Belated Friday mystery object #328 answer

The other Friday I gave you this specimen to have a go at identifying, but alas when the time came to write an answer I was at the Natural Sciences Collections Association (normally just called NatSCA) conference (which has been referred to as “the highlight of the natural history curator’s year”) and as a result I didn’t get much of a chance to write an answer or even read the comments.

Now I’m back, buoyed up by the fantastic shared experience of the conference (take a look at the #NatSCA2018 hashtag to get an idea of what was going on) and I’ve finally have a chance to look at the specimen, read the comments and write an answer. I was delighted to find some great cryptic poetry, prose and comments – some requiring perhaps a little more intellectual prowess than I’m capable of commanding, especially after an intense few days of conferencing (sorry salliereynolds!)

This specimen has a somewhat thrush-like appearance, but the hooked tip of the bill doesn’t quite sit right for a member of the Turdidae (the family of true thrushes). This somewhat raptorial feature of the beak is seen more in birds like the Laniidae (shrikes) and some of the Saxicolinae (chats). It’s the chats that I’m interested in with regard to this specimen, although not the “typical” chats. The ones I’m interested in have been moved around taxonomically a fair bit.

A lot of birds with a thrush-like general appearance will have been called a “something-thrush” by Europeans and will have kept that in their common name even after taxonomy has moved on and that species has been moved out of the Turdidae. In the Saxicolinae there are a lot of birds that were once considered thrushes and one genus in particular tends towards being a fairly dark colour with blue elements – Myophonus or the whistling-thrushes.

The distribution of glossy blue feathers on members of Myophonus is variable and reasonably distinctive. Also, because these glossy feather colours are structural, they don’t tend to fade in old museum specimens like the colour from pigments. In this specimen the blue patch is fairly dull and confined to the shoulder (or epaulet) and the rest of the plumage is even more dull – possibly faded, but also possibly because it’s female (we all know that it’s usually the boys that are show-offs).

Keeping in mind the distinctive bill, overall size and pattern of colouration, a trawl through the epic Del Hoyo, et al. Handbook of the Birds of the World -Volume 10 yielded one description that fit rather well – that of the female Javan Whistling-thrush Myophonus glaucinus (Temminck, 1823).

These forest dwelling birds live in, you guessed it, Java. They feed on various invertebrates and frogs, a slightly ramped-up diet from thrushes, necessitating a hooked bill tip to keep the more jumpy morsels from getting away.

More mysteries to come this Friday!

Friday mystery object #328

This Friday I have a feathery object for you to have a go at identifying. I stumbled across this specimen in the Dead Zoo stores and noticed it didn’t have a species identification (and the genus name also looked dubious to me). Any ideas what species this might be?

As usual, you can put your thoughts, questions and suggestions in the comments box below. Cryptic clues are fun, poems are delightful but I do love a short story, so if you want to include the identification in a bit of short prose please give it a go!

Friday mystery object #327 answer

Last week I gave you this mystery bone to identify:

As I suspected, it was simultaneously easy and difficult: easy because it’s clearly an os penis or baculum; difficult because it can be hard to narrow down the species to which a baculum belongs without having specimens for comparison. For some reason people can be funny about penis bones and, despite the fact that male animals tend to be over-represented in museums, the baculum will often have been removed or not included in skeletal mounts.

That said, Steph came closest, getting the right family with the clue:

Bac to the bear-minimum I would guess?

If you remember one of my past posts I showed an image of the baculum mounted on the skeleton of a Giant Panda in Berlin (more about this below):

Panda_penis_bone

You can see that, although it differs slightly with a bit of a dip towards the tip, it’s rather similar in structure to the mystery object.

Oddly however, it appears that this baculum on the Berlin Panda specimen has been switched for that of a different bear species. Pandas have a very distinctive reduced baculum with wings (see below), that looks nothing like this, which is more similar to the os penis of a Spectacled Bear (or possibly a Polar Bear at a push).

