[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
RE: "Abominable Mystery": Rise of Angiosperms in the Cretaceous
Something worth keeping in mind, however, is that the great diversity (and in
the first two phases, essentially the ENTIRE
diversity) of angiosperms were as herbs and very small shrubs. Angiosperm trees
only show up in the later part of the Cretaceous.
Furthermore, tree-nesting is not as widely distributed in even crown-group Aves
as people think. Not all birds are tree-nesters, and
assuming Mesozoic avialians were mostly tree nesters because many neoavians are
is similar to assuming that Mesozoic eutherians
lived in herds because many modern ungulate placentals do.
Thomas R. Holtz, Jr.
Email: email@example.com Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Faculty Director, Science & Global Change Program, College Park Scholars
Mailing Address: Thomas R. Holtz, Jr.
Department of Geology
Building 237, Room 1117
University of Maryland
College Park, MD 20742 USA
> -----Original Message-----
> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] On Behalf Of
> Stephen Poropat
> Sent: Friday, December 07, 2012 7:23 AM
> To: firstname.lastname@example.org
> Subject: Re: "Abominable Mystery": Rise of Angiosperms in the Cretaceous
> Further to your comments, Tim, would it be too much of a stretch to suggest
> that these same branches would have provided them
> with locations for nests, not to mention nest building materials?
> On Fri, Dec 7, 2012 at 4:54 AM, Tim Williams <email@example.com> wrote:
> > Not directly dinosaur-related... but I'd hazard a guess that the rise
> > of angiosperms had a profound impact on the evolution of one
> > particular branch of the Theropoda.
> > C. Coiffard, B. Gomez, V. Daviero-Gomez, D. L. Dilcher. (2012) Rise to
> > dominance of angiosperm pioneers in European Cretaceous environments.
> > PNAS DOI: 10.1073/pnas.1218633110
> > Abstract: "The majority of environments are dominated by flowering
> > plants today, but it is uncertain how this dominance originated. This
> > increase in angiosperm diversity happened during the Cretaceous period
> > (ca. 145?65 Ma) and led to replacement and often extinction of
> > gymnosperms and ferns. We propose a scenario for the rise to dominance
> > of the angiosperms from the Barremian (ca. 130 Ma) to the Campanian
> > (ca. 84 Ma) based on the European megafossil plant record. These
> > megafossil data demonstrate that angiosperms migrated into new
> > environments in three phases: (i) Barremian (ca. 130?125 Ma)
> > freshwater lake-related wetlands; (ii) Aptian?Albian (ca. 125?100 Ma)
> > understory floodplains (excluding levees and back swamps); and (iii)
> > Cenomanian?Campanian (ca. 100?84 Ma) natural levees, back swamps, and
> > coastal swamps. This scenario allows for the measured evolution of
> > angiosperms in time and space synthesizing changes in the physical
> > environment with concomitant changes in the biological environment.
> > This view of angiosperm radiation in three phases reconciles previous
> > scenarios based on the North American record. The Cretaceous plant
> > record that can be observed in Europe is exceptional in many ways. (i)
> > Angiosperms are well preserved from the Barremian to the Maastrichtian
> > (ca. 65 Ma). (ii) Deposits are well constrained and dated
> > stratigraphically. (iii) They encompass a full range of environments.
> > (iv) European paleobotany provides many detailed studies of Cretaceous
> > floras for analysis. These factors make a robust dataset for the study
> > of angiosperm evolution from the Barremian to the Campanian that can
> > be traced through various ecosystems and related to other plant groups
> > occupying the same niches."
> > Article reported here:
> > http://www.sciencedaily.com/releases/2012/12/121206094131.htm
> > The report concludes: "... co-evolution with insects gave angiosperms
> > an evolutionary advantage. Insects played a vital role in
> > cross-pollinating plants and accelerating the spread of genetic
> > material. Plants evolved the means to "advertise themselves" with
> > fragrances and bright colors while producing pollen and nectar that
> > provided food for insects."
> > The diversification of Avialae might also correlate with the
> > diversification of angiosperms. Not only because of the radiation of
> > certain angiosperm-pollinating insect groups that basal birds
> > (avialans) could have fed on. As with today's flowering plants,
> > Cretaceous angiosperms tended to be branched, giving birds something
> > to perch on (conifers also diversified in the mid-Cretaceous). Most
> > "gymnosperms" (cycads etc) tended to be sparsely branched or not
> > branched at all (monocaulous). So although cycads & co could be
> > climbed (such as to gain access to seeds or insects), these sturdy
> > plants didn't really offer a convenient refuge.
> > I think it's telling that many studies indicate that some small
> > maniraptorans (including _Microraptor_ and _Archaeopteryx_) have claw
> > curvatures consistent with climbing (e.g., most recently Birn-Jeffery
> > et al., doi:10.1371/journal.pone.0050555). However, these same
> > maniraptoran taxa show few (if any) arboreal adaptations. So perhaps
> > the earliest stages of flight evolution were associated with
> > tree-climbers (cycad-climbers?) that did not stay in trees. Only
> > later, with the spread of tall conifers and angiosperms, did birds
> > habitually perch in trees.
> Dr. Stephen Poropat
> Postdoctoral Research Fellow
> Uppsala University
> Villavägen 16
> SE-752 36 Uppsala
> Research Associate
> Australian Age of Dinosaurs
> PO Box 408
> Winton 4735