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DISPLAYING POSTS TAGGED: fossil (3)

Small(er) is beautiful

Author
by Wayne
Publish date
4 May 2014
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When we think of Ice Age land animals, we often add the word ‘giants’; certainly many of the mammals of the Pleistocene were very large  – including many here in Australia. In a previous post, we’ve defined megafauna, and looked at a few Australian examples from the Quaternary. There is a different way of looking at this, though – rather than thinking of the Ice Age megafauna as ‘ancient giants’, it is equally valid to study modern-day animals from the perspective of them being dwarf or pygmy forms of their Ice Age relatives.

The phenomenon of dwarfism in post- Ice Age mammals changes the question from “why were they so big back then?” to “why are they so small now?”

Before we go any further, we should keep in mind that not everything was giant-sized in the Pleistocene; there were many ‘normal’ sized animals (by today’s standards) living happily alongside the big guys – it was just that the big ones were really big. It’s also important to remember that many of the ‘pygmy’ forms lived alongside their ‘giant’ relatives, rather than replaced them – there’s no such thing as a succession plan in evolution.

Having said this, here are a few examples of ‘dwarf megafauna’ alive today that had gigantic skeletons in their closets.

An example of ‘miniature giant’ is the modern day Eastern Grey Kangaroo Macropus giganteus; certainly large for an Australian land mammal, but 40-something thousand years ago it was overshadowed by its immense relative Macropus titan by 30%.

  skull of Macropus titan Skull of the Giant Grey Kangaroo Macropus titan. The ‘giant’ part is correct, but the ‘grey’ part is speculative; the colour of the Giant ‘roo is unknown…
Image: Tim Holland
Source: Museum Victoria
 

Similarly, the largest living Goanna, the Perentie Varanus giganteus, impresses with its size….but is smallfry against the immense extinct evolutionary ‘cousin’ Varanus “Megalania” priscus, – estimated at over twice (some have said thrice) the size.  

­­This also holds true on the Tasmanian Devil Sarcophilus laniarus, which had an over-sized, mainland-resident relative at least 15% larger than its living subspecies. All of these animals are at least in the same genus as their megafaunal relatives, in some cases they are subspecies of their modern-day pygmy forms.

Tasmanian devil skull Skull of the Giant Mainland (rather than Tasmanian) Devil Sarcophilus laniarus
Image: Tim Holland
Source: Museum Victoria
 

So, whilst it is true to say that in broad terms, there was an extinction event about 45, 000 years ago that led to the ‘end of the Megafauna’, this event was complex - there were other patterns at play that saw downsizing as a successful survival strategy.

Obviously many Australian megafauna taxa became entirely extinct as well, inconveniently leaving no close descendants or relatives, but their story is for yet another blog…

First fossil of Pygmy Right Whale

Author
by Kate C
Publish date
10 August 2012
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The Pygmy Right Whale (Caperea marginata) is the oddball of the whale world. The bizarre anatomy of this species has confounded researchers for years – even its common name demonstrates our historical lack of understanding. Its arched upper jaw and skim-feeding behaviour is similar to the right whales however DNA analysis shows that Pygmy Right Whales are more closely related to the rorquals (family Balaenopteridae) than the true right whales (family Balaenidae).

The puzzle of the evolutionary history of this species was not helped by the fact that it appeared completely absent from the fossil record. Palaeontologist and whale expert Erich Fitzgerald was therefore extremely pleased to identify a lone fossil specimen in the Museum Victoria as a partial periotic (the bone that surrounds the inner ear) of an ancient relative of the Pygmy Right Whale.

