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June 10, 2020 by wpengine

The Bromacker Project Part V: Orobates pabsti, Pabst’s Mountain Walker

New to this series? Read The Bromacker Fossil Project Part I, Part II, Part III, and Part IV.

In 1995, my first year of field work at the Bromacker quarry, Stuart Sumida discovered a fossil that we initially thought was that of the amphibian Seymouria, based on the size and shape of the exposed vertebrae. This tentative identification made sense, because before our collaboration began, Thomas Martens had discovered in the Bromacker a skull of Seymouria, a creature known from localities in the USA. Months later, while I was preparing the specimen, Dave Berman and I realized the fossil wasn’t Seymouria, and that it belonged to the same unnamed animal that Thomas had collected a partial skeleton of before our collaboration began.

image of orobates pabsti — Specimen of *Orobates pabsti* collected in the 1995 field season. We determined that it is a juvenile. Photo by Dave Berman.

In the 1998 field season I discovered a third specimen, which is by far the most spectacular fossil that I have ever discovered. I found it towards the end of the field season when I pried up a piece of rock from the quarry floor. Upon turning over the rock piece, I saw an articulated foot preserved in it. I couldn’t believe my eyes! I knew that at the Bromacker if an articulated foot was found, the rest of the articulated skeleton should be attached to it. The problem was, we didn’t know if I had discovered a front or a hind foot, so we weren’t sure how the specimen was oriented in the quarry and whether it penetrated the nearby rock wall. Dave carefully lifted another piece of rock and thought the bones exposed in it were part of the shoulder girdle. Unfortunately, closer examination revealed that it was a piece of skull roof—another lobotomy—but, lacking x-ray vision, this is how we find fossil bone at the Bromacker. The good news was that the fossil specimen appeared to parallel the quarry wall.

A film crew from the regional MDR television station visited us early on the day of my discovery to interview Dave and Thomas. The discovery was made after they left, so Thomas immediately notified them. They returned and recorded a reenactment of my discovery. The piece of rock I am holding contains the foot. The rest of the fossil lies in the low mound of rocks in front of me. Photo by Dave Berman, 1998.

Dave and Stuart finish plastering the block. The red flag is a north arrow to indicate the orientation of the block in the quarry. Photo by the author, 1998.

Dave, Stuart, Thomas, then-graduate student Richard Kissel (University of Toronto, Mississauga), and I named the animal Orobates pabsti, which is from the Greek “oros,” meaning mountain, and “bates,” meaning walker, in reference to the Bromacker fossil environment being an intermontane basin. “Pabsti” is in honor of Professor Wilhelm Pabst for his pioneering work on the Bromacker fossil trackways.

We determined that Orobates is very closely related to Diadectes, and like Diadectes, was herbivorous. Orobates differs from Diadectes and other diadectomorphs in the group Diadectidae in a number of features, some of which are as follows: spade-shaped cheek teeth that are oriented on the jaw at an angle of 30–40° to the jaw line, rather than being close to 90°; narrower and shorter vertebral spines; 26 vertebrae between the head and hip (Diadectes has 21); proportions and shapes of individual toe bones; and digit (finger or toe) length.

The Bromacker has long been famous for its exquisitely preserved fossil trackways. Identification of the particular fossil animal that made a given trackway is almost always very difficult, because body fossils often lack completely preserved hands and feet and typically are not found in association with trackways. As a result, trackways are given their own set of names, called ichnotaxa (“ichno” means track or footprint), which are typically referred to major groups of animals instead of individual species. The Bromacker is unique, however, because nearly completely preserved body fossils occur in a rock unit above the trackways, indicating they are very nearly contemporaneous. Five ichnotaxa are known from the Bromacker, and one of them, Ichniotherium, has been attributed to Diadectidae.

A large slab of rock being inspected for trackways shortly after it was unearthed in the commercial rock quarry. The polygonal patterns in the rock are mudcracks. Photo by the author.

Graduate student and trackway expert Sebastian Voigt (now Director at Urweltmuseum GEOSKOP, Burg Lichtenberg, Germany) often visited us at the Bromacker. In 2000, a time when Diadectes was the only known Bromacker diadectid, Sebastian and his advisor Hartmut Haubold (now emeritus at Martin Luther University Halle-Wittenberg, Germany) proposed that Ichniotherium cottae made two track types, designated as A and B, that differed according to the speed at which the trackmakers moved. This contrasted previous studies that proposed three species of Ichniotherium at the Bromacker.

