Bucket-o-earbones from a lowcountry river site: preliminary findings and analysis

Last weekend I had a river tour for Charleston Fossil Adventures get cancelled owing to some pretty nasty thunderstorms, and so Ashby Gale and I instead went and worked a table at the first annual fall Artifact and Fossil show at Cypress Gardens*. I saw a number of familiar faces, including Cade Kaufmann, a tour guide for Charleston Outdoor Adventures - Cade takes folks kayaking around the lowcountry, and makes many visits to some fossil sites that are difficult for just about anyone else to get to. I know exactly where they are, but 1) of course won't share publicly and 2) wouldn't go there without asking Cade to show me. Back in 2016, Cade donated a few pieces to CCNHM collections (Mace Brown Museum of Natural History) including a nice partial tooth of Coronodon, which we published in our ginormous PeerJ monograph earlier this year. He also donated a tympanic bulla of a waipatiid dolphin at the time. For a while he's been telling me he had saved up quite a few earbones from his sites. When I first saw him at the show last weekend, it had been a couple years, but he nonchalantly reminded me that he "had a few earbones" for me. Now, I'm happy to find one periotic bone a week out on the river - so I was not expecting much, a couple of specimens, at most. I expressed some gratitude, and quickly forgot about it as I began setting up our table.

*Cypress Gardens is where they filmed many scenes from The Patriot, including all of the cypress swamp scenes and the small Spanish mission where Mel Gibson's militia was hiding out. Most of the movie was filmed in and around Charleston!

 Cade Kaufmann and his bucket of earbones! Cade is a guide for Charleston Outdoor Adventures.

About an hour later Cade comes by and hands me a small 14 oz container like what a small to-go salad might be kept in - and it was overflowing with dolphin periotics! The number of periotics was so absurd my reaction was just maniacal laughter - followed by a quick reversal to polite, but effusive thanks to Cade. I asked him whether he had locality data for all these - and he indicated that they were all from ONE small location! I was floored. These specimens were from one dredge site, most are nearly complete, and most are well-preserved enough to be of publication quality. Now, Ashby Gale has found many periotics (and bullae) over the past 6-7 years or so doing his fossil tours, and he was just as floored as I was. 

 The bucket-o-earbones.

I've already started work on a sample of about 200-300 periotics collected by Ashby, his clients, and Sarah and I from various Lowcountry waterways - some locations a bit secret, and from other well-known fossil sites like Folly Beach, Northbridge Park, and Drum Island - and this single bucket-o-periotics increased the sample by ~25-20% or so! This increases the sample size, and also the amount of work considerably - almost ensuring that this study will end up being a short monograph in length (that's a LOT of periotics to figure!).

All of the earbones laid out in approximate taxonomic groupings.

 So, I thought it might be fun to do a blog post about what we can learn from this collection. First off, sample size: there are 48 periotics and 24 tympanic bullae in here. That's a damned good sample! For example, the periotic sample from the entire Purisima Formation in California where I started my whaleontological studies, with the exception of one private collection, is less than that. 

 Xenorophid periotics - Xenorophus above, Albertocetus below.

1) Xenorophidae

Two periotics are identifiable as xenorophids. One is larger than the other, and is a good match for Xenorophus sloanii; the other is likely Albertocetus meffordorum.

 Periotics of "spear-toothed" waipatiid dolphins, including those similar to skulls I've preliminarily identified as aff. Waipatia.

 A beautiful periotic closely resembling Ediscetus osbornei.

2) 'Waipatiidae'

Ten periotics and eight bullae are identifiable as waipatiids - noting of course that waipatiids may be an evolutionary 'grade' rather than a clade. Several periotics closely resemble one morphotype from the Chandler Bridge Formation with a skull that closely resembles Waipatia maerewhenua from New Zealand, although the periotics are not quite so close a match; they are distinctive in having a bit of a wedge-shaped pars cochlearis. This taxon I have preliminarily identified as aff. Waipatia. One periotic with a more spherical pars cochlearis has a pronounced articular process, making it a rather good, albeit imperfect, match for Ediscetus osbornei and is perhaps best identified as Ediscetus sp. for the time being.

Periotics most closely resembling Ankylorhiza (and Squalodon).

3) 'Agorophiidae' - Ankylorhiza spp.

Four periotics and two bullae represent 'giant' dolphins in the genus Ankylorhiza, which in a couple of phylogenies form a clade with Agorophius and may represent a redefined Agorophiidae*. There are at least a couple of periotic morphotypes present, and none of these are massive enough to represent "Genus Y", the still-unnamed larger species of Ankylorhiza from the Chandler Bridge Formation; Ankylorhiza tiedemani is still not yet known from specimens with periotics.

Though the skull is quite different, the periotics of Ankylorhiza - and these - do share many features in common with true Squalodon, and detailed comparisons with Squalodon, Agorophius, and Eosqualodon are clearly warranted.

*Agorophiidae used to include virtually all stem odontocetes more primitive than Squalodon, including the xenorophids, and has been considered a wastebasket taxon. A redefined Agorophiidae would include Agorophius, Patriocetus, and Ankylorhiza, which form a reasonably supported clade in some analyses - for example, in our 2020 paper introducing Ankylorhiza.

