One of the biggest stories in paleontology this past month was the announcement of a beautifully complete fossil of an Eocene primate scientifically christened Darwinius messilae, and given the popular moniker “Ida.” A massive publicity campaign, including a book release and a documentary hosted by Sir Richard Attenborough, was launched in tandem with the fossil’s description in the online journal PLoS ONE. A backlash erupted throughout the science-minded blogosphere/twitterverse, deriding the more breathless claims that this one specimen was the “missing link” that will “change everything.”

Some of the earliest and most insightful comments came from Brian Switek at Laelaps. Earlier today, Brian compiled a collection of his and others’ Darwinius-related posts into a blog carnival called Uncovering “Ida”—an excellent resource for anyone interested in the interaction between science, publicity, and media (new and old).

This is the first of these conferences I’ve had the pleasure to attend, and I am grateful to Judy Peterson for inviting me up to show some of my drawings & paintings in the Symposium’s paleo-art show. Judy put together a roster of about 25 artists who participated in the show, including a couple of folks I’d met previously and several faces who were new to me.

Above: Russell Hawley, from the Tate Museum at Casper College, showed off some of his amazingly detailed pen-and-ink drawings of ancient environments. Below: The prolific Greg Sweatt brought along his easel and put the finishing touches on one oil painting, then began two more during the one-day show.

Above: Neffra Matthews and some of her fantastic ichnological quilts. Below: In addition to his meticulous drawings, Todd Green displayed his beautifully pieced-together skeleton of a hatching emu.

Other artists (with online galleries) at the show included Tiffany Miller, Eric Parrish, and Gary Raham.

The theme of this year’s Symposium was Paleoclimates: Exploring Past Environments, and I was able to sit in on a handful of talks by various workers and students exploring the topic. Much attention was given to the Paleocene-Eocene Thermal Maximum (PETM), a fairly rapid spike in global temperature 55 million years ago, when Wyoming was covered in tropical forests and alligators lived well north of the Arctic Circle. An analogy that came up in several talks could be summed up as follows:

Today’s climatologists : PETM :: Today’s economists : The Great Depression

Interestingly (perhaps frighteningly), multiple speakers noted that when models used in current climate change predictions were run with Paleocene-Eocene parameters, they ended up with polar temperatures nearly 10°C cooler than geologic/fossil evidence suggests…

The giant Titanoboa (detail)
Credit: Jason Bourque,
University of FloridaFrom the UF press release.

• New Snake: Titanoboa cerrejonensis
• Name Means: Titanic Boa from Cerrejón
• Relations: Boid Snake
• Holotype: UF-IGM 1, a precloacal vertebra
• Location: Cerrejón, northeastern Colombia
• Age: Middle Paleocene, 58,000,000 to 60,000,000 years old
• Length: ~13 meters (42 feet)
• Weight: 1,135 kg (2,500 lbs)
• Info:
  A vertebra from a modern Anaconda boid Anaconda compared with the type vertebra of Titanoboa.
  Photo by Ray Carson, UF News Bureau. From the UF press release.
• The hefty vertebrae of newly-described Titanoboa dwarf their modern counterparts, and are by far the largest known from any fossil serpents, as well. Size estimates for this South American giant reach well over 40 feet in length and weighing in at just over a ton!
• Today, the largest snakes are found in the equatorial tropics, where high ambient temperatures allow them to maintain their “cold-blooded” bulk. If today’s anacondas and pythons need a mean annual temperature of 27° Celsius (80° F) to grow 20 feet long, then a giant like Titanoboa would have required mean annual temperatures of 32° Celsius (96° F) to support its serpentine bulk.
• Reference: Head, J. J., Bloch, J. I., Hastings, A. K., Bourque, J. R., Cadena, E. A., Herrera, F. A., Polly, P. D., and Jaramillo, C. A., 2009. Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures. Nature 457: 715-717. doi:10.1038/nature07671. [Figures] [Supplementary Info]
• Further Reading:
  • University of Florida Press Release [multimedia]
  • Cryptomundo: Snake longer than school bus discovered!
  • The Dragon’s Tales: Now THAT’S a SNAKE!
  • microecos: Why is a protarded boa constrictor like a writing desk, I mean, thermometer?
  • Not Exactly Rocket Science: Titanoboa – thirteen metres, one tonne, largest snake ever.

Credit: John Klausmeyer,
University of Michigan
Museums of Natural History.
From the U. of Mich. press release.

• New Mammal: Maiacetus inuus
• Name Means: Fecund Mother whale
• Relations: Protocetid whale
• Holotype: GSP-UM 3475a, partial skeleton of an adult female, containing the partially ossified skeleton of a near-term fetus (GSP-UM 3475b)
• Location: Balochistan Province, Pakistan
• Age: Middle Eocene, ~47,500,000 years old
• Length: ~2.5 meters (about 8 feet)
• Info: Artist’s conception of male Maiacetus inuus as it would have appeared in life.
  Credit: John Klausmeyer, University of Michigan Museums of Natural History.
• A team of paleontologists led by Philip Gingerich have described a new species of early whale. Buried along the shrinking shores of the Tethys Sea (and collected well above sea level in present-day Pakistan), the holotype of Maiacetus is the partial skeleton of a pregnant mother, preserved with the remains of its near-term fetus still in its womb. A more complete skeleton found one kilometer away is thought to be male, due to differences in size and pelvic proportion, and shows that this early whale retained the ancestral ability to stroll the shores on four fully-functional limbs (including an artiodactyl-style “double-pulley” ankle). The position of the fetus in the female indicates that Maiacetus gave birth head-first and most certainly on land, unlike modern whales that give birth tail-first into the water, which reduces the risk of drowning and helps orient the newborns parallel to their mothers. There are several excellent articles around the blogosphere for those who want to learn more, and the description is freely accessible through PLoS ONE at the link below.
  Fossils of female Maiacetus inuus with near-term fetus in utero, as found in the field. The female’s skull is shaded white (teeth brown), and other parts of her skeleton are shaded red. The single fetus, in birth position inside the mother whale, is shaded blue (teeth orange). The specimen was collected in three plaster jackets (blue dashed lines), and additional bones were picked up separately. The red dashed line indicates the edge exposed by erosion.
  Copyright: University of Michigan Museum of Paleontology.
• Reference: Gingerich, P. D., Haq, M-u., von Koenigswald, W., Sanders, W. J., Smith, B. H., and Zalmout, I. S., 2009. New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and Sexual Dimorphism. PLoS One 4(2): e4366. doi:10.1371/journal.pone.0004366.
• Further Reading:
  • University of Michigan Press Release
  • Greg Laden’s Blog: Amazing Fossil Finding: Proto Whales Gave Birth on Land, not at sea
  • Laelaps: Maiacetus, the good mother whale
  • The Loom: The Backward Whale
  • Not Exactly Rocket Science: Fossil foetus shows that early whales gave birth on land
  • The Questionable Authority: A Fossil Fetus and what it can tell us about the life history of early whales.

