Kings of the jungle

When I visit New York City, one of my favorite places is, unsurprisingly, the American Museum of Natural History.  

And my favorite spot in that museum is the Hall of Mammals in the paleontology section.  I've always had a fascination for prehistoric mammals, especially those lineages that are extinct -- strange animals like the gargantuan brontotheres, the oddly rodent-like multituberculates, and the diverse South American hoofed litopterns.

Seeing all the dioramas of what these creatures may have looked like always highlights two things, which I was chatting about with a paleontologically-inclined friend a couple of days ago.  The first is that even though we know a great deal about Earth's biological history, there's a ton that we don't know and will probably never know.  Fossilization requires a very specific (and rare) set of conditions -- most organisms that die are never fossilized in the first place.  Then, those few fossils that form have to survive all of the geological processes that happen afterward, and not get eroded, melted, or crushed.  And last, a paleontologist (or interested amateur) has to find it.  So chances are, for every one species we know about, there are likely to be hundreds of others that we don't -- because the remains from those species haven't been found, or perhaps never were preserved in the first place.

Second, the natural world has often been a very, very dangerous place, with large quantities of animals with Big Nasty Pointy Teeth roaming around.  My friend and I both agreed that as fascinating as they are, neither of us would be keen on hopping into a time machine and visiting the Cretaceous-age Western Interior Seaway or the shallow sea that led to the Kem Kem Formation in what is now Morocco.  Both were chock-full of enormous BNPT-owners who would have been thrilled to turn any human-sized animal into a light snack.

Well, a recent discovery has added another place and time to the "Fascinating Spot, But Let's Not Visit, Mmmkay?" list: Oligocene-age Egypt.  It was the home of an extinct lineage of carnivorous mammals called hyaenodonts -- named after, but only distantly related to, modern hyenas -- in particular one spectacularly scary beast called Bastetodon, a complete skull of which was the subject of a paper last week in The Journal of Vertebrate Paleontology.  

Study lead author Shorouq Al-Ashqar of Mansoura University, along with the Bastetodon skull (and a statue of the Egyptian goddess Bastet, after which the species was named) [Image credit photographer Hesham Sallam]

The skull was found in a fossil-rich stratum in the Faiyum Depression, a green oasis in central Egypt surrounded by trackless desert.  During the Oligocene, Faiyum (and the rest of northern Africa) was a lush jungle, and Bastetodon and the other hyaenodonts were apex predators, preying not only on the hippos and elephants of the time, but on primates like Aegyptopithecus -- a close cousin of our own ancestors, who evolved farther south in what is now Kenya and Tanzania.

Bastetodon was brilliantly equipped to fill its niche.  "I think of them as like really beefy wolverines or basically like pitbulls," said Matthew Borths, of Duke University, who co-authored the paper.  "They have really big heads that were just covered in muscle."

That, combined with an impressive set of BNPTs, made it a fearsome animal, but it bears mention that it wasn't the largest of the hyaenodonts.  That honor goes to Megistotherium osteothlastes -- the name is Greek for "giant bone-crushing beast" -- which is estimated to have weighed five hundred kilograms, with a sixty-centimeter-long skull.

Yeah, fascinated as I am with prehistoric mammals, I think Oligocene-age north Africa is a place I'd just as soon not visit.

Interestingly, though, not long after Bastetodon and Megistotherium reached their apogee, the entire group went into steep decline.  No one is quite sure why, but it's probably that climate change had a lot to do with it.  The region was getting hotter and drier, reducing the amount of vegetation and ultimately producing the desert we have now.  These sorts of changes percolate their way up the food chain, ultimately hitting carnivores the hardest; the last of the hyaenodonts went extinct during the Miocene Epoch.  (Even bigger changes were on the way, however -- during the Pliocene Epoch, the Straits of Gibraltar closed for a time, the Mediterranean Sea dried up almost completely, and the entire region became so hot it was uninhabitable -- then when the Straits reopened, it created a flood the likes of which is nearly impossible to imagine.)  

But for a while, when northern Africa was lush jungle, the hyaenodonts were on the top of the heap.  There was nothing that could come close to matching their strength and fierceness, until the climate and the passage of time ended their hegemony.  Just showing that no species is immortal -- and that today's powerful are tomorrow's (pre)historical footnote.

****************************************

Death... with big, nasty, pointy teeth

Today I'm going to write about a piece of research that isn't controversial, or deeply thought-provoking, or politically relevant, but because it's just plain awesome.