Once the skeletal anatomy of Orobates became known, Sebastian realized that there were two species of Ichniotherium, and they were made by Diadectes and Orobates, respectively. He invited Dave and me to co-author a paper to present this hypothesis. We supplied Sebastian with information about skeletal differences between Diadectes and Orobates, and Sebastian used these data to firmly establish that Diadectes made Ichniotherium cottae (type B) tracks and Orobates was the trackmaker of trackways formerly identified as I.sphaerodactylum (aka I. cottae type A). Even though the makers of the trackways are now known, the ichnotaxon names are still used when referring to the trackways.

Photographs of trackways of Ichniotherium sphaerodactylum made by *Orobates pabsti* (top) and Ichniotherium cottae made by *Diadectes absitus* (bottom). Modified from Voigt (2007).

In Diadectes, the fifth digit of the hind foot is relatively shorter than it is in Orobates, which can be seen in the tracks of I. cottae and I. sphaerodactylum, respectively. Furthermore, in I. cottae trackways, the hind foot track overlaps the track of the front foot, whereas in I. sphaerodactylum the hind foot track typically doesn’t overlap the front foot track. This is because Diadectes has less vertebrae between the head and hip (21 vertebrae) than Orobates (26 vertebrae) does.

Front and hind foot track pair of *Ichniotherium sphaerodactylum*. Track made by the front foot is above the hind foot track. Digits 1–5 indicated. Modified from Voigt, 2007.

Front and hind foot track pair of *Ichniotherium cottae*. Track made by the front foot is above the hind foot track. Digits 1–5 indicated. Notice that the hind foot track overlaps the front foot track. Drawings are of different specimens than the one photographed. Modified from Voigt, 2007.

A cast of the holotype skeleton of Orobates pabsti is exhibited in the Fossil Frontiers display case in Carnegie Museum of Natural History’s Dinosaurs in Their Time exhibition. Be sure to look for it once the museum re-opens. And stay tuned for my next post, which will feature the amphibian Seymouria sanjuanensis.

For those of you who would like to learn more about Orobates, you can access the abstract here or contact Amy Henrici here. The publication on the track-trackmaker association can be found here.

Amy Henrici is Collection Manager in the Section of Vertebrate Paleontology at Carnegie Museum of Natural History. Museum staff, volunteers, and interns are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Keep Reading

The Bromacker Fossil Project Part VI: Seymouria sanjuanensis, the Tambach Lovers

June 9, 2020 by wpengine

Hip and “Trashy” Ice Cream

I grew up in the country, on a gravel back road where the diary truck drove by to fill its tank at the local dairy farms. Those cows, I know now, were living the high life. Grazing idyllic in oak tree savanna fields, with miles of territory to wander. I knew the farmers’ kids. I even helped them with their chores, although not often because it wasn’t fun, even though they said it would be.

My assistance did result in my first taste of milk squirted straight from the udder! The term “Organic” was not used then, but now I know those were family owned organic farms in every sense of the term. No hormones. No cages. Hey, the farm kids even gave the cows names! At the time, my mom would buy name brand ice cream from the town’s market. My favorite was mint chocolate chip ice cream (the green kind). The flavor is super hip right now for being a “trashy” flavor. When I say hip and trashy, I mean in a weird nostalgic unhealthy food like tater tots and grilled cheese kind of way. Some basic research reveals those cheap ice creams were, for their time, wholesome, waaaayyyy more wholesome than they are now.

Things have since changed in my hometown. Those family owned dairy farms are gone, replaced with mega dairy farms. And ice cream, especially my favorite trashy and hip flavor, has changed into what I consider to be really unhealthy in an environmentally unfriendly way. Palm oil. You might not know this, but palm oil is an ingredient in most frozen desserts and frozen dairy desserts (ice cream with a sub label). Palm oil is high in saturated fat and can affect cardiovascular health. The FDA does not require palm oil to be labeled, and instead the term vegetable oil is frequently substituted. Because most palm oil plantations are unsustainable, their spread across the landscape threatens rain forests, causes habitat loss for endangered species, violates human rights, and impacts climate change. Most name brand ice cream manufacturers currently use the stuff, but don’t want to be identified with its impacts. Carnegie Museum of Natural History’s Assistant Curator of Amphibians and Reptiles, and tropical conservation ecologist Jennifer Sheridan has some serious concerns about the palm oil industry and has witnessed firsthand its impacts on rainforest ecology. Check out her work here.