The mystery object is actually the baculum of a Sloth Bear Melursus ursinus (Shaw, 1791).

N.B. note that the writer of this label couldn’t quite bring themselves to write the full word “penis”

In future, should you ever find yourself with an unidentified bear penis on your hands, I suggest taking a look at this handy figure by Abella et al. 2013¹:

Baculum in laterial view of: A Helarctos malayanus; B Ursus thibetanus; C Tremarctos ornatus; D Ursus americanus; E Melursus ursinus; F Ursus arctos; G Ursus maritimus; H Indarctos arctoides; I Ventral view of the Baculum of Ailuropoda melanoleuca; J Dorsal view of the baculum of Ailuropoda melanoleuca.

So in answering one mystery object we’ve uncovered a far bigger mystery – how did the Berlin Panda end up with the wrong penis?

¹Abella J, Valenciano A, Pérez-Ramos A, Montoya P, Morales J (2013) On the Socio-Sexual Behaviour of the Extinct Ursid Indarctos arctoides: An Approach Based on Its Baculum Size and Morphology. PLoS ONE 8(9): e73711. https://doi.org/10.1371/journal.pone.0073711

Friday mystery object #327

This week I have a mystery object for you that I expect you will find simultaneously easy and difficult:

If you’ve been following my blog for a while, I expect you’ll be able to work out what this bone is quite easily – however, you may struggle a bit more to work out which species it came from.

Cryptic answers are encouraged as always – but mainly have some fun with this one!

Friday mystery object #326 answer

Last week I gave you this dissected mandible to have a go at identifying:

I thought it might be fun to get a poetic response and I wasn’t disappointed. There were some great efforts and I thoroughly enjoyed unpicking the clues from the verses people crafted in response. Of course, a poetic soul is only so much use in this game – you also need to work out what it is.

Bob Church was the first with a bardic response that was unambiguously on target for the identity of the mystery specimen:

Though the bone’s a disaster
There’s enough left to answer
What this rolly polly animal could be
It might sound a bit funny
But mix a turtle and bunny
And you’ll find the bowled over family

Of course, if you mix a turtle and a bunny you get something that looks like the artistic creation by John Tenniel in 1865 to illustrate Lewis Caroll’s Mock Turtle from Alice’s Adventures in Wonderland:

Gryphon and Mock Turtle with Alice, by John Tenniel in 1865

The animal in question is actually remarkably similar in appearance:

9-banded Armadillo by Ereenegee, 2011

It’s the Nine-banded Armadillo, Dasypus novemcinctus Linnaeus, 1758, a decidedly odd animal that lives in South, Central and southern parts of North America.

Most mammals have well differentiated teeth, so the homogeneity of these in shape (or homodont condition) suggested that you were dealing with something a bit unusual, with simple peg-like teeth, open roots and no enamel. That makes the mandible quite distinctive, even with some missing teeth.

The one slightly confusing thing about this half a jaw is that it appears to have tooth holes (or dental alveoli) for 10 teeth (as recognised by salliereynolds, who also got the identification right), but armadillos are only meant to have eight teeth in each side of their upper and lower jaws.

I thought this difference might throw you off the Armadillo scent a bit, but clearly I was wrong. The difference in this jaw will probably be because it comes from a young animal which still has milk teeth (or the alveoli for them) that aren’t all replaced by the adult teeth.

These insectivorous armoured animals are unusual in a variety of ways beyond their dental idiosyncrasies. They have imbricated bony nodules or plates embedded in their skin (or osteoderms) that forms a tough armour:

Dorsal view

Ventral view (width ~5cm)

They also consistently give birth to four offspring every time, originating from a single egg that splits into four. So every Nine-banded Armadillo has three identical siblings. I think this fact alone qualifies them as one of the weirder animals out there.

More mysteries next week!

*Juliette Kings may have got in with the first identification, with reference to the Armadillo’s habit of jumping straight up in the air when alarmed and occasionally screaming, but it sounded a bit more like she was suggesting Goat.

