Saturday, May 29, 2010

Palintropus is not a crown bird

When it comes to crown Aves, I'm less sure of my self than I am for other theropods.  This is because the vast majority of modern species are not described osteologically, and I'm still gathering references on the Tertiary species.  Mesozoic Aves are generally extremely fragmentary of course, with even the most complete specimens (Vegavis, Polarornis) being only partial skeletons.  With that caveat in mind, here are my thoughts on Palintropus...

Palintropus Brodkorb, 1970

Diagnosis- (after Longrich, 2009) acrocoracoid process massive and knob-like (also in Gansus and Ichthyornis); edge of humeral articular facet with a prominent lip in ventral view (also in Yixianornis); prominent scar inside supracoracoid sulcus (unknown in most non-avian euornithines).

Other diagnoses- Marsh (1892) first noted the absent procoracoid process as diagnostic, but this is shared with Apsaravis.
Here I interpret the very large, centrally and distally placed supracoracoid foramen noted as diagnostic by Hope (2002) as the proximal edge of a dorsal coracoid fossa as in Apsaravis. This same feature was described as "prominent dorsal groove in coracoid shaft" by Longrich (2009).
Longrich also included the supracoracoid foramen opening into a medial groove of the coracoid shaft, which is shared with Apsaravis.

Palintropus sp. nov. proximal coracoid RTMP 88.116.1, after Longrich (2009).

Comments- Marsh (1892) originally included retusus in Cimolopteryx, as C. retusa. Shufeldt (1915) noted it was not referrable to Cimolopteryx and probably not even closely related, though he felt it was too fragmentary for further evaluation. Brodkorb (1963) first removed it to Apatornis, which he viewed as an ichthyornithine. He then (1970) placed it in a new genus Palintropus, which he believed was a cimolopterygid charadriiform.

Palintropus a galliform? Hope (2002) questionably referred this taxon to Galliformes. This was based on the reduced procoracoid process, coracoid facet for scapula placed entirely distal to glenoid. Several other characters were listed in Hope's Galliformes diagnosis as being reasons why she placed "specimens below" (consisting solely of Palintropus) in that order, but are eithjer undescribed (coracoid neck with stout and triangular cross section) or unknown (elongate coracoid shaft; narrow sternal end of coracoid; rudimentary lateral process) in that genus. She also noted the acrocoracoid was similar in size to galliforms (larger than tinamiforms, smaller than anseriforms and most neoavians), the absence of a pneumatic foramen is unlike tinamiforms, and the laterally positioned coracoid tubercle which merges with the glenoid is similar to galliforms. However, the procoracoid process is also absent in Patagopteryx and (as noted by Longrich, 2009) Apsaravis, while it is still present though reduced in basal galliforms like Paraortygoides, Paraortyx and Ameripodius. I also note Apsaravis has a coracoid facet placed distal to the glenoid. Lack of coracoid pneumatization is present in all non-avians (except perhaps Jixiangornis and Jianchangornis). The laterally positioned coracoid tubercle that merges with the glenoid is also found in galliforms, tinamiforms, Lithornis, Patagopteryx, Yixianornis, Jianchangornis, Ichthyornis and Ambiortus, so seems symplesiomorphic for Aves. Gansus and Ichthyornis also have moderate sized acrocoracoid processes.

Hope referred it questionably to the basal galliform family Quercymegapodiidae based on the large free lateral flange on the coracoid glenoid, further reduced procoracoid process (only with Quercymegapodius and not Ameripodius), and scar within the supracoracoid sulcus (only verified in Ameripodius). Also she correctly noticed the deep cup-like scapular facet is unlike crown galliforms. Apsaravis, Ichthyornis, Gansus, Yixianornis, Patagopteryx and Archaeorhynchus also have a large lateral flange on the coracoid glenoid. Almost all non-avian euornithines also have scapular cotyla which are deeper than those of crown galliforms. The texture of the supracoracoid sulcus is generally indeterminable in non-avian euornithines, even when they expose the sulcus as in Yixianornis. Hope, Mayr (2009) and Longrich all noted that it was unlike Tertiary Galliformes in having a supracoracoid foramen, and Longrich stated it differed further in lacking a strongly hooked acrocoracoid.

Thus Palintropus does not share any characters with galliforms not seen in Apsaravis except for the larger acrocoracoid (which is also seen in some non-avian euornithines). As Palintropus has some characters which exclude it from Galliformes, and the only character shared with a quercymegapodiid (the supracoracoid sulcus scar) is indeterminate in Apsaravis and most other non-avian euornithines, it is near certainly not a member of Quercymegapodiidae.

Palintropus related to Apsaravis? Longrich (2009) suggested Palintropus was related to Apsaravis based on the absent procoracoid process and medial supracoracoid groove. They also seem to share a deep dorsal fossa in the coracoid. While these characters are also shared with most enantiornithines, the scapulocoracoid articulation is unlike that clade. The referred dorsal and femur also lack enantiornithine synapomorphies (e.g. they have anteriorly placed parapophyses and no posterior trochanter). When added to a modified version of Clarke's phylogenetic analysis of birds (with basal galliforms such as Paraortygoides, Quercymegapodius and Ameripodius also added), Palintropus emerges as sister to Apsaravis. Longrich's hypothesis is thus supported.

P. retusus (Marsh, 1892) Brodkorb, 1970
= Cimolopteryx retusa Marsh, 1892
= Apatornis retusus (Marsh, 1892) Brodkorb, 1963
Late Maastrichtian, Late Cretaceous
Lance Formation, Wyoming, US
Holotype- (YPM 513) proximal coracoid

Diagnosis- (after Longrich, 2009) smaller than both Campanian species; lacks kink in the ridge connecting the humeral articular facet and acrocoracoid; acrocoracoid process shorter and more expanded; humeral articular facet broader anteriorly than posteriorly; dorsal groove extends to level of scapular cotyle.

P. sp. nov. (Hope, 2002)
Late Campanian, Late Cretaceous
Dinosaur Park Formation, Alberta, Canada
Material- (RTMP 86.36.126) proximal coracoid (Hope, 2002)
?(RTMP 89.81.12) dorsal vertebra (Longrich, 2009)
?(RTMP 2001.12.150) distal femur (Longrich, 2009)

Diagnosis- (after Longrich, 2009) over twice as large as P. retusus, a third larger than the other Campanian species; kink in the ridge connecting the humeral articular facet and acrocoracoid; acrocoracoid process shorter and more expanded; humeral articular facet broader anteriorly than posteriorly; dorsal groove extends to level of scapular cotyle.

Comments- Hope (2002) referred RTMP 86.36.126 to a new species of Palintropus, along with RTMP 86.146.11, 88.116.1 and five other RTMP specimens. She noted some of these specimens were smaller, so might belong to another species, or that Palintropus may have been sexually dimorphic. Longrich referred RTMP 86.36.126 to his Palintropus species A, along with a dorsal vertebra and femur based on their size.

