Thursday, June 1, 2017

SPECIAL POST: HOW TO COLLECT FOSSILS

Hello, everyone! As the trip to Montana dawns on me, I've been thinking a lot about how important it is to take good field notes. Many museums around the world receive donated specimens from amateurs or other enthusiasts, but many of these are of little to no academic value because the collector did not record the necessary information. For this reason, Dr. David Burnham and I have decided to write up this post to show exactly what type of data any fossil collector should record when they find something in the field. With this information readily accessible, we hope that more amateur collectors will take these into account.



FIELD DISCOVERY AND COLLECTION GUIDE
By Kyle Atkins-Weltman and David Burnham
The types of data we are interested in collecting:
1.      Fossils (bone, teeth, plant, etc.)
2.      Rocks (sandstone, mudstone, concretion, etc.)
3.      Photos or sketches of the fossils and rocks
4.      Personal observations

1)      Basics to be recorded if you find something:
a.      Date, page number, name(s) of helper(s), weather or general comments. These things help you remember important contextual information.
b.      Diary of work accomplished that led you to the discovery.
2)       Record the geographic location:
a.      We need to have the geographic coordinates of the discovery (Latitude and Longitude). These will allow us to relocate the site and plot it on a map with other similar finds. If we do not know where a fossil came from we can’t place it in any meaningful context.
b.      Record the elevation to help tell us where it’s located in geologic time. Rock units, such as the Hell Creek Formation, may be deposited over a time of 2 million years so without elevation, we cannot place the fossil precisely within that span. A lot can happen over 2 million years and where a fossil falls within that time is very important for understanding its evolutionary context.
c.       Sketch the field positions of any fossils (bones or fragments) that you have found. These positions help us evaluate the discovery and determine whether or not there is likely to be any other material from the same individual(s), or if there is another reason to follow up on the discovery.
3)       Description of the object collected (fossil, rock or unknown)
a.      Color—this is a clue to confirm it’s a valuable object and how it’s preserved. Pictures are extremely useful for this purpose, though you must make sure to get decent lighting to capture adequate detail.
b.      Orientation (in place or loose on the surface) can help determine if there is likely more there to be found and in what direction to explore further.
c.       Preservation (solid or crumbly) speaks to the quality of preservation and is important in evaluating its significance.
d.      Quantity of material (a few pieces or many fragments)— If there are many bones or fragments, this may indicate a skeleton has been found.
e.      Layer in which it was found— If it is found in a rock layer that is good! If not, it is likely that it has floated away from its source.
4)      Describe surrounding rocks—from this we can tell what the land looked like when the animal was fossilized:
a.      Color—sand is usually tan and represents river or beach; clay is grey and represents a swampy area or a pond.
b.      collect a small sample of the rock and label it—this would be a reference for us to look at without going back into the field.
5)      Photo Log:
a.      Write down what you think the object is, where it occurs, direction of view (North, South, Southwest, etc.), names of people, date and time.
6)      Suggested gear
a.      10X magnifying lens—examine the object for details that may indicate bone vs rock, a small brush to clean away the dirt from the object (its usually better to leave it alone), knife or something to poke around with to tell if its in the rock or laying on the surface, a GPS or a smart phone app, hat, daypack, water, foil to wrap the fossil, zip locs for storage, and a notebook and pencil to record data.
7)      REMEMBER—anything collected belongs to the landowner or the government—there is no such thing as “Finder’s Keepers”. Permission or a permit is always required.

Wednesday, January 11, 2017

Creature Feature 26

Hello, fans! It's been a long time since I've posted, but we now have a new model ready to present. Meet Emarginochelys cretacea, the earliest known Chelydrid turtle!
 Emarginochelys cretacea model, unpainted.

As stated above, Emarginochelys cretacea is the earliest known member of the family Chelydridae. The only extant members of this family are Chelydra and Macrochelys - the snapping turtles. The genus was spelled as Emarginachelys in the original description (Whetstone, 1978), but has since been changed to Emarginochelys (Bryant, 1989; Holroyd & Hutchison, 2002). Luckily, the holotype for this species is actually housed here at KU, so I was able to examine the specimen myself to make observations on anatomy.

Several features unite Emarginochelys with Chelydridae. These include a cross-shaped plastron attached to the carpace by ligaments, a reduced entoplastron, and several other skeletal characters (Whetstone, 1978). Furthermore, its robust limbs and heavy body indicate that it likely would have walked along the bottom of channels or swampy areas.

However, there are several notable differences that separate this basal species from its more derived kin. Several differences involve the structure of the shell. In Emarginochelys, the neurals (the scutes running down the midline on the carapace) and peripherals (the scutes along the border of the carapace) are much thicker than in derived forms. Furthermore, there is no emargination at the anterior end nor scalloping at the posterior end.

Perhaps the most interesting differences from its modern relatives are the features seen in the skull. Emarginochelys completely lacks the premaxillary "hook" seen in derived forms, nor does it have the extremely developed parietals - both of these features are important in feeding for modern chelydrids. In modern chelydrids, the sharp hooked shape of the beak is critical in grasping prey, and the large parietals (at their most extreme in Macrochelys) provide a large area for jaw muscle attachments (which is why snapping turtles can do so much damage). Emargionchelys, therefore, would have likely had a significantly weaker bite than its derived kin, and would not have been able to grasp prey in the same way. It's quite possible that its diet was not the same as derived snappers, and it may have been a generalist omnivore, with derived features representing specialization towards carnivory. Interestingly enough, another species of turtle from Hell Creek, Compsemys victa, had a skull indicating a highly carnivorous diet, yet its modern relatives are herbivores.

Unfortunately, not much work has been done with this species as far as I've seen. I was lucky enough to see the holotype myself, which allowed us to reconstruct the neck since there were no figures showing the cervical vertebrae in the original publication (there are a few vertebrae missing but we took that into account with our model). Unfortunately, no caudal vertebrae were preserved, so the tail length is based on proportions for modern relatives.

Hope this has taught you a bit more about this interesting turtle!

Acknowledgements:
Whetstone, Kenneth N. 1978. A New Genus of Cryptodiran Turtles (Testudinoidea, Chelydridae)
From the Upper Cretaceous Hell Creek Formation of Montana.
University of Kansas Science Bulletin 51(17): 539-563.
Bryant, L. J. 1989. Non-dinosaurian lower vertebrates across the Cretaceous-Tertiary boundary in northeastern Montana. University of California Publications in Geological Sciences 134:1-107
Holryod, P. A.; Hutchison, J. H. 2002. Patterns of geographic variation in latest Cretaceous vertebrates: evidence from the turtle component. Geological Society of America Special Paper 361:177-190