Thursday, April 12, 2012

Fruitadens: how small can a dinosaur get?

Dinosaurs have become known, for the most part, as huge reptiles from the past. Huge carnivores like Tyrannosaurus rex would have been chasing hadrosaurs, like Parasaurolophus, and ceratopsids, like Triceratops. Gigantic battles may have been waged, with the outcome being life or death struggles. While this paints an incredible picture and is commonly what people think of when hearing the word "dinosaur", many others realize that dinosaurs could also be quite small. Velociraptor, of Jurassic Park fame, was not actually very large, with adults measuring 6-7 feet long (including the tail), protoceratopsids (small relatives of Triceratops) were only roughly sheep-sized and grew to about 6 feet with their tails included. While these are slightly more well-known, various other dinosaurs stayed diminutive compared to the larger things around them.

In the Late Jurassic (around 150 Mya) of the USA, famous dinosaurs such as Allosaurus, Stegosaurus, Apatosaurus (= Brontosaurus), and Brachiosaurus were roaming the American west. Running around their feet, and doing their best not to get trampled, was a tiny dinosaur named Fruitadens haagarorum, named by Butler and colleagues in 2010). Fruitadens was a tiny, plant-eating dinosaur from the group known as heterdontosaurids. 

Artist’s reconstruction of Fruitadens ( by Smokeybjb, and licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.)

Heterodontosaurids were a group of plant-eating ornithiscians related to iguanodontids (like Iguanodon) and hadrosaurids (like Parasaurolophus and Edmontosaurus), among others. These dinosaurs were commonly fairly small, and had "fangs" towards the front of their mouths.You should be able to see the fangs if you look close enough at the reconstruction. They actually get their name from their strong heterodont dentition. Even so, their morphology is relatively generalized, suggesting more of an omnivorous lifestyle, with plants, insects, and some other small organisms making up the majority of their diets.

Fruitadens was named based on a few individuals (4), but the holotype consists of incomplete jaws, several vertebrae, and partial hind limbs of a nearly full grown individual. This was sufficient, however, to determine that it was, indeed, something unique and new.

Reconstructed skull of Fruitadens (Butler et al., 2012)

Fruitadens was estimated by Butler et al. (2010) to have only been about 28 cm long (less than a meter) and weighed less than 1 kg (less than 2 lbs)! That size estimate is quite incredible, especially for a dinosaur that is thought to be nearly full-grown. Overall size would have probably not changed at all, or at least very little, once it became fully mature!

Full-size Fruitadens haagarorum model with co-author Luis Chiappe (from AP).

But why bring this up now if this dinosaur was named in 2010? In the original publication, Butler et al. (2010) were unable to go into much detail regarding the description and morphology of this new taxon. But a new, thorough study just published by Butler et al. (2012) has given this small dinosaur its descriptive due. The new study seeks to document this dinosaur in great detail, giving new information not only on Fruitadens, but also on the whole heterdontosaurid family of dinosaurs. This study helps us understand a group of dinosaurs that were not very well known before, and helps clarify a picture that can seem somewhat blurry at times (or all the time...).

This seems to be an excellent example of a taxon that was named in a relatively short paper, but then had a follow-up study to give us a much clearer picture of exactly what it was/is. Too often taxa (not just dinosaurs) are named in short papers or with short blurbs. Little detail is given, and sometimes proper diagnoses are not even provided. I can't tell you how many times I have come across taxa and, when going to the original publications, I find little information other than the name itself. And, going a step further, often times little work has been done on the taxa after the initial publication. This was far worse decades ago and has gotten better since, but various examples can be found still today (e.g. Atrociraptor) with little work done on the taxa themselves and more work done regarding their inclusion in cladograms.
Depiction of some of the largest known hadrosaurs and, therefore, some of the largest known ornithischians, with a adult male for scale

Depiction of Fruitadens haagarorum, with a portion of an adult male for scale


Butler RJ, Galton PM, Porro LB, Chiappe LM, Henderson DM, Erickson GM (2010) Lower limits of ornithischian dinosaur body size inferred from a diminutive new Upper Jurassic heterodontosaurid from North America. Proceedings of the Royal Society B 277: 375–381.

Butler RJ, Porro LB, Galton PM, Chiappe LM (2012) Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS ONE 7(4): e31556. doi:10.1371/journal.pone.0031556

Miracinonyx: American cheetah or something else.....

This will be a somewhat short post on a subject that has intrigued me for quite awhile. Not that long ago, geologically speaking, North America was home to numerous felids (cats). While ones that many people know of were present, such as Lynx (bobcat and lynx), Puma (mountain lion) and Panthera onca (jaguar), several others were present that are no longer around. These include, among others, Smilodon (saber-toothed cat), Panthera atrox (American lion), and Miracinonyx (American cheetah). Here, we fill focus briefly on the final one listed, Miracinonyx.

The Carnivores of Rancho La Brea.
From left to right. The dire wolf (Canis dirus), the sabre-toothed cat (Smilodon fatalis), the short-faced bear (Arctodus simus), the cheetah-like cat (Miracinonyx sp.), and the American lion (Panthera atrox). Modified from Turner, A., and Anton, M., The Big Cats and Their Fossil Relatives. Columbia University Press: New York, 1997.

