Report from SICB '99

Dr. Thomas Holtz, Jr.

Part I

I'm back from the Society of Integrative and Comparative Biology meeting (January 1999).

The abbreviation is SICB, pronounced (much to Farlow & my surprise) "sick-bee". Paul Davis actually began his talk with the joke "When I told my colleague I was going to SICB, he said I should bring it some honey."

First, some practicalities about the hotel, which is also the hotel of this year's SVP meeting. Nice location (right along the 16th Street mall, 2 miles of pedestrian walkways, shops, restaurants, etc.), fairly inexpensive restaurant in the hotel (although service could be faster). BUT, if you give a talk in the big ballrooms, the ambient light is a bit high, so plan slides with a lot of contrast.

So, why was I at SICB. Well, since I was there, and Farlow, and Greg Erickson, and Phil Currie (who wasn't giving a talk) were all there, and Ken Carpenter was in town, we COULD have had one kick-ass Tyrannosaurus rex symposium! However, I was part of a paper (given by Farlow, with co-authors Gatsey, Hutchinson & Robinson) on dinosaur locomotion, which was part of the symposium on the Evolutionary Origin of Feathers.

In Part II I'll address talks that weren't part of that symposium, including what I think was the best dino related talk at the meeting. Too bad it was the day AFTER most of the paleo folks had left. Briefly, though, SICB is a conference more paleo people should go to: lots and lots of experimental work on functional anatomy and behavior. You get to find out important things, such as the fact that gliding in flying squirrels and snakes isn't at all like the people involved in the origins of flight debate think it is...

Okay, the Feathers symposium. It was originally planned as a functional, developmental, and molecular look at the avian integument, but the discovery of the feathered Chinese forms from Liaoning were used to bring in a lot of paleo folk. What we wound up with was a bunch of people who work on modern feather development and structure, a bunch involved with paleo aspects of feathers, and a few physiologists thrown in the batch.

The talks:

Peter Stettenheim gave a great overview of the diversity of modern feathers (doubly good overview due to the constant malfunction of the slide machine). It doesn't matter how much diverse you think feathers are: the reality is even greater.

Walter Bock (who I had never met before: it turns out he had interviewed for a job at U. Maryland College Park before being hired by Columbia!!) gave a talk which surprised me in many ways. Instead of a review of the pseudophylogeny method and scenario-based hypotheses (some of his classic stuff), he instead pointed out that a) we don't have direct evidence of the origin of feathers; b) what we do have is bones only for most of the pertinent forms; and c) that it is extraordinarily difficult, if not impossible, to test different scenario-based hypotheses for feather origin against each other (e.g., insulation vs. display vs. flight) in order to determine which should be preferred. Agreed!! I never thought I'd find more to agree with in a paper by Bock than one by Dodson...

Due to non-interest or lack of time, several different people who were asked to give the token "dinosaur origins of birds" speaker position turned down the organizers. (No, they didn't ask me. I would have done it, though...). The paper was given, somewhat reluctantly, by Stuart Sumida, who admitted he mostly works on the other side of the amniote tree (basal synapsids). He made a few errors in his presentation (including the spelling of Protarchaeopteryx and phytosaurs as crocodylomorphs, when they are only distantly related to that group) which will be corrected in the published volume. His paper would be a basic review for most folks on this list, but some of the neontologists at SICB may not have been familiar with the details.

Peter Dodson's talk, titled "Archosaur-avian relationships: review and comment", focused a little bit on the first four words, and a lot on the last. Little in the way of scientific information that would be new to readers of this list (although it might be new to some in the audience there). However, Dodson made it clear that he doesn't like cladistics (the unofficial subtitle he mentioned was "cladistics sucks"). That's all well and good, but I wish I could agree with his reasonings as to why cladistics sucks. In part he complained about the attitude of the practitioners (curiously in this talk and others "the practitioners" equals "Padian, Chiappe & Norell", as if these three are somehow a majority when compared to the rest of the people involved in dinosaur systematics, much less systematics in general). Okay, so these guys might be a bit (or more than a bit) abusive in print: does that mean that the phylogenetic systematic method is wrong? Dodson also argued about the reductionist approach to transforming everything to "0" and "1" (whatever happened to "2", "3", "4", "?"...) as somehow ignoring the richness of life. Funny, last time I looked at Steel, Romer, or other classic precladistic work at systematics, I see a list or table of characters described as present or absent in the forms listed, but somehow this is more holistic than an appendix listing characters and an accompanying data matrix? Dodson also complained about the phrase "nonavian theropods", which [I admit] wasn't coined until cladistics, but [does have] its analogies in pre-1956 phrases like "non-human primates." And, of course, there was the requisite complaint about monophyletic taxonomy. (Incidentally, Colin Patterson's idea of incorporating all of Dinosauria in Aves was not completely tongue-in-cheek, but reflects the differing taxonomic practices among actinopterygian workers (who often prefer stem-based definitions for traditional names) and tetrapod wokers (who prefer node-based)).

