Bones That Look Like Other Bones: A MiniPost About Rodents and Fish

Yet another minipost in my comparative anatomy series! But this one might be the strangest paring of all.

Rodents and fish – could there be any more different animals? And yet, I find that students just starting out in archaeology tend to confuse the two together. To be fair, it’s very understandable – the size of rodent bones can be comparable to the size of many fish bones. So let’s break it down and see how different they really are.

Rat and Fish Cranium

For starters, let’s look at the cranium of a rat (left) and an Atlantic cod (right). As you can see, most elements of the skeleton look completely different. The rat has the sort of skull you would expect to see with any animal, while the fish…well, fish are basically made of a head and a tail, so most fish bones you find will be part of the cranium. As I’ve mentioned before in my previous post on fish bone, they will also have a different sort of texture and look compared to mammal bone – in my opinion, its a very “fish-like” texture, a bit shiny and flaky. Always a good giveaway that you’re dealing with a fish!

Rat and Fish Vertebrae

So how is it possible to even confuse the two? Well, let’s look at something a bit trickier…here’s the vertebrae from a rat (left) and from a fish (right). Now, if you don’t know that there’s a difference in shape between rat and fish vertebrae, you might not be able to differentiate the two right away. And given how weird vertebrae can be in varying shapes between types of vertebrae in an individual body, who knows! Maybe they’re from the same animal?

Luckily, there is a visual difference between the two. Rat vertebrae look relatively similar to any other mammal vertebrae (“relatively” being the key word here, of course…but talking about the differences in mammal vertebrae is a post for a different day!). Fish, on the other hand, have very distinct-looking vertebrae and vertebral bodies. Unfortunately, distinguishing between the two can be more difficult if the vertebrae are more fragmented – I’ve seen many students get the two confused if most of the vertebral arches and “wings” are missing.

“But Alex!” I hear you say, “these bones look so different, I don’t believe that anyone could get them confused!” Okay then…let’s take two random, slightly fragmented bones from a herring and a mouse then, shall we?

Mouse scapula and herring fragment
Can you tell the difference?

As you can see, it can get tricky! Fragmentation, size, preservation of bone – these are variables that you encounter with archaeological bones that make things a bit more challenging than you’d think! The best way to get better, of course, is to practice, practice, practice. It gets easier…

…well, eventually.

 

Spooky, Scary, Inaccurate Skeletons

Happy Halloween from Major Buzzkill! To celebrate, I’m going to ruin everyone’s fun and take a look at a recent trend in Halloween decorations: the inaccurate animal skeletons.

Let me preface this by saying I think these decorations are super cute and if I ever get past my ever-growing student debt and get a house, I will most likely buy a whole menagerie of spooky animal skeletons.

However…as cute as these decorations are, the zooarchaeologist in me dies a little inside when I see how…well, unrealistic they are.

Let’s start with the raven. Thanks to Mr. Poe, the raven is probably one of the spookiest birds for the season. But what’s even spookier is…well, whatever that plastic skeleton is (left). In reality (right), raven skeletons are a less more hollow, with lots of space throughout the skeleton and larger long bones. Also, the fake raven’s eye sockets are terrifying…or is it just me?

Unsurprisingly, bats have also become spooky, scary skeletons for Halloween. Now, this was a little unfair in that I’m not entirely sure what kind of bat the decoration was going for (seen on the left, the skull is probably a little closer to a vampire bat), but for the sake of comparison, here’s a fruit bat (right) – I’ll give the fake skeleton credit for the bones of the wings being kinda…sorta…close. But look at those ears!

Speaking of ears…what I’ve noticed is that most of these animal skeleton decorations get these strange, bony ears – probably for the sake of differentiating them, but how weird are they?! As for cats…you know, the fake one (left) almost gets it right…minus the ears and the significantly elongated skull that most domestic cats (right) lack – although that’s probably just to give them a cute nose.

And now…perhaps one of the scariest decorations of all…the dog. Judging by those weird bony ears alone (left), I imagined that it was supposed to be a Rottweiler (right)? I’m actually fascinated by the ears on this one…are they weird, floppy bones? How do they work? If anyone wants to brainstorm with me later, let me know.

Again, this is all in good fun – I understand that its a silly Halloween decoration and that some adjustments are made to make them recognisable to the general public! But seriously…what the hell is this, Party City?

Skeletal Spider
I mean…come on, what the hell?

Have a safe and fun Halloween, everyone!

All skeleton decorations are from Party City and all actual skeletons are replicas from Bone Clones.

Bones That Look Like Other Bones: Rodent Week Edition

According to Twitter, last week was #RodentWeek. So here’s another comparative anatomy minipost about some commonly found rodents: squirrels, rats, and mice!

Skulls and mandibles from left to right: squirrel, rat, and mouse.

Now, when it comes to differentiating between these three, size matters. As you can see from the above photo, there’s a huge difference between the skull of a squirrel and the skull of a mouse!