P. sp. nov. (Longrich, 2009)
Late Campanian, Late Cretaceous
Dinosaur Park Formation, Alberta, Canada
Material- (RTMP 83.36.70) coracoid fragment (Longrich, 2009)
(RTMP 88.116.1) proximal coracoid (Hope, 2002)
?(RTMP 89.50.53) dorsal vertebra, partial synsacrum (Longrich, 2009)
(RTMP 92.53.3) coracoid fragment (Longrich, 2009)
?(RTMP 96.12.336) femur (Longrich, 2009)
(RTMP 2005.12.190) partial coracoid (Longrich, 2009)
Late Campanian, Late Cretaceous
Foremost Formation, Alberta, Canada
?(RTMP 86.146.11) proximal scapula (Hope, 2002)

Diagnosis- (after Longrich, 2009) intermediate in size between other species; lacks kink in the ridge connecting the humeral articular facet and acrocoracoid; acrocoracoid process taller and less expanded; humeral articular facet strongly semicircular; dorsal groove does not extend to level of scapular cotyle.

Comments- Hope (2002) referred RTMP 86.146.11 and 88.116.1 to the same undetermined Palintropus species as RTMP 86.36.126, though she noted the latter might belong to a different species or sex. Longrich (2009) placed the former specimens in his new Palintropus species B, which he stated differed markedly in morphology from P. retusus or P. species A.

P. sp. (Hope, 2002)
Late Campanian, Late Cretaceous
Belly River Group, Alberta, Canada
Material- (RTMP coll.) three partial coracoids (Hope, 2002)

Comments- Hope (2002) referred five coracoids in the RTMP collections to her new Palintropus species, two of which are probably RTMP 83.36.70 and 92.53.3 that were later mentioned by Longrich (2009) and referred to his Palintropus species B. Whether the other three belong to P. species A or B is unknown.

References- Marsh, 1892. Notes on Mesozoic vertebrate fossils. American Journal of Science. 55, 171-175.

Shufeldt, 1915. Fossil birds in the Marsh Collection of Yale University. Transactions of the Connecticut Academy of Arts and Sciences. 19, 1-110.

Brodkorb, 1963. Birds from the Upper Cretaceous of Wyoming. in Sibley (ed.). Proceedings of the XIII International Ornithological Congress. 50-70.

Brodkorb, 1970. The generic position of a Cretaceous bird. Quarterly Journal of the Florida Academy of Science. 32(3), 239-240.

Hope, 2002. The Mesozoic radiation of Neornithes. In Chiappe and Witmer (eds). Mesozoic birds: Above the heads of dinosaurs. Berkeley: University of California Press. 339-388.

Longrich, 2009. An ornithurine-dominated avifauna from the Belly River Group (Campanian, Upper Cretaceous) of Alberta, Canada. Cretaceous Research. 30(1), 161-177.

Mayr, 2009. Paleogene Fossil Birds. Springer-Verlag, Heidelberg & New York. 262 pp.

Thursday, May 27, 2010

Rinehart et al. 2009's Coelophysis monograph- A review

It's funny how the most complete specimens are often the most poorly described.  Coelophysis is known from more individuals than any Mesozoic theropod except Confuciusornis, but it was only in 1989 that we even got an attempt at a detailed osteology (Colbert, 1989).  Alas, Colbert's paper suffers from simplistic description and schematic illustrations that are restored in a Chatterjee-esque manner and oftentimes misrepresent the anatomy (Downs, 2000).  If you want to know what Ghost Ranch Coelophysis' anatomy actually is, you have to try to interpret the unlabeled photographs in Colbert's paper, which don't feature most of the postcrania up close.  So imagine my joy to see a new Coelophysis monograph was published.  Not just an article, but an entire NMMNH Bulletin devoted to the taxon!  Alas, it was too good to be true.

I should preface this by saying that even ignoring my criticisms below, this volume was mostly not designed to be the kind of study I was looking forward to.  Benson's recent megalosaur papers are a good example of my ideal- in depth osteology highlighting characters used in cladistic analyses and differences from related taxa, photographs and detailed illustrations of material that clearly indicate morphological and taphonomic features, and a phylogenetic analysis to top it off.  Rinehart et al.'s monograph is mostly history, geology, accompanying fauna, and paleobiology though.  On most of these topics I have little to say- I'm not an expert on stratigraphy, non-dinosaurian animals, population biology, or optics (though Rinehart et al.'s analysis of the sclerotic ring is certainly interesting).  I can't really blame them for this, it's just not what I was expecting.  Guess I should have noticed it's titled "The Paleobiology of Coelophysis bauri..." and not the Osteology of Coelophysis bauri. heh

One amusing part is in the history section, where the authors describe the ICZN petition to use Coelophysis bauri for the Ghost Ranch material instead of Hunt and Lucas' replacement name Rioarribasaurus colberti.  "This step would validate C. bauri, invalidate R. colberti, and confirm Colbert's identification of the Whitaker quarry theropod as C. bauri through legislation rather than scientific consensus.  Although it violated the principle of priority and was proposed without the necessary revisionary work called for by the International Code of Zoological Nomenclature, the comission approved the petition of Colbert et al. (1992).  Thus the Ghost Ranch dinosaur is now "legally" called Coelophysis bauri."  Still a tad sore about the whole thing? ;)

In the faunal section, they follow their 2007 paper in sinking Effigia into Shuvosaurus as S. okeeffeae.  I really can't determine why they would do such a thing.  Everyone agrees genera are subjective, so it doesn't increase taxonomic accuracy.  They attribute Effigia to their Apachean age and Shuvosaurus to Revueltian age, so it's not to help their problematic faunachrons.  They even include cranial reconstructions of the two, which look more dissimilar than Gorgosaurus vs. Tyrannosaurus.

