Fossilized ambergris from the Pleistocene of Italy: tales of marine taphonomy 1

I’ve wanted to somewhat regularly cover marine taphonomy on this blog for a while now, and with the recent publication of Baldanza et al. (2013), I thought that now is as good a time as any to start. It’s been a pretty busy last couple of weeks, but I’ve just delivered a department talk and have also spent the past few days recouping from a nasty cold, and now have some spare time again. So, here's installment 1 of a new series, tales of marine taphonomy. I'll occasionally cover papers discussing some of the weirder and less familiar aspects of marine taphonomy - and the taphonomy of marine vertebrates in particular. To be honest, it's not a subject that has been given much attention any way (so many "regular" concepts will probably be foreign to terrestrial workers), and many studies have butchered the subdiscipline altogether.

The last couple of weeks have seen some exciting advances in paleontology, but while everyone on the paleo-part of the internet was busy discussing the two papers reporting on new Jurassic mammals – in the same issue – but disagreeing whether or not they were mammals or something further down the stem – a new discovery was published that is actually interesting (and not just controversial from the standpoint about cladistic disagreements, which – no offense – can be horribly dull). Fossilized ambergris was reported by Baldanza et al. (2013) in the journal Geology from the Pleistocene of Italy. This is pretty damn neat, as it’s something I never had much hope in being preserved in the fossil record.

 

An atrociously humongous slab of ambergris. From pbs.org

First off, what is ambergris? Ambergris – or gray amber – is a waxy substance formed from bile secretions in the digestive tract of sperm whales. It is often found with embedded squid beaks, and is thought to be a sort of protective lining that forms along the sides of the intestinal wall to protect against the sharp beaks. Ambergris can be expelled as fecal matter, or if too large it may be regurgitated. In the days of whaling, ambergris could be found within the intestines of freshly killed whales. It is often picked up by beachcombers along the shoreline (and beachcombers often pick up all sorts of other goodies that they think is ambergris). Ambergris is buoyant, and will float all the way to shore. Unlike cetacean feces – which has the consistency of greek yogurt and rapidly disaggregates once pooped out – ambergris is formed as somewhat consolidated chunks. Ambergris is perhaps most famous for its smelly qualities: although the soft, fatty and white precursor to ambergris (unsurprisingly) retains a strong fecal smell (how pleasant), once aged properly (apparently by sustained floating in the ocean) it can become quite hard and will produce a sweet smell, often compared to rubbing alcohol. The smell itself is of course not fantastic or of serious note, but it is rather its potency as a fixative for odors that makes it desirable for perfumes. It’s currently illegal to own or sell ambergris in the United States, and has long been rendered obsolete by synthetic fixatives; it is still possible to find perfumes made with ambergris in some European countries.

In their new paper, Baldanza et al. (2013) report about 25 coprolites from early Pleistocene (~1.75 Ma) marine rocks in Italy. These coprolites were calcareous, equidimensional to oval/lozenge shaped, up to 1 meter in length, and discolored relative to the background sediment; they were found to occur within only ~1200 square meters. A series of concentric ring traces are present, which argues against these structures representing things like recently described lungfish burrow traces. Occasionally, some specimens showed longitudinal wrinkles, which in modern in situ ambergris specimens occur on conical parts tapering towards the anus. Most damning of all, many of the coprolites were filled with squid beaks – oddly enough, mostly lower beaks, and upper beaks were rare and poorly preserved. Several chemical analyses were undertaken, and liquid chromatography analysis detected the presence of lipid derived organic compounds, and cholic acids which might be related to mammalian gastric activity were also found. Traces of eight amino acids were also detected, and relate to the decomposition of squid beaks.

Some ambergris coprolites - from Baldanza et al. (2013).

