Prehistoric Trackways National Monument
Ever hear of Prehistoric Trackways National Monument? No? Me neither until pretty recently. The undeveloped monument is basically a chunk of protected land in the Robledo Mountains northwest of Las Cruces that so happens to contain over 150 sites where Permian Era fossils have been found. Some of the most important of these include prints from the meat-eating reptile Dimetrodon that lived 280 million years ago, which is waaaaaaay before dinosaurs.
The monument also includes thousands of trackways however, long stretches of prints that show locomotion and interactions between species such as predation activities – which are very rare in the fossil record according to the signs posted by the BLM. Thousands of different plant species, marine dwelling animals, and even rain drops are preserved here as well, and paint an uncommonly-complete picture of the late Paleozoic Era during which southern New Mexico sat in a swampy sea on one of the edges of the supercontinent Pangea.
The sandstone and limestone slabs containing the largest and most scientifically-important trackways have been removed for protection to the nearby New Mexico Statue University Museum, but there are thousands of remaining fragments and smaller slabs present in and around the washes, uncovered by erosion. These are what Abby and I were off to see on our first visit.
We took the one developed walking trail, the Ridgeline Trail, northwest up – you guessed it – a ridge. Here we had commanding views of the Organs to the east and soon gained views into the canyons below as we walked for about a mile and a half. Suddenly the well-defined trail along the uplands disappeared however and Abby and I followed the narrowed trail as it switchbacked into one of the canyons below. I had been seeing intermittent fossilized waves on sandstone scattered about the ridge but now as we entered the depths of the dry streambed I began noticing shapes appearing in the red sandstone. I followed the canyon downstream for a half mile before coming upon a sign announcing that a) fossils were around here and b) I shouldn’t take any. I crossed to the other side of the wash and immediately noticed the 25 pound slabs of sandstone with tracks. The five-toed Dimetrodon prints were pretty easy to pick out as were the marine brachiopods but there were definitely others that I had no idea what I was looking at. I’ve included photos of the best ones below.
Our second visit was purely a walking opportunity. I had noticed a map of the extensive OHV/ATV trail system that criss-crosses the monument when we visited last time. Presumably these trails both pre-date the designation of the area as a national monument and do not cross sensitive areas but it was still unusual to me that off-road trails exist in a place where there’s a significant fossil record. But anyway, I thought these would be perfect for some dog-walking so we ended up following some routes on the south/southwest side, climbing up hills and crossing canyons. Not unsurprisingly Abbs and I came across some neat rocks, but no fossilized tracks. We walked around for 3 hours or so until the midday sun started getting hot and generally had some pretty nice views the whole time.