 The best example periotic of a squalodelphinid from the sample; the remainder are partials.

4) Squalodelphinidae

Four periotics and five bullae represent the squalodelphinids, the sister taxon of the Platanistidae. These are somewhat longirostrine dolphins with thickened bone over the orbit, and typically possessing somewhat large single-rooted teeth with rugose, conical tooth crowns. Several species formerly assigned to the Platanistidae such as Dilophodelphis and Araeodelphis now appear to represent squalodelphinids along with Squalodelphis, Notocetus, Huaridelphis, and Phocageneus. The best-preserved periotics here most closely resemble periotics formerly assigned to Phocageneus from the Pungo River Formation/Limestone at the Lee Creek Mine, but are somewhat smaller; I described a similarly small periotic from the Oligo-Miocene Belgrade Formation at Belgrade Quarry, North Carolina, last year.

Two periotics of eurhinodelphinids, the top one representing Xiphiacetus, perhaps X. bossi. The bottom one is not clearly any described eurhinodelphinid taxon, differing somewhat from Xiphiacetus, Schizodelphis, and Eurhinodelphis.

5) Eurhinodelphinidae

Nine periotics and nine bullae represent the Eurhinodelphinidae, with one complete periotic closely resembling Xiphiacetus bossi from the Calvert Formation of Maryland and Pungo River Formation of North Carolina (Lee Creek Mine). Eurhinodelphinids are common Miocene longirostrine dolphins with a distinctive toothless extension of the rostrum beyond the mandible, much like a swordfish (hence why I call these "swordfish dolphins" when talking to the public). There is certainly more than one morphotype represented here.

 Four of the periotics assignable to Eoplatanista or Eoplatanistidae.

For comparison, here is the figure showing three periotics of Eoplatanista spp. from Muizon's 1988 paper on the "Acrodelphidae".

6) Eoplatanistidae

Six adorable periotics represent Eoplatanista or something similar within the Eoplatanistidae. These periotics were a bit of a mystery to me until I re-read Christian de Muizon's 1988 paper on the "Acrodelphidae" in which he included some great figures of periotics of Eoplatanista from Europe: they closely resemble eurhinodelphinid periotics but are tiny and have very short anterior and posterior processes. The tympanic bullae of Eoplatanista have a convex ventral side and are otherwise very similar to eurhinodelphinids - no such bullae are present in this sample. I reported cf. Eoplatanista from the Belgrade Formation of NC last year, based on such a bulla. Eoplatanista is otherwise unknown outside Europe; there are a shocking number of these periotics found in the South Carolina lowcountry, always close to the coast. Surprisingly, no such specimens have ever been reported from Calvert Cliffs and no skulls of Eoplatanista were reported in the Lambert et al. 2023 chapter on odontocetes from the Calvert Formation, aside from the newly described Caolodelphis milleri which has some similarities with Eoplatanista, and was reported from low in the Calvert Formation (early Burdigalian Pope's Creek Sand member, ~19 Ma). Similarly, no such periotics are known from the spoils of the Lee Creek Mine.

Periotics belonging to unidentified family/genera of early odontocetes: the top two resemble an unnamed dolphin from Europe, and the bottom one resembles Papahu taitapu and cf. Papahu from the early Miocene of New Zealand.

7) Family Uncertain

A number of strange periotics with a mix of waipatiid-like and eurhinodelphinid-like features have also turned up in the South Carolina lowcountry, also close to the coastline, and within Cade's sample there are twelve of these. Some of these approach Papahu taitapu (early Miocene, New Zealand) in some features and there are also some similarities with Yaquinacetus meadi. There is an unpublished odontocete from Europe that these periotics may be referable to, but I won't spoil it for now and will update this post after the beast is published. These periotics are similarly not known from the spoils from the Lee Creek Mine or from Calvert Cliffs.

Geology, Age, and Interpretations

I obviously won't "spoil" the location at all since it's Cade's secret - but I can share that these are dredge spoils along a local riverbank. The fossils are a bit different from what Ashby and I collect from our tours through Charleston Fossil Adventures; our specimens are virtually all black, dark grey, and occasionally have a bit of brown. At Cade's locality, these periotics are a variety of earth tones including quite a bit of red - the earbones from Cade's collections are just *pretty*.

Now, what formation are they from? It's a simple question with a complex answer, I'm afraid. There are loads of dredge islands all over the South Carolina lowcountry. River channels have been deepened and canals have been dug all over the lowcountry in order to permit maritime shipping: the Ashley, Cooper, and Wando rivers during the 19th century, the Intracoastal Waterway in the late 19th and early 20th century, and Charleston harbor pretty continuously since the age of steam. What candidate rock units could our fossils come from? 