Some interesting hypotheses have been proposed to explain the occurrence of these ambergris coprolites. What’s strange is that they all occur in a single stratum in a small area (1200 square meters – approximately 35 by 35 meters, or just less than ¼ the area of an American football field), which is a pretty high density of ambergris. Baldanza et al. (2013) argued that their ambergris masses represent remains present within dead sperm whales, rather than coprolites naturally excreted in life – although, based on what information, I am unaware. Baldanza et al. (2013) suggest that the presence of whale fall mollusks in the vicinity are suggestive of a mass mortality event – and the carcasses were apparently preserved elsewhere. They further suggested that the paleogeography of the area may have served as a ‘natural trap’ for pods of sperm whales pursuing squid into shallow waters.

Some more ambergris specimens. From Baldanza et al. (2013).

I am certainly happy with the discovery of fossil ambergris – that is surprising enough. However, I don’t really think it’s at all necessary to invoke some sort of catastrophic interpretation for an assemblage that cannot really even be called a death assemblage, because there isn’t any evidence of death. There aren’t even any skeletons – the analogy would be digging up a vault toilet at a summer camp and identifying it as a mass grave. If there’s no body, it’s hard to claim that a murder has taken place. What mechanism would there be for removing the skeletal remains, but leaving instead coprolites with a far lower preservation potential? I can’t really think of one, save for a bunch of whales defecating at death and having the presumably easier to transport ambergris chunks transported elsewhere on the seafloor.I think a far more plausible hypothesis would be as follows: the locality was sort of a paleogeographic ‘eddy’ where ambergris floated and concentrated by surface currents, eventually becoming waterlogged and sinking to the seafloor.

Now, why was I never very optimistic about cetacean coprolites? Here's a youtube clip showing what happens when a dolphin defecates (it's not really that gross):

Ambergris, on the other hand, is a bit more cohesive and solid, so to speak. It probably won't be so diffusive upon its exit from the body. What hopes can we have for finding ambergris in older parts of the rock record? It mostly rests on two questions: 1) is ambergris restricted to the extant sperm whale Physeter? and 2) how far back does the fossil record of Physeter extend? According to Rice (2009), the answer to the first question is 'yes'. Answering the second question is a bit more difficult, as Physeter doesn't really have much of a fossil record, although Physeter-like sperm whales were around during the early Pliocene (Whitmore and Kaltenbach 2008), and a close relative that already had adaptations for teuthophagy is known from the middle Miocene of California (Aulophyseter).

Baldanza, A., Bizzari, R., Famiani, F., Monaco, P., Pellegrino, R., and Sassi, P. 2013. Enigmatix, biogenically induced structures in Pleistocene marine deposits: a first record of fossil ambergris. Geology doi:10.1130/G34731.1
 
Rice, D.W. 2009. Ambergris. Encyclopedia of Marine Mammals, 2nd addition. p.28-29.

Whitmore, F.C., and J. A. Kaltenbach. 2008. Neogene Cetacea of the Lee Creek Phosphate Mine, North Carolina. Virginia Museum of Natural History Special Publication 14:181-269

For the love of science, the pygmy right whale was NOT originally thought to have gone extinct 2 million years ago!

While I have not yet seen the fake documentary “Megalodon: the monster shark that lives” which has put yet another nail in the coffin of the discovery channel’s reputation for quality programming (what with shows like Moonshiners, Amish Mafia, Auction Kings, Pot Cops, and Weed Country – among others), I have heard that the show has inaccurately reported research from our lab here at Otago in order to support bogus claims that C. megalodon still exists. Now, it’s also important to note as a disclaimer for the uninitiated that the writers never intended their show to be taken at face value as anything but a fake documentary – although it is hardly forgiveable that it was not marketed as such, and that there wasn’t any “WARNING: TOTALLY FAKE” or “100% FANTASY” disclaimer at the beginning of the show.

I won’t be getting into any of the details about C. megalodon survival or other shortcomings of the show, for two reasons: 1) I will discuss the former when it’s appropriate, as I have a paper in preparation on the subject (or rather, the timing of the extinction) and 2) I haven’t actually seen the fake documentary and it would be pretty tacky of me to further rake the muck, and others such as Brian Switek have done a good enough job already (Here and here).

