Author Archives: jamesboy2013

About jamesboy2013

Currently starting my 4th year as a PhD student at the University at Buffalo under Chuck Mitchell. Working on graptolite community structure and evolutionary dynamics.

New Data on Titanichthys At Last

Since the last time I posted here I’ve managed to have two new papers published. One in Paleobiology on graptolite extinction risk (Boyle et al. 2017), which I’ll summarize in another post, and one in the Journal of Paleontology (Boyle & Ryan 2017) on the placoderm Titanichthys. The work on Titanichthys was part of my undergraduate capstone research that started waaaay back in 2010 with Dr. Ryan at the Cleveland Museum casually remarking that a new nearly complete skeleton had just been prepared and somebody needed to describe it. So today I’ll be summarizing the results of that paper and where I’d like to get more done on this taxon in the future.

To start, a little background on Titanichthys. It is an old taxon named in 1885 by John Strong Newberry (an interesting man for a number of reasons worthy of his own post) and also a very large animal. Ballpark estimates are a total length >5 meters, making it larger than its more famous contemporary Dunkleosteus and possibly the largest vertebrate animal that had evolved up to that time. The genus is confined to the latest Devonian (Frasnian?-Fammennian) making it one of the last arthrodire placoderms before the entire group perished at the end of the Devonian. The remains of Titanichthys are the second most common taxon after Dunkleosteus but are commonly isolated and fragmentary making its overall morphology somewhat mysterious. Of the 7 currently recognized species only 3 (T. agassiziT. clarki, and T. termieri) are known from at least partially complete specimens. While the description of T. termieri (Lehman 1956) is pretty good by modern standards the other two well-known species were described in the late 19th or earliest 20th century without many modern morphologic conventions and without designation of a holotype. In fact, the effective “holotype” of T. clarki described by Eastman (1907) is a composite of several individuals and has been partially restored with plaster making interpretation of the figures somewhat dubious.

So prior to this new paper the most recent publication on Titanichthys was over 50 years old and we lacked definitive reference material to work from. The new specimen of Titanichthys (CMNH50319) is unique because it is articulated and nearly complete, only lacking parts of the thoracic shield and the ventral shield (Fig. 1). This has allowed for the first description of five new plates (rostral, postmarginal, postsuborbital, submarginal, and posterior superognthal; see Placoderm primer for plate info) and updated descriptions for every other plate that’s been previously described for the genus, with exception of the anterior dorsal lateral. So now we have a very nice specimen to compare new material to and could start looking at the range of variation in morphology. The posterior superognathal was perhaps the most interesting because it is tiny relative to the lower jaw (inferognathal) especially when compared to other arthrodires. This, along with the animals overall large size, the flattened body shape, and elongated lower jaws without anything resembling teeth are all strongly convergent with large filter-feeding vertebrates that are known today such as the Whale Shark, Basking Shark, and Megamouth Shark as well as the fossil teleost fishes Pachycormids. The suggestion that Titanichthys was a filter-feeder wasn’t a novel idea but the new data does lend a lot more support to this hypothesis which could now be tested explicitly.

Figure 2_2col

Figure 1. Reconstruction of CMNH50319 (Titanichthys cf. clarki) in lateral view. Lightly shaded regions are portions of plates that are overlapped. Dark shaded regions are empty space. IG = Inferognathal. Scale Bar = 10cm.

One other important feature we were able to sort out from this specimen was the orientation of inferognathal, which has a deep groove and an anterior tip that bends noticeably from the rest of the jaw. Originally, the groove was thought to be the dorsal surface and to have held tooth plates, making the anterior tip projecting dorsally as well. However, Dunkle and Bungart (1942) presented evidence that the groove faced ventrally making the anterior tip project ventrally as well. When Lehman (1956) described T. termieri he favored the original orientation. Because CMNH50319 had the left inferognathal preserved and articulated with the cheek shield we can now definitively say that the Dunkle and Bungart’s hypothesis is correct. That ventrally projecting tip is odd among arthrodires and can be very strongly developed (Fig. 2) based on observations in the Cleveland Musueum collections. This ventral curve makes the most sense, in my opinion, as an adaptation to increase gape size for filter-feeding.

Tusk Jaw

Figure 2. Reconstruction of undescribed left inferognathal of Titanichthys from the Cleveland Museum of Natural History showing the extreme condition of the ventrally projecting anterior tip. I refer to this as the tusk morph.

