Sunday, November 9, 2014

SVP 2014 Day 4

Brink et al. have a poster on Bathygnathus, which I blogged about here as an ex-theropod.  Turns out Case was right in 1905 that it belongs to Dimetrodon, as Brink et al. found it to be nested within that genus and sister to D. grandis.  This is problematic, since Bathygnathus was named 25 years before Dimetrodon, so the ICZN will need to be petitioned if we are to retain the latter genus.

Zanno et al. present a poster on what was previously reported by Zanno (2008) as another Falcarius bonebed in the Cedar Mountain Formation of Utah, but which seems to be a more derived therizinosaur now.  Originally differences were thought to be ontogenetic, but size comparisons and histology disproved this.  In the new taxon, "the more prominent development of the altiliac condition of the ilium, large distal boot of the pubis measuring more than half the pubic length, relatively straight and acuminate symphyseal aspect of the dentary, reduced recurvature of the dentary teeth, and marked ventral displacement of the mandibular condyle of the quadrate appear distinct."

Larson et al. performed a morphometric analysis of Dinosaur Park coelurosaur frontals, and found that supposed therizinosaur frontal CMN 12355 grouped with Troodon, so is troodontid instead.  Since Erlikosaurus wasn't included, I'm not sure how powerful this analysis is however.  They say CMN 12355 "shares the following features with Troodon: a shallow lateral wall defining the fossae for the olfactory system, the exclusion of the supratemporal fossa from the dorsal surface of the frontal, and a raised orbital rim."  Yet Erlikosaurus also has a shallow lateral olfactory wall (Lautenschlager et al., 2014), both therizinosaurs and troodontids are polymorphic for raised orbital rims (e.g. present in Falcarius and the Nanchao therizinosaur embryo, absent in Sinornithoides), and Troodon, Erlikosaurus and CMN 12355 all have dorsal exposure of the supratemporal fossa.  They further state CMN 12355 "differs from the holotype of Erlikosaurus (IGM 100/111) in the construction of the lacrimal-frontal joint", and indeed the prefrontal-frontal articular surface in Erlikosaurus (which doesn't even have lacrimal-frontal contact) isn't exposed dorsally, unlike the contact in Troodon and CMN 12355.  In comparing them myself, CMN 12355's orbital outline resembles Erlikosaurus more, but the supratemporal fossae are intermediate in their separation.  Ventrally, the less anteriorly expanded olfactory bulbs and more posteriorly expanded cerebral fossae are similar to Troodon, but the prefrontal/lacrimal facet is placed far more anteromedially then in either Troodon or Erlikosaurus.  So in the end I'm not convinced either way, and think CMN 12355 might belong to something else entirely.  Larson et al. state "this removes the only record of a therizinosaur from the well-sampled Campanian-Maastrichtian fossil record of North America, suggesting the extinction of this group in North America prior to the Campanian,", but besides two more Dinosaur Park frontals referred to therizinosaurs by Currie (1992, 2005), there's also the pedal ungual RTMP 79.15.1 he mentions.  Ryan and Russell (2001) list a cervical from the Scollard Formation of Alberta (RTMP 86.207.17), and Russell (1984) reported a therizinosaurid astragalus from the Hell Creek Formation of Montana.  So maybe these other records are misidentified too, but there's more work to be done before we can reach Larson et al.'s conclusion.

Supposed therizinosaur or troodontid frontal CMN 12355 (after Sues, 1978).  Ventral (left) and dorsal (right) views.

Allain reports a new Ichthyovenator specimen which preserves "the complete cervical skeleton and the first dorsal vertebra, as well as the left pubis, seven additional caudal vertebrae and three teeth."  Interestingly, "the first dorsal vertebra of Ichthyovenator is nearly identical to the holotypic vertebra of the enigmatic theropod Sigilmassasaurus brevicollis", so there's more evidence Sigilmassasaurus is Spinosaurus.  "In addition to the peculiar morphology of posterior cervical and anterior dorsal vertebrae, the straight unserrated crowns of the teeth of Ichthyovenator suggest it is more closely related to Spinosaurinae than previously thought."  Since my analysis including Ichthyovenator in partially corrected versions of Allain et al.'s and Carrano et al.'s matrices found it to take 0-2 more steps to be a spinosaurid than a carnosaur, and this new data provides those extra steps, I now agree the genus is spinosaurid and possibly spinosaurine.

McFeeters et al. do a rather cool thing and examine reports of ornithomimids from Foremost, Oldman and Milk River Formations of Western North America.  They find pedal material from the Foremost and Oldman Formations, but the older Milk River and Foremost Formations have no definite ornithomimid material.  Previously reported and catalogued material from there is indeterminate or misidentified, with "the only described specimen previously referred to Ornithomimidae" (I assume the RTMP pedal phalanx reported by Ryan and Russell in 2001 the CMN pedal phalanx in plate II figure 10 of Russell, 1935) being more similar belonging to probable Orodromeus synonym "Laosaurus" minimus a 'basal ornithopod' (so probably a thescelosaurid)The lead author notes below in a comment it is also similar to a phalanx referred to Elmisaurus though, so its identity remains uncertain for now.  They suggest "the Late Cretaceous ornithomimid clade did not migrate into Laramidia until the beginning of the Late Campanian", which is possible, but I wonder just how much Foremost and Oldman material they found.  After all, I'd say ~ 99% of paravian remains from these sediments are teeth, so remains of toothless taxa like ornithomimids are going to be rare by default and might not have been collected yet if the sample size is low.  But if later formations preserve many thescelosaurid and ornithomimid pedal elements and earlier formations only preserve many thescelosaurid pedal elements and no ornithomimid ones, the statistical argument seems valid.