Miracinonyx, commonly called the American cheetah by some, has been found various places throughout North America. Cope (1895) named Uncia inexpectata from some isolated teeth from a cave in Pennsylvania. A second species was named "Felis" studeri from Texas by Savage (1960). Both these would eventually be referred to the genus Miracinonyx (aka American cheetah). Both these taxa were alive pre-Rancholabrean (>240,000 ybp), and Kurten (1976) synonymized both felids with the idea that there was only one Miracinonyx species before the Rancholabrean. Not long after the erection of studeri, Orr (1969) named "F." trumani baed on a skull from a cave in Nevada.

Adams (1979) grouped these taxa together within Acinonyx, the genus of the modern cheetah, due to morphological similarities. He went a step further, however, and grouped them in the subgenus Miracinonyx. The taxonomy of these cats was in a state of flux for awhile, with numerous workers considering the only valid genera to be A. studeri and A. trumani. Van Valkenburgh et al. (1990), however, reported on a remarkable specimen from Hamilton Cave in West Virginia, and concluded that, while A. trumani was valid, it was A. inexpectatus that was the second valid species, with A. studeri as its junior subjective synonym.They also elevated Miracinonyx to the generic level. Van Valkenburgh et al. (1990) were also keen to call them American "cheetah-like cats" rather than American "cheetahs".

Osteological reconstruction of Miracinonyx inexpectatus based on material from Hamilton Cave, West Virginia. Scale = approximately 240 cm (from Van Valkenburgh et al., 1990).

Miracinonyx inexpectatus is the species that first came to be viewed as the "American cheetah". In many ways, the cranial and post-cranial morphology were quite reminiscent of cheetahs today. They have been also, however, commonly compared to Puma, and many researchers have debated which they are more closely related to. While M. inexpectatus had longer and somewhat gracile limbs, M. trumani was, in comparison, a smaller and relatively more robust cat. 

Phylogenetic relationships of the Miracinonyx-Acinonyx lineage based on 27 morphological characters with Leopardus pardalis as the outgroup (from Christiansen and Mazak (2009)).

Miracinonyx has been considered more of a plains species, commonly using Acinonyx (cheetah) as a modern analogue. This is true for both species, even though M. trumani is less similar to Acinonyx than M. inexpectatus, and seems to be more similar morphologically to Puma. This was discussed not long ago by J.P. Hodnett. Hodnett, in an upcoming study, discusses remains of M. trumani from caves in the Grand Canyon of Arizona. Rather than living in a plains habitat, it seemed to be living in a more mountainous terrain with lots of elevation change. 

Adult Snow Leopard (Uncia uncia)

Hodnett took it a step further though, and compared Miracinonyx trumani to the ultimate modern felid adventurer, Uncia uncia, or the snow leopard. He felt that, in order to be agile and a top predator in the Grand Canyon, that M. trumani would have been behaving similar to the snow leopard. 

So, Miracinonyx similar to the snow leopard? It seems like a bit too extreme. Puma behaves, in some ways, similar to Uncia, although in many ways the former is more of a habitat generalist, doing well in a wide variety of habitats throughout North America. Acinonyx, on the other hand, is specialized for open habitat, and Uncia tends to stick to mountainous areas.

With that being said, is Miracinonyx still the American cheetah? Is it the "American Puma"/ancient ancestor of the modern Puma? Or could it be the American snow leopard? While I would lean towards it being more of a generalist like the puma, it could also turn out that M. inexpectatus behaved like the cheetah, while M. trumani behaved like the mountain lion, so one answer will not suffice. Presumably, time and further research will tell us the answer.


Adams, D.B. 1979. The cheetah: native American. Science 205:1155-1158.

Christiansen, P. and Mazák, J.H. 2009. A primitive Late Pliocene cheetah, and evolution of the cheetah lineage. Proceedings of the National Academy of Sciences 106(2):512-515.

Cope, E.D. 1895. The fossil vertebrates from the fissure at Port Kennedy Cave, Pennsylvania. Proceedings, Academy of Natural Sciences, Philadelphia 1895:446-451.

Hodnett, J-P., White, R.S., Carpenter, M., and Mead, J.I. in prep. Miracinonyx trumani (Carnivora: Felidae) from the Rancholabrean of the Grand Canyon, Arizona and its implications on the ecology of the “American cheetah”.

Kurtén, B. 1976. Fossil puma (Mammalia: Felidae) in North America. Netherlands Journal of Zoology 26:502-534.

Orr, P.C. 1969. Felis trumani a new radiocarbon dated cat skull from Crypt Cave, Nevada. Bulletin of the Santa Barbara Museum of Natural History Department of Geology 2:1-8.

Savage, D.E. 1960. A survey of various late Cenozoic vertebrate faunas of the panhandle of Texas. Part III, Felidae. University of California Publications in Geological Sciences 36:317-343.

