Friday mystery object #367 answer

Last week I gave you this rather exciting new specimen from County Kerry, Ireland to have a go at identifying:

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Perhaps unsurprisingly, it was recognised by pretty much everyone. For people based in the Americas it’s not that unusual a species and for people on the other side of the Atlantic, especially those with an interest in birds, there has been a bit of a stir in the press about this specimen.

This bird is clearly a member of the heron family – the Ardeidae – with its distinctive spear-shaped bill, relatively long legs and long and somewhat kinked neck. But it’s tiny. In fact, this is one of the smallest members of the Ardeidae, perhaps a bit longer in the body than a Dwarf Bittern, but just a bit lighter and quite different in plumage.

Dwarf Bittern in South Africa. Image by Mark Tittley, 2011

Dwarf Bittern in South Africa. Image by Mark Tittley, 2011

And this particular specimen is very light indeed. Sadly it was probably undertaking a migration south from its North American breeding grounds, when it got caught up in hurricane Lorenzo, which blew it off course, forcing it across the Atlantic Ocean, where it finally made landfall in Farranfore in County Kerry, on the west coast of Ireland on 7th October this year.

Exhausted, emaciated and severely dehydrated, the poor bird lasted less than an hour in Ireland, despite efforts to keep it going by John O’Donoghue, the owner of the garden it ended up in. John and his neighbour Anthony O’Connor recognised that it wasn’t a bird normally found in Ireland, so they got in touch with BirdWatch Ireland to find out what it was and let people know about their unfortunate visitor.

Brian Burke and colleagues from BirdWatch Ireland identified the specimen as being a Least Bittern Ixobrychus exilis (Gmelin, 1789) and they got in touch with me at the Dead Zoo about getting the specimen added to the collections, since it’s a first record of this species occurring in Ireland – and only the 10th known to have made it across the Atlantic.

Of course, I was delighted to accept on behalf of the Museum and John arranged to get the bird to me in Dublin via his local Teachta Dála (the Irish equivalent of a Member of Parliament). Now the bird is safely stowed in the Museum’s freezer awaiting assessment by a taxidermist, to see whether it’s in good enough condition to be mounted, or if I’ll need to find another way of preserving the specimen as part of the permanent collection.

If not as taxidermy, this might be as a study skin, a fluid preserved specimen or even a skeleton – each offers different information for future use. But however it gets preserved, it will provide an important physical record of an unusual visitor to the Nation for future scientists and members of the public. After all, that’s a huge part of what collections are for.

 Friday mystery object #355 answer

Last week I gave you a unfairly tricky mystery object:

My excuse for the poor photography and lack of scale was the fact I was preoccupied with the epic NatSCA conference (whose hashtag is still yielding some great photos and thoughts if you want to see what it was all about).

It probably doesn’t help that this specimen is missing the toes from its right foot, because it makes it hard to tell if the two toes on its left are the natural state for the bird, or if one toe just happens to be missing. This is an important distinction, as picked up on by sallie reynolds, since a bird with two forward-facing toes will have two rear-facing toes, which is a condition known as zygodactyly and it helps narrow down the possible group of birds it belongs to.

As it turns out, the left foot is intact and the specimen does have the zygodactyl toe arrangement, so it will be from one of nine possible groups (owls, ospreys, parrots, cuckoos, cuckoo-rollers, mousebirds, turacos, some swifts and most woodpeckers and their relatives). The bill makes it pretty clear that this isn’t an owl, osprey, parrot, mousebird, or swift. The big head narrows it down further – more than enough for Wouter van Gestel to identify that it’s a Barbet (in Dutch “Baardvogel” or bearded bird), but it doesn’t really provide enough information to get a species identification.

As it turns out, the taxonomy of the existing identification was more than a little out of date, with the label from 1881 reading Heliobucco bonapartii. Now Heliobucco has not been used as a valid genus for at least 100 years, but fortunately the species name indicates that it was named after Bonaparte (not the Emperor, but a French ornithologist who did happen to be the Napoleon’s nephew). This meant that the fantastic Eponym Dictionary of Birds by Beolens, Watkins & Grayson was able to yield the information I was after. The valid name is now Gymnobucco bonapartei Hartlaub, 1854 which is the Grey-throated Barbet.