Ashley Formation: the major bedrock unit here in the lowcountry and typically the unit that all manmade holes bottom-out within. This is a light tan to khaki and occasionally olive green sandy limestone with sparse invertebrates, phosphate pebbles, and well-preserved vertebrate remains; the unit is quite thick, 10-30+ meters, and the bottom is only ever exposed locally in deep core samples. The Ashley Formation is late Rupelian in age (early Oligocene), dating to 28-30 Ma. Fossil cetaceans include the toothed baleen whale Coronodon, eomysticetids like Micromysticetus, xenorophid dolphins (Xenorophus, Albertocetus), waipatiid dolphins (Ediscetus), and giant dolphins (Ankylorhiza).

Chandler Bridge Formation: the major fossil-producing unit in West Ashley, North Charleston, and Summerville: a thin (10-100 cm) unit consisting of sand and silt with abundant phosphate pebbles, shark teeth, and other marine vertebrates that is completely leached of all calcareous material - however, this unit is generally not exposed, even in the subsurface, south of highway 17 or within the I-526 corridor - in other words, generally not present near the coast or near downtown. It's been eroded away - but may produce fossils that were reworked into the basal Pleistocene unconformity, which is mantled with a mix of Oligocene-Pleistocene fossils wherever it is present in Charleston. This unit is late Oligocene in age, approximately 24-23.5 Ma. The Chandler Bridge Formation preserves cetaceans including: Coronodon; Eomysticetus; xenorophids like Xenorophus, Albertocetus, Echovenator, and Cotylocara; waipatiid dolphins (all unnamed taxa, but NOT Ediscetus); and the giant dolphin Ankylorhiza.

Edisto Formation: a bit of a mystery unit that dates to about the Oligocene-Miocene boundary (~23-23.5 Ma). This unit is quite thin and mostly exposed in the subsurface, but is a light yellow-brown sandy limestone, somewhat similar in lithology to the Ashley Formation. Much of the commercially mined phosphate from the "Ashley Phosphate Beds" is hypothesized to have been derived from this unit - the type locality of which does not exist, since it was named based on a block of white phosphate. Supplementary sections have since been defined along the Edisto River, and it's been identified in the subsurface from auger holes and core samples. However, it looks quite similar to the Ashley Formation from what I can tell and is never separated from it by the Chandler Bridge, so the capacity for misidentification of this unit is high - the Ashley Formation, after all, does vary quite a bit in lithology. Some land mammals (Daeodon mento, Anchippus texanus) from the "Ashley Phosphate Beds" have been reported that indicate earliest Miocene age (e.g. late Arikareean/Hemingfordian NALMA correlative) but have adhering calcareous matrix, clearly post-dating the Ashley and must derive from the Edisto Formation.* Barry Albright suggested in his 2019 monograph that the matrix adhering to the holotype rostrum of Ankylorhiza tiedemani may better represent the Edisto rather than Ashley Formation; we suggested the latter in our 2020 paper, but Barry may be correct as we reported an S. tiedemani skeleton from the Chandler Bridge Formation (but, also, from the Ashley Formation). No other fossil cetaceans are certainly known from the Edisto Formation.

*This suggests I may have been too cavalier in referring isolated specimens from our rivers to the Ashley Fm., and some specimens might actually be derived from the Edisto Formation.

Mark's Head Formation: another unit that's locally a bit enigmatic as it is only exposed in the subsurface. However, it is thick and well-exposed along river bluffs in Georgia where it was named, and is contemporaneous with zones 7-8 of the Calvert Formation further north in Maryland, and Burdigalian in age (early Miocene, ~18 Ma). When exposed or penetrated by auger holes, this unit is an olive brown calcareous sandstone/sandy limestone.

So, what are the likely stratigraphic origins of these dolphin specimens? The xenorophid periotics could originate from either of the two well-known Oligocene units, the Ashley or Chandler Bridge formations - and in theory, the Edisto Formation as well. The waipatiid Ediscetus is so far known only from the Ashley, suggesting that at least some of these Oligocene specimens originate from the basalmost unit out here. The other waipatiids more closely resemble Chandler Bridge formation morphotypes, which doesn't necessarily preclude Ashley or Edisto formation origin. Eurhinodelphinid specimens, on the other hand, are strictly Miocene, and the occurrence of one so similar to Xiphiacetus bossi strongly suggests origin from the Mark's Head Formation.

More puzzling are the specimens that belong to taxa not recorded anywhere else in the North Atlantic: Eoplatanista, and the unusual unidentified periotics. We have plenty of early middle Miocene and late early Miocene dolphins from places like the Calvert Cliffs, Lee Creek Mine, and the copious assemblages from Belgium, but very, very few earliest Miocene (Aquitanian) dolphin assemblages along the western Atlantic margin. Given how intensely sampled Calvert Cliffs and Lee Creek are, it's tempting to suggest that these periotics belong to dolphins and/or originate from some unit that is younger than the Chandler Bridge and older than the fossil assemblages further north from the Calvert and Pungo River formations. The Edisto Formation would be such a prime candidate - however, there is also the Parachucla, another 'ghost' unit present in a few auger holes west of Charleston that are correlated with thicker deposits further south in Georgia and Florida. There's also a mystery bed of the Chandler Bridge that continually produces unusually derived-looking fossil cetaceans - we encountered it and documented it in 2018 at a nearby construction site, where it consisted of two meters of clean, quartzose sandstone with eurhinodelphinid-and squalodelphinid-like odontocetes (in addition to Ankylorhiza and xenorophids).