Most puzzling of all was his comment of the hegemony of morphology in cladistics, and that genetics, biogeography, behavior, and stratigraphy shouldn't be excluded. This is puzzling since, outside of the small world of paleontology, genes are THE dominant mode of doing cladograms (hey, they were giving away free copies of an issue of Molecular Phylogenies and Evolution, and there are a couple of other journals devoted specifically and solely to this topic), and that the other three methods have been employed to varying degrees of success.

(And, a side note: Dodson in his talk, and others during coffee hours and elsewhere, also complained about people who just do cladograms and then stop without doing more research. First off, I find that a description that doesn't map onto anyone in the field of bird origins (Norell and Clark do excellent anatomical descriptions as well as cladograms, Chiappe has added important information with regards to South American Cretaceous stratigraphy, Padian has made many contributions to functional morphology and to the historical study of paleontology, etc.). Secondly, I had several functional morphologist there tell me that they thought it was fine for some people to devote most of their time to systematics: that way they could devote most of their time to their own functional studies, while drawing upon the analyses done by others.)

Harumph.

Derek Briggs & Paul Davis's paper (presented by Paul) was, for this paleontologist, THE most useful and important paper in the symposium. It was precisely what I've been hoping for: a look at the processes by which feathers are preserved in different lithologies and in different taphonomic settings. Note that the Solnhofen is different from most fossil feather preservation, in that the Solnhofen is mostly impressions ("double-struck", so that only one surface is preserved, both in positive and negative relief) whereas bacterial-induced forms of preservation characterize the others. Some really cool fossils were shown, including feathers with what are probably fossil mite eggs, and some feathers in amber. The authors have discovered some taphonomic features which are unique to the decay process of feather keratins, so we will now be able to search for feather homologues independent of their morphology... (i.e., a taphonomic test to see if something could be a "protofeather", whatever that is). As I've been telling people before, fossilization is different that tossing a specimen in formalin: you've got to look at the geology.

I missed the Maderson & others talk on the development of sauropsid integument (I was off to see some other papers), but it discussed (among other things) developmental data, the similarities and differences between the total "reptilian" and avian integument, and the fact that there are still some big gaps in our knowledge in living forms.

The next several talks had to do with aspects of modern avian scales, feathers, and skin. Sawyer et al. presented the keratin paper, which featured (among other things) some featherless and scaleless mutant chickens. Menon et al.'s talk was on avian epiderman lipids, with comparisons to those of "reptiles." Homberger's talk was a look at the functional and evolutionary microanatomy of avian skin, with some excellent photomicrographs of the complexity of the muscles systems attached the feathers. She argued that feathers might not have evolved for flight, insulation, or display (since other simpler structures work just fine for these) but instead for streamlining the body while still terrestrial. Unfortunately, she didn't explain what advantages such streamlining would produce. Wolf & Walsberg discussed heat transfer in bird feathers, both to keep heat in or heat out, through radiative, convective, conductive, and evaporative processes.

