Fossil Friday - packrat molar

For this week's Fossil Friday I'm sticking with teeth. In contrast to last week's large camel molar, this time I chose the other end of the size spectrum with a tiny tooth that's only about 3 mm long.For all the attention that large animals receive, rodents and other small mammals are probably the most common vertebrate fossils in the Pleistocene deposits around Diamond Valley Lake. One of the more common rodents in our collection is the genus Neotoma, the packrat.Packrats (or woodrats) are in the Family Cricetidae, the same family that includes voles, lemmings, and hamsters. They shouldn't be confused with the brown rat (genus Rattus), which is what many people think of when they hear "rat". Rattus (including the white forms commonly used in laboratories) is a member of the Family Muridae. Rattus is only distantly related to the cricetids and was introduced into the Americas by humans.Packrats have a reduced dentition, with only one incisor and three molars in each half of both the upper and lower jaws. The molars have five cusps that are arranged in such a way that as they wear down they form three enamel-edged oval basins in occlusal view:

Different genera have distinctive cusp patterns, and in fact each individual tooth position has a unique, easily-identified pattern (see the images at this site). This particular tooth is the first lower right molar from Neotoma.There are a number of species of Neotoma known from California, and unfortunately the different Neotoma species are not as easily identified on the basis of an individual tooth. So, at least for now, this tooth can only be identified as Neotoma sp.

Bison vertebrae on the prep table

Last week we started a new preparation project, a roll-out cart where we do fossil prep work on the exhibit floor. Our first project for the cart is a jacket containing a series of bison vertebrae.The way the jacket has been opened, the vertebrae are exposed on the left side, so they're seen above in left-lateral view, with anterior to the left. As I mentioned a couple of weeks ago, mammal backbones are generally divisible into five different regions based on their position and particular features.This small sequence actually contains vertebrae from three of the five different regions, as shown in the annotated image below. Bones outlined in red are thoracic vertebrae, those in blue are lumbars, and the ones in green are sacrals and the associated hip bones:Typically, bison have 14 thoracic vertebrae. We have part of the last one, the extra neural spine at the front of the jacket. We also have part of the main body (the centrum) of this vertebrae, but it's separated from the jacket.Bison generally have five lumbar vertebrae, so we have the entire lumbar series preserved (compare them to this image of a modern bison lumbar series, shown in dorsal instead of lateral view). We are missing the long transverse processes that should be sticking out of the left side of each vertebrae; it's not unusual for them to break off before burial.Bison also have five sacral vertebrae that are generally fused to each other and to the hip bones (at least in adults). We have at least the first sacral vertebra, and some additional portion of the sacrum, but that area is still kind of a mess and it will be awhile before we know exactly what's in there.I'll be posting periodic updates on our progress with this jacket as preparation continues. The preparation cart is currently on display at Western Science Center from 10:00-12:00 on Tuesdays, with additional times to be added soon.

Fossil Friday - camel molar

For this week's Fossil Friday we'll return to camels, specifically the large extinct camel Camelops hesternus that's pretty common in Pleistocene deposits in California.This specimen is an upper molar collected near the west dam of Diamond Valley Lake. I'm pretty sure this is the upper right first molar, although I can't yet rule out the possibility that it's the second molar. This tooth was found associated with several other molars and premolars, as well as small skull fragments that all appear to be from one individual.The image above is in occlusal view, showing the chewing surface. The tooth is fairly heavily worn, showing the pattern of folded enamel ridges; the shiny grayish-white ridges are enamel, with softer dentine in between. By having these alternating areas of hard enamel and softer dentine, the enamel ridges always stick out slightly beyond the occlusal surface, so the tooth maintains a sharp chewing surface even as it's being worn down. The elevated enamel ridges are especially noticeable in lingual view (since this is an upper tooth, the occlusal surface is at the bottom):

The particular pattern of enamel ridges is one of the primary means of distinguishing between different groups of mammals, even down to individual species. For some species it's possible to make an identification on the basis of a single well-preserved tooth.Camels have a general tooth pattern that's called selenodont, in reference to the crescent-shaped enamel ridges in occlusal view. Camels share the selenodont pattern with many of the camel's artiodactyl relatives, including cervids (deer) and bovids (bison, cows, antelopes, etc.).Just for the sake of completeness, here's the labial view of the same tooth:

WSC's Fossil Preparation Exhibit

Like most collections-based museums, the Western Science Center has far more specimens than we could ever put on exhibit. We want to make our collections and procedures accessible to as many people as we can, but there are all kinds of technical, financial, and security hurdles. Even so, we're always exploring new ways to accomplish this, and today we're launching our latest effort — a fossil preparation demonstration area on the exhibit floor.Many natural history museums now have "fish-bowl"-style preparation labs so that visitors can observe staff and volunteers cleaning specimens. We hope to open such a lab one day at WSC, but that will take a lot of time and money and I'm not willing to wait. So we've put together a rolling preparation cart that our lab volunteers can take to the exhibit floor to do their work while answering questions and giving visitors an up-close look at the fossils.Two of our lab volunteers, Phyllis and Margit, have agreed to help us test out this new system by doing their prep work on the exhibit floor. Their initial specimen is an articulated series of seven Bison vertebrae that were partially prepared but are still in their field jacket.