Lu et al. (misspelled as La in the abstract book) report yet another new oviraptorid from the Nanxiong Formation in addition to the prefix-triangle of Ganzhousaurus nankangensis, Nankangia jiangxiensis and Jiangxisaurus ganzhouensis, as well as the juvenile Banji long.  These all actually fall out in different parts of the tree in the Lori analysis, and at least three do in the Anzu analysis, so maybe they're all valid.  This new taxon is known from a partial skeletopn with incomplete skull and mandible and is "characterized by an anterodorsally sloping occiput and quadrate (shared with Citipati), a small circular supertemporal fenestra (much smaller than the lower temporal fenenstra), and the dorsal margin of the dentary above the external mandibular fenestra is strongly concave ventrally."  In what I assume is a version of the Maryanska et al. analysis used in all current oviraptorosaur papers, it falls out sister to Citipati.  This matches one of the named Nanxiong species in the Lori analysis, so maybe we finally have a synonymy.  Might I suggest we start a new prefix-triangle and name this one 'Longia nanxiongia', then the next named species can be 'Nanxiongsaurus banjiensis'.

Button et al. have a poster on a new coelurosaur found in 2012 what was originally listed as "Ornithomimidae? new genus and species" by Kirkland et al. in 1998 from the Mussentuchit Member of the Cedar Mountain Formation of Utah.  Turns out this is an "associated right hind limb consisting of a partial femoral shaft, nearly complete tibia, distal two-thirds of metatarsal IV, and pedal phalanges IV-2 and IV-4."  While arctometatarsalian, "metatarsal IV most resembles Coelurus (YPM 2010) from the Upper Jurassic Morrison Formation in general proportion, mediolateral compression of the distal aspect, and near absence of a lateral collateral ligament pit, yet is unique in possessing an obliquely oriented groove marking the extensor surface and a dorsally bulbous distal condyle."  Is this an ornithomimosaur, coelurid, or something else like a troodontid?  Scheetz et al. had an SVP abstract in 2010 about a basal coelurosaur convergent on ornithomimosaurs from the Yellow Cat Member of this formation, but that has a non-arctometatarsalian pes, so may be unrelated.  We'll have to see.

Poust et al. present the tenth supposed new Jehol microraptorian species, D2933 from the Jiufotang Formation.  This "possesses several autapomorphies, including more than 29 tail vertebrae, inclined pneumatic foramina on the dorsal vertebrae, and an unusually large coracoid fenestra", and is supposedly sister to Sinornithosaurus  The Cryptovolans holotype has 28-30 caudals, other Microraptor specimens often have about 26, and no complete tail is known in described Sinornithosaurus.  While the Microraptor hanqingi specimen lacks inclined dorsal pleurocoels (I assume that means anterodorsally oriented), we don't know the condition in any other described microraptorian specimen.  Finally, I don't know how big the supracoracoid fenestra is in D2933, but Sinornithosaurus specimens have fenestrae varying in size between 27 and 35 percent of coracoid height.  Poust et al. state "all visible neurocentral sutures, and proximal tarsals remain unfused. The porous surface texture of the cortical bone and poor ossification of long bone articular surfaces further supports an immature status. Histologic samples of the tibia, fibula, and humerus confirm that it was about one year old and still growing at death."  As D2933 is smaller than Sinornithosaurus, differences could be ontogenetic, and indeed increased ossification with age could shrink the supracoracoid fenestra's size.  It has "filamentous feathers, pennaceous feathers extending from the fore- and hindlimbs, and two long plumes extending more than 12 cm beyond the caudal series", which the authors contrast with Sinornithosaurus that shows "only branching filamentous feathers."  They propose "that this simplified condition is a secondary loss of feathers, either as a feature of the genus [Sinornithosaurus], or as part of an ontogenetic loss of 'advanced' feather types in adults."  Or maybe it's taphonomic, as described Sinornithosaurus specimens are disarticulated.  Much as with Lefevre et al.'s talk, I think we need a Lagerstatten rule for dinosaurs- 'Do not ascribe to phylogeny that which can be explained by taphonomy'. 

Kobayashi et al. present a poster on what I assume is a specimen of "Gallimimus" mongoliensis that's basically identical to their 2007 SVP abstract, so I hope we see this taxon published soon.