One very odd part is their description of a supposed specimen of Eucoelophysis in one of the blocks.  This skeleton is articulated and is only missing most cervicals, the skull, mid and distal caudals, and the forelimbs except for a humerus.  You would think this would be rather important, since otherwise the genus is only known from some hindlimb elements, unfigured dorsals, partial ilium and dentary fragment, and it was originally described as a coelophysid but later claimed to be a non-dinosaurian dinosauriform like Silesaurus. But the phylogenetic controversy is never discussed (it's merely said to be a dinosauromorph) or even mentioned in relation to any of the characters listed.  Not that you'll find many characters listed, since the description is appallingly short.  Want to know about the vertebrae?  The cervicals have pleurocoels, there are 13 or 14 dorsals, the sacrum has four vertebrae of which the last two are not fused, and... that's it.  Maybe you're interested in the presence of hyposphenes, the depth of the pleurocoels, the vertebral laminae, the form of the transverse processes, the details of the sacral vertebrae and their articulation with the ilium?  Well too bad.  Maybe we could examine the humerus to see if it has a dinosaur-like elongate deltopectoral crest?  Sorry, the humerus' position warranted a sentence, but we get no actual description.  How about the ilium?  That's pretty different in coelophysoids and silesaurs.  All we're told is that it has a well developed supracetabular shelf and deep brevis fossa ("posteroventral arch"), both of which are present in both taxa.  Care how long the preacetabular process is, how open the acetabulum is, if the supracetabular crest is continuous with the brevis fossa edge, if the brevis fossa is posteriorly expanded, etc.?  You won't find that information here.  The photo of the specimen is too small to see anything but its basic position, and the pelvic closeup doesn't help much (the preacetabular process appears to be of intermediate length, but it's said to be complete, yet also fragmented... hmm).  Besides those, we get a stereophoto of the femur in proximal and anterolateral views.  Honestly, I wouldn't be surprised if this is just another Coelophysis specimen.  Other coelophysoids have been described as having four sacrals when they had five (Dilophosaurus, Liliensternus), the supposedly less distally rounded scapula with a broader shaft is never illustrated, nor are the supposedly more robust distal tarsals.  As for the femoral differences, the proximal sulcus looks much less prominent than in Eucoelophysis (which is claimed to be due to lighting conditions and angle) but similar to Coelophysis specimens such as UCMP 129618 and NMMNH 29046.  They themselves note the femoral head is more rounded and medially projected than in Eucoelophysis, but say it's "probably due to the weathered condition of the holotype."  As for the dorsolateral trochanter, with how the rest of the femur is fragmented, it could be damage for all I know.  What would have been especially useful and easy to do is add this specimen to Ezcurra's (2006) matrix which includes both Coelophysis and the Eucoelophysis holotype.  This would have provided a wealth of anatomical information, and would be quite illuminating.  As it is, the description is more frustrating than anything.

And that sets the stage for the section I was looking forward to- the osteology.  As Rinehart et al. state, "significant redundancy of elements allows a thorough description of each element of the postcranium and description of intraspecific variation within various functional complexes."  If only that were taken advantage of.  For a start, don't think you're getting a description of the skull or forelimb, because those are being worked on by other people.  You can also cross the pes off your list, since it gets all of five sentences.  Basically you could substitute my above complaints for Eucoelophysis and they'd work almost as well here, though at least the photos are more numerous and larger.  Unfortunately, because the material is fragmented and the same color as the matrix, features on the photos are often unclear.  This could be resolved with detailed illustrations indicating where breakage had occured and showing the shape of the bone surface, but instead we get basic outlines with very few contour lines.  So the coracoids are all irregular ovalish blobs, one with the glenoid indicated and another with a contour line representing who knows what.  It's odd these drawings are often so large, since the included detail would have been just as visible at a fraction of the size.  Figure 73 just consists of the outlines of 4-5 bones, with the only internal detail being the glenoid on two of them.  Yet it takes up an entire page.  Perhaps the most annoying part of the description though is the lack of phylogenetic context and comparisons.  Nearly everything they say could be applied to Megapnosaurus or "M." kayentakatae equally well, or even Liliensternus.  But not quite everything I bet.  But since other taxa are literally never mentioned, the significance of any feature is unknown.  Having a huge sample of different sizes of one species of Coelophysis also sounds like an ideal opportunity to compare them to other fragmentary specimens like Padian's (1986) UCMP 129618, Podokesaurus, or the original Cope material.  But no such luck.  It's not that these authors are incapable of good osteological study either, as Spielmann et al.'s (2007) paper on Snyder Quarry coelophysoids shows.  That had clear photos from numerous angles, detailed descriptions, and a decent comparison to UCMP 129618 and Ghost Ranch material, along with characters used in phylogenetic analyses that apply to the remains at hand.

If you want to know the history of the Ghost Ranch Quarry, the visual acuity of Coelophysis, the position of its vent, or if you just want a ton of biometric information on a population of theropods, this is a fine volume.  If you want a good osteology of Coelophysis though, it looks like we'll have to wait.  Hopefully Reisz's cranial study and Nesbitt's forelimb study will improve matters.

References- Padian, 1986. On the type material of Coelophysis Cope (Saurischia: Theropoda) and a new specimen from the Petrified Forest of Arizona (Late Triassic: Chinle Formation). in Padian (ed.). The Beginning of the Age of Dinosaurs: Faunal Change Across the Triassic-Jurassic boundary. Cambridge University Press, Cambridge, England. 45-60.

Colbert, 1989. The Triassic dinosaur Coelophysis. Museum of Northern Arizona Bulletin. 57, 1-174.

Downs, 2000. Coelophysis bauri and Syntarsus rhodesiensis compared, with comments on the perparation and preservation of fossils from the Ghost Ranch Coelophysis quarry. in Lucas and Heckert (eds.). Dinosaurs of New Mexico. New Mexico Museum of Natural History and Science Bulletin 17, 33-37.

Ezcurra, 2006. A review of the systematic position of the dinosauriform archosaur Eucoelophysis baldwini Sullivan & Lucas, 1999 from the Upper Triassic of New Mexico, USA. Geodiversitas. 28(4), 649-684.

Spielmann, Lucas, Rinehart, Hunt, Heckert and Sullivan, 2007. Oldest records of the Late Triassic dinosaur Coelophysis bauri. in Lucas and Spielmann (eds.). The Global Triassic. New Mexico Museum of Natural History and Science Bulletin 41, 384-401.

Rinehart, Lucas, Heckert, Spielmann and Celeskey, 2009. The paleobiology of Coelophysis bauri (Cope) from the Upper Triassic (Apachean) Whitaker Quarry, New Mexico, with detailed analysis of a single quarry block. New Mexico Museum of Natural History and Science Bulletin 45, 260 pp.

Saturday, May 22, 2010

Rapator in Agnolin et al. 2010 and the concept of nomen dubium

I recently engaged in a discussion about nomina dubia on the DML with Tim Williams and Jaime Headden, specifically regarding Ceratops.  Agnolin et al.'s (2010) extensive new review of Australian and New Zealand dinosaurs provides an excellent example of someone labeling a taxon a nomen dubium incorrectly.  Remember, a nomen dubium is an undiagnostic specimen.  It does not preserve any apomorphies, so cannot be distinguished from other taxa.  Here are the facts of the matter in regard to Rapator according to Agnolin et al.

- Rapator is easily distinguishable from most theropods- ceratosaurs, Tugulusaurus, Szechuanosaurus? zigongensis, Torvosaurus, Allosaurus, Acrocanthosaurus, and coelurosaurs including Ornitholestes and Nqwebasaurus.
- Rapator is most similar to Megaraptor and Australovenator, so is a megaraptoran.
- "Rapator and Australovenator differ from Megaraptor in the presence of a more dorsoventrally developed mediodistal condyle and a lateral facet for articulation with the metacarpal II lying in almost the same plane as the lateral margin of the shaft. Thus, albeit being very similar in morphology, Rapator and Australovenator are clearly distinct from Megaraptor."
- "Hocknull et al. (2009) recognized subtle differences between Rapator and Australovenator (e.g. more subequal distal condyles, flat proximal articular surface, straight lateral distal condyle) and we add here the presence of a distal medial condyle ventrally extended in Rapator."

