Bryan Gee, Ph.D.
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Temno Talk: a blog about all things temnospondyl

New publication: Size matters: the effects of ontogenetic disparity on the phylogeny of Trematopidae (Amphibia: Temnospondyli) (Gee; Zoological Journal of the Linnean Society)

2/21/2020

 
Title: Size matters: the effects of ontogenetic disparity on the phylogeny of Trematopidae (Amphibia: Temnospondyli)
​Authors: B.M. Gee
Journal: ​Zoological Journal of the Linnean Society, no. 170 (Advance Articles)
DOI to paper: 10.1093/zoolinnean/zlz170
General summary:​ Phylogenies represent our inference of the relationships between different organisms, and can be as broad-scale as all living things to as fine scale as species of rhinos. It is of course an inference because in very few instances can be observe or capture speciation in short time intervals, and reconstructing the relationships of long-extinct taxa, especially those without close living relatives, is even more complicated. Phylogenies are therefore very controversial because there are a slew of different ways that one can go about doing one, and different scientists have different preferences. Which taxa are included, which features are analyzed, and how each taxon is "scored" for each feature can vary widely across studies, which unsurprisingly produces very different results and in turn, very different scenarios of evolutionary history (e.g., temporal origin, rates of diversification, geographic origin, relation to modern taxa, etc.). The hot topic in early tetrapod research right now is early amniote phylogeny, particularly with respect to parareptiles, 'microsaurs,' and varanopids. That doesn't mean that there isn't a lot of work to do with temnospondyls though, which of course is what this paper is about!

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New publication: A re‐description of the late Carboniferous trematopid Actiobates peabodyi from Garnett, Kansas (Gee & Reisz; Anatomical Record)

2/10/2020

 
Title: A re‐description of the late Carboniferous trematopid Actiobates peabodyi from Garnett, Kansas
Authors: B.M. Gee, R.R. Reisz
Journal: Anatomical Record
​DOI to paper: 10.1002/ar.24381
General summary: Back in 1973, American paleontologist Theodore Eaton described a new dissorophoid from the late Carboniferous of Kansas. Represented by the pancake-iest of the pancaked fossils, Actiobates was confusing because it looked like a cross between a dissorophid and a trematopid, so much so that Eaton suggested that these weren't distinct groups (also bearing in mind that terrestrial amphibamiforms were lumped in with dissorophids at the time). Eaton's taxonomy wasn't widely accepted, but it took arguably decades to fully resolve the dissorophid-trematopid issue, which was compounded by disputed affinities of Ecolsonia, first described in 1969 but subsequently known from much better material described in 1985.

The reconstruction to the right is the only figure of Actiobates in any form (drawing, photograph, interpretative line drawing, interpretative dance) that existed until it was photographed in brief in a paper on other trematopids by Andrew Milner in 2019. To top it off, Eaton alluded to a large portion of the postcranial skeleton that was articulated with the skull and indicated that he was going to describe it, but it never happened before his passing in 1981 (he retired from a professorship at the University of Kansas in 1977). Many trematopids have no postcrania, which has complicated their phylogenetic relationships a bit, but there is obviously a need to describe postcrania when it does exist. Actiobates has also rarely been included in phylogenetic analyses because it's hard to assess the accuracy of the original description without photos to validate the reconstruction. The holotype and only known specimen has also been categorized as a "larval form" and explicitly excluded from these analyses. All of these uncertainties clearly warranted a re-examination of Actiobates, which happened mostly by accident in the first year of my PhD when we were doing a return-specimens/collections trip to Kansas (note: they have metoposaurid material in their collection too).
Picture
Eaton's original reconstructions of Actiobates peabodyi.