So how do I fix this? Or maybe, how do I get my chocolate mint chip ice cream fix?

First off, during the pandemic, I’ve been making homemade ice cream. I’ve been able to control the ingredients and add in special touches like fresh mint (growing out of control in my neighbor’s garden). Here’s a quick blender recipe I’ve used. When I need ice cream from the store for my movie binges, I choose companies that clearly label their ice cream to be palm oil free. Ben and Jerry’s does this very well. As the ice cream shops open up, I will go local.

bowl of mint chocolate chip ice cream with mint leaves and spoon — Homemade mint chocolate chip ice cream.

All of these options may seem high priced or too much work. Surprisingly the homemade recipes are really easy to make, and pretty cheap considering the quality of ice cream produced. The great thing is you can enjoy the process, sit back and not feel guilty about using palm oil, the really unhealthy and not cool ingredient in ice cream. And for me, it takes me back, to when ice cream had ingredients I could point to.

Asia Ward is CMNH Anthropocene Program Manager and Science Communication Fellow. Museum staff, volunteers, and interns are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

June 9, 2020 by wpengine

Our Eureka Moment!

Searching for rare or endangered plants has become a passion for me. It’s always exciting to find something that hasn’t been seen by very many people. It’s also special when I can share these finds with someone close to me who cares as much about them as I do. I am rather lucky in that my husband, Joe, is also a botanist and shares my passion for finding rare plants. Our household pursuit has even become a bit competitive. I will freely admit, when Joe spots a rare plant first, there is some jealousy intermingled with my excitement that we were in the right place at the right time.

For the last couple of years, we have been on a quest to find Viola glaberrima, a yellow violet last seen in Pennsylvania in 1920, May 30, 1920, to be exact.

I’ve pressed my friend Harvey Ballard, a professor at Ohio University and a renowned Violet expert, for details about habitats to investigate, the characteristics that distinguish the plant from other violets, and any tidbits I could glean to help us find this elusive plant. At least a dozen of my emails to Harvey involved questions about information I’d found in other sources relating to the plant commonly called the smooth yellow violet.

In all honesty, I was suspicious that this violet ever grew in Pennsylvania, even going so far as questioning Harvey about whether he had correctly identified one of the historic specimens. In many ways Viola glaberrima resembles other yellow violets. Pennsylvania has about 30 different kinds of violets, five of which are yellow. The other yellow stemmed violets known to occur in the Commonwealth are usually many stemmed with stems that more-or-less lay down on the ground. These other violets also have either heart shaped or what are termed hastate shaped leaves, that is leaves with outlines reminiscent of a spear point with two points protruding from its base. Many of the plants in this group have flowers that are yellow on the front and back. Some of these flowers develop purple coloring on the back of the petals with age. The violet we’ve been searching for has a single, upright stem with cuneate or wedge-shaped leaves and always has purple on the back of the petals.

Harvey served as a coach for our search for Viola glaberrima, and in doing so he did much more than advise us to look on moist wooded slopes. Many floras list our target plant as merely a variety of Viola tripartita, a flower commonly known as the threepart violet. Harvey assured us that Viola glaberrima is a good species in its own right, and provided additional motivation by making a prediction. He told us that if we found it in the field we would have a “Eureka” moment, because the species is visibly different from the other yellow violets.

