Having finally made it to Seattle and gotten some semblance of stability, I'm cautiously optimistic that I can reboot the blog on a more regular note again! As regular readers may notice, I'm a big fan of alliteration, so having missed the entirety of Metoposaurid May, which I did last year, August will be Amphibamiform August! This week will provide a general overview of amphibamiforms. Amphibami– what now?
All but one of my dissertation chapters is already published, so in many respects, regular readers of this blog have already read much of my dissertation, and there isn't really much new info in the university-formatted form that will be released online in a few months (December-ish). However, one major component that can't be found anywhere else is the acknowledgments section, a deeply personal and nuanced section for every graduate student that is sometimes the best part to write (or the only part if you're trying to finish amidst a global pandemic). It is often said that it takes a village to raise a child. At every step of my academic career, I have benefited from a village that showed me the ropes, took me under their wing, and set me up for long-term success. Many of those people had no obligation (or compensation) for taking the time to mentor me and to teach me various arcane arts, and at least some of those in my early days may have been initially non-plussed to be working with a high schooler given stereotypes of teens. Their generosity in time and energy was ultimately the biggest contributor to my ability to finish this dissertation and to achieve what I have accomplished to date. I think it is important to share these stories that so that people who see my CV or my website will not think that I am some kind of genius or that I did it largely by myself. I am just someone obsessed with temnospondyls who had a remarkable support network from the very beginning. Below, you can find a verbatim copy of my acknowledgments section (with hyperlinks enabled for many of these amazing people). “And once the storm is over, you won’t remember how you made it through, how you managed to survive. You won’t even be sure, whether the storm is really over. But one thing is certain. When you come out of the storm, you won’t be the same person who walked in. That’s what this storm’s all about.” -Haruki Murakami This dissertation would not be a true document from my hand if it did not include a lengthy acknowledgments section of an equally loquacious nature to the lengthy compilation of my research on Paleozoic temnospondyls. I want to acknowledge that simply having the opportunity to pursue a Ph.D. is far more than my own diligence and hard work – it was the collective investments of countless individuals who devoted time, energy, and knowledge to mentor me and to provide me with opportunities that enabled me to pursue this opportunity in turn and that endowed me with the foundation to succeed at this level. I have long believed that one’s present success is first and foremost a reflection of one’s past preparation, and I have been prepared by a great many people from a great many places to be where I am now. I first want to thank my parents, Glenn and Doreen Gee. They always encouraged my pursuit of this career trajectory and made quite a lot of sacrifices on their weekends and on vacations to get me to just about every major natural history museum in the United States. In particular, my mom spent a lot of time driving me home from my volunteer work at the LA County Museum of Natural History in peak LA rush-hour traffic (no small feat) during my summers. They invested tremendously in my education and always sought to provide me with intellectually broadening and stimulating opportunities (most of which have proven to be useful in one way or another) I would not be the scientist I am today without the investment of many faculty and staff at my undergraduate institution, Pomona College, who prepared me for graduate school and the world beyond it. The faculty and staff of the geology department not only provided an enriching and stimulating learning environment but also created a closely-knit family that supported each other beyond our academic confines. They remain the gold standard that I one day hope to achieve. I would like to extend a special thanks to my undergraduate advisor, Dr. Eric Grosfils, who, in spite of knowing far more about volcanism than vertebrates, was always an excellent source of thoughtful commentary, feedback, and inquiry. I would also like to thank Dr. Lynne Miyake of Pomona’s Japanese department, who, among many other things (including introducing me to Murakami’s writing), is undoubtedly the single most responsible person for my writing aptitude after putting me through the ringer in her first-year writing seminar. Dean Ric Townes was an invaluable teacher on topics of leadership and mentorship who prepared me for many of the less-academic challenges of graduate school, and I continue to draw on his lessons to this day, in spite of his fervent support of the Boston Celtics. Outside of the classroom, I benefited greatly from the mentorship of countless people who patiently guided me through the growing pains of academia and who provided me with invaluable opportunities to explore my curiosity and passion for palaeontology. To this end, I thank Dr. Luis Chiappe (Natural History Museum of Los Angeles County), who saw my interest in palaeontology and who was willing to take a chance on an eager and entirely unfocused 16-year-old as a volunteer in the collections, the prep lab, and the field, for so many years. The opportunities I gained through the LACM were some of the most formative of my life, both inside and outside of academia. Luis has continued to be an excellent mentor and inspiration over the