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BURROWING IN PALEOZOIC AND MESOZOIC TIMES
> According to new evidence presented recently by Sundell (1997),
> mercoidodontoids were, in fact, burrowers. Whole families of
> merycoidodontoid have now been found preserved in burrows, and this
> lifestyle is supported by the stocky merycoidodontoid body, their
> broad, clawed feet and big heads with robust canines. I think
> Sundell compared them to living warthogs.
> One thing that may strike you as odd is that mammalogists are always
> adding to the list of fossorial/semi-fossorial mammal taxa, yet the
> Mesozoic seems strangely depauperate in its number of archosaurian
While we're talking about burrowing in fossil taxa, we should give
dicynodonts their due.
In the Beaufort beds of the South African Karoo, R. Smith of the
South African Museum has discovered several helical burrow casts,
very similar to the ichnofossil Daimonelix from the Miocene of
Nebraska. Daimonelix has been attributed to the digging activities of
the primitive beaver Paleocastor. In the Karoo, the maker and
inhabitant of the spiral-like burrow were dicynodonts of the genus
Diictodon; several specimens have been found coiled, and sometimes
intertwined at the terminal end of the cast, which appears to have
been a widened, terminal chamber in the burrow. Scratch marks at the
sides of the burrow cast suggest that the burrow was made by the aid
of both the claws and the beak of the dicynodonts.
Next to Diictodon, the genera Cistecephalus (Kistecephalus),
Cistecephaloides and Kawingasaurus have been considered as probably
fossorial animals, based on the morphology of the body and especially
the forelimbs. Cistecephalus shows a striking general resemblance to
the extant moles and molerats.
Apart from the dicynodonts, there is also some evidence for burrowing
in some small parareptiles, the procolophonids. Bones of the genus
Procolophon have been identified in an elliptical burrow cast in
fossil riverbanks of the Early Triassic. Broadening of the three
inner digits of the manus of Procolophon has been interpreted as an
adaptation to digging. Von Huene was already pointing to digging
habits of procolophonids and Sclerosaurus in some publications in the
Recently, an assemblage of juvenile Youngina has been found in
Permian strata from the Karoo, intertwined and apparently killed
together while sheltering in a den.
Apart from the Karoo basin, in which taphonomic circumstances
probably favoured the preservation of fossorial structures,
there are very few mentions or remains of digging vertebrates in the
Paleozoic or Mesozoic.
A recently discovered diapsid from the Early/Middle Jurassic Boca
formation of Mexico, Tamaulipasaurus, displays a morphology
strikingly adapted to a fossorial way of living.
And if I remember correctly, the first amphisbaenid has been
recovered from Late Cretaceous sediments of the Gobi some years ago.
For the completeness of matters, the Italian Triassic
archosauromorph(?) Drepanosaurus was described initially as fossorial
animal (with the enlarged claws and hooked tail considered as
adaptations to burrowing) until new material and new descriptions
allowed correction: drepanosaurs are now considered as tree-dwellers.
Drifted far away from dinosaurs but still arriving at