Rats and squirrels may be a toss up, depending on the age and size of the animal – but there’s differences in the shape as well! Personally, I’ve always associated squirrels with a more rounded cranium than rats, who normally have a more flattened skull, but your mileage may vary on that.

Skulls from left to right: Squirrel, rat, and mouse

What will be very difficult is if the only elements available to you are the incisors, or the front teeth. Again, size is beneficial here, as otherwise incisors will more or less look the same across the board for rodents!

Also, take another look at those skulls – lots of similarities between the mouse and rat, less so for the squirrel. And you can kinda see what I mean about the more flattened top of the rat in comparison! There’s a similar elongation that both the rat and mouse share as well.

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Mandibles from top to bottom – squirrel, rat, and mouse

For the most part, identification of rodent remains requires close examination. As you can see above, there are many slight differences between the different rodents, but it requires a bit more study than say, differentiating between a rodent and a frog.  In some cases, complete identification may not be possible without some references on hand!

That said, those incisors are often huge clues that point towards a rodent – if all else fails, at least you might be able to point to that! Those incisors also create a very specific gnaw mark on bones that will help ID the presence of rodents at the site (this will be the topic of a future blog post though!).

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Femurs from top to bottom – squirrel, rat, and mouse

I’ve spent most of this post (as I do with most of these comparative anatomy miniposts) talking about the skulls for identification – to be honest, skulls are usually the easiest part of the body to ID and compare. So here’s something a bit different – let’s quickly look at some long bones of rodents.

As I said previously, rodents require a bit more investigation in differentiating between them. As you can see by the femurs above, there are certainly some differences between a squirrel, rat, and mouse! Compare the straighter edge of the squirrel femur towards the more curved femurs of the rat and mouse, for example.

I hope these miniposts are somewhat helpful for you – obviously a more detailed comparative anatomy post would be much longer, but hey! Maybe one day I’ll write up some manuals – let me know if that sounds interesting to anyone!

On Animal Teeth, or Why I’m Not a Dentist

Since my last post using comparative anatomy was rather popular, I figured I should write a similar post for this week, starting with the most important part of the skeleton for zooarchaeologists (in my opinion) – teeth!

In my experience, teeth are the best skeletal elements to recover. Why? They’re one of the more easily identifiable parts of the skeleton and one of the more variable skeletal elements across different species.

Unfortunately for me, they’re also some of the…well, grossest parts of the skeleton. Nothing will put the fear of root canals and cavities in you like looking at any worn down tooth from a cow or sheep!

Here is a small sampling of teeth from different animals and how you can easily identify them, in very informal and non-technical-sounding ways:

Pig

Pig teeth might be the weirdest looking teeth I encounter regularly (besides my own…and if you’re my dentist reading this, no I will never get braces, I can’t afford them!). The easiest way to ID them is to recognise how similar they look to human teeth…but just slightly off. Basically, I like to say that the molars look like human teeth that have popped a bit like popcorn. Yes, I’m aware of how gross that is – but that’s how I remember them!

Pig Teeth
Yuck – here are the teeth of a domestic pig.

Dog

Dog teeth have a sort of “wave”-like shape to them that makes them a bit distinct. Often, I’ve found that their molars and premolars not as pointed and sharp as a cat’s teeth (see below), but that isn’t always the case, of course. In any case, dog teeth are quite bulky in comparison to cat teeth.

Dog Mandible
A detailed look at a dog mandible (Photo Credit: Melissa Rouge, Colorado State University)

Cat

Cat teeth have a somewhat similar shape to dog teeth, but I’ve found that they are somewhat more pointy than most dog teeth (although again, this may not always be the case). In comparison to dog teeth, cat teeth are also relatively smaller and not as bulky. A larger set of teeth that may look cat-like could indicate you’ve got another member of the Felidade family (i.e; lion, lynx).

Cat teeth
The dainty, pointy teeth of a domestic cat.

Sheep

The easiest way to ID sheep teeth is to check for a “house shingle”-like appearance. I have found that in comparison to animals with similar looking teeth (cows and horses), sheep teeth are also rather thinner. Be careful, though – sheep and deer teeth are remarkably similar in size and appearance!

Sheep Teeth
The maxilla and mandible of a sheep – note that house shingle look!

Cow

As mentioned above, cow teeth are similar in appearance to sheep with a slight “house shingle”-like appearance. However, given the difference in size, cow molars and premolars will be larger and bulkier, usually.

Cow teeth
Compare these cow teeth with the sheep teeth above

Rodents

And finally, some of the smallest teeth you’ll run into: rodents! To be frank, if you find very small teeth, it is most likely from a rodent of some kind. The front incisors may be a bit more difficult to ID if found alone as they are much larger than the other teeth and may be mistaken for a bit of rib bone. These teeth are what create the pattern of gnawing attributed to rodents that looks like long striations or lines on the bone (more on that in a future post!).

Rat teeth
The skull and mandible of a rat – look at that incisor!

If you’re looking for a more in depth comparison of mammal teeth, I would recommend Mammal Bones and Teeth by Simon Hillson (1992). It’s a great guide that I use in my work with some really clear diagrams.