years, and arguably no one was more instrumental in my early career development. Doug Goodreau, the head honcho in the prep lab and in the field quarry at the LACM during my time there, provided endless humour, far-fetched (yet true) tales, MacGyver-esque fieldwork hacks, and companionship in domesticating the local herpetofauna. Dr. Lars Schmitz (W.M. Keck Science) and Dr. Brian Kraatz (Western Medical University) took me on as a research assistant for their respective projects and gave me my first exposure to academic conferences (which included my first trip to Canada for GSA 2014). Their valiant efforts to subtly influence me toward eyeballs and mammals, respectively, were much appreciated. Nothing was more formative for my academic development during graduate school than my summers spent as an intern at Petrified Forest National Park. It was a second academic home, with a thriving sense of curiosity for all aspects of vertebrate palaeontology and a strong sense of community among my peers. Dr. Bill Parker and Dr. Adam Marsh were instrumental in guiding me through the stressful process of my first academic publications and in developing many of the core skills and concepts that I rely upon. More broadly, they always encouraged me and gave me wide latitude to develop my own research ideas and independence. They were the first academics to tell me “you’re the expert” well before I ever considered myself much of anything, which was tremendously encouraging to hear. Matt Smith and Cathy Lash provided invaluable advice and expertise in matters of collection, curation, and preparation of fossil material, and Brad Traver authorized me to destroy federal specimens for three different publications. Also deserving of my gratitude are the terms (Natalie Toth and Chuck Beightol) and interns (Emily Lessner, Candice Stefanic, Ben Kligman, Alexander Beyl, and Elizabeth Evans) who I spent a lot of hot summer days working with and a lot of not-much-cooler nights entertaining ourselves in the absence of internet. My advisor, Dr. Robert Reisz took a chance on me as an unproven (or at least unpublished) undergraduate trying to jump straight into a Ph.D. program and has been generous in his financial support. Robert provided me with a veritable wealth of specimens to explore a host of questions throughout my program, including many beyond the confines of my dissertation. I greatly benefited from the many pastries and desserts that arrived in the lab, and I thank Robert for overlooking my egregious sin of not being a coffee-drinker and for begrudgingly adopting my frequent use of the term ‘dude.’ I owe tremendous thanks to our lab technician, Diane Scott, for her enthusiastic support of students through instruction, photography, discussion, lab snacks, and humour. We developed quite the rapport as the only people to reliably come into the lab before 9 AM, and she has had a hand, quite literally, on all of the specimens that are published in this thesis in one way or another (and often in several). Her dog, Shiloh, is also to be thanked for frequently falling asleep on my feet when he was a puppy; there is nothing quite like the unpalatable prospect of disturbing a small dog to keep you focused on your work. I benefited greatly from my labmates at Mississauga over these four years. I owe a tremendous amount of gratitude to my former labmate Yara Haridy for all that she is and does for me. She taught me the requisite methods for bone histology, a method instrumental to my research, made (makes) valiant attempts to get me to put down my work and to go outside, and was fully responsible for my hair being bright fuchsia during my appraisal. In spite of abandoning me for greener pastures across the pond, she remains a constant source of support, inspiration, no-nonsense advice, and random musings about weird animals. Thanks to Kayla Bazzana for the west coast vibes, for the limitless supply of snark, for humouring my own supply of snark, and for a very random assortment of shared adventures. Thanks to Sigi Maho for her patience with me and my copious editing tendencies during her BIO481 (my first academic supervising experience), for celebrating all of my successes way more than I do, for smiling an awful lot every day in lab, and for keeping me (virtual) company at absurd hours of the morning. I would also like to thank to Tea Maho, Adam Snyder, and Paige Urban, all of whom were undergraduate students in our lab and who placed some modicum of trust in me in allowing me to mentor them in various unstructured ways through their projects. The opportunity to mentor undergraduates is first and foremost a privilege for the mentor and one that I cherish greatly. I am grateful to the members of my appraisal examination committee, Dr. Luke Mahler, Dr. Njal Rollinson, Dr. Saša Stefanović, and Dr. Denis Walsh, for taking the time to thoughtfully question me on a research proposal that was mostly outside of their own research areas. Thanks to Karma Nanglu, Ashley Reynolds, and Jade Simon for putting me through a practice grilling that made the real deal less daunting. Thanks to the members of my defence examination committee: Robert, Njal, Denis, Dr. David Evans, Dr. Mary Silcox, and Dr. Jean-Sébastien Steyer; and to my exam chair, Dr. Jessica Sommerville. Thanks to Njal and Denis for serving on my supervisory committee for these past four years. I benefited greatly from the collegiality and academic support of my fellow graduate students in the Evans lab, principal among them, Tom Cullen, Kentaro Chiba, Denise Maranga, Talia Lowi-Merri, Ashley Reynolds, Jade Simon, and Cary Woodruff. Many thanks to Dr. Kevin Seymour for all of his assistance with collections numbers and curation and the occasional humor at my expense. Thanks to Dr. David Evans for