We're going to be testing and refining this system over the next few months. The preparation cart will be on the exhibit floor whenever we have staff or volunteers available to do preparation work, initially on Tuesdays from 10:00-12:00 but with additional hours to be added later.

Fossil Friday – bison cervical vertebra

For today's Fossil Friday we have a vertebra from one of the more common Pleistocene animals in the region, the bison.The vertebral column (backbone) in mammals is typically divided into five separate regions, based on common characteristics and the location in the body. From front to back these are the cervical vertebrae, which form the neck; thoracic vertebrae, which make up part of the back and have ribs attached; the lumbar vertebrae, which form the lower back; sacral vertebrae, which form part of the hip girdle; and caudal vertebrae, which make up the tail.Nearly all mammals have vertebrae from each of these regions. The main exceptions are whales and sea cows, which have no sacral vertebrae. (In fact, they almost certainly do have sacrals, but they are modified to the point that they're indistinguishable from lumbar vertebrae. Very primitive whales and sea cows still had identifiable sacrals.) Even tailless mammals such as humans still have caudal vertebrae; our tailbone, or coccyx, is formed by five fused caudal vertebrae.Another peculiarity of mammals is that almost every living species has exactly 7 cervical vertebrae, whether the neck is short, long, rigid, or flexible. In many animals the cervical vertebrae are very intricate, with all kinds of slender projections and holes passing through them. This happens because a lot of things are happening in the neck. Besides the spinal cord passing through the vertebrae (as it does in all vertebrae) the carotid arteries and jugular veins run alongside the cervicals as they carry blood to and from the brain, both the esophagus and trachea pass directly under the cervicals, and there are numerous muscles and their associated nerves and tendons that control the complex movement of the head and neck. With so much going on, these vertebrae have to be complex to make room for everything while still providing attachment areas for all the neck muscles.The image at the top is an anterior (or cranial) view of a bison cervical vertebra. The bone should be close to symmetrical, but has been somewhat deformed, probably after burial. The prominent oval structure near the bottom is the anterior articulation, the ball part of a "ball-and-socket" joint with the next vertebra forward. Immediately above that is a dark circular area (dark because it's still filled with sediment) called the neural canal, which is the passage for the spinal cord.Here's a posterior (caudal) view of the same vertebra:

The round area at the bottom is the posterior articulation, which is a concave socket that articulates with the ball from the next posterior vertebra. The sediment-filled neural canal is the bell-shaped structure immediately above the articulation.This is the left lateral view, with anterior to the left:

The vertebra should actually be quite a bit taller, but most of the neural spine is missing. The neural spine is a prominent bony projection along the top of the vertebrae that serves as an attachment point for some of the muscles responsible for raising the head.The label on this specimen identifies it as the fourth cervical vertebra, which looks like a pretty good match to me (compare with the modern bison vertebrae shown here). There are two different species of bison known from Southern California, the long-horned Bison latifrons and the (relatively) short-horned Bison antiquus. Based on its size this vertebra probably came from the smaller B. antiquus.This vertebra was collected close to the same locality as the mastodon tooth from last week's Fossil Friday, about 15 miles southwest of the museum.

Fossil Friday - mastodon lower molar

For this week's Fossil Friday we have a tooth from this blog's namesake, the mastodon Mammut americanum. This particular tooth was collected about 15 miles southwest of the museum, not far from Temecula in Riverside County.This tooth is the lower left 3rd molar. The image above is the side, or lateral view, often referred to in teeth as the labial view (literally "near the lips"). The front of the tooth is to the left, and a lot of wear is visible on the crown at the anterior edge. Below is the same tooth in medial, or lingual view (literally, "near the tongue"):

In this view the front of the tooth is to the right, and the wear is much less obvious. The discrepancy in wear between the lingual and labial sides of the tooth are even more obvious when looking at the chewing surface of the tooth (occlusal view):

The front of the tooth is to the left. Mastodon teeth have enamel cusps arranged into a series of transverse ridges. There are five of them on this tooth. The first ridge is almost completely worn away, especially on the labial side where the enamel is completely gone. The second ridge is also heavily worn. The third and fourth ridges show moderate wear, with only the top of the enamel ridges worn away, while the small fifth ridge has very little wear. In occlusal view an unworn mastodon tooth is completely covered in enamel, but as the tooth is used the enamel wears away, exposing the softer underlying dentine. In the image below the dentine is colored red, giving an idea of how much enamel has been lost:

There are a few things that we can say about this mastodon based on the variations in wear patterns across this tooth. Because of the way mastodon teeth occlude when the mouth is closed, it's not unusual for the labial side of the lower teeth to wear more rapidly that the lingual side. The upper teeth usually show the reverse, with heavier wear initially on the lingual side. In both the upper and lower jaws the teeth eventually wear down until are essentially flat, but his tooth never reached that level of wear.The difference in wear across the tooth from the front to back is a result of the unusual method of tooth replacement in elephants and many other proboscideans, including mammoths and mastodons. Instead of having a mouthful of teeth all at once, mastodons grow in their teeth gradually and sequentially. As a tooth wears down, it moves forward in the jaw, eventually falling out and being replaced by the next tooth in the sequence. Since an individual tooth moves into position gradually, the front part of the tooth starts wearing down before the back part of the tooth has erupted. That's what we see in this tooth, in which the first enamel ridge is almost completely worn away while the last enamel ridge has almost no wear at all.Because of the sequential tooth replacement, we can also say a little about the age of this mastodon when it died. This tooth is the 3rd molar, which is the last one in the sequence, and it shows only a moderate amount of wear. This suggests that this mastodon was a fully mature adult, but not elderly, when it died. In modern elephants the 3rd molar doesn't erupt and begin to wear until the animal is about 25-30 years old. Assuming mastodon growth and tooth replacement rates were comparable to living elephants, this mastodon would likely have been 30-40 years old when it died.