On another note, it is pretty depressing to see what the Discovery Channel has devolved into: the same kind of reality show crap that’s on A&E and The “Learning” Channel. When I was a kid I couldn’t get enough of documentaries with all sorts of beautiful shots of things like reef fish, big cats in their native environment, reptiles in the desert in Africa, and sharks and whales in the open ocean. I ate that stuff up. Nowadays, all it seems like you get on DC is a bunch of rednecks in the swamp, forest, or Alaskan tundra. So many of these shows are deliberate knock-offs of deadliest catch, which I’ll admit can be mildly entertaining. At least Mythbusters and Dirty Jobs, while technically are of the reality show strain, are genuinely aimed at being educational and happen to be really entertaining; however, all of these other Deadliest Catch clones are 5% education, 95% dramatized BS.

 

Caperea, the baleen whale that, according to the Discovery Channel, was recently rediscovered and formerly thought to be extinct since the Pliocene. 

Okay, rant over, now for some (real) science. In the show, numerous lines of evidence were touted (or completely invented) to indicate that C. megalodon was not in fact extinct, but was still very much alive. One of these arguments was the ‘fact’ that the pygmy right whale (Caperea marginata) had been thought to be extinct for the last two million years and was recently ‘rediscovered’ – which suggests that relatively large bodied marine vertebrates in the open ocean can go undetected, and contribute to someone’s hopes that such a monster as C. megalodon might have survived. However, this is so patently false it’s absurd, and I have a good idea where this misleading tid bit originated from. I mean, the claim is just so... odd that if it weren't a misrepresentation of my lab's researcg, it would be hilariously befuddling. Some of what follows is going to be a brief re-tread of some previous posts on the pygmy right whale I’ve done, so I’ll be brief. Here are a list of things we actually know, written in order so as to tell the story of how the writers got it so damn wrong:

1) The pygmy right whale did not have a published fossil record until 2012. Neobalaenids were not known from the fossil record – at all – until a fragmentary earbone was published from the late Miocene of Australia (read about it here), and a nearly complete skull was published from the late Miocene of Peru (Miocaperea: read more here). This disproves the argument that Caperea was long known only from a Pliocene, pre 2 Ma fossil record. In fact, the fossil record of Caperea has only been known to science for about 11 months.

 

The skull of Miocaperea pulchra, one of two published neobalaenid fossils. The pygmy right whale fossil record did not exist in the published literature until 2012 (contra the Discovery Channel).

2) Caperea has been known about since the 19^th century. It was encountered during southern hemisphere voyages in the 1830’s and 1840’s. Sure, it is a poorly known extant whale – but it is far better known than many ziphiids, some of which are known from thin threads of recorded data. It, however, is by no means anything close to what you could call a cryptid or anything marginally close to a rediscovered ‘living fossil’ like the coelacanth; it was known in the flesh for a century and a half before it ever had a fossil record, quite the opposite of the claim in the show.

3) Caperea has recently been reinterpreted as a member of the family Cetotheriidae, based on phylogenetic research by my adviser, R. E. Fordyce, and fellow labmate Felix Marx. The Cetotheriidae were formerly known only from the fossil record, and were known – at the time of their writing – to have a fossil record as young as about 2 Ma, based on the youngest fossils of my favorite whale, Herpetocetus. Subsequent work published by myself earlier this year documented Herpetocetus surviving as late as the middle Pleistocene (~1-0.7 Ma). This effectively means that Caperea has been transferred in terms of familial placement – i.e. it’s a cetothere rather than a member of the (formerly) monotypic Neobalaenidae. This obviously doesn’t change the status of Caperea as far as extinctions go; it still has a shitty fossil record, although it’s now identified to be more closely related to a group with a decent fossil record.

Which brings me to point 4) When the Fordyce and Marx phylogeny was published, the LiveScience press release ended up with a pretty misleading title: “Found: Whale thought extinct for 2 million years”. The rest of the article is fine, and accurately describes the research, but I don’t know what happened with the title. When you search on google for details about that research, that article comes up, and I believe that this poorly titled press release happens to be the origin of the “Caperea was thought to be extinct!” myth cited on the fake documentary.