Historically, the smooth yellow violet was collected 5 or 6 times in Pennsylvania. The earliest collection is pretty vague, “Mercersburg Pa. in 1845.” The other collections aren’t any more precise. One collection from 1900 is from somewhere “between Ruffsdale and Jacobs Creek in Westmoreland County.” There are two collections from the area of Hillside, PA collected in 1907 and again in 1909. The site we felt we had the best chance of relocating this difficult to find violet was Killarney Park in Fayette County. This seemed to be the most precise locality and the most recent. In May of 1920 Otto Jennings of Carnegie Museum fame and Ernest Gress, a student of Jennings who later worked for the Pennsylvania Department of Agriculture, both collected this violet at this location on the same day. Killarney Park, established in 1909, was a popular place for folks to get out of town and have a picnic or a reunion. It featured a dance hall, lakes for boating, picnic grounds and overnight accommodations. With a stop on the Indian Creek Valley Railroad, the park was easily accessible to rail travelers.

The park property changed hands a few times over the years. Its name changed in 1926 and again in 1939, and it was eventually sold in 1941 to the Christian Church of Somerset for use as a summer camp. Thus, the current name of Camp Christian came into being. In June of 2016, Joe and I spent some time at Camp Christian helping guide field trips for the Botanical Society of America, Northeast Section Joint Field Meeting. I got to know the manager of Camp Christian and told him about the rare violet that had last been collected there. June was a little late, the violets were pretty much done blooming. We looked around for the violet without any luck, but the manager invited us to come back and look anytime. Last year, 2019, we spent parts of two days looking around the property again for the little yellow violet that seemed so elusive.

Most of the violets had already gone to fruit at the time of our 2019 visit, which coincided with the historic collection calendar date of May 30. This year, we visited earlier in May, found many violets blooming, and checked thousands of them without finding a smooth yellow violet.

photo of viola glaberrima showing underside of petals

So, in the process of doing field work and looking for other rare plants, it became a habit for us to look for what seemed to be mythical yellow gems. During a field work day in Indiana County on May 16, while cutting up over a hill to take a shorter route back to the car, we came upon a small patch of yellow violets that were different than any we had seen before. They had single stems, with lance shaped leaves and purple coloring on the backs of the petals. There was no denying that this violet was different than any we had seen before. The plants fit all the characteristics that Harvey had so patiently described for us over the many e-mails. This was finally our promised “Eureka” moment.

Begrudgingly I’ll admit that Joe was first to spot it. (He walks faster than I do.) Of course, Harvey was one of the first people I contacted, I sent him several photographs and to my delight we received the following response: “Hi Bonnie and Joe, YOU NAILED IT!!! You found Viola glaberrima! What a great find! It is likely rare and sporadic along that mountain range. Congratulations. Big ice cream sundaes for you!” How did Harvey know I love ice cream sundaes?

I would love to say this was a “Eureka “moment 100 years in the making, but it was only 99 years and 351 days.

Bonnie Isaac is the Collection Manager in the Section of Botany. Museum staff, volunteers, and interns are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Is that snow…in June?

Collected on this Day in 1942

cottonwood seeds covering an outdoor trail

It can’t be snow, right? It’s summer! Maybe that is cotton falling from the sky? Well, kind of! It is cottonwood seeds!

Perhaps you’ve seen little cotton-like white particles falling from the sky in early summer, especially around Pennsylvania’s rivers or lakes. It is a common site along the dunes of Presque Isle, for example, and in areas along southwestern PA’s rivers. Aptly named, Eastern cottonwood (Populus deltoides) is a native tree found across the eastern United States that produces seeds that fall from high up in the canopy, attached to cotton-like strands. These fibers act like mini-parachutes and allow the wind to widely distribute the seeds.

This specimen of Eastern cottonwood was collected by Henry T. Skinner on June 8, 1942 on the sand dunes of Presque Isle, Erie. You might notice this specimen is not from the Carnegie Museum herbarium like most of these posts. But instead, this specimen is held at the Morris Arboretum (part of the University of Pennsylvania). Now that museum collections are being digitized, we can search for species of interest, or plants collected from certain places or by certain people, or more…that’s the power of specimen digitization. The Mid-Atlantic Megalopolis Project, funded by the National Science Foundation, is digitizing nearly a million specimens across our region, including Carnegie Museum specimens. This makes our collections all the more powerful, combining all specimens collected in the region and making them accessible to scientists and the public alike.

Find this and more Eastern cottonwood specimens from Presque Isle here.

