PRI on the Mall

We had a great time last weekend on the National Mall in Washington, DC. Six PRI staff members traveled to our nation's capital for the first ever Science & Engineering Festival on October 23 & 24. We trucked down a van-load of Devonian shale and set up our booth with two large bins for participants to dig through. Anyone who found a fossil was invited to take it home with them as a souvenir. Over two days we interacted with around 5,000 people. Sometimes our booth was so crowded it was impossible to tell exactly how many people we met! We all had a lot of fun and hope that there will be a festival next year to participate in. Here are some pictures from the festival.

A view of the festival from outside our booth. We had great weather and a ton of people came out to explore science!

Kids examine shale for fossil brachiopods and trilobites

Staff member Richard Kissel helps identify fossils.

Staff member Kelly Cronin tells kids about the Devonian seas.

Fossil of the Week

10/27/10 – Moa Pelvis

The moa are a group of extinct flightless birds found only in New Zealand.  They belong to the ratites, a group of flightless birds including living members on four continents: the emu (Australia), the ostrich (Africa), the kiwi (New Zealand), the cassowary (Australia and New Guinea), and the rhea (South America).  The moa, however, are distinctive from all other known ratites, and in fact all other birds, in lacking wings entirely.

There were probably ten to fifteen species of moa upon the Earth. The number of species names, however, exceeds the actual number of species because the two sexes were often mistakenly named separately, principally because females were significantly larger than males. Moa lived in a wide range of areas from the coasts to the mountains of New Zealand and ranged significantly in size, the largest being around 2 meters (6.5 feet) at the hip. Preserved gizzard contents consisted mainly of tree material, suggesting that they lived in forests. Most known moa specimens are subfossils rather than true fossils (still consisting of bone, not rock), and there are even some dried and one mummified specimens known, allowing paleontologists the opportunity to extract DNA for some species.

Moa became extinct at least 600 years ago due to human hunting. Prior to humans’ arrival on New Zealand, it is thought that their only predator was the enormous (and now also extinct) Haast’s Eagle. At least 40% of New Zealand’s endemic species have become extinct since humans arrived on the islands.

Pictured here is the extremely robust pelvis of a moa (Emeus crassus, PRI 50004-50005) viewed from the ventral side (the underside). The pelvis is a compound bone – a fused combination of several vertebrae, the ilium, ischium, and pubis bones. PRI has a large number of bones from this moa specimen and the skull, jaw, and one of the leg bones can be seen on display in the Museum of the Earth. Most moa bones are large, as they are necessary to support the immense weight of the bird, but the skull is significantly more fragile and a much rarer fossil find.

Text by Ursula Smith (reprinted from “Fossil Focus” in American Paleontologist, Fall 2010).

Fossil of the Week

10/20/10 – Boring Bivalve

This week’s Fossil of the Week is another specimen from our type collection. It’s a boring bivalve, not in the sense of being uninteresting, but in the sense of a clam that burrows itself into solid rock. This is Lithophaga gainesensis [the species name was misspelled on the hand-written label in the photo], a member of the mussel family, Mytilidae. It was, as the label indicates, originally called Lithodomus, but that name is now (for technical nomenclatural reasons) considered a synonym of the genus Lithophaga, which still has members alive today. Lithophaga gainesensis was named from the Middle Eocene (Mcbean Formation), of Ft. Gaines, Georgia.

Lithophaga species are called Date Mussels because of their smooth cylindrical body form. The name literally means “rock eater,” an epithet that is partly true. The soft tissue lining the shells in life contains a gland that secretes an acid-like mucus that dissolves calcium carbonate or limestone (the soft “rock” that most date mussels inhabit). The Date Mussels do not literally consume the rock for nutrition, as the name might imply, but the rock is “eaten away” resulting in a smooth, blind-ended tube within which the mussel can safely protrude its siphons from the open end to access seawater for oxygen and food particles. The empty burrows of date mussels and other boring bivalves in the fossil record are given the trace fossil name Gastrochaenolites.

This species was named and described by PRI’s founder, Gilbert Harris, in the fourth issue of Bulletins of American Paleontology in 1896. The title of the monograph was simply “The Midway Stage,” referring to the basal-most subdivision of the Eocene Epoch in the southern United States. Ft. Gaines, Georgia, is on the Chattahoochee River at the border of Georgia and Alabama. Harris wrote, “[the deposits here] consist of light gray or yellowish impure limestone…frequently eroded in a peculiar rough and irregular manner. … Fossils are of frequent occurrence in this formation, but here… they consist only of impressions, moulds and casts … the shelly matter of the specimens inclosed [sic] is entirely removed, and hence one is left to work out the details of the various specific forms by means of gutta-percha moulds.” [“Gutta-percha” is an interesting phrase here – it’s a rubbery latex-like material produced by a tropical tree, and was one of the first natural plastics to be used by humans; it is waterproof, and has been used to insulate underwater cables or in dentistry for temporary fillings.] Indeed the syntype* here (PRI 58 – a really early catalog number!) is a shell-less internal mould (with its siphon end pointing toward the right).

