Re: Longisquama's "feather-like" appendages in new study

[Tim Williams <tijawi@gmail.com>]

Brad McFeeters <archosauromorph2@hotmail.com> wrote:

> Does this study finally put to rest the hypothesis that the "appendages" are 
> part of a plant?

This study seems pretty convinced that they are *not* plant material :

   "The appendages’ imprints closely adjoin elements of bony
    substance referable to the spines of thoracal vertebrae (gray
    shaded in Fig. 3)."

   "The first six appendages are
    attached to the thorax with nos. 1–4 contacting the vertebral
    column. Arguably they are adjacent to the spines of
    subsequent thoracal vertebrae (but vertebral features are
    difficult to discern (Fig. 3)."

The authors then go on to say, more explicitly:

   "Why the appendages of Longisquama are not plant
    remains

    The bizarreness of Longisquama’s appendages and their
    remotely leaf-like morphology lead to the suggestion that
    the appendage exemplars in the holotype may not be part of
    the skeletal specimen, but that they represent a frond-like
    plant organ, which became associated with the skeleton
    through or after the death of the animal (Paul 2001, p. 64;
    Fraser 2006, p. 130). We believe this is unlikely for several
    reasons:

    1. The arrangement is regular; there is no sign that the
    association was coincidental. Except for the caudalmost
    impression, all elongate imprints set in along the
    dorsal thorax, some are more strongly curved and
    tapering close to the vertebral column. They do not
    appear to continue below or above the skeleton.

    2. Type of preservation: There is no indication of
    carbonaceous preservation, otherwise occurring for
    many plant fossils from the Longisquama type locality.
    Moreover, plant organs preserved three-dimensionally,
    with the impressions of the outer surfaces separated by
    a core of fine-grained sediment, are not known from
    macrofloral remains of the Madygen Formation.

    3. We know of no plant organ which matches all the
    principal characteristics of the appendages. Mesenteriophyllum
    kotschnevii (Sixtel 1962), an endemic plant
    fossil of unknown affinity, bears some similarity,
    because it has a folded surface; it lacks the characteristic
    curvature, hockey-stick-like outline, and asymmetric
    partition, however. If their belonging to the
    skeleton is questioned, a plausible alternative, explaining
    what the elongate projections could be, would add
    weight to these claims."






Cheers

Tim