Visiting the Raymond M. Alf Museum

I spent today continuing to familiarize myself with Southern California by visiting the Raymond M. Alf Museum of Paleontology, located in Claremont on the campus of The Webb Schools. Once I arrived, Museum Director Don Lofgren, Curator Andy Farke, and Outreach Director Kathy Sanders kindly spent the better part of a day showing me around their museum and discussing museum operations and California paleontology.The Raymond Alf Museum is operated by The Webb Schools, a private high school, and paleontology and museum operations are heavily integrated into the school's curriculum. Many students participate as authors on research projects, including the description of "Joe", a baby Parasaurolophus published last year in PeerJ, and now on exhibit in the museum:

Of course, the Western Science Center also shares a campus with a school, the Western Center Academy. One of my goals in visiting the Alf Museum is to see how they've combined their research and educational efforts.Besides "Joe" there are tons of interesting fossils and casts on display in the museum. There are numerous titanothere skulls from Eocene deposits in South Dakota and Nebraska:

The Alf has one of the most impressive displays of fossil vertebrate trackways I've ever seen. There are plenty of dinosaur tracks, but how many museums have multiple examples of fossil camel tracks?

Or how about cats?

There are also numerous impressive slabs of Permian Coconino Sandstone that are covered with multiple reptile trackways:

I'd like to thank Don, Andy, Kathy, and the rest of the staff at the Raymond Alf Museum for taking the time to meet and show me around their excellent museum.

Exfoliation weathering

Last week I stopped by the office of WSC Board President Todd Foutz for a meeting. There were several decorative granite boulders in the landscaping outside his office with interesting features that caught my attention.The boulders are more-or-less ovoid, but with a slightly depressed area on the top surface that's a few millimeters below the boulder edges. The lower area is visible in the photo at the top because of its jagged edges and somewhat different color; it's more white, and less brown, than the higher surrounding areas. It almost appears as if the rock is composed of concentric layers that are peeling away like an onion skin, but this rock is a granite with little or no internal layering.This is caused by a type of weathering called exfoliation (or sometimes exfoliation jointing). The onion analogy is somewhat apt, because the outer parts of the rock are in fact flaking away in thin sheets. That's why the depressed area is whiter in color; it has only recently been exposed to the air, and as a result hasn't experienced as much oxidation as the surrounding rock.But, if the granite doesn't have internal layering, what causes it to flake off in sheets? There are actually several different ways that exfoliation joints can form. A rock that has been buried can start to exfoliate if the overlying rock has been removed, releasing pressure on the deeper rocks; these exfoliation events can be rather dramatic. But that's not the case in our rock, which has been quarried and moved to this location.Another possible cause of exfoliation is freeze-thaw cycles. If the outer part of a rock soaks up water and then freezes, the resulting ice can expand and split off the outer part of the rock. That's not likely the case here for several reasons. This granite is not very porous and so has a hard time absorbing much water (although some would get in eventually). More significantly, this rock is sitting in Hemet, which only averages about 28 cm of rain a year and where the temperature almost never drops below freezing.I think the most likely cause of exfoliation in these rocks is thermal expansion. It may almost never drop below freezing here in Hemet, but it does get hot! Temperatures above 38C are not uncommon for much of the year, and that heats up the outer surface of the rock. As with most materials, rocks expand when they heat up. But rocks are terrible conductors of heat. That means that even though the outside of a rock may get painfully hot sitting in the sun, just a few millimeters below the surface the rock's temperature barely changes at all. So the outer part of the rock expands and contracts as the temperature cycles throughout the day and eventually weakens to the point that pops off of the rest of the rock. (Incidentally, the low thermal conductivity of rocks is also the reason most caves stay at a fairly constant temperature inside, no matter what the weather is like outside.)Of course, this type of weathering can potentially occur anywhere there is variation in temperatures, which is pretty much everywhere on the Earth's surface. Yet this is not something I frequently observed in Virginia, not because it wasn't happening but because other processes have such a big influence. In Virginia higher rainfall amounts, sub-freezing winter temperatures, and abundant vegetation with rock-splitting roots often make it almost impossible to determine the cause of exfoliation weathering. Here in Southern California those other variables are minimized, making the effects of thermal expansion more obvious.