Gerke and Wings have an interesting study of Late Jurassic German theropod teeth.  "Four Langenberg Quarry teeth, previously assigned to velociraptorine dinosaurs, are removed from Dromaeosauridae and regarded as belonging to Tyrannosauroidea, Neotheropoda and Megalosauridae based on their dental characters."  Maybe their DFA analysis could be used to classify other supposed dromaeosaur teeth that plague studies depending on Dinosaur Park morphologies.  

Malafaia et al. present information on a new Lourinha megalosauroid specimen represented by "several cranial fragments including an incomplete left maxilla."  Several characters differ from Torvosaurus, known there from T. gurneyi.  So this may be Lourinhanosaurus, which is coelurosaurian in Carrano et al.'s tetanurine matrix partly due to miscoding it as lacking a pubic obturator fenestra.

Velocipes guerichi holotype proximal fibula in a (lateral), b (posterior), c (medial) and d (anterior) views, with proximal view on top and cross sections at right (after Huene, 1932).
Czepinski et al. had a poster on Triassic dinosaurs from Poland, which is one of my favorite kinds of papers- reevaluating historical taxa.  Middle Triassic supposed dinosaurs can't even be referred to Dinosauromorpha, but "new analysis of the Velocipes guerichi holotype from Kocury site (Silesia) suggests that it is probably the proximal part of an elongated and flattened fibula of a neotheropod dinosaur."  So Huene was right 80 years ago, whereas Rauhut and Hungerbuhler (2000) listed it as Vertebrata indet.?!  Because it was plausibly a fish?  One negative effect of cladistics is that some authors (Nesbitt et al., 2007 *cough*) only use characters coded in an analysis to classify specimens, when plenty of other differences exist between clades.  I'm glad Czepinski et al. didn't follow this method.  Now we just need a good reexamination of Avipes, Dolichosuchus and Halticosaurus.

That's it for SVP 2014.  Hope you enjoyed my theropod rundown. 

Edit: Thanks to Brad McFeeters for correcting some of the information here, with the corrected info bolded above and the original wrong text crossed out.  It's like peer review for blogs. :)

Saturday, November 8, 2014

SVP 2014 Day 3- drepanosaurs and sauropods

Okay, it's become apparent this day by day format is flawed because similar talks are grouped together at SVP.  This year, basically all of the interesting theropod talks/posters were on Wednesday and Saturday.  So tomorrow's post should be huge, but here's a couple interesting of ones from today.

Pritchard and Nesbitt report on a 3D drepanosaur braincase from the Ghost Ranch quarry.  Many of its characters "are surprisingly plesiomorphic (e.g., squamosal with massive descending process, quadrate lacking posterior concavity, occipital condyle with notochordal pit), sharing more in common with non-saurian diapsids than early archosauromorphs."  "A phylogenetic analysis of 300 characters and 40 early diapsids supports the hypothesis that drepanosaurs fall outside of Sauria."  Wouldn't it be funny if pterosaurs were related to drepanosaurs, and thus non-saurians convergent on archosaurs?  Even crazier than them being lizards.  Also relevant is Paul's (2002) idea Protoavis' type braincase is from a drepanosaur, but Protoavis lacks a ventral squamosal process or a notochordal pit, though its quadrates are straight to slightly concave.  So the braincase still seems closest to derived theropods.

Madzia and Borsuk-Bialynicka have a talk titled "New sauropod material from the Nemegt Formation supports the conspecificity of Opisthocoelicauda skarzynskii and Nemegtosaurus mongoliensis."  That's an idea Paul supported in his 'field guide', but has generally been considered unlikely to undemonstrable given known remains- a skull for Nemegtosaurus and skeleton lacking neck and skull for Opisthocoelicaudia.  Alas, this presentation only says two caudal centra and five pedal unguals were found in the Polish-Mongolian expedition collections, from three different sites in the Nemegt.  The unguals "strongly resemble those of O. skarzynskii in their crescent-shaped morphology, great bilateral flattening, and generally subtriangular cross-sections adjacent to their proximal articular surfaces", while the centra "are slightly opisthocoelous and subcircular in cross-section."  That's great, but are other titanosaur unguals different?  Nor is Opisthocoelicaudia the only titanosaur with opisthocoelous caudals.  See Borealosaurus for instance.  They say "Since the postcranial elements provide no evidence for the presence of more than one titanosaur in the mid- Maastrichtian of the Nemegt Formation, there is no reason to assume that the type of N. mongoliensis belongs to a different species."  This is highly flawed reasoning.  We have at best three caudal specimens including the Opisthocoelicauda holotype.  The likelihood all three are from one species if two species lived there is pretty high, 25% if my vestigial stat skills are correct (if they were equally abundant, equally likely to be fossilized there, etc.).  Just look at another case of large Nemegt dinosaurs- Deinocheirus and Tarbosaurus.  The ZPAL has 35 Tarbosaurus but only one Deinocheirus (well, none now since it was moved to the IGM).  Even if all of those caudals and unguals are diagnostically Opisthocoelicaudia and from different individuals, that's still only 8:1 for Opistho vs. Nemegt compared to 35:1 for Tarbo vs. Deino.