John Ruben's paper summarized many lines of evidence familiar to most readers of this list (nasal turbinates, diaphragm breathing theropods, Sinosauropteryx fibres as internal collagen, etc.). One new analysis showed the difference in scaling (numerical, not integumentary) between typical theropods and modern ground birds when total hind limb length was plotted against trunk size. (Caudipteryx plots with the birds, incidentally). This is a plot I've wanted to do for a while, but I was waiting to get a big enough data base on complete glenoacetbular measurements of fossils before doing this (Ruben made do with reconstructions). He related this to Steve Gatsey's work on the differences between "typical" theropod and avian hindlimb movement. What Ruben did not mention (although Steve did in his own talk in the Vertebrate Axial Skeleton symposium, after most of the Feathers people had left the conference!) was that the difference is not a dichotomy, but is a transition, correlated with many associated changes in theropod anatomy from the basal condition through basal tetanurines into coelurosaurs, through maniraptorans to basal birds, and continuing changes well up into modern birds. To show this one (albeit interesting) scaling difference misses the gradational nature of the shift in theropod locomotory history.

I missed most of Porter et al.'s talk on mechanistic models of feathers and fur in heat and mass transfer, so I'll have to wait for the proceedings volume to see. Alan Brush's talk was very interesting, adding to his DinoFest presentation, and showing how all the vast diversity of feather types can all be formed by slight differences in development of a single tubercular structure. Variations in the development and timing of various subunits of the follicle would produce everything from natal and adult down to flight feathers to barbs to eyelashes and so on. He also stressed that any individual follicle produces different sorts of feathers throughout the life of the bird.

Farlow et al. has some strange paper on dino (mostly theropod) locomotion. When not being attacked by the microphone & its associated cords, or having just about everybody miss his Groucho joke, Jim mentioned a) that "cursoriality" is a poorly understood concept in modern animals, much less extinct ones, but that we agree that arctometatarsalians seem to have more of it than do most other nonavian theropods; b) to our surprise, modern birds take shorter steps than did "theropods" of the same body size; c) like Ruben, we found longer legs in modern birds than in Mesozoic theropods, but that plotting just the "fuctional leg" (tibiotarsus + metatarsus) of ground birds brought them right in line with non-avian theropods; d), etc., lots more. There will be lots of plots in that paper for all to enjoy. We still don't know why we were invited to give this talk at a feathers symposium, but it was interesting nonetheless.

Alan Feduccia was not able to make it, so Nick Geist stepped in at the last minute to fill in that spot. Perhaps because of this, Geist had some significant errors in his presentation. For example, he (like a lot people on all sides of this argument) polarized the debate as: Dinosaur origins of birds = only found by cladisitics = bipedal ancestry = necessitates "ground up" origin vs. some other archosaur = not found by cladistics = quadrupedal ancestry = necessitates arboreal origin. However, Ostrom (and Huxley, of course) didn't use cladistics, yet it was Ostrom's papers in the 1970s which convinced most workers on the dinosaurian origin (Gauthier and later workers simply used cladistics to try and determine WHICH theropod taxon was closest to birds). More importantly, the figures used to illustrate the arboreal hypothesis were from Chatterjee's 1997 book. This is ironic in that a) the hypothetical proavians in the figures shown are bipedal; b) they are dinosaurs ("protodromaeosaurs" to use Chatterjee's phrase); c) the work is based on a numerical cladistic analysis. So much for the dichotomy... Geist also mentioned, while discussing Megalancosaurus, that no theropod had a posteroventrally facing foramen magnum. This was a surprise to Currie & me: I guess all those ornithomimosaur, troodontid, oviraptorosaur, advanced tyrannosaur, etc., skulls that show that condition must not be theropods. Still, I don't know how much of this was due to Geist having to fill in at the last moment. He did have some new info on the hypopubic cup of birds and its relation to breathing, about which we will here a lot more in the near future. Too bad he had left before Carrier & Farmer's talk on archosaur breathing (more in Part II).

Tarsitano et al.'s talk was on lots of different aspects of flight origins, bird relations, and feather development, but concentrated on the latter. Like Alan Brush, he argued that one of the key features of feather origins (and later development) was a cylindrical follicle.

Larry Martin gave the last talk. In it, he redescribed Caudipteryx as a flightless herbivorous ?enantiornithine bird and gave his interpretation of the structures on the Sinosauropteryx specimens. He also mentioned that he agreed that theropods had furculae (as did, in his interpretation, Longisquama). Martin suggested that birds were descended from forms at the very base of archosaurs, perhaps from forms we would have a hard time calling "archosaurian". (Okay, so I didn't have the heart or stomach to bring up the phylogenetic taxonomic definition of Archosauria... :-S ).

