SVP 2011 meeting, Day 3

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I got an early start today, with several talks on marine reptiles. Sue Beardmore, Patrick Orr, and Heinz Furrer did a taphonomic study of pachypleurosaurids, small Triassic reptiles from Switzerland (including Neusticosaurs, like the above example at the Denver Museum of Natural History). Small environmental differences have effects that result in variations in completeness and articulation of skeletons, as well as orientation effects (there are examples of these animals with the long necks and tails in single individuals both arranged parallel to the current). I think some of the methods presented in this talk maybe applicable to Carmel Church.

Robin O’Keefe and Luis Chiappe reported two associated skeletons of the Cretaceous plesiosaur Polycotylus latippinus, one adult and one juvenile (below is a different polycotylid species, from the Wyoming Dinosaur Center). The juvenile skeleton was located partially inside the pelvic region of the adult, and had partially cartilaginous and undeveloped bones, suggesting that it was an unborn fetus, indicating that Polycotylus was viviparous (gave live birth). The pre-term fetus was about 1/3 the length of the adult, which is a ration comparable to that seen in modern whales, suggesting the plesiosaurs may have exhibited similar social behaviors related to child-rearing.

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Carole Gee combined literature on Morrison Formation plant and pollen, combined with new discoveries, to conclude that this unit is dominated by large conifers and other gymnosperms that would have been adequate to feed the Morrison’s large population of sauropod dinosaurs. The example below is a conifer needle from the Two Sisters Site.

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Estelle Bourdon and Joel Cracraft examined the relationships of Gastornis (which includes the better-known name Diatryma; example below from the Oklahoma Museum of Natural History). They conclude that Gastornis is related to the other extinct “terror birds”, the phorusrhacids. The closest living relatives of the group are the South American seriemas.

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Michael Habib and Justin Hall gave a fascinating presentation on the flight characteristics of the pelagornithids (or pseudodontorns). It has long been suspected that Pelagornis was excellent at soaring, but I don’t think anyone suspected a glide ratio of 27:1 as was suggested by Habib and Hall. That means that starting from an altitude of 100 meters, Pelagornis could glide (no flapping) 2.7 kilometers. That’s far better than any extant bird.

In the poster session, Matt Davis examined the published records of skin impressions of various dinosaurs. He found that, even after controlling for the frequency with which different types of dinosaurs are found and different sediment types, hadrosaurs seem to have skin preserved at a higher rate than other groups (including Edmontosaurus, below, from the American Museum of Natural History).

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Laura Vietti, Jake Bailey, and Beverly Flood reported the growth of framboidal crystals on submerged bone that was a result of the colonization of the bone by bacteria. It may be possible to determine how long a bone was exposed to the water by looking at the size of the crystals.

Julia Fahlke, Katherina Bastl, and Gina Semprebon examined tooth wear in various protocetid and basilosaurus whales, including Pakicetus and Basilosaurus. They suggest heavy tooth wear in Basilosaurus (such as in the example below from the US National Museum) indicates that heavy-boned animals such as marine mammals and turtles may have been an important component of their diet, a hypothesis that is consistent with known Basilosaurus stomach contents.

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Elizabeth Varadian, Brian Beatty, and Jonathan Geisler did a pilot study that attempted to quantify variation in the petrosals of modern toothed whales. Their initial results some of these characters can at least be used to reliably identify different families.

Joseph El Adli and Bobby Boessenecker reconstructed the lower jaw musculature of the baleen whale Herpetocetus. The unusual lower jaw shape in Herpetocetus seems to preclude it from opening its mouth very wide, and it seems that it’s feeding style may have been quite different from other mysticetes.

I presented a poster summarizing the unusual taphonomic features of the Carmel Church bone bed. In fact, readers of this blog have already seen a good deal of the information I presented; about 1/4 of my poster was drawn directly from this post. Carmel Church differs from California’s famous marine bonebed, Sharktooth Hill, in several respects, including a high percentage of articulated skeletons, abundant microfossils, and extensive evidence of scavenging. While Sharktooth Hill is pretty clearly a deposit that formed over a long period of time through winnowing of fine sediments, Carmel Church seems to have a more complex depositional history.

After the posters was the SVP benefit auction. I was able to pick up a few reprints, but I was easily outbid on the cast Centrosaurus skull I was looking at for the museum. Oh, well. Tomorrow is the last day of the meeting, and includes the whale talks.

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