Visiting the Cooper Center

Last Thursday I had my first opportunity to visit The Cooper Center, Orange County's primary repository for paleontological and archaeological remains (WSC performs a similar role for Riverside County). The Cooper Center recently hosted the Prehistoric OC festival, but things had settled down enough for paleontology curator Meredith Riven to show me around the collections.The Cooper Center's collections are vast, and are the result of many decades of collection by many different professional and amateur paleontologists as well as by various mitigation companies. As might be expected with such a large collection amassed over many years by different sources, much of the material is in need of cataloging, preparation, and rehousing. Fortunately, the National Science Foundation has a program to address such issues, and the Cooper Center recently received a collections improvement grant to help with this monumental task.

Note the earthquake restraints, something I didn't have to bother with in Virginia!A lot of the Cooper Center specimens represent marine animals, including this huge partial whale skeleton:

A tiny, rather enigmatic skull of a baleen whale:

Meredith and I also spent part of the day at California State, Fullerton to meet with Jim Parham and Gabe Santos. Many of the CS Fullerton paleontology students work on Cooper Center specimens, and there's currently an impressive exhibit at the campus library about Orange County fossils and student research on them:

Thanks to Meredith, Jim, and Gabe for spending the day teaching me about Orange County fossils (and also to Jim for providing dark glass so I could see the solar eclipse)!

Fossil Friday - Cretaceous invertebrate donation

Last Wednesday, Hemet resident Jeanette Hughes visited the Western Science Center to donate a box of Cretaceous invertebrate fossils that she and her late husband Richard collected more than a decade ago in Texas.Most of the specimens in the donation were ammonites, extinct cephalopods related to the modern chambered nautilus:

There were also several sea biscuits, a type of echinoid related to sand dollars:

A number of species of bivalve mollusks were represented, including oysters from the genus Gryphaea (or a close relative):

One of the oysters is impressively large (note the 10 cm scale bar):

Jeanette was able to provide us with pretty precise locality information for these specimens, making them potentially much more useful from a scientific standpoint. WSC did not have much of material from these taxa or from this time period, so this is a nice addition to our collection. I'd like to thank Jeanette for her kind donation.

Fossil Friday - Harlan's ground sloth jaw

For this week's Fossil Friday we have a partial lower jaw of Harlan's ground sloth, Paramylodon harlani, collected near the eastern end of Diamond Valley not far from the museum's current location.This particular fragment is the back half of the left dentary (the left and right dentaries are the bones that make up the lower jaw in mammals). The image above is the lateral (side) view with the front to the left. The small projection sticking out on the middle of the back edge is the mandibular condyle, the part of the jaw that forms the joint with the rest of the skull.Here's the medial view of the same jaw:

And here's the dorsal (top) view:

In this view we can see that, while the teeth are missing, the tooth sockets for the 3rd and 4th molars are preserved, as well as the back and inner edges of the socket for the 2nd molar. The mandibular condyle also appears much larger from this angle, because while it is relatively short vertically it is quite wide transversely (from side-to-side).There are several different species of sloths known from the Diamond Valley Lake region and that are represented in the WSC collections. Paramylodon harlani is by far the most common, making up over 93% of the individual sloth bones from the valley (Springer et al. 2010).Reference:Springer, K., E. Scott, J. C. Sagebiel, and L. K. Murray, 2010. Late Pleistocene large mammal faunal dynamics from inland southern California: the Diamond Valley Lake local fauna. Quaternary International 217:256-265.

Harley Garbani exhibit opens at WSC

Last night more than 70 WSC members and supporters attended the sneak preview of our new permanent exhibit "Harley Garbani: Dinosaur Hunter".Harley Garbani grew up in the San Jacinto Valley, and it was during his childhood here that he developed his interest in paleontology and archaeology. He spent most of his life collecting fossils and artifacts in Southern California and in Garfield County, Montana. The Cretaceous Hell Creek Formation produced some of his most famous finds, including skulls of Tyrannosaurus and a juvenile Triceratops, casts of which are on display in our exhibit. His discoveries are housed in several museums, and he was the first recipient of the Society of Vertebrate Paleontology's Morris F. Skinner Award for "...outstanding and sustained contributions to scientific knowledge through the making of important collections of fossil vertebrates."After several years of fundraising and design work, we held a reception last night that was attended by Harley's wife Mary and other members of the Garbani family, as well as by numerous WSC members and board members.

Starting today the Harley Garbani exhibit is open to everyone, and is included as part of the normal WSC admission.

Prehistoric OC

I spent several hours yesterday at Prehistoric OC, a science festival organized by The Cooper Center and held at Ralph B. Clark Regional Park in Buena Park. Over 25 different information booths and attractions were available for visitors, as well as lectures throughout the day.

There is also a small museum at the park that focuses on fossils from Orange County, many of which we're found in the park itself. Among the specimens on display are a large, essentially complete baleen whale. Below is part of the ventral side of the cranium and the lower jaw:

One of the more unusual specimens is a skull of Paleoparadoxia, a member of the enigmatic marine mammal order Desmostylia:

There were also plenty of land mammals, including this partial bison skeleton:

Thanks to The Cooper Center for putting on such a fun and educational event!