During the formal discussion section, Phil Currie was given time to give his interpretation of the Sinosauropteryx integument. He also clarified that many people who accept the theropod origin of birds also accept a "trees down" origin of flight.

There was little consensus on most major issues, either during the conference or in the discussion. Birds either evolved from some kind of theropod or from something else. Feathers either first evolved for insulation to trap heat, or to reflect heat, or to streamline, or to protect the body, or for flight, or for display, or for something else.

Some thoughts:

There was a lot of talk about what "the cladists" do. When pinned down, "the cladists" seem to be Padian and Norell and Chiappe, but other times it seems to be more general. I wanted to get up during the discussion section and say "Hi. My name is Tom, and I'm a cladist", but good taste got the better of me... Ruben expressed surprise when I told him that cladists don't always agree with each other, and in fact often have disagreements.

(I also think it is unusual how people are labeled for, of all things, their approach to systematics. Sure I use cladistics for systmetics, but my approach to historical geology is process uniformitarianism, to the motion of the continent is plate tectonics, and to bivariate morphometrics plots is Reduced Major Axis lines. Why call me a "cladist" but not a "process uniformitarianist", a "plate tectonicist", or a "Reduced Major Axist"?)

The funny (?!?) thing is that while many of the speakers were upset with "the cladists" for dichotomizing everything, the very same speakers were dichotomizing the field! "The cladists" don't just do systematics, but (as I mentioned above) do detailed anatomical work and/or functional morphology and/or biogeography and/or stratigraphy and/or etc.

Similarly, many of the same speakers talked as if "theropods" or "dinosaurs" (both in the non-avian sense) all had one typical morphological condition, and birds [had] another entirely different one. In fact, there is a continuum of form between the non-avian and the avian condition. The great gap between birds and other diapsids in the modern record begins to disappear as you add fossil taxa. All fossil birds do not show the full set of modern bird features (huge keeled sacrum, short pygostyle, carpometacarpus, etc.) but instead these appear at different points within bird evolution. Furthermore, there are many characters which distinguish birds from other living amniotes which we don't think of as "avian" because they have long been known at various levels of the dinosaur hierarchy (retroverted pubis, particular types of cranial and vertebral pneumaticity, reduced metatarsal I, ascending process of the astragalus). Until recently, furculae and feathers were 'unquestionably' bird characters, but now the former (and depending on the phylogenetic position of Caudipteryx and Protarchaeopteryx, the latter as well) are known to be more widely distributed.

Ah, well.

Part II

First, some brief comments:

SICB is a conference that more paleontologists (vert & invert) should be going to. Not to say that there weren't some there: in addition to those listed in the Part I report, paleomammalogists Blaire Van Valkenburgh & Audrone Biknevicius were there, Rick Blob was presenting the neontological side of his work on limb mechanics (his dissertation work also included a lot on synapsid limb evolution), there were posters on scaphopod ("tusk shell") paleontology and on cervid (deer) evolution with regards to breeding behavior and Greg Erickson's (of T. rex tooth and turd fame) poster on mudskippers and so on. In fact, there was a whole session on starfish evolution, which obviously featured some paleontologists. Nevertheless, there were very few of us bone jockeys (and even fewer shell jockeys).

Which is a shame, because a LOT of interesting work is being presented on modern animals which has a direct bearing on paleontology. I often see comments on this list along the lines of "well, surely someone has examined [fill in the blank with your favorite modern animal adaptation]." It turns out that in a lot of cases that just isn't so. Some really interesting aspects of modern animals are still under investigation, as the presentations at SICB attest.

One drawback with SICB is the price: $220 for members early, $320 for non-members early, $205 for non-member postdocs early. Ugh. On the other hand, the price for non-member students is $130, for student/high school and community college teachers is only $70. There are four full days of talks, with eight to eleven different sessions going simultaneously (so a lot more like the American Geophysical Union or Geological Society of America than like SVP in terms of scale).

In any case, if you are at all interested in functional morphology (and particularly if you are a student) I would encourage you to attend.

So, on to the non-feathers talks.