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New publication:  Histological skeletochronology indicates developmental plasticity in the early Permian stem lissamphibian Doleserpeton annectens (Gee, Haridy & Reisz; Ecology & Evolution)

2/7/2020

 
Title: Histological skeletochronology indicates developmental plasticity in the early Permian stem lissamphibian Doleserpeton annectens
​Authors: B.M. Gee, Y. Haridy, R.R. Reisz
Journal: Ecology & Evolution
DOI to paper: 10.1002/ece3.6054
General summary: ​​Doleserpeton is an early Permian amphibamiform from Richards Spur that has long been of great interest in hypotheses of the origin of modern amphibians. It's also reported as one of the most abundant taxa from Richards Spur - the scientist who described it, the late John Bolt, termed certain deposits from the caves as "D-concentrate" to refer to the extreme density of Doleserpeton material (largely limbs). Because of its hypothesized close relationships to lissamphibians and the sheer abundance of material, there's a natural import for doing histological work on Doleserpeton. 

So in this study, we cut an absurd number of limb bones (60 right femora) and then looked at growth patterns (or lack thereof) to figure out how a putative stem lissamphibian grew. We found absolutely no pattern other than femur size scaled positively with inferred age (phew!) - there is a huge spread of data points, which can be attributed to several (not mutually exclusive) causes. We also utilized this large sample size to run some sensitivity analyses i.e. what could happen with more traditionally low sample sizes? When you sample in the 10 or 20 bracket, you can get some wild results, like negative scaling ​between femur size and inferred age and near perfect fits to simple linear regressions (growth is rarely linear). This is really just visualizing the obvious truism that more data improves representation and robusticity of interpretations, and low sample size...well be careful with low sample size.
Picture
#AcademicAlbum cover for this paper, something new that Yara and I are trying out for our scicomm (this riffs off The Life of Pablo album by Kanye West if you're confused).
Picture
Thin section through the mid-shaft of a femur of Doleserpeton annectens. Colours are a result of the oil enrichment of the fossils when transmitted light is passed through them.
Picture
Skeletal reconstruction of Doleserpeton by Sigurdsen & Bolt (2010).

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A edopoid that time forgot: Nigerpeton

2/4/2020

 
Note: This was supposed to be out last week, but then the Kobe Bryant tragedy happened, and as a native Angeleno, that was a lot to deal with, so I put the post off to this week.

The Land That Time Forgot is a classic 1918 trilogy (technically combined into a single volume in 1924 and itself part of the Caspak trilogy) in which a hardy bunch of Americans and Brits hijack a U-boat in the middle of WWI and find themselves in a weird island with a bunch of prehistoric creatures including various purported stages of human evolution living as distinct tribes. The trailer for the 1975 movie tells you that you can learn the "secrets of evolution." I have never seen the movie, but since I liked The Valley of Gwangi, which I watched on a mobile projector displayed on a bedsheet draped over the soccer mom van of the education department of the LACM, I am sure that it is of high cinematic quality in spite of its Rotten Tomatoes rating. These movies capture a certain affinity for the notion that pockets of animals thought to be long-extinct might exist, and indeed there are various cryptozoological monsters themed around this, like the mokele-mbembe, based on the notion of a sauropod-like beast living in the depths of the jungles of the Congo. For some reason, nobody's ever come up with a cryptozoological creation based on a temnospondyl, which seems like a real missed opportunity to put a 3-meter amphibian in the Mississippi River, and I am not proposing one now, although as I have told some people in person, I am amenable to the idea of donning a temnospondyl body suit and cruising around a body of water. 

Temnospondyls are not forgotten by time - if anything, they are just forgotten, period - but there are a few records of lineages where one taxon shows up way after its compatriots were thought to have kicked the can. We call these "relict taxa," a name obviously referring to the remnant of something much more common or widespread in earlier days (which were usually better days if you were a temnospondyl, back when the world was warm and humid and probably humming with crunchy invertebrates). Edopoids, already regarded as one of the more primitive temnospondyl groups, are one of the few for which a relict taxon is known: Nigerpeton, aptly named for Niger from which it is known.

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    About the blog

    A 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).

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