So there you have it. The writers must have seen that press release and latched onto that as gold, to the exclusion of all the good, accurate information on the web regarding the pygmy right whale. Oddly enough, a I wrote a decent synopsis of the research here on my blog (see here), and had the writers of the show bothered to read it, the published article, or even the rest of the mis-titled press release, this misrepresentation of our lab’s research could have been totally avoided.

For more on Caperea:

The first fossil pygmy right whale. Coastal Paleontologist down under.

Introducing Miocaperea. Coastal Paleontologist down under.

Resurrection of the Cetotheriidae from extinction. Coastal Paleontologist down under.

Caperea alive! Tetrapod zoology.

Did I mention that Caperea is really, really weird? Tetrapod Zoology.

There's something about Caperea. Laelaps.

Once more on little Caperea. Tetrapod Zoology.

Otago Peninsula preview

Two weekends ago my labmate Cheng-Hsiu Tsai (nickname Tsai) lent us his car for a day so that I could drive Sarah, visiting EAPSI student (and coauthor) Morgan Churchill, and new labmate Josh Corrie out to the Otago Peninsula. Sarah and I don't have a car here, and can't really afford to rent one. So this was a great opportunity, and we saw a lot of great stuff out there (sadly, no penguins though). On the way back, I took a large panorama from the peninsula looking back west along the Otago Harbor:

(Click for mega-size)

The mountain on the right is Mt. Cargill, and the bright white light left of center is the Forsyth stadium; the black patch to the right of it is Signal Hill, with the lights of Ravenbourne below. Dunedin is obvious all the way to the left, and on the right extreme is Port Chalmers.

More photos are coming soon!

A new Pelagiarctos specimen, part 2

 After the test casts with dental plaster turned out pretty well, I knew the mold would be well-suited to move on and upgrade to resin. In our lab in the geology dept. we have laminating resin, which works best in thin coats; it reproduces fine details excellently – but if poured into a thick, solid shape, it can crack from expansion during the curing process. With small molds – this one for example required about 5ml of resin or plaster – it won’t expand enough to crack.

Pouring resin is a bit less friendly than plaster – it irritates the eyes, and is harmful if inhaled, and the catalyst is even worse on both counts. Because of these issues, goggles, a respirator, and gloves are necessary (and a labcoat, of course). Pouring resin takes a number of mostly simple steps. First, removing any remaining resin fragments from the last pour is a necessity. A cheap cup can be used on a scale which reads to the hundredths place (and expect it to get messy - you will drip resin and silicone during mold making onto the scale), and make sure to tear off. The appropriate catalyst needs to be measured in tiny increments, and if you need under 10ml, you’ll be able to count the number of drops of catalyst going into the cup. Too much catalyst – particularly for batches of resin over 10-20ml – and the mixture will heat up and potentially catch fire.

Freshly poured resin cures in the mold.

After pouring the resin, carefully mix (so as not to introduce air bubbles) with a popsicle stick or tongue depressor, and then mix in any pigment (otherwise, the cast will be slightly translucent; surface details will be less evident unless a solid color pigment is mixed in). When mixed, two techniques can be used for filling the mold: a straight pour, or a thin layer can be painted into the mold. Painting a thin layer was necessary in order to fill all the cusps at the base of the crown of this tooth. After the cast is poured, it will take about 45-60 minutes to cure. After about 30-45 minutes, it will be solid enough to remove; if it is still warm and slightly pliable, then trimming it with an X-acto knife will be possible (and next to impossible if it is totally cured). However, if it is too pliable, then holding the cast while trimming it can leave imprints of your fingerprints in the resin.

After a couple weeks of molding and casting, now I have more than ten high quality casts of the Pelagiarctos tooth. I’ll be able to send the mold and the original specimen back to Wyoming, and casts to numerous institutions including UCMP (Berkeley), the LA County museum, Cooper Center (Orange County), San Diego Natural History Museum, Smithsonian, and probably the National Museum of Nature and Science in Tokyo (pretty much to any museum where fossil walruses – or walrus researchers – exist).
 