Friday mystery object #326

Yesterday I was doing some work in the gallery of the Dead Zoo and found a specimen that needs a little light repair work to stick teeth back into sockets. I thought it might make an interesting object for you to have a go at identifying:

Any idea what this piece of mandible might belong to? It’s probably a bit too easy for some of the mystery object veterans, so please keep your suggestions cryptic and, if you’re in the mood, poetic.

Have fun!

Friday mystery object #325 answer(ish)

Last week I gave you the challenge of identifying this bit of bone found in a rockpool in Kimmeridge by 7 year old Annie:

mystery325a

It’s not the easiest item to identify for a variety of reasons. First of all it’s broken, only showing one end and probably missing quite a lot of the element. Next, the images don’t show all of the angles you might want to see and because the object is small the images aren’t as clear as you might like.

However, there are a few angles visible (see below) and there is a scale, so the main requirements to get an approximate identification are in place. I say approximate, because with something like this I think you really need the object in your hand where you can compare it to other material in detail if you want to make a confident identification.

Excuses aside, let’s take a look and see what it might be…

The first thing to note is that the bone is hollow with thin walls. This rules out fish, reptiles, amphibians and mammals (including humans jennifermacaire) – leaving birds.

Weathered mammal bones may have a void in the bone where the marrow would have been, but the cortex (outside layer) will be thicker and near the articular surface it tends to be quite solid.

Hollow bone = bird (usually)

Next, the articular surface of the bone is concave, which palfreyman1414 picked up on:

As far as I recall (mentally running through images in my head) both ends of the proximal limb bones in tetrapods have convex ends?

This is accurate, but while the proximal (near end) of the limb bones are convex, the more distal (far end) limb bones tend to have concave ends, so that helps narrow down what this bony element might be.

Concave articulation

For me the give-away here is the fact that there’s no ridge within the concavity of the articular surface, which means that it will allow movement in several directions – something that the bones of bird feet don’t really need, which is why bird lower legs, feet and toes have a raised ridge inside the articular surface that corresponds with a groove in the other surface, keeping the articulation of the joint tightly constrained.

Articulation of Shag phalanx showing raised ridge

However, bird wing need to make a wider range of motion (at least in some species), so the mystery object is most likely the distal end of a bird radius (the ulna tends to have a hook at the distal end). This is the conclusion that Wouter van Gestel and DrewM also came to (joe vans should’ve stuck to his guns).

Distal articulation if duck radius

Identifying the species of bird is a lot more complicated. The size suggests a pretty big bird, which narrows it down and the locality in which it was found makes some species more likely than others. I took a look at the radius of some species that are commonly found on the coast, like Guillemot, Herring Gull, Duck, Cormorant/Shag and Gannet, Skimmer, Pigeon and I also checked out Chicken, since their bones are probably the most commonly occurring on the planet.

Gannet radius with some distinctive structure around the articulation

Many of the species I checked had quite a distinctive structure around the distal radius articulation, but the gulls, ducks and chickens that I looked at had fairly unremarkable distal radius articulations, making it hard to definitively decide what the mystery object is based on the images.

Herring Gull radius

Chicken radius

So with that somewhat disappointing conclusion I admit partial defeat, but I can say that it’s not from a Cormorant, Shag, Gannet, Pigeon or Guillemot. Sorry I can’t be more specific Annie!

Unfortunately that’s just how the identification game works sometimes… we’ll try again with something new next week!

Friday mystery object #325

This week I have a genuine mystery object for you passed on from my NatSCA colleague Holly, that was found in a rockpool in Kimmeridge by 7 year old Annie when she was out fossil hunting on the beach:

mystery325a mystery325b mystery325c

Any idea what this object could possibly be?

I don’t think there’s any need for cryptic clues this time, as it’s a proper challenge and I’d love to hear what you think it is and what it’s from. Have fun!

