Protostega gigas dig:

October 21 and 23, 2011


Copyright ©2012-2012 by Mike Everhart


  Page created 10/24/2011- Last updated 04/18/2016









RIGHT: Ventral view of the cast of the Protostega gigas Cope (FHSM VP-17979) recently completed by Triebold Paleontology. Photo by Triebold Paleontology © 2013.

Protostega gigas Cope was the largest marine turtle in the Western Interior Sea during the deposition of the Smoky Hill Chalk. The first fragmentary specimen (YPM 1408) was actually discovered a few miles east of Fort Wallace by O.C. Marsh and the 1871 Yale Scientific Expedition, but was never described. 

E.D. Cope discovered and collected the type specimen of Protostega gigas (AMNH FR 1503) during his only trip to the Kansas chalk in 1871. He wrote about his experiences, including the discovery of Protostega, in a letter dated October 9, 1871 to Professor Lesley of the American Philosophical Society:

"On another occasion, we detected unusually attenuated bones projecting from the side of a low bluff of yellow chalk, and some pains were taken to uncover them. They were found to belong to a singular reptile, of affinities probably to the Testudinata, this point remaining uncertain. Instead of being expanded into a carapace, the ribs are slender and flat. The tubercular portion is expanded into a transverse shield to beyond the capitular articulation, which thus projects as it were in the midst of a flat plate. These plates have radiating lines of growth to the circumference, which is dentate. Above each rib was a large flat ossification of much tenuity, and digitate on the margins, which appears to represent the dermo-ossification of the Tortoises. Two of these bones were recovered, each two feet across. The femur resembles in some measure that ascribed by Leidy to Platecarpus tympaniticus, while the phalanges are of great size. Those of one series measured eight inches and a half in length, and are very stout, indicating a length of limb of seven feet at least. The whole expanse would thus be twenty feet if estimated on a Chelonian basis. The proper reference of this species cannot now be made, but both it and the genus are clearly new to science, and its affinities not very near to those known. Not the least of its peculiarities is the great tenuity of all the bones. It may be called Protostega gigas."              E. D. Cope, 1871

LEFT: The left plastron from the type specimen of Protostega gigas Cope 1872 as published on Plate IV by Hay, 1895. It measures 1.2 m (almost 4 ft) from left to right and came from a turtle that measured about 3.0 m (10 ft) long (from nose the end of the tail). The specimen is curated in the American Museum of Natural History as FR 1503.  (Anterior to the left).  "This plate represents the hyoplastron and hypoplastron of the left side of Protostega gigas seen from below. A view is also given of the nuchal bone." (Hay, 1895).

RIGHT: Plate V from Hay 1895: “A partial restoration of the plastron of Protostega, to show the relative positions of the bones and the size of the fontanelle. Only the bases of the epiplastra and of the xiphiplastra are shown.”  

Since the initial discovery by Cope, a number of fairly completeProtostega specimens have been collected from Kansas, mostly by Charles Sternberg and his son, George F. Sternberg. The incomplete specimen (above) currently on exhibit at the Sternberg Museum of Natural History in Hays was collected by George F. Sternberg from Gove County in April, 1930. The specimen is missing the skull and most of the limbs. It's carapace is about 42 inches in diameter, a bit larger than the new specimen.  More about Cretaceous turtles in Kansas here.

Paddle bones and other elements of the new fossil turtle were discovered eroding out of the Smoky Hill Chalk during the summer of 2011 in eastern Gove County by Susan Liebl. Initially the bones were considered to be part of a mosasaur, but when elements of a carapace were also recovered, it became apparent that it was part of a marine turtle that once swam in the Western Interior Sea more than 85 million years ago. Susan contacted me and we made plans to visit the site on September 29, 2011. At this point, it was unclear what kind of turtle was there. The age of the specimen is early Middle Santonian (about 86 million years ago). This is the same canyon where I collected the earliest known Tylosaurus proriger (FFHM 1997-10) in 1995-96.

Citation: Everhart, M.J. 2013. A new specimen of the marine turtle, Protostega gigasCope (Cryptodira; Protostegidae), from the Late Cretaceous Smoky Hill Chalk of Western Kansas. Kansas Academy of Science, Transactions 116(1-2):73.

LEFT:  On September 29, Susan and I returned to the site and uncovered some additional bones, including what appeared to be a complete rear paddle of the turtle.  It became quickly apparent that these bones represented the tail end of a fairly large turtle and I decided that we did not have the right resources to dig further. 

