Monophyletic Taxa Are Fake Too

FIRSTLY: Matt Wedel has written a fairly eye-opening account of his recent experience with having his words distorted by the production company Dangerous Ltd. for their recent show Clash of the Dinosaurs, followed up heah and neah. These provide some valuable insight as to why so many shows on the Discovery Channel suck balls, as well as some suggestions on how to improve the situation. Moving on...

The following story is a work of fiction, though inspired by true events.

Once upon a time, there lived a population of drab and uninteresting terrestrial carnivorous reptiles that ate mice. “This is bullshit,” they thought, “to be so drab and uninteresting.” However, since adaptations are driven by random mutation and natural selection, they could do nothing about it. One day, one of them committed suicide by drowning herself in a river. She was buried and fossilized. Her name was Cecilia.

One day, three million years later, a subset of the population was isolated on a distant island, and random mutation and natural selection resulted in the development of a row of low spines running down their back, along with a larger and more robust body, allowing them to tackle larger prey animals which lived on the islands. “HELL yeah!” They said. “This is more like it!” They threw a massive kegger, and one named Ralph drank too much and died of alcohol poisoning. His friends overreacted and buried him in the floodplain, swearing to never speak of it again. He was also fossilized.

After another million years, some members of Ralph’s species decided to found a nudist colony on another island inhabited by the same prey species. Random mutation and natural selection resulted in the development of a distinctive coloration and mating display which caused their parent species to regard them as perverts. This display involved a prominent frill which grew over the pelvis, and a short horn on the nose. Other than that, their body plan and lifestyle didn’t change. One day, one of them got swept out to sea and drowned. He was buried and fossilized in marine mudstones. His name was Terence.
Four million years later, some members of Terence’s species just decided they wanted to live on a new island. They evolved into specialized marine predators with a long slender snout, flippers and a long, fin-like tail. They reduced the pelvic fin and nasal horn, but did not lose them entirely. They developed not only a different body plan and lifestyle, but genetic differences from Terence’s species far more extreme than those between Terence and Ralph’s species. One day one of them just died, in her sleep. It was very peaceful. Her name was Selma. She was buried and fossilized on the mainland, because she had always wanted to go there. It was really beautiful.
Seventy million years passed, and one day a species of primate took an interest in paleontology. Through perseverance and luck, they found the fossilized skeletons of Cecilia, Ralph, Terence and Selma. They correctly deduced, in broad terms, their evolutionary history, including the fact that Terence and Selma, despite their extremely different anatomical specializations, had a more recent common ancestor than Terence and Ralph due to the fact that they uniquely shared a pelvic fin and a nasal horn lacking in Ralph and Cecilia. They drew a picture with Cecelia, Ralph, Terence, and Selma on it. It may sound strange to turn a series of events into an abstract concept like a diagram, but this primate species found it helpful in order to grasp things conceptually.
Now comes the odd part. This primate species had a hard time drawing a distinction between real history and they abstract concepts that they used to describe and communicate about this real history. For example, they decided that Terence and Selma, simply due to the fact that they had a common ancestor, were the same…thing. Specifically, they were a thing shaped like a “V.” They lived on separate islands in separate times and had totally different lifestyles, but they were the same…thing. A thing shaped like a fucking “V.”

Then they realized, that Selma, Terence, and Ralph have a common ancestor too, and decided that also made them a single…thing. It was also shaped like a ‘V’. And Selma, Terence, and Ralph shared a common ancestor with Cecilia too, and that also made them the same…thing. Shaped like a “V.” These “V”s all fit nicely inside of each other, appealing to the primates sense of symmetry and order.

Then they decided that these “V”s were not just abstractions to help our visual primate brains grasp common descent. The “V”s were, well….real.

It gets weirder though.

Other primates noted that there were other interesting things to look at with Cecelia, Ralph, Terence, and Selma besides common descent. They noted for instance that Ralph and Terence shared a bunch of morphological adaptations related to their predatory lifestyle, which they inherited from a common ancestor, and set them apart from Cecelia and Selma. They decided to describe Ralph and Terence as being the same…thing. They didn’t mean for Selma’s fossilized bones to feel bad by being left out, but she didn’t strike them as being the same…thing.

