The recent Royal Society meeting "Sexual Selection: Patterns in the History of Lifeâ had a few dinosaur items.Â
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1:00-11:30 Variation rates as an indication of sociosexual display in horned dinosaurs, and other ornithischians
Dr Caleb Brown, Royal Tyrrell Museum, Canada
Abstract
Phenotypic variation is the basic material upon which selection acts, and as such quantifying this variation is an important aspect of evolutionary biology. Specifically, research on a diverse array of living animals has documented higher rates of morphological variation in sociosexual display structures, than those under natural selection.
Many dinosaur species, particularly ornithischians, exhibit âexaggeratedâ skeletal structures that lack obvious mechanical functions and have been hypothesized to have function is sexual and social display. These are often manifested as outgrowths/hypertrophy of the skull roof, including the solid and hollow crests of Hadrosauridae, the horns and frills of Ceratopsia, and the thickened domes of Pachycephalosauria. For dinosaur palaeobiology, however, intraspecific variation is often regarded as merely an obstacle to robust taxonomy.
Here morphological variation was quantified (using coefficient of variation) for the well-sampled species of horned dinosaur Centrosaurus apertus, as well as complementary dataset of the horned dinosaurs Anchiceratops, Chasmosaurus, Protoceratops, and the duck-billed dinosaurs Lambeosaurus, and Corythosaurus.Â
Levels of variation for the putative ornamentation structures (e.g. frills, horns, crests) are significantly higher (~2-3 times) than those for the remainder of the skull. These results are consistent with, and often statistically indistinguishable from, the known sexual displays of a comprehensive dataset of extant amniotes analogues (including mammals, birds, and squamates).
When combined with previous research suggesting these same structures in ornithischians are ontogenetically delayed, positively allometric, rapidly evolving, and highly species-specific, these data provide further support to the hypothesis that sociosexual selection was the evolutionary driver of these âexaggeratedâ structures.Â
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3:30-14:00 Quantifying the evolution of theropod cranial ornaments
Dr Terry Gates, North Carolina Museum of Natural Sciences, USA
Abstract
Ornamental signalling structures function to convey messages about an individual organismâs defensive capability, physiology and genetic identity. Across evolutionary time these ornamental structures can be subject to directional selection that increases their size and/or complexity. These same forces may also act on other aspects of an organismâs physiology or morphology, such that ornamental and non-ornamental traits evolve in tandem. Work from the Gates lab has shown that non-avian theropod species with bony cranial ornaments evolved large body size faster and in most cases topped a greater maximum size than those non-avian species that lacked such bony structures. Terry follows this work by exploring the link between body size and osteological cranial ornaments in galliform birds with two important results. First, bony cranial ornaments in galliforms also characterize species of the largest body size. Ornstein-Uhlenbeck modelling suggests that species of the largest body size tend to have the most ornamented crania when osteological and soft tissue ornaments are taken together. The groupâs data also indicate that habitat (coded as a discrete character) of modern Galliformes plays a role in the presence or absence of cranial ornamentation, providing evolutionary biologists with a possible tool for interpreting the ecology of extinct non-avian theropods. The use of quantitative analyses is essential to understanding the effect of ornaments on organismal evolution. Practitioners of these methods should interpret their results in light of null models based on sexual selection or species recognition theory, which can vary dramatically depending on the conditions of selection.
Also, I added this video at the last minute the other day and missed a dumb (but common) typo. Here's a correction...
(Non-dino video, but "Dinosaur Renaissance" mentioned to compare with proposed "Cephalopod Renaissance"; stuff on ammonites)
Danna Staaf: "Squid Empire: The Rise and Fall of the Cephalopods"Â
Talks at Google
46 min.