Saturday, January 24, 2015

BANDit cladogram evaluated - James and Pourtless 2009

Besides Hou et al. (1996), the only BANDit (Birds Are Not Dinosaurs) cladistic analysis has been that of James and Pourtless (2009).  Little has been said about this paper, with most of the commentary noting the backwards philosophy the authors had in coding characters with supposedly controversial homology as unknown instead of letting phylogenetic analysis establish homology.  Well I finally looked at it in a little detail, and found a far larger issue.

First, let's go over the basic tests and conclusions of James and Pourtless' study.  After making the almost correct observation that no published cladistic analysis has tested whether birds are dinosaurs (Senter 2004 did, but while the authors cite it they don't comment on it in that regard), James and Pourtless aim to correct this by constructing their own dataset with alternative proposed bird ancestors included.  With basal archosauriforms as the outgroup, the authors also include crocodylomorphs,  Longisquama, a few other pseudosuchians and numerous theropods.  Running their dataset of 242 characters and 79 taxa, they recover a large number of MPTs.  These are only ever illustrated as majority rule bootstrap trees after a posteriori pruning of taxa, and each alternative tree is basically a well supported Archosauria with a massive polytomy between crocodylomorphs, numerous theropod lineages and birds.  Longisquama weakly (55% bootstrap) groups with birds if 21 "controversially homologous" characters (which are only coded for non-dinosaurs) are excluded and non-bird maniraptorans are pruned away.  Statistical tests were done, seemingly showing the 'basal archosaur' (= Longisquama), crocodylomorph and dinosaur hypotheses of bird origins aren't any worse than each other.

Figure 12 of James and Pourtless (2009), showing majority rule bootstrap tree with numerous taxa including all maniraptorans pruned away a posteriori.  *Gasp* It looks like birds are closer to non-dinosaur Longisquama and that even crocs could be as close to birds as dinosaurs.  Were BANDits right all along? (Spoiler- NO)
How to explain this?  First, I should note that when you run their data, the resulting MPTs are pretty standard.  As shown in my typed cladogram below, while there are plenty of weird details going on in Theropoda, the basic structure of birds within Pennaraptora within Maniraptora within Coelurosauria within Theropoda within Saurischia within Archosauria is present.  The only odd relevant aspects are Effigia is an ornithomimosaur and Longisquama is deeply embedded in Pennaraptora.  Note there's no way of knowing Effigia groups with ornithomimosaurs by reading the paper, as its exact results aren't mentioned and it's always pruned out of the figured trees.  I find this suspicious.  In any case, Longisquama being sister to ornithines is discussed since this is the current favored alternative of BANDits.  Besides the paltry literature, the authors depended on photos at the KU for their coding of the genus, and present a cranial reconstruction.  This reconstruction looks as if it was done assuming a theropodan morphology for the taxon.  For example, there's a T-shaped structure at the anterodorsal corner of the orbit, interpreted as a lacrimal by the authors.  But it would also compare well to a prefrontal in a basal diapsid like Coelurosauravus, where the lacrimal is reduced.  Similarly, the strip under the supposed supraorbital ridge (yellow) would match the posterodorsal strip of the lacrimal/prefrontal in Coelurosauavus.  Or the wedge just behind this, while unidentified by the authors, would match the postfrontal of Coelurosauravus.  The supposed antorbital fossa (red) matches the external naris of Coelurosauravus well, and even the big posterodorsal hole ("?" in their figure) would match Coelurosauravus' if it's a supratemporal fenestra as identified by most previous authors.  This isn't to say that Longisquama is a close relative of Coelurosauravus (as Senter 2004 recovered), merely that the lens you view a fossil like Longisquama through based on photos can affect your identifications.  The controversial aspects of Longisquama's anatomy are similarly all coded as theropod-like- thecodont teeth, antorbital fenestra with maxillary fenestra, furcula, etc..

