In another ornithischian abstract, Borinder et al. redescribe the hadrosaur Tanius. As the authors state, it's been 86 years since the genus was described. The only known specimen is immature and has a flexor canal on the femur. Unfortunately, it emerges in a big polytomy with other taxa just outside Hadrosauridae. I do wonder if excluding some of these nine taxa a posteriori might show some resolution between the remaining ones and Tanius.
|Cranial elements of Tanius sinensis holotype (after Wiman, 1929).|
Cuesta et al. argue that the ulnar bumps of Concavenator are homologous to the secondary remix attachment points of birds. This was disputed separately by Naish and myself shortly after the genus was described. I still don't see how the authors interpret the bumps as posterolateral instead of anterolateral. I argued the structure was an intermuscular line between the flexor ulnaris and the extensor carpi radialis brevis (sensu Meers, 2003), or flexor digitorum profundus and extensor carpi ulnaris (sensu Gishlick, 2002). Cuesta et al. state that (besides the triceps brachii which we both agree is back on the olecranon) they reconstructed the anconeus and abductor polices longus and that the bumps are not located between them. The abductor polices longus (pronator quadratus in Meers) is a more proximodorsally located scar I agree has nothing to do with the bumps. I think anconeus is another term for the extensor carpi ulnaris, based on Gishlick's figure of Corvus and Hudson and Lanzillotti's (1964) description. So with the caveats that there seems to be no consensus for muscle names or homology between crocodylians and birds, I don't think Cuesta et al. had the same muscles in mind as I did.
Fortner reports "parts of an associated postcranial skeleton of a small theropod dinosaur recently collected from the uppermost Aguja Formation." This is another frustrating example of the information-bereft abstract, with the first twelve lines devoted to introduction and background knowledge. The only other bit of information is- "The specimen exhibits some unique features, but is compatible with identification as either Troodontidae or Dromaeosauridae." This is very intriguing, as while both eudromaeosaur and troodontine teeth are known from the Aguja, we have Richardoestesia and Paronychodon from there too. As I think these are microraptorine and basal troodontid respectively, this specimen could fit the bill. Did anyone get more details?
Harding et al. have the non-dinosaurian abstract I think could be most important to dinosaur studies. They examined all "published characters for discriminating Sceloporus from the related iguanian lizards Uta and Urosaurus, and for discriminating among species of Sceloporus" for 14 species, "11 of [which] had more than ten individual skeletal specimens, and for four of them sample sizes exceeded 50 specimens." Perhaps astonishingly "almost all characters published in the literature to identify fossil specimens have no power to discriminate reliably between Uta, Urosaurus, and Sceloporus, nor between species of Sceloporus we examined." In our field where most species are only known from single specimens, and most known from multiple specimens don't have more than one or two described in detail, what does this mean for our autapomorphy lists?
Holtz et al. report more information on an Anzu specimen (anyone know the collection number?) they announced last year. Interestingly, only distal tarsal IV is fused to the unfused metatarsus, and "a pair of pronounced cruciate ridges on the plantar surface of metatarsal III" are present as in Elmisaurus but don't extend as far proximally. This would make it intermediate in pedal morphology between Chirostenotes and Elmisaurus.
Maddin et al. present a hypothesis based on the development of skull roof bones in mice and chickens. In mice (and axolotls) the suture between the frontal and parietal corresponds to the boundary between the neural crest and mesoderm in the embryo. In chickens, the latter embryonic boundary is within the frontal itself. Thus the authors suggest the avian 'frontal' is actually a fused frontal and parietal, while the avian 'parietal' is actually a postparietal. They say that hypothesis "is also supported phylogenetically where data from the fossil record reveal separate frontal, parietal, and postparietal bones are present in all stem lineages of extant taxa, including that of birds (e.g., the stem archosaur Euparkeria)." The problem I see is that the postparietal in basal archosauriforms is a tiny wedge between the parietals and supraoccipital, while the parietals have the same topological relationships and morphology in these basal archosauriforms that they do in basal dinosaurs. It seems more likely to me that this is a case like manual homology where the developmental process itself evolves, so that somewhere on the sauropsid line, the neural crest-mesoderm boundary moved into the frontal. Also interesting would be to know what the state in lepidosaurs and crocodylians is.