Obviously, there was too much going on for me to have seen more than a fraction of it, and I can't be expected to report on all of it, but here are some highlights that dinosaur fans might find interesting.:

D.J. Irschick & B.C. Jayne presented a paper on the 3-D kinematics of lizards running at high speeds. Most previous work on limb kinematics has been on slow moving individuals, but (as the presenters pointed out) many lizard species are adapted to high speed locomotion. They presented some great stills and video of lizard species in fast runs. They were looking at smaller lizards, and found that they run bipedally in different ways than (say) frilled lizards. In fact, some of the faster small species they examined ran with their hips very high (for the body size), the body held almost horizontally, the feet entirely digitigrade throughout the step cycle, so that none of the metatarsus contacted the ground ("Sound familiar?" commented Jim Farlow...). In the case of Callisaurus (sorry, can't remember the common name) the tail was curled up at the base, and the stiff distal portion held vertically! (The tail reminds me a LOT of dromaeosaurs, so it's got me wondering...). In any case, a fast running lizard is not a sprawler at all.

I missed a series of talks on vertebrate locomotion I wanted to see because of the Feathers talks: K. Earls latest on take off of starlings (saw some of her preliminary work at Bristol in 1997), Gleeson et al.'s talk on why the cost of locomotion often does not reflect cost of activity (of obvious importance for those concerned with dinosaur energetics), and S.M. Reilly's talk on the kinematics of the sprawling-to-erect transition. I did get to see Stuart Sumida & Elizabeth Rega's back-to-back talks about skeletal biology, mechanics, anatomy, sexual dimorphism, and animation: cool things for teaching purposes (must get "Chuck Amock"!), learned some stuff about the new Disney Tarzan and previous Disney and other animated movies, and had a good time. (Sumida & Rega's party was great, especially as I missed the one at SVP. Unfortunately hotel security only told us to quiet down once, not twice: I figured it was because we didn't have enough rowdy paleontologists...).

Rick Essner presented a paper on the biomechanics of gliding in the flying squirrel (Glaucomys volans), which showed first off that there is a major leaping component to their "flight" (i.e., they aren't just dropping from the trees and gliding, as some have argued). Furthermore, the ballistic portion of their jump isn't at 45 degrees (as some have thought, because this would maximize total distance traveled). Instead, it is closer to 23 degrees or so: this way they travel a lot further faster. Other good stuff in there, too. It goes to show that less is known about gliding in living animals than a lot of people assume (or model in their origin of flight studies...).

Similarly, J.J. Socha presented a paper (which I missed, but was updated on) on the "flight" kinematics of the flying snake Chrysopelea paradisi. Although they sometimes start the glide from a controlled fall, they too can use a propulsive phase (either horizontally, or occasionally at a more vertical angle). I wish I could have seen the video, though: as I entered the room just as people were leaving, I heard a lot of "That was so *cool*..." comments.

There were a fair number of interesting talks at the Symposium on the Function and Evolution of the Vertebrate Axis. I finally got to see (legendary morphologist) S.A. Wainwright give a talk: I will steal a few of his bits for my teaching... D.A. Pabst presented work showing convergence in soft tissue features (peripheral cross-helically wound connective tissue, etc.) between tunas and cetaceans, which function as springs against the axial skeletomuscular system. Blubber ain't just for fat storage!! It has me wondering about ichthyosaurs...

Steve Gatsey presented a review of the structural and functional evolution of the theropod tail. I was familiar with a lot of this (although the electromyographs of different muscles during slow walk, fast walk, and flight of a pigeon was still very cool). I was very happy to see it at the meeting, especially after so many people at the Feathers conference were making it seem as if there was this huge morphological gap between "The Theropod Condition" and "The Avian Condition" (as if either non-avian theropods or birds were all identical...). Some really cool aspects of the soft tissue of bird tails were explored.

As I said, Gatsey's talk was mostly stuff I was familiar with: if it had been new to me, I would have pegged it as the best dino-related talk at the meeting. Instead, that honor (for me) goes to Carrier & Farmer's (I think) talk on archosaurian respiration and locomotion. It was a damned shame that most of the people at the Feathers symposium had left by the time it was presented, because it directly applied to the work of some of them (Ruben, Geist, etc.), and would certainly have interested others (Farlow, Currie, Dodson). Doubly unfortunate was the fact that the title, authorship, and abstract had changed from that listed in the abstract volume: if the others had known about it, perhaps they would have stayed.