Ultimately, it's anyone's guess - informed or no - where some of these specimens are derived from. However, there is adhering matrix on most of these specimens, and perhaps something can be gleaned from it. Regardless, it does indicate that Cade's locality represents spoils either produced by dredging that cut through multiple rock units, or that these rock units were all eroded into and a composite lag was then dredged and dumped into a spoil pile. In reality, both are likely. Further study and expansion of the collection will help - along with publication of more specimens of Oligocene and early Miocene dolphins with associated earbones, from all corners of the globe.

Some recent finds from Charleston, SC waterways - August

For those of you unaware, Sarah and I recently both resigned from our positions at the College of Charleston - we had been contemplating this for quite some time. Neither of us has been terribly happy there. We put up with a toxic work environment, decreasing liberties, and some pretty unfair work practices. For a while, the incredible fossil collection made it worth it. Eventually I got sick of carrying someone else's water and doing work for someone else's paycheck. That's all I'll say for now. But, I've left academia and am no longer an overworked, underpaid, and exploited adjunct.

Since mid-August, I've been working for Charleston Fossil Adventures as a fossil tour guide, as well as taking the occasional tour for Palmetto Fossil Excursions - a big thank-you to both Ashby Gale (CFA) and Skye and Josh Basak (PFE) for rescuing me. After a few days on the job I realized when I came home in the evenings that I was actually happy and relaxed - normally I'd be stewing over something a shitty colleague said to me at the office or some petulant student mouthing off to me, or stressed about having to do something without pay amongst other mounting demands. Being out on the boat, seeing wildlife, getting a nice tan, exercise, and showing folks how to find fossils and identifying them has been a lot of fun and surprisingly relaxing. And I get tipped! What a foreign concept - I still am surprised most days when I get tip money. "OH right, I'm in the hospitality industry now!" I have to remind myself, and thank them profusely.

Anyway, here are some of my finds, and the finds of our clients, over the past few weeks on our boat tours through Charleston Fossil Adventures.

This distinctive tooth is a rather well-preserved specimen of the snaggletooth shark, Hemipristis serra. These are by far and away the most common (and distinctive) 'medium-sized' shark teeth at our sites. Most of the teeth at this spot are all derived from the Oligocene Ashley Formation; all of these sand grains are bits of limestone and Oligocene shell fragments. For example, the little cylinder to the left of the tooth is a sea urchin spine!

A rather large tympanic bulla (earbone) from a large xenorophid dolphin - initially I thought it was so huge, it had to be something new - however, I realized that it's just slightly larger (by 1-2 mm) than the very largest earbones of Xenorophus sloanii. This specimen has a modern oyster shell stuck in the tympanic cavity. Almost certainly from the Oligocene Ashley Formation.

One of our clients took the patient, fine-scale approach of sitting down and searching the immediate sand/gravel near her - and it paid off. This is a tooth of Parotodus sp., an unnamed species of "false mako" and progenitor of the "other" megatoothed shark, Parotodus benedeni. This unnamed species frequently retains cusplets (like its possible ancestor Otodus obliquus) and is only found in Oligocene strata - making it a very rare shark indeed. Absolute killer find! Probably from the Oligocene Ashley Formation.

 

One of my favorite personal finds from the past few weeks - a gorgeous inner ear bone (periotic) of a squalodelphinid dolphin. This one is very similar to Notocetus and Araeodelphis (the former known from the early Miocene of Argentina and Calvert Cliffs, the latter only known from Calvert Cliffs).

 This periotic even has a few bite marks on it! Here's a couple more views. Squalodelphinids are longirostrine dolphins, and some of the only extinct species that seem to truly form a sister group with the Ganges River dolphin Platanista - in other words, some of the only really convincing fossil Platanistoidea. Squalodelphinids are quite diverse, and include some taxa that were formerly considered to be platanistids (e.g. Araeodelphis, Dilophodelphis). Most squalodelphinids have absurdly inflated zygomatic processes of the skull and thickened bone over their orbits, perhaps a precursor of the incredible bony ridges over the orbits in modern Platanista gangetica. This specimen is almost certainly early Miocene in age, and probably derived from the Marks Head Formation.

 Hammerhead shark teeth (genus Sphyrna) are uncommon, but usually if you pick up enough teeth that look like reef shark teeth, after cleaning the sand off at the end of a tour, there's usually at least one. I estimate a regular sort of hammerhead - perhaps Sphyrna zygaena - is found for every 40-60 reef shark teeth (Carcharhinus). This is an actually quite rare tooth - great hammerhead, Sphyrna mokarran. It is much larger than all the other hammerheads, and is unique in having serrated cutting edges and a very deep nutrient groove. This one was found by a client, and is probably Pliocene or Pleistocene in age.

 We always keep our eyes peeled for wildlife - and I'm a habitual tidepooler. I saw this cute little mud crab (Panopeus herbstii) that was unusually blue in color, and had to get a photo. Usually they are, well, mud-colored. I've accidentally introduced two of these into my saltwater tank before (and fished them out and threw them into the pond near my house before they did any serious damage!).

