Trends in Ammonite Shell Shape Over Time
Lindsey Howard
Author
08/03/2021
Added
30
Plays
Description
Study of change in Ammonite shell shape over time.
Searchable Transcript
Toggle between list and paragraph view.
- [00:00:00.810]Hello. My name is Lindsey Howard.
- [00:00:02.790]I'm a senior studying animal biotechnology and biology at UNL. This summer,
- [00:00:07.620]I took part in the UCARE research program,
- [00:00:10.170]studying the trend in ammonite shell shape over time.
- [00:00:15.930]Ammonites are an extinct cephalopod species related to octopuses and squids.
- [00:00:20.850]Ammonites lived in a wide variety of environments for a long period of time. As
- [00:00:25.380]seen in the photo to the right,
- [00:00:27.000]these animals also had dramatic and intricate shell designs,
- [00:00:30.240]which help with the identification of the specimen.
- [00:00:33.180]These are all reasons why ammonite are a great zonal specimen so that all
- [00:00:37.110]groups are used to date beds and fossils in a noninvasive way.
- [00:00:44.160]My goals for this project were to examine the collections for species diversity
- [00:00:49.020]and collect basic data on invertebrate fossil specimens,
- [00:00:53.400]to quantify the trends in shell shape of Ammonites in the collections over
- [00:00:57.120]different areas and to assess which intervals of time are better sampled than
- [00:01:01.230]others. Some more goals were to develop Excel knowledge, learn to use R code,
- [00:01:06.180]to process large amounts of data in a timely manner,
- [00:01:09.240]and to develop a hands-on skill to measure and examine specimens.
- [00:01:16.840]Different shell shape types were better evolved for different areas of the water
- [00:01:20.440]column. Ammonites had three overall shell shape types. The first,
- [00:01:25.120]serpenticone, was very narrow and floated near the top.
- [00:01:28.510]The second, sphereocone, was very bulbous with an overinflated shell.
- [00:01:32.890]This type tended to be lower in the water column. The final shape was oxycone,
- [00:01:37.390]which stayed primarily in the shallower, more shelf like,
- [00:01:40.450]part of the water column. On the right is a ternary plot,
- [00:01:45.520]which I use to plot my data.
- [00:01:47.230]These graphs were used when comparing three different data types. On the top left
- [00:01:51.610]it's the serpenticone shell type. These Ammonites have an exposed umbilicus,
- [00:01:56.590]which is the hole in the center of the shell.
- [00:01:58.990]This shell type had difficulty swimming. So it used a plankton hunting style.
- [00:02:03.250]This is a passive swimming style that uses currents to move. The top right
- [00:02:07.660]is the bulbous spherocone.
- [00:02:09.340]This shell had a covered in umbilicus and relied on a vertical migrant
- [00:02:13.090]swimming style to hunt.
- [00:02:14.890]The bottom shell shape is the oxycone. Oxycone had a covered umbilicus like
- [00:02:19.840]the sphereocone but was much more compressed.
- [00:02:22.570]This shell shape was great for an active or nektonic hunting and swimming
- [00:02:27.100]style.
- [00:02:29.500]I use the Westerman Morphospace method to measure the shells.
- [00:02:33.040]This included measuring the length and width of the whorls,
- [00:02:35.890]and then applying simple equations to stabilize the data.
- [00:02:41.290]For my UCARE project,
- [00:02:43.060]I first combed through the invertebrate paleontology collections for proper
- [00:02:47.650]Ammonite specimens.
- [00:02:49.180]I then measured and collected data from a wide variety of the specimens. In total,
- [00:02:53.650]163. Finally,
- [00:02:56.050]I used Excel equations in R code to transfer data to an
- [00:03:00.700]understandable graph.
- [00:03:06.110]As you can see on this slide,
- [00:03:07.550]there was a large range in the amount of data I was able to collect over the
- [00:03:11.840]different periods.
- [00:03:13.190]The most was Cretaceous at 74 and the smallest was Jurassic at only
- [00:03:17.870]six.