his enthusiasm about the oft-maligned taxa that I study and for the many conversations on many different topics, usually occurring with chicken wings in front of a TV screen showing the basketball game. I would also like to thank the many collaborators I have had on various projects, both those contained in this dissertation and those beyond it, as well as the colleagues who have been a part of valuable conversations and debates. In particular, Dr. Jason Anderson, Jason Pardo, Dr. Hillary Maddin, and Arjan Mann have been of great help in this regard. I would also like to thank the many reviewers and editors who have taken valuable time to perform the frequently thankless task of peer review and to provide constructive feedback on the wordy manuscripts that form part of my dissertation. Thanks to Bill May, who selflessly donated many of the specimens that I have been able to work on. Special thanks to our collaborator at ANSTO, Dr. Joseph Bevitt, for his tireless dedication to producing high-quality tomographic datasets and for being a very charitable host in the winter of 2018 (which fortunately translated to a warm summer down under). Thanks to Dr. Jessie Maisano and the UTCT team at UT Austin for an excellent 2017 CT workshop that facilitated the prolific use of CT in my research. I also want to thank the many collections staff and curators who have facilitated collections visits and loans (often to my predecessors in the lab), chiefly among them Carl Mehling and Mark Norell of the AMNH, Pat Holroyd of the UCMP, Bill Simpson of the FMNH, and Jennifer Larsen of the OMNH. Lastly, I would like to thank Chloe An, Sophia Choi, Haley Land-Miller, and Sara Murphy. Abe Lincoln once said, “I'm a success today because I had a friend who believed in me and I didn't have the heart to let him down.” Each of you believed in me wholeheartedly from the very beginning, and each of you was that friend at one point or another. In these four years spent very far from the sunny southern California desert, you have supported me through my worst moments, remind me that life is much bigger than my esoteric research on dead animals, keep me grounded with unfiltered commentary, and continue to inspire me in countless ways.
Having finished writing my thesis, I've been finding some weird ways to keep myself busy, and I spent all of yesterday putting together a genealogy of metoposaurid taxonomy over the years! This isn't really a blog post, but I may do a couple more of these in the next couple weeks on things that actually on groups that are related to my dissertation. Metoposaurid taxonomy is very complicated, and there's also this prevalence of subspecies concepts being used for them, so my goal was to make a visual that could be a useful guide for people who don't have it all memorized in their head like me! The full version is above, but as you can probably tell, you can't read anything because the entire image is 1.5 meters long (no typo) even though I'm using a pretty small font size. I think my website builder downsamples images when it uploads them, so you can find the full version here! This is still a WIP (and hypothetically I might use it myself for something at one point), so please do not use this without asking me first! This is the right half of the diagram, which is maybe marginally more readable than the full version (and also the way less complicated side of the diagram).
Title: Reassessment of historic ‘microsaurs’ from Joggins, Nova Scotia, reveals hidden diversity in the earliest amniote ecosystem Authors: A. Mann; B.M. Gee, J.D. Pardo, D. Marjanović, G.R. Adams, A.S. Calthorpe, H.C. Maddin, J.S. Anderson Journal: Papers in Palaeontology DOI to paper: 10.1002/spp2.1316 General summary: In what is my biggest collaboration to date with nearly all of the early tetrapod workers in Canada, here's probably my last paper of 2020: a very thorough revision of the 'microsaur' Asaphestera from Joggins, Nova Scotia! Joggins is one of the oldest sites with a well-preserved late Carboniferous tetrapod community (315-318 Ma), and it preserves a unique forest swamp environment in which animals are frequently preserved inside of logs (whether or not they lived in the logs is another question). Because of its age, Joggins is critical for exploring the early origins of many groups, as it often preserves the oldest members of many Paleozoic clades in North America, if not globally. For example, the temnospondyl Dendrerpeton from Joggins is the oldest known temnospondyl on the continent. There's a rich suite of 'microsaurs,' the ever controversial group of tetrapods of unclear affinities to either crown reptiles or to crown amphibians, that have been reported from Joggins, but many of the original studies are dated such that the interpretations are of limited utility for modern workers trying to elucidate phylogenetic relationships and other macroevolutionary trends. The frequent disarticulation and fragmentation of specimens also makes referrals of specimens to the same taxon somewhat suspect, with the potential for purportedly well-known taxa to be represented by a chimeric blend of multiple taxa. We spent a lot of time looking at historic specimens of one such 'microsaur,' Asaphestera, because we were particularly interested in exploring some of these very poorly known Carboniferous 'microsaurs' that are really important for understanding the evolution and relationships of the much better known early Permian taxa that everybody on this paper has studied to various degrees. Through this, we identified that the various specimens lumped under Asaphestera intermedia are actually a hodge-podge of different taxa, at least one of which is not even a 'microsaur,' but as we propose, is perhaps the earliest definitive synapsid! The oldest synapsid?