Friday mystery object #324 answer

Last Friday I gave you this rather beautiful object to have a go at identifying:

mystery324

I thought it might prove fairly easy for some of you and I wasn’t disappointed. Both in the comments here and on social media there were lots of you who managed to work out what this is, largely from images or illustrations of the model that could be tracked down online.

This is a glass model of a sea-slug made by the Blaschka father-and-son team of lampworkers, who were based in Dresden in the second half of the 19th Century. They made a huge number and variety of models of marine organisms, based on illustrations they found in a variety of scientific publications, which they adapted to enable reproductions in glass.

Beccaria tricolor by Leopold Blaschka (between 1863-1886). From the collection of the Corning Museum of Glass and Digitized by Boston Photo Imaging May 2011

Design illustration of Beccaria tricolor by Leopold Blaschka. From the collection of the Corning Museum of Glass and Digitized by Boston Photo Imaging May 2011

Illustration of Caliphylla mediterranea by S. Trinchese in Æolididae e famiglie affini del porto di Genova, Pt.1 (c.1877-1879). Image from Harvard University, MCZ, Ernst Mayr Library, via Biodiversity Heritage Library

This particular specimen has the number 373 on its label, which corresponds with the number on the Blaschka design illustration above, so we can be confident that the design is for this model.

Label for the specimen – note the National Museum of Ireland – Natural History (NMINH) number which starts with the year the specimen was acquired. This specimen arrived in August 1886 and cost the fairly modest sum of 3d (for some context, an average UK farm labourer’s weekly wage in 1886 was 13s 4d*, which would be enough to buy 53 of these models).

I should probably say the design is for this type of model, since the Blaschkas produced multiple versions of each design. These sold all around the world to museums and universities, who ordered them from a catalogue to be used in display and teaching in lieu of real specimens, which would often look like nothing more than tiny grey lumps once preserved in alcohol.

To give you an idea of what these creatures look like alive, here’s an image of an undetermined species of Caliphylla

Caliphylla sp. from Réunion, by Nathalie Rodrigues, 2015

As you might imagine, as soon as you take one of these animals out of water their complex frills start to stick together like a piece of damp fancy lettuce and it becomes hard to see their leafy structure.

And they really are leafy, because Calliphyla is one of the solar-powered Sacoglossa sea-slugs that steal chloroplasts from algae, which they then store in their bodies and can use to obtain energy from the sun. So all those leafy bits are a result of convergent evolution with plants, providing a large surface area for light to reach the chlorophyll. This means they also end up being well camouflaged against predators, although they may get nibbled by the occasional confused herbivore.

* British Labour Statistics: Historical Abstract 1886-1968 (Department of Employment and Productivity, 1971)

Friday mystery object #324

This week I’ve decided to give you a mystery invertebrate from the collections of the Dead Zoo:

mystery324

Now there are a variety of levels of identification for this object: species (obviously), materials, makers and if you really want to show off, you might even be able to provide a year and information about how much it cost at the time.

As always, I’d be delighted to see what you think and to hear about any similar specimens you might know about.

Have fun!

Friday mystery object #323 answer

Last week I gave you this incredibly cute mystery floofball to identify:

It took approximately 10 minutes for palfreyman1414 to work out what it was and come up with an excellent cryptic clue as to the identity of the genus:

Right, best guess is that this is a genus of tiny anno domini public transportation.

Tiny (=micro) anno domini (=AD aka Christian/Common Era, abbreviated to CE) public transportation (=bus) which gives us Microcebus.

Microcebus É. Geoffroy, 1834 are commonly known as the Mouse Lemurs, a genus containing 24 currently recognised species of tiny Malagasy primates.

Lesser Mouse Lemur by Arjan Haverkamp, 2007

Normally I’d be looking for a species level identification, but that would be a real challenge, since the members of this diminutive genus are remarkably similar in appearance – especially if you only have a very faded 100+ year old specimen to work from.

In fact, before genetic analysis was available, only two species of Mouse Lemur were formally recognised, with another couple proposed but disputed. In the last 20 years there have been a further 20 new species recognised, meaning that despite the label on the Dead Zoo specimen saying it’s Microcebus murinus (Miller, 1777), it could well be something else – perhaps even a new species yet to be described.

