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Theropod tracks from Lower Cretaceous of Spain, morphometric analysis

Ben Creisler

A new online paper:

Diego Castanera, Jorge Colmenar, Víctor Sauqué and José I. Canudo (2014)
Geometric morphometric analysis applied to theropod tracks from the
Lower Cretaceous (Berriasian) of Spain.
Palaeontology (advance online publication)
DOI: 10.1111/pala.12132

Geometric morphometric methods applied to theropod tracks from the
Huérteles Formation (Berriasian, Spain) are here shown to be
invaluable for drawing comparisons between theropod tracks with
different preservation modes (true tracks, shallow undertracks and
natural casts) or differing in the preservation of anatomical features
(e.g. digital pads). Principal components analysis and thin-plate
spline methods can quantitatively distinguish between the broad groups
of tracks in a sample and establish the main differences between them.
These methods offer a promising approach for estimating
ichnodiversity, achieved by evaluating just the morphology of the
tracks independent of other factors such as size. The theropod tracks
of the Huérteles Formation can be classified into two broad groups:
minute-to-medium-sized gracile theropod tracks (Kalohipus bretunensis)
and medium-to-large-sized robust theropod tracks (Iberosauripus). The
presence of a third group of more gracile medium-to-large-sized
theropod tracks (Megalosauripus) cannot be proven with certainty on
the basis of the current data. These results indicate that the
theropod ichnodiversity of the Huérteles Formation is probably lower
than that estimated by means of conventional methods alone (e.g.
qualitative description of the tracks) and that many of the described
theropod morphotypes may represent extramorphological or ontogenetic
variations of other morphotypes.