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Grey-throated Barbet. Photo by Francesco Veronesi, 2006

My apologies for setting such a tricky object – I promise to try harder to make it easier next week!

Friday mystery object #339 answer

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

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I was deliberately mean and only provided a lateral view, since I reckoned that many of you would be able to work out what it was from that.

I was not disappointed, although it definitely made things a bit more difficult.

The bill shape is fairly long and fairly thin, which is often characteristic of birds that feed in water or wet mud, but there a lot of birds which do that.  This one is somewhere between a mud-probing and worm-catching wader like a Redshank and one of the stabby-faced-fish-catchers, like an Egret.  However, there are a couple of things that make the skull different to things like either of these – unlike the herons it has an inferior angular process (that bit that sticks down at the bottom of the mandible near the articulation with the cranium). A lot of birds don’t have this, although many of the charadriiforms (waders like the Redshank) do, although theirs is a different shape – tending to be broader, rounder and generally less well-defined.

This combined with the size (around 75mm) and the bump in the upper part of the bill near the junction with the cranium leads us towards a more secretive bird that does a bit of stabby-faced-fish-catching and a bit of worm-catching. As ably hinted at by Richard Lawrence, Wouter van Gestel, salliereynolds and joe vans, this is in fact the skull of a Water Rail Rallus aquaticus Linnaeus, 1758.

These odd birds are omnivorous and well-adapted for skulking through reed-beds, with a narrow profile and high-stepping gait. As with most birds of dense habitats, they have a loud and distinctive call referred to as ‘sharming’, which they will do while they are feeding – which may contribute to their vulnerability to introduced Mink, which follow their sound and ambush the birds while they’re preoccupied with feeding themselves.

Tune in next week for another mystery object!

Friday mystery object #339

This week I have a mystery skull for you to have a go at identifying:

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I’ve made it a bit more tricky by only providing one view, but I think it should be identifiable from this.

By the way, I hope you like the NatSCA scale bar – the most useful swag I’ve ever received in a conference pack. Hoping to get another one at the Caring for Natural Science Collections one-day conference in October – really looking forward to geeking out about conservation of natural history collections!

Enjoy the mystery object!

Friday mystery object #332

This week I’ve been looking at birds, so I thought I’d share the joy with you. Do you have any thoughts about what this might be?

I expect that quite a few of you will have a pretty good idea, so please keep your suggestions cryptic, to let people who are less familiar with avian identification have a chance of improving their skills.

Have fun!

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.

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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?

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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 #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:

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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.

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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.

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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.

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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).

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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.

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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.

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Herring Gull radius

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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 #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.20171228_163420.jpg

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:

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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.

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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 #318 answer

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

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It’s a fairly distinctive looking specimen with that massive bill, immediately narrowing down the possible families to two likely contenders – the Toucans (Ramphastidae) or the Hornbills (Bucerotidae).

On closer examination it lacks the serrated bill margins and remarkably long medial (in this case that means ‘towards the midline of the skull’) process of the quadrate bone (a part of the jaw in birds that I’ve blogged about before) that you see in Toucans. So, it’s a Hornbill – as everyone correctly spotted in the comments – but then we have the question of the species.

There are around 60 Hornbill species, with most of them sporting quite distinctive casques which make them quite identifiable (I’ve blogged about several before):

Ceratogymna atrata skull

Black Hornbill Ceratogymna atrata

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Great Hornbill Buceros bicornis

Bucorvus abyssinicus (Boddaert, 1783) sectioned skull

Northern Ground-hornbill Bucorvus abyssinicus

However, this specimen seems to be lacking a casque. This could be due to a few reasons. There are some casqueless species, such as the Sri Lanka Grey Hornbill, it could be a young female adult from a small casqued species with sexual dimorphism in casque development, or it could be a young juvenile from a species that has a small casque that grows as the animal matures.

Assuming it’s one of these, it’s easy to check the few casqueless species by looking at the overall bill shape, the position of the nares (nostrils) relative to the orbits (eye sockets) and checking the structure of the jugal and quadratojugal (the thin bones on the side of the skull under the orbit) – this last only if you can find a reliable skull image for comparison.

Using Skullsite and images on the internet it’s time-consuming, but straightforward to rule out a lot of possibilities, since most Hornbills have a fairly robust jugal/quadratojugal and nares located much further away from the orbit than you see in the mystery specimen. In fact the only Hornbills with a similar nares/orbit position and gracile (skinny) jugal/quadratojugal and in the right size range (that I was able to find) were in the genus Rhyticeros L. Reichenbach, 1849.