Unfortunately I don't have any more photos from the casting process; your gloves tend to get pretty sticky from resin and catalyst, and I wouldn't bother ruining an expensive camera just so you guys can have a couple extra photos (no offense). Anyway, here's the finished product - two test casts and a bunch of resin casts (there are even more now).

This isn't the end of the molding and casting, however; we've gotten a hold of a modern New Zealand sea lion skull, currently loaned to us from Steve Dawson over in Marine Sciences, who has graciously allowed Carol to take a premolar and section it (for science). With this, we'll have teeth of the NZ fur seal (Arctocephalus forsteri) and the sea lion (Phocarctos hookeri) for SEM comparison with Pelagiarctos thomasi. Steve knew that we have the capability of making high quality molds and casts, so he said it would be alright if we molded and casted the tooth first. Here are some photos from the second mold.
 

Silicone is poured into the acetate dam, around the tooth. Trust me, it's buried in there.

We're left with a solid cylinder of silicone with a tooth buried in the middle, and a 

clay plug on one end.

An X-acto knife is used to make a planar cut so that the mold can be split and the tooth (and later, casts) can be removed. In order to cut everything, the two halves can be gently pulled apart in order to see the remaining uncut portions of mold. It's probably important to be careful here and not end up with a ragged seam line, as that can add quite a large amount of 'flashing' (paper-thin amounts of resin that fill in the seams, which you can see on plastic model parts and cheap green plastic army men).

The clay plug is removed...

...to show the root of the tooth.

And Voila! The tooth is removed, with a great mold left. I've made several casts of this 

specimen and they've all turned out great.

A visit to Tunnel Beach

Without a car, it's a bit difficult to make it out of town here in Dunedin. We've made friends with some other folks who own cars, who have been nice enough to invite us on trips out of town. Last fall (spring in the northern hemisphere) our friend Luke, the scientific illustrator in the geology department, took us down to Tunnel Beach southwest of Dunedin. It's a beautiful spot, and famous for its fantastic exposures of the Caversham Sandstone - a pervasively bioturbated, thick, and monotonously bedded middle to outer shelf sandstone deposited during the early Miocene. A few cetaceans have been recovered from the unit, including some kentriodontids studied by my former labmate Gabriel Aguirre-Fernandez, and some other bits. It is generally considered to be coeval with the Mt. Harris Formation, a shaley unit that overlies the late Oligocene Otekaike Limestone further north in the Waitaki river region.

 The view back east towards Dunedin and the peninsula from the top of the hill.

 The sea cave at Tunnel Beach.

The view west along the cliffs towards Black Head and Brighton.

Sarah getting a bit closer to the edge than her mother appreciates.

 Sarah on the point at Tunnel Beach.

View east from Tunnel Beach.

The best wedding gift ever

Back in 2011 my wife and I got married up at Lake Tahoe in California - being paleontologists, we generally have stranger tastes than most folks. Previous birthday presents from my wife Sarah have included skulls of racoons, badgers, and river otters, rock hammers, clam knives, field bags, and others. Sarah's first rock hammer was a birthday gift from me, and I've given her similar presents since. For the purposes of a wedding present, however, she would have been pretty disappointed if I had gotten anything other than something expensive in a tiny box - but she decided to have a little more fun and be a bit more unorthodox about her wedding present for me.

It arrived a few days before the wedding, in a large (and heavy) box. She had been boasting about how awesome the present was, and I suspected it was a skull of some sort.

 Awesome. My favorite animal.

Also, if I had a spirit animal, this would probably be it. She was initially disappointed when she found out it wasn't a complete skull - but to be honest, I'm happier with this as when I get my first office in the US, it will look totally awesome on a wall. Edit: this is a Bone Clones cast.