 Here's a tympanic bulla of a pygmy sperm whale - family Kogiidae. There's a surprising amount of the fragile outer lip that was still preserved, despite the bulla being so beat up. This is probably Pliocene in age.

"Hubbell teeth" are small heart-shaped teeth from juvenile Carcharocles megalodon; there are probably only a couple of tooth positions that produce these funny, stubby little teeth. On rare occasions you can find "Hubbell teeth" of the older megatoothed shark Carcharocles angustidens - like these two, found a few days apart. Probably Oligocene Ashley Formation.

 Last earbone for this post: a beautiful, pale blue periotic of the early Miocene odontocete Eoplatanista. Eoplatanista is a preliminary ID, but these basically resemble the periotics of eurhinodelphinids like Xiphiacetus and Schizodelphis, but are much smaller and more compact. Both Eoplatanista and Eurhinodelphinidae are longirostrine dolphins and possibly quite closely related to one another. Eoplatanista has not yet been reported outside Europe and I am looking forward to publishing these records.

An Oligocene reef shark tooth embedded in a tiny chunk of Ashley Formation limestone. This is a tooth of Carcharhinus gibbesi. Same Gibbes as the discoverer of the original skull of the early dolphin Agorophius pygmaeus, and the same family as the Gibbes Museum in downtown Charleston. "Matrix" specimens like this are uncommon here in South Carolina, but locally common at this location.

And an exciting one to finish with: Ashby found this very, very rare example of a sawshark rostral spine - Pristiophorus sp. NOT sawfish (Pristis/Pristidae), but sawshark - Pristiophoridae. These are smaller than sawfish, and are true sharks within the Selachii (sharks) rather than the Batoidea like the sawfish (Pristidae) and the extinct sclerorhynchoids. These rostral spines differ from the substantially more common sawfish in having enameloid rather than only being composed of osteodentine. Oligocene Ashley Formation.

 

Excavation of a dwarf baleen whale, Herpetocetus, from the Pliocene Purisima Formation

Last December I paid a visit to one of my longtime research localities in the Purisima Formation in northern California - one I've been visiting for nearly 20 years now (I found the site in 2004 after getting a tip from a surfer), and have received three permits for collecting. I've published several articles on fossils from this site, and back in 2011 to 2013 published two papers providing an account of the entire marine vertebrate fauna. Since 2013, I've been seeking a permit to return to the locality and was awarded one earlier this year. In December, I was checking up on spots where I had found fossils in the past, and l came across a medium-sized concretion in the base of a cliff. The bone was difficult to see, but the fact that the concretion protruded from the top of the shell bed drew my attention to it. Once I got close, I could clearly see relatively porous bone, complicated structure, and symmetry - when combined with size, these told me that I was looking at a fossil skull. A relatively large skull - about 16 inches wide (~40 cm) - but belonging to one of the smallest baleen whales to ever evolve, Herpetocetus.

 The Herpetocetus skull as I first found it - the rock hammer (for scale) is sitting on top of it.

Unfortunately for the completeness of the specimen, the entire rostrum of the specimen as well as the orbits had eroded away. This was partially mediated by the structural geology of the locality: there is a small fault line with an unknown, but likely minor degree of slip here - perhaps calling it a fault is a bit grandiose, but either way, there is a bit of shearing going on here. We are only a mile or so off from the San Gregorio fault, one of the largest faults in the California coast range; as a result, there are loads of more minor fractures paralleling the cliff face with a few millimeters to about 20 cm of offset. In older parts of the section this can result in many parallel fractures spaced a few centimeters apart with some larger fossils fractured like an accordion! I usually leave those behind, but a couple of larger specimens I've collected from that end of the locality have required some challenging preparation as a result. Though less common in the sandier upper parts of the section, a fracture has cleaved the specimen in half and there is a deep sand-filled trench - I suspect there were several parallel fractures in this zone that resulted in weakening of the sandstone, and this zone was blasted out by wave action - including the remainder of our skull.

Explanation of the fossil as discovered in December 2022.

Fortunately for us, this meant that the fossil could be collected in one nice self-contained block that would certainly not exceed 100 lbs (45 kg). This is extremely fortunate, as the specimen was found about a mile from the nearest road! I knew it would take some creativity in physically removing the specimen from the beach. At the time of discovery I wondered how much it would weigh if I just popped the concretion out - I decided against it when I realized that in addition to the skull, there was at least one partial mandible and some ribs, meaning that a somewhat more careful excavation lasting at least a couple hours would be needed. In 2022 when I found this, I was by myself - Chris Pirrone joined me for a half day, but had other obligations. I would not have the help. Certainly, I could have excavated and jacketed the specimen by myself - it would have been a bit of a pain, but it would be doable. However, I would have been unable to move the specimen on my own. Sure, you can always leave a plaster jacket and come back for it another day - that's nearly standard practice in western interior paleontological fieldwork (e.g. Montana, Dakotas, Wyoming, Colorado). But all of those places lack something significant and irritating that I have to deal with: tides. The ocean is great when it's eroding fossils out for you to discover, but it's also dangerous and always trying to kill you and your team and can make life very difficult. As a result of this, I prefer to keep excavations short and remove specimens ASAP. Plaster jackets get blasted away by waves if left until tide cycles and weather catch up. Excavations in the intertidal zone can only last a few hours. We were well up out of the intertidal here, but a jacket would have been buried or blasted away by wave action if left for a few weeks. Plaster is also bright white and attracts attention: this section of beach is remote, but still attracts a few beachgoers and fishermen walking down every day. So, I made the decision to leave the specimen in the field without touching it. 