I have no actual opinion on the validity of these statements, as I haven't studied Rapator yet myself.  Let's assume they're all correct.  What conclusion would we reach about the status of Rapator?  There are only two possibilities- it's diagnostic compared to Australovenator or it isn't.  If the former is true, it's a valid taxon.  If the latter is true, Australovenator is a junior synonym.  Yet Agnolin et al. confusingly state "However, due to the fragmentary condition of Rapator and the absence of autapomorphies and clear differences with Australovenator, we consider the taxon to be a nomen dubium."

Put bluntly, a taxon can't be a nomen dubium if it's only undiagnostic compared to one other taxon!  In that case, it's a synonym.  It has to be undiagnostic compared to TWO other taxa in order to be undiagnostic, since then we couldn't tell which taxon it came from.  If Agnolin et al. didn't want to sink the more complete Australovenator into Rapator, they could have relied on the differences they noted.  But if they don't think those differences warrant such a separation, then to be honest they'd have to synonymize the taxa.  But you can't have it both ways.

Another less explicit example is Timimus.  Agnolin et al. consider it Paraves indet., though they distinguish it from Troodontidae and eudromaeosaurs.  They end up viewing it as most similar to unenlagiines, but don't bother trying to distinguish it from any.  Yet Rahonavis is obviously different in having a trochanteric crest, while both Unenlagia and Buitreraptor have downturned femoral heads.  If Timimus is an unenlagiine, it's a valid taxon.

In general, the paper seems confused in regard to "indet." and "nomen dubium".  In their Table 1, the terms are listed separately, with some taxa they consider determinable being labeled as indeterminate (e.g. Kakuru, Muttaburrasaurus).

These are all great examples of why I don't trust pronouncements of nomen dubium status by authors without them going through a rigorous anaysis.  Agnolin et al. are actually much more detailed in their analysis than most authors when it comes to this, but they still end up declaring fragmentary taxa to be indeterminate even when their own written conclusions would indicate it cannot be so.

Reference- Agnolin, Ezcurra, Pais and Salisbury, 2010. A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: Evidence for their Gondwanan affinities. Journal of Systematic Palaeontology. 8(2), 257-300.

Tuesday, May 18, 2010

Huge Theropod Database Update

I added an entirely new section to the website- Evaluating Phylogenetic Analyses. This portion of the website is devoted to past phylogenetic analyses of theropods. Each page is devoted to a particular analysis and any published modifications it has been through, noting the general importance of the paper with citation. I then note which codings are inaccurate, re-run the analysis, check both the original and corrected versions against different topologies, and even try adding in interesting taxa.

All named non-avian avepods are now online! New taxa include Austrocheirus, "Rahiolisaurus", Cruxicheiros, Leshansaurus, Raptorex, Sinotyrannus, Bistahieversor, Kileskus, Haplocheirus, Xixianykus, Luoyanggia, Banji, Pneumatoraptor, Tianyuraptor, Linheraptor, Dromaeosaurus, Utahraptor, Xixiasaurus, Jianchangornis and Longicrusavis. Taxa which have been significantly updated include Sarcosaurus, Dilophosaurus "breedorum", Megalosaurus? "tibetensis", "Merosaurus", "Ngexisaurus", Chuandongocoelurus, "Allosaurus" tendagurensis, Megalosaurus "dapukaensis", "Metriacanthosaurus" "reynoldsi", "Poekilopleuron" schmidti, Prodeinodon? "tibetensis", "Saltriosaurus", Megalosaurus, "Megalosaurus" "phillipsi", Microvenator? "chagyabi", Embasaurus, Alioramus (including A. altai as a junior synonym of A. remotus), Elaphrosaurus "philtippettensis" (as a junior synonym of Tanycolagreus). You saw many of those here beforehand of course. :)

Basal Tetanurae and Megalosauroidea have been completely reorganized to reflect Benson's (2010) and Benson et al.'s (2010) new data, and Megaraptora has been formed within Coelurosauria. Alvarezsauroidea has also been reorganized with revised diagnoses. In addition, I've made sure all family-level names are valid according to ICZN Article 13.1.1.

Things to do include finishing evaluating Holtz's (1994) analysis; reorganizing Dromaeosauridae now that I've incorporated the Tianyuraptor, new Anchiornis and Hesperonychus data; getting the ex-Theropoda section uploaded; adding Tawa with Nesbitt et al.'s data, ceratosaur data and more carnosaurs to the saurischian supermatrix to update those topologies; adding the rest of the Mesozoic Aves; and eventually incorporating all the new data from basal tyrannosauroids and proceratosaurids to reorganize that section.

Monday, May 17, 2010

Utahraptor ostrommaysorum

One of the few old taxa I have yet to post an entry on in The Theropod Database.  A big update will be coming to that site soon, btw.  All the new taxa that have been described, new tetanurine phylogeny, the first installments of my analyses of prior cladistic analyses, and more.

Utahraptor Kirkland, Gaston and Burge, 1993
= "Utahraptor" Kirkland, 1992
U. ostrommaysorum Kirkland, Gaston and Burge, 1993 emmend. Olshevsky, 2000
= "Utahraptor spielbergi" Bonar, Lassieur, McCafferty and Voci, 1993
= Utahraptor ostrommaysi Kirkland, Gaston and Burge, 1993
Barremian, Early Cretaceous
Yellow Cat Member of the Cedar Mountain Formation, Utah, US
Holotype- (CEU 184v.86) pedal ungual II
Paratypes- (BYU 9429) (3.89 m) mid caudal vertebrae (67 mm)
(BYU 9435) distal caudal vertebra
(BYU 9436) distal caudal vertebra
(BYU 9438) pedal ungual II
(BYU 13068) pedal ungual II
(CEU 184v.260) (5.03 m) tibia (503 mm)
(CEU 184v.294) pedal ungual II
(CEU 184v.400) premaxilla
Referred- (BYU 15465) (~5.9 m) femur (600 mm) (Erickson et al., 2009)
(BYU coll.) teeth (Kirkland et al., 2005)
(BYU and CEU coll.) (at least nine individuals; juvenile to adult; ~3-5.6 m, some ~11 m?) 190 elements including premaxillae, nasal, quadratojugal, cervical vertebrae, dorsal vertebrae, sacral vertebrae, proximal caudal vertebrae, coracoid, partial ilium, incomplete ischium, femora (310-565 mm), astragalus, metatarsal II, phalanx II-1, metatarsal III, metatarsal IV (Britt et al., 2001)

Comments- The name Utahraptor was first used in a press release from Kirkland and Dinamation International Society (Olshevsky, 2000) and subsequently published in several articles in July 1992 (e.g. Browne, 1992). Its species name was originally going to be U. spielbergi, but Steven Spielberg's lawyers apparently objected (Bakker pers. comm. to Tegowski, 1996). That name has only been published in a children's magazine and merchandise, which of course lacked a proper description. Once the taxon was properly published, Kirkland et al. (1993) spelled the species name ostrommaysi, but this was emmended by Olshevsky to ostrommaysorum as it honors both Ostrom and Mays. The name Utahraptor "oweni" has also appeared online in various places but is probably a mistake for Valdoraptor oweni.