Longisquama skull (counterslab of PIN 2584/4) and interpretation of James and Pourtless (2009) on top.  Coelurosauravus skull reconstruction at bottom after Evans and Haubold (1987), modified so that the entire spiked temporal element is the squamosal after Schaumberg et al. (2007).  I see the supposed antorbital fossa (afo in red), but don't think its obviously a fossa, as opposed to a fenestra (e.g. the naris) or bone process itself.  Similarly, the entire ventral edge of the supposed antorbital fenestra (aof) looks like a crack to me, including the supposed dorsal process of the maxilla (dpm), supposedly there to support an interfenestral bar.  I don't see any posterior edge of the antorbital fenestra either, so that that whole area could be a solid maxilla.  The ventral process (vp) is apparent, but if anything seems separated from the nasal by a suture (shown by the green space).
As for the matrix, there are of course lots of miscodings (e.g. character 5 is for dermal armor, which is coded unknown for almost all theropods and Effigia, plus coded absent in Ceratosaurus, the one theropod that actually has it).  Some of the characters are formed terribly while others are partitioned in a way that weights them (e.g. each dentigerous element has its own character for tooth serrations, each a three state ordered character of the form '0- all serrated; 1- some serrated; 2- none serrated'; thus any taxon leading from serrated to unserrated teeth needs six steps to do so).  The 21 "controversially homologous" characters include every manual character due to the I-II-III vs. II-III-IV issue, though oddly these aren't even coded for dinosaurs with five digits like Herrerasaurus.  There's also a huge imbalance of taxa, with a whopping 45 non-avian theropods plus 16 birds, only 9 pseudosuchians, 3 non-archosaurs, Eoraptor, Marasuchus and Scleromochlus.  These are all issues, but not the most important one.


Actual strict consensus of James and Pourtless' data, simplified so that genera which form monophyletic clades are represented by their clade names.  Note no dinosaurs were coded for manual characters, Effigia is an ornithomimosaur, and Longisquama is deeply nested in Theropoda.

No, the biggest problem with James and Pourtless' analysis is that its matrix consists mostly of characters designed to diagnose coelurosaur clades (e.g. 96 from Clark et al.'s 2002 TWG analysis; 26 from Chiappe's 2002 bird analysis) plus those suggested by BANDits to group Longisquama and crocs with birds.  So what happens when you analyze Longisquama in a coelurosaur/bird matrix after reconstructing its skull with theropod presumptions and pretending no dinosaur preserves hands?  Given it doesn't preserve sacrum, pelvis, hindlimbs or tail, and that the vertebrae are basically uncodable, it emerges as a coelurosaur.  When chatting with Nick Gardner about this I joked "I bet if you coded e.g. Coelurosauravus' front half into the matrix, it would be coelurosaurian too."  So I coded Coelurosauravus' front half, the same parts preserved for Longisquama, and lo...

....................................|.....`--Ornithomimo (inc. Pele,Longisquama)

I won my own bet.  Interestingly, this tree also has a lot more resolution and details which agree with the consensus (e.g. Pelecanimimus in Ornithomimosauria, Caudipteryx in Oviraptorosauria), and Longisquama is moved from Avialae to Ornithomimosauria.  Note Coelurosauravus is not thought by anyone to have anything to do with dinosaurs or birds, but still ends up as a maniraptoriform in James and Pourtless' matrix.  This fairly neatly proves my idea that Longisquama could be a far more basal diapsid and still emerge as a coelurosaur.  Note too that Longisquama is also an ornithomimosaur once the front half of Coelurosauravus is included, perhaps suggesting more signal between them than between Longisquama and birds.

So my conclusion is that very few characters were included that would support e.g. Tetanurae, Avepoda, Theropoda, Saurischia, Dinosauromorpha.  Just enough are included to get a basically consensus phylogeny even without manual characters, though not enough to properly place Effigia or the front half of Coelurosauravus.  The latter plus the theropodan assumptions in Longisquama's anatomy makes placement of thus genus particularly untrustworthy.  Certainly, not enough characters were included to survive bootstrap analysis, where random characters are deleted or repeated and the analysis is rerun.  It doesn't mean that "both the "early-archosaur" and "crocodylomorph" hypotheses are at least as well supported as the BMT [BAD] hypothesis", it means that James and Pourtless made a crappy analysis.