This decision gave me no shortage of anxiety. Two weeks after I left California, an incredible and unprecedented train of spectacular winter storms began hammering the coast. I spent my last semester of teaching here in Charleston with the *worst* case of FOMO ever, watching all of this incredible erosion take place and being unable to check out any of the freshly exposed fossils! And worse, fearing that this little baleen whale skull had eroded away. It wouldn't be until May 2023 that I visited the spot and confirmed that the skull was intact. I was also worried that the skull would be buried by several meters of beach sand.

 The distinctive lectotype mandible of Herpetocetus scaldiensis from the Pliocene of Belgium, illustrated by Van Beneden.

Before we continue with the excavation - what's the deal with Herpetocetus, anyway? Herpetocetus scaldiensis was first named in 1872 by Joseph-Pierre Van Beneden, a Belgian paleontologist who named a large number of (occasionally chimaeric) cetaceans from Miocene and Pliocene strata near Antwerp, Belgium. The fossils included a distinctive mandible with a tall joint (condyle) and a long angular process, the combination of which resembled a reptile mandible - hence the name, 'reptile whale'. For years the taxonomy of Herpetocetus was frozen because it became clear that the mandible and other elements such as the tympanic bulla (earbone) were not associated with one another and represented completely different families of mysticetes. Worse, the designation of type specimens had not yet fully caught on and Van Beneden did not select a type specimen. Starting in the 1960s and 1970s more specimens began to be collected in California, Japan, and North Carolina that either consisted of or included mandibles with the same distinctive morphology. Paleontologist and later Nazi Othenio Abel XXX. The long-awaited Lee Creek Mine Volume IV included an entire chapter on Herpetocetus and Nannocetus, written by Frank Whitmore and Larry Barnes in the 1970s and 1980s and submitted in the 1990s. The manuscript and volume were in press (somewhat analogous to 'development hell' in film) for over a decade, but it finally came out. In this study, Whitmore and Barnes (2008) reviewed the material belonging to Herpetocetus scaldiensis and XXX. Chief among these observations was that a skull fragment figured by Van Beneden and likely associated with the mandible included the highly diagnostic squamosal of Herpetocetus, permitting several new skull specimens to be referred to the genus even though they lacked the mandible. These authors also described Herpetocetus transatlanticus, based on a partial braincase from the lower Pliocene Yorktown Formation at the Lee Creek Mine, and Herpetocetus bramblei, based on a fragmentary skull and mandible from the Purisima Formation near Santa Cruz, California! It was good timing for them, because in 2007, I collected about 2/3 of a skull of Herpetocetus from a sandy bed near what would soon be the Herpetocetus bramblei type locality. I would have certainly named it as a new species at the time. I held off study because just when I completed preparation of the specimen, the Whitmore and Barnes (2008) paper had come out - and it was very clearly referable to Herpetocetus bramblei. The timing was further quite good, because just two years later a seawall was built over the entire section of cliffs. This specimen catapulted me down a road studying Herpetocetus and finding many more fossils - and virtually all of this is unpublished still! Now that I'm no longer teaching and my research fellowship has expired, I plan on returning to this research after leaving it for nearly 15 years. It was only a matter of time before I found more Herpetocetus remains.

Comparison of the erosional cross-section through the concretion (flipped upside down) with the CT scan of Herpetocetus bramblei from the Purisima Formation in Santa Cruz, and approximate location of the cross-section based on the reconstruction of Herpetocetus morrowi from the coeval San Diego Formation (from El Adli et al., 2014).

I managed to scrape together a small field crew before leaving for the east coast at the tail end of a vacation - Dr. Ash Poust (San Diego Natural History Museum), Sarah, and our amateur colleague (and friend of the blog) Chris Pirrone helped us. I knew between the four of us we'd be able to get it excavated and transported off the beach, hopefully with time to spare. We spent some time cleaning dust off of it to get our bearings, and then began trenching around it. The concretion stuck a bit further into the rock, but in most places the surrounding sandstone could easily be carved away. Within an hour we had found a couple of bones behind the skull and otherwise had a competent trench around most of it. We started undercutting it, which was surprisingly easy - like a hot knife through butter.

Chris and I exposing the concretion with this tiny brush. I neglected to bring along a whisk broom: my old whisk broom had plastic bristles, which finally decomposed and disintegrated in December after 20 years.

We encountered a couple of bones in one of the trenches pretty early on. Here Ash is trying to make sense out of what is exposed without attempting to 'field prep' the bone. We decided it was probably a rib - but it may have actually been a small mandible.

