Sunday, 6 November 2011

SVP 2011 - Some Highlights

So SVP is over for another year and, embargoes now lifted, we can report on, and discuss, some of the excellent content that was presented in Las Vegas. Here I report on some of the highlights that, from a purely personal point of view, are amongst the most fascinating.

One of the most famous dinosaurs in recent years is a specimen of Thescelosaurus neglectus known as Willo who made worldwide headlines as possibly being the first dinosaur found with a fossilised four chambered heart. Naturally this has led to some controversial discussion as to whether the structure located within the thoracic cavity is actually what it appears to be.

But now, following on from his previous work (2011), Timothy Cleland of North Carolina State University has performed an extensive morphological examination of the specimen and has demonstrated that the “heart” of this dinosaur is almost certainly a geological artefact. However, there is also evidence of structures that are not conducive with being of geological origin and are actually similar to both plant and animal cells. Further examination using scanning electron microscopy suggest a biological origin for these structures which is somewhat intriguing although the overall evidence from this intense study overwhelmingly supports a geological origin for the structure.

Direct evidence of predator-prey relationships in the fossil record is always fascinating and brings the prehistoric world to life. Evidence of predation on fossil bone is more common than people realise and to see the serration and gouge marks, sometimes so clear on the surface of bone, is always a thrill. But now a specimen of Microraptor, from the Early Cretaceous of China, has taken this interaction to another level.


O’Connor, Zhou and Xu of the Institute of Vertebrate Palaeontology & Palaeoanthropology (IVPP) in Beijing reveal that the specimen appears to have the remains of an enantiornithine bird in its stomach. The authors  suggest that Microraptor did indeed hunt in the tree canopy since the birds were obviously arboreal. And, the authors also suggest, that this may be further evidence for a “tree down” origin for avian flight. Looking forward to the paper being published for this one.

The Morrison Formation is one of the most heavily sampled vertebrate bearing strata in the world and is rightly famous for providing a multitude of Late Jurassic dinosaurs. But there is also a varied mammalian community that is not so well known but is equally as fascinating and now Anthony Martin et al have revealed a wonderful discovery that captures one of those unique moments in time.

A quarry near Bluff in Utah has revealed an extensive network of burrows that have been dug by fossorial mammals probably weighing as much as 500gm – quite large for the time and represents an as yet unknown taxon. It is a typical burrowing system with main tunnels, side offshoots and various chambers and, amazingly, some of the smaller tunnels wind through and around the skeleton of a camarasaurid sauropod skeleton.

Palaeoenvironmental studies reveal that the sauropod had died millennia before in a waterhole environment and was buried in sediment and detritus. Eventually, the site was covered in newly formed soil as a result of pedogenesis. It was this soil that was tunnelled through by the mystery mammals who gradually penetrated through to the sauropod skeleton. The burrows within the skeleton actually change direction to get around the bones demonstrating how the mammals were affected by the obstruction. A wonderful and rare discovery capturing, indirectly, mammalian and dinosaurian interaction during the Jurassic.

Back in August, Robin O’Keefe and Luis Chiappe announced in Science that a specimen of Polycotylus latippinus, recovered from the Pierre Shale in Logan County, Kansas, was found in association with, what they describe as, embryonic remains of a juvenile. At SVP there was yet more detail displayed describing the specimen and shows that the bones of the juvenile are poorly ossified and are at an early ontogenetic stage.

The fact that the bones of the juvenile were found within the body cavity of the larger specimen and that they show no sign of being digested or chewed leads to the conclusion that this specimen of Polycotylus was a gravid female that died prior to giving birth. It is apparent that the embryo still had a period of significant development to undergo before coming to term and it appears likely that Polycotylus gave birth to single, very large new borns.


Strangely, you would think that there would have been other specimens of pregnant plesiosaurs found by now, especially when you consider how many plesiosaurs have been collected over the years. Perhaps the most interesting part of this discovery is the hypothesis, because a single birth by implication suggests as much, that plesiosaurs may have demonstrated parental care for their young which in turn leads to suggestions that they also engaged in a form of social structure and interaction. This leads to all sorts of new conjecture and may redefine how we interpret reproductive and behavioural patterns in other marine reptiles.

Finally, here’s one for you palaeoartists out there and is amazing in its own right. A hadrosaur, tentatively referred to Gryposaurus, recovered from the Upper Cretaceous Kaiparowits Formation of southern Utah has revealed some unique and illuminating skin impressions displaying previously unknown morphologies.

Katherine Clayton et al have demonstrated that there is a single line of large scutes that sit proud along the dorsal ridge of the tail - totally unknown before now. On the flank of the tail, it is apparent that the skin tubercles are bigger dorsally at the proximal end whilst distally the largest tubercles are situated ventrally. The tubercles themselves are polygonal and irregular in size and display various lines of ridges that terminate in a scalloped edge that are non-uniform. This find is comparable to other skin impressions found in this and other similar formations but is quite distinct from other hadrosaurs such as Edmontosaurus.

References


Clayton, K., Irmis, R., Getty, M., Lund, E. and Nicholls, W. 2011. An Exceptionally Preserved Hadrosaurid Dinosaur Skeleton with Integument Impressions From The Upper Cretaceous Kaiparowits Formation of Utah. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011,pp90.

Cleland, T., Stoskopf, M.K. and Schweitzer, M.H. 2011. Histological, Chemical, and Morphological Reexamination of the “Heart” of a Small Late Cretaceous Thescelosaurus. Naturwissenschaften 98: 203-211.

Cleland, T. 2011. Chemical and Morphological Reinvestigation of the Dinosaur Heart. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011 pp90.

Martin, A., Noto, C. and Chiappe, L. 2011. A Burrow Runs Through It: Unusual Co-occurrence of a Large Mammal Burrow System and Dinosaur Skeleton in the Morrison Formation of Utah. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011 pp152.

O’Connor, J., Zhou, Z. and Xu, X. 2011. Small Theropod with Bird in Stomach Indicates Both Lived in Trees. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011 pp168.

O’Keefe, F.R. and Chiappe, L. 2011. Viviparity and K-Selected Life History in a Mesozoic Marine Plesiosaur (Reptilia: Sauroppterygia). Science 333, 870-873.

O’Keefe, F.R. and Chiappe, L. 2011 Viviparity and Cetacean-Like Life History in a Mesozoic Marine Plesiosaur (Reptilia: Sauropterygia). Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011 pp 168.

3 comments:

davidmaas said...

'strongly suggests that Microraptor did indeed hunt in the tree canopy"

Seems logically biased to me. "May have"... okay. But it seems equally unlikely that an animal that isn't adapted to the canopy could successfully hunt animals that are.

Thanks for the report. Also look forward to these.

Henrique Niza said...

^ Indeed. Scavenging is a possibility to have in mind too.

I thought Willo's supposed heart was a matter of time until a study disproved it as biological in origin, so no surprised.

The mammalian and dinosaurian interaction find on the other hand is quite fascinating. The Morrison Formation still surprises in these days.

Mark Wildman said...

Thanks for the comments guys. To be fair to the authors of the Microraptor poster, I could have worded my description a little better. To quote the authors:

".....this fossil suggests that Microraptor hunted in trees and strongly supports inferences that this taxon was also an aborealist."

A little better I think! But, as Henrique points out,perhaps the bird was already dead and picked up from ground below the trees - there's just no way of knowing.

For me, this is still an awesome fossil and the paper will prove to be extremely interesting.

As for the Morrison, I agree that these formations are so heavily sampled that it seems incredible that there are still new discoveries to be made. But the Morrison has an awful lot of completely new specimens to be announced in the coming years - and I mean a lot!

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