Upcoming Article on Massospondylus (Sauropodomorpha) Embryos from the Lower Jurassic of Africa

A bunch of news articles have come out over the last two days discussing an upcoming article in the Journal of Vertebrate Paleontology discussing details of embrionic remains of the Jurassic sauropodomorph Massospondylus.

At this time it is unclear how this paper will differ from the original find of Massospondylus embryos in 2005.

You can check out two of the new stories (including photos) here and here.



from http://www.msnbc.msn.com/id/40133043/ns/technology_and_science-science/



New Paper on the Triassic Dinosaur Staurikosaurus pricei

Bittencourt, J.S., and A.W.A. Kellner. 2009. The anatomy and phylogenetic position of the Triassic dinosaur Staurikosaurus pricei Colbert, 1970. Zootaxa 2079:1-56.

Abstract: We redescribe the holotype of the saurischian dinosaur Staurikosaurus pricei Colbert, 1970 from Late Triassic Santa Maria Formation (southern Brazil), following additional preparation that revealed new anatomical features. A revised diagnosis is proposed and the published synapomorphies for Dinosauria and less inclusive clades (e.g. Saurischia) are evaluated for this species. Some characters previously identified as present in the holotype, including the intramandibular joint, hyposphene-hypantrum articulations in dorsal vertebrae, and a cranial trochanter and trochanteric shelf on the femur, cannot be confirmed due to poor preservation or are absent in the available material. In addition, postcranial characters support a close relationship between S. pricei and Herrerasaurus ischigualastensis Reig, 1963 (Late Triassic, Argentina), forming the clade Herrerasauridae. Several pelvic and vertebral characters support the placement of S. pricei as a saurischian dinosaur. Within Saurischia, characters observed in the holotype, including the anatomy of the dentition and caudal vertebrae, support theropod affinities. However, the absence of some characters observed in the clades Theropoda and Sauropodomorpha suggests that S. pricei is not a member of Eusaurischia. Most morphological characters discussed in previous phylogenetic studies cannot be assessed for S. pricei because of the incompleteness of the holotype and only known specimen. The phylogenetic position of S. pricei is constrained by that of its sister taxon H. ischigualastensis, which is known from much more complete material.

New Basal Sauropodomorph from South America

Martinez, R.N., and O.A. Alcober. 2009. A Basal Sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the Early Evolution of Sauropodomorpha. PLoS ONE 4: e4397. doi:10.1371/journal.pone.0004397

Abstract

Background: The earliest dinosaurs are from the early Late Triassic (Carnian) of South America. By the Carnian the main clades Saurischia and Ornithischia were already established, and the presence of the most primitive known sauropodomorph Saturnalia suggests also that Saurischia had already diverged into Theropoda and Sauropodomorpha. Knowledge of Carnian sauropodomorphs has been restricted to this single species.

Methodology/Principal Findings: We describe a new small sauropodomorph dinosaur from the Ischigualsto Formation (Carnian) in northwest Argentina, Panphagia protos gen. et sp. nov., on the basis of a partial skeleton. The genus and species are characterized by an anteroposteriorly elongated fossa on the base of the anteroventral process of the nasal; wide lateral flange on the quadrate with a large foramen; deep groove on the lateral surface of the lower jaw surrounded by prominent dorsal and ventral ridges; bifurcated posteroventral process of the dentary; long retroarticular process transversally wider than the articular area for the quadrate; oval scars on the lateral surface of the posterior border of the centra of cervical vertebrae; distinct prominences on the neural arc of the anterior cervical vertebra; distal end of the scapular blade nearly three times wider than the neck; scapular blade with an expanded posterodistal corner; and medial lamina of brevis fossa twice as wide as the iliac spine.

Conclusions/Significance: We regard Panphagia as the most basal sauropodomorph, which shares the following apomorphies with Saturnaliaand more derived sauropodomorphs: basally constricted crowns; lanceolate crowns; teeth of the anterior quarter of the dentary higher than the others; and short posterolateral flange of distal tibia. The presence of Panphagia at the base of the early Carnian Ischigualasto Formation suggests an earlier origin of Sauropodomorpha during the Middle Triassic.

Latest Literature

A few new papers which recently came to my attention and that deal (at least somewhat) with Triassic vertebrates....