After 90 minutes, we had quite a bit of the specimen already trenched.

You really couldn't ask for a more scenic backdrop to an excavation than this. A gorgeous view of the Pacific ocean whenever we turned around.

Ash undercutting the whale block while Sarah labels bags containing some of the associated bones of our little whale.

After trenching was deemed complete, it was time to get ready for plaster jacketing. The first step is to make a barrier to keep the plaster from bonding directly to the bone or rock. I prefer paper towel as it is quite thick, has perforated lines for easy tearing (sometimes a liability), and if several layers are added it can give a slight extra bit of padding. Aluminum foil is also quite popular and requires no water. All of our water had to be carried in: saltwater will apparently make plaster cure extremely fast and generally cannot be used. I used my camelback hose to carefully drip water onto the paper towel so it would stick to the specimen.

After the separator is applied, we can now start the plastering process. I like to make my plaster runny (think about the viscosity of olive oil or melted ice cream), but I've found that on the cold, foggy, and humid coast of California the outer layer of the jacket never completely cures. Runny plaster means you get more working time - thicker plaster has considerably less working time, and the difference in water added can be quite small (a few table spoons worth). So, I decided instead this time to try an experiment: mix plaster at the viscosity of a milkshake in small batches. This worked great, and we had about 5-6 minutes working time, just enough for a few strips at a time. Also, not bad, because the relatively little volume of plaster and freshwater we had meant that precision was needed.

We ended up using every single ounce of plaster mix we carried out with us to finish the top jacket! After about 20 minutes of curing (during which I found a rather large palatoquadrate cartilage from a skate, and a nearly complete humerus of a fur seal), we flipped it and were delighted to find that there were no obvious broken bones in the pedestal. We expected that given the bones we found in the trench, but fractures made during excavation fortuitously manifested between the jacket and these bones. Ash quickly dug these out while Chris and I finished the jacket and tried rigging up our makeshift sled made out of a laundry basket and 60 feet of nylon cord. Sarah and I wrapped and labeled the associated bone blocks and we distributed these amongst the different backpacks.

At first we tried this admittedly clumsy approach with one person (Chris) stooped over and lifting the front of the laundry basket. We would make it about 100 feet at a time before the person in back would need to rest.

Chris and Ash were a bit skeptical of my engineering efforts and preferred this for a hundred yards. My shoulder was killing me when I took my turn so I insisted we try something else. The relative ease at which Chris and I had been able to move the sled with only one person pulling on the ropes gave me an idea.

 

 

I thought - what if we loop the rope forward and put it on a piece of driftwood to be used as a "yoke", like for oxen on the Oregon Trail? The front end of the sled just needs to be slanted up with the center of mass close to the back in order for it to be dragged efficiently. Ash got up in front and took the "reins", analogous to a husky, with Chris and I each lifting about 30-40 lbs continuously while advancing at a walking pace.

 

 This method worked so well that we did not bother trading off and we slid the jacket about an entire kilometer down the beach this way. We also had a convenient tire track in the sand that we could use as a rut for the 'sled'.

 

 By 4:30, only four hours after we parked, we had the plaster jacket in the back of the vehicle! Ash, half jokingly, suggested getting ice cream and I immediately agreed. It tasted very, very good.

 

More on maintaining research notebooks - some Q & A

I recently received these questions as a comment on a recent post by Dr. Aretha Guimaraes, a botanist at the Instituto Nacional de Pesquisas da Amazônia. Dr. Guimaraes writes: "Hey Robert, thanks for answering my comment! I have a few questions regarding the organization of your notes."

 
1) I’ve read that you divide your notebooks using tabs according to the specimen that you are describing. But how do you continue your note about a certain fossil if the pages that you left for that description are over? Do you continue in another notebook? And if you do continue to write in another notebook, how do you store the complete description later? 

Great question! This happens all the time - either I 1) have supplementary observations or 2) mitigating circumstances require me to interrupt an entry and begin a new entry. In this case, I write up at the top of the page "continued on page X" and typically write this at the very end of the entry as well. When I get a chance to get back to the original entry, I write in "continued from page X" at the very beginning, so it is clear where I should flip to. Now, this becomes a problem when you split an entry between two different notebooks - I tend to use roman numerals for my notebooks, so I can cross-reference entries between notebooks. For example, Notebook I is one I started in 2008 on fossil pinnipeds from California; Notebook II is chiefly on fossil cetaceans, and Notebook III is on miscellaneous marine vertebrates (birds, otters, sharks, bony fish, sea turtles) from California. I think I stopped there, though I have a single notebook dedicated to fossils of Herpetocetus, one or two more on Eomysticetidae from my Ph.D., and two full notebooks of descriptions I've made while at CCNHM in South Carolina.

2) By now you should have lots of notebooks stored. Do you keep a “master index” where you can check when you are looking for a particular description or info?

No, not yet, but in a few more years that might be needed!

3) Do you make any copies of these notebooks? Like a digital copy or something?