Friday, November 7, 2014

SVP 2014 Day 2

Continuing from yesterday...

Not a theropod talk, but something very cool indeed.  Does anyone remember Chatterjee's supposed pachycephalosaur domes from the Triassic Maleri Formation of India?  They've never been published, but he apparently mentioned them in his SVP 1998 talk "Dinosaurs in the land of gonds."  There was some talk about them on the DML in 2000 where Weinbaum says they "look exactly like" pachycephalosaur domes, and Olshevsky mentioned Goodwin would classify them as pachycephalosaurian if they were found in the Cretaceous.  Indeed, Goodwin is listed as working with Chatterjee on Indian pachycephalosaurs in the latter's CV.  Well it looks like the mystery has been solved.  Stocker et al. report finding a basal archosauriform from the Dockum Group with a dome convergent with pachycephalosaurids.  "Like pachycephalosaurs, this Triassic specimen preserves a thickened and domed skull roof with obliterated cranial sutures, an expanded posterior margin of the skull (a synapomorphy of Marginocephalia), and large orbits."  They don't mention the Maleri specimen, but the connection seems obvious.  How ironic this was found in the Dockum, where Chatterjee did tons of work.

Makovicky et al. have a poster on dinosaurs from the Mussentuchit Member of the Cedar Mountain Formation in Utah and report on the partial skeleton of a giant oviraptorosaur.  They say "a midcaudal vertebra is highly pneumatic, and a series of four distal caudals form a pygostyle-like structure", so it's probably a caenagnathoid or close relative.  This is interesting, as the material is Albian, so is earlier than known caenagnathoids.  Because Macroelongatoolithus shells were found close by, the presenters think it may belong to this taxon.

Again not theropodan, but just amusing.  On page 137, Gerwitz and Green had an abstract about change in size throughout time in Florida deer bones, but there's a huge WITHDRAWN plastered over it.  Apparently it was supposed to be a poster on Thursday.  I've never seen a withdrawn presentation at SVP, and wonder what the story is behind what seems like an innocuous statistical study.

Good thing I padded this entry, since it seems Thursday was basically bereft of Mesozoic theropod talks.  In other news, I finished coding Deinocheirus today and it emerged in a different position than found by Lee et al. or Andrea's post.  Maybe the Angeac taxon or Datanglong will affect things, so I'm adding them now.

Thursday, November 6, 2014

SVP 2014 Day 1

Hi everyone.  Sorry about the lack of posts- coding ornithomimosaurs in the Lori matrix.  We'll see where Deinocheirus ends up.  Also, that new Erlikosaurus cranial description with fully rotatable 3D elements that you can separate and view any cross section of- coolest theropod osteology ever.  Everyone should be doing that with their material.  But hey, SVP started.  No, I'm not in Berlin, but I figured I'd report on cool theropod abstracts.  The embargo states we can't post about them until the talks have been given, and it's now Thursday in Berlin, so let's cover Wednesday's interesting talks and posters.

Dyke et al. are presenting on Balaur being an avialan instead of a dromaeosaurid, which I agree with.

Rauhut and Foth suggest Juravenator has "a number of characters shared with basal theropods, such as the presence of a posterior pleurocoel in the cervical vertebrae, a lateral brevis shelf that is continuous with the supraacetabular crest and a well-developed antitrochanter in the pelvis..."  Very interesting.  Those are ceratosaur-grade characters, which would make it even more basal than the supposedly megalosauroid Sciurumimus.  They say "Recently discovered casts [of the Compsognathus longipes holotype] show that the specimen is better preserved than first described and provide new data on its morphology, indicating that it is not the same taxon as the French Compsognathus."  I'd love a redescription since Ostrom's 1978 publication, but I think these Lagerstatten theropods are always oversplit, so color me doubtful.  Especially since they say Archaeopteryx "includes probably at least three, and as many as four to five species."

Speaking of which, Kundrat et al. CT scanned the Daiting (8th) Archaeopteryx specimen and found "the internasal and interfrontal sutures are obliterated in the Daiting specimen in contrast to the Eichstätt and Thermopolis specimens which are of similar size. This and numerous other cranial features that distinguish the Daiting specimen from the other specimens of Archaeopteryx suggest that it may represent a new species."  We'll have to see what those numerous other features are, and the fact the Daiting specimen is from a younger formation than the others gives some a priori reason to expect a new species, but sutures are often destroyed by taphonomy (e.g. Apsaravis' apparent notarium), so I'll need better evidence than that considering how crushed the skull is.

Lefevre et al. report three new paravian specimens from the Tiaojishan Formation of China, the same formation as Anchiornis, Aurornis, Eosinopteryx and maybe Xiaotingia.  All of these emerge as basal Avialae in their analysis, though at least one is stated to have troodontid characters, and we know how easily all of these Tiaojishan taxa switch positions.  Interestingly, Eosinopteryx is said to be immature based on histology despite the original description stating "the holotype of Eosinopteryx had reached a late ontogenetic stage (subadult or adult): neurocentral sutures are closed on all exposed vertebrae and the suture between the astragalus–calcaneum complex and the tibia cannot be discerned."  I'd caution again that taphonomy can hide sutures, and think that the situation here will prove similar to the Solnhofen one- the specimens will all be different from each other in ways that suggest individual and ontogenetic variation.  If not ontogenetic, the plumage variations are bound to be taphonomic.  The Lori analyses does suggest one of these taxa is distinct and not what we think it is, but that will have to wait...