Turner, A. and Anton, M. 1997. The Big Cats and Their Fossil Relatives. Columbia University Press, New York. 234 pp.

Van Valkenburgh, B. Grady, F. and Kurtén, B. 1990. The Plio-Pleistocene cheetah-like cat Miracinonyx inexpectatus of North America. Journal of Vertebrate Paleontology 10(4):434-454.


Thursday, February 9, 2012

If I could be an Allosaurus: The sounds of the Jurassic

Have you ever wondered what it would have been like in the time of the dinosaurs? What they would have looked like and how they would have behaved? What the plants would have been like? Perhaps how hot it would have been, or what smells you could have smelled? What sounds would you have heard as you crouched in a bush and tried not to be found by any large meat-eating carnivores?

Broad-winged katydid (Microcentrum rhombifolium)

A group of scientists from China is filling in one small piece of that complex puzzle. A new study recently published by Gu et al. (2012) in the Proceedings of the National Academy of Sciences names a new stem (or basal) katydid (Archaboilus musicus) from the late Middle Jurassic (Bathovian-Callovian interval at about 165 Ma) of northwest China, namely from the Jiulongshan (or called the Haifanggou) Formation.

Hangingfly (Harpobittacus tillyardi)

This formation is known for several fossil species, although none of them are vertebrates. Its taxa includes the tangle-veined fly Ahirmoneura neimengguensis, the aphid Sinojuraphis ningchengensis, and the hangingflies Formosibittacus macularis, Jurahylobittacus astictus, and Mongolbittacus daohugoensis. The known flora of the formation includes the early flowering plant Xingxueanthus sinensis and the possible early flowering plant Schmeissneria sinensis. Most of these taxa are known from single specimens at the moment, but the preservation is quite exceptional. This preservation means that many features that would normally not be preserved or identifiable are within this formation and in some of these specimens. This leads directly into the new basal katydid Archaboilus musicus.

The type of Archaboilus musicus consists of the part and counterpart of a pair of forewings. Many insects today, including crickets, are able to generate sound using their wings. One of the wings has a row of "teeth", similar to a file. The other acts as a "scraper". One of the co-authors of the study, Montealegre-Zapata, stated that "When they close the wings, the teeth of the file produce vibrations that are amplified as sound by the wing membranes." Many people are currently aware of these sounds. When you are outside, or even inside, and here a cricket "chirping", you are hearing the same actions.

Type of Archaboilus musicus (CNU-ORT-NN2009001PC) showing leftand right forewings. Red arrows in B and D point to area of stridulation and where the noise would been created by the katydid, E and F help show close up versions of the two areas (from Gu et al., 2012).

Stridulation, or the ability to create sounds by rubbing certain body parts together, is well-known in various insects today. With this knowledge in hand, the researchers found that their new insect was preserved well enough to give key details about important morphology of the wings. With this, the researchers conducted thorough comparisons of the forewings of Archaboilus musicus with those of 59 other modern insects. With this comparison, the researchers were able to gain potential insight into something quite incredible and not before really found from the fossil record.

Gu et al. (2012) were able to recreate what this 165 million-year old katydid would have sounded like. Really think about that, a sound not heard for 165 million years has now been recreated. And now you can hear something that the dinosaurs and other animals from that time and region would have heard as well. It may not seem like much, but the ability to recreate that part of the late Middle Jurassic world of northwest China is truly incredible.

The sound was found to be at a low frequency, allowing it to travel relatively far distances. This, combined with the idea that the environment would have been filled with relatively wide-spaced coniferous trees like Araucaria (approximately 1.5 to 20.3 m nearest neighbor distances) and giant ferns (e.g. Angiopteris, Osmunda, and Caniopteris) occupying the lower levels of the forest understory, would have allowed for these low-pitched mating calls to travel much further distances.

Archaboilus musicus reconstructed

The researchers also found that, through comparison with a species of modern katydid, the roughly 4-inch long Archaboilus musicus would have probably been making this call multiple times every second when ready to mate. In essence, the paleoacoustic reconstruction of its call was similar to those of modern crickets, although it would have been of a relatively lower-frequency. In fact, in the movie Jurassic Park, crickets were used for background noise, and it turns out that both sound would have been similar.

Just as interesting as this new insect is what animals would have actually heard these calls while they roamed northwest China all those years ago? While no other vertebrates have been recovered from the Jiulongshan (or called the Haifanggou) Formation, the overlying Tiaojishan Formation does have a diverse assemblage of vertebrates which may have been around at the time of the lyrical Archaboilus musicus and heard its call. As a note, both the Haifanggou and Tiaojishan formations were formerly grouped together as the Lanqui Formation, but that is no longer accepted.


In the Tiaojishan Formation (mainly from Laioning), the rhamphorhynchoid pterosaurs are relatively common and include Changchengopterus pani (from Hebei), Darwinopterus modularis, Fenghuangopterus lii, Jianchangnathus robustus, Jianchangopterus zhaoianus, and Qinglongopterus guoi. The istiodactylid pterosaur Archaeoistiodactylus linglongtaensis is also present in the formation.