Despite all the anatomical detail we were able to report, when it came to assigning CMNH50319 to a particular species we ran into a problem. It had a mix of features from the well-known species and because all the species are poorly known (sample size of 1 or 2) we don’t really have any idea whether those differences are variable within or between species. We did have the inferognathal which is the easiest way to distinguish between T. agassizi and T. clarki, CMNH 50319 was definitively closer to the T. clarki form (it’s worth noting that the inferognathal of T. termieri is not known). So in the end we decided to classify CMNH50319 as Titanichthys cf. clarki, the cf. stands for confers and means close to. We probably could have just called it T. clarki without any complaints but I thought that would mask the uncertainty and variation within the genus.

We were able to perform a phylogenetic analysis with the specimen expanding on previous analyses (Carr 1991, Trinajstic & Dennis-Bryan 2009, Carr & Hlavin 2010,  Zhu & Zhu 2013, and Zhu et al. 2015). We added CMNH50319, T. agassiziBungartius perissus, and Tafilalichthys lavocati to the analysis with 121 characters. The resulting consensus tree (Fig. 3) is not very robust in all honesty. Too many taxa for the number of characters and A LOT of missing data. However, Titanichthys was recovered as a basal aspinothoracid in a monophyletic clade with Tafilalichthys and Bungartius. It will be interesting to see if that clade holds up in the long run because Tafilalichthys and Bungartius have both been associated with taxa that have crushing dentition. That would be a lot of variation in jaw morphology within a single group. I’m convinced the key to resolving arthrodire relationships are the Wildungen taxa from west Germany that seem perfectly placed in time and space to bridge the phylogenetic gap that currently exist.

Phylogeny

Figure 3. Strict consensus of 2769 trees from a PAUP analyis.

Looking ahead to more research in this area several questions are clear. First, we can explicitly test the hypothesis that Titanichthys was a filter-feeder. Second, I gleaned over the geographic distribution of the species but as of right now there were 5! species of Titanichthys coexisting in the Appalachian Basin of North America. For giant filter-feeding organisms that seems incredibly unlikely to me and I suspect that most of the species should actually be synonomized. Looking through the Cleveland Museum collections for this research revealed a large amount of variation in Titanichthys jaws and I wouldn’t be surprised if the different morphs grade into one another or are ontogenetic. There’s plenty of material to work with to explore this project and I’d like to get to it sometime in the future, but if somebody beats me to it I’d be happy just to know that it’s being worked on.

References

Boyle, J. & M.J. Ryan, 2017, New Information on Titanichthys (Placodermi, Arthodira) from the Cleveland Shale (Upper Devonian) of Ohio, USA. Journal of Paleontology, v. 91, p. 318-336.

Carr, R.K., 1991, Reanalysis of Heintzichthys gouldii, an aspinothoracid arthrodire: Zoological Journal of the Linnean Society, v. 103, p. 349–390.

Carr, R.K., and Hlavin, W.J., 2010, Two new species of Dunkleosteus Lehman, 1956, from the Ohio Shale Formation (U.S.A., Famennian) and the Kettle Point Formation (Canada, upper Devonian) and a cladistic analysis of the Eubrachythoraci (Placodermi, Arthrodira): Zoological Journal of the Linnean Society, v. 159, p. 195–222.

Dunkle, D.H., and Bungart, P.A., 1942, The infero-gnathal plates of Titanichthys: Scientific Publications of the Cleveland Museum of Natural History, v. 8, p. 49–59.

Eastman, C.R., 1907, Devonic fishes of the New York formations: New York State Museum Memoir, v. 10, p. 1–235.

Lehman, J.-P., 1956, Les Arthrodires du Dévonien superieur du Tafilalet (sud Marocain): Notes et Mémoires du Service Géologique du Maroc, v. 129, p. 1–114.

Trinajstic, K., and Dennis-Bryan, K., 2009, Phenotypic plasticity, polymorphism and phylogeny within placoderms: Acta Zoologica, v. 90, p. 83–102.

Zhu, Y.-A., and Zhu, M., 2013, A redescription of Kiangyousteus yohii (Arthrodira: Eubrachythoraci) from the Middle Devonian of China, with remarks on the systematics of the Eubrachythoraci: Zoological Journal of the Linnean Society, v. 169, p. 798–819.