The type material was discovered in 1975 (BYU material) and 1991-1992 (CEU material), but only described in 1993. The other CEU type material may belong to the same individual as the holotype. A supposed lacrimal (CEU 184v.83) was also a paratype, but was later found to be a postorbital from the ankylosaur Gastonia (Britt et al., 2001). Britt et al. also state a previously identified surangular is actually a long bone fragment, but no surangular was identified in the original description. They determined that the supposed manual unguals BYU 9438, BYU 13068 and CEU 184v.294 are actually pedal unguals, which was confirmed by Senter (2007a).

New material was announced by Britt et al. (2001) in an abstract, but has yet to be described in detail. This consists of one individual from the Yellow Cat (=Gaston) Quarry (CEU coll.) and at least eight from the Dalton Well Quarry (70 elements in the BYU coll.). Anatomical information on these specimens can be gleaned from the matrices of Senter (2007b) and Longrich and Currie (2009). Of particular interest are caudal vertebrae about twice as long as those belonging to a specimen with a 565 mm long femur. If this turns out to be correct and not due to misidentification or unusual proportions, it could indicate individuals over ten meters long.

References- Browne, 1992. A creature to make T. rex tremble. The New York Times. July 21st.

Bonar, Lassieur, McCafferty and Voci, 1993. Disney Adventures. 3(9), 27-37.

Kirkland, Burge and Gaston, 1993. A large dromaeosaur (Theropoda) from the Lower Cretaceous of eastern Utah. Hunteria. 2(10), 1-16.

Tegowski, DML 1997.

Olshevsky, 2000. An annotated checklist of dinosaur species by continent. Mesozoic Meanderings. 3, 1-157.

Britt, Chure, Stadtman, Madsen, Scheetz and Burge, 2001. New osteological data and the affinities of Utahraptor from the Cedar Mountain Fm. (Early Cretaceous) of Utah. Journal of Vertebrate Paleontology. 21(3), 36A.

Kirkland, Scheetz and Foster, 2005. Jurassic and Lower Cretaceous dinosaur quarries of Western Colorado and Eastern Utah. in Rishard (compiler). 2005 Rocky Mountain Section of the Geological Society of America Field Trip Guidebook, Grand Junction Geological Society. Field Trip 402, 1-26.

Senter, 2007a. A method for distinguishing dromaeosaurid manual unguals from pedal "sickle claws". Bulletin of the Gunma Museum of Natural History. 11, 1-6.

Senter, 2007b. A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda). Journal of Systematic Palaeontology. 5(4), 429-463.

Erickson, Rauhut, Zhou, Turner, Inouye, Hu and Norell, 2009. Was dinosaurian physiology inherited by birds? Reconciling slow growth in Archaeopteryx. PLoS ONE. 4(10), e7390. doi:10.1371/journal.pone.0007390

Longrich and Currie, 2009. A microraptorine (Dinosauria–Dromaeosauridae) from the Late Cretaceous of North America. Proceedings of the National Academy of Sciences. 106(13), 5002-5007.

U. sp. (Carpenter, online)
Aptian, Early Cretaceous
Poison Strip Member of Cedar Mountain Formation, Utah, US
Material- ? pelvic element
Reference- (offline)

U. sp. (Carpenter, online)
Early Albian, Early Cretaceous
Ruby Ranch Member of Cedar Mountain Formation, Utah, US
Material- ? manual ungual
Reference- (offline)

Wednesday, May 12, 2010

Alioramus altai is the same as A. remotus, which is probably juvenile Tarbosaurus

Alioramus Kurzanov, 1976
A. remotus Kurzanov, 1976
= Alioramus altai Brusatte, Carr, Erickson, Bever and Norell, 2009

Maastrichtian, Late Cretaceous
Nogonn Tsav Beds, Mongolia
(GI 3141/1) (juvenile) incomplete skull (~700 mm), mandible, four cervical vertebrae, partial tibia, proximal fibula, pedal ungual I, distal metatarsal II, phalanx II-1, pedal ungual II, distal metatarsal III, phalanx III-1, pedal ungual III, distal metatarsal IV, phalanx IV-1, pedal ungual IV

Early Maastrichtian, Late Cretaceous
Nemegt Formation, Mongolia

Referred- (IGM 100/1844; holotype of Alioramus altai) (9 year old juvenile; 369 kg) incomplete skull (~635 mm), mandible, atlas, axis (36 mm), third cervical vertebra (42 mm), fourth cervical vertebra (42 mm), fifth cervical vertebra (65 mm), sixth cervical vertebra (75 mm), seventh cervical vertebra (57 mm), eighth cervical vertebra (60 mm), ninth cervical vertebra (67 mm), tenth cervical vertebra (51 mm), at least eight cervical ribs, fifth dorsal vertebra (55 mm), eighth dorsal vertebra, tenth dorsal vertebra (55 mm), thirteenth dorsal vertebra, dorsal rib, sacrum (?,?,75,79,97 mm), proximal caudal vertebra (87 mm), distal caudal vertebra (82 mm), distal caudal vertebra (84 mm), mid chevron, incomplete ilium, ischium (430 mm), femur (560 mm), distal tibia, distal fibula, proximal tarsal, metatarsal I, phalanx I-1, pedal ungual I, metatarsal II, phalanx II-1, phalanx II-2, pedal ungual II, metatarsal III, phalanx III-1, phalanx III-2, phalanx III-3, pedal ungual III, metatarsal IV, phalanx IV-1, phalanx IV-2, phalanx IV-3, phalanx IV-4, pedal ungual IV, metatarsal V

Diagnosis- (after Kurzanov, 1976) 16-17 maxillary teeth (ontogenetic?); 18-20 dentary teeth (ontogenetic?).
(after Brusatte et al., 2009 for A. altai) accessory pneumatic fenestra posterodorsal to promaxillary fenestra of maxilla (ontogenetic?); maxillary fenestra enlarged and 1.9 times longer than deep; laterally projecting jugal horn; thick ridge on dorsal surface of the ectopterygoid; anteroposteriorly elongate anterior mylohyoid foramen of splenial; thin epipophysis on atlantal neurapophysis that terminates at a sharp point; pneumatic pocket on anterior surface of cervical transverse processes (ontogenetic?); external pneumatic foramina on dorsal ribs (ontogenetic?); anterodorsally inclined midline ridge on the lateral surface of the ilium.