Stiegler et al. (with Xu as a coauthor) state "Optimization of manual characters suggests that the manual morphology of Limusaurus is unlikely to be representative of the averostran ancestor as previously hypothesized."  Which might translate as 'we were wrong that the reduced manual digit I means tetanurines lost digit I', and yet they say "we argue that the presence of bilateral digit reduction in Limusaurus and other ceratosaurs remains a key piece of evidence for understanding theropod digit homologies."  So from the abstract, that sounds like saving face.

Foth et al. say that in Sciurumimus, "Along the dorsal side of the tail the skin is decayed, revealing a horizontal meshwork of thick, short, wrinkly filaments overlain by an outer skin layer. Due to their different morphology and different luminescence, we interpret these filaments as remains of collagen fibers from the dermis, covered by epidermis, rather than as feathers."  See, Lingham-Solier-  collagen can be preserved, but it's not feathers.  Wish the guy would buy a high-resolution camera.

Funston and Currie reveal Elmisaurus rarus has a cranial crest, and agree with me that Leptorhynchos is unnecessary.

Tanaka et al. present a poster on the Japanese hesperornithine.  Seems it would fall within Hesperornis sensu lato as far as the Database is concerned.

Dal Sasso et al. present a poster on new cranial remains of Razanandrongobe, which suggest it's a basal mesoeucrocodilian.  One more potential theropod down.

Holtz et al. have a poster which includes a new probable Anzu specimen from the Hell Creek of Montana.  It "includes distal hindlimb, pelvic elements, dorsal ribs, and caudal vertebra. Given the origination of these bones relative to the local outcrop, it seems quite likely that more the skeleton is preserved and is slated for field recovery."  Excellent.

Thursday info coming next...

Wednesday, September 17, 2014

No giant Egyptian Deltadromeus

The Spinosaurus news has led to me reviewing the African mid Cretaceous taxa on the Database.  This means I've been working my way through the untranslated Stromer (1934), which describes Spinosaurus B and Bahariasaurus among other theropod remains. The result is that what I thought I knew about the supposed giant Deltadromeus remains described there is wrong.  The recent literature would have you believe it's a partial skeleton (Carrano and Sampson, 2008) identical (Sereno et al., 1996) to the Deltadromeus holotype.  Not so.

Sereno et al. (1996) referred the Baharija 'IPHG 1912 VIII' (described by Stromer, 1934) to Deltadromeus, specifying a coracoid, pubes, femur, proximal tibia and fibula as the material. Yet this specimen number corresponds to 32 specimens described by Stromer. The coracoid IPHG 1912 VIII 60 was associated with a scapula that shares that number, the femur is IPHG 1912 VII 69 based on the size Sereno et al. reported, and the fibula must be IPHG 1912 VIII 70 as no others are reported. Yet the pectoral girdle was found in layer m while the femur and fibula were found in layer p. The only proximal tibia reported is IPHG 1912 VIII 78, which is far too small to belong with the other hindlimb elements and from a different locality. Finally, the only pubes with that number are IPHG 1912 VIII 81, which are from yet another locality and much smaller than even the tibia. This materials list agrees with Carrano and Sampson, though note contrary to their statement, it is not a "partial postcranial skeleton". Stromer used the pubes as a paratype of Bahariasaurus, questionably referred the pectoral girdle, femur and fibula to the taxon as they cannot be compared to the holotype, and referred the tibia to aff. Erectopus. Thus all material was not referred to Bahariasaurus, contra Sereno et al..

Comparison of Baharija elements on the left to Deltadromeus holotype on the right, scaled to match in size.  From left to right- pectoral girdles in lateral view, proximal femora in lateral view, tibiae in proximal view, and proximal fibulae in medial view. Modified from Stromer (1934) and Sereno et al. (1996).

The Baharija pectoral girdle actually lacks the anteroposterior expansion considered diagnostic for Deltadromeus by Sereno (length excluding posteroventral process 117% of height vs. 150% in Deltadromeus), which is also found in Elaphrosaurus and Limusaurus. Due to breakage of the posteroventral process, it's uncertain if the coracoid's subacromial notch ('notch in anterior margin' of Sereno et al., as it is the only notch in Deltadromeus' coracoid) is shallow as in Deltadromeus or deeper as in Elaphrosaurus and Limusaurus. Though again, a shallow notch might not be diagnostic of Deltadromeus as it is also found in Ceratosaurus. The pectoral girdles also differ in other ways if scaled to similar overall size, with Deltadromeus having a narrower scapular shaft, a more abruptly expanded acromion, smaller glenoid, and deeper posteroventral process.