It's from the realm of paleontology, and is about a gigantic carnivore, which is part of its appeal.  Have you noticed how the little-kid fascination with dinosaurs usually revolves around carnivorous ones like Velociraptor and Tyrannosaurus rex?  They're seldom as impressed by herbivores like Pachycephalosaurus, which also has the disadvantage of meaning "thick-headed lizard," so it's kind of unimpressive right from the get-go.  Velociraptor, though?  "Swift hunter?"  Now that's cool.  You can bet that those wicked pack-hunters would never have put up with being given a humiliating name.  I bet if the paleontologists had decided to name them Brocchodentidorkosaurus ("buck-toothed dorky lizard"), the raptors would have eaten them for lunch, and that's even considering the fact that they've been extinct for seventy million years.

The dinosaurs, not the paleontologists.

But I digress.

The subject of today's post is a mammal called Simbakubwa kutokaafrika, which means "humongous lion from Africa" in Swahili (speaking of impressive names), even though it wasn't a lion at all.  It was a hyaenodont, a predatory group of mammals that are in Order Creodonta, a group only distantly related to modern Order Carnivora (i.e., cats, dogs, bears, weasels, seals, and a few other families).  The creodonts are an interesting group, at least to evolutionary biologists, because there's still a major argument going on regarding how to assemble their family tree.  Some paleontologists believe they're monophyletic -- all descended from a single common ancestor -- while others say they're polyphyletic, with different groups of creodonts coming from different ancestors that were further apart on the mammalian clade.

Whichever it is, they've now been shown through detailed skeletal analysis to have a closer connection to the bizarre pangolins than they do to today's carnivores -- yet another example of how common sense can lead to the wrong answer.

Reconstruction of a hyaenodont by Heinrich Harder [Image is in the Public Domain]

In any case, Simbakubwa was discovered recently by Duke University paleontologist Matt Borths, who was going through some fossils in the back rooms of the Nairobi National Museum when he found something that made him sit up and take notice:

The remains of a carnivorous mammal that was an estimated 1.2 meters tall at the shoulder, 2.4 meters from tip to tail, weighed an estimated five hundred kilograms, had canine teeth the size of bananas, and had three sets of incisors, two of which were big, nasty, and pointy.

That, my friends, is one serious carnivore.  That's a carnivore that could have turned your average African lion into an African lion meatloaf.

Simbakubwa is estimated to have lived around 23 million years ago, placing it in the early Miocene, but the creodonts as a group were apex carnivores for a lot longer than that.  They originated in the Paleocene (the epoch that began with the K-T extinction, 66 million years ago), and made it to the mid-Miocene (14 million years ago).  Modern(ish) true carnivores (i.e. Order Carnivora) first showed up 42 million years ago (the mid-Eocene epoch), and only reached Africa around 22 million years ago -- right around the time Simbakubwa was lumbering around the place.  So no wonder the true carnivores only began to diversify in Africa after the hyaenodonts were safely out of the way, eight million years later.

All of this highlights two things -- first, what amazing discoveries might be lurking on dusty museum shelves, forgotten and unstudied; and second, that we honestly don't know very much about what critters were out there in prehistoric times.  The conditions required for generating a fossil are thought to be mighty uncommon -- most animals don't leave any traces at all, only a few years after they die, so it's likely that the vast majority of the living things that have ever existed aren't represented in today's fossil record.

So the number of species we know about are far outnumbered by the ones we don't know about.  Meaning that as bizarre, fascinating, and wonderful as are the prehistoric animals we've classified, if we were to time-travel back to whatever epoch you choose, we'd find ones more bizarre still.  And that's even including a banana-fanged predator the size of a polar bear.

All of which puts me in mind of the last sentence of Charles Darwin's Origin of Species, which seems a fitting way to end:

There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

**********************************

Monday's post, about the institutionalized sexism in scientific research, prompted me to decide that this week's Skeptophilia book recommendation is Evelyn Fox Keller's brilliant biography of Nobel Prize-winning geneticist Barbara McClintock, A Feeling for the Organism.

McClintock worked for years to prove her claim that bits of genetic material that she called transposons or transposable elements could move around in the genome, with the result of switching on or switching off genes.  Her research was largely ignored, mostly because of the attitudes toward female scientists back in the 1940s and 1950s, the decades during which she discovered transposition.  Her male colleagues laughingly labeled her claim "jumping genes" and forthwith forgot all about it.

Undeterred, McClintock kept at it, finally amassing such a mountain of evidence that she couldn't be ignored.  Other scientists, some willingly and some begrudgingly, replicated her experiments, and support finally fell in line behind her.  She was awarded the 1983 Nobel Prize in Physiology and Medicine -- and remains to this day the only woman who has received an unshared Nobel in that category.

Her biography is simultaneously infuriating and uplifting, but in the end, the uplift wins -- her work demonstrates the power of perseverance and the delightful outcome of the protagonist winning in the end.  Keller's look at McClintock's life and personal struggles, and ultimate triumph, is a must-read for anyone interested in science -- or the role that sexism has played in scientific research.

[Note: If you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]