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Alycia talks up brachiopods and running her paleontology lab on the Common Descent Podcast

I was recently a guest on the Common Descent podcast.  Will and David were really wonderful to talk with and had really great and insightful questions.  Our discussion was broad ranging and included brachiopods (of course), the Great Ordovician Biodiversification Event, running a paleontology lab, why my students are family to me, and running an international conference.

Spotlight – Alycia Stigall (3/5)

Welcome to our Spotlight Series! We’re talking paleo-science with some paleo-people! In this 5-part series, we’ve interviewed 5 different invertebrate paleontologists about their research and other work. In Episode 3, our guest is Dr. Alycia Stigall, shar…

Be sure to also check out the Common Descent interviews with lab alumni Adriane Lam and Ranjeev Epa!  Links here.

Ranjeev’s research on speciation in Tanzanian gastropods is published!

Ranjeev’s research on speciation in Tanzanian gastropods is published!

Congratulations to Ranjeev Epa (MS ’17)!  The research paper based on his MS thesis on systematics and morphology of Oligocene gastropods is now published in Papers in Paleontology.

Epa, Y.R., Stigall, A.L., Roberts, E.M., O’Brien, H., Stevens, N.J. 2018. Morphological diversification of ampullariid gastropods (Nsungwe Formation, late Oligocene, Rukwa Rift Basin) is coincident with onset of East African rifting. Papers in Palaeontology, 4:327-348.


A new freshwater gastropod fauna is described from the late Oligocene Nsungwe Formation of the Rukwa Rift Basin, Tanzania. Six new species of ampullariids are established including five species of Lanistes (L. microovum,L. nsungwensis, L. rukwaensis, L. songwellipticus and L. songweovum) and one species of Carnevalea (C. santiapillaii). These taxa occupy a morphospace region comparable to nearly half of extant Lanistes, a common and widespread genus in Africa and Madagascar. Palaeoecological evidence indicates that Nsungwe ampullariids inhabited fluvial, pond and paludal environments. Among these species are the oldest high‐spired and fluvially adapated Lanistes taxa. We suggest that Nsungwe Lanistes rapidly diversified in concert with habitat heterogeneity associated with the initiation of rifting along the western branch of the East African Rift System (EARS). Taxonomy, evolution and the biogeographical affinities of Nsungwe Formation freshwater gastropods contributes significantly to expanding the undersampled Palaeogene invertebrate fossil record of continental Africa.


Here is the university writeup about Ranjeev’s paper:

Paleontologists Find New Snail Species with Evolutionary Speed – Ohio University | College of Arts & Sciences

Snails may be physically rather slow, but the six new species identified by Ohio University researchers put on plenty of evolutionary speed when they had to. Ohio University paleontologists analyzing snail fossils from 24 to 26 million years ago have identified six new species-and published the first documentation of rapid …


Nilmani’s study of Ames Limestone Paleocommunities is published!

Nilmani’s study of Ames Limestone Paleocommunities is published!
So many beautiful brachiopods

Congratulations to Nilmani Perera (MS ’17)!  Her thesis project, which identified hierarchical biogeographic patterns in the paleo communities of the Pennsylvanian Ames Limestone has been published in Palaeogeography, Palaeoclimatology, Palaeoecology.

Perera, S.N. and Stigall, A.L. 2018. Identifying hierarchical spatial patterns within paleocommunities: An example from the Late Pennsylvanian Ames Limestone of the Appalachian basin. Palaeogeography, Palaeoclimatology, Palaeoecology, 506:1-11.

Abstract: Identifying ecological mechanisms that produce hierarchically arrayed spatial variation in community structure can be difficult in the fossil record due to conflation of spatial and temporal patterns. However, this difficulty can be mediated by minimizing the temporal duration of deposition within the unit examined. In this study, the fauna of the Upper Pennsylvanian Ames Limestone (Conemaugh Group) was analyzed to explore whether Ames paleocommunities exhibited hierarchical structure in a spatial dimension. This widespread carbonate unit was deposited during the maximum flooding interval of a glacio-eustatically influenced fifth order sea level cycle, and preserved taxa are contemporaneous within only a few thousand years. Paleocommunity structure and variability was assessed at multiple spatial scales using samples collected from seven outcrops of the Ames Limestone throughout southeastern Ohio which form a northeast to southwest trending transect parallel to the paleoshoreline. Abundance data were collected using quadrat sampling for brachiopods, bivalves, gastropods, bryozoa, corals, crinoids, echinoids, trilobites and foraminifera. Paleocommunity structure was analyzed via cluster, ordination, guild, and abundance analyses at multiple spatial scales (within a single locality, among localities and within the total study area) to provide insight on geographic partitioning of paleocommunity variation. Multiple levels of paleocommunity organization were recovered within the Ames fauna. All levels exhibited spatial partitioning, but the inferred proximate controls shifted from abiotic environmental controls at higher hierarchical levels to biotic controls at the lowest level. At the highest level, differentiation into a northern and southern regional paleocommunity was controlled primarily by substrate consistency and habitat heterogeneity related to variation in fluvial input within the basin. Local paleocommunity differentiation reflects biotic responses to topographic and environmental conditions that were geographically distributed within the region; whereas within outcrop variation was due largely to biotic feedback mechanisms.