Check back for more! Botanists at the Carnegie Museum of Natural History share digital specimens from the herbarium on dates they were collected. They are in the midst of a three-year project to digitize nearly 190,000 plant specimens collected in the region, making images and other data publicly available online. This effort is part of the Mid-Atlantic Megalopolis Project (mamdigitization.org), a network of thirteen herbaria spanning the densely populated urban corridor from Washington, D.C. to New York City to achieve a greater understanding of our urban areas, including the unique industrial and environmental history of the greater Pittsburgh region. This project is made possible by the National Science Foundation under grant no. 1801022.

Mason Heberling is Assistant Curator of Botany at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

June 8, 2020 by wpengine

Tulips in June?!

Collected on this Day in 1920

Your tulips may be long gone as spring has faded, but tulip trees are in full force! Although it’s hard to catch a glimpse of them way up in the canopy, tulip tree flowers are just as stunning. Completely unrelated to tulips, Liriodendron tulipifera (called tulip tree, tulip poplar, or sometimes yellow poplar) is named such because its leaves have a distinctive shape reminiscent of tulips.

Found across eastern North America, Tulip trees are one the tallest and fast-growing trees native to Pennsylvania, growing up to nearly 200 feet tall! Tulip trees are relatively shade intolerant and therefore are especially common in young forests (early successional). However, the species can still be found in older forests too. Its tall straight trunks can be impressive, and its wood is widely used by woodworkers, who often refer to it as “poplar.” The tree is not related to true poplars (Populusspecies), which are in the willow family, Salicaceae. Tulip trees are a member of the magnolia family (Magnoliaceae). This beautiful specimen was collected on June 6, 1920 near Trafford, Pennsylvania by Otto Jennings. Jennings was an influential botany curator at the museum for many years.

Find this stunning specimen here.

June 4, 2020 by wpengine

The Bromacker Project Part IV: Diadectes absitus, A Project-Saving Fossil

New to this series? Read The Bromacker Fossil Project Part I, Part II, and Part III.

This post will be the first of a series focusing on notable fossil animals discovered in the Bromacker quarry. I selected Diadectes absitus, a member of the ancient group Diadectomorpha, to present first because, had it not been discovered in the first year of the collaborative field work, the project might not have continued.

Dave Berman and his colleague Stuart Sumida (California State University, San Bernardino) joined Thomas Martens for five weeks of field work in the summer of 1993. They dug a quarry over six feet deep in their search for fossils, while working in a mix of hot and humid or near freezing temperatures, with plenty of rain. It wasn’t until the second-to-last day of the field season that the Diadectes specimen was discovered. By then, as Dave later told me, he was so discouraged by the lack of fossils that he assumed this would be his first and last field season in Germany. I should mention that Stuart had previously uncovered a few small vertebrae, but because the vertebrae resembled an animal described from the Bromacker in 1991, the team was not very excited about the discovery. They couldn’t have been more wrong in their field identification of the vertebrae, however, but more on that in a later post.

The 1993 quarry shortly before discovery of *Diadectes absitus*. Pictured are Stuart Sumida standing in the quarry and Thomas Martens crouched to his right. The *Diadectes* fossil was found in the corner opposite Stuart’s left shoulder, which is out of sight in this image. Photo by Dave Berman, 1993.

The team’s collective attitude changed when Stuart knocked off a chunk of bone-bearing rock from a bench in the quarry corner while shoveling away rock rubble. Careful examination of the fragment revealed part of the top of a roughly five-inch-long skull. We have since joked that Stuart gave it a lobotomy. While collecting the large block of rock containing the remainder of the skull, another piece of rock popped off the the edge of the block adjacent to the quarry wall. This piece had vertebrae in it. The team then realized that only the front portion of the animal was in the block freed from the quarry. The rest of the fossil skeleton remained in the quarry wall. Thomas later excavated the rest of the specimen and shipped it separately to Carnegie Museum of Natural History (CMNH).

You can watch Dave and Stuart excavate the fossil-bearing block by clicking on the video link at the end of this post.

Based on the shape of both the exposed teeth in the broken skull and the exposed vertebrae, Dave and Stuart were able to identify the fossil animal as the genus Diadectes. Thomas had already collected a juvenile skull and other bones of Diadectes before his collaboration with Dave, but the specimen discovered in 1993 was by far the most complete and best preserved.