RIGHT: On the second day of our dig (October 20), we began uncovering more of the turtle and discovered that the rear limbs appeared to be complete and articulated. The right rear paddle was in place and Susan had collected most of the left rear paddle as float during her initial visit to the site. Much of the chalk containing the ribs of the carapace was already fragmented due to weathering.  We marked and removed some of the ribs and discovered the bones of the pelvis. We eventually removed the right rear paddle and the left tibia and fibula to keep them from being damaged. 

LEFT: In this photo, the left femur is visible (still in articulation with the pelvis), as is the right tibia and fibula. The bones of the pelvis are beginning to emerge from the surrounding chalk just above the ruler. As we moved deeper into the slope, we had to remove the left femur and the right tibia/fibula. In the process, the right femur was located, still articulated with the pelvis. It was also removed. It appears that the turtle is preserved upright. All the bones appear to be in excellent condition. 

RIGHT: As the dig expanded we also located both edges of the shell (carapace) and discovered that the shell was 80 cm (31 inches) wide, probably much too large to be Toxochelys latiremis, the most common turtle in the Smoky Hill Chalk. We also located what appeared to be elements of the skull at the deepest point in the dig... but as shows very well in the photograph, the sun was getting low in the western sky and the shadows made it difficult to continue.  By then we also realized that the project was much larger than the two of us could handle.

LEFT: Adapted from Wieland 1906, Figure 4. Protostega gigas. Right shoulder girdle and flipper in dorsal view (CMNH 1421): S. scapular; PC, procoraco-scapular; C. coronoid; H. humerus; R. radius; U. ulna; r. radiale; i. intermedium; u. ulnare; c. centrale; 1-5 first to fifth carpalia; p. pisiform; m. metacarpal 1; p. phalanx 1; I.-V. first to fifth fingers and ungual phalanges.

RIGHT: Adapted from Wieland 1906, Figure 5. Protostega gigas. Right pelvic girdle and flipper in dorsal view: P. pubis; F. fibula; t. tibiale intermedium and centrale fused, or calcano-astralar element; 1-3, first to third tarsalia; 4, fourth and fifth tarsalia fused; m metatarsal 1; p phalanx 1; I.V., first to fifth toes and ungual phalanges.

Fortunately, Mike Triebold and his crew were also in Kansas collecting fossils. I contacted him and he agreed to come over on October 22 to assist us in recovering the turtle.

LEFT: On Saturday morning, we met in Quinter and drove out to the locality where the turtle had been discovered. The first order of the day was to remove the debris that Susan and I had put on top of the turtle remains two days earlier to protect them. Photo by Susan Liebl.

RIGHT: We had used plastic to cover the specimen previously. Photo by Susan Liebl.


LEFT: Mike Triebold (center), Anthony Maltese and Jacob Jett begin enlarging the dig site, using an electric jack hammer.  The gray chalk at this stratigraphic level is dense and doesn't split cleanly, but the jack hammer made relatively short work of it. The specimen is at the center of the photo, covered with black plastic.  Susan is looking through the chalk fragments to make sure we didn't miss any bone. 

RIGHT: Mike, Anthony and Jacob continue to enlarge the excavation to give us enough space to work around the turtle fossil without damaging it. 

LEFT: The excavation is enlarged and cleaned up so that we can actually start working on further isolating the specimen. Charlie Sternberg would have referred to this process as "preparing the floor" and I am sure he would have appreciated the use of power tools. 

RIGHT: A view looking at the turtle site from the northwest. Mike was able to get his truck right next to the dig site, which was good, considering all the equipment he was able to bring with him, and the expected weight of the jacket enclosing the turtle. I was not looking forward to carrying the thing up the hill to where my van is parked. 

LEFT: Another view of the beginnings of the dig from above. Anthony, Mike and Susan are moving debris away from the fossil while Jacob is breaking up more chalk with the jack hammer.

RIGHT:  Once we had the work space cleared, we settled in around the specimen to clean up the area. Photo by Anthony Maltese. 

LEFT: Here Susan, Mike T., Mike E. and Jacob look at the project to start making decisions about how the turtle will come out. 

RIGHT: Once we decided what needed to be done, it was time to locate the outer edges of the turtle. Here Anthony is taking a close look at the chalk to see where bone may be exposed. Photo by Susan Liebl.