What Carrier and (I think) Farmer did was examine respiration and locomotion (and their interrelationship) in modern archosaurs, and speculated on the same in various extinct groups. They looked at the hepatic piston/diaphragm breathing in living crocodilians. Not just "modern crocodilians", as most previous workers (through dissections, etc.), but in living *breathing* crocs. With electromyographic studies and such. It turns out that the hepatic pistion as found in modern crocs seems to require a mobile pubis, something crocs have (the pubis does not meet the acetabulum as in most amniotes, and in fact is on a joint with the ischium & ilium) but which dinosaurs did not. In fact, there are muscles running from the ischium to the pubis which are involved in breath and recovery. Like many active animals, crocs breath in synch with the step cycle while moving fast. Birds breath with a combination of the movement of their huge sterna and rocking of the pelvic & tail region.

So, what about extinct forms? If theropods were diaphragm breathers, they were not doing it the same way crocs do: their pubes were immobile and fully incorporated into the acetabulum. Carrier & Farmer, based on some earlier work by Leon Claessens, hypothesized a gastralia-based breath pump for theropods. Although having gastralia is primitive for amniotes, theropod gastralia have some very interesting adapations. In the system they suggested, theropod breath would be in synch with the step cycle (and, curiously, 180 degrees phase shifted from the breath cycle of neornithine birds!). As with many things, the shift from a primitive theropod breath system to the modern bird breath system would involve a series of transitions rather than one big jump, so that advanced non-avian maniraptorans (like dromaeosaurids) and basal birds (like Archie) would presumably be more similar to each other than to breathing in Eoraptor or neornithines, respectively. There is some question about the myology of this system (and I wonder about the change from the more basal theropod ischial condition to the more derived, slender and/or reduced condition in coelurosaurs), but it should prove interesting working it all out.

Ornithischians and sauropodomorphs weren't dealt with to any great detail. It was suggested that pterosaurs were (curiously) a combination of croc AND neornithine type breathers: their pelvis morphology suggested the rocking-breaths of birds, and their prepubis bone as the functional analog to the pubis of crocs in a hepatic pistion. Carrier alluded to some study on breathing in modern marsupials suggesting that the epipubic bone ("marsupial bone") was also a functional analog to croc-pubes in the diaphragm breathing of marsupials: sounds intriguing, and must look into it.

I don't know when they plan on publishing this study, but I look forward to it. It was a great integration of skeleton, soft tissues, dissections, studies of living animals, and speculations.

All-in-all, a busy time. Now to get ready for the Ostrom Symposium... :-)

Final thoughts

Lastly, some thoughts on various aspects of the dinosaur-bird relationship as seen by various workers at the SICB Feathers conference.

Trying to make an effort to understand the "other side," if you will, I found some common complaints. Some have more to do with the personalities involved than the science, so I'll have to let those pass. Others are more significant:

A) The "hype" behind the Chinese feathered forms. Many of the folks there thought that Caudipteryx and Protarchaeopteryx MUST have been flightless birds and that Currie & company were grossly mistaken about their phylogenetic position.

I was asked "what derived feature shows that C. was a pre-Archaeopteryx form." This is actually almost a nonsensical question: it asks what derived feature shows that it lacks the derived features uniting Archie and more advanced birds. It is like asking "what derived features show that lungfish are a pre-tetrapod form?". It isn't derived features which demonstrate that lungfish lie outside Tetrapoda: it is their lack of the derived features uniting all tetrapods. Better questions would be "are the features which unite C. with birds more advanced than Archie?" (as suggested by Martin and some others) or "are their features which unite C. with *previously known* non-avian theropod taxa?" (for which see the Ostrom symposium... :-).

However, I (and some others on the net) have pointed out that the hype around the already described feathered forms from China are not ground-shattering if they lie in the phylogenetic position found in the analysis presented by Ji et al. in their Nature paper. As they presented it, Caudipteryx is only one branch further out: with no known taxa in between it and known feather forms, it isn't a surprise (or shouldn't be, in a phylogenetic context. I suppose if some people still think that Archie itself was THE first form to have feathers, it would be a surprise...).