Along with the pterosaurs, a few other vertebrates are also present in the formation. These include the plant-eating heterodontosaurid Tianyulong confuciusi. The holotype got a lot of recognition due to a row of long, filamentous integumentary structures that appear to be on its back, tail and neck.

Tianyulong confuciusi
Anchiornis huxleyi

Along with the above-mentioned Ornithischian are two theropods that are considered either archaeopterygids or basal deinonychosaurs. Anchiornis huxleyi is a small dinosaur known from several specimens. Xiaotingia zhengi, on the other hand, is known from a single specimen. Anchiornis has gotten publicity lately due to a more in depth look at the coloration of its feathers, giving scientists a better idea of how it may have looked.  

Xiaotingia zhengi

Xiaotingia has gotten recent publicity because in the corresponding phylogeny, Archaeopteryx, long thought to be the "first bird" and a key figure in the evolution of dinosaurs to birds was positioned as a dinosaur rather than a bird. Still, neither of those are the purpose of this post.

Juramaia sinensis

The earliest known placental mammal, Juramaia sinensis, is also found in the Tiaojishan Formation. Juramaia , while not only showing the morphology and transition of a mammal from a metatherian to a eutherian, was also able to push pack this transition 35 million years earlier than had been previously thought. While quite small, this furry little friend would have been scurrying around the trees and doing its best to stay out of the clutches of Anchiornis and Xiaotingia, among other predators that I'm sure have not yet been discovered.

The Tiaojishan Formation has a few invertebrates as well including a few ostracods and a bivalve. There are also a large number of plants present in the formation. For more information on them, try the wiki page for the Tiaojishan Formation.

But, the main point of this post is to try to hear what these dinosaurs, pterosaurs and mammals, among other things, would have heard on a clear night. So, without further ado, I leave you with the movie file below. It is something that I find almost as good as bringing the insect back to life to be able to hear it. You can close your eyes and imagine it is at night 165 million years ago in northwest China. The small Juramaia scurries between your legs, a herd of Tianyulong travel through a few of the trees off to your left, an Anchiornis is sitting in a tree to your right, and you just barely catch a glimpse of a Xiaotingia gliding from a tree in front of you until you lose sight of it. Various pterosaurs can be seen through the trees, and a few land in some trees off in the distance, just visible with the setting sun. And finally you hear a katydid just a little younger than Archaboilus musicus making these calls. The ability to make the picture that much clearer shows just how incredible the science of paleontology, coupled with numerous other fields, can be.

For a different, but very good review of this incredible discovery and study, make sure to check out the post by my colleague David over at the Meniscus!


Gu J.-J., Montealegre-Z, F., Robert, D., Engel, M.S., Qiao G.-X., and Ren D. (2012). "Wing stridulation in a Jurassic katydid (Insecta, Orthoptera) produced low-pitched musical calls to attract females." Proceedings of the National Academy of Sciences, (advance online publication) doi:10.1073/pnas.1118372109

Monday, December 19, 2011

Why can't we all just get along?: Morphological vs. Molecular Data

Hello everyone, staying on top of things in a timely manner is far harder then I care to admit. Still, here is a new post. These may still be somewhat infrequent until I can finish up my thesis, or a least the first draft of it. But once February hits, perhaps these will be more on track. Here's hoping.....

So, for those of you who have looked into phylogenies, especially those concerning modern taxonomic groups and modern genera in particular, you may have run into some problems (or you may not have, I don't actually know for sure). I will focus on a specific case, but this will not be the end.

Many people are aware of phylogenies, cladograms, and the concept of systematics in general. These are ways to convey the relationships between organisms and help (or possibly help) show evolution through time. These are commonly used in biology and paleontology today. These two fields don't always use the same data sets though. This is not really surprising, since biologists working with modern taxa have the ability to get far more data, while paleontologists commonly only have morphological characters from the fossils they can find. While biologists commonly have several types of data they can use to acquire phylogenies, a relatively common one is molecular data. And this makes sense, DNA should be able to be used for discussing and discovering the relationships of living things to each other.

Sure enough, phylogenies based on molecular data are quite common. A simple search for "molecular phylogeny" in Google Scholar gives >326,000 results. While these can deal with anything from bacteria, to plants to animals, to distinct parts of animals. These have allowed people to discover far more information about relationships of living things. The concept is simple enough, use the same basic thing to compare, say a certain nucleotide or protein, pick your set of organisms with one or more outgroups, align them, then compare them. As a note, you want to have roughly the same numbers for each individual you use. So, say you investigate the cytochrome b protein in felids, you would want the total number of proteins in each taxon to be roughly, say all around 200 total aa proteins (or whichever number you decide upon).

After aligning all of them and running them through a program like PAUP, you will get at least one cladogram. It may look something like this:
Stephens and Wiens 2003, fig. 3

The above figure is figure 3 from Stephens and Wiens (2003). It shows two molecular phylogenies, one as maximum parsimony (a) and the bottom as maximum likelihood (b). I won't be getting into the difference between the two at the moment, just realize they are two slightly different ways of analyzing the same data. The two phylogenies actually do combine three separate data sets though and combine them. They both use cytochrome b, 16S and ND4 data sets.

