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Heteromorph

I thought this might be something that would be interesting enough for someone to take a stop a Penn Farm one of these days. 

 

Penn Farm in Cedar Hill State Park is a very historic and tranquil place in the rolling hills along the Eagle Ford/Austin Chalk contact that is a much loved attraction in the DFW area. I have been going to Penn Farm since I was a very young child, but in April of 2017 I went there with fossils on my mind. In Febuary I had found an ammonite on a rock used to support the door to a cellar (FIG. 37) but had not looked closely at any of the nearby rocks used as stepping stones. As I was going through Penn Farm enjoying the scenery and sights I also scrutinized any rocks that I saw. When I came upon the New Penn Farm House (see map in FIG. 1) I studied the rocks used as stepping stones and started finding both the gracile and robust forms of Collignoniceras woollgari scattered all over many of the rocks with two rocks in particular having the most specimens. It seems that all of the C. woollgari specimens are just impressions. Not sure why.  I have since gone back and studied the rocks closer and have identified them as being from the local Kamp Ranch subunit based on the fauna and matrix type. 

 

On the rocks, I have found C. woollgari plates, oyster hash, and on the rock first shown in FIG. 25 I found what appears to be some type of shark tooth. I have also looked more closely at the specimen on one of the rocks used to support the door to a cellar that is right next to the stepping stones and I am pretty sure that it is a very large robust C. woollgari. HGMS’ book Texas Cretaceous Ammonites and Nautiloids does say that C. woollgari can have diameters of 200 mm which would place this specimen well within that range, but it is still the largest specimen of this species that I have seen in person if it is indeed C. woollgari.

 

In July, I talked to a couple park rangers about the rocks and they told me that they were aware of them and that when the Penn family originally build the house in 1876 they specifically chose the rocks with fossils on them. It shows the hardiness of the matrix that these rocks have been trampled upon for 142 years and the fossils are still in decent shape. I know I wouldn’t be able to say the same for the Austin Chalk. 

 

Here are the pictures. They were taken on Wednesday, April 18, 2018. A ruler is included in many of the photos for scale. 

 

75DA98C5-5464-4E88-B96C-83AFE1D269D9.thumb.jpeg.6d46194100d4620d44e3c7cf01576fd4.jpeg

FIG 1: Map of Penn Farm. 

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Heteromorph

86DF3270-0F0F-42E9-BB8F-99A5D4468FD0.thumb.jpeg.9728b434f2a313cf50280592b641aae2.jpeg

FIG 2: Veiw of most of the stepping stones with the house in the background. 

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FIGS 3-4: More fossiliferous parts of the pathway.

 

05F608E7-22F2-4A4F-AF3C-387DF58A7242.thumb.jpeg.ba66002324ffea359a5150ec5f3d48fd.jpeg

FIG 3.

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AAD99A1D-6868-4C28-86A5-A8189703B6F8.thumb.jpeg.b1572891c446d08fae4599479bc371ab.jpeg

FIG 4.

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FIGS 5-6: Burrows.

 

780F0829-3B35-4391-BFCA-3625FC1DA085.thumb.jpeg.b9e4276ea680e340925f977402fefc9f.jpeg

FIG 5.

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25C0F124-48E9-4DE4-87A4-15A48727958F.thumb.jpeg.e5eb5ecbdd255856feb7c99a23ca4c22.jpeg

FIG 6.

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FIG 7-14: Various rocks with oyster hash and occasional C. woollgari impressions. 

 

02DE8463-8641-45E0-88C0-AB2EDD89D42A.thumb.jpeg.d82af469af252be56c557e3d9d07c828.jpeg

FIG 7.

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161C30A3-4885-4F9D-A2E2-8C29E5FA0982.thumb.jpeg.f1f9ad091ba25f809dfee6bd6c5ef338.jpeg

FIG 8.

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D1284661-69E3-451E-9CCB-035FBCAEE393.thumb.jpeg.d392d898fc44ec5eff3a260ac5915c4a.jpeg

FIG 9. 

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52D361A8-929A-4CBB-87F0-E4B53B237807.thumb.jpeg.14bb7b08f2cc6d24466fc36a5e5d6e3b.jpeg

FIG 10.

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873D952B-FED1-4CAD-952E-C2F97F28DB01.thumb.jpeg.d5d664c235531800e3b823a518eae0e6.jpeg

FIG 11.

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C3B88F4D-3A96-4453-AE40-915362B4A440.thumb.jpeg.c5d89024df23790de57c35a2bae430e8.jpeg

FIG 12.

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2A1D1A85-70F6-4568-ACE8-1C0B2F3D4DD0.thumb.jpeg.c2faa5d59db5a19f183e3ba513771dd7.jpeg

FIG 13.

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4E22F4F1-992E-49D5-8D82-2C2898068581.jpeg

FIG 14.

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FIG 15-16: Two C. woollgari on same rock.

 

22255F07-2104-4A1E-AD50-5F23B3DEE188.thumb.jpeg.fed9989174c7ee1fc66bd56f543f27ea.jpeg

FIG 15.

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doushantuo

Nice post!

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FFFAFA36-A7A9-48D5-B4CA-874DBF2ADDCA.thumb.jpeg.8459a17839222b6c1910c3fe454372b1.jpeg

FIG 16.

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doushantuo

(Turonian)C.morphotypes ornament:

sha5wyykmicroraptuydge64sllifernakristlanthc.jpg

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FIG 17-23: First major C. woollgari plate. Various pictures of the fossils on it. Notice the big oyster impression on top. 

 

16CCF1B6-9F58-4D6C-9A86-B9F8DF719FF5.thumb.jpeg.c2c0f1a342f1a47f0e347145f8b1dc35.jpeg

FIG 17.

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doushantuo

sha5wyykmicroraptuydge64sllifernakristlanthc.jpg

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6ABFE2B8-FC7E-477B-AAE4-880CFE1EB50C.thumb.jpeg.fde88f7da67d12868c7196b565401c03.jpeg

FIG 18. 

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6F9A002F-57E7-4DB4-B5A1-F96CC747AAA8.thumb.jpeg.75c2a5e3aef17bf50552a98a257b8615.jpeg

FIG 19.

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doushantuo

wow.

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A2712B92-0D40-4E7C-AFCF-255A96D4DC07.thumb.jpeg.26ab8120eeb4a636ccbb9d5ff29b7666.jpeg

FIG 20: Gracile C. woollgari center. Oyster impression on the left. Also notice the spherical impression on the right. Pearl impression? 

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428FAB2D-789C-47C6-90C7-C5D23EA9C74A.thumb.jpeg.298f1c2afe7b4c195dfcf3c7c3b074a2.jpeg

FIG 21.

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