Unfortunately I’ve not found good skull images of juveniles for all of the species to make a final comparison and you can’t just compare the skull of a juvenile with an adult and expect to see the same configuration and development of features, as there’s still growth to happen (something else I’ve talked about before).

So based on the information it looks like jennifermacaire was the closest with her suggestion of Wreathed Hornbill, although I’m leaning slightly more towards the Papuan Hornbill Rhyticeros plicatus (J.R.Forster, 1781).

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Hope you enjoyed the challenge!

Friday mystery object #317 answer

Last week I gave you this unidentified bird skull from the Dead Zoo to try your hand at identifying:

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It seems that everyone recognised it as being from a charadriiform, and one of the waders at that. The first response was from Chris, who made reference to Lewis Carroll’s poem the Walrus and the Carpenter in which the eponymous characters eat an enormous quantity of oysters – hinting that this is an Oystercatcher.

There were some other suggestions that it could be from one of the birds in the genus Tringa, which includes the ‘shanks’ (Redshank, Greenshank, etc.), but the morphology fits one of the Oystercatchers better – in particular that weird constriction about halfway down the mandible when you look at the skull in profile.

This mandibular ‘waist’ is quite unusual and it doesn’t even seem to occur strongly in all of the Oystercatchers, which helps narrow down the likely species within the genus Haematopus, especially when you factor in things like the relative bill proportions, although you have to be careful doing this as there is some sexual dimorphism in the shape of the bill, with the females’ being longer.

The three closest species are the American Oystercatcher, the Sooty Oystercatcher and the Blackish Oystercatcher, but unfortunately I’ve not been able to find good reference skulls all of these species to be able to look for any distinguishing cranial characters. Based on bill morphology I’m leaning towards this being the skull of the American Oystercatcher, Haematopus palliatus Temminck, 1820.

American Oystercatcher by DonaldRMiller, 2010

American Oystercatcher by DonaldRMiller, 2010

My next step will be to check through our collections to see if we have comparative material to check the identification (once I get some time – a sadly rare commodity). If I can’t confirm I’ll just stick with Haematopus sp. on the label.

If you’re not familiar with Oystercatchers, they walk along the tideline either prying or breaking open bivalves. In my experience they seem more fond of mussels than oysters, but what do I know?

Another mystery next week!

Friday mystery object #307 answer

Last week I gave you this specimen from the Irish Room of the Dead Zoo to try your hand at identifying:

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Now it’s not a particularly difficult species to identify for a keen birder, so I asked for cryptic clues to the identity, and I was not disappointed. Some suggestions were so cryptic I still haven’t managed to work them out!

First in was Jennifer Mccaire who quoted a brief line of poetry:

“…Thou hast no sorrow in thy song, No winter in thy year.”

This is a section of a poem published in 1770 by John Logan – the title being “Ode to the Cuckoo“. Now, it seems likely that Scottish born Logan wrote this about the Common Cuckoo Cuculus canorus Linnaeus, 1758 that breeds in Europe and which looks like this:

Common Cuckoo. Image by Chris Romeiks, 2011

Common Cuckoo. Image by Chris Romeiks, 2011

Clearly it’s a different bird (one which mimics the appearance of a female Sparrowhawk) and it’s not quite the same as the mystery object – although there are similarities. However, we must keep in mind that Jennifer is of the North American persuasion, so her thoughts on Cuckoos will probably veer towards the Black-billed Cuckoo or Yellow-billed Cuckoo (or maybe the Mangrove Cuckoo, but that’s not as widespread as the other two).

If you don’t know the difference between these two North American Cuckoos, here’s a handy illustration to help differentiate:

Black-billed Cuckoo (left), Yellow-billed Cuckoo (right). Watercolour by Louis Agassiz Fuertes between 1910 and 1914.

Black-billed Cuckoo (left), Yellow-billed Cuckoo (right). Watercolour by Louis Agassiz Fuertes between 1910 and 1914.

Continue reading

Friday mystery object #302 answer

Last week I gave you this egg to try your hand at identifying:

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Eggs can be tricky, since they are largely similar in shape and, since egg collecting was banned many years ago, there are few modern resources for identification.