Zhu, Y.-A., Zhu, M., and Wang, J,-Q., 2015, Redescription of Yinosteus major (Arthrodira: Heterostiidae) from the Lower Devonian of China, and the interrelationships of Brachythoraci: Zoological Journal of the Linnean Society, v. 176, p. 806–834.

Placoderm Nurseries

Many sharks and bony fishes make use of protected shallow habitats for their young to grow in today. Typically these habitats provide protection from predators and abundant resources that rush downstream from the eroding highlands. This allows the maximum number of offspring to grow quickly before reaching adult size where they are less vulnerable to predation and can migrate out to deeper waters. Given how common this is today it would be expected that extinct organisms would have done this as well. Unfortunately, even if they were common we still might not be likely to find evidence of nurseries in the fossil record for two reasons. First, nurseries tend to be in shallow environments such as rivers and estuaries which are likely to be eroded as sea level rises and falls or continents collide erasing the environment. Second, identifying a nursery requires finding a location that is dominated by juvenile organisms and in most nurseries the juveniles are either eaten (no fossils left) or successfully reach adulthood and leave the nursery. So it’s only in the rare circumstance where there is a mass death of juveniles due to some catastrophe (at least from the organisms’ perspective) and then up to luck that the sediments aren’t eroded away for millions of years before they are discovered and sampled by paleontologists.

Despite these unlikely circumstances there are a number of likely nursery site of chondrichthyans (sharks and their relatives) in Triassic rocks of Kyrgyzstan (Fischer et al. 2011) and Pennsylvanian rock of Illinois (Sallan & Coates 2014). The longer ago sediments were formed the more likely they will have been destroyed by geological processes so it was exciting news this past week when a new study in interpreted a site in Belgium as a placoderm nursery (figure 1) from the Late Devonian (bonus points for being placoderms!). I’ll detail some of the bits I find the most interesting here. The study (Olive et al. 2016) was published in PLoS One and thus is open-access so I encourage everybody to go read the full paper for themselves, it’s a light read at nine pages.

journal.pone.0161540.g002

Figure 1. From Olive et al. 2016 showing a reconstruction of the Strud nursery site. Scale bar =2cm. Illustration by J. Jacquot Hameon (MNHN, Paris).

 

The locality in Strud, Belgium would have been along the edge of the paleocontinent of Laurussia/Euramerica, a combination of North America and northern/western Europe, in the Late Devonian. It most likely represents the river deposits on an alluvial plain, a relatively calm environment, except in the case of flooding events. The authors report the recovery of 105 fragments of placoderms comprised of three species all of which were relatively small and showed other morphological correlates of juveniles based on previous studies of closely related placoderms (Werdelin & Long 1986; Deaschler et al. 2003). So what happened to these young placoderms that they weren’t eaten and yet they didn’t survive into adulthood? At Strud the most likely explanation is that these juveniles were in a pond or small tributary that dried up and became isolated from the main channel. So bad luck for the placoderms, good luck for paleontologists. What’s even more interesting though is that the Strud locality is the second known placoderm nursery of the Late Devonian. The other is in Tioga County, Pennsylvania (Downs et al. 2011) with similar species. In that case the hundreds of specimens are more complete and tend to be oriented in the same direction. Again, the explanation for their remains is that they were isolated in a shrinking body of water that also slowly became anoxic (aiding preservation) leading to a mass kill.

Both of these placoderm nurseries had large numbers of similarly aged individuals, and in the case of the Pennsylvania site there’s strong evidence that they represent a life assemblage, rather than one which has been time-averaged. So these sites probably show us that these placoderms had large numbers of offspring, though how exactly is up for debate. Some placoderms are known to have had live offspring (Ptyctodonts; Long et al. 2008) while there is questionable evidence of egg-laying behavior in other (Ritchie 2005; figure 2). Because of the number of similarly aged juveniles both nurseries most strongly support an egg-laying behavior in the species found there (primarily antiarchs). Given the position of placoderms as the outgroup to the rest of the jawed vertebrates their reproductive strategies can help us chart the evolution of reproductive strategies in Earth’s early history. It will be exciting to see if more of these nursery sites appear in other parts of the world outside of Luarussia and even earlier in fossil record. There are also tantalizing hints that large placoderm species (e.g. Dunkleosteus) might have used nearshore habitats for their juveniles as well (Daeschler & Cressler 2011)!