“We mean no harm”, they said. “We just think there are other things to talk about besides common descent. Like common descent and morphology, or common descent and lifestyle. We just want a word to encompass these patterns of variation. CAN WE JUST HAVE A WORD?”

Then they went on to say: “Common descent between two organisms may be a reality. It may be a historical fact that two organisms have a more recent common ancestor than a third. However, if you start talking about organisms separated by millions of years of time and thousands of years of time as a single “thing”, than you are talking about an abstraction. A clade does not exist anywhere except in our imaginations. And this is OK! This is perfectly all right! We need abstractions to communicate. However, when you start saying that another type of abstraction should not be used because it is less ‘real’, things are getting silly."

Then they went on to say: “Why are we so obsessed with the idea that a classification system has to be ‘real?’ Why can’t we just admit that classification systems are inherently fake, because ‘natural groups’ with tidy, un-arbitrarily defined boundaries do not exist in nature? Why can’t we just acknowledge that we need abstractions to communicate about concepts and history, and that a concept can be both abstract and imaginary and still be useful?”

They were punished for heresy. God, it was fucking horrible. They used the CHIMP CANON.
LNJ

Phytosaurs And Evolution

"There are no transitional fossils” is one of the most commonly repeated and blatant lies propagated by creationists, who are often either grotesquely ignorant (or pretend to be) of the spectacularly exploding fossil record, or have no idea what a transitional fossil is supposed to look like (e.g. Kirk Cameron’s retarded chimera “crocoduck”, which in fact existed, although it looked quite different. You get an "A" for effort Kirk).

However, one of the most compelling evidences of macroevolution is not just the existence of transitional fossils, but the order they appear in the rock record. The basic principles of biostratigraphy, the method paleontologists use to order fossils in time using thier stratigraphic sequence, was developed in the early 19th century by British canal surveyor named William Smith, and more or less independantly by the brilliant French naturalist Georges Cuvier and his collaborator Alexandre Brogniart.

Biostratigraphy as a means of ordering fossils is based on a very simple idea: If you have a pile of sediments, the ones at the bottom (and therefore the fossils in them) are oldest, and the ones at the top (and therefore the fossils in them) are youngest. This is based on the recognition that it is hard to bury something that isn't already there. Makes sense, ja? An added bonus of biostratigraphy is that if you can recognize the same species in piles of sediment from around the world, you can match them up (or "correlate" them) to produce a composite history of life on Earth, like so:

Smith and Cuvier were not evolutionists, and made thier observations that fossils appear in a certain order in a vertical sequence of strata decades before the publication of Origin of Species. Biostratigraphy therefore does not depend on any assumptions about evolution in order to work. As a result, it can be used as an independent check on macroevolution by determining whether or not transitional fossils actually appear in the expected order. The big picture of the origin of life was reconstructed almost entirely using biostratigraphy and biostratigraphic correlation, and gives us a picture of change through time consistent with macroevolution. However, this ordination also supports evolution on smaller macroevolutionary scales.

Archosaurs are better than any other kind of animal, as everyone agrees who is not a complete fool. However, basal archosauriforms and pseudosuchians (crocodile-line archosaurs) are rarely used to demonstrate the reality of evolution, in spite of the fact that both phytosaurs and early crocodylomorphs have beautiful fossil records. The theropod-bird transition is used a lot more commonly, presumably because theropods are dinosaurs and therefore deemed more “sexy” than pseudosuchian archosaurs. However, this is bullshit, because birds are pussies. Just look. Fuck birds.

Phytosaurs were the most common group of archosauriforms in western North America during the Late Triassic. Most phylogenetic analyses have found them to be the most basal members of the pseudosuchian lineage (e.g. Juul, 1994; Benton, 2004), although this opinion may be changing slightly in the near future. Or may not, I don't know. Forget I said anything.

Phytosaurs were the most common aquatic predators, and had a body form, and probably a lifestyle, similar to modern crocodilians (Hunt, 1989). They also got quite large, possibly reaching ten meters in length, although most were in the size range of big modern crocodilians. Phytosaurs are sometimes described as “crocodile-mimics”, although this is crap because they developed the crocodilian body form and lifestyle before crocodilians, and in fact so did earlier and more basal Triassic archosauriforms: the proterosuchids, proterochampsids, and that hideous little freak Vancleavea.