Allain, R., and E. Lang. In Press. Origine et evolution des saurischiens (Saurischian origins and evolution). Compte Rendus Palevol. doi:10.1016/j.crpv.2008.09.013

Abstract: We propose here a short synthesis of the saurischian evolutionary history. Our knowledge of the diversity and evolution of the saurischian non-avian dinosaurs has increased during the past decade. The generalized use of cladistics has led to various phylogenetic hypotheses, some of them in agreement on the evolution of saurischians, even if some controversy remains. The saurischian evolution is closely linked to two of the five great mass extinctions, which punctuated life history, but probably also to a third, less important, extinction event at the end of the Early Jurassic.

Dyke, G. J., McGowan, A.J., Nudds, R.L., and D. Smith. In Press. The shape of pterosaur evolution: evidence from the fossil record. Journal of Evolutionary Biology. doi:10.1111/j.1420-9101.2008.01682.x

Abstract: Although pterosaurs are a well-known lineage of Mesozoic flying reptiles, their fossil record and evolutionary dynamics have never been adequately quantified. On the basis of a comprehensive data set of fossil occurrences correlated with taxon-specific limb measurements, we show that the geological ages of pterosaur specimens closely approximate hypothesized patterns of phylogenetic divergence. Although the fossil record has expanded greatly in recent years, collectorship still approximates a sigmoid curve over time as many more specimens (and thus taxa) still remain undiscovered, yet our data suggest that the pterosaur fossil record is unbiased by sites of exceptional preservation (lagerstatte). This is because as new species are discovered the number of known formations and sites yielding pterosaur fossils has also increased – this would not be expected if the bulk of the record came from just a few exceptional faunas. Pterosaur morphological diversification is, however, strongly age biased: rarefaction analysis shows that peaks of diversity occur in the Late Jurassic and Early Cretaceous correlated with periods of increased limb disparity. In this respect, pterosaurs appear unique amongst flying vertebrates in that their disparity seems to have peaked relatively late in clade history. Comparative analyses also show that there is little evidence that the evolutionary diversification of pterosaurs was in any way constrained by the appearance and radiation of birds.

Reichel, M., Schultz, C.L., and M.B. Soares. 2009. A new traversodontid cynodont (Therapsida, Eucynodontia) from the Middle Triassic Santa Maria Formation of Rio Grande Do Sul, Brazil. Palaeontology 52:229-250. doi: 10.1111/j.1475-4983.2008.00824.x

Abstract: Remains of a peculiar traversodontid cynodont, Protuberum cabralensis gen. et sp. nov., are described herein. The material was collected from two outcrops representing the Therapsid Cenozone (Middle Triassic) of the Santa Maria Formation, and consists of a cranium with most of its dentition preserved and an associated postcranial skeleton. The upper postcanines have two sharp cusps that are connected by a medial crest on unworn postcanines. The specimens possess several autapomorphies, including: (1) presence of thickened bone on the dorsal surface of the skull; (2) thick dorsal ribs, with remarkable processes situated on their dorsal borders that decrease in size distally; and (3) an iliac blade with a series of rugosities along its dorsal border. The lumbar ribs bear overlapping costal plates and have distally projecting rib shafts that differ from the pattern observed in Thrinaxodon, Pascualgnathus and Cynognathus.

Mystery Fossil #2 is.....

...the astragalus of the basal saurichian Chindesaurus bryansmalli. Kudos to Adam and Jaime who got it right. This element is from the holotype specimen, and one of the autapomorphies of the taxon as proposed by Long and Murry (1995) was an astragalus that is "glutealiform" in ventral view, which probably ranks as one of my favorite descriptive terms of all time. Unfortunately (if you are a fan of this character), we (Sterling Nesbitt, Randy Irmis, and myself) determined that the element is actually broken and worn and actually was similar to the astragalus of other basal saurischians including Saturnalia and Herrerasaurus (Nesbitt et al, 2007).

The SVP meeting was very well attended with a fabulous program of oral and poster presentations. It is always great to catch up with colleagues (and to meet lots of new people), although unfortunately I did have to miss the bloggers lunch. I was at the open SVP Executive Committee meeting and hopefully my absence at the lunch was understood. There were some excellent (and important ) Triassic talks which I may feature here in the near future. As directly blogging on the content of posters and talks is discouraged by the SVP, I will focus on the published abstracts and my take on their implications. Stay tuned.

REFERENCES

Long, R.A., and P.A. Murry. 1995. Late Triassic (Carnian and Norian) tetrapods from the Southwestern United States. New Mexico Museum of Natural History and Science Bulletin 4:1–254.

Nesbitt, S.J., Irmis, R.B., and W.G. Parker. 2007. A critical re-evaluation of the Late Triassic dinosaur taxa of North America. Journal of Systematic Palaeontology 5:209-243.