At first glance, it seems that these do a very good job of agreeing with the known taxonomy presented by the different genera. The only problem is that Clemmys is strongly split at the bottom of the phylogenies. This was cleaned up after this paper was published, however, with the Western pond turtle (Actinemys) and the wood turtle and bog turtle (Glyptemys) being placed in different genera.
Actinemys marmota (left) Glyptemys muhlenbergii (top), Glyptemys insculpta (bottom)

 So, in just looking at the molecular data, the family Stephens and Wiens (2003) were investigating seems to be pretty well off. But they didn't leave it to just that data. They also looked into the morphological data as well:

Figures 4 and 5 from Stephens and Wiens (2003)

Graptemys flavimaculata
These two figures above [figs 4 and 5 from Stephens and Wiens (2003)] show the authors' results on there morphological data alone. They did use soft tissue, osteological, morphometric, and statistical data as part of this set. The use of any of those sets can be debated, and has by some people. They also use two ways of attempting to scale the data so that weighting would be, presumably, the same. I won't get into those here, but be aware of them and that they are not agreed upon fully. What can be easily seen is that the two phylogenies above do not agree with each other. The relationships shown are not the same. In the phylogeny on the left, Pseudemys comes out as the most derived member, while the one on the right has Graptemys in the same position.

Trachemys scripta elegans

I would like to focus on Trachemys though. The slider turtles are the subject of my Master's thesis at the moment, and have been the topic of much debate for quite a while now. Without getting too detailed at the moment, it is apparent that many researchers have been well aware of the problems, but no one has taken it upon themselves to completely clear it up. Dale Jackson did some work on the group in the 1970's and 1980's, but their is still far too little known about them. What can be seen is that the members of Trachemys in the phylogenies above does not come out as a cohesive or monophyletic group. Not only the genus, but, many times, the supposed species (with their respective subspecies) don't group together well either. In these instances, Trachemys comes out as either paraphyletic or polyphyletic. It can even be seen in the phylogeny on the right that the Pseudemys group is well nested within Trachemys.

This is a bit disturbing to someone researching the group. What exactly is going on? One key aspect to keep in mind is that convergence due to similar lifestyles can be a big problem. If different taxa have evolved the same or similar features to do the same things, they may be seen as more closely related then they truly are. This depends on the characters and features that people use to make their phylogenies though. The hope is that, with enough characters and features being used, the true relationships will come to light. If that is the case or not is not actually known at the moment.

Paleontologists only have the luxury of morphological data sets. Perhaps one day we will get some DNA from a dinosaur or other long extinct species, but that is not so today. They use what they can, and come up with phylogenies and relationships based on that data alone. It has been said by some researchers, including John Wiens on numerous occasions, that combining the molecular and morphological data sets is a good idea. The idea being that they will strengthen each other, assuming that they are both working towards the same end (correct?) phylogeny. It was suggested to me that, even working with fossils and modern taxa, and even only having molecular data for the modern taxa, that combining the data sets would be recommended and should strengthen all the relationships in a phylogeny of fossil and modern taxa. Stephens and Wiens (2003) did this as well with their modern taxa, combining all their data sets with the following phylogeny:

Figure 7 from Stephens and Wiens (2003)
Malaclemys terrapin
In the figure above, which shows all taxa in their study, Trachemys first appears to fall out all together. All Trachemys species appear within a "group", all their names above or below each other, with no other nested genera present. If you look more closely though, you will see that Trachemys is still not monophyletic. In this instance, they should either be split apart into 5 (yes 5!) different genera, or have other genera combined as Trachemys. This seems somewhat crazy, since most researchers have felt that the group was either fairly well set, or that they should be combined with Pseudemys and/or Chrysemys. In fact, with this grouping, it would be Graptemys and Malaclemys that should be grouped with Trachemys to make it a monophyletic group. As a note, I DON'T believe that the idea of subgenera is a good idea and/or the answer.

They also had a second phylogeny which only took into account the taxa with complete data sets (Stephens and Wiens, 2003, fig. 8), which is to the right here-------------------------------->

These groupings seem to become far nicer and follow known taxonomic groups. It is of note, though, that only a single Trachemys species is present in this table. So, is it Trachemys alone that is causing all these problems?

I am not so sure of that. It makes more sense for it to be a problem with a number of taxa within the Deirochelyinae, although Trachemys may be the biggest trouble-maker. I believe that convergence is one of the biggest problems here. Many of these turtles live in similar environments and do similar things. Because of this, they have developed many of the same features. A key area to look at may simply be what features are being used for these phylogenies. Another key area could be that more molecular data needs to come to light on this group in general.

Regardless, I have talked with Dr. Jacques Gauthier, who has informed me that this kind of concept, where the molecular and morphological data do not agree, is a relatively common occurrence. Not just with this group, or even just turtles, but many groups. This is especially true when dealing with fossils and fossil groups.