LEFT: There were several small pieces of bone exposed in the chalk where the head and front limbs should have been located. As they were found, Anthony coated them with preservative to mark them, and protect them during the next part of the dig. Photo by Susan Liebl.

RIGHT: Once the area was cleared around the specimen, a perimeter was marked with orange spray paint to serve as a guide for the next step... cutting around the fossil with a chain saw. Note that the chalk matrix containing the specimen is badly fragmented. Consolidant has been applied to help hold the chalk together, but mostly we are depending on the strength of the plaster jacket to secure everything in one block. In this photo, the pelvis is at the top of the image; the skull, if present, would be at the bottom. 

LEFT: In this photo, the size of the excavation is more apparent.  Fortunately there was not a lot of matrix over the top of the specimen. The turtle's pelvis is toward the lower right of this photo. The orange debris is a a half inch layer of volcanic ash (bentonite) that was located about 2 inches below the bones. We were concerned that this might cause problems when turned the jacket over.

RIGHT: Here Mike Triebold begins cutting through the chalk around the specimen.  The carbide tipped blade of the saw went through the chalk without any problems, enabling us to isolate the specimen without having to use hammers and chisels. 

LEFT: Once the first cut was completed around the specimen, Mike made a second cut further way to allow us to open a trench and get under the specimen to make the plaster jacket. The blade of the saw is angled under the edge of the block containing the fossil to provide a lip for anchoring the plaster jacket.

RIGHT: Mike finishes the perimeter cut around fossil as the crew and one of the landowners watch. The day had started off cloudy and cool but by noon, the sky was clear. 

LEFT: Jacob uses an air hammer to chisel way the chalk between the two saw cuts.  Eventually we had two air hammers going with the rest of us clearing out the broken chalk. 

RIGHT: Once the trench was open, the block was prepared for jacketing. Aluminum foil was placed over areas where bone was exposed to prevent the plaster from adhering to the bones. Thin-walled steel pipe was added for reinforcement and also to serve as handles under the jacket once it is turned over.

LEFT: This photo shows the large amount of undercutting that Mike did with the chainsaw. This undercut allowed us to securely support the lower portion of the matrix. Note the pre-existing, large cracks in the block of chalk. 

RIGHT: Jacob begins mixing the plaster that will be used to saturate the strips of burlap used in making the jacket. The tinfoil is used to keep the plaster from sticking to the exposed bones of the turtle. The lumps of chalk on the tin foil were there to keep the wind from blowing them away. At this point, I put the camera down and helped Anthony jacket the specimen. Photo by Susan Liebl.

LEFT: Here Anthony is getting plastered... um, applying the plaster bandages to the edges of the block of chalk containing the turtle bones. Who says you can't have fun while you work? The disposable gloves are a "why didn't I think of that" addition to the plastering process. We've always done it bare handed in the past. Photo by Susan Liebl.

RIGHT: Once the perimeter of the jacket was complete we began applying layers of plaster and burlap bandages to the exposed upper surface. Several layers of bandages crossing the block in different directions are used to make a strong jacket that will support the specimen when it  is turned over. Photo by Susan Liebl.

LEFT: Anthony and I finish the jacket by embedding steel pipe that will be used as handles for carrying the jacket once it is turned. Photo by Susan Liebl.

RIGHT: The finished product... a solid, reinforced plaster jacket that will hopefully contain the turtle specimen when we turn it over.  But first we waited about an hour for the plaster to thoroughly set up. During that time, we also dug deeper on the west side of the jacket (top of photo) to give us space to drive chisels into the underlying chalk and break the jacket loose.  However,  we used the jack hammer instead to free the specimen before rolling it.

LEFT: The moment of truth came and went uneventfully. The jacket was rolled with no problem. We then removed a two inch layer of chalk to lighten the jacket before we carried it to the truck.

RIGHT: Once the jacket had been turned, it was time to load up the equipment and get ready to leave. The jacket containing the turtle bones was loaded last.

Thanks to Mike Triebold and his crew for helping on the dig. The use of power tools in this case saved us at least two days on the dig and minimized the risk of damaging the specimen.

LEFT: Plate XXXI from Wieland 1906 showing the appendicular skeleton of Protostega gigas Cope (Carnegie Museum No. 1420) in dorsal view as collected by Charles Sternberg from near Elkader in Logan County, Kansas.

