by Sarah Boessenecker (@tetrameryx)
It seems like December has become a month of basilosaurid whales – in December of 2019, we finished cleaning up, adding 3D prints of missing elements, painting, and hanging our cast basilosaurid whale of Dorudon atrox, affectionately known as ‘Manaia.” This past December, we had yet another basilosaurid whale – this one was fossil rather than a cast, and still in the ground!
DAY 1 (November 18, 2020)
CCNHM was invited by Rich Familia into the Giant Cement Company’s quarry outside of Harleyville, South Carolina in mid-November. This quarry exposes the late Eocene Harleyville Formation, Parker’s Ferry Formation, and Pregnall member of the Tupelo Bay Formation (formally called the Santee Limestone). We expected to just find mainly shark teeth, and possibly some archaeocete material (like a tooth, or maybe a periotic). Museum staff (Collections Manager Sarah Boessenecker, Curator Dr. Scott Persons, and Research Fellow Dr. Robert Boessenecker) were accompanied by Rich Familia, Jordy Wolfe, and Mark Bunce as they went into the field for a relaxing day of surface collecting. We only had a couple of hours out there and the sun was setting soon, when Mark found something halfway down the slope – it was 2 partial earbones (tympanic bullae)! We got excited – Dr. Boessenecker had been hoping to find some archaeocete material – and he really, really, really likes earbones of whales! Having left and right earbones surely indicated the presence of a skull. As we went over to take a look at what he found, we saw more float* and realized there was much more than just ear bones – after about forty minutes we had identified vertebrae and what appeared to be a part of a mandible. We marked the spot, and left for the day – it’s no good trying to dig when it’s getting dark (that’s when mistakes are made!) We regrouped at their vehicles, and made a plan to come back earlier the next day and see what they could uncover.
*Bits of bone eroded out of the ground and scattered over the surface are called “float” by paleontologists – tracing the float up the slope often leads you to the source of the fragments, hopefully a skeleton still remaining in the rock.
DAY 2 (November 19, 2020)
The next morning the same crew came back to the quarry, and added a new member – Ashby Gale joined us late in the afternoon. Rather than prospecting the rest of the quarry, we all went straight for the bone float Mark had found, and set to work digging and uncovering what was below the rock surface. We carefully uncovered bone bit by bit, and confirmed the flat bone we found the prior evening was part of a left mandible. Sarah worked on uncovering a bit more of the mandible to see how complete it was – and found teeth, still in their sockets! Not only that, but the mandible seems to be nearly complete.
Such a find was amazing to see uncovered in the field, but it also let us identify the exact whale it belonged to. Basilosaurus cetoides, Dorudon serratus, and Chrysocetus healeyorum are all known from the late Eocene, so we knew it would most likely be one of these three whales they were working with. However, upon looking at the teeth Sarah uncovered, Dr. B was immediately able to recognize which animal we were working on. The whale in the ground is Chrysocetus healeyorum – the smallest of these 3 whales, which was a positive for us – it would be much easier to dig out of the ground and take into the museum.
We team continued working through the day, uncovering the whale bit-by-bit. As the day wore on and the sun got lower in the sky, Dr. B grew concerned – this skeleton kept growing. As we were digging a trench around the mandible, more and more bone was being discovered – this was turning out to be more of a skeleton, rather than an isolated jaw. The sun was setting, and the temperature was dropping – so we quickly slapped on some small plaster patch-like jackets onto the exposed clusters of bone and covered everything with a tarp, unsure of when schedules would allow for our return to continue the excavation.
DAY 3 (November 22, 2020)
We were able to return on the following Sunday, when there was no active work in the quarry by mining equipment. Rich, Dr. Persons, Ashby, the Boesseneckers, and Jordy were all set to see how much they could uncover with a smaller crew – not everyone would be able to stay the entire day this time. Rich continued working on some associated, but isolated vertebrae near the skeleton – these became affectionately known as “Rich’s lumps” to the crew to differentiate what different projects were happening at the excavation. As they were slightly separated from the main skeletal elements, Rich was able to trench completely around them so they could undercut and jacket them for removal. By the end of the day, we had completed one major goal: completing a plaster jacket to cover up the largest bone cluster that could not be subdivided – a rather large 5×4 foot wide triangular block. We again covered everything with a tarp, as it was Thanksgiving week and the holiday meant it would likely be more than a week before they were able to return.