I say that because even though researchers have been busy finding new species, they are mostly working in the field and several of the species being discovered are incredibly rare due to habitat loss in Madagsacar. When our specimen was collected it could easily have been from an area that was logged before researchers had a chance to do genetic work on the Mouse Lemurs present, so there may have been species there that were never discovered before they were lost.

This idea of species being lost before they’re discovered is a depressing, but very real one. Most taxonomists agree that there are around ten times as many species on Earth as have been described by science so far. More are being discovered all the time, but they tend to be from areas with fewer scientists (unsurprisingly), but not necessarily areas with less human impact.

Rainforests are a good example, where species diversity is incredibly high, but dams, logging and slash-and-burn agriculture to support soy, palm oil and cattle farming are gobbling up huge swathes of habitat before biologists have ever seen it.

To put that into some kind of perspective, England and Wales are much less diverse than a rainforest environment, but new species are still being found despite having a couple of centuries of extensive and systematic recording and collecting. The perspective comes from the fact that an area of rainforest the same size as England and Wales is destroyed every year, before it’s ever had a chance to be studied.

I talked about some of the issues of extinction on the Mooney Goes Wild radio programme recently, which you can listen to here if you’re interested.

More mysteries next week!

Friday mystery object #323

This week I’ve decided to give you a mystery squee from the Dead Zoo:

Any idea what this fuzzy little critter might be? As usual you can leave your questions, thoughts and suggestions in the comments box below.

Friday mystery object #322 answer

Last week I gave you this new acquisition for the Dead Zoo to identify:

mystery322

It’s a detail of something large, and it had a lot of you stumped because it looks like a cross between a marble worktop and pork terrine.

However, if you look closely at the bottom left of the image, you may just be able to make out the shape of a sucker-covered arm, because this – as spotted by palfreyman1414 and jennifermacaire – is a big cephalopod.

When I say big, I mean it’s the second largest species after the Colossal Squid (that I’ve talked about before) – that’s right, it’s a view of part of a large ice cube containing a Giant Squid Architeuthis dux Steenstrup, 1857.

Squid holding sailor by Alphonse de Neuville & Édouard Riou, from Hetzel edition of 20000 Leagues Under the Sea, p. 400.

This individual isn’t actually particularly giant, measuring in at a meagre 5.8m, including its long thin feeding tentacles – quite big, but hardly Kraken-esque. It was caught 118 miles off the Kerry coast after it found its way into shallower waters than the abyssal depths they normally inhabit. You can see details of how it was caught and a photo of the specimen on the Irish Times website.

I haven’t started the process of preserving for the long term yet, as it will require a bit of time to release the kraken from the ice, a large tank and some nasty chemicals – namely a 10% formalin solution and various strengths of Industrial Methylated Spirits (IMS – which is adulterated alcohol), stepping up to 70% in 10-20% increments. I may also need include an alkali buffer in the tank (marble chips are commonly used) since Giant Squid use ammonium chloride in their tissues to increase their buoyancy and that can acidify the solution, leading to accelerated bleaching of the tissues and long-term damage to the specimen.

Even with good preservation it’s unlikely to ever go on display as a full specimen. I can probably find a big enough jar, but the specimen has been dissected and isn’t really looking its best. However, it may be worth showing some of the elements, like an eye, the beak or maybe an arm or tentacle. These may be in good enough condition to use on display to explain some of the interesting features of these denizens of the deep. The rest of the squid will be there for researchers interested in these large, but elusive, molluscs.

Friday mystery object #322

I’ve not had an unusual mystery object for a while, so lets see how this one works out:

Any idea what this identification of this recent acquisition might be?

As always you can leave your thoughts, questions and suggestions in the comments box below. Have fun!