The molecular data seen above does not agree with the morphological data. In essence, because they don't agree, they are working against each other. When combining the two different sets, the one with the most data will simply win out. This is not what we are scientists are striving for. We want the two different kinds of data to agree and give us a stronger idea of the true relationships present. Sometimes this does happen and they data sets essentially agree, but all too often that is not the case.
Ray-finned fish evolution from Hurley et al. (2007), image from Dracovenator blog

So, why can't the molecular data and morphological data agree? While I don't know the exact answer, I believe that eventually they will. We just haven't gotten enough of either. We must believe that the true relationships will eventually come to light with enough good data. So keep plugging away, and we will figure these things out. Even if the organisms themselves do not care how they fit in together; Trachemys doesn't care how it relates to the Alligator that may be trying to eat him, many people, myself included, do care.

Trachemys and alligatorid

Look to the Dracovenator blog post titled: Problems in Ray-Finned Evolution to see another case of disagreement with a different group, the ray-finned fishes.


Stephens, P. R. amd J. J., Wiens. 2003. Ecological diversification and phylogeny of emydid turtles. Biological Journal of the Linnean Society 79:577-610.

Hurley, I.A., Lockridge Mueller, R, Dunn, K.A.,Schmidt, Friedman, M., Ho1, R.K., Prince, V.E., Yang, Z., Thomas, M.G. and Coates, M.I. (2007)A new timescale for ray finned fish evolution. Proc. R. Soc. B 274, 489–498 

Sunday, November 13, 2011

Alamosaurus and the North American sauropod hiatus

Hello all, I know I've really dropped the ball on this one. It's been far too long. But I'm finally back from SVP in Las Vegas and have a bit of free time to try to catch up and write some things. The meetings went rather well and, as is always the case with these things, I gained tons of information and ideas, and I can't begin to actual use all of them. That leads me in to today's post though. Jeff Wilson and Mike D'Emic, two excellent sauropod paleontologists gave two very good talks on titanosaurs, Alamosaurus, and North America at the meeting, and I will discuss them briefly here, along with some of my questions and ideas.

Image of Alamosaurus from SV-POW blog:
Sphaerotholus (also sometimes called Prenocephale)

First, D'Emic's talk (D'Emic, 2011) focused on much of his Ph.D. research on titanosaurs, and this led into the "27 million year sauropod hiatus' in North America toward the end of the Cretaceous. This was ended, for anyone who isn't aware, by the appearance of Alamosaurus in the Late Cretaceous. D'Emic presented a very interesting phylogeny for the Titanosauriformes. Alamosaurus came out on the end of the cladogram as one of, if not the most, dervied member of the Titanosauria. D'Emic hypothesized that the sauropod hiatus was a result of regional extinction. This regional extinction may have been the result of the infusion of other taxa (such as hadrosauroids), or could have been brought about by other factors, of which we are not certain or aware of at this time. Still, many authors have hypothesized that sauropods, namely Alamosaurus, migrated to North America from South America (where titanosaurs are relatively abundant) or from Asia, where a large number of other taxa are thought to have come from, such as anykylosaurids (Nodocephalosaurus) and pachycephalosaurids (Sphaerotholus, Prenocephale). While we aren't sure yet where they came from, we do know they were here.

The presentation by Wilson (actually presented by D'Emic at the meeting) was mainly discussing whether Alamosaurus is a valid taxon (Wilson and D'Emic, 2011). As reported by Jasinski et al. (2011) Alamosaurus was named based on a nearly complete scapula as the holotype and a nearly complete ischium as the paratype, The material was collected by Reeside in 1921 in the Naashoibito Member of the Ojo Alamo Formation in the San Juan Basin of New Mexico, and named and described by Gilmore (1922).

Fig. 12 from Jasinski et al. (2011), showing A-B, USNM10486 (holotype), left scapula and C-D, USNM 10487 (paratype), right ischium, bars scales  = 10 cm.

These specimens, and this taxon have been the topic of a lot of discussion. Part of the reason for this is the fact that they are somewhat scrappy, and this means that the taxon itself is based on less then ideal material. This also makes it quite difficult to confidently refer other material to Alamosaurus. Nevertheless, the prevailing thought has been that there is a single taxon of sauropod present in North America during the Late Cretaceous. Due to the normalized acceptance of this idea, essentially all sauropod material from North America during this time has been referred to Alamosaurus. Some have conservatively identified some material to Sauropoda indet. or to Titanosauria indet., but this is a small minority. Wilson and D'Emic (2011), however, completed a thorough revision of the type material for Alamosaurus and took this re-investigation further. As was commonly the practive in the early twentieth century, Gilmore (1922) did little to offer some kind of diagnosis for a newly named taxon. Wilson and D'Emic (2011) found that the holotype (and other type) material did contain several autapomorphies, signifying that Alamosaurus is, certainly, a valid taxon.

