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Re: Hedwig and the Angry New Paper

Thanks to everyone that sent me the paper!


On Mon, Jun 2, 2008 at 10:26 AM, Thomas R. Holtz, Jr. <tholtz@umd.edu> wrote:
> Don't know if a) that title has been used yet or b) this paper has been
> mentioned yet.
> No, I do not have a copy (our University Library having cancelled the
> subscription due to budget cuts.) Yes, I would love one...
> Ricqlès, A. de, K. Padian, F. Knoll and J.R. Horner. 2008. On the origin of
> high growth rates in archosaurs and their ancient relatives: Complementary
> histological studies on Triassic archosauriforms and the problem of a
> "phylogenetic signal" in bone histology. Annales de Paléontologie 94: 57-76.
> doi:10.1016/j.annpal.2008.03.002
> Abstract
> Three possible hypotheses could explain the polarity of the histological
> features of basal archosauriform and archosauromorph reptiles: either, the
> fibrolamellar complex is basal; or, the lamellar-zonal complex is basal or
> finally, the condition varied, and each complex evolved more than once in
> these early groups. The answer to this question would have broad
> implications for our understanding of the physiological, ecological, and
> behavioral features of the first archosaurs. To this end, we sampled the
> bone histology of various archosauriforms and basal archosaurs from the
> Triassic and Lower Jurassic: erythrosuchids, proterochampsids, euparkeriids,
> and basal ornithischian dinosaurs, including forms close to the origin of
> archosaurs but poorly assessed phylogenetically. The new data suggest that
> the possibility of reaching and maintaining very high growth rates through
> ontogeny could have been a basal characteristic of archosauriforms. This was
> partly retained (at least during early ontogeny) in most lineages of
> Triassic pseudosuchians, which nevertheless generally relied on lower growth
> rates to reach large body sizes. This trend to slower growth seems to have
> been further emphasized among Crocodylomorpha, which may thus have
> secondarily reverted toward more generalized reptilian growth strategies.
> Accordingly, their "typical ectothermic reptilian condition" may be a
> derived condition within archosauriforms, homoplastic to the generalized
> physiological condition of basal amniotes. On the other hand,
> ornithosuchians apparently retained and even enhanced the high growth rates
> of many basal archosauriforms during most of their ontogenetic trajectories.
> The Triassic may have been a time of "experimentation" in growth strategies
> for several archosauriform lineages, only one of which (ornithodirans)
> eventually stayed with the higher investment strategy successfully.
> Our data again raise the problem of a possible "phylogenetic signal" being
> carried by bone histology. Bone histology is highly correlated to
> "functional" characters as size and growth rates which are intensely
> involved in species-specific "life-history traits", are under intense
> scrutiny by selective pressures and may accordingly evolve very rapidly.
> This rapid evolutionary rate would in turn produce patterns of
> species-specific variations that could "erase" higher-order taxonomic
> signals in bone tissue. In other words, this fast turnover would introduce
> autapomorphies (and homoplasies) at the level of apical (terminal) taxa that
> could blur the wider "phylogenetic signal". Thus, the search for generalized
> apomorphic (or plesiomorphic) conditions of bone histological
> character-states at supraspecific levels may often be deceptive.
> Nevertheless, bone tissue phenotypes can reflect a phylogenetic signal at
> supraspecific levels if homologous elements are used, and if ontogenetic
> trajectories and size-dependent differences are taken into consideration.
> Thomas R. Holtz, Jr.
> Email: tholtz@umd.edu   Phone: 301-405-4084
> Office: Centreville 1216
> Senior Lecturer, Vertebrate Paleontology
> Dept. of Geology, University of Maryland
> http://www.geol.umd.edu/~tholtz/
> Fax: 301-314-9661
> Faculty Director, Earth, Life & Time Program, College Park Scholars
> http://www.geol.umd.edu/~jmerck/eltsite/
> Fax: 301-405-0796
> Mailing Address:        Thomas R. Holtz, Jr.
>                        Department of Geology
>                        Building 237, Room 1117
>                        University of Maryland
>                        College Park, MD 20742 USA