Fossil Friday – rabbit teeth

Not all the fossils in the Western Science Center collection came from huge Ice Age mammals. In keeping with my post from a few days ago about possible modern rabbit traces on the WSC grounds, for this Fossil Friday we'll look at an example of a fossil rabbit.Most of the rabbit remains in the WSC collection are isolated teeth, recovered by screening sediment from Pleistocene sites. As you might expect, most of them are tiny; the partial cheek tooth in the image at the top is only about 3 mm long. Like many herbivorous mammals, rabbits have teeth in which the enamel is curved into folds, making a series of sharp ridges on the chewing surface as the tooth wears down. Rabbits have a particularly deep groove running along the lateral side of the tooth, visible in a different view of the same specimen:This tooth is close to square in cross section, Suggesting that it's probably a lower tooth (either the 4th premolar or the 1st or 2nd molar). The upper cheek teeth in rabbits are more rectangular in cross section, roughly twice as wide as they are long. This particular tooth is identified in the collection records as Sylvilagus sp., and while I'm not yet familiar enough with rabbit anatomy to confirm this, the size is consistent with Sylvilagus.Sylvilagus, of course, is a rabbit that's still widespread in California today, which brings up an important point about Pleistocene faunas. We have a tendency when describing the Ice Age of talking about big, impressive animals like mastodons, mammoths, and sabertooth cats (the "charismatic megafauna"), but most of the animals present during the Pleistocene are the same ones that are around today. It's easy to forget that cottontail rabbits were grazing in the same meadows as Columbian mammoths.  

Potential traces everywhere

I haven't had a lot of free time over this summer, what with moving across the country and starting a new job. Even so, I've been slowly working my way through an excellent book on traces and trace fossils, "Life Traces of the Georgia Coast" by Anthony Martin (@ichnologist on Twitter). Due to the insidious influence of this book, I now find myself looking for traces all the time.A few days ago when I was leaving work I spooked a rabbit (probably a desert cottontail, Sylvilagus audobonii) that was hiding in the grass beside the museum. Having just read the chapter in "Life Traces" that included rabbit traces I decided to see if this rabbit had left behind any evidence of its presence.Most of the Western Science Center grounds are landscaped with native, drought-resistant vegetation. The grasses along the edge of the building are mostly deergrass (Muhlenbergia rigens), a bunchgrass that grows in dense clumps, and when I saw the rabbit it was running from a patch of deergrass. When I saw the grasses from above, I noticed that the middle of some of the clumps were brown and missing blades (top). Here's a closeup of the middle of one of the clumps:

The center of the clump was covered with mashed-down, broken blades of grass, over an area of roughly 25 cm by 10 cm. Around the margin of the flattened area there was a dense patch of erect bases of grass blades, clipped off to a height of around 10 cm. The clipped grasses were concentrated on each side of the flattened area, so that the flat area was mostly open on each end of the long axis.A quick survey showed that about 1/3 of the deergrass bunches had these patches in their centers, although there was a lot of variation in their size, and especially in the amount of clipped-off blades. Some patches had only a very small number of clipped blades, although all of them had at least a few. It's interesting that these clipped and flattened areas are only visible when seen from above. When seen from the side the tall grass around the margins of the clumps hide the flat patches at the center.I suspect that the rabbits are eating out the centers of the clumps and using them as hiding places. A rabbit hunkering down in the center of a clump would be completely invisible to predators like coyotes, and while a rattlesnake might be able to sense the rabbit's body heat it might have a hard time finding a way into the center of the clump.So far I haven't found any additional traces to confirm my interpretation. I haven't spotted any rabbit fur or droppings in the clumps (and I'm a little hesitant to stick my hand into them blind, because of the possibility of the aforementioned rattlesnakes). Hopefully one day I'll get better confirmation, like actually seeing a rabbit sitting in the clear patch, chowing down on deergrass.

Fossil Friday – more camel bones

Last week for Fossil Friday I showed an example of a metapodial of an extinct camel, Camelops hesternus, which was collected about a mile from the museum's current location. It turns out that the metacarpals weren't found in isolation. Several other bones were found nearby, including the two large fragments shown above.These relatively large fragments, like the metapodial from last week, are both camel bones. But we've moved up the arm; these are fragments of the humeri (upper arm bones). In each case, only the end near the elbow (the distal end) is preserved. I've photographed them from the front (cranial or anterior view), in the same orientation as you would see them in a complete skeleton. That means that the fragment on the left is actually the right humerus, and the larger one on the right is the left humerus. Almost half the left humerus is preserved. Compare it to this much more complete specimen from the WSC collection (seen in lateral view, with the distal end on the left): It's possible that the two humeral fragments and the metapodial from last week belong to the same individual camel, especially since there were additional bones from the front legs associated with these. However, at this point I can't say with certainty that they come from one animal. I haven't yet seen the original field notes or photos, so I don't know if they were found actually articulated with each other or if they were just nearby, but I do know that there were bones from other species found at the same site. It would be worthwhile to measure each camel bone and compare their proportions to known associated bones of Camelops to see if their relative sizes are consistent with one animal, and to check them for indications of whether or not they're at the same growth stage. These checks won't prove that they come from one animal, but depending on the results they could prove that they don't come from one animal.Finally, another point is worth noticing. The second specimen is only partially prepared, with one side still in the original field jacket. A large number of specimens in the WSC collection have been prepared only enough to make an identification, and still need to be fully cleaned and restored. We have a lot of work to do!