However, the skulls of phyosaurs differ from those of crocodilians, and most other reptiles, in several ways. These include having the external nares pushed back on the snout (whereas they are at the tip of the snout in most reptiles). Moreover most, but not all forms (this is a hint) have features of the back of the skull which are very modified. In most diapsids, the supratemporal fenestrae, the upper of the two diapsid openings at the top of the head, are more or less level with the skull roof. In most phytosaurs however, they are reduced and pushed anteroventrally to varying degrees (another hint). Moreover some phytosaurs (but not all, hint) have a bar forming the lateral border of this opening, which is composed of the postorbital and squamosal bones, which is greatly broadened and sculptured; it is relatively slender and smooth-surfaced bone in some phytosaurs and most reptiles.

In fact, you can roughly line up North American phytosaurs according to how much they differ from the “normal” archosaur condition. Phytosaur alpha taxonomy is notoriously convoluted, but several morphotypes may be identified which fall out in this order in the major phylogenetic analyses of this group (Ballew, 1989; Hungerbeuhler, 2002; Stocker, 2008, in press). Most or all of these may actually be grades, so the genera names are applied loosely. Paleorhinus has nostrils which, although set back on the snout, are anterior to the antorbital fenestra, a slender and smooth postorbitosquamosal bar, and supratemporal fenestrae which are level with the skull roof. Angistorhinus, retains all of these basal features, except that the nostrils are pushed up over the antorbital fenestrae, as they are in all other phytosaurs. Leptosuchus (sometimes called Rutiodon) still has a slender postorbitosquamosal bar, but the supratempotal fenestra are pushed anteroverntrally and more constricted than in Paleorhinus and Angistorhinus. This trend continues in Pseudopalatus and Redondasaurus, and in the latter, the fenestrae are actually completely closed up. Finally, both Pseudopalatus and Redondasaurus have broad and heavily sculptured postorbitosquamosal bars. Click the image to enlarge:

So…how does these different forms fall out stratigraphically? To answer this, we have to look at areas where different forms are known to occur in the same area, so that their stratigraphic relationships can be determined. The Dockum Group of West Texas and eastern New Mexico (see Lehman, 1994; Lucas, 1994; and Martz, 2008 for a lots of really exciting arguments about stratigraphic nomenclature) has all five morphotypes, and the Chinle Formation in the Colorado Plateau region (e.g. Stewart et al., 1972; Dubiel, 1994) has Leptosuchus, Pseudopalatus, and Redondasaurus.

In the Dockum Group, the first Paleorhinus specimens occur in conglomeratic sandstones at the base of the Upper Triassic section (variously called the Santa Rosa Sandstone, Camp Springs conglomerate, and Boren Ranch beds), and continue into the lowest mudstone-dominated units of the Dockum Group overlying these conglomerates (the Tecovas Formation and Garita Creek Formation). These lower mudstones are also where we get the first specimens of Angistorhinus and Leptosuchus. Pseudopalatus appears higher in the section, in sandy units in the middle of the Dockum Group and the upper mudstone-dominated units (in the Trujillo sandstone and Bull Canyon/upper Cooper Canyon Formation), and Redondasaurus appears in the uppermost beds of the Dockum Group (the uppermost Cooper Canyon Formation, and Redonda Formation) (e.g. Hunt and Lucas, 1991; Lucas, 1998; Lehman and Chatterjee, 2005; Martz, 2008).

In the Chinle Formation of northern Arizona, we do not have Angistorhinus, but the other four forms are present. And yes, Paleorhinus and Leptosuchus appear first (from the Placerias Quarry, which may be in either the Bluewater Creek Formation or Blue Mesa Member), Leptosuchus continues higher in the section (in the Blue Mesa and Sonsela Member), Pseudopalatus appears next (in the upper Sonsela Member, Petrified Forest Member, and Owl Rock Member), and Redondasaurus last (in the Rock Point Member at the very top of the Chinle Formation) (e.g. Lucas, 1998; Heckert and Lucas, 2002; Parker, 2006). How about that?