*See Fossil of the Week 11/11/09 - Bellerophon calcifer for a definition of "syntype."

Text by Paula Mikkelsen

Fossil of the Week

10/13/10 –Tropical Antarctica?
In a salute to Museum of the Earth’s new exhibition “Science on the Half Shell: How and Why We Study Evolution” (created by PRI’s Bivalve Evolution project), this week’s fossil of the week is Lahillia wilckensi Zinsmeister, 1984 (PRI 13176). Lahillia is a heart cockle, a member of the bivalve family Cardiidae. This group of clams still living today is prevalent in the tropics and subtropics of the world’s oceans. What is special about Lahillia is that it was discovered and described from Eocene deposits in Antarctica – a decidedly un-tropical location today!

The world during the Eocene Period, 56 to 34 million years ago, was very different from the modern world. Globally, it was a very warm “hothouse” world – the air temperature difference from pole to equator was only half of today’s and the deep-ocean currents were exceptionally warm. Tropical climates extended as far north as Maine and Hokkaido, Japan. On a map of Eocene Earth, most of the modern continents are recognizable, but they have not yet moved to their present positions. There are no polar ice caps, India is still free-floating, and Europe and Asia are bisected by the large shallow Paratethys Sea. The Paratethys was a center of origin for many tropical Pacific bivalves, including Giant Clams, which are now restricted to coral reefs in the Indo-West Pacific.

Lahillia wilckensi was described by Dr. William J. Zinsmeister, a professor of geology at Purdue University. It was collected during a 1974-1975 joint Argentine-American expedition to Seymour Island. PRI received Professor Zinsmeister’s entire research collection in April 2009, and just recently was awarded National Science Foundation funding to curate the collection. The Zinsmeister Collection contains approximately 5,510 lots (almost 22,000 specimens) of Cretaceous-to-Eocene fossil mollusks from Seymour Island, Antarctica, and its vicinity, and is widely recognized as among the largest and finest in the world from this region. The Seymour Island fossil fauna contains species from both southern South America and Australasia and provides the key to understanding the biogeography of the southern Pacific Ocean during the final break-up of the ancient continent Gondwana.

Text by Paula Mikkelsen

This Weekend at Museum of the Earth

Fossil of the Week

10/6/10 – Chambered Nautilus

The living Chambered Nautilus is often considered a classic “living fossil.” It is a cephalopod – in the same group as squid and octopuses. Its subclass, the Nautiloidea*, once claimed extremely diverse and abundant marine predators, with approximately 2,500 fossil species currently known. Today, there are only two living genera and four to ten species. The genus Nautilus is the most common of the two modern genera and contains perhaps six species through the Indo-West Pacific. Pictured here is a modern specimen of Nautilus pompilius, the Chambered Nautilus (PRI acc. 1414), which is the largest and most common of the living species. Like our last Fossil of the Week, it was named by Linnaeus in Systema Naturae in 1758.

The first nautiloids appeared in the Upper Cambrian Period, approximately 490 million years ago, when cephalopods first developed shells. The shell allowed them to become neutrally buoyant (that is, no energy expenditure is required to maintain a constant depth) allowing them to expand their habitat off the sea floor. The group then underwent an evolutionary radiation in the early Ordovician Period, approximately 480 million years ago, becoming an extremely important group of predators in the Early Paleozoic. Fossil nautiloids were diverse and abundant, with many different morphologies known, from straight cone-shaped shells to coiled shells. Today, the only shape remaining is the discus-like, planispiral shell of N. pompilius. The living nautiloids appear to have undergone extremely little change during the nearly 500 million years since their first appearance.

Nautilus has often been used as an analog for understanding its better-known but extinct cousins, the ammonoids. Although there are many similarities in shape and appearance, the ammonoids are a much younger group that first appeared in the Silurian Period (420 million years ago). The ammonoids might in fact have been descendents of the older nautiloids. Nevertheless, reconstructions of the soft parts of extinct coiled ammonites owe much to studies of Nautilus specimens. We know that Nautilus today uses jet propulsion to swim shell-first through the water, and it is likely that some ammonoids moved in a similar way.

Text by Ursula Smith (reprinted from “Fossil Focus” in American Paleontologist, Winter 2008)

*For more about fossil nautiloids, see Fossils of the Week 6/16/10 – The Fourth Variant and 5/5/10 - Bradfordoceras.

Teacher Resource Day

Teacher Resource Day 2010!

Teachers and Guests Free

Saturday, October 2, 2010
9 a.m. – 1 p.m.
Museum of the Earth

This year’s highlights include…

• Meet Museum of the Earth scientists and educators.
• Free fossil & modern specimen giveaway, featuring an amazing collection of minerals from around the world!
• Free publications!
• View our newest exhibit, Science on the Half Shell: Why and How we Study Evolution.
• Behind-the-scenes tours of the Institution.

Refreshments provided.

The first 100 registrants will receive gift bags!

Teacher Admission is free 9am - 1pm
Guest Admission is free 9am - 10 am