Herd of Alamosaurus sanjuanensis

Now this was an important step to take. Many authors had used Alamosaurus in phylogenetic analyses and comparisons without being certain of its validity. Some authors, however, have other questions regarding Alamosaurus. Jasinski et al. (2011) did not question its validity, but they did, however, question whether it was being used as a garbage (or waste-basket) taxon. A garbage taxon is when where many taxa or specimens are commonly lumped together without real distinct reasons or definitions. Their thought was that all sauropod specimens were being thrown together even though they couldn't be confidently referred to Alamosaurus. Regardless of whether it was true or not, Alamosaurus was being made the only possible sauropod in North America at this time.
Who's to say there wasn't more than one sauropod taxa in North America in the Late Cretaceous?

Wilson and D'Emic (2011) attempted to address this issue as well. Due to their re-evaluation of the type material, and the material that could then be referred to the taxon through their determined autapomorphies, they were able to come up with a far more thorough diagnosis. Several of the newly referred specimens were far more complete, and this allowed for several confident referrals.This does clear up some of the confusion and some of the problems. It does not, however, clear up all of them. While Wilson and D'Emic attempted to use this as a way of saying that Alamosaurus was, indeed, not a waste-basket taxon, I must thoughtfully disagree.

Although they were able to refer more specimens to Alamosaurus, they were not able to confidently refer all Late Cretaceous sauropod material from North America to Alamosaurus. Their is still plenty of material out their that has not, or can not, be referred. I have seen several specimens of the same element that appear to be significantly different in various aspects, including morphologically. This means that Alamosaurus is still being used, in many ways, as a waste-basket taxon.

I find it somewhat unlikely that only a single sauropod taxon occupied North America from the time of a "sauropod migration" back into North America until sauropods died at at the end of the Cretaceous or just before. It seems far more likely for there to have been more taxa and, assuming they were rare (or more rare) we have not found their remains or have just not been able to positively identify them as such. Wilson and D'Emic (2011) took a very positive first step in this, and their study is very important. I hope to see a complete paper on this in the not too distant future. One thing to remember is that even some of what they do is referral by provenance, so they do have some problems with their study. Still, this may be a good first step in, not only re-evaluating Alamosaurus, but re-evaluating numerous other taxa that face similar or other key problems.
Alamosaurus defending themselves, special thanks to artist for this great artwork

Let me know if you have any thoughts on this though. I would love to know if I am vastly in the minority on this subject, or if other people share my reservations and thoughts.


D'Emic, M. 2011. Early evolution of titanosuriform sauropod dinosaurs: taxonomic revision, phylogeny, and paleobiogeography. Journal of Vertebrate Paleontology 31(Supplement): 95A. (abstract) 

Gilmore, C. W. 1922. A new sauropod from the Ojo Alamo Formation of New Mexico. Smithsonian Miscellaneous Collections 72: 1-9.

Jasinski, S. E., R. M. Sullivan, and S. G. Lucas. 2011. Taxonomic composition of the Alamo Wash local fauna from the Upper Cretaceous Ojo Alamo Formation (Naashoibito Member), San Juan Basin, New Mexico. New Mexico Museum of Natural History and Science Bulletin 53: 216-271.

Wilson, J. and M. D'Emic. 2011. The validity and paleobiogeographic history of the titanosaur sauropod Alamosaurus sanjuanensis from the latest Cretaceous of North America. Journal of Vertebrate Paleontology 31(Supplement): 215A. (abstract) 

Monday, September 19, 2011

Cretaceous Turtles of New Mexico Part 1: Here comes the meteor?

Since some of you may be aware that one of my major interests revolve around turtles, both alive and dead, its surprising that its taken me this long to post anything on this amazing group or reptiles. While there are an incredible number of things that can be posted, this will be more of a simple post based around one of my recent papers (Jasinski et al., 2011). From what is known about the San Juan Basin, specifically in New Mexico, these are the last turtles known before the K-T extinction event and the moment in time when the bolide hit the Yucatan.
Glyptodontopelta mimus from Naashoibito Member (Ojo Alamo Formation)

Ojoceratops fowleri
The study itself was on all the fossil vertebrates recovered from the Naashoibito Member of the Ojo Alamo Formation (Jasinski et al., 2011). The fossil vertebrates from this stratigraphic unit have been grouped together in what is called the Alamo Wash local fauna and were originally studied by Lehman (1981), but were in thorough need of revision. There are several key dinosaur taxa within this fauna, including the recently named Ojoraptorsaurus boerei. Other endemic taxa to this fauna include the ankylosaur Glyptodontopelta mimus and the ceratopsid Ojoceratops fowleri. It is also contains the types of Alamosaurus sanjuanensis, the youngest sauropod from North America. Alamosaurus has a number of potential problems though, and I will be touching on those in later posts.