Of the three different positions for Protarchaeopteryx, one (P. + (C. + (Archie on up))) is again non-interesting: it doesn't optimize feathers on any form previously known, but not known to be feathered. It is only the other two (with P. as the sister group to velociraptorines, or as the sister group to the velociraptorine + bird clade) that it becomes interesting, because it supports the concept of feathered velociraptorines. However, since velociraptorines were supposed to be the OUTGROUP in the analysis, and P. was found in two of the three trees to be outside the ingroup, there really isn't very strong support for the position of this taxon anywhere within the tree.

The implications of feathered theropod fossils will only become "interesting" when a) a feathered specimen of a previously known non-avian group is discovered (like an oviraptorosaur or a dromaeosaur or a tyrannosaur or an abelisaur...) (Net Alert: THESE ARE HYPOTHETICAL EXAMPLES!! DON'T GO CITING THIS AS EVIDENCE!!) or b) a feathered form is found on strong evidence to be closer to a previously known non-avian group than to birds. These situations would be interesting because they would be evidence that feathers extend deeper into the theropod tree than previously supported (or that feathers evolved more than once...).

So, there are legitimate gripes about the hype around the Chinese fossils *as described at present*. Indeed, these gripes are at least as strong (if not stronger) within a cladistic context than outside of it.

B) Imagine the following hypothetical situation. Say someone (I don't know, maybe a young charming theropod worker... :-) We'll call him "TH" [Thom Holtz]) proposed that tyrannosaurids had proportionately longer metatarsi than typical theropods of the same body size. Say that someone plotted this out morphometrically. Say someone else (call him "JH" [John Horner]) comes along and says "I don't believe this result".

TH: "Okay, then, show how I am wrong."

JH: "Okay, but I'm not going to do a morphometric plot. I don't believe them."

TH: "Huh? Why?"

JH: "Because they keep on giving the same result. Even when different individuals are plotted, and different workers to the plotting."

TH: ----- (semi-stunned silence)

JH: "Anyway, I found that these data points" {points to them} "are measured incorrectly. That shows the analysis is wrong."

TH: "Well, fair enough in the absolute sense. The best-fit lines are going to be different when replotted, as will the confidence intervals and r-squared. Of course, it doesn't mean that the rest of the plot isn't incorrect, or that the main pattern isn't maintained. What did you get when you corrected those data points?"

JH: "I don't see why I should have to plot them myself. Showing those data points are measured incorrectly are enough to show that the whole analysis is flawed, and therefore wrong. And besides, I don't understand you morphametricians obsession with "best-fit lines". Why should we prefer the "best-fit lines" more than the "next best-fit?" Who ever said Nature was "best-fit?""

TH: "No one ever did. Still, as an analytic tool, the preference is to prefer the simplest explanation. If not the "best-fit", what criterion should we use? The one that "feels best?""

JH: "Well, I still think that these points" {points to a different set} "are more important than all the others. Why can't you make them more important in the analysis?"

TH: "We could, mathematically. Still, why that set? I know they're the ones you worked on, but JF worked on these ones over here and probably thinks they might be more significant, and RM on these. Why should I favor yours?"

JH: "Because they will give you the right answer. The other data points will mislead you. Look at how often morphometric plots give you totally different results."

TH: "I thought you said the method was flawed because it always gives you the same result, even when different data were plotted."

JH: "Yeah."

TH: -----

JH: "Anyway, those data points are probably all measured incorrectly. And besides, why plot them at all? You morphometricians just plot up some data points and stop with your plots. You don't try to understand the whole animal, and its ecology, and its evolution."

TH: "Funny, I thought I was plotting these data in order to better understand tyrannosaur locomotion and ecology."

JH: "Well, whatever. Beer?"

TH: "I can agree to beer".

Exeunt.

Well, as you might imagine, the above is not entirely hypothetical (whoooo, big surprise). Of course, the type of analysis involved wasn't morphometrics, but cladistics. JH is a compiliation of various comments I heard, often from many individuals, which I've tried to put together to try and make some sense. Here are the main complaints about cladisitcs I heard from multiple individuals:

1. If a character is coded incorrectly, then the whole cladogram is wrong.

   Okay, in an absolute sense the cladogram would be "incorrect" in that the topology *might* be different and the metrics almost certainly *will* when re-run with corrected data. Too bad there's no way to check it... Oh, wait, there is. Re-run the data.