Gold Fever! comes to Western Science Center

On Saturday we opened a new temporary exhibit, "Gold Fever! Untold stories of the California Gold Rush." The panels that make up the core of the exhibit were developed by the Oakland Museum of California and the California Council for the Humanities.The panels in the exhibit are supported by a selection of artifacts from the WSC archaeology collection, and additional specimens on loan from local residents and businesses:

One of my favorites is this rust-encrusted revolver:

Having arrived in California so recently, this was a fun exhibit for me to explore, since it's essentially a primer on California history during the mid-1800s. The discovery of gold in California in 1848 set of a wave of immigration that had cascading effects, both good and bad. The region grew so abruptly that by 1850 California was granted statehood, barely two and a half years after gold was discovered here.Many of the artifacts on display are on loan from the Gilman Historic Ranch and Wagon Museum and from American Prospector Treasure Seeker, who also did a gold panning demonstration at our WSC members' reception on Friday night. We've also received support on this exhibit from Big 5 Sporting Goods in Hemet, who donated metal detectors, pans, and field equipment for a raffle. Raffle tickets can be purchased at the WSC box office, and winners will be drawn in January after the exhibit closes."Gold Fever!" will be open at WSC until January 15.

Fossil Friday – camel metacarpal

For Fossil Friday, we have the hand bone (front foot bone) of the western camel, Camelops hesternus, seen here in anterior view (the bottom is to the left). It was collected about a mile from where the museum is now located, and was associated with several other camel bones.Like many other members of the Artiodactyla, the "hand bone" (or metapodial) in camels is actually two bones fused together, the 3rd and 4th metacarpals. Even though the two bones are fused together for most of their length, there is still a visible groove indicating where they're fused, and at the distal end the bones are still separated. At the distal end each metacarpal articulates with a separate finger; the articulation is more clearly visible in the posterior view of the same bone, with the articulation on the left:These correspond to the middle and ring fingers in humans. The foot has a similar arrangement. Since most artiodactyls have this two-finger, two-toe arrangement they are sometimes called the "even-toed ungulates".It's easy to forget how big camels are. Camelops hesternus was roughly the size of modern camels, and they are massive animals. This metapodial is close to 35 cm (over a foot) long. Here's what a whole skeleton looks like, from the exhibit at the George C. Page Museum:Even though Camelops hesternus was comparable in size to a modern camel, it was actually more closely related to the llamas and vicuñas from South America, and was the largest member of that group. Camelops went extinct shortly after the end of the last Ice Age.

