What a week it's been for palaeontology in the news, especially related to taphonomy! There's a new paper on the taphonomy of the Cleveland-Llyod Dinosaur Quarry, a paper describing featherless patches of skin on Tyrannosaurus rex, and now a mid-Cretaceous 'bird' (avialan) hatchling has been found encased in Burmese amber!

The hatchling is from a now-extinct group of avialans called enantiornithines. It is a 'bird' in the broadest sense, but just not from the same lineage that modern-day birds belong to (the neornithes).

The preservation of this specimen is fantastic. The right foot is clearly visible with the podotheca, claw sheathes, and feathers still intact. More difficult to see is the head and neck of this hatchling, but with the help of micro-CT and x-ray, Xing et al. (2017) show that they are present and also well preserved.

How did this hatchling end up in a lump of amber? Amber is preserved tree sap or resin, and while tiny animals such as insects are normally the victims of sticky-sap entrapment, small vertebrates such as frogs, lizards, and (as described by the same authors in a previous paper) a small dinosaur or bird tail have also been known to get caught in ancient resin. As for this hatchling, the authors propose that only part of the body was covered in resin (either during or soon after death), with the rest of the body remaining uncovered and exposed to the elements. Later, a second resin flow covered the remainder of the body.

Xing, L., O'Connor, J. K., McKellar, R. C., Chiappe, L. M., Tseng, K., Li, G., Bai, M., 2017. A mid-Cretaceous enantiornithine (Aves) hatchling preserved in Burmese amber with unusual plumage. doi: 10.1016/ j.gr.2017.06.001

I had a chat with Greg Wah and Dan Beeston at the podcast Smart Enough to Know Better about the taphonomy of two beautifully preserved dinosaur fossils in the news: Zuul crurivastator, a new ankylosaur from Montana named after a Ghostbusters character (image below left), and a beautifully preserved nodosaur from the oil sands deposits of Alberta (image below right).

​Have a listen to Episode 126 here:
​https://smartenough.org/episode/126.0

​(In the podcast I talk about a giant tortoise that floated in the the ocean for many months and survived [PDF], but I called it a 'turtle'. My bad!)

EDIT (30/5/2017): The Dinosaur Expeditions centre, where the fossil will be displayed, have offered the following equally likely explanation for this footprint-like impression: 
"Localised compression fractures, deformation of surface & underlying cancellous bone matches a tridactyl print. Parsimonious explanation." (via this tweet).

A dinosaur footprint has been found embedded on the surface of dinosaur backbone, according to the Isle of Wight County Press.

It seems extremely improbable, but it isn't impossible. In taphonomy, we always consider the effect of trampling on decomposing bodies: if a body is laying near a lake or other water source, then it is likely that many other animals will be passing through that area and accidentally walk over the body. This can crush and scatter bone, but I've never heard of a foot landing precisely on the body (centrum) of a vertebrae and leaving a footprint behind.

In this case, it seems a small theropod (meat-eating) dinosaur has walked over the top of a decaying sauropod (long-necked) dinosaur carcass, at one point stepping precisely on a vertebra.

​​From what I can see in the photograph, it appears that there is still some mudstone covering the centrum. I thought perhaps the footprint was in the mud layer covering the bone, but the articles I've read suggest that the theropod foot crushed the bone. The rest of the vertebrae has been preserved quite well. This sauropod must have been decayed enough so that the vertebrae had disarticulated and lay centrum-side up, with the centrum and bone marrow softening and rotting while the rest of the bone remained fairly solid before it was trodden on. Again, improbable, but not outside the realm of possibility.

I also considered whether the footprint was pressed into a muddy bank first, and the bone later laid on top of it, 'sticking' the two together. However for this to be the case, the footprint on the bone would have to be a cast of the original print and would appear raised off the surface of the bone, rather than sunken in like a mold.

I look forward to seeing a thorough examination of this specimen, as if this impression is a theropod footprint, it shows direct evidence of this small theropod and large sauropod co-existing in the same part of the ancient Wealden landscape.

References
County Press reporter, 2017. "Unprecedented dinosaur discovery made on the Isle of Wight". Isle of Wight County Press. URL: http://www.iwcp.co.uk/news/news/unprecedented-dinosaur-discovery-made-on-the-isle-of-wight-315188.aspx Accessed Sunday 28th May​, 2017.

Dinosaur Expeditions (DinosaurInfo). "Localised compression fractures, deformation of surface & underlying cancellous bone matches a tridactyl print. Parsimonious explanation." 29th May 2017, 5:48pm. Tweet.

A white-tail deer has been caught on camera eating human remains.

The remains were part of a taphonomic experiment at the Forensic Anthropology Research Facility (FARF) in Texas, USA, where they were studying what types of scavengers visit human carcasses. They were left uncovered with cameras photographing anything that came to scavenge them. Imagine being the person reviewing those images, expecting to see coyotes, or racoons, or turkey vultures, and instead uncovering the first recorded instance of human bone-munching deer.