   Furthermore, an incorrect character or characters does not guarantee that the topology is incorrect. For example, the discovery that the furcula is present in more theropods than just oviraptorosaurs and birds does not in fact alter the tree topology: instead, it alters the position of that character state change on the tree.

2. I shouldn't be forced to have to do my own cladogram.

   Okay. Still, running PAUP or Hennig86 does not hurt physically; it does not damage the ozone; it does not contribute to crime; and it is no more stressful than using DeltaGraph or PowerPoint or CorelDraw. It is widely found already installed on computers in museums and universities in various labs. So, why not do it? Why the reluctance? I still find it as puzzling as the hypothetical example (i.e., I know that morphometric plot is wrong, but I don't want to be forced to plot the data to show that it is wrong).

3. Cladograms always give the same answer even if each analysis uses many different characters from each other, therefore they are flawed. However, cladograms are always wildly different from each other, therefore they are flawed.

   I have heard both comments from the same individuals (also from different individuals at different conferences, on this list, on sci.bio groups, etc.). In response to the second question I would say: show that this is the case. We can then examine the discrepancies. In response to the first sentence I would suggest that perhaps the convergence of results, even with different data matricies, may perhaps reflect that the method is actually working, and that different workers are observing different suites of characters within the same nested hierarchical pattern of nature. But then, that's just me...

4. Why the "obsession" with parsimony?

   We've gone over that one a lot on this list: see the archives. In brief, parsimony is equivalent to the best-fit of the line: the assumption isn't that Nature is necessarily 'clean', but that as an analytical tool we should prefer the explanation that fits the most data. In the case of plotted data, we want some simple way of describing an equation that is "close to" the most points under some metric: that's why we have best-fit lines of various sorts. For cladistics, we want a descriptor that gives us the fewest number of evolutionary changes required to explain the distribution of characters in the taxa examined. Under some assumptions (primarily concerning types of molecular changes within genomes) we might prefer a maximum likelihood model; for morphology, most workers use some form of parsimony (Wagner, Dollo, etc.).

   It came to my attention how little some of the people making these comments have read up on cladistics as a method. Weighting schemes, different models of parsimony, Bremer support, etc., seemed foreign to them. As with a lot of stuff, I would suggest people try to look into the details (i.e., not just the results and their implications, but the methods of getting there) before rejecting it.

5. My character complex is better than your character complex.

   It would be great if we knew before hand which characters or suites of characters gave the "true" answer, and which were misleading. However, people tend to disagree on which ones will give the "true" answer. That's why, personally, I like to see large data matricies with a fair number of polymorphic characters rather than small 'clean' ones: the former are more likely to capture the actual diversity of form among the taxa, whereas the latter might be more easily swayed by a particular complex of characters of interest to the worker who created it (a complaint I have heard about my 1994 paper, and one I've given about Gauthier's 1986 paper).

6. Data matricies are full of miscoded data.

   Some might well be. And, you know what? If you can justify [that] the [data is] miscoded, you can tell the person who compiled it. They will likely be a) happy to change it or b) show you the reason they coded it such. Either way, somebody (maybe both) will learn something. Is this bad?

   Futhermore, the claim that most data matricies are full of incorrect data should be backed up with data. I have not seen such forthcoming.

7. We can agree on beer.

   Okay, maybe not everybody, and it doesn't have to do with cladisitics, but I wanted to end on a positive note.

Other complaints (that "the cladists" stop with cladograms and do no more; confusion over the difference between phylogenetic reconstruction and phylogenetic taxonomy; equation of the personalities of some of the individuals involved with flaws in the methodology; etc.) have been covered elsewhere ad nauseum.

So, I've found a lot of misunderstanding about the method and a lot of reluctance (which personally I don't understand) to learn more about it or to try it themselves. This was by no means universal, but I heard each of the claims above from more than one individual.

Final comment

Let me clarify one thing: I chose the "JH" initials to oppose the "TH" one in the morphometric example because, well, the possessor of said initials and I don't agree on one or two aspects of tyrannosaur biology. HOWEVER, JH does agree with me on the importance of cladistics, and might even exceed me in its application to taxonomy (esp. at the "species" level). (Yeah, I know this is a big turn around from a few years ago, but he does indeed strongly support cladistic analysis these days).