However, you can pick up clues by thinking about colour and pattern and working out what advantage it may have. So you might expect a brightly coloured egg to be laid in a well disguised and deep nest, where it’s unlikely to be spotted except by the parent, whereas a yellowy speckled egg is more likely to be camouflaged if laid in a fairly open, sandy environment.

So this egg was probably laid somewhere near the sea, which means it’s probably from a charadriiform bird (those are the shorebirds).

Now there are a lot of shorebirds, but this egg is pretty big and it lacks the strongly conical shape you’d expect from a cliff-nester like a Guillemot (the shape means it rolls in tight circle, making it less likely to be blown or knocked off a cliff). That actually narrows it down to a handful of birds that makes comparison easier. Curlew eggs, for example, are a similar size, but they tend to be more grey and have larger blotches, plus they’re a bit less elongated.

This particular egg has the shape and colour of a gull egg and large size means it’s almost certainly the egg of a Greater Black-backed Gull Larus marinus Linnaeus, 1758.

I would say more, but at the moment I’m at the natural history highlight of the year – the NatSCA conference. Here’s the Twitter feed in case you’re interested in the discussion:

Friday mystery object #295

For many of you, last week’s mystery object answer was a little disappointing, since I was unable to pin down what the specimen was. Normally with birds it’s not so difficult, because of useful resources like skullsite.com, but the fact is that some bird groups are still quite poorly represented in collections and finding comparative material is difficult, especially online.

The most frustrating thing about last week’s object is that it did once have a label, but at some point in the past it was lost, so the only information with the specimen now is this:

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However, this label does offer a glimmer of hope, since it identifies the specimen as being from a particular collection and that can often mean there will be more information somewhere.

As it turns out, this specimen is one of several that were purchased in 1867 from an auction of the collections of Dutch anatomist Theodoor Gerard van Lidth de Jeude. This is helpful because auction catalogues can contain information like the species names of the specimens being sold. It is particularly helpful when you have the original catalogue with annotations about the specimens bought by your institution.

Fortunately, at the Dead Zoo we have the auction catalogues. Unfortunately we bought quite a lot of stuff, so working out which of the specimens our mystery object represents is still quite a lot of work.

However, if other specimens from the auction have their names and numbers, it should be easier to narrow down the ones that lost their labels. It also can also help to have an identification of the specimen to track back to the catalogue, which is why I was keen to get your thoughts last time and why this week’s mystery object is from the same collection.

So can you help me work out what species this skull belonged to?

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No need for cryptic clues, but if you want to show off your taxonomic prowess you could always offer the 1860’s scientific name or the name of what you think it is in Dutch.

I hope you have fun with this one!

Friday mystery object #293 answer

Last Friday I gave you this unidentified specimen from Dublin’s Dead Zoo and asked you to help me work out what it was:

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The response was incredibly helpful and it was great to see that most of you were drawn by the morphology to make a similar identification to me.

The fact that it’s from the family Anatidae (the ducks, geese and swans) was immediately noticed, and from there the likely genus was quickly narrowed down to Branta, based on the morphology. This is the genus containing the ‘burnt’ geese (that’s what ‘branta’, derived from the Old Norse, means), which includes: the Brant Goose; Barnacle Goose; Canada Goose; Cackling Goose; Red-breasted Goose, and Hawaiian Goose.

However, the nominate examples of all these species (that means the ones derived from the type on which the species name is based) are either the wrong shape or a bit too large to have this skull, which you can see by checking them on the excellent Skullsite by Wouter van Gestel.

The closest species in terms of morphology are the Cackling Goose (B. hutchinsii), Canada Goose (B. canadensis) and Barnacle Goose (B. leucopsis), but it turns out that there are various subspecies of each and one (that was previously recognised as a subspecies of Canada Goose, but which is now considered a subspecies of Cackling Goose) is rather small, as flagged by the subspecies name minima.

This smallest subspecies seems to fit both the morphology and the size very well, so I’m quite confident to identify the mystery specimen as the Small Cackling Goose Branta hutchinsii minima (Ridgway, 1885).

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A family of Small Cackling Geese, by Tim Bowman, USFWS, 2003

So thanks to you all for helping me to narrow down where in the Anatidae to start looking! More mysteries from the Dead Zoo next week.