References-  Evans and Haubold, 1987. A review of the Upper Permian genera Coelurosauravus, Weigeltisaurus and Gracilisaurus (Reptilia: Diapsida). Zoological Journal of the Linnean Society. 90(3), 275-303.

Hou, Martin, Zhou and Feduccia, 1996. Early adaptive radiation of birds: Evidence from fossils from Northeastern China. Science. 274, 1164-1167.

Senter, 2004. Phylogeny of the Drepanosauridae (Reptilia: Diapsida). Journal of Systematic Palaeontology. 2, 257-268.

Schaumberg, Unwin and Brandt, 2007. New information on the anatomy of the Late Permian gliding reptile Coelurosauravus. Palaontologische Zeitschrift. 81(2), 160-173.

James and Pourtless, 2009. Cladistics and the origin of birds: A review and two new analyses. Ornithological Monographs. 66, 78 pp.

Thursday, January 15, 2015

Is Linheraptor a synonym of Tsaagan?

One of the first theropod papers of 2015 is Xu et al.'s defending Linheraptor as being distinct from Tsaagan, after they were synonymized by Senter (2011) and Turner et al. (2012).  I provisionally synonymized them on the Database because Turner's arguments seemed sound, though I haven't actually studied the problem myself.  One interesting aspect here is that this paper is basically a criticism of the details and methods of Turner et al., which was basically a published version of part of Turner's (2008) thesis.  Yet Norell is a coauthor, who was not only a coauthor of Turner et al., but also Turner's advisor for his thesis. 

Unfortunately, after reading Xu et al.'s arguments, my conclusion is that a LOT of work went into arguing a point no one disputes- the holotypes are not identical.  The authors make a huge point of the number of characters they found which differ between the holotypes- sixty-one.  Also that many of these are found in some dromaeosaurids, but not others.

Xu et al. correctly state "Proposals of synonymy are usually based on a judgment that putative diagnostic differences between the taxa in question are individual, ontogenetic, or sexually dimorphic variations rather than taxonomic ones, making one of the new taxa invalid. Taxonomically informative variations can sometimes be distinguished from intraspecific ones if a sample large enough to provide a basis for rigorous investigation of patterns of variation is available."  They then say "In the present case, Evans et al. (2013), Senter et al. (2012) and Turner et al. (2012) attributed the proposed diagnostic features distinguishing L. exquisitus from T. mangas to individual intraspecific variation, but avenues for testing this hypothesis are limited because each species is currently represented only by a single individual."

Well, no.  You don't need the exact species under consideration to study the extent of individual variation, you can use relatives.  Turner himself had the right idea to use the multiple known skulls of the closely related Velociraptor mongoliensis as the basis for judging differences between Tsaagan and Linheraptor.  Xu et al.'s response to this is rather comical- "a comprehensive taxonomic review [of Velociraptor] has yet to be published to determine how observed morphological variations relate to inter- or possibly intraspecific factors. This can be addressed by including all Velociraptor specimens in a specimen-level phylogenetic analysis, by using morphometric methods to quantify the variation present and by deepening our understanding of the biological significance of the variations observed. Until this work has been completed it is in our view that noticeable variations between L. exquisitus and T. mangas are grounds for taxonomic separation."

So until we perform these studies which have been published so far for zero (specimen-level phylogenetic analysis), ?five (using morphometric methods to quantify the variation present) and ?zero (deepening our understanding of the biological significance of the variations observed) Mesozoic theropods on Velociraptor, we can't treat multiple specimens of it as one taxon?  That's a bit of a far goalpost, don't you think?  The morphometric studies done on other theropods haven't even resolved their taxonomy (e.g. Allosaurus, Archaeopteryx), so I'm skeptical a similar study on Velociraptor would yield useful results either.  If we were to extend Xu et al.'s demands to other taxa, we'd basically have to say we know nothing yet of intraspecific variation in Mesozoic theropods.