Mannion et al. redescribe the famous 'French Bothriospondylus' (MNHN coll.), presumably based on Moine's (1999) thesis. It's great that we're getting all of the historical Bothriospondylus material redescribed in the last decade.
McFeeters et al. do the important job of reevaluating Struthiomimus specimens. Little known to most, the holotype is extremely fragmentary, with most information coming from Osborn's AMNH 5339, Nicholls and Russell's UCMZ 1980.1 and the new RTMP 90.26.1. The authors find "a relatively small partial skeleton from the lower Dinosaur Park Formation" (which based on listed elements must be ROM 1970) to belong to a new taxon of ornithomimid based on several autapomorphies. This specimen forms the basis of the dorsal snout in Russel's (1972) and Paul's (1988) cranial reconstructions, making those composites. Another specimen shares some pelvic characters with Qiupalong, perhaps relating to a Dinosaur Park astragalus reported by McFeeters et al. in last year's SVP abstract.
Nesbitt et al. seem set to provide a detailed description of Asilisaurus, after the original tabloid announcement. Interestingly, Agnosphitys is said to a basal silesaurid as well, which is the fourth proposed identification for the genus. Add this to Agnolin's (2015) Jornadas Argentinas abstract proposing Pisanosaurus belongs to the clade, and its membership is expanding markedly.
We also get yet another description of Nothronychus' braincase. Far be it for me to complain about having too many descriptions of a taxon, but this one specimen of one taxon was described in 2005, 2012 and 2013, and now we'll probably get a fourth portion next year or so. At least this new abstract is about the previously unrecognized anterior portion, but I'd rather have that time and effort go towards... say "Zunityrannus" or describing the Bayan Shiree therizinosaur postcrania. Smith et al. report that "there is a supraorbital evagination in this specimen that is currently interpreted as accommodating a well-developed nasal gland in the frontal. This development has been observed in some other archosaurs, especially marine birds, where it is associated with salt excretion and is consistent with a beach or other evaporitic paleoenvironmental interpretation." So let's all start our All Yesterdays style marine therizinosaur pics.
Finally for this year, Sullivan et al. report a 'sphenosuchian' specimen sister to Junggarsuchus. This has the interesting mix of cursorial features with a webbed hand and distal tail sheathed with armor.
References- Wiman, 1929. Die Kreide-Dinosaurier aus Shantung. Palaeontologia Sinica (series C). 6, 1-67.
Hudson and Lanzillotti, 1964. Muscles of the pectoral limb in galliform birds. The American Midland Naturalist. 71(1), 1-113.
Walker, 1964. Triassic reptiles from the Elgin area: Ornithosuchus and the origin of carnosaurs. Philosophical Transactions of the Royal Society of London, seies B. 248(744), 53-134.
Russell, 1972. Ostrich dinosaurs from the Late Cretaceous of western Canada. Canadian Journal of Earth Sciences. 9, 375-402.
Paul, 1988. Predatory Dinosaurs of the World. Simon & Schuster: New York. 464 pp.
Sereno and Novas, 1993. The skull and neck of the basal theropod Herrerasaurus ischigualastensis. Journal of Vertebrate Paleontology. 13, 451-476.
Zinke and Rauhut, 1994. Small theropods (Dinosauria, Saurischia) from the Upper Jurassic and Lower Cretaceous of the Iberian Peninsula. Berliner Geowissenschaftliche Abhandlungen. E 13, 163-177.
Moine, 1999. Datation, condition de depot et position phylogenetique de 'Bothriospondylus madagascariensis' (Damparis,
Jura, France). MS thesis, Memoires de Maıtrise Magistere Sciences de la Terre ENS-Lyon.
Gishlick, 2002. The functional morphology of the forelimb of Deinonychus antirrhopus and its importance for the origin of avian flight. PhD thesis, Yale University. 142 pp.
Gower, 2003. Osteology of the early archosaurian reptile Erythrosuchus africanus Broom. Annals of the South African Museum. 110(1), 1-88.
Meers, 2003. Crocodylian forelimb musculature and its relevance to Archosauria. The Anatomical Record. Part A, 274A, 891-916.
Agnolin, 2015. Nuevas observaciones sobre Pisanosaurus mertii Casamiquela, 1967 (Dinosauriformes) y sus implicancias taxonomicas. XXIX Jornadas Argentinas de Paleontologia de Vertebrados. Libros de Resumenes. 13-14.