Sereno et al. also diagnose Deltadromeus based on its "accessory trochanter" on the distal femoral shaft, which is presumably the mediodistal crest anteriorly. This is common in basal theropods like ceratosaurs (e.g. Berberosaurus, Elaphrosaurus, Limusaurus), but rarer in Coelurosauria which Sereno et al. referred Deltadromeus too. The development of the mediodistal crest is unclear in the Baharija femur. Carrano and Sampson (2008) equated the "accessory trochanter" of Sereno et al. to the M. adductor femoris 1 insertion scar on the posteromedial distal shaft, but this region is unillustrated in the Baharija femur. Finally, the Bajarija femur does have an anterior process on the lateral margin of its medial condyle, stated as diagnostic of Deltadromeus and hinted at in Sereno et al.'s skeletal reconstruction. Carrano and Sampson equated this with the mediodistal crest discussed above, but that projects largely laterally so is probably not the feature Sereno et al. had in mind. While the anterior process could indicate a relationship between the Baharija femur and Deltadromeus, the latter differs in having a fully medially oriented head and an anterior trochanter that extends distally to the fourth trochanter. The Baharija femur is 165% the size of Deltadromeus, which could lead to questions of ontogenetic change, but neither of these characters are known to change ontogenetically in theropods, and they would leave the older specimen with the more basal morphology, which is unlike at least some theropods (tyrannosaurids, dromaeosaurids).

The tibiae are more similar to each other than to Elaphrosaurus, Camarillasaurus, Ceratosaurus or Eoabelisaurus in proximal view (the only available for Deltadromeus), with Deltadromeus differing in having a smaller, triangular posterior groove and larger lateral condyle. The fibulae are roughly similar, though Deltadromeus has a more projected anteroproximal corner and a proximomedial fossa that is less proximally extensive. The supposed pubes of Deltadromeus are actually ischia (Longrich pers. comm. and DML; Carrano and Sampson, 2008), so cannot be compared to the Baharija pubes.

Thus in total, the pectoral girdle and femur are near certainly not Deltadromeus (contrary to Sereno et al.'s claim the remains are identical), the tibia and fibula could be although no described apomorphies are shared, and the pubes cannot be compared. Coincidentally only the pubes can be compared to Bahariasaurus, though they differ markedly from that taxon*. This makes it quite possible Stromer was right in referring the pectoral girdle and femur to Bahariasaurus, and also possible the tibia and fibula belong to that genus. It also may make it more likely the pubis does belong to Deltadromeus, which might get support from study of its undescribed pubic fragments. Because none of the Bajarija material can be said to be more similar to Deltadromeus than the sympatric Bahariasaurus and some are certainly not Deltadromeus, none should be referred to either genus. This also eliminates any evidence Deltadromeus reached gigantic sizes, as there is no evidence the holotype is immature and the completely fused ischial boot would argue against this.

* Bahariasaurus has a less conspicuous and more proximally placed lateral flaring (15% down the shaft, compared to 21%), the distal end is not flared laterally, there is an extensive separation of the pubic shafts distally, and the interpubic foramen is more distally placed (80% down the shaft, vs. 71%).

References- Stromer, 1934. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltierreste der Baharije-Stufe (unterstes Cenoman). 13. Dinosauria. Abhandlungen der Bayerischen Akademie der Wissenschaften Mathematisch-naturwissenschaftliche Abteilung, Neue Folge. 22, 1-79.

Sereno, Dutheil, Iarochene, Larsson, Lyon, Magwene, Sidor, Varricchio and Wilson, 1996. Predatory dinosaurs from the Sahara and Late Cretaceous faunal differentiation. Science. 272(5264), 986-991.

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

Thursday, September 11, 2014

Spinosaurus surprise

This is a post to discuss some implications of today's huge Spinosaurus reboot by Ibrahim et al. (2014).

What a cool and unexpected morphology.  Stromer was right about the tiny pelvis all along!  With Sigilmassasaurus and bone taxa G, I and J of Russell (1996) as Spinosaurus, we have so much more data now.  Seems Lapparent (1960) had a lot of Spinosaurus material in his Carcharodontosaurus referred specimens (manual phalanx and pedal ungual from Alrar; manual ungual from Dijoua; pedal ungual from from In Abangarit).  These would have been the first Spinosaurus specimens described after Stromer's work and the destruction of the originals in WWII.

MNNHN specimens of Spinosaurus described as Carcharodontosaurus by Lapparent (1960).  1- Distal manual phalanx from Alrar, Algeria initially misidentified as a metatarsal. 11- Manual ungual from Dijoua, Algeria.  12- pedal ungual from Alrar, Algeria.  From Lapparent (1960).

Also interesting is that Medeiros and Schultz (2002) described two caudals from the Alcantara Formation of Brazil as Sigilmassasaurus.  Now that we know these are spinosaurid, they're probably the first postcrania of Oxalaia

Distal caudal vertebra UFMA 1.10.240 probably referrable to Oxalaia, described by Medeiros and Schultz (2002) as Sigilmassasaurus.  From Medeiros and Schultz (2002).