Key points:


  • Paleoecology of a widespread, but temporally-restricted marine fauna was analyzed
  • Community analyses identified hierarchical constraints on spatial structure
  • Abiotic environmental controls were paramount at regional scales
  • Biotic interactions were primary at local scales
  • Hierarchical structure should be considered in paleocommunity analyses


Here is the university writeup about Nilmani’s paper:

Perera and Stigall Publish Study Detailing Ecological Structure of Local Fossil-Rich Limestone – Ohio University | College of Arts & Sciences

Generations of geology students at Ohio University have studied the Ames Limestone, the most fossiliferous rock layer in the Athens area, for class field trips and projects. This unit preserves skeletal remains of marine animals-corals, snails, brachiopods, trilobites, sharks- that inhabited a shallow sea that covered Athens about 300 million …

IGCP 653 Synopsis and Photos

Here is my longer, formal report about all the exciting things that happened as part of the IGCP 653 meeting.

Annual meeting synopsis and photos | IGCP 653

The main Annual Meeting of the IGCP 653, titled “Trekking Across the GOBE (Great Ordovician Biodiversification Event): From the Cambrian through the Katian”, was a great success. The main meeting on the Ohio University campus, brought together a group of 60 scientists from eight nations. Read the Ohio University writeup here.


Two new publications on the Great Ordovician Biodiversification Event

Hot off the presses!  

The Stigall Lab has two new articles published in the Lethaia special issue “Contextualizing the Great Ordovician Biodiversificaiton Event”. This special issue derives from the IGCP 653 opening meeting in Durham in October 2016, and includes papers on many aspects of the GOBE and related topics.  You can access the entire issue online here.

Our lab has two contributions:

Stigall, A.L. 2018. How is biodiversity produced? Examining speciation processes during the Great Ordovician Biodiversification Event. Lethaia, 51 (2), 165-172. https://doi.org/10.1111/let.12232.

–In this paper, I make the case that it is critical to consider biological aspects of speciation, not only aggregate diversity counts, when seeking the causes of diversification events, such as the GOBE.

Trubovitz, S., & Stigall, A.L. 2018. Ecological revolution of Oklahoma’s rhynchonelliform brachiopod fauna during the Great Ordovician Biodiversification Event. Lethaia, 51(2), 277-285. https://doi.org/10.1111/let.12233.

–This is the second half of Sarah Trubovitz MS thesis, which examines community structure and body size in brachiopod communities across the GOBE in the Simpson Group of Oklahoma.

Bayesian estimation of Ordovician dispersal pathways


Today was an exciting day for the lab.  The paper on Ordovician dispersal pathways led by Adriane Lam which incorporates her primary MS thesis research came out. This paper is exciting for several reasons.  First, it’s always great when a student gets their research published! Second, this is the first use of bayesian biogeographic modeling with Paleozoic taxa.  Third, this project represents an evolution beyond a MS thesis project, through collaboration and improvements with additional authors at other institutions, namely Nick Matzke.  I am really so thrilled with how this paper came out.  It is a landmark is methods and has important implications for understanding Ordovician biogeography.  The only downside…Adriane titled it “Dispersal in the Ordovician” as  play on “Pirates of the Carribean” so I can’t get the Pirates theme song out of my head….

Lam, A.R., Stigall, A.L, Matzke, N.J. 2018. Dispersal in the Ordovician: Speciation patterns and paleobiogeographic analyses of brachiopods and trilobites. Palaeogeography, Palaeoclimatology, Palaeoecology, 489: 147-165. Online

Key Points:

  • Bayesian and ML methods were successfully implemented with Ordovician taxa.
  • Founder event speciation was important in the evolution of Paleozoic taxa.
  • Taxa with different larval strategies responded similarly to climate shifts.
  • Ocean currents were key influences on invertebrate dispersal patterns.
  • Results indicate most evolution within clades occurred during climate shifts.


Science—what am I up to anyway?

Science—what am I up to anyway?

