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MAMMALS AS DINOSAUR ANALOGUES II



Rob Meyerson wrote:

> As far as pigs are concerned, modern farm-style pigs have average sized
> neural spines, but consider wild members of the group.  The warthog (as
> well as it's larger/extinct cousins) has rather long neural spines, which
> serve as anchors for the neck muscles (useful for rooting for food).  Bison
> have long neural spines to help support the heavy head.  It is possible
> that animals evolve long neural spines for the same reason ceratopians
> elongated the frill, more muscle attachment gives a stronger structure
> (see, it does relate to dinos).

        In _Acrocanthosaurus atokensis_ the elongate neural spines start on
the first cervical vertebra and continue - increasing to about 3 times the
initial height before reaching the sacrum - all the way down the dorsal
vertebrae and onto the caudal vertebrae before diminishing in height about
a quarter of the way down the tail. The elongate neural spines of
_Ouranosaurus nigeriensis_ and _Spinosaurus aegyptiacus_ begin on the
dorsal vertebrae, rapidly becoming ridiculously large (5 times the height
of the smallest dorsal neural spine on _Ouranosaurus_ and up to 18 times
the height of the smallest cervical spine on _Spinosaurus_); the spines of
_Spinosaurus_ reduce to *normal* size at the sacrum, those of
_Ouranosaurus_ reduce slightly at the sacrum, but continue to be elongate
down the caudals before reducing in a gradual taper. This is a radically
different pattern than that seen in the mammalian forms under discussion.
        In mammals such as wild pigs and bison, the elongate neural spines
are located only on the first third-to-half of the dorsal vertebrae to
supply muscle attachment area for the neck and head. The tallest spines in
the three dinosaurs discussed above are located just before the sacrum, at
the farthest point of the dorsal series from the head and neck. Because of
the high number of elongate spines (compared to mammals), as well as the
placement of the longest spines on the vertebral column, it seems unlikely
that the spines of these dinosaurs served as areas of muscle attachment.
        And I'm not certain I understand the reference to ceratopians. The
ceratopian frill served as an area of muscle attachment for the jaws, not
as support for the head or neck. To help support their massive heads, the
first three cervical vertebrae of ceratopians are fused.


Brian Franczak (franczak@ntplx.net)