Repost – The making of a scientist

This morning Anthony Martin published a beautiful tribute at his blog Life Traces of the Georgia Coast, describing the importance of parental support and maximizing childhood opportunities in becoming a scientist, especially when growing up poor. Seemingly small acts of kindness and support can have dramatic and lasting effects. Reading his post, I was inspired to republish a post from my old blog, Updates from the Paleontology Lab. This was originally published in March 2011, on my 42nd birthday.I turned 42 years old today. According to Douglas Adams in The Hitchhiker’s Guide to the Galaxy, 42 is the answer to life, the universe, and everything – clearly an opportunity for self reflection if there ever was one. And since 42 is, after all, the answer to a question, it seems appropriate to address a question that I’m frequently asked by museum visitors (especially parents with young children) – why did I become a scientist?A full answer to that question would require much more than a blog post. (In fact, it would probably need a book, written by psychiatrists). But there are factors that are easily examined, including the information I was exposed to as a child.As I look at the breadth of resources available today online, it’s jarring when I consider how far information technology has come in my lifetime, and I don’t think it’s an exaggeration to say that the personal computer and the internet are the most significant human inventions since the printing press.I grew up poor in rural Virginia. The nearest natural history museum was the Smithsonian, 200 miles away; by the time I started high school I had managed to visit there twice. We lived too far from the city to get good PBS reception, although I did get to watch it when we visited my grandmother in Roanoke. So initially I depended on libraries for information. Even this was a challenge; Stewartsville Elementary School was 15 miles away, and the nearest public library was 30 miles away in Vinton, so I couldn’t exactly walk there whenever I wanted. But I found enough science-themed books to apparently influence me for life, and by the 1st or 2nd grade I knew I wanted to be a scientist. Three books in particular that I read around that time (1976-78) were very influential:Childcraft Worldbook 1976 Annual – Prehistoric AnimalsMy grandmother had a complete Worldbook Encyclopedia set, as well as the Childcraft “How and Why” Library. Included with that was a subscription to the Childcraft Annuals, which were on a different topic each year. In 1976, the topic was Prehistoric Animals.The Prehistoric Animals issue was wonderful. It went through all kinds of amazing creatures, including eurypterids, trilobites, and crinoids like the ones I collected as a child in the mountains of Botetourt and Craig Counties. I was introduced to the Geologic Time Scale for the first time. There were dramatic paintings that I would stare at for hours, and later attempt to copy; Dunkleosteus, Dimetrodon, all kinds of dinosaurs and mammals. Over the next few years I probably read the book cover to cover at least a dozen times.Danny Dunn and the Fossil Cave, by Raymond Abrashkin and Jay WilliamsThe Danny Dunn books were a series of science-themed children’s novels in which three children (Danny Dunn, Irene Miller, and Joe Pearson) became involved in various science and technology adventures. Danny’s mother was a live-in housekeeper for Professor Bullfinch, who was a kind of generic scientist/inventor, while Irene’s father was an astronomer. Fossil Cave was the first Danny Dunn book I read (although it was the sixth in the series). In the story they discovered a dinosaur skeleton buried in a nearby cave using what was essentially a portable CT scanner. I was enthralled (the fact that I totally had a crush on Irene probably helped), and immediately checked out all the Danny Dunn books I could find. I eventually found and read six of the 15 books in the series. The Nine Planets, by Franklyn M. BranleyThis was a non-fiction science book, again aimed at children. I was already interested in dinosaurs from the Childcraft books. But upon discovering that they were extinct it occurred to me that maybe they were only extinct on Earth, and could still be living on other planets (give me a break, I was in 2nd grade!). I checked out and read The Nine Planets in order to find out.Some of the concepts in The Nine Planets were a bit beyond me at that age, but it was enough to confirm that dinosaurs were unlikely on other planets, and to get me interested in astronomy. That interest has continued, and I didn’t choose between astronomy, paleontology, and field biology until I was in college. All About Whales, by Roy Chapman AndrewsWhen I first read this book I had no idea that Roy Chapman Andrews was one of the most famous of all paleontologists. Year later, while in graduate school I saw a copy in a library discard sale and I finally made the connection. Andrews’ children’s books are fun reads. All About Whales has some chapters that go into a fair amount of detail about whale skeletal anatomy and others in which he talks about accompanying whalers on a hunt and having to fight off sharks after ending up in the water. This book actually influenced me twice; as a child it reinforced the idea of science as an adventure in learning, and as an adult it helped me realize the influence a scientist could have by making their research accessible to everyone.By the end of the 2nd grade I was completely hooked on science. I read every paleontology and astronomy book I could find in my school’s library and the public library in Vinton (we started driving out there every few weeks). This broadened my reading selection considerably. The Lost World, by Sir Arthur Conan DoyleI believe I first read Doyle’s famous book after checking a copy out of the public library. I found myself wishing for the characters to have more encounters with the dinosaurs so I could read more detailed descriptions. It bothered me greatly that there was almost no description of the aquatic creatures in the Central Lake. It’s probably also informative that I found the scientists vastly more interesting than either Roxton or Malone and that, while I found Professor Challenger impressive and amusing, the character I most identified with was Professor Summerlee.Starting around 1980 I found another source of books; flea markets. Paperback books and magazines would generally sell for somewhere between a nickel and a quarter, and while rural Virginia flea markets were not exactly hotbeds of scientific literature, there were some things to choose from.For many decades Isaac Asimov wrote a monthly science column for the Magazine of Fantasy and Science Fiction. A subscription to F&SF was way out of my financial league, but many of Asimov’s essays were republished in paperback compilations; these would sometimes turn up at the flea markets, and I ended up with perhaps 8-10 different compilations. While the majority of these essays were on astronomy topics, Asimov was a biochemist and an eclectic writer, and the topics often involved chemistry, biology, physics, and science history.The other thing that frequently showed up at the flea markets were back issues of National Geographic. Almost every issue would include at least one article related to science in some way, and I would dig through boxes picking out the ones that looked most promising (at 5 or 10 cents each, I could only afford a few at a time). Then one year, around 1980, I hit the jackpot. Someone had been selling a huge collection of Nat Geos, perhaps 150-200 issues. They were asking 25 cents for each one, which was out of my price range. But at the end of the day, they took everything they hadn’t sold (nearly all of them) and threw them in the dumpster. My sister spotted them as we were leaving, and Mom stopped the car while I climbed in the dumpster and pulled out 10 boxes of Nat Geos.Four National Geographic issues in particular always stood out for me.August 1978New Ideas about Dinosaurs, by John OstromBy the time I obtained this issue, I had read dozens of children’s books on dinosaurs. I also loved watching Land of the Lost on Saturday mornings. All of these sources portrayed a very consistent image of dinosaurs as little more than giant, spiky lizards that hung out in swamps all day (although the Tyrannosaurus in Land of the Lost was remarkably quick and agile). In other words, the stuff I was reading in the 1970’s was based on the science of the 1950’s, or even earlier. Ostrom’s article was the first thing I had read that showed paleontology as a dynamic science that was discovering more than just new species. Some of the things in my books could be wrong, and there were still lots of new things to discover.December 1976The Imperiled Giants, by William Graves and Exploring the Lives of Whales, by Victor SchefferJanuary 1979Humpbacks: The Gentle Giants, by Sylvia Earle and Humpbacks: Their Mysterious Songs, by Roger PayneFor many years National Geographic seemed to have a special relationship with whale research, and they published numerous articles on whales in the 1970’s. These two issues really stood out for me. One presented an overview of all different species of whales, and I realized that even among living animals there was much greater diversity than I had realized. The other focused on humpback whales, and is the issue that included the famous whale song record as a plastic insert (I think this is the only record Nat Geo ever released). This got into some of the nitty-gritty of whale research, and emphasized that a lot things were still unknown. I should emphasize that these articles (and Andrews’ book) didn’t directly lead to me working on fossil whales, but they probably helped me make that transition more easily years later.January 1980What Voyager Saw: Jupiter’s Dazzling Realm, by Rick GoreI can’t remember the Voyager spacecraft being launched, and in fact I don’t remember seeing a single news broadcast about their encounters (although there must have been some). So when I read the Nat Geo summary of the Jupiter encounters it was completely new to me. It seemed like practically everything I had read about the Solar System was terribly incomplete if not outright wrong. I also read that the Voyager probes were still going, with more encounters yet to come. I couldn’t wait!I can’t emphasize enough the impact Voyager had on me. After Jupiter revealed what Voyager could find, it was like getting science on a schedule. All we had to do was wait for Voyager to reach Saturn, and new discoveries were all but guaranteed. It seemed like all the efforts of all the scientists through the centuries had barely scratched the surface, and for me, emphasized science as an ongoing endeavor, not a body of facts.My interest in science was no secret among my family by the time I was in upper elementary school. Several of my relatives really supported this, including my parents, my grandmothers, and some of my father’s sisters. Around 1980, my Aunt Virginia joined some type of “Book of the Month” club. For several years, she used her club credits to buy me a science book each Christmas.Cosmos, by Carl SaganI read the book Cosmos before seeing the video series of the same name. Sagan did a great job emphasizing the depth of geologic time and the scale of the universe. He also frequently paid homage to early scientists. I was particularly taken with his description of Eratosthenes’ calculation of the circumference of the Earth, using nothing more than two sticks, careful observation, and relatively simple math. The fact that such a major discovery could be made so simply made my goal of becoming a scientist seem that much more attainable.Another important concept in Cosmos was the distinction between science and pseudoscience. Remember that most of my resources were coming from school libraries and flea markets. Other than a few trips to the doctor, by the time Cosmos was published in 1980 (when I was 11) the only people I had ever met with college degrees were my elementary school teachers; I had never met anyone with a science degree. That made it very difficult to evaluate the other books I would find in the libraries and flea markets, on astrology, the Bermuda Triangle, alien visits to Nazca, or Bigfoot and Nessie, among others. Admittedly, I had begun to have doubts about some of these things (“Why did the characteristics of my astrological sign seem to match me so poorly?  With so many people looking for Nessie in a small lake, why couldn’t anyone get a good picture? Couldn’t the Navy TBMs just have gotten lost and run out of gas?”). So far as I know, Cosmos was the first popular science book that took on pseudoscience en masse and tried to define how science was different.There were many other influences for me along the way, and I’m sure I’ve since forgotten many of them. But these books all stand out from my early childhood. It’s not that all of them contained the best scientific information, even for the time (how much accurate science was there in Danny Dunn and the Fossil Cave, really?). But all of them opened my mind to new concepts, and led me to seek out additional sources of information. As far as I can determine, these books were the genesis of and the major guiding influences in my interest in science.