Finally, with the differences noted by Russell between Kem Kem and Baharija 'Sigilmassasaurus', and those visible between the Kem Kem neotype and Baharija Spinosaurus B, it seems possible the aegyptiacus neotype is not conspecific with the Baharija aegyptiacus holotype.  Awkward.  Interestingly, Russell viewed the Kem Kem form as more derived, and this matches some aspects of Ibrahim et al.'s figure S2 comparison between Spinosaurus B and the neotype- the neotype has a narrower distal femur with more elongate condyles (A below), and flatter pedal unguals (D below).  Was it more adapted to swimming than the Baharija Spinosaurus?

Comparison of Baharija Spinosaurus B (IPHG 1922 X45) in yellow with Kem Kem Spinosaurus aegyptiacus neotype (FSAC-KK 11888) in gray.  After Ibrahim et al. (2014).

References- Lapparent, 1960. Les dinosauriens du "Continental intercalaire" du Sahara central. Memoirs of the Geological Society of France. 88A, 1-57.

Russell, 1996. Isolated dinosaur bones from the Middle Cretaceous of the Tafilalt, Morocco. Bulletin du Muse'um national d'Histoire naturelle. 18, 349-402.

Medeiros and Schultz, 2002. A fauna dinossauriana da Laje do Coringa, Cretáceo médio do Nordeste do Brasil. Arquivos do Museu Nacional. 60(3), 155-162. 

Ibrahim, Sereno, Dal Sasso, Maganuco, Fabbri, Martill, Zouhri, Myhrvold and Iurino, 2014. Semiaquatic adaptations in a giant predatory dinosaur. Science. DOI: 10.1126/science.1258750

Monday, May 26, 2014

Is Thecocoelurus an ornithomimosaur?

Allain et al. (2014) recently claimed Thecocoelurus, a small partial theropod cervical vertebra from Early Cretaceous England, is "morphologically identical" to an undescribed supposed ornithomimosaur from the Early Cretaceous of France (from here on called the Angeac taxon).  After reading Andrea Cau's post on the topic, I decided to do some in depth comparison.

Besides the Angeac taxon, Thecocoelurus has been compared to several taxa with surprisingly similar cervical vertebrae- caenagnathids (Naish et al., 2001; Naish and Martill, 2002); Falcarius (Kirkland et al., 2004; Zanno, 2010a); and noasaurids (Naish, 2011).  These all have elongate amphicoelous cervicals with low neural spines, anterior peduncular fossae, two pairs of pleurocoels and a transversely concave ventral surface defined by lateral ridges confluent with the parapophyses.  Which is most similar to Thecocoelurus?

Naish et al. (2001) and Naish and Martill (2002) both argue it is closer to oviraptorosaurs than to therizinosauroids based on the rounded pleurocoel and thin neural spine, but this is also the case in basal therizinosaurs (Falcarius, Jianchangosaurus) (as noted by Zanno, 2010a) and noasaurids. Naish (2011) on the other hand, felt "the idea that large caenagnathids were present in Western Europe during the Barremian is difficult to reconcile with what we know of oviraptorosaur biogeography and distribution", thus favored an abelisauroid identity (I suppose based on Genusaurus).  I'd argue basal oviraptorosaurs could and do have similar morphologies (e.g. the Early Cretaceous Similicaudipteryx) and that small theropod diversity in Cretaceous Europe is very poorly known. 

Allain et al. make two new comparative arguments for Thecocoelurus being closest to the Angeac taxon.
1. They distinguished both from Noasaurus based on their concave anterior central surface, but this is true in Masiakasaurus as well. It is also true of all coelurosaurs being compared.
2. They also paired Thecocoelurus with the Angeac taxon based on pneumatic foramina above the prezygapophyses which invade the neural arch. Yet these are present in cervicals 6-10 of Masiakasaurus (Allain et al. state they are "in a modified form" but don't elaborate), at least cervical 9 of Heyuannia, and in Conchoraptor and "Ingenia" (Lu, 2004; contra Allain et al.'s claim they are unknown in oviraptorosaurs). They are also only present on the left side of Thecocoelurus (pf? in figure below, lower left), further posterior than in at least Masiakasaurus and the Angeac taxon, perhaps suggesting breakage of a naturally hollow area or pneumatic asymmetry. The only preserved posterior cervical of Falcarius doesn't preserve this area, nor does the illustrated and best preserved cervical of Chirostenotes.

So let's compare!  Contra Naish and Martill, the specimen resembles posterior cervicals more than anterior ones, and indeed the supposedly identical Angeac vertebra matches the seventh or eighth of Harpymimus based on elongation, central articular surface orientation, prezygapophyseal length and orientation, etc. (contra Allain et al.).

Anterior half of posterior cervical vertebrae in (descending) right lateral, anterior, ventral and dorsal views.  From left to right- Thecocoelurus holotype (after Naish and Martill, 2002); Angeac taxon ANG 10/175 (after Allain et al., 2014); Falcarius UMNH VP 14657 (after Zanno, 2010b); Masiakasaurus FMNH PR 2481 (after Carrano et al., 2011); Chirostenotes or Epichirostenotes ROM 43250 (after Sues, 1997); Similicaudipteryx holotype (after He et al., 2008).