So, the focus of this post is on those lovely creatures how keep their houses on their backs. The turtles from the two underlying formations are under study by Dr. Robert Sullivan and others and the study is currently waiting to come out in an upcoming volume on fossil turtles dedicated to Dr. Eugene Gaffney. So we will hope it comes out sooner rather than later. The turtles from the Naashoibito Member are vastly understudied and little attention has been paid to them. Much of this is because most material is very fragmentary, and there has been little there that would even qualify as a potential holotype for a turtle species.

reconstructed Basilemys, similar to Basilemys nobilis
Even so, two turtle species have been named from this unit. The first, called Basilemys nobilis, was named by Hay (1911) based on several carapace and plastron fragments. Basilemys is a member of the Nanhsiungchelyidae, and represents the only definitive terrestrial turtle from this turtle fauna. The forthcoming study by Sullivan et al. came to the conclusion that B. nobilis was a nomen dubium. While a recently recovered specimen may yet prove that a legitimate species of Basilemys is present in the Naashoibito Member, the holotype of B. nobilis will still probably be taxonomically undiagnostic.

reconstructed shell of Adocus
The second holotype, named Adocus vigoratus by Hay (1911), is based on several carapace fragments. Adocus is currently part of the family Adocidae, although at one point it was considered in the same family as Basilemys. Being an aquatic species, it probably inhabited a familiar niche throughout the late Cretaceous and into the Paleocene. Jasinski et al. (2011) felt that the type specimen of A. vigoratus was undiagnostic though, and considered it a nomen dubium, although it does represent an adocid in the fauna.

Kinosternon subrubrum, close living relative of Hoplochelys

Recent studies on Compsemys (Knauss et al., 2011) and Hoplochelys (Lyson and Joyce, 2011), have revealed many synonymies for these two previously ill-studied turtles. While the specimens of the ?pleurosternid Compsemys and the kinosternoid Hoplochelys are generally quite fragmentary in this fauna, both have been referred to specific species. The ?pleurosternid is now called Compsemys victa and all North American Compsemys are thought to represent one species. The kinosternoid Hoplochelys has now been referred to the species H. clark, as has all Cretaceous specimens of Hoplochelys. Both turtles would have represented small aquatic species. Compsemys was a small gracile turtle with a number of distinct places on the shell with small and distinct bumps and small ridges.

Neurankylus (a baenid) showing color spots found on specimen from Paleocene in San Juan Basin
Boremys (Baenidae)
The Baenidae are a group of aquatic turtles well-represented throughout the Cretaceous and Paleocene. They come in a variety of sizes, but are commonly quite robust for water turtles. Considering the overall number of turtle fossils recovered from the Naashoibito Member, baenids are some of the most common. Even with the generally large number of turtle fossils, none have been identified to a given genus yet. This is because most are very fragmentary or undiagnostic.

Plastomenus, similar to a turtle found in Naashoibito Member
The Trionychidae are a group of aquatic turtles today commonly called soft-shell turtles. These turtles have been around since the Cretaceous and continue today around the world. Surface texture makes shell fragments easy to identify to the species, and one or more new species may yet be named from the trionychid material already collected from the Naashoibito Member. The only turtle skull material from this member is also from a trionychid, identified by Jasinski et al. (2011) as the right parietal of a large trionychid called Plastomenus.

A modern trionychid, Apalone spinifera, the spiny softshell turtle

Various other fragments of turtles have been recovered as well, but these are too fragmentary to assign to any specific family of turtles. I realize that this was a relatively small post, but I wanted to put this out there for the future. This is a small look at the last turtles known from the Cretaceous in this region of the world. While the age of this member has been debated for years, the two generalized camps range from either an early Maastrichtian age (~68 Mya) or later Maastrichtian (~66 Mya). I am currently working on a study into how the turtle fauna of the San Juan Basin across the K-T Boundary, which is leading to some interesting conclusions. I won't go into to much detail, but if you are going to SVP this year in Las Vegas, hopefully you will seek me out and ask me about them.


Hay, O. P. 1911. Descriptions of eight new species of fossil turtles from the west of the one hundredth meridian. Proceedings of the United States National Museum 38:307-325.
Jasinski, S. E., R. M. Sullivan and S. G. Lucas. 2011. Taxonomic composition of the Alamo Wash local fauna from the upper Cretaceous Ojo Alamo Formation (Naashoibito Member), San Juan Basin, New Mexico. New Mexico Museum of Natural History and Science Bulletin 53:216-271.
Knauss, G. E., W. G. Joyce, T. R. Lyson, D. Pearson. 2011. A new kinosternoid from the Late Cretaceous Hell Creek Formation of North Dakota and Montana and the origin of Dermatemys mawii lineage. Paläontologische Zeitschrift 85:125-142.
Lehman, T. M. 1981. The Alamo Wash local fauna: A new look at the old Ojo Alamo fauna; pp. 189-221 in Lucas, S. G. (ed.), Advances in San Juan Basin paleontology. University of New Mexico Press, Albuquerque. 
Lyson, T. R., and W. G. Joyce. 2011. Cranial anatomy and phylogenetic placement of the enigmatic turtle Compsemys victa Leidy, 1856. Journal of Paleontology 85:789-801.
Sullivan, R. M., S. E. Jasinski, and S. G. Lucas. in press. Re-assessment of Late Campanian (Kirtlandian) turtles from the Upper Cretaceous Fruitland and Kirtland formations, San Juan Basin, New Mexico; in Brinkman, D., J. Gardner, and P. A. Holroyd. (eds.). Morphology and evolution of turtles. Springer Press, Dordrecht.