It’s occurred to me that I have been writing quite a bit about broadening participation in science lately and have not actually talked much about what science I have been up to. So here is a brief update about recent developments on that front.

At the IGCP 653 meeting in Yichang, China, I presented new research on some very interesting and rare fossils from the lower part of the Cincinnatian Series. Over the past few years, I have been very fortunate to receive a series of rare fossils collected by some of the fantastic amateur paleontologists of the Dry Dredgers in Cincinnati, Ohio. In particular, Ron Fine, has collected some intriguing brachiopods from the lower Cincinnatian Kope Formation (Edenian Regional Stage) that look like they belong to lineages otherwise only known as invasive taxa from the upper Cincinnatian (Richmondian Regional Stage). These pre-Richmondian “invaders” comprise an interesting set of species that shed light on invasion dynamics in the fossil record.

At Yichang, I argued that interbasinal species invasions (or immigrations) could be considered in a hierarchical context, with ranks including ephemeral invasion, incursion epibole, and biotic immigration events. I am currently expanding this invasion hierarchy into a full article for Annual Reviews in Ecology and Evolutionary Systematics. (AREES), so I won’t elaborate here, but I think this is a really exciting and potentially transformative concept about the assembly of diversity through time.

At the GSA meeting in Seattle, I am presenting research related speciation mechanisms and how we can move from a basic correlation of diversity with Earth systems events to a causal mechanism for increasing diversity based on the process of speciation. Much of the arguments for this talk are in press already within my Lethaia paper (here).

So…for the near term, these are the scientific questions that I am investigating and the questions that keep me up at night: how do we really resolve speciation processes in the fossil record, how can we use that information to understand diversification during the Ordovician Radiation/Great Ordovician Biodiversification Event, and how do invasions (of varying intensities) contribute to diversity patterns of life through time?*

*obviously these questions are best addressed with data about articulated brachiopods from the Ordovician Period

IGCP 653: Yichang Reflections

IGCP 653: Yichang Reflections

I’m currently on a 12 hour flight from Shanghai to Chicago as part of my 3 flight (and 29 hour) itinerary home from the 2nd Annual IGCP 653 meeting in Yichang, China. I can say, unreservedly, that this was a fantastic meeting!

Attendees included more than 60 delegates from 10 nations. The fact that most attendees were Chinese—and I am not—provided a wonderful opportunity for me to meet many new and upcoming scientists—both students and early career professionals that I have not previously had the opportunity to interact with. I was so impressed by the quality of their science and their ability to communicate at a high level on an international stage. What a talented group of young scientists! I am incredibly encouraged and inspired by them.

Of course, I was also able to reunite with (and meet new) colleagues from Europe, Africa, and North America as well. Truly this meeting met the spirit of UNESCO, our funding agency for the IGCP project, in terms of bridging international divides and fostering common interests and collaborations.

At this conference, provocative scientific ideas were espoused—generating substantial discussion, important geologic sections were visited (including the GSSPs for both the Hirnantian and Dapingian stages!), and cultural differences were both explored and celebrated. It’s exciting both how much we have learned about the Great Ordovician Biodiverisfication Event in terms of ocean chemistry, oxygenation patterns, diversity patterns of metazoans and also how much we have to learn—such as when did this event start and end, whether such things can be clearly defined, and what does that mean for the Earth system?

Speaking for myself, my favorite parts were probably the fact that we had an international assemblage of brachiopod workers to talk with (it’s great-and rare to be among people that love my favorite fossils as much as I do!) and that there were so many dynamic young female researchers in the group.

As anyone who is relatively close to me knows, I am very concerned with increasing participation in science on both a national and international level. I was so encouraged to see so many young and dynamic female scientists! Female students earned awards for both poster and oral presentations. This is pretty groundbreaking.

To place this in context, I had a conversation with a colleague, who I generally admire very much as a scientist, in which he said to me one evening {I’m paraphrasing} “You know, we always try to hire men instead of women for permanent jobs. You can’t say that in open meetings, but in secret meetings, we always say this.” I asked why this was the case and was told that it could be problematic for women to both be in charge of or be the majority of a field team to remote regions. I pushed back on this concept (I certainly was told the similar things as a grad student), and my friend said “Well, most women are not like you. They are not assertive and independent.” On one level, I was glad that my colleague appreciated that some women could be leaders, but it also made clear to me that there are many countries where women still need to fight hard to be considered scientific equals. I am not special. Female scientists need the chance to grow and shine and deserve the same support as our male colleagues.

The male student at our table noted that the female students work much harder and achieve higher levels of excellence than the male students. He sees the value in this contemporaries, and I am heartened that over time this view will win out…but I’d much rather we achieve equity in the near term and not wait 20 years and lose out on the great science these young women could have done by excluding them.