The elongate parapophyses resemble Falcarius, Chirostenotes and Similicaudipteryx more than Masiakasaurus or the Angeac taxon.
The anterior pleurocoels are placed in an obvious fossa, like Falcarius and the Angeac taxon, but unlike Masiakasaurus, Chirostenotes or Similicaudipteryx.
The infradiapophyseal fossa is developed as an elongate groove, as in Falcarius but unlike Masiakasaurus, the Angeac taxon, Chirostenotes or Similicaudipteryx.
The centrum is taller than wide (midline height / width minus parapophyses 133%) as in Falcarius (118%), but unlike the Angeac taxon (95%) and especially Chirostenotes (74%) and Masiakasaurus (64%).
The anterior peduncular fossae are well defined as in Chirostenotes and at least anterior Falcarius cervicals, but unlike Masiakasaurus or the Angeac taxon. They are however also well defined in anterior Masiakasaurus cervicals, so the condition in Falcarius isn't necessarily better than that genus or the Angeac taxon.
They are also placed far below the diagonal prezygapophyseal surface as in at least anterior Falcarius cervicals, but unlike the Angeac taxon, Chirostenotes or Masiakasaurus. The same could be said re: anterior Masiakasaurus cervicals.
The prespinal fossa is broad like Chirostenotes and Masiakasaurus but unlike the Angeac taxon.
It has anteroposteriorly broad exposure dorsally as in the Angeac taxon and at least anterior Falcarius cervicals, but not Masiakasaurus (including anterior cervicals of the latter).

Overall, Thecocoelurus is most similar to Falcarius and least similar to Masiakasaurus.  There are four good characters shared with Falcarius to the exclusion of the Angeac taxon, and three characters that are more similar to Chirostenotes than to the Angeac taxon, but two characters that are more similar to the Angeac taxon than to Chirostenotes.

Thecocoelurus holotype completed with the posterior of Falcarius (modified from Naish and Martill, 2002 and Zanno, 2010).  This results in a centrum length of 68 mm for Thecocoelurus, compared to Naish's (2011) estimate of 70-90 mm.

Falcarius does differ from Thecocoelurus in having a ventral median ridge on its centra, but this is an autapomorphy not seen in other therizinosaurs.  Besides this, no characters differ between the specimen except exact size and shape of pneumatic features, which themselves vary between right and left sides of Thecocoelurus.  Both are Barremian, and Thecocoelurus is 58% the size of the Falcarius individual that preserved the posterior cervical (though a growth series is known, where that individual falls is unreported).  Whether Thecocoelurus and Falcarius share derived characters to the exclusion of other therizinosaurs would require more study, but at the moment is seems most parsimonious to consider Thecocoelurus a basal therizinosaur and not closely related to the Angeac taxon.

References- Sues, 1997. On Chirostenotes, a Late Cretaceous oviraptorosaur (Dinosauria: Theropoda) from Western North America. Journal of Vertebrate Paleontology. 17(4), 698-716.

Naish, Hutt and Martill, 2001. Saurichian dinosaurs 2: Theropods. In Martill and Naish (Eds). Dinosaurs of the Isle of Wight. The Palaeontological Association. 242-309.

Naish and Martill, 2002. A reappraisal of Thecocoelurus daviesi (Dinosauria: Theropoda) from the Early Cretaceous of the Isle of Wight. Proceedings of the Geologists’ Association. 113, 23-30.

Kirkland, Zanno, DeBlieux, Smith and Sampson, 2004. A new, basal-most therizinosauroid (Theropoda: Maniraptora) from Utah demonstrates a Pan-Laurasian distribution for Early Cretaceous therizinosauroids. Journal of Vertebrate Paleontology. 24(3), 25-26.

Lu, 2004. Oviraptorid dinosaurs from Southern China. PhD Thesis. Southern Methodist University. 249 pp.

He, Wang and Zhou, 2008. A new genus and species of caudipterid dinosaur from the Lower Cretaceous Jiufotang Formation of Western Liaoning, China. Vertebrata PalAsiatica. 46(3), 178-189.

Zanno, 2010a. A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology. 8(4), 503-543.

Zanno, 2010b. Osteology of Falcarius utahensis: Characterizing the anatomy of basal therizinosaurs. Zoological Journal of the Linnaean Society. 158, 196-230.

Carrano, Loewen and Sertich, 2011. New materials of Masiakasaurus knopfleri Sampson, Carrano, and Forster, 2001, and implications for the morphology of the Noasauridae (Theropoda: Ceratosauria). Smithsonian Contributions to Paleobiology. 95, 53 pp.

Naish, 2011. Theropod dinosaurs. In Batten (ed.). English Wealden Fossils. The Palaeontological Association. 526-559.

Allain, Vullo, Le Loeuff and Tournepiche, 2014. European ornithomimosaurs (Dinosauria, Theropoda): An undetected record. Geologica Acta. 12(2), in press.