Postscript on lithostratigraphy: In the last strat column figure, "Cooper Canyon Formation" should really be "Bull Canyon Formation." These units have been considered equivalant by most workers, but one of the findings of my dissertation is that the lower part of the type section of the Cooper Canyon Formation is probably correlative with the Tecovas and Trujillo Formations. This works out fine, since the lower parts of the Cooper Canyon Formation in the type area have Paleorhinus and then Leptosuchus showing up before Pseudopalatus as expected, but I didn't want to delve into the nomenclatural mess.

pps. Thanks to Sterling for reminding me of the Placerias Quarry "Paleorhinus" skull.

REFERENCES
Ballew, K.L. 1989. A phylogenetic analysis of Phytosauria from the late Triassic of the western United States. In Lucas, S.G., and Hunt, A.P. (eds.) Dawn of the Age of Dinosaurs in the American Southwest, pp. 309-339. New Mexico Museum of Natural History, Albuquerque, NM.

Benton, M.J. 2004. Origin and relationships of Dinosauria. In D.B. Weishampel, P. Dodson, and H. Osmólska (eds.), The Dinosauria (2nd edition), pp. 7-19. University of California Press, Berkeley, CA.

Dubiel, R.F. 1994. Triassic deposystems, paleogeography, and paleoclimate of the Western Interior. In Caputo, M.V., J.A. Peterson, and K.J. Franczyk (eds.), Mesozoic Systems of the Rocky Mountain Region, USA, pp. 133-168.

Heckert, A.B., and Lucas, S.G. 2002b. Revised Upper Triassic stratigraphy of the Petrified Forest National Park. In A.B. Heckert and S.G. Lucas (eds.), Upper Triassic Stratigraphy and Paleontology. New Mexico Museum of Natural History and Science Bulletin 21, pp. 1-36. Albuquerque, NM.

Hungerbühler, A. 2002b. The late Triassic phytosaur Mystriosuchus westphali, with a revision of the genus. Palaeontology, vol. 45, pt. 2, pp. 377-418.

Hunt, A.P. 1989. Cranial morphology and ecolog y among phytosaurs. In S.G. Lucas, and A.P. Hunt (eds.), Dawn of the Age of Dinosaurs in the American Southwest, pp. 349-354. New Mexico Museum of Natural History, Albuquerque, NM.

Hunt, A.P., and Lucas, S.G. 1991. The Paleorhinus biochron and the correlation of the non-marine Upper Triassic of Pangaea. Palaeontology, vol. 34, pt. 2, pp. 487-501.

Juul, L. 1994. The phylogeny of basal archosaurs. Palaeontologie Afrique, vol. 31, pp. 1-38.

Lehman, T.M. 1994a. The saga of the Dockum Group and the case of the Texas/New Mexico boundary fault. New Mexico Bureau of Mines and Mineral Resources Bulletin, no.150 (April), pp. 37-51.

Lehman, T. and S. Chatterjee. 2005. The depositional setting and vertebrate biostratigraphy of the Triassic Dockum Group of Texas. Indian Journal of Earth System Sciences, vol. 114, no. 3, pp. 325-351.

Lucas, S.G. 1998. Global Triassic tetrapod biostratigraphy and biochronology. Palaeogeography, Palaeoclimatology, Palaeoecology vol. 143, pp. 347-384.

Lucas, S.G., Anderson, O.J., and Hunt, A.P. 1994. Triassic stratigraphy and correlations, southern High Plains of New Mexico-Texas. New Mexico Bureau of Mines and Mineral Resources Bulletin, no. 150, pp. 105-126.

Stewart, J.H., Poole, F.G., and Wilson, R.F. 1972b. Stratigraphy and origin of the Chinle Formation and related Upper Triassic strata in the Colorado Plateau region. Geological Survey Professional Paper, no. 690, 336 pp.

Stocker, M.R. 2008. The relationships of the phytosaur Leptosuchus Cape 1922 with decriptions of new material from Petrified Forest National Park, Arizona. Unpublished master’s thesis, University of Iowa, IA, 220 pp.