- [00:03:20.330]I expected to find a trend in overall shell shape change over time.
- [00:03:25.220]I also expected to find clear data trends in eras that have a larger number of
- [00:03:29.690]specimens collected versus eras that have a smaller number of
- [00:03:34.340]collected specimens.
- [00:03:39.110]So first off is the Carboniferous. The Carboniferous data trended towards
- [00:03:43.310]oxycoone with one outlier near the serpenticone. On the right is a
- [00:03:48.020]map of the world during the Carboniferous as shown with the yellow circle, the
- [00:03:52.580]specimens used were from the shallower waters off of Laurentia.
- [00:03:59.090]The Permian data also trended towards Oxycone.
- [00:04:02.000]These were also drawn from shallow waters,
- [00:04:04.310]this time off of the supercontinent Gondwana
- [00:04:08.870]Triassic had more data points,
- [00:04:10.910]so the trend towards Oxicone was even more obvious.
- [00:04:14.180]These specimens were also from a shallower ocean system off of Pangea.
- [00:04:21.200]There weren't many points found for Jurassic,
- [00:04:23.450]but those that I did collect pointed once again for oxycone.
- [00:04:27.230]These specimens were from a central sea in Laurasia.
- [00:04:34.520]The Cretaceous period had the most data points and was pretty central with some
- [00:04:38.870]points. The trend, however, was still for oxycone.
- [00:04:42.290]These were from the Midwestern Seaway,
- [00:04:45.080]which is now Nebraska and the surrounding states
- [00:04:51.080]As shown on the right, the trends for all of the eras was for oxycone.
- [00:04:55.280]This is not what I was expecting.
- [00:04:57.050]I was expecting a change in the trends over time as the ocean and prey type
- [00:05:01.520]changed. On the left is my graph.
- [00:05:06.380]And on the right is a Ritterbush outcome. As you can see,
- [00:05:09.950]Ritterbush had a more even trend style while
- [00:05:12.410]mine was much more heavily oxycone.
- [00:05:16.880]I believe this is because most of our specimens came from shallow marine
- [00:05:20.660]environments. Nektonic may be the best swimming style for these environments
- [00:05:24.710]no matter the time or temperature.
- [00:05:29.390]What will I do next?
- [00:05:31.010]I want to apply my data to the University of Nebraska State Museums collections
- [00:05:35.540]digitization effort.
- [00:05:37.340]I want to continue developing understanding of coding to help process large
- [00:05:41.240]amounts of data in the paleontological field.
- [00:05:44.480]I also would like to continue the study of Ammonite shell shape change over
- [00:05:48.470]time, using a wider variety of collections,
- [00:05:51.680]including those that include a larger number of Jurassic and Devonian specimens.
- [00:05:57.860]Finally, I would like to acknowledge and thank Dr.
- [00:06:00.800]Peter Wagner for giving me the guidance I needed to develop and work through
- [00:06:04.610]this project. Along with his assistance in the R code aspect of the work,
- [00:06:08.930]I would also like to thank Dr.
- [00:06:10.460]Robert Diffindal for his assistance and knowledge of the collections.
- [00:06:14.510]I would finally like to thank Miss Justina Clark and the UCARE team for their
- [00:06:18.800]advice over the summer and for giving me the opportunity to work on this project.
The screen size you are trying to search captions on is too small!
You can always jump over to MediaHub and check it out there.
Log in to post comments
Embed
Copy the following code into your page
HTML
<div style="padding-top: 56.25%; overflow: hidden; position:relative; -webkit-box-flex: 1; flex-grow: 1;">
<iframe
style="bottom: 0; left: 0; position: absolute; right: 0; top: 0; border: 0; height: 100%; width: 100%;"
src="https://mediahub.unl.edu/media/17575?format=iframe&autoplay=0"
title="Video Player: Trends in Ammonite Shell Shape Over Time"
allowfullscreen
></iframe>
</div>
Comments
0 Comments