Skeleton of *Diadectes absitus*. Some of the limb bones are preserved on the underside of the block. Photo provided by Thomas Martens.

Once my preparation of the specimen was completed, which took a little over a year, Dave, Stuart, and Thomas begin their detailed study and description of the fossil. They determined that it represented a new species, which they named Diadectes absitus. “Absitus” is Latin for distant or far, in reference to the species being the first occurrence of Diadectes outside of North America. The generic name Diadectes was coined in 1878 by the famous paleontologist Edward Drinker Cope, and is a combination of the Greek “dia,” meaning crosswise, and “dēktēs,” meaning biter, in reference to its broad teeth. Other species of Diadectes occur in similar-aged rocks in the American southwest, and a few specimens are known from the Tri-State area of Pennsylvania, Ohio, and West Virginia.

Diadectes is a member of the group Diadectomorpha, which has oscillated between being considered a member of Amphibia or Amniota. Amphibians lay their eggs in water, which then hatch into tadpoles that later undergo metamorphosis. Today this group includes frogs, salamanders, and caecilians (limbless, worm-like burrowing amphibians). In contrast, amniotes either lay their eggs on land, like reptiles and birds do today, or the embryo develops sufficiently in the mother for live birth, as in most mammals. Except in rare cases, the type of developmental pathways of fossil animals cannot be determined because they are rarely preserved with their eggs or fetuses. Paleontologists instead study a variety of preserved features to determine group membership. As an example, amphibians typically have four fingers, whereas amniotes generally possess five.

Diadectes and its close relatives were herbivorous, that is, they ate plants. Their spatulate, incisor-like front teeth project forwards and were adapted for cropping vegetation. Longitudinal, parallel striations on their broad cheek teeth suggest that Diadectes could move its lower jaw fore and aft to grind plant matter against its upper jaw teeth, a motion called propalinal.

Skull of *Diadectes absitus* in right lateral (= right side) aspect. Notice the forward-angled front teeth and the bulbous cheek teeth. A black pen was used to mark the boundaries of individual bones in the skull, which aided study of the animal. Modified from photo provided by Thomas Martens.

The presence of an enlarged torso and teeth adapted for grinding tough vegetation are evidence that Diadectes absitus likely consumed a diet of high-fiber plants. Animals that eat high fiber plants, such as cows, have enlarged torsos framed by a rounded rib cage to hold large guts for processing plant cellulose through fermentation by microorganisms.

Diadectes absitus lived at a time when herbivores were just beginning to evolve. One of the oldest known herbivores is the diadectomorph Desmatodon hollandi, which lived about 305 million years ago, whereas Diadectes absitus lived roughly 290 million years ago. We discovered a surprisingly high number of herbivores at the Bromacker.

Teeth of one of the oldest known herbivores, the diadectomorph *Desmatodon hollandi*. This specimen was discovered in Pitcairn, PA by Percy E. Raymund (Assistant Curator, Section of Invertebrate Paleontology) in 1907 and named in honor of Dr. William Holland, the second Director of CMNH. The teeth of Desmatodon are very similar to those of *Diadectes absitus*. Photo by the author, 2018.

A cast of the skeleton of Diadectes absitus is exhibited in the Fossil Frontiers display case in the Dinosaurs in Their Time exhibition. Be sure to look for these once the museum re-opens. And stay tuned for my next post, which features another diadectomorph, Orobates pabsti.

Photograph of a model of *Diadectes absitus* made by the Museum der Natur, Gotha exhibit preparator Peter Mildner. Photo provided by Thomas Martens.

Dave and Stuart excavate the fossil-bearing block (video)

Amy Henrici is Collection Manager in the Section of Vertebrate Paleontology at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Keep Reading

The Bromacker Fossil Project Part V: Orobates pabsti, Pabst’s Mountain Walker

The Bromacker Project Part V: Orobates pabsti, Pabst’s Mountain Walker

Keep Reading

Hip and “Trashy” Ice Cream

Our Eureka Moment!

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Is that snow…in June?

Collected on this Day in 1942

Tulips in June?!

Collected on this Day in 1920

The Bromacker Project Part IV: Diadectes absitus, A Project-Saving Fossil

Dave and Stuart excavate the fossil-bearing block (video)

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