One theory about this group, explains Erich, is that "the bizarre features of the Pygmy Right Whale evolved rapidly within the last three to four million years. But this fossil suggests that they're much older than that." The specimen, which Erich describes as "looking like a coconut," is larger than the periotic of the living Pygmy Right Whale and dates to the late Miocene. This makes it six million years old, which will help calibrate the whale phylogenies (evolutionary trees) that are based on DNA sequences.

four views from different angles of whale earbones. Comparison of the incomplete fossil specimen (left) with a complete earbone of a juvenile Pygmy Right Whale.
Image: Erich Fitzgerald
Source: Museum Victoria / Journal of Vertebrate Paleontology

 
It is the peculiar skeleton of the Pygmy Right Whale, particularly of its ear bones, that allowed Erich to identify such an odd and incomplete fossil. "Baleen whales in general have strange skulls but in Pygmy Right Whales the ear bones are particularly strange because the back end, of the periotic, is enormous and bulbous. This fossil has no features that would ally it with any other family."

The strangeness of this whale doesn't end with its skull. First up, there is its size; at just 6.5 metres long, it's the smallest living baleen whale. Compare this with its colossal distant relatives, such as the 33 metre Blue Whale. But there's more, says Erich. "If we look beyond the head, there are some really strange things. In particular, the Pygmy Right Whale has ribs that are flattened and expanded. It almost looks like the ribs have formed a shield over the organs." This may relate to their unusual way of swimming which requires a stiffer trunk. "A young animal filmed underwater in South Africa shows that they flex their entire body not just the tail. It's thought that the ribs may be expanded to help keep the body rigid during this movement."

Until this footage, almost all knowledge of the species came from stranded individuals. Recent aerial photographs of a pod of Pygmy Right Whales off the coast near Portland showed some kind of social behaviour but exactly what it is – feeding, reproducing or something else – is still unknown.

Museum of New Zealand Te Papa Tongarewa made this video with a dissection of a stranded whale which clearly shows the unusual ribs.

 

Links:

Erich M. G. Fitzgerald. 2012. Possible neobalaenid from the Miocene of Australia implies a long evolutionary history for the pygmy right whale Caperea marginata (Cetacea, Mysticeti). Journal of Vertebrate Paleontology 32(4): 976-980. DOI:10.1080/02724634.2012.669803

The Tetrapod Zoology blog has a series of three terrific posts about Pygmy Right Whales:
Caperea is really weird
More on little Caperea
Caperea alive

...but is it real?

Author
by Wayne
Publish date
6 August 2012
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Your Question: ...but is it real?

"I love the Discovery Centre at Melbourne Museum and wanted to know more about the animals and fossils on display. Are they all real? "

Not all of the displayed material is 100% ‘real’, but a surprisingly large percentage of the displays are certainly real...although it depends on how you would define reality! Let me explain with a few examples:

Dinosaur Skulls

The two dinosaur skulls in the Discovery Centre (of Tarbosaurus and Centrosaurus) are both casts from real specimens, but aren’t themselves ‘real’. For many reasons, casts of dinosaur remains outnumber the real dinosaur fossils on display here at Melbourne  Museum, but you can see real dinosaur fossils in the Dinosaur Walk and 600 Million Years exhibitions in the Science and Life Gallery.

Centrosaurus skull The cast skull from the Cretaceous dinosaur Centrosaurus
Image: Wayne Gerdtz
Source: Museum Victoria
 

Cephalopod slab

Yes, this is also real, but it has had some enhancement – the fossils themselves have been cut and polished in contrast to the rough, unpolished rock in which they are embedded. It looks quite different to what the slab looked like originally, but it is certainly real – just a bit more polished, literally!

Cephalopod slab A slab of ancient sea bed sediemnts with cephalopod shells embedded.
Image: Wayne Gerdtz
Source: Museum Victoria
 

Mammal and Bird Mounts

We have a variety of these in the Discovery Centre, ranging from small local Honeyeater species to the impressive Jaguar mount. These are all real in the sense that the skins/hides are preserved from the original animals, but the remaining soft tissue such as eyes and muscles, are not real – just as you would expect for taxidermy animals.

DC Jaguar The Discovery Centre's mounted Jaguar specimen
Image: Wayne Gerdtz
Source: Museum Victoria
 

Got a question? Ask us!

Links:

600 Million Years – Victoria Evolves

Dinosaur Walk

Live Exhibits blog posts

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Updates on what's happening at Melbourne Museum, the Immigration Museum, Scienceworks, the Royal Exhibition Building, and beyond.

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