Differences between the Tsaagan (first and third rows) and Linheraptor (second and fourth rows) holotypes. After Xu et al. (2015).
Xu et al. include extensive comparisons to other dromaeosaurid taxa for each difference noted.  They say "Taken together, the distributions of these features among dromaeosaurids not only demonstrate that L. exquisitus is a valid taxon distinct from T. mangas but also provide important information on dromaeosaurid interrelationships."  Yet in almost every case, there's only one skull known for each other taxon as well.  Thus if e.g. Tsaagan shares a character with the Dromaeosaurus holotype not found in Linheraptor, yes it could mean that's a phylogenetically useful character uniting the first two genera, but it could also mean it's an individually variable character that the one preserved specimen of Dromaeosaurus happens to share with the only specimen of Tsaagan and not the only specimen of Linheraptor.

You'd have to see how the character distribution worked out in total, as if e.g. Tsaagan and Dromaeosaurus shared a lot of derived characters not found in Linheraptor, that would be increasingly good evidence for a phylogenetic signal (or sexual dimorphism or ontogenetic change, I suppose) instead of coincidence.  Needless to say, Xu et al. do not do this and indeed find even more characters shared between Tsaagan and Linheraptor.

My basic response to Xu et al. is "Could I find 61 comparable differences between two skulls and necks of specimens near universally agreed to be Tyrannosaurus rex? Yes I could."  Indeed, in every example I've looked into, from Allosaurus to Microraptor to Archaeopteryx, every specimen differs in numerous other ways from every other.  Importantly, the differences never sort themselves into mutually exclusive pools, so that instead of Morph A having traits ABCD and Morph B having traits 1234, we instead get a specimen with 1B34, one with 123D, one with A2C4, one with 12C4, etc..  So either every known relatively complete and described Mesozoic theropod individual is its own species, or Mesozoic theropods had significant individual variation, just like living organisms.  I know which option I choose.

Variation in three Velociraptor mongoliensis skulls. Top- holotype AMNH 6515, middle IGM 100/25 (fighting specimen), bottom IGM 100/982.  Note the numerous differences (anterior premaxillary angle in holotype, maxillary fenestra shape in top two, anterior antorbital fenestra shape, ventral lacrimal process angle in 982, posterior jugal outline in holotype, etc.).  After Norell et al. (2006).

To finish up the criticisms, I find Xu et al.'s statement that "In some taxonomic studies, some taxonomic indicators have been based on superficial rather than detailed morphological comparisons" to be based on problematic examples.  They say "Saurornitholestes and Deinonychus have been regarded as junior synonyms of Velociraptor based on overall similarities (Paul, 1988), although both are now widely accepted as valid taxa (e.g., Turner et al., 2012)."  But Paul never advocated those as being the same species, merely different species in one genus.  That's a completely different issue, since genera are (more) subjective and Turner's analysis even finds these to be monophyletic to the exclusion of Dromaeosaurus, the only other decently described dromaeosaurid Paul knew of (Paul questioningly includes Adasaurus as a dromaeosaurine but notes "not enough has been published for us to be certain of anything").  If the authors wanted an example of bad Paul synonymization, they had the easy target of his 2010 synonymization of Tsaagan with Velociraptor, but not Deinonychus or Saurornitholestes.

"Similarly, the basal tyrannosauroid Guanlong has been suggested to be a sub-adult individual of the basal tetanuran Monolophosaurus based on the fact that the two taxa are both characterized by a cranial crest and several other superficially similar features (Carr, 2006), though this proposal has received little acceptance (Brusatte et al., 2010, 2012)."  Well, Carr's argument was only an SVP abstract, so it hasn't had a chance to be detailed yet.  Seems like a low blow.