A new Pelagiarctos specimen, part 1

Late last year on the fossil forum (www.thefossilforum.com) where I help identify fossils for amateur collectors, I saw a photo of a pinniped tooth collected by my good friend and Tate Museum preparator JP Cavigelli from the Sharktooth Hill bonebed. It looked like it had a few too many cusps to represent any pinniped other than Pelagiarctos thomasi, so I asked JP to take a few measurements - and sure enough, the tooth is huge, and double the size of the smaller walrus Neotherium mirum. The additional cusps and presence of a cuspate lingual cingulum (cingulum is a ridge of enamel just above the base of the crown, and lingual means the tongue side of the tooth) are unique among walruses to Pelagiarctos and Imagotaria. Imagotaria is far younger (late Miocene, rather than middle Miocene). JP was kind enough to donate the specimen to the Tate museum where he worked, and Morgan Churchill and I actually referred the specimen to Pelagiarctos thomasi in our PLoS article on Pelagiarctos.

The new specimen of Pelagiarctos thomasi (TATE 2694) collected by J.P. Cavigelli in 2012.

Preparator Sophie sculpts a pedestal onto the broken root of the tooth.

Morgan is down here in New Zealand and Australia for a two month EAPSI (East Asia and Pacific Summer Institute) fellowship, with the intent to utilize a statistical analysis to test the phylogenetic position of the problematic Pleistocene sea lion Neophoca palatina from New Zealand. About two months ago my labmate Carolina Loch-Silva suggested Morgan bring a Pelagiarctos tooth with him in order to secure an enamel fragment to examine its enamel structure - possibly as a way to take another stab at the feeding ecology of Pelagiarctos. To recap, Larry Barnes (1988) originally hypothesized Pelagiarctos to be a macrophagous 'killer' walrus, although our reevaluation of the data (Boessenecker and Churchill 2013) suggests that it was a dietary generalist like most modern pinnipeds, including robust sea lions.

The tooth on its pedestal.

Even though Carolina's sampling method will not remove much of a tooth fragment, I was still interested in molding and casting the specimen. There are less than a dozen teeth of Pelagiarctos in museum collections (many more exist in private hands, which us researchers have to ignore for all intents and purposes), it would be useful to provide casts of the specimen to various west coast museums such as UCMP, LACM, the San Diego NHM, and the Cooper Center; casts of the specimen will also be sent back to the Tate Museum, the Smithsonian, and the National Museum of Nature and Science in Tokyo.

Mixing silicone and silicone catalyst requires careful measuring on a scale.

 The tooth on its pedestal and base, with a single coat of silicone painted on to capture fine detail. Unfortunately, this coat never cured - we're using somewhat expired silicone, and it can be finicky when it cures, often requiring extra catalyst. We ended up pulling the rubber off and redoing it as a single pour.

For an easy small fossil like a tooth, comparably fewer steps are necessary for molding and casting. Firstly, in order to keep silicone (or latex for that matter) from invading small pores and cracks and pulling out fragments of bone, a consolidant such as vinac or PVB needs to be painted on the specimen. For a small specimen like this, there are three ways to mold it: 1) with latex, paint several layers on to make a sleeve, which can be pulled off the tooth (or cast) and inverted; 2) a two part mold, or 3) a single pour 'plug' mold. For small specimens, my friend and fellow student at MSU Denver Fowler suggested cutting up older latex molds, pouring the fragments in to a film canister, embedding the small fossil within said latex clippings, and then pouring in latex to fill the voids and form a nice plug; after enough casts are made, you recycle the latex and do it again with another specimen. We decided to do a similar single pour mold. Instead of using a film canister, Sophie made a small cylinder of clay as a base, planted it on a flat sheet of clay, and then taped a cylinder of plastic sheet and planted that into the clay to act as a dam. We first tried to paint a layer of silicone onto the tooth to capture fine details, but for whatever reason it never cured properly, so Sophie stripped that layer off and we mixed up some more silicone for a single pour. We ended up having too much silicone mixed up, and asked Ewan if he had anything handy which we could mold, so he gave us a small squalodontid tooth.

The squalodontid tooth showing the acetate sheet dam. At this stage, once the silicone is mixed, it can be poured directly into the tube.

Both plug molds, with dental plaster freshly poured and waiting to cure.

Next up: pouring plaster and resin casts.