RIGHT: Plate XXXII from Wieland 1906 showing a closer, dorsal view of the right rear (left) and front paddles of Protostega gigas Cope (Carnegie Museum No. 1420) as collected by Charles Sternberg from near Elkader in Logan County, Kansas. The Carnegie Protostega exhibit is a composite of two specimens collected by Charles Sternberg. 

LEFT: The right humerus of the new specimen (FHSM VP-17979) compared with a large humerus (CMNH 1421) figured by Wieland in 1906. The adult humerus (34 cm) is almost twice as long and much more massive as the new specimen (18 cm).. The new humerus was found in association with possible elements of the skull. Preparation and photo courtesy of Anthony Maltese, Triebold Paleontology, Inc.

RIGHT: Dorsal and ventral views of the right humerus (FHSM VP-17979). Preparation and photo courtesy of Anthony Maltese, Triebold Paleontology, Inc. 

LEFT: The right femur of the juvenile Protostega gigas (FHSM VP-17979). Preparation and photo courtesy of Anthony Maltese, Triebold Paleontology, Inc.

RIGHT: The right tibia and fibula of the turtle (FHSM VP-17979). Preparation and photo courtesy of Anthony Maltese, Triebold Paleontology, Inc.

The turtle specimen (FHSM VP-17979) is now in the preparation lab where the bones will be cleaned and repaired for casting and reconstruction. Stay tuned for updates!

LEFT: The reconstruction of FHSM VP-17979 in left oblique view.  Photo courtesy of Triebold Paleontology. 

RIGHT: The reconstruction of FHSM VP-17979 in ventral view. Photo courtesy of Triebold Paleontology. 

Other Protostega specimens:

The following information was provided by Dr. Kraig Derstler of the University of New Orleans. Kraig is one of the few people currently studying protostegid turtles.

"Very little is written about Protostegids, other than the descriptive stuff by Wieland and his colleagues in the 1890's and earliest 1900's. Protostega is a huge-headed sea turtle. The species are pretty poorly defined at present. Specimens come from the Niobrara of Kansas, the Pierre of Kansas, Colorado, Wyoming, and South Dakota, the Mooreville, Demopolis, and Eutaw formations of Alabama and Mississippi, and the Campanian - Santonian marls of Texas. Possible scraps also come from other Santonian-lowermost Maastrichtian deposits around the world. Other Protostegids (Calcarichelys, Chelosphargis, and a couple of unnamed things) range from the Albian through the latest Maastrichtian worldwide.

Archelon ischyros has a normal-sized skull, proportionally much smaller than Protostega. However, it has that distinctive hooked snout. It is so far confirmed only from the upper half Pierre in South Dakota. (Reports from Colorado and elsewhere are pretty unbelievable.)

I've never seen any Niobrara Protostega material from an animal that was more than about 2-2.5 m long. Niobrara giants may have existed, but I haven't seen any evidence. And, I've never seen any signs of Archelon in the Niobrara. However, there are lots of small to medium-size Chelosphargisspecimens and possibly some pieces of the "thorny Protostegid" Calcarichelys". 

DallasProtoa.jpg (22612 bytes)

Dr. Kraig Derstler - "Concerning size, the largest Protostega is a 3.4 m beast in the Dallas Museum of Natural History. I was consultant for this exhibit and I'm pretty confident of the identification as well as the size. The Yale Archelon is 3.0-3.1 m, but another I've studied is 4.6 m long! It is virtually perfect and articulated. As a result, the size and the identification are both solid."

LEFT: A cast of the Dallas Protostega gigas in the McWane Center, Birmingham, AL. (Cast by Triebold Paleontology). A view of the underside of the skull is HERE

RIGHT: The right front limb of a Protostega gigas turtle discovered in the Cretaceous of Greene County, Alabama in 1933 (from Renger 1935). The humerus is 42 cm long and came from an animal with a shell length of 150 cm (5 ft). Renger estimated that the animal when alive would have weighed 2.5 to 3 tons.  

USNMProta.jpg (11938 bytes) LEFT: The partial carapace and plastron on a large Protostega gigas collected and prepared by George F. Sternberg (USNM 4886-A) and later acquired by the United States National Museum (Smithsonian).  Sternberg noted that the specimen was found without limbs or skull. 

RIGHT: The skull, lower jaw and other fragments from another Protostega specimen that was collected by George Sternberg in the 1920s and sent to the University of Nebraska State Museum. It is probably the same specimen as shown below. Both photos from Sternberg archives, Forsyth Library, Fort Hays State University.