Other diagnoses- Kurzanov (1976) listed many additional characters, most of which are probably due to the Alioramus type's juvenile age- 'average' size; low skull; elongate snout; series of prominent nasal rugosities; small postorbital boss; labiolingually compressed teeth. Two rows of maxillary nutrient foramina are present in most tyrannosaurids (Currie, 2003), as are the laterosphenoid contacts noted by Kurzanov (forms part of the supratemporal cavity and contacts the postorbital). Currie also noted the trigeminal foramen near certainly contacted the laterosphenoid as opposed to being completely contained by the prootic. While he defended the prominence of the nasal rugostities as potentially diagnostic, they are lower in IGM 100/1844.

Brusatte et al. (2009) stated several characters united the Alioramus specimens in their analysis, most being previously used by Kurzanov except for the long posterior squamosal process. Yet Carr (2005) notes that juvenile Tyrannosaurus have long processes, making this potentially ontogenetic. Among characters listed in the diagnosis for A. altai which are unknown in the A. remotus holotype, the palatine pneumatic recess extends posteriorly beyond the posterior margin of the vomeropterygoid process in juvenile Daspletosaurus and Tyrannosaurus more than in adults.

Comments- Currie et al. (2003) found Alioramus to be the sister taxon of Tarbosaurus because they both lack a lacrimal process on the nasal, though this is present in Daspletosaurus as well. In addition, Hurum and Sabath (2003) note Alioramus and Tarbosaurus share a dentary-angular interlocking mechanism which makes the mandible rigid. Currie (2003) suggested the specimen could be a juvenile Tarbosaurus based on skull proportions and juvenile characters. He stated the prominent nasal rugosities and high tooth count argue against this, but juvenile Tyrannosaurus have high tooth counts and some juvenile Daspletosaurus and Tarbosaurus have rows of nasal rugosities, albeit lower ones as in the A. altai holotype. Holtz (2004) recovered Alioramus in two possible positions- just basal to Tyrannosauridae or sister to Tarbosaurus + Tyrannosaurus. The former position is due to the high tooth count, low snout and slender dentary, which are all possible juvenile characters. The latter position was due to the thick parietal nuchal crest, reduced basal tubera, and posteroventrally directed occipital region. Carr (2005) recovered Alioramus in an uncertain position basal to Tyrannosauridae, but this could be due to juvenile characters. However, the evidence cannot be examined as characters excluding the taxon from Tyrannosauridae were not given, nor was Alioramus included in the printed data matrix. Brusatte et al. (2009) found Alioramus to be a basal tyrannosaurine using an updated version of Carr's matrix, but importantly coded it as if it were an adult when both morphology and histology show known specimens are juveniles. Thus its position is suspect, as similarly aged Tyrannosaurus individuals also emerge as basal tyrannosaurines if run in a similar matrix (Carr, 2005). IGM 100/1844 also provides further evidence for a relationship to Tarbosaurus, as it has a subcutaneous flange on the maxilla and a deep pneumatic fossa on the dorsal surface of the posterior centrodiapophyseal lamina, both otherwise only known in that genus. However, they also noted additional characters which differ between Alioramus and Tarbosaurus of the same size (ZPAL MgD-I/29, 31 and 175)- shallow maxilla and dentary; maxilla less convex ventrally; smaller postorbital boss; postorbital lacks an orbital process; more dentary teeth; muscular fossa above surangular foramen faces mostly dorsally; laterally projecting jugal horn; deep pocket behind surangular fenestra; fibular facet of tibia faces strongly laterally; lateral malleolus of tibia projects less distolaterally. The first six characters are typical of juveniles and could potentially indicate Alioramus individuals are larger at a younger age than ZPAL MgD-I/29 and 31, or that different individuals acquire adult features at different ages. The jugal horn and surangular pocket are ornamental and pneumatic features respectively, which show a high amount of individual variation. Brusatte et al. even state that an ontogenetic decrease in pneumaticity is known in theropods and that Tarbosaurus itself is known to lose pneumatic vertebral features with age, potentially explaining the surangular pocket and some of A. altai's supposed diagnostic features (see diagnosis above). Ontogenetic variation in tyrannosaurid tibiae has not been examined yet. Whle Brusatte et al. claimed that ornamentation increases in ontogeny in dinosaurs, this is not always the case as shown by juvenile tyrannosaurines with larger nasal rugosities and the newly discovered ontogenetic changes in Triceratops (= Torosaurus) and Pachycephalosaurus (= Stygimoloch and Dracorex). The fact most differences could be explained by ontogeny, coupled with the unique similarities present in Alioramus and the contemporaneous Tarbosaurus strongly suggest the former is a juvenile of the latter. The alternative presented by Brusatte et al., where a distinct genus known only from juvenile specimens and based on characters largely found in juvenile tyrannosaurs is contemporaneous with a taxon it is not the sister group of yet shares autapomorphies with, is considered unlikely.

Brusatte et al. (2009) erected a new species Alioramus altai based on a partial skeleton discovered in 2001 from the contemporaneous Nemegt Formation. However, the listed diagnostic characters are problematic. Most are not determinable in A. remotus (accessory pneumatic fenestra posterodorsal to promaxillary fenestra of maxilla; maxillary fenestra enlarged and 1.9 times longer than deep; thick ridge on dorsal surface of the ectopterygoid; palatine pneumatic recess extending posteriorly beyond posterior margin of vomeropterygoid process; thin epipophysis on atlantal neurapophysis that terminates at a sharp point; external pneumatic foramina on dorsal ribs; anterodorsally inclined midline ridge on the lateral surface of the ilium) or potentially determinable but unreported (anteroposteriorly elongate anterior mylohyoid foramen of splenial; pneumatic pocket on anterior surface of cervical transverse processes). The laterally projecting jugal horn was also coded as present in A. remotus. Having 20 dentary teeth instead of 18 is within the range of variation in other tyrannosaurid species. The subcutaneous flange on the maxilla is known to vary in Tarbosaurus. The authors themselves note in the supplementary information that some of the characters they list as distinguishing A. altai from A. remotus vary within other tyrannosaurid species- anterior process of quadratojugal terminates posterior to anterior margin of lateral temporal fenestra; squamosal anterior process extends anterior to anterior margin of lateral temporal fenestra; epipterygoid not bifurcated ventrally. The number and prominence of nasal rugosities is highly variable in tyrannosaurids, so A. remotus having six large rugosities is not significant compared to A. altai's three low ones. Finally, Brusatte et al. list three characters which are size-related in other tyrannosaurid taxa- 17 maxillary teeth instead of 16; single dorsoventral groove between basal tubera; tapering anterior process of the parietals overlapping frontals on the midline. They considered these potentially diagnostic since the holotypes are similar in size, but at least the maxillary tooth count is variable in similar-sized specimens. Here the other two characters are considered individual variation as well.

References- Kurzanov, 1976. A new Late Cretaceous carnosaur from Nogon-Tsav Mongolia. Sovmestnaa Sovetsko-Mongolskaa Paleontologiceskaa Ekspeditcia, Trudy. 3, 93-104.

