Geoscience Reference
In-Depth Information
er (male tracemaker) just behind but slightly offset to the right or left of two other
paired footprints (female tracemaker). All four tracks should be nearly identical in
size and form, but perhaps with slight differences accounting for gender differen-
ces (
sexual dimorphism
). Bipedal ornithopods would have had similar patterns, al-
though distinguishing these from those of theropods feeds into the old “what made
thethree-toedtrack”dilemmadiscussedinthepreviouschapter.Furthermore,many
ofussincerelyhopethatnomistakenattemptsatinterspeciesmatingtookplaceand
became registered in the fossil record, wherein a theropod found a same-sized orni-
thopod winsome, or vice-versa.
For quadrupedal dinosaurs, such as sauropods, ceratopsians, ankylosaurs,
some ornithopods, and other dinosaurs that got around on all fours, mating traces
would differ appropriately from those of bipedal dinosaurs by adding a few more
tracks to the mix: two, specifically. This situation would have been a result of
the male, having approached his potential partner from behind and not being re-
buffed—sexual selection or rejection writ large—then likely rearing up and putting
his front feet onto the back of the female. This positioning also means that her rear
legs would have supported at least part of his weight, which should have deepened
her hind tracks relative to her front tracks. Hence the full sequence of trace fossils
might be:
• Normal quadrupedal diagonal walking pattern by both dinosaurs, either
subparallel to each other or perhaps showing a shortening of pace as the
male approached from behind.
• Two sets of four (front-rear) tracks, one behind the other and perhaps
offsettotherightorleft—accounting forbypassingthefemale'stailonone
side—denoting pre-mating positions. These tracks also might be accom-
panied by a central mark behind the male's tracks, caused by his tail press-
ing against the ground as he adopted a tripod-like stance.
• Noticeably deeper rear tracks in both sets of tracks (mounting in progress),
but maybe with one of the male's legs draped over the female's tail, and
some evidence of shuffling forward if she needed adjusting to his weight