Friday mystery object #321 answer

Last week I gave you this fuzzy object from the stores of the Dead Zoo:

mystery321

It’s a slightly generic looking creature and I’m not surprised a few ideas for identification were mooted, because it lacks any single distinctive feature in this image (partly because the characteristic grizzled facial hair is a bit indistinguishable due to historic soot). That didn’t stop Wouter van Gestel, Mike Shanahan, RobinBirrrd, James Bryant, and jor from recognising it though.

This is the wonderfully weird Bearcat or Binturong Arctictis binturong Temminck, 1824 which is a South and Southeast Asian carnivore in the viverid family (those are the civets) that is one of only two carnivores with a prehensile tail (I’ve talked about the other one, the Kinkajou, in a previous blogpost).

Like the Kinkajou, the Binturong isn’t a very carnivorous carnivore. It eats more figs than meat and it lacks the restless dynamism of the average predator, plodding flat-footedly on the ground and climbing well, albeit in a much slower and more measured way than other arboreal carnivores that take killing a bit more seriously.

Binturong displaying characteristic levels of activity. Image by Greg Hume, 2017

Apart from the unusual prehensile tail, the living Binturong has one other unusual characteristic (as pointed out by RobinBirrrd) – it smells like popcorn. This is due to the emissions of its musk gland, situated conveniently near the genitals and anus. Sadly our specimen smells more like a half-washed dog that’s been rolling in mothballs.

More mysteries next week!

Friday mystery object #321

This week I thought I’d give you a break from the bones and offer up a fuzzball for some Friday fun: mystery321

Any idea what this (slightly dusty looking) critter from the collections might be?

It’s probably a bit too easy for some of you, so cryptic clues and subtly veiled hints would be appreciated in the comments section please. Have fun!

Friday mystery object #320 answer

Happy New Year everyone!

Last week I gave you this skull to identify from the collections of the Dead Zoo in Dublin :

King Vulture Sarcoramphus papa (Linnaeus, 1758)

I also included the label, since it offers an interesting taxonomic twist.

If there’s one principle that I hope I’ve managed to convey over the last eight and half years of doing the Friday mystery object, is that you should never fully trust the label.

For starters, the number NMINH:2006.12.1698 could be misleading, as it reflects the year the specimen was catalogued rather than the year it was acquired. To explain, the NMI uses a very sensible numbering system that starts with the collection (NMINH = National Museum of Ireland Natural History) the year of registration (usually the year of acquisition) which allows you to know which register to look in, followed by the lot number (a sequential number reflecting how many acquisitions have come in that year), followed by the individual object number (the sequential number of that individual item in a particular lot). This system can have additional numbers added if necessary, such as if a piece of an individual object is removed for sampling.

However, some older objects were not registered when they entered the collection and as such they get a number that reflects the year they were documented rather than the year they were acquired. In this case the specimen was registered in 2006, but purchased from an auction of the collections of van Lidth de Jeude who died in 1863, as Nigel (the Dead Zoo Keeper) helpfully pointed out in the comments.

If the specimen had been accessioned and numbered on entering the collection back in the 1860’s then issues with the name would be expected since taxonomy constantly changes and old names are often wrong, but because of the new label and the 2006 date, you’d generally expect the name to be more up-to-date. However, it appears that the information on an old label was directly transcribed without being updated.

This is relevant because the name Orogyps auricularis is what we call a junior synonym, which means it has been used to describe a species that already has an older valid name. When this happens the older name takes precedence. In this case, Orogyps auricularis is a name applied in 1867 by Degland and Gerbe to a species that had already been named Vultur tracheliotos by J.R. Forster in 1796 and which is now placed in a different genus, giving the name Torgos tracheliotos (Forster, 1796) – where the parentheses around the author name indicate that the scientific name has changed from the original version that was published by Forster.

These taxonomic and documentation twists are however rendered redundant as soon as you realise that this specimen is from a totally different species. In fact it’s not really anything like Torgos tracheliotos the Lappet-faced Vulture:

Lappet-faced vulture

In fact, the only real similarity lies in the tip of the beak, which is a functional feature for tearing meat and which is convergent between the Old World Vultures and the New World Vultures. The Lappet-faced Vulture is an African species, while the mystery object has the distinctive deflection of the bill in the nasal region that indicates it’s a species from the Americas. This discrepancy in region was noted by palfreyman1414 and Gerard van den Brink.