​This is not the first case of a classically herbivorous (plant-eating) animal eating bones from rotting carcasses--a behaviour called osteophagy--but it is the first time a deer has been captured nibbling on human remains.

Herbivorous animals practice osteophagy when they need more phosphate, calcium, and other nutrients in their diet. Porcupines, giraffes, cows, and even tortoises have been seen chewing on bones, most often already dry and easily accessible bones like ribs.

When recording traces of tooth-marks on bones in the modern, archaeological, or palaeontological record, it is important to remember that not all scavengers that interact with carcasses are trying to consume flesh. And that while carnivorous scavengers typically eat soft tissue and fresh bone leaving behind puncture holes and pits, bone-eating herbivores chew on the ends of older bones with teeth normally used to eat plants leaving behind long scores and forked splinters.

References
Meckel, L. A., McDaneld, C. P., Wescott, D. J., 2017. White-tailed Deer as a Taphonomic Agent: Photographic Evidence of White-tailed Deer Gnawing on Human Bone. DOI: 10.1111/1556-4029.13514.

Warm, dark-brown, sticky tar oozes out of the ground at Rancho La Brea in California, creating deep lakes of asphalt belching forth bubbles of methane. These asphalt lakes, or tar seeps, are particularly hazardous to animals passing by, trapping and swallowing up carcasses whole. And the tar seeps at La Brea have been trapping animals and luring predators to their deaths for 50, 000 years.

Rancho La Brea has produced around 3 million Pleistocene and Holocene fossils belonging to hundreds of vertebrate, invertebrae, and plant species, including dire wolves, sabertooth cats, mammoths, ground sloths, hawks, geese, owls, snakes, frogs, scorpions, spiders, ants, beetles, poison oak, juniper, red cedar, and thistle. The majority of fossils belong to mammalian predators that probably attempted to eat rotting carcasses stuck in tar, then found themselves similarly stuck in the asphalt ooze, then died and decayed thus becoming new lures for passing predators and scavengers. But no-one is quite sure how long decay might take before the carcass becomes a less appetising jumble of asphalt-soaked bones, and if those bones separate from each other and are pushed along by currents while floating at the surface, or disarticulate after sinking to the bottom of the tar seep.

A new paper by Brown et al. (2017) explores these questions by using actualistic taphonomic experiments. The authors took limbs from carcasses of a modern mammalian predator, the bobcat (Lynx rufus), and placed them in wire cages that were then lowered into tar seeps in Chivo Canyon, California. Over 10 weeks, they removed a limb from the tar seep every 2 weeks and noted how much soft tissue had decayed, as well as the types of microbes feeding on the flesh and living in the tar.

​They found that decay occurred surprisingly quickly and surmised that a rich bacterial community exists in the tar seep, ready and waiting to consume flesh. Their microbial tests showed the bacteria did not hitch-hike into the tar seep on the bobcat carcasses. We know that hundreds of petroleum-eating bacteria species already exist in the tar seeps - they produce the methane bubbles - but it now seems that there are bacteria living in these tar seeps that specialise in eating organic material.

The authors conclude that modern bobcat limbs take around 2-3 months to fully decay in tar seeps. It appears that without the presence of the experimental wire cage, their bones would disarticulate (separate) after only a few weeks. The authors propose that the majority of decay and disarticulation therefore occurs at or just below the surface of tar seep, with single bones then being buoyed along by wind or water currents. The authors admitted that while these smaller limbs portions immediately sank into the tar, larger bodies may float at the surface while decaying with parts of the body exposed to the elements, and plan to conduct more actualistic experiments using whole carcasses in the future. I'd like to see more data on the temperatures of the tar seep, and how that might speed up or slow down decay depending on the types of bacteria present. Overall, this is a very thoughtful and interesting paper, so check it out (if you can get past the paywall).

Brown, C., Curd, E., Friscia, A. 2017. An actualistic experiment to determine skeletonization and disarticulation in the La Brea tar seeps. PALAIOS, 32:119-124.

This crisp and dynamic illustration of a Protoceratops is one of the featured dinosaurs from the Institute for the Study of Mongolian Dinosaurs (ISMD), established by palaeontologist Bolortsetseg Minjin (who has been instrumental in repatriating fossils stolen from the Gobi Desert for auction in the USA).

Two weeks ago, a group of scientists started chatting on Twitter about carnivores and their prey, and started sharing gory pictures of carcasses. Things got a little (lightheartedly) competitive, and after Julien Fattebert shared a photo of a leopard cub killed by lions, and added the hashtag #bestcarcass, a Twitter battle was born.

Since then, Twitter users have shared fascinating, strange, and sometimes disturbing images of decaying animals from all over the world in weird and wonderful poses.

Listed below are my top 10 picks (in no particular order) for some of the most taphonomically interesting #bestcarcass contenders. And, unsurprisingly, some people may find the follow images disturbing: click 'read more' at your own peril...