Microsaur math
RM 2-1131 was the original holotype of Hylerpeton intermedium and became the holotype of the new Asaphestera intermedia. Here it is above on the right. If the figure does not look that impressive...that's because the specimen is not very impressive. We couldn't identify it to a particular tetrapod clade, let alone diagnose it as a unique taxon of whatever clade that might be, and we designated it as a nomen dubium ("doubtful name"), which is the fancy way of saying "this is not valid because it is not clearly unique." So at this point, we've killed one 'microsaur.' Net: -1 microsaur
In any event, we then set about examining the referred specimens of "Asaphestera intermedia," at this point a sunk taxon, because some of them are much nicer. The one above was sufficiently complete to be diagnosed and differentiated from other taxa, and we made it a holotype of a new 'microsaur' taxon: Steenerpeton silvae, which we named for Margaret Steen, (the same Steen I keep mentioning throughout this post), and for 'of the forest,' referring to Joggins original paleoenvironment. So now we've added back one 'microsaur!' Net: +0 microsaurs Steenerpeton appears fairly derived already, in contrast to traditional interpretations of Asaphestera of any flavour, and we suggest that it may be a recumbirostran, the derived group of 'microsaurs' that host a suite of fossorial adaptations. This actually lines up well with the documented presence of other derived 'microsaurs' like possible pantylids and gymnarthrids at Joggins and provides more evidence that the origin and diversification of recumbirostrans begin earlier than has been historically conceived and probably occurred in an interval without substantial body fossils. The former point in particular is a real running theme at this point for most of the research that all of us do.
Avengers assemble!This is the biggest collaboration I've ever worked on (some might say the most ambitious crossover ever). It was born nearly 2.5 years ago at the SVP Annual Meeting in Calgary, which is where Arjan and I both gave talks on different 'microsaurs' (Arjan's turned into his published paper on the new Mazon Creek 'microsaur' Diabloroter, and mine turned into my published paper on new material of Llistrofus from Richards Spur). Jason Pardo (and Jason Anderson) had just had a high-profile paper come out that summer that recovered 'microsaurs' as crown amniotes, a paper I didn't stop hearing about from my advisor even though I spent the whole summer doing fieldwork in Arizona. We all ended up talking about future directions for 'microsaur' work and agreed on needing to reevaluate a lot of the earliest records of what are called "tuditanomorphs" to better characterize them for big tetrapod analyses to continue to sort out different relationships. This in turn spawned what's become a dynamic working group among the three of us and eventually led to us jokingly assigning ourselves as different members of the Avengers as this team of early career researchers doing early tetrapod work on basically every single clade that's out there. If you add up everything that we've collectively published, we account for actinopterygian and sarcopterygian fish, aïstopods (stem tetrapods), temnospondyls, parareptiles, seymouriamorphs, embolomeres, synapsids, and 'microsaurs.' You can see some of the other fruits of this working group in Pardo & Mann (2018), Mann, Pardo & Maddin (2019) and Mann & Gee (2020), with plenty of future work slated for the immediate future (or once things sort of go back to normal)! I will leave it to the readers' imagination as to which members we have self-assigned as... The final sumThe Joggins 'microsaurs' are the only taxa from Carboniferous localities that have experienced these sorts of "lump/split" boom-bust cycles, going from being remarkably taxonomically diverse to remarkably intraspecific variable and back again. The classic Joggins temnospondyl, Dendrerpeton, is another great example of this; the type species, D. acadianum, includes several defunct genera such as Smilerpeton (great name) and Dendryazousa. There are numerous taxa that have been named that weren't even assigned to the correct clade! A lot of this has been because of historic interpretations based on the often fragmentary and disarticulated specimens at Joggins; we don't get many 3-D specimens, and the distortions can affect interpretations of the anatomy. This means that there's a lot of room to go back and look at specimens that were often collected more than 120 years ago and that haven't been re-examined in detail in more than 60, 70, 80... years to assess the original interpretations. Particularly in light of new discoveries at other localities, updated taxonomy, and the recognition that a lot of clades have deeper origins than was often hypothesized in the early 20th century, exploring one of the oldest (crown) tetrapod assemblages in the world is essential for unraveling a lot of the mysteries of the origin of the modern tetrapod clades. When we started this project, there were seven 'microsaurs' recognized from Joggins: Archerpeton, Asaphestera, Hylerpeton, Leiocephalikon, Ricnodon, and Trachystegos. We added Steenerpeton (total: 8), but deep-sixed Archerpeton, recognized Asaphestera proper as a synapsid, and cast doubt on the Joggins records of Ricnodon (final count: 5). We've got plans for some of those other ones that didn't get addressed here...stay tuned for plenty more studies coming out on Joggins material and other Carboniferous faunas! Refs