Currie, 2003. Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontologica Polonica. 48(2), 191-226.

Currie, Hurum and Sabath, 2003. Skull structure and evolution in tyrannosaurid dinosaurs. Acta Palaeontologica Polonica. 48(2), 227-234.

Hurum and Sabath, 2003. Giant theropod dinosaurs from Asia and North America: Skulls of Tarbosaurus bataar and Tyrannosaurus rex compared. Acta Palaeontologica Polonica. 48(2), 161-190.

Holtz, 2004. Tyrannosauroidea. In Weishampel, Dodson and Osmolska (eds). The Dinosauria Second Edition. University of California Press. 861 pp.

Carr, 2005. Phylogeny of Tyrannosauroidea (Dinosauria: Coelurosauria) with special reference to North American forms. Unpublished PhD dissertation. University of Toronto. 1170 pp.

Brusatte, Carr, Erickson, Bever and Norell, 2009. A long-snouted, multihorned tyrannosaurid from the Late Cretaceous of Mongolia. Proceedings of the National Academy of Sciences. 106(41), 17261-17266.

Saturday, May 1, 2010

Pickering's taxa 6: Dilophosaurus breedorum

"Liassaurus" involves somewhat difficult decisions in regard to Sarcosaurus and the relationships of both taxa, so here's Dilophosaurus "breedorum" first.

Dilophosaurus Welles, 1970
D. wetherilli (Welles, 1954) Welles, 1970
= Megalosaurus wetherilli Welles, 1954
= Dilophosaurus "breedorum" Welles, 1995 vide Welles and Pickering, 1995
Hettangian, Early Jurassic
Silty Facies Member of Kayenta Formation, Arizona, US

Referred- (UCMP 77270; intended holotype of Dilophosaurus "breedorum") (~6.4 m; ~340 kg; robust adult) incomplete skull (619 mm), mandible (635 mm), anterior dentary, atlantal centrum (17 mm) plus axis (88 mm), incomplete third cervical vertebra (77 mm), fourth cervical vertebra (80 mm), fifth cervical vertebra (90 mm), sixth cervical vertebra (104 mm), seventh cervical vertebra (100 mm), eighth cervical vertebra, ninth cervical vertebra (82 mm), tenth cervical vertebra (92 mm), atlantal rib (295 mm), axial rib, seven cervical ribs, incomplete second dorsal vertebra (75 mm), partial third dorsal vertebra (86 mm), partial fourth dorsal vertebra (87 mm), fragmentary fifth dorsal vertebra, fragmentary sixth dorsal vertebra, partial seventh dorsal vertebra, partial eighth dorsal vertebra, partial ninth dorsal vertebra, partial tenth dorsal vertebra (97 mm), eleventh dorsal vertebra (92 mm), incomplete thirteenth dorsal vertebra (83 mm), second dorsal rib (370 mm), fifth dorsal rib (450 mm), sixth dorsal rib, seventh dorsal rib, tenth dorsal rib (280 mm), eleventh dorsal rib (280 mm), twelfth dorsal rib fragment, gastralial fragments, partial sacrum (78, 86, ?, ?, ? mm), sixth or seventh caudal centrum (87 mm), few caudal vertebrae, scapulocoracoid, radius (180 mm), incomplete ulna (215 mm), partial ilium fused to proximal pubis, distal pubis, fragmentary ischia, femur (590 mm), tibia (558 mm), proximal fibula, incomplete metatarsal I (~106 mm), metatarsal II (248 mm), pedal ungual II (70 mm), metatarsal III (300 mm), pedal ungual III (68 mm), metatarsal V (125 mm) (Welles, 1970)

Comments- The incomplete skeleton UCMP 77270 was discovered in 1964 which was initially mentioned by Welles (1970) as a larger specimen of Dilophosaurus wetherilli. This was the first specimen of the genus to preserve a nearly complete cranial crest, the bases of which had been preserved but unnoticed in the holotype. Welles later (1984) believed UCMP 77270 to be a new related genus of theropod based on undescribed differences in skull proportions, vertebrae and especially the femur. Gauthier (1986) retained the specimen in D. wetherilli and stated Welles had remarked on its trochanteric shelf in 1984, yet as Charig and Milner (1990) noted, Gauthier was mistaken and Welles never described the femur of the specimen. Rowe and Gauthier (1990) also referred it to D. wetherilli and incorrectly stated it was of similar ontogenetic stage as the holotype. Paul (1988) was not certain whether it was the same species or not, but noted the differences might be due to the same kind of dimorphism that coelophysids show. Welles wrote a description of UCMP 77270 in which he names it Dilophosaurus breedorum, which was eventually released by Pickering in 1995. This paper has controversial status, as it describes the only one of Pickering's taxa to be accepted as valid by another paleontologist (Olshevsky, DML online 1999). Olshevsky noted that the publication had no evidence of following ICZN Articles 8.1.2 and 8.1.3, but considered D. "breedorum" valid on the condition that Pickering could supply copies in response to orders. While I have received a copy from Pickering, he has refused to send them to several other workers or to archive them in public libraries. Thus Olshevsky's condition has been only partially met, and whether he still considers the species to be valid is unknown. Other workers such as Ford ( consider "breedorum" a nomen nudum. Incidentally, Olshevsky used the date 1999 for the "breedorum" paper and stated 1995 "must be a manuscript date, since the description was not published then and has only appeared through Pickering's efforts this year (1999)." I personally do not doubt Pickering printed the "breedorum" paper in 1995, though its distribution at that time is questionable. I provisionally accept the 1995 date here, though I also consider the taxon a nomen nudum under Article 8.1. Note that contra Olshevsky, if the "breedorum" paper is accepted as valid under the ICZN, "Newtonsaurus" and "Walkersaurus" from the comparative section would also be valid. In any case, "breedorum" was definitely used in Pickering's 1995 bibliographic work "Jurassic Park: Unauthorized Jewish Fractals in Philopatry" as a nomen nudum. In that work, the name is a label for a photograph of UCMP 77270's skull. Gay (2005) believed it was a specimen of D. wetherilli, feeling there is a "lack of significant morphological differences" and considered "breedorum" invalid, noting "uncertain validity of this name resulting from publication practices." Gay refers to two femora of differing lengths (575, 605 mm) and two tibiae (560, 585 mm), believing more than one individual might be involved, but Welles states only the right hindlimb is preserved. Tykoski (2005) used the specimen as an example of D. wetherilli in his thesis and concluded it was an adult (unlike the types and TMM 43646) using an ontogenetic analysis. He states "at the behest of Kevin Padian (pers. comm., April, 2003) I refrain from giving a description of the crest morphology in the skull of UCMP 77270", perhaps indicating Padian or someone else is working on a new description of this specimen. Tykoski also states the quadratojugal, quadrate, sacral centra, distal pubis and metatarsals are not present in the specimen, which may mean they were lost after Welles' description. However, he notes a fibula is present, which is not mentioned by Welles. Tykoski further states the cervical ribs of UCMP 77270 are not fused to their vertebrae, contra Welles and Pickering. Irmis (2007) referred it to D. wetherilli and noted it had closed dorsal and proximal caudal neurocentral sutures, unlike the holotype. Madsen and Welles (2000), Yates (2005), Sampson and Witmer (2007), Smith et al. (2007) and Carrano and Sampson (2008) all assigned it to D. wetherilli without comment.