Cowralepis egg

Figure 2. Possible egg case of the plcaoderm Cowralepis. From Ritchie 2005. 

 

References

Daeschler, E.B. and W.L. Cressler III. 2011. Late Devonian paleontology and paleoenvironments at Red Hill and other fossil sites in the Catskill Formation of north-central Pennsylvania. Geological Society of America Field Guide 20:1-16.

Daeschler, E.B., A.C. Frumes, and C.F. Mullison. 2003. Groenlandaspid placoderm fishes from the Late Devonian of North America. Records of the Australian Museum 55:45-60.

Downs, J.P., K.E. Criswell, and E.B. Daeschler. 2011. Mass mortality of juvenile antiarchs (Bothriolepis sp.) from the Catskill Formation (Upper Devonian, Famennian Stage), Tioga County, Pennsylvania. Proceedings of the National Academy of Science Philadelphia 161:191-203.

Fischer, J., S. Voigt, J.W. Schneider, M. Buchwitz, and S. Voigt. 2011. A selachian freshwater fauna from the Triassic of Kyrgyzstan and its implication for Mesozoic shark nurseries. Journal of Vertebrate Paleontology 31:937-953.

Long, J.A., K. Trinajstic, G.C. Young, and T. Senden. 2008. Live birth in the Devonian period. Nature 453:650-652.

Olive, S., G. Clement, E.B. Daeschler, and V. Dupret. 2016. Placoderm assemblage from the tetrapod-bearing locality of Strud (Belgium, Upper Famennian) provides evidence for a fish nursery. PLoS One 11:e0161540.

Ritchie, A. 2005. Cowralepis, a new genus of phyllolepid fish (Pisces, Placodermi) from the late Middle Devonian of New South Wales, Australia. Proceedings of the Linnean Society of New South Wales 126:215-259.

Sallan, L.C. and M.I. Coates. 2014. The long-rostrumed elasmobranch Bandringa Zangerl, 1969, and taphonomy within a Carboniferous shark nursery. Journal of Vertebrate Paleontology 34:22-33.

Werdelin, L. and J.A. Long. 1986. Allometry in the placoderm Bothriolepis canadensis and its significance to antiarch evolution. Lethaia 19:161-169.

Placoderm Primer

This post has been a long time in coming but hopefully I’ll be able to start posting regularly after this and get a steady stream of updates going. Here, finally, is a primer on placoderms since I’m likely to be posting about them more.

Placoderms are an entirely extinct group of armoured fishes that were most common in the seas of the Devonian Period (419-459 mya). They were an impressively diverse group of organism containing both ray-like bottom feeders (Rhenanids) and giant predators (Dunkelosteus). Placoderms also include some of the smallest known vertebrates (Minicrania lirouyii ) [1] with a head and thoracic shield of only 20mm) and the largest vertebrates to have evolved up to the Devonian (Titanichthys; probably maxed out at over 5 meters long). Despite their diversity and dominance for over 40 million years no placoderms survived past the end of the Devonian for reasons unknown. So this is a whole branch of life that originated, diversified, and went extinct just as vertebrates were starting to move onto land!

There are nine orders of placoderms currently recognized [2] Stensioellida, Pseudopetalichthyida, Petalichthyida, Ptyctodontida, Acanthothoraci, Rhenanida, Antiarchi, Phyllolepida, and Arthrodira with the first two being poorly known. They were long thought to be a monophyletic group but recent discoveries have turned the old relationships on its head, especially the discovery of a mid-Silurian vertebrate, Entelognathus primordialis, that has a combination of characters seen in placoderms and bony fishes (osteichthyes) [3]. I might do a separate post just about that strange beast sometime. Anyway, the different orders of placoderms are now thought to be paraphyletic with Antiarchs as the most basal, arthrodires as intermediate, and ptyctodontids as the sister-group to the remaining jawed vertebrates [4], figure 1 although this is still in flux.

In terms of morphology placoderms as a whole have an ossified dermal skeleton, that is the bones form from the dermal layer near the surface of the skin rather than internally like most of the bones in our own bodies (Interestingly most of our skull bones are dermal in origin). This external skeleton is commonly referred to as armor and it protects the soft internal body of the fishes including the internal skeleton which is rarely preserved and appears to be largely composed of cartilage. The armor of the placoderm is typically broken down into four groups of armor plates that are tightly connected to each other: head, cheek, thoracic, and ventral armors (figure 2). In antiarchs the pectoral fins are enclosed by jointed appendages reminiscent of arthropods.