I never got the chance to meet Bob Carroll, a giant in vertebrate paleontology and arguably the most influential and foundational Canadian paleontologist. Bob was best known among the broader paleo community for his landmark textbook "Vertebrate Paleontology and Evolution", which was first published in 1987 as a follow up to Romer's seminal 1966 text and which was used by perhaps tens of thousands of students in paleontology courses around the world. He was a prolific publisher on early tetrapods, including temnospondyls, 'microsaurs,' and other Paleozoic tetrapods from North America and Europe, and much of his work laid the foundations for ongoing work in the 21st century. By the time I moved to Canada for my PhD, Bob's health was in decline for a number of years, and last week, he unfortunately passed away due to COVID-related complications, the latest revered member of our community to pass within the past few months (John Bolt, Jenny Clack). I wanted to dedicate this week's blog post to his legacy with a specific focus on many of the groups that he worked on that I find myself working on these days (at varying degrees of enthusiasm) .
My indirect ties to Bob are two-fold: (1) he was the PhD supervisor of my own advisor, Robert Reisz (as well as that of more or less all of the famous living Canadian paleontologists); and (2) he was one of the preeminent workers of both dissorophids and 'microsaurs' at a time when both really surged in notoriety for their proposed relationships to modern amphibians. I've read dozens of Bob's papers over the course of my dissertation and draw considerably on them for much of my research, so Many people who knew Bob personally have written beautifully about it (Twitter tributes collated here), including in the 2003 festschrift for him, and I won't try to re-summarize them here. Those with access to the Canadian Journal of Earth Sciences can find a brief summary of Bob's life from the festschrift here, otherwise there is conveniently a publicly accessible archived version of the same PDF here. The link for the entire festschrift with regular journal articles (subscription-only) is here.
The dissorophoid revolution
Prior to the mid-20th century, dissorophoids were "just another temnospondyl group," so to speak. Various representatives had long been known from different parts of the world, ranging from the terrestrial Acheloma/Trematops, Cacops, and Dissorophus from the Texas red beds of North America to aquatic branchiosaurids and micromelerpetids with remarkable quality and detail of preservation from former lakes of western Europe. However, their relationship to modern amphibians could not have been more understated. Virtually all aspects of the origin of modern amphibians, including how closely related the three clades (anurans, caudates, gymnophionans) truly were and the extinct group to which they were most closely allied remained hotly debated and without much consensus (Parsons & Williams, 1963 is a good historical review). While temnospondyls were long recognized as a possible ancestor, there were (are) many other groups generically termed 'amphibians,' and among the temnospondyls, there was no clear consensus as to which clade might hold the key to the flourishing of the modern lineages. As remains largely true now, the record of crown lissamphibians remains very patchy, and the timing of their origin remains largely unconstrained such that back in the 1950s, basically any temnospondyl known to humanity could have been fair game. For reference, the oldest frog, Czatkobatrachus is from the Early Triassic and was named in 1998, and the oldest caecilian, Eocaecilia is from the early Jurassic, by which point almost all temnospondyls were extinct, and was named in 1993.
Miscellaneous amphibian stuff
'Microsaurs' and friends
Suffice it to say that Bob Carroll was an absolute legend and perhaps the single person most responsible for what is now a flourishing Canadian paleontological community with its own professional society (with a prize for best student talk named after Bob). His influence will be clearly felt for generations to come and his mark on the history of our discipline eternal.
I'll be back next week for regular temno content and will make an earnest effort to keep it going weekly throughout this pandemic for the immediate future. Note that what is an extremely lengthy ref list for this week's blog is below.
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About the blogA blog on all things temnospondyl written by someone who spends too much time thinking about them. Covers all aspects of temnospondyl paleobiology and ongoing research (not just mine). Categories
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