"In addition to considering L. exquisitus to be a synonym of T. mangas, Turner et al. (2012) scored some character states for [Sinornithosaurus] millenii based on IVPP V 169041). However, V 16904 is not referable to S. millenii for two key reasons. First, V 16904 is inferred to be more ontogenetically advanced than the holotype specimen of S. millenii (V 12811) based on fusion features (the neurocentral sutures are fully closed in the preserved vertebrae of V 16904 but are evident in at least some vertebrae of V 12811, the proximal tarsals are fused to the tibia in V 16904 but remain separate in V 12811), but is significantly smaller than the latter specimen; and second, V 16904 differs from the holotype of S. millenii in some important morphological features, such as the fact that all of the teeth lack denticles in the former specimen but have denticles in the latter."  Here we have a brief example of the splitter mindset- differences equal taxonomic separation.  For just a few counter-examples- the Mei referred specimen has a tibiotarsus and fused presacral neurocentral sutures but is 80% the size of the holotype that doesn't; the Sinovenator paratype has a tibiotarsus but is 89% the size of the holotype that doesn't; Microraptor specimens can have serrations on both carinae (NGMC 00-12-A), only distal serrations (holotype) or no serrations (IVPP V13320).  Again, either we have a ton of unrecognized coexisting species, or species exhibit variation.

As far as good points go, besides more details and gorgeous photos of the amazingly complete Linheraptor skull (e.g. both scleral rings are articulated and in place), Xu et al. are right to criticize some sloppiness in Turner's work.  But they missed out on the least justified problem Turner had regarding Linheraptor- if he viewed it as synonymous with Tsaagan, WHY didn't he code the basically complete Linheraptor specimen for Tsaagan's OTU?!

In conclusion, Xu et al. state "... the contrast between our own perception of L. exquisitus as a valid taxon with many distinguishing features and the view that L. exquisitus is a junior synonym of T. mangas (Evans et al., 2013; Senter et al., 2012; Turner et al., 2012) presents an example of the principle that “similarity lies in the eyes of the beholder” (Clark, 1992)."  As seven of the eight authors of this paper were authors of the Linheraptor description, I might be forgiven for wondering if "similarity lies in the eyes of the namer" has some relevance as well. :)

References- Norell, Clark, Turner, Makovicky, Barsbold and Rowe, 2006. A new dromaeosaurid theropod from Ukhaa Tolgod (Omnogov, Mongolia). American Museum Novitates. 3545, 51 pp.

Turner, 2008. Phylogenetic relationships of paravian Theropods. PhD Thesis. Columbia University. 666 pp.

Senter, 2011. Using creation science to demonstrate evolution 2: Morphological continuity within Dinosauria. Journal of Evolutionary Biology. 24, 2197-2216.

Turner, Makovicky and Norell, 2012. A review of dromaeosaurid systematics and paravian phylogeny. Bulletin of the American Museum of Natural History. 371, 1-206. 

Xu, Pittman, Sullivan, Choiniere, Tan, Clark, Norell and Wang, 2015. The taxonomic status of the Late Cretaceous dromaeosaurid Linheraptor exquisitus and its implications for dromaeosaurid systematics. Vertebrata PalAsiatica. 53(1), 29-62.

Saturday, January 10, 2015

Big "New Years" Theropod Database update

Happy only over a week from New Years everyone!  Time for a Theropod Database update.  Besides all of the new taxa, there's a huge revising of Morrison allosaurids and Baharija taxa (check out the tetanurine Bahariasaurus).  Enjoy all of the updates.

Thursday, January 8, 2015

"Madsenius" and "Wyomingraptor"

As part of the huge Allosaurus rehaul coming in my annual "New Years" (*cough* it's already January 8th *cough*) Database update, I looked over all proposed Morrison allosaurs.  Two of the most mysterious are the nomina nuda "Madsenius" and "Wyomingraptor", but I think I have them figured out.  Enjoy.


Tithonian, Late Jurassic
Brushy Basin Member of the Morrison Formation, Wyoming, US
(Nail Quarry)
(TATE 542) (adult) tooth (36 mm) (Bakker, 1997)
(TATE 543) (adult) tooth (20 mm) (Bakker, 1997)
(TATE 544) (adult) tooth (9.9 mm) (Bakker, 1997)
(TATE 550) (juvenile) tooth (6.6 mm) (Bakker, 1997)
(TATE coll.; material of "Wyomingraptor") 138 juvenile to adult teeth, three adult individuals including distal caudal vertebrae, forelimb, pubes and ischia (Bakker, 1997)