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UNSMProto1a.jpg (25894 bytes) LEFT: A wall-mounted reconstruction of the partial remains of a Protostega gigas turtle in ventral view at the University of Nebraska State Museum. Collected by George F. Sternberg.

RIGHT: The skull of the turtle shown at left in right lateral view. Note that Protostega lacks the large bony extension of the beak (premaxilla) found in Archelon.

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DMNHProto1a.jpg (9223 bytes) LEFT: The exhibit specimen of Protostega gigas in the Denver Museum of Nature and Science. This specimen was collected by George F. Sternberg (GFS 101-45) in September, 1945 from Logan County.

RIGHT: Left lateral view of the skull of the exhibit specimen in the Denver Museum of Science and Nature. Click here for an original photo of the skull.

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DMNS Proto1a.jpg (9391 bytes) LEFT: Photograph (circa 1945) by George F. Sternberg of the above Denver Museum Protostega gigas in dorsal view. As described by Sternberg, this was probably a juvenile turtle with a shell that is about 3'8" wide... and a length of about 5 feet from tip of beak to the back edge of the carapace

RIGHT:   Right lateral view of the same specimen as prepared and photographed by G.F. Sternberg about 1945. Sternberg's field number on this specimen was 10145 (the 101st specimen he collected in 1945). The specimen is about 5 feet in length, with a maximum shell width of 44 inches. Sternberg also noted that the skull was 16 inches long.

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CMNH1420a.jpg (14086 bytes) LEFT: An early photo by C.H. Sternberg of Protostega gigas from the chalk of western Kansas. The specimen is actually a composite of  two specimens (CMNH #1420 and #1421), both discovered by Sternberg about "three miles northwest of Monument Rock" in western Gove County in 1903 and acquired by the Carnegie Museum of Natural History in Pittsburgh, PA in 1904.  Sternberg (1906) noted that this specimen measured 10 feet (3 m) across the front paddles. A more recent picture is HERE.

RIGHT: A dorsal view of a Protostega gigas (FHSM VP-79) carapace and plastron on exhibit at the Sternberg Museum of Natural History.  This badly flattened specimen was collected by George Sternberg in 1930 (GFS 2-30), southeast of Gove in Gove County.  According to Sternberg/s notes, it was upside down when collected. The shell is 40 inches across and 36 inches long. There was no skull and only fragments of the limbs in association with the shell.  The specimen was purchased by FHSU.  Side view

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LEFT:  An oblique frontal view of the cast of FHSM VP-17979, courtesy of Anthony Maltese, Triebold Paleontology, Inc., showing the very reduced skeletal structure of the carapace. 

RIGHT: The carapace of CMNH 1421 in ventral view from Wieland (1906, fig. 2), showing the dorsal vertebrae and the very limited extent of the costal plates (less than 1/3 the length of the ribs). The distal ends of the ribs fit into depressions on the inside of the marginals, but are not fused there.

Microstega (Protostega) Copei - The type specimen of Protostega copei (YPM VP 1787)  was collected by Charles Sternberg from along Hackberry Creek in Gove County, Kansas. It was named and first described by Wieland in 1909. Later, Zangerl (1953) changed the genus name to Archelon, and Hooks (1998) redescribed it again as Microstega. 

LEFT: The reconstructed skull of Protostega copei (YPM VP 1787) in right lateral view as figured by Wieland in 1909.

RIGHT: The pectoral and pelvic girdles of Protostega copei in dorsal view as figured by Wieland in 1909.

LEFT: The carapace of Protostega copei in dorsal view as figured by Wieland in 1909. Wieland reported that the carapace was on exhibit in the Yale Peabody Museum in 1909, but I did not see it in 2010. 

RIGHT: The plastron of Protostega copei in dorsal view as figured by Wieland in 1909.

Chelosphargis (Protostega) advena Hay- The type specimen of Protostega advena (KUVP 1219) was described by Hay (1908). It was collected by S.W. Williston in 1891, probably from Gove County. While showing some protostegid characters, it is a relatively small individual with only a little cranial or limb material present in the specimen. The genus name was changed to Chelosphargis by Zangerl in 1953.

LEFT: The remains of the type specimen of Chelosphargis advena (KUVP 1219) as figured by Hay in 1908.

RIGHT: Photograph of the type specimen of Chelosphargis advena (KUVP 1219) in the University of Kansas Museum of Natural History. 


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