I have digitized my field notebooks, but have not bothered digitizing any of my research notebooks. I tend to type up my descriptions shortly after writing them out by hand, so in a way it gets digitized. I use the marked up photographs as guides to constructing my figures (which are generally based on the same edited photographs). 

4) I have the same problem that you described in one of your posts, where you told us you had to move to the US with a bag full of heavy notebooks. I’ve been moving a lot recently (Brazil – UK – Amazon and so on) and I’ll probably move a lot until I can become a full professor somewhere. I tried to use a digital notebook in order to be more practical to carry things around (since I’m not available to afford shipping all of my notebooks) but I didn’t like it. Did you manage to solve that problem? 

I have not solved this problem - in my opinion this is a good, but intractable problem to have. I don't like staring at screens, and in my experience it is much easier to have a hard-drive failure than to lose your physical notebook or have them destroyed by water or fire.
 

5) Regarding the fieldnotes, do you have a field notebook or do you keep your notes in the same notebooks that you use every day?

I have a completely different set of field notebooks that are regionally or project specific: for example, I have two general field catalogues (1 and 2) for fieldwork in Santa Cruz county with the prefix RWB, a notebook for Point Reyes (RBPR), and an east coast field notebook (RBEC).
 

6) Are you still using A4 notebooks? When you have a drawing of something larger to stick in your notebook, how you do to prevent damage? 

I use the XL moleskine notebooks which measure 19x25cm (7.5x9.75"), just slightly smaller than "letter" size paper here in the US (letter = 8.5x11", 22x28cm). I do not paste in anything that is larger than the page in both dimensions - but I do paste in foldouts that unfold laterally. I'm not exactly sure what kind of damage you're referring to, but I prevent tearing and tattering of the edges by making sure everything pasted in is small enough so it doesn't protrude from the sides of the notebook.
 

7) Do you keep daily notes like research diary?

I do not - I am much too scatterbrained to do that consistently. I only take notes when I've blocked off some time to focus and pour my undivided attention onto one task.

Also, I’d like to tell you that I always share your notebook posts with my students so that I can convince them to keep their notes, especially my husband (who is also a scientist) and refused to take notes on stuff. I used your notebooks post to convince him of my point and now he keeps things more organized.
 

Thanks again for your content! I found you by randomly searching in google a few years ago and I always keep an eye on your posts.
Best wishes,
Aretha Guimaraes

I'm so glad you find these posts and tips helpful! Thanks for the great questions, Aretha!

Lowcountry riverbank fossils from July 4

 One month ago I spent the day on my first paid river fossil tour with Ashby Gale and Charleston Fossil Adventures. Ashby recently got his captain's license, and can now take clients out along lowcountry waterways to collect fossils from hard-to-reach spots that cannot be walked to - and locations known only to the two of us and a couple others. Ashby had three tours back to back booked for July 4, and he was kind enough to not make me join him for the early morning tour at 9am! It was still a long day, though, with a heat index of 105. We took out a couple of different families and found some great stuff; this post will be more of a slideshow with commentary than anything else.

 

Ashby Gale and I, the first secondary tour guide hired for Charleston Fossil Adventures! I gotta say, this really beats the hell out of teaching introductory geology labs. The office is considerably nicer.

 An osteoderm of the extinct "beautiful" armadillo Dasypus bellus, which was slightly larger than the modern nine-banded armadillo (Dasypus noveminctus) often seen lying by the side of the road in South Carolina. Dasypus bellus is known only from the Pleistocene in North America. 

A tooth of the devil ray Plinthicus stenodon, my favorite batoid. When collecting with Ashby, Sarah, and I, it's basically illegal to not call out "Ooh a Plinthicus!" Plinthicus is only known from Oligocene through middle Miocene rocks, and was named by E.D. Cope. 

 

A single lower tooth of Galeocerdo aduncas/Physogaleus contortus, an Oligocene-Miocene tiger shark with long, twisted cusps- at least on its lower teeth. Whether or not these species are synonymous is a controversial topic in shark paleontology, and I've been yelled at by shark experts on facebook for daring to consider synonymy as likely.

 A rather large blade of a mako (Isurus) tooth found by a client - Isurus desori? flandricus? Clearly not I. hastalis or I. oxyrhinchus.

 Another Physogaleus contortus tooth amidst a field of phosphate, limestone, and oysters.

 A partial tooth of the extinct megatoothed shark Carcharocles angustidens with an incomplete root.

A large upper lateral tooth of the snaggletooth shark Hemipristis serra.

Another mako tooth (Isurus desori? flandricus? retroflexus?), although one with a complete root. This looks like it weathered directly out of the Ashley Formation rather than being derived from reworking.

 Another megatooth, this time a juvenile tooth of Carcharocles megalodon.  

An adorable lateral tooth of the megatoothed shark Carcharocles angustidens - I love finding tiny teeth of extinct giants.

The highlight find of the day – a beautiful tooth of Squalodon! And yes, an actual, factual tooth of Squalodon from South Carolina. Unlike Ankylorhiza, teeth of true Squalodon have highly rugose enamel rather than the more gently fluted enamel of its Oligocene relative. Found and donated for study by the Hammond family!