Cast of "Wyomingraptor" forelimb (TATE coll.) (originally hosted on Tate Geological Museum website).
This name was published in the column 'Dr. Bob's Dinofacts' in response to a question from a reader (Anonymous, 1997). The author (possibly Bakker himself) suggested it for a Tate Geological Museum specimen currently labeled Allosaurus. From 1997 until 2006, the Tate Museum included a "Wyomingraptor" section in its exhibits page, stating Bakker has proposed that name for a new genus of allosaur found at Como Bluff including a photographed forelimb. In the PaleoWorld episode "Killer Raptors" (episode 7 of season 4) aired in 1997, Bakker claims the only theropod preserved in Nail Quarry is "Wyomingraptor" (though note this is untrue, as the "Brontoraptor" material was also found there). The material (three adults and numerous juvenile to adult teeth) was detailed in Bakker (1997) where he simply calls them Allosaurus. Hartman (DML, 2000) wrote that Bakker has been "attempting to erect a new genus of allosaur, which he dubs "Wyomingraptor." He has been using this name for some time, but recently has found a specimen he thinks is different enough from the type(s) to warrant generic distinction." Given Bakker's notoriety as a splitter, the Nail specimens are likely to just be Allosaurus fragilis in any case. The photographed forelimb is similar to A. fragilis USNM 4734 except for being more robust, at least in metacarpal I, phalanx II-1 and II-2. Indeed, the robust first metacarpal is similar Torvosaurus, though the elongate phalanx I-1, radius and ulna are not. The forelimb is stated to be a cast, so it's not certain how much is based on real Nail fossils. It's possible some elements were scaled incorrectly from other specimens or are complete fabrications. It's also possible some material such as metacarpal I actually comes from the "Brontoraptor" individuals and that the forelimb is a chimaera. Further evaluation awaits description of the Nail material, which has yet to be distinguished from Saurophaganax either.


Tithonian, Late Jurassic
Brushy Basin Member of the Morrison Formation, Utah, US
(Cleveland-Lloyd quarry)
(DINO 2560, = UUVP 6000; probable intended holotype of "Madsenius trux") (7.9 m, 1.32 tons) complete skull (845 mm), nearly complete skeleton (lacking first caudal vertebra, chevrons, forearms, several pedal phalanges) including femora (880, 850 mm), tibiae (730, 745 mm), astragalus and metatarsals III (375, 372 mm) (Madsen, 1976)

Figure from Bakker (2000), which I think demonstrates his concept of "Madsenius trux", represented by the lower 'creosaur' skull of DINO 2560 (= UUVP 6000).
This name was orginally reported in a children's book (Lambert, 1990) as "a proposed new allosaurid theropod to be formally named and described." Olshevsky (1991) listed it under Allosauridae as a taxon "to be described from the Morrison Formation by R. T. Bakker; based on distinctive skull material and other remains previously referred to Allosaurus and Creosaurus." Williams (online, 2004) mentioned the combination "Madsenius trux", leading Olshevsky (online, 2004) to say "trux" "was to have been Bakker's original type species epithet for the as-yet-unpublished genus Madsenius. According to him, it fits Madsen as appropriately as it fits Madsenius" [etymology- Latin trux means "fierce, rough, savage, wild"].

While nothing else unique has been written regarding "Madsenius", I believe clues in the literature point to its probable identity. Since at least 1988, Bakker has proposed two kinds of Morrison allosaur, the classic short-snouted fragilis vs. long-snouted 'atrox' dichotomy. Bakker (2000) cited the latter species as "The creosaur-type allosaurid (unfortunately, the type of Creosaurus MARSH is, by itself, indeterminate): Dinosaur National Monument skeleton University of Utah UUVP 6000 ..." as opposed to "True Allosaurus MARSH: specimens from the type locality of Allosaurus fragilis MARSH - the skeleton United States National Museum USNM 4734 ..." In that paper, he stated "These two types of skulls are easy to tell apart from the quadrate, lower temporal fenestra, and depth of the mandible; however, I find it impossible to separate the two taxa from isolated snout bones or post-crania." This matches the "distinctive skull material" noted by Olshevsky, and the 'long-snouted' skulls have been referred to both Allosaurus and Creosaurus by different workers, also matching Olshevsky's comment. Furthermore, UUVP 6000 (later recatalogued as DINO 2560) was the basis of Madsen's (1976) classic Allosaurus monograph and "Madsenius" clearly refers to Madsen. Putting everything together, I think it's apparent "Madsenius" was to be Bakker's name for creosaur-type allosaurs when he realized the Creosaurus holotype couldn't be assigned to either variety. UUVP 6000 was probably supposed to be the holotype.