UCMP 77270, intended holotype of Dilophosaurus "breedorum"- A skull; B braincase in ventrolateral view; C atlas and axis; D fifth cervical in lateral top, anterior left, posterior right and ventral bottom views; E sixth cervical; F ninth cervical in lateral, anterior and posterior views; G tenth cervical in lateral, ventrolateral, anterior and posterior views; H ninth, tenth and eleventh dorsals; I scapulocoracoid (all after Welles and Pickering, 1995; A, H and I modified).

Welles and Pickering diagnosed Dilophosaurus "breedorum" compared to D. wetherilli using several characters. Assessing their validity is made difficult by UCMP 77270 being older than the types (based on neurocentral fusion if nothing else) and some of Welles' (1984) description being based on casted features of the type patterned after Allosaurus. "Two, very thin, markedly developed parasagettal crests composed of the nasals + lacrimals + prefrontals" is also true in D. wetherilli, except that the participation of the prefrontals (on the medial surface) is uncertain due to UCMP 37302's crests being crushed together. Welles and Pickering later list the prefrontal participation as a separate autapomorphy. The dental formula only differs in having two more maxillary teeth and one less dentary tooth, which is usual individual variation in theropods. Welles and Pickering claim a separate postfrontal ossification is present in "breedorum", but state "the sutures are not obvious, and it could be absent or fused with the postorbital." Also they note the area in D. wetherilli is badly crushed, so this has little value as an apomorphy. The authors describe a deep groove along the posteroventral edge of the postorbital, which sounds similar to the condition in most megalosauroids (though I'm not sure if theirs also extends on to the posterior process). The quadratojugal has a posterolateral sulcus above the quadrate condyles and below the paraquadrate foramen. Both of these features are apparently different from the wetherilli holotype, but their significance is uncertain. Finally, Welles and Pickering state the cervical ribs are fused to their vertebrae (contra Tykoski), but this varies ontogenetically in "Megapnosaurus" kayentakatae anyway so would not be unexpected in an old Dilophosaurus individual. Being a Welles paper, most elements also include comparisons to their counterparts in D. wetherilli and other taxa. Most of these differences seem minor, though several support an adult stage of development- more elongate premaxilla, quadratojugal fused to quadrate, atlantal centrum and axial intercentrum fused to axis, deeper cervical pleurocoels, scapulocoracoid fusion, iliopubic fusion, trochanteric shelf present. Tykoski (2005) also noted other adult characters lacking in the holotype- various braincase and intersacral fusions, ilium fused to the sacrum, proximal femoral articular surfaces well developed, medial femoral epicondyle well developed, and an oblique ridge on the proximomedial fibula. Additionally, sacral central fusion was present as noted by Welles and Pickering. According to Tykoski, the interdental plates are unfused and tall in UCMP 77270 and TMM 43646, but that they are fused in UCMP 37302 and 37303. These differences cannot be explained by ontogeny and are not subject to individual variation in other taxa as far as I know. While they and some of the differences noted by Welles might suggest multiple species of Kayenta Dilophosaurus, other theropods known from large numbers of specimens (e.g. Allosaurus, Tyrannosaurus, Microraptor, Archaeopteryx) also show a high amount of morphological variation. I follow my recommendations for those taxa and only recognize a single species of Dilophosaurus, with UCMP 77270 simply being an older individual of D. wetherilli.
References- Welles, 1970. Dilophosaurus (Reptilia: Saurischia), a new name for a dinosaur. Journal of Paleontology. 44, 989.

Welles, 1984. Dilophosaurus wetherilli (Dinosauria, Theropoda): Osteology and comparisons. Palaeontographica Abteilung A. 185, 85-180.

Gauthier, 1986. Saurischian Monophyly and the Origin of Birds. Memoires of the California Academy of Sciences. 8, 1-55.

Paul, 1988. Predatory Dinosaurs of the World. Simon and Schuster, New York. A New York Academy of Sciences Book. 464 pp.

Charig and Milner, 1990. The systematic position of Baryonyx walkeri, in the light of Gauthier's reclassification of the Theropoda. in Carpenter and Currie (eds.). Dinosaur Systematics: Approaches and Perspectives. Cambridge University Press, Cambridge. 127-140.

Rowe and Gauthier, 1990. Ceratosauria. In Weishampel, Dodson and Osmolska (eds.). The Dinosauria. University of California Press, Berkeley, Los Angeles, Oxford. 151-168.

Pickering, 1995. Jurassic Park: Unauthorized Jewish Fractals in Philopatry. A Fractal Scaling in Dinosaurology Project, 2nd revised printing. Capitola, California. 478 pp.

Welles and Pickering, 1995. An extract from: Archosauromorpha: Cladistics and osteologies. A Fractal Scaling in Dinosaurology Project. 70 pp.

Olshevsky, DML online 1999.

Madsen and Welles, 2000. Ceratosaurus (Dinosauria, Theropoda) a revised osteology. Miscellaneous Publication 00-2, Utah Geological Survey. 80 pp.

Gay, 2005. Sexual dimorphism in the Early Jurassic theropod Dilophosaurus and a comparison with other related forms. In Carpenter (ed.). The Carnivorous Dinosaurs. Indiana University Press. 277-283.

Tykoski, 2005. Anatomy, ontogeny and phylogeny of coelophysoid theropods. PhD Dissertation. University of Texas at Austin. 553 pp.

Yates, 2005. A new theropod dinosaur from the Early Jurassic of South Africa and its implications for the early evolution of theropods. Palaeontologia Africana. 41, 105-122.

Mason, 2006. The thrill of the frill: Wear and tear demands restoration of a Dilophosaurus wetherilli skull, UCMP 77270. Journal of Vertebrate Paleontology. 26(3), 96A.

Irmis, 2007. Axial skeleton ontogeny in the Parasuchia (Archosauria: Pseudosuchia) and its implications for ontogenetic determination in archosaurs. Journal of Vertebrate Paleontology. 27(2), 350-361.

Sampson and Witmer, 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. in Sampson and Krause (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. SVP Memoir 8. 32-102.

Smith, Makovicky, Hammer and Currie, 2007. Osteology of Cryolophosaurus ellioti (Dinosauria: Theropoda) from the Early Jurassic of Antarctica and implications for early theropod evolution. Zoological Journal of the Linnean Society. 151, 377-421.

Carrano and Sampson, 2008. The phylogeny of Ceratosauria (Dinosauria: Theropoda). Journal of Systematic Palaeontology. 6, 183-236.