The smallest known Palaeozoic mantis shrimp specimen, and possibilities for where to find more

Mantis shrimps are fierce predatory crustaceans in modern day oceans. Fossils of mantis shrimps are still a rarity. They occurred back in the Carboniferous, 300 million years ago, but already with quite a diversity of different forms. Interestingly, all these fossils are comparably large, usually several centimetres body length. From the Mesozoic, numerous mantis shrimp fossils have also been reported, the largest specimens being far in the centimetre range as well, but the smallest specimens being only about 4–5 mm. With this data set, we can reconstruct aspects of the life history for (at least some) Mesozoic mantis shrimps, but not for Palaeozoic forms. We report here a new fossil mantis shrimp specimen from the Carboniferous Bear Gulch limestones, USA. The specimen is quite small, in its rolled-up position about 10 mm across the laterally preserved body, but 25 mm in estimated total length. This is considerably shorter than any mantis shrimp so far known from the Palaeozoic. Hence, the specimen provides an important data point. Furthermore, it provides some indications where we could possibly find more specimens of comparable or even smaller size: The specimen resembles certain co-occurring fossils, representatives of Cyclida, in some aspects, suggesting that among the material of Cyclida we might find more small-sized mantis shrimps.

COUGAR CREEK: QUANTITATIVE ASSESSMENT OF OBSIDIAN USE IN THE GREATER YELLOWSTONE ECOSYSTEM

With more than 15 sources of obsidian and other lithic materials, the Greater Yellowstone Ecosystem of Montana, Wyoming, and Idaho is one of the richest toolstone regions in northwestern North America. This article introduces a quantitative assessment technique to compare attributes of seven Yellowstone obsidians used by Native Americans over at least 11,000 years. The proposed assessment technique is replicable and adaptable to other regions. This article also analyzes the procurement, use, and distribution of the poorly studied Cougar Creek obsidian. Archaeological research documented Cougar Creek obsidian outcrops, procurement areas, and secondary processing sites. Native Americans acquired the material at surface exposures, as well as occasional trench and pit excavations. There is a significant distance decay reduction in its use, especially when compared with Obsidian Cliff obsidian. Using a weighted z-score analysis, the material attributes of Cougar Creek were compared with those of six regional obsidians to determine the factors involved in their differential use. Based on these rankings, Cougar Creek obsidian experienced low demand and usage due to poor quality and availability. In contrast, due to their high quality, abundance, and aesthetics, Obsidian Cliff and Bear Gulch obsidians were preferred for stone tool production.