DAY 4 (December 3, 2020)
We came back on December 3rd to assess the excavation – luckily, the tarp held and kept (some) of the water from the heavy rains out of the pit – kind of. The bones didn’t wash away, which was the important part – it just meant we had to go back to digging more trenches to get rid of some of the excess water. We took turns using their giant pick-ax, making trenches to divert much of the water to make work easier, and bailed out the pooled water that had collected (much of the water was from the fact that the quarry sits on top of a giant aquifer, so water was constantly seeping in). We quickly realized they would not be removing the skeleton this day – the more we tried to trench around the exposed elements, the more bone we discovered. The skeleton just kept growing. Knowing we wouldn’t be able to come back for a few days again (those pesky jobs getting in the way of things) we made a top jacket to cover the exposed elements. We laid down wetted paper towel to act as a separator, and then dipped burlap strips into plaster of paris and laid them on top of the paper towel – this took quite a lot of burlap and plaster, as we extended as far out as they could since it wasn’t possible to trench through the middle of the block – there was just too much bone to safely make the block much smaller! We laid 3 2x4s across the top of the jacket in an a-frame, and fixed them in place with burlap strips and plaster – these were to help strengthen this massive jacket along its long axis.The plaster would cure to a hard shell and protect the bones from the elements; we placed the tarp back over and called it a day, as the sun was once again setting, making fieldwork not possible. There were 3 smaller partial jackets we were able to remove though – Rich’s lumps. We made partial jackets of these, and left the tops uncovered – they were small enough to hand-carry out of the quarry.
DAY 5 (December 8, 2020)
We came back on December 8th, determined to finish the excavation.
Spoiler: we did not complete the excavation, but made excellent progress!
The plaster caps held over the weekend, and we set to work, trenching (again – water was a constant battle at this site) and got to work. While this plaster was curing, we began to pedestal the jacket – this is when they undercut the sediment along the bottom of the jacket, narrowing the support to make it easier to break away and flip. This is a back-breaking task – luckily, we had a ton of help this day to make it go quickly as people could trade off and work in shifts, and multiple people working on the jacket at a time, as it was so large they all fit. We also were able to use a reciprocating saw – which cut through the soft limestone like butter, and was so much faster than hammer and chisel! As we exposed more along the bottom of the jacket from undercutting, we added more burlap strips with plaster, to keep the bottom from falling out.
Once the jacket was on enough of a pedestal and the plaster had cured, there was very little rock left supporting it – meaning it didn’t take a huge amount of work to flip! We used crowbars and were able to pry it off it’s rocky pedestal, and used moving straps to gently let it down as we flipped it. Success! The jacket was flipped safely, and no bone was left behind underneath it – we had successfully dug down low enough below the bone later to not leave anything behind and no damage done to the fossil. We knew we didn’t have the manpower to get the jacket out on our own – we would need to take Rich up on his suggestion/offer of getting the heavy mine equipment in to help with that. However, we needed to complete this jacket – but removing some of the excess rock off the bottom (now top) to help lighten it and make preparation easier. We used the reciprocating saw to cut a grid into the matrix, and then used chisels and hammers to remove small blocks of sediment – this probably removed at least 150-200 pounds of sediment from the block! Once we had shaved off a good bit of the matrix, we were able to plaster the remaining area, thus sealing the fossil in a complete jacket. We knew we would be able to remove it when Rich had talked to the contract construction workers to get their help – in the meantime, we set our sights on finishing up the smaller partial jackets we had made. Once again, easier said than done; as we began trenching to pedestal these smaller bone groupings, more fossils were exposed. We were working against the clock again – the sun was getting lower, but we were determined to get these jackets pedastled, flipped, and completed. As they were too heavy to carry out by hand, they were placed next to the giant jacket – they would be transported to their vehicles with heavy machinery from the mine.