Once you focus on the New World Vultures it becomes quite easy to make an identification, since there are only seven species and at 121mm this specimen is the third largest species after the condors – something easy to check on Skullsite. So well done to everyone who recognised the skull as belonging to the King Vulture Sarcoramphus papa (Linnaeus, 1758), especially palfreyman1414 who got there first.

514px-sarcoramphus_papa_-national_zoo_-washington_-usa-8a

King Vulture by Eric Kilby, 2008

As you can see, not only was the taxonomy very out of date for this specimen, it was also completely wrong, because it was misidentified 150 years ago. This is why you should never fully trust labels – they will often be wrong and if you base research on misidentified specimens, that will be wrong too.

Another mystery specimen next week!

Friday mystery object #320

I hope everyone had a lovely Christmas break!

This week I have another specimen from the Dead Zoo to identify – this one has an identification already, but the taxonomy is rather archaic and I think that once you’ve investigated the modern version of the name, you’ll realise that it’s wrong.

Skull length = 121mm

So, any idea what this name should actually be and, more importantly, what the identification actually is?

As always, you can put your thoughts, questions and suggestions in the comments box below – have fun!

Friday mystery object #319 answer

Last week I gave you this unidentified skull from the Dead Zoo to have a go at identifying:

It seems that everyone recognised this as the skull of a gull straightaway – the scars from the salt-glands on the top of the head and the shape of the bill combined to make it a bit of a give-away.

However, working out which species of gull is a bit more tricky, since many are remarkably similar in morphology, making size an important factor for consideration (I’ve talked about this before).

Now size is always a somewhat tricky thing to use for identification, for a variety of reasons. One is that there may be an overlap in size between species, another is that there will often be sexual dimorphism within a species that means you can’t just compare the length against another specimen of a species without considering sex. Then of course there’s age – if it’s not fully grown, it’s going to be smaller. Of course you also have to consider whether the bill sheath is present or absent, as this will add a few millimetres.

On top of all these issues, there’s the problem of how you actually measure the length in the first place. This is something I’ve researched in the past (link to pdf) and it’s a more significant problem than you might think. For example, when looking at the image I originally provided for the mystery object, it looks like the skull measures around 125mm, but if I chop the scale bar from the image, reduce the transparency to 50% and lay it directly over the centreline of the image of the specimen, it turns out to be around 128mm.

Length is apparently 128mm

Add to this the fact that in the original image you can see a shadow under the scale bar, it becomes clear that the scale is somewhat elevated. This is because I raise the scale to be near the vertical midline of the specimen, to help keep everything in focus and limit the effect of parallax error. Normally this is good, because it allows a more accurate estimation of the length of a 3D specimen with a longest axis near the vertical midline, but in this case the longest part of the specimen is actually at the lowest part of the skull, so the elevated scale will make it look slightly shorter than it really is (due to the parallax error I was hoping to avoid…). This means that the specimen is probably closer to 129mm or 130mm in length.

With this in mind, the discussion about the lengths of various gull skulls between Wouter van Gestle (of Skullsite fame), Ric, Tim Dixon, Richard Lawrence, Gerard van den Brink and jennifermacaire needs to be reconsidered.

Richard Lawrence reported skull lengths for a variety of gulls as follows:

6x GBBG: 129 to 141 mm
2x LBBG: 117 mm
6x HG: 111 to 117mm
9x YLG: 111 to 126 mm ( larger with beak sheath though so would be smaller without).

So factoring in a length of 129-130mm for the mystery object it seems to fit well into the range for the Great Black-backed Gull Larus marinus Linnaeus, 1758. So well done to everyone who went for GBBG – this does seem most likely to be a skull from the largest gull species.