Fossil Friday – mammoth jaw

It's Fossil Friday, and in what I intend to be a regular feature we'll look at different specimens in the Western Science Center collection. To kick off, we'll examine a mammoth jaw to show that not not everything in the Valley of the Mastodons is a mastodon!The image above is an oblique view, with the front of the jaw to the left. Mammoths (and their close relatives, the elephants) have massive but remarkably short lower jaws. The example above is missing the condyles that articulate with the cranium, but is otherwise complete and has almost its entire length preserved. This particular specimen is from a Columbian mammoth (Mammuthus columbi), and was collected from Late Pleistocene deposits during the Diamond Valley Lake Project.Here's the same jaw from directly above (dorsal view), with the front of the jaw at the top: The two roughly oval patches with the ridges and grooves cutting across them are the teeth. Here's an oblique close-up of the right one:One thing that you may find a bit curious is that in this huge jaw there are only two teeth, one on each side (although, to be fair, each tooth is enormous). That is a function of the unique method of tooth replacement found in elephants and their relatives. Unlike most mammals, elephants grow in their teeth one at a time, and as each tooth wears down it gradually moves forward in the jaw and falls out. As this happens, the next tooth in line moves forward and becomes functional, so the teeth act as if they're on a conveyer belt. Because the new tooth starts to become functional before the older one falls out, at most points in its life an elephant will have approximately one and a half functional teeth in each half of its jaw at any one time.There are two points in an elephant's life cycle that are exceptions to this general rule. A very young elephant that has only just had its first tooth erupt has, of course, only one functional tooth instead of one and a half. Moreover, an elephant only ever grows a total of six teeth in each half of its jaw, three premolars and three molars (excluding the tusks in the upper jaw, which are also teeth). That means that an elderly elephant that has already lost its first five teeth will only have a single, very large tooth remaining in each half-jaw.That's exactly what we see in the mammoth jaw shown here. The enormous teeth on each side of the jaw are the lower 3rd molars, which had almost completely erupted but still had a lot of wear to go. The three premolars and the first two molars have already worn down and fallen out, making this a fully mature mammoth. We can even compare this to modern elephants to get an estimate of how old this mammoth was when it died. Assuming that mammoths and elephants grew and replaced their teeth at the same rate (and there's pretty good evidence that they did), and assuming that their diets were equally abrasive (less certain, but not unreasonable), the Diamond Valley Lake mammoth was probably at least 40 years old when it died.