Geology is an important component of any taphonomic investigation. This helps to 'set the scene' when considering potential taphonomic pathways: what environment did these ancient creatures live in? What happened to their bodies after they died? What environment were they buried in, and how quickly were they buried?

To this end, my colleagues and I have just published a paper about the ancient environment of the Winton Formation at Isisford to better understand the taphonomic history of crocodyliforms, osteichthyan fish, and dinosaur fossils uncovered there. We propose that around 100 million years ago, Isisford lay in the middle of a river delta that flowed into the nearby Eromanga Sea. 

We came to this conclusion by studying the sandstone concretions that encase each of the fossils found at Isisford. These concretions formed when sand grains were cemented together with calcium carbonate (calcite) from calcium-rich groundwater. The majority of fossils appear not to be distorted or warped in any way, and as fossilisation occurs under high temperature and high pressure, it seems the concretions surrounding the buried bones and afforded them some protection. If this calcite cement, and therefore the concretions formed before fossilisation, then information about groundwater quality where the bones were buried would be locked away in the calcite minerals themselves - specifically, isotopes of carbon and oxygen. 

​We tested the carbon and oxygen stable isotopic values of the calcite cement, and by comparing our results to what is ‘typical’ for fresh water and sea water, found that it formed in a brackish water environment. This wasn’t terribly surprising: the regional geology indicates that the Eromanga Sea was nearby Isisford at this time, but until now we hadn't known whether it affected the environment at Isisford or not. When we examined geological core logs from near Isisford, and compared it to the types of rocks we found at the site, we concluded that these animals were buried in a river delta that flowed into the sea, with fresh river water mixing with salty ocean water. Unfortunately, there aren’t large exposures of Winton Formation at the site that would allow for typical facies analysis, but we worked with the material we had and came up with some pretty solid conclusions.

Our next question is: if these animal's carcasses were buried in a river delta, did they die there or were their bodies washed in from far away? Did they even live nearby at all? That is the subject of future papers that we will be publishing mid to late next year.

References
Syme, C., Welsh, K., Roberts, E., and Salisbury, S. 2016. Depositional environment of the Lower Cretaceous (upper Albian) Winton Formation at Isisford, central-western Queensland, inferred from sandstone concretions. Journal of Sedimentary Research, 86: 1067-1082. DOI: 10.2110/jsr.2016.67

​The powerful bite of a crocodile can cut through flesh and bone. Their teeth puncture, scratch, scrape and crush the skeletons of their prey. They leave behind tooth marks etched into bone, taphonomic traces which have been identified in the fossil record, and can tell us about the feeding behaviours and morphologies of ancient crocodylians. Or so we thought.

A new study by Drumheller et al. (2016) found that crocodile bite marks on bones do not seem to differ between crocodiles young and old, or male and female, or long-snouted and short-snouted. They collected bones bitten by 21 species of modern crocodylians and studied the types of bite marks left on bones surfaces – whether they were pits, punctures, scores, or furrows, and whether these marks were bisected (with extra notches or scoring from serrated teeth) or hooked (marks that changed direction). They compared the types and shapes of these bite marks to the snout shape, size, sex, age, feeding behaviour (the famous ‘death roll’), and captive or wild status of each individual crocodylian that created them. They found no significant difference between the shape of the bite marks and the individual who made them – even for crocodylians of different ages, with different snout shapes, or different feeding behaviours!

However, they did determine that bisected bite marks – those showing extra notches or scoring – were indicative of the teeth of crown Crocodylia. And as bisected bite marks have been found on fossil bones, the culprits can be successfully identified as a crocodylian (or perhaps a non-crocodylian crocodyliform – that is, animals not related to modern crocodylians, but instead an ancient offshoot of crocodyliforms that are now extinct). But not every individual crocodylian creates bisected bite-marks every time they feed, depending on whether their teeth are freshly erupted and sharply serrated, or old and worn down.
​
So, it seems you might be able to identify a crown Crocodylian as the culprit of a bone bite-mark, but cannot predict its age, sex, snout shape, or which method it chose to dispatch of its prey.  

References
​
Drumheller, Stephanie K., and Brochu, Chris A. 2016. Phylogenetic taphonomy: a statistical and phylogenetic approach for exploring taphonomic patterns in the fossil record using crocodylians. PALAIOS, 31: 463-478. [Paywalled]

Soapbox Science is coming to Australia for the first time!

As a part of National Science Week 2016, Soapbox Science will take place in Brisbane where leading female researchers will talk about their scientific projects and why they love science.

Soapbox Science is a public speaking and outreach event aimed at encouraging girls and women to take up careers in science. You can hear all about why these scientists love their jobs, ask questions about their research, and see that women belong in the sciences just as much as men do.    

I will be speaking at this years Soapbox Science event at King George Square in Brisbane, on the 20th August between 1-4 pm. My talk title (coming as no surprise to long time readers of this blog) is: “Fossil forensics: how taphonomy helps us understand the death and decay of dinosaurs”. Keep an eye out for updates between now and August!