The Hammerschmiede clay pit (German: Tongrube Hammerschmiede) is a fossil bearing locality in Pforzen, Bavaria, Germany most well known for the discovery of Danuvius guggenmosi, the potentially earliest known bipedal ape. With an age of 11.66-11.42 Ma the site dates to the transition between the Middle and Late Miocene epoch, providing an important window into the faunal changes taking place during this time. This correlates to the time just after the Serravallian-Tortonian boundary, and the MN zones 7/8. It is one of the most well-known Miocene sites, with over 15,000 individual fossils and 117 species having been discovered as of 2020. It has been called "the most important German paleontological discovery of the last decades".

Hammerschmiede's first fossils were first discovered by the hobby archaeologist Siegulf Guggenmos in 1965. The site became known in academic circles following publications on its rich fauna of micromammals in 1975. Since 2011, the excavations are led by a collaboration between the University of Tübingen and the Senckenberg Museum, and led by Madelaine Böhme, with the help of local volunteers. Excavations were intensified in 2015, following the discovery of a variety of scientifically significant finds. Media attention increased following the description of Danuvius guggenmosi in 2019, its name honoring the discoverer of the site. Nicknamed "Udo", the discovery was described as the oldest known example of an upright ape in Hominidae, with some media even going so far as to call it proof that the cradle of humanity was located in Bavaria. The site is threatened by clay mining.

The Hammerschmiede clay pit is located within the eastern Allgäu region of Bavaria, within the municipality of Pforzen, at a height above sea level of almost 700 m. It is located just west of the district Hammerschmiede, after which it is named, and lies between the stream Riedgraben to its south, and the river Wertach to its East. Furthermore, the locality Irsee, where fossil plant remains had already been discovered in the 1950s, is located 4.3 km to its southwest. The closest town is Kaufbeuren to its south-east.

The Hammerschmiede locality is part of the Upper Freshwater Molasse within the North Alpine foreland Basin. It is part of the Obere Serie, which includes Germany's youngest Molasse sediments. The 25.7 m thick section is best exposed at the southern end of the clay pit.

The horizontally bedded layers are mostly grey-colored, carbonatic and fine-grained silts, fine sands and claystone. The sedimentary succession can be traced over 150 m in a northern direction, with seven marker beds being traceable across the whole distance. These are three lignite horizons, three sand horizons and one marlstone. The circa 0.45 m thick homogeneous silty-clayey marlstone contains a variety of terrestrial gastropods, and is located in the basal part of the northern profile. Meanwhile, up to 10 mm thick pedogenic carbonate concretions are abundant in the upper 20 cm. A 20 cm thick blackish lignite horizon occurs 1.5 m above this horizon, overlaying 70 cm of yellowish and brownish mottled dark-grey clay. The color of this lignite is platy, it is partly xylitic and can be horizontally replaced by carbonatic peat clay. This succession may be viewed as a complete calcic paleosol, with the marlstone representing the Bk-horizon, the mottled clay the Bt-horizon, and the lignite the A-horizon. Three horizontally continuous bodies of fine-sand are located between the upper and lower lignite horizons, with the lower one being 1.05 m thick, greenish-grey, showing no bedding structures, but containing iron-hydroxide stains. The middle sand horizon, made up of mica rich grey-blue to greyish sand and containing iron-hydroxide stains, is 2.8 m thick at the southern part of the clay pit, and develops into an up to 4 m deep channel at its erosional base in the North. The upper sand horizon, consisting of grey silty fine-sand showing iron-hydroxide stains, is 1.4 m thick and is divided by a 20 cm thick pedogenic bed 0.70 m above its base. This bed, which includes small fossilised roots, consists of mottled clayey and sandy silts. Reworked pedogenic carbonates clay pebbles with a diameter of up to 3 cm occur 30 cm above the base of the horizon.

A 35 cm thick lignite horizon marks the top of the presently exposed sedimentary succession in the Hammerschmiede outcrop. Its basal 25 cm are platy colored and rarely contain xylit, while the upper 10 cm are blackish carbonatic organic clay instead of lignite. It overlays about 10 cm of carbonate-free, grey-greenish and rusty-yellowish mottled sandy and clayey slits. As a 40 cm thick rooted silt horizon, containing abundant powdery, whitish soft carbonate occurs below it, the topmost succession can be interpreted as an immature calcic paleosol.

Directly below this, another, shallower calcic paleosol is developed. Its A-horizon is formed by 7 cm thick blackish carbonatic peat clay, overlaying the Bt-horizon (5 cm thick grey clay) and Bk-horizon (8 cm thick whitish clay horizon with abundant powdery carbonate). The paleosols rooting system reaches 50 cm below the A-horizon.

Furthermore, several truncated paleosols, which either completely or partly lack the A-horizon, occur especially between the two lower sand horizons. Those are characterized by up to 0.60 m thick grey green-yellowish mottled clayey marls, which contain matrix-supported pedogenic carbonate concretions. Two less developed calcic-paleosols, which are completely lacking A-horizons but clay-rich Btk horizons, make up the basal 4 meters of the succession in the southern profile.