-cone (pic middle left, above red object, specimen as found, untouched). It is a chunk of a coral colony that is very nicely weathered all around, with absolutely no ding. Skeletal elements are more strongly weathered than the infilling sediment, so the specimen is essentially a negative. I have tried the usual method inverting the greyscale pic, see lower left. Preservation is very good, I think it is a Montastraea sp., considering the size of the corallites, strong costae and spongy columella. Such nicely weathered specimens are very rare, its only the second one that nice that I have found in this area.

 

Any thoughts as to if this is a Montastraea?

 

 

Franz Bernhard

 

 

ADMIN NOTE:  This was split out from the Fossil of the Month entry thread, as it strayed from the intent of that topic. 

It was decided that this might be useful as a learning tool. 

 

 

Thanks, Franz.

 

Slow month so far but hopefully not everybody is out shopping for Halloween costumes and are instead taking advantage of the autumn temps to go out and add to their collections. Hoping to see the usual last minute addition of some enviable finds.

 

Atlantic corals are something I know just a bit about (the extant ones anyway). A few years back the reef coral family Mussidae was analyzed using analysis which combined new DNA evidence along with the traditional morphological methods of classifying corals. Former students of a coral reef scientist friend of mine published an important paper resulting in the reclassification of several modern corals.

 

ANN F. BUDD, HIRONOBU FUKAMI, NATHAN D. SMITH, NANCY KNOWLTON, Taxonomic classification of the reef coral family Mussidae (Cnidaria: Anthozoa: Scleractinia), Zoological Journal of the Linnean Society, Volume 166, Issue 3, November 2012, Pages 465–529, https://doi.org/10.1111/j.1096-3642.2012.00855.x

 

The upshot of this as it applies to the genus Montastraea is that it now only contains Montastraea cavernosa, a species with large exerted "vocano-like" polyps which are roughly 5.5-7.5 mm in diameter and contain 36/48 septa. Here is a living Montastraea cavernosa colony:

 

 

 

The other three extant species of Atlantic corals formerly in Montastraea were moved to the resurrected genus Orbicella (O. annularis, O. faveolata, and O. franksi).

 

https://en.wikipedia.org/wiki/Orbicella

 

These species (and the various hybrids or intergrates between them) have much smaller polyps (2.1-3.5 mm) with 24-26 septa. This genus is one of the primary reef building corals in deeper fore reefs. Here is an example of a living colony of Orbicella faveolata:

 

 

I have no idea if taxonomic changes in the modern (extant) corals have any effect on what may be ancestral corals from the Miocene fossil record. I guess we would have to either know an invertebrate paleontologist (which I do) or find some papers online dealing with these Miocene (Badenian) corals that were published since the 2012 revision. If I can find further information, I'll post it here.

 

Cool coral--whatever genus it belongs to currently.

 

 

Cheers.

 

-Ken

 

 

 

[FranzBernhard]

Hello Ken,

thanks for the information and the beautiful coral pics!

The most recent paper about Badenian Paratethys coral facies that I have is from 2000:

WienerBecken_Korallen_3.pdf (english)

Fig. 4 gives the coral species distribution in a small, but very diverse occurrence not far away from my site. Generally, most abundant coral genera in the Styrian basin (= Weißenegg-formation, Badenian) seem to be Porites, Tarbelastrea and Montastraea.

Thanks again!
Franz Bernhard

[digit]

Ah, thanks for the paper--it was 2000 which was more than a decade before the shake-up in coral genera. Bernhard, the lead author is a good friend of mine. The Montastraea species mentioned in the paper seems to be M. oligophylla. I'll check with him to see if Bernie remembers if this would be one of the smaller polyp forms now considered Orbicella. I'll report back if I hear anything conclusive.

 

 

Cheers.

 

-Ken

[digit]

Heard back from Bernhard.

 

He mentioned that in the Miocene, the paratethys fauna which includes the Weissenegg Formation was more strongly linked to the Indo-Pacific than to the Atlantic fauna. Montastraea as it stands now has been split into the single species in the Atlantic (Montastraea cavernosa), and Orbicella covering the three smaller-polyp forms. In the Indo-Pacific the former Montastraea have now been assigned to the genus Phymastrea). Bernard suggested that it be left "as is" till someone revisits the fossil corals of the Austria region and decides what new name (if any) should be applied.

 

In short, no change to your entry but a bit of knowledge gained along the way.

 

 

Cheers.

 

-Ken

[FranzBernhard]

Hello Ken,

thanks for your efforts and the infos!

Did you show the pic to Bernie?

Oh well, new names are lurking...

Thanks again!
Franz Bernhard

[digit]

Yup. I sent him the photo and he suggested conservatively keeping it Montastraea until someone revisits the coral taxa of the area for a possible update on the taxonomy.

 

 

Just over a week left in this month, folks. Let's see those entries.

 

 

Cheers.

 

-Ken

[HansTheLoser]

Montastrea is not a well defined taxon going back to a specimen figured by Guettard in 1774. The type material is lost and even the type locality is unknown. I would replace the genus completely by Orbicella and/or Phyllocoenia. Phymastrea is now with the Merulinidae, this is another family. The above mentioned specimen should be at least polish to learn more about its fine skeletal structure.