Meet Indohyus

The image above, created by artist Carl Buell, shows a charming little animal called Indohyus, about the size of a modern raccoon, that lived some 50,000,000 years ago in what is now northern India. Indohyus is a member of the Raoellidae, an obscure, extinct family of hoofed mammals closely related to the artiodactyls (even-toed hoofed mammals, currently represented by pigs, hippos, camels, deer, etc.) Raoellids are only known from Eocene-aged (56–34 million year-old) fossils from southern and southeastern Asia.

Like any good group of obscure, extinct mammals, the raoellids were primarily known from fossil teeth. Until this week, that is, when a team of scientists led by Hans Thewissen described new cranial and postcranial fossils of Indohyus in the journal Nature. These new fossils are helping to provide a more complete picture of raoellid appearance, life habits, and possible relationships.

She is heavy, she’s my sister

As the restoration above shows, Indohyus was a long-legged animal, with the characteristic “double-pulley” ankle that gives artiodactyls a little extra swing to their step. Yet despite it’s relatively graceful profile, the walls of the bones of Indohyus are much thicker than in most other mammals. This is an adaptation commonly seen in aquatic animals, where thick bones act as ballast—helping them move underwater without automatically floating to the surface. Thewissen et al. suggest that the heavy skeleton of Indohyus allowed it to walk along the bottom of rivers and lakes, possibly as protection from predators or to help it search for food. Analysis of isotopes within the fossils add some additional weight (no pun intended) to this aquatic hypothesis.

The semi-aquatic lifestyle of raoellids seems to have been the start of something very big. Key features in the skull of Indohyus led Thewissen and his team to the conclusion that raoellids were the closest known relatives (or sister group) to whales.

Indohyus by Carl Buell

The Telltale Involucrum

Indohyus shares several dental features with early whales, including a front-to-back arrangement of the incisors, high crowns on its back molars, and similar wear facets. But the clincher is a little thickened lip of bone on the inside of the middle ear cavity, known as the involucrum, which likely assists in hearing underwater. Until this week, only whales were known to possess this feature. But one of the new Indohyus skulls shows that this little raoellid had a lovely little involucrum as well (see it here, and be amazed).

Shaking the Tree?

We know from the fossil record that, back when whales had ankles, they had double-pulley ankles. But exactly where whales fit into the artiodactyl family tree has been a matter of some debate. Molecular studies showed a close relationship to hippos, but there is a 35 million year gap between the oldest fossil whales (50 million years old) and the presumed origin of the Hippopotamidae (15 million years ago). Some researchers have held up the pudgy, long-faced anthracotheres as relatives of both hippos and whales, but the middle ear of Indohyus is very strong evidence that the little, long-legged raoellids were the whales’ closest kin.

That still leaves the question of how raoellids are related to other artiodactyls. Thewissen et al. propose a phylogeny showing that, as raoellids are the sister group to whales, then whales + raoellids form the sister group to all other artiodactyls. This keeps a close relationship between the whales, raoellids, and artiodactyls (as shown by their similar ankles), but removes whales from a close relationship to any particular artiodactyl lineage, such as hippos or anthracotheres.

Still, the classification of cetaceans has changed quite a bit in the past 15 years or so, and it will be interesting to see what future studies and discoveries have to say on the topic.

Reference:

Thewissen, J. G. M., Cooper, L. N., Clementz, M. T., Bajpai, S., and Tiwari, B. N. 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature vol. 450, 20/27 December 2007, pp. 190–195.

Elsewhere online:

• The Loom: Whales: From so Humble a Beginning…
• Laelaps: Shaking the Cetacean evolutionary bush: Indohyus and the origin of whales
• Greg Laden’s Blog: A Whale of a Missing Link : Indohyus
• Pharyngula: Indohyus
• Pondering Pikaia: Transitional whale ancestor unveiled
• National Geographic News: Whales evolved from tiny deer-like mammals

And a big thanks to Carl Buell for graciously granting permission to reproduce his excellent art in this post!

Over at Catalogue of Organisms, Christopher has put up an interesting post about recently described bipedal adaptations in an extinct relative of camels, the tylopod Anoplotherium. Well worth a read!

The reference is:

Erich M. G. Fitzgerald, A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales. Proceedings of the Royal Society B. First-Cite Early Online Publishing. doi:10.1098/rspb.2006.3664 1

Here’s the story from the Australian Broadcasting Company.

And Carl Zimmer has an in-depth review with figures at The Loom.

Update 8/16: More Janjucetus info and artwork available on Brian Choo’s website.