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The head shield in most arthrodires consists of seven paired plates (postnasal, central, preorbital, postorbital, paranuchal, marginal, and postmarginal) and three median plates (rostral, pineal, and nuchal). In some primitive arthrodires the rostral and pineal plates are fused (Buchanosteidae) to form a rostropineal and in other forms the postnasals appear to have been lost. The head shield is connected to the thoracic shield by a hinged contact between the paranuchal and the anterior dorsal lateral. The thoracic shield is composed of five to seven plates in arthrodires (median dorsal, anterior dorsal lateral, anterior lateral, posterior dorsal lateral, posterior lateral, interolateral, and spinal). The interolateral and spinal plates are lost in independent lineages, coccosteids and aspinothoarcids (surprise surprise) respectively. Depending on the species the thoracic armor is articulated to varying degrees with the ventral armor which would have protected the soft underbelly. This part of the armor consists of four plates (anterior median, posterior median, anterior ventral lateral, and posterior ventral lateral) which are typically found in isolation or fragmented. Finally, the cheek shield is connected to the head shield either loosely with the preorbital or intimately with both the preorbital and lateral portion of the head shield. The cheek shield consists of three plates (suborbital, postsuborbital, and submarginal).

I’ll stop there for now. I’ve updated the placoderm occurrence database so I might do something about placoderm diversity next. I also have a paper on Titanichthys under review so maybe more on that soon too!

References

1. Zhu, M. & P. Janvier. 1996. A small antiarch, Minicrania lirouyi Gen. et sp. nov., from the Early Devonian of Qujing, Yunnan (China), with remarks on antiarch phylogeny. Journal of Vertebrate Paleontology 16:1-15.

2. Denison, R.H. 1978. Handbook of Paleoichthyology: Placodermi. Gustav Fischer Verlag,             Stuttgart, New York, 128 pp.

3. Zhu, M., X. Yu, P. E. Ahlberg, B. Choo, J. Lu, T. Qiao, Q. Qu, W. Zhao, L. Jia, H. Blom, and Y. Zhu. 2013. A Silurian placoderms with osteichthyan-like marginal jaw bones. Nature 502:188-193.

4. Davis, S.P., J.A. Finarelli, and M.I. Coates. 2012. Acanthodes and shark-like conditions in the last common ancestor of modern gnathostomes. Nature 486:247-250.

5. Dunkle, D.H. and P.A. Bungart. 1947. A new genus and species of arthrodiran fish from the Upper Devonian Cleveland Shale. Scientific Publication of the Cleveland Museum of Natural History 8:103-117.

What is a fish?

Since a lot of what I’ll be posting will have to do with placoderms and other marine animals I thought it would be a good idea to explore what the word ‘fish’ actually means. What makes something a fish? The question is not as simple as it first appears, we all know in general what we mean when we refer to fish in conversation but this is partially due to the fact that the overwhelming majority of fish today belong to the actinopterygians (ray-finned fishes) which includes everything from gars to goldfish. All these fish share a similar body with paired fins, a tail fin, gills, a bony skeleton, and swim bladders. So let us take the idea that fish are water-dwelling organism with fins, scales, gills, and who are poikilothermic (their body temperature fluctuates with the temperature of their environment). This covers most of the organisms you would refer to as fish in normal conversation but what about eels that don’t have the paired fins or scales? Or the even stranger (and uglier) lampreys and hagfishes that also lack jaws in addition to scales and fins? There are even some fish that can regulate their body temperatures both by more active circulation (Salmon sharks)1 or by producing antifreeze proteins in their blood2. For every rule defining fish there are many exceptions to counter them. The reality is that the group we refer to as ‘fish’ is a grouping of human convenience for swimming organisms in the water, which usually possess scales and gills.

A quick side note I feel obligated by a former professor to pass on! Fish is the proper plural when referring to multiple individuals of the same species while fishes is used when referring to a group of individuals containing more than one species.

Today if we consider only the kinds of fish with scales, paired fins, and gills (teleosts) they are the most diverse group of vertebrates on the planet. If we look at the evolutionary history of marine organisms similar to teleosts there was an even greater diversity in the past. The figure below is from a review of fishes over the last 500 million years and I would highly recommend giving it a read if you have any interest in ichthyology (reference is at the end of the post). The first thing you might notice is that all terrestrial vertebrates (including you dear reader!) are descended from the sarcopterygians (lobe-finned fishes) and thus a technically a fish. Those swim bladders I mentioned earlier are primitively lungs so it is not just land animals that have lungs but the majority of vertebrates. In fact you are more closely related to a goldfish or salmon than either of those is to a shark.