I hope that my work in the international community can help to foster a sense of empowerment for female (and other underrepresented) scientists in both the USA and other nations. At this meeting, I was assertive. I capitalized on my leadership as a co-chair of IGCP 653 role to be present, to chair sessions, to judge and present awards, to invite everyone to Athens, Ohio in 2018, and I hope that seeing one woman do that in a sea dominated by male leadership can help to inspire the fantastic and talented women that I met at this meeting to be assertive and empowered in their own scientific lives.


Nilmani passes her final defense!

by Alycia Stigall

Nilmani is now a Master of Science!  She successfully defended her thesis titled: Hierarchical Spatial Patterns in Paleocommunities of the Late Pennsylvanian Ames Limestone.  Nilmani did a really nice job in her thesis analyzing and interpreting regional vs. local differentiation in contemporanous shallow marine communities across southeastern Ohio.  Congratulations, Nilmani!


Reflections on the International Biogeography Society Meeting in Tucson: Celebrating diversity and deep time

Reflections on the International Biogeography Society Meeting in Tucson: Celebrating diversity and deep time

This post was initially written as a guest blog for the International Biogeography Society blog

The International Biogeography Society Biennial Conference is one of my favorite meetings to attend. These conferences consistently profile outstanding and cutting edge science, opportunities to interact with a set of colleagues that I don’t have the opportunity to see at my paleontology-centric conferences, and interesting destinations to explore. This year’s conference in Tucson hit the mark in all areas.

A key strength of IBS conferences is that they are fundamentally a celebration of diversity in many ways: diversity of approaches ranging from molecular to big data and ecological to phylogenetic frameworks; diversity of focal ecosystems and taxa; diversity of temporal lens from modern to deep time; diversity of nationalities and cultures; diversity of genders and identities. This diversity makes the scientific contributions and opportunities so much stronger. Developing such a diverse conference is not a coincidence, the IBS board and meeting organizers actively work to promote scientific and culture diversity. And the dedication and hard work pays off. For example, someone like me, who studies paleobiogeography of marine life from 400 million years ago feels at home with colleagues studying geographic structure of genetic variation in modern tree species.

From my perspective, two aspects of this year’s IBS conference particularly struck me: the increasing inclusion of a deep time perspective and fossil data and increasing recognition and participation of women in biogeography.

Each of the symposia featured at least one talk involving paleodata. The “Modeling large-scale ecological and evolutionary dynamics” symposium featured paleo data in nearly every talk and showcased a wide range of paleo data from historical records to the Pleistocene. Contributed sessions, posters, and mini-talks also prominently focused on the relevance of paleodata, including analyses that employed Paleozoic data to address questions relevant to modern biodiversity concerns (abstract book here).

Geologic and paleontological data, particularly the breakup of Pangaea and the waxing and waning of the Pleistocene ice sheets, have long been incorporated in biogeographic analyses. What was exciting about this meeting is the fact that paleodata beyond those two cases are being employed and being employed broadly within the field in many different contexts ranging from species distribution models, quantifying community functioning and species richness processes, and calibrating projections of biotic impacts of future climate changes.

Rising above this pervasive paleontological mist was the fact that the winners of the MacArthur & Wilson and the Alfred Russell Wallace Awards, Jessica Blois and Margaret Davis, are paleobiogeographers, which further underscores the significance that the field ascribes to research emphasizing fossil data.

Both awardees are also women, which leads to my second point. This meeting celebrated the accomplishments of outstanding women in biogeography, like Jessica and Margaret, and at the same time acknowledged and celebrated the additional hurdles and barriers that were (and still are) faced by women in science. Steve Jackson, in his citation of Margaret Davis, provided a wonderful discussion that contextualized some of the hurdles that Margaret faced as the sole women in pollen analysis, the significance of her indomitable spirit, and the inspiration she has provided to others.

Today, women are not usually alone in our departments or subdisciplines, but we and members of other underrepresented groups still face obstacles, additional requests on our time as token representatives, and implicit bias in reviews and in other contexts. But meetings like IBS, where a group of women met at 7:30 am over coffee to discuss shared issues and plan a support group and where we have lunch mentoring groups that discuss early career issues, provide clear and positive steps forward.

Women have been leaders in biogeography for many years, as evidenced by the Margaret Davis’s well deserved Wallace award, and women are poised to continue leading and innovating, as evidenced by female students winning 3 of 5 poster awards.

I ended the conference by raising my glass with a group of a dozen female paleobiogeographers. For me it was a fitting end to a conference that celebrated diversity of science, of timescales, and of individuals.