If we accept this explanation, Bakker's characters supporting "Madsenius" can be evaluated. Bakker states the ventral quadrate angles posteriorly in DINO 2560, forming a deeply concave posterior edge to the element unlike A. fragilis AMNH 600. The posterior angle formed by the dorsal and ventral quadrate edges is 24 degrees in AMNH 600 compared to 30 degrees in the UUVP coll. quadrate illustrated by Madsen and 27 degrees in his cranial reconstruction of DINO 2560. Bakker's DINO 2560 illustration shows an unprecedented angle of 52 degrees. Angles in other specimens are 18 (AMNH 30798), about 44 (BYU 571/8901), 30 (DINO 11541), 43 (MOR 693), 15 (SMA 005/02) and 34 degrees (USNM 4734). For the laterotemporal fenestra, Bakker states the restriction caused by the ventral squamosal process is greater in A. fragilis AMNH 600 (least anteroposterior length of fenestra 15% of dorsoventral height) than DINO 2560 (26% in Madsen's reconstruction, 28% in Bakker's). Measurements in other specimens are about 25% (AMNH 666), 31% (AMNH 30798), < 24% (BYU 571/8901), 38% (DINO 11541), 20% (ML 415), 40% (MOR 693), 38% (SMA 005/02) and 16% (USNM 4734). Mandibular depth is 19% of length in Bakker's DINO 2560 (similar to 19% in Madsen's reconstruction) and 24% in his A. fragilis illustration, though the latter is a composite between AMNH 666 (which has only a partial surangular) and 5753 (which does not include mandibular elements). So even this minor 5% difference cannot be determined. Values in other specimens are  about 19% (AMNH 30798), about 21% (BYU 571/8901), 17% (DINO 11541), 19% (MOR 693) and 20% (SMA 005/02). The above comparison suggests mandibular depth is fairly constant in known allosaurids, though quadrate angling and laterotemporal fenestra proportions vary widely. Yet importantly, the latter conditions both exhibit intermediates instead of two distinct clusters, and do not covary- AMNH 30798 and SMA 00/02 have low quadrate angles but wide laterotemporal fenestrae, while USNM 4734 has a high angle but restricted fenestra. Note neither of these conditions vary with stratigraphy either, and indeed the A. fragilis types and DINO 2560 are both from the Brushy Basin Member. Nor does it vary geographically, with Wyoming specimens encompassing almost the entirity of the variation. Based on this study then, "Madsenius" can be considered a synonym of Allosaurus fragilis and another example of Bakker's notorious splitting.

References-  Madsen, 1976. Allosaurus fragilis: A revised osteology. Utah Geological and Mineral Survey Bulletin. 109, 1-163.

Lambert, 1990. The Dinosaur Data Book. New York, Avon Books. 320 pp.

Olshevsky, 1991. A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings. 2, 196 pp.

Anonymous, 1997. Dr. Bob's dinofacts. Tate Geological Times. 5(2), 3.

Bakker, 1997. Raptor family values: Allosaur parents brought great carcasses into their lair to feed their young. In Wolberg, Sump and Rosenberg (eds). Dinofest International, Proceedings of a Symposium, Academy of Natural Sciences. 51-63.

Bakker, 2000. Brontosaur killers: Late Jurassic allosaurids as sabre-tooth cat analogues. Gaia. 15, 145-158.

Hartman, DML 2000.

Olshevsky, 2004 online.

Williams, 2004 online.