Image

Figure 1. A phylogeny of fishes, extant and extinct from Friedman and Sallan 2012.

It is also probably clear that there a large number of entirely extinct lineages of fishes. Everything from the anapsida to Osteoraci, excluding the eel-like unarmored conodonts, are historically referred to as ostracoderms or agnathans. They are primitive armored fishes that lack any jaws and had their greatest diversity in the late Silurian to early Devonian (~420 mya) hundreds of millions of years before the dinosaurs walked the land and before any vertebrates walked the land for that matter. The many lineages of ostracoderms are a fascinating array of creatures that has only recently received renewed attention for understanding the evolution of all jawed vertebrates. Unfortunately, there is still relatively little known but they more posts about them will probably appear as new publications come out.

Moving into the gnathostomes (vertebrates with jaws) one of the earliest branches were the paraphyletic acanthodians (spiny sharks), which are known from mostly fragmentary remains. The lines including the acanthodians lead on to both chondrichthyes (sharks and rays) as well as teleosts (ray-finned fish, lobe-finned fish, and terrestrial vertebrates). The other branch led to the placoderms (armor skin) which were a highly diverse group of fishes with armor around their heads and part of the trunk. Below are reconstructions of the many forms of placoderms which dominated the Devonian seas before becoming extinct at the end of that period. Placoderms include the earliest known instance of live birth4 and included the largest vertebrates to have ever evolved up to the end of the Devonian likely greater than five meters in length.

Image

Figure 2. The placoderms Coccosteus from Wikipedia.

The next post will be a primer on placoderms before I really start to delve in on specific hypotheses, publications, or theories. I’ll attempt to answer reasonable comments in a timely manner and be glad to answer any questions.

References

1Goldman, K. J., S. D. Anderson, R. J. Latour, and J. A. Musick. 2004. Homeothermy in adult

salmon sharks, Lamma ditropis. Environmental Biology of Fishes 71:403-411.

2Fletcher, G. L., C. L. Hew, and P. L. Davies. 2001. Antifreeze proteins of teleost fishes. Annual

Review of Physiology 63:359-390.

3Friedman, M. and L. C. Sallan. 2012. Five hundred million years of extinction and recovery: a

Phanerozoic survey of large-scale diversity patterns in fishes. Palaeontology 55:707-742.

4Long, J. A., K. Trinajstic, G. C. Young, and T. Senden. 2008. Live birth in the Devonian Period.

Nature 453:650-652.

What am I doing?

Hello world!

I’ve been brainstorming about starting a blog for a while but kept putting it off for another day but no more! For most of my life I’ve been interested in paleontology and that’s what I’m going to write about for the most part on this blog. I can’t say I have a very specific focus on any particular group but there are a few that will probably be the majority of post to start with at least.  This blog was in large part inspired by SVPOW which has been an enormous amount of fun for me to follow over the past two years. 

I’m currently a master’s student working on evolutionary patterns in graptolites (if you don’t know what those are don’t worry I’m sure they’ll appear here from time to time) and will be continuing on to a PhD in the fall. My undergraduate career was spent working on placoderms from the Cleveland, Ohio area and I’ve really gotten fond of them but I don’t have much opportunity to work on them where I am now so I’m partially using this blog as a way to keep myself involved in that literature by trying to get other people interested in them as well.

It’s my hope that this blog will help me work on a couple things. First, helping me improve my scheduling and time-management which could definitely use some work. Second, to help me learn how to write and portray ideas more effectively. And third, to get some ideas bouncing around my head somewhere easily accessible so other people can learn, provide feedback, and maybe answer some of the questions I haven’t been able to.

I’ve already alluded to the fact that this blog will probably cover some graptolites and definitely placoderms. Both groups are from the Paleozoic and I’m expecting most of my posts on specific groups or organisms to be from that time. However, I also was introduced to paleontology like most people through dinosaurs and so they’ll creep into discussion too I have no doubt. But most things in the fossil record younger than the Cretaceous just don’t interest me as much for whatever reason and so this blog will almost exclusively be Before the Bolide.