Upper Coniacian Austin Chalk Vertebrate Remains, North Texas

[Heteromorph]

At a site where I have been finding heteromorphs, I have recently come across some vertebrate material. So far I have only found three vertebrate specimens; one bone fragment and two fish scales. I am hoping to get some information on their affinities. I am most interested in the fish scales, since it seems they would be the most easily identified. 

 

The site is in North Texas, the Austin Chalk group, Atco formation, upper Coniacian stage. For biostratigraphic reference, at this same site I have also found the ammonites Protexanites planatus, Phlycticrioceras trinodosum, Tridenticeras peramplum, Scaphites semicostatus, and Glyptoxoceras sp., among others. 

 

The bone (Figs 1-17) was found on Saturday the 14th of July. It is a small fragment from a more marly layer than the fish scales and most of the rare ammonites that I am finding are from, but still from the same site. The main part of it has 39 mm exposed length wise as shown in Figs 11-12 (some of it is still buried in the rock), and has a branch coming from the main part that is 22 mm long that forms a depressed canal structure in the rock (Fig. 14). The maximum thickness of the specimen that I can see is about 2 ½ mm. The branch begins to curve around when it meets the main part of the bone. The other end of the rock and the underside don't show much exposure of the bone except for a few bits poking through (Figs 16-17). I don’t know if the specimen came from a fish or some other vertebrate, but I would guess fish. If anyone can give more information on what kind of animal this came from and where this might have been located in the animal’s skeleton, that would be much appreciated. But I also know that due to its very fragmentary nature, a more definite identification may not be possible. 

 

The two fish scales (Figs 18-20) were both found on Friday the 27th of July over 100 yards from where the bone was found. These specimens are from a more chalky matrix than the bone, the same matrix that the rare ammonites are in. The first specimen (Figs 18-19) was found breaking open a large chunk of chalk. It is basically flawless and in excellent condition, and only has a little bit of obscuring matrix on the right side that could be prepped off. In the same chunk of rock that I cracked open to find this I also found a T. peramplum specimen. The fish scale is 5 ½ mm long by 5 ½ mm wide. 

 

The second fish scale I found (Fig. 20) was found within a few feet of the first one, possibly from the same fish specimen. It is a bit beat up and less complete than the first scale, but is larger from what I can see. It is 7 mm wide including the flatended area upon which the scale once was before it flaked away during excavation. The front part of it is still buried in the rock but could hopefully be prepped out. It is also in a chalky chunk of rock, not marly.

 

I have noticed that these are less shiny than scales preserved in shales, though they still do glimmer a bit in direct light. They are also differently colored than most fish scales preserved in shales, with mine being on the red/brown spectrum while those in shale are usually black or dark gray. 

 

I am hoping that the distinctive symmetrical 7 way splitting shown on the first fish scale could narrow down the identification. I know that getting to the species or genus level could be very difficult, but could a family or order be at least possible? I have heard that identifying fish scales is challenging, but this paper indicates that it is not impossible. 

 

@oilshale, you’re a fishy guy (in a good way of course). Any ideas? 

 

Fig. 1.

[Heteromorph]

Fig. 2.

 

Fig. 3.

[Heteromorph]

Fig. 4. 

 

Fig. 5.

[Heteromorph]

Fig. 6.

 

Fig. 7.

 

Fig. 8.

[Heteromorph]

Fig. 9.

 

Fig. 10.

 

Fig. 11.

[The Amateur Paleontologist]

@Heteromorph If one day I'm in the area, could you show me to that site you go to? Please?? A Cretaceous site - with heteromorphs and fish (and who knows what other vertebrates...) - is one that I'd love to go to...

-Christian

 

P.S. I'm quite sure that some of those bones are cranial remains

[Heteromorph]

Fig. 12.

 

Fig. 13.

 

Fig. 14.

 

[Heteromorph]

Fig. 15.

 

Fig. 16.

[Heteromorph]

Fig. 17.

[Heteromorph]

Fig. 18.

[Heteromorph]

Fig. 19.

 

Fig. 20.

[ynot]

I think all of the pieces shown so far are fish bits.Last couple are scales.

[The Amateur Paleontologist]

I agree with @ynot - Nº 17, 18, 19 and 20 are all fish scales

[Innocentx]

Nice little scale. I hope I find some fish parts one day.