DAY 6 (December 15, 2020)
The day was finally here – the jackets were going to be lifted out of the quarry! We arrived on December 15th – it was by far the worst conditions we had experienced in the quarry yet (the multiple days between returning to the quarry were from a combination of job commitments and rain). It was in the low 40’s and WINDY – the wind cut through all of our layers! However, we had work to do – namely, getting prepared for the heavy machinery to come and collect our massive jacket(s) to hall down the slope and across the muddy flats into the bed of a pickup. We climbed up the slope to assess everything – and were shocked when the mining equipment was already headed their way! They were ready to go and they were more than happy to work on their schedule, since they were allowing the museum access to the quarry, halting work on the slope the fossil was found in, and taking time out of their day to help them with moving the jackets. When the giant equipment got closer to us, Dr. B started laughing – the sheer size of it was incredible – it was actually large enough to make their gigantic jacket look tiny! It took 8 people (more would have been welcome, but there wasn’t space around the jacket for them to fit) to move the ~400 pound jacket into the bucket of the bulldozer – an immense task of its own. We then moved the two smaller (but still too large to carry easily down the slick slope) into the bucket, and then the bulldozer moved down the hill with half the crew to get it into the bed of a pickup truck. This half of the crew then went downtown to deliver the specimens to the museum, while the other half remained at the (very cold) quarry, continuing to work on the associated bone scatters – more vertebrae and the right mandible. Work was going well, but we ended up having to leave the quarry earlier than expected – it turns out, Rich’s MSHA (Mine Safety and Health Administration) certification had expired. This wasn’t a huge deal on most other days, as there were others in the quarry while they were in there that had current MSHA certifications – but the quarry operators were leaving early that day. We hurriedly made top jackets for the two bone clusters we were working on; with Christmas right around the corner, we figured it would be a few weeks before we were able to return (when quarry workers were back in the quarry again.)
DAY 7 (January 20, 2021) – THE FINAL DAY!
We knew they only had a few hours of work left finalizing this dig – after a (very) long break, we were finally able to return to the quarry and wrap this dig up! The mine operators requested we go in after the mining crew was done actively working for the day, so we showed up at 2, and were in the quarry around 2:30 after paperwork was signed and finished. We immediately set to work – we didn’t have much to do, but needed to finish before the sun set. We continued trenching the smaller block of vertebrae, and by 3:30 work with a reciprocating saw made a quick pedestal of the jacket containing the right mandible, which was then flipped and the plaster jacket completed on the other side. The cluster of vertebrae were also moving quickly – having a large team to all work together and trade off when someone was getting tired (and then hitting their hand with a hammer too many times…) worked beautifully. Some more bone was found in the trench wall, but was also removed in blocks with the reciprocating saw – the final blocks were jacketed, and removed from the quarry – they had finalized and wrapped this excavation up after 7 days of hard (albeit spread out) quarry work!
Why this specimen is so important?
We’re a small museum with limited resources, so why go through all this trouble? Many basilosaurid fossils have been found, after all. Letting one be turned into concrete would certainly be a minor tragedy – though more are guaranteed to be discovered. In this case, the identification of this specimen is key: we had a species-level identification within the first few hours of digging. What’s so special about Chrysocetus healeyorum? For starters, it’s not very well known: the holotype specimen – the specimen that the species naming was based on – has a very fragmentary skull and partial mandibles associated with proportionally large teeth, and an assortment of vertebrae and ribs, along with a partial pelvis. Simply put, there’s a lot to gain just from the standpoint of filling in missing pieces.
More critical, however, is the potential evolutionary story told by the original specimen. Chrysocetus was proposed to have only a single set of teeth – either milk or permanent teeth – a key evolutionary step in the evolution of modern whales and dolphins. Baleen whales do not have adult teeth, and all modern toothed whales (Odontocetes) only have a single set. As it turns out, it’s extremely difficult to tell whether the retained teeth in modern dolphins are the adult or milk teeth – and we actually don’t know if they lost their milk teeth, or lost the ability to produce the adult set (their “adult” teeth might actually just be milk teeth).
As a result, Chrysocetus healeyorum has been interpreted as the basilosaurid most closely related to the Neoceti – the group including baleen whales (Mysticeti) and dolphins and other toothed whales (Odontoceti). The early radiation of the Neoceti is typically studied in the context of Oligocene age early dolphins and baleen whales – a key focus here at CCNHM – but this specimen gives us an opportunity to look at this diversification event from the other side, to speak. Our new whale has a more complete lower jaw (and likely skull) than the original specimen, and appears to have much more of the dentition. These teeth are also hollow shells that have not been completely formed yet, perhaps giving us an earlier window into the growth of Chrysocetus. This new skeleton will allow us to test the hypothesis that Chrysocetus had only one set of teeth, and its relationship with the Neoceti.
CCNHM is extremely grateful to Giant Cement Quarry for allowing us to conduct fieldwork in their quarry, and for facilitating removal of large plaster jackets with their equipment. We thank Rich Familia for getting us into the quarry and arranging for mining equipment to help out. We also thank Mark Bunce for discovering this whale (and causing everyone a bunch of well-earned backaches), and all of the volunteers who helped along us the way: Ashby Gale, Jordy Wolfe, Shelley Copeland, Schuyler and Josh Basak, Matt Gibson, Jessie Peraginie, Alex Mertz, Everett White, Laurel Black, Scott Harris, Stuart Clayman, and Michael Musick.